Patent Publication Number: US-2011062790-A1

Title: System  for wirelessly powering three-dimension glasses and wirelessly powered 3d glasses

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Ser. No. 61/241,702, filed Sep. 11, 2009, the entire contents of which are hereby incorporated by reference herein for all purposes. 
    
    
     TECHNICAL FIELD 
     Embodiments herein relate to a system for wirelessly powering and controlling a pair of shutter glasses for viewing three-dimensional images, films, games and various video content. 
     INTRODUCTION 
     Stereoscopy is a technique creating an illusion of depth out of two-dimensional images, also called “third dimension” or 3D. The illusion of third dimension is created by taking images at different angles, and presenting those images independently to each eye. Generally, there are two stereoscopic techniques: a passive configuration and an active configuration. 
     The passive configuration uses linearly or circularly polarized three-dimensional (3D) glasses to create the illusion of 3D images by restricting the light that reaches each eye. To present a stereoscopic movie, two images are superimposed onto a screen using orthogonal polarizing filters. Projecting two superimposed images simultaneously requires two projectors, which results in higher costs. Because of the prohibitive costs, the passive configuration is not widely used for 3D home theater systems. 
     The active configuration uses Liquid Crystal Shutter (LCS) glasses and alternates the right and left eye shutters in a rapid succession so as to present each of the images in successively to a corresponding eye. Generally, the active configuration provides a higher resolution and a wider viewing angle than the passive configuration. Although active 3D glasses are more complex and expensive than passive 3D glasses, the overall cost of a 3D imaging system based on the active configuration is usually less expensive as only one projector is required. Furthermore, active configuration systems can be used with standard computer and TV screens. Thus, the active 3D glasses and corresponding 3D imaging systems are more attractive for 3D home theater systems. 
     Typical 3D glasses are powered by means of batteries or a wired DC power supply. However, such powering means are inconvenient for users of 3D glasses. The batteries need to be replaced or charged at certain intervals, and replacement of batteries or charging while viewing a 3D movie is not particularly convenient. Use of a wired DC power supply is also not generally desirable, as it requires proximity to an electric outlet. Furthermore, the electric wire has a non-negligible weight which tends to make wearing 3D glasses less comfortable. 
     The inventors have therefore identified a need for a 3D glasses and systems for 3D imaging that attempt to alleviate at least some such power problems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the present description, the following drawings are used to describe and exemplify the present system and 3D glasses, where like numerals denote like parts. 
         FIG. 1  is an exemplary schematic representation of a rectenna. 
         FIGS. 2A to 2E  are representations of 3D glasses and variants of antennas. 
         FIG. 3A  is a schematic representation of a system for wirelessly powering 3D glasses in accordance with an infrared control scheme. 
         FIG. 3B  is a schematic representation of a system for wirelessly powering 3D glasses in accordance with a duplex control scheme. 
         FIG. 3C  is a schematic representation of a system for wirelessly powering and controlling 3D glasses with two rectennas. 
         FIG. 4  is a table defining transmitter and receiver requirements for different controlling schemes. 
         FIG. 5  is an exemplary schematic representation of a rectenna including a duplexer. 
     
    
    
     DETAILED DESCRIPTION 
     The present embodiments propose a system and 3D glasses that tend to alleviate the problems encountered with current powering means. More particularly, the present system and 3D glasses describe wirelessly powering 3D glasses, and wirelessly powering and controlling 3D glasses. 
     To this end, one present system comprises a wireless powering device and a rectenna. The wireless powering device generates and transmits a wireless power signal, and the rectenna is integrated within the 3D glasses for receiving the wireless power signal and converting it into direct current or “DC” for powering the 3D glasses. 
     In another aspect, the powering device further generates and transmits a wireless power and control signal, and the rectenna receives the wireless control and power signal and converts it into direct current for powering and controlling the 3D glasses. 
     In another aspect, the present 3D glasses comprise a frame, a pair of Liquid Crystal Shutters (LCSs) supported by the frame, and a rectenna for receiving a wireless power signal and transforming the wireless power signal into direct current for powering the 3D glasses. 
