• Restorative Dentistry and Endodontics
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• 제23권2호
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• pp.575-585
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• 1998

Use of the digital camera as a color measuring device was proposed. Digital camera can save, adjust and transmit image using computer. But it has great disadvantage that color of image possibly altered by environment of image capturing state, so the color reproducibility of digital camera can severly damage, Casmatch, the supplement for color correction, was proposed for enhance the color reproducibility of digital camera. Thus for study the efficacy of the Casmatch in enhancing the color reproducibility of digital camera, image of 78area in 39teeth was captured three times during two days and color reproducibility was evaluated and analyzed in terms of the use of Casmatch, teeth positions, and area within the tooth and comparatively analyzed. Results were as follow ; 1. ${\Delta}$E the color reproducibility of digital camera was 6.90${\pm}$3.27 in same day and 7.43${\pm}$3.94 in different day, and the color reproducibility when using Casmatch correction was 6.21${\pm}$3.86, 7.59${\pm}$4.48, there is no enhancement in using Casmatch correction. 2. There is no difference in color reproducibility between teeth, but color reproducibility of the middle third was greater(p<0.05) than the gingival third before color correction using Casmatch.

• Investigative Magnetic Resonance Imaging
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• 제20권4호
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• pp.215-223
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• 2016

Purpose: The management of metal-induced field inhomogeneities is one of the major concerns of distortion-free magnetic resonance images near metallic implants. The recently proposed method called "Slice Encoding for Metal Artifact Correction (SEMAC)" is an effective spin echo pulse sequence of magnetic resonance imaging (MRI) near metallic implants. However, as SEMAC uses the noisy resolved data elements, SEMAC images can have a major problem for improving the signal-to-noise ratio (SNR) without compromising the correction of metal artifacts. To address that issue, this paper presents a novel reconstruction technique for providing an improvement of the SNR in SEMAC images without sacrificing the correction of metal artifacts. Materials and Methods: Low-rank approximation in each coil image is first performed to suppress the noise in the slice direction, because the signal is highly correlated between SEMAC-encoded slices. Secondly, SEMAC images are reconstructed by the best linear unbiased estimator (BLUE), also known as Gauss-Markov or weighted least squares. Noise levels and correlation in the receiver channels are considered for the sake of SNR optimization. To this end, since distorted excitation profiles are sparse, $l_1$ minimization performs well in recovering the sparse distorted excitation profiles and the sparse modeling of our approach offers excellent correction of metal-induced distortions. Results: Three images reconstructed using SEMAC, SEMAC with the conventional two-step noise reduction, and the proposed image denoising for metal MRI exploiting sparsity and low rank approximation algorithm were compared. The proposed algorithm outperformed two methods and produced 119% SNR better than SEMAC and 89% SNR better than SEMAC with the conventional two-step noise reduction. Conclusion: We successfully demonstrated that the proposed, novel algorithm for SEMAC, if compared with conventional de-noising methods, substantially improves SNR and reduces artifacts.

• 대한방사성의약품학회지
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• 제3권2호
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• pp.65-71
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• 2017

To assess the effects of filter and reconstruction of Cu-64 PET data on Siemens scanner, the various reconstruction algorithm with various filters were assessed in terms of spatial resolution, non-uniformity (NU), recovery coefficient (RC), and spillover ratio (SOR). Image reconstruction was performed using filtered backprojection (FBP), 2D ordered subset expectation maximization (OSEM), 3D reprojection algorithm (3DRP), and maximum a posteriori algorithms (MAP). For the FBP reconstruction, ramp, butterworth, hamming, hanning, or parzen filters were used. Attenuation or scatter correction were performed to assess the effect of attenuation and scatter correction. Regarding spatial resolution, highest achievable volumetric resolution was $3.08mm^3$ at the center of FOV when MAP (${\beta}=0.1$) reconstruction method was used. SOR was below 4% for FBP when ramp, Hamming, Hanning, or Shepp-logan filter were used. The lowest NU (highest uniform) after attenuation & scatter correction was 5.39% when FBP (parzen filter) was used. Regarding RC, 0.9 < RC < 1.1 was obtained when OSEM (iteration: 10) was used when attenuation and scatter correction were applied. In this study, image quality of Cu-64 on Siemens Inveon PET was investigated. This data will helpful for the quantification of Cu-64 PET data.

