Abstract: An image reading apparatus comprises a light source for simultaneously radiating, onto a pattern formed by etching a plurality of recessed characters in a semiconductor wafer, an incoherent parallel slit light beam having a radiation spot of dimensions corresponding to those of a region to be measured, a CCD camera, having a light-receiving surface which is shifted from an optical axis of a regular reflection beam so as to receive a reflection beam offset from the regular reflection beam by the region to be measured, for measuring the pattern on the basis of the received beam, and a light-shielding plate, arranged between the light source and the member to be measured, for preventing a peripheral beam of the parallel slit light beam from being incident on the region to be measured.