Patent Publication Number: US-11663942-B1

Title: Near-eye display system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The instant application is a continuation of International Application No. PCT/US2022/032576 filed on 7 Jun. 2022, which claims benefit of prior U.S. Provisional Application Ser. No. 63/197,777 filed on 7 Jun. 2021, and claims benefit of prior U.S. Provisional Application Ser. No. 63/222,978 filed on 17 Jul. 2021. Each of the above-identified applications is incorporated herein by reference in its entirety. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
       FIG.  1    illustrates a schematic block diagram of a first aspect of a near-eye display system incorporating a flat-panel two-dimensional image-display array of light-emitting image-display pixels; 
       FIG.  2    illustrates a schematic diagram of the first aspect of the near-eye display system illustrated in  FIG.  1   , illustrating an embodiment of a first aspect of an associated optical subsystem incorporating a plurality of lenses, absent the associated processor and controller elements; 
       FIG.  3    illustrates a plan view of the flat-panel two-dimensional image-display array of light-emitting image-display pixels of the first aspect of the near-eye display system illustrated in  FIGS.  1  and  2   ; 
       FIG.  4    illustrates a plan view of an aperture stop and a two-dimensional modulation array that respectively define an entrance pupil and an associated plurality of modulated subpupils of the first-aspect near-eye display system illustrated in  FIGS.  1  and  2   , with the two-dimensional modulation array controlled so as to provide for a first aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being centered on the optical axis of the associated optical subsystem; 
       FIG.  5    illustrates a plan view of an exit pupil and associated active exit subpupils associated with the aperture stop and the two-dimensional modulation array of the first-aspect near-eye display system illustrated in  FIGS.  1  and  2   , for the active subpupil region (ASR) illustrated in  FIG.  4   ; 
       FIG.  6    illustrates a plan view of the aperture stop and two-dimensional modulation array of the first-aspect near-eye display system illustrated in  FIGS.  1  and  2   , with the two-dimensional modulation array controlled so as to provide for the first aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being rotated upwards and to the left relative to the optical axis of the associated optical subsystem; 
       FIG.  7    illustrates a plan view of an exit pupil and associated active exit subpupils associated with the aperture stop and the two-dimensional modulation array of the first-aspect near-eye display system illustrated in  FIGS.  1  and  2   , for the active subpupil region (ASR) illustrated in  FIG.  6   ; 
       FIG.  8    illustrates angular magnification provided for by an embodiment of the first aspect of the near-eye display system illustrated in  FIGS.  1  and  2   ; 
       FIG.  9    illustrates a longitudinal cross section of an associated volumetric visual environment of the first aspect of the near-eye display system illustrated in  FIGS.  1 ,  2  and  8   , along the optical axis of the associated optical subsystem; 
       FIG.  10    illustrates a plan view of the aperture stop and two-dimensional modulation array of the first-aspect near-eye display system illustrated in  FIGS.  1 ,  2 ,  8  and  9   , with the two-dimensional modulation array controlled so as to provide for a second aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being rotated upwards and to the left relative to the optical axis of the associated optical subsystem; 
       FIG.  11    illustrates a plan view of an exit pupil and associated active exit subpupils associated with the aperture stop and two-dimensional modulation array of the first-aspect near-eye display system illustrated in  FIGS.  1 ,  2 ,  8  and  9   , for the active subpupil region (ASR) illustrated in  FIG.  10   ; 
       FIG.  12    illustrates a plan view of the aperture stop and two-dimensional modulation array of the first-aspect near-eye display system illustrated in  FIGS.  1 ,  2 ,  8  and  9   , with the two-dimensional modulation array controlled so as to provide for a third aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being centered on the optical axis of the associated optical subsystem; 
       FIG.  13    illustrates a plan view of an exit pupil and associated active exit subpupil associated with the aperture stop and two-dimensional modulation array of the first-aspect near-eye display system illustrated in  FIGS.  1 ,  2 ,  8  and  9   , for the active subpupil region (ASR) illustrated in  FIG.  12   ; 
       FIG.  14    illustrates a plan view of the aperture stop and two-dimensional modulation array of the first-aspect near-eye display system illustrated in  FIGS.  1 ,  2 ,  8  and  9   , with the two-dimensional modulation array controlled so as to provide for the third aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being rotated upwards and to the left relative to the optical axis of the associated optical subsystem; 
       FIG.  15    illustrates a plan view of an exit pupil and associated active exit subpupil associated with the aperture stop and two-dimensional modulation array of the first-aspect near-eye display system illustrated in  FIGS.  1 ,  2  and  9   , for the active subpupil region (ASR) illustrated in  FIG.  14   ; 
       FIG.  16    illustrates a schematic block diagram of a second aspect of a near-eye display system incorporating a flat-panel two-dimensional array of light sources that define an associated array of modulated subpupils of the second-aspect near-eye display system, in cooperation with a separate flat-panel two-dimensional image-display array of light-modulating image-display pixels; 
       FIG.  17    illustrates a schematic diagram of a portion of a first embodiment of the second aspect of the near-eye display system illustrated in  FIG.  16   , illustrating a first embodiment of a second aspect of an associated optical subsystem incorporating a plurality of lenses, absent the associated processor and controller elements; 
       FIG.  18    illustrates a schematic block diagram of a third aspect of a near-eye display system incorporating a curved two-dimensional light array of light sources that define an associated array of modulated subpupils of the third-aspect near-eye display system, in cooperation with a separate flat-panel array of light-modulating image-display pixels; 
       FIG.  19    illustrates a schematic diagram of a portion of a first embodiment of the third aspect of the near-eye display system illustrated in  FIG.  18   , illustrating the first embodiment of the second aspect of an associated optical subsystem incorporating a plurality of lenses, absent the associated processor and controller elements; 
       FIG.  20    illustrates a plan view of the flat-panel two-dimensional image-display array of light-modulating image-display pixels of the second and third aspects of the near-eye display system illustrated in  FIGS.  16 - 19 ,  44 ,  45  and  47   ; 
       FIG.  21    illustrates a plan view of an aperture stop and a two-dimensional modulation array that respectively define an entrance pupil and an associated plurality of modulated subpupils of each of the second- and third-aspect near-eye display systems illustrated in  FIGS.  16 - 19 ,  44 ,  45  and  47   , with the two-dimensional modulation array controlled so as to provide for the first aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being centered on the optical axis of the associated optical subsystem; 
       FIG.  22    illustrates a plan view of an exit pupil and associated active exit subpupils associated with the aperture stop and a two-dimensional modulation array of each of the second- and third-aspect near-eye display systems illustrated in  FIGS.  16 - 19 ,  44 ,  45  and  47   , for the active subpupil region (ASR) illustrated in  FIG.  21   ; 
       FIG.  23    illustrates a plan view of the aperture stop and two-dimensional modulation array of each of the second- and third-aspect near-eye display systems illustrated in  FIGS.  16 - 19 ,  44 ,  45  and  47   , with the two-dimensional modulation array controlled so as to provide for the first aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being rotated upwards and to the left relative to the optical axis of the associated optical subsystem; 
       FIG.  24    illustrates a plan view of an exit pupil and associated active exit subpupils associated with the aperture stop and a two-dimensional modulation array of each of the second- and third-aspect near-eye display systems illustrated in  FIGS.  16 - 19 ,  44 ,  45  and  47   , for the active subpupil region (ASR) illustrated in  FIG.  23   ; 
       FIG.  25    illustrates a plan view of the aperture stop and two-dimensional modulation array of each of the second- and third-aspect near-eye display systems illustrated in  FIGS.  16 - 19 ,  44 ,  45  and  47   , with the two-dimensional modulation array controlled so as to provide for a second aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being rotated upwards and to the left relative to the optical axis of the associated optical subsystem; 
       FIG.  26    illustrates a plan view of an exit pupil and associated active exit subpupils associated with the aperture stop and two-dimensional modulation array of each of the second- and third-aspect near-eye display systems illustrated in  FIGS.  16 - 19 ,  44  and  45   , for the active subpupil region (ASR) illustrated in  FIG.  25   ; 
       FIG.  27    illustrates a plan view of the aperture stop and two-dimensional modulation array of each of the second- and third-aspect near-eye display systems illustrated in  FIGS.  16 - 19 ,  44  and  45   , with the two-dimensional modulation array controlled so as to provide for a third aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being centered on the optical axis of the associated optical subsystem; 
       FIG.  28    illustrates a plan view of an exit pupil and associated active exit subpupil associated with the aperture stop and two-dimensional modulation array of each of the second- and third-aspect near-eye display systems illustrated in  FIGS.  16 - 19 ,  44  and  45   , for the active subpupil region (ASR) illustrated in  FIG.  27   ; 
       FIG.  29    illustrates a plan view of the aperture stop and two-dimensional modulation array of each of the second- and third-aspect near-eye display systems illustrated in  FIGS.  16 - 19 ,  44  and  45   , with the two-dimensional modulation array controlled so as to provide for the third aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being rotated upwards and to the left relative to the optical axis of the associated optical subsystem; 
       FIG.  30    illustrates a plan view of an exit pupil and associated active exit subpupil associated with the aperture stop and two-dimensional modulation array of each of the second- and third-aspect near-eye display systems illustrated in  FIGS.  16 - 19 ,  44  and  45   , for the active subpupil region (ASR) illustrated in  FIG.  29   ; 
       FIG.  31    illustrates a schematic block diagram of a fourth aspect of a near-eye display system incorporating a scanned beam of light in cooperation with a curved light-redirecting surface that together define an associated modulated subpupil of the fourth-aspect near-eye display system, in cooperation with a separate flat-panel array of light-modulating image-display pixels; 
       FIG.  32    illustrates a schematic diagram of a portion of a first embodiment of the fourth aspect of the near-eye display system illustrated in  FIG.  31   , illustrating the first embodiment of the second aspect of an associated optical subsystem incorporating a plurality of lenses, absent the associated processor and controller elements; 
       FIG.  33    illustrates a plan view of the flat-panel two-dimensional image-display array of light-modulating image-display pixels of the fourth aspect of the near-eye display system illustrated in  FIGS.  31  and  32   ; 
       FIG.  34    illustrates a plan view of an aperture stop and the scanned beam of light redirected from the curved light-redirecting surface that respectively define an entrance pupil and a modulated subpupil of the fourth aspect of the near-eye display system illustrated in  FIGS.  31 ,  32  and  46   , with the scanned beam of light controlled so as to provide for the first aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being centered on the optical axis of the associated optical subsystem; 
       FIG.  35    illustrates a plan view of an exit pupil and associated exit subpupil associated with the aperture stop and the scanned beam of light redirected from the curved light-redirecting surface of the fourth aspect of the near-eye display system illustrated in  FIGS.  31 ,  32  and  46   , for the active subpupil region (ASR) illustrated in  FIG.  34   ; 
       FIG.  36    illustrates a plan view of an aperture stop and the scanned beam of light redirected from the curved light-redirecting surface that respectively define an entrance pupil and a modulated subpupil of the fourth aspect of the near-eye display system illustrated in  FIGS.  31 ,  32  and  46   , with the scanned beam of light controlled so as to provide for the first aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being rotated upwards and to the left relative to the optical axis of the associated optical subsystem; 
       FIG.  37    illustrates a plan view of an exit pupil and associated exit subpupil associated with the aperture stop and the scanned beam of light redirected from the curved light-redirecting surface of the fourth aspect of the near-eye display system illustrated in  FIGS.  31 ,  32  and  46   , for the active subpupil region (ASR) illustrated in  FIG.  36   ; 
       FIG.  38    illustrates a plan view of an aperture stop and the scanned beam of light redirected from the curved light-redirecting surface that respectively define an entrance pupil and a modulated subpupil of the fourth aspect of the near-eye display system illustrated in  FIGS.  31 ,  32  and  46   , with the scanned beam of light controlled so as to provide for a second aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being rotated upwards and to the left relative to the optical axis of the associated optical subsystem; 
       FIG.  39    illustrates a plan view of an exit pupil and associated exit subpupil associated with the aperture stop and the scanned beam of light redirected from the curved light-redirecting surface of the fourth aspect of the near-eye display system illustrated in  FIGS.  31 ,  32  and  46   , for the active subpupil region (ASR) illustrated in  FIG.  38   ; 
       FIG.  40    illustrates a plan view of an aperture stop and the scanned beam of light redirected from the curved light-redirecting surface that respectively define an entrance pupil and a modulated subpupil of the fourth aspect of the near-eye display system illustrated in  FIGS.  31 ,  32  and  46   , with the scanned beam of light controlled so as to provide for a third aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being centered on the optical axis of the associated optical subsystem; 
       FIG.  41    illustrates a plan view of an exit pupil and associated exit subpupil associated with the aperture stop and the scanned beam of light redirected from the curved light-redirecting surface of the fourth aspect of the near-eye display system illustrated in  FIGS.  31 ,  32  and  46   , for the active subpupil region (ASR) illustrated in  FIG.  40   ; 
       FIG.  42    illustrates a plan view of an aperture stop and the scanned beam of light redirected from the curved light-redirecting surface that respectively define an entrance pupil and a modulated subpupil of the fourth aspect of the near-eye display system illustrated in  FIGS.  31 ,  32  and  46   , with the scanned beam of light controlled so as to provide for the third aspect of an associated active subpupil region (ASR) in cooperation with an eye pupil of the user being rotated upwards and to the left relative to the optical axis of the associated optical subsystem; 
       FIG.  43    illustrates a plan view of an exit pupil and associated exit subpupil associated with the aperture stop and the scanned beam of light redirected from the curved light-redirecting surface of the fourth aspect of the near-eye display system illustrated in  FIGS.  31 ,  32  and  46   , for the active subpupil region (ASR) illustrated in  FIG.  42   ; 
       FIG.  44    illustrates a schematic block diagram of a second embodiment of the second aspect of the near-eye display system incorporating a flat-panel two-dimensional array of light sources that define an associated array of modulated subpupils of the second-aspect near-eye display system, in cooperation with a separate flat-panel two-dimensional image-display array of light-modulating image-display pixels, further illustrating a second embodiment of the second aspect of an associated optical subsystem incorporating a free-form-surface/prism lens; 
       FIG.  45    illustrates a schematic block diagram of a second embodiment of the third aspect of a near-eye display system incorporating a curved two-dimensional light array of light sources that define an associated array of modulated subpupils of the third-aspect near-eye display system, in cooperation with a separate flat-panel array of light-modulating image-display pixels, further illustrating the second embodiment of the second aspect of an associated optical subsystem incorporating a free-form-surface/prism lens; 
       FIG.  46    illustrates a schematic block diagram of a second embodiment of the fourth aspect of a near-eye display system incorporating a scanned beam of light in cooperation with a curved light-redirecting surface that together define an associated modulated subpupil of the fourth-aspect near-eye display system, in cooperation with a separate flat-panel array of light-modulating image-display pixels, further illustrating the second embodiment of the second aspect of an associated optical subsystem incorporating a free-form-surface/prism lens; 
       FIG.  47    illustrates a schematic block diagram of a third embodiment of the third aspect of a near-eye display system incorporating a curved two-dimensional light array of light sources that define an associated array of modulated subpupils of the third-aspect near-eye display system, in cooperation with a separate flat-panel array of light-modulating image-display pixels further illustrating an embodiment of a third aspect of an associated optical subsystem incorporating an associated conditioner lens and an associated first embodiment of a magnifier lens, each of which incorporate at least one Fresnel surface. 
       FIG.  48    illustrates a portion of a hypothetical embodiment of a second-aspect near-eye display system, including the associated exit pupil, a Fresnel-surface magnifier lens and the associated flat-panel two-dimensional image-display modulation array, together with a ray-trace simulation of light propagating from the flat-panel two-dimensional image-display modulation array through the magnifier lens to form a virtual image associated with the light entering the exit pupil during the process illustrated in  FIG.  49    for determining a prescription of the associated magnifier lens; 
       FIG.  49    illustrates an embodiment of a process for determining the prescription of a magnifier lens of a near-eye display system; 
       FIG.  50    illustrates an embodiment of a process for determining a prescription of a conditioner lens of a near-eye display system; 
       FIG.  51    illustrates an embodiment of a hybrid magnifier lens of a near-eye display system; 
       FIG.  52    illustrates a schematic block diagram of a waveguide projector light source; 
       FIG.  53    illustrates a model of the waveguide projector illustrated in  FIG.  52   , incorporating a planar light source array in cooperation with a condenser lens, further illustrating the propagation of light rays from the planar light source array to and through the condenser lens; 
       FIG.  54    illustrates a schematic block diagram of a first embodiment of a fifth aspect of a near-eye display system incorporating a waveguide projector light source that defines an array of modulated subpupils thereof, in cooperation with a separate flat-panel array of light-modulating image-display pixels, further illustrating a third aspect of an associated optical subsystem incorporating the optics of the waveguide projector in cooperation with an associated conditioner lens and a magnifier lens, the conditioner and magnifier lenses of which incorporate at least one Fresnel surface, further illustrating an incorporation of the hybrid magnifier lens illustrated in  FIG.  51   ; 
       FIG.  55    illustrates a schematic block diagram of the first embodiment of a fifth aspect of a near-eye display system as illustrated in  FIG.  54   , but with the associated waveguide projector replaced with the model thereof illustrated in  FIG.  53   ; 
       FIG.  56    illustrates a schematic block diagram of a second embodiment of a fifth aspect of a near-eye display system incorporating a waveguide projector light source that defines an array of modulated subpupils thereof, as illustrated in  FIG.  54   , but further incorporating a varifocal lens between the associated waveguide projector and the associated conditioner lens, further illustrating a fourth aspect of an associated optical subsystem incorporating the optics of the waveguide projector and the varifocal lens in cooperation with an associated conditioner lens and a magnifier lens, the conditioner and magnifier lenses of which incorporate at least one Fresnel surface; 
       FIG.  57    illustrates a third embodiment of a fifth aspect of a near-eye display system incorporating a waveguide projector light source that defines an array of modulated subpupils thereof, similar to that illustrated in  FIGS.  54  and  56   , incorporating a fifth aspect of an optical subsystem comprising a modified second-aspect optical subsystem for which the combination of the controllable light source and the conditioner lens thereof is replaced with a waveguide projector, further illustrating an optional varifocal lens of an associated sixth aspect of an optical subsystem; 
       FIG.  58    illustrates a general, fourth embodiment of a fifth aspect of a near-eye display system incorporating a waveguide projector light source that defines an array of modulated subpupils thereof, similar to that illustrated in  FIGS.  54 ,  56  and  57   , incorporating a seventh aspect of an optical subsystem comprising a modified second-aspect optical subsystem for which the combination of the controllable light source and conditioner lens thereof is replaced with a waveguide projector, further illustrating the incorporation of one or both of an optional conditioner lens and an optional varifocal lens; 
       FIG.  59   a    illustrates an example of a hypothetical intensity profile of an active modulated subpupil illustrated in any of  FIGS.  4 ,  6 ,  10 ,  12 ,  14 ,  21 ,  23 ,  25 ,  27 ,  29 ,  34 ,  36 ,  38 ,  40   , and  42  in respect of any of the first-through fifth-aspect near-eye display systems incorporating idealized components operating under an idealized mode of operation; 
       FIG.  59   b    illustrates an example of a hypothetical intensity profile of an active subpupil in an exit pupil image illustrated in in any of  FIGS.  5 ,  7 ,  11 ,  13 ,  15 ,  22 ,  24 ,  26 ,  28 ,  30 ,  35 ,  37 ,  39 ,  41 , and  43    in respect of any of the first-through fifth-aspect near-eye display systems incorporating idealized components operating under an idealized mode of operation; 
       FIG.  59   c    illustrates an example of a hypothetical intensity profile of an active subpupil in an exit pupil image illustrated in  FIG.  60    in respect of any of the first-through fifth-aspect near-eye display systems incorporating realistic components subject to realistic constraints and operating under a more realistic configuration and mode of operation relative to the configuration associated with  FIG.  59     b;    
       FIG.  60    illustrates a plan view of an exit pupil and associated active exit subpupils associated with the aperture stop and the two-dimensional modulation array of any of the first-, second-, third-, or fifth-aspect near-eye display systems illustrated in  FIGS.  1 ,  2 ,  16 ,  17 ,  18 ,  19 ,  44 ,  45 ,  47 , and  54  through  58   , for the active subpupil region (ASR) illustrated in either of  FIGS.  4  and  21   ; 
       FIG.  61    illustrates a first aspect of a process for controlling a subpupil modulator, which provides for activating a single subpupil located closest to a central location an eye pupil of an eye being illuminated by a near-eye display system; 
       FIG.  62    illustrates a process for mapping locations, lateral extents and intensity profiles of each of a plurality of subpupils for use by one or more processes to control a subpupil modulator; 
       FIG.  63    illustrates a second aspect of a process for controlling a subpupil modulator that provides for deactivating subpupils for which a substantial portion thereof is located outside of an eye pupil of an eye being illuminated by a near-eye display system; 
       FIG.  64    illustrates a hypothetical intensity profile of a plurality of the subpupils illustrated in  FIG.  60   , responsive to control in accordance the second aspect of the process for controlling the subpupil modulator; 
       FIG.  65    illustrates a hypothetical intensity profile of a plurality of the subpupils illustrated in  FIG.  60   , responsive to control in accordance the third aspect of the process for controlling the subpupil modulator; 
       FIG.  66    illustrates a third aspect of a process for controlling a subpupil modulator that provides for deactivating subpupils that are not proximate to a location of an eye pupil of an eye being illuminated by a near-eye display system, and for controlling an intensity of remaining subpupils responsive to a location and extent of the eye pupil; 
       FIG.  67    illustrates a fourth aspect of a process for controlling a subpupil modulator that provides for controlling the intensities of light through each of a plurality of subpupils responsive to a predetermined stored lookup table of subpupil intensity as a function of the location of the subpupil, and as a function of the location and extent of an eye pupil of an eye being illuminated by a near-eye display system; 
       FIG.  68    illustrates a side view of a sixth aspect of a near-eye display system incorporating a catadioptric magnifier, showing optical ray traces from three regions of an associated light-generating subpupil modulator associated with the central and lateral extreme portions of the subpupil modulator; 
       FIG.  69    illustrates a side view of a sixth aspect of the near-eye display system illustrated in  FIG.  68   , but showing optical ray traces from only two regions of the associated light-generating subpupil modulator associated with the central and one of the lateral extreme portions of the subpupil modulator; and 
       FIG.  70    illustrates a typical luminous intensity distribution of a light-emitting diode. 
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS.  1 - 58   , a near-eye display system  10  incorporates an image generator  12  that, in cooperation with an associated optical subsystem  14 , provides for projecting light  16 ′ of an image  16  generated by the image generator  12  onto an exit pupil  18  of the optical subsystem  14 , into the eye  20  of a user  22 , and as a real image  16 ″ onto the retina  24  of the eye  20  for viewing by the user  22 , wherein the exit pupil  18  of the optical subsystem  14  is located proximate to the front surface  20 ′ of the eye  20 , the real image  16 ″ is associated with a magnified, apparently distant virtual image  16 ′″ of a two-dimensional array  26  of the image generator  12  that is the object of the image  16 , and the exit pupil  18  comprises an image of an aperture stop  28  within, or associated with, the optical subsystem  14 , wherein the aperture stop  28  acts as an associated entrance pupil  28 ′ and provides for constraining the lateral extent of the associated field of light  16 ′ therewithin. The real image  16 ″ is projected onto the onto the retina  24  of the eye  20  without vignetting by the optical subsystem  14 , independent of the rotation of the user&#39;s eye  20  as a result of that rotation providing for directing the center of the fovea of the eye  20  to any location on the real image  16 ″. 
     The near-eye display system  10  further incorporates a subpupil modulator  30  that is imaged by the optical subsystem  14  as an associated exit-pupil image  18 ′ within the surface  18 ″ of the exit pupil  18 . The subpupil modulator  30  provides defining one or more exit subpupils  32  within the exit pupil  18 , and provides for individually controlling the transmission of light  16 ′ through each of the one or more exit subpupils  32  and onto, or into, the eye  20 . Each of the exit subpupils  32  is associated with light  16 ′ of the image  16  propagating along a corresponding particular direction  34  at an associated angle relative to the optical axis  36  of the associated optical subsystem  14 , but otherwise contains light  16 ′ from each and every point of the image  16  from which light  16 ′ emanates at that associated angle. For example, light  16 . 1 ′ (also designated by “A” in  FIG.  1   ) associated with a first gaze direction  34 . 1 —that is generally along the optical axis  36  of the associated optical subsystem  14 —is imaged through a corresponding first exit subpupil  32 . 1  that is also along the optical axis  36 . Furthermore, light  16 . 2 ′ (also designated by “B” in  FIG.  1   ) associated with a second gaze direction  34 . 2 —that has a first angular offset from the optical axis  36 —is imaged through a corresponding second exit subpupil  32 . 2  that has a corresponding first lateral offset from the optical axis  36 . Yet further, light  16 . 3 ′ (also designated by “C” in  FIG.  1   ) associated with a third gaze direction  34 . 3 —that has a second angular offset from the optical axis  36 —is imaged through a corresponding third exit subpupil  32 . 3  that has a corresponding second lateral offset from the optical axis  36 . 
     The light  16 ′ of the image  16  is received by the eye  20  through an eye pupil  38  thereof, the opening of which is controlled by the iris  40 , and the angular orientation of which, along with that of the eye  20 , is responsive to the gaze direction  34  of the user  22 . Although the transverse extent of the exit pupil  18  is sufficiently large to provide for light  16 ′ of the image  16  to be viewed over a range of gaze directions  34 ,  34 . 1 ,  34 . 2 ,  34 . 3 , for a particular gaze directions  34 ,  34 . 1 ,  34 . 2 ,  34 . 3 , only that portion of the light  16 ′ that is within the boundary of the edge of the eye pupil  38  will reach the retina  24  to be perceived as the image  16  by the user  22 . The projected transverse location and projected shape of the eye pupil  38  is responsive to the associated gaze direction  34 ,  34 . 1 ,  34 . 2 ,  34 . 3  of that eye  20 , ranging from a circular shape with no transverse offset relative to the optical axis  36  associated with the first gaze direction  34 . 1  when gazing along the optical axis  36 , to an elliptical shape with an associated transverse offset relative to the optical axis  36  associated with other gaze directions  34 ,  34 . 2 ,  34 . 3 . Light  16 ′ that is outside the edge of the eye pupil  38  will be backscattered by the surrounding tissue of the eye  20  or face of the user  22 , thereby increasing ambient light which may reflect or scatter from components of the display system into the eye  20  that can otherwise degrade the quality of the image  16  being intentionally viewed by the user  22 . Accordingly, the near-eye display system  10  incorporates an eye-tracking subsystem  42  comprising an infrared illuminator  44  and an associated infrared-responsive camera  46  in cooperation with an associated eye-tracking processor  48  that provides for tracking at least the lateral location of the eye pupil  38  responsive to an image of the infrared light from the infrared illuminator  44  that is scattered by the iris  40  and received by the associated infrared-responsive camera  46 , and processed by the eye-tracking processor  48  to identify the edge of the eye pupil  38  and estimate the transverse location and transverse extent thereof, which is then communicated to a subpupil modulation controller  50  that generates an associated subpupil modulation control signal  51  that provides for controlling the activation of the associated modulated subpupils  32 ′ of the associated subpupil modulator  30  so as to activate one or more modulated subpupils  32 ′ that provide for light  16 ′ of the image  16  to be received by the retina  24  of the eye  20  of the user  22 , and so as to provide for deactivating the remaining portion of the exit pupil  18  so as to prevent propagation of light  16 ′ therethrough, and thereby limit otherwise associated backscattering of light  16 ′ off the eye  20  or face of the user  22 . 
     For example, in one set of embodiments, the eye-tracking subsystem  42  in configured in accordance with one or more of the following Internet websites from the group consisting of https://pupil-labs.com/products/core/; https://www.tobiipro.com/product-listing/hardware/; https://imotions.com/biosensor/eye-tracking-vr/; https://www.ergoneers.com/en/hardware/eye-tracking/; https://www.adhawkmicrosystems.com/eye-tracking/; and https://www.eye-square.com/en/headmounted-eye-tracking/. In one set of embodiments, for which the near-eye display system  10  provides for displaying an image  16  to each eye  20  of the user  22 , a single eye-tracking subsystem  42  may be incorporated into the near-eye display system  10  to provide for tracking for one of the eyes  20  of the user  22 , with the resulting tracking information provided to the subpupil modulation controller  50  for the other eye  20 , based upon the assumption that the eye pupils  38  of both eyes  20  generally track to the same location in the image  16 . 
     Referring to  FIGS.  1 - 15   , and to  FIG.  3    in particular, in accordance with a first aspect  10 . 1  of a near-eye display system  10 ,  10 . 1 , an associated first aspect image generator  12 ,  12 . 1  comprises a flat-panel two-dimensional image-display array  52  of light-emitting image-display pixels  54 , each of which generates and emits, or transmits, —over a range of directions—the light  16 ′ of the image  16  from a corresponding point thereof. The light-emitting image-display pixels  54  can be embodied in various ways, for example, in one set of embodiments, as light-emitting-diode (LED) elements, and in another set of embodiments, as backlit liquid-crystal-display (LCD) elements. Referring to  FIGS.  1 ,  2 ,  8  and  9   , an associated first-aspect optical subsystem  14 ,  14 . 1  of the first-aspect near-eye display system  10 ,  10 . 1  comprises a plurality of—for example, three—dioptric-power optical elements  56 ,  56 . 1 ,  56 . 2 ,  56 . 3 , for example, respective first  56 . 1 ′, L 1 , second  56 . 2 ′, L 2 , and third  56 . 1 ′, L 3  convergent magnifier lenses, located along the associated optical axis  36 . 
     The first dioptric-power optical element  56 ,  56 . 1 ,  56 . 1 ′, L 1  is located between the flat-panel two-dimensional image-display array  52  and an associated flat-panel two-dimensional modulation array  58  of an associated first-aspect subpupil modulator  30 ,  30 . 1  of the first-aspect near-eye display system  10 ,  10 . 1 , with the first dioptric-power optical element  56 ,  56 . 1 ,  56 . 1 ′, L 1  separated by one focal length f 1  from each of a first side  58 . 1  of the flat-panel two-dimensional modulation array  58  and the subpupil modulator  30 ,  30 . 1 , so that light  16 ′ emitted from each light-emitting image-display pixel  54  of the flat-panel two-dimensional image-display array  52  at a particular angle is focused onto a corresponding particular transverse location on the flat-panel two-dimensional modulation array  58 . The flat-panel two-dimensional modulation array  58  is located at or near the location of the aperture stop  28 , wherein light  16 ′ from each of the light-emitting image-display pixels  54  passes through the entirety of the aperture stop  28 , or in other words, each location within the aperture stop  28  receives a component of light  16 ′ from each and every light-emitting image-display pixel  54  of the flat-panel two-dimensional image-display array  52 , i.e. each point on the associated image  16  that is generated by the image generator  12 ,  12 . 1 . 
     The flat-panel two-dimensional modulation array  58  incorporates a plurality of light-modulating pixels  60 , for example, an array of liquid crystal pixels  60 ′, wherein the intensity modulation of each light-modulating pixel  60  is independently controlled by the subpupil modulation controller  50  responsive to a measure by the eye-tracking subsystem  42  of the location of the eye pupil  38  relative to the exit pupil  18 . For example, in one set of embodiments, the light-modulating pixels  60  are controlled to one of two states, an ON state that provides for enabling, and an OFF state that provide for blocking, the transmission of light  16 ′ therethrough. 
