Abstract:
A display device for detecting light includes a display surface, at least one light sensitive element arranged behind the display surface, and a liquid crystal element arranged between the display surface and the at least one light sensitive element. The liquid crystal element is operative to polarization shift light incident on the at least one light sensitive element based on an orientation of the plurality of molecules. The display device further includes at least one electrode operative to change an orientation of the plurality of molecules. The at least one electrode is patterned to define a geometry of at least one field of view of the at least one light sensitive element. A controller is electrically coupled to the at least one electrode, wherein the controller is configured to apply a voltage to the at least one electrode to effect selection of the at least one field of view.

Description:
TECHNICAL FIELD 
     The present invention relates to a display panel. In particular, the present invention relates to the detection of light incident within electrically selectable fields of view upon an array of light sensors embedded within electronic layers of the display panel. Such a panel may be applied, for example, to the three-dimensional detection of the position of one or more user-controlled stylus/fingertips/scattering objects above or below the display panel&#39;s surface. The panel may also be applied, for example, to increase optical scanning resolution without increasing the number of embedded light sensors in the array. The panel may also be applied, for example, to achieve color scanning without increasing the number of embedded light sensors in the array and without loss of resolution. Further, the panel may be applied, for example, to acquire and simultaneously display stereoscopic images. 
     BACKGROUND OF THE INVENTION 
     WO2006132384 (Sharp Kabushiki Kaisha Corp.) This publication describes a display having switchable wide and narrow fields of view that make use of a variation in intensity with viewing angle and control a grey level curve of the display. In particular, the invention relates to electrical control of fields of view of light emitted from a display using intrinsic properties of the liquid crystal. This publication does not disclose the use of an in-cell polariser nor is the display implemented with an embedded sensor array. 
     WO2009/002446A1 (Chiefway Engineering Co. Ltd) 
     This publication describes a light-regulation membrane that uses polymer dispersed liquid crystal films sandwiched between polymer compound and a liquid crystal layer sandwiched in-between two conductive layers. In this invention, a field of view is not created through specific patterning of one of the ITO layers. 
     WO2007/058924 (Planar Systems Inc.) 
     This invention describes a display having embedded light sensors. One of the embodiments shows an LCD arrangement where the rear polariser is placed above the electronic layers. This is in contrast to the common position of the rear polariser which is below the electronics. In the invention, a field of view is not created on a sensor through specific patterning of one of the ITO layers. 
     There is an increasing interest in touch-sensitive panels, as they provide a simplified means of interaction with the user through the measurement of two-dimensional positioning of user-controlled objects on the display panel surface. 
     More particularly, the implementation of electrically switchable functions embedded with the touch-sensitive panel is of great advantage as it provides a simple efficient way to combine different functions into one display configuration. 
     Among these functions, three-dimensional detection of objects on top of the display, adaptation of display intensity to ambient light levels and document/fingerprint scanning generates a great interest for embedded light sensor display manufacturers. 
     SUMMARY OF THE INVENTION 
     The present invention provides a design for an optical structure embedded within electronic layers of a display so as to effect electrical switching of at least one field of view for light incident upon an array of light sensors embedded within the display. In this, an in-cell polarising element is inserted within the liquid crystal cell of the display and at least one of the liquid crystal electrodes is patterned in a manner that defines a geometry of at least one field of view. 
     According to one aspect of the invention, a display device for detecting light includes: a liquid crystal display element including at least one electrode patterned thereon; and at least one light sensitive element arranged behind the liquid crystal display element, wherein the at least one electrode, in conjunction with a voltage applied to the liquid crystal display element via the at least one electrode, is operative to change an optical transmission characteristic of the liquid crystal display element to define at least one field of view of the at least one light sensitive element relative to light transmitted through the liquid crystal display element, and wherein the at least one electrode is patterned to define a geometry of the at least one field of view of the at least one light sensitive element. 
     According to one aspect of the invention, the liquid crystal display element is operative to polarization shift light incident on the at least one light sensitive element 
     According to one aspect of the invention, the device further includes a controller electrically coupled to the at least one electrode, the controller configured to apply a voltage to the at least one electrode to effect selection of the at least one field of view. 
     According to one aspect of the invention, the device further includes an in-cell polarizing element arranged in the liquid crystal element. 
     According to one aspect of the invention, the liquid crystal element is arranged over the in-cell polarizing element. 
