Abstract:
A pair of stereoscopic eyewear includes an element for integral assembly with the eyewear including a conductive circuit trace. The conductive pattern provides electrical contact between a contact area of the frame (which is hardwired to an electrical cable) and the contact pads of the liquid crystal shutter pair. Preferably, a conductive elastomer is used to facilitate the electrical contact to the shutters and the frame. Additionally, each wire of the cable is terminated with a fixed electrical contact adapted to securely mate with a slot in the frame that correspond to the contact area. A lens assembly attaches to the frame to rigidly hold the frame, the shutters and the conductive trace in intimate juxtapostion.

Description:
BACKGROUND OF THE INVENTION 
     The time-multiplexed technique for viewing electronic stereoscopic images is now a standard viewing modality for computer graphics and video. During the past decade, electro-stereoscopic displays have become a well-established means for viewing images on workstations in applications such as molecular modeling and various types of scientific visualiztion. In addition, video systems for various applications such as medical imaging have had some success in the marketplace. Lately, the application of time-multiplexed displays for the mass consumer personal computer market has been attempted with mixed success. 
     All of these systems use liquid crystal (“LC”) shuttering eyewear for viewing stereoscopic images, such as CrystalEyes® eyewear or SimulEyes® eyewear, both manufactured by StereoGraphics Corporation of San Rafael, Calif. Various aspects of these products are described in the following patents: U.S. Pat. No. 4,884,876 entitled “Achromatic Liquid Crystal Shutter For Stereoscopic And Other Applications;” U.S. Pat. No. 4,967,268 entitled “Liquid Crystal Shutter System For Stereoscopic And Other Applications;” U.S. Pat. No. 5,117,302 entitled “High Dynamic Range Electro-Optical Shutter For Stereoscopic And Other Applications;” U.S. Pat. No. 5,181,133 entitled “Drive Method For Twisted Nematic Liquid Crystal Shutters For Stereoscopic And Other Applications; U.S. Pat. No. 5,463,428 entitled “Wireless Active Eyewear For Stereoscopic Applications;” and U.S. Pat. No. 5,572,250 entitled “Universal Electronic Stereoscopic Display.” 
     LC shuttering eyewear for the mass consumer market must be manufactured at the lowest possible cost of goods in order to compete in what is essentially a commodity marketplace. Therefore, it is vitally important for the manufacturer of such eyewear to obtain every cost cutting competitive advantage in order to prevail in the marketplace. Such means are the subject of this disclosure. 
     SUMMARY OF THE INVENTION 
     The present invention is an apparatus and corresponding method for reducing the cost of manufacture of stereoscopic eyewear. The apparatus includes several features which lower the manufacturing cost by reducing the labor content and by providing an appropriate housing for the electronic components. One feature reduces assembly time by eliminating a complex wiring harness and the need to make individual connections. Another feature includes the driver electronics within the wired eyewear itself rather than within a cable or an adapter. 
     The apparatus includes a pair of liquid crystal shutters each having a contact pad for receiving electrical drive signals and a frame having a pair of eye openings therein suitable for receiving the shutters. An electrical cable is incorporated with the frame. The cable has a plurality of wires for providing drive signals to the shutters. Each wire has its end terminated with a fixed electrical contact. The frame includes an electrical contact area which includes a portion adapted to securely receive the electrical wire contacts. A conductive circuit trace is formed on an insulating material; which may be the frame or the lens assembly, or a separately added mask. The lens assembly attached to the frame to rigidly hold the frame, the shutters and the conductive trace in intimate juxtaposition. 
     In a preferred embodiment, conductive elastomers are used to provide electrical contact between portions of the conductive trace and the shutter contact pads and/or the electrical contact area of the frame. 
     In another embodiment, a printed circuit board is incorporated at the contact area of the frame. The printed circuit board is adapted to condition the drive signals to appropriately drive the liquid crystal shutters, thereby eliminating the need for a separate driver circuit external to the eyewear. 
     Many useful variations will be obvious to one with skill in this technology upon considering the following detailed description and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view showing a conventional pair of shuttering eyewear. 
     FIG. 2 is an exploded perspective view showing a pair of shuttering eyewear constructed in accord with the present invention. 
