TOP > 外国特許検索 > HOLOGRAPHIC MEMORY REPRODUCTION DEVICE AND HOLOGRAPHIC MEMORY REPRODUCTION METHOD, DEMODULATION DEVICE AND DEMODULATION METHOD, AND OBSERVATION DEVICE AND OBSERVATION METHOD

HOLOGRAPHIC MEMORY REPRODUCTION DEVICE AND HOLOGRAPHIC MEMORY REPRODUCTION METHOD, DEMODULATION DEVICE AND DEMODULATION METHOD, AND OBSERVATION DEVICE AND OBSERVATION METHOD 新技術説明会

外国特許コード F120006550
整理番号 SHINGI20120228
掲載日 2012年5月10日
出願国 世界知的所有権機関(WIPO)
国際出願番号 2011JP005841
国際公開番号 WO 2012053198
国際出願日 平成23年10月19日(2011.10.19)
国際公開日 平成24年4月26日(2012.4.26)
優先権データ
  • 特願2010-234640 (2010.10.19) JP
発明の名称 (英語) HOLOGRAPHIC MEMORY REPRODUCTION DEVICE AND HOLOGRAPHIC MEMORY REPRODUCTION METHOD, DEMODULATION DEVICE AND DEMODULATION METHOD, AND OBSERVATION DEVICE AND OBSERVATION METHOD 新技術説明会
発明の概要(英語) The present invention relates to a reproduction device of a holographic memory capable of precisely reproducing multi-value phase information without being influenced by noise. This holographic memory reproduction device comprises: a hologram diffraction ray generation unit which irradiates a first reference ray to the holographic memory and generates a diffraction ray of the first hologram; a hologram generation unit which changes the phase of a second reference ray which may interfere with the diffraction ray of the first hologram and generates a second hologram from the diffraction ray of the first hologram and the second reference ray to which the phase has been changed; a detection unit which detects the intensity distribution of the second hologram; and a processing unit which demodulates the phase modulation signal or the space quadrature amplitude modulation signal on the basis of the intensity distribution.
従来技術、競合技術の概要(英語) BACKGROUND ART
To this, the optical memory, CD or DVD, a Blu-ray Disc 2 of the three-dimensional recording method has been developed in the center of the optical disk. However, the three-dimensional recording system 2 is led to the diffraction limit is reached and, as a result of a large capacity is more difficult. Therefore, in recent years, led to the three-dimensional recording system 3 has been actively developed. 3 2 Three-dimensional recording method is adopted if the recording capacity than a three-dimensional recording system can be increased to be 100-1000 times or more. In theory can also be a secondary optical memory 100TB.
Have led to an increase in the capacity as a technology that is, 1) near-field light recording system, 2) two-photon absorption in the memory 2, 3) and one 3 of a holographic memory. 1) Near-field light recording method, the size of the light in the wavelength of light in the 'near-field light' is used in a recording method. The near-field light recording system, basically the three-dimensional recording method and in the 2, the near-field light is used for high-density recording that exceeds the diffraction limit that can be realized. Also, 2) in the memory 2 is two-photon absorption, the nonlinear effect of the intensity dependence can be used to access two-dimensionally on the recording medium 3 can be three-dimensional recording method in the optical memory 3. To these techniques, 3) is a holographic memory, interference between the signal light and reference light generated by the multiple-recorded by the hologram, the recording medium 3 without a two-dimensional multi-recording can be performed in the optical memory.
The above-mentioned 1) -3) of the optical memory is, at the present time in the range between about 500 GB - 1TB to achieve a recording capacity. Therefore, from the viewpoint of the recording capacity, the above-mentioned 1) -3) of the superiority or inferiority between the led is not a significant difference. However, from the viewpoint of data transfer rate, above 1) -3) of the optical memory 2 among the two-dimensional spatial function of the parallel-input to the holographic memory is a large advantage. In recent years, in response to a speed of more than two microseconds (Spatial Light Modulator spatial light modulator; hereinafter may be referred to as' SLM ') and the like have been developed. Such a high-speed response can be applied to the SLM in the holographic memory, with transfer rates above 100Gbps could be realized.
