• Journal of the Optical Society of Korea
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• v.19 no.5
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• pp.456-466
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• 2015

We investigated an anti-aliasing (AA) filter for digital camera photography by which the excessively high-frequency components of the image signal are suppressed to avoid the aliasing effect. Our optomechanical AA filter was implemented by applying rapid relative motions to the imaging sensor. By the engineered motion blur of the mechanical dithers, the effective point-spread function (PSF) of the imaging system could be tailored to reject the unwanted high-frequency components of the image. For optimal operations, we developed a spiral filter motion protocol that could produce a Gaussian-like PSF. We experimentally demonstrated that our AA filter provides an improved filtering characteristic with a better compromise of the rejection performance and the signal loss. We also found that the pass band characteristic can be enhanced further by a color-differential acquisition mode. Our filter scheme provides a useful method of digital photography for low-error image measurements as well as for ordinary photographic applications where annoying $moir{\acute{e}}$ patterns must be suppressed efficiently.

• Journal of the Semiconductor & Display Technology
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• v.20 no.1
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• pp.77-82
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• 2021

Using a multi-array needle module developed for coating of high-density cylindrical microlens array (C-MLA), we have fabricated an anti-Moiré filter for LED screens. The Moiré phenomenon appears due to the interference between the array pattern of image sensors in a camera and the non-emission area (grid pattern) of a LED screen. To suppress it, we have employed poly(methyl methacrylate) (PMMA) and coated it on a glass substrate in the form of a grid and non-grid (parallel lines). We have rotated the needle module in order to increase the number of C-MLAs. With this scheme, we have fabricated the 150 mm × 150 mm anti-Moiré filters where 836 microlens lines are formed. They show the average width of 255.4 ㎛, the average distance between CMLs of 94.6 ㎛, and C-MLA width non-uniformity of 4.7%. We have shown that the Moiré patterns still appear in the presence of the parallel (non-grid)-type filter, whereas they disappeared completely by the grid-type filter. It is due to the fact that the Moiré patterns are diffused more effectively by the grid-type C-MLA.

• Journal of the Semiconductor & Display Technology
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• v.22 no.3
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• pp.28-35
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• 2023

Moiré patterns emerge due to the interference between the non-emission area of the LED screen and the grid line in an image sensor of a video recording device when taking a video in the presence of the LED screen. To reduce the moiré intensity, we have fabricated an anti-moiré filter using hollow glass microspheres (HGMs) by slot-die coating. The LED screen has a large non-emission area because of a large pitch (distance between LED chips), causing more severe moiré phenomenon, compared with a display panel having a very narrow black matrix (BM). It is shown that HGMs diffuse light in such a way that the periodicity of the screen is broken and thus the moiré intensity weakens. To quantitatively analyze its moiré suppression capability, we have calculated the spatial frequencies of the moiré fringes using fast Fourier transform. It is addressed that the moiré phenomenon is suppressed and thus the amplitude of each discrete spatial frequency term is reduced as the HGM concentration is increased. Using the filter with the HGM concentration of 9 wt%, the moiré fringes appeared depending sensitively on the distance between the LED screen and the camera are almost completely removed and the visibility of a nature image is enhanced at a sacrifice of luminance.