• 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.

• Current Optics and Photonics
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• v.6 no.1
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• pp.104-113
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• 2022

We present a method to count the overall length of the zoom system in an initial design stage. In a zoom-lens design using the concept of the group, it has been very hard to precisely estimate the overall length at all zoom positions through the previous paraxial studies. To solve this difficulty, we introduce T_eq as a measure of the total track length in an equivalent zoom system, which can be found from the first order parameters obtained by solving the zoom equations. Among many solutions, the parameters that provide the smallest T_eq are selected to construct a compact initial zoom system. Also, to obtain an 8× four-group zoom system without moving groups, tunable polymer lenses (TPLs) have been introduced as a variator and a compensator. The final designed zoom lens has a short overall length of 29.99 mm, even over a wide focal-length range of 4-31 mm, and an f-number of F/3.5 at wide to F/4.5 at tele position, respectively.

• Journal of Korea Multimedia Society
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• v.16 no.11
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• pp.1261-1271
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• 2013

Zoom tracking involves the automatic adjustment of the focus motor in response to the zoom motor movements for the purpose of keeping an object of interest in focus, and is typically achieved by moving the zoom and focus motors in a zoom lens module so as to follow the so-called "trace curve", which shows the in-focus motor positions versus the zoom motor positions for a specific object distance. Thus, one can simply implement zoom tracking by following the most closest trace curve after all the trace curve data are stored in memory. However, this approach is often prohibitive in practical implementation because of its large memory requirement. Many other zoom tracking methods such as GZT, AZT and etc. have been proposed to avoid large memory requirement but with a deteriorated performance. In this paper, we propose a new zoom tracking method called 'Approximate Feedback Zoom Tracking method (AFZT)' on DM36x-based IP network camera, which does not need large memory by approximating nearby trace curves, but generates better zoom tracking accuracy than GZT or AZT by utilizing focus value as feedback information. Experiments through real implementation shows the proposed zoom tracking method improves the tracking performance and works in real-time.

• 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.

• 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.

• 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.

• 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.

• 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.

• International Journal of Advanced Culture Technology
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• v.8 no.3
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• pp.198-205
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• 2020

The purpose of this study is to investigate the effect of real-time remote video instruction using zoom on learners' English reading achievement. The study also sought to identify the efficiency of zoom video lectures and consider supplementing them by surveying learners' opinions and satisfaction regarding zoom video lectures. To this end, control and experimental groups were set up, and two achievement tests and a questionnaire were conducted. The study's results demonstrated that zoom video lectures have a positive effect on learners' English reading achievement. The questionnaire found that learners are satisfied with zoom video lectures for the following reasons: 'increased interest in and motivation towards learning', 'self-directed learning', 'active interaction', 'ease of access', 'ease of information retrieval'. At the same time, the questionnaire also found that some learners are dissatisfied with zoom video lectures due to 'mechanical errors or defects', 'poor audio quality', and 'the need to add customized functions for efficient classes'. In practice, zoom video lectures must be supplemented with automatic attendance processing, convenient data upload and download, and more efficient video screen management. Given the recent increase in online classes, we, as instructors, must develop teaching activities and/or strategies for video lectures that can encourage active participation by learners.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.1
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• pp.11-19
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• 2013

A video-zoom driven audio-zoom algorithm is proposed to provide audio zooming effects according to the degree of video-zoom. The proposed algorithm is designed based on a super-directive beamformer operating with a 4-channel microphone array in conjunction with a soft masking process that uses the phase differences between microphones. The audio-zoom processed signal is obtained by multiplying the audio gain derived from the video-zoom level by the masked signal. The proposed algorithm is then implemented on a portable digital imaging device with a clock speed of 600 MHz after different levels of optimization, such as algorithmic level, C-code and memory optimization. As a result, the processing time of the proposed audio-zoom algorithm occupies 14.6% or less of the clock speed of the device. The performance evaluation conducted in a semi-anechoic chamber shows that the signals from the front direction can be amplified by approximately 10 dB compared to the other directions.