JP4479282B2 - Recording medium curing method and hologram recording apparatus - Google Patents

Description

  The present invention relates to a hologram recording apparatus, and more particularly to a cure method for stabilizing a hologram recording medium on which data is recorded.

  In recent years, holographic technology has been rapidly developed for the practical application of holographic memory, which is attracting attention as a candidate for powerful storage that competes with next-generation and next-generation optical discs. Thus, a hologram recording / reproducing system for recording / reproducing a large amount of data has been proposed (see, for example, Non-Patent Document 1).

  In such a hologram recording / reproducing apparatus, coherent laser light emitted from a laser light source is separated into signal light and reference light by a beam splitter, and then the signal light is intensity-modulated with recording data and irradiated onto a hologram recording medium. At the same time, since the reference light is irradiated onto the hologram recording medium, interference fringes generated by the interference between the signal light and the reference light are recorded on the hologram recording medium.

  When the hologram recording medium is made of a photopolymer, the interference fringes are recorded while the monomer is changed to a polymer, but after data recording, a process called curing is generally required to polymerize the remaining monomer. This includes a method of applying an incoherent laser beam to the entire hologram recording medium or a halogen lamp. However, in these methods, a separate optical system must be prepared to cure the hologram recording medium, which increases the scale of the apparatus. In addition, when the hologram recording medium is locally cured, there are many inconveniences such as masking other than the portion to be cured.

Therefore, in order not to increase the scale of the apparatus, there is a method in which the reference beam is applied to the entire hologram recording medium at an angle different from that at the time of recording and cured. However, since the reference light is a coherent light, when the hologram recording medium is irradiated, the reflected light in the hologram recording medium interferes with the reference light, and a new interference fringe (noise) is recorded in the curing process. There is a problem that this causes deterioration of the recorded image, which leads to an increase in the error rate.
IBM J.RES DEVELOP VOL 44 NO.3 MAY 2000 `` Holographic data storage ''

  In order to solve the above problem, when the hologram recording medium after data recording is cured using the reference light, for example, in the case of an angle multiplexing recording apparatus, the incident angle of the reference light to the hologram recording medium There is also a method of reducing the coherency of the reference light by changing the angle of the mirror changing the light at high speed and swinging the reference light irradiation angle at high speed. However, in order to use this method, a device other than the angle multiplexing method requires a mirror that swings the reference light at a high speed, which also increases the size of the device.

  The present invention has been devised in view of the above circumstances, and an object of the present invention is to facilitate a hologram recording medium using signal light without increasing the scale of the apparatus or deteriorating the recorded image due to curing. There are provided a recording medium curing method capable of curing surely and locally curing a hologram recording medium without using a jig such as a mask, and a hologram recording apparatus using the recording medium curing method. There is.

In order to solve the above problems and achieve the object of the present invention, the recording medium curing method of the present invention records interference fringes generated by interference between signal light intensity-modulated by data and reference light on a hologram recording medium. , A recording medium curing method for stabilizing the hologram recording medium, in which the signal light has almost no coherency, and the signal light is generated by a random pattern that changes at high speed so that the signal light becomes pseudo incoherent light. And a step of irradiating the recorded hologram recording medium with the signal light intensity-modulated by the random pattern.

The hologram recording apparatus of the present invention is a hologram recording apparatus that records interference fringes generated by interference between signal light intensity-modulated by data displayed on a spatial light modulator and reference light on a hologram recording medium, Display means that displays a random pattern that changes at high speed on the spatial light modulator and a random pattern that changes at high speed so that the coherency of the signal light is almost eliminated and this signal light becomes pseudo-incoherent light. Irradiating means for irradiating the hologram recording medium after data is recorded with the signal light whose intensity is randomly modulated by the spatial light modulator.

  As described above, in the present invention, when the signal light is intensity-modulated with a random pattern that changes at high speed, the wavefront changes at high speed, so that the coherency is almost eliminated and the light becomes pseudo incoherent light. Therefore, if the hologram recording medium after data recording is irradiated with the signal light that has been intensity-modulated by this random pattern and cured, no interference will occur even if this signal light and its reflected light intersect, so noise will be generated on the recording medium. Since recording is not performed, curing can be performed without deterioration of the recorded image.

