Patent Publication Number: US-2015083917-A1

Title: Infrared light director for gesture or scene sensing fsc display

Description:
TECHNICAL FIELD 
     This disclosure relates to techniques for touch and gesture recognition, and, more specifically, to a field sequential color (FSC) display that provides a user input/output interface, controlled responsively to a user&#39;s touch and/or gesture. 
     DESCRIPTION OF THE RELATED TECHNOLOGY 
     Increasingly, electronic devices such as personal computers and personal electronic devices (PED&#39;s) provide for at least some user inputs to be provided by means other than physical buttons, keyboards, and point and click devices. For example, touch screen displays are increasingly relied upon for common user input functions. The display quality of touch screen displays, however, can be degraded by contamination from a user&#39;s touch. Moreover, when the user&#39;s interaction with the device is limited to a small two dimensional space, as is commonly the case with touch screen displays of, at least, PEDs, the user&#39;s input (touch) may be required to be very precisely located in order to achieve a desired result. This results in slowing down or otherwise degrading the user&#39;s experience with the device. 
     Accordingly, it is desirable to have a user interface that is responsive, at least in part, to “gestures” by which is meant, the electronic device senses and reacts in a deterministic way to gross motions of a user&#39;s hand, digit, or hand-held object. The gestures may be made proximate to, but, advantageously, not in direct physical contact with the electronic device. 
     Current commercially available gesture systems include camera-based, ultrasound and projective capacitive systems. Ultrasound systems suffer from resolution issues; for example, circular motion is difficult to track and individual fingers are difficult to identify. Projective capacitive systems yield good resolution near and on the surface of a display but are resolution limited further than about an inch from the display surface. Camera-based systems may provide good resolution at large distances and adequate resolution to within an inch of the display surface. However, the cameras are 1) placed on the periphery of the display and 2) have a limited field of view. As a result, gesture recognition cannot be achieved at or near the display surface. 
     Thus, improved techniques for providing a touch screen interface are desirable. 
     SUMMARY 
     The systems, methods and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein. 
     One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus that includes a field sequential color (FSC) display, having a display front surface and a viewing area. The FSC display includes a display lighting system that includes at least one visible light emitter and at least one infrared (IR) light emitter. The FSC display also includes an arrangement for spatial light modulation, the arrangement including a plurality of apertures, and devices for opening and shutting the apertures. The FSC display also includes a light directing arrangement including at least one light turning feature. The display lighting system is configured to emit visible light and IR light through at least a first opened one of the plurality of apertures. The light turning feature is configured to redirect IR light emitted through the opened aperture into at least one lobe, and to pass visible light emitted by the display lighting system through the opened aperture with substantially no redirection. 
     In some implementations, the apparatus may further include a processor and at least one IR light sensor configured to output a signal representative of a characteristic of received IR light, the received IR light resulting from scattering of the at least one lobe of IR light by an object. The devices for opening and shutting the apertures may be switched in accordance with a first modulation scheme to render an image. The IR light sensor is configured to output, to the processor, a signal representative of a characteristic of the received IR light. The processor may be configured to switch the devices for opening and shutting the apertures in accordance with a second modulation scheme to selectively pass object illuminating IR light through at least one of the respective apertures, the object illuminating IR light being at least partially unrelated to the image; and recognize, from the output of the light sensor, a characteristic of the object. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a method that includes switching, with a processor, one or more devices for opening and shutting apertures included in an arrangement for spatial light modulation. The devices for opening and shutting the apertures are switched in accordance with a first modulation scheme to render an image. A field sequential color (FSC) display has a display front surface and a viewing area, the FSC display including the arrangement for spatial light modulation. The FSC display includes a light directing arrangement including at least one light turning feature, the light turning feature being configured to redirect IR light emitted through the opened aperture into at least one lobe, and to pass visible light emitted by the display lighting system through the opened aperture with substantially no redirection. The FSC display also includes at least one infrared (IR) light sensor configured to output a signal representative of a characteristic of received IR light, the received IR light resulting from scattering of the at least one lobe of IR light by an object. The method includes emitting visible light and infrared (IR) light through at least a first opened one of the plurality of apertures and switching the devices for opening and shutting the apertures in accordance with a second modulation scheme to selectively pass object illuminating IR light through at least one of the respective apertures, the object illuminating IR light being at least partially unrelated to the image. The method also includes recognizing, with the processor, from the output of the light sensor, a characteristic of the object. 
     Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a block diagram of an example of an electronic device having an interactive display according to an implementation. 
         FIG. 1B  shows a cross sectional view of an electronic display  110 , according to an implementation. 
         FIG. 2  illustrates a schematic diagram of an example of an arrangement for spatial light modulation of an interactive display. 
         FIG. 3  is a cross sectional view of an interactive display incorporating a light modulation array. 
         FIG. 4  illustrates an example of an interactive display according to an implementation. 
         FIG. 5  illustrates an example of directionally structured lobes of object illuminating light. 
         FIG. 6  illustrates an example of an interactive display according to an implementation. 
         FIG. 7  illustrates a further example of an interactive display, according to an implementation. 
         FIG. 8  illustrates another example of an interactive display according to an implementation. 
