Abstract: A laser heterodyne interferometric straightness measurement apparatus and method with six DOFs determination includes a part for determining the straightness and its position based on laser heterodyne interferometry and a part for error determination and compensation. The optical path for determination of four DOFs errors including three common beam-splitters, a polarizing beam-splitter, a planar mirror, a convex lens, a position-sensitive detector and two quadrant detectors is added in the optical configuration of the part for determining the straightness and its position based on laser heterodyne interferometry.

Abstract: The present invention discloses a processing method for laser heterodyne interferometric signal based on locking edge with high frequency digital signal. A reference signal and a measurement signal of heterodyne interferometer, after being processed by photodetector, signal amplifier, filtering circuit, voltage comparator and high frequency digital edge locking module, are transferred to pulse counting synchronized latching processing module, to obtain entire cycle interference fringe numbers and filling pulse numbers in one interference fringe cycle, of the reference signal and the measurement signal; the numbers are transferred to a computer to obtain displacement and speed of a measured object; usage of a high frequency digital pulse signal to lock the rising edge of laser heterodyne interferometric signal can improve the gradient of the rising edge of interference signal and eliminate wrong pulse caused by noises, and improve the accuracy and stability of the processing for the following signals.

Abstract: Measuring refractive index of air based on laser synthetic wavelength interferometry. The Apparatus includes a dual-frequency laser that emits orthogonal linear polarized light of wavelengths ?1 and ?2, a beamsplitter, two polarizing beamsplitters, two corner-cube retroreflectors, a quartz vacuum cavity of length L disposed in the measuring optical path in parallel to the light propagation direction, and two detectors. The apparatus is used to measure the refractive index of air using the dual-frequency laser to emit orthogonal linear polarized light with wavelengths ?1 and ?2, using the beamsplitters, corner-cube retroreflectors, quartz vacuum cavity, and detectors. The integer N and fraction ? of interference fringes of wavelength ?2 are determined. The refractive index of air n is obtained by using the length L of the vacuum cavity, integer N and fraction ? of the interference fringes of wavelength ?2.

Abstract: The present invention discloses a method and an apparatus for measuring the refractive index of air based on the laser synthetic wavelength interferometry, wherein a laser synthetic wavelength interferometer comprises a dual-frequency laser, a beamsplitter, a first polarizing beamsplitter, a second polarizing beamsplitter, a first corner-cube retroreflector and a second corner-cube retroreflector; a quartz vacuum cavity is disposed in the measuring optical path in parallel to the light propagation direction; when the measurement is performed, air is introduced into the quartz vacuum cavity until it is consistent with outside environment; the variation of the refractive index of air inside the cavity will cause change of the interference signal of the wavelength ?2; the first detector of photoelectric type is used to directly detect the integer N of the interference fringes of the wavelength ?2; then the first corner-cube retroreflector is moved to make the phase difference between the interference signals of