Development of Dual-Wavelength, Large-Diameter, Liquid-Crystal Photoelasticity-Measuring Instrument

Yuzhi Chen; Tonglu Xing; Qiang Lin; Cheng Liu; Jianqiang Zhu

doi:10.3788/CJL231513

Chinese Journal of Lasers, Volume. 51, Issue 13, 1304008(2024)

Development of Dual-Wavelength, Large-Diameter, Liquid-Crystal Photoelasticity-Measuring Instrument

Yuzhi Chen^1,2, Tonglu Xing^1,2, Qiang Lin¹, Cheng Liu^1,2、*, and Jianqiang Zhu¹

¹Key Laboratory of High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China

²University of Chinese Academy of Sciences, Beijing 100049, China

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Figures & Tables(12)

Fig. 1. Optical path of photo-elastic stress measured by elliptically polarized light

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Fig. 2. Schematic diagrams of the dual-wavelength phase extraction method. (a) $a r c c o s [c o s (2 π δ / λ_{1})]$ and $a r c c o s [c o s (2 π δ / λ_{2})]$ ;(b) $2 π δ / λ_{1}$ ; (c) $δ$

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Fig. 3. Light source structure and liquid crystal performance measurement optical path diagram. (a) Schematic diagram of straight down backlight structure; (b) long and short axis direction measurement optical path

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Fig. 4. Design diagrams of the large-diameter liquid crystal photoelastic stress measuring instrument. (a) Structural schematic diagram; (b) mechanical structure diagram

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Fig. 5. Structure and software interface diagrams of the large-diameter liquid crystal photoelastic stress measuring instrument. (a) Diagram of instrument device; (b) diagram of six-hole structure; (c) diagram of structure of LED light source arrangement; (d) diagram of operation interface and measurement results

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Fig. 6. Sample images and measurement images. (a) Sample image; (b)‒(g) bright and dark field difference images recorded by CCD

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Fig. 7. Plots of the results obtained at different steps of the experimental procedure. (a1)(a2) $c o s δ_{1}$ , $c o s δ_{2}$ ; (b) wrapped $δ_{1}$ ; (c) $σ_{1} - σ_{2}$

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Fig. 8. Measurement results of the conventional six-step phase-shift method. (a1)‒(a6) Intensity images of photoelastic acquisition by the conventional six-step phase-shift method; (b) $σ_{1} - σ_{2}$ ; (c) difference between the results of the two methods

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Fig. 9. Stress direction angle measurement results. (a) Photo-elastography measurement results; (b) conventional six-step phase shift method measurement results

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Table 1. Measured output light intensity variance of TN LCD panels

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Table 1. Measured output light intensity variance of TN LCD panels

Gray level / arb. units	Difference / ${(a r b . u n i t s)}^{2}$	Gray level / arb. units	Difference / ${(a r b . u n i t s)}^{2}$	Gray level / arb. units	Difference / ${(a r b . u n i t s)}^{2}$
0	9.16	90	10.39	180	8.71
15	12.34	105	9.78	195	13.43
30	16.89	120	19.12	210	12.45
45	7.85	135	17.54	225	14.28
60	15.12	150	11.36	240	10.56
75	17.30	165	15.27	255	13.14

Table 2. Measured output light intensity variance of VA LCD panels

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Table 2. Measured output light intensity variance of VA LCD panels

Gray level / arb. units	Difference / ${(a r b . u n i t s)}^{2}$	Gray level / arb. units	Difference / ${(a r b . u n i t s)}^{2}$	Gray level / arb. units	Difference / ${(a r b . u n i t s)}^{2}$
0	50.70	90	45.54	180	37.26
15	40.36	105	38.14	195	42.15
30	54.69	120	31.72	210	47.63
45	35.81	135	57.58	225	39.92
60	54.89	150	39.16	240	49.25
75	48.68	165	36.89	255	41.33

Table 3. Measured output light intensity variance of IPS LCD panels

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Table 3. Measured output light intensity variance of IPS LCD panels

Gray level / arb. units	Difference / ${(a r b . u n i t s)}^{2}$	Gray level / arb. units	Difference / ${(a r b . u n i t s)}^{2}$	Gray level / arb. units	Difference / ${(a r b . u n i t s)}^{2}$
0	62.17	90	59.48	180	74.27
15	70.39	105	58.74	195	75.33
30	68.25	120	64.28	210	69.80
45	71.41	135	78.58	225	69.04
60	73.63	150	66.29	240	60.32
75	58.12	165	61.21	255	71.03

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Yuzhi Chen, Tonglu Xing, Qiang Lin, Cheng Liu, Jianqiang Zhu. Development of Dual-Wavelength, Large-Diameter, Liquid-Crystal Photoelasticity-Measuring Instrument[J]. Chinese Journal of Lasers, 2024, 51(13): 1304008

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Paper Information

Category: Measurement and metrology

Received: Dec. 12, 2023

Accepted: Feb. 6, 2024

Published Online: Jul. 2, 2024

The Author Email: Cheng Liu (chengliu@siom.ac.cn)

DOI:10.3788/CJL231513

CSTR:32183.14.CJL231513

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology