Television – Video display – Projection device
Reexamination Certificate
1999-06-30
2001-10-02
Kostak, Victor R. (Department: 2711)
Television
Video display
Projection device
C348S189000, C348S602000
Reexamination Certificate
active
06297859
ABSTRACT:
This invention relates to the field of image sensing, and in particular to the detection of incident illumination of a sensor in a video projection display.
BACKGROUND OF THE INVENTION
In a projection video display, geometrical raster distortions result from the physical placement of the cathode ray display tubes. Such raster distortions are exacerbated by the use of cathode ray tubes with curved, concave display surfaces and the inherent magnification in the optical to projection path. The projected image is composed of three scanning rasters which are required to be in register one with the other on a viewing screen. The precise overlay of the three projected images requires the adjustment of multiple waveforms to compensate for geometrical distortion and facilitate the superimposition of the three projected images. However, manual alignment of multiple waveforms is labor intensive during manufacturing, and without the use of sophisticated test equipment may preclude setup at a user location. Thus an automated convergence system is disclosed which simplifies manufacturing alignment and facilitates user location adjustment. An automated alignment system may employ raster edge measurement at peripheral screen locations in order to determine raster size and convergence. However, wide variations in sensor illumination levels may result in inaccurate measurement. To obviate measurement inconsistencies resulting from widely varying illumination levels requires the unambiguous detection of sensor output signal levels.
SUMMARY OF THE INVENTION
A projection display comprises a display device forming an image for projection onto a display screen. A photo sensor is adjacent to the display screen and generates a first signal responsive to a level of the projected image illumination incident on the photo sensor. A detector is coupled to receive the first signal and generates an output signal indicative of detecting the first signal. A source of a predetermined detection threshold value is coupled to the detector for determining a threshold at which the detection of the first signal occurs. Wherein the first signal exceeds the predetermined detection threshold value, the detector detects and generates the output signal indicative of signal detection, and generates a second signal for coupling to the source to change the predetermined detection threshold value.
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patent: 5241281 (1993-08-01), Wilkes et al.
patent: 5398083 (1995-03-01), Tsujihara et al.
patent: 5483299 (1996-01-01), Mimoura
patent: 5883476 (1999-03-01), Noguchi et al.
patent: 5949494 (1999-09-01), Tamagata et al.
Davenport Francis A.
Fried Harvey D.
Kostak Victor R.
Thomson Licensing S.A.
Tripoli Joseph H.
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