Method for rapid imaging of absorption defect distribution on surface of large-diameter optical element

Abstract

The invention discloses a method for rapid imaging of absorption defect distribution on the surface of a large-diameter optical element. The method comprises the following steps: carrying out collimation and beam expanding of high-energy pulse laser to form a large-size excitation light spot for radiation heating on an optical element, enabling absorption defects on the surface and the subsurfaceof the optical element to be at transient temperature distribution and refractive index distribution; after certain time delay, carrying out collimation and beam expanding of another beam of high-energy pulse laser to form a large-size detection light spot which penetrates through an identical area radiated by the optical element, and recording diffraction light field distribution of the light spot by using a CCD; controlling time delay between excitation and detection laser pulses and analyzing characteristics of diffraction light field images recorded by using the CCD, thereby confirming whether the radiated area of the optical element has absorption defects or not and corresponding characteristics. By adopting the method, advantages that a conventional optical-thermal lens technique ishigh in detection sensitivity, high in resolution ratio, and the like are retained, a single-time detection area can be greatly increased, and rapid detection on absorption defect distribution of large-diameter optical elements is achieved.

Description

technical field [0001] The invention relates to the field of optical component detection, in particular to a method for high-resolution, fast and non-destructive imaging detection of the surface and subsurface absorption defect distribution of large-diameter optical components. Background technique [0002] Light absorption characteristics are an important index to measure the quality of optical components. For high-power laser systems, the characterization and control of the absorption loss distribution of optical components is particularly important, because the absorption center will lead to loss of laser energy, enhanced local temperature rise, degradation of beam quality, and even laser damage. Among the many causes of the above problems, surface and subsurface absorption defects of optical components are a major one. Surface and subsurface absorption defects are more common than bulk absorption defects. A lot of practice shows that the actual measured laser damage th...

AI Technical Summary

Problems solved by technology

Among the many reasons for the above problems, surface and subsurface absorption defects of optical components are a major one

[0004] However, for large-aperture optical components (generally 100×100mm in size 2 (above) the demand for spatial distribution imaging of absorption characteristics, the above-mentioned photothermal technology based on focused laser excitation and single-point detector measurement takes a very long time to complete the imaging covering the entire optical element in the point-by-point scanning mode: assuming point-by-point scanning The step size is 50μm, each measurement point needs 1s data acquisition, processing, and time to move to the next measurement point (already very fast), then complete a 400×400mm 2 It takes about 2 years to detect the components of the system, which obviously lacks technical reality; if the scanning step is increased and the number of detection points is reduced to speed up the scanning, then this imaging detection can only be regarded as random sampling for large-aperture optical components. The randomness of its defect detection will make the characterization effect greatly reduced

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