Electric control system for photoelectric touch input apparatus

A photoelectric touch input apparatus adapted to be placed in front of a display device, comprising:

• a housing having a frame adapted to be placed in front of a display surface of said display device, said frame defining an opening therein;
• a plurality of light-emitting elements mounted on said frame in a row along at least one side of said opening to produce a plurality of light beams in parallel spaced relationship on a common plane;
• a plurality of photosensitive elements mounted on said frame in a row along the opposite side of said opening from said plurality of light-emitting elements and aligned with said light-emitting elements to receive the light beams emitted therefrom, said photosensitive elements being arranged to produce a plurality of light-receiving signals in response to the light beams applied thereto from said light-emitting elements;
• first means for producing a plurality of drive signals respectively representative of a control value for adjustment of each quantity of light of said light-emitting elements, said first means including means for applying said drive signals to said light-emitting elements in sequence and means for adjusting said control value in such a manner that each level of said light-receiving signals reaches an optimum level, and for memorizing said adjusted control value;
• second means for adjusting each level of said drive signals in accordance with said memorized control value only after adjustment of said control value and for maintaining said drive signals at the adjusted level, said second means including means for determining whether or not an object such as an operator's finger interrupts one of the light beams, and if so, producing a switchover signal indicative of the position of the object;
• and
• means responsive to said switchover signal to produce a control signal for switching over an indication or picture on the display surface of said display device to another indication or picture defined by said switchover signal.