     The second  56 ,  56 . 2 ,  56 . 2 ′, L 2  and third  56 ,  56 . 3 ,  56 . 3 ′, L 3  dioptric-power optical elements—for example, corresponding second  56 . 2 ′, L 2  and third  56 . 3 ′, L 3  convergent magnifier lenses—of the optical subsystem  14 ,  14 . 1  are located between a second side  58 . 2  of the flat-panel two-dimensional modulation array  58  and the exit pupil  18  of the optical subsystem  14 ,  14 . 1 , and together provide for forming an image at the exit pupil  18  of both the subpupil modulator  30 ,  30 . 1 /flat-panel two-dimensional modulation array  58  and the associated aperture stop  28 . For example, referring to  FIG.  2   , in accordance with one set of embodiments, a second convergent magnifier lens  56 . 2 ′, L 2  located one focal length f 2  from the subpupil modulator  30 ,  30 . 1 /flat-panel two-dimensional modulation array  58  provides for transforming light  16 ′ emanating from each location on the subpupil modulator  30 ,  30 . 1 /flat-panel two-dimensional modulation array  58  to a corresponding beam  64  of light  16 ′ propagating at a corresponding angle relative to the optical axis  36 ; and a third convergent magnifier lens  56 . 3 ′, L 3  located between the exit pupil  18  and the rear focal plane  62  of the second convergent magnifier lens  56 . 2 ′, L 2 , one focal length f 3  from each, provides for transforming each beam  64  of light  16 ′ from second convergent magnifier lens  56 . 2 ′, L 2  propagating at a particular angle relative to the optical axis  36  to a corresponding spot within the exit pupil  18 . Furthermore, the first  56 . 1 ′, L 1 , second  56 . 2 ′, L 2 , and third  56 . 1 ′, L 3  convergent magnifier lenses, in combination with the lens  66  of the eye  20 , provide for forming the real image  16 ″ of the image generator  12 ,  12 . 1 /flat-panel two-dimensional modulation array  58  on the retina  24  of the eye  20 , wherein the third convergent magnifier lens  56 . 3 ′, L 3  provides for adjusting the focus and for adjusting the apparent distance of the virtual image  16 ′″ associated with the real image  16 ″ that is formed on the retina  24  of the eye  20 . 
     For example, light  16 . 1 ′ from each of the light-emitting image-display pixels  54  of the flat-panel two-dimensional image-display array  52  emitted in a direction that is substantially parallel with the optical axis  36  of the optical subsystem  14 ,  14 . 1 , i.e. associated with the first gaze direction  34 . 1 , is focused by the first dioptric-power optical element  56 ,  56 . 1 ,  56 . 1 ′, L 1  onto a first set of light-modulating pixels  60 . 1  of the subpupil modulator  30 ,  30 . 1  at a central location thereof associated with a first modulated subpupil  32 . 1 ′, wherein the control state (i.e. ON or OFF) of the first set of light-modulating pixels  60 . 1  controls whether or not that light  16 . 1 ′ can propagate therethrough to become transformed to a first beam  64 . 1  of light  16 . 1 ′ (also designated by “A” in  FIG.  1   ) by the second dioptric-power optical element  56 ,  56 . 2 ,  56 . 2 ′, L 2 , and then be focused by the third dioptric-power optical element  56 ,  56 . 3 ,  56 . 3 ′, L 3  to form the corresponding first exit subpupil  32 . 1  at a corresponding first location  68 . 1  at the exit pupil  18 , wherein the control state of the first set of light-modulating pixels  60 . 1  is controlled by the subpupil modulation controller  50  responsive to whether the location of the eye pupil  38 —as determined by the eye-tracking subsystem  42 —is either aligned with, or sufficiently close to, infra, the first exit subpupil  32 . 1 . 
     Furthermore, light  16 . 2 ′ from each of the light-emitting image-display pixels  54  of the flat-panel two-dimensional image-display array  52  emitted in a direction associated with the second gaze direction  34 . 2 , is focused by the first dioptric-power optical element  56 ,  56 . 1 ,  56 . 1 ′, L 1  onto a second set of light-modulating pixels  60 . 2  of the subpupil modulator  30 ,  30 . 1  at a first relatively offset location thereof associated with a second modulated subpupil  32 . 2 ′, wherein the control state (i.e. ON or OFF) of the second set of light-modulating pixels  60 . 2  controls whether or not that light  16 . 2 ′ can propagate therethrough to become transformed to a second beam  64 . 2  of light  16 . 2 ′ (also designated by “B” in  FIG.  1   ) by the second dioptric-power optical element  56 ,  56 . 2 ,  56 . 2 ′, L 2 , and then be focused by the third dioptric-power optical element  56 ,  56 . 3 ,  56 . 3 ′, L 3  to form the corresponding second exit subpupil  32 . 2  at a corresponding second location  68 . 2  at the exit pupil  18 , wherein the control state of the second set of light-modulating pixels  60 . 2  is controlled by the subpupil modulation controller  50  responsive to whether the location of the eye pupil  38 —as determined by the eye-tracking subsystem  42 —is either aligned with, or sufficiently close to, infra, the second exit subpupil  32 . 2 . 
     Yet further, light  16 . 3 ′ from each of the light-emitting image-display pixels  54  of the flat-panel two-dimensional image-display array  52  emitted in a direction associated with the third gaze direction  34 . 3 , is focused by the first dioptric-power optical element  56 ,  56 . 1 ,  56 . 1 ′, L 1  onto a third set of light-modulating pixels  60 . 3  of the subpupil modulator  30 ,  30 . 1  at a second relatively offset location thereof associated with a third modulated subpupil  32 . 3 ′, wherein the control state (i.e. ON or OFF) of the third set of light-modulating pixels  60 . 3  controls whether or not that light  16 . 3 ′ can propagate therethrough to become transformed to a third beam  64 . 3  of light  16 . 2 ′ (also designated by “C” in  FIG.  1   ) by the second dioptric-power optical element  56 ,  56 . 2 ,  56 . 2 ′, L 2 , and then be focused by the third dioptric-power optical element  56 ,  56 . 3 ,  56 . 3 ′, L 3  to form the corresponding third exit subpupil  32 . 3  at a corresponding third location  68 . 3  at the exit pupil  18 , wherein the control state of the third set of light-modulating pixels  60 . 3  is controlled by the subpupil modulation controller  50  responsive to whether the location of the eye pupil  38 —as determined by the eye-tracking subsystem  42 —is either aligned with, or sufficiently close to, infra, the third exit subpupil  32 . 3 . 
     Referring to  FIGS.  4 - 7  and  11 - 14   , the subpupil modulator  30 ,  30 . 1  is controlled by the subpupil modulation controller  50  in accordance with a subpupil modulation scheme  70  that provides for identifying an Active Subpupil Region (ASR)  72  of the subpupil modulator  30 ,  30 . 1  responsive to the location, size, and possibly the shape, of the eye pupil  38  as determined by the eye-tracking subsystem  42 , and responsive thereto, that generates a subpupil modulation control signal  51  that provides for activating a subset of modulated subpupils  32 ′ within the Active Subpupil Region (ASR)  72  (i.e. by controlling to an ON state), and that provides for deactivating the remainder of the modulated subpupils  32 ′ of the subpupil modulator  30 ,  30 . 1  (i.e. by controlling to an OFF state), so as to provide for blocking light  16 ′ of the image  16  that is outside the Active Subpupil Region (ASR)  72  from reaching the eye  20 . 
     Referring to  FIGS.  4 - 7   , in accordance with a first aspect  70 . 1  of a subpupil modulation scheme  70 ,  70 . 1 , the Active Subpupil Region (ASR)  72  is set to a fixed size and shape that is sufficiently large to surround the eye pupil  38  regardless of the orientation of the eye  20 , and regardless of the associated state of the iris  40 , with accommodation for the largest anticipated lateral extent of the eye pupil  38  and accommodation of possible error in the determination of the location, size and/or shape of the eye pupil  38  by the eye-tracking subsystem  42 , so as to mitigate against a potential uneven vignetting by an edge of the eye pupil  38  that might otherwise result if the edge of the eye pupil  38  were to not be fully illuminated by an associated exit subpupil  32 , for example, as might otherwise result from a misalignment between the eye pupil  38  and the Active Subpupil Region (ASR)  72  that could otherwise cause a spatial transition of the edge of the eye pupil  38  from an active subpupil  32  inside the Active Subpupil Region (ASR)  72  to an inactive subpupil  32  outside the Active Subpupil Region (ASR)  72  for example, as a result of relative motion between the eye pupil  38  and the Active Subpupil Region (ASR)  72 . The location of the Active Subpupil Region (ASR)  72  is continuously updated responsive to the eye-tracking subsystem  42 , at a rate of update sufficient to accommodate rotations of the eye  20  by the user  22  so that the exit subpupils  32  surrounding and within the eye pupil  38  are maintained in an active state. Referring to  FIGS.  4  and  5   , for the eye  22  of the user  22  rotated for viewing in the first gaze direction  34 . 1  as illustrated in  FIG.  5   , and as a result, a detection by the eye-tracking subsystem  42  of the eye pupil  38  being centered on the optical axis  36 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is concentric both with the eye pupil  38  and with the optical axis  36 , with a diameter sufficiently greater than that of the eye pupil  38  so that the eye pupil  38  will be fully illuminated by active exit subpupils  32 , wherein, as illustrated in  FIG.  4   , the light-modulating pixels  60  and associated modulated subpupils  32 ′ within the Active Subpupil Region (ASR)  72  are activated by the subpupil modulator  30 ,  30 . 1 , and the remaining modulated subpupils  32 ′ intersecting or outside of the boundary of the Active Subpupil Region (ASR)  72  are deactivated, resulting in the image  16  being presented to the eye  20  via only the activated exit subpupils  32  that are associated with the activated modulated subpupils  32 ′, as illustrated in  FIG.  5   . Referring to  FIGS.  6  and  7   , for the eye  22  of the user  22  rotated up and to the left as illustrated in  FIG.  7   , and as a result, a detection by the eye-tracking subsystem  42  of an elliptically-shaped eye pupil  38  located up and to the left of the associated optical axis  36 , in accordance with the first-aspect subpupil modulation scheme  70 ,  70 . 1 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is centered about the offset eye pupil  38 , but with the same diameter as illustrated in  FIGS.  4  and  5   , wherein, as illustrated in  FIG.  6   , the light-modulating pixels  60  and associated modulated subpupils  32 ′ within the Active Subpupil Region (ASR)  72  are activated by the subpupil modulator  30 ,  30 . 1 , and the remaining modulated subpupils  32 ′ intersecting or outside of the boundary of the Active Subpupil Region (ASR)  72  are deactivated, resulting in the image  16  being presented to the eye  20  via only the activated exit subpupils  32  that are associated with the activated modulated subpupils  32 ′ that are aligned with the eye pupil  38 , as illustrated in  FIG.  7   . Accordingly, notwithstanding the resulting mitigation against uneven vignetting by the eye pupil  38 , the first-aspect subpupil modulation scheme  70 ,  70 . 1  results in the illumination of a portion of the eye  20  surrounding the eye pupil  38  with extraneous light  16   iv  that is then reflected or scattered by the front surface  20 ′ of the eye  20  rather than being imaged onto the retina  24 . 
     With the first  56 . 1 ′, L 1 , second  56 . 2 ′, L 2 , and third  56 . 1 ′, L 3  convergent magnifier lenses positioned as illustrated in  FIG.  2   , a virtual image of the flat-panel two-dimensional image-display array  52  by the first convergent magnifier lens  56 . 1 ′, L 1  is located at infinity, which becomes the object of the second convergent magnifier lens  56 . 2 ′, L 2 , the image of which is then located at the rear focal plane  62  of the second convergent magnifier lens  56 . 2 ′, L 2 , which becomes the object of the third convergent magnifier lens  56 . 3 ′, L 3 , the virtual image  16 ′″ of which is then located at infinity, which is projected onto the retina  24  of the eye  20  for perception thereof by the user  22 . Referring to  FIG.  8   , the location of the third convergent magnifier lens  56 . 3 ′, L 3  can be adjusted to provide for an angularly-magnified virtual image  16 ′ located at a comfortable viewing distance. 
     During operation of the first-aspect near-eye display system  10 ,  10 . 1 , an electronic image signal  74  is output from an associated display controller  76  to the flat-panel two-dimensional image-display array  52  for generating the image  16  thereupon, the light  16 ′ therefrom of which illuminates, and, as described hereinabove, is subsequently processed by, the associated subpupil modulator  30 ,  30 . 1 , wherein the electronic image signal  74  is either based upon a signal  74 ′ received via an associated wireless communication link  78 , or is generated from a local image source  74 ″, for example, either from a stored memory or from a camera. 
     Referring to  FIG.  9   , the near-eye display system  10 ,  10 . 1  provides for a volumetric visual environment (VVE)  80  between the user  22  and the image generator  12  that is sufficiently large to enable the eye  20 , when positioned at a comfortable distance from the image generator  12 , to receive unvignetted light  16 ′ from the entirety of the associated virtual image  16 ′″ regardless of the gaze direction  34  of the eye  20  toward different points on that virtual image  16 ′″, so as to provide for a relatively large angular field of view provided by the virtual image  16 ′ of the image generator  12 , particularly in support of greater perceived immersion in that associated virtual environment. The full volumetric visual environment (VVE)  80 —also referred to as the “eye box”—can be adequately represented by a geometric surface construct  82  within that volumetric visual environment (VVE)  80  as a result of the distance from the eye  20  to the image generator  12  being relatively fixed when the near-eye display system  10 ,  10 . 1  is attached to the user  22 , wherein the exit subpupils  32 —located on an associated subpupil surface  84  within the exit pupil  18 —are located on, and constitute portions of, that geometric surface construct  82 , with each exit subpupil  32  being formed as a real image of a corresponding modulated subpupil  32 ′ formed by the subpupil modulator  30 ,  30 . 1 . 
     In view of the volumetric visual environment (VVE)  80  providing for unvignetted viewing of the entire virtual image  16 ′″, any location within the volumetric visual environment (VVE)  80 , including therefore any location on the associated subpupil surface  84  within or of the volumetric visual environment (VVE)  80 , and therefore any exit subpupil  32  itself, will pass rays of light  16 ′ from the entirety of the associated image  16  of the associated image generator  12 ,  12 . 1 . Accordingly, for each point on the image generator  12 , and for each exit pupil  18 , there is at least one optical ray that can be geometrically traced therebetween, and that would therefore also extend through each corresponding modulated subpupil  32 ′, because each exit subpupil  32  is an image of a corresponding modulated subpupil  32 ′. Accordingly, each light-modulating pixel  60  associated with a corresponding modulated subpupil  32 ′ represents a location in the optical subsystem  14 ,  14 . 1  for either receiving light  16 ′ from the entirety of the image generator  12  or from which light propagating in reverse would flood the entirety of the image generator  12 . 
     The unvignetted virtual image  16 ″′ visible through any particular exit subpupil  32  is referred to herein as a component image  86 , with all component images  86  perceived by the eye  20  at any given time—including those visually persisting—being referred to herein as the associated composite image  88 . For example, in the special case when the eye  20  receives light  16 ′ from only one exit subpupil  32 , the associated composite image  88  will be given by the component image  86  as seen through that exit subpupil  32 . 
     Each of the light-modulating pixels  60  of the flat-panel two-dimensional modulation array  58  is referred to herein generally as a modulation element  90 , which is located on an associated modulation surface  92 . Generally, the modulation of light  16 ′ through a given modulation element  90  refers to any means of partially or fully restricting the intensity of the component image  86  as perceived by the eye  20  through the exit subpupil  32  corresponding to that modulation element  90  such as, for example, modulation or redirection of light  16 ′ incident thereon, or, for example, in respect of the second through fourth aspects of the near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 3 , infra, modulation of light emanating from an associated modulation location. Any exit subpupil  32  for which the associated light throughput is most limited or restricted, i.e. for which the associated modulation element  90  is in an OFF state, is referred to herein as having been deactivated, to being in a state of deactivation, or to being deactivated, whereas any lesser restriction that provides for a subsequent increase in the intensity of the component image  86  through the associated exit subpupil  32  as perceived by the eye  20 , up to and including the minimum level of restriction possible, is referred to herein as an “activation” of that exit subpupil  32 , resulting in that exit subpupil  32  as having been activated, to being in a state of activation, or to being activated. 
     Whereas a real image  16 ″ of the image generator  12 ,  12 . 1  is formed on the retina  24  of the eye  20 , that real image  16 ″ is perceived as a magnified virtual image  16 ′″ generally appearing some comfortable distance from the user to minimize eye strain. As illustrated in  FIG.  8   , the optical rays passing through the volumetric visual environment (VVE)  80  toward the eye  20  can be geometrically traced backwards without regard to the optical subsystem  14 ,  14 . 1  to locate the apparent location of the virtual image  16 ′. 
     The volumetric visual environment (VVE)  80  is the entire volume for which light  16 ′ from the entire image  16  passes through at any location therewithin, with the exit pupil  18  of the optical subsystem  14 ,  14 . 1  being one possible associated aperture thereof, albeit the largest possible such aperture. Accordingly, if the eye pupil  38  is located anywhere within that volumetric visual environment (VVE)  80 , then the user  22  will be able to see the entire image  16 . The near-eye display system  10  has an exit pupil  18  which, by definition, represents an image of the aperture stop  28 , beyond which light is restricted. 
     Referring to  FIGS.  10  and  11   , in accordance with a second aspect  70 . 2  of a subpupil modulation scheme  70 ,  70 . 2 , the Active Subpupil Region (ASR)  72  is set to a variable size and shape that is adapted to be sufficiently large so as to surround the eye pupil  38  regardless of the orientation of the eye  20 , and regardless of the associated state of the iris  40 , which—the same as for the first-aspect subpupil modulation scheme  70 ,  70 . 1 , but accompanied by a lesser amount of extraneous light  16   iv —also provides for mitigating against a potential uneven vignetting by an edge of the eye pupil  38  that might otherwise result if the edge of the eye pupil  38  were to not be fully illuminated by an associated set of active exit subpupils  32 . The location, size and shape of the Active Subpupil Region (ASR)  72  is continuously updated responsive to the eye-tracking subsystem  42 , at a rate of update sufficient to accommodate rotations of the eye  20  by the user  22 , so that the exit subpupils  32  within and surrounding the eye pupil  38  are maintained in an active state. Similar to that illustrated in  FIGS.  4  and  5   , if the eye  22  of the user  22  is rotated for viewing in the first gaze direction  34 . 1  as illustrated in  FIG.  5   , the resulting associated Active Subpupil Region (ASR)  72  as determined by the subpupil modulation controller  50  is also concentric both with the eye pupil  38  and with the optical axis  36 , but with a relatively smaller diameter—relative to that associated with the first-aspect subpupil modulation scheme  70 ,  70 . 1 —that is sufficiently large to account for possible error in the determination of the location, size and/or shape of the eye pupil  38  by the eye-tracking subsystem  42 . Referring again to  FIGS.  10  and  11   , for the eye  22  of the user  22  rotated up and to the left as illustrated in  FIG.  11   , and as a result, a detection by the eye-tracking subsystem  42  of an elliptically-shaped eye pupil  38  located up and to the left of the associated optical axis  36 , in accordance with the second-aspect subpupil modulation scheme  70 ,  70 . 2 , the associated Active Subpupil Region (ASR)  72  as determined by the subpupil modulation controller  50  is centered about the offset eye pupil  38 , but elliptically shaped, similar that of the eye pupil  38 , wherein, as illustrated in  FIG.  10   , the light-modulating pixels  60  and associated modulated subpupils  32 ′ within the Active Subpupil Region (ASR)  72  are activated by the subpupil modulator  30 ,  30 . 1 , and the remaining modulated subpupils  32 ′ intersecting or outside of the boundary of the Active Subpupil Region (ASR)  72  are deactivated, resulting in the image  16  being presented to the eye  20  via only the activated exit subpupils  32  that are associated with the activated modulated subpupils  32 ′ that are aligned with the eye pupil  38  of the near-eye display system  10  and within the Active Subpupil Region (ASR)  72 , as illustrated in  FIG.  11   . Accordingly, as a result of the Active Subpupil Region (ASR)  72  being dynamically sized and shaped responsive to the size and shape of the eye pupil  38  as determined by the eye-tracking subsystem  42 , the size and shape of the Active Subpupil Region (ASR)  72  can more closely match that of the eye pupil  38  while still mitigating against uneven vignetting by the edge of the eye pupil  38 , which—in comparison with the first-aspect subpupil modulation scheme  70 ,  70 . 1 —results in a relatively lesser amount of illumination of the portion of the eye  20  surrounding the eye pupil  38 , and a corresponding relatively lesser amount of extraneous light  16   iv  that is then reflected or scattered by the front surface  20 ′ of the eye  20  rather than being imaged onto the retina  24 . 
     In accordance with a third aspect  70 . 3  of a subpupil modulation scheme  70 ,  70 . 3 , rather than making the Active Subpupil Region (ASR)  72  so large as to avoid a spatial transition of the edge of the eye pupil  38  from an active to an inactive exit subpupil  32 , instead the Active Subpupil Region (ASR)  72  is constrained to a size that is smaller than that of the eye pupil  38 , and aligned with the center of the eye pupil  38  so as to prevent vignetting that could otherwise result with the presence of such a spatial transition. Accordingly, the third-aspect subpupil modulation scheme  70 ,  70 . 3  substantially eliminates an illumination of the portion of the eye  20  surrounding the eye pupil  38  with extraneous light  16   iv  that would otherwise be reflected or scattered by the front surface  20 ′ of the eye  20  rather than being imaged onto the retina  24 . Furthermore, a relatively smaller Active Subpupil Region (ASR)  72  provides for improving the perceived quality of the image  16  by decreasing the effective aperture size through which the light  16 ′ passes into the eye  20 , thereby decreasing the impact of aperture-size-related optical aberrations, which increases the clarity of the image  16 , which is particularly effective in a near-eye display system  10 ,  10 . 1  that provides for a large field-of-view together with relatively high magnification. Taken to the extreme—and similar to a pinhole camera—the smallest Active Subpupil Region (ASR)  72  would comprise a single exit subpupil  32  corresponding to a corresponding single modulation element  90  that is continuously identified to best align with the center of the eye pupil  38 . 
     For example, referring to  FIGS.  12  through  15   , based upon an estimate from the eye-tracking subsystem  42  of the location of the center of the eye pupil  38 , the subpupil modulation controller  50  identifies and activates the modulated subpupil  32 ′—i.e. the associated light-modulating pixel  60 —of an associated Active Subpupil Region (ASR)  72 , associated with the exit subpupil  32  that is most-closely aligned with the eye pupil  38 , and deactivates the remaining modulated subpupils  32 ′/light-modulating pixels  60  of the subpupil modulator  30 ,  30 . 1 /flat-panel two-dimensional modulation array  58 . The location of the Active Subpupil Region (ASR)  72  is continuously updated responsive to the eye-tracking subsystem  42 , at a rate of update sufficient to accommodate rotations of the eye  20  by the user  22  so that only the one or more exit subpupils  32  having corresponding one or more projected transverse locations within transverse projection of the eye pupil  38  are maintained in an active state. Referring to  FIGS.  12  and  13   , for the eye  22  of the user  22  rotated for viewing in the first gaze direction  34 . 1  as illustrated in  FIG.  13   , and as a result, a detection by the eye-tracking subsystem  42  of the eye pupil  38  being centered on the optical axis  36 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is concentric both with the eye pupil  38  and with the optical axis  36 , and, in one set of embodiments, limited in size so as to encompass a corresponding single exit subpupil  32 , wherein, as illustrated in  FIG.  12   , the light-modulating pixel  60  and associated modulated subpupil  32 ′ within the Active Subpupil Region (ASR)  72  is activated by the subpupil modulator  30 ,  30 . 1 , and the remaining modulated subpupils  32 ′ outside the boundary of the Active Subpupil Region (ASR)  72  are deactivated, resulting in the image  16  being presented to the eye  20  via only the activated exit subpupil  32  associated with the activated modulated subpupil  32 ′, as illustrated in  FIG.  13   . Referring to  FIGS.  14  and  15   , for the eye  22  of the user  22  rotated up and to the left as illustrated in  FIG.  15   , and as a result, a detection by the eye-tracking subsystem  42  of an elliptically-shaped eye pupil  38  located up and to the left of the associated optical axis  36 , in accordance with the third-aspect subpupil modulation scheme  70 ,  70 . 3 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is located—for example, centered—within the offset eye pupil  38 , wherein, as illustrated in  FIG.  14   , the light-modulating pixel  60  and associated modulated subpupil  32 ′ within the Active Subpupil Region (ASR)  72  is activated by the subpupil modulator  30 ,  30 . 1 , and the remaining modulated subpupils  32 ′ outside the boundary of the Active Subpupil Region (ASR)  72  are deactivated, resulting in the image  16  being presented to the eye  20  via only the activated exit subpupil  32  associated with the activated modulated subpupil  32 ′, as illustrated in  FIG.  15   . 
     A number of practical considerations may impose a lower limit to the size of the Active Subpupil Region (ASR)  72  used in the third-aspect subpupil modulation scheme  70 ,  70 . 3 . First, if the associated modulation surface  92  incorporates an array of relatively-small modulation elements  90 , then there can be an increased complexity in the electronic manufacturing and addressing of the correspondingly large number of such elements corresponding to the exit subpupils  32  of the entire subpupil surface  84 . Second, a relatively smaller modulation element  90  such as a light-modulating pixel  60 —or a light-source element, infra, —contained in array may be interleaved with relatively large gaps therebetween that provide for supporting electronic components and circuitry through which no light is generated or passes, leading to discontinuities in the associated subpupil surface  84  that is otherwise ideally associated with a relatively more continuous volumetric visual environment (VVE)  80 . Third, there is a practical limit to how much light  16 ′ a single modulation element  90  can either pass—or generate, infra,—per unit area of that modulation element  90 , which under some circumstances could potentially otherwise limit the perceived intensity of the image  16  from that single modulation element  90  to a level less than desirable. Fourth, in respect of the fourth aspect of the near-eye display system  10 . 4 , infra, there are practical limits to both the minimal size and minimal light per unit area that can be generated by an associated light-source spot provided by a modulated light beam. Finally, the effects of diffraction and scattering associated with relatively-small modulation elements  90  may act to increase the effective size of the Active Subpupil Region (ASR)  72 . 
     Notwithstanding these practical considerations, an Active Subpupil Region (ASR)  72  smaller than the eye pupil  38  can provide for improved image quality in a near-eye display system  10  with a relatively-large field of view and a relatively-high magnification, the latter of which can provide for utilizing a relatively-smaller image generator  12 ,  12 . 1 , relative to that provided for by the use of a relatively-larger Active Subpupil Region (ASR)  72 . Even if the Active Subpupil Region (ASR)  72  were to not be maintained entirely within the eye pupil  38  during momentary situations such as rapid eye rotation, manual user adjustments or bumping the near-eye display system  10 , the resultant image  16  will simply show some level of vignetting during those situations before returning to an unvignetted mode of operation after settling to a more stable environment. 
     If the size of the Active Subpupil Region (ASR)  72  is smaller than the minimal size of the eye pupil  38 , then the iris  40  of the eye  20  will be ineffectual in its normal biological function of modifying image intensity changes through a biological change in the diameter of the eye pupil  38 . This functionality can be replaced by adjusting overall transmission through the Active Subpupil Region (ASR)  72  responsive to a restriction of the modulation range of all active modulation elements  90  by the subpupil modulation controller  50  in accordance with the overall brightness of the image content as indicated by polling either samples, or the entirety, of the pixel intensity values of the associated electronic image being displayed. For example, this modulation range can be based upon a model of the biological pupillary response to light, for example, based upon experimentally measuring the size of the eye pupil  38  in response to the amount of light to which the eye  20  is exposed. Furthermore, the third-aspect subpupil modulation scheme  70 ,  70 . 3  can further provide for a calibration mode by which the eye pupil  38  is flooded with light—for example, in cooperation with an Active Subpupil Region (ASR)  72  that exceeds the size of the eye pupil  38 —for example, as provided for by either the first  70 . 1  or second  70 . 2  subpupil modulation schemes  70 , supra,—and utilizing measurements from the eye-tracking subsystem  42  of the size of the eye pupil  38  for various test images with various levels of brightness of the associated illumination, and then limiting the maximum brightness of the light  16 ′ of the image  16  to a level that resulted in the smallest diameter eye pupil  38  during the calibration mode, so as to provide for each user  22  a brightness response that is customized to their particular physiology. 
     Referring to  FIGS.  16 - 19 ,  31 , and  32   , in accordance with second  10 . 2 , third  10 . 3  and fourth  10 . 4  aspects of a near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 4 , an associated second-aspect image generator  12 ,  12 . 2  comprises a flat-panel two-dimensional image-display modulation array  94  of light-modulating image-display pixels  96 —for example, liquid-crystal light-modulating image-display pixels  96 ′, for example, as illustrated in  FIGS.  20  and  33   —in cooperation with a controllable light source  97  that provides for illuminating the entirety of the flat-panel two-dimensional image-display modulation array  94  from a controllable location, the latter of which provides for defining the associated modulated subpupil  32 ′. 
     Referring to  FIGS.  16 ,  17  and  20 - 30   , in accordance with the second aspect  10 . 2  of the near-eye display system  10 ,  10 . 2 , and an associated first embodiment  10 . 2 ′ thereof, the controllable light source  97  is provided for by a flat-panel two-dimensional light-source array  98  of associated light-source elements  100 —for example, light-emitting-diode elements  100 ′, or fiber-optic illuminator elements  100 ″, —with a conditioner lens  102 , L 1  interposed between a first side  94 . 1  of the flat-panel two-dimensional image-display modulation array  94  and the flat-panel two-dimensional light-source array  98 , for example, a plano-convex conditioner lens  102 ′, L 1 , with the planar surface  102 . 1 ′ thereof abutting the first side  94 . 1  of the flat-panel two-dimensional image-display modulation array  94  and located one focal length f 1  from the flat-panel two-dimensional light-source array  98 . The second-aspect near-eye display system  10 ,  10 . 2  incorporates an associated second-aspect optical subsystem  14 ,  14 . 2  comprising the conditioner lens  102 ,  102 ′, L 1  in combination with a second dioptric-power optical element  56 ,  56 . 2 ,  56 . 2 ′, L 1 , for example, in accordance with a first embodiment of the second-aspect optical subsystem  14 ,  14 . 2 ,  14 . 2 ′, a second convergent magnifier lens  56 . 2 ′, L 2 , each of which shares a common optical axis  36 . 
     Further in accordance with the second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′, the flat-panel two-dimensional light-source array  98  constitutes an associated second-aspect subpupil modulator  30 ,  30 . 2 , wherein each associated light-source element  100 ,  100 ′,  100 ″ constitutes the associated modulation element  90  of the second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′ so as to provide for controlling an associated modulated subpupil  32 ′. Each light-source element  100 ,  100 ′,  100 ″ of the flat-panel two-dimensional light-source array  98  illuminates the entirety of the flat-panel two-dimensional image-display modulation array  94  from a particular direction, and along a corresponding angle, associated with the location of that light-source element  100 ,  100 ′,  100 ″ within the flat-panel two-dimensional light-source array  98 . Accordingly, with the flat-panel two-dimensional light-source array  98  located one focal length f 1  from the flat-panel two-dimensional image-display modulation array  94 , the light  104  generated by each light-source element  100 ,  100 ′,  100 ″, and subsequently intensity-modulated by the flat-panel two-dimensional image-display modulation array  94 , is transformed into a corresponding beam  64  of light  16 ′ propagating at a corresponding angle relative to the optical axis  36 . 
