Abstract:
An application for a three-dimensional television system includes content encoded with left/right frame indicators at a pre-determined location on each frame. For example, during display frames meant for a first eye, the set of pixels contain a first pattern while during display of frames meant for the second eye, the set of pixels contain a second pattern. A detector interfaced to the screen of the television detects the left/right indication and provides synchronization to shutters of three-dimensional eyewear. The detector is positioned over the set of pixels and determines which pattern is displayed, generating a synchronization signal based upon the patterns. The synchronization signal is then transmitted to three-dimensional eyewear where it is used to control the shutters. In some embodiments, a phased-locked loop is provided within the three-dimensional eyewear to continue operation during periods when the transmission of the synchronization signal is blocked or otherwise interrupted.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is related to U.S. patent application titled “PIXEL SYSTEM, METHOD AND APPARATUS FOR SYNCHRONIZING THREE-DIMENSIONAL EYEWEAR,” attorney docket 10.0001 filed even date here within. This application is also related to U.S. patent application titled “PIXEL BASED THREE-DIMENSIONAL ENCODING METHOD,” attorney docket 10.0003 filed even date here within. This application is also related to U.S. patent application titled “FRAME BASED THREE-DIMENSIONAL ENCODING METHOD,” attorney docket 10.0004 filed even date here within. 
     
    
     FIELD 
       [0002]    This invention relates to the field of display devices worn over an individual&#39;s eyes and more particularly to a system for synchronizing the display devices with content presented on a display screen. 
       BACKGROUND 
       [0003]    There are several ways to present a three-dimensional image to a viewer of a television. The common aspect of the existing methods is to present an image or frame from two perspectives, a left-eye perspective of the content to the left eye and present an image or frame from a right-eye perspective to the right eye. This creates the proper parallax so that the viewer sees both perspectives and interprets what they are seeing as three-dimensional. 
         [0004]    Early three-dimensional content was captured using two separate cameras aimed at the subject but slightly separate from each other providing two different perspectives. This simulates what the left eye and right eye see. The cameras simultaneously exposed two films. Using three-dimensional eyewear, the viewer looks through one film with the left eye and the other film with the right eye, thereby seeing what looks like a three-dimensional image. 
         [0005]    Progressing to motion pictures, three-dimensional movies were produced in a similar way with two cameras, but the resulting images were color encoded into the final film. To watch the film in three-dimension, eyewear with colored filters in either eye separate the appropriate images by canceling out the filter color. This process is capable of presenting a three-dimensional movie simultaneously to a large audience, but has marginal quality and, because several colors are filtered from the content, results in poor color quality, similar to a black and white movie. 
         [0006]    More recently, personal headsets have been made that have two separate miniature displays, one for each eye. In such, left content is presented on the display viewed by the left eye and right content is presented on the display viewed by the right eye. Such systems work well, but require a complete display system for each viewer. 
         [0007]    Similar to this, Eclipse methods uses a common display, such as a television, along with personal eyewear that have fast-response shutters over each eye. In such, the left eye shutter is open allowing light to pass, the right eye shutter is closed blocking light and the television displays left-eye content, therefore permitting the light (image) from the television to reach the left eye. This is alternated with closing of the left eye shutter, opening of the right eye shutter and displaying right-eye content the television. By alternating faster than the typical human response time, the display appears continuous and flicker-free. 
         [0008]    The problem with the latter two methods is that the three-dimensional content must be encoded on, for example, a disk and decoded by a player that switches between left/right eye content in synchronization with the left-eye and right-eye shutter. With such, one cannot connect an industry standard player (e.g. BlueRay or DVD) to an industry standard television (e.g., Plasma or LCD television) and watch three-dimensional content with a set of three-dimensional eyewear. 
         [0009]    What is needed is a three-dimensional presentation system that utilizes existing, industry standard media delivery devices and provides three-dimensional viewing. 
       SUMMARY 
       [0010]    Digital video content is encoded such that an encoded frame or sequence of encoded frames is used to encode an indicator of whether the subsequent frame or frames is/are intended for the left eye or intended for the right eye. For example, using two marker frames, a first marker frame having all black pixel values and the a second marker frame having all white pixel values, an exemplary sequence of three-dimensional video content is: first marker frame; second marker frame, left content frame-1, left content frame-2, second marker frame, first marker frame, right content frame-1, right content frame-2, first marker frame; second marker frame, left content frame-3, etc. Detection hardware detects the all-black then all white sequence and opens the left-eye shutter and detects the all-white then all-black sequence and opens the right-eye shutter. 
