Patent Publication Number: US-2015084994-A1

Title: Touch-enabled field-sequential color (fsc) display using a light guide with light turning features

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 
     Electronic devices such as smart phones, tablets, laptops, personal computers, and the like increasingly feature a touchscreen user interface. The power, cost and durability requirements typical of handheld devices are not well-achieved by known techniques. For example, projected capacitance touch (PCT), presently the most commonly used technology for handheld devices, generally employs transparent layers of indium tin oxide (ITO) or other transparent conductor materials stacked together above the display. This reduces the clarity of the display, adds significant cost, and additional controller electronics are needed to read out the finger locations. In addition, there can be cross talk and noise between the display electronics and the touch electronics, reducing the performance of both. 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 an interactive display having a front surface including a viewing area, the interactive display including a display lighting system and an arrangement for spatial light modulation, the arrangement for spatial light modulation including an array of light modulators, each light modulator configured to be switched between an open position that permits transmittance of light from the display lighting system through a respective aperture to the front surface and a shut position that blocks light transmission through the respective aperture. The apparatus also includes a first light guide, disposed between the display lighting system and the front surface and substantially parallel to the front surface, and having a periphery at least coextensive with the viewing area; at least one light sensor disposed proximate to the periphery of the first light guide; and a processor. The light modulators are switched in accordance with a first modulation scheme to render an image. The first light guide is configured to pass light emitted by the display lighting system toward the front surface and to receive light reflected through the front surface from an object, the first light guide including a first light-turning arrangement that redirects a portion of the received light toward the at least one light sensor. The light sensor is configured to output, to the processor, a signal representative of a characteristic of the received, redirected light. The processor is configured to switch the light modulators in accordance with a second modulation scheme to selectively pass object illuminating light through at least one of the respective apertures, the object illuminating light being at least partially unrelated to the image. The processor is also configured to recognize, from the output of the light sensor, a characteristic of the object. 
     In some implementations, the object may include one or more of a hand, finger, hand held object, and other object under control of a user. In some implementations, the object may include a document to be imaged. 
     In some implementations, the display lighting system may include at least one infrared (IR) light emitter, configured to emit IR light. The at least one light sensor may include an IR light sensor. The first light guide may be configured to pass IR light emitted by the display lighting system toward the front surface and to receive IR light reflected through the front surface from the object. The first light-turning arrangement may redirect a portion of the received IR light toward the IR light sensor. 
     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 light modulators of an array of light modulators. An interactive display has a front surface including a viewing area, the interactive display including a display lighting system and an arrangement for spatial light modulation, the arrangement for spatial light modulation including the array of light modulators, each light modulator configured to be switched between an open position that permits transmittance of light from the display lighting system through a respective aperture to the front surface and a shut position that blocks light transmission through the respective aperture. A first light guide is disposed between the display lighting system and the front surface and substantially parallel to the front surface, and having a periphery at least coextensive with the viewing area. At least one light sensor is disposed proximate to the periphery of the first light guide. The light modulators are switched in accordance with a first modulation scheme to render an image, and in accordance with a second modulation scheme to selectively pass object illuminating light through at least one of the respective apertures, the object illuminating light being at least partially unrelated to the image. The first light guide is configured to pass light emitted by the display lighting system toward the front surface and to receive light reflected through the front surface from an object, the first light guide including a first light-turning arrangement that redirects a portion of the received light toward the at least one light sensor. The method further includes outputting from the light sensor to the processor, a signal representative of a characteristic of the received, redirected light, and recognizing, 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 electronic display. 
         FIG. 1B  and  FIG. 1C  show an example of an arrangement including a planar light guide and a light sensor. 
         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 electronic display incorporating a light modulation array. 
         FIG. 4  illustrates an example of an interactive display according to an implementation. 
         FIG. 5  illustrates a further example of an interactive display, according to an implementation. 
         FIG. 6  illustrates an example of a scanning pattern for a second modulation scheme in accordance with some implementations. 
         FIG. 7  illustrates a further example of a scanning pattern for a second modulation scheme in accordance with some implementations. 
