APPARATUS FOR MEASURING DIFFERENCE IN BEAM PATH LENGTH

Japanese Patent JPS6385301

A

PURPOSE:To remove a measuring error, by separating a beam signal for detection into two linearily polarized components different by 90 deg. in a plane of polarization from each other and setting the difference between both components to a detection signal. CONSTITUTION:The laser beam 2 emitted from a laser 1 is shifted in beam frequency by a beam frequency shifter 3 and beam 8 is emitted from said shifter. This beam 8 emitted is divided into two by a non-polarizing beam splitter (BS)9 and the reflected beam 10 among them is separated into transmitted beam 12A and reflected beam 12B by a polarizing beam spliter BS11A and both beams are respectively incident on beam detectors 13A, 13B to be converted to electric signals which are, in turn, inputted to an operation circuit 34 and the difference between both of them is taken to send out an output signal wherein a noise component is removed. The transmitted beam 14 of BS9 is divided into P-polarized beam 26 of an azimuth 0 deg. and S-polarized beam 27 of an azimuth 90 deg. by a polarizing beam splitter BS15 and both beams are outputted as signal components got rid of a noise component through a polarizing beam splitter BS28, beam detector 30A, 30B and an operation circuit 35. The phase difference between both signals inputted is detected by a phase detector 31 to be displayed on a display device 33 through an operation circuit 32.

KOIKE OSAMU
MIURA NOBUHIKO
YAMAGAMI TORU

JP22977186A

April 15, 1988

September 30, 1986

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HOYA CORP

G01B9/02; (IPC1-7): G01B9/02

Masaki Yamakawa

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