     Wireless Power Transmission 
     In the past few decades, wireless and contactless powering and wireless power transmission have been introduced. Applications for radio and microwave power transmission (hereinafter referred as wireless power transmission) have been proposed for helicopter powering, solar-powered satellite-to-ground transmissions, inter-satellite power transmissions including utility power satellites, mechanical actuators for space-based telescopes, small DC motor driving, short range wireless power transfer as well as low-power near-field interrogation with RFID tags, and medium- and low-powering density powering of low-power sensors. 
     Wireless power transmission is accomplished by receiving incident waves (wireless power) by means of an antenna and rectifying the received incident waves to output a corresponding direct current (DC) voltage. Integration of a receiving antenna and a rectifier is referred to as a “rectenna”. 
     Rectenna 
     Reference is made to  FIG. 1 , which depicts an exemplary schematic representation of a rectenna. This exemplary rectenna  100  includes an antenna  102 , a matching network  104 , a band-pass filter  106 , a rectifying circuit  108  and a DC pass filter  110 . The antenna  102  receives a wireless power signal and the rectifying circuit converts the received wireless power signal to direct current electric power (DC voltage). 
     The received wireless power signal is attenuated by free-space path loss, and the amount of power that can be transmitted wirelessly is limited for security and safety reasons by regulations, such as Safety Codes on limits for human exposure to radiofrequency (RF) fields. 
     Other similar designs of rectennas  100 , including at least an antenna and one or several rectifying circuits could be used without departing from the scope of the present embodiments. 
     The rectenna  100  is to be installed on 3D glasses. For comfort and aesthetic reasons, the 3D glasses are normally of a small dimension or size. In turn, this normally means that the antenna  102  of the rectenna  100  will be of a small dimension or size. This results in a small physical antenna area, which favors the choice of higher frequency for more efficient power collection. 
     The band-pass filter  106  (inserted between the antenna  102  and the rectifying circuit  108  and depicted by a single diode on  FIG. 1 ) is designed so that a fundamental frequency or narrow band of frequencies is allowed to pass, while other frequencies received by the antenna  102  are rejected effectively. 
     The band-pass filter  106  further suppresses a significant portion of higher order harmonics generated by the rectifying circuit  108 . The rectifying circuit  108  may consist of a single diode shunt or any other similar component adapted to passively convert an alternating signal into DC voltage. 
     In some embodiments, power conversion efficiency may be maximized by substantially confining all higher order harmonics between the band-pass  106  filter and the DC pass filter  110 , using an efficient diode  108  and matching the diode&#39;s input impedance to the antenna  102  impedance by means of the matching network  104 . The DC pass filter  110  blocks remaining fundamental and harmonic frequencies, and thus ensures that no oscillating signal exits the DC pass filter, and only a DC voltage is outputted. The power conversion efficiency of the diode  108  changes as the operating power level changes. Thus the power conversion efficiency of the rectenna  100  varies with the received wireless power signal. 
     Although not shown in  FIG. 1 , in some embodiments the rectenna  100  could further include two parallel band-pass filters  106 , two rectifying circuits  108  and two DC pass filters  110  to simultaneously receive and convert wireless power signals of different frequencies. Each frequency of the wireless power signal could then power and control one of the Liquid Crystal Shutters (LCSs) of the 3D glasses. 
     Other variants could further be applied to the rectenna  100 . For example, two polarizations of the wireless power signal could each correspond to one of the LCSs, and the rectenna  100  could be adapted to separate the polarized components of the wireless power signal to power a corresponding LCS. 
     Thus, the rectenna  100  is generally not limited to receiving a wireless power signal, but may also be adapted to receive a wireless power and control signal. 
     Many variants may be applied to the rectenna  100  for optimization purposes. Those skilled in the art of Radio Frequencies and Radio Frequency circuit designs will note that the rectenna of  FIG. 1  is a simplified schematic circuit to which many improvements can be introduced without departing from the scope of the present embodiments. 
     3D Glasses 
     As the 3D glasses must normally have a shape and size that are ergonomic and aesthetic, integration of the rectenna  100 , and more particularly the antenna  102  of the rectenna, within a frame of the 3D glasses requires particular consideration. To increase the amount of wireless power signal or wireless power and control signal, the antenna  102  will be preferably integrated in the frame surrounding the LCSs. 
