A photo-detection apparatus includes a light-shielding film, an optically-coupled layer, a photodetector, and an optical system. In the light-shielding film, light-transmitting regions and light-shielding regions are alternately arranged in at least a first direction within a plane. The optically-coupled layer faces the light-shielding film and includes a grating that propagates light in the first direction. The photodetector includes first photo-detection cells and second photo-detection cells arranged on an imaging area. The optical system is disposed between the optically-coupled layer and the photodetector. An image of light transmitted by parts of the optically-coupled layer that face each of the light-transmitting regions and light-shielding regions is enlarged or reduced by the optical system and formed on a corresponding one of the first and second photo-detection cells.

A measurement method for interferometrically measuring the shape of a surface (112) of a test object (114). A test wave (125-1, 125-2) directed at the test object has a wavefront that is at least partially adapted to the desired shape of the surface, and a reference wave (128-1, 128-2) directed at a reflective optical element (130-1, 130 2) has a propagation direction that deviates from the propagation direction of the test wave (125-1, 125-2) for each of two input waves by diffraction at a diffractive element (124). For each wavelength, the test wave is superimposed after interaction with the test object with the associated reference wave after the back-reflection at the first reflective optical element. The test and reference waves are diffracted again at the diffractive element for superposition. An interferogram produced by the superposition is captured in a capture plane (148-1, 148-2). The interferograms are jointly evaluated.

A grating measuring device includes: a light source module (300) for generating two light beams having different frequencies, one of which serves as a measuring beam and the other as a reference beam; a grating (200); and a grating measuring probe (100) including a dual-frequency light reception module, a vertical measurement module, a vertical detection module and a reference detection module. The dual-frequency light reception module is configured to receive the measuring and reference beams, and the vertical measurement module is adapted to project the measuring beam onto the grating (200), collect a zeroth-order diffracted beam resulting from double diffraction occurring at the grating, and feed the zeroth-order diffracted beam to the vertical detection module. The zeroth-order diffracted beam interferes with the reference beam in the vertical detection module, resulting in a vertical interference signal. In addition, the measuring and reference beams interfere with each other also in the reference detection module to result in a reference interference signal. The vertical and reference interference signals are received by a signal processing module and serve as a basis for calculating a vertical displacement of the grating (200). This grating measuring device allows a great vertical displacement measurement range at any working distance.

Auto-alignment beam tracking apparatus and methods. In one example, an auto-alignment beam tracking system includes an optical train that receives an auto-alignment beam, a linear detector array including a plurality of photosensitive detectors each configured to measure intensity of electromagnetic radiation incident thereon, and a lateral shearing interferometer positioned between the optical train and the linear detector array. The optical train is configured to direct the auto-alignment beam to the lateral shearing interferometer. The lateral shearing interferometer is configured to produce an interference pattern at the linear detector array from the auto-alignment beam, wherein changes in the intensity measured by the plurality of photosensitive detectors over time corresponding to a lateral shift of the interference pattern on the linear detector array indicate an angular tilt of the auto-alignment beam.

Auto-alignment beam tracking apparatus and methods. In one example, an auto-alignment beam tracking system includes an optical train that receives an auto-alignment beam, a linear detector array including a plurality of photosensitive detectors each configured to measure intensity of electromagnetic radiation incident thereon, and a lateral shearing interferometer positioned between the optical train and the linear detector array. The optical train is configured to direct the auto-alignment beam to the lateral shearing interferometer. The lateral shearing interferometer is configured to produce an interference pattern at the linear detector array from the auto-alignment beam, wherein changes in the intensity measured by the plurality of photosensitive detectors over time corresponding to a lateral shift of the interference pattern on the linear detector array indicate an angular tilt of the auto-alignment beam.

An optical displacement sensor comprises a reflective surface and one or more diffraction gratings which, together with the reflective surface, each define a respective interferometric arrangement. The reflective surface is moveable relative to the diffraction grating(s) or vice versa. Light from a light source propagates via the interferometric arrangement(s) to produce an interference pattern at a respective set of photo detectors. Each interference pattern depends on the separation between the reflective surface and the respective grating. A collimating optical arrangement at least partially collimates the light between the light source and the diffraction grating(s). For the or each interferometric arrangement, when the reflective surface or the diffraction grating is in a zero-displacement position, the optical path length L of the light propagating between the diffraction grating and the reflective surface satisfies the relationship:

[00001]$L=\frac{T_{z}n}{2},$

to within 20% of

[00002]$\frac{T_z}{2},$

where n is an integer; where T.sub.z is the Talbot length, defined by:

[00003]$T_z=\frac{}{1-\sqrt{1-\frac{{}^2}{p^2}}},$

where is the wavelength of the light, and where p is the grating period of the respective diffraction grating.

The disclosure provides a microphone chip, a microphone, and a terminal device. The microphone chip includes a substrate and a diaphragm that are disposed oppositely, a reflector located on a side that is of the diaphragm and that is close to the substrate, a grating group located between the substrate and the diaphragm, and an optical emitter and an optical detector that are located between the substrate and the grating group. The grating group includes a plurality of gratings, and distances between at least two gratings in the plurality of gratings and the reflector are different.

The phase shift interferometer is configured to measure the shapes of measurement objects by acquiring a plurality of images of interference fringes while shifting the phases of the interference fringes. The interference fringes are provided with a phase difference of 90 relative to each other utilizing polarization of light. Images of the interference fringes are captured by two respective cameras while, in accordance with a conventional phase shift method, mechanically displacing a reference surface or a reference optical path to shift the phases. The phases of the interference fringes are calculated independently from the respective images acquired by the cameras and an average of the two phase calculation results is calculated.

A grating measuring device includes: a light source module (300) for generating two light beams having different frequencies, one of which serves as a measuring beam and the other as a reference beam; a grating (200); and a grating measuring probe (100) including a dual-frequency light reception module, a vertical measurement module, a vertical detection module and a reference detection module. The dual-frequency light reception module is configured to receive the measuring and reference beams, and the vertical measurement module is adapted to project the measuring beam onto the grating (200), collect a zeroth-order diffracted beam resulting from double diffraction occurring at the grating, and feed the zeroth-order diffracted beam to the vertical detection module. The zeroth-order diffracted beam interferes with the reference beam in the vertical detection module, resulting in a vertical interference signal. In addition, the measuring and reference beams interfere with each other also in the reference detection module to result in a reference interference signal. The vertical and reference interference signals are received by a signal processing module and serve as a basis for calculating a vertical displacement of the grating (200). This grating measuring device allows a great vertical displacement measurement range at any working distance.

A system that may include a radiation source to generate a beam of coherent radiation; traveling lens optics to focus the beam so as to generate multiple spots on a surface of a sample and to scan the spots together over the surface; collection optics to collect the radiation scattered from the multiple spots and to focus the collected radiation so as to generate a pattern of interference fringes; and a detection unit to detect changes in the pattern of interference fringes.