A displacement detection device is capable of stably and accurately detecting an amount of displacement. A polarization maintaining fiber has a length not to be equal to a length obtained by dividing, a product of an integral multiple of twice a length of a resonator times a refractive index of the resonator and a beat length obtained from a difference between propagation constants of two polarization modes, by a wavelength of the light source, is selected from a range including a length equal to the above length. The polarization maintaining fiber includes multiple polarization maintaining fibers fitted to each other by removable connectors.

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.

Disclosed is a method for measuring etch depth including the following steps: splitting a light beam into a first, and respectively second, incident beam directed towards a first, respectively second, area of a sample exposed to an etching treatment to form a first, and respectively second, reflected beam, recombining the first reflected beam and the second reflected beam to form an interferometric beam; detecting a first, and respectively second, interferometric intensity signal relative to a first, respectively second, polarisation component; calculating a lower envelope function and an upper envelope function of a differential polarimetric interferometry signal; determining an offset function and a normalisation function from the first lower envelope function and the first upper envelope function; and calculating a differential polarimetric interferometry function normalised locally at each time instant.

An interferometer uses a phase shift mask that includes an array of pixels that are aligned with a corresponding array of pixels of a detector. Each pixel in the phase shift mask is adapted to produce one of a number of predetermined phase shifts between a test beam and a reference beam. For example, the pixels may be linear polarizers or phase delay elements having one of the number of polarizer orientations or phase delays to produce the predetermined phase shifts between the test beam and the reference beam. The pixels in the phase shift mask are arranged in the array to include each of the predetermined phase shifts in repeating pixel groups in rows that are one column wide, columns that are one row high, or blocks of multiple rows and columns.

An interferometric distance-measurement device includes a multi-wavelength light source which provides a beam having at least three different wavelengths. An interferometer unit splits the beam into measuring and reference beams. The measuring beam propagates in the direction of a measuring reflector movable along a measuring axis and undergoes a back-reflection, and the reference beam propagates in the direction of a stationary reference reflector and undergoes a back-reflection. The back-reflected measuring and reference beams interfere with each other in an interference beam. A detection unit splits the interference beam such that several phase-shifted partial interference signals result for each wavelength. A signal processing unit determines absolute position information regarding the measuring reflector from the partial interference signals of different wavelengths and an additional coarse position signal.

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.

Optical coherent receiver arrays are described. The optical coherent receiver arrays include an integrated array of photodetectors separated by integrated mirrors which may cause interference of received free space optical and local oscillator signals. The mirrors may serve as splitters, helping to align the received signal and local oscillator to cause interference. The photodetectors of the optical coherent receiver array may be electrically coupled in various manners to read out the signals. The optical coherent receiver array may be implemented in an optical coherence tomography (OCT) imaging system in some embodiments.

An optical system includes a polarized light phase shift optical circuit that includes a polarizing beam splitter that splits light having a coherence length shorter than a difference in optical path length between a normal optical path and a delay optical path having an optical path length longer than the normal optical path, the light being split into normal light, which travels along the normal optical path, and delay light, which travels along the delay optical path; a separator where the normal light and the delay light are individually emitted at a reference flat and the separator divides the reflected light that reflects off the reference flat into a plurality of light beams; and a plurality of image capture elements that respectively detect the intensities of the plurality of divided light beams, and the optical system also includes an information processor that includes a calibrator.

An interferometric position sensor for sensing the position of an object is disclosed. The position sensor comprises a light source arranged to emit light, a beam splitter, and a detector array. The beam splitter is arranged to split the light between first and second optical paths, which are configured such that the split light is recombined so as to form an optical interference pattern dependent on the difference between the optical path lengths of the first and second optical paths. The detector array is arranged to measure the intensity of at least a part of the optical interference pattern. At least one of the first and second optical path lengths is arranged to be dependent on the position of the object, such that changes in the optical interference pattern can be related to changes in the position of the object.

The optical distance measurement device is configured to include an optical interference unit for separating the reflected light into a reflected light of a first polarized wave and a reflected light of a second polarized wave, extracting first and second components orthogonal to each other from an interference light of the reflected light of the first polarized wave and the reference light, and extracting third and fourth components orthogonal to each other from an interference light of the reflected light of the second polarized wave and the reference light, and a polarization rotation unit for acquiring one or more components of horizontal and vertical components of a polarized wave by rotating a polarization angle of a first complex signal having the first and second components and a polarization angle of a second complex signal having the third and fourth components, so that a distance calculation unit calculates, on the basis of the components acquired by the polarization rotation unit, a difference between a frequency of the reflected light and a frequency of the reference light, and calculates a distance to a measurement target from the difference.