Application of medium wave infrared lens

The application of medium wave infrared lens is extremely wide, mainly in the following aspects: Length measurement: In the double-beam interferometer, if the refractive index of the medium is uniform and constant, the movement of the interference fringe is caused by the change in the geometric distance of the two coherent beams. According to the number of movement of the fringe, the length can be compared or excellently measured. . The Michelson interferometer and the Fabry-Perot interferometer have been used to express the international meter in terms of the wavelength of the cadmium red line. Refractive index measurement: The geometric distance of the two beams remains unchanged, and the change of the refractive index of the medium can also cause the change of the optical path difference, which causes the fringe to move. Rayleigh interferometer is a typical interferometer that uses fringe movement to measure the relative refractive index. The Mach-Qinter interferometer used in the wind tunnel is used to observe the changes in the refractive index of the airflow in real time. Wavelength measurement: Any method that uses wavelength as a unit to measure a standard meter is also a method of measuring wavelength in units of a standard meter. Taking the international meter as the standard, the wavelength of light can be measured by an interferometer. The Fabry-Perot interferometer (etalon) has been used to determine the primary standard of the wavelength (the wavelength of the cadmium red line) and several secondary wavelength standards, so as to determine the wavelength of other spectral lines through the comparison method. Inspection of optical components: Mid-wave infrared lenses are commonly used to inspect the quality of optical components such as flat plates, prisms, and lenses. Place the plate or prism to be inspected in an optical path of the Thaiman interferometer, and any non-uniformity of the refractive index or geometrical size of the plate or prism will be reflected on the interference pattern. If a lens is placed in the optical path, the wavefront distortion caused by the lens can be understood based on the interference pattern, so as to evaluate the wave aberration of the lens. Gravitational wave measurement: The mid-wave infrared lens can also be used for gravitational wave detection (Saulson, 1994). The concept of laser interferometer gravitational wave detector was proposed by former Soviet scientists Gertsenshtein and Pustovoit in 1962 (Gertsenshtein and Pustovoit 1962). In 1969, American scientists Weiss and Forward built preliminary test systems at MIT and Hughes Laboratories respectively in 1969 (Weiss 1972). As of today, the laser interferometer gravitational wave detector has been developed for more than 40 years. The current LIGO laser interferometer experiment claims** to directly measure gravitational waves (LIGO collaboration 2016). LIGO can be regarded as a two-path interferometer, and another type of gravitational wave detection experiment, a timing array can be regarded as a multi-path interferometer (Hellings and Downs, 1983).