Measuring device and recording medium utilizing a polarized light phase difference to obtain a stress distribution

A measuring device comprising:

• a light emitter configured to selectively emit each of a plurality of beams of light having respective different wavelength bands;
• a splitter configured to split light in a wavelength band selected and emitted by the light emitter into measurement light and reference light, and to emit the measurement light and the reference light;
• a light transceiver to irradiate a measurement object with the measurement light from the splitter and to receive reflected light obtained by reflection of the emitted measurement light by the measurement object;
• an interferometer configured to combine the reference light with the reflected light from the light transceiver, to separate the combined light into two orthogonal beams of polarized light, to convert the two beams of polarized light into two analog electrical signals, and to output the two analog electrical signals;
• an analog-to-digital converter configured to convert the two analog signals from the interferometer into digital electrical signals and to output the digital electrical signals as two digital signals;
• and
• calculation processing circuitry configured to convert the digital electrical signals corresponding to the two beams of polarized light from the analog-to-digital converter into frequency spectra for each of the plurality of beams of light emitted from the light emitter, to calculate an optical path length difference between the reference light and the measurement light, to obtain a polarized light phase difference between the two beams of polarized light for each of the plurality of beams of light, and to obtain wavelength dependency of the polarized light phase difference,
• wherein the light emitter includes:
• at least one light source configured to emit a plurality of laser beams having respective wavelengths, a first laser beam among the plurality of laser beams having a first wavelength, a second laser beam among the plurality of laser beams having a second wavelength different from the first wavelength;
• a wavelength selector configured to receive, as an input, the plurality of laser beams from the light source to select the first laser beam from the input plurality of laser beams and output the first laser beam;
• and
• a sweeper configured to perform a wavelength sweep of the first laser beam selected by the wavelength selector in a corresponding first one of bands and to emit the swept first laser beam as first swept light to the splitter,
• wherein the measuring device further includes a switching controller configured to transmit a selection signal to the wavelength selector to select another wavelength in response to receiving a signal from the sweeper that the wavelength sweep of the first laser beam is complete,
• wherein the wavelength selector is further configured to select the second laser beam from the input plurality of laser beams based on the selection signal and output the second laser beam to the sweeper, and
• the sweeper is configured to perform the wavelength sweep of the second laser beam selected by the wavelength selector in a corresponding second one of bands and to emit the swept second laser beam as second swept light to the splitter.