• Korean Journal of Optics and Photonics
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• v.13 no.4
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• pp.275-282
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• 2002

We derived analytic formulae for the correction of spherical aberration, coma, and axial color of a two-components lens system consisted of a cemented doublet and a singlet by using the thin lens approximation. The correction formulae were applied to design a telephoto lens system. We examined two kinds of glass combinations in the design, one was crown-flint-crown combination and the other was flint-crown-flint combination. We found two kinds of achromatic aplanat solutions in the crown-flint-crown combination. For the case of flint-crown-flint combination, there were also two kinds of solutions, but their configurations are not useful in practice.

• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.214-215
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• 2001

• 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.

• Korean Journal of Optics and Photonics
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• v.31 no.6
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• pp.281-289
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• 2020

This paper reports a slim mobile lens design using a hybrid refractive/diffractive optical element. Conventionally a wide field of view (FOV) camera-lens design adopts a retrofocus type having a negative (-) lens at the forefront, so that it improves in imaging performance over the wide FOV, but with the sacrifice of longer total track length (TTL). However, we chose a telephoto type as a baseline design layout having a positive (+) lens at the forefront, to achieving slimness, based on the specification analysis of 23 reported optical designs. Following preliminary optimization of a baseline design and aberration analysis based on Zernike-polynomial decomposition, we applied a hybrid refractive/diffractive element to effectively reduce the residual chromatic spherical aberration. The optimized optical design consists of 6 optical elements, including one hybrid element. It results in a very slim telephoto ratio of 1.7, having an f-number of 2.0, FOV of 90°, effective focal length of 2.23 mm, and TTL of 3.7 mm. Compared to a comparable conventional lens design with no hybrid elements, the hybrid design improved the value of the modulation transfer function (MTF) at a spatial frequency of 180 cycles/mm from 63% to 71-73% at zero field (0 F), and about 2-3% at 0.5, 0.7, and 0.9 fields. It was also found that a design with a hybrid lens with only two diffraction zones at the stop achieved the same performance improvement.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.243-251
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• 1993

We have derived Gaussian bracket expressions of aplanatic and achromatic conditions and obtained the numerical solutions for each of two modules of the telephoto type telescope objective free from the Seidel first order spherical aberration, coma, and longitudinal chromatic aberration. The system which is for use in sighting a target is optimized within the resolution of eyes. The objective lens satisfying the aplanatic and achromatic condition has f/8.5 with the half field angle 0.$3^{\circ}$, and the telephoto ratio is 0.839 with the focal length of 30 cm.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.645-648
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• 2003

This paper presents an active vision system for on-line traffic sign recognition. The system is composed of two cameras, one is equipped with a wide-angle lens and the other with a telephoto lends, and a PC with an image processing board. The system first detects candidates for traffic signs in the wide-angle image using color, intensity, and shape information. For each candidate, the telephoto-camera is directed to its predicted position to capture the candidate in a large size in the image. The recognition algorithm is designed by intensively using built in functions of an off-the-shelf mage processing board to realize both easy implementation and fast recognition. The results of on-road experiments show the feasibility of the system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.471-476
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• 2004

This paper presents an active vision system for on-line traffic sign recognition. The system is composed of two cameras, one is equipped with a wide-angle lens and the other with a telephoto lends, and a PC with an image processing board. The system first detects candidates for traffic signs in the wide-angle image using color, intensity, and shape information. For each candidate, the telephoto-camera is directed to its predicted position to capture the candidate in a large size in the image. The recognition algorithm is designed by intensively using built in functions of an off-the-shelf image processing board to realize both easy implementation and fast recognition. The results of on-road experiments show the feasibility of the system.

• Korean Journal of Optics and Photonics
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• v.9 no.4
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• pp.251-257
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• 1998

The equivalent lens conversion is extended to lens group conversion, and the more generalized conversion method is developed. The new conversion method can be used for hte direct thick-to-thick lens conversion. By using the equivalent lens conversion, a thin lens system can be converted into various thick lens system which have different axial thicknesses, but those converted lens systems have identical paraxial property and similar aberration characteristic. For an example, the equivalent lens conversion technique is applied to modification of a thelephoto lens design. The axial thicknesses of the front group elements of the system are reduced to 75% of their original values. The modified design by using the equivalent lens conversion has same focal length with original, and it has smaller aberration changes than the other design of which axial thicknesses are changed only.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.2
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• pp.45-50
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• 2009

This paper presents an active vision system for on-line traffic sign recognition. The system is composed of two cameras, one is equipped with a wide-angle lens and the other with a telephoto lends, and a PC with an image processing board. The system first detects candidates for traffic signs in the wide-angle image using color, intensity, and shape information. For each candidate, the telephoto-camera is directed to its predicted position to capture the candidate in a large size in the image. The recognition algorithm is designed by intensively using built in functions of an off-the-shelf image processing board to realize both easy implementation and fast recognition. The results of on-road experiments show the feasibility of the system.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.99-103
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• 2003

This paper presents lens optimization of the resolution and the distortion for a four-element lens design. In order to have compact optical system, we used the tele-photo type lens composed of a positive and a negative power elements instead of retro-focus lens. The specifications of optical lens design are the focal length of 7.2 mm, the F/number of 2.8 and the field angle of $54.7^{\circ}C$. The MTF values are higher than 0.5 in the spatial frequency range up to 110 lp/mm for all of the designed object heights. Also, it is expected to fulfill all the requirements of a digital still camera lens and especially suited for building low-cost, compact digital cameras because of the low-profile property of the lens design.