• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.12
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• pp.75-82
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• 1998

Many multiplexing techniques are proposed for high storage densities in a volume hologram. In this paper, we present a hybrid angularly and spatially multiplexed volume holographic memory system. Multiple holograms are recorded by using reference and object waves with different incident angles and positions that are changed by step motors. A hologram is written by exposing the crystal with recording time schedule to the interference pattern of the object beam and a reference plane wave. Finally, we show experimental results of the storage of three layers of 300 multiplexed holograms in a LiNbO$_3$ : Fe crystal.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.10
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• pp.61-70
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• 1999

In this paper, we analyze several exposure time schedules to obtain uniform multiple hologram and measure the diffraction efficiencies of holograms stored in $LiNbO_3$:Fe(0.015wt%) crystal through experiments. The minimum angular selectivity and the intensity ration of two incident beams are investigated precisely by the high resolution system(minimum angle : $0.0028^{\circ}$). Considering initial recording time, total exposure time and time constants, the efficiency distribution(0.014 ${\pm}$ 0.005%) of 100 holograms is measured and the 330 analog images are recorded in the same place. Also, total 500 holograms are retrieved by spatial multiplexing.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.5
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• pp.16-22
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• 2000

This paper presents a compression algorithm applicable for transmitting a HPO hologram data. The proposed algorithm exploits a modulating function to compress the bandwidth of the hologram pattern, resulting in decimation due to relaxed Nyquist sampling constraints. At the receiver, the compressed data will be interpolated and compensated via being divided by the modulating function. We also present compression rate and analyze the resolution of a reconstructed image and the periodicity of harmonic interferences. Finally, we shows the validity of the proposed algorithm by simulation where a reconstructed image from undersampled data is compared with a reconstructed image obtained through decimatioin by modulating function, interpolation and compensation.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.345-353
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• 2005

We proposed a new and cost-effective method fer assembling holographic pickup modules without any high resolution vision system. Assembling was accomplished by adjusting photodiode package only, leading to a low cost, holographic pickup module. Focus and tracking error signals were simply determined by comparing spot sizes and by using the 3 beam method, respectively, based on four-sectional holographic optical elements. In experiment, we assembled a hologram module and estimated performance of the proposed method fur a holographic pickup module used in compact disc system.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.4
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• pp.180-185
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• 2018

We have developed an interactive signage system based on floating hologram by combining hologram technology and ICT technology, which can be competitive to small businesses that have excellent products and services. The developed interactive signage system can be used for publicity and marketing of small business owners at low cost, introducing menus with 3D hologram images, and providing various contents responding to user's hand movements. The developed system is able to detect 10 finger movements at a rate of 290 frames per second in a range of 60cm and a range of 150 degrees. We also confirmed that the virtual touch function operates normally by dividing the user's motion recognition into the hover zone and the touch zone by the physical motion experiment of the leap motion object.

• Journal of the HCI Society of Korea
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• v.8 no.2
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• pp.21-27
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• 2013

Recently, the use of floating hologram has increased in many different aspects, such as exhibitions, education, advertisements, and so on. Especially, the floating hologram that makes use of half-mirror is widely used. Nevertheless, half-mirror, unfortunately, cannot lead users to the perfect three dimensional hologram experience. Even though it can make the vision look to be up on the air, it does not have the capacity to display itself up on the air, which is the ultimate goal of hologram. In addition, it looks inconsistent when a real object is located behind the half-mirror in order to show the convergence of the two (object and the half-mirror). In this paper, we did the study on comparison of 3D space perception for the stereoscopic AR holography. At first, we applied stereoscopic technology to the half-mirror hologram system for the accurate and realistic AR environment. Then, the users can feel as if the real 3D object behind half-mirror and the reflected virtual image are converged much better in the 3D space. Furthermore, by using depth camera, the location and direction of graphics can be controlled to change depending on the user's point of view. This is the effective way to produce augmented stereoscopic images simply and accurately through half-mirror film without any additional devices. What we saw from the user test were applying 3D images and user interaction leads the users to have 3D spatial awareness and realism more effectively and accurately.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.27-29
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• 2010

깊이데이터는 CG 또는 실사 영상에서 획득되는데 입체 영상 분야에서 활용도가 높다. 예를 들어 2D영상의 3D화질 개선, 입체영상의 입체감 개선 등의 활용이 되고 있다. 본 논문에서는 이러한 추세에 맞추어 홀로그램을 생성하는 입력 데이터의 전처리과정으로 통하여 CGH 홀로그램을 개선하는 영상처리 기술을 제안한다. 입력 데이터의 전처리를 통해 생성된 홀로그램 영상의 화질 개선을 제안하고, 실험을 통해 제안 방법의 우수성을 보여준다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.4
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• pp.820-828
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• 2017

Service of digital hologram that has been recognized as a visual system for next generation requires various signal processing technologies. A transform is the most frequently used tool among signal processing techniques for 2-dimensional(D) and 3-D natural picture. A digital hologram has totally different property with a natural picture, so it is rarely efficient to apply transform tools used in 2-D image processing to a digital hologram. To overcome this a Fresnelet transform for a digital hologram has been proposed. We derive a Fresnelet transform by using the Daubechie's filter after applying an unitary Fresnel transform to a wavelet basis function. We also implement the transform as types of device and kernel code to improve operational performance. In consideration of the average time that is required for a pixel we can have observed the performance is improved up to 242 and 30 times for using the (9,7) and (5,3) filters in case of using device code.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.8
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• pp.76-81
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• 1998

This paper presents a new method to synthesize a digital hologram that meets the resolution of a currently manufactured LCD while capable of displaying a 3-D object. That is accomplished by segmenting a hologram, resulting in relaxed sampling constraint. We show that the segmentation of a hologram enables us to utilize the planewave approximation and, unlike in a holographic stereogram, it does not require projection process, but directly takes fourier transform of horizontally sliced 2-D images that constitute a 3-D object, which makes it possible to reconstruct a higher resolution image with depth information. We also show that proposed hologram contains data significantly smaller than the conventional hologram does, which is quite useful for constructing wide-viewing hologram. Finally, simulation results obtained by both methods are compared.

• Broadcasting and Media Magazine
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• v.16 no.2
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• pp.109-117
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• 2011

디지털 홀로그래피는 현재 입체영상 서비스의 주류를 이루고 있는 스테레오스코픽(Stereoscophic)이나 다시점(Multi-view) 3D와 달리 주어진 관찰각도에서 관찰자의 위치에 따른 입체영상을 볼 수 있다. 또한 입체영상을 디스플레이하는 장치가 물리적 매체가 아닌 공간으로 한다는 점에서도 차이가 있다. 최근 홀로그래피, 홀로그램이란 용어가 상업적인 용도로 사용되면서 해당기술의 본질적인 의미가 상당히 변질되는 경우가 많이 있다. 본 기고에서는 일부에서 변질/왜곡하여 사용하고 있는 "유사한 홀로그래피(Fake holography)"가 아닌 간섭현상(Interference)을 수학적으로 모델링한 후 이를 컴퓨터에서 계산하여 디지털 홀로그램을 생성하는 컴퓨터 생성 홀로그램(Computer-Generated Hologram, CGH) 기술을 다룬다. 특히, 국내외의 연구개발 결과 중에서 전용 하드웨어나 범용 프로세서 등을 이용해 CGH 연산을 고속화하는 기술에 중점을 두었다.