     Such integration is not essential for proper functioning of the 3D glasses, but is recognized as having many advantages. By integrating the antenna  102  around the LCSs, it is possible to be in a quasi-line of sight with the transmitted wireless power signal or wireless power and control signal. Such quasi line of sight tends to increase the power of the received signal, and thus enables generation of more DC voltage. As the received signal is of better quality with less loss, it further allows for reduced transmission power of the wireless power signal or wireless power and control signal. Such advantages are interesting to ensure sufficient wireless power transmission with lower transmission power. 
     Although integration of the antenna  102  around the LCSs has been described, several other alternatives could be considered. The antenna  102  could be added to any portion of the frame of the 3D glasses, or could further be located outside of the frame and be a separate component to the frame. 
     Various types of technologies, materials, substrates, shapes and designs may be used to implement the antenna  102  and the rectenna  100  on the 3D glasses. For example, low-temperature co-fired ceramic (LTCC) technology, used for radio and microwave applications may be used. Three-dimensional (3-D) integration capabilities of LTCC enable size-reduction and low-cost design. Another advantage of LTCC technology resides in its low dielectric loss tangent, which makes it an interesting choice for medium and high frequency applications. 
     Reference is now made to  FIG. 2A , which shows the 3D glasses  200 . As can be appreciated, the 3D glasses  200  are designed so as to have a shape to be comfortably worn by a viewer, without being too bulky or heavy. The rectenna  100  is incorporated to a frame  202  of the 3D glasses  200 . 
       FIG. 2B  depicts an exemplary side view of a multi-layered LTCC-based structure.  FIGS. 2C to 2E  depict examples of rectenna  100  and layers to be implemented in the frame  202 . More particularly,  FIG. 2C  corresponds to a top view of a square loop antenna.  FIG. 2D  depicts a solid ring ground plane, while  FIG. 2E  represents an exemplary meshed ring ground plane. 
     Depending on the control scheme selected, one or two antennas  102  and one or two rectennas  100  may be integrated in the frame  202  of the 3D glasses to either power or power and control the LCSs. 
     System for Wirelessly Powering 3D Glasses 
     Reference is concurrently made to  FIGS. 1 ,  2  and  3 A, where  FIG. 3A  is a schematic representation of a system for wirelessly powering 3D glasses in accordance with an infrared control scheme. The system  300  comprises a wireless powering device  306 , a transmitting antenna  308  and wirelessly powered 3D glasses  200 . The system  300  is adapted to be used with a 3D reading device  302 , a control unit  303  and a screen  304 . 
     The 3D glasses  200  include a pair of LCSs  312  and  314 , which are to be actuated in synchronicity with images displayed on the screen  304 . The synchronizing information to be applied by the 3D glasses  200  to synchronize with images presented on the screen  304  may be stored or otherwise provided using the same medium as the images to which it is to be applied. For movies, for example, the synchronization information may be extracted by any of the following reading devices  302 : an active 3D home theater amplifier, an active 3D DVD reader, a 3D active Blu-ray reader, a video synchronization control box, or any other type of device adapted to extract synchronization information from a 3D movie or image to be presented. 
     Examples of mediums on which the 3D image(s) or movie and synchronization information may be stored include: Digital Video Disks, Blu-Ray disks, a computer, or any other type of medium on which three-dimensional images, and movies may be stored. 
     The reading device  302  outputs a signal to be ultimately displayed on the screen  304 . The screen  304  may consist of a plasma screen, a Liquid Crystal Display, a Light Emitting Diode screen, a projected image from a video projector or any other type of screen having sufficient definition and refresh rate to support three-dimensional images and movies. 
     The control unit  303  may be integrated within the reading device  302 , or be in addition thereto. The control unit  303  receives the synchronization information and generates therefrom a control signal to be sent to the 3D glasses  200  by wire, infrared or wirelessly. 
     The 3D glasses  200  receive the control signal and accordingly control shuttering of the LCSs  312  and  314  following the control scheme of images presented on the screen  304 . Thus each eye sees only the appropriate image, and 3D effect can be achieved. More particularly in the present aspect, the control signal is an infrared signal emitted by the control unit  303  and received by a controlling unit  310  of the 3D glasses  200 , which accordingly actuates each one of the pair of LCSs  312  and  314 . 