     According to one aspect of the invention, the in-cell polarizing element is arranged within the liquid crystal element. 
     According to one aspect of the invention, the device further includes at least one electronic layer, wherein the at least one light sensitive element is embedded within the at least one electronic layer. 
     According to one aspect of the invention, the device further includes a polarizing element arranged over the liquid crystal element, the polarizing element configured to linearly polarize light incident on the at least one light sensitive element. 
     According to one aspect of the invention, the device further includes a polarizing element arranged under the liquid crystal element, the polarizing element configured to linearly polarize light incident on the at least one light sensitive element. 
     According to one aspect of the invention, the at least one electrode is arranged such that a position and shape of the at least one electrode relative to the at least one light sensitive element induces the field of view of the at least one light sensitive element toward a predetermined direction. 
     According to one aspect of the invention, when the liquid crystal element is in a first state, incident polarized light is either transmitted through the liquid crystal element and impinges on a surface of the at least one light sensitive element, or the incident polarized light blocked from passing through the liquid crystal element, wherein the at least one light sensitive element generates a scaled signal corresponding to a light input pixel. 
     According to one aspect of the invention, the at least one electrode is patterned in a rectangular, square, circular, or elliptical shape. 
     According to one aspect of the invention, the at least one electrode is a ground electrode and positioned adjacent to an edge of another electrode. 
     According to one aspect of the invention, the ground electrode is patterned in a rectangular, square, circular, or elliptic shape. 
     According to one aspect of the invention, the at least one electrode comprises a plurality of electrodes patterned in distinct regions above the at least one light sensitive element. 
     According to one aspect of the invention, the distinct regions are electrically isolated from one another, and distinct fields of view of the at least one light sensitive element are electrically selectable based on a voltage applied to one or more of the distinct regions. 
     According to one aspect of the invention, switching of each field of view is made on a pixel-by-pixel basis. 
     According to one aspect of the invention, the at least one light sensitive element comprises a color filter. 
     According to one aspect of the invention, adjacent light sensitive elements of the plurality of light sensitive elements have fields of view that co-extend to fields of view of adjacent light sensitive elements. 
     According to one aspect of the invention, the device further includes an optical element arranged over the at least one light sensitive element, the optical element configured to modify a direction of the field of view of the at least one light sensitive element to be normal to a surface of the display device. 
     According to one aspect of the invention, the optical element comprises a lens array. 
     According to one aspect of the invention, the device further includes an optical element arranged over the at least one light sensitive element, the optical element configured to modify a direction of the field of view of the at least one light sensitive element to be at an angle to the normal of a surface of the display device. 
     According to one aspect of the invention, the optical element comprises a lens. 
     According to one aspect of the invention, the light sensitive element is responsive to non-homogeneous light. 
     According to one aspect of the invention, the at least one electrode is patterned such that only incident light from a distinct field of view of the at least one light sensitive element impinges on a predetermined area of the at least one light sensitive element, and the incident light is contained within a total internal refraction limit such that the incident light does not impinge on another part of the at least one light sensitive element associated with a different field of view. 
     According to one aspect of the invention, the device further includes a reflective electrode arranged over the at least one electrode, the reflective electrode patterned to include an aperture arranged over the at least one electrode. 
     According to one aspect of the invention, the device further includes an infrared light source arranged below the at least one light sensitive element so as to transmit infrared radiation through the liquid crystal element and illuminate objects above a surface of the display device such that scattered infrared radiation is incident on the at least one light sensitive element. 
     According to one aspect of the invention, the at least one electrode is arranged over the at least one light sensitive element. 
     According to one aspect of the invention, the device further includes a light source, wherein the at least one light sensitive element is arranged between the light source and the liquid crystal display element. 
     According to one aspect of the invention, a display device for detecting light incident within an electrically selectable field of view includes: at least one electronic layer including at least one light sensitive element; a liquid crystal element arranged over the at least one light sensitive element and including a plurality of molecules, wherein the liquid crystal element is operative to polarization shift light incident on the at least one light sensitive element based on an orientation of the plurality of molecules; and at least one electrode operative to change an orientation of the plurality of molecules, the at least one electrode patterned to define a geometry of a field of view of the at least one light sensitive element, wherein light passing through the at least one electronic layer undergoes polarization-by-reflection, and a field of view of the at least one light sensitive element is bounded by the angular dependence of the polarization-by-reflection. 
