Abstract:
A three-dimensional viewing device for providing images to a user includes a receiver receiving source 3D synchronization signals from a transmitting device, wherein the source 3D synchronization signals comprise a source frequency and a source phase, a plurality of LCD shutters including a right LCD shutter and a left LCD shutter are for alternatively entering a translucent state in response to local 3D synchronization signals in response to the source 3D synchronization signals, and an adjustment portion for adjusting parameters of the local 3D synchronization signals in response to parameters of the source 3D synchronization signals.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to stereoscopic 3D image viewing methods and apparatus. More particularly, the present invention relates to stereoscopic 3D image viewing devices and systems incorporating robust synchronization capability. 
         [0002]    When two-dimensional images that represent left and right points of view are sensed by respective left and right eyes of a user, the user typically experiences the perception of a 3D image from the two-dimensional images. The inventors are aware of several systems that allow users (e.g. individuals or groups) to perceive stereoscopic 3D depth in images, photos, pictures, moving pictures, videos, or the like, by the selective transmission of images to a user&#39;s eyes. Such systems include the use of display systems including light projection/reflection within a public or home theater or emissive or transmissive displays (e.g. LCD, plasma display, flat-panel display, or the like) to alternately or simultaneously output right eye images and left eye images to a user. To view such 3D images, a variety of approaches have been provided to the user including prisms, static polarized glasses, LCD shutter glasses, or the like. The inventors of the present invention have recognized that existing approaches have many drawbacks, as will be discussed below. 
         [0003]    One approach has been with the use of polarized glasses, where the left and right lenses have a fixed orthogonal polarization (e.g. clockwise-circular and counter-clockwise-circular polarization). The inventors of the present invention have determined that such systems have a number of drawbacks. One such drawback is that such systems typically rely upon images provided by a light projector and thus such systems are limited for use in darkened environments. Another drawback is that such systems typically reply upon expensive silver or metalized reflective screens that maintain the appropriate polarization of light from the projector to the right and left eye images. Such screens are often too expensive for the average consumer. Additional drawbacks include that both left and right eye images are displayed to the user at the same time and polarizers are often imperfect. Further, light can change polarization when it reflects off a screen; accordingly, despite the polarized glasses, right eye images are often visible to the left eye and left eye images are often visible to the right eye. This light pollution degrades the quality of the 3D images and can be termed as “ghosting” of 3D images. 
         [0004]    The inventors are aware of a number of techniques that may be used to reduce this ghosting effect. Some techniques may include deliberate degradation of left eye images to account for right eye image ghosting and the deliberate degradation of right eye images to account for left eye image ghosting. The inventors believe that such techniques are disadvantageous as they tend to reduce the contrast of objects in an image, and they may result in a visible halo around objects in the image. As a result of using these circular or linear polarized glasses, the inventors have recognized that 3D versions of features often do not appear as aesthetically pleasing as 2D versions of such features. 
         [0005]    Another approach to 3D visualization has included the use of stereoscopic shutter glasses that are based upon physical shutters, or more commonly liquid crystal display (LCD) technology. With such approaches, left and right images are alternatively displayed to the user, and the right and left LCD lenses alternate between a dark and transparent state. When the shutter glasses quickly alternate between transparency in the left then right eyes in synchronization with an image which presents alternating left and right points of view, the left and right eyes receive different 2D images and the observer experiences the perception of depth in a 3D image. 
         [0006]      FIG. 1A  illustrates a typical stereoscopic system. As illustrated, such systems typically include a computer  1 , an infrared transmitter  3 , a display  12 , and a pair of liquid crystal display glasses (LCD shutter glasses)  8 . In such systems, computer  1  alternatively provides left eye images and right eye images on signal line  2 , in addition to a signal that distinguishes when the left eye image or right eye image is displayed. 
         [0007]    In response to the signal, IR transmitter  3  outputs infrared data  6  that indicate when the right eye image is being output and when the left eye image is being output. The inventors note that many different manufacturers currently have different IR data packet definitions and protocols. For example, one simple format for infrared data is a simple square wave with a high signal indicating left and a low signal indicating right and another format includes an 8-bit word. Because of these different data formats, IR transmitters from one manufacturer often cannot be used with LCD glasses from another manufacturer. 
         [0008]    In various systems, infrared data  6  is received by LCD glasses  8 , and in response, for example, the right LCD of the LCD glasses  8  becomes opaque and the left LCD becomes translucent (e.g., clear), or the left LCD of the LCD glasses  8  becomes opaque and the right LCD becomes translucent. Ideally, at the same time the right LCD becomes translucent, display  12  is displaying a right eye image, and when the left LCD becomes translucent, display  12  is displaying a left eye image. 
         [0009]    In theory, systems illustrated in  FIG. 1A  are expected to provide a workable, robust system. However, in practice, the inventors have determined that there are many limitations that degrade the performance of such systems and that limit the applicability of such systems from being successfully and widely adopted. 
         [0010]    One such limitation includes the difficulty in synchronizing the glasses to the images that are displayed. Synchronization data is typically based upon when the images are provided to the 3D display. Limitations to such approaches, determined by the inventors, include that both latency and timing jitter are introduced as it is processed and rendered by the 3D display device. In various embodiments, jitter as little as 50 microseconds or 10 microseconds can affect the performance of the glasses. As a result of such latency and jitter information, the LCD lenses or shutters are often opened and closed often at improper times, e.g., out of phase, with some of the image intended for the left eye being shown to the right eye and vice versa. This is perceivable by the user as light pollution or ghosting effects. Additionally, as the inventors have determined that the phase difference is not constant and is subject to jitter, the user may see the image brightness change or flicker undesirably. 
         [0011]      FIG. 1B  illustrates a more detailed typical signal diagram of a stereoscopic system. As can be seen, computer  1  may include a computer graphic subsystem clock  15  from which the left/right images displayed to display  12  are controlled. Various timing signals  19  (e.g., left/right timing) are initially synchronous with computer graphics subsystem&#39;s clock  15 . As illustrated, timing signals  15  are typically vulnerable to the addition of random disturbances  16  including jitter, delay, and loss of signal from sources including delays in the computer hardware or operating system while propagating from the computer&#39;s graphics subsystem to embedded or externally attached signal transmitter  3 . 
         [0012]    Additionally, as illustrated, a transmitted signal  17  is also vulnerable to the further addition of random disturbances  18  including jitter, delay, and loss of signal from interferences and attenuation sources while propagating from the transmitter  3  to glasses  8 . Because these disturbances are random, it is impossible for delay adjustment  13  to properly compensate or account for the disturbances. 
         [0013]    Typically, the collective effect of disturbances  16  and  18  is that the prior art glasses  8  exhibit undesirable behavior including flicker, double vision in each eye and other function which ruins or interferes with the stereoscopic effect for the viewer or results in visual disturbances. 
