Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels

A new cross-polarized heterodyne optical technique is developed for two-dimensional (2D) simultaneous mapping of both birefringence and thickness variations in large flat glass panels commonly used in liquid-crystal displays (LCDs). Weak depolarization of a linearly polarized probe beam due to glass...

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Bibliographic Details
Published in:Review of scientific instruments 2006-05, Vol.77 (5), p.053107-053107-6
Main Authors: Protopopov, Vladimir V., Cho, Sunghoon, Kim, Kwangso, Lee, Sukwon, Kim, Hyuk, Kim, Daesuk
Format: Article
Language:English
Subjects:
BEAMS
BIREFRINGENCE
DATA ACQUISITION
DESIGN
GLASS
INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
INTERFERENCE
LIQUID CRYSTALS
MAPPING
POLARIMETERS
POLARIZATION
SPATIAL RESOLUTION
THICKNESS
VARIATIONS
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Summary:A new cross-polarized heterodyne optical technique is developed for two-dimensional (2D) simultaneous mapping of both birefringence and thickness variations in large flat glass panels commonly used in liquid-crystal displays (LCDs). Weak depolarization of a linearly polarized probe beam due to glass birefringence is detected by means of heterodyne mixing of the two cross-polarized and frequency shifted waves generated by Zeeman-type laser. Amplitude variations of the transmitted laser beam due to interference of the partial waves reflected from the both sides of a sample provide information about glass thickness. Measurements are being performed at the intermediate frequency of 2.3 MHz , providing several orders of magnitude higher speed of data acquisition with respect to traditional polarimeters. That high speed of measurements makes it possible to perform quality assessment of LCD glass panels not only in few randomly chosen points as it was in common practice before but to obtain entire 2D maps of both birefringence and thickness variations with millimeter scale spatial resolution. The medium-scale prototype of the LCD glass inspection system is developed and tested. Design and performance of the prototype are described.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.2202916