Linear density measuring method for optical grating

Abstract

The invention relates to a linear density measuring method for an optical grating. Laser sent out by a laser light source is coupled through an optical fiber coupler, is coupled by a single-mode 2*2 optical fiber coupler, is collimated by an optical fiber collimator, and is then illuminated onto the surface of the optical grating to be tested to generate diffraction; different levels of diffraction light is generated; an irradiation area illuminated by the laser onto the optical grating is reduced by using the optical fiber, the conditions that zero stage diffraction light and first stage diffraction light of optical grating measuring points return in an incidence direction, the angle difference between the zero stage diffraction light and the first stage diffraction light is just a first stage diffraction angle alpha are respectively measured; the calculation is performed according to the angle difference of the measured two beams of diffraction light; groove density is obtained. The measuring stability is high; the light spot dimensions are small; the collimation performance is good; the measuring precision is high. In the practical operation process, the optical grating to be measured only needs to be put onto an electric displacement table; by regulating the angle position of an electric rotating table, the groove density of each measuring point on the meridian plane of the optical grating to be tested can be obtained. The linear density measuring method has the advantages that the higher-precision linear density measurement can be performed on the optical grating; the method can be used for a plane optical grating or a concave surface optical grating with greater curvature radius.

Description

technical field [0001] The invention relates to a spectroscopic technique, in particular to a grating linear density measurement method. Background technique [0002] As an important spectroscopic element, the grating occupies a pivotal position in the field of spectroscopic technology. It is not only widely used in small spectroscopic instruments, but also widely used in soft X-ray and vacuum ultraviolet bands in synchrotron radiation monochromators. [0003] The commonly used methods for measuring grating linear density mainly include interferometry, Moiré fringe method, long-range surface profiler method and diffraction method. Among them, the measurement accuracy of the first three measurement methods is relatively low, and they have certain usage restrictions. Using the principle of diffraction to measure the linear density of the grating has more advantages in terms of measurement accuracy. The traditional diffraction method generally uses a CCD or a spot detector t...

AI Technical Summary

Problems solved by technology

[0004] Aiming at the defects and accuracy problems existing in the current grating linear density testing method, the present invention proposes a grating linear density measurement method, which uses optical fibers to reduce the irradiation area of ​​laser light on the grating, and respectively makes the grating measurement points The 0th-order and 1st-order diffracted light returns along the incident direction, and the angle difference between them is exactly the 1st-order diffraction angle α

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