• 한국정밀공학회지
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• 제23권2호
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• pp.181-190
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• 2006

In the industry, three-dimensional coloring has been needed for a realistic prototype. The Z-corporation developed a 3D printer which provides a three-dimensional colored prototype. However, the process cannot be adopted to models fabricated by other rapid prototyping processes. In addition, time and cost for manufacturing colored prototypes still remain to be improved. In this study, a new coloring process using an ink-jet head is proposed for color printing on a three-dimensional surface. Process parameters such as the angle and the distance between the ink-jet nozzle and the three-dimensional surface should be investigated through experiments. In order to minimize the distortion of a 2D image, the correction matrix according to the sloped angle is proposed and obtained by analysis of printing errors. An image on the doubly curved surface is printed so as to verify the proposed method. As a practical example, a helmet is chosen for printing images on the curved surface. The practical applicability of the correction matrix is then demonstrated by printing the character images on the surface of the helmet.

• ETRI Journal
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• 제31권4호
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• pp.448-450
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• 2009

In multiview imaging systems, color correction is adopted to eliminate color inconsistency between views. However, the influence of highlights on color correction has not been considered before. In this letter, a new color correction method based on highlight detection is proposed. The method is designed to treat highlight and highlight-removal regions independently when calculating correction parameters. Finial correction is implemented with a fusion mechanism. Experimental results show that the proposed method can improve objective and subjective correction performance, while achieving better coding performance than other correction methods.

• 정보처리학회논문지B
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• 제9B권1호
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• pp.91-98
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• 2002

In this paper, an implementation method of the efficient image transmission stage using watermarking and channel ceding is proposed. Usually, image communication system consists of both a transmitter part and a receiver part. The transmitter part takes charge of copyright protection of the generated image data, and image coding and compression that can deal with channel noises when transmitting. In the transmitter part, we propose a channel coding method which protects both the watermark signal and the original signal for protecting the copyright of image data and solving channel noises when transmitting. Firstly, copyright protection of image data is conducted. For this, image structure analysis is performed, and both the improvement of image quality and the generation of the watermark signal are made. Then, the histogram is constructed and the watermark signals are selected from this. At this stage, by embedding of the coefficients of curve fittness into the lower 4 bits of the image data pixels, image quality degradation due to the embedding of watermark signals are prevented. Finally, turbo coding, which has the most efficient error correction capability in error correction codes, has been conducted to protect signals of watermark and preserved original image quality against noises on the transmission channel. Particularly, a new interleaving method named "semi random inter]easer" has been proposed.

• International Journal of Advanced Culture Technology
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• 제10권2호
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• pp.252-259
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• 2022

Artificial intelligence is used in fusion with image processing techniques using cameras. Image processing technology is a technology that processes objects in an image received from a camera in real time, and is used in various fields such as security monitoring and medical image analysis. If such image processing reduces the accuracy of recognition, providing incorrect information to medical image analysis, security monitoring, etc. may cause serious problems. Therefore, this paper uses a mixture of YOLOv4-tiny model and image processing algorithm and uses the COCO dataset for learning. The image processing algorithm performs five image processing methods such as normalization, Gaussian distribution, Otsu algorithm, equalization, and gradient operation. For RGB images, three image processing methods are performed: equalization, Gaussian blur, and gamma correction proceed. Among the nine algorithms applied in this paper, the Equalization and Gaussian Blur model showed the highest object detection accuracy of 96%, and the gamma correction (RGB environment) model showed the highest object detection rate of 89% outdoors (daytime). The image binarization model showed the highest object detection rate at 89% outdoors (night).

• 한국의학물리학회지:의학물리
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• 제10권2호
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• pp.73-81
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• 1999

