POSITIONAL SIGNAL DETECTOR

摘要

PROBLEM TO BE SOLVED: To detect with high precision a relative positional error between an image forming surface of a hologram and a two-dimensional photodetector without detecting a positional deviation using complicated pattern matching. SOLUTION: A spot (bright spot)αis formed on the image forming surface 2 by light 6 diffracted from a disk shaped area 4 on the surface 1 of the hologram by waveguide light within a single mode plane type optical waveguide, and simultaneously a spotβis formed on the image forming surface 2 by light 7 diffracted from a disk shaped area 5 on the surface 1 of the hologram. Both spots are closely positioned.