• 반도체디스플레이기술학회지
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• 제6권3호
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• pp.65-70
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• 2007

A method to focus the object in camera system by applying the Hill climb algorithm from optical lens moving device (VCM; Voice coil motor) is proposed. The focusing algorithm from VCM is focus on the object but in these criteria is a well-known drawback; the focus is good only at same distance objects but the focus is bad (blur image) at different distance objects because of the DOF (Depth of focus) or DOF (Depth of field) at the optical characteristic. Here, the new camera system that describes the Reflector of free curvature systems (or Diffractive Fresnel lens) and the partition of focusing window area is proposed. The method to improve the focus in all areas (different distance objects) is proposed by new optical system (discrete auto in-focus) using the Reflector of free curvature systems (or Diffractive Fresnel lens) and by applying the partition of all areas. The proposal is able to obtain good focus in all areas.

• Journal of the Optical Society of Korea
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• 제18권2호
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• pp.151-155
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• 2014

Although various ophthalmic imaging methods, including fundus photography and optical coherence tomography, have been applied for effective diagnosis of ocular diseases with high spatial resolution, most of them are limited by shallow imaging penetration depth and a narrow field of view. Also, many of those imaging modalities are optimized to provide microscopic anatomical information, while functional or cellular information is lacking. Compared to other ocular imaging modalities, photoacoustic imaging can achieve relatively deep penetration depth and provide more detailed functional and cellular data based on photoacoustic signal generation from endogenous contrast agents such as hemoglobin and melanin. In this paper, array-based ultrasound and photoacoustic imaging was demonstrated to visualize pigmentation in the eye as well as overall ocular structure. Fresh porcine eyes were visualized using a real-time ultrasound micro-imaging system and an imaging probe supporting laser pulse delivery. In addition, limited photoacoustic imaging field of view was improved by an imaging probe tilting method, enabling visualization of most regions of the retina covered in the ultrasound imaging.

• 천문학회보
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• 제39권1호
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• pp.59.2-59.2
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• 2014

Radiative transfer models in a spherical, turbulent interstellar medium (ISM), in which the photon source is situated at the center, are calculated to investigate the correlation between the scattered light and the dust column density. The medium is modeled using fractional Brownian motion structures that are appropriate for turbulent ISM. The correlation plot between the scattered light and optical depth shows substantial scatter and deviation from simple proportionality. It was also found that the overall density contrast is smoothed out in scattered light. In other words, there is an enhancement of the dust-scattered flux in low-density regions, while the scattered flux is suppressed in high-density regions. The correlation becomes less significant as the scattering becomes closer to being isotropic and the medium becomes more turbulent. Therefore, the scattered light observed in near-infrared wavelengths would show much weaker correlation than the observations in optical and ultraviolet wavelengths. We also find that the correlation plot between scattered lights at two different wavelengths shows a tighter correlation than that of the scattered light versus the optical depth.

• Current Optics and Photonics
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• 제8권1호
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• pp.72-79
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• 2024

Recent flat-panel displays have become increasingly complicated to facilitate multiple display functions. In particular, the form of multilayered architectures for next-generation displays makes precise three-dimensional alignment of multiple panels a challenge. In this paper, a diffractive optical alignment marker is proposed to address the problem of three-dimensional alignment of distant dual panels beyond the depth-of-focus of a vision camera. The diffractive marker is effective to analyze the positional correlation of distant dual panels. The possibility of diffractive alignment in multilayer display fabrication is testified with numerical simulation and a proof-of-concept experiment.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.440-441
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• 2004

A volumetric three-dimensional (3D) display system was presented, which utilizes a rotating two-dimensional (2D) display panel of light emitting diodes (LEDs) to generate more than 10 million volume pixels (voxels) within a cylindrical volume of 165 mm in height and 292 mm in diameter. Due to persistence of vision, momentarily addressed voxel information is perceived and fused into a 3D image. Important cues for depth perception, such as binocular parallax, accommodation, convergence and motion parallax are satisfied automatically and naturally, thus it is suitable for individual or group viewing, without the need for any special visual aids.

• 전자공학회논문지D
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• 제34D권4호
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• pp.62-72
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• 1997

The optical power splitter/couplers based on MMI(multimode interference) in GaAs/AlGaAs are studied. We presetn a design of optical power splitter/couplers, which have deeply etched multimode waveguide. The properties and fabrication tolerance on the etching depth, multimode waveguide width are simulatedusing a FD-BPM (finite difference beam propgation method). Proposed 1*N optical of designed device is 0.7dB smaller than the optical power splitter with a shallowly etched MMI section. For 0.5dB excess loss, the predicted fabrication tolerance is 0.6.mu.m on the multimode waveguide width of the 14 optical power splitter with a deeply etched MMI section. Also excess loss and uniformity of poposed 32*32 optical power coupler are below 0.3dB. The excess loss of proposed 32*32 optical power coupler is 2dB smaller than the optical power coupler with a shallowly etched MMI section. It is shown that the optical power splitters/couplers with a deeply etched mMI section have low loss, good uniformity, and improved fabriction tolerance.

• 한국광학회지
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• 제18권4호
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• pp.274-279
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• 2007

광간섭 단층촬영(OCT)용으로 원통형 압전소자(PZT)와 단일모드 광섬유를 이용한 광경로 지연기를 제작하여 정현파로 구동하고 특성을 분석하였다. 제작한 OCT 시스템은 검침단과 기준단을 대칭 구동하는 이중 광경로 지연방식을 사용하였다. 정현파 구동을 통한 PZT 광경로 지연 방식은 삼각파 구동과 비교하여 입력파형의 첨두 부분에서의 비선형현상을 제거하여 높은 반복성을 나타냄을 보였고, 삼각파 구동으로는 불가능했던 부분을 영상화 할 수 있었다.

• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.33-36
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• 2009

Laser ablation with femtosecond lasers is highly promising for microfabrication of materials. Also, the high peak power of femtosecond lasers could induce a multiphoton absorption to ablate transparent materials. Similar results have also been were obtained in the case of optical fibers. In this paper, we present our experimental results of femtosecond laser microstructuring of optical fiber and its applications to microelectronic components and fiber optic devices. Finally, we directly produced micro holes with femtosecond laser pulses in a single step by moving an optical fiber in a preprogrammed structure. When water was introduced into a hole drilled from the bottom surface of the optical fiber, the effects of blocking and redeposition of ablated material were greatly reduced and the aspect ratio of the depth of the hole was increased. We have presented circular and rectangular-shaped holes in optical fiber.

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 동계학술발표회 논문집
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• pp.131-132
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• 2006

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 동계학술발표회 논문집
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• pp.187-188
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• 2008