• Title/Summary/Keyword: Gaussian optics

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CA/C Ratio of Adults in Their Early Twenties with Normal Binocular Vision (양안시가 정상인 20대 초반 성인의 CA/C비)

  • Lee, Mu-Hyuk;Yu, Dong-Sik
    • Journal of Korean Ophthalmic Optics Society
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    • v.17 no.2
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    • pp.153-158
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    • 2012
  • Purpose: The purpose of this study was to evaluate the convergence accommodation to convergence (CA/C) ratio and to investigate relationships among age, accommodative amplitude and PD (interpupillary distance) of adults in their early twenties with normal binocular vision. Methods: 44 subjects (mean age, $21.75{\pm}1.16$ years) with healthy eyes were examined. The CA/C ratios were measured by using the difference of Gaussian (DOG) target with retinoscopy. Results: The mean CA/C ratio was $0.052{\pm}0.017$ D/$\Delta$. A moderate negative correction was present between CA/C ratio and age (r = -0.50, p = 0.0005), and a highly positive correction was found between CA/C ratio and accommodative amplitude (r = 0.79, p<0.0001). There was no relation between PD and CA/C ratio. Conclusions: The CA/C ratio presented was mean value for adults in their early twenties with healthy eye between 19 and 25 years of age. There was a high correlation between accommodative amplitude and CA/C ratio. Therefore, the CA/C ratio will be useful basic information for comparison in age, gender and binocular anomalies with similar data from other countries.

An Analysis on the Properties of Beam Coupling by Using Gaussian Beam Propagation Theory (가우시언 빔 전송 이론을 이용한 빔 결합 특성 해석)

  • Han, Seog-Tae;Kang, Jin-Man;Lee, Jeong-Won;Je, Do-Hyung;Jung, Moon-Hee;Kim, Soo-Yeon;Wi, Seog-Oh
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.11
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    • pp.1324-1333
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    • 2010
  • In this paper, three kinds of beam coupling losses which occur in a quasi-optics circuit for millimeter wave receiver system have been intensively investigated. First, the beam coupling losses which are caused by mismatch of beam waists radii and their positions between those of one and the other have been evaluated. It shows that beam coupling losses due to mismatch of beam waists radii and their positions between two quasi-optics circuits can be minimized if beam waist radius is chosen as larger than 3 times the operation wavelength. Second, the beam coupling losses have been studied when the axis of propagation of one beam is tilted with respect to that of the other beam. It is noted that smaller beam waist radius results in greater tolerance to tilts and angular misalignments. Third, the beam coupling cases in which two beams are offset if their axes of propagation are parallel but one is displaced relative to the other have been investigated. It is confirmed that beam waists radii with larger than 3 times operation wavelength are less sensitive to lateral offsets.

Improved method of lateral offset calculation for optical waveguide (광도파로의 곡률 반경에 따른 모드특성과 Lateral Offset 변화)

  • 박순룡;김우택;라상호;오범환
    • Korean Journal of Optics and Photonics
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    • v.9 no.6
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    • pp.408-412
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    • 1998
  • As the radius of curvature of curved optical waveguide gets smaller, the loss increases at the junction of linear-curved waveguide by the cross sectional mode mismatch. The concept of lateral offset has been used widely to minimize it, and simple method of maximum matching has been efficient for most cases of silica waveguide with low optical confinement and large radius of curvature. Here, we analyzed that the propagation mode characteristics of the lateral offset and propagation mode characteristics of general case with effective index method and Airy function solution. As the normalized frequency varies, mode characteristics changes near the boundary of 1/V=0.7 and the simple matching of gaussian profile might give -35% of error at most. We proposed improved method with a new correction factor to improve the mode mismatch problem of conventional methods for general cases, and showed the convenience and feasibility of this method for the calculation of the lateral offset.