         [0011]    To reduce the required number of marker frame or marker frame sequences, the detection hardware preferably includes a timing circuit that locks onto the marker frame or marker frame sequence and then anticipates alteration between future left-eye frames and right-eye frames. For example, in a frame sequence of: first marker frame, second marker frame, left content frame-1, second marker frame, first marker frame, right content frame-1, first marker frame, second marker frame, left content frame-2, right content frame-2, left content frame-3, right content frame-3, first marker frame, second marker frame, left content frame-4, second marker frame, first marker frame, right content frame-4, etc, the detection hardware detects the all-black then all-white sequence and the all-white then all-black sequence and determines the frame timing, thereafter timing the shutter system to alternate at appropriate points in time synchronized to the display of the corresponding content frames. 
         [0012]    In another example, the marker frame(s) are used to establish timing. For example, first marker frame, second marker frame, first marker frame, left content frame-1, right content frame-1, left content frame-2, right content frame-2, left content frame-3, right content frame-3, first marker frame, second marker frame, first marker frame, left content frame-4, right content frame-4, etc. In this sequence, the detection hardware detects the all-black then all-white sequence then all-black sequence and determines the frame timing, opening the left eye shutter for the next frame timing (e.g. while the left content frame-1 is displayed) then opening the right eye shutter for the next frame timing (e.g. while the right content frame-1 is displayed), etc. 
         [0013]    In a system not equipped to view three-dimensional content, the marker frames are ignored and the left content and right content frames result in a slight blurring of the image. 
         [0014]    A standard content delivery mechanism (e.g. Internet, cable, fiber-optic, DVD, BlueRay) delivers the content to a standard television. A detector is interfaced to or integrated within eyewear to detect the marker frames and provide synchronization to shutters of three-dimensional eyewear. The marker frame or marker frame sequence is any detectable frame or frames including a set or sets of pixels. 
         [0015]    In one embodiment, a three-dimensional eyewear synchronization system is disclosed. The three-dimensional eyewear synchronization system interfaces to a television that has a display. The television displays a sequence of frames of a three-dimensional program. The frames include left-eye frames, right-eye frames and synchronization frames. Three-dimensional eyewear has a shutter system for alternating image viewing to each eye of a wearer. The three-dimensional eyewear detects the synchronization frames and synchronizes the shutter system to the synchronization frames such that a left-eye shutter of the shutter system is open when left-eye frames are displayed on the display and a right-eye shutter of the shutter system is open when the right-eye frames are displayed on the display. 
         [0016]    In another embodiment, a method of synchronizing three-dimensional eyewear to a television is disclosed including receiving light receiving light from a display screen of the television and extracting a synchronization signal from the light. The synchronization signal is transmitted to the three-dimensional eyewear where it is used in shuttering at least one shutter of the three-dimensional eyewear in synchronization with the synchronization signal. 
         [0017]    In another embodiment, a three-dimensional eyewear synchronization system is disclosed including a television that has a display. A device detects a specific set of changes of light from the display and converts the changes of light into a synchronization signal. The synchronization signal is transmitted to eyewear having a mechanism for shuttering light from the display to each eye of a user. The eyewear receives the synchronization signal and uses the synchronization signal to time shuttering of the light from the display alternately to each of the eyes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: 
           [0019]      FIG. 1  illustrates a plan view of a television and three-dimensional eyewear of the prior art. 
           [0020]      FIG. 2  illustrates a plan view of a television and a first embodiment of three-dimensional eyewear. 
           [0021]      FIG. 3  illustrates a plan view of a television and a second embodiment of three-dimensional eyewear. 
           [0022]      FIG. 4  illustrates a block diagram of a transmitter of the first embodiment of three-dimensional eyewear. 
           [0023]      FIG. 5  illustrates a schematic view of a typical transmitter of the first embodiment of three-dimensional eyewear. 
           [0024]      FIG. 6  illustrates a block diagram of a typical transmitter of the second embodiment of three-dimensional eyewear. 
           [0025]      FIG. 7  illustrates a schematic view of a typical transmitter circuit of the second embodiment of three-dimensional eyewear. 
           [0026]      FIG. 8  illustrates a schematic diagram of a typical receiver circuit of the first embodiment of three-dimensional eyewear. 
           [0027]      FIG. 9  illustrates a schematic view of a typical receiver of the second embodiment of three-dimensional eyewear. 
           [0028]      FIG. 10  illustrates a synchronization timing chart. 
           [0029]      FIG. 11  illustrates a block diagram of a third embodiment. 
