Abstract:
A method and apparatus relate to a projection module having an input port with light source module mounting structure, an output port with lens module mounting structure, an image forming section, and optics. The method and apparatus involve: routing radiation arriving through the input port along a first path of travel defined by the optics to the image forming section; generating images at the image forming section from the radiation arriving along the first path of travel; and routing images from the image forming section to and through the output port along a second path of travel defined by the optics.

Description:
[0001]    This application claims the priority under 35 U.S.C. §119 of provisional application No. 61/224,210 filed Jul. 9, 2009, the entire disclosure of which is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates in general to optical systems and, more particularly, to techniques for projecting images. 
       BACKGROUND 
       [0003]    There are a variety of different applications in which digital images are converted into optical images and then projected onto a screen. As one specific example, flight simulators have various instrument panels that display varying information to a pilot. Each display is unique in size, depending on the information being displayed. As a result, different display areas and/or different technologies are often used to implement each application. Some displays present color information, while others present monochrome information. Consequently, the projection apparatus for each display application has traditionally been a custom design tailored to the specific requirements, but this approach tends to drive up the overall cost of a flight simulator system. Also, displays have often been implemented with cathode ray tube (CRT) technology, but these types of displays take up space, and are inefficient in their use of energy. Consequently, although existing arrangements of this type have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    A better understanding of the present invention will be realized from the detailed description that follows, taken in conjunction with the accompanying drawings, in which: 
           [0005]      FIG. 1  is a diagrammatic perspective view of a projection apparatus that embodies aspects of the invention, and that includes a light source module, a projection engine module, and a projection lens module. 
           [0006]      FIG. 2  is a diagrammatic fragmentary exploded perspective view of a portion of the apparatus of  FIG. 1 , showing how the projection lens module is detachably coupled to the projection engine module. 
           [0007]      FIG. 3  is a diagrammatic fragmentary perspective view of a portion of the projection engine module of  FIG. 1 . 
           [0008]      FIG. 4  is a diagrammatic fragmentary perspective view of an end portion of the light source module of  FIG. 1 . 
           [0009]      FIG. 5  is a diagrammatic top view of optical components provided within the projection engine module and projection lens module of  FIG. 1 . 
           [0010]      FIG. 6  is a diagrammatic side view of the optical components of  FIG. 5 . 
           [0011]      FIG. 7  is a diagrammatic rear view of the optical components of  FIG. 5 . 
           [0012]      FIG. 8  is a diagrammatic sectional view taken along section line  8 - 8  in  FIG. 7 . 
           [0013]      FIG. 9  is a diagrammatic perspective view of a projection apparatus that is an alternative embodiment of the projection apparatus of  FIG. 1 . 
           [0014]      FIG. 10  is a diagrammatic view showing optical components that are provided within a projection lens module of the projection apparatus of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1  is a diagrammatic perspective view of a projection apparatus  10  that embodies aspects of the invention, and that can project images onto a not-illustrated screen. The projection apparatus  10  includes a polychromatic light source module  12 , a projection engine module  13 , and a projection lens module  14 . The projection engine module  13  and projection lens module  14  are sometimes referred to collectively as a projection engine.  FIG. 2  is a diagrammatic fragmentary exploded perspective view of a portion of the apparatus  10  of  FIG. 1 , showing how the projection lens module  14  is detachably coupled to the projection engine module  13 . 
         [0016]    The projection engine module  13  includes a housing  17  having two spaced flanges  18  and  19  at one end. The flange  18  has two spaced threaded holes  21  and  22 , and the flange  19  has two spaced threaded holes  23  and  24 . A cylindrical alignment pin  26  projects outwardly from the flange  18  at a location between the threaded holes  21  and  22 , and a cylindrical alignment pin  27  projects outwardly from the flange  19  at a location between the threaded holes  23  and  24 . The projection engine module  13  has a prism  31  supported between the flanges  18  and  19 . The prism  31 , which will be described in more detail later, has a surface  32 . As indicated diagrammatically by an arrow  33 , a series of optical images exit the projection engine module  13  through the surface  32  of prism  31 . This represents an optical outlet port of the projection engine module  13 . 
