• Title, Summary, Keyword: Zoom lens

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Zoom Lens Design for a 10x Slim Camera using Successive Procedures

  • Park, Sung-Chan;Lee, Sang-Hun
    • Journal of the Optical Society of Korea
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    • v.17 no.6
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    • pp.518-524
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    • 2013
  • This study presents a new design method for a zoom lens, in which real lens groups are designed successively to combine to form a lens modules zoom system. The lens modules and aberrations are applied to the initial design for a four-group inner-focus zoom system. An initial design with a focal length range of 4.2 to 39.9 mm is derived by assigning the first-order quantities and third-order aberrations to each module along with the constraints required for optimum solutions. After obtaining the lens module zoom system, the real lens groups are successively, not separately, designed to get a zoom lens system. Compared to the separately designed real lens groups, this approach can give a better starting zoom lens and save time. The successively designed groups result in a zoom system that satisfies the basic properties of the zoom system consisting of the original lens modules. In order to have a slim system, we directly inserted the right-angle prism in front of the first group. This configuration resulted in a compact zoom system with a depth of 12 mm. The finally designed zoom lens has an f-number of 3.5 to 4.5 and is expected to fulfill the requirements for a mobile zoom camera having high zoom ratio of 10x.

Design of an 8x Four-group Inner-focus Zoom System Using a Focus Tunable Lens

  • Lee, Daye;Park, Sung-Chan
    • Journal of the Optical Society of Korea
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    • v.20 no.2
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    • pp.283-290
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    • 2016
  • This study presents an 8x four-group inner-focus zoom lens with one-moving group for a compact camera by use of a focus tunable lens (FTL). In the initial design stage, we obtained the powers of lens groups by paraxial design based on thin lens theory, and then set up the zoom system composed of four lens modules. Instead of numerically analytic analysis for the zoom locus, we suggest simple analysis for that using lens modules optimized. After replacing four groups with equivalent thick lens modules, the power of the fourth group, which includes a focus tunable lens, is designed to be changed to fix the image plane at all positions. From this design process, we can realize an 8x four-group zoom system having one moving group by employing a focus tunable lens. The final designed zoom lens has focal lengths of 4 mm to 32 mm and apertures of F/3.5 to F/4.5 at wide and tele positions, respectively.

Distortion Correction Modeling Method for Zoom Lens Cameras with Bundle Adjustment

  • Fang, Wei;Zheng, Lianyu
    • Journal of the Optical Society of Korea
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    • v.20 no.1
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    • pp.140-149
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    • 2016
  • For visual measurement under dynamic scenarios, a zoom lens camera is more flexible than a fixed one. However, the challenges of distortion prediction within the whole focal range limit the widespread application of zoom lens cameras greatly. Thus, a novel sequential distortion correction method for a zoom lens camera is proposed in this study. In this paper, a distortion assessment method without coupling effect is depicted by an elaborated chessboard pattern. Then, the appropriate distortion correction model for a zoom lens camera is derived from the comparisons of some existing models and methods. To gain a rectified image at any zoom settings, a global distortion correction modeling method is developed with bundle adjustment. Based on some selected zoom settings, the optimized quadratic functions of distortion parameters are obtained from the global perspective. Using the proposed method, we can rectify all images from the calibrated zoom lens camera. Experimental results of different zoom lens cameras validate the feasibility and effectiveness of the proposed method.

Unified Analytic Calculation Method for Zoom Loci of Zoom Lens Systems with a Finite Object Distance

  • Ryu, Jae Myung;Oh, Jeong Hyo;Jo, Jae Heung
    • Journal of the Optical Society of Korea
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    • v.18 no.2
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    • pp.134-145
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    • 2014
  • The number of lens groups in modern zoom camera systems is increased above that of conventional systems in order to improve the speed of the auto focus with the high quality image. As a result, it is difficult to calculate zoom loci using the conventional analytic method, and even the recent one-step advanced numerical calculation method is not optimal because of the time-consuming problem generated by the iteration method. In this paper, in order to solve this problem, we suggest a new unified analytic method for zoom lens loci with finite object distance including infinite object distance. This method is induced by systematically analyzing various distances between the object and other groups including the first lens group, for various situations corresponding to zooming equations of the finite lens systems after using a spline interpolation for each lens group. And we confirm the justification of the new method by using various zoom lens examples. By using this method, we can easily and quickly obtain the zoom lens loci not only without any calculation process of iteration but also without any limit on the group number and the object distance in every zoom lens system.

Compact Zoom Lens Design for a 5x Mobile Camera Using Prism

  • Park, Sung-Chan;Lee, Sang-Hun;Kim, Jong-Gyu
    • Journal of the Optical Society of Korea
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    • v.13 no.2
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    • pp.206-212
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    • 2009
  • This study presents the compact zoom lens with a zoom ratio of 5x for a mobile camera by using a prism. The lens modules and aberrations are applied to the initial design for a four-group inner-focus zoom system. An initial design with a focal length range of 4.4 to 22.0 mm is derived by assigning the first-order quantities and third-order aberrations to each module along with the constraints required for optimum solutions. We separately designed a real lens for each group and then combined them to establish an actual zoom system. The combination of the separately designed groups results in a system that satisfies the basic properties of the zoom system consisting of the original lens modules. In order to have a slim system, we directly inserted the right-angle prism in front of the first group. This configuration resulted in a more compact zoom system with a depth of 8 mm. The finally designed zoom lens has an f-number of 3.5 to 4.5 and is expected to fulfill the requirements for a slim mobile zoom camera having high zoom ratio of 5x.

