A frequency modulation continuous wave (FMCW)-based system configured to convert measurements of a linearly modulated wave from a time-domain into a frequency-domain to produce a non-linear frequency signal, where the non-linear frequency signal comprises a known linear component representing the desired linear modulation and an unknown non-linear component representing the non-linearity of the modulation. The FMCW-based system is further configured to determine coefficients of a basis function approximating a difference between the non-linear frequency signal and the linear frequency component in the frequency domain. The FMCW-based system is further configured to detect one or multiple spectrum peaks in the distorted beat signal with the distortion compensated according to the basis function with the determined coefficients to determine one or multiple distances to the one or multiple objects in the scene.

A method of determining residual intensity noise (RIN) of a sensor may comprise determining a first amplitude of a first harmonic of the sensor while a signal propagating through the sensor is modulated at a modulating frequency corresponding to twice an eigenfrequency of the sensor. The method may further comprise determining a second amplitude of a second harmonic of the sensor while the signal propagating through the sensor is modulated the modulating frequency, and determining the RIN of the sensor as a ratio of the first amplitude and the second amplitude.

A system comprises a faceted structure imaging assembly and a faceted structure image analyzer. The system is configured to determine carat weight of a gemstone while in a mounted setting. In a first mode, the imaging assembly obtains a first image of a top gemstone surface. The image analyzer uses the first image to obtain at least one gemstone dimension, such as table and diameter dimensions. In a second mode, the imaging assembly obtains a second image of the top gemstone surface while a colored light pattern is reflected onto the gemstone. The image analyzer uses the second image to obtain at least one other gemstone dimension, such as crown and pavilion angles. The image analyzer uses the dimensions obtained from the first and second images to determine weight information of the gemstone. The system quickly determines gemstone weight reliably and consistently without skilled gemologists or removal from the setting.

Disclosed herein are systems, methods, and devices for calibrating contrast measurements from laser speckle imaging systems to accurately determine unknown particle motion characteristics, such as flow rate. The calibration stores to memory calibration data, which may include a set of measurements from samples with known particle characteristics and/or estimates of noise, including the effects on contrast arising from undesired signals unrelated to the unknown particle motion characteristics. The calibration data may be accessed and used to correct an empirical measurement of contrast and/or interpolate a value of the unknown particle motion characteristic. The system may include a light source, photodetector, processor, and memory, which can be combined into a single device, such as a wearable device, for providing calibrated flow measurements. The device may be used, for example, to measure blood flow, cardiac output, and heart rate, and can be used to amplify the pulsatile signal.

Systems and methods are provided for identifying a suitable surgical location and/or trajectory for proceeding with a surgical procedure based on local polarization-sensitive optical coherence tomography imaging (PS-OCT). PS-OCT images are obtained of a tissue region and are processed to provide a spatial map of anisotropic structure within the tissue region. The anisotropic structure is processed to determine one or more suitable surgical locations and/or trajectories for avoiding or reducing damage to local anisotropic tissue structure identified within the tissue region. The spatial map of the anisotropic structure is registered with pre-operative volumetric image data identifying anisotropic tissue structure within a second tissue region that is larger than the tissue region imaged by PS-OCT.

An implementation cost of a line-scan optical coherence tomography (OCT) apparatus is reduced by miniaturizing a scanning mirror and using a light source with relaxed requirement in intensity uniformity. The mirror reflects a probe light beam to different parts of a sample for line-scanning the sample. A line-compressing lens compresses the probe light beam's cross-sectional length before the beam reaches the mirror, allowing the mirror to be miniaturized to reflect only the compressed beam. In generating a linear light beam that gives the probe light beam, a cascade of collimating lens, Powell lens and focusing lens generates the linear light beam from a raw light beam of a point source. A slit further filters the linear light beam to remove a peripheral portion thereof such that the linear light beam is substantially uniform in intensity even if an asymmetrical divergent light source is used.

An optical coherence tomography (OCT) apparatus includes a light source unit to generate light, a coupler unit to generate coupled light using reference light and measurement light generated by splitting the light, split the coupled light into n coupled and split lights and irradiate the n coupled and split lights, wherein n is a natural number greater than or equal to 2, a detection unit to irradiate the incident n coupled and split lights to n spectroscopes respectively and sequentially scan each light separated from each of the spectroscopes by wavelength range, and an image generation unit to generate a 2-dimensional single image using a result of the scanning by the detection unit. Accordingly, it is possible to improve the OCT image acquisition rate by distributing the scan time for a plurality of split lights using a plurality of array detectors.

The present disclosure relates to an apparatus and a method for a thickness and a profile of a multilayer thin film using a vibration insensitive interference method are provided, which allow measuring the phase of a measurement object by acquiring a plurality of different phase-shifted interference signal images at a time through interference signals between a reference flat and the measurement object by a polarizing beam splitter, a quarter-wave plate, a shutter and a pixelated polarizing camera, and which also allow measuring reflectance of the measurement object by acquiring a plurality of reflected signal images obtained at a time through respective reflected lights for each of a reference surface and the measurement object by a plurality of different polarizers.

Measurement cavities described herein include a cylindrical chamber having a first open end and a second open end; a first cap covering the first open end of the cylindrical chamber and a second cap covering the second open end of the cylindrical chamber, wherein the first and second caps hermetically seal the cylindrical chamber and wherein the first cap is rigidly coupled to the second cap; and a wafer holder positioned within and coupled to the cylindrical chamber. The measurement cavity has a mass m, a stiffness k, and a damping constant c configured such that the transmissibility $.Math.\frac{x}{F}.Math.$
of an input force at 60 Hz in the measurement cavity is reduced by a factor of at least 10 and the measurement cavity has a natural frequency of greater than 300 Hz.

The present invention addresses to a multidirectional dynamic phase shifting interferometry (DPSI) shearography and interferometry sensor. The present invention uses a configuration with three fixed prisms, or a single fixed three-facet optical prism constructed so as to achieve the same effect as three prisms and thus simultaneously obtain three images with phase shifting. The present invention also encompasses a method of inspection and measurement of vibration modes using said sensor.