• Current Optics and Photonics
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• 제5권4호
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• pp.402-408
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• 2021

An off-axis system refers to an optical system in which the optical axis and normal vector at the vertex of each surface do not match. The most important specification in an optical system is its focal length. Among the various methods for measuring the focal length, the most suitable method for the off-axis system is the method that adopts magnification. However, head-mounted display (HMD) optics must be measured while considering the virtual image distance, which is not infinity owing to product characteristics. For the virtual image distance, a camera with a focusing function was used. By measuring HMD optics via this magnification method, the error generated in this measurement was 0.68% of the HMD's focal length, which is within the 1%-3% range of the conventionally permitted design error for the focal length allowed at the optical design stage. Therefore, it can be verified that the measurement accuracy of the method proposed in this study is sufficiently feasible in practice.

• Current Optics and Photonics
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• 제7권6호
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• pp.761-765
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• 2023

We analyzed the absorption spectra of acetone in the 3.37 ㎛ mid-infrared range using the off-axis integrated cavity output spectroscopy technique to develop a real-time, in-line breath analysis device. The linear relationship between acetone concentration and absorption increase was confirmed as 0.32%/ppm, indicating that the developed device allows for a quantitative analysis of acetone concentration in exhaled breath. To further confirm the feasibility of using our device for breath analysis, we measured the acetone concentration of human breath samples at the sub-ppm level.

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.394-397
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• 2011

For the purpose of fabricating off-axis aspheric optics, we propose an 8-axis-polishing machine combined with a testing tower whose height is up to 9 m. The proposed polishing machine was designed and analyzed by using a well-known finite element method. The eight axes of the machine have a synchronized motion generated by a computer, and each axis was calibrated by a heterodyne laser interferometer or an optical encoder. After calibration, the maximum positioning error of the machine was less than 2 ${\mu}m$ within a whole 2 m ${\times}$ 2 m area. A typical fabrication result of a ${\phi}1.5$ m concave mirror was also described in this manuscript.

• 한국광학회지
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• 제32권1호
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• pp.9-14
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• 2021

본 논문에서는 인공위성용 비축 삼반사 망원경의 조리개 위치에 따른 광학계 연구를 진행하였다. 인공위성 광학 탑재체로 주로 사용되는 비축 삼반사 망원경은 높은 해상도와 넓은 화각을 가져야 한다. 또한, 광학계가 구조적으로 비축상에 위치하여 조립이 어려우므로 넓은 공차범위를 가져야 한다. 그러나 조리개의 위치 선정에 따라 광학계의 성능 차이 이외에도 민감도의 차이가 있어, 사용 목적에 따른 적합한 조리개의 위치 선정이 중요하다. 따라서 본 논문에서는 조리개 위치가 각각 다른 비축 삼반사 망원경을 설계하고 성능 및 민감도 분석을 진행하여 적합한 조리개의 위치를 제시하였다.

• 한국광학회지
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• 제32권6호
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• pp.296-305
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• 2021

본 논문은 OLED 제작 공정에 사용하는 레이저 박리(laser lift-off, LLO) 장비의 실린더 렌즈를 사용하는 선형 빔 광학계의 장축 성능에 대한 연구로서, 실린더 렌즈의 편심을 7가지로 분류하고 정의하였으며, 측정 방법을 제시하였다. 또한 실린더 잠자리 눈 렌즈의 면정밀도와 편심, 사용방식 등이 선형 빔 광학계의 장축 성능에 미치는 영향에 대한 분석 및 실험 결과를 제시하고, 장축 성능을 향상시키기 위한 향후 진행방향을 제시하였다.

• 한국광학회지
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• 제2권2호
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• pp.83-88
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• 1991

공간불변(space-invariant) 패턴인식에 대한 연구는 여러 접근방식에서 많은 시도가 이루어지고 있다. 학습 이미지의 가중치 선형조합(weighted linear summation)에 의한 SDF(synthetic discriminant function) 필터를 이용한 패턴인식은 그 중의 한 방식으로서 꾸준히 많은 관심을 받고 있다. 본 논문에서는 off-axis 평면기준파의 각분할(angular multiplexing) 방식과 pseude-inverse 알고리듬에 의한 pSDF 필터를 결합하여 상관기를 구성하고 상관면에서의 상관반응을 관측하여, off-axis pSDF 공간정합필터가 유형분류에 유용함을 입증하고, 광상관기로의 적용가능성을 보여주고자 한다.

• Current Optics and Photonics
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• 제1권4호
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• pp.364-371
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• 2017

Compared to one made of glass, an aluminum mirror features light weight, compact design, low cost, and quick manufacturing. Reflective mirrors and supporting structures can be made from the same material, to improve the athermal performance of the system. With the rapid development of ultraprecise machining technologies, the field of applications for aluminum mirrors has been developed rapidly. However, most of them are rotationally symmetric in shape, and are used for infrared applications. In this paper, the design and manufacture of an off-axis aluminum mirror used for a three-mirror-anastigmat (TMA) optical system at visible wavelengths is presented. An optimized, lightweight design provides a weight reduction of more than 40%, while the surface deformation caused by earth's gravity can meet the required tolerance. The two pieces of an off-axis mirror can be diamond-turned simultaneously in one setup. The centrifugal deformation of the off-axis mirror during single-point diamond turning (SPDT) is simulated through the finite-element method (FEM). The techniques used to overcome centrifugal deformation are thoroughly described in this paper, and the surface error is reduced to about 1% of the original value. After post-polishing, the form error is $1/30{\lambda}$ RMS and the surface roughness is better than 5 nm Ra, which can meet the requirements for visible-light imaging.

• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.270-276
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• 2012

An off-axis integral floating system using a concave mirror is analyzed to resolve the image distortion incurred by the off-axis optical arrangement. The concave mirror can be adopted as the floating device to improve the optical efficiency. The image distortion due to the tilting axis of the concave mirror needs to be analyzed precisely to generate the pre-distortion image. In this paper, we calculate the image deformation in the off-axis structure of the concave mirror using the geometrical optics. Using the calculation results, the compensated elemental image can be generated for the pre-distortion integrated image, which can be projected to the floating 3D image without image distortion. The basic experiments of the off-axis integral floating are presented to prove and verify the proposal.

• 한국정밀공학회지
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• 제11권1호
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• pp.150-156
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• 1994

To meet the process requirement of semiconductor device manufacturing, it is necessary to improve the alignment accuracy in exposure equipments. We developed the excimer laser stepper and will describe the methodology for alignment measurement and experimental results. Our wafer alignment system consists of off-axis optics, TTL(Through The Lens) optics and high precision stage. Off-axis alignment utilizes the image processing and /or diffraction from thealign marks of off-centered chip area. On the other hand, TTL alignment can be used for the die-by-die alignment using dual beam interferometry. When only off-axis alignment was used, the experimental alignment error(lml+3 .sigma. ) was 0.26-0.29 .mu. m, and will be reduced down to 0.15 .mu. m by adding TTL alignment.

• Current Optics and Photonics
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• 제3권5호
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• pp.374-381
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• 2019

This study examined a method for designing the optical cavity of a non-dispersive infrared gas detector. The infrared gas detector requires an optical cavity design to lengthen the ray path. However, the optical cavity with multiple reflecting surfaces has off-axis aberration due to the characteristics of the reflecting optical system. The rays were parallelized by using the off-axis parabolic mirror to easily increase the ray path and eliminate off-axis aberration so that the rays are admitted to the effective area of the infrared detector uniformly. A prototype of an infrared gas detector was produced with the designed optical cavity to confirm the performance.