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Performance Criterion of Bispectral Speckle Imaging Technique (북스펙트럼 스펙클 영상법의 성능기준)

  • 조두진
    • Korean Journal of Optics and Photonics
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    • v.4 no.1
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    • pp.28-35
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    • 1993
  • In the case of an imaging system affected by aberrations which are not precisely known, the effect of aberrations can be minimized and near-diffraction-limited images can be restored by introducing artificial random phase fluctuations in the exit pupil of the imaging system and using bispectral speckle imaging. In order to determine the optimum value of the correlation length for Gaussian random phase model, computer simulation is performed for 50 image frames of a point object in the presence of defocus, spherical aberration, coma, astigmatism of 1 wave, respectively. In terms of the criterion of performance, the FWHM of the point spread function, normalized peak intensity, MTF and visual inspection of the restored object are employed. The optimum value for the rms difference $\sigma$ of aberration on the exit pupil in the interval of Fried parameter ${\Upsilon}_0$ is given by 0.27-0.53 wave for spherical aberration, and 0.24-0.36 wave for defocus and astigmatism, respectively. It is found that the bispectral speckle imaging technique does not give good results in the case of coma.

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Coupling loss variation as the shape of fiber ends and the fiber arrangement in a fiber Fabry-Perot filter (광섬유 Fabry-Perot필터에서 광섬유 단면의 모양과 배치에 따른 결합손실 변화)

  • 김종호;예윤해
    • Korean Journal of Optics and Photonics
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    • v.8 no.3
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    • pp.230-235
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    • 1997
  • Coupling loss variation as the shape of fiber ends and the fiber arrangement in a fiber Fabry-Perot cavity, formed with two optical fibers with dielectric mirror coatings on their ends, is analyzed. For the intended features it is assumed that one of two fibers is processed to have a concave mirror whose curvature is the same as that of the wavefront of the Gaussian beam from the first fiber. In this assumption, it was turned out that the coupling loss at the cavity length of 15 ${\mu}{\textrm}{m}$ is less than 0.5% even with tilt angle of 0.2$^{\circ}$, curvature error of 70 ${\mu}{\textrm}{m}$, cavity length error of 8 ${\mu}{\textrm}{m}$, and lateral alignment error of 0.5 ${\mu}{\textrm}{m}$. Thus, low loss and high-finesse fiber Fabry-Perot filters whose cavity length is greater than several ${\mu}{\textrm}{m}$ can be obtained easily if the receiving fiber end is properly formed.

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DPSS UV laser projection ablation of 10μm-wide patterns in a buildup film using a dielectric mask (Dielectric 마스크 적용 UV 레이저 프로젝션 가공을 이용한 빌드업 필름 내 선폭 10μm급 패턴 가공 연구)

  • Sohn, Hyonkee;Park, Jong-Sig;Jeong, Su-Jeong;Shin, Dong-Sig;Choi, Jiyeon
    • Laser Solutions
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    • v.16 no.3
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    • pp.27-31
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    • 2013
  • To engrave high-density circuit-line patterns in IC substrates, we applied a projection ablation technique in which a dielectric ($ZrO_2/SiO_2$) mask, a DPSS UV laser instead of an excimer laser, a refractive beam shaping optics and a galvo scanner are used. The line/space dimension of line patterns of the dielectric mask is $10{\mu}m/10{\mu}m$. Using a ${\pi}$ -shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam; and a telecentric f-${\theta}$ lens focuses it to a $115{\mu}m{\times}105{\mu}m$ flat-top beam on the mask. The galvo scanner before the f-${\theta}$ lens moves the beam across the scan area of $40mm{\times}40mm$. An 1:1 projection lens was used. Experiments showed that the widths of the engraved patterns in a buildup film ranges from $8.1{\mu}m$ to $10.2{\mu}m$ and the depths from $8.8{\mu}m$ to $11.7{\mu}m$. Results indicates that it is required to increase the projection ratio to enhance profiles of the engraved patterns.

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Optical Structural Design using Gaussian Optics for Multiscale Gigapixel Camera (상분할 방식의 기가픽셀 카메라를 위한 가우스 광학적인 구조설계)

  • Rim, Cheon-Seog
    • Korean Journal of Optics and Photonics
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    • v.24 no.6
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    • pp.311-317
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    • 2013
  • It was reported in Nature and the Wall Street Journal on June 20th, 2012 that scientists at Duke university have developed a gigapixel camera, capable of over 1,000 times the resolution of a normal camera. According to the reports, this super-resolution camera was motivated by the need of US military authorities to surveil ground and sky. We notice the ripple effect of this technology has spread into the area of national defense and industry, so that this research has started to realize the super-resolution camera as a frontier research topic. As a result, we can understand the optical structure of a super-resolution camera's lens system to be composed of a front, monocentric objective of a single lens plus 98 rear, multiscale camera lenses. We can also obtain the numerical ranges of specification factors related to the optical structure, such as the diameter of the aperture, and the focal length.

