In order to acquire a tomographic image of the eye to be inspected with high precision even in case where an optical path length and intensity vary depending on a scanned position in an OCT apparatus acquiring the tomographic image of a predetermined part of an object to be inspected, based on the intensity of interference light obtained by combining return light from the object that has been irradiated with the measuring light, with reference light corresponding to the measuring light, includes: a scanning optical system which scans the object with the measuring light in an optical path of the measuring light; an image forming unit which generates the tomographic image based on the intensity of the interference light; and an image correcting unit which subjects the tomographic image to a correction process appropriate to the scanned position with the measuring light on the object.

Methods, systems and devices for estimating a parameter of interest in a borehole. The method may include generating information from an optical displacement device relating to relative motion between two or more reflective surfaces thereof that is indicative of the parameter of interest; and preventing changes in the information resulting from changes at the optical displacement device in at least one of i) temperature, or ii) pressure, by compensating for the changes. Compensating may include adjusting at least one light source generating an electromagnetic beam at least partly received by the optical displacement device responsive to information relating to a control optical displacement device at the optical displacement device. Compensating may include using an optical displacement device and configuring the optical displacement device such that a difference between a first variable gap and a second variable gap is substantially zero while the apparatus is subject to nominal conditions.

The present invention provides a novel simple, portable, compact and inexpensive approach for interferometric optical thickness measurements that can be easily incorporated into an existing microscope (or other imaging systems) with existing cameras. According to the invention, the interferometric device provides a substantially stable, easy to align common path interferometric geometry, while eliminating a need for controllably changing the optical path of the beam. To this end, the inexpensive and easy to align interferometric device of the invention is configured such that it applies the principles of the interferometric measurements to a sample beam only, being a single input into the interferometric device.

Methods are known for implementing general optical functions using wave splitters. However, these methods rely on these wave splitters having maximal extinction ratio, which is difficult to achieve in practice. The present invention provides methods for automatically adjusting wave splitters to provide maximal extinction ratio.

A system for optical coherence tomography using multiple interferometers presented. The interferometry system includes a source configured to generate a variable wavelength light beam. A first splitter is configured to split the variable wavelength light beam to at least a first light beam and a second light beam. A first delay element is configured to delay the first light beam by a first time delay. A second delay element is configured to delay the second light beam by a second time delay, such that the delayed first light beam and the delayed second light beam are out of coherence with each other. A first interferometer is configured to receive the delayed first light beam as an input. A second interferometer is configured to receive the delayed second light beam as an input.

Systems and methods for measuring a surface topography of a semiconductor chip are disclosed. A disclosed system comprises a light source configured to provide low coherent light to a first beam splitter, a scanner configured to use the low coherent light reflected from the first beam splitter to scan positions on a surface of a semiconductor chip, a second beam splitter configured to receive reflected signals from the positions on the surface of the semiconductor chip, a detector configured to detect interference signals from a first output of the second beam splitter, wherein each of the interference signals corresponds to a respective one of the positions, and a spectrometer configured to detect spectrum signals from a second output of the second beam splitter, wherein each of the spectrum signals corresponds to the respective one of the positions.

A laser processing apparatus includes a laser oscillator that oscillates processing laser light incident on a processing point on a processing surface, a coupling mirror that deflects or transmits the processing laser light and measurement light incident on the processing point toward the processing point, a measurement light deflection unit that changes an incident angle of the measurement light on the coupling mirror, a lens that concentrates the processing laser light and the measurement light on the processing point, a controller, a measurement processor that measures a depth of a keyhole generated at the processing point by the processing laser light using an optical interference signal based on interference generated by an optical path difference between the measurement light reflected at the processing point and reference light, and a beam position measurement unit that measures positions of the processing laser light and the measurement light.

An optical fiber includes multiple optical cores configured in the fiber including a set of primary cores and an auxiliary core. An interferometric measurement system uses measurements from the multiple primary cores to predict a response from the auxiliary core. The predicted auxiliary core response is compared with the actual auxiliary core response to determine if they differ by more than a predetermined amount, in which case the measurements from the multiple primary cores may be deemed unreliable.

A measurement apparatus for measuring a thickness of a semiconductor wafer includes: an optical system configured to perpendicularly irradiate a sample wafer and a reference wafer with light, and receive interference signals of the light reflected on front and back surfaces of the respective wafers; a signal processor configured to perform frequency analysis of the interference signals received by the optical system to obtain peak positions of a point spread function of the respective wafers; and a calculator configured to calculate a thickness tsample of the sample wafer based on the peak position x of the sample wafer and the peak position y of the reference wafer obtained by the signal processor, and a thickness treference of the reference wafer.

A method to derive phase-coherent images with an interferometer, in situations where interferometric phase errors can be factorized into element-based terms (piston phases) is disclosed. The method is preferably implemented completely in the image domain, without resort to aperture plane measurements of visibilities, or element-based voltage complex gains.