Internal Defects Detection Technology For Quartz Glass By In-line Digital Holography

Quartz glass is widely used in national defense equipment,inertial navigation and other fields because of its excellent performance.Due to the limitation of technology,bubbles and other defects often appear in quartz glass,which will affect the performance of quartz glass.The existing internal defect detection technology of quartz glass has some problems,such as complex operation,high price and heavy dependence on technicians.Based on the in-line digital holography,this paper uses the advantages of digital holography without contact,damage and high resolution to extract the size and three-dimensional position information of internal defects in quartz glass without contacting quartz glass samples.Realize the nondestructive testing function with low cost,portability and simple operation.The research contents of this paper mainly include:(1)According to the characteristics of internal defects in quartz glass,based on the analysis of the recording and reproduction principle of digital holography,the in-line digital holography is applied to the detection of internal defects in quartz glass;Then three classical reconstruction algorithms are compared and analyzed,and the angular spectrum method is determined to reconstruct the hologram of quartz glass,which provides a new method for the full field high-precision detection of internal defects of quartz glass.(2)Aiming at the noise inevitably introduced in the recording process of in-line digital holography,the background subtraction algorithm and Wiener filter operation are applied to suppress the noise introduced by laser and optical devices in the optical path of in-line digital holography,and improve the signal-to-noise ratio of hologram.In order to identify and extract the shape,size and other information of internal defects in quartz glass from the reconstructed image,the gray gradient threshold algorithm is applied to combine the gray information with the gradient information to improve the accuracy of size identification of internal defects in quartz glass.In order to extract the internal defects of quartz glass in the focusing state,the focusing position of internal defects of quartz glass is automatically obtained by Laplace operator function method.In order to further restore the accurate morphological information of the internal defects of quartz glass,the morphological processing is applied to the internal defects of quartz glass.The edge information of the internal defects of quartz glass is refined through expansion operation and corrosion operation,and the internal defect image of quartz glass containing more detailed information is obtained.(3)Aiming at the problem that the size error of the extracted internal defects of quartz glass is large due to the blurring of the contour edge caused by the phase object,the bicubic interpolation iterative extrapolation algorithm in super-resolution reconstruction technology is applied to the contour reconstruction of internal defects of quartz glass.Firstly,the amplified hologram is obtained by using the bicubic interpolation algorithm,and the amplified hologram information and object surface information are iterated repeatedly to recover more high-frequency information of internal defects of quartz glass,which provides technical support for high-precision measurement of internal defects of quartz glass.