Hitachi Electronics Engineering Co., Ltd.

Tuneo Yamaba

Hideo Ishimori

Shigeru Serikawa

Kenji Aikou

In a phase interference detecting system with use of an interferometer, a height from a reference surface on a measurement surface is detected by receiving interference components of reflection lights from the reference surface and a measurement surface, which lights are divided from a laser beam and are modulated with a frequency being different therefrom, i.e., by irradiating only one laser beam. A light detector is constructed with a line type sensor for receiving the interference components of the reflection lights, and has a plurality of pixel groups for common use of a measurement surface and a plurality of pixel groups for exclusive use of a reference surface, which are provided at both thereof. A reference surface phase detecting means calculates a reference surface phase signal with respect to the pixels at a measurement point within the pixel group for common use of measurement surface, on a basis of an average value of signals of a predetermined number of pixel groups positioned at both sides in symmetric with respect to said measurement point. A measurement point phase calculating means calculates a measurement point phase signal of said reflection lights being incident upon the pixels at said measurement point on a basis of signals of the pixels at said measurement point. A height calculating means calculates out a signal corresponding to height of said measurement point by subtracting said reference surface phase signal from said measurement point phase signal.

Phase interference detecting method and system in interferometer, and light detector therefor

Interference light occurring between a first laser light of a reference phase and a second laser light of a measuring phase is divided via a light divider into two interference light beams to be directed in two directions. One of the divided interference light beams is received by a polarizing light separator, which separates components of the first and second laser lights from the received interference light beam. First and second light detectors convert respective light energy of the separated components into corresponding electric signals. Adder adds together the converted electric signals. Third light detector converts light energy of the other divided interference light beam into an electric signal. Comparator compares the electric signal from the third light detector with the output of the adder as a reference value, to generate a detection output of a predetermined phase. In an alternative, the output from the adder is subtracted from the converted electric signal from the third light detector and a square root of a product between the electric signals output from the first and second light detector is evaluated, so that a signal, indicative of interference intensity of the interference light occurring between the first and second laser lights, is provided by dividing the output of the subtracter by the square root.

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Odawara, Japan

Tuneo Yamaba