Device for extracting a plurality of space frequency components

A device for extracting a plurality of spaces frequency components from an optical image formed by an image forming optical system, comprising:

• (a) a photoelectric element array including at least N photoelectric elements disposed in or near the image formation plane of said image forming optical system;
• and
• (b) means for generating, on the basis of the output of each of the photoelectric elements of said array, an electrical output varying in phase in accordance with the displacement of said optical image in the direction of arrangement of said photoelectric elements, said means including first vectorizing means for converting the outputs of said photoelectric elements into vectors so that the output of the nth photoelectric element of said array becomes a vector having an absolute value related to said output and a phase given by .pi./N.times.p.sub.1 .times.n, first adding means for adding together the vector outputs of said first vectorizing means, second vectorizing means for converting the outputs of said photoelectric elements into vectors so that the output of the nth photoelectric element of said array becomes a vector having an absolute value related to said output and a phase given by 2.pi./N.times.p.sub.2 .times.n, and second adding means for adding together the vector outputs of said second vectorizing means, where p.sub.1 and p.sub.2 are different integers less than N/2.