           [0030]      FIG. 12  illustrates a block diagram of a fourth embodiment. 
           [0031]      FIG. 13  illustrates a schematic diagram of the third embodiment. 
           [0032]      FIG. 14  illustrates a schematic diagram of the fourth embodiment. 
           [0033]      FIG. 15  illustrates a block diagram of a fifth embodiment. 
           [0034]      FIG. 16  illustrates a schematic diagram of the fifth embodiment. 
           [0035]      FIG. 17  illustrates a sequence of frames according to a first transmission arrangement. 
           [0036]      FIG. 18  illustrates a sequence of frames according to a second transmission arrangement. 
           [0037]      FIG. 19  illustrates an exemplary sequence of displayed frames according to a second transmission arrangement. 
           [0038]      FIG. 20  illustrates a second exemplary sequence of displayed frames according to a second transmission arrangement. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures. The bezel of the present invention is the facing surface surrounding an image producing surface such as an LCD panel, CRT, Plasma panel, OLED panel and the like. 
         [0040]    Referring to  FIG. 1 , a plan view of a television and three-dimensional eyewear of the prior art is described. In prior technology, three-dimensional eyewear  10  functioned with specialized content delivery hardware, such a personal computer or specially equipped television  5 . The personal computer or television  5  displays three-dimensional content on a display  7  and controls the eyewear  10  through a cable  18  that provided control of each eye shutter  14 / 16 , synchronizing the eye shutters  14 / 16  to the content being displayed on the display  7 . The eyewear often includes frames with ear rests  12 . In such systems, specialized content is usually required containing left-eye and right-eye encoded frames. Specialized hardware and/or software is also required in the personal computer or television  5  to properly display the content and synchronize operation of the left/right shutter with the display of the content. 
         [0041]    It is advantageous to utilize existing content delivery mechanisms (e.g. Internet delivery, DVD disks, BlueRay disks, etc) and existing display technology (e.g. monitors, televisions, etc) without modification, The prior art does not provide for such. 
         [0042]    Referring to  FIG. 2 , a plan view of a display device (e.g. television)  5  and a first embodiment of three-dimensional eyewear  50 A is described. In this, a transmitter device  20  is attached to cover a subset of the pixels of the display  7 . As will be described, the transmitter  20  receives light from the subset of the pixels, detects a predetermined value of the light and generates a synchronization signal from the predetermined value of the light. The synchronization signal is transmitted to the three-dimensional eye wear  50 A, in this example, by a radio frequency signal  57 . For example, the synchronization signal is transmitted by a pre-determined frequency modulation, pulse code modulation, etc, as known in the industry. The radio frequency signal is received by an antenna  58  and decoded within the eyewear  50 A or by an attached circuit to the eyewear  50 A, controlling the eyewear shutters  54 / 56  as will be described. Note, in some embodiments, the eyewear  50 A includes ear rests  52  for support. 
         [0043]    Referring to  FIG. 3 , a plan view of a television  5  and a second embodiment of three-dimensional eyewear  50 B is described. In this, a transmitter device  30  is attached to cover a subset of the pixels of the display  7 . As will be described, the transmitter  30  receives light from the subset of the pixels, detects a predetermined value of the light and generates a synchronization signal from the predetermined value of the light. The synchronization signal is transmitted to the three-dimensional eye wear  50 B, in this example, by a light signal  67 . For example, the synchronization signal is transmitted by a pre-determined modulated wavelength of light, preferably non-visible light such as Infra-red light, etc, as known in the industry. The modulated light signal  67  is received by a light detector  68  and decoded within the eyewear  50 B or by an attached circuit to the eyewear  50 B, controlling the eyewear shutters  54 / 56  as will be described. Note, in some embodiments, the eyewear  50 B includes ear rests  52  for support 
         [0044]    Referring to  FIG. 4 , a block diagram of a transmitter  20  of the first embodiment of three-dimensional eyewear  50 A is described. The transmitter  20  has a light detector  22  that interfaces to the display  7  over an area of the predetermined subset of pixels that convey the left-eye/right-eye synchronization signal. The light detector  22  receives light from the display  7  and converts it into an electrical signal and presents the electrical signal to a detection circuit  26  that analyzes the electrical signal to determine which pre-determined light value is being displayed on the predetermined subset of pixels and generates a synchronization signal based upon such. There are many encoding values for the left/right eye synchronization signal into a subset of pixels such as a first color for left and a second color for right, a first series of pixel color values for left and a second series of pixel colors for right, etc. As an example, all of the subset of pixels is red for left-eye content and black for right-eye content. The detector  26  then receives a first value of electrical signal for red light and a second value of the electrical signal for black (absence of light). 
