Television – Video display – Projection device
Reexamination Certificate
1998-09-16
2001-11-13
Eisenzopf, Reinhard J. (Department: 2614)
Television
Video display
Projection device
C348S781000, C359S670000, C359S668000, C359S207110
Reexamination Certificate
active
06317171
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to spatial light modulator display systems, and more particularly to a television set having a spatial light modulator whose images may be either narrow or wide, as selected by positioning an anamorphic lens.
BACKGROUND OF THE INVENTION
One type of display system is a projection display system, where a projection lens is used to project the image to a screen. Movie theaters are one example of such display systems on a large scale. More recently, television sets and digital cinema systems have been developed that also use projection lenses. The projection lens may be for either front or rear projection, depending on whether the lens is on the viewer side of the screen or behind the screen.
Spatial light modulators (SLMs) are a type of display device that may use a projection lens. In general, SLMs are arrays of pixel-generating elements that emit or reflect light to the display screen via the projection lens. The SLM modulates light by turning the pixel-generating elements on or off.
An example of an SLM is a DMD (digital micro-mirror device). A DMD is an electromechanical device, whose pixel-generating elements form an array hundreds or thousands of tiny tilting mirrors. To permit the mirrors to tilt, each is attached to one or more hinges mounted on support posts, and spaced by means of an air gap over underlying control circuitry. The control circuitry provides electrostatic forces, which cause each mirror to selectively tilt. Incident light on the mirror array is reflected by the “on” mirrors in one direction and by the “off” mirrors in the other direction. The pattern of “on” versus “off” mirrors forms an image. In most applications, the light from the DMD is projected by a projection lens to a screen.
The size of the array of an SLM's pixel-generating elements determines the aspect ratio of the image it generates. For example, an SLM might have an array size of 1024×768, thereby generating images with an aspect ratio of 4:3. This 4:3 aspect ratio is consistent with NTSC television broadcast signals as well as those used for personal computer displays.
As display systems become more advanced, the variety of source data that they are capable of displaying has increased. Each type of source data may have its own format, that is, its own aspect ratio and vertical and horizontal resolution. For example, one advance is the availability of “digital cinema”, in which movie films are digitized for display. Movie films are characterized by a wide aspect ratio, such as 2:1. Another advance is high definition television with wide aspect ratios, such as the 16:9 format.
For television applications, the conventional approach to displaying multiple formats with the same television set has been to use various data processing techniques, such as sampling or scaling, so that the data fits the SLM. For example, the television set might have a 4:3 SLM, and for displays having a different aspect ratio, the image is scaled so that it fills the SLM in at least one dimension. This can result in a display that does not fill the screen vertically for wide-screen displays, a display known as a “letterbox” display. U.S. patent application Ser. No. 08/333,200, entitled “A Multi-Format Television Architecture”, and U.S. patent application Ser. No. 08/091,852, entitled “Method and Device for Multi-Format Television”, describe methods of processing data to accommodate various display formats.
SUMMARY OF THE INVENTION
One aspect of the invention is a projection optics unit for a television receiver that uses a spatial light modulator to generate images to be displayed on a screen. The images may have different formats, such that they may have aspect ratios that differ from that of the spatial light modulator in at least one dimension. A projection lens projects the images along an optical path from the spatial light modulator to a screen. An anamorphic lens is moveable in and out of the optical path by a mechanism attached to the anamorphic lens. This mechanism is activated, in response to automatic format detection or user input, when the aspect ratio of the signal to be displayed is different, in at least one dimension, from that of the spatial light modulator. The anamorphic lens optically adjusts the image in that dimension. In typical applications, the anamorphic lens adjusts the image in the horizontal dimension, to provide an image whose aspect ratio is wider than that of the spatial light modulator.
In general, the invention recognizes that the image can be “squeezed” when generated by the SLM and then optically “stretched” to provide wide-screen images. Further, the means for optically widening the image can be moved in and out of the optical path, resulting in a “home theater” that can display a variety of display formats. For example, the same television set can display both 4:3 NTSC broadcasts and 2:1 movie films. The picture quality of the optically stretched image is comparable to that produced by conventional movie projection lenses.
The anamorphic lens permits the entire SLM array to be active for all formats. Thus, the same SLM can be used to display all formats without loss of picture size and light efficiency.
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Brady III Wade James
Brill Charles A.
Eisenzopf Reinhard J.
Telecky Frederick J.
Texas Instruments Incorporated
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