Intrinsic point defect-based fused quartz optical element subsurface damage detection method

Abstract

The invention belongs to the technical field of optical element processing, and particularly relates to a fused quartz optical element subsurface damage detection method based on intrinsic point defects. Comprising the following steps: selecting a laser type according to optical absorption characteristics of intrinsic point defects; setting a fluorescence signal acquisition wave band of the laser confocal microscope according to the intrinsic point defect emission spectrum; an ultraviolet laser is used for irradiating the fused quartz optical element, intrinsic point defects in subsurface damage are excited, and a fluorescence signal is generated; the laser confocal microscope obtains a sub-surface damage fluorescence tomography image by using a fluorescence signal pseudo colorization function, and the image is preprocessed to realize three-dimensional reconstruction of the sub-surface damage; and extracting the depth of the subsurface damage according to the position information of the bottommost pixel point of the three-dimensional reconstruction model. According to the method disclosed by the invention, no other fluorescent marker is used, so that additional pollution of the fluorescent marker to the element is fundamentally avoided, the application of the fluorescent microscopy to pollution-free and high-efficiency detection of the subsurface damage of the fused quartz optical element with large aperture and high cost becomes possible, and the precision of depth detection is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical element processing, and in particular relates to a sub-surface damage detection method for a fused quartz optical element based on intrinsic point defects. Background Art

[0002] Subsurface damage of fused silica optical components will adjust the electromagnetic field of the strong laser in the high-power laser system, causing thermal effects and reducing the laser damage threshold of the system, directly affecting the output power and overall performance of the laser system. Therefore, accurate detection of the depth of subsurface damage is crucial to guide the formulation of subsequent processing technology.

[0003] At present, the methods for detecting the depth of subsurface damage are divided into two categories: destructive and non-destructive. Among them, fluorescence microscopy is a non-destructive detection method. The fluorescent markers used can already characterize subsurface damage in real time, in situ and intuitively. Commonly used fluorescent markers include quantum dots, fluorescent polishing agents, fluorescent dyes and fluorescent residual impurities.

[0004] However, the fluorescent markers used in the prior art will inevitably cause contamination to the components, limiting the improvement of the laser damage threshold of the components. Therefore, the fluorescence microscopy method is only suitable for subsurface damage depth detection of small-sized, low-cost components, and can only be used for sampling detection, and cannot be popularized to large-caliber, expensive components. At the same time, the subsurface damage depth detection standard of the prior art uses the tomographic depth when the fluorescence signal intensity of the fluorescent medium is the maximum as the depth detection value. At this time, whether the position represented by the tomographic depth can represent the bottom of the subsurface damage is still inconclusive, so it is only suitable for rough measurement, difficult to measure accurately, and even more impossible to measure quantitatively. Summary of the invention

[0005] The present invention provides a sub-surface damage detection method for a fused quartz optical element based on intrinsic point defects to overcome the problem in the prior art that fluorescent markers cause additional contamination to the element when performing deep detection on sub-surface damage.

[0006] In order to achieve the above object, the technical solution of the present invention is: a method for detecting subsurface damage of fused quartz optical elements based on intrinsic point defects, comprising the following steps:

[0007] Step 1: Selecting an ultraviolet laser according to the optical absorption characteristics of the intrinsic point defect;

[0008] Step 2: setting the fluorescence signal acquisition band of the laser confocal microscope according to the emission spectrum of the intrinsic point defect; using an ultraviolet laser to irradiate the fused silica optical element to excite the intrinsic point defects in the sub-surface damage and generate a fluorescence signal; the laser confocal microscope uses the fluorescence signal pseudo-colorization function to obtain the sub-surface damage fluorescence tomography image, and the image is pre-processed to achieve three-dimensional reconstruction of the sub-surface damage;

[0009] Step 3: Extract the depth of sub-surface damage based on the bottom pixel position information of the 3D reconstructed model.

[0010] Furthermore, in the above step three, by writing Python code, the position information of the bottom pixel point of the three-dimensional reconstructed model is used as the depth value of the sub-surface damage to extract.

[0011] Compared with the prior art, the advantages of the present invention are:

[0012] 1. Through simulation calculation and actual measurement of the absorption spectrum of intrinsic point defects of fused quartz, it is found that the ultraviolet band is the main optical absorption band of intrinsic point defects, which provides parameter guidance for the selection of lasers. Therefore, the present invention proposes a method for detecting the depth of subsurface damage of fused quartz optical components based on intrinsic point defects, the core of which is to use ultraviolet lasers to excite intrinsic point defects. This method does not use any other fluorescent markers, which fundamentally eliminates the additional contamination of components by fluorescent markers, making it possible to apply fluorescence microscopy to the pollution-free and efficient detection of subsurface damage of large-caliber, expensive fused quartz optical components.