         [0045]    The synchronization signal is then modulated for transmission, in this example, using radio frequencies over an antenna  24 . The modulation is any known modulation scheme. For example, a simple modulation scheme includes a carrier frequency and a signal frequency, wherein a left-eye signal is transmitted as the carrier frequency and the right-eye signal is transmitted as the signal frequency. Alternately, the left-eye signal consists of a first sequence of carrier frequency alternating with signal frequency and the right-eye signal consists of a second sequence of carrier frequency alternating with signal frequency. There are many known methods of transmitting a signal over radio frequencies, all of which are included here within. 
         [0046]    The transmitter  20  has either an internal power source  28  (such as a battery or rechargeable capacitor; or has an external power source such as a wall-wart/brick (not shown). 
         [0047]    Referring to  FIG. 5 , a schematic view of a typical transmitter  20  of the first embodiment of three-dimensional eyewear system is described. The transmitter  20  has a light detector  22  that detects light from the display  7  and converts the light into an electrical signal which is amplified by an operational amplifier  23  and is presented to a detection circuit  26  that analyzes the electrical signal to determine which pre-determined light value is being displayed on the predetermined subset of pixels and generates a synchronization signal based upon such. The detection circuit has a decoder  25  that extracts the synchronization signal from the electrical signal. Any type of detection circuit is anticipated, including, but not limited to, counters, frequency high-pass and/or low-pass filters, etc. The synchronization signal is fed to a radio frequency modulator  27  that uses any known radio frequency modulation technique and the modulated radio frequency is transmitted by way of an antenna  24 , which is preferable a solid-state, micro-miniature antenna, though any antenna is anticipated. 
         [0048]    The transmitter is powered by a power source  28 , as known in the industry, including, but not limited to batteries, rechargeable batteries, charged capacitors, wall bricks, etc. It is anticipated that the power source  28  be replaceable and/or rechargeable inside or outside of the transmitter  26 . In some embodiments, light from the television display  7  is used to charge the power source  28 . 
         [0049]    Referring to  FIG. 6 , a block diagram of a typical transmitter  30  of the second embodiment of three-dimensional eyewear is described. The transmitter  30  has a light detector  22  that interfaces to the display  7  over an area of the predetermined subset of pixels that convey the left-eye/right-eye synchronization signal. The light detector  22  receives light from the display  7  and converts it into an electrical signal and presents the electrical signal to a detection circuit  26  that analyzes the electrical signal to determine which pre-determined light value is being displayed on the predetermined subset of pixels and generates a synchronization signal based upon such. There are many encoding values for the left/right eye synchronization signal into a subset of pixels such as a first color for left and a second color for right, a first series of pixel color values for left and a second series of pixel colors for right, etc. As an example, all of the subset of pixels is red for left-eye content and black for right-eye content. The detector then receives one value of electrical signal for red light and a second value of the electrical signal for black (absence of light). 
         [0050]    The synchronization signal is then modulated for transmission, in this example, using light waves emitted from a light output device  34  such as a light emitting diode (LED). The modulation is any known modulation scheme. For example, a simple modulation scheme includes modulation on/off of a light of a specific wavelength, preferably an invisible light such as infra-red light. In such, a left-eye signal is transmitted as a first on/off frequency or sequence of the light and the right-eye signal is transmitted as a second on/off frequency of the light. There are many known methods of transmitting a signal utilizing one or more wavelengths of light, all of which are included here within. 
         [0051]    Referring to  FIG. 7 , a schematic view of a typical transmitter circuit of the second embodiment of three-dimensional eyewear system is described. The transmitter  20  has a light detector  22  that detects light from the display  7  and converts the light into an electrical signal which is amplified by an operational amplifier  23  and is presented to a detection circuit  26  that analyzes the electrical signal to determine which pre-determined light value is being displayed on the predetermined subset of pixels and generates a synchronization signal based upon such. The detection circuit has a decoder  25  that extracts the synchronization signal from the electrical signal. Any type of detection circuit is anticipated, including, but not limited to, counters, frequency high-pass and/or low-pass filters, etc. The synchronization signal is fed to a light modulator  37  that uses any known light modulation technique and the modulated light is transmitted by way of light output device  34  which is preferable a light emitting diode  34 , though any suitable light output device is anticipated. 