         FIG. 9  illustrates a yet further example of an interactive display according to an implementation. 
         FIG. 10  illustrates an example of a scanning pattern for a second modulation scheme in accordance with some implementations. 
         FIG. 11  illustrates a further example of a scanning pattern for a second modulation scheme in accordance with some implementations. 
         FIG. 12  illustrates a technique for detecting a bright object, according to some implementations. 
         FIG. 13  illustrates a technique for detecting a dark object, according to some implementations. 
         FIG. 14  illustrates an example of a scanning strategy for the second modulation scheme in accordance with some implementation. 
         FIG. 15  illustrates an example of a process flow for touch and gesture recognition with an interactive FSC display according to an embodiment. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     The following description is directed to certain implementations for the purposes of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations may be implemented in any device or system that can be configured to display an image, whether in motion (e.g., video) or stationary (e.g., still image), and whether textual, graphical or pictorial. More particularly, it is contemplated that the described implementations may be included in or associated with a variety of electronic devices such as, but not limited to: mobile telephones, multimedia Internet enabled cellular telephones, mobile television receivers, wireless devices, smartphones, Bluetooth® devices, personal data assistants (PDAs), wireless electronic mail receivers, hand-held or portable computers, netbooks, notebooks, smartbooks, tablets, printers, copiers, scanners, facsimile devices, GPS receivers/navigators, cameras, MP3 players, camcorders, game consoles, wrist watches, clocks, calculators, television monitors, flat panel displays, electronic reading devices (i.e., e-readers), computer monitors, auto displays (including odometer and speedometer displays, etc.), cockpit controls and/or displays, camera view displays (such as the display of a rear view camera in a vehicle), electronic photographs, electronic billboards or signs, projectors, architectural structures, microwaves, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable memory chips, washers, dryers, washer/dryers, parking meters, packaging (such as in electromechanical systems (EMS), microelectromechanical systems (MEMS) and non-MEMS applications), aesthetic structures (e.g., display of images on a piece of jewelry) and a variety of EMS devices. The teachings herein also can be used in non-display applications such as, but not limited to, electronic switching devices, radio frequency filters, sensors, accelerometers, gyroscopes, motion-sensing devices, magnetometers, inertial components for consumer electronics, parts of consumer electronics products, varactors, liquid crystal devices, electrophoretic devices, drive schemes, manufacturing processes and electronic test equipment. Thus, the teachings are not intended to be limited to the implementations depicted solely in the Figures, but instead have wide applicability as will be readily apparent to one having ordinary skill in the art. 
     Described herein below are new techniques for an interactive display with improved user input/output functionality. In some implementations, a gesture-responsive user input/output (I/O) interface for an electronic device is provided. “Gesture” as used herein broadly refers to a gross motion of a user&#39;s hand, digit, or hand-held object, or other object under control of the user. The motion may be made proximate to, but not necessarily in direct physical contact with, the electronic device. In some implementations, the electronic device senses and reacts in a deterministic way to a user&#39;s gesture. In some implementations, a document scanning capability is provided. 
     Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. The presently disclosed techniques provide a significant improvement in touch and/or gesture I/O using an interactive field sequential color (FSC) display. The FSC display includes an array of light modulators configured to be individually switched between an open position that permits transmittance of light through a respective aperture and a shut position that blocks light transmission through the respective aperture. The interactive FSC display includes a transparent substrate, such as a glass or other transparent material, which has a rear surface proximate to which light sensors or other photo-sensitive elements are disposed. The interactive FSC display is configured to determine the location and/or relative motion of a user&#39;s touch or gesture proximate to the display, and/or to register an image of the object. 
     Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. The user&#39;s gesture may occur over a “full range” of view with respect to the interactive display. By “full range” is meant that the gesture may be recognized, at a first extreme, even when made very close to, or in physical contact with, the interactive display; in other words, “blind spots” exhibited by prior art camera systems are avoided. At a second extreme, the gesture may be recognized at a substantial distance, up to approximately 500 mm, from the interactive display, which is not possible with known projective capacitive systems. The above functionality may be provided by configuring the transparent substrate with light directing features, thereby avoiding the cost and thickness associated with adding an additional light-guide layer. 
       FIG. 1A  shows a block diagram of an example of an electronic device having an interactive display according to an implementation. An apparatus  100 , which may be, for example, a personal electronic device (PED), may include an electronic display  110  and a processor  104 . The electronic display  110  may be a touch screen display, but this is not necessarily so. In some implementations, the processor  104  may be configured to control an output of the electronic display  110 , or an electronic device (not shown) communicatively coupled with apparatus  100 . The processor  104  may control the output of the electronic display  110  in response, at least in part, to a user input. The user input may include a touch or a gesture, where the user gesture may include, for example, a gross motion of a user&#39;s appendage, such as a hand or a finger, or a handheld object or the like. The gesture may be located, with respect to the electronic display  110 , at a wide range of distances. For example, a gesture may be made proximate to, or even in direct physical contact with the electronic display  110 . Alternatively, the gesture may be made at a substantial distance, up to, approximately 500 mm from the electronic display  110 . In some implementations, the processor  104  may be configured to collect and process data received from the electronic display  110  regarding the user input. The data may include a characteristic of a touch, gesture, or object related to the user input. The characteristic may include location and motion information of a touch or a gesture, or image data, for example. 