         FIG. 8  shows an example of a light turning arrangement and light sensors, according to an implementation. 
         FIG. 9  shows an example of a light turning arrangement and light sensors, according to a further implementation. 
         FIG. 10  shows an example of a light turning arrangement and light sensors, according to another implementation. 
         FIG. 11  shows an example of a light turning arrangement and light sensors, according to a yet further implementation. 
         FIG. 12  shows an example of a light turning arrangement and light sensors, according to another implementation. 
         FIG. 13  shows an example of a scanning pattern in which a size of aperture blocks may be adjusted. 
         FIG. 14  illustrates an example of an interactive display, configured for document scanning, according to an implementation. 
         FIG. 15  illustrates an example of an interactive display, configured for document scanning, according to a further implementation. 
         FIG. 16  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 interactive 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. 
       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. 
     An arrangement  130  (examples of which are described and illustrated herein below) may be disposed substantially parallel to a front surface of the electronic display  110 . In an implementation, the arrangement  130  may be substantially transparent and optically coupled to the electronic display  110 , such that at least most light emitted by a display lighting system (not shown) of the electronic display  110  is transmitted through the arrangement  130 . The arrangement  130  may output one or more signals responsive to light received from the display lighting system and/or a source exterior to the electronic display  110 . In some implementations, the signals may be responsive to light reflected into the arrangement  130  from a user&#39;s appendage, an object or a document, for example. 
     In some implementations, signals outputted by the arrangement  130 , 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  and  FIG. 1C  show an example of an arrangement including a planar light guide and a light sensor. In the illustrated implementation, the arrangement  130  includes a planar light guide  135  (which may be referred to herein as the “first light guide”) and a light sensor  133 . Referring now to  FIG. 1B , which may be referred to as a perspective view, the arrangement  130  is illustrated as being disposed above and substantially parallel to an upper surface of the electronic display  110 . The light sensor  133  is shown disposed proximate to the periphery of the planar light guide  135 . In the illustrated implementation, the perimeter of the planar light guide  135  is substantially coextensive with the perimeter of the electronic display  110 . Advantageously, the perimeter of the planar light guide  135  is coextensive with, or is larger than and fully envelopes, the perimeter of the electronic display  110 . 
     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, and light sensors may be disposed on or near a single side, or adjacent or opposite sides, or three or four sides of the planar light guide  135 , for example. In some implementations, the light sensor  133  may be disposed above or below the planar light guide  135 . Advantageously, the light sensor  133  may be disposed near, either within or outside of, the perimeter of the planar light guide  135 . 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. 
     In the illustrated implementation, the light sensor  133  is disposed at the periphery of the planar light guide  135 . Alternative configurations are within the contemplation of the present disclosure, however. For example, the light sensor  133  may be remote from the planar light guide  135 , in which case light detected by the light sensor  133  may be received from the planar light guide  135  by way of additional optical elements such as, for example, one or more optical fibers (not illustrated). 
     The planar light guide  135  may be optically coupled to the electronic display  110 . The planar light guide  135  may be substantially transparent such that at least most light  143  from the electronic display  110  passes through the planar light guide  135  and may be observed by a user (not illustrated). 
     The planar light guide  135  may include a substantially transparent, relatively thin, overlay disposed on, or proximate to, the front surface of the electronic display  110 . In some implementations, for example, the planar light guide  135  may be approximately 0.5 mm thick, while having a planar area in an approximate range of tens or hundreds of square centimeters. The transparent material may have an index of refraction greater than 1. For example, the index of refraction may be in the range of about 1.4 to 1.6. The index of refraction of the transparent material determines a critical angle ‘a’ with respect to a normal to the material surface such that a light ray intersecting the surface at an angle less than ‘a’ will pass through the surface, but a light ray intersecting the surface at an angle greater than ‘a’ will undergo total internal reflection (TIR). 
     As illustrated in  FIG. 1C , 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 toward the planar light guide  135 . 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, including a document to be imaged, but is herein referred to, for simplicity, as the “object.” 