Design and Fabrication of Binary Diffractive Optical Elements for the Creation of Pseudorandom Dot Arrays of Uniform Brightness (균일 밝기 랜덤 도트 어레이 생성을 위한 이진 회절광학소자 설계 및 제작)

  • Lee, Soo Yeon;Lee, Jun Ho;Kim, Young-Gwang;Rhee, Hyug-Gyo;Lee, Munseob
    • Korean Journal of Optics and Photonics
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    • v.33 no.6
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    • pp.267-274
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    • 2022
  • In this paper, we report the design and fabrication of binary diffractive optical elements (DOEs) for random-dot-pattern projection for Schlieren imaging. We selected the binary phase level and a pitch of 10 ㎛ for the DOE, based on cost effectiveness and ease of manufacture. We designed the binary DOE using an iterative Fourier-transform algorithm with binary phase optimization. During initial optimization, we applied a computer-generated pseudorandom dot pattern of uniform intensity as a target pattern, and found significant intensity nonuniformity across the field. Based on the evaluation of the initial optimization, we weighted the target random dot pattern with Gaussian profiles to improve the intensity uniformity, resulting in the improvement of uniformity from 52.7% to 90.8%. We verified the design performance by fabricating the designed binary DOE and a beam projector, to which the same was applied. The verification confirmed that the projector produced over 10,000 random dot patterns over 430 mm × 430 mm at a distance of 5 meters, as designed, but had a slightly less uniformity of 84.5%. The fabrication errors of the DOE, mainly edge blurring and spacing errors, were strong possibilities for the difference.

Direct UV laser projection ablation to engrave 6㎛-wide patterns in a buildup film (빌드업 필름의 선폭 6㎛급 패턴 가공을 위한 직접식 UV 레이저 프로젝션 애블레이션)

  • Sohn, Hyonkee;Park, Jong-Sig;Jeong, Jeong-Su;Shin, Dong-Sig;Choi, Jiyeon
    • Laser Solutions
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    • v.17 no.3
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    • pp.19-23
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    • 2014
  • To directly engrave circuit-line patterns as wide as $6{\mu}m$ in a buildup film to be used as an IC substrate, we applied a projection ablation technique in which an 8 inch dielectric ($ZrO_2/SiO_2$) mask, a DPSS 355nm laser instead of an excimer laser, a ${\pi}$-shaper and a galvo scanner are used. With the ${\pi}$-shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam. The galvo scanner before the $f-{\theta}$ lens moves the flat-top beam ($115{\mu}m{\times}105{\mu}m$) across the 8 inch dielectric mask whose patterned area is $120mm{\times}120mm$. Based on the results of the previous research by the authors, the projection ratio was set at 3:1. Experiments showed that the average width and depth of the engraved patterns are $5.41{\mu}m$ and $7.30{\mu}m$, respectively.

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The radio-frequency excited matrix waveguide CO2 laser (고주파 여기식 매트릭스형 도파관 이산화탄소 레이저)

  • 최종운;안명수;이영우
    • Korean Journal of Optics and Photonics
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    • v.15 no.4
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    • pp.343-348
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    • 2004
  • We report the design and basic operating characteristics of an radio frequency excited waveguide $CO_2$ laser. Four picecs of waveguide channels are placed in one laser cavity to increase a power per unit length with the form of a 2 ${\times}$ 2 matrix. Four independent optical outputs are measured from the front of output coupler, and these beams are combined to a Gaussian mode beam far from the output coupler. A 12 W output power has been obtained with $CO_2$ : $N_2$ : He : Xe = 1 : 1 : 3 : 0.2 of the gas mixture and 200 W of radio frequency.