DISTANCE MEASURING DEVICE

PURPOSE:To improve the precision and accuracy of the noncontacting distance measurement of a contact type semiconductor printer by using a simple optical system, photosensor, and a few electronic circuits in combination. CONSTITUTION:Luminous flux 11 generated by reflecting luminous flux 10 from a laser light source 6 by a half-mirror 4 becomes luminous flux 12 converged by a lens 3. Part of the light 30 when passing through the edge part 8a of a mask 1 is scattered. Unscattered light 31 reflected directly by a mask pattern 8, scattered light 32 which is scattered directly by the edge part 8a of the mask 1 and returns, scattered light 33 which is reflected by a wafer 2 and returns after being reflected by the edge 8a, and unscattered light 34 which is reflected directly by the wafer are detected by the photosensor 7. Then, the light beams 31 and 32, and 33 and 34 interfere with each other and their interference fringes vary with variation in the distance D between the mask 1 and wafer 2.