Television – Stereoscopic – Stereoscopic display device
Reexamination Certificate
1997-08-12
2002-04-23
Kelley, Chris (Department: 2613)
Television
Stereoscopic
Stereoscopic display device
C359S463000
Reexamination Certificate
active
06377295
ABSTRACT:
The present invention relates to an observer tracking directional display. Such a display may be used as a three dimensional (3D) autostereoscopic display, for instance in 3D television, medical imaging, computer games, telephony, scientific visualisation, virtual reality and office automation equipment.
Observer tracking 3D autostereoscopic displays are disclosed in EP 0 721 131 and EP 0 726 482. These patents are primarily concerned with displays in which observer tracking is achieved in arrangements with no moving parts. However, reference is made to the possibility of using mechanical tracking arrangements.
EP 0 625 861 discloses a spatial light modulator (SLM) of liquid crystal device (LCD) type having a picture element (pixel) configuration which is particularly suitable for use in autostereoscopic displays. In particular, this configuration allows contiguous display windows to be produced and enhanced horizontal display resolution to be achieved. European Patent Application No. 96304959.8 discloses a technique for making SLMs having such a pixel configuration.
“An in-cockpit “situation awareness” autostereoscopic avionics display”, J. B. Eichenlaub, T. Touris, SPIE vol. 2219 “Cock-pit Displays” 1994 pages 395 to 406 discloses an observer tracking system for a flat panel display in which viewing windows are switched between discrete positions by switching a light source. However, such an arrangement has a number of disadvantages. For instance, switching takes place so that one light source has to be switched off while another is switched on. If this is not done accurately or if there is a decay of the phosphors of the lamps, the display will appear to become brighter or darker during switchover, thus causing significant image flicker. Also, the intensities of the light sources must be matched in order to avoid unwanted image flicker which would be visible as an observer moved position. Further, if a large number of individual positions is required, then a large number of lamps will be required, thus increasing the display cost and-bulk. Additionally, an arrangement for mechanically translating a lenticular screen to allow observer tracking is disclosed.
EP 0 404 289 discloses a 3D display in which an observer is tracked by moving a curved lenticular screen with respect to an image display. The lenticular screen can be moved laterally and longitudinally so as to track observer movement. However, no details of tracking are disclosed.
“Eye-position tracking stereoscopic display using image shifting optics”, H. Imai et al, SPIE vol. 2653, (1996) pages 49 to 55 discloses an arrangement in which an image is projected onto the rear of a lenticular screen and is tracked with respect to the screen by moving the projection optics in accordance with the measured position of an observer.
U.S. Pat. No. 5,264,964 discloses a display which is switchable between autostereoscopic and stereoscopic modes of operation by means of mechanical movement.
A known type of autostereoscopic 3D display uses a single display panel, such as a liquid crystal device spatial light modulator, on which several two dimensional (2D) reviews are spatially multiplexed. Vertical slices of the 2D views are interleaved and a parallax optic is used to allow the views to be seen in the intended directions. This creates “viewing windows” as described in more detail hereinafter. The spatial resolution, especially the lateral or horizontal resolution, of the panel has to be shared among the 2D views so that, for N 2D views, each view is displayed with a (horizontal) resolution of R×N, where R is the (horizontal) spatial resolution of the panel. For a large number of 2D views, the (horizontal) resolution has to be sacrificed and/or a panel of higher (horizontal) resolution and hence cost must be used.
Some observer tracking displays of this type require that the viewing windows be repeated in several lobes. This requires that the optical performance, such as aberrational and diffractional performance of the display, particularly of the parallax optic, be sufficient to avoid undesirable visual artefacts from being visible in non-zero lobes.
Some observer tracking displays of this type require good window performance. For instance, to avoid visible variations in intensity or flicker as the observer moves, the intensity may vary laterally across a large part, or even all, of the window by only a relatively small amount. Also, the window edge performance may be critical to avoiding undesirable visual artefacts. For instance, it may be necessary for the windows to be accurately contiguous with minimal overlap and underlap. This can place stringent physical requirements, for instance on the manufacturing tolerances of the components such as the panel and on the accuracy of assembly and alignment of the components.
For some applications, mechanical tracking systems, ie: tracking system with moving parts, may have advantages over non-mechanical systems, ie: systems without moving parts. For instance, in mechanical tracking systems, it is possible to use only two viewing windows in a single lobe, such as the zero order lobe where optical performance is best. For spatially multiplexed single panel displays, this minimises the loss of resolution for each 2D view compared with the spatial resolution of the panel so that lower resolution (and less expensive) panels may be used or the resolution of the 3D image may be improved. The use of only one lobe allows the optical performance requirements of the parallax optic to be relaxed so that a less expensive parallax optic may be used. Because the windows track the observer position, contiguity of the windows may not be necessary and low variation in intensity may be required across only a smaller part of each window. This reduces the physical requirements and the cost of the display.
Although mechanically tracked systems have been suggested, for instance as mentioned hereinbefore, the practical problems of realising such systems have not previously been considered or addressed. For instance, all mechanical tracking systems will have inertia. Thus, although the delays involved in measuring the observer position will be common to all observer tracking displays, the time between detecting a new observer position and causing the display to move the viewing windows to the desired new position is inherently longer for a mechanically tracked system than for a non-mechanical system. Also, there will be backlash in many types of mechanical system resulting in reduced accuracy of positioning of the viewing windows.
According to the invention, there is provided an observer tracking directional display comprising an image display, a parallax device co-operating with the image display to define at least one viewing zone from which the image display is visible, and an observer tracker for determining the position of an observer, characterised by an electromechanical system responsive to the observer tracker for moving the parallax device relative to the image display to any one of a plurality of discrete stationary positions so that the viewing zone tracks the position of the observer.
The mechanical system may be arranged to provide, at least for an observer at a predetermined longitudinal distance from the display, a number n of discrete stationary positions of viewing windows per interocular distance e given by:
e
≡
Vmax.
t+&Dgr;x
where Vmax is the maximum lateral observer speed for the display, &Dgr;x is the lateral position error of the observer tracker and t is the time delay between measurement of an observer position and completion of relative movement between the parallax device and the image display to track an observer movement.
The electromechanical system may be arranged to provide, for an observer at at least one longitudinal distance from the display different from the predetermined distance, a number n′ of discrete stationary positions of viewing windows per interocular distance greater than n.
The display may be for three dimensional autostereoscopic viewin
Ezra David
Moseley Richard Robert
Woodgate Graham John
Kelley Chris
Philippe Gims
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