         [0017]    The projection lens module  14  has a housing  36  that includes a plate-like flange  37 . The flange  37  has two spaced cylindrical alignment holes  38  and  39  that each snugly and slidably receive a respective one of the alignment pins  26  and  27 . In addition, the flange  37  has two cylindrical holes  41  and  42  that extend therethrough on opposite sides of the alignment hole  38 , and two further cylindrical holes  43  and  44  that extend therethrough on opposite sides on the alignment hole  39 . Four screws  46 - 49  each extend through a respective one of the holes  41 - 44  in the flange  37 , and each engage a respective one of the threaded holes  21 - 24  in the flanges  18  and  19 , in order to fixedly secure the projection lens module  14  to the projection engine module  13  with an accurate alignment, so that images exiting the projection engine module  13  at  33  enter the projection lens module  14 . A setscrew  52  engages a threaded opening that extends through a wall of the housing  36  of the projection lens module  14 , for a purpose that will be discussed later. 
         [0018]      FIG. 3  is a diagrammatic fragmentary perspective view of a portion of the projection engine module  13 . A support  56  of approximately rectangular shape is movably supported on the housing  17  of the projection engine module  13 . Two adjusting screws  57  and  58  cooperatively engage the support  56  and the housing  17 , so that rotation of the screws moves the associated end of the support  56  toward or away from the housing  17  in a manner that involves approximately pivotal movement of the support  56  about an end remote from the screws. 
         [0019]    The housing  17  of the projection engine module  13  has an approximately circular flange  61 . The flange  61  has an axially-facing planar side surface  63  on an outer side thereof. A cylindrical opening  62  extends through the center of the flange  61 . Due to the opening  62 , the flange  61  may sometimes be referred to herein as an annular flange. The flange  61  has three threaded openings  67 ,  68  and  69  that extend therethrough at respective locations which are spaced angularly about the opening  62 . The opening  62  serves as an inlet port through which radiation can enter the projection engine module  13 . 
         [0020]    The polychromatic light source module  12  is a device that is described in detail in U.S. application Ser. No. 12/823,725 filed Jun. 25, 2010, and U.S. Application No. 61/220,378 filed Jun. 25, 2009, the entire disclosures of which are hereby incorporated herein by reference. The light source module  12  is discussed here only briefly, to an extent that will facilitate an understanding of certain aspects of the present invention. 
         [0021]      FIG. 4  is a diagrammatic fragmentary perspective view of an end portion of the polychromatic light source module  12  of  FIG. 1 . With reference to  FIGS. 1 and 4 , the module  12  has at one end an approximately circular flange  73  with an axially-facing planar side surface  74  on an outer side thereof. A cylindrical projection  77  extends axially outwardly from a central portion of the flange  73 , and has an axially-facing planar end surface  78  at the outer end thereof. A radially-outwardly facing cylindrical surface  79  extends circumferentially around the projection  77 , and has a diameter only slightly smaller than the diameter of the cylindrical opening  62  ( FIG. 3 ). A rectangular opening  81  extends axially through the centers of the projection  77  and the flange  73 . Three arcuate slots  82 ,  83  and  84  each open through the flange  73  at respective locations spaced angularly about the projection  77 , and each extend approximately circumferentially with respect to the projection  77 . A rectangular tube  86  has an end portion that extends outwardly through the opening  81  and projects beyond the outer end of the cylindrical projection  77 . The rectangular tube  86  is part of a light pipe that is disposed within the light source module  12 . 
         [0022]    The light source module  12  includes three light emitting diode (LED) modules  87 ,  88  and  89 , which respectively emit red, green and blue light into the light pipe at respective locations within the module  12 . The radiation from these modules then travels through the light pipe and exits the light source module  12  through the tube  86 , as indicated diagrammatically at  91  in  FIG. 4 . The LED modules  87 - 89  are selectively and independently controlled by a not-illustrated control circuit. At any given point in time, one, two or all three of the LED modules  87 - 89  may be energized and emitting radiation. When two or more of the LED modules are simultaneously emitting radiation, that radiation is mixed within the light pipe. Consequently, by appropriately controlling the LED modules  87 - 89 , the radiation exiting the light pipe at  91  can have virtually any desired color within the visible spectrum. 
