Laser Triangulation Method for Glass Thickness by Automatically Adapting to Displacement Change

Kaimei Liu; Wei Tao; Xiao Chen; Zhi Li; Hui Zhao

doi:10.3788/CJL202047.0104003

Chinese Journal of Lasers, Volume. 47, Issue 1, 0104003(2020)

Laser Triangulation Method for Glass Thickness by Automatically Adapting to Displacement Change

Kaimei Liu, Wei Tao, Xiao Chen, Zhi Li, and Hui Zhao^*

Department of Instrument Science and Engineering, School of Electronic Information and Electric Engineering,Shanghai Jiao Tong University, Shanghai 200240, China

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Figures & Tables(15)

Fig. 1. Principle of glass-thickness measurement based on laser triangulation

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Fig. 2. Schematic of glass-thickness measurement when glass position changes

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Fig. 3. Overall structure of measurement system

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Fig. 4. Schematic of optical system simulation by ZEMAX

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Fig. 5. Schematic of ZEMAX simulation of imaging waveform on CMOS

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Fig. 6. Experimental system for glass-thickness measurement

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Fig. 7. CMOS waveforms in actual measurement when glass is at different positions. (a) Proximal; (b) close to standard position; (c) distal

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Fig. 8. Spot spacing on CMOS as a function of glass thickness when glass is at different positions

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Fig. 9. Spot spacing on CMOS as a function of glass displacement when glasses with different thicknesses are measured

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Fig. 10. Comparison of thickness measurement error for 3.018-mm-thick glass

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Fig. 11. Comparison of thickness measurement error for 4.389-mm-thick glass

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Fig. 12. Schematic of thickness measurement when glass is tilted

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Table 1. Thicknesses of glass used for calibration
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Table 1. Thicknesses of glass used for calibration
Number of glass 1 2 3 4
Thickness /mm 1.100 1.850 3.318 5.822

Table 2. Data of thickness measurement for 3.018-mm-thick glass at different positions

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Table 2. Data of thickness measurement for 3.018-mm-thick glass at different positions

Displacement ofglass /mm	Distance betweenspots /pixel	Measurementresult /mm	Measurementerror /mm	Absoluteerror /m	Relativeerror /%
40.0000	331.6672	3.006	0.012	0.012	0.38
40.4212	310.3207	3.030	-0.012	0.012	0.39
40.8117	291.6010	3.033	-0.015	0.015	0.48
41.2035	274.4923	3.030	-0.012	0.012	0.39
41.6443	257.7499	3.028	-0.010	0.010	0.33
42.0509	243.6491	3.021	-0.003	0.003	0.11
42.4594	231.3922	3.021	-0.003	0.003	0.10
42.8529	220.3813	3.015	0.003	0.003	0.11
43.2557	210.1754	3.007	0.011	0.011	0.37
43.6527	202.6494	3.023	-0.005	0.005	0.17
44.0747	194.1861	3.022	-0.004	0.004	0.14

Table 3. Data of thickness measurement for 4.389-mm-thick glass at different positions

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Table 3. Data of thickness measurement for 4.389-mm-thick glass at different positions

Displacement ofglass /mm	Distance betweenspots /pixel	Measurementresult /mm	Measurementerror /mm	Absoluteerror /mm	Relativeerror /%
40.2224	435.717	4.384	0.005	0.005	0.16
40.6425	408.5386	4.403	-0.014	0.014	0.47
41.0540	384.2368	4.397	-0.008	0.008	0.27
41.4802	361.4038	4.383	0.006	0.006	0.20
41.8618	344.5201	4.389	0.000	0.000	0.01
42.2498	328.0131	4.379	0.010	0.010	0.33
42.6555	313.0257	4.380	0.009	0.009	0.30
43.0428	300.0813	4.383	0.006	0.006	0.19
43.4139	289.0668	4.385	0.004	0.004	0.12
43.6162	283.9852	4.397	-0.008	0.008	0.26

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Kaimei Liu, Wei Tao, Xiao Chen, Zhi Li, Hui Zhao. Laser Triangulation Method for Glass Thickness by Automatically Adapting to Displacement Change[J]. Chinese Journal of Lasers, 2020, 47(1): 0104003

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Paper Information

Category: measurement and metrology

Received: Jun. 25, 2019

Accepted: Sep. 26, 2019

Published Online: Jan. 9, 2020

The Author Email: Hui Zhao (huizhao@sjtu.edu.cn)

DOI:10.3788/CJL202047.0104003

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology

Table 1. Thicknesses of glass used for calibration

Table 1. Thicknesses of glass used for calibration

Table 2. Data of thickness measurement for 3.018-mm-thick glass at different positions

Table 2. Data of thickness measurement for 3.018-mm-thick glass at different positions

Table 3. Data of thickness measurement for 4.389-mm-thick glass at different positions

Table 3. Data of thickness measurement for 4.389-mm-thick glass at different positions