PURPOSE: To facilitate measurement of the operation waveform of a polariscope by a method wherein emitted beams from the polariscope are led to an integrating sphere through an optical wedge and the change in luminous energy is measured by a photosensor.

CONSTITUTION: Emitted beams from a light source 1 such as a laser is deflected by a polariscope 2 operated by an oscillator 3 and is led to the integrating sphere 4 with the optical wedge 6 provided in the aperture thereof, and through an emitting aperture 7 the change in the luminous energy is measured by the photosensor 8 such as a phototransistor. The distance D between the polariscope 2 and the optical wedge 6 is adjusted so that the maximum deflection interval L of the beams can be included in the optical wedge. The optical wedge is a neutral filter whose transmittance changes rectilinearly from zero to 100% in the direction of beam scanning, and in order to make the part of rectilinear change definite, the outside of the point where the transmittance is zero is made to be transparent, while the outside of the point where it is 100% is made to be opaque. Accordingly, the change in luminous energy is detected corresponding to a polarizing angle θ, the measurement of the operating waveform thereof becomes very easy.