         [0014]      FIG. 1C  illustrates a typical timing diagram illustrating jitter, delay, dropped signals, and the like. In this example, referring to  FIG. 1B , frames one and three may be typical times where the left-eye shutter should open and frames two and four may be typical times where the right-eye shutter of the 3D glasses should be open. In this example, frame one signal  28  (various timing signals  19 ) may be synchronous with graphic subsystem clock  15 , but because of a delay  32 , the left-eye shutter is opened at time  20 . As illustrated with regards to frame two signal  29 , the amount of delay  33  may change, resulting in the signal jittering. This jittering may delay the time  21  when the right-eye shutter should be opened (shortening the amount of time the right-eye image is viewed causing a darker right-eye image) or may cause the right-eye shutter to open too early (when a left-eye image is being displayed, causing a ghosting effect). In the example where a frame signal  30  is missing, for example, the left-eye shutter may not open at time  22  and the right-eye shutter may not close at time  22 . As a result, the user&#39;s right eye would be exposed to both the right and left image (ghosting), while the left eye image would appear darker. As can be seen in this example, the random jittering may reduce the viewer&#39;s enjoyment in watching 3D images. 
         [0015]    One approach to reduce such latency or jitter effects has been to reduce the amount of time the left LCD shutter and the amount of time the right LCD shutter are translucent. In such approaches, instead of the left shutter being open for example 50% of the time, the left shutter may be open 35% of the time, or the like. This reduction in open time should reduce the amount of ghosting. 
         [0016]    The inventors recognize drawbacks to such approach to image ghosting. One such drawback is the reduction in net amount of light transmitted to the user&#39;s eyes. In particular, as the exposure time for each eye is reduced, the user will perceive a darkening of the images for each eye. Accordingly, a 3D version of a feature will appear darker and duller compared to a 2D version of the feature when using IR-type shutter glasses. 
         [0017]    Another limitation is the use of the IR communications channel itself. The inventors of the present invention have determined that LCD glasses based upon IR receivers often lose synchronization with the display as a result of stray reflections. For example, it has been observed by the inventors that IR LCD glasses may become confused as a result of sunlight reflecting from household objects; heat sources such as candles, open flames, and heat lamps; IR remote controls (e.g. television remotes, game controllers); light sources (e.g. florescent lights); and the like. Additionally, it has been observed by the inventors that IR LCD glasses may also lose synchronization as a result of clothing, hair, portions of other users&#39; bodies (e.g., head), or the like that temporarily obscures an IR receiver of the LCD glasses. The loss of synchronization may lead the user to seeing a series of flickering or rolling images and/or the left eye seeing the right eye image. The inventors believe these types of anomalies are highly disturbing to most users and should be inhibited or minimized 
         [0018]    In some cases manufacturers of such devices specifically instruct users to use IR LCD glasses in highly controlled environments. For example, they suggest that the 3D displays and glasses be used only in darkened rooms. The inventors believe such a solution limits the applicability and attractiveness of such 3D display devices to typical consumers. This is believed to be because most consumers do not have the luxury of a dedicated, light-controlled room for a home theater, and that most consumer entertainment rooms are multipurpose family rooms. 
         [0019]    An additional drawback to such devices, determined by the inventors, is that multiple 3D display systems cannot easily be operated in the vicinity of each other. As described above, each 3D display system includes its own IR transmitter and 2D field timing and phase data. Then, when two such systems are in close proximity, a user&#39;s IR LCD glasses may receive IR transmissions from either of the 3D display systems. Because of this, although a user is viewing a first 3D display, the user&#39;s 3D glasses may be synchronizing to a different 3D display, causing the user to undesirably view flickering and rolling images. The inventors of the present invention thus recognize that multiple 3D display systems cannot easily be used in applications such as for public gaming exhibitions, tournaments, or contests, trade shows, in stadiums, in restaurants or bars, or the like. 
         [0020]    An additional drawback to conventional 3D shutter glasses includes the real-world introduction of latency and jitter into the system. Such uncorrelated latency and jitter typically affect the synchronization information as it is transmitted to the 3D shutter glasses and the electrical or electromechanical shutters of the 3D glasses as they are actuated. The inventors believe that as a result of the latency and jitter, it is likely that the shutters of the 3D glasses and the image being displayed will repeatedly be in and out of phase. To a user, a result is that some of the images intended for the left eye will be shown to the right eye and vice versa. The perception of this phase discrepancy is commonly called ghosting and causes the images to jitter, causes changes in perceived brightness of the images, and/or causes disruptive flickering of the images. 
         [0021]    Accordingly, what is desired are improved methods and apparatus for 3D image viewing without the drawbacks discussed above. 
       BRIEF SUMMARY OF THE INVENTION 
       [0022]    The present invention relates to stereoscopic 3D image viewing methods and apparatus. More particularly, the present invention relates to stereoscopic 3D image viewing devices incorporating robust synchronization capability. 
         [0023]    In various embodiments of the present invention, a stereoscopic 3D image viewing device is based upon liquid crystal display (LCD) shutters that are synchronized to a source of 3D images. In various embodiments, the synchronization is based upon RF protocols such as Bluetooth, ZigBee radio (ZigBee Alliance), IEEE Standard 802.11, IEEE Standard 802.15.4, or any other type of RF communications protocol. In some embodiments of the present invention, the stereoscopic 3D image viewing device may transmit data back to the source of 3D images, via the RF communications mechanism or protocol, to increase the level of synchronization between the two devices. 
         [0024]    In various embodiments, by using a multitude of communications protocols (e.g., RF) and adding feedback from 3D shutter glasses back to the 3D image source, a system, method, and apparatus of perceiving stereoscopic 3D can be generated which improves the level of synchronization between the alternating images and the alternating action of shutter glasses. A system, apparatus, method, and computer-readable media are provided to enable stereoscopic viewing. In particular, according to one method, the physical method of connecting the display system to stereoscopic glasses is the IEEE 802.11 wireless radio, IEEE 802.15.4 wireless radio, ZigBee radio or Bluetooth technology. This allows a user to move his/her head into positions that would normally lose reception of wireless transmissions (e.g., IR) thus simplifying the user experience of wearing stereoscopic glasses. The wireless radio connection also has the advantage of replacing the infra-red light transmission method and its associated interference with remote controls and tendency to accept interference from natural and artificial light sources, thus enhancing the user experience. 
         [0025]    In various embodiments, a shutter glasses control timer and multi-layer timer feedback loop are provided to 3D glasses for improved stereoscopic viewing. In particular, according to one embodiment, the control timer and multi-layer timer feedback loop operate the liquid crystal shutter action of the 3D glasses. Further, these components utilize the 3D source synchronization signal (e.g., system), in one example the VESA signal, along with RF-based communications mechanisms, as discussed herein, e.g., IEEE 802.15.4 wireless radio. The RF-based communications channel between the display system and the 3D stereoscopic glasses allows a user to move his head into positions and to locations that would normally cause loss of reception of 3D glasses based upon infrared transmissions. Further, the shutter control timer and multi-layer feedback loop improve the three dimensional perception by eliminating jitter and noise in the system (3D source) synchronization signal. In various embodiments, the shutter control timer and multi-layer feedback loop of the 3D glasses can quickly synchronize with the system synchronization signal and can maintain the synchronization of the display and shutter action of the glasses although actual synchronization may be temporarily lost. Such embodiments improve the user&#39;s 3D experience. 
