US 11,885,879 B2
Measurement apparatus and measurement method
Yoshimasa Suzuki, Ibaraki (JP); Shinichi Hara, Ibaraki (JP); and Hiroki Ujihara, Ibaraki (JP)
Assigned to Mitutoyo Corporation, Kanagawa (JP)
Filed by Mitutoyo Corporation, Kanagawa (JP)
Filed on Aug. 19, 2020, as Appl. No. 16/997,823.
Claims priority of application No. 2019-153780 (JP), filed on Aug. 26, 2019.
Prior Publication US 2021/0063573 A1, Mar. 4, 2021
Int. Cl. G01C 3/08 (2006.01); G01S 17/34 (2020.01); G01S 7/4913 (2020.01); G01S 7/4912 (2020.01)
CPC G01S 17/34 (2020.01) [G01S 7/4913 (2013.01); G01S 7/4917 (2013.01)] 16 Claims
OG exemplary drawing
 
1. A measurement apparatus comprising:
a laser apparatus that has an optical cavity and outputs a frequency-modulated laser beam with a plurality of modes;
a branch that branches a first portion of the frequency-modulated laser beam output by the laser apparatus as a reference light and at least some of a remaining second portion of the frequency-modulated laser beam as a measurement light;
a beat signal generator that generates a beat signal by mixing the reference light and a reflected light that is reflected by radiating the measurement light onto an object;
first analyzer circuitry configured to analyze a first signal component corresponding to a difference in a propagation distance between the reference light and the measurement light on the basis of the beat signal;
second analyzer circuitry configured to analyze a second signal component corresponding to a cavity frequency of the optical cavity on the basis of the beat signal; and
calculation circuitry configured to calculate the difference in the propagation distance between the reference light and the measurement light based on analysis results of the first signal component and the second signal component.