• Journal of Internet of Things and Convergence
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• v.10 no.2
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• pp.51-60
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• 2024

Aiming at the problem of low contrast and difficult to recognize video images in low-light environment, we propose an adaptive contrast compensation enhancement algorithm based on human visual perception. First of all, the video image characteristic factors in low-light environment are extracted: AL (average luminance), ABWF (average bandwidth factor), and the mathematical model of human visual CRC(contrast resolution compensation) is established according to the difference of the original image's grayscale/chromaticity level, and the proportion of the three primary colors of the true color is compensated by the integral, respectively. Then, when the degree of compensation is lower than the bright vision precisely distinguishable difference, the compensation threshold is set to linearly compensate the bright vision to the full bandwidth. Finally, the automatic optimization model of the compensation ratio coefficient is established by combining the subjective image quality evaluation and the image characteristic factor. The experimental test results show that the video image adaptive enhancement algorithm has good enhancement effect, good real-time performance, can effectively mine the dark vision information, and can be widely used in different scenes.

• Journal of the Korean Institute of Telematics and Electronics
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• v.5 no.4
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• pp.36-40
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• 1968

새로운 반사형 텔레비젼 디스푸레이를 소개한다. 이 방법에서는 선상의 액체결정의 다이나믹 스캣터링 모오드(Dynamic Scattering Mode, DSM)를 이용하며 주위가 밝은 곳에서도 볼 수 있다. 6∼12μm 두께의 액체결정은 뜯을 수 있는 음극선관 위에 와이어-모자의 훼이스 프레이트를 사용하는 전자속으로 실시간에 번지선택된다. 두가지 종류의 액체결정물질-Anasyliden Para-Amino Phenyl Acetate(APAPA)와 RCA 특유의 실온액체결정-을 시험했는데 동작온도(APAPA는 82°∼110℃이고 다른 것은 실온)를 제외하고는 비슷한 결과가 나왔다. 사방 3.1cm의 디스푸레이에서는 해상도가 적용 텔레비젼에 필요한 150line 보다 약간 떨여졌는데 그 원인은 액정결정 때문이 아니고 모자익의 구조에 의한 제한 때문이다. 더 나은 해상도를 얻으려면 디스푸레이를 좀더 크게하면 된다. 콘트라스트는 최적화(7.5:1)하지 않았다. 그러나 이 값을 정적인 디스푸레이에서 본 바와 같이 15∼20대 1로 개선하기 위해서는 몇가지의 기술을 사용할 수 있다. 이 디스푸레이 방법의 매력으로는 적당한 외부조명하에서는 약 ±45°의 넓은 관람각을 갖는데 있다고 하겠다. 액체결정내에서 DSM이 일어나도록 하는데 필요한 전류, 전압치들을 보면 평평한 텔레비젼 화면에 적합한 완전한 번지선택법에의 근사방법이 발견될 수 있으리라는 희망을 갖일 수 있다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.7
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• pp.112-124
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• 1989

In order to evaluate imaging performance of newly developed digital radiography system which requires scanning time as short as 0.7 sec and patient exposure as low as 3 mR, we have investigated its imaging and physical properties such as sensitivity characteristic, scatter fraction, detective quantum efficiency, modulation transfer function, and contrast detail diagram. The results show that the digital radiography system has linear sensitivity to the incident energy, and superior contrast resolving power with less X-ray exposure than conventional film-screen system. These performances are resulted from excellent scatter rejection capability and high detective quantum efficiency of digital radiography system.

• Journal of radiological science and technology
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• v.44 no.5
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• pp.465-471
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• 2021

Dual-energy X-ray imaging (DEI) techniques can provide X-ray images that a certain material is suppressed or emphasized by combining two X-ray images obtained from two different x-ray spectrum. In this paper, a single-shot DEI, which uses stacked two detectors (i.e., multilayer detector), is proposed to reduce the patient dose and increase throughput in angiography. The polymethyl methacrylate (PMMA) and aluminum (Al) were selected as two basis materials for material decomposition, and material-specific images are reconstructed as a vector combination of these two materials. We investigate the contrast and noise performance of material-decomposed images using iodine phantoms with various concentrations and diameters. The single-shot DEI shows comparable performances to the conventional dual-shot DEI. In particular, the single-shot DEI shows edge enhancement in material-decomposed images due to the different spatial-resolution characteristics of upper and lower detectors. This study could be useful for designing the multilayer detector including scintillators and energy-separation filter for angiography purposes.

• The Journal of the Korea Contents Association
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• v.9 no.4
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• pp.189-197
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• 2009

A digital image usually has 8 bits of depth basically representing pixel intensity ranging for [0 255]. These pixel range allow 256 step levels of pixel values in the image. Thus the greyscale value for a given image is an integer. When we carry out interpolation of a given image for resizing we have to round the interpolated value to integer which can result in loss of quality on perceived color values. This paper proposes a new method for recovering this loss of information during interpolation process. By using the proposed method the pixels tend to regain more original values which yields better looking images on resizing.

• Journal of radiological science and technology
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• v.34 no.1
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• pp.9-15
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• 2011

In this paper, an image quality evaluation of amorphous selenium based x-ray system was performed using modulation transfer function (MTF) measurement. MTF as a main factor of imaging quality evaluation was investigated by contrast method from acquired test pattern image. The MTF value was measured to 36.1% at 3.0 lp/mm which is twice as high as that in the film image. Compared with other studies, the results demonstrate that amorphous selenium based x-ray detector is clinically meaningful.