         [0026]    In various embodiments, such shutter control timer includes hardware based upon a microprocessor in the LC shutter glasses. In such embodiments, the microprocessor receives the timing information (e.g., system synchronization signals) received from the 3D system synchronization source via wireless signal and the feedback loop synchronizes the localized control timer within the 3D glasses with the system synchronization signal. Based upon the localized clock, in the short term absence of input synchronization information or in short periods of high signal jitter, the timer control system in the 3D glasses does not adjust the frequency of phase of the LCD switching, and relies upon its own internal clock. Accordingly, in such conditions, the synchronization between display and shutter action is maintained. 
         [0027]    According to other aspects, a method is provided for synchronization between the video transmitter and the shutter glasses. Synchronization is provided via a protocol that provides timing information such as a beacon offset or any series of packets that is used as the energy to excite a clock. A precision timing protocol may be utilized to provide synchronization between the transmitter and the receiver. 
         [0028]    The above-described subject matter may also be implemented as a computer-controlled apparatus, a computer process, a computing system, or as an article of manufacture such as a pair of electronic glasses, an earbud or headset, a computer program product or a computer-readable medium. These and various other features will be apparent from a reading of the following Detailed Description and a review of the associated drawings. In various embodiments, the shutter glasses and the transmission device may include executable computer programs resident in a memory that instructs a respective processor to perform specific functions or operations, such as to transmit data, to determine a latency, or the like. 
         [0029]    This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
         [0030]    According to one aspect of the invention, a method for operating a pair of shutter glasses including a right LCD shutter and a left LCD shutter is disclosed. One process includes receiving synchronization data via radio frequency transmissions from a radio frequency transmitter, and determining shutter timings for the right LCD shutter and the left LCD shutter in response to the synchronization data. A technique may include applying the shutter timings to the right LCD shutter and the left LCD shutter to enable the viewer to view right-eye images via the right LCD shutter and left-eye images via the left LCD shutter. 
         [0031]    According to another aspect of the invention, a method for transmitting stereoscopic display information includes: converting one or more video synchronization signals into wireless radio signals; and decoding the wireless radio signal in a pair of shutter glasses or other device; wherein the wireless radio is the IEEE Standard 802.11, WiFi, or components thereof. 
         [0032]    According to another aspect of the invention, a method for transmitting stereoscopic display information includes: a pair of shutter glasses or other consumer electronics device which contains a localized clock such that the device remains synchronous to the video display system even when the connection to the source transmitting the synchronization information is interrupted or is not present. In some aspects, the synchronization information between the display system and the glasses or other device are determined by a precision timing protocol in which bidirectional communication of timing information occurs. 
         [0033]    According to another aspect of the invention, a method for transmitting stereoscopic display information includes: a pair of shutter glasses or other consumer electronics device which receives synchronous information from the video display system, and a means and method of storing the delay and synchronization information in the transmitter or the video source generating computer, home theater system, or device. In some aspects, the delay and synchronization information are stored and then transmitted to multiple devices to allow multiple users to simultaneously use the same system. 
         [0034]    According to another aspect of the invention, a method for transmitting stereoscopic display information includes: a pair of shutter glasses or other consumer electronics device which receives synchronous information from the video display system, and a means of determining the delay and synchronization information through information contained in the display and transmitter from the display via the video signal cable. 
         [0035]    Another aspect of the invention is a method for transmitting stereoscopic display information, the method including: a transmitter of synchronization information and a pair of shutter glasses or other consumer electronics device which is capable of receiving synchronization information from infrared, visible light and radio sources. In various aspects, the shutter glasses or other receiving device can incorporate a computer program which allows the device to automatically determine which source or sources of synchronization information are available and automatically use the best source or sources. 
         [0036]    According to another aspect of the invention, shutter glasses include various radio frequency receiving capabilities along with a feedback mechanism and a localized clock. The introduction of a synchronized timer in the shutter glasses improves the synchronization between the alternating source images and the alternating action of shutter glasses. It is with respect to these considerations that a LC shutter control timer and multi-layer timer feedback loop are provided for improved perception of stereoscopic 3D viewing. 
         [0037]    According to another aspect of the invention, a method of combining ordinary or automatically darkening sunglasses with a wireless headset, Bluetooth headset, or stereo Bluetooth headset is disclosed. 
         [0038]    According to another aspect of the invention, a three-dimensional viewing device for providing images to a user is disclosed. One apparatus includes a receiver configured to receive source 3D synchronization signals from a transmitting device, wherein the source 3D synchronization signals comprise a source frequency and a source phase. A device may include a plurality of LCD shutters including a right LCD shutter and a left LCD shutter, wherein the right LCD shutter and the left LCD shutter are configured to alternately enter a translucent state in response to local 3D synchronization signals. A system may include a localized timing source coupled to the receiver and to the plurality of LCD shutters, wherein the localized timing source is configured to generate the local 3D synchronization signals in response to the source 3D synchronization signals, and an adjustment portion coupled to the localized timing source and to the receiver, wherein the adjustment circuit is configured to adjust parameters of the local 3D synchronization signals in response to parameters of the source 3D synchronization signals. 
         [0039]    According to yet another embodiment, a method for operating a three-dimensional viewing device including a right LCD shutter and a left LCD shutter is disclosed. One method includes receiving source 3D synchronization signals from a transmitting device, wherein the source 3D synchronization signals comprise a source frequency and a source phase, and generating local 3D synchronization signals in response to the source 3D synchronization signals. A process may include adjusting parameters of the local 3D synchronization signals in response to parameters of the source 3D synchronization signals, and driving the right LCD shutter and the left LCD shutter with the local 3D synchronization signals, wherein the right LCD shutter and the left LCD shutter are configured to alternately enter a translucent state in response to local 3D synchronization signals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0040]    In order to more fully understand the present invention, reference is made to the accompanying drawings. Understanding that these drawings are not to be considered limitations in the scope of the invention, the presently described embodiments and the presently understood best mode of the invention are described with additional detail through use of the accompanying drawings in which: 
           [0041]      FIGS. 1A-C  are block diagrams illustrating aspects of the prior art; 
           [0042]      FIGS. 2A-D  include block diagrams of various embodiments of the present invention illustrating the process of elements of a system in which stereoscopic glasses are synchronized with the display device by incorporation of a wireless radio into the system; 
           [0043]      FIG. 3  illustrates a block diagram of a process according to various embodiments of the present invention; 
           [0044]      FIG. 4  is a timing diagram of various embodiments of the present invention illustrating a method of sending image information to a display in which the frames which compose the image are sent sequentially; 
           [0045]      FIG. 5  illustrates various embodiments incorporated into a mobile phone&#39;s hardware, firmware, and software and into a pair of stereoscopic shutter glasses; 
           [0046]      FIG. 6  illustrates various embodiments incorporated into a mobile phone. Some of the methods are incorporated into a pair of stereoscopic shutter glasses, and other methods are incorporated into a cradle or other device that attaches to the mobile phone; 
           [0047]      FIG. 7  illustrates various embodiments incorporated into a pair of stereoscopic shutter glasses combined with a mobile phone headset; 
           [0048]      FIG. 8  illustrates various embodiments of the present invention; 
           [0049]      FIG. 9  illustrates various embodiments of the present invention; 
           [0050]      FIG. 10  illustrates a block diagram according to various embodiments of the present invention; and 
           [0051]      FIG. 11  illustrates a block diagram according to various embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0052]      FIGS. 2A-D  illustrate various embodiments of the present invention. In particular,  FIGS. 2A-D  illustrate various arrangements of embodiments of the present invention. 
