Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Patent
1992-04-15
1998-11-17
Saras, Steven
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
345182, 345207, 349 12, G09G 328
Patent
active
058383085
ABSTRACT:
An optical touch input device comprises an array of actively addressed sensing elements (18) for sensing a light input, e.g. from a light pen, each of which comprises a capacitor (25) which is charged periodically through operation of a switch device (24) and a discharge circuit, including a photosensitive device (28) and a further switch device (27) connected across the capacitor, which circuit in operation demonstrates an optical threshold characteristic whereby the capacitor (25) is discharged in response to the sensing elements being subjected to light which is at or above a predetermined intensity level so as to discriminate from ambient light. Elements written into are determined by detecting the charge stage of their capacitors. The sensing element array can be integrated with a matrix display device with the sensing elements (18) and display elements components (12) provided on a common support using thin film technology.
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Knapp Alan G.
Shannon John M.
Botjer William L.
Saras Steven
U.S. Philips Corporation
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