     To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a two-dimensional context for optical touch-sensitive panels. 
         FIG. 2  illustrates a three-dimensional context for optical touch-sensitive panels. 
         FIG. 3  is a cross-sectional view of exemplary electronic layers that constitute a first embodiment of the invention and field of view created on a sensor. 
         FIG. 4  is across-sectional view of exemplary electronic layers that constitute a second embodiment of the invention and field of view created on a sensor. 
         FIG. 5   a  is a cross-sectional view of exemplary electronic layers that constitute a third embodiment of the invention and left, central and right electrically switchable fields of view created on a sensor. 
         FIG. 5   b  is a simplified cross-sectional view of exemplary electronic layers that constitute a third embodiment of the invention and left, central and right electrically switchable fields of view created on the sensor implemented with red, green and blue colour filters. 
         FIG. 5   c  illustrates an example of ITO patterning to generate three distinct fields of view and the sharpening of the local electric field within the liquid crystal layer. 
         FIG. 6   a  is cross-sectional view of exemplary electronic layers that constitute a fourth embodiment of the invention and left, central and right electrically switchable collimated fields of view created on a sensor. 
         FIG. 6   b  is a cross-sectional view of exemplary electronic layers that constitute a fourth embodiment of the invention and left, central and right electrically switchable fields of view created on a sensor for acquisition of stereoscopic images. 
         FIG. 7  is a cross-sectional view of exemplary electronic layers that constitute a fifth embodiment of the invention and left, central and right electrically switchable fields of view created on a sensor having non-homogeneous intrinsic sensitive regions. 
         FIG. 8  is a cross-sectional view of exemplary electronic layers that constitute a sixth embodiment of the invention and left, central and right electrically switchable fields of view created utilizing polarisation-by-reflection of light through various electronic layers to act as a substitute for an in-cell polariser. 
         FIG. 9  is a cross-sectional view of exemplary electronic layers that constitute a seventh embodiment of the invention, wherein a patterned reflective electrode is used to create apertures above the ITO patterned layer. 
         FIG. 10  is a cross-sectional view of exemplary electronic layers that constitute a eighth embodiment of the invention and left, central and right electrically switchable fields of view, wherein infrared radiation is transmitted through the liquid crystal cell and substitutes to illuminate objects above the display surface. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a two-dimensional context for touch-sensitive panels using optical means for the two-dimensional detection of the position of objects on the LCD display panel  100  surface. In this type of system, one or more user-controlled light scattering objects such as a finger  400  or object  401  interact with an array of optical sensors embedded within electronic layers  300  of a display panel  100 . The interaction is by means of light scattered by the objects  400  or  401  through the display panel  100  to electronic layers  300  as a result of being illuminated by a backlight element  200  emitting light  201  through the semi-transparent electronic layers  300  and display panel  100 . Alternatively, one or more user-controlled light emitting objects such as  410  may also interact directly with an array of optical sensors embedded within electronic layers  300 . 
     In this type of light sensor array embedded within electronic layers  300 , multiple light scattering or emitting objects  400 ,  401 ,  410  may simultaneously interact optically with the electronic layers  300 . The objects may be spatially localised on the display panel  100  surface relative to a reference or coordinate system  500  (having axes  501 ) as distinct pattern entities from a pixelated image. Each pixel then represents a scaled signal generated by one or more light sensors embedded in electronic layers  300 . 
     Electronic layers  300  may also comprise various layers that modify the passage of scattered or emitted light from one or more light scattering or light emitting objects through to one or more light sensors in a suitable manner with a desired effect. 
     In some cases, electronic layers  300  may incorporate layers that will define an optical configuration allowing the differentiation between a scattering/emitting object in contact with LCD display panel surface  100  and a light scattering or light emitting object hovering above LCD display panel surface  100 . 
       FIG. 2  illustrates a problem of three-dimensional detection of the position of one or more user-controlled light scattering objects such as a finger  400  or object  401 . The objects interact with an array of optical sensors embedded within electronic layers  300  of the display panel  100  by scattering light through the display panel  100  to the electronic layers  300  (e.g., backlight element  200  illuminates the electronic layers and the light passes through both the semi-transparent electronic layers and the display panel surface, where it interacts with the objects so as to scatter back toward the panel and electronic layers). Alternatively, one or more user-controlled light emitting objects such as  410  may also interact directly with an array of optical sensors embedded in electronic layers  300 . 
