Title:
MEASURING INSTRUMENT EQUIPPED WITH ORTHOGONAL TWO-FREQUENCY LASER LIGHT SOURCE
Document Type and Number:
Japanese Patent JPH01173801
Kind Code:
A
Abstract:
PURPOSE:To remove distortion due to higher harmonics and to improve the accuracy of measurement by a Michelson interferometer, etc., by taking a measurement on the basis of the difference signal between a reference light signal and an electric signal indicating a beat frequency. CONSTITUTION:Two kinds of laser light beams from a laser light source 10 which have planes of polarization orthogonally to each other and differ in wavelength pass through a lambda/4-wavelength plate 12 and split by a polarization beam splitter 14 into the reference light and measurement light. The reference light passes through a lambda/4- wavelength plate 16 and is reflected by a half-mirror 18, passed through an analyzer 20, and detected by a photosensor 22. The measurement light passes through a lambda/4-wavelength plate 24 and is reflected by a mirror 26 and multiplexed with the reference by the photosensor 22 to become light having the beat frequency. Part of the reference light passing through the mirror 18 is inputted to a differential amplifier 36 through an analyzer 20, a reference light sensor 32, and a differential amplifier 34. Then the difference signal based upon the beat signal is outputted from the amplifier 36 to obtain a beat signal having no distortion after the secondary higher harmonic is removed. Thus, the high-accuracy measurement is performed.
Inventors:
KONDO MICHIO
BESSHO YOSHINORI
BESSHO YOSHINORI
Application Number:
JP33524387A
Publication Date:
July 10, 1989
Filing Date:
December 28, 1987
Export Citation:
Assignee:
BROTHER IND LTD
International Classes:
G01B9/02; (IPC1-7): G01B9/02
Attorney, Agent or Firm:
Haruyuki Ikeda (2 outside)