&lt;title&gt;Optical system of holographic memory card writing/reading equipment&lt;/title&gt;

Erdei, Gábor; Szarvas, G.; Loerincz, Emoeke; Fodor, Jozsua; Újhelyi, Ferenc; Koppa, Pál; Varhegyi, Peter; Richter, Péter

doi:10.1117/12.402415

Cited by 6 publications

(7 citation statements)

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“…2. This small value was necessary to allow room for other imaging components in the light path (see [1,2]) as well as for the tolerances (see Tab. 3). The front focal length (i.e.…”

Section: System Specificationmentioning

confidence: 99%

“…The inverse formula of Fourier transformation is as follows: g(x0 ;y) = JJG(fx ; fy).ei2(fXxO+fYYO)dfXdfy . (2) In case a light pattern described by the complex amplitude distribution u(x0; Yo) is positioned into the front focal plane of a thin converging lens (see Fig. 1), the field U(x, y) will have the following form in the back focal plane (assuming a paraxial light propagation through the lens and neglecting the truncating effects of its aperture):…”

Section: Imaging Properties Of Fourier Transforming Objectivesmentioning

confidence: 99%

“…7 a schematic drawing of the mounting of the objective can be seen. The aspheric lens was cut as shown in the figure in order to allow room for the other elements of the optical head (especially the SLM and the CCD), see [1,2]. Tab.…”

Section: Fabrication Processmentioning

confidence: 99%

“…The back focal length was selected large enough to place into the light path a coupler prism, see polarisation beam splitter (PBS) in Fig. 2 and [1,2], which couples the writing and reading channels together. The aperture stop size is equal to the diameter of one micro-hologram, while the image size corresponds to the semi-diameter of the CCD array (i.e.…”

Section: System Specificationmentioning

confidence: 99%

“…Holographic systems are also insensitive to dust and other environmental influences. In our laboratories we are developing such an equipment to simultaneously write and retrieve multiple bits of information stored at 1 bit/.tm2 data density in the form ofpolarisation Fourier micro-holograms recorded in a thin layer of rewritable photoanisotropic polymer [1,2].…”

Section: Introductionmentioning

confidence: 99%

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Design of high-numerical-aperture Fourier objectives for holographic memory card writing/reading equipment

Erdei¹,

Fodor²,

Kalló³

et al. 2000

Current Developments in Lens Design and Optical Systems Engineering

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A pair of special Fourier transforming objectives intended for use in a Holographic Memory Card (HMC) writing/reading equipment have been designed and fabricated. At writing in, the objectives Fourier transform a binary pattern, representing the data displayed by an SLM, into the storage medium of the HMC, where the Fourier transform is recorded as a polarisation hologram. At reading out, the objectives inverse Fourier transform the reconstructed hologram onto the surface of a CCD array. The Fourier space NA of the objectives is high enough to achieve a theoretical data density of 1 bit/im2. For comparison reasons we designed two optically identical objectives of basically different structures: one is an aspheric glass doublet, the other is an all-spherical five-element system (arranged in two lens groups). Computer analysis of the objectives shows that both systems are diffraction limited in object and Fourier space and have a distortion of less than 1%. In this paper we overview the theory of Fourier objectives, present our design method, describe the optical behaviour of the designed systems, show our test results performed on the fabricated aspheric objective and present our experiences at manufacturing aspheric glass lens prototypes.

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“…2. This small value was necessary to allow room for other imaging components in the light path (see [1,2]) as well as for the tolerances (see Tab. 3). The front focal length (i.e.…”

Section: System Specificationmentioning

confidence: 99%

Section: Imaging Properties Of Fourier Transforming Objectivesmentioning

confidence: 99%

Section: Fabrication Processmentioning

confidence: 99%

Section: System Specificationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Design of high-numerical-aperture Fourier objectives for holographic memory card writing/reading equipment

Erdei¹,

Fodor²,

Kalló³

et al. 2000

Current Developments in Lens Design and Optical Systems Engineering

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A secure data storage system based on phase-encoded thin polarization holograms

Ujvári

Koppa

Lovasz

et al. 2004

J. Opt. A: Pure Appl. Opt.

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Multilayer thin-film holographic storage-a new approach

Szarvas¹,

Koppa

Sütó³

et al.

International Symposium on Optical Memory and Optical Data Storage Topical Meeting

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ut 8, Hungary OFTILINK has developed and presented a polarization holographic reading writing system using 1-2 pm thick storage layer on a card form media [1,2,3]. Storage density of 1.3 bit/pm2 has been achieved without multiplexing with sparse code modulation and Fourier-filtering. Because of using thii storage layer the volume data density is extremely high in the system. Further enhancement of the areal density up to -100 bit/km2 can be achieved in an improved new polarization holographic system using a multilayer media instead of the thin film. A 6f system for reading with a suitable second spatial filter allows separation of the signal fiom different layers. This technique combines the advantage of the thin film holography with the idea of the confocal filtering.The thin-film polarization holographic memory card system of Optilink [1,2,3] has practical advantages, e.g. the card works in reflection mode, we do not use hardware servo, it is possible to read and write with different wavelengths, data encryption is possible, there is no problem with material shrinkage, etc. Using thin-film holography the possibilities of multiplexing are limited, but theoretical and experimental calculations show that with an accordingly optimized system (optical elements and codes) the data density can be increased without multiplexing.In optical memories data density is limited first of all by the wavelength and by the numerical aperture (NA) of the readinglwriting objectives. For data density optimization different custom Fourier objectives With high numerical aperture (2 0.74) were designed, fabricated and tested [2,6]. Theoretically in thin-film holographic memories the data density is inversely proportional to the hologram area. In OUT optical system the hologram s u e is controlled by a specially arranged Fourier filtering mirror [2,3]. This mirror cuts the higher diffraction orders. The role of cutting in the Fourier plane is twofold it controls the hologram size and prevents inter-page (hologram) cross-talk. Decreasing the Fourier aperture size causes failure of the optical system resolution which results in a higher inter pixel interference and an increasing bit error rate. -3 -a--= 3,OO 0 2 3 0 '5 2,oo 5 1,50 U 1,oo 2 0,50 0,oo 6% 15% 19% 25% 50% White rate Fig. 1. Calculated data density 0-7803-7379-0/02/$17.0002002 IEEE A well know method to avoid the effect of different error sources is the optimization of codes. Theoretical and experimental investigations show [ 1,4,5,7] that in our optical system the optimal code is a constantweight sparse modulation code. In this case we convert 8 bits ASCII characters into 4x5 binary matrices. The constant number of white pixels in every symbol is combined with disabling white neighbors of each white pixel. This code has advantageous effects to the noise reduction: the sparse code relives the effect of 2D interpixel interference arising from the low-pass nature (Fourier cutting) of the optical imaging system and the diffracted light intensity per pixel increases by using fewer...

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<title>Optical system of holographic memory card writing/reading equipment</title>

Cited by 6 publications

References 0 publications

Design of high-numerical-aperture Fourier objectives for holographic memory card writing/reading equipment

Design of high-numerical-aperture Fourier objectives for holographic memory card writing/reading equipment

A secure data storage system based on phase-encoded thin polarization holograms

Multilayer thin-film holographic storage-a new approach

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