• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.494-498
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• 2005

In order to design the aspherical lens, the revisions and the steps of the mathematical method are influenced with a lot of variables. The accuracy of the aspherical lens can be changed by these variables. Besides, to design the aspherical lens, many mathematical functions should be used. To use these mathematical functions is protected by patent administration. Therefore it is very difficult for most of developed countries to use them. This fact has been interrupting not only the development of the technique of a design of the aspherical lens but also the development of the equipments of optics. Because approximate values are used in most of common programs which create the aspherical lens : basically these common programs have variations. Therefore these aspherical lens are not accurate. In the paper, we calculated accurate values by using the refractive index of lens. Based on these data, wee created self-operating design programs. Consequently, our lens is more accurate than the aspherical lens which is created by the common programs influenced with approximate values. The used programs belonging to AutoCAD is Visual LISP.

• Korean Journal of Optics and Photonics
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• v.20 no.1
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• pp.6-15
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• 2009

A mobile phone camera consisting of two aspheric lenses is designed, and stray light distribution on the image plane is analyzed. We assume that most of the incident light is absorbed on the inner surfaces of the lens barrel and spacers, only a small fraction of the light is scattered uniformly. Assuming that 10% of the incident light is scattered on the barrel and spacers, the maximum value of stray light is 7.1% of the ideal image intensity. The result of analysis shows that stray light originated mostly from internal reflection on the ribs. The contributions of scattering by the barrel and spacers are relatively small. To reduce the internal reflection, thin absorbing plates are inserted between lenses, and the shapes of spacers are modified. After the redesigning of the lens barrel, the maximum value of stray light is reduced to 1.1% of the ideal image intensity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.39-46
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• 2013

This study aims to develop a plastic aspheric lens for a 13-megapixel mobile phone camera by injection-compression molding. A mold for injection-compression molding experiments was fabricated with a movable upper plate and four springs. During cavity filling for an aspheric lens with a thickness ratio of 2, a weldline was formed under conventional injection molding, whereas no weldline was formed under injection-compression molding with a compression stroke of 0.3 mm. The flow patterns were in good agreement with the simulation results. The birefringence decreased as the compression stroke increased, and the birefringence produced by injection-compression molding was very low and more uniform compared with that produced by injection molding. In addition, the bulk birefringence of an assembly composed of four plastic lenses was significantly affected by the orientation of the lenses to be mounted.

• Korean Journal of Optics and Photonics
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• v.31 no.6
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• pp.328-333
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• 2020

In this paper, we study the analysis method for the aspherical tolerance of a Korsch telescope using a Q polynomial. It is important to analyze the tolerances for evaluating quality in high-precision fabrication of aspherical reflectors for high-resolution satellites. Thus we express the aspheric surface in terms of a Q polynomial in which each coefficient term is composed independently, and analyze the tolerance of a Korsch telescope. We also analyze the tolerance using Zernike fringe sag, which expresses the shape error of an aspherical mirror. By comparing the two results, we confirm that the Q-polynomial method can be used to analyze an aspherical mirror.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.574-581
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• 2014

This paper presents the design and evaluation of the optical zoom system for an LWIR camera. The 12.8operating wavelength range of this system is from $7.7{\mu}m$ to $12.8{\mu}m$. Through a paraxial design and optimization process, we have obtained the extended four-group inner-focus zoom system with focal lengths of 10 to 100 mm, which consists of the six lenses including four aspheric surfaces and two diffractive surfaces. The diffractive lenses were used to balance the higher-order aberrations, and its diffraction properties were evaluated by scalar diffraction theory. We have calculated the polychromatic integrated diffraction efficiency and the MTF drop generated by background noise. The f-number of the zoom system is F/1.4 at all positions. Fields of view are given by $51.28^{\circ}{\times}38.46^{\circ}$ at wide field and $5.50^{\circ}{\times}4.12^{\circ}$ at narrow field positions. In conclusion, this design procedure results in a $10{\times}$ compact zoom lens system useful for an LWIR camera.

