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:
Jan. 29, 1991
Filed:
Sep. 02, 1988
Wayne J Wehrer, Austin, TX (US);
Carroll Touch, Incorporated, Round Rock, TX (US);
Abstract
A touch input device having infrared light beams defined by a plurality of pairs of light emitters and phototransistors is disclosed. A feedback loop containing a programmable amplifier is employed to compensate for the effects of ambient light and for device irregularities. The phototransistor current is first converted to a signal voltage by an operational amplifier and then is input into a low pass filter. The output of the lowpass filter is input into a feedback loop containing a summing amplifier, a programmable amplifier and an integrator. As light emitters and phototransistors are sequentially activated, the feedback loop with the programmable amplifier compares outputs signals in the unactivated state with those input when the light emitters are activated to compensate for ambient conditions and errors.