| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that compacting is difficult because a focusing detection optical system and a measuring light-receiving optical system are required to be installed separately, when improving measurement accuracy by using light having a wavelength in an ultraviolet region as a measuring beam. SOLUTION: This device has an illumination optical system 1 for irradiating a measuring object 10 with the measuring beam P1 having the wavelength in the ultraviolet region, an image formation optical system 18 arranged on the backside of an objective lens 15, the measuring light-receiving optical system 2 for performing image formation of a measuring reflected beam P2 reflected from the measuring object 10, and the focusing detection optical system 3 for projecting a focusing detection beam P3, introducing the beam to a photoelectric detector 28, and detecting the focusing position of the measuring object 10 based on the output signal. In order to focus the focusing detection beam P3 through the objective lens 15 and introduce to the measuring object 10, and to converge the focusing detection beam P3 through the objective lens 15 and introduce to the photoelectric detector 28 on the outside of a passing region where the measuring reflected beam P2 passes, a perforated lens 16 having the center axis O1 coincident with the optical axis O2 of the objective lens 15 is disposed in a passing region of the measuring reflected beam P2. |