     The planar light guide  135  may be configured to collect the scattered light  144 . Advantageously, the planar light guide  135  may include a light-turning arrangement that redirects the scattered light  144 , toward the light sensor  133 . The light-turning arrangement may include a number of light turning elements  166 , described in more detail hereinbelow. Redirected scattered light  146  may be turned in a direction having a substantial component parallel to the upper surface of the electronic display  110 . More particularly, at least a substantial fraction of the redirected scattered light  146  intersects a front surface  167  of the planar light guide  135  and a rear surface  169  of the planar light guide  135  only at an angle to normal greater than critical angle ‘a’ and, therefore, undergoes TIR. As a result, such redirected scattered light  146  does not pass through the front surface  167  or the rear surface  169  and, instead, reaches the light sensor  133 . The light sensor  133  may be configured to detect one or more characteristics of the redirected scattered light  146 , 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. 
     In some implementations, the light turning elements  166  may include reflective or refractive microstructures, holographic film, volume holograms, and/or surface relief gratings that turn light by diffraction and/or surface roughness that turns light by scattering. In some implementations, the light turning elements  166  may be configured as films laminated to the planar light guide  135 . In some implementations, the light turning elements  166  may be configured as a dielectric or metal layer deposited on the planar light guide  135 . The light turning elements  166  may be holographic, diffractive, or refractive, for example. 
     In the illustrated implementation, the light turning elements  166  are shown to be disposed near the rear surface  169  of the planar light guide  135 , but other implementations are within the contemplation of the present disclosure. For example, the light turning elements  166  may be disposed near a front surface of the planar light guide  135 . 
     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 the 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 ( a ) and  118 ( c ) are depicted in the open position, whereas, the shutter  118 ( b ) is depicted in the closed position. 
     In some implementations, the optical cavity  113  may be formed from a light guide (the “second 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. 
       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 first light guide  135 , the light sensor  133 , the light modulation array  111  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 light emitters, designated R (red), B (blue) and G (green). 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 the 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. 
     In some implementations, the first light guide  135  may be disposed between the display lighting system  415  and the front surface  401 . The first light guide  135  may be substantially parallel to the front surface  401  and have a periphery at least coextensive with a viewing area of the interactive FSC display  400 . In the illustrated implementation, the first light guide  135  is depicted as being disposed between the light modulation array  111  and the front surface  401 , but this is not necessarily so. In some implementations, for example, the first light guide  135  may be disposed between the light modulation array  111  and the display lighting system  415 . 
     As illustrated in  FIG. 4 , when the object  150  interacts with object illuminating light  442 , scattered light  444 , resulting from the interaction, may be directed toward the first light guide  135 . 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, including a document to be imaged, but is herein referred to, for simplicity, as the “object.” 
     The first light guide  135  may be configured to collect the scattered light  444 . Advantageously, the first light guide  135  may include a light-turning arrangement (not illustrated) that redirects the scattered light  444  toward the light sensor  133 . Redirected scattered light  446  may be turned in a direction having a substantial component parallel to the front surface  401 . More particularly, at least a substantial fraction of the redirected collected scattered light  446  may be redirected at an angle to normal greater than critical angle ‘a’ and, therefore, may undergo TIR until reaching the light sensor  133 . The light sensor  133  may be configured to detect one or more characteristics of the redirected scattered light  446 , 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. 
     Although a single light sensor  133  is illustrated in  FIG. 4 , it will be appreciated that any number of light sensors  133  may be disposed about or proximate to a periphery of the first light guide  135 . In various implementations contemplated by the present disclosure, the number of light sensors may range from about four light sensors to some thousands of light sensors, for example. 
     In some implementations, there may be one or more optical components disposed between the first light guide  135  and the light sensor  133 . 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 redirected scattered light  446  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  (“image rendering light”) into the optical cavity  113 . Advantageously, at least a portion of the image rendering light  443  may undergo TIR and be distributed substantially uniformly throughout the optical cavity  113 . A portion of the image rendering light  443  may be transmitted through one or more of the apertures  119  and contribute to the rendered image. 
