Light source device for photoelectric equipments

Claim 1

A light source device comprising an incandescent lamp having a thermal time constant, a voltage source for supplying a pulsating lighting voltage to said lamp, said voltage source including a d. c. voltage source having a voltage control interconnected therewith, said d. c. source being connected with said lamp for energization thereof, a reference frequency generator having a frequency not exceeding the reciprocal of said thermal time constant, a reference voltage generator connected with said reference frequency generator and producing an output voltage alternating between two voltage levels at a rate determined by the reference frequency generator, a comparator interconnected with said lamp to sense the voltage Applied thereto and interconnected with said output reference voltage, said comparator producing an output control signal related to the difference between the lamp voltage and said output reference voltage and a connection between said comparator and said voltage control for applying a controlled voltage to said lamp varying between two voltage levels at a rate determined by said reference frequency whereby said lamp will produce a pulsating light output that may be sensed by a photoelectric element.