     In some implementations, light sensor  133  may output one or more signals responsive to light reflected into the electronic display  110  from a user&#39;s appendage, or an object under the user&#39;s control, for example. In some implementations, signals outputted by light sensor  133 , via a first signal path  103 , may be analyzed by the processor  104  so as to recognize an instance of a user input, such as a touch or a gesture. The processor  104  may then control the electronic display  110 , responsive to the user input, by way of signals sent to the electronic display  110  via a second signal path  105 . In some implementations, signals outputted by the arrangement  130 , via the first signal path  103 , may be analyzed so as to obtain image data. 
       FIG. 1B  shows a cross sectional view of an electronic display  110 , according to an implementation. Although one light sensor  133  is shown in the illustrated implementation, it will be appreciated that numerous other arrangements are possible. Any number of light sensors may be used. Although the light sensor  133  is illustrated as located at the periphery of optical cavity  113 , it may be located at, for example, on the top or as part of the display, along a bezel at the side of the display, at the bottom of the optical cavity  113 , as well as other locations that could receive light scattered from object  150 . The light sensor  133  may include one or more photosensitive elements, such photodiodes, phototransistors, charge coupled device (CCD) arrays, complementary metal oxide semiconductor (CMOS) arrays or other suitable devices operable to output a signal representative of a characteristic of detected visible light. The light sensor  133  may output signals representative of color of detected light, for example. In some implementations, the signals may also be representative of other characteristics, including intensity, polarization, directionality, frequency, amplitude, amplitude modulation, and/or other properties. The electronic display  110  may have a substantially transparent front surface  101  such that at least most light  143  from the electronic display  110  passes through the front surface  401  and may be observed by a user (not illustrated). 
     As illustrated in  FIG. 1B , when an object  150  interacts with light  142  (which may be referred to herein as “object illuminating light”) from the electronic display  110 , scattered light  144 , resulting from the interaction, may be directed through front surface  401  and be received by light sensor  133 . The object  150  may be, for example, a user&#39;s appendage, such as a hand or a finger, or it may be any physical object, hand-held or otherwise under control of the user but is herein referred to, for simplicity, as the “object.” The light sensor  133  may be configured to detect one or more characteristics of the scattered light  144 , and output, to the processor  104 , a signal representative of the detected characteristics. For example, the characteristics may include intensity, polarization, directionality, frequency, amplitude, amplitude modulation, and/or other properties. 
     Referring again to  FIG. 1A , the processor  104  may be configured to receive, from the light sensor  133 , signals representative of the detected characteristics, via the first signal path  103 . The processor  104  may be configured to recognize, from the output signals of the light sensor  133 , an instance of a user gesture. Moreover, the processor  104  may control one or more of the electronic display  110 , other elements of the apparatus  100 , and/or an electronic device (not shown) communicatively coupled with apparatus  100 . For example, an image displayed on the electronic display  110  may be caused to be scrolled up or down, rotated, enlarged, or otherwise modified. In addition, the processor  104  may be configured to control other aspects of the apparatus  100 , responsive to the user gesture, such as, for example, changing a volume setting, turning power off, placing or terminating a call, launching or terminating a software application, etc. 
     The electronic display  110  may include an arrangement for spatial light modulation.  FIG. 2  illustrates a schematic diagram of an example of an arrangement for spatial light modulation of an interactive display. The arrangement  111  (which may be referred to as the “light modulation array”) may include a plurality of light modulators  112   a - 112   d  (generally, “light modulators  112 ”) arranged in rows and columns. 
     Each light modulator  112  may include a corresponding aperture  119 . Each light modulator  112  may also include a corresponding shutter  118 , or another means to switch the corresponding aperture  119  between an open position and a shut position. In order to render an image  114 , the electronic display  110  may be configured to switch the light modulators in a time domain in accordance with a particular modulation scheme (the “first modulation scheme”). For example, to illuminate a pixel  116  of the image  114 , a shutter  118  corresponding to the pixel is in an open position that permits transmittance of light from a display lighting system (not illustrated) through the corresponding aperture  119  toward a viewer (not illustrated). To keep the pixel  116  unlit, the corresponding shutter  118  is positioned such that it blocks light transmission through the corresponding aperture  119 . Each aperture  119  may be defined by an opening provided in a reflective or light-absorbing layer, for example. 
     In the illustrated configuration, light modulators  112   a  and  112   d  are switched to an open position, whereas light modulators  112   b  and  112   c  are switched to a shut position. As a result of selectively switching the positions of the light modulators  112   a - 112   d  in accordance with the first modulation scheme, the electronic display  110  may render the image  114 , as describe in more detail herein below. In some implementations, the first modulation scheme may be controlled by a computer processing arrangement that may be part of or may be communicatively coupled with the processor  104 . 
