To improve assembling work efficiency by eliminating the need of accurately aligning optical axes of an optical system and light projecting and receiving elements, in setting a light projecting direction and a light receiving direction at a proper angle.

The cylindrical lenses 14b of a light projecting optical system 14E and a light receiving optical system 14R focus light rays only in a y direction (direction orthogonal to an xz plane) and make the light rays pass through without stopping in an x direction. The light projecting element 11 and the light receiving element 12 are arranged so that their optical axes Ze and Zr are inclined toward the side of an axis Z. Thus, the optical axes Ze and Zr cross with each other at a predetermined distance on the axis Z.

COPYRIGHT: (C)2009,JPO&INPIT