초록 ▼

A circuit for reducing noise and increasing the reliability of touch panels involves the use of a supplemental noise or electromagnetic interference pickup lead which extends generally coextensively with the parallel connected outputs from a series of successively coupled photodetectors and a high p

A circuit for reducing noise and increasing the reliability of touch panels involves the use of a supplemental noise or electromagnetic interference pickup lead which extends generally coextensively with the parallel connected outputs from a series of successively coupled photodetectors and a high pass filter for substantially reducing the noise signals created by variations in the level of ambient light. When the photodetectors output is connected to one of the inputs of a differential operational amplifier, and the compensating pickup lead is connected to the opposite polarity other input, the noise is substantially cancelled out, and a cleaned-up photodetector pulse is provided. A pulse forming circuit squares up the photodetector output signal pulse; and a hysteresis type storage or buffer 15 circuit is employed to indicate the presence or absence of photodetector output signals, from successive photodectors, thereby indicating whether or not the light beams are interrupted either fully or partially.

대표청구항 ▼

An interference reduction circuit comprising: means for providing at least one pair of light emitting devices and photodetectors each disposed along a light beam path extending therebetween; a photodetector output circuit; switching means for successively coupling the output of said at least one pho

An interference reduction circuit comprising: means for providing at least one pair of light emitting devices and photodetectors each disposed along a light beam path extending therebetween; a photodetector output circuit; switching means for successively coupling the output of said at least one photodetector to said photodetector output circuit; an electromagnetic noise compensation pickup circuit extending generally coextensively with and electrically balanced with said photodetector output circuit; and circuit means including combining means for differentially combining the outputs from said photodetector output circuit and said electromagnetic noise compensation pickup circuit to substantially eliminate the electromagnetic noise component present on the output signal of said photodetector output circuit.