| 摘要 |
High speed pattern and defect detection in flat panel displays, integrated circuits, photo mask reticles, CRT color masks, printed circuit boards, and any other patterned devices, regular or irregular, uses analog optical computing. Using appropriate illumination and optics, the Fourier transform of the image of a device under test is formed. The Fourier transform components of an ideal pattern are compared to the Fourier transform components of a measured pattern, and differences in relative intensities of the spatial components indicate a defect. A spatial separator is used to direct different components of the Fourier transform in different directions for parallel, simultaneous measurement and analysis. Utilizing Statistical Process Control, and properly comparing the different Fourier transform components, the defect is partially classified. Optical image processing is done in real time at the speed of light. Image acquisition at video rates is not a requirement, therefore detection can be performed on the fly while scanning the device under test.
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