• Title, Summary, Keyword: calibration

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Detection of Calibration Patterns for Camera Calibration with Irregular Lighting and Complicated Backgrounds

  • Kang, Dong-Joong;Ha, Jong-Eun;Jeong, Mun-Ho
    • International Journal of Control, Automation, and Systems
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    • v.6 no.5
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    • pp.746-754
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    • 2008
  • This paper proposes a method to detect calibration patterns for accurate camera calibration under complicated backgrounds and uneven lighting conditions of industrial fields. Required to measure object dimensions, the preprocessing of camera calibration must be able to extract calibration points from a calibration pattern. However, industrial fields for visual inspection rarely provide the proper lighting conditions for camera calibration of a measurement system. In this paper, a probabilistic criterion is proposed to detect a local set of calibration points, which would guide the extraction of other calibration points in a cluttered background under irregular lighting conditions. If only a local part of the calibration pattern can be seen, input data can be extracted for camera calibration. In an experiment using real images, we verified that the method can be applied to camera calibration for poor quality images obtained under uneven illumination and cluttered background.

Analysis of Geometric Calibration Accuracy using the Results from IR Channel Nominal Radiometric Calibration (적외채널 기본 복사보정 결과를 이용한 기하보정 처리의 정확도 분석)

  • Seo, Seok-Bae;Kwon, Eun-Joo;Jin, Kyoung-Wook
    • Aerospace Engineering and Technology
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    • v.12 no.2
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    • pp.147-155
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    • 2013
  • The nominal radiometric calibration equation and additional five algorithms are applied in the infrared channel radiometric calibration for the COMS (Communication, Ocean, Meteorological Satellite) MI (Meteorological Imager). The processing end time of the radiometric calibration is directly related with the start time of geometric calibration processing since the geometric calibration processing is followed by that of the radiometric calibration. This paper describes comparison and analysis results for geometric calibration processing using two types of the radiometric calibration results, outputs from only the nominal radiometric calibration equation and outputs from the complete one (the nominal radiometric calibration equation with additional five algorithms), to propose a method with the earlier start time of the geometric calibration processing. Experimental results show that both of radiometric calibration results, from the nominal radiometric calibration equation with a fast processing speed and from the complete one with accurate radiometric values, can be used in the geometric calibration as the appropriate inputs because those processing results satisfied the requirements of geometric calibration processing accuracy. Thus the radiometric calibration results from the nominal radiometric calibration equation can be used to improve geometric calibration processing time.

In-Process Relative Robot WorkCell Calibration

  • Wang, Jianjun;Sun, Yunquan;Gan, zhongxue
    • 제어로봇시스템학회:학술대회논문집
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    • pp.269-272
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    • 2003
  • Industry is now seeing a dramatic increase in robot simulation and off-line programming. In order to use off-line programming effectively, the simulated workcell has to be identical to the real workcell. This requires an efficient and accurate method for the workcell calibration. Currently used techniques in the industry, however, are typically time-consuming, expensive and therefore not suitable for in-process application. This is because most of these techniques are based on the so-called “absolute calibration” method. In contrast to absolute method, relative calibration only measures the difference of an interested object relative to a standard reference. Owing to the small measurement range requirement, relative calibration method is very cheap and can achieve very high accuracy. In this paper the relative method is applied to calibrate an entire grinding workcell. Linear gauge is the only measurement device used. This workcell calibration includes tool center point (TCP) calibration and work object frame calibration. Due to the efficiency of the calibration algorithm and the simplicity of the calibration setup, the described calibration procedure can be done in process.

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Array Calibration for CDMA Smart Antenna Systems

  • Kyeong, Mun-Geon;Park, Hyung-Geun;Oh, Hyun-Seo;Jung, Jae-Ho
    • ETRI Journal
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    • v.26 no.6
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    • pp.605-614
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    • 2004
  • In this paper, we investigate array calibration algorithms to derive a further improved version for correcting antenna array errors and RF transceiver errors in CDMA smart antenna systems. The structure of a multi-channel RF transceiver with a digital calibration apparatus and its calibration techniques are presented, where we propose a new RF receiver calibration scheme to minimize interference of the calibration signal on the user signals. The calibration signal is injected into a multi-channel receiver through a calibration signal injector whose array response vector is controlled in order to have a low correlation with the antenna response vector of the receive signals. We suggest a model-based antenna array calibration to remove the antenna array errors including mutual coupling errors or to predict the element patterns from the array manifold measured at a small number of angles. Computer simulations and experiment results are shown to verify the calibration algorithms.

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On-Site vs. Laboratorial Implementation of Camera Self-Calibration for UAV Photogrammetry

  • Han, Soohee;Park, Jinhwan;Lee, Wonhee
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.34 no.4
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    • pp.349-356
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    • 2016
  • This study investigates two camera self-calibration approaches, on-site self-calibration and laboratorial self-calibration, both of which are based on self-calibration theory and implemented by using a commercial photogrammetric solution, Agisoft PhotoScan. On-site self-calibration implements camera self-calibration and aerial triangulation by using the same aerial photos. Laboratorial self-calibration implements camera self-calibration by using photos captured onto a patterned target displayed on a digital panel, then conducts aerial triangulation by using the aerial photos. Aerial photos are captured by an unmanned aerial vehicle, and target photos are captured onto a 27in LCD monitor and a 47in LCD TV in two experiments. Calibration parameters are estimated by the two approaches and errors of aerial triangulation are analyzed. Results reveal that on-site self-calibration excels laboratorial self-calibration in terms of vertical accuracy. By contrast, laboratorial self-calibration obtains better horizontal accuracy if photos are captured at a greater distance from the target by using a larger display panel.

