Apparatus include a polarization state generator situated to provide an interferometer source beam with a region of polarized source light with a polarization state that is in-plane as subsequently incident on a sample and a region of polarized source light with a polarization state that is perpendicular to in-plane as subsequently incident on the sample, and an interferometer unit configured to split the interferometer source beam into test and reference arm beams, to direct the test arm beam to the sample and the reference arm beam to a reference surface, and to recombine the test and reference arm beams to produce an interferometer output beam. Methods use a polarization state generator to produce an interferometer source beam and use an interferometer unit which splits the interferometer source beam into test and reference arm beams.

An interferometer includes a coherent light source and an array of electrically coupled light-sensitive pixel elements. The interferometer is configured to direct an internal optical path of the coherent light source and an external optical path of the coherent light source into a monolithic unit cell. In addition, the monolithic unit cell is configured to direct the internal optical path first through the monolithic unit cell and then onto the array and also configured to direct the external optical path back outside the monolithic unit cell through an external environment and then back into the monolithic unit cell and finally onto the array. In addition, interferometer is further configured to combine the internal optical path and the external optical path at the array and produce a first interferogram on the array, the interferogram characterizing an optical property of the external environment.

A laser interferometer includes alight source that emits first laser light, an optical modulator that includes a vibrator and modulates the first laser light by using the vibrator to generate second laser light including a modulated signal, a photodetector that receives interference light between third laser light including a sample signal generated by reflecting the first laser light on an object and the second laser light to output a light reception signal, a demodulation circuit that demodulates the sample signal from the light reception signal based on a reference signal, and an oscillation circuit that outputs the reference signal to the demodulation circuit, and the vibrator is a signal source of the oscillation circuit.

An optical complex amplitude measurement apparatus causes a polarization controller to perform control of making a polarized beam of a signal beam having a frequency that is output from a first laser and then passes through a measurement target match with a polarized beam of a reference beam from a second laser. A spatial filter extracts, from the matched signal beam, a plane wave component in which a wave front is distorted due to the passage, and outputs a signal beam having the frequency. The second laser performs a phase synchronization control of a frequency of the reference beam such that a frequency difference due to multiplexing of the signal beam and the reference beam by a homodyne interferometer becomes 0. The controlled reference beam and the signal beam from the polarization controller are multiplexed by a beam splitter.

A system and method for demodulation of a fiber optic interferometric sensor are provided. Another aspect pertains to a system and method employing a single laser to generate multiple quadratic wavelengths to demodulate fiber optic interferometric sensors with approximately sinusoidal fringes. Yet another aspect of the present system and method uses a single frequency laser which is split into multiple paths using a fiber optic coupler, with one path including an intensity modulator and another path including an acousto-optic modulator, whereafter the paths are recombined into a fiber which leads to an interferometric sensor, and the light reflected from the sensor is then directed to a photodetector. A further aspect employs a single frequency laser which is split into multiple paths, with the light in the paths being modulated at different frequencies, whereafter the paths are recombined into a fiber which leads to an interferometric sensor.

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.

Disclosed is a heterodyne grating interferometry system based on secondary diffraction, including a single-frequency laser, an input optical fiber, an acousto-optic modulator, a reading head, and a measurement grating, an output optical fiber, a photoelectric conversion unit and an electronic signal processing unit, wherein the single-frequency laser emits a single-frequency laser, which enters the acousto-optic modulator through the input optical fiber, and is divided into a reference light and measurement light to be input to the reading head, wherein the reading head and the measurement grating convert the reference light and measurement light into a reference interference optical signal and a measurement interference optical signal and send them to the photoelectric conversion unit through the output optical fiber and wherein the photoelectric conversion unit converts the measurement interference optical signal and the reference interference optical signal into a measurement interference electrical signal and a reference interference electrical signal.

A system for polarization-sensitive optical coherence tomography (PS-OCT) of a sample comprises an interferometric arrangement comprising a reference arm and a sample arm, the sample arm being arranged to emit optical radiation towards the sample; a phase modulation system arranged at an input to the sample arm; and a detector arranged to detect a signal generated by interference between a reference beam from the reference arm and a sample beam from the sample arm. The phase modulation system comprises: an electro-optic modulator; a polarizer arranged at a rotation angle relative to the fast axis of the electro-optic modulator; and a signal generator for delivering a driving voltage to the electro-optic modulator; wherein the rotation angle and the driving voltage are selected such that the phase modulation system generates three mutually orthogonal polarization states.

An Optical Coherence Tomography receiver may include prisms, polarizing beam splitters, reflectors, lenses, and a photodetector array arranged in a compact package. Sample and reference beams are combined into an interference beam and split in two. The two resulting interference beams are then split into two polarization sates each. The optical path lengths for both pairs of interference beams with the same polarization state are equal or nearly equal.

The present disclosure provides an OCT imaging system having a variety of advantages. In particular, the OCT system of the present disclosure may provide a more intuitive interface, more efficient usage of controls, and a greater ability to view OCT imaging data.