Double Focus Laser Displacement Sensor Suppressing Laser Jitter and Target Tilt

Abstract

Abstract:Measurement precision of laser displacement sensor is subject to various factors, among which laser jitter and target tilt will directly lead to the position movement and shape variation of the laser spot, resulting in displacement measurement errors, so that researchers have to do a lot of research on the spot centering algorithm to weaken the above effects, which can treat the symptoms but not the root cause. Starting from the source of the problem, this paper proposes a double focus double peak solution, which uses a reflector to change the direction of the optical path, so that the imaging spots of the designed two optical paths focus on the same CMOS, forming a double peak structure. When laser jitter or target tilt occurs, the center of the two laser spots is shifted, but they move in the same direction, while their relative position remains unchanged. Therefore, the displacement can be characterized by the relative position of the two laser spots, so that laser jitter and target tilt are suppressed from the source. However, the two spots imaged on CMOS form a non-Gaussian distributed double peak structure, so the conventional laser spot centering algorithms are no longer applicable. To this end, a double peak adaptive threshold waveform extraction method combined with grayscale gravity method is proposed for spot centering algorithm, which combines the suppression of laser jitter and target tilt from the source and the improvement of spot positioning precision which represents the displacement measurement precision, and is experimentally verified.

Key words:laser displacement sensor, double focus, laser jitter, target tilt, waveform extraction

摘要：激光位移传感器的测量精度受制于各种因素，其中激光抖动和目标倾斜将直接导致激光光斑的位置移动和形状改变，造成位移测量误差。国内外研究人员在光斑定位补偿算法上做大量研究，但却治标不治本。本文从问题源头出发，提出双聚焦双峰成像方案，利用反射镜改变光路方向，使得两光路的像斑聚焦在同一CMOS上，形成双峰结构，当激光抖动和目标倾斜发生时，两个光斑中心虽产生偏移，却是同向移动，他们的相对位置不变，于是由两光斑相对位置表征位移量，激光抖动和目标倾斜从根源上得到抑制。但CMOS上的两个光斑形成非高斯分布的双峰结构，常规的光斑中心定位算法已不再适用，为此提出了双峰自适应阈值波形提取法与灰度重心法相结合的光斑定位算法，兼具了激光抖动和目标倾斜从源头上的抑制，以及光斑定位的准确性也即测量精度的提高，并进行了实验验证。

关键词:激光位移传感器，双聚焦，激光抖动，目标倾斜，波形提取

CLC Number:

TP212

CHEN Ruochen, LÜ Na, TAO Wei, ZHAO Hui. Double Focus Laser Displacement Sensor Suppressing Laser Jitter and Target Tilt[J]. J Shanghai Jiaotong Univ Sci, 2025, 30(6): 1171-1178.

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