斜照明式彩色共聚焦测量系统设计及其实验研究

张雅丽; 余卿; 尚文键; 王翀; 刘婷; 王寅; 程方

doi:10.37188/CO.2021-0181

斜照明式彩色共聚焦测量系统设计及其实验研究

doi: 10.37188/CO.2021-0181

华侨大学机电及自动化学院, 福建厦门 361021

基金项目: 国家自然科学基金资助项目(No. 52075190, No. 62075067)；福建省科技计划项目(No. 2019I0013)；华侨大学中青年教师科研提升资助计划项目(No. ZQN-PY604)。

详细信息

作者简介:
张雅丽（1997—），女，安徽六安人，硕士研究生，2019年于山东科技大学获得学士学位，主要研究方向为光电检测。E-mail: 1612737648@qq.com

余　卿（1983—），男，江西新余人，博士，副教授，2005年，2011年于合肥工业大学分别获得学士、博士学位，主要研究方向为光电检测、精密机械设计等。E-mail: yuqing@hqu.edu.cn

中图分类号: TH742
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出版历程
- 收稿日期: 2021-10-21
- 修回日期: 2021-11-17
- 录用日期: 2022-01-21
- 网络出版日期: 2022-02-18
- 刊出日期: 2022-05-20

Chromatic confocal measurement system and its experimental study based on inclined illumination

College of Mechanical Engineering and Automation, Huaqiao University, Fujian 361021, China

Funds: Supported by National Natural Science Foundation of China (No. 52075190, No. 62075067); Science and Technology Program of Fujian, China (No. 2019I0013); Promotion Program for Young and Middle-Aged Teachers in Science and Technology Research of Huaqiao University (No. ZQN-PY604).

More Information

Corresponding author: yuqing@hqu.edu.cn

摘要

摘要: 彩色共聚焦测量技术因无需轴向扫描，测量精度和测量效率高等优点，被广泛应用于工业领域，如高度测量和透明材料厚度检测等。然而，常见的彩色共聚焦系统多为同轴照明结构，即照明光轴和成像光轴都垂直于被测试样，系统的信噪比和光能利用率大大降低。现有的斜照明系统成像面光点漂移量较大，测量精度和应用范围受限。为此，本文提出一种改进的斜照明式彩色共聚焦测量方法，将现有斜照明系统的“V字形”结构调整为“三轴结构”，通过增加调节支路限制光点的漂移；同时，利用面阵彩色相机作为光电接收器件，结合颜色转换算法通过光点颜色得到所需高度值。本文先进行标定实验确定本装置的测量范围及精度；再依次以自制台阶和透明材料作为测量对象，得到相应的被测值。同时，为了验证改进后的系统性能，在相同条件下利用“V字型”系统进行对比实验。实验结果表明，该系统的轴向测量范围为350 μm，重复性优于1.69，轴向测量精度可达到微米级，且该系统具有良好的透明材料厚度测量能力。通过对比试验可以验证，系统对于光点漂移具有良好的抑制效果，且抑制后系统的测量准确度有明显提升。
- 彩色共聚焦 /
- 斜照明 /
- 三轴结构 /
- 透明材料
Abstract: Because the chromatic confocal technique has no axial scanning, high measurement speed, high precision, good axial tomography ability, and good axial resolution ability, it is widely used in industrial fields such as height measurement and transparent specimen thickness measurement. However, most chromatic confocal systems are coaxial illumination structures in which the illumination optical axis and imaging optical axis are perpendicular to the tested specimen which reduces its signal-to-noise ratio and light energy utility. However, the existing inclined illumination system has high light spot drift on the imaging surface, and the measurement accuracy and application range are limited. To overcome the above shortcomings, a chromatic confocal measurement method with inclined illumination is proposed in this paper. The "V-shaped" structure is changed to a triaxial structure, and the drift of the light spot is limited by adding an adjusting branch. Also, an array color camera is used as the photoelectric receiving device, and the height value is obtained by the light spot’s color processed by a color conversion algorithm. In this study, the calibration experiment was first carried out to determine the measurement range and accuracy of the device. Then, the self-made steps and transparent specimens were measured and the corresponding measured values were determined. In order to better verify the performance of the improved system under unchanged conditions, the V-shaped system was used for comparison. The experimental results show that the axial measurement range of the system is 350 μm, and the repeatability is greater than 1.69 μm. The axial measurement accuracy can reach the micron level and the system is highly capable of measuring the thickness of transparent specimens. Through comparison, it can be verified that the system has a good suppression effect on spot drift, and the measurement accuracy of the system has been significantly improved after suppression.
- chromatic confocal /
- inclined illumination /
- triaxial structure /
- transparent specimen

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图 1 彩色共聚焦系统原理图

Figure 1. Schematic diagram of the chromatic confocal measurement system

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图 2 “V字型”斜照明式彩色共聚焦系统。(a) 系统原理图; (b) 光点漂移示意图

Figure 2. Inclined illumination chromatic confocal system with V-shaped structure. (a) Schematic diagram of the system; (b) spot drift diagram

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图 3 平面镜反射示意图

Figure 3. Schematic diagram of the reflection by the plane mirror

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图 4 改进后的斜照明式彩色共聚焦测量方案。(a) 系统原理图; (b) 抑制后的光点示意图

Figure 4. The improved inclined illumination chromatic confocal measurement system. (a) Schematic diagram of the system; (b) improved spot drift diagram

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图 5 不同系统的轴向光强响应。(a) 共焦系统的轴向光强响应; (b) 彩色共聚焦系统的轴向光强响应

Figure 5. Axial light intensity response of different systems. (a) Axial light intensity response ofconfocal system; (b) axial light intensity response of chromatic confocal system.