     During operation of the second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′, an electronic image signal  74  is output from an associated display controller  76  to the flat-panel two-dimensional image-display modulation array  94  that in turn modulates the light  104  from the flat-panel two-dimensional light-source array  98  so as to provide for generating the image  16  therefrom, the light  16 ′ thereof of which propagates as one or more beams  64  of light  16 ′, each of which is associated with a corresponding activated light-source element  100 ,  100 ′,  100 ″—if activated—propagating at a corresponding angle relative to the optical axis  36 , wherein the electronic image signal  74  is either based upon a signal  74 ′ received via an associated wireless communication link  78 , or is generated from a local image source  74 ″, for example, either from a stored memory or from a camera. 
     The second dioptric-power optical element  56 ,  56 . 2 ,  56 . 2 ′, L 2  in cooperation with the conditioner lens  102 ,  102 ′, L 1  provide for forming an image of both the subpupil modulator  30 ,  30 . 2 /flat-panel two-dimensional light-source array  98  and the associated aperture stop  28 , at the exit pupil  18  located proximate to the front surface  20 ′ of the eye  20  and associated with a corresponding planar subpupil surface  84 . For example, referring to  FIGS.  16  and  17   , in accordance with one set of embodiments, the second convergent magnifier lens  56 . 2 ′, L 2  is located one focal length f 2  from the image generator  12 ,  12 . 2 /flat-panel two-dimensional image-display modulation array  94 —i.e. from the second side  94 . 2  of the flat-panel two-dimensional display-modulation array  94 —and provides for transforming each beam  64  of light  16 ′—propagating at a corresponding angle relative to the optical axis  36 —to a corresponding exit subpupil  32 , associated with the corresponding light-source element  100 ,  100 ′,  100 ″ of the flat-panel two-dimensional light-source array  98 , acting in cooperation with the entirety of the flat-panel two-dimensional image-display modulation array  94 , as the corresponding associated modulated subpupil  32 ′. Furthermore, the second convergent magnifier lens  56 . 2 ′, L 2 , in combination with the lens  66  of the eye  20 , provide for forming the real image  16 ″ of the image generator  12 ,  12 . 2 /flat-panel two-dimensional image-display modulation array  94  on the retina  24  of the eye  20 , wherein the second convergent magnifier lens  56 . 2 ′, L 2  provides for adjusting focus and for adjusting the apparent distance of the virtual image  16 ′″ associated with the real image  16 ″ that is formed on the retina  24  of the eye  22 . 
     For example, light  104  from an active—if activated—first light-source element  100 . 1  at a central location of the flat-panel two-dimensional light-source array  98  illuminates the entirety of the flat-panel two-dimensional image-display modulation array  94  and, in cooperation with transformation by the conditioner lens  102 ,  102 ′, L 1 , is transformed to a corresponding first beam  64 . 1  of light  16 . 1 ′, and then be focused by the second convergent magnifier lens  56 . 2 ′, L 2  to form the corresponding first exit subpupil  32 . 1  at a corresponding first location  68 . 1  at the exit pupil  18 , wherein the control state of the first light-source element  100 . 1  is controlled by the subpupil modulation controller  50  responsive to whether the location of the eye pupil  38 —as determined by the eye-tracking subsystem  42 —is either aligned with, or sufficiently close to, infra, the first exit subpupil  32 . 1 , wherein the control state (i.e. ON or OFF) of the first light-source element  100 . 1  controls whether or not light  104  from the first light-source element  100 . 1  can illuminate the corresponding first exit subpupil  32 . 1 . If the eye pupil  38  is either aligned with, or sufficiently close to, infra, the first exit subpupil  32 . 1 , then the first light-source element  100 . 1  is activated by the subpupil modulation controller  50  so as to cause the entirety of the image  16  from the perspective of the first exit subpupil  32 . 1  to be presented to the eye  20  by the second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′. Otherwise, if the eye pupil  38  is not either aligned with, nor sufficiently close to, infra, the first exit subpupil  32 . 1 , then the first light-source element  100 . 1  is deactivated so that the first exit subpupil  32 . 1  is void of light  16 . 1 ′. 
     Furthermore, light  104  from an active—if activated—second light-source element  100 . 2  at a first relatively offset location of the flat-panel two-dimensional light-source array  98  illuminates the entirety of the flat-panel two-dimensional image-display modulation array  94  and, in cooperation with transformation by the conditioner lens  102 ,  102 ′, L 1 , is transformed to a corresponding second beam  64 . 2  of light  16 . 2 ′, and then be focused by the second convergent magnifier lens  56 . 2 ′, L 2  to form the corresponding second exit subpupil  32 . 2  at a corresponding second location  68 . 2  at the exit pupil  18 , wherein the control state of the second light-source element  100 . 2  is controlled by the subpupil modulation controller  50  responsive to whether the location of the eye pupil  38 —as determined by the eye-tracking subsystem  42 —is either aligned with, or sufficiently close to, infra, the second exit subpupil  32 . 2 , wherein the control state (i.e. ON or OFF) of the second light-source element  100 . 2  controls whether or not light  104  from the second light-source element  100 . 2  can illuminate the corresponding second exit subpupil  32 . 2 . If the eye pupil  38  is either aligned with, or sufficiently close to, infra, the second exit subpupil  32 . 2 , then the second light-source element  100 . 2  is activated by the subpupil modulation controller  50  so as to cause the entirety of the image  16  from the perspective of the second exit subpupil  32 . 2  to be presented to the eye  20  by the second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′. Otherwise, if the eye pupil  38  is not either aligned with, nor sufficiently close to, infra, the second exit subpupil  32 . 2 , then the second light-source element  100 . 2  is deactivated so that the second exit subpupil  32 . 2  is void of light  16 . 2 ′. 
     Yet further, light  104  from an active—if activated—third light-source element  100 . 3  at a second relatively offset location of the flat-panel two-dimensional light-source array  98  illuminates the entirety of the flat-panel two-dimensional image-display modulation array  94  and, in cooperation with transformation by the conditioner lens  102 ,  102 ′, L 1 , is transformed to a corresponding third beam  64 . 3  of light  16 . 3 ′, and then be focused by the second convergent magnifier lens  56 . 2 ′, L 2  to form the corresponding third exit subpupil  32 . 3  at a corresponding third location  68 . 3  at the exit pupil  18 , wherein the control state of the third light-source element  100 . 3  is controlled by the subpupil modulation controller  50  responsive to whether the location of the eye pupil  38 —as determined by the eye-tracking subsystem  42 —is either aligned with, or sufficiently close to, infra, the third exit subpupil  32 . 3 , wherein the control state (i.e. ON or OFF) of the third light-source element  100 . 3  controls whether or not light  104  from the third light-source element  100 . 3  can illuminate the corresponding third exit subpupil  32 . 3 . If the eye pupil  38  is either aligned with, or sufficiently close to, infra, the third exit subpupil  32 . 3 , then the third light-source element  100 . 3  is activated by the subpupil modulation controller  50  so as to cause the entirety of the image  16  from the perspective of the third exit subpupil  32 . 3  to be presented to the eye  20  by the second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′. Otherwise, if the eye pupil  38  is not either aligned with, nor sufficiently close to, infra, the third exit subpupil  32 . 3 , then the third light-source element  100 . 3  is deactivated so that the third exit subpupil  32 . 3  is void of light  16 . 3 ′. 
     Referring again to  FIG.  9   , if the modulation surface  92  of the near-eye display system  10 ,  10 . 1 ,  10 . 2 ,  10 . 2 ′ is implemented as a flat structure at the aperture stop  28  of the associated optical subsystem  14 ,  14 . 1 ,  14 . 2 , then the surface underlying the associated exit pupil  18  formed as the image of the associated planar modulation surface  92 ,  92 ′ will also be flat, i.e. a planar subpupil surface  84 ,  84 ′, for example, as illustrated in  FIG.  9    by the vertical dashed line bounded by the exit pupil  18 . However, the image of any modulation surface  92  that is formed by the associated optical subsystem  14  within the associated volumetric visual environment (VVE)  80  can also serve to modulate light  16 ′ through the image of that modulation surface  92 . Accordingly, and alternatively, referring also to  FIGS.  18  and  19   , a concave-curved subpupil surface  84 ,  84 ″ may be formed as the image of a corresponding curved modulation surface  92 ,  92 ″—for example, with the latter formed as a curved two-dimensional light-source array  106  of light-source elements  100  on, or associated with, an underlying concave-curved surface  107 —wherein the curvature of the curved modulation surface  92 ,  92 ″ may be configured so that the resulting concave-curved subpupil surface  84 ,  84 ″ substantially conforms to the curvature of the front surface  20 ′ of the eye  20 , thereby providing for the axial distance from the eye pupil  38  to the associated concave-curved subpupil surface  84 ,  84 ″ to be substantially invariant with respect to rotation of the eye  20 , so as to provide for visibility of exit subpupils  32  in their entirety without vignetting regardless of the rotation of the eye  20 . Accordingly, positioning the exit subpupil  32  sufficiently close to the eye pupil  38  provides for all rays forming the component image  86  through that exit subpupil  32  to pass through the eye pupil  38  without vignetting. Otherwise, as the axial distance between the eye pupil  38  and a given exit subpupil  32  increases, the periphery of the component image  86  through that exit subpupil  32  is susceptible to eventually becoming increasingly vignetted by the edge of the eye pupil  38 . 
     Referring again to  FIG.  9   , in accordance with the first- and second-aspect near-eye display system  10 ,  10 . 1 ,  10 . 2 ,  10 . 2 ′, for a range of rotations of the eye  20 , the eye pupil  38  traces a concave geometric surface construct  82 ,  82 ′, so that for either a flat-panel two-dimensional modulation array  58  of light-modulating pixels  60 , or a flat-panel two-dimensional light-source array  98  of light-source elements  100 , respectively,—wherein the flat nature thereof is compatible with typical electronic device manufacturing approaches,—that provide for associated planar subpupil surfaces  84 ,  84 ′ of the associated exit subpupils  32 , the distance between the associated exit subpupil  32  and the eye pupil  38  will change as the eye  20  rotates, thereby increasing the prospect of vignetting of the associated component images  86  as that distance increases, wherein the concavity of the concave geometric surface construct  82 ,  82 ′ is from the point of view, and with respect to, the associated eye  20  of the user  22 . 
     Referring to  FIGS.  18 - 30   , the third aspect  10 . 3  of the near-eye display system  10 ,  10 . 3 , and an associated first embodiment  10 . 3 ′ thereof, is substantially the same as the second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′, supra, except that an associated third-aspect image generator  12 ,  12 . 3  incorporates a controllable light source  97  that incorporates a curved two-dimensional light-source array  106  of light-source elements  100 ,  100 ′,  100 ″, instead of a flat-panel two-dimensional light-source array  98 , which provides for an associated curved modulation surface  92 ,  92 ″. With the subpupil surface  84  being an image of the modulation surface  92 , this results in a corresponding associated concave-curved subpupil surface  84 ,  84 ″ that, referring to  FIG.  9   , conforms to a concave geometric surface construct  82 ,  82 ′ defined by the front surface  20 ′ of the eye  20  over a range of rotations, which provides for minimizing the variation in axial distance between the eye pupil  38  and any active exit subpupil  32  over a range of possible rotations of the eye  20 . Referring to  FIG.  19   , in accordance with one set of embodiments, the relatively outboard light-source elements  100 ,  100 . 2 ,  100 . 3  are located one focal length f 1  from the associated first dioptric-power optical element  56 ,  56 . 1 ,  56 . 1 ′, L 1 . 
     For example, the curved two-dimensional light-source array  106  of light-source elements  100 ,  100 ′,  100 ″ may be embodied by either a curved array of independently controllable light sources, such as light-emitting diodes; or of a flat array of such light-emitting diodes, with the light from each light-emitting diode coupled to one or more entrances of one or more associated optical light pipes, the corresponding exits of which are coupled to form an associated light-source element  100 ,  100 ′,  100 ″ that is operatively coupled to, or a part of, an underlying concave-curved surface  107  of curved two-dimensional light-source array  106 , so that the exits of these light pipes collectively form the light-source elements  100 ,  100 ′,  100 ″ of the curved two-dimensional light-source array  106 . 
     Further in accordance with the third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′, the curved two-dimensional light-source array  106  constitutes an associated third-aspect subpupil modulator  30 ,  30 . 3 , wherein each associated light-source element  100 ,  100 ′,  100 ″ constitutes the associated modulation element  90 , similar to that of the second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′ so as to provide for controlling an associated modulated subpupil  32 ′, but on an underlying concave-curved surface  107 . Each light-source element  100 ,  100 ′,  100 ″ of the curved two-dimensional light-source array  106  illuminates the entirety of the flat-panel two-dimensional image-display modulation array  94  from a particular direction, and along a corresponding angle, associated with the location of that light-source element  100 ,  100 ′,  100 ″ within the curved two-dimensional light-source array  106 . Accordingly, with the curved two-dimensional light-source array  106  located one focal length f 1  from the flat-panel two-dimensional image-display modulation array  94 , the light  104  generated by each light-source element  100 ,  100 ′,  100 ″, and subsequently intensity-modulated by the flat-panel two-dimensional image-display modulation array  94 , is transformed into a corresponding beam  64  of light  16 ′ propagating at a corresponding angle relative to the optical axis  36 . 
     The second dioptric-power optical element  56 ,  56 . 2 ,  56 . 2 ′, L 2  in cooperation with the conditioner lens  102 ,  102 ′, L 1  provide for forming a curved subpupil array image  108  of both the subpupil modulator  30 ,  30 . 3 /curved two-dimensional light-source array  106  and the associated aperture stop  28 , at the exit pupil  18  located proximate to the front surface  20 ′ of the eye  20  and associated with the corresponding concave-curved subpupil surface  84 ,  84 ″. 
     The light  104  originating from each light-source elements  100 ,  100 ′,  100 ″ is independently controlled, e.g. ON or OFF, by the subpupil modulation controller  50  responsive to the eye-tracking subsystem  42  in the same manner as described hereinabove for the second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′. 
     Referring to  FIGS.  21 - 30   , the second- and third-aspect subpupil modulators  30 ,  30 . 2 ,  30 . 3  are controlled by the subpupil modulation controller  50  in accordance with a subpupil modulation scheme  70  that provides for identifying an Active Subpupil Region (ASR)  72  of the subpupil modulator  30 ,  30 . 2 ,  30 . 3  responsive to the location, size, and possibly the shape, of the eye pupil  38  as determined by the eye-tracking subsystem  42 , and responsive thereto, that generates a subpupil modulation control signal  51  that provides for activating a subset of modulated subpupils  32 ′ within the Active Subpupil Region (ASR)  72  (i.e. by controlling to an ON state) by activating the corresponding associated light-source elements  100 ,  100 ′,  100 ″, so as to generate light  104  therefrom; and that provides for deactivating the remainder of the modulated subpupils  32 ′ of the subpupil modulator  30 ,  30 . 2 ,  30 . 3  (i.e. by controlling to an OFF state), by deactivating the corresponding associated light-source elements  100 ,  100 ′,  100 ″, so as to not generate light  104  therefrom. In comparison with the first-aspect near-eye display system  10 ,  10 . 1 , for which the powering of the light-emitting image-display pixels  54  of the entire flat-panel two-dimensional image-display array  52  is independent of which exit subpupils  32  are activated, for the second- and third-aspect near-eye display systems  10 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′, only light-source elements  100 ,  100 ′,  100 ″ associated with active exit subpupils  32  are powered, and the associated flat-panel two-dimensional image-display modulation array  94  consumes only a negligible amount of power, which together therefor provides a substantial reduction in power consumption relative to that of the first-aspect near-eye display system  10 ,  10 . 1 . 
     Referring to  FIGS.  21 - 23   , in accordance with the first aspect  70 . 1  of the subpupil modulation scheme  70 ,  70 . 1 , the Active Subpupil Region (ASR)  72  is set to a fixed size and shape that is sufficiently large to surround the eye pupil  38  regardless of the orientation of the eye  20 , and regardless of the associated state of the iris  40 , with accommodation for the largest anticipated lateral extent of the eye pupil  38  and accommodation of possible error in the determination of the location, size and/or shape of the eye pupil  38  by the eye-tracking subsystem  42 , so as to mitigate against a potential uneven vignetting by an edge of the eye pupil  38  that might otherwise result if the edge of the eye pupil  38  were to not be fully illuminated by an associated exit subpupil  32 , for example, as might otherwise result from a misalignment between the eye pupil  38  and the Active Subpupil Region (ASR)  72  that could otherwise cause a spatial transition of the edge of the eye pupil  38  from an active subpupil  32  inside the Active Subpupil Region (ASR)  72  to an inactive subpupil  32  outside the Active Subpupil Region (ASR)  72 , for example, as a result of relative motion between the eye pupil  38  and the Active Subpupil Region (ASR)  72 . The location of the Active Subpupil Region (ASR)  72  is continuously updated responsive to the eye-tracking subsystem  42 , at a rate of update sufficient to accommodate rotations of the eye  20  by the user  22  so that the exit subpupils  32  surrounding and within the eye pupil  38  are maintained in an active state. Referring to  FIGS.  21  and  22   , for the eye  22  of the user  22  rotated for viewing in the first gaze direction  34 . 1  as illustrated in  FIG.  22   , and as a result, a detection by the eye-tracking subsystem  42  of the eye pupil  38  being centered on the optical axis  36 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is concentric both with the eye pupil  38  and with the optical axis  36 , with a diameter sufficiently greater than that of the eye pupil  38  so that the eye pupil  38  will be fully illuminated by active exit subpupils  32 , wherein, as illustrated in  FIG.  21   , the light-source elements  100 ,  100 ′,  100 ″ and associated modulated subpupils  32 ′ within the Active Subpupil Region (ASR)  72  are activated by the subpupil modulator  30 ,  30 . 2 ,  30 . 3 , and the remaining modulated subpupils  32 ′ intersecting or outside of the boundary of the Active Subpupil Region (ASR)  72  are deactivated so as to thereby not consume power, resulting in the image  16  being presented to the eye  20  via only the activated exit subpupils  32  that are associated with the activated modulated subpupils  32 ′, as illustrated in  FIG.  22   . Referring to  FIGS.  23  and  24   , for the eye  22  of the user  22  rotated up and to the left as illustrated in  FIG.  24   , and as a result, a detection by the eye-tracking subsystem  42  of an elliptically-shaped eye pupil  38  located up and to the left of the associated optical axis  36 , in accordance with the first-aspect subpupil modulation scheme  70 ,  70 . 1 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is centered about the offset eye pupil  38 , but with the same diameter as illustrated in  FIGS.  21  and  22   , wherein, as illustrated in  FIG.  23   , the light-source elements  100 ,  100 ′,  100 ″ and associated modulated subpupils  32 ′ within the Active Subpupil Region (ASR)  72  are activated by the subpupil modulator  30 ,  30 . 2 ,  30 . 3 , and the remaining modulated subpupils  32 ′ intersecting or outside of the boundary of the Active Subpupil Region (ASR)  72  are deactivated so as to thereby not consume power, resulting in the image  16  being presented to the eye  20  via only the activated exit subpupils  32  that are associated with the activated modulated subpupils  32 ′ that are aligned with the eye pupil  38 , as illustrated in  FIG.  24   . Accordingly, notwithstanding the resulting mitigation against uneven vignetting by the eye pupil  38 , the first-aspect subpupil modulation scheme  70 ,  70 . 1  results in the illumination of a portion of the eye  20  surrounding the eye pupil  38  with extraneous light  16   iv  that is then reflected or scattered by the front surface  20 ′ of the eye  20  rather than being imaged onto the retina  24 , although with benefit from a substantial reduction in electrical power consumption compared with that required by the first aspect near-eye display system  10 ,  10 . 1  to power the entire flat-panel two-dimensional image-display array  52  of light-emitting image-display pixels  54 , 
     Referring to  FIGS.  25  and  26   , in accordance with the second aspect  70 . 2  of the subpupil modulation scheme  70 ,  70 . 2 , the Active Subpupil Region (ASR)  72  is set to a variable size and shape that is adapted to be sufficiently large surround the eye pupil  38  regardless of the orientation of the eye  20 , and regardless of the associated state of the iris  40 , which—the same as for the first-aspect subpupil modulation scheme  70 ,  70 . 1 , but accompanied by a lesser amount of extraneous light  16   iv —also provides for mitigating against a potential uneven vignetting by an edge of the eye pupil  38  that might otherwise result if the edge of the eye pupil  38  were to not be fully illuminated by an associated exit subpupil  32 . The location, size and shape of the Active Subpupil Region (ASR)  72  is continuously updated responsive to the eye-tracking subsystem  42 , at a rate of update sufficient to accommodate rotations of the eye  20  by the user  22  so that the exit subpupils  32  surrounding the eye pupil  38  are maintained in an active state. Similar to that illustrated in  FIGS.  21  and  22   , if the eye  22  of the user  22  is rotated for viewing in the first gaze direction  34 . 1  as illustrated in  FIG.  22   , the resulting associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is also concentric both with the eye pupil  38  and with the optical axis  36 , but with a relatively smaller diameter—relative to that associated with the first-aspect subpupil modulation scheme  70 ,  70 . 1 —that is sufficiently large to account for possible error in the determination of the location, size and/or shape of the eye pupil  38  by the eye-tracking subsystem  42 . Referring to  FIGS.  25  and  26   , for the eye  22  of the user  22  rotated up and to the left as illustrated in  FIG.  26   , and as a result, a detection by the eye-tracking subsystem  42  of an elliptically-shaped eye pupil  38  located up and to the left of the associated optical axis  36 , in accordance with the second-aspect subpupil modulation scheme  70 ,  70 . 2 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is centered about the offset eye pupil  38 , but elliptically shaped, similar that of the eye pupil  38 , wherein, as illustrated in  FIG.  25   , the light-source elements  100 ,  100 ′,  100 ″ and associated modulated subpupils  32 ′ within the Active Subpupil Region (ASR)  72  are activated by the subpupil modulator  30 ,  30 . 2 ,  30 . 3 , and the remaining modulated subpupils  32 ′ intersecting or outside of the boundary of the Active Subpupil Region (ASR)  72  are deactivated, resulting in the image  16  being presented to the eye  20  via only the activated exit subpupils  32  that are associated with the activated modulated subpupils  32 ′ that are aligned with the eye pupil  38 , as illustrated in  FIG.  26   . Accordingly, as a result of the Active Subpupil Region (ASR)  72  being dynamically sized and shaped responsive to the size and shape of the eye pupil  38  as determined by the eye-tracking subsystem  42 , the size and shape of the Active Subpupil Region (ASR)  72  can more closely match that of the eye pupil  38  while still mitigating against uneven vignetting by the edge of the eye pupil  38 , which—in comparison with the first-aspect subpupil modulation scheme  70 ,  70 . 1 —results in a relatively lesser amount of illumination of the portion of the eye  20  surrounding the eye pupil  38  with extraneous light  16   iv  that is then reflected or scattered by the front surface  20 ′ of the eye  20  rather than being imaged onto the retina  24 , and thereby also provides a benefit from a substantial reduction in electrical power consumption compared with that required by the first aspect near-eye display system  10 ,  10 . 1  to power the entire flat-panel two-dimensional image-display array  52  of light-emitting image-display pixels  54 ; and, to a lesser extent, compared with that of the first-aspect subpupil modulation scheme  70 ,  70 . 1 , although to a lesser extent. 
     The first- and second-aspect subpupil modulation schemes  70 ,  70 . 1 ,  70 . 2 , supra, may each be configured to dynamically adapt the size and/or shape of the Active Subpupil Region (ASR)  72  to that of the eye pupil  38 , so as to provide for reducing the amount of extraneous light  16   iv  reflected or scattered by the front surface  20 ′ of the eye  20 , or, in the case of the second- or third-aspect near-eye display systems  10 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′, so as to provide for further reducing the associated amount of electrical power consumption. The diameter of the eye pupil  38  is controlled by the iris  40  of the eye  20  within a typical range of 2 millimeters to 8 millimeters, depending upon, and responsive to, changes in the brightness of the image  16 , wherein the relatively-smallest diameter of the eye pupil  38  results from the relatively-highest perceived intensity of the image  16 , which, in respect of the second- or third-aspect near-eye display systems  10 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′, provides the greatest opportunity for power savings if the Active Subpupil Region (ASR)  72  diameter is reduced responsive to detection by the eye-tracking subsystem  42  of the size and/or shape of the eye pupil  38 . 
     In accordance with the third aspect  70 . 3  of the subpupil modulation scheme  70 ,  70 . 3 , rather than making the Active Subpupil Region (ASR)  72  so large as to avoid a spatial transition of the edge of the eye pupil  38  from an active to an inactive exit subpupil  32 , instead, the Active Subpupil Region (ASR)  72  is constrained to a size that is smaller than that of the eye pupil  38 , and is aligned with the center of the eye pupil  38 , so as to prevent vignetting that could otherwise result from a spatial transition straddling edge of the eye pupil  38 . Accordingly, the third-aspect subpupil modulation scheme  70 ,  70 . 3  substantially eliminates the illumination of the portion of the eye  20  surrounding the eye pupil  38  with extraneous light  16   iv  that would otherwise be reflected or scattered by the front surface  20 ′ of the eye  20  rather than being imaged onto the retina  24 . Furthermore, a relatively smaller Active Subpupil Region (ASR)  72  provides for improving the perceived quality of the image  16  by decreasing the effective aperture size through which the light  16 ′ passes into the eye  20 , thereby decreasing the impact of aperture-size-related optical aberrations, which increases clarity of the image  16 , which is particularly effective in a near-eye display system  10 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′ that provides for a relatively-large field-of-view together with relatively-high magnification. Referring to  FIGS.  27  through  29   , based upon an estimate from the eye-tracking subsystem  42  of the location of the center of the eye pupil  38 , the subpupil modulation controller  50  identifies and activates the modulated subpupil  32 ′—i.e. the associated light-source element  100 ,  100 ′,  100 ″—of an associated Active Subpupil Region (ASR)  72 , associated with the exit subpupil  32  that is most-closely aligned with the eye pupil  38 , and deactivates the remaining modulated subpupils  32 ′/light-source elements  100 ,  100 ′,  100 ″ of the subpupil modulator  30 ,  30 . 2 ,  30 . 3 /flat-panel  98  or curved  106  two-dimensional light-source array. The location of the Active Subpupil Region (ASR)  72  is continuously updated responsive to the eye-tracking subsystem  42 , at a rate of update sufficient to accommodate rotations of the eye  20  by the user  22 , so that the exit subpupils  32  having corresponding one or more projected transverse locations so as to be located entirely within transverse projection of the eye pupil  38 , are maintained in an active state. Referring to  FIGS.  26  and  28   , for the eye  22  of the user  22  rotated for viewing in the first gaze direction  34 . 1  as illustrated in  FIG.  28   , and as a result, a detection by the eye-tracking subsystem  42  of the eye pupil  38  being centered on the optical axis  36 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is concentric both with the eye pupil  38  and with the optical axis  36 , and, in one set of embodiments, limited in size so as to encompass a corresponding single exit subpupil  32 , wherein, as illustrated in  FIG.  27   , the light-source element  100 ,  100 ′,  100 ″ and associated modulated subpupil  32 ′ within the Active Subpupil Region (ASR)  72  is activated by the subpupil modulator  30 ,  30 . 2 ,  30 . 3 , and the remaining modulated subpupils  32 ′ outside the boundary of the Active Subpupil Region (ASR)  72  are deactivated, resulting in the image  16  being presented to the eye  20  via only the activated exit subpupil  32  associated with the activated modulated subpupil  32 ′, as illustrated in  FIG.  28   , and thereby also provides a benefit from a substantial reduction in electrical power consumption compared with that required by the first aspect near-eye display system  10 ,  10 . 1  to power the entire flat-panel two-dimensional image-display array  52  of light-emitting image-display pixels  54 , and, to a lesser extent, compared with that of the first- and second-aspect subpupil modulation schemes  70 ,  70 . 1 ,  70 . 2 . Referring to  FIGS.  29  and  30   , for the eye  22  of the user  22  rotated up and to the left as illustrated in  FIG.  30   , and as a result, a detection by the eye-tracking subsystem  42  of an elliptically-shaped eye pupil  38  located up and to the left of the associated optical axis  36 , in accordance with the third-aspect subpupil modulation scheme  70 ,  70 . 3 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is located—for example, centered—within the offset eye pupil  38 , wherein, as illustrated in  FIG.  29   , the light-source element  100 ,  100 ′,  100 ″ and associated modulated subpupil  32 ′ within the Active Subpupil Region (ASR)  72  is activated by the subpupil modulator  30 ,  30 . 2 ,  30 . 3 , and the remaining modulated subpupils  32 ′ outside the boundary of the Active Subpupil Region (ASR)  72  are deactivated, resulting in the image  16  being presented to the eye  20  via only the activated exit subpupil  32  associated with the activated modulated subpupil  32 ′, as illustrated in  FIG.  30   , and thereby also provides a benefit from a substantial reduction in electrical power consumption compared with that required by the first aspect near-eye display system  10 ,  10 . 1  to power the entire flat-panel two-dimensional image-display array  52  of light-emitting image-display pixels  54 , and, to a lesser extent, compared with that of the first- and second-aspect subpupil modulation schemes  70 ,  70 . 1 ,  70 . 2 . 
     The subpupil modulation schemes  70 ,  70 . 1 ,  70 . 2 ,  70 . 3  may be adapted to accommodate errors—by the eye-tracking subsystem  42 —in estimates of the position and/or size of the eye pupil  38 , or errors in the position of the eye pupil  38  relative to the associated subpupil surface  84  and associated one or more exit subpupils  32 , for example, which may result from a lag in the detection and determination of those parameters, or a lag in the implementation by the subpupil modulation controller  50  of changes to the Active Subpupil Region (ASR)  72  responsive to those parameters. For example, these errors may occur, or be accentuated, as a result of either rapid eye movement or a mechanical misalignment of the near-eye display system  10 ,  10 . 1 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′ relative to the eye  20 , for example, as a result of manual adjustment or a physical bumping that may be optionally reported to the subpupil modulation controller  50  by an optional accelerometer incorporated in the near-eye display system  10 ,  10 . 1 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′. For example, responsive to the detection of a condition—for example, rapid eye movement or a physical bumping of the near-eye display system  10 ,  10 . 1 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′—associated with prospective eye-tracking errors, the subpupil modulation controller  50  can provide for increasing the size of the Active Subpupil Region (ASR)  72  to accommodate the associated uncertainty in the location of the eye pupil  38  relative to the associated exit subpupil surface  84  and associated one or more exit subpupils  32 . Accordingly, the size, shape and location of the Active Subpupil Region (ASR)  72  implemented by the subpupil modulation schemes  70 ,  70 . 1 ,  70 . 2 ,  70 . 3  can be dynamically modified during such events to compensate for such temporary prospective errors, and then later reduced in size to either, or both, reduce the reflection or scattering extraneous light  16   iv , or reduce electrical power consumption, after the situation has stabilized. 
     The first- and second-aspect subpupil modulators  30 ,  30 . 2 ,  30 . 3 , supra, each generate an associated array of discrete, spatially adjacent exit subpupils  32  on a subpupil surface  84 , where each exit subpupil  32  is an image of an associated corresponding modulation element  90  within a corresponding array of modulation elements  90 , the physical implementation of which typically includes boundary regions between adjacent modulation elements  90  that, for example, incorporate, or provide for, associated electronic circuitry, the edges of a light pipes, or other structures that result in a physically discontinuous modulation surface  92 , and a resulting similarly discontinuous array of corresponding associated exit subpupils  32  at the subpupil surface  84 , which causes, within the subpupil surface  84 , a grid-like pattern of darkness between active exit subpupils  32 . 
