PURPOSE: To obtain polychromatic picture information from an image sensor, by installing a transmissive color liquid crystal element in the optical path between a light source having a wide luminous band width and the image sensor having a wide light receiving band width and turning on/off the driving of the color liquid crystal.

CONSTITUTION: A sheet-like original 16 is lighted by a light source 11 and the reflected light from the original 16 forms an image on an image sensor 12 through a mirror 14, color liquid crystal panel 13, and lens 15. A color changeover controlling circuit 17 delivers a driving command to a liquid crystal driver 18 first. Since the liquid crystal driver 18 applies an alternating voltage across the color liquid crystal panel 13 upon receiving the command, dyes in the panel 13 become almost parallel to the optical path and hardly influential to the incident light. Therefore, the image sensor 12 generates video signals of black and white after reading one line of picture information of the original 16 and stores the video signals in a storage device 19 after they are amplified 20 and then quantitized 21. Then the color changeover controlling circuit 17 issues a driving inhibit command to the liquid crystal driver 18. By the command, the dyes in the liquid crystal panel 13 act to have a fixed angle against the optical path and a specific chrominance component is added to the image sensor without receiving any attenuation.