PURPOSE: To control optical beams extremely simply by arranging plural plane lens elements adjacently with each other on a plane waveguide formed on the surface of a ferroelectric substance in the width direction of optical beams propagated on the plane waveguide.

CONSTITUTION: When an optical beam having an expanding angle α radiated from a light source 33 to a plane lens 32 is made incident, only an optical beam part made incident on a plane lens element 31b and having an angle β is made collimate light 37 and optical beam parts having expanding angles γ1, γ2 are made incident on plane lens elements 31a, 31c and reach an unnecessary optical beam absorbing area 37 and a dispersed end surface area 38 respectively. If light absorbing bodies are arranged on the areas 37, 38 as shown in the figure, light beams 35, 36 are absorbed by the light absorbing bodies, and if there is nothing on the areas 37, 38, the light beams 35, 36 are projected to the external. Consequently, stray light to be the cause of malfunction can be removed. Thus, diffracted light and dispersed light supposed to be generated in a space filter are not generated in said constitution, so that collimate light 34 can be completely separated from unnecessary optical beams 35, 36.