     For a subpupil surface  84  that does not conform to the concave geometric surface construct  82 ,  82 ′, supra, the effect of this grid-like patterns on the uniform perceived brightness of the composite image  88  increases with axial separation of the eye pupil  38  from the associated exit subpupil  32  as a result of a rotation of the eye  20 . This effect can be somewhat mitigated by blurring the image of adjacent exit subpupils  32 —for example, by increasing the sizes thereof, —or by implementing other means of reducing spatial structures in the image of the exit subpupils  32 , however, a relative increase in the size of the exit subpupil  32  may not otherwise be desirable. The fixed spatial organization of the array of exit subpupils  32  resulting from the fixed spatial organization of the corresponding array of modulation elements  90  results in a corresponding relatively-fixed location of any individual exit subpupil  32  on the subpupil surface  84 . 
     Referring to  FIGS.  31 - 43   , the fourth aspect  10 . 4  of the near-eye display system  10 ,  10 . 4 , and an associated first embodiment  10 . 4 ′ thereof, is substantially the same as the third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′, supra, except that an associated fourth-aspect image generator  12 ,  12 . 4  incorporates a controllable light source  97  that incorporates a curved light-redirecting surface  110  in cooperation with a modulated scanned beam of light  112  that is generated by scanning—in two dimensions—a beam of light  114  with a light-beam scanner  116  to generate the light  104  to illuminate the associated flat-panel two-dimensional image-display modulation array  94  of light-modulating image-display pixels  96 , for example, the latter of which is illustrated in  FIG.  33   , which also provides for an associated curved modulation surface  92 ,  92 ″, but without utilizing a set of individual light-source elements  100 ,  100 ′,  100 ″ of the curved two-dimensional light-source array  106 . The modulated scanned beam of light  112  is generated by an intensity-modulatable light-beam source  118  that illuminates a light-beam-directing element  120 —for example, and electro-mechanically actuated mirror, holographic element, or diffractive element—of the light-beam scanner  116 , wherein the light-beam source  118 , and the light-beam scanner  116  are each operatively coupled to, and under control of, the sub pupil modulation controller  50  that provides for controlling the activation and intensity of the light-beam source  118  responsive to a light-beam-magnitude subpupil modulation control signal  51 ′, and that provides for controlling the location of the modulated scanned beam of light  112  on the curved light-redirecting surface  110  responsive to a light-beam-position subpupil modulation control signal  51 ″, so as to collectively provide for both temporal and angular modulation of the modulated scanned beam of light  112 , respectively. Accordingly, the modulated scanned beam of light  112  in cooperation with the curved light-redirecting surface  110 —including the underlying light-beam source  118  and light-beam scanner  116  under control of the subpupil modulation controller  50 —constitute a fourth-aspect subpupil modulator  30 ,  30 . 4  associated with the fourth aspect near-eye display system  10 ,  10 . 4 ,  10 . 4 ′, with the underlying curved light-redirecting surface  110  constituting an associated curved modulation surface  92 ,  92 ″. The same as for the third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′, with the subpupil surface  84  being an image of the modulation surface  92 , this results in a corresponding associated concave-curved subpupil surface  84 ,  84 ″ that conforms to the concave geometric surface construct  82 ,  82 ′ (illustrated in  FIG.  9   ) defined by the front surface  20 ′ of the eye  20  over a range of rotations, which provides for minimizing the variation in axial distance between the eye pupil  38  and any active exit subpupil  32  over a range of possible rotations of the eye  20 . 
     The region  122  of the curved light-redirecting surface  110  over which the modulated scanned beam of light  112  is scanned constitutes—in the context of the fourth-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′—an effective light source  124  that can be continuous over an arbitrary shape, of an arbitrary size, at an arbitrary location, and with an arbitrary intensity profile, and which is associated with a corresponding single modulated subpupil  32 ′, wherein the light  104  redirected from the curved light-redirecting surface  110  is transformed by the conditioner lens  102 ,  102 ′, L 1  into a corresponding beam  64 ′ of light  16 ′ that propagates in a direction that is responsive to the location of the region  122  on the curved light-redirecting surface  110  from which the light  104  originates, in association with a corresponding single exit subpupil  32 . The curved light-redirecting surface  110  provides for redirecting and redistributing—for example, by scattering or diffraction, or a combination thereof—the light  104  of the modulated scanned beam of light  112  with a sufficient diversity of scattering angles therefrom so as to provide for illuminating the entirety of the flat-panel two-dimensional image-display modulation array  94  from every location on the curved light-redirecting surface  110  that can be associated with an associated modulated subpupil  32 ′ and the exit subpupil  32 , while also providing for forming an image of the associated effective light source  124  on the concave-curved subpupil surface  84 ,  84 ″ as an associated curved subpupil image  126 . 
     At any given time, when actuated, the beam of light  114  from the light-beam source  118  as directed by the light-beam-directing element  120  of the light-beam scanner  116  inherently forms a light spot  104 ′ within the region  122  of the curved light-redirecting surface  110 , which may be steered to any location on the curved light-redirecting surface  110  responsive to angular modulation of the light-beam scanner  116 . The ultimate shape and size of the resulting effective light source  124  are provided for by rapidly angularly modulating or “scanning” the light spot  104 ′ along an associated path within the region  122  of the curved light-redirecting surface  110  corresponding to the associated Active Subpupil Region (ASR)  72 , wherein, as a result of persistence of the eye  20 , the rapid and repetitive scanning of the light spot  104 ′ along the associated path—similar to the working of a vector-based graphical display—gives the appearance of a relatively continuously filled effective light source  124 . In one set of embodiments, either the light-beam source  118 , or of the associated beam of light  114 , may be intensity modulated during the scanning process to provide for controlling the resulting intensity, or the associated intensity profile, of the effective light source  124 . 
     Notwithstanding that the light-beam scanner  116  and light-beam-directing element  120  are illustrated in  FIGS.  31  and  32    at an off-axis location relative to the optical axis  36  of the associated optical subsystem  14 ,  14 . 2  so as to not obstruct the illumination of the flat-panel two-dimensional image-display modulation array  94  from the curved light-redirecting surface  110 , alternatively, the light-beam scanner  116  and light-beam-directing element  120  could be used in cooperation with a beam splitter to provide for on-axis illumination of the curved light-redirecting surface  110 . 
     Referring also to  FIG.  32   , in accordance with one set of embodiments, the relatively outboard region of the curved light-redirecting surface  110  is located one focal length f 1  from the associated first dioptric-power optical element  56 ,  56 . 1 ,  56 . 1 ′, L 1 /conditioner lens  102 ,  102 ′, L 1 . The second dioptric-power optical element  56 ,  56 . 2 ,  56 . 2 ′, L 2  in cooperation with the conditioner lens  102 ,  102 ′, L 1  provide for forming the curved subpupil image  126  of both the subpupil modulator  30 ,  30 . 4 /curved light-redirecting surface  110  and the associated aperture stop  28 , at the exit pupil  18  located proximate to the front surface  20 ′ of the eye  20  and associated with the corresponding concave-curved subpupil surface  84 ,  84 ″. For example, the curved light-redirecting surface  110  may comprise, but is not limited to, a light-scattering surface, a holographic surface, a diffractive surface, or a combination thereof. 
     The light  104  originating from the region  122  of the curved light-redirecting surface  110  is controlled by the subpupil modulation controller  50  responsive to the eye-tracking subsystem  42 , depending upon the associated subpupil modulation scheme  70 . In comparison with the first-, second- and third-aspect near-eye display systems  10 ,  10 . 1 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′, the fourth aspect near-eye display system  10 ,  10 . 4 ,  10 . 4 ′ provides for more precisely positioning and sizing an associated single exit subpupil  32  that forms the associated composite image  88 , without the presence of a grid-like pattern of darkness within the associated curved subpupil image  126 . 
     Referring to  FIGS.  34 - 42   , the fourth-aspect subpupil modulator  30 ,  30 . 4  is controlled by the subpupil modulation controller  50  in accordance with a subpupil modulation scheme  70  that provides for identifying an Active Subpupil Region (ASR)  72  of the subpupil modulator  30 ,  30 . 4  responsive to the location, size, and possibly the shape, of the eye pupil  38  as determined by the eye-tracking subsystem  42 , and that provides for scanning the region  122  of the curved light-redirecting surface  110  so as to form the effective light source  124  associated with a corresponding modulated subpupil  32 ′ within the Active Subpupil Region (ASR)  72  so as to generate light  104  therefrom; and for not illuminating the remaining portion of the curved light-redirecting surface  110  with the modulated scanned beam of light  112  so as to not generate light  104  therefrom. In comparison with the first-aspect near-eye display system  10 ,  10 . 1 , for which the powering of the light-emitting image-display pixels  54  of the entire flat-panel two-dimensional image-display array  52  is independent of which exit subpupils  32  are activated, and in comparison with the second- and third-aspect near-eye display systems  10 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′, for which a light-source element  100  is illuminated in association with each active exit subpupil  32 , in accordance with the fourth aspect near-eye display system  10 ,  10 . 4 ,  10 . 4 ′, only the light-beam source  118  and light-beam scanner  116  are powered, and the associated flat-panel two-dimensional image-display modulation array  94  consumes only a negligible amount of power, which therefor provides a substantial reduction in power consumption relative to that of the first-aspect, and possibly also the second- and third-aspect, near-eye display systems  10 ,  10 . 1 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′. 
     Referring to  FIGS.  34 - 37   , in accordance with the first aspect  70 . 1  of the subpupil modulation scheme  70 ,  70 . 1 , the Active Subpupil Region (ASR)  72  is set to a fixed size and shape that is sufficiently large to surround the eye pupil  38  regardless of the orientation of the eye  20 , and regardless of the associated state of the iris  40 , with accommodation for the largest anticipated lateral extent of the eye pupil  38  and accommodation of possible error in the determination of the location, size and/or shape of the eye pupil  38  by the eye-tracking subsystem  42 , so as to mitigate against a potential uneven vignetting by an edge of the eye pupil  38  that might otherwise result if the edge of the eye pupil  38  were to not be fully illuminated by an associated exit subpupil  32 , for example, as might otherwise result from a misalignment between the eye pupil  38  and the Active Subpupil Region (ASR)  72  that could otherwise cause a spatial transition of the edge of the eye pupil  38  from an active subpupil  32  inside the Active Subpupil Region (ASR)  72  to an inactive subpupil  32  outside the Active Subpupil Region (ASR)  72  as a result of relative motion between the eye pupil  38  and the Active Subpupil Region (ASR)  72 . The location of the Active Subpupil Region (ASR)  72  is continuously updated responsive to the eye-tracking subsystem  42 , at a rate of update sufficient to accommodate rotations of the eye  20  by the user  22  so as to provide for the active-state exit subpupil  32  to continuously surround the eye pupil  38 . Referring to  FIGS.  34  and  35   , for the eye  22  of the user  22  rotated for viewing in the first gaze direction  34 . 1  as illustrated in  FIG.  35   , and as a result, a detection by the eye-tracking subsystem  42  of the eye pupil  38  being centered on the optical axis  36 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is concentric both with the eye pupil  38  and with the optical axis  36 , with a diameter sufficiently greater than that of the eye pupil  38  so that the eye pupil  38  will be fully illuminated by the active-state exit subpupil  32 , wherein, as illustrated in  FIG.  34   , the modulated scanned beam of light  112  of the associated subpupil modulator  30 ,  30 . 4  is scanned so as to form—in the region  122  of the curved light-redirecting surface  110 —an effective light source  124  and associated modulated subpupil  32 ′ that spans the Active Subpupil Region (ASR)  72 ; and a remaining portion of the curved light-redirecting surface  110  is not illuminated, so as to present the image  16  to the eye  20  via a single exit subpupil  32  that fills the associated Active Subpupil Region (ASR)  72 , as illustrated in  FIG.  35   . Referring to  FIGS.  36  and  37   , for the eye  22  of the user  22  rotated up and to the left as illustrated in  FIG.  37   , and as a result, a detection by the eye-tracking subsystem  42  of an elliptically-shaped eye pupil  38  located up and to the left of the associated optical axis  36 , in accordance with the first-aspect subpupil modulation scheme  70 ,  70 . 1 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is centered about the offset eye pupil  38 , but with the same diameter as illustrated in  FIGS.  34  and  35   , wherein, as illustrated in  FIG.  36   , the modulated scanned beam of light  112  of the associated subpupil modulator  30 ,  30 . 4  is scanned so as to form—in the region  122  of the curved light-redirecting surface  110 —an effective light source  124  and associated modulated subpupil  32 ′ that spans the Active Subpupil Region (ASR)  72 ; and a remaining portion of the curved light-redirecting surface  110  is not illuminated, so as to present the image  16  to the eye  20  via a single exit subpupil  32  that fills the associated Active Subpupil Region (ASR)  72  that is aligned with the eye pupil  38 , as illustrated in  FIG.  37   . Accordingly, notwithstanding the resulting mitigation against uneven vignetting by the eye pupil  38 , the first-aspect subpupil modulation scheme  70 ,  70 . 1  results in the illumination of a portion of the eye  20  surrounding the eye pupil  38  with extraneous light  16   iv  that is then reflected, or scattered, by the front surface  20 ′ of the eye  20  rather than being imaged onto the retina  24 , and thereby also provides a benefit from a substantial reduction in electrical power consumption compared with that required by the first aspect near-eye display system  10 ,  10 . 1  to power the entire flat-panel two-dimensional image-display array  52  of light-emitting image-display pixels  54 , 
     Referring to  FIGS.  38  and  39   , in accordance with the second aspect  70 . 2  of the subpupil modulation scheme  70 ,  70 . 2 , the Active Subpupil Region (ASR)  72  is set to a variable size and shape that is adapted to be sufficiently large surround the eye pupil  38  regardless of the orientation of the eye  20 , and regardless of the associated state of the iris  40 , which—the same as for the first-aspect subpupil modulation scheme  70 ,  70 . 1 , but accompanied by a lesser amount of extraneous light  16   iv —also provides for mitigating against a potential uneven vignetting by an edge of the eye pupil  38  that might otherwise result if the edge of the eye pupil  38  were to not be fully illuminated by an associated exit subpupil  32 . The location, size and shape of the Active Subpupil Region (ASR)  72  is continuously updated responsive to the eye-tracking subsystem  42 , at a rate of update sufficient to accommodate rotations of the eye  20  by the user  22  so as to provide for the active-state exit subpupil  32  to continuously surround the eye pupil  38 . Similar to that illustrated in  FIGS.  34  and  35   , if the eye  22  of the user  22  is rotated for viewing in the first gaze direction  34 . 1  as illustrated in  FIG.  35   , the resulting associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is also concentric both with the eye pupil  38  and with the optical axis  36 , but with a relatively smaller diameter—relative to that associated with the first-aspect subpupil modulation scheme  70 ,  70 . 1 —that is sufficiently large to account for possible error in the determination of the location, size and/or shape of the eye pupil  38  by the eye-tracking subsystem  42 . Referring to  FIGS.  38  and  39   , for the eye  22  of the user  22  rotated up and to the left as illustrated in  FIG.  39   , and as a result, a detection by the eye-tracking subsystem  42  of an elliptically-shaped eye pupil  38  located up and to the left of the associated optical axis  36 , in accordance with the second-aspect subpupil modulation scheme  70 ,  70 . 2 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is centered about the offset eye pupil  38 , but elliptically shaped, similar that of the eye pupil  38 , wherein, as illustrated in  FIG.  38   , the modulated scanned beam of light  112  of the associated subpupil modulator  30 ,  30 . 4  is scanned so as to form—in the region  122  of the curved light-redirecting surface  110 —an effective light source  124  and associated modulated subpupil  32 ′ that spans the Active Subpupil Region (ASR)  72 ; and a remaining portion of the curved light-redirecting surface  110  is not illuminated, so as to present the image  16  to the eye  20  via a single exit subpupil  32  that fills the associated Active Subpupil Region (ASR)  72  that is aligned with the eye pupil  38 , as illustrated in  FIG.  39   . Accordingly, as a result of the Active Subpupil Region (ASR)  72  being dynamically sized and shaped responsive to the size and shape of the eye pupil  38  as determined by the eye-tracking subsystem  42 , the size and shape of the Active Subpupil Region (ASR)  72  can more closely match that of the eye pupil  38  while still mitigating against uneven vignetting by the edge of the eye pupil  38 , which—in comparison with the first-aspect subpupil modulation scheme  70 ,  70 . 1 —results in a relatively lesser amount of illumination of the portion of the eye  20  surrounding the eye pupil  38  with extraneous light  16   iv  that is then reflected or scattered by the front surface  20 ′ of the eye  20  rather than being imaged onto the retina  24 , and thereby also provides a benefit from a substantial reduction in electrical power consumption compared with that required by the first aspect near-eye display system  10 ,  10 . 1  to power the entire flat-panel two-dimensional image-display array  52  of light-emitting image-display pixels  54 , and, to a lesser extent, compared with that of the first-aspect subpupil modulation scheme  70 ,  70 . 1 . 
     The first- and second-aspect subpupil modulation schemes  70 ,  70 . 1 ,  70 . 2 , supra, may each be configured to dynamically adapt the size and/or shape of the Active Subpupil Region (ASR)  72  to that of the eye pupil  38 , so as to provide for reducing the amount of extraneous light  16   iv  reflected or scattered by the front surface  20 ′ of the eye  20 . The diameter of the eye pupil  38  is controlled by the iris  40  of the eye  20  within the typical range of 2 millimeters to 8 millimeters, depending upon, and responsive to, changes in the brightness of the image  16 , wherein the relatively-smallest diameter of the eye pupil  38  results from the relatively-highest perceived intensity of the image  16 . 
     In accordance with the third aspect  70 . 3  of the subpupil modulation scheme  70 ,  70 . 3 , rather than making the Active Subpupil Region (ASR)  72  so large as to avoid a spatial transition of the edge of the eye pupil  38  from an active to an inactive exit subpupil  32 , instead the Active Subpupil Region (ASR)  72  is constrained to a size that is smaller than that of the eye pupil  38  and aligned with the center of the eye pupil  38  so as to prevent vignetting that could otherwise result with the presence of such a spatial transition. Accordingly, the third-aspect subpupil modulation scheme  70 ,  70 . 3  substantially eliminates the illumination of the portion of the eye  20  surrounding the eye pupil  38  with extraneous light  16   iv  that would otherwise be reflected or scattered by the front surface  20 ′ of the eye  20  rather than being imaged onto the retina  24 . Furthermore, a relatively smaller Active Subpupil Region (ASR)  72  provides for improving the perceived quality of the image  16  by decreasing the effective aperture size through which the light  16 ′ passes into the eye  20 , thereby decreasing the impact of aperture-size-related optical aberrations, which increases clarity of the image  16 , and which is particularly effective in a near-eye display system  10 ,  10 . 2 ,  10 . 2 ′,  10 . 3 ,  10 . 3 ′,  10 . 4 ,  10 . 4 ′ that provides for a large field-of-view together with relatively high magnification. Referring to  FIGS.  40  through  43   , based upon an estimate from the eye-tracking subsystem  42  of the location of the center of the eye pupil  38 , the subpupil modulation controller  50  identifies an associated Active Subpupil Region (ASR)  72  that is aligned with the eye pupil  38 , and the modulated scanned beam of light  112  of the associated subpupil modulator  30 ,  30 . 4  is scanned so as to form—in the region  122  of the curved light-redirecting surface  110 —an effective light source  124  and associated modulated subpupil  32 ′ that spans the Active Subpupil Region (ASR)  72 ; wherein a remaining portion of the curved light-redirecting surface  110  is not illuminated, so as to present the image  16  to the eye  20  via a single exit subpupil  32  that fills the associated Active Subpupil Region (ASR)  72  that is aligned with the eye pupil  38 . The location of the Active Subpupil Region (ASR)  72  is continuously updated responsive to the eye-tracking subsystem  42 , at a rate of update sufficient to accommodate rotations of the eye  20  by the user  22  so that the associated active-state exit subpupil  32  is maintained within the eye pupil  38 . Referring to  FIGS.  40  and  41   , for the eye  22  of the user  22  rotated for viewing in the first gaze direction  34 . 1  as illustrated in  FIG.  41   , and as a result, a detection by the eye-tracking subsystem  42  of the eye pupil  38  being centered on the optical axis  36 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is concentric both with the eye pupil  38  and with the optical axis  36 , and limited in size so as to not overlap an edge of the eye pupil  38 , wherein, as illustrated in  FIG.  40   , the modulated scanned beam of light  112  of the associated subpupil modulator  30 ,  30 . 4  is scanned so as to form—in the region  122  of the curved light-redirecting surface  110 —an effective light source  124  and associated modulated subpupil  32 ′ that spans the associated Active Subpupil Region (ASR)  72 ; and a remaining portion of the curved light-redirecting surface  110  is not illuminated, so as to present the image  16  to the eye  20  via a single exit subpupil  32  that fills the associated Active Subpupil Region (ASR)  72  that is aligned with, but smaller than, the eye pupil  38 , as illustrated in  FIG.  41   , and thereby also provides a benefit from a substantial reduction in electrical power consumption compared with that required by the first aspect near-eye display system  10 ,  10 . 1  to power the entire flat-panel two-dimensional image-display array  52  of light-emitting image-display pixels  54 , and, to a lesser extent, compared with that of the first- and second-aspect subpupil modulation schemes  70 ,  70 . 1 ,  70 . 2 . Referring to  FIGS.  42  and  43   , for the eye  22  of the user  22  rotated up and to the left as illustrated in  FIG.  43   , and as a result, a detection by the eye-tracking subsystem  42  of an elliptically-shaped eye pupil  38  located up and to the left of the associated optical axis  36 , in accordance with the third-aspect subpupil modulation scheme  70 ,  70 . 3 , the associated Active Subpupil Region (ASR)  72  determined by the subpupil modulation controller  50  is located—for example, centered—within the offset eye pupil  38 , wherein, as illustrated in  FIG.  42   , the modulated scanned beam of light  112  of the associated subpupil modulator  30 ,  30 . 4  is scanned so as to form—in the region  122  of the curved light-redirecting surface  110 —an effective light source  124  and associated modulated subpupil  32 ′ that spans the Active Subpupil Region (ASR)  72 ; wherein a remaining portion of the curved light-redirecting surface  110  is not illuminated, so as to present the image  16  to the eye  20  via a single exit subpupil  32  that fills the associated Active Subpupil Region (ASR)  72  that is aligned with, but smaller than, the eye pupil  38 , as illustrated in  FIG.  43   , and thereby also provides a benefit from a substantial reduction in electrical power consumption compared with that required by the first aspect near-eye display system  10 ,  10 . 1  to power the entire flat-panel two-dimensional image-display array  52  of light-emitting image-display pixels  54 , and, to a lesser extent, compared with that of the first- and second-aspect subpupil modulation schemes  70 ,  70 . 1 ,  70 . 2 . 
     Referring to  FIGS.  44 - 46   , in accordance with a second embodiment  14 . 2 ″, the second-aspect optical subsystem  14 ,  14 . 2 ″ of each of the second-aspect  10 . 2 ,  10 . 2 ′, third-aspect  10 . 3 ,  10 . 3 ′ and fourth-aspect  10 . 4 ,  10 . 4 ′ near-eye display systems  10 , respectively, may be alternatively embodied with a free-form-surface/prism lens  56 . 2 , L 2 ,  128  providing for the associated second dioptric-power optical element  56 ,  56 . 2 , L 2 . For example, free-form-surface/prism lenses are described the following technical papers, which are incorporated herein by reference in their entirety: Dewen CHENG, Yongian WANG, Hong HUA and M. M. TALHA, “Design of an optical see-trough head-mounted display with a low f-number and large field of view using a freeform prism”, APPLIED OPTICS, Optical Society of America, Vol. 48, No. 14, 10 May 2009, pp. 2655-2668; and Hong HUA, “Sunglass-like displays become a reality with free-form optical technology”, 20 Aug. 2012, SPIE Digital Library, 2021, Internet download from: https://spie.org/news/4375-sunglass-like-displays-become-a-reality-with-free-form-optical-technology?SSO=1. 
     More particularly, referring to  FIG.  44   , a second embodiment  10 . 2 ″ of a second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ″ incorporates the same second-aspect image generator  12 ,  12 . 2  as described hereinabove and illustrated in  FIG.  17   , which provides for generating a corresponding associated beam  64  of light  16 ′ for each associated modulated subpupil  32 ′. Referring to  FIG.  45   , a second embodiment  10 . 3 ″ of a third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ″ incorporates the same third-aspect image generator  12 ,  12 . 3  as described hereinabove and illustrated in  FIG.  19   , which also provides for generating a corresponding associated beam  64  of light  16 ′ for each associated modulated subpupil  32 ′. Referring to  FIG.  46   , a second embodiment  10 . 4 ″ of a fourth-aspect near-eye display system  10 ,  10 . 4 ,  10 . 4 ″ incorporates the same fourth-aspect image generator  12 ,  12 . 4  as described hereinabove and illustrated in  FIG.  32   , which also provides for generating a corresponding associated beam  64  of light  16 ′ for each associated modulated subpupil  32 ′. For each of the embodiments illustrated in  FIGS.  44 - 46   , and for each associated modulated subpupil  32 ′, the corresponding associated beam  64  of light  16 ′ enters a free-form refractive first surface  128 . 1  of the associated free-form-surface/prism lens  56 . 2 , L 2 ,  128 , then reflects from a free-form second surface  128 . 2  due to total internal reflection, then reflects from a free-form third surface  128 . 3  with a reflective coating, and finally exits the free-form-surface/prism lens  56 . 2 , L 2 ,  128  through the free-form second surface  128 . 2  into the exit pupil  18  of the associated optical subsystem  14 ,  14 . 2 ″ for viewing of the associated virtual image  16 ′″ by the eye  20 . Otherwise, each of the second-aspect  10 . 2 , third-aspect  10 . 3  and fourth-aspect  10 . 4  near-eye display systems function as described hereinabove in conjunction with  FIGS.  16 - 17 ,  18 - 19  and  31 - 32   , respectively. 
     In one set of embodiments, the infrared illuminator  44  and the infrared-responsive camera  46  of the eye-tracking subsystem  42  are located proximate to the rear focal plane  62  of the second lens  56 . 2 ′, L 2  of the first aspect near-eye display system  10 ,  10 . 1 , and proximate to the same plane as the flat-panel two-dimensional image-display modulation array  94  of the second  10 . 2 , third  10 . 3  and fourth  10 . 4  aspect near-eye display systems  10 . 
     Generally, the subpupil surface  84 ,  84 ′,  84 ″ and accordingly, the associated surface  18 ″ of the exit pupil  18 , are located sufficiently close to, supra, the eye pupil  38  so that an activated exit subpupil  32  can pass optical rays of the light  16 ′ of the image  16  into the eye pupil  38  so as to provide for viewing the entire image  16 . The near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 4  provides for viewing the image  16  at a comfortable distance so that the associated virtual image  16 ′″ appears to the either corrected (e.g. by eyeglasses or contact lenses) or uncorrected vision of the user  22  to be located at a distance from the user  22  of between 2 meters and an infinity. 
     Each exit subpupil  32  is an image of its respective modulation element  90  formed by the associated components of the associated optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″. A simple-single-lens optical imaging system typically forms an inverted image of the associated object. The first-aspect optical subsystem  14 ,  14 . 1  effectively acts as two simple-single-lens optical imaging systems in tandem that provide for imaging the flat-panel two-dimensional image-display array  52 , wherein a first of the two forms an intermediate, inverted image of the plane where the infrared illuminator  44  and the infrared-responsive camera  46  of the eye-tracking subsystem  42  are located, and the second of the two provides a virtual image  16 ′″ of that intermediate image, whereas the second-aspect optical subsystem  14 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″ instead directly forms the virtual image of the virtual image  16 ′ of the flat-panel two-dimensional image-display modulation array  94 . Accordingly, the resulting virtual images  16 ′″ of the first aspect  14 . 1  and second aspect  14 . 2 ,  14 . 2 ′,  14 . 2 ″ optical subsystems  14  are relatively inverted with respect to one another, which is accommodated by orienting the image  16  on the associated flat-panel two-dimensional image-display array  52  or flat-panel two-dimensional image-display modulation array  94  so that the image  16  appears to appear correctly oriented to the user  22 . 
     When incorporated as the second dioptric-power optical element  56 ,  56 . 2 , L 2  of a near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 4 , the free-form-surface/prism lens  56 . 2 , L 2 ,  128  can provide for relatively lower cost, weight and design volume thereof so as to provide for a relatively more compact near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 4 , which can also be configured to combine the imagery from an associated flat-panel two-dimensional image-display modulation array  94  with that from the real environment of the user  22 . 
     Referring to  FIG.  47   , a third embodiment  10 . 3 ′″ of a third aspect of a near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″ incorporating a third embodiment  14 . 2 ′″ of the second-aspect optical subsystem  14 ,  14 . 2 ′, is similar to the first-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′, supra, except that the second convergent magnifier lens  56 . 2 ′, L 2  is replaced with a Fresnel magnifier lens  130 , and the conditioner lens  102 ,  102 ′, L 1  is replaced with a Fresnel conditioner lens  132 , wherein each of the Fresnel magnifier  130  and conditioner  132  lenses incorporates at least one Fresnel surface  134 , the latter of which, for example, incorporates Fresnel structure  134 ′ incorporating a plurality of annular refractive segments, each incorporating a surface curvature similar to that of a conventional lens, but stepped relative to the adjacent segment so as to reduce the overall thickness thereof to being that of the thickest refractive segment, resulting in a corresponding relatively-thin, macroscopically-flat structure that is relatively-lighter weight than a corresponding conventional lens, and that is relatively easier to package. If the Fresnel magnifier  130  and conditioner  132  lenses were illuminated over the entirety of their surfaces—some of which light is intended to enter the eye pupil  38 , the remainder of which would otherwise illuminate the face of the user  22 —the Fresnel surfaces  134  thereof would tends to scatter a substantial amount of light from the discontinuities in the associated Fresnel structures  134 ′, some of which scattered light would ultimately enter the eye pupil  38  of the user  22  to cause a noticeable decrease in perceived image contrast. In view of the source of this scattered light including both light  16 ′ through the associated optical subsystem  14  that is intended to reach the eye pupil  38  as well as light  16 ′ that would unnecessarily reach other areas of the user&#39;s face, the use of modulated subpupils  32 ′, supra, provides for reducing the amount of otherwise unnecessary light  16 ′, so as to therefore provide for improving the perceived image contrast relative to that which would result from a fully illuminated Fresnel magnifier  130  and conditioner  132  lenses. 
     The third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″ illustrated in  FIG.  47    further incorporates two flat fold mirrors  136 —i.e. upper  136 . 1  and lower  136 . 2  fold mirrors  136 , for example, each at a 45 degree angle relative to the optical axis  36  aligned with the eye  20  of the user  22 —that provide for folding the associated light path between the subpupil modulator  30 ,  30 . 3  and the Fresnel magnifier lens  130 , so as to provide for a relatively-more compact physical assembly. It should be understood that any of the first- 10 . 1 , second— 10 . 2 , or third— 10 . 3  aspect near-eye display systems  10 , supra, could incorporate one or more fold mirrors  136 ,  136 . 1 ,  136 . 2  so as to provide for a relatively-more compact physical assembly thereof, for which one or both of the upper  136 . 1  and lower  136 . 2  fold mirrors  136  incorporated in the third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″ are otherwise optional. 
     Regardless of the particular aspect  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4  of the near-eye display system  10 ,  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4 , for purposes of determining the prescriptions of the underlying dioptric-power optical elements  56 ,  56 . 1 ,  56 . 2 ,  56 . 3 , the action of the associated optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′ may be decomposed into: 
     a) the generation of the virtual image  16 ′″—as viewable by the user  22 —of either i) the flat-panel two-dimensional image-display array  52  of the first aspect near-eye display system  10 ,  10 . 1  by the first  56 . 1 ′, L 1 , second  56 . 2 ′, L 2 , and third  56 . 1 ′, L 3  convergent magnifier lenses thereof, or ii) the flat-panel two-dimensional image-display modulation array  94  by the second convergent magnifier lens  56 . 2 ′, L 2  of the second-  10 . 2 , third- 10 . 3  or fourth-  10 . 4  aspect near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 4 ; and 
     b) the generation of the exit-pupil image  18 ′—i.e. a real image—of either i) the subpupil modulator  30 ,  30 . 1  by the second  56 . 2 ′, L 2  and third  56 . 3 ′, L 3  convergent magnifier lenses of the first aspect near-eye display system  10 ,  10 . 1 , or ii) the subpupil modulator  30 ,  30 . 2 ,  30 . 3 ,  30 . 4  by the conditioner lens  102 ,  102 ′, L 1  in cooperation with the of the second convergent magnifier lens  56 . 2 ′, L 2  of the second-  10 . 2 , third- 10 . 3  or fourth- 10 . 4  aspect near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 4 . 
