An interferometer arrangement includes a beam splitter (8), two retroreflectors (15, 16), a drive (24) that moves at least one of the retroreflectors to alter an optical path difference between interferometer arms (13, 14), a converging element (18) for reference light, and a reference light detector (19) with at least three detector areas (19a-19d). First and second pairs of detector areas are aligned in respective first and second directions, wherein the first direction, the second direction and a central propagation direction of the reference light at the reference light detector are linearly independent. At least two actuators (9, 10) alter a lateral shear between two reference light partial beams (11, 12), which are reflected back from the interferometer arms and superimposed at the beam splitter, in at least two degrees of freedom. Control electronics (38) control the actuators depending on signals (Sa-Sc) at the detector areas, thereby minimizing the shear.

An interferometric measurement system includes ports configured to receive an optical signal from an optical source and an optical signal from a target. A photonic integrated circuit includes a variable delay configured to select between at least two optical paths from the input to an output such that the optical signal from the optical source passes to the output while experiencing an optical delay based on a selected one of the at least two optical paths where a loss of the optical signal from the optical source provided to the input that passes to the output is nominally the same for each of the at least two optical paths. An optical receiver is configured to receive the optical signal from the target and to receive the optical signal from the optical source that experiences the optical delay based on the selected one of the at least two optical paths and generates a corresponding electrical receive signal at an electrical output. A processor is configured to generate an interferometric measurement signal based on the receive signal.

The disclosure discloses a phase delay extraction and compensation method in a PGC phase demodulation technology. The sinusoidal phase modulation interference signal is converted into a digital interference signal by an analog-to-digital converter after amplification and filtering, and the digital interference signal is subjected to orthogonal downmixing of first-order, second-order, and fourth-order harmonics simultaneously to obtain three pairs of orthogonal harmonic amplitude signals. The three pairs of orthogonal harmonic amplitude signals are used to extract phase delay, and the result is used to calculate the corresponding phase delay correction coefficients, and the phase delay correction coefficient are multiplied by the corresponding absolute harmonic amplitude signal equal to the sum of the absolute value of the orthogonal harmonic amplitude signals to obtain a new harmonic amplitude signal that is not affected by the phase delay, then the phase to be measured is obtained through the arc tangent operation.

An interferometric measurement system includes ports configured to receive an optical signal from an optical source and an optical signal from a target. A photonic integrated circuit includes a variable delay configured to select between at least two optical paths from the input to an output such that the optical signal from the optical source passes to the output while experiencing an optical delay based on a selected one of the at least two optical paths where a loss of the optical signal from the optical source provided to the input that passes to the output is nominally the same for each of the at least two optical paths. An optical receiver is configured to receive the optical signal from the target and to receive the optical signal from the optical source that experiences the optical delay based on the selected one of the at least two optical paths and generates a corresponding electrical receive signal at an electrical output. A processor is configured to generate an interferometric measurement signal based on the receive signal.

OCT measuring device in the present exemplary embodiment includes: wavelength sweep light source that emits light of which a wavelength is swept; optical interferometer that divides the light into measurement light and reference light, emits measurement light toward measurement surface of measuring target object, and generates an optical interference intensity signal indicating an intensity of interference between measurement light reflected from measurement surface and reference light; electro-optic element which is a phase modulator arranged in a light path of optical interferometer; measurement processor which is a signal generator that derives a position of measurement surface and generates a phase amount indicator signal that indicates a phase amount of phase modulator based on the optical interference intensity signal; and electro-optic element controller which is a phase amount controller that controls the phase amount given to the light that is transmitted through phase modulator.

Various disclosed embodiments provide illustrative interferometers, optical phase locked loops, laser systems, interferometry methods, and phase locked loop methods. In illustrative embodiments, light from a laser is split into a first arm and a second arm. Light in an arm chosen from the first arm and the second arm is time delayed. The light in the first arm is split into third, fourth, and fifth arms. The light in the second arm is split into sixth, seventh, and eighth arms. Light in the seventh and eighth arms is phase shifted relative to light in the sixth arm. Light in the third, fourth, and fifth arms is combined with light in the sixth arm and phase shifted light in the seventh and eighth arms, respectively. A frequency correction signal for the laser is generated.

A multimodality system includes first and second modalities, a catheter, and a processor. The catheter collects fluorescent light from a plurality of locations of a sample which has been irradiated with excitation light of the second modality; a detector detects intensity of the fluorescent light received from the plurality of locations as a function of an angle α formed between the normal to the sample surface and the optical axis of the excitation light. A processor calculates the angle α at each of the plurality of locations based on radiation of the first modality incident on the sample, and corrects the intensity of the detected fluorescent light using a calibration factor g(α). The calibration factor g(α) is a function of the angle α calculated at two or more of the plurality of locations. The angle α is composed of a transversal angle α.sub.t and an axial angle α.sub.a.

An image acquisition apparatus includes a light source configured to emit light, a dividing unit configured to divide the light from the light source into reference light and measurement light, an image forming unit configured to form a tomographic image of a subject based on interfered light in which return light from the subject irradiated with the measurement light and the reference light are interfered, a focus adjusting unit configured to adjust a focus of the measurement light, an optical-path-length adjusting unit configured to adjust an optical path length of the reference light, and a control unit configured to adjust the optical path length of the reference light by controlling the optical-path-length adjusting unit according a change in an optical path length of the measurement light caused by adjustment of the focus using the focus adjusting unit.

Disclosed is a stitching-measurement device adapted for performing stitching-measurement on a surface of a concave spherical lens, including: an interferometer, a reference lens, a first plane mirror, a second plane mirror, a first adjustment mechanism, a second adjustment mechanism, a concave spherical object to be measured, a motion table and a control mechanism, the first plane mirror being mounted on the first adjustment mechanism configured to change a position of the first plane mirror; the second plane mirror being mounted on the second adjustment mechanism configured to change a position of the second plane mirror; the concave spherical object to be measured being placed on the motion table configured to change a position of the concave spherical object to be measured; the control mechanism communicating with the interferometer, the first adjustment mechanism, the second adjustment mechanism, and the motion table for issuing control signals, wherein by the first adjustment mechanism and the second adjustment mechanism, an included angle between the first plane mirror and the second plane mirror is adjusted in such a way that light beam incident on the concave spherical object to be measured is inclined by a first angle relative to light beam emitted from the reference lens, thereby avoiding an operation of inclining the concave spherical object to be measured during the stitching-measurement.

Our high phase sensitivity wide-field phase cancellation interferometry system allows single-shot, label-free optical sensing of neural action potentials via imaging of optical path length changes. Single-shot sensing and monitoring of single neurons within a neural network should lead to a more comprehensive understanding neural network processing, which is beneficial for the advancement in the field of neuroscience as well as its biomedical applications and impact. Our system cancels the phase profile of the resting neuron from the phase profile of the spiking neuron, improving the sensitivity by two orders of magnitude. Using a detector with an extremely large well depth and an appropriately biased interferometer increases the sensitivity by another order of magnitude, yielding a measurement that is three orders of magnitude more sensitive than those possible with other microscopes.