         [0023]    With reference to  FIGS. 3 and 4 , the cylindrical projection  77  on the light source module  12  is inserted into the cylindrical opening  62  in the housing  17  of the projection engine module  13 . The cylindrical surface  79  slidably engages the cylindrical inner surface of the opening  62 , and the axially-facing annular surface  74  on the module  12  slidably engages the axially-facing annular surface  63  on the module  13 . The three slots  82 - 84  are respectively aligned with the three threaded openings  67 - 69 , and three screws each extend through a respective one of the slots  82 - 84  and engage a respective one of the threaded openings  67 - 69 , one of these screws being visible at  92  in  FIG. 1 . By loosening these three screws slightly, the module  12  can be pivoted or “clocked” slightly relative to the housing  17  of the module  13 , within limits imposed by engagement of the screws with the ends of the slots  82 - 84 . This allows the orientation of the rectangular beam of light exiting the rectangular light tube  86  ( FIG. 4 ) to be pivotally adjusted about the path of travel  91  relative to the inlet port defined by the opening  62  in the housing  17  of module  13 . The three screws can then be tightened to fixedly secure the light source module  12  in an appropriate pivotal position with respect to the projection engine module  13 . 
         [0024]    As shown in  FIG. 1 , the housing  17  of the projection engine module  13  includes two mounting plates  96  and  97  that can be used to removably mount the entire projection apparatus  10  within a larger system. With reference to  FIG. 1 , light from the light source module  12  enters the inlet port of the projection engine module  13  through opening  62  ( FIG. 3 ), is converted into images as it travels through the module  13 , then exits at  33  ( FIG. 2 ) through the outlet port of the module  13  while entering the projection lens module  14 , and eventually exits the module  14  along a path of travel  101 . The modules  13  and  14  each include several optical components.  FIG. 5  is a diagrammatic top view of the optical components provided within the projection engine module  13  and projection lens module  14 .  FIG. 6  is a diagrammatic side view of the optical components of  FIG. 5 .  FIG. 7  is a diagrammatic rear view of the optical components of  FIG. 5 .  FIG. 8  is a diagrammatic sectional view taken along section line  8 - 8  in  FIG. 7 . 
         [0025]    Within the projection engine module  13 , radiation  91  that enters the inlet port  62  passes through a stationary collimating lens  110 , and is reflected by a stationary fold mirror  111 . This radiation then passes through a stationary relay lens  116 , is reflected by a stationary fold mirror  117 , and then passes through an optional stationary filter  121 , and three stationary relay lenses  122 ,  123  and  124 . In the disclosed embodiment, when the optional filter  121  is present, it is an interference filter that reduces the color range of the radiation passing through it, in a manner so that images ultimately exiting the apparatus  10  at  101  ( FIG. 1 ) have a generally monochrome appearance that simulates low-light nighttime conditions. However, it would alternatively be possible to provide a different type of filter at  121  that influences radiation passing through it in some other manner. 
         [0026]    After passing through the filter  121  and the relay lenses  122 - 124 , radiation is reflected by a fold mirror  126  that is fixedly supported on the inner side of the support  56  ( FIG. 3 ). By turning the screws  57  and  58  ( FIG. 3 ), the support  56  and thus the fold mirror  126  can be adjusted through a small range of pivotal movement. This permits a slight adjustment in the path of travel followed by radiation after it is reflected by the mirror  126 . After being reflected by the fold mirror  126 , the radiation passes through a field lens  128 . 
         [0027]    As best seen in  FIG. 8 , after radiation has passed through the field lens  128 , it enters a stationary prism  136 . The prism  136  is a total internal reflection (TIR) prism having a planar surface  137  that reflects substantially all radiation impinging on it. In the disclosed embodiment, this reflection is achieved through the principle commonly known as total internal reflection, which is a function of the angle at which radiation impinges on the surface  137 , and a function of the differences in indexes of refraction of the materials (air and glass) disposed on opposite sides of the surface  137 . The previously-mentioned prism  31  is also a TIR prism. The prism  31  has a planar surface  140  thereon, and the prism  136  has a planar surface  138  thereon. The planar surfaces  136  and  140  are parallel and spaced slightly from each other, with an air gap therebetween. 
