Electric control system for photoelectric touch input apparatus

Abstract

An electric control system for a photoelectric touch input apparatus including a plurality of light-emitting elements arranged to produce a plurality of light beams in parallel on a common plane and a plurality of photosensitive elements opposed to and aligned with the light-emitting elements to receive the light beams so as to produce a plurality of light-receiving signals at each level of the light beams applied thereto. The control system is arranged to produce a plurality of drive signals respectively representative of a control valve for adjustment of each quantity of light of the light-emitting elements, to apply the drive signals to the light-emitting elements in sequence, to determine as to whether or not each level of the light-receiving signals is less than an optimum level, and if so, to adjust the control value in such a manner that each level of the light-receiving signals reaches the optimum level, and if not, to maintain the control value, to adjust each level of the drive signals in accordance with the control value, and to produce a switchover signal indicative of the position of an object such as an operator's finger when it interrupts one of the light beams. In this manner, relative differences in the quantity of light between the light-emitting elements and relative differences in the levels of the light-receiving signals may be compensated for, thereby maintaining the light-receiving signals of the photosensitive elements at an optimum level prior to use of the touch input apparatus.