OPTICAL INSULAING POSITION SENSOR

PURPOSE:To reduce size by providing a slit plate having a slit to allow the passage of the light across n-rows of photodetecting region parts between a photodetector having the n-rows of the photodetecting region parts of the specific width and pitch and a light source and moving the light source and the slit plate relatively with the photodetector. CONSTITUTION:An LED10 which is a light source is provided to a movable side object (not shown in a figure) moving in the direction X and a photodetector 11 is provided to a stationary side object (not shown), respectively. Photodetecting region parts D1... which have the widths W1... corresponding respectively to the weights of the respective digits of n-digits, for example, 6 digits of binary codes are formed on the detector 11 in a way as to be arrayed in the direction X at the pitch P1 of two-fold the respective widths W1... A slit plate 17 formed with a slit 16 at the width W1 into the slender shape toward the direction intersecting orthogonally with the direction X is disposed between the LED10 and the detector 11. The plate 17 is provided to the moving side object and is moved together with the LED10. Then the light from the LED10 does not irradiate the adjacent photodetecting regions and therefore n-rows of the arranging width is made narrow.