• Journal of Sensor Science and Technology
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• v.7 no.1
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• pp.39-44
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• 1998

Low reflectance optical fiber mirrors in the continuous length of the single mode fiber were fabricated using mechanical splices and pieces of fiber coated with $TiO_{2}$ dielectric film at the cleaved end. When fiber mirrors of refelctance of about 1% were produced, the insertion loss ranged from 0.055dB to 0.3dB and the average insertion loss was 0.15 dB. These mirrors could be produced easy in the field.

• Korean Journal of Optics and Photonics
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• v.19 no.2
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• pp.144-149
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• 2008

Thermal distortion of the laser mirrors which are the Coude mirrors of the laser beam director and the wavefront error caused by the thermal distortion are studied. Coude mirrors consist of three relay mirrors and one fast steering mirror. The mirrors have reflectivity of 99.5% with respect to the laser wavelength of $3.8\;{\mu}m$, and absorption of 500 W per second. Thermal distortion and its related wavefront errors are studied with laser beam irradiation for 5 seconds. For the relay mirror, the wavefront error is 334 nm_PV, 98 nm rms and for fast steering mirror, $11.5\;{\mu}m$_PV, $3{\mu}m$ rms.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.26-27
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• 2000

고휘도 다이오드(Superluminescent Diodes : SLD)는 fiber gyroscope의 광원으로서 가장 적당한 소자로 알려져 있다$^{(1)}$ . 본 연구는 실제의 광섬유 자이로 스코프에 적용하기 위하여 활성층의 발진파장이 1.55$mu extrm{m}$인 SLD의 제작을 목적으로 하고 있다. SLD제작의 핵심은 거울면에서의 반사도를 낮추어 거울면의 반사에 의하여 일어나는 발진을 억제하는 것으로, 이를 위하여 단면이 각을 가진 stripe$^{(2)}$ , 계면의 무반사 코팅(antireflection coating : AR coating)$^{(3)}$ , window buried heterostructure$^{(4)}$ , unpumped absorbing region$^{(5)}$ , bent-buried absorbing region$^{(6)}$ 등과 같은 방법이 이용이 되고 있다 (중략)

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.417-421
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• 2004

We can see that two images of reflection are observed on the surface of a ophthalmic lens. These are the image reflected from front surface and back surface of lens, respectively. The reflective image shows to be affect by surface refractive power of front and back surface of lens. Total refractive power of lens is calculated by refractive power of front and back surface of lens. Accordingly, the ratio of image on the lens surface is able to measure refractive power of ophthalmic lens without helping of the lensmeter. The ratio of two reflective image measured on the lens surface is compared with the calculated ratio by the power measurement.

• Journal of Software Assessment and Valuation
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• v.15 no.2
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• pp.101-109
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• 2019

Lasers for optical broadband communication systems should have excellent frequency selectivity and modal stability. DFB(Distributed Feedback) lasers have low lasing frequency shift during high speed current modulation. In this paper, I have developed a simulation software and analysed threshold gain and lasing frequency of a lasing mode in longitudinal direction of an 1.55um DFB laser with two mirrors and without anti-reflection coatings, that have both an index- and gain-gratings. The grating phase on a left mirror face is fixed as π/2 and the grating phase on a right mirror face is varied. As the phases of the index and gain gratings on the right mirror facet are π and 0, κL should be in the range of 2~6 in order to enhance the frequency stability. In order to reduce the threshold current of a lasing mode, κL should be greater than 8, regardless of the grating phases on the mirror faces.

• The Journal of the Acoustical Society of Korea
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• v.20 no.3
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• pp.91-97
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• 2001

Since the new field information of target signal is important in the development and verification of active sonar system, experimental method and simulation technique are widely used in order to analyze the detail characteristics of target scattered echoes. Therefore, in this paper, the scale target experiment is performed to develope and Improve the target signal simulation model. Since the experimental results show that the specular reflection is the major component among scattering mechanisms, the target signal simulation model based on the Geometric Optics Theory (GOT) is developed. Complex target is separated into simple shapes, known as canonical shape. The contribution from individual canonical shapes are summed with proper phase and amplitude to produce the target strength of the whole complex body. Simulated target signal is compared with the experimental results and discussed.

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.327-333
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• 2008

In general, a lens with large NA makes image quality better. There are many kinds of cheap concave mirrors with large aperture and NA. This paper presents a method that uses a large aperture projection imaging system to enhance the image used for 3D shape measurement. This method makes it possible to enhance reflection uniformity on the object surface and increases SNR (Signal to Noise Ratio). Using a large aperture lens, it is possible to obtain a brighter image, reducing the shading nature in the image boundary, and enhancing the reflection uniformity even on woven surfaces. Because of the exorbitant cost of a large aperture projection lens larger than 150 mm in diameter, a refractive lens was exchanged with a concave mirror resulting in the same optical effect. In experiment, changing NA $0.15{\sim}0.8$, image contrast was enhanced from 46 to 1.33. Incidentally, the effect of the concave mirror was tested successfully through the experiment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.5
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• pp.371-383
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• 2011

It is important to secure illumination for the driver's safety because the tunnel is a space for changing brightness quickly, and lighting fixtures of the tunnel have consumed a lot of electric lighting energy for operating in both the daytime and at night. This study aims to evaluate daylighting performance of Mirror Reflector System for luminous environment improvement of tunnel space by using RADIANCE simulation program. The results of simulation show that illuminance of bar type is higher than illuminance of pole type at 20 m from the tunnel entrance.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.150-151
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• 2003

비구면은 점광원에서 출발한 광이 측정면에서 반사한 후 다시 한 점으로 모이지 않아 일반적인 간섭계로 측정하는데 어려움이 있다. 이 때 비구면이 만들어내는 파면과 반대되는 파면을 생성하는 null compensator를 설치하여 null test를 수행할 수 있다. CGH는 렌즈나 거울과 같은 기계적인 가공을 하지 않고, 이론상 수식적으로 표현이 가능한 모든 파면을 만들 수 있으므로 많이 사용되어 왔다. (중략)

• Journal of Software Assessment and Valuation
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• v.16 no.1
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• pp.55-63
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• 2020

Lasers for optical broadband communication systems should have excellent frequency selectivity and modal stability. DFB lasers have low lasing frequency shift during high speed current modulation. In this paper, when a refractive index grating and a gain grating are simultaneously present in a DFB laser having a wavelength of 1.55 ㎛, the dielectric film is coated so that reflection does not occur on the right mirror surface, so that ρ_r=0. For the first mode, which requires a minimum gain at the threshold, the beam distribution of the oscillation mode in the longitudinal direction and the radiated power ratio P_l/P_r were analyzed and compared for the cases of the phase of ρ_l=π and π/2. If the phase of ρ_l=π, in order to obtain a low threshold current and high frequency stability, κL should be greater than 8. In the case of the phase of ρ_l=π/2, for low threshold current, κL is necessary to be 1.0, where the oscillation frequency coincides with the lattice frequency. DFB lasers with an anti-reflection coated mirror have excellent mode selectivity than 1.55um DFB lasers with two mirror facets