Optical gap measuring apparatus and method

Details Optical gap measuring apparatus and method Optical gap measuring apparatus and method

Filed on

1995-03-22

Date issued

1996-09-17

Examiner

Gonzalez, Frank

Patent Class

Optics: measuring and testing

SubClass

By dispersed light spectroscopy

SubSubClass

Utilizing a spectrometer

Other Related Categories

356351, G01B 902

Type

Patent

Status

active

Patent number

055573991

Description

ABSTRACT:
Optical method and means for high-speed measurement of the distance between two surfaces, the first of which (25) is part of a substantially transparent element (20) and the second of which (35) is part of a test object (30). In a first step, a lens (3) directs a light beam (2) through a polarizing component (4) towards the first surface at an oblique angle of incidence. In a next step, the polarized light beam (5) reflects back through the transparent element by means of the combined effect of reflections from the first surface of the transparent element and from the surface of the test object (30). In a further step, a polarization-sensitive intensity detector (12) and a phase detector (13) measure the strength and relative phase of the polarization components defined by the plane of incidence. A computer (99) then analyzes these measured parameters to determine the size of the gap between the two surfaces (25,35). An additional method and means are provided to measure the complex index of refraction of the object surface (35) by changing the gap between the surfaces (25,35).

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