     In this type of light sensor array embedded in electronic layers  300 , multiple objects may simultaneously interact optically with the electronic layers  300 . The objects can be spatially localised above the display panel  100  surface relative to a three-dimensional reference system  500  as distinct pattern entities from a pixelated image, each pixel of which represents a scaled signal generated by one or more light sensors embedded in the electronic layers  300 . Electronic layers  300  may also comprise various layers that modify the passage of scattered or emitted light from scattering or emitting objects through to one or more light sensors in a suitable manner with a desired effect. 
     If the surface of the LCD display panel  100  is made of a flexible material that allows for local deformations when subjected to pressure effected by one or more light scattering or light emitting objects, the light sensor array embedded in the electronic layers  300  may also provide three-dimensional detection of the position of one or more light scattering or light emitting objects that effect pressure on or below the LCD display panel  100  surface. This can result in negative positional information relative to the axis Z of three-dimensional reference system  500 , normal to the LCD display panel  100  surface. 
     First Embodiment of the Invention 
       FIG. 3  illustrates a first embodiment in accordance with the present invention. Transmitted light  704  which is incident on an embedded light sensitive element  301  has been polarisation shifted by a liquid crystal element  110  after being polarised  705  by polarising element  130 , located on the top glass substrate  120 . The liquid crystal element  110  may be, for example, but not limited to, a twisted nematic (TN) configuration. 
     An in-cell polarising element  103  absorbs polarised light according to its respective absorption axis  703 . Within a liquid crystal display panel, alignment of the molecules is required at each of the internal surfaces to facilitate the correct function of the display. This alignment is achieved by the alignment layers  102  and  112 . Polarising element  103  may also be used as an alignment layer for liquid crystal element  110  as it maintains the alignment created by layer  102 . The alignment of the liquid crystals is maintained on the opposite surface by alignment layer  112 . In-cell polarising element  103  may be constituted, for example, of a combination of a reactive mesogen and a dichroic dye. In-cell polariser may also be constituted, for example, by the electronic layers  302 , for polarisation selective transmission effects which are induced through multiple successive reflections within the various electronic layers  302 . 
     Depending on the orientation of the absorption axis  703  relative to the absorption axis of polarising element  130 , various levels of absorption of the light incident on the in-cell polariser  705  can be achieved. 
     In effect, this system constitutes a light valve when using ITO electrode elements  101  and  111  to change the orientation of the molecules of liquid crystal element  110 , having the effect of inducing a change in the polarisation of the incident light  701  from within field of view  600  going through the various electronic layers. According to the switching state of liquid crystal element  110 , incident light  701  is either absorbed or transmitted by polarising element  103 . When transmitted, polarised light  704  impinges on light sensitive element  301  and generates a scaled electrical signal that characterizes a light input pixel in the display. When absorbed, light incident on the in-cell polariser  705  does not impinge on light sensitive element  301  and therefore does not generate any signal. The light input pixel is therefore in its dark state. 
     In the case where polarising elements  130  and/or  103  are not ideal polarisers, some amount of residual polarisation is maintained in the polarisation-shifted incident light, having the effect of generating a scaled electrical signal that characterizes the dark state of the light input pixel. 
     ITO electrode  101  is patterned such that electric field  750  between ITO electrodes  111  and  101  induces a local change in the orientation of the molecules of liquid crystal  110  to effect a polarisation change in the incident light  705 . Thus, field of view  600  is dependent on the extent of patterned ITO electrode  101  and the relative position of light sensitive element  301 . 
     Switching liquid crystal element  110  to a voltage potential that induces a local change in the orientation of the molecules will affect the transmission of incident light  701 ,  705  on light sensitive element  301  when polarising elements  103  and  130  have cross-aligned polarising directions. When polarising elements  103  and  130  have parallel transmission axes, switching liquid crystal element  110  will effect reflection or absorption (depending on the type of polarising element  103 ) of incident light  701 ,  705 . When polarising elements  103  and  130  have polarising directions that are neither identical nor cross-aligned, switching liquid crystal element  110  will effect a combination of both transmission and reflection/absorption. Any of these configurations can be implemented in any of the embodiments in accordance with the present invention. 