         [0052]    The transmitter is powered by a power source  28 , as known in the industry, including, but not limited to batteries, rechargeable batteries, charged capacitors, wall bricks, etc. It is anticipated that the power source  28  be replaceable and/or rechargeable inside or outside of the transmitter  26 . In some embodiments, light from the television display  7  is used to charge the power source  28 . 
         [0053]    Referring to  FIG. 8 , a schematic diagram of a typical receiver circuit  80  of the first embodiment of three-dimensional eyewear  50 A is described. In such, the radio frequency signal  57  is picked up by the antenna  58  and, optionally amplified by an operation amplifier  51  and detected/demodulated by a demodulator  53 , recovering the transmitted synchronization signal  70 . A timing circuit  55  translates the synchronization signal  70  into a left-eye (Q) control signal and a right-eye (-Q) and is coupled to the left-eye shutter  54  and right-eye shutter  56 , respectively, by shutter drivers  57 / 59 . In the preferred embodiment, the timing circuit  55  includes a phased-locked-loop that provides the left-eye and right-eye control signal during a loss of the shutter signal  70 . 
         [0054]    Referring to  FIG. 9 , a schematic view of a typical receiver  82  of the second embodiment of three-dimensional eyewear  50 B is described. In such, the light signal  67  is picked up by a light detector  68  (e.g., photo diode  68 ) and, optionally amplified by an operation amplifier  61  and detected/demodulated by a demodulator  63 , recovering the transmitted synchronization signal  70 . A timing circuit  55  translates the synchronization signal  70  into a left-eye (Q) control signal and a right-eye (-Q) and is coupled to the left-eye shutter  54  and right-eye shutter  56 , respectively, by shutter drivers  57 / 59 . In the preferred embodiment, the timing circuit includes a phased-locked-loop that provides the left-eye and right-eye control signal during a loss of the shutter signal  70 . 
         [0055]    Referring to  FIG. 10 , an exemplary synchronization timing chart is described. In this example, the alternation of the eye shutters  54 / 56  is intended to occur during the leading edge transition. In other examples, the alternation is at the trailing edge or the open shutter  54 / 56  is dependent upon a specific signal level, frequency or voltage. It is anticipated that when non-three-dimensional content is displayed, either transmission is halted or a special transmission is made to signal the eyewear  50 A/ 50 B to open both shutters  54 / 56 . 
         [0056]    The first waveform  90  C 1 /C 2  represents the signal from the subset of pixels of the television display  7 . For exampled, C 1  is represented by the subset of pixels being a first color and C 2  is represented by the subset of pixels being a second color, for example, C 1  is represented by white and C 2  is represented by black. Many other representations are anticipated. The second waveform  92  M 1 /M 2  is the output of the modulator  27 / 37 . M 1  represents a high value of the synchronization signal while M 2  represents a low value of the synchronization signal. As an example, M 1  is represented by an infrared light output modulated at 100 Khz and M 2  is the infrared light output modulated at 125 Khz. Many representations of the synchronization signal are anticipated. 
         [0057]    The third waveform  94  R 1 /R 2  represents the received synchronization signal at the eyewear  50 A/ 50 B and the fourth waveform  96  Q/-Q represents control signals to the left and right shutter, respectively. In this example, the left shutter is open and the right shutter is closed when Q is zero (-Q is one). At each leading edge of the synchronization signal, Q/-Q is reversed, thereby opening the shutter  54 / 56  for the other eye. When reception of the synchronization signal is lost as indicated by a suspension of R 1 /R 2 , the internal timing circuit  55  (e.g. phase locked loop) attempts to continue the timing of the shutters  54 / 56  based on an internal clock such as a crystal-controlled oscillator. Since the internal clock does not accurately track the synchronization signal, the internal timing eventually drifts slightly until reception of the synchronization signal restarts, at which time the internal timing circuit again locks to the received synchronization signal. The loss of the received synchronization signal occurs when, for example, the light transmission is blocked or the radio frequency transmission is scrambled by interference. 
         [0058]    Referring to  FIGS. 11-12 , a block diagram of a third and fourth embodiments are described. In this, the display  7  of the standard television  7  periodically emits a light synchronization signal  181  that is received by a light detector  182  that is part of synchronization detector  180 / 190 . The synchronization signal is any alteration of the display  7  output such as a white frame followed by a black frame followed by a white frame. In some embodiments when the television systems  5  uses a scanning technique (e.g. cathode-ray tube television systems  5 ), the synchronization signal is a certain sequence of pixel brightness. For example, B represents a black pixel, W represents a white pixel, and one possible sequence is BWBWWBWB. It is preferred that the light synchronization signal  182  is rarely a normal part of any typical television viewing (e.g., the sequence would not normally appear as a feature of any particular content), so as to not produce false synchronization signals. In some embodiments, the light detector  182  is a camera  182  (e.g. CCD camera) and the light detector  182  detects a pattern within a frame such as a pre-determined geometric pattern. 