       FIG. 3  is a cross sectional view of an interactive display incorporating a light modulation array. The electronic display  110  includes the light modulation array  111 , an optical cavity  113 , and a display lighting system  115 . The light modulation array  111  may include any number of light modulators  112 , as described hereinabove and illustrated in  FIG. 2 . As shown in the implementation illustrated in  FIG. 3 , each light modulator may include a corresponding shutter  118  and be configured to be switched between an open position and a shut position. In the illustrated implementation, for example, the shutters  118 ( b ) and  118 ( c ) are depicted in the open position, whereas, the shutter  118 ( a ) is depicted in the closed position. Advantageously, the light modulators may be disposed on or proximate to a rear surface  369  of a transparent substrate  335 . 
     In some implementations, the optical cavity  113  may be formed from a light guide that may be about 300 microns to about 2 mm thick, for example. The display lighting system  115  may be configured to emit light  343  into the optical cavity  113 . Advantageously, at least a portion of the light  343  may undergo TIR and be distributed substantially uniformly throughout the optical cavity  113  as a result of judicious placement of light scattering elements (not illustrated) on one or more surfaces enclosing the optical cavity  113 . For example, some light scattering elements may be formed in or on the rear enclosure of the optical cavity  113  to aid in redirecting the light  343  through the apertures  119 . 
     The electronic display  110  may be referred to as a field sequential color (FSC) display, because, in some implementations, images are rendered by operating the display lighting system  115  so as to sequentially alternate the color of visible light emitted by the display lighting system  115 . For example, the display lighting system  115  may emit a sequence of separate flashes of red, green and blue light. Synchronized with the sequence of flashes, a sequence of respective red, green and blue images may be rendered by appropriate switching, in accordance with the first modulation scheme, of the light modulators  112  in the light modulation array  111  to respective open or shut positions. 
     As a result of the persistence of vision phenomenon, a viewer of rapidly changing images, for example, images changing at frequencies of greater than 20 Hz, may perceive an image which is the combination, or approximate average, of the images displayed within a particular period. In some implementations, the first modulation scheme may be adapted to utilize this phenomenon so as to render color images while using as few as a single light modulator for each pixel of a display. 
     For example, in a color FSC display, the first modulation scheme may include dividing an image frame to be displayed into a number of sub-frame images, each corresponding to a particular color component (for example, red, green, or blue) of the original image frame. For each sub-frame image, the light modulators of the display are set into states corresponding to the color component&#39;s contribution to the image. The light modulators then are illuminated by a light emitter of the corresponding color. The sub-images are displayed in sequence at a frequency (for example, greater than 60 Hz) sufficient for the brain to perceive the series of sub-frame images as a single image. 
     As a result, an FSC display may require only a single light modulator per pixel, instead of a pixel requiring a separate spatial light modulator for each of three or more color filters. Advantageously, an FSC display may not suffer a loss of power efficiency due to absorption in a color filter and may make maximum use of the color purities available from modern light emitting diodes (LEDs), thereby providing a range of colors exceeding those available from color filters, i.e. a wider color gamut. 
     In some implementations the FSC display may be configured to emit changing patterns of visible and nonvisible light, for example infrared (IR) and near IR light.  FIG. 4  illustrates an example of an interactive display according to an implementation. In the illustrated implementation, an interactive FSC display  400  includes a front surface  401 , the transparent substrate  335  the light modulation array  111 , the optical cavity  113  and a display lighting system  415 . The interactive FSC display  400  may be configured to render color images, visible to a user through the front surface  401 , by sequentially flashing one or more wavelength specific light emitters of the display lighting system  415  into the optical cavity  113 , while synchronously performing spatial light modulation according to the first modulation scheme. In the illustrated implementation, the display lighting system  415  includes three wavelength specific visible light emitters, designated R (red), B (blue) and G (green) and an IR light emitter  475 . It will be appreciated, however, that other arrangements of wavelength specific light emitters are possible. For example, in addition to, or instead of one or more of the RGB light emitters, light emitters of white, yellow, or cyan color may be included in the display lighting system  415 . 
     In the illustrated implementation, the display lighting system  415  is a backlight, however implementations including only a frontlight or both a frontlight and a backlight are within the contemplation of the present disclosure. 
     The light modulation array  111  may include an array of light modulators as described hereinabove. As shown in the illustrated implementation, each light modulator may include corresponding shutter  118  and be configured to be switched between an open position and a shut position. For example, in the illustrated implementation, the shutters  118 ( a ) and  118  ( c ) are each in the open position, and the shutter  118 ( b ) is in the closed position. 
     Referring still to  FIG. 4 , IR emitter  475  may be configured to emit IR light  442  into optical cavity  113 . Advantageously, at least a portion of the IR light  442  may undergo TIR and be distributed substantially uniformly throughout the optical cavity  113  as a result of judicious placement of light scattering elements (not illustrated) on one or more surfaces enclosing the optical cavity  113 . For example, some light scattering elements may be formed in or on the rear enclosure of the optical cavity  113  to aid in redirecting the IR light  442  through the apertures  119 . 
     Light directing features  455  may be configured such that IR light  442  is selectively turned, by, for example, refractive, diffractive or holographic means, whereas visible light  443  passes through the light directing features substantially unaffected. Light directing features  455  may be volume holographic features configured such that light at a particular wavelength is diffracted with high efficiency; and light at other wavelengths experiences little or no diffraction. More particularly, in the illustrated implementation, light emitted by IR emitter  475  experiences substantial diffraction so as to be redirected (or “structured”) into one or more particularly oriented lobes. Visible light emitted by the display lighting system  415 , on the other hand, may pass through light directing features  455  with substantially no redirection. 
