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.