Patent ID: 8111406

Claim:
A surface position detecting apparatus which detects position information of a first surface in an object, comprising: a first optical system which projects, from an oblique direction to the first surface, light having traveled via a predetermined pattern onto the first surface; a second optical system which forms an image of the predetermined pattern, based on the light reflected by the first surface; a detecting system which detects the position information of the first surface in a direction intersecting the first surface, based on the light having traveled via the image of the predetermined pattern; and a phase difference imparting system which includes a phase shifting portion that is arranged within at least one of the first and second optical systems and on an optical path of the light and that changes a phase of at least a portion of the light, and which changes the phase of at least the portion of the light by the phase shifting portion so that a predetermined phase difference is imparted between a first portion and a second portion of reflected light that is included in the light having passed through the second optical system and that is reflected on a second surface in the object, the second surface being different from the first surface.