[0013] 2. Intrinsic point defect fluorescence signals are difficult to observe and collect under a black background and ordinary microscope. Therefore, the use of the pseudo-colorization function of the fluorescence signal of the laser confocal microscope can ensure the subsequent high-precision three-dimensional reconstruction and depth extraction based on the sub-surface damage fluorescence tomography image. The present invention proposes to directly perform depth extraction based on the position information of the bottom pixel of the sub-surface damage three-dimensional reconstruction model, thereby improving the accuracy of depth detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a flow chart of the method of the present invention;

[0015] Figure 2 Simulation and measured absorption spectra of intrinsic point defects in fused silica optical elements;

[0016] Figure 3 is the emission spectrum of the intrinsic point defect in the fused silica optical element under 405nm UV laser irradiation;

[0017] Figure 4Comparison process of subsurface damage depth detection of fused silica optical components based on CdSe / ZnS quantum dots and intrinsic point defects;

[0018] Figure 5 The results of three-dimensional reconstruction and depth extraction of sub-surface damage of fused quartz optical components based on CdSe / ZnS quantum dots and intrinsic point defects. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] Example:

[0021] The present invention provides a method for detecting subsurface damage of a fused quartz optical element based on intrinsic point defects, comprising the following steps:

[0022] Step 1: Select the laser type based on the optical absorption characteristics of the intrinsic point defect:

[0023] The setup of the fluorescence tomography image acquisition system for subsurface damage of fused silica optical components is mainly based on the analysis of the optical absorption characteristics of intrinsic point defects of fused silica, including the calculation of the simulated absorption spectra of four main intrinsic point defect molecular structure models: non-bridging oxygen center (NBOHC), E' center, oxygen vacancy ODC (Ⅰ) and ODC (Ⅱ), as well as the actual measurement of the absorption spectra of intrinsic point defects in fused silica optical components, such as Figure 2 shown.

[0024] By analyzing the simulation and measured results, this embodiment selects a 405 nm ultraviolet laser to excite the intrinsic point defects.

[0025] Step 2: Set the fluorescence signal collection band of the laser confocal microscope according to the emission spectrum of the intrinsic point defect, use an ultraviolet laser to irradiate the fused silica optical element to excite the intrinsic point defects in the sub-surface damage to generate a fluorescence signal, and use the laser confocal microscope to obtain a fluorescence tomography image of the sub-surface damage using the fluorescence signal pseudo-colorization function.

[0026] like Figure 3 As shown, in this embodiment, under the irradiation of a 405 nm ultraviolet laser, the emission spectrum of the intrinsic point defect in the fused silica optical element is measured, and it is determined that the fluorescence signal band of the intrinsic point defect is 440-480 nm.

[0027] A 405nm ultraviolet laser is used to irradiate the fused silica optical element to excite the intrinsic point defects in the sub-surface damage and generate fluorescence signals. When obtaining the sub-surface damage fluorescence tomography image, only the fluorescence signals in the 440-480nm band are collected.

[0028] Using the pseudo-colorization function of the fluorescence signal of the confocal microscope, the fluorescence signal can be rendered into bright, easy-to-observe specified colors in real time, making the fluorescence signal easier to observe and collect

[0029] Step 3: Extract the depth of sub-surface damage based on the bottom pixel position information of the 3D reconstructed model:

[0030] In this step, Python code is written to extract the position information of the bottom pixel of the 3D reconstructed model as the depth value of the sub-surface damage.

[0031] The above-mentioned intrinsic point defect subsurface damage depth detection method of fused silica optical components is compared with the detection method using CdSe / ZnS quantum dots as fluorescent markers. The specific process is as follows: Figure 4 As shown;

[0032] CdSe / ZnS quantum dots are embedded into the subsurface damage of fused quartz optical elements by grinding to achieve marking, and an ultrasonic cleaner is used to wash away the residual quantum dots and impurities; the laser uses a 405nm ultraviolet laser, and the emission peak of CdSe / ZnS quantum dots is in the band of 520-580nm, and the intrinsic point defects and CdSe / ZnS quantum dots fluorescence signals are collected separately; a laser confocal microscope is used to obtain subsurface damage fluorescence tomography images based on CdSe / ZnS quantum dots and intrinsic point defects, and image preprocessing is performed; finally, three-dimensional reconstruction and depth extraction are achieved respectively, and the detection effects are compared. The results are shown in the figure. Figure 5 As shown: Compared with CdSe / ZnS quantum dots, high-precision three-dimensional reconstruction and depth extraction of sub-surface damage of fused quartz optical components can also be achieved based on intrinsic point defects.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. It should be pointed out that any improvements and modifications made by ordinary technicians in this technical field without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method for detecting subsurface damage of fused quartz optical elements based on intrinsic point defects, characterized in that: The following steps are involved: Step 1: Selecting an ultraviolet laser according to the optical absorption characteristics of the intrinsic point defect; Step 2: setting the fluorescence signal acquisition band of the laser confocal microscope according to the emission spectrum of the intrinsic point defect; using an ultraviolet laser to irradiate the fused silica optical element to excite the intrinsic point defects in the sub-surface damage and generate a fluorescence signal; the laser confocal microscope uses the fluorescence signal pseudo-colorization function to obtain the sub-surface damage fluorescence tomography image, and the image is pre-processed to achieve three-dimensional reconstruction of the sub-surface damage; Step 3: Extract the depth of sub-surface damage based on the bottom pixel position information of the 3D reconstructed model.

2. The method for detecting subsurface damage of fused silica optical elements based on intrinsic point defects according to claim 1, characterized in that: In the step three, Python code is written to extract the depth value of the sub-surface damage using the position information of the bottom pixel of the three-dimensional reconstructed model as the depth value of the damage.

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