• Journal of the Optical Society of Korea
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• v.19 no.5
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• pp.487-493
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• 2015

A wavefront coding (WFC) technique provides an extension of the depth of field for a microscopy imaging system with slight loss of image spatial resolution. Through the analysis of the relationship between the incidence angle of light at the phase mask and the system pupil function, a mixing symmetrical cubic phase mask (CPM) applied to 5X-40X micro-objectives is optimized simultaneously based on point-spread function (PSF) invariance and nonzero mean values of the modulation transfer function (MTF) near the spatial cut-off frequency. Optimization results of the CPM show that the depth of field of these micro-objectives is extended 3-10 times respectively while keeping their resolution. Further imaging simulations also prove its ability in enhancing the defocus imaging.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.27 no.1
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• pp.56-74
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• 2023

In order to obtain practical and high-quality satellite images containing high-frequency components, a large aperture optical system is required, which has a limitation in that it greatly increases the payload weight. As an attempt to overcome the problem, many multi-aperture optical systems have been proposed, but in many cases, these optical systems do not include high-frequency components in all directions, and making such an high-quality image is an ill-posed problem. In this paper, we use deep learning to overcome the limitation. A deep learning model receives low-quality images as input, estimates the Point Spread Function, PSF, and combines them to output a single high-quality image. We model images obtained from three rectangular apertures arranged in a regular polygon shape. We also propose the Modulation Transfer Function Loss, MTF Loss, which can capture the high-frequency components of the images. We present qualitative and quantitative results obtained through experiments.

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.434-439
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• 1996

To investigate influence of the incident beams which have the truncated Gaussian amplitude and of the shapes of bump on read-out signal is an optical disc, and the point spread function on bump, the scalar diffraction theory is used in this paper. We consider the truncated Gaussian amplitudes which are $\sigma$=0, 0.5, 1.5, and 2.5, the height of bump which is given by $n{\Delta}_0={\lambda}/4$, and the phase height of bump which is then given by ${\Phi}_0={\pi}$. We also consider the shapes of the bump which are a rectangular shape, a frustoconical shape, and a conical shape. It is shown that as the truncation of incident beam reduces the radius of central spot on bump decreases, the maximum value of read-out signal increases, and that the size of bump decreases. From these results, we get better read-out signal and the reduced cross-talk in optical disc when the truncation of incident beam reduces. Therefore a laser beam having less truncated Gaussian amplitude may useful for an actual optical disc.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.5
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• pp.39-48
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• 2009

Many super-resolution reconstruction algorithms have been proposed since it was the first proposed in 1984. The spatial domain approach of the super-resolution reconstruction methods is accomplished by mapping the low resolution image pixels into the high resolution image pixels. Generally, a super-resolution reconstruction algorithm by using the spatial domain approach has the noise problem because the low resolution images have different noise component, different PSF, and distortion, etc. In this paper, we proposed the new super-resolution reconstruction method that uses the L1 norm to minimize noise source and also uses the Huber norm to preserve edges of image. The proposed algorithm obtained the higher image quality of the result high resolution image comparing with other algorithms by experiment.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.129.1-129.1
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• 2011

We have applied an advanced multi-aperture indexing photometry and sophisticated de-trending method to existing Taiwanese-American Occultation Survey (TAOS) data sets. TAOS, a wide-field ($3^{\circ}{\times}3^{\circ}$) and rapid photometry (5Hz) survey, is designed to detect small objects in the Kuiper Belt. Since TAOS has fast and multiple exposures per zipper mode image, point spread function (PSF) varies in a given image. Selecting appropriate aperture among various size apertures allows us to reflect these variations in each light curve. The survey data turned out to contain various trends such as telescope vibration, CCD noise, and unstable local weather. We select multiple sets of stars using a hierarchical clustering algorithm in such a way that the light curves in each cluster show strong correlations between them. We then determine a primary trend (PT) per cluster using a weighted sum of the normalized light curves, and we use the constructed PTs to remove trends in individual light curves. After removing the trend, we can get each synthetic light curve of star that has much higher signal-to-noise ratio. We compare the efficiency of the synthetic light curves with the efficiency of light curves made by previous existing photometry pipelines. Our photometric method is able to restore subtle brightness variation that tends to be missed in conventional aperture photometric methods, and can be applied to other wide-field surveys suffering from PSF variations and trends. We are developing an analysis package for the next generation TAOS survey (TAOS II) based on the current experiments.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.327-329
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• 2017