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图 6 轴向位移与聚焦点位移的几何关系

Figure 6. Geometric relation between axial displacement and focal displacement

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图 7 不同波长位置处的光谱光强分布

Figure 7. Spectral light intensity distribution with different wavelengths

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图 8 (a) RGB颜色空间与 (b) HSI颜色空间

Figure 8. (a) RGB color space and (b) HSI color space

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图 9 三轴结构的斜照明式彩色共聚焦系统图

Figure 9. Inclined illumination chromatic confocal system with a triaxial structure

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图 10 样品位于不同轴向位置时相机采集到的图像

Figure 10. Images obtained by the camera when the specimen is at different axial positions

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图 11 标定实验。(a) 标定实验结果; (b) 线性拟合结果

Figure 11. Calibration experiment. (a) Calibration result; (b) linear fitting result

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图 12 台阶实物图

Figure 12. Picture of the step

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图 13 量块表面H值测量结果

Figure 13. H value of gauge block

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图 14 透明材料实物图

Figure 14. Picture of the transparent glass slides

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图 15 透明材料测量颜色示意图

Figure 15. Color diagram of transparent specimen

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图 16 “V字型”结构的斜照明式彩色共聚焦系统图

Figure 16. Inclined illumination chromatic confocal system with the V-shaped structure

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图 17 光点漂移抑制效果对比图。(a) “V字型”系统; (b) 三轴结构系统

Figure 17. Contrast diagram of the spots drift suppression effect. (a) V-shaped structure; (b) triaxial structure

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图 18 光点漂移的像素计算

Figure 18. Pixel calculation of the spot drift

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图 19 改进前系统的标定实验。(a) 标定实验结果; (b) 线性拟合结果

Figure 19. Calibration experiment before improvement. (a) Calibration result; (b) linear fitting result

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图 20 量块表面H值测量结果

Figure 20. H value of gauge block

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图 21 透明材料测量颜色示意图

Figure 21. Color diagram of transparent specimen

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表 1 标定实验数据

Table 1. Calibration of experimental data

Number	Axial displacement/μm	H value
1	0	120.00
2	50	119.99
3	100	119.93
4	150	118.15
5	200	114.21
6	250	91.84
7	300	76.19
8	350	63.39
9	400	54.37
10	450	47.88
11	500	38.96
12	550	30.32
13	600	23.24
14	650	16.77
15	700	11.62
16	750	6.58
17	800	7.01
18	850	8.98
19	900	9.78
20	950	10.06

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表 2 台阶实验数据及台阶高度计算结果

Table 2. Experimental data and calculation results of step height

Number	H value of 1.08 mm	H value of 1.03 mm	H Value of difference
1	19.68	28.10	8.42
2	19.62	28.11	8.49
3	19.67	28.08	8.41
4	19.62	28.07	8.45
5	19.67	28.09	8.42
6	19.62	28.07	8.45
7	19.69	28.12	8.43
8	19.64	28.06	8.42
9	19.68	28.15	8.47
10	19.69	28.08	8.39
11	19.68	28.03	8.35
12	19.66	28.08	8.42
13	19.73	28.14	8.41
14	19.67	28.08	8.41
15	19.63	28.07	8.44
16	19.65	27.52	7.87
17	19.65	28.07	8.42
18	19.67	28.07	8.40
19	19.65	28.08	8.43
20	19.64	28.10	8.46
The average value of the difference			8.40
The height value of the step (μm)			55.44
Relative error			−1.91%

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表 3 透明材料实验数据及厚度计算结果

Table 3. Experimental data and calculation results of transparent specimen

Number	H value of upper surface	H value of lower surface	H Value of difference
1	29.23	41.63	12.40
2	29.10	41.30	12.20
3	29.10	41.75	12.65
4	29.66	41.46	11.80
5	29.12	40.71	11.59
6	29.66	41.35	11.69
7	29.20	40.66	11.46
8	29.06	41.59	12.53
9	29.66	39.89	10.23
10	29.26	40.72	11.46
11	29.14	40.71	11.57
12	29.66	40.81	11.15
13	29.70	40.76	11.06
14	29.61	40.74	11.13
15	29.69	40.66	10.97
16	29.09	40.56	11.47
17	29.22	40.42	11.20
18	29.64	40.84	11.20
19	29.20	40.67	11.47
20	29.13	40.83	11.70
The average value of the difference			11.55
The thickness value of the transparent specimen (μm)			184.21
Relative error			1.73%

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表 4 标定实验数据

Table 4. Calibration experimental data

Number	Axial displacement(μm)	H value
1	0	120.00
2	50	119.98
3	100	118.78
4	150	116.55
5	200	112.80
6	250	94.00
7	300	86.06
8	350	78.00
9	400	69.16
10	450	61.38
11	500	54.19
12	550	48.03
13	600	40.83
14	650	32.96
15	700	25.58
16	750	18.36
17	800	12.10
18	850	6.18
19	900	5.14
20	950	10.37

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