PURPOSE: To prevent the breakdown of the storage images through read-out light by otpically separating a thin plate for writing and a thin plate for reading-out through the use of a mirror composed of dielectric.

CONSTITUTION: A mirror 13 of dielectric is inserted between a thin plate B for writing composed of the crystal having electro-optic effect formed with a transparent electrode layer 12A on one side and a thin plate A for reading-out disposed with a transparent insulation layer 14A on one side and the laminate of a transparent insulation layer 14B and transparent electrode layer 12B on the other. If with this arrangement the read-out light L2 is radiated through a polarizer P1 toward the transparent electrode layer 12A of the space light modulating element 15, it directly transmits through the thin plate A and receives the polarization by electro-optic effect, after which it is reflected by the mirror 13 and goes toward a polarizer P2. Hence, the read-out light L2 no longer gives any adverse influence to the thin plate B which has substantially stored the images.