We report a spatial fluctuation analysis of the sky brightness in the near-infrared from observations towards the north ecliptic pole (NEP) by AKARI at 2.4 and $3.2{\mu}m$. As a follow up study of our previous work on the Monitor field of AKARI, we used NEP deep survey data, which covered a circular area of about 0.4 square degrees, in order to extend fluctuation analysis at angular scales up to 1000". After pre-processing, additional correction procedures were done to correct time varying components and instrumental effects such as MUXbleed. To remove resolved objects, we applied $2{\sigma}$ clipping and point spread function (PSF) subtraction. We finally obtained mosaicked images which can be used for the study of various diffuse emissions in the near-infrared sky and found that there are spatial structures in the mosaicked images using a power spectrum analysis.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.349-354
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• 1999

Electro-Optical Camera (EOC) is the main payload of the KOMPSAT-1 satellite to perform the mission of cartography that builds up a digital map of Korean territory including a digital terrain elevation map. This paper discusses the issues of the digital image simulation of EOC for the generation of EOC simulated scene as taken by EOC at 685km altitude on orbit. For the purpose, simulation work has been performed with the sensor models of EOC and the satellite platform motions models through image chain analysis from the illumination source (Sun) to a simulated image output in digital number. MODTRAN fur radiance calculation, MTF models of optics, detector and motions of EOC for system point spread function (PSF), and signal chain equations for digital number output are described. Several noise models of EOC are also considered. The final output is the EOC simulated image in digital number. The simulation technique can be used in several phase of a spaceborne electro-optical system development project, feasibility study phase, design, manufacturing, test phases, ground image processing phases, and so on.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.1
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• pp.43-48
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• 2012

This paper proposes a practical linear recursive robust motion deblurring filter using the inertial sensor measurements for strapdown image seekers. The angular rate information obtained from the gyro mounted on the missile is used to define the PSF(point spread function). Since the gyro output contains a unknown but bounded bias error. the motion blur image model can be expressed as the linear uncertain system. In consequence, the motion deblurring problem can be cast into the robust Kalman filtering which provides reliable state estimates even in the presence of the parametric uncertainty due to the gyro bias. Through the computer simulations using the actual IR scenes, it is verified that the proposed algorithm guarantees the robust motion deblurring performance.

• Proceedings of the KOSOMBE Conference
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• v.1985 no.06
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• pp.22-25
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• 1985

본고에서, "나선형 주사 방법에 의한 고속 NMR 영상화" 방법을 제안하고 그에 따른 실험 결과를 보였다. 이것은 2차원 FID 영역을 나선형 궤적으로 스캐닝하며 데이타를 받을 수 있도록 경사 자계 파형 (gradient pulse)을 가하여 빠른 시간에 (수십 msec - 수초)내에 영상 정보를 얻어낸 후, 재구성 알고리즘을 씀으로써 영상을 얻어내는 방법이다. 이 방법의 장점은 첫째로 $T_2$ 감쇄에 의한 PSF (Point Spread Function)가 윈형 대칭으로 주어지므로 영상화 했을때 물체의 구조 식별이 기존의 EPI (Echo Planar Imaging) 방법에 비해서 선명하며, 둘째로 나선형 궤적을 구현하기 의한 경사 자계 파형에서 불연속 점을 없앰과 동시에 파형의 세기가 점차로 증가하는 형태이므로, 기존의, 파형 왜곡에 의해 영상에 미치는 영향을 최소화 할 수가 있으며, 세째로 나선형 스캔을 사이 사이에 끼워 넣는 방법을 씀으로써 해상도를 향상시킬 수가 있다.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.55.3-55.3
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• 2016

By comparing MIRIS Paschen-${\alpha}$ ($Pa{\alpha}$) Galactic Plane Survey (MIPAPS) data with Anderson's H II region catalog (the most complete Galactic H II region catalog up to date), we confirmed $Pa{\alpha}$ detections from ~50% of the H II region candidates in Cepheus (Galactic longitude from $+96^{\circ}$ to $116^{\circ}$). The detection of the hydrogen recombination line identifies these candidates as clear H II regions. If we extend this result to the whole plane, more than 1000 candidates are expected to be identified as H II regions. In this contribution, we present the results of quantitative estimations (brightness, size, etc.) for the $Pa{\alpha}$ blobs detected in Cepheus. To obtain intensity of $Pa{\alpha}$ emission line, we perform background and point spread function (PSF) matching between two filter images (line and continuum filters) as well as flux calibration.