     ITO electrode  101  may be patterned in a rectangular, square, circular, elliptic or arbitrary shape in a manner suitable with a desired effect. Patterned ITO electrode  101  may also be positioned such that its shape and position relative to light sensitive element  301  induce a field of view  600  oriented toward a preferred direction. Patterned ITO electrode  101  may also be patterned and/or positioned regularly or irregularly within an array of embedded light sensitive elements  301  in a manner suitable with a desired effect. 
     In this embodiment and all others in accordance with the present invention, ITO electrode  101  may be patterned in a manner suitable with a desired effect and ITO electrode  111  may be uniformly deposited (un-patterned). Alternatively, ITO electrode  111  may be patterned in a manner suitable with a desirable effect and ITO electrode  101  uniformly deposited. Additionally, both ITO electrodes  101  and  111  may be patterned in a manner suitable with a desirable effect or both ITO electrodes  101  and  111  may be uniformly deposited. 
     In this embodiment and in all others in accordance with the present invention, field of view  600  may be more clearly defined by implementing the electronic layer structure or the display surface with a patterned mask. In the patterned configuration, less precision is needed on the patterning of ITO electrode  101  or  111 . This, however, is not applicable when multiple fields of view such as described, for example, in embodiment 3, are in close proximity or even overlap. 
     In all embodiments in accordance with the present invention, polarising element  103  may be constituted with a material of which the absorption/reflection spectrum encompasses the infra-red, visible and ultra-violet wavelength range or any specific part of it only. 
     Polarising element  103  may be constituted such that its spectral response is specific to one or more wavelength ranges, which may be monochromatic or polychromatic, this being defined by a general consensus related to the spectral width of each of the individual wavelength ranges. 
     The embodiment herein described may be used also, for example, as a two-colour state measurement within the fields of view of the light sensitive element  301 , when switching. 
     In all embodiments in accordance with the present invention, polarising element  103  may be uniformly deposited or patterned in a manner suitable with a desirable effect. Such may be the case, for example, to create a field of view switchable in dependence on the ambient light level by patterning polarising element  103  in a manner such that light incident on light sensitive element  301  is confined within the total internal reflection boundary of the arrangement comprised by the various electronic layers and the relative position of light sensitive element  301 . 
     In use, the output of the light sensor may represent the measurement of the intensity of light incident on light sensitive element  301  when the polarising element  103  is driven to one state. Alternatively and more generally, the output of the light sensor may represent a function of two or more simultaneous or sequential measurements of the intensity of the light incident on light sensitive element  301  when the polarising element  103  is driven to two or more corresponding states. 
     All embodiments in accordance with the present invention may be applied to any type of liquid crystal display, having an active or a passive matrix for addressing the pixels, or liquid crystal on silicon (LCoS). 
     Embodiment 2 
       FIG. 4  illustrates another embodiment in accordance with the present invention. In this embodiment, patterned ITO grounded electrodes  104  are positioned to the edge of patterned ITO electrode  101 . This sharpens the local electric field  751  gradient induced by ITO electrodes  101  and  111  in order to more precisely define the active volume of liquid crystal element  110 . This has the effect of more precisely defining the field of view  600 . 
     ITO grounded electrode  104  may be patterned in a rectangular, square, circular, elliptic or arbitrary shape in a manner suitable with a desired effect. Patterned ITO grounded electrode  104  may also be patterned and/or positioned regularly or irregularly within an array of embedded light sensitive elements  301  in a suitable manner with a desired effect. Patterned ITO grounded electrode  104  may be used in any of the embodiments in accordance with the present invention to sharpen the local electric field  751  induced by ITO electrodes  101  and  111 . 
     Embodiment 3 
       FIG. 5   a  illustrates another embodiment in accordance with the present invention. In this embodiment, patterned ITO electrode  101  is patterned in distinct regions (e.g., discrete regions that may be electrically isolated from one another) on top of light sensitive element  301 . Each of the regions is electrically connected to different voltages, resulting in electrically switchable distinct fields of view from which incident light impinges on light sensitive element  301 . 
