US 12,386,069 B2
Measurement apparatus and measurement method
Hiroki Ujihara, Ibaraki (JP)
Assigned to Mitutoyo Corporation, Kawasaki (JP)
Filed by Mitutoyo Corporation, Kawasaki (JP)
Filed on Feb. 17, 2022, as Appl. No. 17/674,111.
Claims priority of application No. 2021-027060 (JP), filed on Feb. 24, 2021.
Prior Publication US 2022/0268931 A1, Aug. 25, 2022
Int. Cl. G01S 17/34 (2020.01); G01S 7/48 (2006.01)
CPC G01S 17/34 (2020.01) [G01S 7/4808 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A measurement apparatus comprising:
a laser apparatus, having a frequency shifter in an optical cavity, that outputs a frequency-modulated laser beam with a plurality of modes of a main lobe;
a branch that splits the frequency-modulated laser beam output from the laser apparatus into a reference light, a measurement light, and a monitor 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 to be measured;
extraction circuitry configured to extract a signal component including a plurality of self-beat signals based on the main lobe from an electrical signal generated by converting the monitor light;
identification circuitry configured to identify a cavity frequency of the optical cavity on the basis of the signal component extracted by the extraction circuitry; and
calculation circuitry configured to calculate a difference between propagation distances of the reference light and the measurement light on the basis of the cavity frequency of the optical cavity identified by the identification circuitry and the beat signal to generate a measurement.