         [0053]      FIG. 2A  includes a 3D source  34  of image data, a transmission device  37 , a display  43 , and shutter glasses  42 . In various embodiments, 3D source  34  may be a computer, a Blu-ray or DVD player, a gaming console, a portable media player, set-top-box, home theater system, preamplifier, a graphics card of a computer, a cable box, or the like, and 3D display  43  may be any 3D display device such as an LCD/Plasma/OLED display, a DLP display, a projection display, or the like. In various embodiments, transmission device  37  and shutter glasses  42  may be embodied by a product developed by the assignee of the current patent application, Bit Cauldron Corporation of Gainesville, Fla. In some embodiments, shutter glasses  42  may be implemented with mechanical shutters or LCD shutters. For example, LCD shutters based upon twisted nemic, super-twisted nemic, or pi-cell technology may be used. 
         [0054]    In operation, 3D source  34  sends 3D display signals to display  43  through a video cable  35 , typically through a standards-based interface such as VGA, DVI, HDMI, Display Port (DP), or the like. Such 3D display signals are often configured as one or more interleaved full right-eye images then full left-eye images (e.g., field sequential); double wide (e.g., side by side) or double height (e.g., stacked) images including both left and right images; images interleaved with right-eye images and left-eye images on a pixel by pixel basis; or the like. As shown in  FIG. 2A , a transmission device  37 , e.g., a radio transmitter may be inserted between the 3D source  34  or other video source and 3D display  43 . 
         [0055]    In various embodiments, transmission device  37  determines 3D timing information by decoding the 3D display signals as they pass through to display  43  on signal line or cable  44 . In  FIG. 2A , transmission device  37  includes a transmitter based upon radio frequency (RF) signals. The RF signals may use or may be combined with any conventional transmission protocol such as IEEE Standard 802.15.1 (e.g., Bluetooth), IEEE 802.11 (e.g., Wi-Fi), IEEE Standard 802.15.4 (e.g., ZigBee Alliance radio), or the like. In various embodiments, synchronization signals  40  are then transmitted via antenna  39 . 
         [0056]    In various embodiments, transmission device  37  may be a stand-alone device, e.g. a dongle, a USB “key,” or the like and transmission device  37  may be powered by power source  36  and  38 , self-powered, powered from 3D data source, USB powered, or the like. In other embodiments, transmission device  37  may be incorporated into another device, such as 3D source  34 , 3D display  43 , a pre-amplifier, or the like. 
         [0057]      FIG. 2B  illustrates additional embodiments of the present invention. In particular,  FIG. 2B  includes a source of 3D images  100 , a transmission device  110 , and a 3D display  120 . As illustrated, 3D image source  100  provides 3D images (e.g., double-wide or double-height images including both right and left images) to 3D display  120  via a signal line  130  such as a VGA, DVI, Display Port (DP), cable, or the like. Additionally 3D image source  100  provides a synchronization signal along signal line  140  to transmission device  110 . In various embodiments, 3D image source  100  includes an industry standard interface such as a VESA miniDIN-3 connector, VESA 1997.11, USB connector, or the like, to which transmission device  110  may be coupled. 
         [0058]      FIG. 2C  illustrates additional embodiments of the present invention. In particular,  FIG. 2C  includes a source of 3D images  160 , a transmission device  170 , and a 3D display  180 . As illustrated, 3D image source  160  provides 3D images (e.g. double-wide or double-height images including both right and left images) to 3D display  180  via a signal line  190  such as a VGA, DVI, HDMI cable, Display Port (DP), or the like. In turn, 3D display  180  provides a synchronization signal along signal line  200  to transmission device  170 . In various embodiments, 3D display  180  includes an industry standard interface such as a VESA miniDIN-3 connector, USB connector, or the like, to which transmission device  170  may be coupled. 
         [0059]      FIG. 2D  illustrates other additional embodiments of the present invention. In particular,  FIG. 2D  includes a source of 3D images  220 , a transmission device  230 , and a 3D display  240 . As illustrated, 3D image source  220  provides 3D images (e.g., double-wide or double-height images including both right and left images) to 3D display  240  via a signal line  250  such as a VGA, DVI, HDMI cable, Display Port (DP), or the like. In these embodiments, transmission device  230  may be disposed within 3D display  240 . For example, transmission device  230  may be installed within the manufacturing facility of 3D display  240 , or the like. In such embodiments, 2D display  240  may also power transmission device  230 . Similar to the embodiments described above, 3D display  240  provides a (derived) synchronization signal along signal line  260  to transmission device  230 . 
         [0060]    In various embodiments described herein, shutter glasses  42  include a radio receiver  41  that receives the synchronization signals  40 . In response to synchronization signals  40 , shutter glasses  42  alternately change the properties of one lens from translucent to opaque (e.g., dark) to translucent and of the other lens from opaque to translucent (e.g., clear) to opaque. Because the shutters of shutter glasses  42  operate under the direction of synchronization signals  40 , a user/viewer views 3D display images  45  from display  43  at the proper timing. More particularly, the user&#39;s right eye is then exposed to a right-eye image from 3D display images  45 , and then the user&#39;s left eye is then exposed to a left-eye image from 3D display images  45 , etc. 
         [0061]    The inventors of the present invention recognize that transmission device  37  based upon a radio frequency transmitter has several advantages over an infrared transmitter. One advantage recognized is that radio signals can be received in many situations where an infrared signal would be blocked. For example, this allows the user of a pair of 3D shutter glasses or the like to move their head much farther away from the 3D display or transmission device than if IR were used, and allows the user to move throughout a room with a larger range of motion while maintaining synchronization with the 3D display. As another example, RF transmitters allow other people or objects to pass in front of the user/viewer without interrupting the signal. 
         [0062]    Another advantage goes beyond the improved range and reliability of radio technology for synchronization purposes. For example, the inventors believe that the avoidance of infrared is itself a benefit, as infrared signals can interfere with remote controls, such as those popular in households and home theater systems. Additionally, another benefit includes that IR receivers are often interfered with and are confused by IR remote controls, natural and artificial light sources, and video displays themselves. 
         [0063]    In various embodiments of the present invention, shutter glasses  42  may include its own localized clock. Benefits to such a configuration include that it allows shutter glasses  42  to remain approximately synchronized to display  43  even though the connection to transmission device  37  is interrupted and/or synchronization signals  40  are not received. 
