A photoelectric conversion apparatus includes an interferometer configured to cause interference in wavelength swept light Lx output from a wavelength swept light source X and is configured to convert the interfered wavelength swept light by photoelectric conversion. A signal processing apparatus calculates, in chronological order, relative frequencies fr(t) indicating frequencies relative to interference signals i(t) obtained by the photoelectric conversion of the interference light iL, and measures a difference between a maximum value and a minimum value of the relative frequencies fr(t), as a sweep frequency width Δf of the wavelength swept light Lx.

An exemplary aspect is a method of processing data acquired by applying an optical coherence tomography (OCT) scan to a sample. The method includes preparing a three dimensional data set acquired from a sample, creating a two dimensional map based on representative intensity values of a plurality of pieces of A-scan data included in the three dimensional data set, placing the three dimensional data set based on the two dimensional map, and executing a process based on at least a partial data set of the three dimensional data set on which placement based on the two dimensional map has been performed.

Aspects of the disclosure relate to systems, methods, and algorithms to perform wavenumber linearization and dispersion correction in optical systems without the need for hardware modifications, empirical adjustments, precise mirror alignment, and which can be conducted at low computational costs and in real-time. A one-time calibration process can generate spectra or calibration criteria, including wavenumber-linearization criteria, dispersion correction, and spectral flattening spectra, which can be used to correct an optical coherence tomogram in real time.

An interferometer system, including a heterodyne interferometer and a processing system. The heterodyne interferometer is arranged to provide a reference signal and a measurement signal. The reference signal has a reference phase. The measurement signal has a measurement phase and an amplitude. The processing system is arranged to determine a cyclic error of the heterodyne interferometer based on the reference phase, the measurement phase and the amplitude.

A thickness evaluation method of the cell sheet according to the invention includes tomographically imaging a cell sheet by optical coherence tomography and obtaining a thickness distribution of the cell sheet based on a result of the tomography imaging. A tomographic image corresponding to one cross section of the cell sheet is obtained by tomography imaging while scanning the light in a main scanning direction. The tomography imaging is performed in every time while moving an incident position of the light at a predetermined feed pitch in a sub-scanning direction, thereby a plurality of the tomographic images corresponding to a plurality of cross-sections are obtained. One-dimensional thickness distributions of the cell sheet in the corresponding cross-sections are obtained based on each of the plurality of tomographic images, and a two-dimensional thickness distribution of the cell sheet is obtained by interpolating the one-dimensional thickness distributions.

Embodiments of systems and methods for measuring a surface topography of a semiconductor structure are disclosed. In certain examples, a plurality of interference signals, each corresponding to a respective one of a plurality of positions on a surface of the semiconductor structure, are measured. Calibration signals, associated with a baseline region corresponding to a first category of a plurality of categories and a calibrated region corresponding to a second category of the plurality of categories, are measured. A surface height offset, associated with the baseline region and the calibrated region, is determined based on original surface heights and the calibration signals. The original surface heights are determined based on the plurality of interference signals corresponding to the baseline region and the calibrated region. The surface topography of the semiconductor structure is characterized based, at least in part, on the surface height offset and the original surface heights.

A calibration method includes the steps of placing a structure to be measured at a first position, measuring a first distance from a laser interferometer to a reflector, and measuring first coordinates of a body to be measured, moving the structure to be measured to a second position, measuring a second distance from the laser interferometer to the reflector and measuring second coordinates of the structure to be measured with the coordinate measuring apparats, while the structure to be measured is at the second position, determining a scale error of the reference instrument, mounting the reference instrument, measuring the interval between objects to be measured, and calculating a calibration value of the interval between the objects to be measured.

Various disclosed embodiments provide illustrative interferometers, optical phase locked loops, laser systems, interferometry methods, and phase locked loop methods. In illustrative embodiments, light from a laser is split into a first arm and a second arm. Light in an arm chosen from the first arm and the second arm is time delayed. The light in the first arm is split into third, fourth, and fifth arms. The light in the second arm is split into sixth, seventh, and eighth arms. Light in the seventh and eighth arms is phase shifted relative to light in the sixth arm. Light in the third, fourth, and fifth arms is combined with light in the sixth arm and phase shifted light in the seventh and eighth arms, respectively. A frequency correction signal for the laser is generated.

Interferometer system, including optical means (2, 3, 4, 5) arranged for directing light along a first interferometer path and (separate) second interferometer path, and for combining the light for allowing interferometry, characterized in that the first interferometer path (PI) is provided with a first light transmitting structure (10) having a rotational position that is adjustable with respect to an optical axis of the first path.

We describe apparatus for measurement of thickness and topography of slabs of materials employing probes with filters using polarization maintaining fibers.