A system for compensating for phase noise, with particular application in lidar, includes a compensation interferometer that receives a signal from a source, and splits it into a first and second path, with a path length difference Δτ between them. Typically the path length is significantly less than that of the return distance to a target. The output of the compensation interferometer, which consists of phase noise generated in time Δτ is vectorially summed during a time similar to a signal flight time to a target, and the result used to reduce phase noise present on measurements of a target. It further includes means for selecting Δτ such that competing noise elements are reduced or optimised.

A low-coherence Fizeau interferometer includes a first beamsplitter, a test arm and a reference arm, the first beamsplitter splits light into a first portion of light directed to the test arm and a second portion of light directed to the reference arm, and an imaging arm comprising a first collimating lens, a flat reference surface, and a test element. The test arm focuses the first portion of light at a first focal point, such that a virtual image of the first focal point appears at a focal point of the test element. The reference arm focuses the second portion of light at a second focal point, the first collimating lens collimates the light that then reflects off the flat reference surface. The second beamsplitter directs the first portion of light to reflect off the test element. The reflection of the first and second portion of light form an interference pattern.

Distance to a target is sensed using a common path interferometer, wherein a first fraction of light from a light source is collected after reflection by a partially reflective element together with reflection from a target of a second fraction of light from the light source that has been transmitted by the partially reflective element. The collected light is split in two parts, both containing a part of the first fraction and part of the reflection from the target. The parts are fed through a first and second optical branch path to an input side of a three-way optical coupler respectively. Light from at three terminals on a second side of the N way coupler is fed to respective light intensity detectors. Information representing an excess distance traveled by the first fraction from detection signals determined by the least three light intensity detectors.

The present document relates to a scanning probe microscopy system and method for mapping nanostructures on the surface of a sample. The system comprises a sample support structure, a scan head including a probe comprising a cantilever and a probe tip, and an actuator for scanning the probe tip relative to the sample surface. The system also includes an optical source, and a sensor unit for obtaining a sensor signal indicative of a position of the probe tip. The sensor unit includes a partially reflecting element for reflecting a reference fraction and for transmitting a sensing fraction of the optical signal. It further includes directional optics for directing the sensing fraction as an optical beam towards the probe tip, and for receiving a reflected fraction thereof to provide a sensed signal. Moreover the sensor includes an interferometer for providing one or more output signals, and signal conveyance optics for conveying the sensed signal and the reference signal to the interferometer. The directional optics is configured for directing the sensing fraction such that at least a part of the sensing fraction is reflected by the probe tip such as to form the reflected fraction.

A holographic interferometer, comprising: an imaging device capturing an interference pattern created by at least two polarized light beams; a structured phase retardation element located in an optical path of at least one polarized light beam of the at least two polarized light beams; and a polarizer located between the imaging device and the structured phase retardation element, the polarizer projects each polarization of each of the at least two polarized light beams on a single axis to create the interference pattern on the imaging device.

A holographic interferometer, comprising: an imaging device capturing an interference pattern created by at least two polarized light beams; a structured phase retardation element located in an optical path of at least one polarized light beam of the at least two polarized light beams; and a polarizer located between the imaging device and the structured phase retardation element, the polarizer projects each polarization of each of the at least two polarized light beams on a single axis to create the interference pattern on the imaging device.

A low-coherence interferometer apparatus for determining information on interfaces of an object including: a polychromatic light source; an optical system generating a measurement optical beam and a reference optical beam; a delay line introducing a variable optical delay between the optical beams; detection optics combining the beams, and producing a spectral signal representative of an optical-power spectral density of the resulting interference signal; a control and processing module acquiring a plurality of spectral signals for a plurality of optical delays, determining, for each spectral signal, optical retardation information between interfering beams within a spectral measurement range, analyse the variation in the retardations, and assign the optical retardation determined on the basis of the different spectral signals to interface curves, corresponding to straight lines with positive, negative, zero or almost-zero gradient, depending on the respective optical delay of the acquisition of the spectral signals, and to deduce information of the object.

An interferometer and an imager may include a tunable light source, a beam splitter, a digital imager, and a processor system. The tunable light source may be configured to emit a beam. The beam splitter may be configured to direct the beam toward a sample with a floor surface and a raised surface feature. The digital imager may be configured to receive a reflected beam and to generate an image based on the reflected beam. The reflected beam may be a coherent addition of a first reflection of the beam off a reference plate and a second reflection of the beam off the raised surface feature and third reflection of the beam off the floor surface. The processor system may be coupled to the digital imager and may be configured to determine a distance between the reference surface and the feature surface based on the image. A second digital imager may also be configured to receive a reflected beam and scattered beam to generate a two-dimensional grayscale image of the surface based on these beams and may also be configured to receive fluorescent light generated by the incident light to generate a two-dimensional gray scale an image of the surface based on fluorescent emission.

An interferometer and an imager may include a tunable light source, a beam splitter, a digital imager, and a processor system. The tunable light source may be configured to emit a beam. The beam splitter may be configured to direct the beam toward a sample with a floor surface and a raised surface feature. The digital imager may be configured to receive a reflected beam and to generate an image based on the reflected beam. The reflected beam may be a coherent addition of a first reflection of the beam off a reference plate and a second reflection of the beam off the raised surface feature and third reflection of the beam off the floor surface. The processor system may be coupled to the digital imager and may be configured to determine a distance between the reference surface and the feature surface based on the image. A second digital imager may also be configured to receive a reflected beam and scattered beam to generate a two-dimensional grayscale image of the surface based on these beams and may also be configured to receive fluorescent light generated by the incident light to generate a two-dimensional gray scale an image of the surface based on fluorescent emission.

A cascaded interferometric system for Fourier domain optical coherence tomography (OCT) in which the output of one sub-system interferometer is directed through a second sub-system interferometer for performing the Fourier transform in hardware.