         [0064]    In various embodiments, a precision timing protocol can be used so that the clock that is local to shutter glasses  42  is synchronized with a clock within transmission device  37  and/or the 3D display signals. A precision timing protocol may include the transmission of data packets with a time stamp time associated with the 3D display signals to shutter glasses  42 . In other embodiments, the protocol may include transmission of a data packet with a time stamp associated with shutter glasses  42  to transmission device  37 . In operation, shutter glasses  42  receive the time stamp from the 3D data source, compare the received time stamp to its local clock and returns a data packet with its local time stamp. Using this information, transmission device  37  can determine a round-trip time for data between transmission device  37  and shutter glasses  42 . In some embodiments of the present invention, the round-trip time offset is evenly divided between transmission device  37  and shutter glasses  42 . In other embodiments, if one or both devices are capable of determining a difference in speed or lag between the two transmissions, then a more precise determination of the relative values of both clocks (offsets) can be determined. 
         [0065]    As a result, in various embodiments, more precise synchronization between the two clocks can be established. 
         [0066]    In various embodiments of the present invention, by repeating this process periodically, the difference in rate (e.g., frequency) between the two clocks (transmission device  37  or 3D source  34  and shutter glasses  42 ) can be more precisely determined In some embodiments if there is a low degree of consistency in the latencies, the period of time between the determination of a latency process may be made small, e.g., once a minute; and if there is a higher degree of consistency in the latencies, the period of time between the determination of a latency process may be increased, e.g., once every ten minutes. 
         [0067]    Embodiments of the present invention enable the use of multiple pairs of shutter glasses  42 . In such embodiments, a single pair of shutter glasses  42  may be used to determine delay and jitter as was discussed above. Next, a simpler protocol, such as a unidirectional or broadcast protocol, may be used by transmission device  37  to communicate this synchronization information to the remaining pairs of shutter glasses. In various embodiments, the delay and jitter information can be stored in transmission device  37 , in 3D source  34 , or other consumer electronics device generating the 3D data, either in a volatile or non-volatile manner. 
         [0068]    In other embodiments of the present invention other methods can be used to determine the synchronization and delay information. In various examples, this data may be determined using bidirectional communications on cable  44 , such as the DisplayPort protocol, or the like, as illustrated in  FIG. 2C . Communications protocols such as display data channel (DDC and DDC2) protocols, PanelLink serial protocol or a similar protocol allows the display to communicate information back to the computer, home theater system, video source, or the like. In various embodiments, this serial protocol can be enhanced to provide the appropriate latency and synchronization characteristics of 3D display  43  back to 3D source  34  and/or transmission device  37 . In other embodiments, these protocols can be used to determine the manufacturer, vendor, or other identifying information for 3D display  34 , and a table of pre-determined synchronization information can be retrieved, either locally, across a local area network, across a network, or the like. This information may include an appropriate delay and synchronization information for respective 3D displays. 
         [0069]      FIG. 3  illustrates a block diagram of a process according to various embodiments of the present invention. More specifically,  FIG. 3  illustrates a process for synchronizing shutter glasses to a source of 3D images. 
         [0070]    Initially, a 3D data source provides 3D images, step L. In various embodiments, the 3D images may be provided in any number of specific formats, such as right and left images: sequentially transmitted, packed vertically or horizontally into a single image and transmitted, combined on a pixel by pixel basis into a single image and transmitted, or the like. In other embodiments, as illustrated in  FIG. 2B , 3D data source may provide specific timing data. 
         [0071]    Next, in response to the data from 3D data source, synchronization data, such as an identifier of a timing clock resident on 3D data source is determined, step  310 . In various embodiments, this may include a packet of data including a source time stamp, or the like. The synchronization data may then be transmitted through radio frequency transmissions to a first pair of shutter glasses, step  320 . 
         [0072]    In various embodiments, the shutter glasses receive the source time stamp and synchronize the operation of the right/left shutters to the synchronization data, step  330 . The synchronization data can then be maintained within the shutter glasses by an internal clock within such glasses, step  340 . As synchronization data is received, the internal clock can be resynchronized. Such embodiments are believed to be advantageous as the glasses need not wait for synchronization data from the 3D data source to be able to switch. Accordingly, synchronization data from the transmission device may be dropped or lost while the shutter glasses continue to operate properly. When synchronization data is reestablished, the synchronization described above may be performed. 
         [0073]    In various embodiments of the present invention, RF communications using the ZigBee radio (IEEE 802.15.4 standard) occur at 2.4 GHz, the same band as most Wi-Fi transmissions. In the case of interference with Wi-Fi transmissions, embodiments of the present shutter glasses are designed to inhibit communications, and defer to such Wi-Fi signals. As discussed above, in some embodiment, the shutter glasses will continue to operate autonomously, until the interference stops and new synchronization data is received from the transmission server. 
         [0074]    In some embodiments of the present invention, the shutter glasses may transmit data back to the RF transmission device. More specifically, the shutter glasses may transmit the received source time stamp and/or the glasses time stamp back to the transmission device via the same RF communications channel, or the like, step  350 . 
         [0075]    In  FIG. 3 , in response to the received source time stamp and/or the glasses time stamp, and the source time stamp when these data are received, the transmission device may determine adjustments to subsequent synchronization data that will be sent to the shutter glasses, step  360 . As an example, the transmission device may determine that it should output synchronization data to the shutter glasses, even before the synchronization data is determined or received from the 3D data source. As a numeric example, if it is determined that the shutter glasses lag the 3D data source by 100 microseconds, the shutter glasses may trigger their shutters 100 microseconds before the expected arrival of a synchronization pulse. 
         [0076]    In various embodiments of the present invention, this adjustment to synchronization data may be used to drive 3D glasses of other viewers of the 3D image. In other embodiments of the present invention, 3D glasses of other viewers in the room may also have synchronization data adjusted using the process described above. In such embodiments, the transmission device may output the synchronization data at different times for different 3D glasses. 
         [0077]    In other embodiments, other adjustments may be performed by the shutter glasses. For example, based upon received time stamps and the shutter glasses&#39; own internal clocks, the shutter glasses may verify that they are in sync. If not, the shutter glasses may adjust the frequency of its own internal clocks until they are kept in a higher amount of synchronization. 
         [0078]    As seen in  FIG. 3 , the process may be repeated. In various embodiments, the synchronization process may be performed periodically, with the period dependent upon how well the 3D data source and the shutter clock stays in synchronization—if highly synchronized, the synchronization process may be performed at longer time intervals (e.g., 2 minutes) than if these devices continually have synchronization problems (e.g., every 10 seconds). Further detail regarding the above synchronization process may be found in the provisional application referenced above. 
         [0079]    Various embodiments of the present invention may include shutter glasses or other devices that include multiple physical methods for receiving synchronization information. For example, some embodiments may contain both an infrared and radio receiver; an infrared and visible light receiver; a radio or visible light receiver; a combination of infrared, visible light and radio receivers; or the like. In such embodiments, the shutter glasses or other receiving device may include an executable computer program that instructs a processor to automatically determine which communications channel or channels are available, and automatically use the communications channel having the strongest signal, lowest number of dropped data packets, or the like. 