     In the illustrated implementation, the green light emitter of the display lighting system  415  is also configured to emit the object illuminating light  442  into the optical cavity  113 . At least a portion of the object illuminating light  442  may undergo TIR and be distributed substantially uniformly throughout the optical cavity  113 . 
     It should be noted that, in the illustrated implementation, the object illuminating light  442  and the image rendering light  443  are depicted as geometrically different ray traces only for clarity of illustration, and that the primary distinction between the object illuminating light  442  and the image rendering light  443  is temporal and/or spectral, rather than spatial. In the illustrated implementation, for example, where the image rendering light  443  and the object illuminating light  442  may have the same wavelength, the image rendering light  443  and the object illuminating light  442  may be emitted by the display lighting system  415  at different times, for example as part of different sub-frames. As a further example, the object illuminating light  442  may be visible light emitted during a document scanning operation during which the display viewing area is not ordinarily observable by a user. 
     In some implementations, the object illuminating light  442  may be light of a different wavelength than the image rendering light  443 . For example, the object illuminating light  442  may be of a nonvisible wavelength such as infrared (IR) or near IR. In such implementations, temporal separation between the object illuminating light  442  and the image rendering light  443  may or may not also be provided. 
     The present inventors have appreciated that an optical touch and gesture recognition functionality, as well as a document scanning capability, may be provided by using the object illuminating 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, the object illuminating light  442  being at least partially unrelated to the rendered image. In some implementations, a document scanning capability may also be provided by substantially similar hardware. 
     Advantageously, the second modulation scheme may provide that the object illuminating light  442  is passed only when there is one or both of temporal separation and spectral separation with respect to the image rendering light  443 . In some implementations, the second modulation scheme may provide for interspersing of sub-frames during which the object illuminating light  442  is passed with sub-frames during which the image rendering light  443  is passed. For example, where the object illuminating light  442  is at an IR wavelength, and 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 an IR emitter 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 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  400  may be determined, for example. 
       FIG. 5  illustrates a further example of an interactive display, according to an implementation. In the illustrated implementation, the interactive FSC display  500  includes an IR emitter  575  that may be configured to emit IR light into the optical cavity  113 . Emitted IR light  542  may strike the object  150  and be scattered back toward the front surface  401 . The object may be on or above the front surface  401 . Scattered light  544  resulting from interaction of the emitted IR light  542  with the object  150  may interact with a light-turning arrangement (not shown) within the first light guide  135  so as to be turned (“redirected”) toward an IR sensor  533 . The IR sensor  533  may be configured to output, to a processor (not shown), a signal representative of a characteristic of redirected scattered light  546 . The processor may be configured to recognize, from the output of the IR sensor  533 , the characteristic of the object  150 . 
     In some implementations, a wavelength of the IR light may be within a range that inexpensive silicon detectors may detect (700 nm to 1000 nm wavelength, for example). 
     The light-turning arrangement may be configured to capture light that is coming into the first light guide  135  via the front surface  401  of the interactive display and turn the captured light toward the periphery of the first light guide  135 . More particularly, the scattered light  544  may be redirected to an angle larger than the critical angle of the glass or other transparent material of which the first light guide  135  may be composed. The redirected scattered light  546  may be guided by total-internal-reflection (TIR) within the first light guide  135  to the edges of the first light guide  135 . The light turning arrangement may include elements disposed on either or both of an upper and lower surface of the first light guide  135  and may include holographic, diffractive, refractive, and/or reflective elements. 
     In some implementations, the light turning elements may be selectively located in areas not directly above the pixel apertures, e.g. in regions ‘A’ of the first light guide  135 . Advantageously, because the shutter aperture area of an FSC display is a relatively small fraction (e.g., one tenth to one half) of a total viewing area of the interactive FSC display  500 , a significant portion of the first light guide  135  may be occupied by light turning elements without any appreciable quality degradation of a displayed image. 
