Rectangular Amplitude Mask-Based Auto-Focus Method with a Large Range and High Precision for a Micro-LED Wafer Defects Detection System

He, Wenjun; Ma, Yufeng; Wang, Wenbo

doi:10.3390/s23177579

Cited by 2 publications

References 25 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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A Rapid Nanofocusing Method for a Deep-Sea Gene Sequencing Microscope Based on Critical Illumination

Gao,

Shu,

Zhou

et al. 2024

Sensors

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In the deep-sea environment, the volume available for an in-situ gene sequencer is severely limited. In addition, optical imaging systems are subject to real-time, large-scale defocusing problems caused by ambient temperature fluctuations and vibrational perturbations. To address these challenges, we propose an edge detection algorithm for defocused images based on grayscale gradients and establish a defocus state detection model with nanometer resolution capabilities by relying on the inherent critical illumination light field. The model has been applied to a prototype deep-sea gene sequencing microscope with a 20× objective. It has demonstrated the ability to focus within a dynamic range of ±40 μm with an accuracy of 200 nm by a single iteration within 160 ms. By increasing the number of iterations and exposures, the focusing accuracy can be refined to 78 nm within a dynamic range of ±100 μm within 1.2 s. Notably, unlike conventional photoelectric hill-climbing, this method requires no additional hardware and meets the wide dynamic range, speed, and high-accuracy autofocusing requirements of deep-sea gene sequencing in a compact form factor.

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Rectangular Amplitude Mask-Based Auto-Focus Method with a Large Range and High Precision for a Micro-LED Wafer Defects Detection System

Cited by 2 publications

References 25 publications

A fast and precise autofocus method using linear array CCD

A fast and precise autofocus method using linear array CCD

A Rapid Nanofocusing Method for a Deep-Sea Gene Sequencing Microscope Based on Critical Illumination

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