多源离面扰动下激光直接成像机视觉自标定方法

    Visual Self-calibration Method for Laser Direct Imaging Machines Against Multiple Out-of-plane Disturbances

    • 摘要: 激光直接成像(Laser Direct Imaging,LDI)是数字光刻装备的核心技术,其成像精度取决于印制电路板(Printed Circuit Board,PCB)表面与投影物镜焦平面的匹配精准度。然而LDI机在长期运行过程中,基板翘曲、热致变形、机械振动等多扰动源导致二者发生离面偏移,匹配精准度降低,成像质量劣化。为此,本文提出针对多源离面扰动的LDI机视觉自标定方法。首先构建了基于仿生柔顺机构的视觉调焦系统,然后设计了前端柔顺机构控制、动态调焦与靶标识别算法,实现PCB表面自适应对焦。最后建立后端焦面标定模型,量化分析离焦量与成像精度的映射关系,并完成了自标定系统原型样机开发与性能测试。实验结果表明,本文所提方法可将离焦量控制在± 0.5 mm内,同轴度误差稳定在5.0 μm内,提升了LDI机在多源离面扰动下的成像精度。

       

      Abstract: Laser direct imaging (LDI) technology is the core of digital lithography equipment. The imaging accuracy depends on the precise matching between the surface of the printed circuit board (PCB) and the focal plane of the projection lens. Unfortunately, during the long-term operation of the equipment, multiple factors, such as substrate warping, thermal deformation, and mechanical vibration, collectively cause the imaging surface to deviate from its intended surface. The problem seriously deteriorates the imaging quality and alignment accuracy. In this research, a visual self-calibration method for out-of-plane disturbance suppression is proposed. A self-calibration system based on a bionic compliance mechanism is formulated to achieve Z-direction micro-motion focusing of the camera. A front-end dynamic focusing algorithm, integrating the compliant mechanism and target recognition, is designed to achieve local adaptive focusing on the PCB surface. A back-end focal plane calibration model is quantitatively established to analyze the mapping relationship between defocus and imaging accuracy. The development and performance test of the self-calibration system prototype is completed. The experimental results show the performance of the proposed method. The defocus is within ±0.5 mm, and the co-axiality error is below 5 μm. The proposed approach significantly improves the imaging accuracy and alignment reliability of the LDI machine under multiple out-of-plane disturbances.

       

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