         [0059]    The synchronization detector  180 / 190  relays the detected synchronization signal to the eyewear  50 A/ 50 B (see  FIGS. 2 and 3 ) either by a radio frequency signal  57  ( FIG. 11 ) or a light wave signal  67  ( FIG. 12 ). The radio frequency signal  57  is emitted on an antenna  184  (either internal or external) and received at the eyewear  50 A at an antennal  58 . If a light wave  67  is used, the light wave  67  is emitted by a light output device  194  (e.g., LED) and received at the eyewear  50 B by a light detector  68  (e.g. photodiode  68 ). The eyewear  50 A/ 50 B then operates as previously described. 
         [0060]    Referring to  FIGS. 13 and 14 , schematic diagrams of the third and fourth embodiments are described. The light synchronization signal  181  is received by a light detector  182  (e.g. photo diode or camera) of the synchronization detector  180 / 190 . The light synchronization signal  181  is any alteration of the display  7  output as described above. The output of the light detector  182  is, optionally amplified by amplifier  183  and then is detected by a detector  185 . The detector  185  looks for the display output fluctuation that indicates synchronization such as a white-frame, black-frame then white-frame sequence. The detector  185  relays the detected signal to a radio frequency modulator  189  (as in  FIG. 13 ) or a light modulator  199  (as in  FIG. 14 ) for transmission to the eyewear  50 A/ 50 B. The radio frequency modulator  189  outputs a radio frequency signal onto an antenna  184  as known in the industry. The light modulator  199  drives an output device  194  such as a light emitting diode  194 , preferably an LED  194  that emits invisible light such as infrared light. 
         [0061]    Referring to  FIGS. 15 and 16 , a block diagram and schematic diagram of the fifth embodiment is described. In this, the display  7  of the standard television  7  periodically emits a light synchronization signal  181  that is received by a light detector  282  that is part of the three-dimensional eyewear  200 . The light synchronization signal is as before any alteration of the display  7  output such as a white frame followed by a black frame followed by a white frame. In some embodiments when the television systems  5  uses a scanning technique (e.g. cathode-ray tube television systems  5 ), the light synchronization signal is a certain sequence of pixel brightness. For example, B represents a black pixel, W represents a white pixel, and one possible sequence is BBWWBBWWBBWWBB. It is preferred that the light synchronization signal is rarely a normal part of any typical television viewing (e.g., the sequence would not normally appear as a feature of any particular content), so as to not produce false light synchronization signals  181 . 
         [0062]    The light synchronization signal  181  is converted to an electrical signal by the light detector  282  (photo diode, camera, etc) and, optionally, amplified by an amplifier  283  then presented to a detector  285 . The detector  285  looks for the sequence of alteration of display output and develops a synchronization signal  70 . The synchronization signal  70  is fed to the timing circuit  255  which uses the synchronization signal  70  to control the shutters  254 / 256  through, for example, shutter drivers  257 / 259 . In the preferred embodiment, the timing circuit  255  includes a phase-locked-loop for continued operation of the shutters  254 / 256  during loss of the light synchronization signal  181 . 
         [0063]    Referring to  FIG. 17 , a sequence of displayed frames according to a first transmission arrangement is described. This is an exaggeration of what the left eye (frames F 1  and F 3 ) and the right eye (frame F 2 ) sees from a three-dimensional perspective. As depicted, in three-dimensional perception, the left eye sees the left side of the box  310 A and the right eye sees the right side of the box  310 B. In a true video transmission, the viewing angle would be much less than that in this exaggerated view. When frame F 1   300  is displayed, the frame relationship indicator area has a first pattern  320 . When frame F 2   302  is displayed, the frame relationship indicator area has a second pattern  322 . When frame F 3   304  is displayed, the frame relationship indicator area has, again, the first pattern  320 . The transmitter device  20 / 30 , as described above, is optically coupled to the frame relationship indicator area and detects which pattern (first pattern  320  or second pattern  322 ) is present and generates the synchronization signal from this detection. As stated, the only requirement is that the first pattern  320  is in some way detectably different from the second pattern  322 . For example, the first pattern  320  is a set of pixels in the shape of a ‘V’ colored white and the second pattern  322  is the same set of pixels in the shape of a ‘V’ colored blue. In this example, the detector looks for the color change between white and blue and back to white. To an observer, the frame relationship indicator area appears, in this example, as a light-blue ‘V’. Note, only three frames  300 / 302 / 304  are shown from a sequence of many. Also note that, although two distinct patterns  320 / 322  are used in this example, it is anticipated that additional patterns/color changes are used for other synchronization purposes. For example, a first pattern  320  is a red ‘V’ indicating left-eye content is being displayed (e.g. open the left eye shutter) and the second pattern  322  is a blue ‘V’ indicating right-eye content is being displayed (e.g. open the right eye shutter) and a third pattern (not shown) is a purple ‘V’ (red+blue) indicating that two dimensional frames are being displayed, or both-eye content (e.g. open both the left eye shutter and the right eye shutter). 
