PURPOSE: To obtain a vivid and correct picture signal even in the case of materials having a large difference of height by arranging plural optical systems while shifting them by extents of their focal depth and arranging a pinhole in the rear focus position of an intermediate image forming lens.

CONSTITUTION: A material 1 is moved in the Y direction at a uniform speed by an XY stage 8 to pick up its image by a one-dimensional photo sensor 6. Then, the image of a pattern on the material 1 is continuously picked up to input a two-dimensional image of the material 1. Optical systems which form the image of the sensor 6 are so arranged that their focus positions are shifted by extents of focal depth, and their picture signals are added to practically extend the focal depth twice. In the in-focus optical system, the optical image formed by an intermediate image forming lens 3 passes a pinhole 4 and is formed on the sensor 6 again by an image reforming lens 5. In the cut-of-focus optical system, the optical image cannot pass the pinhole 4 because the forming position of the optical image due to the intermediate image forming lens 3 is deviated from the pinhole 4, and the picture signal is weak.