         [0028]    With reference to  FIGS. 5 and 6 , two plano-plano glass side plates  141  and  142  are adhesively secured to the sides of each of the prisms  136  and  31 , in order to fixedly hold the two prisms in place with respect to each other, and thus maintain the air gap between the surfaces  138  and  140 . In the disclosed embodiment, the side plates  141  and  142  are adhesively secured to the prisms  31  and  136  with a commercially-available epoxy adhesive of a type well known in the art, but could alternatively be secured to the prisms in any other suitable manner. Radiation reflected by the surface  137  of prism  136  travels through that prism to the surface  138 . This radiation exits the prism  136  through the surface  138 , enters the prism  31  through the surface  140 , travels through the prism  31  to a bottom surface, and then exits the prism at  33  through the surface  32 . 
         [0029]    The radiation then reaches an imaging section of the projection engine module  13 . The imaging section includes a protective window  143  that is transparent to visible light, and the radiation passes through the window  143 . The imaging section also includes a digital imaging device  144  of a type that is known in the art, and therefore not described here in detail. The imaging device  144  has a plurality of micromirrors arranged in a rectangular array on an upper side thereof. After passing through the window  143 , radiation impinges on the array of micromirrors. The above-mentioned clocking of the light source module  12  ensures the rectangular beam of light that exits the light pipe  86  at  91  and later arrives at device  144  is accurately aligned with respect to the rectangular array of micromirrors. 
         [0030]    The imaging device  144  is supported on a circuit board  146 , and a not-illustrated control circuit transmits electrical control signals through a ribbon cable  147  to the circuit board  146 . These electrical control signals selectively effect independent pivotal movement of each of the micromirrors through a limited angle bounded by actuated and deactuated positions in which the micromirror reflects radiation in respective different directions. In particular, when a micromirror is actuated, reflected radiation travels to and enters the projection lens module  14 . In contrast, when a micromirror is deactuated, reflected radiation does not travel to and enter the projection lens module  14 . 
         [0031]    A heat sink  151  engages a back side of the imaging device  144 , in order to accept and dissipate heat. A leaf spring  152  urges the heat sink  151  upwardly in  FIG. 8 , in order to maintain the heat sink in firm contact with the device  144 . The array of micromirrors in the device  144  take radiation arriving from the light source module  12 , and convert it in a known manner into a series of successive images that are directed by actuated micromirrors to travel back into the prism  31 . In the prism  31 , substantially all of the energy of these images is reflected at the surface  140 , due to the principle of total internal reflection. This energy then travels to and exits the prism  31  through the surface  32 . As discussed above, the surface  32  of the prism  31  is considered to be the output port of the projection engine module  13 . 
         [0032]    Images that exit the projection engine module  13  and enter the projection lens module  14  successively pass through an adjustable focusing lens  171 , a stationary illumination lens  172 , a stationary illumination lens doublet  173 , another stationary illumination lens doublet  174 , stationary illumination lenses  175 ,  176 ,  177  and  178 , and two adjustable field curvature lenses  181  and  182 . During manufacture of the projection lens module  14 , the assembled module  14  is placed in a not-illustrated calibration device at the factory, and then the position of the focusing lens  171  is axially adjusted until the center of a projected image is in focus. Next, the positions of the field curvature lenses  181  and  182  are axially adjusted until the outer portions of that image are also in focus. When the central portion and the outer portions of the image are all in focus, the setscrew  52  ( FIG. 1 ) is tightened, and secures the focusing lens  171  in its correct position. In addition, the focusing lens  171  and the two field curvature lenses  181  and  182  are each adhesively bonded in position. In the disclosed embodiment, the adhesive is a commercially-available epoxy adhesive, but the lenses  171 ,  181  and  182  could alternatively be secured in position using any other suitable adhesive, or in other suitable manner. 
         [0033]    With reference to  FIGS. 5 and 8 , a path of travel extends within the projection engine module  13  from the inlet port  62  to the imaging device  144 . This path of travel has five successive segments that are each approximately linear, and each segment is approximately perpendicular to each segment adjacent to it. More specifically, an approximately linear segment  201  ( FIG. 5 ) extends from the inlet port through the collimating lens  110  to the fold mirror  111 , another approximately linear segment  202  that is approximately perpendicular to segment  201  extends from the fold mirror  111  through relay lens  116  to the fold mirror  117 , another approximately linear segment  203  ( FIG. 5 ) that is approximately perpendicular to segment  202  extends from the fold mirror  117  through the filter  121  and relay lenses  122 - 124  to the fold mirror  126 , another approximately linear segment  204  ( FIGS. 5 and 8 ) that is approximately perpendicular to segment  203  extends from the fold mirror  126  through the field lens  128  to the reflective surface  137  of prism  136 , and another approximately linear segment  205  ( FIG. 8 ) that is that is approximately perpendicular to segment  204  extends from the surface  137  through the two prisms  136  and  31  to the micromirror array in the digital imaging device  144 . 
