초록 ▼

A CRT touch screen having raster-generated light patterns at the viewing screen borders of a conventional CRT. Reflective surfaces proximal to the screen borders reflect the light patterns across the CRT surface to external photodetectors. Modulating the horizontal blanking signal or employing perio

A CRT touch screen having raster-generated light patterns at the viewing screen borders of a conventional CRT. Reflective surfaces proximal to the screen borders reflect the light patterns across the CRT surface to external photodetectors. Modulating the horizontal blanking signal or employing periodic non-reflective patterns on the reflective surfaces effects raster-generated light patterns having a unique time frequency higher than the vertical synch frequency, but lower than the horizontal synch frequency. A screen pointer blocks the lights patterns reflecting across the screen to two or more of the photodetectors. The blocking is time-relative to the CRT's horizontal and vertical synch signals. The photodetector outputs are bandpass filtered at the unique pattern frequency to suppress electromagnetic interference from the CRT's horizontal raster synch, the CRT's vertical synch and other electromagnetic and optical sources. The screen pointer's position is calculated based on which photodetectors' received patterns are blocked, and the times of the blocking relative to the horizontal and vertical synch.

대표청구항 ▼

[ We claim:] [1.] A touch screen input apparatus used to determine the position of a pointer on a computer screen, comprising:a computer interface screen having a screen surface comprising a main area extending between a pair of parallel borders, a filet border adjacent a first of said pair of borde

[ We claim:] [1.] A touch screen input apparatus used to determine the position of a pointer on a computer screen, comprising:a computer interface screen having a screen surface comprising a main area extending between a pair of parallel borders, a filet border adjacent a first of said pair of borders and a second border area adjacent a second of said pair of borders;a raster scanner means forming the screen surface along a plurality of rows from the first to the second of said pair of borders at a raster frequency, havingmeans for indexing after a cycle of the raster frequency from one of said rows to another of said rows across the screen in a second direction approximately perpendicular to the first direction, so as to cycle through said plurality of rows at a scanning frequency andmeans for illuminating within a cycle of said scanning frequency a first and a second plurality of edge points within said first border area and said second border area, respectively, said first and second plurality of edge points being arranged in a periodic spacing in said second direction, and said spacing being so that the inverse of the time period from illuminating one of said first and second plurality of edge points to a next of said first and second plurality of edge points, respectively, is equal to a predetermined pattern frequency which is greater than said scanning frequency and less than said raster frequencyfirst and second light reflective surfaces adjacent to the first and second borders, respectively, the first reflective surface reflecting the light luminescing from said first plurality edge points across the screen surface in a direction toward the second border and the second reflective surface reflecting the light luminescing from said second plurality edge points across the screen to the first border;means for receiving the light luminescing from said first plurality of edge points reflected by said first reflective surface, said means having a spatially separated first and second light receiving means proximal to said second border, and for generating a first and second detection signal in response;means for receiving the light luminescing from said second plurality of edge points reflected by said second reflective surface, said means having a spatially separated third and fourth light receiving means proximal to said first border, and for generating a third and fourth detection signal in response;bandpass filter means for receiving said first, second, third, and fourth detection signals, substantially suppressing frequencies other than said pattern frequency, and generating a filtered first, a filtered second, a filtered third, and a filtered fourth detection signal, respectively, in response;andmeans for determining a position of an object blocking one or more of a light reflected by said second reflective surface from reaching the first and second light receiving means and a light reflected by said first reflective means from reaching said third and fourth receiving means based on said filtered first, filtered second, filtered third, and filtered fourth detection signals.