A reference laser beam locked to a femtosecond optical frequency comb is modulated through a high frequency electro-optic phase modulator, and laser sidebands with equal intervals are generated. Beat frequency is performed on the sixth-order sideband and the frequency sweeping laser beam, a beat signal and a frequency sweeping signal source are down-mixed to generate a difference frequency signal, and the difference frequency signal is locked to a reference clock through a digital phase detector and a PID controller. The frequency sweeping laser beam is locked to reference laser beam with a dynamic offset frequency under the closed loop control, and sinusoidal frequency sweeping is simultaneously performed together with the frequency sweeping signal source. The locked laser beam is used for absolute distance measurement, and a distance to be measured is obtained according to the synthetic wavelength transition theory.

The present disclosure provides an external parameter calibration method for robot sensors as well as an apparatus, robot and storage medium with the same. The method includes: obtaining first sensor data and second sensor data obtained through a first sensor and a second sensor of the robot by collecting position information of a calibration reference object and converting to a same coordinate system to obtain corresponding first converted sensor data and second converted sensor data, thereby determining a first coordinate and a second coordinate of a reference point of the calibration reference object; using the first coordinate and the second coordinate are as a set of coordinate data; repeating the above-mentioned steps to obtain N sets of the coordinate data to calculate the external parameter between the first sensor and the second sensor in response to a relative positional relationship between the robot and the calibration reference object being changed.

A digital measuring device implemented on a photonic integrated circuit, the digital measuring device including a laser source configured to provide light, a first ring resonator configured to produce a first frequency comb of light from the laser source, wherein at least a portion of the first frequency comb of light is directed at a moving object, a local oscillator configured to provide a reference beam, at least one waveguide structure configured to combine the reference beam with light reflected from the moving object to produce a measurement beam, a first multiplexer configured to split the measurement beam into a plurality of channels spaced in frequency, and a plurality of detectors configured to detect an intensity value of each channel of the plurality of channels to measure a distance between the digital measuring device and the moving object.

Improved optical coherence tomography systems and methods to measure retinal data are presented. The systems may be compact, provide in-home monitoring, and have automation to allow the patient to measure himself or herself.

An interferometer system including: an optical system arranged to split a radiation beam from a laser source into a first beam along a first optical path and a second beam along a second optical path, and recombine the first beam and the second beam to a recombined beam, a detector to receive the recombined beam and to provide a detector signal based on the received recombined beam, and a processing unit, wherein a first optical path length of the first optical path and a second optical path length of the second optical path have an optical path length difference, and wherein the processing unit is arranged to determine a mode hop of the laser source on the basis of a phase shift in the detector 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.

A five-degree-of-freedom heterodyne grating interferometry system, comprising a single frequency laser device (1) and an acousto-optic modulator (2); the single frequency laser device (1) emits a single frequency laser, and the single frequency laser is coupled by optical fiber and, after being split, enters the acousto-optic modulator (2) to obtain two linearly polarized lights of different frequencies, one being a reference light, and one being a measurement light; an interferometer lens group (3) and a measurement grating (4), used for forming the reference light and the measurement light into a measurement interference signal and a compensation interference signal; and multiple optical fiber bundles (5), respectively receiving the measurement interference signal and the compensation interference signal, each optical fiber bundle (5) having multiple multimode optical fibers respectively receiving signals at different positions on the same plane. The present measurement system has the advantages of high measurement precision, a large measurement range, not being sensitive to temperature drift, and small overall size, and can be used as a photoetching machine ultra-precision workpiece table position measurement system.

An optical proximity sensor includes a first vertical cavity surface-emitting laser configured for self-mixing interferometry to determine distance to and/or velocity of an object. The optical proximity sensor also includes a second vertical cavity surface-emitting laser configured for self-mixing interferometry to determine whether any variation in a fixed distance has occurred. The optical proximity sensor leverages output from the second vertical cavity surface-emitting laser to calibrate output from the second vertical cavity surface-emitting laser to eliminate and/or mitigate environmental effects, such as temperature changes.

A method, measuring device, machining system and computer program product are provided for determining a corrected height signal from measurement data obtained with optical coherence tomography. The measurement data comprises an object signal and a background signal superimposed on the object signal, the object signal and the background signal being subject to different dispersion. A first transformation is performed comprising transforming the measurement data, the first transformation being targeted at the background signal to obtain a height signal, background components in the height signal are determined, the background components in the height signal are compensated to obtain a background-compensated height signal, an inverse transformation is performed comprising back-transforming the background-compensated height signal to obtain background-compensated measurement data, dispersion compensation for the object signal is performed to obtain dispersion-compensated and background-compensated measurement data, and a second transformation is performed comprising transforming the dispersion-compensated and background-compensated measurement data to obtain a dispersion-compensated and background-compensated height signal.

The invention relates to a device for measuring a substrate for semiconductor lithography with a reference interferometer for ascertaining the change in the ambient conditions, wherein the reference interferometer comprises a means for changing the optical path length of a measurement section of the reference interferometer, wherein the means is configured to bring about a change in the refractive index.

Furthermore, the invention relates to a method for correcting cyclic error components of a reference interferometer, wherein the reference interferometer comprises a means for changing the optical path length of a measurement section of the reference interferometer, comprising the following method steps: starting up the reference interferometer, continuously detecting measurement values of the reference interferometer, changing the optical path length of the measurement section of the reference interferometer until a path length change of at least one quarter of the wavelength of the reference interferometer is detected, determining the cyclic errors on the basis of the continuously detected measurement values of the reference interferometer, and correcting the current measurement values ascertained by the reference interferometer on the basis of the cyclic errors ascertained.