Optical autofocus system and method for short-wave infrared cameras

By employing a two-step strategy of coarse focusing with large step distance and fine focusing with small step distance, combined with a laser altimeter module and dynamic calibration, the focusing instability problem of short-wave infrared cameras under multi-layer structures and depth-of-field limitations was solved, achieving efficient and accurate automatic focusing and detection.

CN122340356APending Publication Date: 2026-07-03SHANGHAI TECHSENSE CO LTD
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Patent Information

Application Number
CN202610547773.4
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2026-04-23
Publication Date
2026-07-03

AI Technical Summary

Technical Problem

Existing shortwave infrared cameras suffer from unstable focusing in chip inspection due to interference from multi-layer structures and depth-of-field limitations. Traditional methods are inefficient, and industrial cameras are prone to misjudgment or missed detection in the inspection of products with inconsistent heights. The offset between the height measurement of the laser sensor and the position of the camera's focal plane leads to inaccurate focusing.

Method used

A two-step strategy combining large-step coarse focusing with small-step fine focusing is adopted. The optimal focus point is determined by normalized cross-correlation algorithm and sharpness calculation. Combined with laser altimeter module and dynamic calibration mechanism, the camera focal plane position is adjusted in real time to achieve fast and accurate focusing.

Benefits of technology

It effectively distinguishes the target chip layer from other layers, improves focusing accuracy and efficiency, ensures detection accuracy, eliminates the influence of mechanical installation errors, and increases production line detection speed.

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Abstract

This invention provides an optical autofocus system and method for a short-wave infrared camera. The system includes a Z-axis motor, a camera, a lens, an image acquisition module, and a control processing module. The method includes: a coarse focusing stage using the target chip layer feature region as a template, moving the camera with a step size of 0.5 to 1 times the lens depth of field, calculating image matching similarity, and determining the optimal coarse focusing point; and a fine focusing stage moving the camera near the coarse focusing point with a step size of 0.1 to 0.3 times the depth of field, calculating image sharpness, and determining the optimal fine focusing point. Furthermore, dynamic calibration and coordinated motion control using laser height measurement and visual optimization are employed to pre-drive the camera to the predicted focus position during product movement. This invention avoids misjudgment of multi-layer structures through a two-step focusing strategy and multi-peak recognition, balancing speed and accuracy, and eliminating the time consumption of serial focusing and the impact of system assembly errors.
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Citation Information

Patent Citations

  • Focusing method and system of infrared camera

    CN121357418A