     Instead of relying on batteries or a DC power adapter, the present 3D glasses  200  use a wireless power signal and a rectenna  100 . The control unit  303  further outputs a signal to actuate the wireless powering device  306  when a 3D image is to be presented on the screen, and deactivate the wireless powering device  306  when reading of the 3D images or movies is interrupted. 
     When actuated, the wireless powering device  306  generates a wireless power signal transmitted to the 3D glasses  200  by means of the transmitting antenna  308 , and received by the rectenna  100 . The rectenna  100  receives the wireless power signal and transforms it into a DC voltage to power the 3D glasses  200 . 
     The wireless powering device  306  and transmitting antenna  308  may operate within various frequency bands, such as Industrial, Scientific and Medical (ISM) frequency bands, 900 MHz, 2.4 GHz and 5.8 GHz. The selected frequency band depends on propagation properties, the rectenna antenna  102  size and gain, and safety regulations for radio frequencies power levels. 
     Reference is now made concurrently to  FIGS. 2 and 3B  and  5 , where  FIG. 3B  is a schematic representation of a system for wirelessly powering 3D glasses in accordance with a duplex control scheme, and  FIG. 5  is an exemplary schematic representation of a rectenna comprising a duplexer. In this aspect, the two LCSs  312  and  314  function using the same polarization, but a distinct frequency is assigned to each LCS. 
     When a first LCS  312  is to be activated, the wireless power signal is generated on the corresponding frequency of the LCS to be activated. When the other LCS  314  is to be activated, the wireless power signal is generated on the other frequency. In this aspect, the rectenna  100  further comprises a duplexer  320  with two parallel circuits, where each circuit corresponds to one specific frequency, as shown on  FIG. 5 . 
     Thus, the control unit  303  communicates solely with the wireless power device  306 , which generates a wireless power. The wireless power is then provided to the transmitting antenna  308 , which wirelessly transmits the wireless power signal. The wireless power signal is received by the rectenna  100 . Instead of a single band-pass filter as shown on  FIG. 1 , the duplexer  320  includes two band-pass filters  106   a  and  106   b , each corresponding to one of the two frequencies. Thus depending on the frequency received, a corresponding path of the rectenna will be functional. Each path of the rectenna  100  powers one of the two LCS  312  or  314 . 
     Reference is now made to  FIGS. 1 ,  2  and  3 C, which show a schematic representation of a system for wirelessly powering and controlling 3D glasses with two rectennas. In this particular aspect, the control unit  303 , the wireless power device  306  and the transmitting antenna  308  function similarly to the previously described aspect. In this aspect, however, the 3D glasses  200  however include two independent rectennas  100 . Each rectenna  100  powers a corresponding LCS  312  and  314 . The wireless power device  306 , the transmitting antenna  308  and the rectennas  100  may use different frequencies, with each rectenna&#39;s antenna resonating at a different frequency, or different polarizations at the same frequency or a combination of both to power each of the LCS  312  and  314 . 
     Reference is made to  FIG. 4 , which provides a table defining transmitter (control unit  303 ) and receiver requirements (controlling unit  310 ) for different controlling schemes. Transmitter and receiver requirements depend on the type of control scheme used to present the image(s) and movies. 
     Three examples of control schemes are provided in  FIG. 4 . For each control scheme, the main corresponding transmitter and receiver requirements are provided. The polarization scheme uses a single frequency for controlling both LCSs, with different polarization states, i.e. horizontal and vertical polarizations or right hand and left hand circular polarizations, to turn on and off the LCSs in alternance. 
     The duplexer scheme uses two separate frequencies at the transmitter and a duplexer at the receiver, where each frequency controls one LCS. 
     The infrared (IR) control scheme uses an IR emitter in the transmitter and an IR sensor in the receiver. The IR emitter is connected to the control unit  303  while the IR sensor controls a controlling unit  310  to turn on/off proper LCS of the 3D glasses. Other variants and combinations based on the described embodiments can be anticipated by those skilled in the art. 
     The present invention has been described by way of preferred embodiments. It should be clear to those skilled in the art that the described preferred embodiments are for exemplary purposes only, and should not be interpreted to limit the scope of the present invention. The 3D glasses and systems as described in the description of preferred embodiments can be modified without departing from the scope of the present invention. The scope of the present invention should be defined by reference to the appended claims, which delimit the protection sought