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.

The disclosure provides a device for detecting a wavefront error by modal-based optimization phase retrieval using an extended Nijboer-Zernike (ENZ) theory. The detection device includes a point light source (1), a half mirror (2), a lens (3) to be tested, a plane mirror (4) and an image sensor (5). The wavefront error of the component under test is characterized by using a Zernike polynomial, and a Zernike polynomial coefficient is solved based on an ENZ diffraction theory. The present disclosure realizes the one-time full-aperture measurement on the wavefront error of a large-aperture optical component, and can use a partially overexposed image to achieve accurate wavefront error retrieval. Meanwhile, the present disclosure overcomes the contradiction between underexposure and high signal-to-noise ratio (SNR) caused by a limited dynamic range when the image sensor (5) acquires an image. The detection device is simple and does not have high requirements for the experimental environment.

The source light having a range of optical wavelengths is split into sample light and reference light. The sample light is delivered into a sample, such that the sample light is scattered by the sample, resulting in signal light that exits the sample. The signal light and the reference light are combined into an interference light pattern having optical modes having oscillation frequency components respectively corresponding to optical pathlengths extending through the sample. Different sets of the optical modes of the interference light pattern are respectively detected, and high-bandwidth analog signals representative of the optical modes of the interference light pattern are output. The high-bandwidth analog signals are parallel processed, and mid-bandwidth digital signals are output. The mid-bandwidth digital signals are processed over an i number of iterations, and a plurality of low-bandwidth digital signals are output on the ith iteration. The sample is analyzed based on the low-bandwidth digital signals.

A truncated non-linear interferometer-based sensor system includes an input that receives an optical beam and a non-linear amplifier that generates a probe beam and a conjugate beam from the optical beam. The system's local oscillators are related to the probe beam and the conjugate beam. The system includes a sensor that transduces an input with the probe beam and the conjugate beam. The transduction detects changes in the phase of each of the probe beam and the conjugate beam. The system's phase sensitive detectors detect phase modulations between the respective local oscillators, the probe beam, and the conjugate beam and outputs phase signals based on detected phase modulations. The system measures phase signals indicative of the sensor's input resulting from a sum or difference of the phase signals. The measurement exhibits a quantum noise reduction in an intensity difference, a phase sum, or an amplitude difference quadrature.

A method for determining a separation distance between a working head in a machine for laser processing a material and a surface of the material includes generating a measurement beam of low coherence optical radiation, leading the measurement beam towards the material and a reflected or diffused measurement beam towards an optical interferometric sensor arrangement in a first direction of incidence, generating a reference beam of low coherence optical radiation, leading the reference beam towards the optical interferometric sensor arrangement in a second direction of incidence superimposing the measurement and reference beams on a common region of incidence, detecting a position of a pattern of interference fringes between the measurement and reference beams on the common region of incidence, and determining a difference in optical length between the measurement and reference optical paths based on the position of the pattern of interference fringes along an illumination axis.

A digital measuring device implemented on a photonic integrated circuit, the digital measuring device including a laser source configured to provide light, a first ring resonator configured to produce a first frequency comb of light from the laser source, wherein at least a portion of the first frequency comb of light is directed at a moving object, a local oscillator configured to provide a reference beam, at least one waveguide structure configured to combine the reference beam with light reflected from the moving object to produce a measurement beam, a first multiplexer configured to split the measurement beam into a plurality of channels spaced in frequency, and a plurality of detectors configured to detect an intensity value of each channel of the plurality of channels to measure a distance between the digital measuring device and the moving object.

A background subtraction method and tilt stage device for eliminating contaminated or spurious interference patterns by reducing retrace errors. An optical reference surface secured in a pivoting mount coupled to a tilt actuator is configured to angularly displace the pivoting mount and optical reference surface. A microcontroller coupled to the tilt actuator controls the tilt displacement of the tilt actuator providing a plurality of wavefront measurements of the reference surface at a plurality of angles to provide a system and method for background measurement.

The present specification relates to Master-Slave (MS) interferometry for sensing the axial position of an object subject to optical coherence tomography (OCT) imaging, and to MS-OCT applied to curved and axially moving objects. The methods and apparatuses allow producing OCT signals from selected depths within the object irrespective of its axial position in respect to the imaging system. Images are obtained for curved objects that are flattened along a layer of interest in the object, images that are used to provide OCT angiography images less disturbed by axial movement or lateral scanning.

A method for determining local position of an optical element associated with an optical path for transporting a laser beam in a working head of a machine for laser processing a material, includes generating a measurement beam of low coherence optical radiation traveling a measurement optical path, leading the measurement beam towards the optical element and the reflected or diffused measurement beam towards an optical interferometric sensor arrangement, generating a reference beam of low coherence optical radiation traveling a reference optical path and leading the reference beam towards the interferometric optical sensor arrangement, superimposing the measurement and reference beams on a common region of incidence, detecting a position of a pattern of interference fringes between the measurement and reference beams, and determining a difference in optical length between the measurement and reference optical paths as a function of the position of the interference pattern along an illumination axis, or of the frequency of the interference pattern in the frequency domain.

An analysis apparatus includes an acquisition part that acquires a plurality of interference images of the object to be measured from the interference measurement apparatus, a calculation part that calculates a sine wave component and a cosine wave component of an interference signal for each pixel in the plurality of interference images, respectively, an error detection part that detects an error between a first Lissajous figure constructed on the basis of the sine wave component and the cosine wave component for each pixel and an ideal second Lissajous figure, a correction part that corrects the sine wave component and the cosine wave component for each pixel on the basis of the error, and a geometry calculation part that calculates surface geometry of the object to be measured on the basis of the corrected sine wave component and cosine wave component.