Patent ID: 11879975
Assignee: MITUTOYO CORPORATION
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 7:
8. A measurement method of a measurement apparatus for measuring a distance to an object to be measured, the method comprising:
outputting a frequency-modulated laser beam;
splitting the frequency-modulated laser beam such that a portion of the frequency-modulated laser beam is a reference light and at least some of the remaining portion of the frequency-modulated laser beam is a measurement light;
outputting, as a reference signal, a signal including a reference beat signal obtained by mixing the reference light and an end-face reflected light reflected from an exit end face that emits the measurement light in a state without the object to be measured;
storing information obtained by converting the reference signal into a frequency signal, as a reference frequency signal;
generating a plurality of beat signals by mixing the reference light and a reflected light that is reflected by radiating the measurement light onto the object to be measured;
performing a frequency analysis on a frequency signal obtained by subtracting, for each frequency, a signal level of the reference frequency signal from a signal level of frequency signals which are converted from the beat signals into frequency domain signals; and
calculating a difference between propagation distances of the reference light and the measurement light based on a result of the frequency analysis.