       FIG. 5  illustrates an example of directionally structured lobes of object illuminating light. Each lobe  542  of IR light, as illustrated by  FIG. 5 , may be shaped approximately as a cone, and may be selectively disposed at a wide range of azimuth and elevation angles with respect to the front surface  401 . Each aperture  119  may be selectively opened to illuminate the corresponding lobe  542  associated with the light directing feature  455  at that aperture. In this illustration, four apertures  119  are open, thus illuminating four lobes  542 . A lobe  542  of IR light may interact with a finger (or hand, or stylus, or other hand-held object, not illustrated) controlled by a user and be reflected back toward front surface  401 . The object may be on or above the front surface  401 . 
       FIG. 6  illustrates an example of an interactive display according to an implementation. In the illustrated implementation, an interactive FSC display  600  includes the front surface  401 , the transparent substrate  335 , the light modulation array  111 , the optical cavity  113  and the display lighting system  415 . As illustrated in FIG.  6 , when the object  150  interacts with object illuminating IR light  442 , scattered IR light  644 , resulting from the interaction, may be scattered back toward the front surface  401  and be received by IR light sensor  433 . The object  150  may be, for example, a user&#39;s appendage, such as a hand or a finger, or it may be any physical object, hand-held or otherwise under control of the user, but is herein referred to, for simplicity, as the “object.” 
     Scattered IR light  644  may pass through light turning feature  455 , enter optical cavity  113  and be at least partially received by IR light sensor  433 . It will be appreciated that, as a result of optical reciprocity, each light turning feature  455  may absorb or reflect light reaching it from locations outside its respective, particularly oriented lobe(s). Therefore, for example, light reflected from an object not located within a lobe associated with a respective light turning feature  455  may not be redirected by light turning feature  455  and ultimately received by IR light sensor  433 . Put another way, only light that is reflected from an object located within a lobe associated with a respective light turning feature  455  may be received by IR light sensor  433 . 
     The IR light sensor  433  may be configured to output a signal representative of a characteristic of received IR light  646  resulting from interaction of the object illuminating IR light  442  with the object  150 . For example, IR light sensor  433  may be configured to detect one or more characteristics of the received light  646  and output, to a processor (not illustrated), a signal representative of the detected characteristics. For example, the characteristics may include intensity, polarization, directionality, frequency, amplitude, amplitude modulation, and/or other properties. The processor may be configured to recognize, from the output of the IR light sensor  433  a characteristic, such as the location and/or motion, of the object  150 . 
     Although a single IR light sensor  433  is illustrated in  FIG. 6 , it will be appreciated that any number of IR light sensors  433  may be contemplated. In some implementations, a wavelength of the IR light may be within a range (700 nm to 1000 nm wavelength, for example) such that IR light sensors  433  may include inexpensive silicon detectors. 
     In some implementations, there may be one or more optical components disposed between the front surface  401  and the IR light sensor  433 . For example, an aperture array, a mask, a lens, a lens array, or another method of focusing light, increasing efficiency, or better discriminating angular versus spatial information for the scattered light  644  may be provided. 
     Spatial light modulation may be performed to produce a rendered image by switching a selected subset of the shutters  118  to an open position in accordance with the first modulation scheme. In some implementations, switching of the shutters  118  may be performed in synchronization with sequential flashing of the one or more wavelength specific light emitters of the display lighting system  415 . 
     For example, a green wavelength specific light emitter of the display lighting system  415  may be configured to emit light  443 (G) (“image rendering light”) into the optical cavity  113 . Advantageously, at least a portion of the image rendering light  443 (G) may undergo TIR and be distributed substantially uniformly throughout the optical cavity  113 . A portion of the image rendering light  443 (G) may be transmitted through one or more of the apertures  119  and contribute to the rendered image. 
     The present inventors have appreciated that an optical touch and gesture recognition functionality may be provided by using the object illuminating IR light  442 . More particularly, light modulators may be switched in accordance with a second modulation scheme to selectively pass the object illuminating light  442  through at least one of the respective apertures. 
     In some implementations, the second modulation scheme may provide for interspersing of sub-frames during which the object illuminating IR light  442  is passed with sub-frames during which the image rendering light  443  is passed. For example, where the image rendering light  443  is passed in a series of groups of sub-frames of visible red, green and blue image patterns, the second modulation scheme may provide that the IR emitter  475  is flashed between each group of sub-frames. In some implementations a group of sub-frames may include ten sub-frames each of visible red, green and blue image patterns, for example. 
     In the implementations described above light directing features  455  were illustrated as being coplanar with apertures  119 . Other arrangements are within the contemplation of the present disclosure, as described in more detail hereinafter. 
       FIG. 7  illustrates a further example of an interactive display according to an implementation. In the illustrated implementation, an interactive FSC display  700  includes the front surface  401 , the transparent substrate  335 , the light modulation array  111 , the optical cavity  113  and the display lighting system  415 . In the illustrated implementation, light directing features  455  are disposed proximate to a rear surface  369  of transparent substrate  335 . 
