Patent ID: 8411249

Claim:
A surface position detecting apparatus comprising: a light-sending optical system which makes first light from a first pattern and second light from a second pattern incident to a predetermined surface to project an intermediate image of the first pattern and an intermediate image of the second pattern onto the predetermined surface; a light-receiving optical system which guides the first light and the second light reflected on the predetermined surface, to a first observation surface and to a second observation surface, respectively, to form an observation image of the first pattern on the first observation surface and an observation image of the second pattern on the second observation surface; and a detecting section which detects a position information piece of the observation image of the first pattern on the first observation surface and a position information piece of the observation image of the second pattern on the second observation surface and which calculates a surface position of the predetermined surface, based on the position information pieces, wherein the light-sending optical system projects one intermediate image out of the intermediate image of the first pattern and the intermediate image of the second pattern as an inverted image in a predetermined direction relative to the other intermediate image.