Is a holographic memory, and high data transfer rate of the high-density recording can be realized from both, the practical use as a next generation optical memory has been expected. The current recording capacity of a holographic memory has been developed, about 600 GB - 1TB/disk (for example, see Non-Patent Document 1). HDD 1 (3.5 - inch, 2TB storage capacity) of 333 GB has a recording capacity of one of the two platters is made, is a holographic memory, magnetic recording media in practical use from the viewpoint of the recording capacity compared to the present invention to 2-3 times. In addition, the holographic memory is, in theory can be extended to 10-100 times the recording capacity further considered. In such a situation, to increase the recording capacity of a holographic memory as an object, but only up to this point the intensity modulation method, phase modulation has been studied also a holographic memory. However, the holographic method is phase modulation, phase modulation by the light detector cannot be detected directly by the signal, the phase modulation signal in some way to convert the signal must be detected from a problem.
The intensity modulation method is the most popular modulation method, so far have been reported many cases (for example, see Non-Patent Document 1-3). Information can be recorded using holography and has been suggested that the first (non-patent document 2) from the document, a product placed in the field of recent literature (Non-Patent Document 1, 3) up to, using many of the holographic recording system, the value 2 (0 and 1) using the intensity modulation of the present invention. However, intensity modulation is of a simple optical system while the advantage of being able to construct a system, the laser light irradiation region and the peripheral area of the central portion of the exposure intensity difference is increased, the dynamic range of the recording medium significantly for consumption, has a problem of poor recording efficiency. This problem is, in general the Fourier transform hologram, the Fourier transform image of all of the pixels near the center of the intensity proportional to the sum of the amplitude, the laser light is irradiated near the center and the peripheral portion of the exposure increases the intensity difference occurs due to (for example, see Non-Patent Document 4).
The intensity of the modulation method as a method to mitigate the problem, the value information to the block 2 is referred to as encoding the plurality of pixels dispersed, only the portion of the pixels in the block representing data can recognize the method of using the modulation code. By using a modulation code in this manner, errors due to crosstalk between pixels can be reduced. In addition, the modulation code is used, the laser light is irradiated near the center portion and the peripheral portion to reduce a difference between the exposure intensity can be increased by increasing the number of multiplex recording, efficient recording can be achieved (for example, Non-Patent Document 5, reference 6). However, the modulation code is used for, '(the number of bits per block 1 of the recording) /(number of pixels per block 1) ' defined in the code rate is below 1. This is, in the case of using a modulation code with a recording capacity of each block, a modulation code is not used in principle less than the recording capacity of the means.
In order to increase the recording capacity of a holographic memory, a plurality of information per one pixel 1 is recorded, that is code rate is greater than 1 and method is needed. 1 In order to realize more than one code rate, 0, 1 of the multi-level signal exceeds the threshold value 2 and it is necessary to use. Is divided into several levels of the multilevel signal by the light intensity can be realized, whereby the code rate can be dramatically improved. However, the current in the direct detection method, accuracy of the detection system for the noise, an increase in the number of the reproduction by the multi-valued signal to noise ratio considerably deteriorates (for example, see Non-Patent Document 7).
In the intensity modulation method, laser light irradiation region of the central portion and the peripheral portion becomes large and the difference of the exposure intensity, the dynamic range of the recording medium is a problem that the consumption significantly, can be solved by a method in which phase modulation. The phase modulation method is, the phase of the lightwave is modulated using a method of performing, in recent years been attracting attention. For example, phase modulation, the phase of the pixel when the light waves 0, the other pixel signals of the phase information as π representation. A spatial light modulator (SLM) 2 generated by one of the pixels included in the two-dimensional page data, and when the pixel is equal to the number of 0 π, the vicinity of the center of the laser beam irradiation regions at the peripheral portions of the exposure intensity difference does not occur, thereby preventing useless consumption of the dynamic range of the recording medium can be suppressed. This is, contribute significantly to the increase in the number of multiplex recording. However, such as a CCD is a photoelectric conversion device has sensitivity only to the intensity of light, phase information cannot be directly detected. Therefore, in order to detect the phase information, prior to light detection in the phase must be converted to intensity. The phase modulation method, and this point is a large problem.
The holographic phase modulation type in order to realize the phase detection scheme of some embodiments to have been proposed (for example, see Non-Patent Document 4, 8, 9).
In non-patent document 4, a holographic memory used as a phase detection method, edge detection (Edge-Detection) method has been proposed. The edge detection method, a phase modulation type of a holographic memory in the method to take advantage of the features. A phase modulation type in the holographic memory, the intensity of the center of the Fourier transform image (DC component) are missing, the playback is performed only in the AC component of the other. This is, the reproduced image (the actual spatial distribution) and 0 π boundary portion of the pixels in the intensity of the enhancement means. In other words, known as a reference pixel, the intensity of the highlighted boundary for all the pixels if it follows the fact that the phase can be determined. In this method, an intensity-modulation type phase modulation optical system and does not change any holographic type holographic memory can achieve the advantage that on the other hand, is not suitable for the detection of multi-level phase modulation signal has a problem.
In non-patent document 8, using a birefringent medium is a phase detection method has been proposed. This technique is, π / 4 wavelength plate is used for the reproduction light and the circularly polarized light, then passes through a birefringent medium. Thereby a slight deviation of the reproducing light beam interfere with each other, the intensity pattern is obtained. The pre-designed number of pixels shifted by the birefringent medium can be determined, the resulting intensity pattern is determined from the phase information can be discarded. This technique, the experiment conducted by the positional deviation in the literature that high resistance is known and, for the deviation of the phase detection is sensitive to a very attractive approach. However, this method, it is difficult to detection of the multilevel signal, further high-precision design is required of the birefringent medium has a problem.
In non-patent document 9, optical beam as the recording method is noted that the collinear optical system as a specialized holographic phase modulation type, the optical phase lock type collinear hologram has been proposed. In this method, the time of reproduction of collinear hologram, a hologram recorded in the other collinear and the normal of the reference light, the phase of the known phase-locked can be irradiated simultaneously, the intensity information is recorded in the phase information is read. In this method, for transmitting through the hologram in a recording phase-locked, the phase distribution of the phase hologram having a diffraction grating in the affected due to propagation. This is, the phase of the detection surface can be a cause of an error. Also in this method, the phase with high accuracy is difficult to record and reproduce information, the number remains in the multi-phase 2-4 value.
  • 出願人(英語)
  • ※2012年7月以前掲載分については米国以外のすべての指定国
  • NATIONAL UNIVERSITY CORPORATION HOKKAIDO UNIVERSITY
  • 発明者(英語)
  • OKAMOTO, Atsushi
  • KUNORI, Keisuke
  • TAKABAYASHI, Masanori
国際特許分類(IPC)
指定国 National States: AE AG AL AM AO AT AU AZ BA BB BG BH BR BW BY BZ CA CH CL CN CO CR CU CZ DE DK DM DO DZ EC EE EG ES FI GB GD GE GH GM GT HN HR HU ID IL IN IS JP KE KG KM KN KP KR KZ LA LC LK LR LS LT LU LY MA MD ME MG MK MN MW MX MY MZ NA NG NI NO NZ OM PE PG PH PL PT QA RO RS RU RW SC SD SE SG SK SL SM ST SV SY TH TJ TM TN TR TT TZ UA UG US UZ VC VN ZA ZM ZW
ARIPO: BW GH GM KE LR LS MW MZ NA RW SD SL SZ TZ UG ZM ZW
EAPO: AM AZ BY KG KZ MD RU TJ TM
EPO: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
OAPI: BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG
ライセンスをご希望の方、特許の内容に興味を持たれた方は、下記までご連絡ください

PAGE TOP

close
close
close
close
close
close