         [0080]    In various embodiments, the combination of a visible light receiver (e.g., IR) with another synchronization transmission technology (e.g., RF) may be advantageous. More specifically, the information transmitted via visible light and the synchronization information transmitted via another transmission technology may be combined within shutter glasses  42  to deduce unknown elements of the delay in 3D display  43  and other synchronization information. In various embodiments, the data from the different communication channels are compared to more precisely synchronize 3D display  43  and shutter glasses  42 . As merely an example, the two communications channels can be used to verify that a left image displayed on 3D display  43  is going to the left eye and the right image displayed on 3D display  43  is going to the right eye. In such an example, this would prevent the error of a reversal of synchronization information somewhere in the system that results in sending the left image to the right eye and vice versa. 
         [0081]    In various embodiments of the present invention, shutter glasses  42  may be used to provide a variety of new functions.  FIG. 4  illustrates typical video output timing where frame one  26 , frame two  28 , frame three  30  and frame four  32  are output sequentially. In some embodiments, left images (frames) and right images (frames) are alternately output. For example, frame one  26  is left, frame two  28  is right, frame three  30  is left and frame four  32  is right, creating the sequence L, R, L, R images to the user. 
         [0082]    Various embodiments of the present invention may be applied to 3D displays having display rates on the order of 120 Hz and higher. In embodiments where the refresh rate is 120 Hz, right and left images will be displayed and refreshed at 60 Hz. Accordingly, the viewer should not be able to detect significant flickering; however, the viewer may detect a darkening of the images. As refresh rates for future televisions, projectors or the like, are increasing, the inventors have determined that the higher refresh rate may enable new features, as described below. 
         [0083]    In various embodiments, depending upon the output frame rate of the 3D display, more than one left image and right image may be output. For example, in various embodiments, multiple viewers may view a 3D display, and different viewers may see different 3D images. For example, a two viewer sequence of output images may be user 1 left, user 1 right, user 2 left, user 2 right, etc. This could be represented as: L1, R1, L2, R2. In such examples, shutter glasses of a first viewer will allow the first viewer to see images L1 and R1 and shutter glasses of a second viewer will allow the second viewer to see images L2 and R2. In other examples, other sequences are contemplated, such as L1, L2, R1, R2, and the like. With respect to refresh rate, for a 3D display having a 240 Hz refresh rate, a viewer will see the respective right and left images at a refresh rate of 60 Hz. As noted above, this frequency should be above the typical sensitivity of the eye; however, viewers may detect a darker image. Such artifacts may be mitigated by increasing the brightness of the images. 
         [0084]    Other embodiments may be extended to additional (e.g., three or more viewers). Applications of such embodiments may include for computer or console gaming, or the like. As an example, two or more viewers may initially see the same 3D image, and subsequently one or more viewers “break off” to view a different 3D image. For example, three people could be playing a multiplayer game in which all three are traveling together and see the same 3D images. Next, one player then breaks away from the other players. Using the additional communications protocols disclosed in various embodiments of the present invention, the player&#39;s glasses can be reprogrammed to allow the third person to see a different 3D image. Subsequently, the third person may return to the group, and then see the same 3D image. In such an example, a sequence of images output by the 3D display could begin with L0-R0-L0-R0, where 0 indicates everyone in the party. Next, when the third person leaves the party, the 3D display could switch and output images in a sequence such as L1&amp;2, R1&amp;2, L3, R3; L1&amp;2, L3, R1&amp;2, R3; or the like. When the third person returns to the party, the sequence may revert to L0, R0, L0, R0. In various embodiments, switching back and forth may occur with little, if any, visible interruption in the 3D images viewed by the viewer. In various embodiments, the inventors recognize that the brightness of each frame may have to be adjusted to correct for the changes in overall viewing time. 
         [0085]    In other embodiments, other sequences of images enable still other types of functionality. For example, one sequence of frames can be sent such that viewers wearing 3D glasses see a stereo display and viewers without glasses see only one side of the image (e.g., left or right). In such an example, a three frame sequence may include: Left, Right, Left-minus-Right. In response, a user using embodiments of the present invention may see a stereoscopic image by viewing the left image in their left eye and the right image in their right eye. That user would be prevented from viewing the Left minus Right image. A viewer without the glasses, would see in succession: L, R, (L−R)=2L, or only the left image with both eyes. In other embodiments, separate anti-left, anti-right images or both may also be sent. With such embodiments, theatergoers can decide whether they care to watch the same movie or feature with or without 3D glasses; game players can play in 3D while viewers watch the same display in 2D. 
         [0086]    In still other embodiments, users not utilizing embodiments of the 3D glasses may view other arbitrary images. As an example, a sequence may be: Left, Right, and Arbitrary-minus-Left-minus-Right=Arbitrary image. In operation, the viewer with 3D glasses may see the left image in the left eye and the right image in the right eye, and may not see the Arbitrary image. Further, the viewer without 3D glasses would see the arbitrary image, in succession: L, R, (A−L−R)=A, that may be a non-stereo version of the same program, a blank or solid color screen, or a completely different piece of content such as an advertisement, a copyright warning, or the like. 
         [0087]      FIG. 5  illustrates additional embodiments of the present invention. More specifically,  FIG. 5  illustrates a general purpose consumer device (e.g., mobile phone, personal media player, laptop, or the like) capable of 3D image output. In such embodiments, the synchronization information to the shutter glasses may be provided by/with the consumer device including embodiments of the RF transmitter described above, or unused or available transmitters available in the consumer device. Various examples may use infrared, WiFi, Bluetooth, or the like, to provide synchronization signals to shutter glasses according to embodiments of the present invention. 
         [0088]      FIG. 6  illustrates additional embodiments of the present invention wherein existing consumer devices (e.g., mobile phone) may be augmented to better support stereoscopic 3D viewing. In various embodiments, a cradle or dongle which attaches to the mobile device or holds the mobile device may be used. In such examples, the cradle or dongle may incorporate a projection system such that the image may be projected at a larger size than the screen on the mobile device. The cradle or dongle or consumer device may also provide the synchronization signals to the shutter glasses. For example, the cradle or dongle may include a ZigBee radio-type transmitter (IEEE 802.15.4) that transmits the synchronization data to the shutter glasses, or the like. 
         [0089]    In other embodiments of the present invention, stereoscopic shutter glasses that are to be used with the consumer device described above can be used for other purposes. For example, if such glasses incorporate a visible light sensor, they can be worn as ordinary sunglasses but make improved automatic decisions about the appropriate level of perceived darkening. This information can be based on computer algorithms, information about the user and the environment that is stored on a mobile device, information retrieved from a computer network via the mobile device, and the like. 
         [0090]      FIG. 7  illustrates yet another embodiment of the present invention. In such embodiments, a user of the consumer device may desire to perform multiple functions at the same time, such as: talk on a Bluetooth headset, view stereoscopic 3D content, and wear sunglasses. Embodiments illustrated in  FIG. 7  may include a pair of shutter glasses  57  combined with a pair of sunglasses and a Bluetooth or stereo mobile Bluetooth headset with a left earpiece  58  and a right earpiece  55 , or the like. 