     As illustrated in  FIG. 7 , when the object  150  interacts with object illuminating IR light  442 , scattered IR light  644 , resulting from the interaction, may be scattered back toward the front surface  401  and be received by IR light sensor  433 . Scattered IR light  644  may pass through light turning feature  455 , enter optical cavity  113  and be at least partially received by IR light sensor  433 . The IR light sensor  433  may be configured to output a signal representative of a characteristic of received IR light  646  resulting from interaction of the object illuminating IR light  442  with the object  150 . 
       FIG. 8  illustrates another example of an interactive display according to an implementation. In the illustrated implementation, an interactive FSC display  800  includes the front surface  401 , the transparent substrate  335 , the light modulation array  111 , the optical cavity  113  and the display lighting system  415 . In the illustrated implementation, light directing features  455  are disposed proximate to a front surface  801  of transparent substrate  335 . 
     As illustrated in  FIG. 8 , when the object  150  interacts with object illuminating IR light  442 , scattered IR light  644 , resulting from the interaction, may be scattered back toward the front surface  401  and be received by IR light sensor  433 . Scattered IR light  644  may pass through light turning feature  455 , enter optical cavity  113  and be at least partially received by IR light sensor  433 . The IR light sensor  433  may be configured to output a signal representative of a characteristic of received IR light  646  resulting from interaction of the object illuminating IR light  442  with the object  150 . 
       FIG. 9  illustrates a yet further example of an interactive display according to an implementation. In the illustrated implementation, an interactive FSC display  900  includes the transparent substrate  335 , the light modulation array  111 , the optical cavity  113 , the display lighting system  415  and a front layer  902 . In the illustrated implementation, light directing features  455  are disposed within the front layer  902 . Front layer  902 , in some implementations, may be a transparent substrate such as glass, for example. 
     As illustrated in  FIG. 9 , when the object  150  interacts with object illuminating IR light  442 , scattered IR light  644 , resulting from the interaction, may be scattered back toward the front surface  401  and be received by IR light sensor  433 . Scattered IR light  644  may pass through light turning feature  455 , enter optical cavity  113  and be at least partially received by IR light sensor  433 . The IR light sensor  433  may be configured to output a signal representative of a characteristic of received IR light  646  resulting from interaction of the object illuminating IR light  442  with the object  150 . 
     In some implementations, the second modulation scheme may provide, periodically, a “blank” sub-frame, during which the display lighting system is caused to turn off all light sources. During such a blank sub-frame, a level of ambient light proximate to the interactive FSC display  500  may be determined, for example. In some implementations, the light sensors may be configured to sense the pattern of shadows cast by an object  150  on the FSC display  500  during such blank sub-frames. The shutters for all the pixels may be closed during such blank sub-frames, in some implementations. 
     As indicated above, outputs of the IR sensor  433  may indicate one or more characteristics of the object  150 . Such characteristics include location, motion, and image characteristics of the object  150 . Particular implementations for obtaining location and motion characteristics, which may relate to a user input including a touch or a gesture, are described hereinbelow. In such implementations, the second modulation scheme may include selectively opening of light modulators according to one or more scanning patterns. In order to provide a better understanding of features and benefits of the presently disclosed techniques, illustrative examples of scanning patterns will now be described. 
     In some implementations, a scanning pattern may resemble a raster scan.  FIG. 10  illustrates an example of a scanning pattern for a second modulation scheme in accordance with some implementations. In the illustrated arrangement  1000 , the second modulation scheme includes selectively switching of light modulators to the open position in a temporal sequence according to a scanning pattern  1001 . As a result, object illuminating light may be passed through a sequentially through a series of apertures, or blocks of apertures according to the scanning pattern  1001 , where each aperture is associated with a respective pixel. As a result, substantially all of the viewing area of the electronic display  110  may be encompassed by the scanning pattern  1001 . 
     In some implementations, a raster scan line may be composed of a series of adjacent apertures. However, taking into account that apertures are typically much smaller in size than the object  150 , it may be advantageous to scan blocks of apertures. For example, referring to Detail A, each pixel block may include multiple apertures and be approximately one to 25 square millimeters in size. Two or more blocks in a successive series of blocks of apertures may include at least some apertures in common. That is, in some implementations, there may be an overlap of apertures between a first block of apertures and a second, succeeding or preceding block of pixels. 
     It will be appreciated that the illustrated scanning pattern  1001  is only an illustrative aspect of a feature of the second modulation scheme. Other scanning patterns are within the contemplation of the present disclosure. For example, a spiral scanning pattern may be implemented. 
       FIG. 11  illustrates a further example of a scanning pattern for a second modulation scheme in accordance with some implementations. In such implementation, a total viewing area of the electronic display  110  is treated as separate regions, with each separate region being separately scanned. In the illustrated implementation  1100 , for example, the total viewing area of the electronic display  110  is treated as four separate quadrants. Scanning of each region by way of a scanning pattern  1101  may be performed, advantageously, in parallel. As a result, in each sub-frame in which object illuminating light is to be emitted through an open aperture, at least one aperture of a respective scanning pattern in each quadrant may be switched to an open position. Although in the illustrated implementation, a similar scanning pattern  1101  is executed in four similarly sized quadrants, it will be appreciated that other arrangements are within the contemplation of the present disclosure. One or more the separate regions may be of a different size, for example. As a further example, a scanning pattern for any region may be different from a scanning pattern region for another region. 