     As indicated above, outputs of the IR sensor  533  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. A scanning pattern may be selected in view of a combination of various configurations of one or more light sensors and light turning arrangements. 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. 6  illustrates an example of a scanning pattern for a second modulation scheme in accordance with some implementations. In the illustrated arrangement  600 , the second modulation scheme includes selectively switching of light modulators to the open position in a temporal sequence according to a scanning pattern  601 . 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  601 , 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  601 . 
     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  601  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. 7  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 700, 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  701  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  701  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 one or more wavelength specific light emitters of the display lighting system  415 . Referring again to  FIG. 5 , blocks of light modulators may be switched to the open position sequentially according to the scanning, in synchronization with flashes of IR emitter  575 , for example. In the illustrated implementation a display lighting system  515  included the IR emitter  575 , but this is not necessarily so. 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  542 . The scattered light  544  resulting from interaction of the emitted IR light  542  with the object  150  may interact with a light-turning arrangement (not shown) within the first light guide  135  so as to be turned (“redirected”) toward the IR sensor  533 . The IR sensor  533  may be configured to output, to a processor (not shown), a signal representative of a characteristic of the received, redirected scattered light  546 . The processor may be configured to recognize, from the output of the IR sensor  533 , the characteristic of the object  150 , such as location and relative motion, for example. 
     As noted above, a scanning pattern may be selected in view of a combination of various configurations of one or more light sensors and light turning arrangements. In order to provide a better understanding of features and benefits of the presently disclosed techniques, illustrative examples of various configurations of light sensor and light turning arrangements will now be described. 
       FIG. 8  shows an example of a light turning arrangement and light sensors, according to an implementation. The illustrated implementation includes a single IR light sensor  533  and a planar light guide  835  including a light turning arrangement that includes light turning elements  866  that, at least in aggregate, turn the scattered light  544  in a substantially omnidirectional manner. The light turning elements  866  may include microstructures such as reflective or refractive cones, screen printed scattering dots, bubbles, hologram, diffractive features, or the like. The scattered light  544  received by the planar light guide  835 , interacting with such light turning elements, may be turned omnidirectionally in the x-z plane by the light turning arrangement. The redirected scattered light  546  may be turned in a direction having a substantial component parallel to the upper surface x-z plane, and undergo TIR. As a result of omnidirectionally turning the scattered light  544 , a portion of the redirected scattered light  546  will reach the light sensor  533 . 
     Light modulators may be selectively switched to the open position in a temporal sequence according to a scanning pattern in synchronization with flashes of one or more IR light emitters of the display lighting system. When the object  150  is approximately above a light modulator, or block of light modulators, switched to the open position, the object  150  may interact with the emitted IR light  542 . The scattered light  544  resulting from interaction of the emitted IR light  542  with the object  150  may interact with the light-turning arrangement, as described above, and the portion of redirected scattered light  546  may reach the IR light sensor  533 . IR light sensor  533  may be configured to output, to a processor (not shown), a signal representative of a characteristic of the received, redirected scattered light  546 . The processor may be configured to recognize, from the output of the IR sensor  533 , the location and/or relative motion of the object  150 , for example. 
       FIG. 9  shows an example of a light turning arrangement and light sensors, according to a further implementation. The illustrated implementation includes a single IR light sensor  533  and a planar light guide  935  including a light turning arrangement that includes light turning elements  966  that, at least in aggregate, turn the scattered light  544  toward a focal point. The light turning elements  966  may be configured with directional turning features, such as curvilinear grooves or ridges, holographic, or diffractive features, for example. 
     Advantageously, the scattered light  544  received by the planar light guide  935 , interacting with such light turning elements, may be turned directionally toward the IR light sensor  533 . The redirected scattered light  546  may be turned in a direction having a substantial component parallel to the upper surface x-z plane, and undergo TIR. As a result of directionally turning the scattered light  544 , at least a large fraction of the redirected scattered light  546  may reach the IR light sensor  533 . 
