Video projector with optical feedback
First Claim
1. A video beam projector system, comprising:
- at least one beam generator adapted to generate an illuminating beam;
a projection viewing screen;
beam deflection control means for modulating said beam in synchronism with an incoming video signal, and for deflecting said beam so as to raster-scan said screen with a projected video image field on at least a portion of said screen;
opto-electronic sensing means for sensing the actual time of arrival of said beam at particular points on said screen;
means for comparing said actual beam arrival time at each of said screen points with a predetermined beam arrival time;
means connected to said beam control means for re-aligning said projected video image with respect to said screen in response to said comparing means so as to reduce any differences between said actual and predetermined beam arrival times, wherein said opto-electronic sensing means comprises a single sensor at each given one of said particular screen points, so as to minimize the number of such single sensors.
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Accused Products
Abstract
Geometric distortion in a scanning beam video laser porjector, or the like, is corrected by comparing the time of arrival of the projection beam at a selected pixel on the projection screen with a predetermined time of arrival, and computing therefrom the changes in beam control required to remove the distortion. A peripheral portion of the projected video field is blank, being reserved for projection of bright beam alignment fiducials comprising selected pixels of the peripheral field portion. An optical fiber is placed on the screen periphery so as to receive one pixel of each projected fiducial, its output being applied (through a light sensitive diode) to a beam control processor or the like. Geometric distortion or a change in projector alignment shifts the beam time of arrival at the sensor. The processor compares the time of arrival of the projector beam at each sensor with a lock-up table and, from this comparison, determines the beam control corrections required to remove geometric distortion. Significantly, only one sensor is required in a given portion of the projected image to precisely measure any alignment shift of a projected beam fiducial, because such a shift changes the beam time of arrival at the sensor by an amount proportional to the magnitude of the alignment shift and by a direction in time (backward or forward in time) corresponding to the direction of the alignment shift.
54 Citations
19 Claims
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1. A video beam projector system, comprising:
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at least one beam generator adapted to generate an illuminating beam; a projection viewing screen; beam deflection control means for modulating said beam in synchronism with an incoming video signal, and for deflecting said beam so as to raster-scan said screen with a projected video image field on at least a portion of said screen; opto-electronic sensing means for sensing the actual time of arrival of said beam at particular points on said screen; means for comparing said actual beam arrival time at each of said screen points with a predetermined beam arrival time; means connected to said beam control means for re-aligning said projected video image with respect to said screen in response to said comparing means so as to reduce any differences between said actual and predetermined beam arrival times, wherein said opto-electronic sensing means comprises a single sensor at each given one of said particular screen points, so as to minimize the number of such single sensors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. In a video beam projector system comprising at least one beam generator adapted to generate an illuminating beam, a projection viewing screen and control means for modulating said beam in accordance with an incoming video signal and for deflecting said beam so as to scan said screen with a projected video image field on at least a portion of said screen, a geometric distortion control system comprising;
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opto-electronic means for sensing the actual time of arrival of said beam at particular locations on said screen; means for comparing said actual beam arrival time at each of said screen locations with a predetermined beam arrival time; and means connected to said beam deflection control means for re-aligning said projected video image with respect to said screen in response to said comparing means so as to reduce any differences between said actual and predetermined beam arrival times. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A video beam projector system, comprising:
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a projection screen; means for scanning an optical beam across said screen; means mounted on said screen for providing optical feedback to said beam scanning means coincident with the time of arrival of said beam at specific locations on said screen; means for storing predetermined times of arrival corresponding to each of said specific locations; feedback control means sensitive to said optical feedback for controlling said scanning means so as to alter the motion of said beam across said screen whereby to minimize the differences between said times of arrival of said beam and corresponding ones of said predetermined times of arrival. - View Dependent Claims (19)
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Specification