PURPOSE: To remove an obstructive lattice caused by a small aperture ratio of a shutter cell to obtain a sharp and beautiful print image by providing an optical shutter generating a pattern for reversing a dark lattice to be bright or white.

CONSTITUTION: A shutter 14 for shutting a light W having predetermined R, G, B spectra by a specific pattern is added to an optical shutter printer forming means generating a dark lattice. The pattern of the shutter 14 for shutting the light W functions to reverse a lattice part to be white. The pattern is not applied to an effective part. Therefore, a shaded part is black. The R, G, B image and the lattice W image are synthesized by a condensing prism 15, and the synthesized image is led to a lens 12. As a result, the condensing prism 15 receives the image from four surfaces and emits it from one surface. In this manner, an obstructive dark lattice is eliminated, and a printed image which is bright and beautiful as a whole can be obtained.