High-accuracy differential autofocus system with an electrically tunable lens

du, kuangwei; Zhou, Dakai; zhou, Sijia; Zhang, Jinfeng; liu, qingqing; Liu, Qiulan; Chen, Youhua; Liu, Wenjie; Kuang, Cuifang

doi:10.1364/ol.488673

Cited by 2 publications

References 14 publications

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A fast and precise autofocus method using linear array CCD

Wang,

Ma,

Zeng

et al. 2024

Optical Metrology and Inspection for Industrial Applications XI

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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.

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A fast and precise autofocus method using linear array CCD

Wang,

Ma,

Zeng

et al. 2024

Optical Metrology and Inspection for Industrial Applications XI

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High-robustness autofocusing method in the microscope with laser-based arrayed spots

Wang,

Zhang,

Chen

et al. 2024

Opt. Express

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Accurate and rapid autofocus technology plays a crucial role in various fields, including automatic optical inspection technology, bio-chips scanning, and semiconductor manufacturing. The current photoelectric autofocus methods have limitations because of detecting the focal plane solely at the center of the microscope field of view. In the application of Stereo-seq the risk of autofocus errors will be increased, which have reduced the robustness of the system, like when the surface of the tested samples are wrinkling and inconsistent thickness, or the detection spot is at the edge of the sample. To enhance the robustness of the autofocus system and mitigate the constraints of the photoelectric autofocus methods, the laser-based arrayed spots photoelectric autofocus method has been proposed. To achieve the uniform light splitting, a 2D-Dammann grating is incorporated into the optical path of the autofocus system, resulting in the formation of an n × n arrayed spots on the surface of the sample. Through experimental verification, it has been demonstrated that this method can achieve the autofocus range of ±100μm and the autofocus accuracy of ±1/4 DOF when applied to a microscope equipped with a 10× objective lens, thereby satisfying the requirements for microscopic focusing. The arrayed light autofocus method devised in this study presents what we believe is a novel research concept for active autofocus detection and holds significant application value.

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High-accuracy differential autofocus system with an electrically tunable lens

Cited by 2 publications

References 14 publications

A fast and precise autofocus method using linear array CCD

A fast and precise autofocus method using linear array CCD

High-robustness autofocusing method in the microscope with laser-based arrayed spots

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