Effects of the in-process calibration from IR detector for thermal diffusivity measurement by laser flash method (레이저 섬광법에 의한 열확산계수 측정시 적외검출소자에서 실시간 온도보정이 미치는 영향)

  • 이원식;배신철
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.6
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    • pp.795-802
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    • 1998
  • For measuring the thermal diffusivity by laser flash method, raw data have to be calibrated using temperature data. We have developed in-process calibration method and polynomial calibration in which thermal diffusivity can be calibrated during measuring, This method is different from existing temperature pre-process calibration method and exponential calibration having various source of error. Using this new calibration method, measurement accuracy was improved about 1∼2% compare to the value by the existing method. We also studied more accurate fitting curve as in Figure 4 was shown the result of measuring output characteristics of IR radiometer with temperature. As illustrated in data, in-process calibration method and polynomial calibration equation is proper than pre-process calibration method and exponential calibration.

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Characteristics of COMS MI Radiometric Calibration

  • Cho, Young-Min
    • Proceedings of the KSRS Conference
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    • v.1
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    • pp.71-74
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    • 2006
  • Communication Ocean Meteorological Satellite (COMS) is planned to be launched onto Geostationary Earth Orbit in 2008. The meteorological imager (MI) is one of COMS payloads and has 5 spectral channels to monitor meteorological phenomenon around the Korean peninsular intensively and of Asian-side full Earth disk periodically. The MI has on-board radiometric calibration capabilities called 'blackbody calibration' for infrared channels and 'space look' for infrared/visible channels, and radiometric response stability monitoring device called 'albedo monitor' for visible channel. Additionally the MI has on-board function called 'electrical calibration' for the check of imaging path electronics of both infrared and visible channels. The characterization of MI performance is performed to provide the pre-launch radiometric calibration data which will be used for in-orbit radiometric calibration with the on-board calibration outputs. The radiometric calibration of the COMS MI is introduced in the view point of instrument side in terms of in-orbit calibration devices and capabilities as well as the pre-launch calibration activities and expected outputs.

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Evaluation of Robot Calibration Performance based on a Three Dimensional Small Displacement Measuring Sensor (3차원 미소변위센서 기반 로봇 캘리브레이션 성능 검토)

  • Nguyen, Hoai-Nhan;Kang, Hee-Jun
    • Journal of Institute of Control, Robotics and Systems
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    • v.20 no.12
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    • pp.1267-1271
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    • 2014
  • There have been many autonomous robot calibration methods which form closed loop structures through the various attached sensors and mechanical fixtures. Single point calibration among them has been used for on-site calibration due to its convenience of implementation. The robot can reach a single point with infinitely many configurations so that single point calibration algorithm can be set up and easily implemented relative to the other methods. However, it is not still easy to drive the robots' sharp edge to its corresponding edge of the fixture. This is error-prone process. In this paper, we propose a 3 dimensional small displacement measuring sensor and a robot calibration algorithm based on this sensor. This method relieves the difficulty of matching two edges in the single point calibration and improves the resulting robot accuracy. Simulated study is carried out on a Hyundai HA06 robot to show the effectiveness of the proposed method over the single point calibration. And also, the resulting robot accuracy is compared with that from 3D laser tracker based calibration to show the dependency of robot accuracy on range of the workspace where the measurement data are collected.

Full angle range pressure coefficient maps of five-hole probe and new calibration coefficients (5공프로브의 전 각도 범위 압력계수 지도와 새로운 보정계수)

  • Kim, Jin-Gwon;Gang, Sin-Hyeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.11
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    • pp.1437-1448
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    • 1997
  • Pressures of a five-hole probe were measured for a full range of yaw and pitch angles and complete pressure coefficient maps were obtained. Based on these maps, various features of five-hole probe pressures were revealed and new five-hole probe calibration coefficients were devised. The new calibration coefficients show non-diverging characteristics for any flow direction and one-to-one correspondence for a wide range of flow angles. These calibration coefficients expand the valid flow angle range of five-hole probe calibration by .+-.10 degrees and complement a critical defect of five-hole probe zone-division calibration method which has not been known yet. Moreover new non-diverging calibration coefficients have advantages in nulling methods, too.

Camera Calibration and Barrel Undistortion for Fisheye Lens (차량용 어안렌즈 카메라 캘리브레이션 및 왜곡 보정)

  • Heo, Joon-Young;Lee, Dong-Wook
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.9
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    • pp.1270-1275
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    • 2013
  • A lot of research about camera calibration and lens distortion for wide-angle lens has been made. Especially, calibration for fish-eye lens which has 180 degree FOV(field of view) or above is more tricky, so existing research employed a huge calibration pattern or even 3D pattern. And it is important that calibration parameters (such as distortion coefficients) are suitably initialized to get accurate calibration results. It can be achieved by using manufacturer information or lease-square method for relatively narrow FOV(135, 150 degree) lens. In this paper, without any previous manufacturer information, camera calibration and barrel undistortion for fish-eye lens with over 180 degree FOV are achieved by only using one calibration pattern image. We applied QR decomposition for initialization and Regularization for optimization. With the result of experiment, we verified that our algorithm can achieve camera calibration and image undistortion successfully.