     It will be appreciated that selectively switching of light modulators to the open position in a temporal sequence according to a scanning pattern as described above may be performed in synchronization with flashes of IR emitter  475 . Referring again to  FIG. 6 , blocks of light modulators may be switched to the open position sequentially according to the scanning pattern, in synchronization with flashes of IR emitter  475 , for example. 
     When the object  150  is approximately above a block of light modulators switched to the open position, the object  150  will interact with the emitted IR light  442 . The scattered light  644  resulting from interaction of the emitted IR light  442  with the object  150  may be received by the IR sensor  433 . The IR sensor  433  may be configured to output, to a processor (not shown), a signal representative of a characteristic of the received, redirected scattered light  646 . The processor may be configured to recognize, from the output of the IR sensor  433 , the characteristic of the object  150 , such as location and relative motion, for example. 
     As noted above, each light turning feature  455  may be configured so as to absorb or reflect light reaching it from locations outside its respective, particularly oriented lobe(s). As a result, only light that is reflected from an object located within a lobe associated with a respective light turning feature  455  may be received by IR light sensor  433 . The lobe may also be referred to as the “field of view” of the light turning feature. 
       FIG. 12  illustrates a technique for detecting a bright object, according to some implementations. Bright object  1250  is illustrated as being located in a particular geometric position with respect to a front surface of display  110 . It will be appreciated that bright object  1250  may be “bright”, in some implementations, as a result of scattering object illuminating IR light emitted from the display. In other implementations bright object  1250  may be an IR light source, or may scatter ambient IR light or IR light from an external source (not illustrated). 
     Each of a plurality of pixels, as disclosed hereinabove, may be associated with a respective light turning feature  455  and a respective aperture  119 . Each light turning feature  455  may have a particular field of view, which may or may not overlap with a field of view of a different light turning feature. In the illustrated example, bright object  1250  may be detected when the respective aperture associated with “Pixel 2” is open. When the respective aperture associated with “Pixel 2” is shut, the bright object may be undetected even when apertures associated with at least some other pixels are open. For example, in the illustrated implementation, the respective fields of view of light turning features associated with pixels 1, 3 and 4 do not include bright object  1250 . 
     It will be appreciated that the respective apertures of successive pixels may be opened in a temporal sequence according to the second modulation scheme. For example, the temporal sequence may correspond to the raster scan patterns illustrated in  FIGS. 10 and 11 . The second modulation scheme may include opening apertures to collect IR light at timer intervals interspersed between color sub-frames. The second modulation scheme may include a compressive sensing pattern such as a pseudorandom pattern, or be performed according to a discrete cosine basis, for example. 
     Referring again to  FIG. 6 , each opened aperture may couple, into the optical cavity  113 , IR light received within a specific angular cone corresponding to the field of view of the light turning element associated with the opened aperture. As described hereinabove, the received IR light  646  may be detected by IR light sensor  433 . As a result, a location and/or motion of the bright object  1250  may be detected. 
       FIG. 13  illustrates a technique for detecting a dark object, according to some implementations. Dark object  1350  is illustrated as being located in a particular geometric position with respect to a front surface of display  110 . It will be appreciated that dark object  1350  may be regarded as a shadow cast as a result of dark object  1350  being interposed between display  110  and a source of IR light, for example. 
     Each of a plurality of pixels may be associated with a respective light turning feature  455  and a respective aperture  119 . Each light turning feature  455  may have a particular field of view, which may or may not overlap with a field of view of a different light turning feature. In the illustrated example, a shadow cast by dark object  1350  may be detected when the respective aperture associated with “Pixel 2” is open. When the respective aperture associated with “Pixel 2” is shut, the shadow may be undetected even when apertures associated with at least some other pixels are open. For example, in the illustrated implementation, the respective fields of view of light turning features associated with pixels 1, 3 and 4 do not include dark object  1350 . 
     It will be appreciated that the respective apertures of successive pixels may be opened in a temporal sequence according to the second modulation scheme. For example, the temporal sequence may correspond to the raster scan patterns illustrated in  FIGS. 10 and 11 . The second modulation scheme may include opening apertures to collect IR light at timer intervals interspersed between color sub-frames. The second modulation scheme may include a compressive sensing pattern such as a pseudorandom pattern, or be performed according to a discrete cosine basis, for example. 
     Referring again to  FIG. 6 , each opened aperture may couple, into the optical cavity  113 , IR light received within a specific angular cone corresponding to the field of view of the light turning element associated with the opened aperture. As described hereinabove, the received IR light  646  may be detected by IR light sensor  433 . As a result, a location and/or motion of the dark object  1350  may be detected. 