According to the present invention, the hologram recording medium is cured using pseudo-incoherent signal light whose intensity is modulated by a random pattern that changes at high speed and the wavefront changes at high speed, so that the recorded image is not deteriorated. The recording medium can be cured easily and reliably.
In addition, by using the servo of the signal light optical system as it is, it is possible to accurately irradiate only the predetermined range of the hologram recording medium with the signal light intensity-modulated by the random pattern and cure only the range, such as a mask. The hologram recording medium can be locally cured easily without using the jig.
Furthermore, since the intensity of the signal light can be randomly modulated by displaying a random pattern that changes at a high speed on the spatial light modulator that modulates the intensity of the signal light during recording, any type of hologram recording device can be used. However, since there is no need to add a dedicated part or optical system, the above effect can be obtained easily and inexpensively without increasing the scale of the apparatus.

  The hologram recording medium can be cured easily and reliably using signal light, and the hologram recording medium can be used without using a jig such as a mask. The purpose of locally curing the hologram recording medium is easily realized by curing the hologram recording medium using signal light whose intensity is modulated by a random pattern that changes at high speed and the wavefront changes at high speed.

  FIG. 1 is a diagram showing a configuration of a main part of a hologram recording apparatus according to an embodiment of the present invention. The hologram recording apparatus intensity-modulates the signal light 100 with a data page, and also a spatial light modulator 1 that modulates the intensity with a random pattern, which will be described later, and a Fourier lens 2 that focuses the intensity-modulated signal light 100 onto the hologram recording medium 3. The hologram recording medium 3 for recording the interference fringes of the signal light 100 and the reference light 200, the inverse Fourier lens 4 for imaging the diffracted light generated from the hologram recording medium 3 during reproduction on the image sensor 5 such as a CCD, The image sensor 5 that performs photoelectric conversion and converts it into an image signal, and the spatial light modulator driving device 6 that performs display control of the spatial light modulator 1 and control to generate and display a random pattern. Note that the hologram recording apparatus does not include the inverse Fourier lens 4 and the imaging element 5, but for the sake of convenience, the reproducing light optical system is also described for the sake of clarity of the positional relationship of the signal light optical system.

  Next, the operation of the present embodiment will be described. At the time of recording, the spatial light modulator driving device 6 displays a data page on the spatial light modulator 1. Laser light emitted from a laser light source (not shown) is divided into a signal light 100 and a reference light 200 by a beam splitter or the like, and the signal light 100 is intensity-modulated by a data page displayed on the spatial light modulator 1 and then a Fourier lens. 2 is focused on the hologram recording medium 3. At the same time, since the reference light 200 is also focused on the hologram recording medium 3 by a reference light optical system (not shown), interference fringes generated by the interference between the signal light 100 and the reference light 200 are recorded on the recording spot (here, three-dimensional). Recorded). When recording of data on the hologram recording medium 3 is completed by the same recording operation, curing for stabilizing the hologram recording medium 3 is performed.

  Next, the curing operation described above will be described. When the curing operation is started, the reference light 200 is blocked by a shutter or the like (not shown) and is not irradiated onto the hologram recording medium 3, and only the signal light 100 is incident on the spatial light modulator 1. The random pattern is switched at a high speed by the spatial light modulator driving device 6 and displayed at the detail level of the minimum pixel unit. Thereby, the hologram recording medium 3 is irradiated with signal light that is randomly intensity-modulated with a random pattern that is switched at a high speed of the spatial light modulator 1, and curing is performed. At this time, when the entire hologram recording medium 3 is cured, the recording optical system such as the Fourier lens 2 moves or the hologram recording medium 3 moves, and the signal light whose intensity is randomly modulated is generated by the hologram recording medium 3. It is assumed that a servo operation that irradiates the whole is performed.

  FIG. 2 is a flowchart showing an operation procedure of the spatial light modulator driving device 6 during the cure operation. When the spatial light modulator driving device 6 enters the cure operation (step S1), a random pattern is generated (step S2), and this is displayed on the spatial light modulator 1 as shown in FIG. 3A (step S3). ). Thereafter, when the switching timing of the currently displayed random pattern comes (step S4), if the curing operation is not completed (step S5), the process returns to step S2, generates the next random pattern, and proceeds to step S3. .

  After that, as long as the curing operation is not finished, the spatial light modulator driving device 6 generates different random patterns one after another, and these random patterns are applied to the spatial light modulator 1 as shown in FIGS. 3 (B), 3 (C), ... are displayed in sequence as shown in. The display switching of the random pattern is performed at a very high speed in time for the display response of the spatial light modulator 1 set at the switching timing in step S4. Thereafter, when the curing operation is finished (step S5), the spatial light modulator driving device 6 finishes the process.

  Therefore, at the time of curing, the signal light 100 is intensity-modulated by various random patterns displayed and displayed on the spatial light modulator 1 at high speed, and the wavefront is changed at high speed, so that the coherency is almost eliminated, and the pseudo incoherent light become. Therefore, since the signal light does not interfere with the reflected light during curing and noise is not recorded, the hologram recording medium 3 can be cured without deterioration of the recorded image data.

