Abstract:
A method for presenting secondary information to a video-viewing audience comprises projecting video images onto a screen and projecting invisible light signals encoded to represent secondary information associated with said video images onto the screen concurrently with said video images.

Description:
BACKGROUND  
       [0001]     Projection systems for displaying motion pictures, television, video games, digital video discs (DVDs), VCR tapes, digital cable, and the like (collectively, “video”) generally include various electronic components that receive, process, and selectively channel light from one or more light sources (such as a light bulb) along one or more corresponding optical paths to a projection lens. The projection lens projects the channeled light onto a screen to form visible images, which can be viewed by human observers. Various versions of such systems are commonly used in movie theaters, corporations, and residential homes for allowing people to view motion pictures, television, video games, and presentations.  
         [0002]     Projection systems also commonly include an audio source that transmits audio information relating to the projected images (a “soundtrack”) to speakers, which are typically hard-wired to the audio source. The speakers may be integral with or physically-separated from the projection system. The human observers can then hear the soundtrack as they view the video.  
         [0003]     Many times, there are multiple soundtracks associated with a given video. For example, many DVDs include a standard soundtrack for the motion picture and a “director&#39;s narration” soundtrack, wherein the director of the motion picture narrates commentary over the standard soundtrack. Further, for example, many DVDs include soundtracks in multiple languages for the same video. Currently, when several people simultaneously watch the same video in the same room, they are constrained to listen to the same soundtrack. The inventors have recognized that it would be desirable to have a projection system that allows different human observers watching the same video to listen to different associated soundtracks simultaneously. For example, when a group of people watch a video at the same time, some people in the group may want to listen to the standard soundtrack, whereas others may want to listen to the “director&#39;s narration” soundtrack (or a different language).  
         [0004]     Furthermore, it is common for the audio portion of many projection systems to include some version of “surround sound”, wherein the soundtrack is delivered from speakers located at different places around the room. The speakers used in most surround sound systems are hard-wired to the audio source of the projection system. Many times it is difficult to hard-wire remote speakers to the audio source in a convenient and aesthetically-pleasing way. Accordingly, the inventors have recognized that it would be desirable to have a projection system that facilities convenient, effective wireless installation of surround sound systems to be used with the projection system.  
         [0005]     The disclosed invention was developed in view of these and other problems associated with video projection systems.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  illustrates an audio-visual system, implemented according to one embodiment of the invention.  
         [0007]      FIG. 2A  illustrates an embodiment of a projection device, showing one possible location of an integral secondary signal transmitter.  
         [0008]      FIG. 2B  illustrates an embodiment of a projection device, showing a second possible location of an integral secondary signal transmitter.  
         [0009]      FIG. 2C  illustrates an embodiment of a projection device, showing a third possible location of an integral secondary signal transmitter. 
     
    
     DETAILED DESCRIPTION  
       [0010]      FIG. 1  illustrates an exemplary embodiment of a projection system implemented in accordance with the present invention. The projection system generally includes a projection device  10 , a secondary signal transmitter  12 , a screen  14 , and at least one receiver  16   a, b.  The projection device  10  projects video onto the screen  14  for human observers to watch. The screen  14  can comprise a number of different types of surfaces upon which video images can be projected, such as reflective screens and surfaces (as used with front projection systems shown in  FIG. 1 ) and transflective screens (as used with rear projection systems, not shown). The secondary signal transmitter  12  projects a secondary light signal onto the screen  14  that is not visible to naked human eyes. Useful formats for the secondary signals include, for example, infrared (IR) signals and ultraviolet (UV) light. The secondary signal is encoded with secondary information associated with the video, such as, for example, audio information. The secondary light signal is reflected off of the screen  14  (or a second screen, not shown) to the receiver(s)  16 , where it is received and decoded. When the secondary information is audio information, it is decoded into audibly-perceptible sounds. When the projection system is a rear-projection system, the secondary light signal is transmitted through the transflective screen to the receivers in the viewing room.  
