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Proceedings Paper

Moiré reducing two-dimensional diffractive optical low-pass filter made from molded plastic
Author(s): Yosuke Sakohira; Kazuya Yamamoto; Makoto Okada
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Paper Abstract

A two dimensional sinusoid diffraction grating is developed for a moiré-reducing low-pass filter. Typical display units have image pixels arranged systematically in two dimensions, with non-illuminating regions between the image pixels. Using a conventional lens to view this display, the image pixels and the region between the pixels are both magnified, and the resulting image is unpleasant to the human eye, especially with color displays, called the screen door effect. This pixel problem is typically solved with a low-pass filter using a diffraction grating. However, depending on the period of the diffraction grating compared to the period of the image pixels, moiré can be seen. In recent years, organic electroluminescence displays with a small fill factor are growing popular, but such displays are usually more prone to the screen door effect and moiré. With conventional optical low-pass filters, only the pixel pitch in the vertical and horizontal directions are taken into account, but this is insufficient with small fill-factor pixels, and consideration for various diagonal periods is needed. A two dimensional sinusoid structure diffraction grating is developed for a moiré-reducing low-pass filter. The angle of the grating with the image pixel arrangement, the distance between the display and the grating, the grating depth, and the grating period are all chosen appropriately, and take into account multiple non-adjacent diagonal image pixel periods for all colors, consequently reducing moiré and the screen door effect. We present the calculations and evaluation results from plastic samples made by lithography tooled molds.

Paper Details

Date Published: 7 March 2016
PDF: 7 pages
Proc. SPIE 9770, Advances in Display Technologies VI, 97700A (7 March 2016); doi: 10.1117/12.2211972
Show Author Affiliations
Yosuke Sakohira, Nalux Co., Ltd. (Japan)
Kazuya Yamamoto, Nalux Co., Ltd. (Japan)
Makoto Okada, Nalux Co., Ltd. (Japan)

Published in SPIE Proceedings Vol. 9770:
Advances in Display Technologies VI
Liang-Chy Chien; Sin-Doo Lee; Ming Hsien Wu, Editor(s)

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