Measuring device and measuring method for tiny surface defect through post-magnification digital holographic microscopy

Abstract

The invention relates to a measuring device and a measuring method for a tiny surface defect through post-magnification digital holographic microscopy. The measuring method comprises the steps that a short coherent light source is adopted; scattered light information of the tiny surface defect of an optical element is obtained in an oblique incidence manner; scattered light interferes with a reference beam; interference image information is magnified in a post-magnification manner and received by a CCD (Charge Coupled Device) camera; and finally a pattern of the tiny surface defect and quantification information of depth distribution are computed and analyzed through a digital holographic principle. The device is mainly used for achieving detection of the tiny surface defect of the smooth optical element. The device can obtain depth and phase information of the surface defect by acquiring a single image and conducting related processing, can distinguish surface dust and indentation of the optical element, and can dynamically and rapidly measure. The device adopts a parallel light irradiation and off-axis holographic technique, and forms a post-magnification digital holographic recording system, so that the device is good in dynamic property and has the characteristics of non-destruction and information quantification.

Description

technical field [0001] The invention relates to a post-magnification digital holographic microscopic surface micro-defect measurement device and method. Background technique [0002] The processing quality evaluation of the surface of precision optical components mainly includes four main aspects: surface shape detection, surface roughness detection, surface waviness detection and surface defect detection. Surface shape deviation refers to the difference between the surface shape to be processed and the actual surface shape. Its horizontal scale is on the order of millimeters, which belongs to the macro-scale deviation. Usually, the interference fringes formed by the superposition of the measured wave surface and the standard wave surface are used for inversion. , so as to obtain this deviation. Surface roughness refers to the microstructure of the processed surface with small spacing and peak-to-valley values. For the surface of precision optical components, the lateral sc...

AI Technical Summary

Problems solved by technology

However, the shortcomings of this method are also obvious: human subjectivity factors, the size of the defect cannot be quantified, the detection speed is slow, the labor cost is high, and the observer needs to be trained; 2) The filter imaging method is different from the visual method. The principle is exactly the same, the only difference is that the human eye is replaced by an optical sensor array, which eliminates the subjectivity of human eye judgment, improves the detection speed, and can quantify the detection results

Its disadvantage is that the detection accuracy is not high, and it is easily affected by the environment such as light; 3) Diffuse scattered light receiving method

Its advantage is that the location of the defect is accurate; the disadvantage is that it cannot accurately reflect the size of the defect; 4) Diffraction light intensity method

Its advantage is that the error is small; the disadvantage is that it is only for the defect of a specific shape; 5) laser spectrum method

Its advantage is that it has high sensitivity; but it only detects defects of specific shapes

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