Zoom Lens Calibration for a Video Measuring System (컴퓨터 비젼을 이용한 정밀 측정 장비의 줌 렌즈 캘리브레이션)

  • Hahn, Kwang-Soo;Choi, Joon-Soo;Choi, Ki-Won
    • Journal of Internet Computing and Services
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    • v.6 no.5
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    • pp.57-71
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    • 2005
  • Precise visual measurement applications, like video measuring system (VMS), use camera systems with motorized zoom lens for fast and efficient measurement. In this paper, we introduce an efficient calibration method for zoom lens of VMS controlled by servo motor. For the automated zoom lens calibration of the VMS, only zoom lens setting needs to be calibrated and parameters calibrated by zoom lens settings are image center and pixel size changed by zoom levels, The extrinsic parameters, like focus and iris, do not need to be calibrated since the parameters are usually fixed, It needs a lot of time and effort to calibrate the camera for ali the different zoom levels. In this paper, we also propose an efficient and fast zoom lens calibration method, which calculates the calibration parameters of the zoom lens settings for the minimum number of zoom levels and estimates other parameters for the uncalculated zoom levels using the interpolation of the calculated parameter values.

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Evaluation of a Corrected Cam for an Interchangeable Lens with a Distance Window

  • Kim, Jin Woo;Ryu, Jae Myung;Jo, Jae Heung;Kim, Young-Joo
    • Journal of the Optical Society of Korea
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    • v.18 no.1
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    • pp.23-31
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    • 2014
  • Recently, the number of camera companies that produce commercializing interchangeable lens systems such as digital single lens reflex (DSLR) and compact system camera (CSC) lenses has been gradually increasing. These interchangeable lenses have various kinds of lenses with distinct specifications. In particular, the distance window among these specifications is the function most preferred by customers. Mechanical manual zoom and manual focus in these high end camera lenses with a distance window are in particular desirable specifications and are required for product quality. However, the AF lens group is linked to the zoom cam and moves. Because the AF lens group moves along with the object distance, we can not realize the distance window with only zoom locus calculation. In this paper, in order to solve the problem, we suggest an optical calculation method for a corrected AF zoom cam for an interchangeable lens with a distance window to achieve product differentiation and analyze the error in the calculation.

Zoom Lens Distortion Correction Of Video Sequence Using Nonlinear Zoom Lens Distortion Model (비선형 줌-렌즈 왜곡 모델을 이용한 비디오 영상에서의 줌-렌즈 왜곡 보정)

  • Kim, Dae-Hyun;Shin, Hyoung-Chul;Oh, Ju-Hyun;Nam, Seung-Jin;Sohn, Kwang-Hoon
    • Journal of Broadcast Engineering
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    • v.14 no.3
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    • pp.299-310
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    • 2009
  • In this paper, we proposed a new method to correct the zoom lens distortion for the video sequence captured by the zoom lens. First, we defined the nonlinear zoom lens distortion model which is represented by the focal length and the lens distortion using the characteristic that lens distortion parameters are nonlinearly and monotonically changed while the focal length is increased. Then, we chose some sample images from the video sequence and estimated a focal length and a lens distortion parameter for each sample image. Using these estimated parameters, we were able to optimize the zoom lens distortion model. Once the zoom lens distortion model was obtained, lens distortion parameters of other images were able to be computed as their focal lengths were input. The proposed method has been made experiments with many real images and videos. As a result, accurate distortion parameters were estimated from the zoom lens distortion model and distorted images were well corrected without any visual artifacts.

Optical Design and Fabrication of a Large Telephoto Zoom Lens with Fixed f/2.8 and Light Autofocus Lens

  • Ryu, Jae Myung;Gang, Geon Mo;Lee, Hyuck Ki;Lee, Ki Woo;Heu, Min;Jo, Jae Heung
    • Journal of the Optical Society of Korea
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    • v.19 no.6
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    • pp.629-637
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    • 2015
  • Compact system cameras (CSCs) are commonly used nowadays and feature enhanced video functions and thin yet light interchangeable lenses. They differ from digital single-lens reflex (DSLR) cameras in their lack of mirror boxes. CSCs, however, have autofocus (AF) speeds lower than those of conventional DSLRs, requiring weight reduction of their AF groups. To ensure the marketability of large telephoto zoom lenses with fixed f/2.8 regardless of field angle variation, in particular, light weight AF groups are essential. In this paper, we introduce a paraxial optical design method and present a new, large, telephoto zoom lens with f/2.8 regardless of the field angle variation, plus a lightweight AF group consisting of only one lens. Using the basic paraxial optical design and optimization methods, we fabricated a new and lighter zoom lens system, including a single-lens, lightweight AF group with almost the same performance.

Numerical Calculation for Autofocus of Zoom Lenses by Using Gaussian Brackets (가우스 괄호법을 이용한 줌 렌즈의 조출량에 대한 수치해석 계산법)

  • Jo, Jae-Heung;Lee, Do-Kyung;Lee, Sang-On;Ryu, Jae-Myung;Kang, Geon-Mo;Lee, Hae-Jin
    • Korean Journal of Optics and Photonics
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    • v.20 no.3
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    • pp.166-174
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    • 2009
  • When the object distance of a zoom lens with finite object distances is varied, we can fix the image at a fixed image plane by moving only one zoom lens group (autofocus group) without moving all zoom lens groups for the autofocus. We theoretically formulated and numerically calculated the moving distances of the autofocus group by using Gaussian brackets and a paraxial ray tracing method. The solutions of this method can be consistently and flexibly used in the initial design for the moving distance of autofocus group within these zoom loci in all types of zoom lens. Finally, in order to verify the usefulness of this method, we show that the moving distance of an autofocus group can be rapidly and diversely obtained in one example of $M_{5n}$ zoom lens type.