The present disclosure provides a multi-frequency hybrid heterodyne laser tracker system based on a single light source. According to the laser tracking system proposed in the present disclosure, multi-frequency laser is obtained by conducting multi-acousto-optic frequency shift on a dual-longitudinal-mode laser unit, and an absolute ranging precision gauge is constructed by using a dual-longitudinal-mode interval of a light source. With the frequency shift difference of a multi-acousto-optic frequency shifter, an absolute ranging roughness gauge is constructed, and the relative displacement measurement of dual-frequency light interference is achieved. Meanwhile, by utilizing the reflection of multiple reflectors and light splitting and combining of polarization prisms, synchronous measurement of multi-wavelength absolute distance, relative displacement and PSD position is achieved, resolving the problem that an existing laser tracker uses multiple light sources, which leads to difference in measurement datum, and consequently to the difficultly in traceback.

The present invention discloses a dual-homodyne laser interferometric nanometer displacement measuring apparatus and method based on phase modulation. The linearly polarized beam with single wavelength emitted from a single frequency laser is projected onto a dual-homodyne laser interferometer consisting of four beam splitters and two retroreflectors to respectively form a measurement interference signal and a reference interference signal received by two photodetectors, respectively; an electro-optic phase modulator is placed in the optical path and a periodic sawtooth-wave voltage signal is applied to modulate the measurement and reference DC interference signals into AC interference signals; the measured displacement is obtained by detecting the variation of the phase difference between the two interference signals caused by the movement of the measured object. The present invention overcomes the error arising from DC drift in the homodyne laser interferometer and avoids the sinusoidal error caused by the direct subdivision of the interference signal or non-quadrature error of measurement interference signal. The present invention is applicable for the precision displacement measurement with sub-nanometer level accuracy in the fields of high-end equipment manufacturing and processing.

The present invention discloses a dual-homodyne laser interferometric nanometer displacement measuring apparatus and method based on phase modulation. The linearly polarized beam with single wavelength emitted from a single frequency laser is projected onto a dual-homodyne laser interferometer consisting of four beam splitters and two retroreflectors to respectively form a measurement interference signal and a reference interference signal received by two photodetectors, respectively; an electro-optic phase modulator is placed in the optical path and a periodic sawtooth-wave voltage signal is applied to modulate the measurement and reference DC interference signals into AC interference signals; the measured displacement is obtained by detecting the variation of the phase difference between the two interference signals caused by the movement of the measured object. The present invention overcomes the error arising from DC drift in the homodyne laser interferometer and avoids the sinusoidal error caused by the direct subdivision of the interference signal or non-quadrature error of measurement interference signal. The present invention is applicable for the precision displacement measurement with sub-nanometer level accuracy in the fields of high-end equipment manufacturing and processing.

Generally, in accordance with the various illustrative embodiments disclosed herein, a homodyne optical interferometer can include a multi-phase beam combining system that receives a composite beam from an optical beam guidance system and uses a diffraction grating to produce a diffracted plurality of light beam members. Each of the diffracted plurality of light beam members is propagated through a birefringent optical element that imposes a differential phase shift on each member based on polarization and differing optical path lengths. In one example implementation, the birefringent optical element can be a parallel plate optical element arranged at an angle with respect to a light-propagation axis of the multi-phase beam combining system and in a second example implementation, the birefringent optical element can be a multifaceted optical element having a first planar external surface that is sloped with respect to an opposing external planar surface.

Stackable and/or nestable box having a bottom wall and a side wall which rises from the bottom wall and which is defined by side panels, a front panel and a rear panel. The side panels include at least one recessed portion which is recessing from the containment volume and at least one portion protruding towards the containment volume. The box is configured to be nested within another box and to be stacked with other boxes or other containers with dimensions compatible with, or close to, the dimensions of box.

An interferometer apparatus comprises an adjustable birefringent device configured to receive an input radiation and produce corresponding replicas having reciprocally orthogonal polarizations and delayed from each other by an adjustable time delay. The birefringent device also introduces an additional time delay between the replicas. The interferometer apparatus also comprises a compensation optical device optically coupled to the adjustable birefringent device and configured to have a respective structural thickness and respective ordinary and extraordinary refractive indexes to introduce a compensation time delay between the replicas having a sign opposite to a sign of the additional time delay.

A detector that detects relative positions of a first object and a second object in directions different from each other on a predetermined plane, includes an illumination optical system configured to illuminate a first mark provided on the first object and a second mark provided on the second object, and a detection optical system configured to detect interference light of diffracted lights from the first mark and the second mark illuminated by the illumination optical system. A light intensity distribution is formed, on a pupil plane of the illumination optical system, to illuminate the first mark and the second mark from a direction tilted with respect to a normal of the predetermined plane. A pupil plane of the detection optical system allows the interference light to pass through and block at least a part light other than the interference light.

Methods are described for obtaining digital data for determining, shaping or testing a semiconductor or anisotropic device or materials under test or manufacture. Optical interferometric techniques can sense a wide region, such as that passing through or reflected off a semiconductor material, which can then be analyzed. In this manner, various characteristics of the resultant transmitted or reflected probing beam, herein called the object wave, are recorded in the resultant interference pattern between the object wave and the reference beam. Likewise, when the semiconductor material, such as an integrated circuit, is stressed by applying a voltage therein by energizing a circuit fabricated therein, the same light will reflect or otherwise pass through the semiconductor material, while being affected by the changes imposed upon or acting within the interior structures or interior surfaces by an applied voltage or signal, or by an incident external stress, thereby resulting in a different pattern.

The embodiments herein relate to a method for deriving topography of an object surface. A linearly polarized light wave is directed towards the object surface and a reference surface. Images of reflected linearly polarized light wave for a plurality of wavelengths are obtained. The images are obtained for at least four polarizations for each of the plurality of wavelengths. The reflected linearly polarized light wave is a reflection of the linearly polarized light wave directed towards the object surface and the reference surface. The topography of the object surface based on the obtained images is obtained.

The present disclosure provides a system and method for cutting a flap in laser ophthalmic surgery using polarization sensitive optical coherence tomography (PS-OCT). The system includes a PS-OCT system, a femtosecond laser, control device, and processor. The PS-OCT system includes a PS-OCT source, a polarization component, a reference reflector, a beam splitter, a wave plate, and a detector. The processor receives data relating to an interference pattern of a reflected PS-OCT beam, received at the detector, determines a relative fiber orientation of the sample, determines whether a photodisruption pattern generated by the femtosecond laser to cut the flap should be adjusted horizontally or vertically, based on the relative fiber orientation, and may generate a control signal to adjust the photodisruption pattern generated by the femtosecond laser. The disclosure further provides a method for cutting a flap on an eye using PS-OCT.