An optical phase modulation amount measurement technology using sound without being affected by noise included in an average light intensity is provided. A sound measurement method includes an interference light generation step of obtaining first light including light subjected to light phase modulation by a sound measurement unit and second light including light subjected to light phase modulation by the sound measurement unit, which differs from the first light, from light emitted from a light source, a first light detection step of obtaining a first electrical signal from the first light, a second light detection step of obtaining a second electrical signal from the second light, and a differential signal generation step of obtaining a differential signal that is a difference between the first electrical signal and the second electrical signal, wherein a phase of the light subjected to light phase modulation included in the first light and a phase of the light subjected to the light phase modulation included in the second light are in an inverted relationship, and an optical phase modulation amount φ.sub.s by sound is measured as a current Δi of the differential signal expressed by an equation Δi=βI.sub.A cos (φ.sub.s+φ.sub.0) (where β is a predetermined constant, I.sub.A is an amplitude of an interference fringe, and φ.sub.0 is an optical phase modulation amount by an element other than sound).

A conversion unit converts a first electrical signal to a first distance value indicating a distance from an interferometer to a measurement target. An inclination value calculation unit calculates an inclination value based on the first distance value. A first distance value correction unit corrects the first distance value based on the inclination value. A second distance value correction unit calculates a second distance value indicating a distance from the optical interference range sensor to the measurement target based on the first distance value that has been corrected by the first distance value correction unit. If the number of times that the first electrical signal is detected is smaller than a second threshold, the first distance value correction unit corrects the first distance value based on an inclination value that precedes the inclination value associated with the first distance value in a storage unit.

There is provided a laser interferometer. The laser interferometer includes a laser light source; a first light splitter configured to split the laser light into first split light and second split light; an optical modulator configured to modulate the first split light into reference light from the first split light; a second light splitter configured to split the reference light and object light generated by an object to be measured reflecting the second split light into third split light and fourth split light; a first light receiving element configured to receive the third split light; and a second light receiving element configured to receive the fourth split light. An optical axis of the first split light that travels from the first light splitter toward the optical modulator is shifted from an optical axis of the reference light that travels from the optical modulator toward the first light splitter. A difference between an optical path length from the second light splitter to the first light receiving element and an optical path length from the second light splitter to the second light receiving element is 20 mm or less.

A laser interferometer includes: a laser light source configured to emit laser light; an optical modulator including a vibrator driven by a drive signal and configured to superimpose a modulation signal on the laser light using the vibrator; a photodetector configured to receive the laser light including a sample signal superimposed thereon due to reflection by an object and the laser light including the modulation signal, and output a light receiving signal; a calculation unit configured to perform a calculation on the light receiving signal based on a reference signal; and a signal generation unit configured to output the drive signal and the reference signal. The calculation unit includes a preprocessing unit configured to perform preprocessing for extracting a frequency modulation component from the light receiving signal based on the reference signal, and output a preprocessing signal including the frequency modulation component, a demodulation processing unit configured to demodulate the sample signal from the preprocessing signal based on the reference signal, and a correction processing unit configured to output a correction signal based on an output signal output in response to driving of the vibrator. The signal generation unit corrects the drive signal and the reference signal based on the correction signal.

A laser interferometer includes: a laser light source configured to emit laser light; an optical modulator including a vibrator driven by a drive signal and configured to superimpose a modulation signal on the laser light using the vibrator; a photodetector configured to receive the laser light including a sample signal superimposed thereon due to reflection by an object and the laser light including the modulation signal, and output a light receiving signal; a calculation unit configured to perform a calculation on the light receiving signal based on a reference signal; and a signal generation unit configured to output the drive signal and the reference signal. The calculation unit includes a preprocessing unit configured to perform preprocessing for extracting a frequency modulation component from the light receiving signal based on the reference signal, and output a preprocessing signal including the frequency modulation component, a demodulation processing unit configured to demodulate the sample signal from the preprocessing signal based on the reference signal, and a correction processing unit configured to output a correction signal based on an output signal output in response to driving of the vibrator. The signal generation unit corrects the drive signal and the reference signal based on the correction signal.

An adjustable beam directing optical system for a focused laser differential interferometer (FLDI) instrument according to various aspects of the present technology may include an optical half waveplate to achieve an incident linear polarization orientation with equal components of laser intensity aligned to the vertical and horizontal axis of the optical system, and an optical prism for splitting these components of an incident laser beam into two orthogonally-polarized beams equally about an optical axis of the FLDI instrument. A series of beam realignment devices positioned downstream of the optical prism are configured to selectively direct each beam to a predetermined location.

An adjustable beam directing optical system for a focused laser differential interferometer (FLDI) instrument according to various aspects of the present technology may include an optical half waveplate to achieve an incident linear polarization orientation with equal components of laser intensity aligned to the vertical and horizontal axis of the optical system, and an optical prism for splitting these components of an incident laser beam into two orthogonally-polarized beams equally about an optical axis of the FLDI instrument. A series of beam realignment devices positioned downstream of the optical prism are configured to selectively direct each beam to a predetermined location.

Systems, methods and apparatuses are used for monitoring material processing using imaging signal density calculated for an imaging beam directed to a workpiece or processing region, for example, during inline coherent imaging (ICI). The imaging signal density may be used, for example, to monitor laser and e-beam welding processes such as full or partial penetration welding. In some examples, the imaging signal density is indicative of weld penetration as a result of reflections from a keyhole floor and/or from a subsurface structure beneath the keyhole. The monitoring may include, for example, automated pass/fail or quality assessment of the welding or material processing or parts produced thereby. The imaging signal density may also be used to control the welding or material processing, for example, using imaging signal density data as feedback. The imaging signal density may be used alone or together with other measurements or metrics, such as distance or depth measurements.

The invention provides a laser processing system having the function of optical diffraction tomography, comprising: an integrated imaging optical path and a processing optical path; the imaging optical path is used to perform optical diffraction tomography on the device to be processed; the processing optical path is used for processing the device to be processed. Moreover, the specific optical path structure is introduced. During the processing of the device to be processed, the laser processing system can also perform real-time imaging of the device to be processed without shifting the device to be processed. That is to say, the laser processing and imaging processing of the device to be processed can be realized at the same time in a laser processing system.

A system and method for delivering stable light to a remote location are provided. The method includes splitting a laser beam generated by a laser into a reference beam and a delivery beam. The delivery beam is coupled into an optical fiber for delivery to the remote location. A reflected portion of the delivery beam comes back as a reflected delivery beam from the remote location through the optical fiber. An interference beam is generated by combining the reference beam and the reflected delivery beam. A phase difference between the reference beam and the reflected delivery beam is detected in order to adjust a phase of the laser beam based on the phase difference to reverse a phase shift of the delivery beam induced by noise added to the delivery beam while the delivery beam is transmitted through the optical fiber.