  FIG. 4 is a cross-sectional view for explaining a change in the state of the hologram recording medium 3 before and after curing. FIG. 4A shows the state of the hologram recording medium 3 before curing, and the monomer 22 remains with respect to the polymer 21. When cured, all of the residual monomer 22 is changed to the polymer 21 and no further reaction takes place, and the hologram recording medium 3 becomes stable.

  Diffracted light generated when the hologram recording medium 3 cured as described above is irradiated with the same reference light (illumination reference light) 200 as that during recording is applied to the image sensor 5 by the inverse Fourier lens 4. An image is formed and data is reproduced.

  According to the present embodiment, when the signal light 100 is randomly intensity-modulated by switching and displaying various random patterns on the spatial light modulator 1 at high speed, the signal light 100 becomes pseudo incoherent light. By curing the hologram recording medium 3 using the signal light 100, even if the signal light 100 intersects with the reflected light, interference does not occur and noise grating can be reduced. Therefore, the hologram recording medium 3 can be cured without causing deterioration of the recorded image. At that time, since any type of hologram recording apparatus is equipped with the spatial light modulator 1, it is not necessary to add a special spatial light modulator or optical system for curing, and therefore the scale of the apparatus is increased. The above effects can be obtained without doing so.

  In addition, when the hologram recording medium 3 is cured locally (for example, where data is recorded), an existing servo mechanism for irradiating a predetermined position of the hologram recording medium 3 with the signal light 100 at the time of recording is provided. Therefore, only the above-mentioned local portion can be accurately irradiated with the signal light 100 whose intensity is randomly modulated, so that local curing can be easily performed without using a jig such as a mask.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, it can implement also with another various form in a concrete structure, a function, an effect | action, and an effect.

It is the figure which showed the structure of the principal part of the hologram recording apparatus which concerns on one embodiment of this invention. 2 is a flowchart showing an operation procedure during a curing operation of the spatial light modulator driving device shown in FIG. 1. It is the figure which showed the example of the random pattern displayed on the spatial light modulator shown in FIG. It is sectional drawing explaining the state change of the hologram recording medium before and behind curing shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Spatial light modulator, 2 ... Fourier lens, 3 ... Hologram recording medium, 4 ... Inverse Fourier lens, 5 ... Imaging element, 6 ... Spatial light modulator drive device, 21 ... Polymer, 22 ……monomer.

Claims (8)

A recording medium curing method for stabilizing an hologram fringe recording medium after recording interference fringes generated by interference between signal light intensity-modulated by data and reference light,
A step of intensity-modulating the signal light with a random pattern that changes at high speed so that the coherency of the signal light is almost eliminated and the signal light becomes pseudo-incoherent light ;
Irradiating the recorded hologram recording medium with signal light intensity-modulated by the random pattern;
A recording medium curing method comprising:   The step of intensity-modulating the signal light with a random pattern that changes at high speed is performed by switching and displaying a plurality of different random patterns at high speed on a spatial light modulator that modulates the intensity of the signal light with a display data pattern. The recording medium curing method according to claim 1, wherein the recording medium curing method is performed by passing a signal light through the device.   2. The recording medium curing method according to claim 1, wherein the signal light intensity-modulated by the random pattern irradiates a predetermined range of the hologram recording medium by servo means during data recording.   2. The recording medium curing method according to claim 1, wherein the hologram recording medium is made of a photopolymer material. A hologram recording apparatus for recording interference fringes generated by interference between signal light intensity-modulated by data displayed on a spatial light modulator and reference light on a hologram recording medium,
Display means for displaying on the spatial light modulator a random pattern that changes at high speed so that the coherency of the signal light is almost eliminated and the signal light is set to be pseudo-incoherent light ;
Irradiation means for irradiating the hologram recording medium after the data has been recorded, with the signal light randomly intensity-modulated by the spatial light modulator displaying the random pattern changing at high speed,
A holographic recording apparatus comprising:   The display means includes pattern generation means for sequentially generating a plurality of different random patterns at high speed, and display control means for sequentially displaying the generated random patterns by switching to the spatial light modulator at high speed. 6. A hologram recording apparatus according to claim 5, wherein:   6. The hologram recording apparatus according to claim 5, wherein the irradiating means irradiates the entire hologram recording medium or a predetermined range with the randomly modulated signal light.   6. The hologram recording apparatus according to claim 5, wherein the hologram recording medium is made of a photopolymer material.

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