         [0064]    Referring to  FIG. 18 , a sequence of displayed frames according to a second transmission arrangement is described. In this example, the change from left-eye frames  400  to right eye frames  406  is signaled by right eye marker frames  402 / 404 . The frame depictions are an exaggeration of what the left eye (frame F 1 ) and the right eye (frame F 4 ) sees from a three-dimensional perspective. As depicted, in three-dimensional perception, the left eye sees the left side of the box  410 A and the right eye sees the right side of the box  410 B. In a true video transmission, the viewing angle would be much less than that in this exaggerated view. Also, in a true display of video, there would be many more frames displayed in sequence. 
         [0065]    The sequence includes content frames F 1   400  and F 4   406  and marker sets F 2   402  and F 3   404 . The marker sets  402 / 404  consist of one or more frames. For example, a marker set includes two frames displayed for one frame-time each (e.g. 33 milliseconds per frame at a 30 frames per second rate). The content of the marker sets  402 / 404  vary enough to be detectable by the detection circuit  185 / 285  but are preferably not easily detected by the human eye. In one example, the marker set includes a first marker frame  402  that is an all-black frame (all black pixels) and the second marker frame  404  is an all-white frame (all white pixels). In another example, the first marker frame  402  is a slightly dimmer copy of the left-eye content frame  400  and the second signaling frame is a slightly brighter left-eye content frame  400 , thereby reducing any noticeable content modification. Although two signaling frames  402 / 404  are shown, any number is anticipated. For example, to switch from a left-eye frame  400  to a right-eye frame  406 , the right-eye marker set displayed is a single brighter left-eye frame. The right-eye marker is displayed before the right-eye content frame  406 . The detector  185 / 285  then detects the increase in brightness to open the right shutter  256  and close the left shutter  254 . To switch from a right-eye view  406  to the left-eye view  400 , a left-eye marker set is displayed and in this example, the left-eye marker set is a single dimmer right-eye frame. The detector  185 / 285  then detects the decrease in brightness to open the left shutter  254  and close the right shutter  256 . Therefore, the detector  185 / 285  detects the brightness increase to synchronize the opening of the right shutter and closing of the left shutter and the detector  185 / 285  detects the brightness decrease to synchronize the opening of the left shutter and closing of the right shutter. For content that is for both eyes, a both-eye marker set is used. For example, a both-eye marker set occurs before one or more frames that are not in three-dimensions. The both-eye marker set is detectably different from the left-eye marker set and detectably different from the right-eye marker set. For example, the both-eye marker set includes three sequential frames, the first and third frames being black frames  402  and the intermediate frame being white  404 . There are many examples of detectably different frames and detectably different sequences of frames or frame sets. In embodiments in which the detector includes a camera, the camera detects a pattern of pixels and therefore, each marker set has a single frame containing a distinguishable set of pixels such as icons or other sets of pixels. 