단일광자방출촬영 (SPECT) 에 대한 산란보정은 영상질을 개선하고 영상을 정량분석하는데 중요한 역할을 한다. 본 연구의 목적은 몬테카를로 시뮬레이션을 이용하여 에너지 창을 이용한 세 가지 산란보정들에 대해 조사하는 것이었다. 몬테카를로 방법을 이용하여 Tc-99m에서 방출되는 광자의 history를 발생시키는 점선원과 Jaszack 팬텀에 대해 시뮬레이션하였다. 시뮬레이션을 위한 SPECT 시스템의 섬광체 NaI(T1) 는 두께 0.95 cm, 40 $\times$ 45 cm이었고, 조준기는 저에너지용 조준기를 사용하였다. 140 keV 에서 SPECT 에 대한 에너지 분해능은 9.8 %, 고유공간분해능은 0.32 cm 이었고, 화소크기는 0.3 $\times$ 0.3 $cm^2$이었다. 산란보정방법에는 컴프턴창을 이용한 방법 (CW), 세 개의 에너지창을 이용한 방법 (TW), 그리고 이중 광봉우리창을 이용한 방법 (DPW)을 사용하였다. DPW의 다항식 계수를 구하기 위해서 직경 20 cm인 팬텀안에서 깊이에 따라 점선원을 위치시켜 평면 영상을 얻었다. 에너지 창은 w1 = 92-125 keV, w2 = 124-126 keV, w3 = 126-140 keV, w4 = 140-154 keV, w5 = 154-156 keV으로 설정하였다. SPECT 투사영상은 360$^{\circ}$ 회전모드로 하여 120개를 얻었다. 회전반경은 15 cm이었다. 산란보정방법들은 삼중 에너지창을 이용한 방법은 cold sphere를 가진 Jaszack phantom 에서 참값에 가장 가까운 대조도를 주었고, hot sphere를 가진 Jaszack phantom에서 image recovery에 있어서 좋은 것으로 나타났다. 컴프턴 창을 이용한 방법은 대조도에 있어서 참값보다 과대평가되어 나타났고 이중 광봉우리창을 이용한 방법은 산란보정하기 전에 비해 대조 도는 좋아졌지만 참값에 비해 과소평가되어 나타났다. 조사된 세 가지 보정방법들은 개선된 영상 대조도를 보여주었다. 결론적으로, 산란보정에 대한 임상적용을 위해서는 SPECT 시스템에 실행하기 용이한 보정방법을 선택해하며, 정확한 정량분석을 위해서는 산란보정이 수행되어야 할 것이다.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2008년도 학술대회 1부
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• pp.39-44
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• 2008

본 논문에서는 변형한 가능 곡면에 가상의 텍스쳐를 투영하기 위한 프로젝터 기반의 실시간 기하 보정 시스템을 제안한다. 다수의 대응점들의 위치를 추적하기 위하여 사용되는 마커들은 프로젝터의 영상이 투영되더라도 그 흔적이 남아있어서 투영 영상을 훼손한다. 또한 출력 영상의 사전 기하 보정 과정에서 병목 현상이 발생하기 때문에 실시간 기하 보정 시스템의 구현이 어렵다. 따라서 본 논문에서는 마커 인식 과정에서 마커에 의해 투영 영상이 훼손되는 현상을 막기 위해 눈에 보이지 않는 적외선 마커를 사용하며, NVIDIA의 Cg ToolKit을 이용하여 고속의 GPU 연산을 수행함으로서 자연스러운 실시간 보정 영상의 출력이 가능하다. 본 논문의 실험 결과에서는 눈에 보이지 않는 마커가 그려진 종이 위에서 사용자와의 상호 작용이 가능한 디지털 영상을 투영한다. 이를 통해 증강 현실 기반의 다양한 디지털 콘텐츠 제작이 가능하다.

• 한국지리정보학회지
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• 제6권1호
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• pp.98-106
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• 2003

위성영상의 장점인 고해상도, 다분광, 주기성, 광범위 촬영 등에 의해 위성영상은 초창기의 군사, 환경 분야의 적용을 뛰어넘어 현재는 많은 활용 분야에 널리 적용되고 있다. 이러한 위성영상을 효율적으로 활용하기 위해서는 여러가지 영상처리를 하여야 하며, 특히 기하보정 영상처리는 모든 활용분야에 있어 꼭 필수적인 단계이다. 따라서 본 연구에서는 이러한 기하보정 작업을 용이하게 하기 위하여 LANDSAT 위성영상을 중심으로 크게 세 가지 작업을 수행하여 기하보정 데이터를 구축하였다. 첫번째는 한반도 지역에 대하여 기하보정에 필요한 지상기준점을 선정하여 데이터베이스를 구축하였다. 두번째는 구축된 지상기준점을 이용하여 연도별로 구분된 LANDSAT 위성영상에 대하여 기하보정을 수행하였고, 마지막으로는 기하보정된 영상을 한반도 지역을 대상으로 모자이크 하였다. 이와 같은 작업을 통하여 576개의 지상기준점, 165장의 기하보정된 영상과 7장의 한반도 모자이크 영상을 구축하였다. 구축된 한반도의 기하보정 데이터는 많은 분야에 기초자료로 활용되리라 기대한다.