     Light modulators may be selectively switched to the open position in a temporal sequence according to a scanning pattern in synchronization with flashes of one or more IR light emitters of the display lighting system. When the object  150  is approximately above a light modulator, or block of light modulators, switched to the open position, the object  150  may interact with the emitted IR light  542 . The scattered light  544  resulting from interaction of the emitted IR light  542  with the object  150  may interact with the light-turning arrangement, as described above, and the portion of the redirected scattered light  546  may reach the IR light sensor  533 . The IR light sensor  533  may be configured to output, to a processor (not shown), a signal representative of a characteristic of the redirected scattered light  546 . The processor may be configured to recognize, from the output of the IR sensor  533 , the location and/or relative motion of the object  150 , for example. 
       FIG. 10  shows an example of a light turning arrangement and light sensors, according to a yet further implementation. The illustrated implementation includes four IR light sensors  533  and a planar light guide  1035 . The planar light guide  1035  includes a light turning arrangement that includes four regions, each region including light turning elements  1066  that, at least in aggregate, turn the scattered light  544  toward a respective focal point. The light turning elements  1066  may be configured with directional turning features, such as curvilinear grooves or ridges, holographic, or diffractive features, for example. 
     Advantageously, the scattered light  544  received by the planar light guide  1035 , interacting with such light turning elements, may be turned directionally toward the respective IR light sensor  533 . The redirected scattered light  546  may be turned in a direction having a substantial component parallel to the upper surface x-z plane, and undergo TIR. As a result of directionally turning the scattered light  544 , at least a large fraction of the redirected scattered light  546  may reach the respective IR light sensor  533 . 
     Light modulators may be selectively switched to the open position in a temporal sequence according to a scanning pattern in synchronization with flashes of one or more IR light emitters of the display lighting system. When the object  150  is approximately above a light modulator, or block of light modulators, switched to the open position, the object  150  may interact with the emitted IR light  542 . The scattered light  544  resulting from interaction of the emitted IR light  542  with the object  150  may interact with the light-turning arrangement, as described above, and the large fraction of the redirected scattered light  546  may reach the respective IR light sensor  533 . Each IR light sensor  533  may be configured to output, to a processor (not shown), a signal representative of a characteristic of the redirected scattered light  546 . The processor may be configured to recognize, from the output of each IR sensor  533 , the location and/or relative motion of the object  150 , for example. 
     It will be appreciated that a scanning pattern whereby multiple regions are scanned in parallel, such as that described above in connection with  FIG. 7 , may advantageously be used in combination with the implementation illustrated in  FIG. 10 . Such a combination may increase the scanning speed, or increase the achievable resolution for a given scanning speed, for example. 
       FIG. 11  shows an example of a light turning arrangement and light sensors, according to a yet further implementation. The illustrated implementation includes a number of IR light sensors  533  disposed along a first side of a planar light guide  1135 . The planar light guide  1135  includes a light turning arrangement that includes light turning elements  1166  that, at least in aggregate, turn the scattered light  544  toward the first side of the planar light guide  1135 . The light turning elements  1166  may be configured with directional turning features, such as linear grooves or ridges, holographic, or diffractive features, for example. 
     Advantageously, the scattered light  544  received by the planar light guide  1135 , interacting with such light turning elements, may be turned directionally toward the respective IR light sensor  533 . The redirected scattered light  546  may be turned in a direction having a substantial component parallel to the upper surface x-z plane, and undergo TIR. As a result of directionally turning the scattered light  544 , at least a large fraction of the redirected scattered light  546  may reach one or more of the IR light sensors  533 . 
     Light modulators may be selectively switched to the open position in a temporal sequence according to a scanning pattern in synchronization with flashes of one or more IR light emitters of the display lighting system. When the object  150  is approximately above a light modulator, or block of light modulators, switched to the open position, the object  150  may interact with the emitted IR light  542 . The scattered light  544  resulting from interaction of the emitted IR light  542  with the object  150  may interact with the light-turning arrangement, as described above, and the large fraction of redirected scattered light  546  may reach one or more of the IR light sensors  533 . Each IR light sensor  533  may be configured to output, to a processor (not shown), a signal representative of a characteristic of the received, redirected scattered light  546 . The processor may be configured to recognize, from the output of each IR sensor  533 , the location and/or relative motion of the object  150 , for example. 
