• Korean Journal of Optics and Photonics
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• v.21 no.4
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• pp.151-160
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• 2010

When the optical image stabilization is implemented by moving one of the lens groups in a zoom system, decentration should be considered in the optical design process. Although it is partially possible to calibrate optical performances in an optical system with non-symmetrical elements by using a lot of commercial software, the results of calibrating longitudinal aberrations have some calibration errors because of the lack of precise consideration of decentered optical systems. In particular, the amount of distortion in paraxial ray tracing is different from the experimental value because paraxial ray tracing in the optical system is not useful. In this paper, in order to solve this problem being from various commercial lens design software, the set of equations of paraxial ray tracing in a zoom lens system with the non-symmetrical elements like decentration or tilt are theoretically induced. Then, the methods to calibrate the equations of longitudinal aberrations by using these equations in a non-symmetrical optical system are presented. The method of calibrating longitudinal aberrations can in practice be used to correct hand shaking effects in a zoom lens system.

• Journal of Broadcast Engineering
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• v.14 no.6
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• pp.692-702
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• 2009

Real-time virtual studios which could run only on expensive workstations are now available for personal computers thanks to the recent development of graphics hardware. Nevertheless, graphics are rendered off-line in the post production stage in film or TV drama productions, because the graphics' quality is still restricted by the real-time hardware. Software-based camera tracking methods taking only the source video into account take much computation time, and often shows unstable results. To overcome this restriction, we propose a system that stores camera motion data from sensors at shooting time as common virtual studios and uses them in the post production stage, named as POVIS(post virtual imaging system). For seamless registration of graphics onto the camera video, precise zoom lens calibration must precede the post production. A practical method using only two planar patterns is used in this work. We present a method to reduce the camera sensor's error due to the mechanical mismatch, using the Kalman filter. POVIS was successfully used to track the camera in a documentary production and saved much of the processing time, while conventional methods failed due to lack of features to track.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.2
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• pp.93-100
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• 2012

The interest in 3-dimensional information and its practical use are rapidly increasing and thus some goods with stereoscopic views are being released. Mobile phones, unlike other units, are being closely utilized in everyday life and their applications are undoubtedly limitless. In this study, taking photographs with the stereo-camera of mobile phones has been accomplished and also the possibility of getting the quantitative information has been examined. In addition, this study aims to evaluate the quantitative practical use of mobile phones, evaluating the accuracy of the obtained quantitative information. Thus, interior orientation parameters were decided through the calibration of the lens of two cameras equipped with mobile phones. Using the determined interior orientation parameters, the 3-dimensional coordinates on the targets of the test field were calculated and then compared with precisely observed coordinates. Moreover, the performance of the orientation on the arbitrary building resulted in the standard deviation of $X={\pm}0.0674m$, $Y={\pm}0.25319$, and $Z={\pm}0.4983m$. The result also shows that the plot is possible. As a result, smart phones could be utilized for the acquisition of the quantitative information at close range and small measurement in which the high-accuracy on the basis of centimeters is not required.

• Korean Journal of Remote Sensing
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• v.30 no.1
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• pp.149-160
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• 2014

Recently studies on application development and utilization using sensors and devices embedded in smartphones have flourished at home and abroad. This study aimed to analyze the accuracy of the images of smartphone to determine three-dimension position of close objects prior to the development of photogrammetric system applying smartphone and evaluate the feasibility to use. First of all, camera calibration was conducted on autofocus and infinite focus. Regarding camera calibration distortion model with balance system and unbalance system was used for the decision of lens distortion coefficient, the results of calibration on 16 types of projects showed that all cases were in RMS error by less than 1 mm from bundle adjustment. Also in terms of autofocus and infinite focus on S and S2 model, the pattern of distorted curve was almost the same, so it could be judged that change in distortion pattern according to focus mode is very little. The result comparison according to autofocus and infinite focus and the result comparison according to a software used for multi-image processing showed that all cases were in standard deviation less than ${\pm}3$ mm. It is judged that there is little result difference between focus mode and determination of three-dimension position by distortion model. Lastly the checkpoint performance by total station was fixed as most probable value and the checkpoint performance determined by each project was fixed as observed value to calculate statistics on residual of individual methods. The result showed that all projects had relatively large errors in the direction of Y, the direction of object distance compared to the direction of X and Z. Like above, in terms of accuracy for determination of three-dimension position for a close object, the feasibility to use smartphone camera would be enough.