         [0091]      FIG. 8  illustrates various embodiments of the present invention. In particular,  FIG. 8  illustrates a block diagram of various embodiments of a dongle  400  providing RF transmissions, as described above. 
         [0092]    In  FIG. 8 , a physical interface  410  is illustrated. In various embodiments, physical interface  410  may be a DVI port, HDMI port, Display Port (DP), USB, VESA 1997.11, or the like, for coupling to a source of 3D data (e.g., computer, DVD/BluRay player, HD display, monitor, etc.). In embodiments illustrated in  FIG. 2A  or  2 C for example, the 3D data may include 3D image data, whereas in the embodiments illustrated in  FIG. 2B , the 3D data may include 3D timing data. In various embodiments, an interface chip or block  420  may provide the electronic interface to physical interface  410 . Next, a processing device such as a CPLD (complex programmable logic device)  430  may be used to decode 3D synchronization data from 3D image data or 3D timing data. 
         [0093]    In various embodiments of the present invention, 3D synchronization data  440  is then provided to an RF interface device  450  that references a clock  440 . In some embodiments, RF interface device  450  is a TI CC2530 System on a Chip, that includes a 8051 MCU (processor), RAM, Flash memory, and a IEEE 802.14.4 ZigBee RF transceiver. The flash memory is configured to store executable computer code or instruction that directs the processor to perform various functions, as described herein. In various examples, the flash memory includes computer code that directs the processor to transmit the 3D synchronization data to the 3D glasses, to receive timing data back from the 3D glasses, to determine a round-trip communication latency, to adjust 3D synchronization data in response to the round-trip communication latency, and the like, as described above. 
         [0094]    In some embodiments of the present invention, dongle  400  may include an output port or  460  driven by an output interface  470 . In various embodiments, as illustrated in  FIG. 2A , the output port may be a DVI port, HDMI port, Display Port (DP), or the like providing 3D image data to a 3D display (e.g. an display, projector, etc.). 
         [0095]      FIG. 9  illustrates various embodiments of the present invention. In particular,  FIG. 9  illustrates a block diagram of a pair of shutter glasses  500  according to various embodiments of the present invention. Shutter glasses  500  is illustrated to include an RF interface device  510  that references a clock  540  and a pair of electronically controlled LCD shutter elements  520  and  530 . 
         [0096]    In various embodiments of the present invention, 3D synchronization data  550 , typically radio frequency signals, is received in RF interface device  510 . In various embodiments, RF interface device  510  is also a TI CC2530 System on a Chip, that includes a 8051 MCU (processor), RAM, Flash memory, and a IEEE 802.14.4 ZigBee RF transceiver. The flash memory is configured to store executable computer code or instructions that direct the processor to perform various functions, as described herein. In various examples, the flash memory includes computer code that directs the processor to receive the 3D synchronization data, to change the states of/drive shutter elements  520  and  530  at the appropriate timing (e.g., L1 and R1 in the sequence L1, L2, R1, R2), to send clock or timing data back to a transmission device via RF communications, and the like. 
         [0097]      FIG. 10  illustrates a block diagram according to various embodiments of the present invention. More specifically, a functional block diagram for a pair of shutter glasses  641  according to various embodiments is illustrated. 
         [0098]    As referred to in  FIG. 1B , a computer system  363  uses a graphics subsystem clock  637  to determine properly synchronized shutter switching or timing data signals  638 . Because of delays in the operating system communicating with the hardware, noise in the system, interferences in the communications to shutter glasses  641 , etc., a cumulative delay  640  is imparted upon data signals  638 . Accordingly, as illustrated, input data signals  642  are received by shutter glasses  641 . As illustrated in  FIG. 10 , LCD shutters  650  are driven using recovered timing data  647  derived from timing data signals  638 . 
         [0099]    In various embodiments of the present invention, shutter glasses  641  include a local clock source  646  in a receiving portion  648 , that enables LCD shutters  650  to be synchronous (i.e., switch at the proper time) with the 3D display. Accordingly, when input data signals  642  are absent or are interrupted, the switching of LCD shutters  650  is maintained at the proper timing. In various embodiments, a precision timing protocol can be implemented in a processor, for example in RF interface device  510  ( FIG. 9 ), to enable tracking of local clock source  646  to timing data signals  638 . In various embodiments, the synchronization can be facilitated through the use of feedback timer control. 
         [0100]    As mentioned above, in various embodiments LCD shutters  650  are kept continuously alternately switching by local clock source  646 . In various embodiments, the frequency speed and phase/offset of local clock  646  are adjusted based on the arrival of input data signals  642 . 
         [0101]    In various embodiments of the present invention, a feedback mechanism may include a comparison ( 644 ) between the expected time of arrival of a sequence signal, (e.g., recovered timing data  647 ) to the actual arrival of a sequence signal (e.g., input data signals  642 ). In one example, if a sequence signal is not received within a time relatively close to the expected time of arrival of a sequence signal, the system can deduce that the sequence message has been lost and can continue to operate at the current frequency (provided by local clock source  646 ) until the reception of signal information (e.g., input data signals  642 ) is regained. Such a condition may occur if the shutter glasses  641  are moved beyond the range of input data signals  642 , if cumulative delay  640  is large, or the like. 
         [0102]    In various embodiments, the difference  644  between the expected signal time  647  and the actual arrival of the signal  642  is used as the input to a controller  651  such as a linear Proportional, Integral, Derivative (PID) controller, or the like. In other embodiments more complicated controller algorithms can be used, such as a Linear Quadratic Regulator. Further, a Linear Quadratic Regulator can be combined with a feedback filter  649  such as a Kalman filter to make other linear, optimal and suboptimal filters, such as an H-2 or H-infinity controller. 
         [0103]    In  FIG. 10 , comparator  643  and forward transfer function  651  can also perform nonlinear or statistical checks to differentiate between input data signals  642  which are slightly different than expected ( 646 ) and indicate that a correction of clock  646  may be appropriate. In various embodiments, a nonlinear test such as an outlier test, statistical test, comparison to a maximum expected error, or if statement is used to determine if a received sequence signal is absent, disturbed, delayed, or otherwise incorrect and the information from that incorrect signal is then ignored and not used to make any change to the local clock ( 646 ). A multitude of signals repeatedly determined to be incorrect are used to determine that the local clock  646  is no longer synchronous with the source clock  638 , possible because of a change in operation of the source clock, and a resynchronization process should be undertaken. 