     More particularly, in respect of the second-  10 . 2 , third- 10 . 3  or fourth-  10 . 4  aspect near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 4 , in accordance with one method, the prescription of the associated second convergent magnifier lens  56 . 2 ′, L 2  is first independently determined in the context of a hypothetical embodiment  10 . 2 ′″ of a second-aspect near-eye display system  10 . 2 ,  10 . 2 ′″ illustrated in  FIG.  48    in accordance with a magnifier-lens prescription design process  4900  illustrated in  FIG.  49   , and then the prescription of the associated the associated conditioner lens  102 ,  102 ′, L 1  is determined in the context of the second-  10 . 2 , third- 10 . 3  or fourth-  10 . 4  aspect near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 4 , in accordance with a conditioner-lens prescription design process  5000  illustrated in  FIG.  50   , with the conditioner lens  102 ,  102 ′, L 1  in cooperation with the second convergent magnifier lens  56 . 2 ′, L 2  prescribed by the magnifier-lens prescription design process  4900 , supra. 
     More particularly, referring to  FIG.  48   , for purposes of illustration—but otherwise not limiting to a particular aspect of the near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 4 —the hypothetical embodiment  10 . 2 ′ of the second-aspect near-eye display system  10 . 2 ,  10 . 2 ′″ comprises a flat-panel two-dimensional image-display modulation array  94  illustrated in cooperation with a Fresnel magnifier lens  56 . 2 , L 2 ,  130 . The flat-panel two-dimensional image-display modulation array  94  is illuminated by a flat-panel two-dimensional light-source array  98  (not illustrated), wherein in  FIG.  48   , six locations of a source image  16  on the flat-panel two-dimensional image-display modulation array  94  are shown, with each being illuminated from three different directions, resulting in three light rays emanating from each of the six locations. Light  16 ′ from the flat-panel two-dimensional light-source array  98  propagates through the Fresnel magnifier lens  56 . 2 , L 2 ,  130  and onto an associated planar exit pupil  18  at three corresponding locations that are responsive to the direction of the corresponding light rays from the corresponding six locations on the flat-panel two-dimensional image-display modulation array  94 . Proximate surfaces of the Fresnel magnifier lens  56 . 2 , L 2 ,  130  are located at distances D P  from the exit pupil  18  and D D  from the flat-panel two-dimensional image-display modulation array  94 , respectively, with the Fresnel magnifier lens  56 . 2 , L 2 ,  130  located therebetween. Accordingly, the three light rays from each of six locations on the flat-panel two-dimensional image-display modulation array  94  are associated with a corresponding six light rays at each of three locations in the exit pupil  18  associated with a corresponding exit-pupil image  18 ′, the latter of which is in turn associated with a virtual image  16 ′″ of the flat-panel two-dimensional image-display modulation array  94  located at a distance of D I  from the exit pupil  18 , responsive to the location of the Fresnel magnifier lens  56 . 2 , L 2 ,  130 , i.e. responsive to distances D P  and D D , and to the focal length of the Fresnel magnifier lens  56 . 2 , L 2 ,  130 . 
     Notwithstanding that in actuality, light  16 ′ associated with the virtual image  16 ′″ propagates from the flat-panel two-dimensional image-display modulation array  94  (that displays an associate source image  16 ) to the exit pupil  18 , the magnifier-lens prescription design process  4900  instead follows the light  16 ′ in reverse from the virtual image  16 ′″ to the exit pupil  18 , then through the Fresnel magnifier lens  56 . 2 , L 2 ,  130  to the flat-panel two-dimensional image-display modulation array  94 , thereby effectively treating the virtual image  16 ′″ as a design object  138  being imaged by the hypothetical embodiment  10 . 2 ′″ of the second-aspect near-eye display system  10 . 2 ,  10 . 2 ′″, and effectively treating the associated resulting light distribution at the flat-panel two-dimensional image-display modulation array  94  as the design image  140  of that design object  138 . In optical design, an object and its image are conjugates of each other, supporting a design option of selecting either as the “object” in the associated a design exercise. By analyzing the propagation of light in reverse from that which would occur in the actual second-aspect near-eye display system  10 . 2 ,  10 . 2 ′″, the field of view and the size and location of the exit pupil  18  can be readily established as fixed parameters in cooperation with the virtual image  16 ′″ being treated as the design object  138 , with the operational exit pupil  18  therefore being treated instead as a design entrance pupil  141 , which provides for a relatively-more efficient prescription design process than if the locations of the design object  138  and the design image  140  were reversed so as to be in correspondence with the causality of the actual second-aspect near-eye display system  10 . 2 ,  10 . 2 ″. 
     More particularly, referring to  FIG.  49   , in accordance with one set of embodiments, and in the context of the hypothetical-embodiment second-aspect near-eye display system  10 . 2 ,  10 . 2 ′″, the magnifier-lens prescription design process  4900  commences in step ( 4902 ) with the definition of the following parameters of the hypothetical-embodiment second-aspect near-eye display system  10 . 2 ,  10 . 2 ′″: 1) the size and shape of the planar exit pupil  18 , i.e. so as to be sufficient to overlay a range of positions of the eye pupil  38  for a range of users  22 ; 2) the horizontal field-of-view angle subtended in a horizontal direction at the exit pupil  18  by the range of light rays associated with the virtual image  16 ′″; 3) the vertical field-of-view angle subtended in a vertical direction at the exit pupil  18  by the range of light rays associated with the virtual image  16 ′″; 4) the distance D P  between the exit pupil  18  and a proximate surface of the Fresnel magnifier lens  56 . 2 , L 2 ,  130 ; 5) the distance D D  between the Fresnel magnifier lens  56 . 2 , L 2 ,  130  and the flat-panel two-dimensional image-display modulation array  94 ; 6) the distance D I  from the exit pupil  18  to the virtual image  16 ′″ of the flat-panel two-dimensional image-display modulation array  94 ; and 7) the thickness t of the Fresnel magnifier lens  56 . 2 , L 2 ,  130 . For example, in one embodiment, a 20 millimeter diameter circular exit pupil  18  (the design entrance pupil) is defined, through which pass the optical rays from a rectangular virtual image  16 ′″ (the design object  138 ) positioned 2 meters (D I ) forward of the exit pupil  18 , the center of which virtual image  16 ′″ is aligned with the center of the exit pupil  18  along an associated optical axis  36 , for which the virtual image  16 ′″ subtends a 76 degree horizontal by 46 degree vertical field of view with respect to the exit pupil  18  and the associated optical axis  36 , wherein the combination of the size of the exit pupil  18  and the associated field of view provide for a favorable viewing experience for the user  22 . A 1.5 millimeter thick (t) Fresnel magnifier lens  56 . 2 , L 2 ,  130  comprising a generally flat optical acrylic substrate is positioned 22 millimeters forward (D P ) of the exit pupil  18  so as to provide sufficient space for corrective glasses, and a flat flat-panel two-dimensional image-display modulation array  94  (the design image plane) is defined an additional 32 millimeters (D D ) beyond the Fresnel magnifier lens  56 . 2 , L 2 ,  130  so as to provide for a relatively compact assembly of an associated third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″. 
     The magnifier-lens prescription design process  4900  provides for determining the prescription of the Fresnel magnifier lens  56 . 2 , L 2 ,  130  that will provide for forming an optimal design image  140  of the virtual image  16 ′″ at the location of the flat-panel two-dimensional image-display modulation array  94  based upon the assumption that the virtual image  16 ′″ of the flat-panel two-dimensional image-display modulation array  94  formed by the Fresnel magnifier lens  56 . 2 , L 2 ,  130  will be similarly optimized, wherein as used herein, the term optimized is associated with a configuration associated with an extremum (e.g. minimum) of an associated merit, or objective, function. Accordingly, following the definition in step ( 4902 ) of the parameters of the hypothetical-embodiment second-aspect near-eye display system  10 . 2 ,  10 . 2 ″, in step ( 4904 ), the operation of the hypothetical-embodiment second-aspect near-eye display system  10 . 2 ,  10 . 2 ′″ is simulated using optical design software, for example, Zemax optical design software, to as to provide for optimizing—in step ( 4906 )—the optical parameters associated with one or both surfaces of the Fresnel magnifier lens  56 . 2 , L 2 ,  130 , for example, under the constraint of limiting the one or both surfaces to vary only in second and higher order aspheric parameters (with the general radius and conic parameters being of minor concern), for example, with the optimization providing for minimizing an optical design merit function given by the two-dimensional peak-to-valley spot size of the design image  140  formed at multiple locations at the flat-panel two-dimensional image-display modulation array  94 , generally as a weighted sum of two-dimensional peak-to-valley spot sizes from various different locations. In accordance with one set of embodiments, each of the different locations is weighted equally. For example, during the optical design simulation, a light distribution at the planar subpupil surface  84 ,  84 ′ of the exit pupil  18  is back-propagated through the Fresnel magnifier lens  56 . 2 , L 2 ,  130  being optimized, and then onto the associated planar surface of the flat-panel two-dimensional image-display modulation array  94  so as to form a corresponding design image  140 , from which the associated optical design merit function is evaluated. In accordance with one set of embodiments, during the optimization process, both distortion and lateral chromatic aberration are ignored in favor of a subsequent reliance upon electronic predistortion and electronic chromatic precorrection of the image  16  to be displayed on the flat-panel two-dimensional image-display modulation array  94  of the associated near-eye display system  10 ,  10 . 2 ,  10 . 2 ′,  10 . 2 ″,  10 . 3 ,  10 . 3 ′,  10 . 3 ″,  10 . 3 ′″,  10 . 4 ,  10 . 4 ′,  10 . 4 ″. 
     Accordingly, the simulated propagation of optical rays from the design object  138  (i.e. the virtual image  16 ′″) through the exit pupil  18  acting as an entrance pupil for the simulation, then through the Fresnel magnifier lens  56 . 2 , L 2 ,  130 , forms a simulated design image  140  at the location of the flat-panel two-dimensional image-display modulation array  94 , with rays generally converging appropriately at multiple representative points as a design image  140  of the rectangular design object  138 . As a result of the optimization, the design image  140  at the location of the flat-panel two-dimensional image-display modulation array  94  subtends a diagonal measurement of approximately 39 millimeters. Accordingly, the use of a flat-panel two-dimensional image-display modulation array  94  of that diagonal measurement at the distance D D  from the designed Fresnel magnifier lens  56 . 2 , L 2 ,  130  in the hypothetical-embodiment second-aspect near-eye display system  10 . 2 ,  10 . 2 ′″ will provide for a virtual image  16 ′″ having a diagonal field of view similar to the diagonal field of view associated with the 76 degree horizontal by 46 degree vertical field of view design parameters, subject to the impact of geometric distortion. 
     In respect of the determination, or optimization, of the prescription of the first  56 . 1 ′, L 1 , second  56 . 2 ′, L 2 , and third  56 . 1 ′, L 3  convergent magnifier lenses of the first-aspect near-eye display system  10 ,  10 . 1 , the magnifier-lens prescription design process  4900  can be simultaneously applied to all three convergent magnifier lenses  56 . 1 ′, L 1 ;  56 . 2 ′, L 2 ; third  56 . 3 ′, L 3  that act collectively as a magnifier lens of the first-aspect near-eye display system  10 ,  10 . 1 , by searching with respect to a composite of the associated parameters from all three convergent magnifier lenses  56 . 1 ′, L 1 ;  56 . 2 ′, L 2 ; third  56 . 3 ′, L 3 , in view of the associated modulation surface  92 ,  92 ′ being located within the associated first-aspect optical subsystem  14 ,  14 . 1  at an associated aperture stop  28 . 
     Accordingly, the magnifier-lens prescription design process  4900  provides for using common optical design approaches to design/prescribe an optimized Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  130 ′ that will provide for forming a virtual image  16 ′″—having a relatively large field of view—of a relatively small flat-panel two-dimensional image-display modulation array  94  through a relatively-large exit pupil  18 , subject to the availability of sufficient light  16 ′ emanating from such flat-panel two-dimensional image-display modulation array  94  that is sufficient to fully illuminate the exit pupil  18 . 
     Referring to  FIGS.  47  and  50   , the conditioner-lens prescription design process  5000  provides for determining the prescription of the Fresnel conditioner lens  56 . 1 , L 1 ,  132  of the associated third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ′″ incorporating the optimized Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  130 ′ that resulted from the magnifier-lens prescription design process  4900 . More particularly, in step ( 5002 ), and referring again to  FIG.  47   , the associated third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′ is first configured in accordance with the parameters of the hypothetical-embodiment second-aspect near-eye display system  10 . 2 ,  10 . 2 ′ that were defined during, or determined by, the magnifier-lens prescription design process  4900 , supra. Furthermore, in step ( 5004 ), additional parameters peculiar to the third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ′, including 1) the curvature and extent of the surface  18 ″ of the exit pupil  18  and the associated concave-curved subpupil surface  84 ,  84 ″ thereat; 2) the distance D C  (illustrated in  FIG.  19   ) between the flat-panel two-dimensional image-display modulation array  94  and the Fresnel conditioner lens  56 . 1 , L 1 ,  132 ; 3) and the distance D S  (illustrated in  FIG.  19   ) between the Fresnel conditioner lens  56 . 1 , L 1 ,  132  and the curved modulation surface  92 ,  92 ″ of the curved two-dimensional light-source array  106  of the associated subpupil modulator  30 ,  30 . 3 ; and 4) the thickness t of the Fresnel conditioner lens  56 . 1 , L 1 ,  132 . For example, further to the embodiment used to illustrate the magnifier-lens prescription design process  4900 , supra, the 20 millimeter diameter of the perimeter of exit pupil  18  defined in step ( 4902 ) forms the perimeter of a concave geometric surface construct  82 ,  82 ′ that bounds a concave-curved subpupil surface  84 ,  84 ″ of 12.5 millimeter radius representing a generalized radius of the eyeball of the human eye  20 . Furthermore, a 1.5 millimeter thick Fresnel conditioner lens  132  is positioned 8 millimeters (D C ) beyond the flat-panel two-dimensional image-display modulation array  94 , i.e. by a distance that is sufficient to preclude visibility of the associated Fresnel structure or structures  134 ′ of the Fresnel conditioner lens  56 . 1 , L 1 ,  132  as viewed through the optimized Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  130 ′, and sufficient to preclude possible moiré effects between the Fresnel structure or structures  134 ′ of the Fresnel conditioner lens  56 . 1 , L 1 ,  132  and the flat-panel two-dimensional image-display modulation array  94 . Yet further, the curved modulation surface  92 ,  92 ″ of a curved two-dimensional light-source array  106  is located 42 millimeters (D S ) beyond the Fresnel conditioner lens  56 . 1 , L 1 ,  132 . 
     Notwithstanding that in actuality light  16 ′ associated with the exit-pupil image  18 ′ propagates from the curved two-dimensional light-source array  106  to the exit pupil  18 , the conditioner-lens prescription design process  5000  instead follows the light  16 ′ in reverse from the surface  18 ″ of the exit pupil  18 , then through the optimized Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  130 ′, then through the flat-panel two-dimensional image-display modulation array  94  acting as a design aperture stop  142 , then through the Fresnel conditioner lens  56 . 1 , L 1 ,  132 , and finally imaged thereby onto the curved modulation surface  92 ,  92 ″ of the curved two-dimensional light-source array  106  of the associated subpupil modulator  30 ,  30 . 3 , thereby effectively treating the concave-curved subpupil surface  84 ,  84 ″ as a design object surface  144  being imaged by the third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″, with the associated resulting light distribution being imaged at the curved modulation surface  92 ,  92 ″ that is effectively treated as the associated design image surface  146  of that design object surface  144 , wherein the flat-panel two-dimensional image-display modulation array  94  also functions as an associated aperture stop  28  of the associated third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ′″ because any subpupil location will pass light  16 ′ from all locations on the flat-panel two-dimensional image-display modulation array  94 . Accordingly, based upon the results of the magnifier-lens prescription design process  4900 , for this example, the diameter of the aperture stop  28  is approximately 39 millimeters, which corresponds to the diagonal measurement, supra, of the flat-panel two-dimensional image-display modulation array  94 . 
     For example,  FIG.  47    illustrates ray tracings of three sets of light rays emanating from three different locations along the design object surface  144  (i.e. the concave-curved subpupil surface  84 ,  84 ″)—ranging from 0 to 10 millimeters in the vertical direction—through the third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ′″. Although the full 10 millimeter range of the vertical subpupil surface is likely unnecessary to view the entire image because—per the design parameters established in step ( 4902 )—the vertical field of view is smaller than the horizontal field of view, the full vertical extent has been illustrated in order to illustrate the prospective propagation of peripheral light rays through the third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ″. 
     The third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″ incorporating the optimized Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  130 ′ generates a virtual image  16 ′″ of the flat-panel two-dimensional image-display modulation array  94  through the exit pupil  18  of the associated third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ′″ of the same image quality as achieved by the magnifier-lens prescription design process  4900 . 
     The conditioner-lens prescription design process  5000  provides for determining both the prescription of an optimized Fresnel conditioner lens  56 . 1 , L 1 ,  132 ′ and the shape of the associated design image surface  146  (the curved modulation surface  92 ,  92 ″) that, in cooperation with the optimized Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  130 ′, will provide for forming an optimal real design image  146 ′ of the design object surface  144  (the concave-curved subpupil surface  84 ,  84 ″) at the design image surface  146  (the curved modulation surface  92 ,  92 ″), based upon the assumption that the exit-pupil image  18 ′—at the design object surface  144  (the concave-curved subpupil surface  84 ,  84 ″)—of the design image surface  146  (the curved modulation surface  92 ,  92 ″) by the optimized Fresnel conditioner lens  56 . 1 , L 1 ,  132 ′, in cooperation with the optimized Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  130 ′, will be similarly optimized, wherein as used herein, the term optimized is associated with a configuration associated with an extremum (e.g. minimum) of an associated merit, or objective, function, e.g. peak-to-valley spot size. Accordingly, following the definition in steps ( 5002 ) and ( 5004 ) of the parameters of the third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ″, in step ( 5006 ), the operation of the third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ′″ is simulated using optical design software, for example, Zemax optical design software, so as to provide for optimizing—in step ( 5008 )—higher order Fresnel prescriptions of both sides of the Fresnel conditioner lens  132 , for example, under the constraint of limiting the one or both surfaces to vary only in second and higher order aspheric parameters (with the general radius and conic parameters being of minor concern), and to provide for optimizing—also in step ( 5008 )—the radius and conic constant of the curved modulation surface  92 ,  92 ″, using an optimization merit function designed to minimize the spot size of the images formed on the curved modulation surface  92 ,  92 ″ from a variety of locations on the design object surface  144  (the concave-curved subpupil surface  84 ,  84 ″), for example, with the optimization providing for minimizing an optical design merit function given by the two-dimensional peak-to-valley spot size of the design image  146 ′ formed at multiple locations at the curved modulation surface  92 ,  92 ″ of the curved two-dimensional light-source array  106 , generally as the weighted sum of the two-dimensional peak-to-valley spot sizes from the different locations. In accordance with one set of embodiments, each of the different locations is weighted equally. 
     For example, during the optical design simulation, a light distribution at the concave-curved subpupil surface  84 ,  84 ″ of the exit pupil  18  acting as the design object surface  144  is back-propagated through the optimized Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  130 ′, then through the flat-panel two-dimensional image-display modulation array  94  acting as the design aperture stop  142 , then through the Fresnel conditioner lens  56 . 1 , L 1 ,  132  being optimized, and then onto the curved modulation surface  92 ,  92 ″ of the curved two-dimensional light-source array  106  acting as the design image surface  146 , so as to form a corresponding design image  146 ′, from which the associated optical design merit function is evaluated. Although functioning like a collimator or condenser lens, the optimized Fresnel conditioner lens  56 . 1 , L 1 ,  132 ′ will not necessarily strictly conform to such classical configuration, but instead is configured to best support an imaging relationship between the curved modulation surface  92 ,  92 ″ and the concave-curved subpupil surface  84 ,  84 ″ of the third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ′″, while providing for fully illuminating the associated flat-panel two-dimensional image-display modulation array  94 . 
     The results of the optical design simulation of the conditioner-lens prescription design process  5000  indicate that the central image location provided for a relatively better imaging relationship between the curved modulation surface  92 ,  92 ″ and the concave-curved subpupil surface  84 ,  84 ″ than did locations that were relatively peripheral thereto. In the context of the third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″, this relatively-higher image quality at the relatively-central locations may result in a sufficiently-high depth-of-field and image clarity so that the associated Fresnel structure or structures  134 ′ becomes visible to the user  22 . If so, this can be mitigated by providing for a relatively-lower image quality at relatively-central locations while relatively-more-highly weighting relatively-peripheral locations that are inherently more blurry, relative to the weighting of relatively-central locations. More generally, relatively weighting of various locations is based upon the particular intended imaging performance of the associated near-eye display system  10 ,  10 . 2 ,  10 . 2 ′,  10 . 2 ″,  10 . 3 ,  10 . 3 ′,  10 . 3 ″,  10 . 3 ′″,  10 . 4 ,  10 . 4 ′,  10 . 4 ″ being optimized. 
     When optimizing any optical system one can allow any parameter of that system to vary as a parameter to be optimized. For example, for optical elements for which thickness is not constrained to a fixed value (e.g. other than Fresnel lenses having predetermined thicknesses) a thickness of an optical element at any point on the element can be constrained so as to either, or both, not exceed a maximum value nor be less than a minimum value, while providing the associated optimization process with the flexibility to vary the element thickness within that range. The prescription of a conventional (i.e. non-Fresnel) optical element is actually a variation in thickness as a function of distance from an optical axis. Accordingly, it is common practice to provide that flexibility to the optimization process while constraining the thickness to be within reasonable limits, for example, greater than a predetermined minimum positive thickness, and less than a maximum thickness associated with a lens that would otherwise either be non-manufacturable or excessively heavy or bulky. These parameters with associated limitations are included in the optimization process and associated constraints, along with the general image quality functionality, for example, the spot size calculations that are included in the associated merit function. In practice, a “centroid” image ray is computed for each field (object) location and then the merit function is evaluated for a series of test field locations in proximity to that centroid, wherein how many and how distributed are accordance with one or more parameters of the optical design software. The optical design software then calculates the distance between each test ray arrival location at the image surface and the centroid location to build up a myriad of samples, for example, with ultimately thousands of rays being traced from the various locations. 
     Referring again to  FIG.  47   , the shape of the optimized curved modulation surface  92 ,  92 ′″ resulting from the conditioner-lens prescription design process  5000  is generally a paraboloid. Despite optimization, optical rays from subpupil point locations on the concave-curved subpupil surface  84 ,  84 ″ do not fully converge at corresponding point locations on the corresponding associated optimized curved modulation surface  92 ,  92 ′″, with decreasing quality toward the periphery thereof. As a consequence, any controllable light source  97  placed relatively more peripherally from the optical axis  36  on the curved modulation surface  92 ,  92 ″ will not form an ideal corresponding image as an exit subpupil  32  on the concave-curved subpupil surface  84 ,  84 ″. These imperfectly formed exit subpupils  32  would be accounted for in the design of the associated Active Subpupil Region (ASR)  72  of the resulting near-eye display system  10 ,  10 . 2 ,  10 . 2 ′,  10 . 2 ″,  10 . 3 ,  10 . 3 ′,  10 . 3 ″,  10 . 3 ′,  10 . 4 ,  10 . 4 ′,  10 . 4 ″ because in some cases they might be larger than the eye pupil  38 , or they might overlap other exit subpupils  32 . However, as is typical with on-axis optical systems generally, the relatively central region of the third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ′″ provides better imaging forming properties than relatively peripheral regions. Accordingly, the Active Subpupil Region (ASR)  72  can be designed to be relatively small in the central region re of the concave-curved subpupil surface  84 ,  84 ″ proximate to the optical axis  36 , and because this is the region that is primarily occupied by the eye pupil  38  of the user  22  when viewing the virtual image  16 ′, the ability to improve spatial clarity by providing an Active Subpupil Region (ASR)  72  smaller than the eye pupil  38  of the user  22  even in this relatively smaller region can be beneficial. 
     Although generally a Fresnel surface  134  may be applied to one or both of the opposing surfaces of the 1.5 millimeter thick Fresnel magnifier lens  130 , the results of the associated optimization processes—i.e. the value(s) of the associated merit function(s)—have been found to substantially better if a high order aspheric Fresnel surface  134  can be applied to both surfaces, rather than just to one, particularly if a relatively high magnification is desired, notwithstanding that two opposing Fresnel surfaces  134 —each with a corresponding Fresnel structure  134 ′, —will produce more scattered extraneous light  16   iv  than a would a single Fresnel surface  134 , because the use of modulated subpupils  32 ′ provides for reducing or minimizing scattered extraneous light  16   iv  that would otherwise be visible through the eye pupil  38 . 
     Alternatively, referring to  FIG.  51   , in accordance with one set of embodiments, the Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  148  may comprise a hybrid lens  148  comprising a conventional convex refractive surface  150  on a front side  148 . 1  thereof, and a Fresnel surface  134  on the rear side  148 . 2  thereof, wherein when incorporated in the third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″, the Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  148  is oriented with the front side  148 . 1  facing the exit pupil  18  so as to mitigate against scattering of extraneous light  16   iv  that would otherwise occur with a front-facing Fresnel surface  134  instead of the front-facing conventional convex refractive surface  150 . 
     In practice, the ideal profile of a Fresnel surface  134  of a Fresnel lens  130 ,  132  is determined through optical design as a continuous function based upon the propagation of rays that extend to the underlying planar surface of the associated Fresnel surface  134 , after which the manufacturer of the Fresnel lens  130 ,  132  would import that information, along with other parameters, into associated CNC diamond turning software to determine the corresponding associated actual groove structure profile of the Fresnel structure  134 ′. 
     The use of Fresnel lenses  130 ,  132  in the third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ′″ provides for a relatively compact, light-weight, wide field-of-view third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″ with a relatively-large exit pupil  18 , which together with the eye-tracking subsystem  42 , the subpupil modulation controller  50 , and the curved two-dimensional light-source array  106  arranged to conform to the optimized curved modulation surface  92 ,  92 ″, and the associated control thereof in accordance with an associated subpupil modulation scheme  70 ,  70 . 1 ,  70 . 2 ,  70 . 3 , supra, provides for a third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″ with relatively higher contrast and relatively-higher clarity of the relatively-central region of the image  16 , using substantially less illumination power than would a near-eye display system that did not otherwise use a controllable light source  97 . 
     The actual size of the exit subpupils  32  in a near-eye display system  10 ,  10 . 1 ,  10 . 2 ,  10 . 2 ′,  10 . 2 ″,  10 . 3 ,  10 . 3 ′,  10 . 3 ″,  10 . 3 ′″,  10 . 4 ,  10 . 4 ′,  10 . 4 ″ will depend upon a plurality of associated design factors and considerations. For example, an exit subpupil  32  made so small as to significantly increase the depth of field of the image through that exit subpupil  32  may reveal structures located relatively distally along the optical axis  36  from the flat-panel two-dimensional image-display modulation array  94 —such as the structures of the Fresnel magnifier lens  56 . 2 , L 2 ,  130  or the Fresnel conditioner lens  56 . 1 , L 1 ,  132 , —overlayed with the image  16 . To the other extreme, an exit subpupil  32  larger than the eye pupil  38  will not provide for the improvement in clarity of the image  16  through that exit subpupil  32  that would otherwise be possible. The actual size of an exit subpupil  32  may be further dependent on the imaging capabilities of the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′″ to form a proper image of the associated subpupil modulator  30 , i.e. either the flat-panel two-dimensional modulation array  58  or the associated controllable light source  97 . Indeed the associated light-modulating pixels  60 /light source elements  100  of the subpupil modulator  30  themselves will in practice each span a finite size, rather than being point pixel or source elements. Accordingly, while any reduction of light  16 ′ through the exit pupil  18  of the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′″ by deactivating at least some of an array of relatively smaller exit subpupils  32  will provide improvements in contrast and power usage, and the degree of such benefits, and the possibility of improved clarity, will be dependent on the actual implementation of the subpupil modulator  30 ,  30 . 1 ,  30 . 2 ,  20 . 3 ,  30 . 4 . 
     Each of the second-, third- and fourth-aspect near-eye display systems  10 ,  10 . 2 ,  10 . 3 ,  10 . 4  provide for using a subpupil modulator  30 ,  30 . 2 ,  30 . 3 ,  30 . 4  incorporating a controllable light source  97  that cooperates with an associated modulation surface  92  to provide for generating a plurality of exit subpupils  32  and an associated subpupil surface  84 , wherein the modulation  92  and subpupil  84  surfaces are images of each other as provided for by the associated optical subsystem  14 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′″, which also provides for the controllable light source  97  to illuminate the entirety of an associated flat-panel two-dimensional image-display modulation array  94  for each of the exit subpupils  32 . The associated conditioner lens  102 ,  102 ′, L 1  provides for gathering light  16 ′ from the relatively-distant (both with respect to along the optical axis  36  and transverse thereto) controllable light source  97  in order to provide illuminating the entirety of the associated flat-panel two-dimensional image-display modulation array  94  for each of the exit subpupils  32 . 
     Accordingly, the associated volume of space between the controllable light source  97  and the flat-panel two-dimensional image-display modulation array  94  that provides for this functionality can be considerable, and potentially limiting to the prospective compactness of the associated second-, third- or fourth-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′,  10 . 2 ″,  10 . 3 ,  10 . 3 ′,  10 . 3 ″,  10 . 4 ,  10 . 4 ′,  10 . 4 ″. 
     Referring to  FIGS.  52 - 53   , a waveguide projector  152 —modeled as a flat-panel two-dimensional image-display array  52  in cooperation with an ideal paraxial lens  154  located one focal-length F therefrom—provides for generating, per the model illustrated in  FIG.  53   , what would be a far-field light distribution  156  of light  16 ′ emanating from a flat-panel two-dimensional image-display array  52 , i.e. a plurality of sets of collimated rays, each ray of each set emanating from a corresponding light-emitting image-display pixel  54  effective point source of the flat-panel two-dimensional image-display array  52 , and propagating at an angle from the optical axis  36  that is responsive to the lateral offset of the corresponding associated light-emitting image-display pixel  54  point source. Accordingly, the far-field light distribution  156  provides a virtual image of the flat-panel two-dimensional image-display array  52  through the exit pupil  158  of the waveguide projector  152 . In one set of embodiments, the waveguide projector  152  comprises a conventional optical system placed in front of a flat panel of image-display pixels to project collimated light from those pixels as a virtual image through the exit pupil of that optical system, which light is thereafter directed or “coupled” into an optical waveguide where the light travels through multiple internal reflections until interacting with features within the waveguide which redirect or “decouple” the collimated light out of the waveguide into an expanded exit pupil  158 . If the associated exit pupil  158  can be made sufficiently large to fill a flat-panel two-dimensional image-display modulation array  94  of the second- or third-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′,  10 . 2 ″,  10 . 3 ,  10 . 3 ′,  10 . 3 ″,  10 . 3 ′″, then the light-emitting image-display pixels  54  of the waveguide projector  152  can act as a flat-panel two-dimensional light-source array  98  of a controllable light source  97  of an associated subpupil modulator  30 ,  30 . 2  of the second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′,  10 . 2 ″, with the light from each controllable light source  97  emerging substantially collimated as is typical of waveguide projectors  152 . For example, U.S. Pat. Nos. 10,732,415 and 10,627,565—each incorporated by reference in its entirety—disclose a substrate-guide optical device, and a waveguide display assembly, respectively, either of which could be used as a waveguide projector  152  in cooperation with a second-aspect optical subsystem  14 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′″ of a second- or third-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′,  10 . 2 ″,  10 . 3 ,  10 . 3 ′,  10 . 3 ″,  10 . 3 ′″ so as to provide for improving the compactness thereof, wherein, for application to a second-aspect near-eye display system  10 ,  10 . 2 ,  10 . 2 ′,  10 . 2 ″, the waveguide projector  152  would also supplant the conditioner lens  102 ,  102 ′, L 1 , and for application to a third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′,  10 . 3 ″, the waveguide projector  152  would be used in cooperation with the associated conditioner lens  102 ,  102 ′, L 1 , the latter of which would provide for conditioning the collimated light from the waveguide projector  152  so as to provide for generating—in cooperation with the associated convergent magnifier lens  56 . 2 ′,  130 ,  130 ′, L 2 —a concave-curved subpupil surface  84 ,  84 ″ at the exit pupil  18 , or an approximation thereto. 