         [0011]      FIG. 1  illustrates secondary signal transmitter  12  in a location independent from projection device  10 , though, as illustrated in other embodiments herein, secondary signal transmitter  12  may be located at a variety of positions inside of or attached to the outside of projection device  10 . Irrespective of its position relative to the projection device  10 , secondary signal transmitter  12  is positioned so as to transmit an invisible encoded light signal to the screen  14  (or to a second screen, not shown). The secondary light signal is reflected from the screen  14  to receivers  16   a  and  16   b  located in the same room as the projection device  10 . The receivers  16   a  and  16   b  are configured to receive the reflected invisible signals and decode those signals into audibly-perceptible sounds, i.e., the soundtrack of the video. In the case of a rear-projection system (not shown), the receivers would receive the secondary light signal transmitted through the transflective screen. In various implementations of the invention, a single receiver could be used, or multiple receivers, as shown in  FIG. 1 , could be used simultaneously. Possible receivers include headphones  16   a  and wireless speakers  16   b,  as well as other types of receivers, that incorporate a receiver device (not shown) and a decoding device (not shown) for receiving the secondary light signal and decoding it into an audibly-perceptible sound.  
         [0012]     The secondary signal transmitter  12  may encode the invisible secondary light signals to represent audio information (or other types of secondary information) using a variety of methods, including digital or analog modulation. Similarly, receivers  16  may be configured to decode the secondary light signal using a variety of methods, such as digital or analog demodulation, provided that the decoding method match the encoding method used by the secondary signal transmitter  12 .  
         [0013]     Though not necessary to implement the invention, in certain embodiments, the secondary signal transmitter  12  may be configured to transmit multiple channels of audio information via the invisible light signals effectively simultaneously. Transmitting multiple channels of audio information may be useful for allowing each human viewer watching a video in the same room to listen to different associated soundtracks, as well as for implementing wireless stereo and surround sound audio delivery systems. One such method of transmitting and receiving different channels of audio information via the invisible signal is by polarizing the secondary signal before it is transmitted to the screen  14  such that each channel of audio information has a different polarization. For example, a first channel of audio information could be transmitted by secondary signal transmitter  12  having a vertical polarization, and a second channel of audio information could be transmitted by secondary signal transmitter  12  having a horizontal polarization. Another method would include using multiple secondary signal transmitters  12 , each being configured to transmit a different channel of invisible signals toward screen  14  using various methods of encoding, such as digital or analog modulation, to separate the different channels of audio information represented by the invisible light signals.  
         [0014]     When the system is configured to transmit multiple channels of audio information toward the screen  14  (or other screen), then it is desirable that the receivers  16  be configured to be able to receive and decode the different reflected channels of light signals carrying audio information. Depending on the implementation of the invention, the different receivers  16  (e.g., the different speakers  16   b  and headphone sets  16   a ) each may be permanently pre-configured to receive and decode a particular channel of audio information. Alternatively, the different receivers  16  may each be configured with a channel selector, dial, or other mechanism for selecting different ones of the available channels of audio information to receive and decode. For example, each speaker  16   b  and/or pair of headphones  16   a  could be equipped with a channel selector (not shown) that would allow a user to selectively configure the speaker to receive and decode a particular channel of audio information. Moreover, where headphones  16   a  are used in the system, each speaker in a given set of headphones (i.e., each “ear”) could be configured (either permanently or selectively using a channel selector) to receive and decode different channels of the reflected audio information, which could be used to deliver stereo sound to the human user.  
         [0015]     The transmission and reflection of different channels of audio information via the invisible light signals can be used in a variety of ways. For example, it is common for surround sound systems to deliver five, seven, or more different channels of audio information, each channel being specific to a different speaker in the room. Therefore, where an embodiment of the invention is used to implement a surround sound system in a room, each channel of audio information (via the invisible secondary light signals) could be received and decoded by a different speaker  16   b  in the room to effectuate the surround sound effect. Moreover, where headphones  16   a  are used as the receiver, each “ear” of the set of headphones could be permanently or selectively configured to receive a different channel of audio information to deliver a stereo sound to the listener. Further, the different channels of transmitted audio information could be used to deliver different soundtracks associated with the same video to the different human viewers in the same room. For instance, the secondary signal transmitter  12  could be configured to transmit one or more channels of encoded audio information that represents a version of the associated soundtrack in English, Spanish, and French, as well as a “director&#39;s narration” soundtrack, all effectively simultaneously. The human viewers could each use different receivers (e.g., headphone sets) to selectively determine which channel(s) of audio information to receive and decode. In this way, different human viewers watching a video in the same room could listen to different soundtracks associated with the video.  