     The redirected scattered light  546  may reach two or more IR light sensors  533  and each IR light sensor  533  may be configured to output, to a processor (not shown), respective signals representative of a characteristic of the respectively received redirected scattered light  546 . In some implementations the processor may be configured to weigh the signals received from the two or more IR light sensors  533  in order to more precisely recognize, from the output of each IR sensor  533 , the location and/or relative motion of the object  150 , for example. 
       FIG. 12  shows an example of a light turning arrangement and light sensors, according to another implementation. The illustrated implementation includes a number of IR light sensors  533  disposed along each of two adjacent sides of a planar light guide  1235 . The planar light guide  1235  includes a light turning arrangement that includes light turning elements  1266  that, at least in aggregate, turn the scattered light  544  towards a first side of the planar light guide  1235  and a second, adjacent side of the planar light guide  1235 . The light turning elements  1266  may include microstructures such as reflective or refractive pyramids or cones, or be configured with holographic, or diffractive features, for example. Advantageously, the scattered light  544  received by the planar light guide  1235 , interacting with such light turning elements, may be turned directionally toward the IR light sensors  533  disposed on the first side and/or the second side. The redirected scattered light  546  may be turned in a direction having a substantial component parallel to the upper surface x-z plane, and undergo TIR. As a result of directionally turning the scattered light  544 , at least a large fraction of the redirected scattered light  546  may reach one or more of the IR light sensors  533 . 
     Light modulators may be selectively switched to the open position in a temporal sequence according to a scanning pattern in synchronization with flashes of one or more IR light emitters of the display lighting system. When the object  150  is approximately above a light modulator, or block of light modulators, switched to the open position, the object  150  may interact with the emitted IR light  542 . The scattered light  544  resulting from interaction of the emitted IR light  542  with the object  150  may interact with the light-turning arrangement, as described above, and the large fraction of the redirected scattered light  546  may reach one or more of the IR light sensors  533 . Each IR light sensor  533  may be configured to output, to a processor (not shown), a signal representative of a characteristic of the redirected scattered light  546 . The processor may be configured to recognize, from the output of each IR sensor  533 , the location and/or relative motion of the object  150 , for example. 
     The redirected scattered light  546  may reach two or more IR light sensors  533  and each IR light sensor  533  may be configured to output, to a processor (not shown), respective signals representative of a characteristic of the respectively received redirected light  546 . In some implementations the processor may be configured to weigh the signals received from the two or more IR light sensors  533  in order to more precisely recognize, from the output of each IR sensor  533 , the location and/or relative motion of the object  150 , for example. 
     Irrespective of the configuration of light turning arrangement and light sensor(s), the second modulation scheme may include a scanning pattern that includes blocks of apertures of a selectably adjustable size.  FIG. 13  shows an example of a scanning pattern in which a size of aperture blocks may be adjusted. In such implementations, the scanning pattern may be initiated with relatively large blocks until a relatively course location of the object  150  is recognized. Subsequently, the aperture block size may be reduced, and scanning continued in a smaller region proximate to the relatively course location. If desired this sequence may be repeated one or more times. Advantageously, the above mentioned implementations may reduce the number of necessary sub-frames, increase the scanning speed, or increase the achievable resolution with the same number of sub-frames. 
     In some implementations, documents or objects proximate to the display may be scanned using visible light.  FIG. 14  illustrates an example of an interactive display, configured for document scanning, according to an implementation. In the illustrated implementation, it is shown how a color scan may be performed on an object or document  1450  that is proximate to the front surface  401 . The object or document  1450  may be scanned by sequentially flashing RGB light emitters of the display lighting system  415 , and taking a separate light sensor reading for each illumination sub-frame using a visible (white) light sensor  1433 . 
     For example, referring still to  FIG. 14 , the green light emitter of the display lighting system  415  may be configured to emit the object illuminating light  442  into the optical cavity  113 . At least a portion of the object illuminating light  442  may undergo TIR and be distributed substantially uniformly throughout the optical cavity  113 . 