     Referring to  FIGS.  54  and  55   , a first embodiment  10 . 5 ′ of a fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ′ is similar to the third-embodiment third-aspect near-eye display system  10 ,  10 . 3 ,  10 . 3 ′″, supra, except that the curved two-dimensional light-source array  106  and the upper fold mirror  136 . 1  are replaced with a waveguide projector  152  constituting an associated fifth aspect of a subpupil modulator  30 ,  30 . 5 . The waveguide projector  152  incorporates a controllable light source  97  that defines an array of modulated subpupils  32 ′, and in cooperation with an alternative Fresnel conditioner lens  56 . 1 , L 1 ,  132 ″ and the associated Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  148 , collectively constitute an associated third-aspect optical subsystem  14 ,  14 . 3 , wherein the combination of the waveguide projector  152 , Fresnel conditioner lens  56 . 1 , L 1 ,  132 , and flat-panel two-dimensional image-display modulation array  94  constitute a fifth-aspect image generator  12 ,  12 . 5 . The waveguide projector  152  is under control of the subpupil modulation controller  50 , responsive to the eye-tracking subsystem  42 . The first-embodiment fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ′ further illustrates incorporation of a hybrid Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  148  that is illustrated individually in  FIG.  51   , supra, which provides for reducing possible scattering from the associated Fresnel structure  134 ′ to occurrence from only the rear side  148 . 2 —facing away from the user  22 —of the hybrid lens  148  relative to a Fresnel magnifier lens  56 . 2 , L 2 ,  130  incorporating Fresnel surfaces  134  on both sides thereof. 
     When applying the conditioner-lens prescription design process  5000 , supra, to the Fresnel conditioner lens  56 . 1 , L 1 ,  132 , the resulting optimized alternative Fresnel conditioner lens  56 . 1 , L 1 ,  132 ′″ resulted in a subpupil surface  84 ,  84 ′ that was mildly convex—i.e. a convex subpupil surface  84 ,  84 ′″—relative to the eye  20  of the user  22 , rather than an ocularly-conforming concave-curved subpupil surface  84 ,  84 ″. 
     Notwithstanding that the waveguide projector  152  can produce well-focused exit subpupils  32  on the resulting convex subpupil surface  84 ,  84 ′″, those exit subpupils  32  form on the convex subpupil surface  84 ,  84 ″′ from which the associated concentrated light  16 ′ of the image  16  is poorly accessible to the eye pupil  38  over the entire range of normal rotation of the eye  20 , so that the associated first-embodiment fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ′ will effectively present relatively-larger exit subpupils  32  to the eye  20  at many associated rotational angles thereof. Accordingly, notwithstanding that the first-embodiment fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ′ can provide for reduced power usage by deactivating—at any given time—exit subpupils  32  that are not visible thereto, and can provide an exceptional imaging relationship between the flat-panel two-dimensional image-display modulation array  94  and the convex subpupil surface  84 ,  84 ″, the resulting imaging performance for the user  22  is relatively inferior to what would otherwise result with relatively smaller exit subpupils  32 . 
     Referring to  FIG.  56   , a second embodiment  10 . 5 ″ of a fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ″ is the same as to the first-embodiment fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ′, supra, except for further incorporating in an associated fourth-aspect optical subsystem  14 ,  14 . 4 , a varifocal lens  160  between the waveguide projector  152  and the Fresnel conditioner lens  56 . 1 , L 1 ,  132 ″, wherein the combination of the waveguide projector  152 , varifocal lens  160 , Fresnel conditioner lens  56 . 1 , L 1 ,  132 , and flat-panel two-dimensional image-display modulation array  94  constitute a sixth-aspect image generator  12 ,  12 . 6 . For example, U.S. Pat. No. 10,627,565, which is incorporated herein by reference in its entirety, discloses an electronic varifocal lens at the exit of the waveguide of a waveguide display so as to provide for changing the apparent distance of the virtual image exiting the waveguide in order to accommodate, inter alia, user preferences. The varifocal lens  160 —under control of the subpupil modulation controller  50  responsive to the eye-tracking subsystem  42 —provides for changing the distance between the subpupil surface  84 ,  84 ′″ and the optimized Fresnel magnifier lens  56 . 2 , L 2 ,  130 ,  130 ′. Under typical use of the second-embodiment fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ″, the distance between the eye  20  of the user  22  and the associated fourth-aspect optical subsystem  14 ,  14 . 4  is relatively fixed. Accordingly, the varifocal lens  160  can be used to position a single exit subpupil  32  or small cluster of exit subpupils  32 —for example, of the Active Subpupil Region (ASR)  72 , —at a controllable distance from the eye  20  of the user  22 , for example, so as to continuously position the Active Subpupil Region (ASR)  72  at the location of the eye pupil  38  of the user  22  responsive to the eye-tracking subsystem  42 , thereby effectively creating a dynamically changing subpupil surface  84  that effectively conforms to the eye pupil  38  regardless of the orientation thereof. If the second-embodiment fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ″ were to further provide for detecting the distance between the eye pupil  38  of the user  22  to the flat-panel two-dimensional image-display modulation array  94 , then the entire volumetric visual environment (VVE)  80  of the fourth-aspect optical subsystem  14 ,  14 . 4  can be accessed with a dynamically positioned exit subpupil  32  wherever the eye pupil  38  of the user  22  is positioned, so as to provide for a compact, lightweight and flexible near-eye display system that can provide for a relatively large field of view and a relatively high image quality, while using substantially less power than would otherwise be required to illuminate the entire exit pupil  18  of the associated optical subsystem. 
     Referring to  FIG.  57   , a third embodiment  10 . 5 ′″ of a fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ′″ is the same as the second aspect near-eye display system  10 ,  10 . 2 , supra, illustrated in  FIG.  16   , except that both the controllable light source  97  provided for by the flat-panel two-dimensional light-source array  98  of associated light-source elements  100 , and the associated conditioner lens  102 ,  102 ′, L 1 , are replaced with a waveguide projector  152  that ideally functions in accordance with the model illustrated in  FIG.  53   , supra, and which therefor provides for substantially the same functionality as the controllable light source  97  in cooperation with the conditioner lens  102 ,  102 ′, L 1  of the second aspect near-eye display system  10 ,  10 . 2 . Accordingly, each point source of light  16 ′ by an associated illumination pixel within the waveguide projector  152  provides for generating a corresponding beam  64  of light  16 ′ that propagates at an angle relative to the optical axis  36  that is responsive to the lateral offset relative to the optical axis  36  of the associated point source of light within the waveguide projector  152 , and which illuminates the entirety of the associated flat-panel two-dimensional image-display modulation array  94 —in accordance with an associated fifth-aspect image generator  12 ,  12 . 5 —which, in cooperation with an associated second dioptric-power optical element  56 ,  56 . 2 , L 2  acting as an associated magnifier lens  56 ,  56 . 2 , L 2  of an associated fifth-aspect optical subsystem  14 ,  14 . 5  provides for generating an associated virtual image  16 ′″ of the flat-panel two-dimensional image-display modulation array  94  for each exit subpupil  32  that is projected onto the associated planar subpupil surface  84 ,  84 ′ at the exit pupil  18 , as described herein above in respect of the second aspect near-eye display system  10 ,  10 . 2 . 
     The third-embodiment fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ′″ may optionally further include—in an associated sixth-aspect optical subsystem  14 ,  14 . 6 —a varifocal lens  160  located between the waveguide projector  152  and the flat-panel two-dimensional image-display modulation array  94 —of an associated sixth-aspect image generator  12 ,  12 . 6 —and under control of the associated eye-tracking subsystem  42 , so as to provide for controlling the axial location of the planar subpupil surface  84 ,  84 ′ to be substantially aligned with that of the eye pupil  38  of the user  22  for the exit subpupils  32  of the associated Active Subpupil Region (ASR)  72  being displayed. 
     Referring to  FIG.  58   , a fourth embodiment  10 . 5 ″″ of a fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ″″ is the same as the third-embodiment fifth-aspect near-eye display system  10 ,  10 . 5 ,  10 . 5 ′″, supra, illustrated in  FIG.  57   , except for optionally further incorporating—in an associated seventh-aspect optical subsystem  14 ,  14 . 7 —a conditioner lens  102 ,  102 ′, L 1  located between the waveguide projector  152  and the flat-panel two-dimensional image-display modulation array  94 , so as to provide for compensating for non-ideal, i.e. realistic, optical elements within the associated seventh-aspect optical subsystem  14 ,  14 . 7 , the latter of which incorporates at least the magnifier lens  56 ,  56 . 2 , L 2 , the flat-panel two-dimensional image-display modulation array  94 , and the waveguide projector  152 , and which may optionally include one or both of the conditioner lens  102 ,  102 ′, L 1  and a varifocal lens  160 . The conditioner lens  102 ,  102 ′, L 1  can further provide for forming a non-planar subpupil surface  84  at the exit pupil  18 , wherein the particular configuration of the associated components thereof is not limiting. For example, a real, practically-produced magnifier lens  56 ,  56 . 2 , L 2 , may include aberrations that might otherwise preclude an ideal formation of associated images of the controllable light sources  97  of the associated exit subpupils  32 . Accordingly, even with an ideal light distribution illuminating the flat-panel two-dimensional image-display modulation array  94 , the conditioner lens  102 ,  102 ′, L 1  works in cooperation with the magnifier lens  56 ,  56 . 2 , L 2  to provide for compensating for aberrations in the magnifier lens  56 ,  56 . 2 , L 2  that might otherwise adversely affect either the associated subpupil surface  84 , or the image of the associated exit subpupils  32  therein. 
     A real magnifier lens  56 ,  56 . 2 , L 2 —which may be imperfect—may not necessarily generate a sharply focused image of an exit subpupil  32  on the subpupil surface  84  from a corresponding associated beam of collimated light that is incident upon the flat-panel two-dimensional image-display modulation array  94 , and that was generated by a corresponding associated controllable light source  97 . Generally, a relatively-smaller size of the associated exit subpupils  32  is beneficial to providing for a relatively greater control of light  16 ′ through the eye pupil  38 , provided that the exit subpupils  32  are co-located with the eye pupil  38 . Although a planar subpupil surface  84 ,  84 ′ can provide for relatively smaller exit subpupils  32  than a concave-curved subpupil surface  84 ,  84 ″, the difference is generally not sufficient to overcome the adverse effects of axial misalignment when the eye pupil  38  rotates away from the planar subpupil surface  84 ,  84 ′. However, the varifocal lens  160  can provide for dynamically creating an effective concave-curved subpupil surface  84 ,  84 ″—notwithstanding there being a planar subpupil surface  84 ,  84 ′—by axially positioning the planar subpupil surface  84 ,  84 ′ so that the associated exit subpupils  32  thereon of the associated Active Subpupil Region (ASR)  72  are maintained in axial alignment with the eye pupil  38 . As a result of the conditioner-lens prescription design process  5000 , it has been discovered that under at least some circumstances, that a convex subpupil surface  84 ,  84 ′ provides for the relatively-smallest and most-highly-focused exit subpupils  32 , which can be accommodated by using the varifocal lens  160  to provide for maintaining an axial alignment of the exit subpupils  32  of the associated Active Subpupil Region (ASR)  72  on the convex subpupil surface  84 ,  84 ′ in axial alignment with the eye pupil  38 . 
     It should be understood that the magnifier-lens  4900  and conditioner-lens  5000  prescription design processes can be generally applied to any of the above-described near-eye display systems  10 ,  10 . 1 ,  10 . 1 ,  10 . 2 ′,  10 . 2 ″,  10 . 2 ′″,  10 . 3 ,  10 . 3 ′,  10 . 3 ″,  10 . 3 ′″,  10 . 4 ,  10 . 4 ′,  10 . 4 ″,  10 . 5 ,  10 . 5 ′,  10 . 5 ″,  10 . 5 ′″,  10 . 5 ″″, notwithstanding detailed illustration thereof in the context of the third-embodiment second-aspect optical subsystem  14 ,  14 . 2 ″′. 
     In accordance with one set of embodiments, a near-eye display system ( 10 ,  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4 ) for displaying an image ( 16 ) to an eye ( 20 ) of a user ( 22 ) of the near-eye display system ( 10 ,  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4 ), incorporates: a) an image generator ( 12 ,  12 . 1 ,  12 . 2 ,  12 . 3 ,  12 . 4 ), wherein the image generator ( 12 ,  12 . 1 ,  12 . 2 ,  12 . 3 ,  12 . 4 ) provides for generating light ( 16 ′) of the image ( 16 ) responsive to an electronic image signal ( 74 ), and the light ( 16 ′) of the image ( 16 ) is projectable onto a retina ( 24 ) of the eye ( 20 ) of the user ( 22 ) when the near-eye display system ( 10 ,  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4 ) is used by the user ( 22 ); b) an optical subsystem ( 14 ,  14 . 1 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′″), wherein the optical subsystem ( 14 ,  14 . 1 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′″) operates in cooperation with the image generator ( 12 ,  12 . 1 ,  12 . 2 ,  12 . 3 ,  12 . 4 ) to provide for projecting the image ( 16 ) onto the retina ( 24 ) of the eye ( 20 ) of the user ( 22 ) when the near-eye display system ( 10 ,  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4 ) is used by the user ( 22 ); and a subpupil modulator ( 30 ,  30 . 1 ,  30 . 2 ,  30 . 3 ,  30 . 4 ), wherein at least a portion of the optical subsystem ( 14 ,  14 . 1 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′″) forms an exit-pupil image ( 18 ′) of the subpupil modulator ( 30 ,  30 . 1 ,  30 . 2 ,  30 . 3 ,  30 . 4 ) in an exit pupil ( 18 ) of the near-eye display system ( 10 ,  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4 ), the exit pupil ( 18 ) is located proximate to an eye pupil ( 38 ) of the eye ( 20 ) of the user ( 22 ) when the near-eye display system ( 10 ,  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4 ) is used by the user ( 22 ), the subpupil modulator ( 30 ,  30 . 1 ,  30 . 2 ,  30 . 3 ,  30 . 4 ) provides for controllably forming at least one subpupil ( 32 ) within the exit pupil ( 18 ), an area of at least one subpupil ( 32 ) is less than an area of the exit pupil ( 18 ); and when activated, each at least one subpupil ( 32 ) incorporates the light ( 16 ′) from an entirety of the image ( 16 ). The near-eye display system ( 10 ,  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4 ) may further incorporate an eye-tracking subsystem ( 42 ), wherein the eye-tracking subsystem ( 42 ) incorporates: a) an infrared illuminator ( 44 ) positioned and configured so as to provide for illuminating at least the eye pupil ( 38 ) of the eye ( 20 ) for a range of gaze directions ( 34 ) of the eye ( 20 ); b) an infrared-responsive camera ( 46 ) positioned and configured so as to provide for acquiring an image of at least the eye pupil ( 38 ) of the eye ( 20 ) for the range of gaze directions ( 34 ) of the eye ( 20 ); and c) an eye-tracking processor ( 48 ), wherein the eye-tracking processor ( 48 ) provides for generating at least a measure of a location of the eye pupil ( 38 ) of the eye ( 20 ), and the eye-tracking processor ( 48 ) provides for communicating the at least the measure of the location of the eye pupil ( 38 ) of the eye ( 20 ), to a subpupil modulation controller ( 50 ), wherein the subpupil modulation controller ( 50 ) may provide for identifying an Active Subpupil Region ( 72 ) within the subpupil modulator ( 30 ,  20 . 1 ,  30 . 2 ,  30 . 3 ,  30 . 4 ) responsive to at least the measure of the location of the eye pupil ( 38 ) of the eye ( 20 ) from the eye-tracking subsystem ( 42 ), the subpupil modulation controller ( 50 ) may provide for activating at least one modulated subpupil ( 32 ′) within the Active Subpupil Region ( 72 ) so as to cause a corresponding at least one subpupil ( 32 ) within the exit pupil ( 18 ) to become activated, and the subpupil modulation controller ( 50 ) may provide for deactivating each remaining modulated subpupil ( 32 ′) that is not within the Active Subpupil Region ( 72 ) so as to cause each remaining at least one subpupil ( 32 ) within the exit pupil ( 18 ) to become deactivated, wherein the Active Subpupil Region ( 72 ) may surround a location corresponding to the location of the eye pupil ( 38 ) of the eye ( 20 ); a size of the Active Subpupil Region ( 72 ) may be independent of the location of the eye pupil ( 38 ) of the eye ( 20 ); the Active Subpupil Region ( 72 ) may be circularly shaped; the eye-tracking subsystem ( 42 ) may further provide for determining and communicating to the subpupil modulation controller ( 50 ) at least one measure selected from the group consisting of a measure of a shape of the eye pupil ( 38 ) of the eye ( 20 ), and a measure of a size of the eye pupil ( 38 ) of the eye ( 20 ), and the Active Subpupil Region ( 72 ) is shaped similarly to the shape of the eye pupil ( 38 ) of the eye ( 20 ); and the Active Subpupil Region ( 72 ) may be located entirely within the eye pupil ( 38 ) of the eye ( 20 ). 
     In accordance with one set of embodiments of first  10 . 1  and second  10 . 2  aspects of the near-eye display system ( 10 ,  10 . 1 ,  10 . 2 ), the subpupil modulator ( 30 ,  30 . 1 ,  30 . 2 ) incorporates at least one modulation element ( 90 ) located on or in cooperation with an associated modulation surface ( 92 ,  92 ′), the associated modulation surface ( 92 ,  92 ′) is substantially planar, and the exit-pupil image ( 18 ′) of the associated modulation surface ( 92 ,  92 ′) is located on a corresponding substantially planar subpupil surface ( 84 ,  84 ′). 
     In accordance with one set of embodiments of the first aspect  10 . 1  of the near-eye display system ( 10 ,  10 . 1 ): a) the image generator ( 12 ,  12 . 1 ) comprises a flat-panel two-dimensional image-display array ( 26 ,  52 ) of light-emitting image-display pixels ( 54 ), b) the optical subsystem ( 14 ,  14 . 1 ) comprises a first dioptric-power optical element ( 56 ,  56 . 1 ,  56 . 1 ′, L 1 ) located between the flat-panel two-dimensional image-display array ( 26 ,  52 ) of light-emitting image-display pixels ( 54 ) and a flat-panel two-dimensional modulation array ( 58 ) of light-modulating pixels ( 60 ), the first dioptric-power optical element ( 56 ,  56 . 1 ,  56 . 1 ′, L 1 ) is located substantially one focal length from each of the flat-panel two-dimensional image-display array ( 26 ,  52 ) of the light-emitting image-display pixels ( 54 ) and a first side ( 58 . 1 ) of the flat-panel two-dimensional modulation array ( 58 ) of the light-modulating pixels ( 60 ), c) the optical subsystem ( 14 ,  14 . 1 ) further comprises a second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) located between the flat-panel two-dimensional modulation array ( 58 ) and the exit pupil ( 18 ), the second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) is located substantially one focal length from a second side ( 58 . 2 ) of the flat-panel two-dimensional modulation array ( 58 ), the first ( 58 . 1 ) and second ( 58 . 2 ) sides of the flat-panel two-dimensional modulation array ( 58 ) oppose one another, d) the optical subsystem ( 14 ,  14 . 1 ) further comprises a third dioptric-power optical element ( 56 ,  56 . 3 ,  56 . 3 ′, L 3 ) located between the second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) and the exit pupil ( 18 ), the second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) is located substantially one focal length from each of a remaining focal plane ( 62 ) of the second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) and the exit pupil ( 18 ), e) the subpupil modulator ( 30 ,  30 . 1 ) comprises the flat-panel two-dimensional modulation array ( 58 ) of the light-modulating pixels ( 60 ), a transmissibility of the light ( 16 ′) through each light-modulating pixel ( 60 ) of the flat-panel two-dimensional modulation array ( 58 ) of the light-modulating pixels ( 60 ) is individually controllable responsive to a corresponding associated subpupil modulation control signal ( 51 ) from a subpupil modulation controller ( 50 ), each the light-modulating pixel ( 60 ) of the flat-panel two-dimensional modulation array ( 58 ) of the light-modulating pixels ( 60 ) is associated with a corresponding at least one subpupil ( 32 ) within the exit pupil ( 18 ), and the exit pupil ( 18 ) is formed as the exit-pupil image ( 18 ′) responsive to a cooperation of the first ( 56 ,  56 . 1 ,  56 . 1 ′, L 1 ), second ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) and third ( 56 ,  56 . 3 ,  56 . 3 ′, L 3 ) dioptric-power optical elements, and the exit pupil ( 18 ) is substantially planar. The first dioptric-power optical element ( 56 ,  56 . 1 ,  56 . 1 ′, L 1 ) may incorporate a first convergent magnifier lens ( 56 . 1 ′, L 1 ), the second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) may incorporate a second convergent magnifier lens ( 56 . 1 ′, L 2 ), and the third dioptric-power optical element ( 56 ,  56 . 3 ,  56 . 3 ′, L 3 ) may incorporate a third convergent magnifier lens ( 56 . 1 ′, L 3 ), and each light-emitting image-display pixel ( 54 ) of the flat-panel two-dimensional image-display array ( 26 ,  52 ) of light-emitting image-display pixels ( 54 ) may incorporate either a light-emitting diode element or a backlit liquid-crystal-display element. 
     In accordance with one set of embodiments of second  10 . 2 , third  10 . 3 , fourth  10 . 4  aspects of the near-eye display system ( 10 ,  10 . 2 ,  10 . 3 ,  10 . 4 ): a) the image generator ( 12 ,  12 . 2 ,  12 . 3 ,  12 . 4 ) incorporates a flat-panel two-dimensional image-display modulation array ( 94 ) of light-modulating image-display pixels ( 96 ,  96 ′) in cooperation with a controllable light source ( 97 ) of the subpupil modulator ( 30 ,  30 . 2 ,  30 . 3 ,  30 . 4 ), b) the optical subsystem ( 14 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′) incorporates a first dioptric-power optical element ( 56 ,  56 . 1 ,  56 . 1 ′, L 1 ,  102 ,  102 ′) located between a first side ( 94 . 1 ) of the flat-panel two-dimensional image-display modulation array ( 94 ) of the light-modulating image-display pixels ( 96 ,  96 ′) and the controllable light source ( 97 ) of the subpupil modulator ( 30 ,  30 . 2 ,  30 . 3 ,  30 . 4 ), wherein the first dioptric-power optical element ( 56 ,  56 . 1 ,  56 . 1 ′, L 1 ,  102 ,  102 ′) is located substantially one focal length from the controllable light source ( 97 ) of the subpupil modulator ( 30 ,  30 . 2 ,  30 . 3 ,  30 . 4 ), and the first dioptric-power optical element ( 56 ,  56 . 1 ,  56 . 1 ′, L 1 ,  102 ,  102 ′) is proximate to the first side of the flat-panel two-dimensional image-display modulation array ( 94 ) of the light-modulating image-display pixels ( 96 ,  96 ′), c) the optical subsystem ( 14 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′″) further incorporates a second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) located between the flat-panel two-dimensional image-display modulation array ( 94 ) and the exit pupil ( 18 ), wherein the second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) is located substantially one focal length from each of a second side ( 94 . 2 ) of the flat-panel two-dimensional image-display modulation array ( 94 ) and the exit pupil ( 18 ), and the first ( 94 . 1 ) and second ( 94 . 2 ) sides of the flat-panel two-dimensional image-display modulation array ( 94 ) oppose one another, and d) the controllable light source ( 97 ) of the subpupil modulator ( 30 ,  30 . 2 ,  30 . 3 ,  30 . 4 ) provides for separately and controllably illuminating or not illuminating each at least one subpupil ( 32 ) within the exit pupil ( 18 ) responsive to a corresponding associated subpupil modulation control signal ( 51 ) from a subpupil modulation controller ( 50 ). Each light-modulating image-display pixel ( 96 ,  96 ′) of the flat-panel two-dimensional image-display modulation array ( 94 ) of the light-modulating image-display pixels ( 96 ,  96 ′) may incorporate a liquid-crystal image-display pixel ( 96 ′). The first dioptric-power optical element ( 56 ,  56 . 1 ,  56 . 1 ′, L 1 ,  102 ,  102 ′) may incorporate a plano-convex conditioner lens ( 102 ′, L 1 ), and a planar surface ( 102 . 1 ′) of the plano-convex conditioner lens ( 102 ′, L 1 ) is proximate to the first side ( 94 . 1 ) of the flat-panel two-dimensional image-display modulation array ( 94 ). The second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) may incorporate a second convergent magnifier lens ( 56 . 2 ′, L 2 ). The second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ) comprises a free-form-surface/prism lens ( 56 . 2 , L 2 ,  128 ). 
     In accordance with one set of embodiments of the second aspect  10 . 2  of the near-eye display system ( 10 ,  10 . 2 ), the controllable light source ( 97 ) may incorporate a flat-panel two-dimensional light light-source array ( 98 ) of light-source elements ( 100 ,  100 ′,  100 ″), wherein the exit pupil ( 18 ) is formed as the exit-pupil image ( 18 ′) by the second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ), and the exit pupil ( 18 ) is substantially planar, wherein each light-source element ( 100 ,  100 ′,  100 ″) of the flat-panel two-dimensional light light-source array ( 98 ) of the light-source elements ( 100 ,  100 ′,  100 ″) may incorporate a light-emitting-diode element ( 100 ′). 
     In accordance with one set of embodiments of the third aspect  10 . 3  of the near-eye display system ( 10 ,  10 . 3 ), the controllable light source ( 97 ) incorporates a curved two-dimensional light light-source array ( 106 ) of light-source elements ( 100 ,  100 ′,  100 ″), the exit pupil ( 18 ) is formed as the exit-pupil image ( 18 ′) by the second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ), and the exit pupil ( 18 ) is curved, wherein each light-source element ( 100 ,  100 ′,  100 ″) of the curved two-dimensional light light-source array ( 106 ) of the light-source elements ( 100 ,  100 ′,  100 ″) may incorporate either a light-emitting-diode element ( 100 ′) located on an underlying concave-curved surface ( 107 ), or a first end of a corresponding fiber-optic light pipe supported from an underlying concave-curved surface ( 107 ), with each second end of the corresponding fiber-optic light pipe is illuminated by a corresponding light-emitting-diode element, wherein the corresponding light-emitting-diode element may be incorporated in a flat-panel light-source array. In one set of embodiments, a curvature of the exit pupil ( 18 ) substantially conforms to a curvature of a front surface ( 20 ′) of the eye ( 20 ). 
     In accordance with one set of embodiments of the fourth aspect  10 . 4  of the near-eye display system ( 10 ,  10 . 4 ), the controllable light source ( 97 ) incorporates a curved light-redirecting surface ( 110 ) in cooperation with a modulated scanned beam of light ( 112 ), the exit pupil ( 18 ) is formed as the exit-pupil image ( 18 ′) by the second dioptric-power optical element ( 56 ,  56 . 2 ,  56 . 2 ′, L 2 ), and the exit pupil ( 18 ) is curved, wherein the curved light-redirecting surface ( 110 ) may incorporate at least one optical surface selected from the group consisting of a light-scattering surface, a holographic surface, and a diffractive surface. The fourth aspect  10 . 4  of the near-eye display system ( 10 ,  10 . 4 ) may further incorporate: a) light-beam source ( 118 ), wherein the light-beam source ( 118 ) provides for generating the beam of light ( 114 ), and provides for modulating an intensity thereof responsive to an light-beam-magnitude subpupil modulation control signal ( 51 ′); b) a light-beam-directing element ( 120 ), wherein the light-beam-directing element ( 120 ) provides for directing the beam of light ( 114 ) onto the curved light-redirecting surface ( 110 ) at a location thereon responsive to an angular orientation of the light-beam-directing element ( 120 ); and c) a light-beam scanner ( 116 ), wherein the light-beam scanner ( 116 ) provides for controlling the angular orientation of the light-beam-directing element ( 120 ), the light-beam scanner ( 116 ) and the light-beam source ( 118 ) are controlled over time responsive to a light-beam-position subpupil modulation control signal ( 51 ″) from a subpupil modulation controller ( 50 ) so as to provide for generating the modulated scanned beam of light ( 112 ), and so as to provide for scanning the modulated scanned beam of light ( 112 ) over a region ( 122 ) of the curved light-redirecting surface ( 110 ) so as to form a corresponding at least one subpupil ( 32 ), wherein the light-beam-directing element ( 120 ) may incorporate at least one optical element selected from the group consisting of a mirror, a holographic element, and a diffractive element. The fourth aspect  10 . 4  of the near-eye display system ( 10 ,  10 . 4 ) may further incorporate: a) an eye-tracking subsystem ( 42 ), wherein the eye-tracking subsystem ( 42 ) provides at least a measure of a location of an eye pupil ( 38 ) of the eye ( 20 ); and b) the subpupil modulation controller ( 50 ), wherein the subpupil modulation controller ( 50 ) provides for controlling an activation state of each of at least one subpupil ( 32 ) of the subpupil modulator ( 30 ,  30 . 4 ) responsive at least to the measure of the location of the eye pupil ( 38 ) of the eye ( 20 ). In one set of embodiments, a curvature of the exit pupil ( 18 ) substantially conforms to a curvature of a front surface ( 20 ′) of the eye ( 20 ). 
     In accordance with one set of embodiments of third  10 . 3  and fourth  10 . 4  aspects of the near-eye display system ( 10 ,  10 . 3 ,  10 . 4 ), the subpupil modulator ( 30 ,  30 . 3 ,  30 . 4 ) incorporates at least one modulation element ( 90 ) located on or in cooperation with an associated modulation surface ( 92 ,  92 ″), the associated modulation surface ( 92 ,  92 ″) is curved, and an associated curved subpupil image  126  of the associated modulation surface ( 92 ,  92 ″) is located on a corresponding curved subpupil surface ( 84 ,  84 ″), wherein a curvature of the curved subpupil surface ( 84 ,  84 ″) may substantially conform to a curvature of a front surface ( 20 ′) of the eye ( 20 ). 