     FIG. 3 is a top plan view of a portion the eyewear of FIG. 2 taken across section  3 — 3 . 
     FIG. 4 is a top plan view of a portion the eyewear of FIG. 2 taken across section  4 — 4 . 
     FIG. 5 is a front plan view of the mask portion of FIG. 2 showing conductive traces. 
     FIGS. 6 a  and  6   b  are block diagrams showing typical applications with shuttering eyewear. 
     FIG. 7 is a front plan view of an alternative embodiment of the frame portion of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows the construction of a conventional pair of stereoscopic eyewear. Hinged earpieces  101  and  102  and frame  103  are formed of molded plastic and snapped together in a well known manner. Cable  109  includes three conductors that are electrically attached to contact pads  107   a  and  100   a  on liquid crystal (“LC”) shutters  107  and  108 , respectively. A mask  106 , preferably made of opaque paper or plastic material with cutouts for the shutters, is placed over the shutters  107  and  108  and frame  103  thereby effectively hiding from view the internal details of the assembly. The shutters  107  and  108  are held in place by a plastic lens  105 , and the whole assembly is secured together by trim piece  104  with provision for integral snaps or the like. 
     The assembly of these eyewear is relatively simple, fast and economical, with the exception of the electrical connection between the cable  109  and the shutters  107  and  108 . Thus, the real problem in producing the eyewear is the method of connecting the wires to the shutters. 
     A direct connection could be made by soldering the wires directly to the contact areas  107   a  and  108   a.  However, soldering must be done very carefllly to avoid damaging the shutter. Also, soldering takes too much time and the shutter remains quite hot afterwards. For these reasons, it is impractical to solder the wires onto the shutters as the eyewear final assembly is taking place. 
     Another method of attaching the wires is to use an electrically conductive adhesive to bond the wires to the contact pads. This is also not practical at final assembly as the adhesive takes a long time to cure. The soldering or gluing could be performed in a separate step prior to assembly, requiring only the placement of a combined cable/shutter assembly into the frame. However, this is impractical due to the delicate and time consuming handling required for the cable/shutter assembly. 
     Yet another method would be to include pins attached to the shutter contact pads and solder the wires to the pins. This is undesirable due to the additional space required. The eyewear would either have to be thicker or larger to make a space available for this soldered wire connection. One practical solution to this problem is to crimp a small metal clip onto the end of each conductor. This can be easily done in a preparatory step. Then, the clips simply slide onto the contact pad areas at final assembly. 
     What remains in this case and in all previously described methods is a wire management problem. The space around the shutters is limited. The wires need to be carefully controlled to pass them through the available channels and avenues between the frame and lens. The wires are wont to bend and move out of their assigned places as soon as they are released. It can be tedious and difficult to get everything aligned properly and the assembly completed. Such an assembly means does not lend itself to the requirements of mass production. 
     An improvement over the prior art is shown in FIG.  2 . In this case, the earpieces  201  and  202 , frame  203 , trim piece  204 , lens  205 , mask  206 , and shutters  207  and  208  are like those in FIG.  1 . Additional features of this embodiment are now shown and described, including the treatment of the ends of the wires in cable  209 , the addition of conductive elastomers  210  and  211  to facilitate electrical contact with the LC shutters  207  and  208 , respectively, and the inclusion of printed conductive traces on mask  206  (as shown in FIG..  5 ). 
     As before, the mask  206  is an opaque material having two cutouts for the shutters. A primary purpose of mask  206  is to hide the wires and contact areas of the shutters. The mask fills the entire area of lens  205  for cosmetic purposes, creating a smooth and continuous surface visible through the lens. 
     As shown in FIG. 5, mask  206  includes a pattern of conductive circuit traces formed on a surface of mask  206 . For example, a conventional spring contact pad  215  is connected by conductive trace  216  to elastomer contact pad  217 , which is simply a flat, rectangular printed contact area A second spring contact pad  218  is connected by conductive trace  219  to elastomer contact pads  220  and  221  (common line to both shutters). A third spring contact pad  222  is connected by conductive trace  223  to elastomer contact pad  224 . These conductive traces are easily and inexpensively printed onto a plastic mask by conventional methods using conductive inks. 
