• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.5
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• pp.374-381
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• 2008

The correlation coefficient method, which was proposed by our research group, is applied to digital particle holography to locate the focal plane of particles. It uses the fact that the correlation coefficient is maximum at the focal plane. The factors influencing this method are discussed with a numerical simulation of holograms. For real holograms, the Wiener filter was proposed to process both recorded holograms and reconstructed images. The application results using the dot array target showed that the Wiener filter is a very effective tool for processing holography-related images. The effects of the dot size and the object distance on the errors in the determination of the focal plane by the correlation coefficient method were investigated by using the calibration target.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.4
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• pp.399-405
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• 2009

The focal plane image stabilization for a satellite camera is one of the an effective method which can increase the satellite camera's image quality by removing the motion disturbance of a focal plane. The objectives of this article are to introduce the concept of the focal plane image stabilization and determine the best driving conditions of the actuator for the response and thrust. Under various driving condition the experiments have been performed to investigate the response and thrust characteristics of the piezoelectric driven stick-slip actuator of the focal plane image stabilizing device. From experiments, the best driving frequency and duty ratio for the magnesium slider are 70 kHz and 27%, respectively.

• Proceedings of the KSRS Conference
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• v.2
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• pp.804-807
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• 2006

The SRI(Super Resolution Imager) with 800mm aperture primary mirror is the ground development model of the high resolution satellite camera. The SRI focal plane electronics including detector array generates the data for high-resolution images by converting incoming light into digital stream of pixel data. Since the focal plane including a detector is the basic building block of the camera system, the main system performances is directly determined by its performance. This paper measures the SRI focal plane electronics’ performance such as the dark signal, the dark signal noise, the linearity, the PRNU(Photo Response Non-Uniformity), the SNR(Signal to Noise Ratio) and the sensor saturation capability. In addition, this paper verifies the various functionalities of the SRI focal plane electronics. The electrical test equipment with the specialized software and the optical test equipments such as the integrating sphere, the rotation stage and the target are implemented and used to verify these functionalities and performances.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2311-2317
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• 2011

In this paper, we study the temperature change of a ${\mu}$-bolometer focal plane array with a capacitive transimpedance amplifier bias cancellation circuit. Thermal analysis is essential to understand the performance of a ${\mu}$-bolometer focal plane array, and to improve the temperature stability of a focal plane array characteristics. In this study, the thermal analyses of a ${\mu}$-bolometer and its two reference detectors are carried out as a function of time. The analyses are done with the $30{\mu}m$ pitch $320{\times}240$ focal plane array operating of 60 Hz frame rate and having a columnwise readout. From the results, the temperature increase of a ${\mu}$-bolometer in FPA by an incident IR is estimated as $0.689^{\circ}C$, while the temperature increase by a pulsed bias as $7.1^{\circ}C$, which is about 10 times larger than by IR. The temperature increase of a reference detector by a train of bias pulses may be increased much higher than that of an active ${\mu}$-bolometer. The suppression of temperature increase in a reference bolometer can be done by increasing the thermal conductivity of the reference bolometer, in which the selection of thermal conductivity also determines the range of CTIA output voltage.

• Journal of Astronomy and Space Sciences
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• v.23 no.1
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• pp.19-28
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• 2006

The noise temperature of existing millimeter-wave receivers is already within two or three times quantum noise limit. One of practical ways to increase the observation speed of single dish radio telescope without longer integration time is use of multi-beam focal plane array receiver as demonstrated in several large single dish radio telescopes. In this context the TRAO (Taeduk Radio Astronomy Observatory), which operates a 143n Cassegrain radio telescope, is planning to develop a 4 x 4 beams focal plane array SIS receiver system for 86-115 GHz band. Even though millimeter-wave HEMT LNA-based receivers approach the noise temperature comparable to the SIS receiver at W-band, it is believed that the receiver based on SIS mixer seems to offer a bit more advantages. The critical part of the multi-beam array receiver will be sideband separating SIS mixers. Employing such a type of SIS mixer makes it possible to simplify the quasi-optics of receiver. Otherwise, an SSB filter should be used in front of the mixer or some sophisticated post-processing of observation data is needed. In this paper we will present a preliminary design concept and components needed for the development of a new 3 mm band multi-beam focal plane array receiver.