• Journal of the Optical Society of Korea
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• v.17 no.2
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• pp.142-147
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• 2013

In order to deduce the difficulty of fixing the Ritchey-Chretien (R-C) dual reflective optical system and enhance the stability of the secondary mirror, a compact integral structure is presented here composed of two transmitting and two reflective aspheric surfaces. The four surfaces were manufactured from a single germanium lens and integrated together. The two reflective surfaces formed by coating the inner reflecting films were assembled in one lens. It makes the installation of the two mirrors easier and the structure of the secondary mirror more stable. A design of mid-wave infrared (MWIR) compact imaging system is presented with a spectral range chosen as $3.7-4.8{\mu}m$. The effective focal length is f=90 mm. The field of view (FOV) for the lens is $4.88^{\circ}$. It has good imaging capability with Modulation Transfer Function (MTF) of all field of view more than 0.55 close to the diffraction limitation. Outdoor experiments were carried out and it is shown that the integral catadioptric optical system performs well on imaging.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.2
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• pp.69-74
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• 2020

In this study, we proposed a method for surface profiling aspheric lens molds using a precision displacement sensor with a spatial scanning mechanism. The precision displacement sensor is based on the confocal principle using a broadband light source, providing a 10 nm resolution over a 0.3 mm measurable range. The precision of the sensor, depending on surface slope, was evaluated via Allan deviation analysis. We then developed an automatic surface profiling system by measuring the cross-sectional profile of a lens mold. The precision of the sensor at the flat surface was 10 nm at 10 ms averaging time, while 200 ms averaging time was needed for identical precision at the steepest slope at 25 deg. When we compared the measurement result of the lens mold to a commercial surface profiler, we found that the accuracy of the developed system was less than 90 nm (in terms of 3 sigmas of error) between the two results.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.178-187
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• 1995

The method that determines the appropriate damping factor is studied for a lens design. When suitable damping factor is applied to the additive damped least-squares (DLS) method, the convergence and the stability of the optimization process are examined in a triplet-type photographic lens design. We calculate eigenvalues of the product of the Jacobian matrix of error functions by using the singular value decomposition (SVD) method. We adopt the median of eigenvalues as an appropriate damping factor. The convergence and the stability of the optimization process are improved by choosing the adequate damping factor for the optimization of a photographic lens. It is known that the numerical inaccuracy in the calculation of normal equation is overcome by using the orthogonal transformations of the Jacobian matrix. Therefore, a combination of the method for setting a proper damping factor and the orthogonal transformations of the Jacobian matrix is good for application to the design of an aspheric lens with high-order terms. terms.

• Journal of the Korea Convergence Society
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• v.9 no.9
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• pp.183-189
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• 2018

This study deals with the design and development of imaging optics having 24mm focal length for MWIR ($3{\sim}5{\mu}m$) with two symmetrical lenses facing each other. We used CodeV in our optical design, and we performed the optimization process to have the resolution and angle of view satisfying the user's requirements. The materials of lenses were limited to two types, including KCIR035 with a refractive index of 1.7589, developed in Korea. The optical system designed in this way consists of two aspherical lenses made of KCIR035 material having the same shape and one spherical lens made of Si. Here, the arrangement of the two aspherical lenses is characterized by having a symmetrical structure facing each other. And this optical system has a resolution of MTF value of 0.35 or more at a line width of 20 lp / mm. Therefore, it is considered that this optical system has the capability to be applied to a thermal imaging camera using a $206{\times}156$ array MWIR detection device having a pixel size of $25{\mu}m$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.19-19
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• 2009

Recently, Light Emitting Diode(LED) has many advantages in comparison with conventional light sources; low power consumption, long lifetime, and less environmental pollution. Therefore, the use of LED is multiplying and increasing rapidly. In general, however, spherical lens is used in LED-lighting which cause many problems induces by optical aberration of spherical lens; low illumination, a yellow belt, unpleasant feeling in human eye. As a potential solution of this problem, aspherical lens can be employed. This study reports the improvement of LED-lighting performance by adopting aspherical lens. From the commercial program, $LightTools^{TM}$, the optical problem were ensured. And then, to improve this problem, optimum aspheric form was designed using Code $V^{TM}$.