Detection of focal point of objective lens by means of a two-spl

Details Detection of focal point of objective lens by means of a two-spl Detection of focal point of objective lens by means of a two-spl

1999-04-20

2000-08-29

Rosenberger, Richard A.

Optics: measuring and testing

By polarized light examination

With light attenuation

2562014, G01B 1114

Patent

active

061116475

ABSTRACT:
A focal point detecting apparatus for an objective lens is disclosed for inspecting whether or not the focal point of the objective lens used in an electron microscope, an optical inspecting apparatus, a laser processing apparatus, etc. is positioned on a surface of a target object. The focal point detecting apparatus comprises for entering an optical beam for detecting a focal point from a position deviant from an optical axis of an objective lens to a surface of a target object to be inspected through at least the objective lens; and two two-split sensors on which the optical beam reflected from the surface of the target object so as to pass again through the objective lens is converged by at least a condenser lens. The two two-split sensors are arranged at the same optical inclination in front of and behind the position on which the reflected optical beam is converged by the condenser lens when the focal point of the objective lens is positioned on the surface of the target object.

REFERENCES:
patent: 3969575 (1976-07-01), Gerritsen et al.
patent: 4548495 (1985-10-01), Suzuki
patent: 4630927 (1986-12-01), Fulkerson
patent: 4843228 (1989-06-01), Nakamura
patent: 4897536 (1990-01-01), Miyoshi

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