PURPOSE: To improve the resolution with a simple circuit constitution, by reading out a picture signal in synchronizing with the picture signal formation timing of a photoelectric converter after a resolution correcting circuit.

CONSTITUTION: The reflected light irradiated from a light source 1 to an original 2 is collected at a lens 3 and the image is formed in a reception window of a CCD image sensor 4. The output of the CCD image sensor 4 is inputted to a resolution correcting circuit 6 via a preamplifier 5. The circuit 6 has a function attenuating unnecessary harmonics and correcting the amplitude. A sample hold circuit 7 reads out an analog signal inputted from the circuit 6 as a rectangular wave at the rear end of a signal corresponding to picture elements in synchronizing with the picture signal formation timing of the sensor 4.