Position detecting system

摘要

A position detecting system includes a light source for producing a light beam for irradiating a reference mark formed on an object which is relatively displaceable relative to the light beam, a detector for detecting a light quantity distribution of the light from the reference mark, and a circuit for comparing a first light quantity distribution at a first position with a second light quantity distribution at a second position spaced from the first position by a predetermined distance, and for determining a reference position of the object on the basis of the comparison.