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.

An optical metrology device, such as an interferometer, detects sub-resolution defects on a sample, i.e., defects that are smaller than a pixel in the detector array of the interferometer. The optical metrology device obtains optical metrology data at each pixel in at least one detector array and determines parameter values of a signal model for a pixel of interest using the optical metrology data received by a plurality of pixels neighboring a pixel of interest. A residual for the pixel of interest is determined using the optical metrology data received by the pixel of interest and determined parameter values for the signal model for the pixel of interest. A defect, which may be smaller than the pixel of interest can then be detected based on the residual for the pixel of interest.

Defects are detected using data acquired from an interference channel and a polarization modification channel in an interferometer. The interference objective splits a polarized illumination beam into a reference illumination that is reflected by a reference surface without modification to the polarization, and a sample beam that is reflected by a sample surface, that may modify the polarization. Light from the sample beam with no change in polarization is combined with the reference illumination and directed to the interference channel, which may measure the reflectivity and/or topography of the sample. Light from the sample beam with modified polarization is directed to the polarization modification channel. The intensity of the light detected at the polarization modification channel may be used, along with the reflectivity and topography data to identify defects or other characteristics of the sample.

A three-dimensional measurement device includes: an optical system that splits incident light into two lights and radiates lights to a measurement object and to a reference surface, and recombines the two lights to emit combined light; a first irradiator that emits first light including first polarized light and entering a first surface; a second irradiator that emits second light including second polarized light and entering a second surface; a first imaging system to which the first output light enters wherein the first output light is emitted from the first surface when the first light enters the first surface; a second imaging system to which the second output light enters wherein the second output light is emitted from the second surface when the second light enters the second surface; and an image processor that performs three-dimensional measurement based on interference fringe images obtained by the first and second imaging systems.

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.

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.

A coherence gated photoacoustic remote sensing system for imaging a subsurface structure in a sample with optical resolution may include an excitation beam source configured to generate an excitation beam that induces ultrasonic signals in the sample at an excitation location; an interrogation team source configured to generate an interrogation team incident on the sample at an interrogation location, a portion of the interrogation beam returning from the sample that is indicative of the generated ultrasonic signals, the interrogation beam being a low-coherent beam; an optical system that focuses the excitation beam onto the sample at an excitation location, and focuses the interrogation beam onto the sample at an interrogation location, at least the interrogation location being below the surface of and within the sample; and a low coherence interferometer that isolates a returning portion of the interrogation beam that corresponds to an interrogation event of the sample.

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.

A three-dimensional measurement device includes: an optical system that splits incident light into two lights, radiates one of the two lights as measurement light to a measurement object and the other as reference light to a reference surface, and recombines the two lights to emit combined light; a first irradiation unit that emits first light entering the optical system; a second irradiation unit that emits second light entering the optical system; a first imaging unit into which output light that is obtained from the first light and is emitted from the optical system enters; a second imaging unit into which output light that is obtained from the second light and is emitted from the optical system enters; and an image processor that executes three-dimensional measurement of the measurement object, based on interference fringe images taken by the first imaging unit and the second imaging unit.

A three-dimensional measurement device includes an optical system that: splits an incident light into two lights; radiates one light to a measurement object and the other light to a reference surface; and emits the combined light; a first irradiator that emits a first light that comprises a polarized light of a first wavelength and enters a first element of the optical system; a second irradiator that emits a second light that comprises a polarized light of a second wavelength and enters a second element of the optical system; a first camera that takes an image of the first light emitted from the second element when the first light enters the first element; a second camera that takes an image of the second light emitted from the first element when the second light enters the second element; and an image processor that performs measurement based on the images.