Laser light irradiator

Abstract

A laser beam irradiation device according to the present invention is so constructed that it may increase or decrease the excitation electric current flowing through its semiconductor laser diode to enable a user to selectively practice both non-thermal and photo-thermal laser treatments. CPUis responsive to switching-on and -off of an output-power switching unit Sfor sending a reference signal to an amplifiervia an I/O portand a D/A converter, so that the amplifiermay provide at its output terminals a reference voltage, with respect to which a control reference voltage for a desired laser output can be determined. Semiconductor laser dioderadiates the laser beam from its opposite sides, and a photo-diodereceives one of the opposite laser beams to provide a light-accepting voltage at its output terminals. The so acquired light-accepting voltage is directed to an amplifierfor amplification, thereby obtaining the monitor voltage. The reference voltage and the monitor voltage are applied to a differential amplifier, and a differential voltage is amplified by an amplifier. Thus a controlled working electric current is made to flow in semiconductor laser diodeso that it may be energized and oscillated at the set output level.