         [0066]    Referring to  FIG. 19 , an exemplary sequence of displayed frames according to a second transmission arrangement is described. In this example, a synchronization sequence of one or more marker frames, in this example three marker frames  502 / 504 / 506 , is followed by a sequence of left and right content frames  510 / 512 / 514 / 516  on a digital media  500  (e.g. DVD disk, Blueray disk, hard disk, memory, etc). The start of the next sequence is shown by the first marker frame  502  of the next sequence. The marker frames  502 / 504 / 506  indicate the start of a sequence of content  510 / 512 / 514 / 516 . Although the synchronization sequence is any number of marker frames including one marker frame, the example of  FIG. 19  shows three marker frames  502 / 504 / 506 . As an example, the first  502  and third  506  marker frames have the same set of pixel values and the second marker frame  504  has a distinguishably different set of pixels. The sequence of left and right content frames  510 / 512 / 514 / 516  is of any predetermined sequence and length, four frames in length in this example. The detector  185 / 285  detects the marker frames  502 / 504 / 506  and measures the duration of the marker frames  502 / 504 / 506  to generate a synchronization signal. For example, by locking onto the time of first detecting (leading edge) each of the marker frames  502 / 504 / 506 , a synchronization signal is determined that predicts when each transition between, for example, left-eye content frames  510 / 514  and right-eye content frames  512 / 516  will occur and, thereby, the shutters  54 / 254 / 56 / 256  are controlled to synchronize with the display of the corresponding content frame. To reduce drift caused by slight variations between clocks, synchronization sequences  502 / 504 / 506  are embedded in the three-dimensional content at fixed positions. In such, the receiver knows to expect a synchronization sequence  502 / 504 / 506  followed by a pre-determined sequence of left-eye content frames  510 / 514 , right-eye content frames  512 / 516 , followed by another synchronization sequence  502 / 504 / 506 , etc. In examples in which the synchronization sequence is one marker frame, the detector determines the start of the marker frame and the duration of the marker frame. From that, it knows that the first content frame (e.g. left-eye content frame  510 ) follows immediately after the marker frame and then exactly one duration later is a second content frame (e.g. right-eye content frame  512 ), etc. 
         [0067]    Referring to  FIG. 20 , a second exemplary sequence of displayed frames according to a second transmission arrangement is described. In this example, a three-dimensional synchronization sequence  602 / 604 / 606  of one or more marker frames, in this example three marker frames  602 / 604 / 606 , is followed by a sequence of left and right content frames  610 / 612 / 614 / 616 / 618 / 620  on a digital media  600  (e.g. DVD disk, Blueray disk, hard disk, memory, etc). After the three-dimensional content frames  610 / 612 / 614 / 616 / 618 / 620 , the content is two-dimensional (e.g. both shutters  54 / 254 / 56 / 256  are open). The start of the two-dimensional, both-eye content frames is indicated by a different synchronization sequence  630 / 632 / 634  shown in this example by the second marker frame  630 , followed by the first marker frame  632  followed by the second marker frame  634 . The synchronization sequence  630 / 632 / 634  (marker frames  630 / 632 / 634 ) indicate a start of a sequence of both-eye content frames  640 / 642 , etc  410 C. Since there is no shutter operation during two-dimensional or both-eye content frames, there is no need to include further two-dimensional synchronization sequence  630 / 632 / 634 , although additional two-dimensional synchronization sequence  630 / 632 / 634  are anticipated in case the first sequence is lost due to interference. 
         [0068]    Although the two-dimensional synchronization sequence  630 / 632 / 634  and three-dimensional synchronization sequence  602 / 604 / 606  is any number of marker frames including one marker frame, the example of  FIG. 20  shows three marker frames. As an example, in the three-dimensional synchronization sequence  602 / 604 / 606 , the first  602  and third  606  marker frames have the same set of pixel values and the second marker frame  604  has a distinguishably different set of pixels. Similarly, in the two-dimensional synchronization sequence  630 / 632 / 634 , the first  630  and third  634  marker frames have the same set of pixel values and the second marker frame  632  has a detectably distinguishably different set of pixels and also being detectably distinguishable from the three-dimensional synchronization sequence  602 / 604 / 606 . 
         [0069]    The sequence of left and right content frames  610 / 612 / 614 / 616 / 618 / 620  is of any predetermined sequence and length, six frames in length in this example. The detector  185 / 285  detects the three-dimensional marker frames  602 / 604 / 606  and measures the duration of the marker frames  602 / 604 / 606  to generate a synchronization signal. For example, by locking onto the time of first detecting (leading edge) each of the marker frames  602 / 604 / 606 , a synchronization signal is determined that predicts when each transition between, for example, left-eye content frames  610 / 614 / 618  and right-eye content frames  612 / 616 / 620  will occur and, thereby, the shutters  54 / 254 / 56 / 256  are controlled to synchronize with the display of the corresponding content frame. To reduce drift caused by slight variations between clocks, synchronization sequences  602 / 604 / 606  are embedded in the three-dimensional content at fixed positions. In such, the receiver knows to expect a synchronization sequence  602 / 604 / 606  followed by a pre-determined sequence of left-eye content frames  610 / 614 / 618 , right-eye content frames  612 / 616 / 620 , followed by another synchronization sequence  602 / 604 / 606  (or a two-dimensional synchronization sequence  630 / 632 / 634 ), etc. 
         [0070]    Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result. 
         [0071]    It is believed that the system and method and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.