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Birefringence measuring equipment currently used has either a high-sampling-rate or large-area measurement without high-spatial resolution. A birefringence distribution measurement of 10 kilopixels or more with high-spatial resolution at a sampling rate of 10 kHz or more has yet to be achieved. To develop the elemental technology to achieve this, this study proposes preliminary equipment, namely, a circular polariscope with a polarized laser, high-speed camera, and photoelastic modulator (PEM). The light source used was a 5-mW He–Ne laser with a wavelength of 632.8 nm; the light-receiving element was a high-speed camera with a photographing speed of 200 kHz, and harmonic analysis of the light intensity was achieved with a PEM. To demonstrate the possibility of high-speed measurement with the proposed equipment, the birefringence of a variable-wave plate was measured using one pixel of the high-speed camera. As a result, the maximum error of the measured value was 5.3% in the birefringence range of 10–20 nm of the specimen, 7.9% between 20–40 nm, and 4.0% between 40–60 nm. To show that measurement is also possible when the imaging range is expanded, the birefringence distribution in the area of 60 × 60 µm of the 40-nm wave plate was measured using 8 × 8 pixels of the high-speed camera. This method returned a smooth monotonously varying birefringence distribution close to 40 nm. The result shows that expanding the 8×8 pixels to 10 kilopixels can achieve the aforementioned research goals.
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