A fast and precise autofocus method using linear array CCD

Zheng Wang; Rui Ma; Chuang Zeng; Lifu Liu; Xinghui Li; Xiaohao Wang; Bo He

doi:10.1117/12.3036393

20 November 2024 A fast and precise autofocus method using linear array CCD

Zheng Wang, Rui Ma, Chuang Zeng, Lifu Liu, Xinghui Li, Xiaohao Wang, Bo He

Author Affiliations +

Proceedings Volume 13241, Optical Metrology and Inspection for Industrial Applications XI; 132411T (2024) https://doi.org/10.1117/12.3036393
Event: SPIE/COS Photonics Asia, 2024, Nantong, Jiangsu, China

Conference Poster

Abstract

In the integrated chip industry, there is a growing demand of defect detection, and the autofocus capability of microscopy can significantly enhance efficiency. This paper presents a novel technique based on an autofocus methodology known as the eccentric light beam approach. Specifically, we have developed a line-stripe-shaped laser beam projection system that uses a linear array CCD, offering high resolution and instant response. The simple design of the linear array CCD overcomes noise interference caused by system processing tolerances and reduces signal processing complexity. In accordance to the proposed system, we designed a novel algorithm called adaptive multiscale windowing to calculate the centroid of the linear array image which is an essential criterion of the defocus value. Additionally, we explore the relationship between sample defocus amount and the centroid position shift of the received signal. We build the motion part with the resolution of less than 1 micron and response speed of less than 100 milliseconds. From the experiments conducted, we achieved the accuracy of less than 1 micron and the focusing speed within 0.2 second.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

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Zheng Wang, Rui Ma, Chuang Zeng, Lifu Liu, Xinghui Li, Xiaohao Wang, and Bo He "A fast and precise autofocus method using linear array CCD", Proc. SPIE 13241, Optical Metrology and Inspection for Industrial Applications XI, 132411T (20 November 2024); https://doi.org/10.1117/12.3036393

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