• Journal of Broadcast Engineering
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• v.21 no.1
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• pp.43-50
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• 2016

In this paper, we present a distortion correction for wearable Augmented Reality (AR) on mobile phones. Head Mounted Display (HMD) using mobile phones, such as Samsung Gear VR or Google's cardboard, introduces lens distortion of the rendered image to user. Especially, in case of AR the distortion is more complicated due to the duplicated optical systems from mobile phone's camera and HMD's lens. Furthermore, such distortions generate mismatches of the visual cognition or perception of the user. In a natural way, we can assume that transparent wearable displays are the ultimate visual system which generates the least misperception. Therefore, the image from the mobile phone must be corrected to cancel this distortion to make transparent-like AR display with mobile phone based HMD. We developed a transparent-like display in the mobile wearable AR environment focusing on two issues: pincushion distortion and field-of view. We implemented our technique and evaluated their performance.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.5
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• pp.427-436
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• 2007

Because the slope made up the construction of any other facilities, has many risks of a collapse, existing inspection methods to collect information for a construction site of slope bring up a long time of inspection period, cost and approach for a measuring instrument and it presents the critical point of collecting materials. For getting images to use zoom lens in any positions this study will use free zoomer constructed values of data classified by the focal length develop Image Loader system to make it load not only camera information but also camera test data values of the focal length took a photograph automatically if it measure to use a variety of cameras or other lens. Also, as it constructs three dimensions spatial image information from images of obtained objects this study presents effective basic materials of slope surveying and inspection and it shows exact surveying methods for dangerous slope not to access.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4108-4114
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• 2015

An image acquisition by using an optical mirror is called as a catadioptric method. The catadioptric imaging method is generally used for acquisition of 360-degree all directional visual information in an image. An exemplar omnidirectional optical mirror is the bowl-shaped hyperbolic mirror. In this paper, a single camera omnidirectional stereo imaging method is studied with an additional concave lens. It is possible to obtain 3 dimensional coordinates of environmental objects from the omnidirectional stereo image by matching the stereo image having different view points. The omnidirectional stereo imaging system in this paper is cost-effective and relatively easy for correspondence matching because of consistent camera intrinsic parameters in the stereo image. The parameters of the imaging system are extracted through 3-step calibration and the performance for 3-dimensional coordinates reconstruction is verified through experiments in this paper. Measurable range of the proposed imaging system is also presented by depth-resolution analysis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.5
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• pp.1157-1163
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• 2000

In this paper, we present a novel and practical stereo vision system that uses only one camera and four mirrors placed in front of the camera. The equivalent of a stereo pair of images are formed as left and right halves of a single CCD image by using four mirrors placed in front of the ten of a CCD camera. An object arbitrary point in 3D space is transformed into two virtual points by the four mirrors. As in the conventional stereo system, the displacement between the two conjugate image points of the two virtual points is directly related to the depth of the object point. This system has the following advantages over traditional two camera stereo that identical system parameters, easy calibration and easy acquisition of stereo data.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.2
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• pp.73-82
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• 2003

For measurements and analysis of dielectric characteristics of planar slabs of microwave absorbing materials, I have applied a free-space method in the frequency range of 8~14 GHz. The measurement system for free-space method consists of transmit and receive antennas, mode transitions, precision coaxal cables, the network analyzer, and a computer Special Spot-focused horn lens antenna was used to eliminate diffraction effects. Diffraction effects at the edges of the sample are minimized by satisfying the condition for minimum transverse dimension of the plate and the beamwidth of the antennas at the focus. The time-domain gating feature of the network analyzer and the thru, reflect, and line(TRL) calibration technique were used to eliminate the effects of undesirable multiple reflections. The complex coefficients of reflection and transmission, $S_{11}$ and $S_{21}$, of planar samples were measured for standard materials such as Teflon, Rexolite$\textregistered$ 2200. The results were compared with existing measurement method. And I applied a free-space method for measurement to measure dielectric constants of some electromagnetic absorbing materials. Dielectric properties for the same samples were also measured with a 7mm coxial transmission line method for purposes of comparison with the free-space method.

• Journal of the Korean Chemical Society
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• v.53 no.6
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• pp.704-708
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• 2009

We studied absorbance of tinted dye absorbed into tinted lenses by Spectrophotometric method. Used lenses and tinted dye were CR-39 plastic optical lenses and Ons & $Lavas^{(R)}$ Blue, respectively. Absorbance values of tinted dye absorbed into tinted lenses were obtained from the differences of absorbance values between tinted lenses and CR-30 lenses. Average concentrations of tinted dye absorbed into tinted lenses were obtained from the mass differences between tinted lenses and CR-30 lenses. The relationship between absorbance and average concentration for tinted dye absorbed into tinted lenses was also confirmed to follow Beer’s law. The absorption coefficient calculated from the tangent of the calibration curve was determined to be a=0.983 $Lg^{-1}cm^{-1}$.