       FIG. 14  illustrates an example of a scanning strategy for the second modulation scheme in accordance with some implementation. In the illustrated example respective apertures of successive clusters (“blocks”) of pixels may be opened in a temporal sequence according to the second modulation scheme. For example, the display area may be divided into a number blocks of pixels. In the illustrated, simplified example, the display area  110  is divided into nine blocks  110 ( 1 ),  110 ( 2 ) . . .  110 ( 9 ), each block including nine pixel apertures. Each of the pixel apertures in a given cluster may be opened simultaneously, and the successive blocks of pixel apertures may be opened in a temporal sequence that may correspond to the raster scan patterns illustrated in  FIG. 10  or  11 , for example. 
     When an object is detected in a particular pixel block, a subsequent raster scan may be performed using a smaller subset of pixel apertures, or individual pixel apertures in a temporal sequence. In the example illustrated in  FIG. 14 , object  1450  may be detected during a first, relatively course scan at pixel block  110 ( 4 ), Detail A. A subsequent, finer scan may then be performed using only pixel apertures within pixel block  110 ( 4 ), Detail B. 
     As described above, the second modulation scheme may include opening apertures to collect IR light at timer intervals interspersed between color sub-frames. The second modulation scheme may include a compressive sensing pattern such as a pseudorandom pattern, or be performed according to a basis that is sparse with respect to the objects to be sensed, such as according to a discrete cosine basis, for example. In some implementations the pattern may include a binary code pattern, such as “Gray” codes typically used for error prevention when reading naturally-occurring binary codes, for example, as well as other possible patterns. 
     It will be appreciated that IR light may be emitted by IR light source  475 , for example, and/or detected by IR light detector  433 , for example during sub-frames during which image rendering light is also being emitted. In some implementations, IR light sensor signals may be back correlated with knowledge of the pixel aperture settings in a relevant sub-frame. Such a correlation may be used, for example, to make an object location determination, to prioritize what areas of the display to raster scan, reduce the number of necessary sub-frames, increase the scanning speed, and/or increase location resolution for a given number of sub-frames. 
     In any of the above-described implementations, the second modulation scheme may be configured such that, during a fraction of the sub-frames all the RGB and IR light turn-off, and the photo-sensitive elements may be configured to sense the pattern of shadows cast by object  250  on the display. For this measurement, the shutters for all the pixels may be closed. 
       FIG. 15  illustrates an example of a process flow for touch and gesture recognition with an interactive FSC display according to an embodiment. At block  1510  of process  1500 , one or more devices for opening and shutting apertures included in an arrangement for spatial light modulation may be switched by a processor. The apertures may be included in an arrangement for spatial light modulation. In some implementations, the devices for opening and shutting the apertures may be switched in accordance with a first modulation scheme to render an image. As described hereinabove, a field sequential color (FSC) display, that includes the arrangement for spatial light modulation, has a display front surface and a viewing area. The FSC display may include a light directing arrangement including at least one light turning feature, the light turning feature being configured to redirect IR light emitted through the opened aperture into at least one lobe, and to pass visible light emitted by the display lighting system through the opened aperture with substantially no redirection. The FSC display may also include at least one infrared (IR) light sensor configured to output a signal representative of a characteristic of received IR light, the received IR light resulting from scattering of the at least one lobe of IR light by an object. 
     At block  1520 , visible light and IR light may be emitted through at least a first opened one of the plurality of apertures. 
     At block  1530 , the devices for opening and shutting the apertures may be switched in accordance with a second modulation scheme to selectively pass object illuminating IR light through at least one of the respective apertures. Advantageously, the object illuminating IR light may be at least partially unrelated to the image. 
     At block  1540 , the processor may recognize, from the output of the light sensor, a characteristic of the object. The characteristic may include one or more of a location, or a motion of the object, or image data. Advantageously, the processor may control the display, responsive to the characteristic. 
     Thus, improved implementations relating to an interactive FSC display have been disclosed. In some of the above described implementations, the display lighting system may include light sources configured to be fully or partially modulated at some frequency or signal pattern. In such implementations, the processor may include and/or be coupled with light sensor readout circuitry that includes an active or passive electrical band-pass frequency filter or other means to correlate the modulator signal pattern. In addition to modulation, the intensity of the light sources may be scaled to the (possibly lower or higher) appropriate amount of light for scanning rather than displaying information. 
     The various illustrative logics, logical blocks, modules, circuits and algorithm steps described in connection with the implementations disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. The interchangeability of hardware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and steps described above. Whether such functionality is implemented in hardware or software depends upon the particular application and design constraints imposed on the overall system. 
     The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or, any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular steps and methods may be performed by circuitry that is specific to a given function. 
     In one or more aspects, the functions described may be implemented in hardware, digital electronic circuitry, computer software, firmware, including the structures disclosed in this specification and their structural equivalents thereof, or in any combination thereof. Implementations of the subject matter described in this specification also can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage media for execution by, or to control the operation of, data processing apparatus. 
     If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. The steps of a method or algorithm disclosed herein may be implemented in a processor-executable software module which may reside on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program from one place to another. A storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection can be properly termed a computer-readable medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above also may be included within the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and instructions on a machine readable medium and computer-readable medium, which may be incorporated into a computer program product. 
     Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. The word “exemplary” is used exclusively herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other possibilities or implementations. Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of an apparatus as implemented. 
     Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Similarly, while operations are depicted in the drawings in a particular order, a person having ordinary skill in the art will readily recognize that such operations need not be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.