     In the embodiment and all other embodiment using more than one switchable field of view, the relative directions of the various fields of view may be set in a plane from each other or out of plane from each other. Thus, patterned ITO electrode  101  may be arranged in such configurations that create specific fields of view, such as  601 ,  602  or  603 , in order to implement the display panel with optical functions using different fields of view. Such may be the case, for example, for implementing an electrically switchable ambient light shield that would enable enhanced contrast ratio for fingerprint scanning in high ambient light levels by blocking any unwanted incident light from reaching light sensitive element  301 . 
     Such may be the case also, for example, for implementing a colour scanning function by de-convolving rows of adjacent light sensitive element  301  having respective red, green and blue colour filters (either located on the top glass substrate  120  or deposited within electronic layers  302 ) and overlapping fields of view. In this, field of view  601  for light sensitive element  301  endowed with a blue colour filter may be configured such that its relative scanning area overlaps that of the field of view  602  for light sensitive element  301  endowed with a green colour filter. Similarly, field of view  603  for light sensitive element  301  endowed with a red colour filter may be configured such that its relative scanning area overlaps that of the field of view  602  for light sensitive element  301  endowed with a green colour filter. In such a manner, colour scanning can be achieved without loss of resolution. This is illustrated in  FIG. 5   b  where scanning areas  191 , located on the plane  190  of the object to be scanned, are denominated as  1 ,  2  and  3  scatter or emit light onto light sensitive elements  301  denominated as S 1 , S 2  and S 3 , thus generating a scaled electrical signal from each which can be termed as I 1 , I 2  and I 3  respectively. In this particular case, scaled electrical signal I 2  is a weighted compound of scattered or emitted light from scanning areas  1 ,  2  and  3 . Light sensitive elements  301  denominated as S 1 , S 2  and S 3  may be covered with red, green and blue colour filters respectively or be respectively made of light sensitive materials exhibiting sensitivity in the red, green and blue wavelength range. As each adjacent light sensitive element  301  possesses fields of view (for example G- 602 ) that co-extend to fields of view of its neighbouring counterpart implemented with a different colour filtering (for example R- 603  and B- 601 ), each light sensitive element  301  may therefore be used to infer the red, green and blue intensity component scattered or emitted from each scanning area. 
     Inference of the scanning areas  191  red, green and blue colour components can then be obtained by processing a simple de-convolution algorithm. A priori knowledge of the respective fields of view and colour filters characteristics can be used to process the de-convolution algorithm, although this can be accomplished without a priori knowledge using a calibration scheme to obtain the system transfer function. 
     Such may be the case also, for example, for implementing an optical depth sensing function that uses oblique incident light as described in GB0909452.5, in conjunction with an electrically switchable ambient light shield and an enhanced resolution scanner. The contents of GB0909452.5 is hereby incorporated by reference in its entirety. 
     In this embodiment and all others in accordance with the present invention, any number or shape of fields of view may be considered and actuated either independently from each other or simultaneously or any combination of these. 
     In this embodiment and all others in accordance with the present invention, liquid crystal  110  related to a specific or all fields of view may be activated by a voltage differential applied on ITO electrodes  101  and  111 . The differential may be between a minimum value and a maximum value related to the deactivation and activation states, respectively, of the liquid crystal  110  such that any amount of polarisation shift may be induced on the incident light impinging on the system. 
     In all embodiments in accordance with the present invention, the switching of each field of view may be addressed individually on each pixel of the display (e.g., on a pixel-by-pixel basis), collectively on all pixels of the display or as a combination of both individually and collectively. 
     When addressing each field of view individually, added electronics are required for each pixel to operate the switching of field of view upon light sensing element  301 , while added electronics are not required for each pixel to operate the switching of field of view upon light sensing element  301  when addressing each field of view collectively or as a combination of collectively and individually.  FIG. 5   c  illustrates an example of ITO patterning to generate three distinct fields of view such as illustrated in  FIG. 5   a  and the sharpening of the local electric field  751  such as described in  FIG. 4 . In this example, three ITO patterned regions  101  are connected to different voltages VR  212 , VL  213  and VC  211  through lines  201  via connector  202  to create fields of view  601 ,  602  and  603  on light sensitive element  301  such as described in  FIG. 5   a . Other ITO patterned regions  104  are connected to ground voltage VC  210  through lines  201  via connector  202  to sharpen the local electric field  751  such as described in  FIG. 4 . Also shown in  FIG. 5   c  is a controller  220  for applying a voltage to the ITO electrodes. The controller  220  may be configured, for example, to apply different voltages to the electrodes so as to select one or more fields of view. 
