A frequency swept laser source for TEFD-OCT imaging includes an integrated clock subsystem on the optical bench with the laser source. The clock subsystem generates frequency clock signals as the optical signal is tuned over the scan band. Preferably the laser source further includes a cavity extender in its optical cavity between a tunable filter and gain medium to increase an optical distance between the tunable filter and the gain medium in order to control the location of laser intensity pattern noise. The laser also includes a fiber stub that allows for control over the cavity length while also controlling birefringence in the cavity.

The invention provides a method and apparatus for applying spatial filtering the optical beam of a free space optical coherence tomography (OCT) system substantially without problematic reflections back to the optical source. The invention teaches spatially filtering the reference beam of the OCT system which is typically designed to provide isolation of the optical source from undesirable optical feed-back, thereby achieving spatial filtering without generating undesirable reflections back to the optical source. Various embodiments are taught.

An object is to enable removal fixed pattern noise even if the intensity of interference light changes during measurement. An image capturing apparatus comprises a light splitting unit that splits light emitted from a light source into reference light and measurement light, an interference signal detection unit that acquires an interference signal from interference light resulting from interference of the reference light and return light generated by irradiating an object to be inspected with the measurement light, a noise signal acquisition unit that acquires a noise signal containing a noise component contained in the interference light, a correction unit that corrects the intensity of one of the interference signal and the noise signal, and a noise removal unit that removes the noise component contained in the interference signal using the interference signal and the noise signal one of which is corrected.

An OCT imaging technique capable of suppressing image noise due to reflection on a wall surface of a carrier for carrying an imaging object by a simple configuration is provided. A light regulating member 28 having a transmission pattern where the high transmission parts P1 and the low transmission parts P2 are alternately arranged is placed on a side opposite to the spheroid Sp (imaging object) across the objective lens 27. The transmission pattern is rotationally symmetric with respect to an optical axis AX of the objective lens 27 and a point located at a position point-symmetric with an arbitrary point in the high transmission part with respect to a point where the optical axis of the objective lens intersects with the light regulating surface is included in the low transmission part.

An optical interferometer includes a branching-combining unit, a first optical system, a second optical system, and a drive unit. The branching-combining unit includes a branching surface, an incident surface, a first output surface, a combining surface, and a second output surface on an interface of a transparent member, the branching surface partially reflects incident light and outputs as first branched light, and transmits the rest of the incident light into the interior as second branched light, the combining surface partially combines the first branched light and the second branched light to be output to the outside as first combined light, and combines the rest of the first branched light and the second branched light to be propagated into the interior as second combined light, and the second output surface partially outputs the second combined light to the outside.

The invention provides a method and apparatus for applying spatial filtering the optical beam of a free space optical coherence tomography (OCT) system substantially without problematic reflections back to the optical source. The invention teaches spatially filtering the reference beam of the OCT system which is typically designed to provide isolation of the optical source from undesirable optical feed-back, thereby achieving spatial filtering without generating undesirable reflections back to the optical source. Various embodiments are taught.

By utilizing the fact that the observation object has a three-dimensional shape and the boundary surface can be regarded as a plane surface, phase or intensity distribution is applied into a luminous flux of reference light, thereby selectively attenuating the influence of the reflected light from the boundary surface so as to obtain a high-quality OCT image.

Disclosed are several technical approaches of using low coherence interferometry techniques to create an autofocus apparatus for optical microscopy. These approaches allow automatic focusing on thin structures that are positioned closely to reflective surfaces and behind refractive material like a cover slip, and automated adjustment of focus position into the sample region without disturbance from reflection off adjacent surfaces. The measurement offset induced by refraction of material that covers the sample is compensated for. Proposed are techniques of an instrument that allows the automatic interchange of imaging objectives in a low coherence interferometry autofocus system, which is of major interest in combination with TDI (time delay integration) imaging, confocal and two-photon fluorescence microscopy.

A device for measuring a substrate for semiconductor lithography with a reference interferometer for ascertaining the change in the ambient conditions, wherein the reference interferometer comprises a means for changing the optical path length of a measurement section of the reference interferometer, and a method for correcting cyclic error components in the reference interferometer using same.

[Solving Means] A signal processing apparatus is a signal processing apparatus for an optical tomographic measurement apparatus that generates measurement light and reference light and measures a tomographic structure of a measurement object on the basis of a signal intensity of interference light between the reference light and return light of the measurement light from the measurement object. An arithmetic unit is configured to calculate a signal intensity of simple reflection among the return light of the measurement light, the simple reflection being one time of reflection at a plurality of layers virtually set in a depth direction from a surface layer side of the measurement object. The arithmetic unit is configured to calculate a signal intensity of multiple reflection on the basis of the signal intensity of the simple reflection, the signal intensity of multiple reflection being a signal intensity of return light generated by being reflected at the plurality of layers three or more times.