         [0104]    In one embodiment, separate feedback loops are active when local clock  646  is not believed to be synchronous to the source clock and when the local clock  646  is believed to be synchronous to the source clock. When the clocks are not synchronous, larger timing corrections  645  are provided to receiving portion  648  to broaden the hunt for synchronization with negligible overshoot. In cases when the clocks are synchronous, smaller timing corrections  645  may be applied. More specifically, when local clock  646  is believed to be out of sync with source clock  638 , a different set of correction factors in  645  can be used compared to when the clocks are believed to be synchronous. As a result, more aggressive gain values with less accumulated error are used in  645  so that synchronization can be reacquired quickly. After the believed reacquisition of synchronization, different gain values, particularly those that weight the accumulation of error more than any one particular error are provided  645  to fine tune synchronization of the local clock  646  to source clock  638 . In other embodiments, when local clock  646  is not believed to be synchronous, in a first phase, the frequency of source clock  638  is determined; next, when local clock  646  is believed to be synchronous, in a second phase, the phase of source clock  638  is determined 
         [0105]      FIG. 11  illustrates a block diagram according to various embodiments of the present invention. More specifically, a functional block diagram for a pair of shutter glasses  641  from  FIG. 10  according to various embodiments is illustrated. 
         [0106]    As illustrated in  FIG. 11 , a smart transmitter  654  may be added to facilitate the synchronization action described. In various embodiments, smart transmitter  654  determines the frequency of the source clock  637  and sends the frequency information and other information to the receiver, as illustrated. In various embodiments, smart transmitter  654  contains its own local clock, feedback mechanism, and statistical tests similar to those in 3D glasses  641 . In operation, disturbances  652  from the computer hardware, operating system, graphics subsystem or other sources are corrected or compensated prior to transmission of the sequence information to 3D glasses  641 . In various embodiments, a smart transmitter may be embodied as a USB device that includes a transceiver for communicating with 3D glasses  641  using any one of the above-mentioned radio-frequency communications channels/protocols. 
         [0107]    As shown, additional disturbances  653  may still be introduced into input data signal  642 . These disturbances  653  are then corrected in the manner described above in  FIG. 10 . It is contemplated that disturbances  653  may have smaller delay and jitter compared to cumulative delay  640  in  FIG. 10 ; accordingly, 3D glasses  641  may have a lower range of jitter to compensate for. 
         [0108]    In various embodiments, smart transmitter  654  may include additional information which 3D glasses  641  may use to improve the quality of the synchronization of local clock  648  with source clock  637 . For example, smart transmitter  654  may determine the intended frequency of source clock  637  from an application programming interface or other mechanism on computer or system  636  and transmit that information to 3D glasses  641 . The transmitter can also use local or computer memory to store previous clock correction information provided by a working or previously working pair of glasses and propagate that information to new glasses or glasses which are repeating the synchronization process. 
         [0109]    In various embodiments, smart transmitter  654  may also include information in each message to allow 3D glasses  641  to determine when a left or right signal has been duplicated or is missing (illustrated in  FIG. 1C ). In such embodiments, smart transmitter  654  may add a pattern that deterministically changes with every message, such as a number. That number may be termed a sequence number and may be incremented for each message. In operation, the processor in 3D glasses  641  may check the pattern or sequence message to determine when an expectedly long delay has occurred due to loss of one or more messages, as opposed to clock synchronization error. Additionally, the processor in 3D glasses  641  may decide not to make any clock corrections based on this long delay. Additionally, the processor may use the sequence number to determine if message duplication has occurred. 
         [0110]    In other embodiments, smart transmitter  654  may also add a device identifier so that 3D glasses  641  (the receiver) do not attempt to synchronize with more than one transmitter. This may be valuable in situations such as a trade show, or the like where multiple sources of 3D image data are being simultaneously displayed. 
         [0111]    In other embodiments of the present invention, 3D glasses may be configured to transmit timing data back to the 3D source. The ability for bidirectional communications also allows a more precise timing protocol to be implemented between the 3D source and 3D glasses. As an example, the transmitter (3D source) and the receiver (3D glasses) each run local clocks that operate at a multiple of the frequency (e.g., 20 KHz) of the sequence information (e.g., 120 Hz) and are divided down to a lower speed which matches the sequence information. Then, the transmitter and the receiver exchange a series of messages at the higher frequency containing timestamps which indicate the value of their local clocks. By exchanging a series of these messages the transmitter and receiver can determine the difference in speed of their local clocks and compensate for these differences. The result is that synchronization is achieved with a much higher precision than the period of the sequence information. 
         [0112]    In various embodiments when there are multiple 3D displays and 3D transmitters present, a user using a pair of 3D glasses that perceives stereoscopic information from one 3D display should not also perceive stereoscopic information from another 3D display at the same time, unless each 3D display is synchronized in time and uses the same left/right sequence. For example, all the 3D displays must start the left frame at the same time and the right frame at the same time. In examples such as an event with multiple monitors, synchronization between these 3D displays may be performed by coordination of the 3D source devices or a single 3D source device. 
         [0113]    In some embodiments, multiple 3D displays and 3D graphics subsystems may act independently in the same field of view, such as in a trade show or a TV store. In such a case, a link which may provide the multidirectional information between multiple 3D display systems may be the bidirectional smart transmitter  654  discussed above. In operation, if one smart transmitter detects the presence of another smart transmitter, the one smart transmitter may communicate with the 3D graphics subsystem to try to adjust the 3D graphics subsystem such that all 3D displays and systems are transmitting their left and right frames synchronously. 
         [0114]    In light of the above disclosure, one of ordinary skill in the art would recognize that many variations may be implemented based upon the discussed embodiments. Embodiments described above may be useful for hand-held consumer devices such as cell-phones, personal media players, mobile internet devices, or the like. Other embodiments may also be applied to higher-end devices such as laptop computers, desktop computers, DVRs. BluRay players, gaming consoles, hand-held portable devices, or the like. Other embodiments may take advantage of existing IR transmission devices for IR shutter glasses. More specifically, in such embodiments, an IR to RF conversion portion may be added to receive the IR 3D output instructions and to convert them to RF 3D transmission signals, described above. In some embodiments, an RF receiver is thus used. The RF 3D transmission signals are then transmitted to the RF 3D shutter glasses, described above. Such embodiments can therefore be a simple upgrade to available IR 3D glasses transmitters. 
         [0115]    In other embodiments of the present invention, feedback from shutter glasses to the transmitter device described above with regards to synchronization may be used for additional purposes. One such embodiment may allow the 3D image source (e.g., a cable box, computer, or the like) to take the indication that a pair of shutter glasses are currently synchronized to mean a person is viewing the 3D content, and to provide that data back to a marketing company such as Media Metrics, Nielsen Ratings, or the like. By doing this, such market research companies may determine the number of viewers of specific 3D features, or the like. The above detailed description is directed to systems, methods, and computer-readable media for stereoscopic viewing. While the subject matter described herein is presented in the general context of program modules that execute in conjunction with the execution of an application program or an operating system on a 3D source, consumer electronics device, and a pair of stereoscopic glasses, those skilled in the art will recognize that other implementations may be performed in combination with other program modules or devices. 
         [0116]    Further embodiments can be envisioned to one of ordinary skill in the art after reading this disclosure. In other embodiments, combinations or sub-combinations of the above disclosed invention can be advantageously made. The block diagrams of the architecture and flow charts are grouped for ease of understanding. However it should be understood that combinations of blocks, additions of new blocks, re-arrangement of blocks, and the like are contemplated in alternative embodiments of the present invention. 
         [0117]    The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope.