WO2008035274A1 - Optical holographic device and method with alingnment means - Google Patents
Optical holographic device and method with alingnment means Download PDFInfo
- Publication number
- WO2008035274A1 WO2008035274A1 PCT/IB2007/053746 IB2007053746W WO2008035274A1 WO 2008035274 A1 WO2008035274 A1 WO 2008035274A1 IB 2007053746 W IB2007053746 W IB 2007053746W WO 2008035274 A1 WO2008035274 A1 WO 2008035274A1
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- blocks
- alignment
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- 230000003287 optical effect Effects 0.000 title claims abstract description 28
- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000001514 detection method Methods 0.000 claims description 9
- 238000004590 computer program Methods 0.000 claims description 8
- 230000005855 radiation Effects 0.000 description 9
- 238000013500 data storage Methods 0.000 description 7
- 238000009826 distribution Methods 0.000 description 6
- 230000001419 dependent effect Effects 0.000 description 4
- 230000002745 absorbent Effects 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
- 229910002056 binary alloy Inorganic materials 0.000 description 2
- 238000004422 calculation algorithm Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 238000003491 array Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005315 distribution function Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
- G11B7/0065—Recording, reproducing or erasing by using optical interference patterns, e.g. holograms
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
- G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
- G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/083—Disposition or mounting of heads or light sources relatively to record carriers relative to record carriers storing information in the form of optical interference patterns, e.g. holograms
Definitions
- the present invention relates to an optical holographic device and a corresponding method for reading out a data page recorded in a holographic recording medium and carrying data modulated using a block modulation code, according to which a data page is divided into a number of blocks and a code constraint is applied defining the number of data symbols in a block having a predetermined symbol value. Further, the present invention relates to an electronic device and a corresponding method for use in such an optical holographic device. Finally, the present invention relates to a computer program for implementing said methods in software.
- Holographic Data Storage Systems promise high data capacities (1 TByte on a 12-cm disc) and high data rates (Gbit/s).
- the advantage of holographic data storage over conventional optical storage is that it uses the real 3D volume of the medium to store the data making high capacities possible.
- An overview of Holographic Data Storage Systems is given in "Holographic Data Storage Systems", Lambertus Hesselink, Sergei S. Orlov, and Matthew C. Bashaw, Proceedings of the IEEE, vol. 92, no. 8, pp. 1231-1280, 2004.
- fiducials i.e. alignment marks
- the alignment marks are detected and the holographic medium is translated and rotated until the right alignment marks are retrieved on the detector.
- a detection method is not suitable for a high-density holographic medium, because the alignment marks require space in the holographic medium, which reduces the possible data density/rate.
- an optical holographic device as defined in claim 1, said device comprising: image forming means for forming an imaged data page, image detection means for detecting said imaged data page, alignment means for determining the alignment of the blocks in said detected imaged data page by iteratively determining, for a different alignment of the blocks in each iteration, whether for said alignments said code constraint is fulfilled or not, and decoding means for decoding the block modulated data from said detected imaged data page based on the determined alignment of the blocks.
- an electronic device as defined in claim 8, said electronic device comprising: alignment means for determining the alignment of the blocks in said detected imaged data page by iteratively determining, for a different alignment of the blocks in each iteration, whether for said alignments said code constraint is fulfilled or not, and decoding means for decoding the block modulated data from said detected imaged data page based on the determined alignment of the blocks.
- a computer program comprising program code means for causing a computer to carry out the steps of the method as claimed in claim 9 or 10, when said computer program is carried out on a computer.
- Corresponding methods are defined in further independent claims.
- Preferred embodiments of the invention are defined in the dependent claims. It shall be understood that the electronic device, the methods and the computer program have similar and/or identical preferred embodiments as defined in the dependent claims.
- the present invention is based on the idea to iteratively check for different alignments whether a given code constraint of the block modulation code is fulfilled or not. For instance, in the above explained example of a balanced block 6:8 code, a code constraint is that each block exactly contains four Os and four Is.
- the present invention can generally be applied, according to preferred embodiments, to both a balanced modulation code and an unbalanced modulation code.
- the detection of the ideal alignment is generally more accurate and easier.
- An unbalanced code is less efficient, i.e. less user bits can be stored in a given number of channel bits. For instance, with 3 "1" pixels and 5 "0" pixels there are 56 unique possibilities which is less than the 70 possibilities in case of using a balanced code. This means that only 5-bits "words" can be encoded using an unbalanced code instead of 6-bits words a balanced code.
- the alignment means are adapted for determining, in each iteration, a significance value or function based on the symbol values per block and based on a number of blocks of said determined imaged data page and for determining, whether, for the alignment of the blocks applied in said iteration, said code constraint is fulfilled or not based on said significance value or function.
- Said significance value or function can generally be any value or function that allows to distinguish between aligned blocks and non-aligned blocks.
- said value or function is selected such that they show large differences for aligned and non-aligned blocks, but that their determination requires only a small overhead in terms of calculation power and storage space.
- the sum of the symbol values and/or the summed intensity values for said number of blocks are used as said significance value according to one embodiment, while according to another embodiment a probability function indicating the probability to find a summed symbol or intensity value in a block is used as said significance function.
- a probability function indicating the probability to find a summed symbol or intensity value in a block is used as said significance function.
- the width of said probability function is determined and used for checking whether said width is smaller than a predetermined width.
- FIG. 1 shows an optical holographic device according to the present invention
- Fig. 2 shows the eight different alignment configurations for 2*4 sub-arrays of a 6:8 balanced block modulation code
- Fig. 3 shows the probability function for configurations 2 - 5 shown in Fig. 2, and Fig. 4 shows a flow-chart illustrating the present invention.
- Fig. 1 shows an optical holographic device according to the present invention using phase conjugate read out.
- This optical device comprises a radiation source 100, a collimator 101, a first beam splitter 102, a spatial light modulator 103, a second beam splitter 104, a lens 105, a first deflector 107, a first telescope 108, a first mirror 109, a half wave plate 110, a second mirror 111, a second deflector 112, a second telescope 113, a detector 114, an alignment unit 115 and a decoding unit 116.
- the optical device is intended to record in and read data from a holographic medium 106.
- the alignment unit 115 and the decoding unit 116 preferably form an electronic device 117, such as a dedicated integrated circuit or other hardware, that is separately distributed and that can, for instance, be added to existing holographic optical devices.
- the functions of the alignment unit 115 and the decoding unit 116 can also be implemented in software running, e.g., on a computer or a microprocessor.
- the signal beam SB is spatially modulated by means of the spatial light modulator 103.
- the spatial light modulator 103 comprises transmissive areas and absorbent areas, which corresponds to zero and one data-bits of a data page to be recorded.
- the signal beam After the signal beam has passed through the spatial light modulator 103, it carries the signal to be recorded in the holographic medium 106, i. e. the data page to be recorded.
- the signal beam is then focused on the holographic medium 106 by means of the lens 105.
- the reference beam RB is also focused on the holographic medium 106 by means of the first telescope 108.
- the data page is thus recorded in the holographic medium 106, in the form of an interference pattern as a result of interference between the signal beam SB and the reference beam RB.
- a data page has been recorded in the holographic medium 106
- another data page is recorded at a same location of the holographic medium 106.
- data corresponding to this data page are sent to the spatial light modulator 103.
- the first deflector 107 is rotated so that the angle of the reference signal with respect to the holographic medium 106 is modified.
- the first telescope 108 is used to keep the reference beam RB at the same position while rotating.
- An interference pattern is thus recorded with a different pattern at a same location of the holographic medium 106. This is called angle multiplexing.
- a same location of the holographic medium 106 where a plurality of data pages is recorded is called a book.
- the wavelength of the radiation beam may be tuned in order to record different data pages in a same book. This is called wavelength multiplexing.
- Other kinds of multiplexing, such as shift multiplexing, may also be used for recording data pages in the holographic medium 106. Such multiplexing techniques are also described in the above-cited document "Holographic Data Storage Systems".
- the spatial light modulator 103 is made completely absorbent, so that no portion of the beam can pass trough the spatial light modulator 103.
- the first deflector 107 is removed, such that the portion of the beam generated by the radiation source 100 that passes through the beam splitter 102 reaches the second deflector 112 via the first mirror 109, the half wave plate 110 and the second mirror 111. If angle multiplexing has been used for recording the data pages in the holographic medium 106, and a given data page is to be read out, the second deflector 112 is arranged in such a way that its angle with respect to the holographic medium 106 is the same as the angle that were used for recording this given hologram.
- the signal that is deflected by the second deflector 112 and focused in the holographic medium 106 by means of the second telescope 113 is thus the phase conjugate of the reference signal that were used for recording this given hologram. If for instance wavelength multiplexing has been used for recording the data pages in the holographic medium 106, and a given data page is to be read out, the same wavelength is used for reading this given data page.
- the phase conjugate of the reference signal is then diffracted by the information pattern, which creates a reconstructed signal beam, which then reaches the detector 114 via the lens 105 and the second beam splitter 104. An imaged data page is thus created on the detector 114, and detected by said detector 114.
- the detector 114 comprises pixels.
- each pixel corresponds to a bit of the imaged data page
- the detector 114 has more pixels than the imaged data page, i.e. the image is oversampled by the detector 114.
- the imaged data page should be carefully aligned with the detector 114, in such a way that one bit or a given number of bits of the imaged data page impinges on the corresponding pixel of the detector 114.
- there are many degrees of freedom in the system so that the imaged data page is not always carefully aligned with the detector 114.
- a displacement of the holographic medium 106 with respect to the detector 114, in a direction parallel to the axis of the reconstructed signal beam leads to a magnification error, which means that the size of a bit (or a give number of bits) of the imaged data page is different from the size of a pixel of the detector 114.
- the data is encoded using a balanced or unbalanced block modulation code to achieve a low user bit error rate.
- a balanced block modulation code e.g. a 6:8 code
- the data page is divided into subarrays of a predetermined number (e.g.
- each of these subarrays contains a predetermined number of zeros and ones (for subarrays of 8 pixels contains exactly 4 zeros and 4 ones).
- the data page is also divided into subarrays of a predetermined number of pixels, but the predetermined number of zeros is different from the predetermined number of ones. These numbers are, however, equal for all subarrays. To illustrate the invention, in the following a balanced 6:8 block modulation code shall be considered.
- the summed intensity of each block will always be 4 (for the exemplary 6:8 code having in each block four ones and four zeros) and thus the variation will ideally be zero.
- the code constraint of four zeros and four ones is absent, resulting in considerable variation over the data page of this summed intensity.
- Fig. 2 shows the eight different alignment configurations Cl to C8 for subarrays of 2*4 pixels of the this exemplary code, of which only the first configuration Cl is aligned.
- the solid lines S indicate the boundary of the 2*4 subarrays
- the dashed lines D indicated the individual pixels
- the filled blocks B are the 2*4 domains (only one shown per configuration) indicating the assumed alignment of the subarrays in said configuration.
- the intensities of a number of said 2*4 domains are summed and evaluated as explained in the following.
- FIG. 4 A flowchart illustrating the main steps of the general idea of the present invention is shown in Fig. 4. After capturing an image (step Sl) as described above in the usual manner an iterative procedure starts in which the correct alignment of the subarrays in the captured image is determined.
- a first alignment of the blocks is assumed, i.e. one of all possible configurations (e.g. for the exemplary 6:8 code one of the eight different configurations Cl to C8 shown in Fig. 2) is selected, and it is determined whether or not said alignment is correct.
- the probability function is determined as described above with reference to Figs. 2 and 3 by summing the intensities for 2*4 blocks for a plurality of blocks, in particular for a substantial part of the image, in order to have sufficient statistics.
- a parameter, preferably the width, of the probability function obtained in said iteration is determined, and based thereon it is decided whether the parameter fulfills a predetermined condition or not, e.g. if the width is smaller than a predetermined width or not.
- the decision in step S3 can be that the blocks are not aligned whereafter in a next iteration steps S2 and S3 will be carried out.
- the assumed alignment will be changed, i.e.
- step S6 the block modulated data from the captured image are decoded based on the determined alignment of the blocks, i.e. the zeros and ones are determined using preferably a standard sorting algorithm. Thereafter, the read-out of the data page is basically finished (step S6).
- the iteration is preferably continued until the correct alignment has been found.
- the optical holographic device of the present invention fulfills the following (not mandatory) conditions, which enable an easier and faster read-out of the data page using the method of the present invention.
- each pixel on the SLM 103 corresponds exactly to one pixel on the detector array 114:
- Scaling pixels of the SLM and the detector array have the same size.
- Rotation the pixel rows/columns of the SLM and the detector are aligned parallel.
- Translation the center of the pixels of the SLM and detector array coincide.
- the invention can also be applied for unbalanced block modulation codes.
- the distribution as shown in Fig. 3 will be distorted, i.e. the peak position shifts and the distribution (probability) function has an asymmetric profile.
- bit as used in the present application shall not be limited to the meaning "binary bit” having only two different values, but shall be construed as meaning "m-ary symbol” being able to having more than two different, distinguishable values.
- bit as used in the present application shall not be limited to the meaning "binary bit” having only two different values, but shall be construed as meaning "m-ary symbol” being able to having more than two different, distinguishable values.
- the pixel intensities are distributed in two peaks (for aligned blocks): one peak around a certain low intensity level and the other peak around a higher intensity level.
- the width of the determined probability function it is also not mandatory to determine the width of the determined probability function, but other features of the probability function could be evaluated as well to get more information, such as, for instance, the level of the highest peak, skewness, kurtosis or other higher order momenta of a (probability) distribution.
