An optical system can include a mirror that reflects incoming light to a sensor for detection. The position and/or orientation of the mirror can be controlled to reflect incoming light from different locations and/or directions. Position and/or orientation of the mirror may be tracked and/or detected by an optical position sensor. The position sensor can transmit a beam to a reflector on the mirror, and the reflected beam can be received by the position sensor. Characteristics of the reflected beam can be measured to determine the position and/or orientation of the mirror. For example, the beam can be used for interferometric and/or intensity measurements, which can then be correlated with a position and/or orientation of the mirror.

In one or more embodiments of an optical interference measurement apparatus, first return light received by a first measurement head is guided to a detector via a first optical path and a fiber coupler. Second return light received by a second measurement head is guided to the detector via a second optical path and the fiber coupler. Optical path lengths D1 and D2 from the fiber coupler to a leading end of the first measurement head and a leading end of the second measurement head respectively, a maximum optical path length R1max of the measurement range of the first measurement head, optical path lengths S1 and S2 of the first reference light that interferes with the first return light and of the second reference light that interferes with the second return light respectively are set such that the relation D1+R1max−S1<D2−S2 is satisfied.

A method for defect inspection of a transparent substrate comprises (a) providing an optical system for performing a diffraction process of object wave passing through a transparent substrate, (b) interfering and wavefront recording for the diffracted object wave and a reference wave to reconstruct the defect complex images (including amplitude and phase) of the transparent substrate, (c) characteristics analyzing, features classifying and sieving for the defect complex images of the transparent substrate, and (d) creating defect complex images database based-on the defect complex images for comparison and detection of the defect complex images of the transparent substrate.

The invention relates to an OCT system comprising an OCT light source, an OCT evaluation unit, a first OCT light guide, a second OCT light guide and a changeover module. The light from the OCT light source passes through the changeover module. In a first state of the changeover module, the OCT light is passed to an entry end of the first OCT light guide. In a second state of the changeover module, the OCT light is passed to an entry end of the second OCT light guide. A scanning device assigned to the first OCT light guide is arranged between the changeover module and the object plane. The OCT system according to the invention can be used in a flexible manner.

The invention relates to an OCT system comprising an OCT light source, an OCT evaluation unit, a first OCT light guide, a second OCT light guide and a changeover module. The light from the OCT light source passes through the changeover module. In a first state of the changeover module, the OCT light is passed to an entry end of the first OCT light guide. In a second state of the changeover module, the OCT light is passed to an entry end of the second OCT light guide. A scanning device assigned to the first OCT light guide is arranged between the changeover module and the object plane. The OCT system according to the invention can be used in a flexible manner.

Techniques for removing interferometry signal phase variations caused by distortion and other effects in a multi-layer stack include: providing an electronic processor sample interferometry data acquired for the stack using a low coherence imaging interferometry system; transforming, by the electronic processor, the sample interferometry data to a frequency domain; identifying a non-linear phase variation from the sample interferometry data in the frequency domain, in which the non-linear phase variation is a result of dispersion introduced into a measurement beam by the test sample; and removing the non-linear phase variation from the sample interferometry data thereby producing compensated interferometry data.

An interferometer detection system, including a beam splitter receiving a collimated light signal and splitting the signal into a first light signal and a second light signal. The system includes a first mirror receiving and reflecting the first light signal along a first path. The system includes a second mirror receiving and reflecting the second light signal along a second path via a transparent material. The system includes a 2D photosensor array configured to receive from the beam splitter the reflected first light signal merged with the reflected second light signal double passing through the transparent material and configured to generate an interference fringe pattern. A non-sinusoidal interference fringe pattern indicates geometrical variation between a wavefront of the reflected first light signal along the first path and a wavefront of the reflected second light signal double passing through the transparent material along the second path.

Metrology apparatus and methods for inspecting a substrate are disclosed. A source beam of radiation emitted by a radiation source is split into a measurement beam and a reference beam. A first target on the substrate is illuminated with the measurement beam. A second target separated from the substrate is illuminated with the reference beam. First scattered radiation collected from the first target and second scattered radiation collected from the second target are delivered to the detector. The first scattered radiation interferes with the second scattered radiation at the detector. The first target comprises a first pattern. The second target comprises a second pattern, or a pupil plane image of the second pattern. The first pattern is geometrically identical to the second pattern, the first pattern and the second pattern are periodic and a pitch of the first pattern is identical to a pitch of the second pattern, or both.

An optical measurement system measuring optical parameters of an object is provided. The object includes at least two light-transmitting layers. The optical measurement system includes a light source module, an image capture module, and a controller. The light source module emits at least two measurement light beams toward the object. The measurement light beams are respectively incident on the object at different angles. The image capture module receives light spots formed on a sensing surface of the image capture module by at least two first light beams after the measurement light beams are reflected by the object and at least two second light beams after the measurement light beams are refracted and reflected between the object. The controller is electrically connected to the image capture module to obtain positions of the light spots. The controller calculates the optical parameters of the object according to the positions of the light spots.

Techniques for removing interferometry signal phase variations caused by distortion and other effects in a multi-layer stack include: providing an electronic processor sample interferometry data acquired for the stack using a low coherence imaging interferometry system; transforming, by the electronic processor, the sample interferometry data to a frequency domain; identifying a non-linear phase variation from the sample interferometry data in the frequency domain, in which the non-linear phase variation is a result of dispersion introduced into a measurement beam by the test sample; and removing the non-linear phase variation from the sample interferometry data thereby producing compensated interferometry data.