PURPOSE: To prevent a slide original placed on the original platen of an OHP from being curled or moved by the heat of light and the wind of a fan.

CONSTITUTION: The original platen 2 of the OHP is constituted of a light transmissive insulating material 21, a light transmissive conductor 22 consisting of a pair of electrode patterns and a light transmissive dielectric 23. By placing the slide original on the dielectric and impressing DC voltage on the electrode pattern of the conductor 22, a charge having a different polarity from the charge of the conductor is generated at a part opposed forward to the conductor in the slide original by electrostatic induction. Thus, the electrostatic attracting force between the charge of the slide original and the charge of the conductor 22 acts and the slide original is attracted forward to the dielectric and fixed on the original platen.