• Journal of the Optical Society of Korea
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• v.5 no.3
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• pp.93-98
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• 2001

In order to verify the performance of the two-stage iterative Fourier transform algorithm[Hankook Kwanghak Hoeji 11, 47 (2000)], a number of phase-only diffractive pattern elements which produce simple 16x16-pixel intensity patterns useful in the field of optical information processing have been designed and their performance has been compared with that from the nonlinear least-squares algorithm[Appl. Opt. 36, 7297(1977)] which is computationally intensive. for all intensity patterns, elements designed by the former algorithm show better overall signal-to noise ratio and uniformity, although they show essentially the same diffraction efficiency. In the case of continuous phase elements, they show far superior uniformity. Computationally,. the former algorithm is far more efficient than the latter.

• Current Optics and Photonics
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• v.5 no.6
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• pp.672-679
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• 2021

We propose a high-speed layer-based algorithm for synthesizing computer-generated holograms (CGHs), featuring sparsity-based image segmentation and computational parallelism. The sparsity-based image segmentation of layer-based three-dimensional scenes leads to considerable improvement in the efficiency of CGH computation. The efficiency enhancement of the proposed algorithm is ascribed to the field localization of the fast Fourier transform (FFT), and the consequent reduction of FFT computational complexity.

• Korean Journal of Optics and Photonics
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• v.35 no.4
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• pp.157-163
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• 2024

We developed a 3-channel fiber laser with a common seed and a phase control system for laser beam combining through a diffractive optical element. Beam combining was performed by adjusting the angles of the beams incident on the diffractive optical elements, and the phase of each beam was controlled to maximize the intensity of the combined laser beam. The power of the 3-channel laser before passing through the diffractive optical elements is about 65 mW. The power of the combined beam varied between 2.9 mW and 48.3 mW depending on the phase change of each channel. Through phase control, the output of the combined beam can be maintained at 42 mW for more than 91.8% of the total time. It is expected that higher combining efficiency can be achieved by improving the transmittance of the diffractive optical elements and the performance of the phase control system.

• Korean Journal of Optics and Photonics
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• v.11 no.1
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• pp.47-57
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• 2000

A two-stage iterative Fourier transform algorithm, based on hybrid input-output algorithm and new Pnoise algorithm, is used to design continuous and quantized phase-only diffractive pattern elements which produce arbitrary given intensity patterns via Fraunhofer diffraction. Numerical results for two $128\times128$ binary patterns and two grayscale patterns are compared with those of other algorithms. It is found that the algorithm yields better signal-to-noise ratio and even better uniformity with slightly lower diffraction efficiency than other algorithms. We investigated the dependence of performance on parameters used in the algorithm, size of noise region, and the number of phase levels for quantized elements. In the case of quantized phase elements, the size of noise region plays a greater role in determining the performance of the algorithm than given intensity pattern itself. tself.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.122-122
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• 2004

최근 휴대폰, 디지털 카메라, 캠코더, MP3 플레이어, 노트북 PC 등 휴대용 디지털 기기의 보급이 확산되면서 휴대용 저장장치의 수요가 급증하고 있다. 휴대용 저장장치의 요구사항으로 초소형화, 대용량화를 들 수 있는데, 이를 만족할 수 있는 기술로 사용될 수 있는 것이 Blu-Ray를 이용한 광 저장장치이다. 초소형 광저장장치에 사용되는 3cm 디스크에는 1.5Gbyte를 기록할 수 있으므로 기존의 휴대용 저장장치에 비해 가격이 저렴하며 대량배포가 가능하다.(중략)

• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.47-50
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• 1987

There are various holographic recording materials, such as Dichromated Gelatin, Silver Halide, Thermoplastic, Photoresist. In this paper especially, we used Photoresist to make the phase holographic grating. Deep-groove diffractive grating formed in relatively thin holographic recording material is to express high diffraction efficiency. Phase holographic grating recorded In photoresist can be used very practical because it has the high diffraction efficiency, and it is possible to make a replication easily. So, it has the merit in recording the optical holographic grating than any other materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.644-647
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• 2001

Amorphous As-Ge-Se-S thin films have been studied with the aim of identifying optimum etching condition which can be used to produce holographic grating structure for use as diffractive optical elements. In this study, holographic gratings have been formed using He-Ne laser(632.8nm), and fabricated by the method of wet etching using NaOH etchant with various concentration(0.26N, 0.33N, 0.40N). The diffraction efficiency was obtained by +1st order intensity of the diffracted beam. The formed grating profiles were observed by atomic force microscope and showed that the expected grating profile could be achieved by controlling the etching time. Over-etching resulted in under-cutting of the grating lines. The highest 1st order diffraction efficiency for these gratings was about 5.05%.

• Korean Journal of Optics and Photonics
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• v.28 no.5
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• pp.241-249
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• 2017

This paper presents the design and evaluation of the optical system for an uncooled thermal-imaging camera. The operating wavelength range of this system is from $7.7{\mu}m$ to $12.8{\mu}m$. Through optimization, we have obtained a LWIR (Long Wave Infrared) optical system with a focal length of 5.44 mm, which consists of four aspheric surfaces and two diffractive surfaces. The f-number of the optical system is F/1.2, and its field of view is $90^{\circ}{\times}67.5^{\circ}$. The hybrid lens was used to balance the higher-order aberrations, and its diffraction properties were evaluated by scalar diffraction theory. We calculated the polychromatic integrated diffraction efficiency, and the MTF drop generated by background noise. We have evaluated the thermal compensation of a LWIR fixed optical system, which is optically passively athermalized to maintain MTF performance in the focal depth. In conclusion, these design results are useful for an uncooled thermal-imaging camera.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.240-249
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• 2001

A high speed ultra-compact lens with a diffractive optical element (DOE) is designed, which can be applied to mobile communication devices such as IMT2000, PDA, notebook computer, etc. The designed hybrid lens has sufficiently high performance of less than f/2.2, compact size of 3.3 mm (1st surf. to image), and wide field angle of more than 30 deg. compared with the specifications of a single lens. By proper choice of the aspheric and DOE surface which has very large negative dispersion, we can correct chromatic and high order aberrations through the optimization technique. From Seidel third order aberration theory and Sweatt modeling, the initial data and surface configurations, that is, the combination condition of the DOE and the aspherical surface are obtained. However, due to the consideration of diffraction efficiency of a DOE, we can choose only four cases as the optimization input, and present the best solution after evaluating and comparing those four cases. On the other hand, we also report dramatic improvement in optical performance by inserting another refractive lens (so-called, field flattener), that keeps the refractive power of an original DOE lens and makes the petzval sum zero in the original DOE lens system. ystem.

• ETRI Journal
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• v.17 no.2
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• pp.1-10
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• 1995

We propose a novel planar optical interconnection scheme for 100 Gb/s optical packet address detection, which consists of waveguide grating couplers and a diffractive microlens integrated on a glass substrate 3-dimensionally. Length and duty cycle of the grating couplers have been determined on the bases of the ray-optic propagation-mode analysis in a slab waveguide and of the rigorous coupled-wave diffraction analysis for out-coupled radiation-modes. The 3-dimensionally integrated planar optics makes it possible to connect each address bit-signals of $TE_ 0-waveguide$ mode to the detector with a power uniformity of 6.4 % and a total coupling efficiency of 72.3 %.