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:
Jul. 24, 1990
Filed:
Dec. 06, 1988
Timothy E Masters, Champaign, IL (US);
Paul B Lucas, Urbana, IL (US);
James E Garrett, Champaign, IL (US);
John K Carstedt, Round Rock, IL (US);
Carroll Touch Inc., Round Rock, TX (US);
Abstract
A touch input device which continuously samples and digitally stores ambient light readings and compares these with previously stored readings is taught. Briefly stated, a phototransistor is turned on before, during and after an LED emitter energization. An ambient value is calculated which is subtracted from the value obtained during LED firing so as to develop a signal indicative of the presence or absence of the LED pulse, irrespective of ambient light fluctuations. The ambient level is stored for comparison purposes during the next sampling of the associated phototransistor.