Optics: image projectors – Stereoscopic
Reexamination Certificate
2001-02-20
2004-05-18
Adams, Russell (Department: 2851)
Optics: image projectors
Stereoscopic
C353S010000, C359S011000, C359S020000, C359S023000, C359S462000, C345S088000, C345S090000, C352S057000, C352S203000, C349S007000, C349S008000, C348S051000
Reexamination Certificate
active
06736512
ABSTRACT:
TECHNICAL FIELD
The object of the invention is a pixel element for a three-dimensional screen. The pixel element of the invention comprises means for generating multiple substantially collimated, controllable light beams. These light beams are emitted in multiple directions, so that each light beam is associated to a predetermined viewing direction.
BACKGROUND ART
Various methods and devices have been suggested to achieve a true three-dimensional image (3D image). The underlying principle of all true 3D methods is the same. If a plane—two-dimensional—image is displayed on a surface, then every point of the surface emits or reflects light with approximately same intensity (and colour) in all directions. This is the working principle of a traditional picture, like a postcard (reflection) or a traditional TV-image (light emission). In the case when a three-dimensional image is presented, the emitted light has a different intensity (and colour) in the different directions, even if it is emitted from the same point. We may regard in this way a window pane or a hologram as a display. Hence, in order to display a three-dimensional image, there is needed a light emitting surface where the intensity (and colour) of the light emitted from a single image point (pixel) may be controlled as the function of the emission angle (exit angle), with other words, the intensity of the light emitted in the different directions may be controlled.
In order to produce true or realistic three-dimensional images, two technical problems must be solved. Firstly, a large number of light beams must be projected in the different directions in space, with the appropriate intensity/colour, which allow the viewer to see different perspectives from different viewpoints. Secondly, means must be provided to allow the feeding of the necessary data to the light sources generating the light beams. This second problem involves difficulties when video images (i.e. moving images) must be displayed, because large amounts of data (kB/s) must be forwarded into each (!) image point or pixel. Obviously, a true 3D video image providing n different viewing directions require n times the data amount of a normal video image.
There are many known technical solutions that addresses the problem of the directed light beams. The Hungarian Patent application published under No. T/63 503 discloses two methods for the presentation of three-dimensional images.
In a first version, a modulated laser beam is subjected to deflection which is controlled in time. The deflection is performed before the image pixels, according to the directions defining the viewing range. In this manner the modulated laser beam enters the image pixel deflected with an angle, the beam is parallel translated. From the image pixel the laser beam propagates with an optical deflection corresponding to the view range, or propagates further in different directions within the viewing range without further deflection. A disadvantage of this solution is that the laser beam must be focused and positioned very precisely, because the entry point of the laser beam within the image pixel defines the direction of the exiting laser beam.
In the second version, the modulated laser beam enters an image pixel in the same entry point, without deflection, and it is deflected towards the different viewing angles within the image pixel, with the help of a controllable active optical element positioned in the image pixel. The deflection of light beam with the angle-dependent intensity is performed by the active optical element. The advantage of the solution is that the positioning and focusing of the beam need not be very exact, but the active optical elements make the device extremely expensive. Also, the problem of the feeding of the data to the active pixels is not discussed.
In other known methods, in order to display true 3D images, two surfaces are used, where the first front surface is a surface with a controllable light transmission, and the second back surface is an illuminating surface comprising light sources. One point of the back surface and one point of the front surface defines unequivocally a direction. With a possible embodiment, the image is created on the back surface by controlling the intensity and/or colour of the light sources, while on the first surface only masking is performed according to the selected viewing directions, by switching the image pixels on and off. With an other possible embodiment, the light sources on the back surface are continuously on, or they are only switched on or off, while the controlling according to the image information is made on the first surface. The first surface comprising the image pixels with controllable light transmission is preferably an LCD display.
Such solutions utilising an LCD display are disclosed, among others, in the documents EP 0 316 465 and U.S. Pat. No. 5,132,839. Here, illuminated strips are used behind an LCD screen, and the light of the strips are either transmitted or blocked by the controlled image pixels of the LCD screen.
In the solution disclosed in EP 0 316 465, there is an illuminated line behind every pair of LCD-pixel columns, and the light of the line passes through either one column or the other, corresponding to the control of the LCD pixels. This arrangement allows the display of a stereoscopic image with two viewing directions, but the resolution of the LCD-display is low, because two LCD-pixels are needed for an image point. The description suggest to increase the number of LCD-pixels associated to one illuminating line, in order to increase the number of viewing directions, but this leads to a further lowering of the resolution. There is no teaching how the data must be fed to the LCD-pixels.
With another possible embodiment, it is suggested to use one illuminating line (light source) behind each LCD-pixel column. In this case every pixel is illuminated by multiple light sources, which results in several viewing directions, having independently controllable light emissions in the same image point. Such a display is described in the publication “A prototype flat panel hologram-like display that produces multiple perspective views at full resolution”, by J. Eichenlaub, in: Proceedings of the SPIE Vol. 2409, pp. 102-112. Here, the number of the light sources is essentially equal to the number of the image pixels in a line. Therefore, in order to produce an image with an acceptable resolution, a large number of very small light sources are needed. These light sources are extremely expensive, due to their small size and the large quantity needed. The light sources may be manufactured by optical methods (e.g. cylindrical lens matrix, disclosed in WO 94/06249), but this requires again a very precise and costly technology, and the illumination angle is also limited. A further disadvantage of this approach is the limited intensity which may be achieved. The application of this system for moving images is clearly limited by the addressing speed of the LCD screen, and the switching speed of the light sources.
The need to provide several emitting directions from one image point is also recognised in the solution described in U.S. Pat. No. 5,521,724 (Shires). In this solution a simple electronic display is presented, which produces 3D images by binocular parallax. The effect is produced by the pixels of a traditional 2D display, which are spatially multiplexed by holographic elements. The problem of the data speed is not discussed.
There are also disclosed various forms of lenticular lens systems, which provide outgoing light beams according to different viewing directions. Such a solution used to create an autostereoscopic display is described in EP 0 786 912 A2. Again, in this document there is no teaching how the large amount of data may be fed into the subpixels of the image pixels (essentially, the pixels of an SLM, see FIG.
11
.), which then produce the different images in different directions through the lenticular lenses.
In the field of laser printers, LED arrays arranged in a line are alre
Adams Russell
Cruz Magda
Frommer William S.
Frommer & Lawrence & Haug LLP
Sony International (Europe) GmbH
LandOfFree
Pixel element for a three-dimensional screen does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pixel element for a three-dimensional screen, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pixel element for a three-dimensional screen will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3230555