A dental optical coherence tomography system for scanning a sample has a swept source laser configured to generate output light having a range of wavelengths. Two or more optical channels each provide a reference and sample path for the output light, wherein each optical channel has a corresponding detector to provide an output signal according to combined light from the sample and reference, wherein the detector output signal characterizes back-reflected or back-scattered light from the sample path over a range of depths below a surface. A scanning reflector simultaneously directs sample path output light from each of the two or more channels toward the sample surface and directs returned light from the sample to the corresponding sample path and detector. A processor is in signal communication with the detector for each optical channel and that is configured to record and store results from the output signals received from each detector.

Apparatus and methods are presented for enhancing the acquisition speed or performance of Fourier domain optical coherence tomography. In preferred embodiments a plurality of wavelength combs containing interleaved selections of wavelengths from a multi-wavelength optical source are generated and projected onto a sample. In certain embodiments the wavelength combs are projected simultaneously onto a plurality of regions of the sample, while in other embodiments the wavelength combs are projected sequentially onto the sample. Light in the wavelength combs reflected or scattered from the sample is detected in a single frame of a sensor array, and the detected light processed to obtain a tomographic profile of the sample. In preferred embodiments the wavelength comb generator comprises a wavelength interleaver in the form of a retro-reflective prism array for imparting different displacements to different selections of wavelengths from the optical source.

In one general aspect, an apparatus can include a first laser subsystem configured to transmit a first laser beam at a first location on an object at a time and a second laser subsystem configured to transmit a second laser beam at a second location on the object at the time. The apparatus can include an analyzer configured to calculate a first velocity based on a first reflected laser beam reflected from the object in response to the first laser beam. The analyzer can be configured to calculate a second velocity based on a second reflected laser beam reflected from the object in response to the second laser beam. The first location can be targeted by the first laser subsystem and the second location can be targeted by the second laser subsystem such that the first velocity is substantially the same as the second velocity.

An interferometry system includes a plurality of coherent light sources that each generate a beam of coherent light. Separate waveguide pathways are optically associated with each coherent light source. Each separate waveguide pathway has an endpoint configured to emit at least a portion of the beam of coherent light from the associated light source. A plurality of photodetectors is optically associated with waveguide pathways. In some cases, a retroreflector receives the light emitted from the endpoints, modulates the received light, and directs the modulated light back to the endpoints. The modulated light and a portion of the coherent light reflected from the endpoint of the waveguide pathway receiving the modulated light is directed a photodetector.

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.

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 atomic force microscope (“AFM”) based interferometer, uses a light source, and a splitting optical interface, splitting the light beam into a signal light beam and a reference light beam. Both the signal and reference light beams are focused in the vicinity of an AFM cantilever. A beam displacer introduces a lateral displacement between the signal light beam and reference light beam, the lateral displacement being such that, in at least one plane between the beam displacer and the focusing lens structure, the center of the signal light beam is separated from the center of the reference light beam by more than half a sum of their beam diameters on that plane. A detector operates to determine differences in optical path length between the signal light beam and reference light beam to determine information about movement of the cantilever.

Self-mixed interferometer (SMI) devices and techniques are described for measuring depth and/or velocity of objects. The SMI devices and techniques may be used for eye-tracking. A light source of an SMI sensor emits coherent light that is directed to a target location with a scanning module. One or more SMI signals are measured. The one or more SMI signals are generated by the SMI sensor in response to feedback light received from the target location. The feedback light is a portion of the coherent light that illuminated the target location.

A single-beam three-degree-of-freedom homodyne laser interferometer based on an array detector. A single-frequency laser beam is input to a Michelson interference structure, the measurement beam and the reference beam perform non-coaxial interference and form a single-beam homodyne interference signal by setting the angle of a reference plane mirror, the array detector is selected to effectively receive the single-beam homodyne interference signal, and finally, three-degree-of-freedom signal linear decoupling on the single-beam homodyne interference signal is achieved through a three-degree-of-freedom decoupling method based on Lissajous ellipse fitting. The laser interferometer does is free of angle decoupling nonlinearity, the period nonlinear error is remarkably reduced, compared with other existing three-degree-of-freedom laser interferometers, the laser interferometer has the advantages of being simple in structure, large in angle measurement range and easy to integrate, and the high-precision requirement of the three-degree-of-freedom laser interferometer for displacement and angle measurement is met.

Self-mixed interferometer (SMI) devices and techniques are described for measuring depth and/or velocity of objects. The SMI devices and techniques may be used for eye-tracking. A light source of an SMI sensor emits coherent light that is directed to a target location with a scanning module. One or more SMI signals are measured. The one or more SMI signals are generated by the SMI sensor in response to feedback light received from the target location. The feedback light is a portion of the coherent light that illuminated the target location.