Abstract: In a laser working apparatus comprising a large power laser oscillator, laser light beam conducting means, and a hand-piece with which the output laser light beam from said conducting means is emanated on desired objectives. The hand-piece comprises a convergence lens for focusing the output light to the desired object and a light detecting means disposed in a casing of the hand-piece, so as to detect the outskirt portion of the converged light beam, which is not utilized for the working, thereby the output laser light is continuously checked for its existence or for its intensity, to assure a reliable operation. By such a detection means, many troubles or defects of the light conducting means are continuously watched.

Abstract: A temperature measurement apparatus comprising a temperature sensitive device such as thermistor and a reference resistor of small temperature coefficient of resistance, which are alternatively connected to an electric circuit which produces an output signal responding to change of resistance, and the apparatus comprises a memory which memorizes a reference output signal by a reference resistor at a predetermined reference environmental temperature and a reference voltage of a power source, and a calibration is made to a measured temperature value by use of said memorized reference output signal.