     Embodiment 4 
       FIGS. 6   a  and  6   b  illustrates another embodiment in accordance with the present invention. In  FIG. 6   a , the configuration of embodiment 3 is implemented with optical element  150 , for example a lens array, placed on top of light sensitive element  301  to modify the fields of view  601 ,  602  and  603  such that their direction is normal to the display surface. The advantage of this configuration is to make the scanning area for fields of view  601 ,  601  and  603  independent of the top glass substrate  120  thickness. 
     In this embodiment, optical element  150  may be constituted by an array of refracting or diffracting elements such as a prism arrangement, a refracting rod arrangement, a deflecting mirror, a diffraction grating or an interference filter. The material denoted by  140  is a material with a refractive index distinct from that of optical element  150 . This may be a solid material, or even a void filled with air. 
     In this embodiment, optical element  150  may be used to direct only one, a plurality or all fields of view of the system. 
     In  FIG. 6   b , optical element  150  may also be, for example, a lens, placed on top of light sensitive element  301  to modify the fields of view  601 ,  602  and  603  such that their direction is at an angle to the normal of the display surface. This configuration is useful, for example, to implement a display panel with capture of stereoscopic images separated by stereoscopic angle  610  such that when displayed the two acquired stereoscopic images create a three-dimensional image for the viewer. 
     Embodiment 5 
       FIG. 7  illustrates another embodiment in accordance with the present invention, which may be used in conjunction with any of the other embodiments. In this, inhomogeneity in the light sensitive element  301  is artificially created by shielding part of parts of it by an opaque light shield  303 . By reducing its sensitive area, less light is therefore collected by light sensitive element  301 , but nevertheless a sharper definition of its associated field(s) of view is obtained. 
     ITO electrode  101  or  111  may also be patterned such that only incident light from a distinct field of view impinges on a specific area only of light sensitive element  301  by using a configuration such that, for example, incident light from field of view  603  is contained only within the refraction limit  710  and therefore cannot impinge on another part of light sensitive element  301  apart from the one associated to field of view  603 . This has the effect of restraining the field of view and therefore to have more flexibility in designing the optical configuration of the system. 
     Embodiment 6 
       FIG. 8  illustrates another embodiment in accordance with the present invention. In this, light incident on light sensitive element  301  is polarisation shifted by liquid crystal element  110  while a polarisation-by-reflection of light going through the various electronic layers  302  acts as a substitute for the in-cell polariser. In this configuration an alignment layer  102  may be required to align the liquid crystal molecules at the lower surface of the liquid crystal element  110 . This could be of a similar form to the alignment layer  112 . 
     Nevertheless, the definition of the fields of view is bounded by the angular dependence of the polarisation-by-reflection phenomena. 
     If a central field of view  602 , such as described in embodiment 3, was to be implemented, its relative intensity variation would be therefore inferred through a subtraction scheme between various states of activation of ITO regions that define fields of view  601 ,  603  adjacent to central field of view  602 . 
     Embodiment 7 
       FIG. 9  illustrates another embodiment in accordance with the present invention. This embodiment consists of implementing each of the embodiments described herein with a patterned reflective electrode  104  to create apertures above the ITO patterned layer  101  such that the fields of view are more clearly defined. 
     In  FIG. 9  an example configuration is presented to which this embodiment is not restricted, but may be implemented, for example, as a single aperture layer or a multi-aperture layer or as a number of any of the formerly stated at different levels within the panel, such as described in GB0909542.5. 
     Embodiment 8 
       FIG. 10  illustrates another embodiment in accordance with the present invention. In this, a light source of infrared radiation  202  is transmitted through the liquid crystal cell substrates. The infrared radiation illuminates objects  801  above the display surface  130  such that scattered infrared radiation  203  may be incident on light sensitive element  301  without being affected by any optical arrangement of all embodiments in accordance with the present invention but embodiment 7. 
     When activating the switching of one or more fields of view such as, for example as depicted in  FIG. 10 ,  601 ,  602  or  603 , depending on the spectral response of the in-cell polariser, a specific spectral shielding of the one or more switched fields of view may be obtained to increase the signal-to-noise ratio in the response of light sensitive element  301  to the incident infrared radiation. 
     Although the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalents and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention includes all such equivalents and modifications, and is limited only by the scope of the following claims.