     Generally, in accordance with one set of embodiments, a near-eye display system ( 10 ,  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4 ) for providing an image ( 16 ′) of an object ( 52 ,  94 ,  16 ) for viewing by an eye ( 20 ) of a user ( 22 ) incorporates a) a geometric surface ( 18 ″,  84 ,  84 ′,  84 ″) having one or more first locations at which rays of light ( 16 ′) from an entirely of an image ( 16 ) intersect; b) a physical surface ( 92 ,  92 ′,  92 ″) having one or more second locations at which the rays of light ( 16 ′) from an entirely of the image ( 16 ) intersect; c) a light-limiting means ( 30 ;  30 . 1   58 ;  30 . 2 ,  98 ;  30 . 3 ,  106 ;  30 . 4 ,  110 ,  112 ,  114 ,  116 ,  118 ) for independently limiting the rays of light ( 16 ′) emitted from or passing through the one or more second locations; and d) an optical system ( 14 ,  14 . 1 ,  14 . 2 ,  14 . 2 ′,  14 . 2 ″,  14 . 2 ′″) the provides for forming the geometric surface ( 18 ″,  84 ,  84 ′,  84 ″) as a real image of the physical surface ( 92 ,  92 ′,  92 ″). The near-eye display system ( 10 ,  10 . 1 ,  10 . 2 ,  10 . 3 ,  10 . 4 ) may also incorporate a) a means ( 42 ,  44 ,  46 ,  48 ) for detecting at least the location of an eye pupil ( 38 ) of the eye ( 20 ) with respect to the geometric surface ( 18 ″,  84 ,  84 ′,  84 ″); and b) a control system ( 50 ) for electronically controlling the light-limiting means ( 30 ;  30 . 1   58 ;  30 . 2 ,  98 ;  30 . 3 ,  106 ;  30 . 4 ,  110 ,  112 ,  114 ,  116 ,  118 ) so that the light ( 16 ′) passing through at least some of the first locations is as least partially limited. The physical surface ( 92 ,  92 ′,  92 ″) may be either substantially planar ( 92 ′) or curved ( 92 ″). 
     Referring again to  FIGS.  16 ,  17 ,  44 , and  53   , in one set of embodiments of the second  10 . 2  and fifth  10 . 5  aspect near-eye display systems  10 , the associated flat-panel two-dimensional light-source array  98  is implemented with a two-dimensional array  26  of associated light-source elements  100  similar to that used as the image generator  12 ,  12 . 1  of the first aspect near-eye display system  10 ,  10 . 1 , but with each associated light-source element  100 —for example, with each light-source element  100 ,  100 ′/light-emitting image-display pixel  54  comprising an associated set of red (R), green (G) and blue (B) light-emitting-diodes—operated in a white-light mode of operation, so as to provide for effectively acting as white-light light-source elements  100 . Similarly, referring to  FIGS.  18 ,  19 ,  45  and  47   , in one set of embodiments of the third aspect near-eye display system  10 ,  10 . 3 , each associated light-source element  100 ,  100 ′ comprises an associated set of red (R), green (G) and blue (B) light-emitting-diodes, similarly operated in a white-light mode of operation. For example, in accordance with a first white-light mode of operation, if the flat-panel two-dimensional light-source array  98  comprises an array of spatially separate color component light-modulating pixels, for example red (R), green (G) and blue (B), in clusters—for example, with each pixel having a color filter to generate its respective color—then the separate color component light-modulating pixels would be operated simultaneously at associated relative intensities sufficient to effectively generate what is perceived to be white light. As a second example, in accordance with a second white-light mode of operation, if the flat-panel two-dimensional light-source array  98  comprises an array of light-modulating pixels that operate in a field-sequential mode where full images of fields of single color components of an image are displayed so that the eye perceives the composite image in full color due to persistence, then each associated light-source element  100 ,  100 ′ would generate individual colors sequentially at associated relative intensities sufficient to so as to be perceived to be white light. Similarly, referring again to  FIGS.  18 ,  19 ,  45  and  47   , in one set of embodiments of the third aspect near-eye display system  10 ,  10 . 3 , each associated light-source element  100 ,  100 ′ comprises an associated set of red (R), green (G) and blue (B) light-emitting-diodes, similarly operated in a white-light mode of operation, supra. 
     The associated optical subsystems  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  provide for a one-to-one correspondence between modulated subpupils  32 ′ of the associated subpupil modulator  30 ,  30 . 1 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5  within the associated aperture stop  28  of the associated optical subsystems  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  and corresponding exit subpupils  32  within the exit pupil  18 . Each point on the aperture stop  28  is imaged to a corresponding point in the exit pupil  18 , i.e. with a one-to-one relationship between points in “object space” of the aperture stop  28 /subpupil modulator  30 ,  30 . 1 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5 , to corresponding points in “image space” of the surface  18 ″ of the exit pupil  18 , and for each of the associated exit subpupils  32  associated with corresponding modulated subpupils  32 ′ that are formed by the subpupil modulator  30 . 
     Referring to  FIGS.  59   a  and  59   b   , under associated ideal conditions and configurations, the associated optical subsystems  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 , also provide for a one-to-one correspondence between modulated subpupils  32 ′ of the associated subpupil modulator  30 ,  30 . 1 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5  and corresponding regions within the exit pupil  18 , i.e. so that the resulting exit subpupils  32  are distinct and separated from one another, i.e. non-overlapping within the exit pupil  18 . For example, referring to  FIG.  59   a   , the hypothetical intensity profile of light  104  through the center of an activated modulated subpupil  32 ′—e.g. a light-modulating pixel  60  of a flat-panel two-dimensional modulation array  58  of the first aspect near-eye display system  10 ,  10 . 1 , or a light-source element  100  of the second  10 . 2  through fifth  10 . 5  aspect near-eye display systems  10 —of the subpupil modulator  30 ,  30 . 1 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5  within the associated aperture stop  28  of an associated optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  comprises a uniform non-zero level across the lateral extent thereof, and a zero level outside the lateral extent thereof. Referring to  FIG.  59   b   , the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  collects the light  16 ′ of the modulated subpupil  32 ′ and forms therefrom an associated exit subpupil  32  within the associated exit pupil  18 . 
     In accordance with one set of embodiments, the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  forms on the surface  18 ″ of the exit pupil  18  a real image of the subpupil modulator  30 ,  30 . 1 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5 , with the boundary of the exit pupil  18  corresponding to the corresponding boundary of the aperture stop  28  of the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 . With the exit pupil  18  located proximate to the outer surface, i.e. the front surface  20 ′, of the eye  20 , this a) provides for enabling the user  22  to see—without vignetting—the full extent of the virtual image  16 ′″ from either the flat-panel two-dimensional image-display array  52  or the flat-panel two-dimensional image-display modulation array  94  over a full range of rotation of the eye  20 , and b) provides for minimizing the size of the associated exit subpupils  32 . 
     For the first aspect near-eye display system  10 ,  10 . 1 , each modulated subpupil  32 ′ of the subpupil modulator  30 ,  30 . 1  receives light from the entirety of the flat-panel two-dimensional image-display array  52 , and for the second  10 . 2  through fifth  10 . 5  aspect near-eye display systems  10 , light  16 ′ from each light-source element  100  of the associated subpupil modulator  30 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5  illuminates the entirety of the associated flat-panel two-dimensional image-display modulation array  94 . Accordingly, in both cases, each associated modulated subpupil  32 ′ contains light  16 ′ of the entirety of the associated virtual image  16 ′″, and the associated optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  generally provides for collecting the light  16 ′ of the virtual image  16 ′″ propagating from the aperture stop  28  of the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  onto the associated exit pupil  18  on a surface  18 ″ proximate to an outer surface  20 ′ of the eye  20 , and, as a result of the source  52 ,  94  of the virtual image  16 ′″ being flat, with each resulting exit subpupil  32  presenting substantially the same virtual image  16 ′. 
     During operation of the near-eye display system  10 , only a subset of the modulated subpupils  32 ′ of the subpupil modulator  30  are activated at any given time, so that at any given time, the aperture stop  28  is not fully illuminated. The maximum extent (i.e. the size) of the exit pupil  18  will depend upon the manner by which the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  forms the associated exit-pupil image  18 ′, i.e. the degree to which the exit-pupil image  18 ′ is a focused real image of the subpupil modulator  30  within the associated aperture stop  28 . However, with the aperture stop  28  not fully illuminated at any given time, the outer boundary of the resulting associated exit-pupil image  18 ′ will not correspond to that of the aperture stop  28 . Accordingly, the outer boundary of the exit pupil  18 /exit-pupil image  18 ′ is delineated with phantom lines in  FIGS.  5 ,  7 ,  11 ,  13 ,  15 . 22 ,  24 ,  26 ,  28 ,  30 ,  35 ,  37 ,  39 ,  41 , and  43    so as to illustrate that the effective aperture of the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  is defined/limited by the associated subpupil modulator  30 , either as a physical “sub-aperture” defined either by the light-restricting, “hard” boundaries of “open” light-modulating pixels  60  (acting as “shutters”) of a flat-panel two-dimensional modulation array  58  of a first-aspect subpupil modulator  30 ,  30 . 1 , or by light-limiting “soft” boundaries of activated light-source elements  100  of a controllable light source  97  of a remaining-aspect subpupil modulator  30 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5 . Furthermore, the spatially-discrete nature of the modulated subpupils  32 ′ of the subpupil modulator  30 ,  30 . 1   30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5 , i.e. with permanently-deactivated gaps between the modulated subpupils  32 ′, the resulting structure will typically be unnoticeable (much like viewing a distant image through a window screen positioned relatively close to the eye), but a perception of this structure can otherwise be mitigated by use of depixelation optics if the associated modulation structure is not otherwise blurred by inherent realistic limitations of the associated optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 . 
     Accordingly, the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  provides for projecting light  16 ′ of a virtual image  16 ″ the eye  20  of a user  22 , wherein modulated subpupils  32 ′ located on a physical modulation surface  92  of a subpupil modulator  30  within the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  at least either partially block a portion of that light  16 ′, or prevent that portion of light  16 ′ from being generated, so as to prevent that portion of light  16 ′ from entering the eye pupil  38  of the eye  20  of the user  22 . In accordance with one set of embodiments, which provide for the relatively smallest associated exit subpupils  32 , the exit-pupil image  18 ′ is formed proximate to the front surface  20 ′ of the eye  20  as a real image of the modulation surface  92 . Alternatively, the exit-pupil image  18 ′ formed proximate to the front surface  20 ′ of the eye  20  may be an image of the modulation surface  92 , albeit a poorly-formed image, while still providing for collecting the light  16 ′ from the modulation surface  92  into the exit pupil  18 . Accordingly, as used herein, an image of the modulation surface  92  is defined as the spatial distribution of light  16 ′ that has passed through, or has emanated from, that modulation surface  92  and has exited the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  to form a surface  18 ″—also referred to herein as an exit pupil  18 —within the volumetric visual environment (VVE)  80  of the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 , wherein the portion of that light  16 ′ passing through, or emanating from, any particular location on that modulation surface  92  passes through less than the entirety of that exit pupil  18 . 
     Referring to  FIGS.  59   c    and  60 , in accordance with a non-ideal optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 , for example, one subject to practical constraints on the nature, construction and imaging properties of the associated dioptric-power optical elements  56 ,  56 . 1 ,  56 . 2 ,  56 . 3 , and associated constraints on the layout of an associated practical, commercially-viable near-eye display system  10 —wherein the associated imaging properties of the associated dioptric-power optical elements  56 ,  56 . 1 ,  56 . 2 ,  56 . 3  might be relaxed in favor of either relatively-simpler optics or a relatively-more-compact optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 , —a resulting corresponding intensity distribution of an associated resulting realized exit subpupil  32 ″ might become laterally expanded beyond the nominal ideal boundaries  162  of a corresponding idealized exit subpupil  32 , so that an ensemble of realized exit subpupils  32 ″ might then overlap one another within the exit pupil  18 , resulting in a prospective violation of one-to-one correspondence between regions within the exit pupil  18  and corresponding modulated subpupils  32 ′, notwithstanding the resulting exit subpupils  32 ,  32 ″ within the exit pupil  18  remaining in one-to-one correspondence with corresponding modulated subpupils  32 ′ of the subpupil modulator  30 . Furthermore, relative to a counterpart idealized exit subpupil  32 , in addition to overlapping with other realized exit subpupil  32 ″, a corresponding realized exit subpupil  32 ″ might prospectively be relatively blurry and of non-uniform size or shape. For example, an expansion in the lateral extent of the realized exit subpupil  32 ″ relative to that of an idealized exit subpupil  32  can be caused by a lack of concentricity of the eye pupil  38  and associated front surface  20 ′ of the eye  20  with respect to the surface  18 ″ of the exit pupil  18 , or a misalignment of the near-eye display system  10  with respect to the eye  20  of the user  22 . Accordingly, for any particular point on the eye pupil  38 , there is a prospect for that point to receive light  16 ′ from a plurality of different modulated subpupils  32 ′. 
     For example,  FIG.  60    illustrates a plan view of an exit pupil  18  of a near-eye display system  10 , the latter of which incorporate an optical subsystem  14 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  that provides for forming a virtual image  16 ′″ of a flat-panel two-dimensional image-display modulation array  94  illuminated by a subpupil modulator  30  comprising a controllable light source  97  incorporating a plurality of associated light-source elements  100 , and that provides for collecting at least a portion of the light  16 ′ that propagates from each light-source element  100  through the flat-panel two-dimensional image-display modulation array  94 , with light  16 ′ from each light-source element  100  forming an associated realized exit subpupil  32 ″ on the surface  18 ″ of the exit pupil  18 , wherein as a result of the nature of the optical subsystem  14 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  and the shape and location of the surface  18 ″ of the exit pupil  18  in relation to that of the front surface  20 ′ of the eye  20 , the lateral extent of at least some of the realized exit subpupils  32 ″ are expanded relative to what would have been corresponding idealized exit subpupils  32 , so that at least some adjacent realized exit subpupils  32 ″ overlap one another by at least twenty (20) percent. Accordingly, the resulting plurality of realized exit subpupils  32 ″ create, and when activated, fill, the associated exit pupil  18  with an array of similar but spatially-distinct, incompletely-overlapping realized exit subpupils  32 ″. Accordingly, each realized exit subpupil  32 ″, although generated by, is not necessarily a well-formed image of, a corresponding light-source element  100 , and the controllable light source  97 /subpupil modulator  30  is not necessarily a corresponding well-formed entrance pupil  28 ′ of the optical subsystem  14 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 . 
     Responsive to the determination by the eye-tracking subsystem  42  of a location and extent of the eye pupil  38 , the subpupil modulation controller  50  provides for deactivating modulated subpupils  32 ′ associated with exit subpupils  32  that are either outside the associated Active Subpupil Region (ASR)  72 , or that do not even partially overlap the eye pupil  38 , which provides for reducing the reflection of extraneous light  16   iv  from the front surface  20 ′ of the eye  20 , and which, for a near-eye display system  10 ,  10 . 2 ,  10 . 3 ,  10 . 4 ,  10 . 5  incorporating a controllable light source  97 , provides for reducing power consumed by the controllable light source  97 . However, for relatively-expanded realized exit subpupils  32 ″, relatively to counterpart idealized exit subpupils  32 . a relatively-higher number of realized exit subpupils  32 ″ would prospectively at least-partially overlap the eye pupil  38 , thereby expanding the associated corresponding effective Active Subpupil Region (ASR)  72 ′, so that under this relatively-simple subpupil control strategy,—i.e. in accordance with either the first-aspect  70 . 1  or second-aspect subpupil modulation scheme  70 , supra—relatively-fewer associated modulated subpupils  32 ′ could be deactivated without impacting perception of the virtual image  16 ′ being viewed by the user  22 . 
     Referring to  FIG.  61   , a first aspect of a subpupil modulation control process  6100  for controlling a subpupil modulator  30  provides for activating a single modulated subpupil  32 ′ most closely associated with a central location of an eye pupil  38  of an eye  20  at a viewing location proximate to the exit pupil  18  within the volumetric visual environment (VVE)  80 , wherein, in step ( 6102 ), the subpupil modulation controller  50  receives from the eye-tracking subsystem  42  a measure of a central location—for example, the center-of-area—of the eye pupil  38 . Then, in step ( 6104 ), the subpupil modulation controller  50  identifies the exit subpupil  32  that is closest to that central location of the eye pupil  32 , and identifies the associated modulated subpupil  32 ′ that corresponds to that eye pupil  32 , or alternatively, directly from a table lookup of a two-dimensional table that provides the identity of the corresponding modulated subpupil  32 ′ as a function of transverse X- and Y- locations within the exit pupil  18  of boundaries of regions illuminated by the corresponding exit subpupils  32 ,  32 ″, responsive to the measure from the eye-tracking subsystem  42  of the central location of the eye pupil  38 . The subpupil modulation controller  50  then activates the resulting identified modulated subpupil  32 ′, and, in step ( 6106 ), deactivates the remaining modulated subpupils  32 ′. In accordance with one aspect, optional step ( 6108 ) provides for the intensity of the single light-source element  100 ,  90  associated with the single active modulated subpupil  32 ′ to be adjusted responsive to input from the user  22  so as to provide for adjusting the level of brightness of the associated virtual image  16 ′ to the preference of the user  22 . For exit subpupils  32  that are smaller in diameter than the opening of the eye pupil  38 , the first-aspect subpupil modulation control process  6100  provides for implementing an embodiment of the third aspect subpupil modulation scheme  70 ,  70 . 3 , supra. 
     Notwithstanding the prospect of activating and viewing only a single exit subpupil  32 ,  32 ″ at a time, and the associated benefit of minimal power usage and lack of, or mitigation against, vignetting, a simultaneous activation of more than one exit subpupil  32 ,  32 ″ also can be beneficial for the following three reasons. First, a single light-source element  100  might be naturally limited in intensity, whereas multiple light-source elements  100  can share the burden and assure that the overall perceived image brightness is relatively constant, independent of gaze direction  34 . Second, it may be challenging to track the eye pupil  38  sufficiently accurately, or sufficiently fast, to provide for activating the light-source element  100  from which light  16 ′ generated thereby would pass through the eye pupil  38 , whereas a plurality of simultaneously-activated exit subpupils  32 ,  32 ″ associated with a relatively-larger Active Subpupil Region (ASR)  72  could help assure that the overall perceived image brightness is relatively constant, independent of gaze direction  34 . Third, and finally, a single light-source element  100 , especially if very small, results in a relatively-large depth of focus, which not only can reveal structures or contaminants of the optical subsystem  14 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  located away from the flat-panel two-dimensional image-display modulation array  94 , but, if sufficiently small, could provide for revealing adverse effects of diffraction or interference that might otherwise detract from a desired naturally appearing virtual image  16 ′″ of the flat-panel two-dimensional image-display modulation array  94 . 
     Notwithstanding the benefit of relatively small, non-overlapping idealized exit subpupil  32  in order to provide for prospectively deactivating the most possible associated light-source elements  100 , and thereby minimizing associated power usage, it should be understood that the exit subpupils  32  need not necessarily be of similar size or shape, nor non-overlapping with respect to one another, nor necessarily well-formed images of the corresponding light-source elements  100 /modulated subpupils  32 ′, which provides for significantly relaxing the requirements of the design of the associated optical subsystem  14 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 . Instead, for a realized exit subpupil  32 ″ of arbitrary size, shape and image quality, in accordance with second through fourth aspects of associated subpupil modulation control processes, infra, the subpupil modulation controller  50  in cooperation with the eye-tracking subsystem  42  provides for further controlling the modulated subpupils  32 ′ for which the corresponding associated realized exit subpupils  32 ″ at least partially overlap the eye pupil  38 , so as to provide for reducing power usage and possibly the reflection of extraneous light  16   iv  from the front surface  20 ′ of the eye  20 . In accordance with one aspect, this is provided for by first establishing a predetermined mapping, for each light-source element  100 /modulated subpupil  32 ′, of the location lateral extent (e.g. shape and size), and intensity profile of each corresponding realized exit subpupil  32 ″. In view of the intensity of the light  16 ′ passing through each exit subpupil  32 ,  32 ″ not likely being uniform thereacross, the intensity profile of the associated exit subpupil  32 ,  32 ″ can be used to adjust/optimize the intensities of the active exit subpupils  32 ,  32 ″ so as to provide for a beneficial/optimal overall intensity profile within the associated Active Subpupil Region (ASR)  72 , to not only maintain a uniform perceived brightness as the eye pupil  38  scans through different gaze directions  34 , but also, to the extent possible, to concentrate the light  16 ′ through the center of the eye pupil for best perceived quality of the virtual image  16 ′″. 
     More particularly, referring to  FIG.  62   , an associated subpupil mapping process  6200  commences, in step ( 6202 ), with the selection of a modulated subpupil  32 ′/light-source element  100  of the of the plurality of modulated subpupils  32 ′/light-source elements  100  of the subpupil modulator  30 . Then, in step ( 6204 ), the selected modulated subpupil  32 ′/light-source element  100  is activated—either actually in cooperation with the hardware of an associated near-eye display system  10 , or by simulation—to provide for illuminating, or simulating the illumination of, an associated exit pupil  18 , so as to generate an associated exit subpupil  32 ,  32 ″ therewithin. Then, the location, lateral extent (e.g. size and shape), and intensity profile of the illuminated exit subpupil  32 ,  32 ″ are determined in step ( 6206 ), and, in step ( 6208 ), stored for future use, for example, in an exit-subpupil characterization table  164 , after which, from step ( 6210 ), the next modulated subpupil  32 ′/light-source element  100  is selected in step ( 6212 ), and the process of steps ( 6202 ) through ( 6212 ) is repeated until all of the modulated subpupils  32 ′/light-source element  100  have been processed, after which, from step ( 6210 ), the mapping process is complete in step ( 6214 ), with the locations, lateral extents, and intensity profiles of all the exit subpupils  32 ,  32 ″ having been determined and stored for future use. Accordingly, for a particular viewing direction and opening of the eye pupil  38 , and a resulting particular area within the exit pupil  18  occupied by the eye pupil  38 , the exit-subpupil characterization table  164  provides for identifying those exit subpupils  32 ,  32 ″ that overlap with that area; and for each such exit subpupil  32 ,  32 ″, the relative amount of light within that overlapping area, relative to the total amount of light of that exit subpupil  32 ,  32 ″, and the identity of the corresponding associated modulated subpupil  32 ′/light-source element  100 . 
     Referring to  FIG.  63   , a second aspect of a subpupil modulation control process  6300  for controlling a subpupil modulator  30  provides for controlling activation of exit subpupils  32 ,  32 ″ responsive to the degree of overlap thereof with an eye pupil  38 , commencing, in step ( 6302 ), with receipt—from the eye-tracking processor  48  of the eye-tracking subsystem  42 —of measures of the location and lateral extent (e.g. size and shape) of the eye pupil  38 . Then, in step ( 6304 ), using the exit-subpupil characterization table  164  determined by the subpupil mapping process  6200 , supra, the subpupil modulator  30  identifies the subset of exit subpupils  32 ,  32 ″ that are proximate to the location of the eye pupil  38 , for example exit subpupils  32 ,  32 ″ either that are within, or that at least in part overlap, the eye pupil  38 . 
     For example, referring to  FIGS.  60  and  64   , —the latter representing an intensity profile of the former through the center of the eye pupil  38 , —the set of exit subpupils  32 ,  32 ″ labeled as “A”, “B”, or “C” are identified as being proximate to the eye pupil  38  as a result of each of these exit subpupils  32 ,  32 ″ either being entirely within (i.e. “A”), or intersecting (i.e. “B” and “C”) the boundary of the eye pupil  38 . Each of the exit subpupils  32 ,  32 ″, except for the central exit subpupil  32  labeled as “A”, is illustrated in  FIG.  60    with a pair of inner and outer concentric circles, with the inner circle representing the extent of a corresponding idealized exit subpupil  32 , and the outer circle representing the extent of the corresponding realized exit subpupil  32 ″. The Active Subpupil Region (ASR)  72  associated with the idealized exit subpupils  32  entirely encircles all of the exit subpupils  32  labeled as “A”, “B”, “C”, “D”, or “E”, whereas a relatively-expanded Active Subpupil Region (ASR)  72 ′ is needed to encircle the corresponding associated realized exit subpupil  32 ″, thereby involving a relative larger proportion of the area of the exit pupil  18 . 
     Returning to  FIG.  63   , in step ( 6306 ), the remaining exit subpupils  32 ,  32 ″ that are not proximate to the eye pupil  38 —for example, entirely outside the boundary of the eye pupil  38 —are deactivated to conserve power and reduce the reflection of extraneous light  16   iv . For example, as illustrated in  FIG.  64   , the exit subpupils  32 ,  32 ″ labeled “D” or “E” are deactivated. Then, beginning with step ( 6308 ), for each exit subpupil  32 ,  32 ″ that was identified from step ( 6304 ) as being proximate to the eye pupil  38 , in step ( 6310 ), using the exit-subpupil characterization table  164  determined by the subpupil mapping process  6200 , supra, the subpupil modulator  30  determines the relative amount of the exit subpupil  32 ,  32 ″ that is within the eye pupil  38 , for example, either the relative area or, based upon the associated intensity profile, the relative amount of light. Then, in step ( 6312 ), if a substantial portion of the exit subpupil  32 ,  32 ″ is located outside the eye pupil  38 , for example, at least 80 percent, then, in step ( 6314 ), the modulated subpupil  32 ′ associated with that exit subpupil  32 ,  32 ″ is deactivated. Otherwise, from step ( 6312 ), if a substantial portion of the exit subpupil  32 ,  32 ″ is not located outside the eye pupil  38 , then, in step ( 6316 ), the modulated subpupil  32 ′ associated with that exit subpupil  32 ,  32 ″ is activated. Then, following either of steps ( 6314 ) or ( 6316 ), if all of the exit subpupils  32 ,  32 ″ identified in step ( 6304 ) as being proximate to the eye pupil  38  have not been processed, then steps ( 6308 ) through ( 6314 )/( 6316 ) are repeated for the next exit subpupil  32 ,  32 ″ that is selected in step ( 6320 ). Then, from step ( 6318 ), after all of the relatively-proximate exit subpupils  32 ,  32 ″ have been processed, in step ( 6324 ), the intensities of the light-source elements  100  of the modulated subpupils  32 ′ associated with the exit subpupils  32 ,  32 ″ that had been activated in step ( 6316 ) are adjusted, possible with input, in step ( 6326 ), from the user  22  in respect of the overall brightness of the perceived associated virtual image  16 ′″. Following step ( 6324 ), the subpupil modulation control process  6300  repeats beginning with step ( 6302 ), so as to provide for continuously tracking and responding to the location and extent of the eye pupil  38 . 
     For example, referring also to  FIG.  65   , as a result of a substantial portion of the exit subpupils  32 ,  32 ″ labeled “C” in  FIGS.  60  and  64    being outside the eye pupil  38 , in step ( 6314 ), the “C”-labeled exit subpupils  32 ,  32 ″ are deactivated, and, in step ( 6324 ), the intensity of modulated subpupils  32 ′/light-source elements  100  associated with the “B”-labeled exit subpupils  32 ,  32 ″ is increased so as to maintain the overall brightness of the virtual image  16 ′″. Alternatively, or additionally, the overall brightness of the virtual image  16 ′″ could be maintained by increasing the intensity of the modulated subpupil  32 ′/light-source element  100  associated with the “A”-labeled exit subpupils  32 ,  32 ″. Absent the intensity adjustment in step ( 6324 ), the overall brightness of the virtual image  16 ′ would otherwise be lowered relative to that of the virtual image  16 ′″ prior to the deactivation of the “C”-labeled exit subpupils  32 ,  32 ″ in step ( 6314 ). The deactivation, in step ( 6314 ), of exit subpupils  32 ,  32 ″ in cooperation the adjustment, in step ( 6324 ), of the intensity of remaining, activated exit subpupils  32 ,  32 ″ provides for more efficient power usage than without the actions of steps ( 6314 ) and ( 6324 ), with the added benefit of a reduction in reflected extraneous light  16   iv . 
     In accordance with the first-aspect near-eye display system  10 ,  10 . 1 , each point on the subpupil modulator  30 ,  30 . 1 /flat-panel two-dimensional modulation array  58 , and therefore, each associated modulated subpupil  32 ′, is illuminated by the entirety of the associated flat-panel two-dimensional image-display array  52 . In accordance with the second-  10 . 2  through fifth-  10 . 5  aspect near-eye display systems  10 ,  10 . 2 ,  10 . 3 ,  10 . 4 ,  10 . 5 , light  104  from each modulated subpupil  32 ′ generated by the associated controllable light source  97  of an associated subpupil modulator  30 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5  illuminates the entirety of the associated flat-panel two-dimensional image-display modulation array  94 . Accordingly, each exit subpupil  32 ,  32 ″ that is generated by a corresponding associated modulated subpupil  32 ′ contains the entirety of the image content of the virtual image  16 ′″, so that the full image content of the virtual image  16 ′″ is viewable by the user  22  with any activated exit subpupil  32 ,  32 ″, regardless of the gaze direction  34  of the eye pupil  38 . Accordingly, although a deactivation of one or more exit subpupils  32 ,  32 ″ overlapping the eye pupil  38 , absent a change in intensity of the remaining exit subpupils  32 ,  32 ″, would simply cause the virtual image  16 ′″ to be dimmer, the apparent brightness of the virtual image  16 ′ can be maintained by the subpupil modulation controller  50  by maintaining the composite intensity of the remaining, activated exit subpupils  32 ,  32 ″. 
     Referring to  FIG.  66   , a third aspect of a subpupil modulation control process  6600  for controlling a subpupil modulator  30  also provides for controlling activation of exit subpupils  32 ,  32 ″ responsive to the degree of overlap thereof with an eye pupil  38 , and is the same as the second-aspect subpupil modulation control process  6300 , supra, except that steps ( 6310 ) through ( 6316 ), ( 6324 ) and ( 6326 ) are replaced by steps ( 6602 ) and ( 6604 ), wherein, following step ( 6308 ), for each exit subpupil  32 ,  32 ″ proximate to the eye pupil  38 , in step ( 6602 ), the subpupil modulation controller  50  adjusts the intensity thereof—e.g. by adjusting the intensity of the corresponding associated modulated subpupil  32 ′/light-source element  100 —in accordance with a predetermined, stored exit-subpupil intensity-control table  166  that provides the intensity of the associated modulated subpupil  32 ′/light-source element  100  as a function of the measures from step ( 6302 ) of location and extent of eye pupil  38 , so as to provide for a prospective optimal level of intensity of the modulated subpupil  32 ′/light-source element  100  to the satisfaction of most users  22 . For example, in accordance with one aspect, the exit-subpupil intensity-control table  166  is predetermined by simulating the second-aspect subpupil modulation control process  6300 , supra, for a range of possible locations and extents of the eye pupil  38 , and recording, as a function of the locations and extents of the eye pupil  38 , the resulting intensity levels of the associated modulated subpupils  32 ′/light-source elements  100  that are determined thereby responsive to the associated exit-subpupil characterization table  164 . In accordance with one set of embodiments, the exit-subpupil intensity-control table  166  contains a set of intensity factors that are used to multiply a corresponding predetermined, stored nominal intensity levels modulated subpupils  32 ′/light-source elements  100 . Similar to the second-aspect subpupil modulation control process  6300 , supra, the intensities of the modulated subpupils  32 ′/light-source elements  100  from the associated exit-subpupil intensity-control table  166  may be adjusted responsive to input from a particular user  22  in step ( 6604 ) so as to provide for a desired level of overall brightness of the perceived associated virtual image  16 ′. 
