Abstract: 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.

Abstract: A photoelectric touch input panel has a plurality of crossed light beams which are broken by an object, the position coordinates of which are identified as outputs. Two spaced apart beam surfaces are provided, and the interrelationship between the beams in the two planes is employed to distinguish between interrupting objects on the basis of their size, attitude, and velocity characteristics. The number of beams broken in any beam plane is counted to determine the relative size of the object, or to determine the center line of the interrupting object. The beams in any beam plane are selected in accordance with the relative significance of the various beams, and interrupted beams are pulsed more rapidly than non-interrupted beams. The light-emitting devices of the various beam planes are constructed as an integral unit.

Abstract: A photoelectric touch input panel has a plurality of crossed light beams which are broken by an object, the position coordinates of which are identified as outputs. Two spaced apart beam surfaces are provided, and the interrelationship between the beams in the two planes is employed to distinguish between interrupting objects on the basis of their size, attitude, and velocity characteristics. The number of beams broken in any beam plane is counted to determine the relative size of the object, or to determine the center line of the interrupting object. The beams in any beam plane are selected in accordance with the relative significance of the various beams, and interrupted beams are pulsed more rapidly than non-interrupted beams. The light-emitting devices of the various beam planes are constructed as an integral unit.

Abstract: A dynamic level shifter for photoelectric touch panels incorporating a plurality of photoelectric transducers periodically senses the ambient light level, immediately before the interval when each transducer can receive a pulse of radiant energy during normal operation of the panel. The output of the phototransducer during the such interval is compared with the output during the previous ambient interval, to develop a signal indicative of the presence or absence of the pulse, irrespective of ambient light fluctuations.