The present invention discloses a real-time normalization apparatus and method of the PGC demodulation in a sinusoidal phase modulation interferometer. An optical setup containing a measuring interferometer and a monitoring interferometer is constructed. An electro-optic phase modulator is placed in the common reference arm of the two interferometers. High-frequency sinusoidal wave modulation and low-frequency triangular wave modulation are applied to the electro-optic phase modulator at the same time. Sinusoidal modulation is used for generating phase carrier, and PGC demodulation is performed to obtain quadrature signals containing the phase information to be measured. Triangular wave modulation makes the quadrature signals change periodically. Ellipse fitting is performed on the Lissajous figure corresponding to the quadrature signals, and real-time normalization of the PGC demodulated quadrature signals is achieved. By calculating the variation of the phase difference between the two interference signals, the measured displacement is obtained, and nanometer scale displacement measurement is achieved.

A sensor is provided. The sensor includes at least one optical waveguide and an optical reflector. The optical reflector is optically coupled to the at least one optical waveguide and includes a first portion and a second portion. The first portion is configured to reflect a first portion of light back to the at least one optical waveguide. The second portion is configured to reflect a second portion of light back to the at least one optical waveguide. The reflected second portion of the light differs in phase from the reflected first portion of the light by a phase difference that is not substantially equal to an integer multiple of when the second portion of the optical reflector is in an equilibrium position in absence of the perturbation.

An illumination apparatus generates an interference fringe. An input arm receives an input light beam from a light source. A splitter splits the input light beam that has passed through the input arm into a first output arm and a second output arm. A phase modulator changes a phase difference between the output light beams of the first output arm and the second output arm. A phase detector detects the phase difference between output light beams respectively output from the first output arm and the second output arm based on a return light beam generated by combining a first reflected light beam and a second reflected light beam respectively reflected by ends of the first output arm and the second output arm.

An apparatus and a method for measuring blood flow of vessels are provided. The apparatus includes a light source, a light splitting module, a reference arm module, a sample arm module, a probing module, and a control system. The sample arm module includes a scanning unit and an optical-path shifting device. A probe light is obtained from the light splitting module, and a central line of a main light of the probe light extends through a rotation axis of the scanning unit. The probe light is reflected by the scanning unit to the optical-path shifting device. When the optical-path shifting device is rotated between a first position and a second position respectively, the probe light scans a vessel in fundus to obtain a first phase shift signal and a second phase shift signal blood flow rates and total blood flow of all the vessels near an optic disc are determined.

Methods and systems for stabilized directional couplers are disclosed and may include a system comprising first and second directional couplers formed by first and second waveguides, where one of the waveguides may comprise a length extender between the directional couplers. The directional couplers may be formed by reduced spacing between the waveguides on opposite sides of the length extender. An input optical signal may be communicated into one of the waveguides, where at least a portion of the input optical signal may be coupled between the waveguides in the first directional coupler and at least a portion of the coupled optical signal may be coupled between the waveguides in the second directional coupler. Optical signals may be communicated out of the system with magnitudes at a desired percentage of the input optical signal. The length extender may add phase delay for signals in one of the first and second waveguides.

The phase shift interferometer is configured to measure the shapes of measurement objects by acquiring a plurality of images of interference fringes while shifting the phases of the interference fringes. The interference fringes are provided with a phase difference of 90 relative to each other utilizing polarization of light. Images of the interference fringes are captured by two respective cameras while, in accordance with a conventional phase shift method, mechanically displacing a reference surface or a reference optical path to shift the phases. The phases of the interference fringes are calculated independently from the respective images acquired by the cameras and an average of the two phase calculation results is calculated.

A non-invasive system and method. Sample light is delivered into an anatomical structure, such that a portion of the sample light passes through a target voxel comprising brain matter in the head and is scattered by the head as signal light. The signal light is detected, changes in the level of water concentration or relative water concentration of the target voxel are detected based on the detected signal light, and a level of neural activity is determined within the target voxel based on the determined changes level of the water concentration or relative water concentration of the target voxel.

Techniques for removing interferometry signal phase variations caused by distortion and other effects in a multi-layer stack include: providing an electronic processor sample interferometry data acquired for the stack using a low coherence imaging interferometry system; transforming, by the electronic processor, the sample interferometry data to a frequency domain; identifying a non-linear phase variation from the sample interferometry data in the frequency domain, in which the non-linear phase variation is a result of dispersion introduced into a measurement beam by the test sample; and removing the non-linear phase variation from the sample interferometry data thereby producing compensated interferometry data.

A method including: scanning a sample over a period of time using an electro-magnetic radiation source, the period of time including a first time period and a second time period, a sample portion of the electro-magnetic radiation source being directed to the sample in a sample arm of an optical interferometric system, and a reference portion of the electro-magnetic radiation source being directed to a reference arm of the optical interferometric system; applying, using a phase modulator, a phase shift comprising a first phase shift and a second phase shift to at least one of the reference portion or the sample portion of the electro-magnetic radiation source, the first phase shift being applied during the first time period and the second phase shift being applied during the second time period, the second phase shift having a difference of 90 degrees from the first phase shift.

A position measurement system configured to measure a position of an object. The system includes an optical system to obtain a first measurement wave and a second measurement wave from a radiation source, and to allow the first and second measurement wave to at least partially interfere with each other after interaction of at least one of the first and second measurement wave with the object to form a first detection beam. The system further includes a first detector to receive the first detection beam. The system also has a processing unit configured to receive an output from the first detector and to determine a signal representative for the position of the object from the output, wherein the optical system includes a phase modulator configured to modulate a phase difference between the first measurement wave and the second measurement wave.