PURPOSE: To decrease the effect of the secondary reflection, by projecting light to a material to be measured, detecting the projecting direction of the spot light, which is scanned in two dimensions, and sequentially selecting one-dimensional photoelectric elements based on the detected data of a spot-light-image detecting means.
CONSTITUTION: Motors connected to reflecting mirrors 13 and 14 are driven by driving circuits 17 and 18. Thus spot light images 5 are scanned on a work 4 in two dimensions. The light projecting direction of the spot light detected by a means III. In this means, the rotary angle of the reflecting mirror 14 is detected by a detector 19. The result is converted into a signal required for the control of a circuit 21 in the next state. A spot-light-image detecting means IV is constituted by arranging an optical lens 22 and a plurality of one-dimensional photoelectric elements 23. Then the one-dimensional photoelectric elements 23 are sequentially selected by a sensor output selecting means based on the output signal of the means III.
MURATA MASAO
KOBAYASHI KEIICHI
