The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 09, 1998
Filed:
Jun. 07, 1995
Ifay F Chang, Katonah, NY (US);
Chengjun Julian Chen, Yorktown Heights, NY (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
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.