- a computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.
- a suitable medium such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.
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- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
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- Holo Graphy (AREA)
- Optical Recording Or Reproduction (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2009528830A JP2010504551A (en) | 2006-09-21 | 2007-09-17 | Optical holographic device and method with alignment means |
EP07826408A EP2067139A1 (en) | 2006-09-21 | 2007-09-17 | Optical holographic device and method with alingnment means |
US12/441,580 US20090323500A1 (en) | 2006-09-21 | 2007-09-17 | Optical holographic device and method with alingnment means |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP06121007 | 2006-09-21 | ||
EP06121007.6 | 2006-09-21 |
Publications (1)
Publication Number | Publication Date |
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WO2008035274A1 true WO2008035274A1 (en) | 2008-03-27 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2007/053746 WO2008035274A1 (en) | 2006-09-21 | 2007-09-17 | Optical holographic device and method with alingnment means |
Country Status (7)
Country | Link |
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US (1) | US20090323500A1 (en) |
EP (1) | EP2067139A1 (en) |
JP (1) | JP2010504551A (en) |
KR (1) | KR20090057123A (en) |
CN (1) | CN101517643A (en) |
TW (1) | TW200830302A (en) |
WO (1) | WO2008035274A1 (en) |
Families Citing this family (2)
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US8742982B2 (en) * | 2010-03-30 | 2014-06-03 | Sony Corporation | Indirect radar holography apparatus and corresponding method |
TWI457921B (en) * | 2011-09-28 | 2014-10-21 | Univ Nat Chiao Tung | Holographic data storage system and image recognition method thereof |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2000268381A (en) * | 1999-03-16 | 2000-09-29 | Fuji Xerox Co Ltd | Method and device for optical reproduction |
WO2005057584A1 (en) * | 2003-12-08 | 2005-06-23 | Koninklijke Philips Electronics N.V. | Alignment of holographic image on detector |
EP1610309A2 (en) * | 2004-06-24 | 2005-12-28 | Daewoo Electronics Corporation | Image correction method for holographic digital data storage system |
US20060203689A1 (en) * | 2005-03-14 | 2006-09-14 | Fujitsu Limited | Reproducing apparatus, recording/reproducing apparatus and reproducing method for optical recording medium |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5838650A (en) * | 1996-06-26 | 1998-11-17 | Lucent Technologies Inc. | Image quality compensation method and apparatus for holographic data storage system |
US7239594B2 (en) * | 2003-02-07 | 2007-07-03 | Imation Corp. | Self-referenced holography using element formed on a holographic medium |
US7656564B2 (en) * | 2004-06-24 | 2010-02-02 | Daewoo Electronics Corporation | Apparatus and method for compensating for pixel distortion in reproduction of hologram data |
JP2007066377A (en) * | 2005-08-30 | 2007-03-15 | Sony Corp | Recorder, recording method and hologram recording medium |
-
2007
- 2007-09-17 WO PCT/IB2007/053746 patent/WO2008035274A1/en active Application Filing
- 2007-09-17 KR KR1020097007785A patent/KR20090057123A/en not_active Application Discontinuation
- 2007-09-17 US US12/441,580 patent/US20090323500A1/en not_active Abandoned
- 2007-09-17 EP EP07826408A patent/EP2067139A1/en not_active Withdrawn
- 2007-09-17 JP JP2009528830A patent/JP2010504551A/en active Pending
- 2007-09-17 CN CNA2007800352600A patent/CN101517643A/en active Pending
- 2007-09-19 TW TW096134969A patent/TW200830302A/en unknown
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2000268381A (en) * | 1999-03-16 | 2000-09-29 | Fuji Xerox Co Ltd | Method and device for optical reproduction |
WO2005057584A1 (en) * | 2003-12-08 | 2005-06-23 | Koninklijke Philips Electronics N.V. | Alignment of holographic image on detector |
EP1610309A2 (en) * | 2004-06-24 | 2005-12-28 | Daewoo Electronics Corporation | Image correction method for holographic digital data storage system |
US20060203689A1 (en) * | 2005-03-14 | 2006-09-14 | Fujitsu Limited | Reproducing apparatus, recording/reproducing apparatus and reproducing method for optical recording medium |
Also Published As
Publication number | Publication date |
---|---|
EP2067139A1 (en) | 2009-06-10 |
US20090323500A1 (en) | 2009-12-31 |
CN101517643A (en) | 2009-08-26 |
TW200830302A (en) | 2008-07-16 |
KR20090057123A (en) | 2009-06-03 |
JP2010504551A (en) | 2010-02-12 |
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