• Current Optics and Photonics
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• v.5 no.5
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• pp.514-523
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• 2021

Methods for absolute depth estimation have received lots of interest, and most algorithms are concerned about how to minimize the difference between an input defocused image and an estimated defocused image. These approaches may increase the complexity of the algorithms to calculate the defocused image from the estimation of the focused image. In this paper, we present a new method to recover depth of scene based on a sharpness-assessment algorithm. The proposed algorithm estimates the depth of scene by calculating the sharpness of deconvolved images with a specific point-spread function (PSF). While most depth estimation studies evaluate depth of the scene only behind a focal plane, the proposed method evaluates a broad depth range both nearer and farther than the focal plane. This is accomplished using an asymmetric aperture, so the PSF at a position nearer than the focal plane is different from that at a position farther than the focal plane. From the image taken with a focal plane of 160 cm, the depth of object over the broad range from 60 to 350 cm is estimated at 10 cm resolution. With an asymmetric aperture, we demonstrate the feasibility of the sharpness-assessment algorithm to recover absolute depth of scene from a single defocused image.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.10
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• pp.784-790
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• 2008

The feasibility and the accuracy of the correlation coefficient(CC) method for the determination of particle positions along the optical axis in digital particle holography were verified by alidation experiments. A traverse system with capable of high precision was used to move the particle objects by exact known distances between several different positions. The particle positions along the optical axis were calculated by the CC method and compared with their exact values to obtain the errors of the focal plane determination. The tested particles were 2D dots in a calibration target along with different sized glass beads and droplets that reflected and caused a three-dimensional effect. The results show that the CC method can work well for both the 2D dots and the 3D particles. The effect of other particles on the focal plane determination was also investigated. The CC method can locate the focal plane of particles with a high precision, regardless of the existence of other particles.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.5
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• pp.396-403
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• 2000

A thermal imaging system is implemented for the measurement and the analysis of the thermal distribution of the target objects. The main part of the system is a thermal camera in which a focal plane array typed sensor is introduced. The sensor detects the mid-range infrared spectrum of target objects and then it outputs a generic video signal which should be processed to form a frame thermal image. Here, a digital signal processor(DSP) is applied for the high speed processing of the sensor signals. The DSP controls analog-to-digital converter, performs correction algorithms and outputs the frame thermal data to frame buffers. With the frame buffers can be generated a NTSC signal and transferred the frame data to personal computer(PC) for the analysis and a monitoring of the thermal scenes. By performing the signal processing functions in the DSP the overall system achieves a simple configuration. Several experimental results indicate the performance of the overall system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.1
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• pp.123-131
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• 2014

An INS/vision integrated navigation algorithm is proposed for environments with insufficient number of landmarks. In the proposed algorithm, the raw measurements on the focal plane are directly used in order to cope with the situation where the number of landmarks are not sufficient. In addition to this, the combination of landmarks, which has smallest value of DOP, is used in the update of measurement in order to improve navigation performance. In order to evaluate the performance of the proposed integrated navigation system, Monte-Carlo simulation and van test was performed. The results of the simulation and experiment show that the proposed navigation system gives better navigation performance than an INS/vision integrated navigation system which does not use the raw measurements on the focal plane and the navigation system provides navigation solutions even in environments with insufficient number of landmarks.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1461-1465
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• 2007

A micromachined sensor part for an infrared focal plane array has been designed and fabricated. Amorphous silicon was adapted as a sensing material, and silicon nitride was used as a membrane material. To get a good efficiency of infrared absorption, the sensor was made as a ${\lambda}/4$ cavity structure. All the processes were done in $0.5\;{\mu}m$ iMEMS fab. in the Electronics and Telecommunication Research Institute (ETRI). The processed MEMS sensor structure had a small membrane deflection less than $0.3\;{\mu}m$. This excellent deflection property can be attributed to the rigorous balancing of the stresses of individual layers. The efficiency of infrared absorption was more than 75% in the wavelength range $8\;-\;14\;{\mu}m$.