         [0016]     The secondary signal transmitter  12  may take a variety of forms and be located at a variety of positions within the system. The secondary signal transmitter  12  may be positioned inside or outside of the projection device  10 , and, if outside, the secondary transmitter  12  may be integral with, attached to, or physically-separate from (as shown in  FIG. 1 ) the projection device  10 . In one embodiment, the secondary transmitter  12  is a light emitting diode (LED) that is configured to emit an infrared (IR) light signal. Of course, various other devices, including lasers, may be used as the secondary signal transmitter  12  to transmit invisible light signal toward screen  14 . If the secondary signal transmitter  12  is located separate from the projection device  10 , then the secondary transmitter  12  may also include a separate lens (not shown) that projects the light signal emitted from the LED into the screen  14  to maximize coverage of the screen  14 . Though not necessary for the invention hereof, maximizing the surface area of the screen onto which the secondary signal is transmitted maximizes the efficiency and performance of the reflected signal.  
         [0017]      FIGS. 2   a - 2   c  illustrate an exemplary projection system  10  in schematic format that could be used in connection with an embodiment of the present invention, as well as different possible implementations of the secondary signal transmitter  12  integrated into the projection system  10 . This particular illustrated projection system  10  includes a light source  20 , such as a bulb. The light source  20  emits light through a color wheel  22 , which reflects off of a digital micromirror device (DMD)  24 , which is comprised of a plurality of very small, individually-tiltable micromirrors (not shown), each of which being configured to correspond to a unique pixel on the screen  14 . Each of the micromirrors on the DMD is tilted so as to direct light from the light source  20  either toward or away from the screen  14 . When directed toward the screen  14 , the light passes through a lens  26 , which projects the light onto the screen  14 . By rapidly tilting each of the micromirrors so as to alternatively direct light toward and away from the screen  14  at different frequencies, viewable images are projected through the lens  26  onto the screen  14 .  
         [0018]     If the secondary signal transmitter  12  is positioned inside of projection device  10 , it could be located at a variety of different positions therein. Though not necessary, it is useful to position the secondary signal transmitter  12  such that it emits its invisible light signal through lens  26 , which projects the signal onto screen  14 . In this way, a single lens  26  can be used to display the visible light image of the video, as well as project the invisible light signal carrying the audio information. The secondary signal transmitter  12  may be positioned in a variety of ways to achieve this result. For example, as shown in  FIG. 2   a,  the secondary signal transmitter  12  could be mounted inside of the projection device  10  essentially in the path of the primary video light signal such that the secondary audio light signal is reflected by the DMD  24  through the lens  26  to the screen  14 . Alternatively, the secondary signal transmitter  12  may be positioned, as shown in  FIG. 2   b,  such that the secondary signal is reflected by the DMD  24  through the lens  26 , but so that it is done outside of the primary light path from light source  20 . In the embodiment shown in  FIG. 2   b,  the secondary signal transmitter is positioned so that the secondary light signal is reflected by each of the micromirrors on the DMD  24  when the micromirror is tilted “away” from the primary light source, and “toward” the secondary signal transmitter  12 . In any given video transmission, each micromirror is tilted “away” from the primary light source a sufficient amount of the time to adequately reflect the secondary light signal in this configuration. Finally, the secondary signal transmitter  12  may be positioned “off-axis” relative to the light path reflected from the DMD  24 , such that the secondary signal transmitter  12  emits the invisible light signal directly through the lens  26  without being reflected by the DMD  24 .  
         [0019]     Embodiments of the invention provide various benefits. One such benefit is that viewers of the same video in the same room can listen to different soundtracks, depending on their preferences. This benefit is best achieved where the receivers  16  are headphone sets  16   a.  Further, where the system is used to implement a surround sound system, the speakers used to implement the system can communicate with the audio source wirelessly. Reflecting the secondary signal off of the screen  14  provides a greater likelihood that the receivers  16  will receive the secondary signal, as there is a greater likelihood that there will be a clear path between the screen  14  and the receivers  16  than between the projection device  10  and the receivers  16 . Other benefits of various embodiments of the invention will be recognized by one skilled in the art.  
         [0020]     While the present invention has been particularly shown and described with reference to the foregoing preferred and alternative embodiments, it should be understood by those skilled in the art that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. The foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application. Where the claims recite “a” or “a first” element of the equivalent thereof, such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Further, the use of the words “first”, “second”, and the like do not alone imply any temporal order to the elements identified. The invention is limited only by the following claims