     Referring to  FIG.  67   , a fourth aspect of a subpupil modulation control process  6700  for controlling a subpupil modulator  30  also provides for controlling activation of exit subpupils  32 ,  32 ″ responsive to the degree of overlap thereof with an eye pupil  38 , and is the same as the third-aspect subpupil modulation control process  6600 , supra, except that steps ( 6304 ) through ( 6320 ), ( 6602 ) and ( 6604 ) are replaced by steps ( 6702 ) through and ( 6706 ), wherein, following step ( 6302 ), for a particular set of measures of the location and lateral extent of the eye pupil  38  from the eye-tracking subsystem  42 , in step ( 6702 ), the subpupil modulation controller  50  determines the intensity control values of each element of a global subpupil intensity control array  168 , the elements of which are in one-to-one correspondence with the modulated subpupils  32 ′/light-source elements  100 ,  90  of the associated subpupil modulator  30 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5 , the values of which can range from OFF or zero for a corresponding deactivated exit subpupil  32 ,  32 ″ to a maximum level corresponding to a maximum level of intensity of the associated modulated subpupil  32 ′/light-source element  100 ,  90 , and include levels therebetween (either continuous or discrete) less than the maximum level of intensity so as to provide for intermediate levels of intensity of the associated modulated subpupil  32 ′/light-source element  100 ,  90 . For example, in accordance with one set of embodiments, the levels of intensity of the elements of the global subpupil intensity control array  168  are the same, or at least substantially the same, as what would be provided for by either the second- or third-aspect subpupil modulation control processes  6300 ,  6600 , supra, possibly limited to the determination for exit subpupil  32 ,  32 ″ within the associated Active Subpupil Region (ASR)  72 , with the remaining exit subpupils  32 ,  32 ″ deactivated, thereby precluding the need to determine in real time which exit subpupils  32 ,  32 ″ are outside of the Active Subpupil Region (ASR)  72  unless the Active Subpupil Region (ASR)  72  is being modified in real time, for example, when compensating for rapid eye movements. In accordance with one set of embodiments, the predetermined intensity values of the exit-subpupil intensity-control table  166  provide for a consistent perceived brightness of the virtual image  16 ′″ while maximizing power efficiency, for example, by maximizing the number of modulated subpupils  32 ′ that are deactivated. 
     In accordance with one aspect, the values of the elements of the global subpupil intensity control array  168  are determined responsive to the measures of the location and lateral extent of the eye pupil  38  from the eye-tracking subsystem  42 , provided from step ( 6302 ), for example, using the third-aspect subpupil modulation control process  6600 , with the associated values of the exit-subpupil intensity-control table  166  predetermined—either by simulation or measurement—for a range of possible values of the measures of the location and lateral extent of the eye pupil  38 , for each of the possible exit subpupils  32 ,  32 ″ within the exit pupil  18 , and associated with the complete set of modulated subpupils  32 ′ of the subpupil modulator  30 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5 . In accordance with one aspect in cooperation with a predetermined exit-subpupil intensity-control table  166  covering the range of possible conditions of the eye pupil  38 , the intensity values of the elements of the global subpupil intensity control array  168  are provided for by a table-lookup process by which the intensity value of each exit subpupil  32 ,  32 ″—ranging from deactivated to maximum intensity, and intensity levels therebetween—is determined for each of the exit subpupils  32 ,  32 ″ by a table lookup of the exit-subpupil intensity-control table  166  responsive to the location and extent of the eye pupil  38 . Following the determination in step ( 6702 ) of the intensity control levels of the global subpupil intensity control array  168 , in step ( 6704 ), each of the corresponding associated modulated subpupils  32 ′ of the subpupil modulator  30 ,  30 . 2 ,  30 . 3 ,  30 . 4 ,  30 . 5  is controlled responsive thereto, and possibly further responsive to input from a particular user  22  in step ( 6706 ) so as to provide for a desired level of overall brightness of the perceived associated virtual image  16 ′″. 
     Notwithstanding the prospective reduction in power as a result of the modulation of variable-intensity light-source elements  100  associated with realized exit subpupil  32 ″, it is possible that one or more regions of activated exit subpupils  32 ,  32 ″ might be larger than the eye pupil  38 , and therefore, not as susceptible to benefit from intensity modulation as would be sufficiently smaller exit subpupils  32 ,  32 ″ of a relatively-more-ideal associated optical subsystem  14 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  for which all of the light  16 ′ from a single light-source element  100  might pass entirely through the eye pupil  38 , so as to provide for deactivating other exit subpupils  32 ,  32 ″. However, from an analysis of one set of embodiments, operating in cooperation with typical locations and extents (diameters) of an eye pupil  38 , even without optimizing the use of variable-intensity light-source elements  100 , it was found that approximately 60 to 80 percent of the light-source elements  100  could be deactivated at any given time, demonstrating the prospect of a relatively-wide field-of-view near-eye display system  10  incorporating relatively simple and realistic components in a relatively-compact arrangement, particularly if the optical path between the light-source elements  100  and the exit pupil  18  is folded with one or more reflective surfaces, infra. 
     The diameter of a typical eye pupil  38  is in the range of 2 to 8 millimeters, and is responsive to the overall intensity of the virtual image  16 ′″, wherein the diameter/size of the eye pupil  38  is inversely related to the brightness of the virtual image  16 ′″, as would the diameter/size of the associated Active Subpupil Region (ASR)  72 , the latter of which provides for deactivating relatively-more exit subpupils  32 ,  32 ″ in association with a relatively-brighter virtual image  16 ′″ than for a relatively-dimmer virtual image  16 ″. 
     Each exit subpupil  32 ,  32 ″ is a collection of light  16 ′ from, and in one-to-one correspondence with, a corresponding modulated subpupil  32 ′, for example, but not limited to, a real image of the modulated subpupil  32 ′. For the first aspect near-eye display system  10 ,  10 . 1 , the modulated subpupil  32 ′ corresponds to a light-modulating pixel  60  of an associated flat-panel two-dimensional modulation array  58 . For a second-  10 . 2 , or third- 10 . 3  aspect near-eye display system  10 ,  10 . 2 ,  10 . 3  the modulated subpupil  32 ′ corresponds to a light-source element  100  of an associated controllable light source  97 . For the fourth aspect near-eye display system  10 ,  10 . 4 , the modulated subpupil  32 ′ corresponds to a modulation element  90  of an associated controllable light source  97 . For the fifth-aspect near-eye display system  10 ,  10 . 5 , the modulated subpupil  32 ′ corresponds to a light-emitting pixel  54  of an associated waveguide projector  152 . 
     The size, shape, and intensity profile of each exit subpupil  32 ,  32 ″ depends upon a) the size, shape, and intensity profile the associated source of light  104  at the associated modulated subpupil  32 ′; b) the ability of the associated optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  to form an image of the modulated subpupil  32 ′; and c) the transverse location of the modulated subpupil  32 ′ relative to the optical axis  36  of the optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 , i.e. the degree to which the modulated subpupil  32 ′ is on- or off-axis relative to the optical axis  36 , wherein an on-axis exit subpupil  32 ,  32 ″ would likely have better image quality than an off-axis exit subpupil  32 ,  32 ″. 
     For relatively-smaller exit subpupils  32 ,  32 ″—even if relatively blurred by either an imperfect optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7  or a misalignment between user  22  and the near-eye display system  10 —relatively more exit subpupils  32 ,  32 ″ would likely be outside the Active Subpupil Region (ASR)  72  and therefore subject to deactivation, so as to provide for a relatively greater power savings. Although generally, relatively-smaller exit subpupils  32 ,  32 ″ are beneficial, practical limits either on a) the density of associated pixels  60 ,  54  or light-source elements  100 , or b) the performance of the associated optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 , or an associated user-caused misalignment thereof, can limit the lower bound on the size of the exit subpupils  32 ,  32 ″. For example, in one set of embodiments, a diameter of exit subpupils  32 ,  32 ″ in the range of 0.5 to 2.0 millimeters is beneficial because: a) a larger diameter would imply greater overlap of adjacent exit subpupils  32 ,  32 ″ and thereby involve relatively more complex mapping and intensity control of any of the second-through fourth-aspect subpupil modulation control process  6300 ,  6600 ,  6700 ; b) a diameter in the range of 0.5 to 2.0 millimeters would be sufficiently smaller than the eye pupil  38  so as to provide for utilizing an Active Subpupil Region (ASR)  72  with a single exit subpupil  32 ,  32 ″ located within the eye pupil  38  so as to provide for maximum power savings; and c) for a smaller diameter, maintenance of a proper image of a point light source would be challenging to implement, and likely not cost effective, even with a relatively good optical subsystem  14 ,  14 . 1 ,  14 . 2 ,  14 . 3 ,  14 . 4 ,  14 . 5 ,  14 . 6 ,  14 . 7 , particularly when subject to an associated user-caused misalignment thereof. 
     Referring again to  FIGS.  59   a  and  59   b   , an ideal optical subsystem  14  forms a real image of each modulated subpupil  32 ′ as a corresponding idealized exit subpupil  32 , possibly with magnification, that is focused on the surface  18 ″ of the exit pupil  18 , i.e. the subpupil surface  84 , which in turn is aligned with the eye pupil  38  and which conforms to the front surface  20 ′ of the eye  20 . However, referring again to  FIG.  59   c   , for an optical subsystem  14  with imperfect optical components, or for a subpupil surface  84  that is either misaligned with respect to the eye pupil  38  or that does not conform to the front surface  20 ′ of the eye  20 , the resulting realized exit subpupil  32 ″, to first order, might be an effectively blurred image of the associated modulated subpupil  32 ′, for which adjacent realized exit subpupils  32 ″ of an array of realized exit subpupils  32 ″ associated with a corresponding array of modulated subpupils  32 ′ of an associated subpupil modulator  30  might overlap with one another, particularly given the typically minimal practical separation between adjacent modulated subpupils  32 ′, for example, adjacent light-source elements  100 . If such blurring and overlapping is relatively consistent across the subpupil surface  84  then the user  22  will not see significant differences in intensity as the eye pupil  38  is rotated and directed at different locations of the virtual image  16 ′″ provided that no light  16 ′ from a deactivated exit subpupil  32 ,  32 ″ would have reached the eye pupil  38  if activated or, in other words, provided that the Active Subpupil Region (ASR)  72  is sufficiently large to prevent such a condition. However, the larger the size of the exit subpupil  32 ,  32 ″, the greater the likelihood of more exit subpupils  32 ,  32 ″ overlapping the eye pupil  38 , and therefore the larger the size of the Active Subpupil Region (ASR)  72  would need to be in order to preclude that condition from occurring. If the region occupied by the exit subpupil  32 ,  32 ″ was entirely outside the eye pupil  38 , then the deactivation thereof would not have an impact on the perceived brightness of the virtual image  16 ′″. Accordingly, one method of mitigating against a prospective perceived reduction in brightness of the virtual image  16 ′″ responsive to a prospective deactivation of exit subpupils  32 ,  32 ″—absent a modification of the brightness of activated exit subpupils  32 ,  32 ″, infra—would be to increase the size of the Active Subpupil Region (ASR)  72  so that only those exit subpupils  32 ,  32 ″ that do not overlap with the eye pupil  38  would be subject to deactivation. Furthermore, as the size of the Active Subpupil Region (ASR)  72  is increased, a relatively lesser proportion of the exit subpupils  32 ,  32 ″ are outside thereof and susceptible to automatic deactivation to reduce power usage. Generally, exit subpupils  32 ,  32 ″ having a diameter between 0.5 and 2.0 millimeters are beneficial because the size of the Active Subpupil Region (ASR)  72  would then need to be only slightly larger than that of eye pupil  38  under the relatively simplest implementation, for example, in accordance with the first aspect subpupil modulation scheme  70 ,  70 . 1 , supra, while also alternatively providing for a relatively smaller Active Subpupil Region (ASR)  72  in accordance either the third aspect subpupil modulation scheme  70 ,  70 . 3 , supra, or any of the first—through fourth-aspect subpupil modulation control processes  6100 ,  6300 ,  6600 ,  6700 , supra. 
     In an extreme case, the exit subpupils  32 ,  32 ″ are not only blurred images of their corresponding associated modulated subpupils  32 ′, but also vary in size, shape and intensity profile (i.e. the profile of propagated optical ray density through each given point within the subpupil) relative to one another as a result of passage through different portions of the optical subsystem  14 . For example, it is anticipated that exit subpupils  32 ,  32 ″ formed from rays that propagate from a modulated subpupil  32 ′ that is relatively distal to the optical axis  36  of the optical subsystem  14  will be formed sub-optimally, resulting in a corresponding relatively-larger exit subpupil  32 ,  32 ″ with a relatively non-uniform intensity profile relative to an exit subpupil  32 ,  32 ″ associated with a modulated subpupil  32 ′ that is relatively proximal to the optical axis  36 . Under the first aspect subpupil modulation scheme  70 ,  70 . 1 , supra, if the Active Subpupil Region (ASR)  72  is sufficiently large to encompass the entirety of such sub-optimally-formed exit subpupils  32 ,  32 ″ that could overlap the eye pupil  38  by even a small amount, then the corresponding associated modulated subpupils  32 ′ would remain activated. 
     Referring to  FIGS.  68  and  69   , a sixth-aspect near-eye display system  10 ,  10 . 6  is the same as the second aspect near-eye display system  10 ,  10 . 2 , supra, except that the sixth-aspect near-eye display system  10 ,  10 . 6  does not incorporate a first dioptric-power optical element  56 ,  56 . 1 ,  56 . 1 ′, L 1 , and, instead of a second dioptric-power optical element  56 ,  56 . 2 ,  56 . 2 ′, L 2 , the sixth-aspect near-eye display system  10 ,  10 . 6  incorporates at the same relative location—i.e. between the flat-panel two-dimensional image-display modulation array  94  and the associated exit pupil  18 —a catadioptric magnifier  170  as the associated eighth-aspect optical subsystem  14 ,  14 . 8 . Accordingly, the associated flat-panel two-dimensional image-display modulation array  94  cooperates directly with the controllable light source  97 /flat-panel two-dimensional light-source array  98  as the associated seventh-aspect image generator  12 ,  12 . 7  that provides for generating the light  16 ′ of the virtual image  16 ′″ by modulating the light  104  from the controllable light source  97 . The catadioptric magnifier  170 —also referred to as a “pancake lens”—incorporates an internally-folded optical path in a compact form that provides for relatively-high image quality and a relatively-large field-of-view in a relatively-compact arrangement of refractive, reflective and polarization components, for example, as described in the following references, each of which is incorporated by reference in its entirety: “Folded optics with birefringent reflective polarizers” by Timothy L. Wong, Zhisheng Yn, Gregg Ambur and Jo Etter, Porc. SPIE 10335, Digital Optical Technologies 2017, 103350E (26 Jun. 2017); doi;10.1117/12.2270266; and U.S. Pat. No. 3,940,203 to Joseph Anthony La Russa, issued on 24 Feb. 1976. 
     More particularly, referring to  FIG.  69   , the catadioptric magnifier  170  incorporates first  172 , second  174 , and third  176  dioptric elements, oriented with a first surface  172 . 1  (also designated as the S 1  surface) of the first dioptric element  172  facing the exit pupil  18 , a second surface  172 . 2  (also designated as the S 2  surface) of the first dioptric element  172  facing a first surface  174 . 1  (also designated as the S 3  surface) of the second dioptric element  174 , a second surface  174 . 2  (also designated as the S 4  surface) of the second dioptric element  174  facing a first surface  176 . 1  of the third dioptric element  176 , and a second surface  176 . 2  (also designated as the S 6  surface) of the third dioptric element  176  facing the flat-panel two-dimensional image-display modulation array  94 . A reflective linear polarizer  178  and a quarter-wave plate  180  are located between the first  172  and second  174  dioptric elements and abutting one another, with the reflective linear polarizer  178  also abutting the second surface  172 . 2  of the first dioptric element  172 , and the quarter-wave plate  180  also abutting the first surface  174 . 1  of the second dioptric element  174 . The reflective linear polarizer  178  provides for reflecting light of a first direction of linear polarization, and provides for transmitting light of a second direction of linear polarization that is relatively orthogonal to the first direction of linear polarization. The quarter-wave plate  180  provides for converting linearly-polarized light to circularly-polarized light, and can provide for converting circularly-polarized light to linearly-polarized light, as described in U.S. Pat. No. 3,940,203. The second surface  176 . 2  of the third dioptric element contains a reflective coating  182  (e.g. half silvered), for example, in one set of embodiments, that provides for reflecting about half of the light incident thereupon. In cooperation with the illustrated catadioptric magnifier  170 , the sixth-aspect near-eye display system  10 ,  10 . 6  is configured so that light  16 ′ entering the catadioptric magnifier  170  from the flat-panel two-dimensional image-display modulation array  94  is preconditioned to be circularly polarized. In one set of embodiments, the first  172 , second  174 , and third  176  dioptric elements are made of injection-moldable acrylic, for example, for the second  174 , and third  176  dioptric elements, with minimum birefringence. 
     In operation of the sixth-aspect near-eye display system  10 ,  10 . 6 , half of the circularly-polarized light  16 ′ from the flat-panel two-dimensional image-display modulation array  94  incident upon the S 6  surface is reflected and lost. The remaining light  16 ′ is transmitted through the S 6  surface and subsequently refracted at the S 5  surface and then refracted at the S 4  surface, and then subsequent transmitted through the S 3  surface and the quarter-wave plate  180  in abutment therewith, which converts the circularly-polarized light  16 ′ to linearly-polarized light  16 ′ having the first direction of linear polarization, which is then reflected by the reflective linear polarizer  178  in abutment with the quarter-wave plate  180 . The reflected linearly-polarized light  16 ′ is then again transmitted a second time through the quarter-wave plate  180  and converted thereby to circularly-polarized light  16 ′, which is then refracted by the S 4  surface and then refracted by the S 5  surface, after which, half of that circularly-polarized light  16 ′ is internally reflected by the reflective coating  182  on the S 6  surface, with the remainder of that light  16 ′ being transmitted through the S 6  surface and lost. The internally reflected light  16 ′—circularly polarized, but of opposite handedness to the light  16 ′ that was initially incident upon the catadioptric magnifier  170 —is then refracted by the S 5  surface and then refracted by the S 4  surface, and then transmitted through the S 3  surface and then transmitted a third time through the quarter-wave plate  180  and converted thereby to linearly-polarized light  16 ′, but having the second direction linear polarization, so as to provide for that light  16 ′ to be transmitted through the reflective linear polarizer  178 , then transmitted through the S 2  surface, and finally refracted by the S 1  surface for propagation to the exit pupil  18 , after having been transmitted three times through each of the S 4  and S 5  surfaces. 
     It should be understood that the particular configuration of the catadioptric magnifier  170  illustrated in  FIGS.  68  and  69   , —and described hereinabove to provide a general description of how refractive, reflective and polarization elements can work in a multi-pass catadioptric arrangement as a catadioptric magnifier  170 , —is not limiting, and that other polarization implementations, assignments of polarization and reflective surfaces and types and numbers of elements may be applied to effectively create other embodiments of a catadioptric magnifier  170  in accordance with the sixth-aspect near-eye display system  10 ,  10 . 6 . 
     In accordance with a first stage of an associated design process, the catadioptric magnifier  170  illustrated in  FIGS.  68  and  69    was designed using a similar optical design process as described hereinabove for other lenses of the near-eye display system  10 , with associated design parameters of virtual image field of view, apparent distance to that virtual image, design entrance pupil (i.e. ultimately the exit pupil of the optical system), and the distance from exit pupil to the magnifier, and, to support moldability, using an acrylic material for the first  172 , second  174  and third  176  dioptric elements, with a space provided for between the second  174  and third  176  dioptric elements, with the S 2  and S 3  surfaces each constrained to be a flat surface that was common to both so as to better support the application of a reflective polarization surface between the first  172  and second  174  dioptric elements as a bonded doublet, and with a flat surface representing the flat-panel two-dimensional image-display modulation array  94 . For design purposes, the exit pupil  18  was treated as a design entrance pupil  141  for the optical simulation of light rays traveling forward therefrom, to and through the first  172 , second  174  and third  176  dioptric elements, and onto the flat surface representing the flat-panel two-dimensional image-display modulation array  94 . The S 6  surface was modeled as a mirror for the first pass of light traveling forward from the design entrance pupil  141  through the first  172 , second  174  and third  176  dioptric elements, and the common, flat S 2 /S 3  surface was modeled as a mirror for the second pass. Effectively the design process therefore includes passing light from the exit pupil  18 /design entrance pupil  141 , through all each of the first  172 , second  174  and third  176  dioptric elements, then reflecting from the S 6  surface to pass again but in reverse back successively through the third  176  and second  174  dioptric elements, then reflecting from the flat S 2 /S 3  surface to pass again in a forward direction successively through the second  174  and third  176  dioptric elements to form an image at the location of the flat-panel two-dimensional image-display modulation array  94 , with the goal of forming a best image of the virtual image thereat. The optical design therefore involves seven total elements for design purposes, wherein the various surfaces are constrained to represent common elements as the light interacts therewith. 
     In a second stage of the optical design process, the optical subsystem  14 ,  14 . 8  may then be modeled in combination with additional optical elements to account for passage of light rays through the flat-panel two-dimensional image-display modulation array  94  and back to the controllable light source  97  of the flat-panel two-dimensional light-source array  98 , using the entrance pupil  28 ′ as the design object  138 , and utilizing a process similar to the conditioner-lens prescription design process  5000  to determine an optimum image of the entrance pupil  28 ′ as a modulation surface  92  of the controllable light source  97  of the flat-panel two-dimensional light-source array  98 . 
     As an alternative to the first stage of the design process, the light rays through the flat-panel two-dimensional image-display modulation array  94  from the first stage of the design process may be continued therethrough to a new geometric surface and aperture  28  which can be modeled as a retroreflective surface (i.e. a phase conjugation surface) wherefrom the optical rays retroreflect back to the flat-panel two-dimensional image-display modulation array  94 . In other words, any ray striking that surface is exactly reversed, and the final geometric image at the flat-panel two-dimensional image-display modulation array  94  is exactly that of the first intermediate image passing through the flat-panel two-dimensional image-display modulation array  94 . These retroreflected rays for purposes of the design would be identical to the rays from the flat-panel two-dimensional image-display modulation array  94  to the controllable light sources  97 . 
     The optical subsystem  14 ,  14 . 8  can therefore be optimized for best image quality using the final surface as the image location (which similarly results in the intermediate image being optimized) while also possessing a surface within that optical subsystem where the lighting surface can be located. Appropriate parameters such as the distance from the flat-panel two-dimensional image-display modulation array  94  to the modulation surface  92  of the flat-panel two-dimensional light-source array  98  can then be varied to reach an optimized overall solution identifying the best location of that modulation surface  92  of the flat-panel two-dimensional light-source array  98 . 
     With the merit function of the design used to provide for a best image of the virtual image. additional operands in the merit function can provide a preference for a smallest size of that retroreflecting aperture while allowing the distance from the flat-panel two-dimensional image-display modulation array  94  to that aperture  28  to vary, with optimization thereof to provide for the smallest, and therefore most economical and compact, two-dimensional array  26  of controllable light sources  97  within that aperture  28 . One can further adjust the relative weights of the quality of the image formed at the flat-panel two-dimensional image-display modulation array  94  with the size and spacing of the two-dimensional array  26  of controllable light sources  97  within the associated aperture  28  so as to provide for the most compact design. Notwithstanding that such an approach may not result in a high-quality image of the two-dimensional array  26  of controllable light sources  97  at the desired exit pupil  18 , it nonetheless provides at least some ability to reduce intensities of those controllable light sources  97  so as to provide for reducing power consumption while best exploiting the advantages of a multi-pass catadioptric magnifier  170 . 
     Referring to  FIG.  68   , optical rays from three different points  184 . 1 ,  184 . 2 ,  184 . 3  on the surface  18 ″ of the exit pupil  18  are traced back to corresponding respective regions  186 . 1 ,  186 . 2 ,  186 . 3  on the modulation surface  92  of the flat-panel two-dimensional light-source array  98 . Whereas these regions  186 . 1 ,  186 . 2 ,  186 . 3  do not represent high-quality images of the corresponding respective points  184 . 1 ,  184 . 2 ,  184 . 3  on the surface  18 ″ of the exit pupil  18 , they can provide for control of the exit subpupils  32 ,  32 ″ to provide for reducing power consumption and reflection of extraneous light  16   iv  as described hereinabove, without need for an additional conditioner lens  102 ,  102 ′,  132 , L 1  to otherwise create such bounding regions within the associated modulation surface  92 . Accordingly, the ray traces illustrate the feasibility of a modulation surface  92  of associated controllable light sources  97 , each of which fully illuminates the entirety of the flat-panel two-dimensional image-display modulation array  94  while also collectively filling the exit pupil  18 . 
     Furthermore, referring to  FIG.  69   , a relatively-smaller region in the exit pupil  18  bounded by the first  184 . 1  and second  184 . 2  points therein correspond to a corresponding relatively-smaller region—bounded by the corresponding first  186 . 1  and second  186 . 2  regions therein—within the modulation surface  92  of associated controllable light sources  97 . Accordingly, for a given position of the eye pupil  38 , each light-source element  100  not having rays that reach the eye pupil  38  can be deactivated, together with activation of the remaining light-source elements  100  that have at least some rays that reach to the eye pupil  38 . Furthermore, in cooperation with an advanced mapping of the optical subsystem  14 ,  14 . 8  to account for the effect of location and extent of the eye pupil  38 , light-source elements  100  for which a relatively-low percentage of light rays therefrom would pass through the eye pupil  38 , can be either dimmed or deactivated, while also relatively increasing the intensity of light-source elements  100  for which a relatively-high percentage of light rays therefrom would pass through the eye pupil  38 , wherein each light-source element  100  is itself illuminating the entirety of the flat-panel two-dimensional image-display modulation array  94  so that the virtual image  16 ′″ viewed by the user would be a composite of the components of the virtual image  16 ′″ illuminated by each of the active light-source elements  100 . 
     Referring to  FIGS.  18 ,  19 ,  31 ,  32 , and  45  through  47   , it should be understood that the associated curved two-dimensional light-source array  106  of the third aspect near-eye display system  10 ,  10 . 3 , and the curved light-redirecting surface  110  of the fourth aspect near-eye display system  10 ,  10 . 4  are beneficial independent of the cooperation thereof with the associated subpupil modulator  30  and associated subpupil modulation processes, i.e. beneficial for illumination of an associated flat-panel two-dimensional image-display modulation array  94  to generate a corresponding virtual image  16 ′ and illuminate an exit pupil  18  therewith, by virtue of providing for the formation of exit pupil  18  having a concave-curved surface  18 ″ that better conforms to the front surface  20 ′ of the eye  20 , so as to provide for maintaining focus independent of the rotational position of the eye pupil  38 . 
     Furthermore, in respect of the third aspect near-eye display system  10 ,  10 . 3  illustrated in  FIGS.  18 ,  19 ,  45  and  47   , when the curved two-dimensional light-source array  106  incorporates non-isotropic light-source elements  100 , for example, light-emitting-diode elements  100 ′ that typically exhibit directivity, the curvature of the underlying concave-curved surface  107  provides for light  104  from each light-emitting-diode element  100 ′ to emanate in a direction that is normal to the underlying concave-curved surface  107 , so as to provide for a relatively-higher degree of uniformity of the illumination of the virtual image  16 ′″ relative to that which would otherwise be provided for by a flat-panel two-dimensional light-source array  98 . 
     For example, referring to  FIG.  70   , illustrating a typical luminous intensity distribution of a light-emitting diode for both horizontal (H) and vertical (V) directions of illumination, a light-emitting-diode element  100 ′ has sufficiently high directivity that if used in a flat-panel two-dimensional light-source array  98 , for example, as illustrated in  FIG.  17    for the second aspect near-eye display system  10 ,  10 . 2 , the angle, relative to the surface normal, of the relatively central optical ray from each light-emitting-diode element  100 ′ that passes through the center of the flat-panel two-dimensional image-display modulation array  94  increases with increasing distance of the light-emitting-diode element  100 ′ from the optical axis  36 , resulting in a corresponding reduction in brightness of that portion of the virtual image  16 ′″ with increasing distance of the corresponding modulated subpupil  32 ′ from the optical axis  36 , causing a variation in the perceived brightness uniformity of the virtual image  16 ′″ as a function of the location of the exit subpupil  32 ,  32 ″. In other words, if illuminated by a flat-panel two-dimensional image-display modulation array  94  of relatively-highly directive associated light-source elements  100 ,  100 ′, the brightness of the virtual image  16 ′″ will be higher in a particular area of the virtual image  16 ′″, gradually fading to a lower brightness around that relatively higher brightness area, with the location of that area of relatively higher brightness changing as the eye pupil  38  is directed at different image locations. 
     However, locating the relatively-highly directive light-source elements  100 ,  100 ′ on an underlying concave-curved surface  107  provides for significantly less deviation of the central optical ray from the surface normal, at any point across the entire curved two-dimensional light-source array  106 . Accordingly, as the eye pupil  38  receives light from different areas of the concave lighting surface for different gaze directions  34 , the center of the perceived virtual image  16 ″′ is still receiving light from that concave lighting surface which is substantially normal to that surface. Notwithstanding there still may be an area of the virtual image  16 ′″ of relatively-higher brightness due to a reduction in intensity from a light-source element  100 ,  100 ′ as a function of angle from the surface normal, that area of relatively-higher brightness will remain relatively fixed as the eye  20  rotates and therefore, if desired, can be compensated for by conventional means such as an overall intensity spatial profile adjustment of the virtual image  16 ′″ shown on the flat-panel two-dimensional image-display modulation array  94 , or the inclusion of a gradient filter. In addition to providing for greater uniformity in perceived intensity responsive to rotation of the eye  20 , the curved two-dimensional light-source array  106  also provides for a more efficient utilization of the light  104  generated by the light-source elements  100 ,  100 ′. 
     Generally, the angular-dependent output of light-source elements  100 ,  100 ′ can cause a “hot spot” of relatively higher perceived image brightness at the flat-panel two-dimensional image-display modulation array  94  through which the primary axis of the light-source element  100 ,  100 ′ passes. Accordingly, whereas the entire virtual image  16 ′″ will be seen through the eye pupil  38  regardless of the gaze direction  34 , this “hot spot” of higher brightness will move around in the virtual image  16 ′″ if these intersections of primary axes of different light-source elements  100 ,  100 ′ with the corresponding flat-panel two-dimensional image-display modulation array  94  locations, vary with gaze direction  34 . But if all those intersections are at the same spot, for example, generally the center of the flat-panel two-dimensional image-display modulation array  94 , then the “hot spot” will be in the same location regardless of gaze direction  34 . An appropriate curvature of the underlying concave-curved surface  107  provides for these normal directions to align with those intersections. This curvature may not necessarily be the best for forming a concave-curved subpupil surface  84 ,  84 ″ matching that of the front surface  20 ′ of the eye  20 , but there is certainly a synergy in providing a concave curvature for at least some benefit towards both goals. 
     It should be understood, that any reference herein to the term “or” is intended to mean an “inclusive or” or what is also known as a “logical OR”, wherein when used as a logic statement, the expression “A or B” is true if either A or B is true, or if both A and B are true, and when used as a list of elements, the expression “A, B or C” is intended to include all combinations of the elements recited in the expression, for example, any of the elements selected from the group consisting of A, B, C, (A, B), (A, C), (B, C), and (A, B, C); and so on if additional elements are listed. Furthermore, it should also be understood that the indefinite articles “a” or “an”, and the corresponding associated definite articles “the” or “said”, are each intended to mean one or more unless otherwise stated, implied, or physically impossible. Yet further, it should be understood that the expressions “at least one of A and B, etc.”, “at least one of A or B, etc.”, “selected from A and B, etc.” and “selected from A or B, etc.” are each intended to mean either any recited element individually or any combination of two or more elements, for example, any of the elements from the group consisting of “A”, “B”, and “A AND B together”, etc. Yet further, it should be understood that the expressions “one of A and B, etc.” and “one of A or B, etc.” are each intended to mean any of the recited elements individually alone, for example, either A alone or B alone, etc., but not A AND B together. Furthermore, it should also be understood that unless indicated otherwise or unless physically impossible, that the above-described embodiments and aspects can be used in combination with one another and are not mutually exclusive. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims, and any and all equivalents thereof