         [0034]    Images produced by the imaging device  144  then follow another path of travel from the device  144  through the remaining optics, and this path of travel includes two approximately linear segments. More specifically, an approximately linear segment extends from the device  144  to the surface  140  of prism  31 , and another approximately linear segment  101  that is approximately perpendicular to segment  206  extends from the prism surface  140  through the lenses  171 - 178  and  181 - 182 . 
         [0035]      FIG. 9  is a diagrammatic perspective view of a projection apparatus  310  that is an alternative embodiment of the projection apparatus  10  of  FIG. 1 . The projection apparatus  310  of  FIG. 9  includes the projection light engine module  13  of  FIG. 1 , without any change. The projection apparatus  310  of  FIG. 9  also includes a monochromatic light source module  312  and a projection lens module  314  that are each detachably coupled to the projection light engine module  13 . 
         [0036]    The light source module  312  is similar to the light source module  12  of  FIG. 1 , except that the module  312  has only a single LED module  89 , which emits green light. Alternatively, it could be an LED module that produces light of some other color. The monochromatic light source module  312  is identical to a device that is disclosed in detail in above-mentioned U.S. application Ser. Nos. 12/823,725 and 61/220,378. The monochromatic light source module  312  is therefore discussed here only briefly, to an extent that will facilitate an understanding of certain aspects of the present invention. 
         [0037]    The light source module  312  has structure at one end that is similar to the structure shown in  FIG. 4  and described above. This structure is used to detachably secure the monochromatic light source module  312  to the flange  61  on the housing  17  of the projection engine module  13 , in the same manner described above for the light source module  12 . The light source modules  12  and  312  are easily interchangeable, and either can be detachably secured to or detached from the flange  61  at the inlet port of the housing  17 . 
         [0038]    The projection lens module  314  shown in  FIG. 9  has a flange  37  that is identical to the flange  37  of the module  14  in  FIG. 1 , and thus can easily be detachably secured to or detached from the housing  17  of the projection engine module  13 , in the same manner described above for the lens module  14 . Thus, the projection lens modules  14  and  314  are easily interchangeable. The lens modules  14  and  314  are designed to project light onto not-illustrated screens that have different sizes and that are spaced by different distances from the respective lens modules. The lens module  314  of  FIG. 9  differs from the lens module  14  of  FIG. 1  only in that (1) the arrangement of lenses within module  314  is different from the arrangement of lenses within module  14 , and (2) the housings  336  and  36  of the modules  14  and  314  have slightly different shapes, in order to accommodate the different arrangements of lenses therein. 
         [0039]      FIG. 10  is a diagrammatic view showing the lenses that are provided within the projection lens module  314  of  FIG. 9 . From right to left, images pass successively through an adjustable focusing lens  351 , stationary illuminating lenses  352 - 355 , stationary illuminating lens doublets  356  and  357 , stationary illuminating lenses  358  and  359 , and an adjustable field curvature lens  361 . During fabrication of the lens module  314 , the adjustable lenses  351  and  361  are successively positioned, and then are adhesively secured in position, in a manner similar to that described above for the adjustable lenses in the projection lens module  14 . 
         [0040]    As discussed earlier, the path of travel followed by radiation and images through the projection engine module  13  has multiple folds that are arranged so the entire apparatus  10  of  FIG. 1  and the entire apparatus  310  of  FIG. 9  are each very compact, but without any degradation to their illumination performance. Moreover, the core projection engine module  13  can be used in a variety of different applications without any modification, simply by detachably coupling to it an appropriate light source module  12  or  312  (or some other suitable light source module), and an appropriate projection lens module  14  or  314  (or some other suitable lens module). 
         [0041]    Although selected embodiments have been illustrated and described in detail, it should be understood that a variety of substitutions and alterations are possible without departing from the spirit and scope of the present invention, as defined by the claims that follow.