     At least a portion of the object illuminating light  442  may be transmitted through a light modulator switched to the open position, and interact with the object or document  1450 . Scattered light resulting from the interaction may be received by the first light guide  135  via the front surface  401 . More particularly, the received light may be redirected to an angle larger than the critical angle of the glass or other transparent material of which the first light guide  135  may be composed. The redirected scattered light  446  may be guided by total-internal-reflection (TIR) within the first light guide  135  to the edges of the first light guide  135  and be received by the light sensor  1433 . 
     For clarity of illustration,  FIG. 14  shows only a single color of light being emitted through a single aperture. Consistent with the techniques disclosed hereinabove however, a temporal sequence of light emissions may be sequentially flashed by each of, for example, the RGB light emitters of the display lighting system  415 . Moreover, the presently disclosed document scanning technique may be performed in conjunction with performing the second modulation scheme that includes selectively opening of light modulators according to one or more scanning patterns. 
     In some implementations, the RGB light emitters of the display light system  415  may be simultaneously illuminated.  FIG. 15  illustrates an example of an interactive display, configured for document scanning, according to a further implementation. In the illustrated implementation, it is shown how a color scan may be performed on the object or document  1450  that is proximate to the front surface  401 . The object or document  1450  may be scanned by simultaneously flashed RGB light emitters of the display lighting system  415 . In the illustrated implementation light sensor  1533  includes multiple photosensitive elements, each sensitized, by way of respective filters, for example, to an individual color. Each individual photosensitive element, for example,  1533 R,  1533 G and  1533 B may output a separate signal reading for each illumination sub-frame. 
     At least a portion of the object illuminating light  442 R,  442 G, and  442 B may be transmitted through a light modulator switched to the open position, and interact with the object or document  1450 . Scattered light resulting from the interaction may be received by the first light guide  135  via the front surface  401 . More particularly, the received light may be redirected to an angle larger than the critical angle of the glass or other transparent material of which the first light guide  135  may be composed. The redirected scattered light  446 R,  446 G, and  446 B may be guided by total-internal-reflection (TIR) within the first light guide  135  to the edges of the first light guide  135  and be received by the light sensor  1533 , including the individual light sensing elements  1533 R,  1533 G, and  1533 B. 
     For clarity of illustration,  FIG. 15  shows light being emitted only through a single aperture. Consistent with the techniques disclosed hereinabove however, the presently disclosed document scanning technique may be performed in conjunction with performing the second modulation scheme that includes selectively opening of light modulators according to one or more scanning patterns. 
       FIG. 16  illustrates an example of a process flow for touch and gesture recognition with an interactive FSC display according to an embodiment. At block  1610  of process  1600 , one or more light modulators of an array of light modulators may be switched in accordance with a first modulation scheme to render an image, and in accordance with a second modulation scheme to selectively pass object illuminating light through at least one of the respective apertures. Advantageously, the object illuminating light may be at least partially unrelated to the image. In some implementations, the light modulators may be switched by a processor configured to control the interactive display. As described hereinabove, the interactive display may have a front surface including a viewing area. The interactive display may include a display lighting system and an arrangement for spatial light modulation, the arrangement for spatial light modulation including the array of light modulators. Each light modulator may configured to be switched between an open position that permits transmittance of light from the display lighting system through a respective aperture to the front surface and a shut position that blocks light transmission through the respective aperture. A first light guide may be disposed between the display lighting system and the front surface and substantially parallel to the front surface. The first light guide may have a periphery at least coextensive with the viewing area. At least one light sensor may be disposed proximate to the periphery of the first light guide. The first light guide may be configured to pass light emitted by the display lighting system toward the front surface and to receive light reflected through the front surface from an object, the first light guide including a first light-turning arrangement that redirects a portion of the received light toward the light sensor. 
     At block  1620 , the light sensor may output to the processor a signal representative of the characteristic of the received, redirected light. 
     At block  1630 , 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.