     The mask and shutter are thus arranged so that conductive elastomer  210  makes electrical contact with the shutter contact pad  207   a  and the elastomer contact pattern areas  217  and  221 , while conductive elastomer  211  makes electrical contact with the shutter contact pad  208   a  and the elastomer contact pattern areas  220  and  224 . 
     Advantageously, the conductive traces are routed to one side of the mask  206  where they terminate at spring contact pads  215 ,  218  and  222 . These spring contact pads  215 ,  218  and  222  contact respective spring pins  213  that have been crimped onto the wires. 
     It should be obvious to one skilled in this technology that many different routes or constructions of conductive patterns could be implemented to provide a suitable electrical interconnection with the LC shutters. In addition, the conductive patterns could conceivably be incorporated on other portions of the assembly, for example, on the frame. 
     FIG. 3 is a more detailed illustration of the area where the shutters are located. In this Figure, only the left eye assembly (as viewed by the user) is shown, but it is recognized that the right shutter area will have the same construction. In assembly, the lens  205  presses the mask  206  onto elastomer  211 , which is located over the contact pad area  208 a of shutter  208 , thereby making electrical contact between the conductive patterns printed on the mask and the LC shutter. The lens  205  is seated in a pocket (not shown) in frame  203 . 
     The elastomer  211  is a “zebra” type elastomer made from alternating layers of conducting and insulating materials in a well known manner. This type of elastomer is common for use with liquid crystal displays (“LCD&#39;s”), allowing one elastomer to bridge contact with several circuits. 
     FIG. 4 shows additional detail of the area where the wires are terminated. Here the lens  205  presses the mask  206  into spring clip  213 , such as Molex part number 08-50-0114, which has been crimped onto the end of each wire in cable  209 . This Molex clip is simple, reliable, inexpensive, and easily attached to the wire prior to final assembly. The clip is inserted into a retaining slot  214  in frame  203  (see FIG. 2) where it is held up against the mask  206  and lens  205 . 
     FIG. 6 a  shows a typical application of the eyewear described in this disclosure. Source  401  is usually a computer but may be any source of time-multiplexed stereoscopic images. Driver electronics  402  are connected to the source  401  at connector  403 , which contains a synchronizing signal and power for the driver circuitry. There are several connectors currently in use. The preferred connector is a 3 pin mini-DIN circular receptacle. Other suitable connectors include the 3.5 mm stereo phone jack and the 9 pin sub-miniature “D” socket. Eyewear  404  is connected to driver electronics  402 , which is a separate electronics package in a separate housing. The driver electronics  402  converts the supplied power and synchronizing signals into the shutter drive voltages required by the eyewear. 
     FIG. 6 b  shows an alternate approach. Eyewear  404  connect directly to the source  401  at connector  403  and do not require a separate driver electronics unit. Instead, the functional part of the driver electronics are constructed in as small a volume as possible and are included in an overmolded circuit board  406  inserted at a point along the cable, typically at the source connector end. Thus, the electronics become part of the cable. The other end of the cable attaches to the shutters within eyewear  404  using the methods as shown in FIG. 2, for example. 
     An improvement to the circuit arrangement of FIG. 6 b  is shown in FIG.  7 . Frame  303  includes an area to accept circuit board  350 . Circuit board  350  is electrically connected to the wires of cable  309 . The circuit board  350  converts the supplied power and synchronizing signals into the required shutter drive voltages. Contact pad area  351  is typical of the three contact pad areas that make contact with an elastomer and an appropriate mask, as previously described, to route the signals to the shutters. The circuit board  350  with cable  309  attached can be assembled and tested as a separate unit and installed quickly and easily at final assembly. Thus, a subassembly known to be operational is installed thereby reducing the probability of failure of a completed unit. Cost reduction is possible with this method compared with the prior art because there is no need to build a separate housing with electronics. Cost is saved by placing the LC drive electronics within the eyewear itself. 
     An alternative embodiment uses the same construction technique shown in FIG. 7, wherein the cable is soldered to a circuit board mounted in a convenient region of the frame  203 , and the circuit board connects via one or more elastomers using techniques described earlier to the mask  206 , thereby creating eyewear compatible with that shown in FIG.  1  and FIG.  2 .