JPH1116375A - Hologram memory device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact hologram memory device which enables the large capacity recording while the high speed accessibility which is the characteristic of a hologram memory device is not deteriorated. SOLUTION: A hologram memory device has micromirror rows A and B which are respectively composed of a plurality of micromirrors 28 and a micromirror row C which is composed of a plurality of micromirrors 22. An onject light and a reference light are respectively introduced along the micromirror rows A and B and introduced into the same micromirror row C by the displaced micromirrors 28, 28,.... The object light and the reference light are respectively guided to the same position of a hologram recording medium by the displaced micromirrors 22, 22,... of the micromirror row C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a hologram memory device using the principle of holography.

[0002]

2. Description of the Related Art FIG. 10 shows an example of a conventional hologram memory device. Information recording in the hologram memory device shown in FIG. 10 is performed as follows. That is, first,
Laser light emitted from the laser light source 101 is separated into object light and reference light by the beam splitter 102.

[0003] Of these, object light passes through a liquid crystal panel 103 functioning as a page composer. When passing through the liquid crystal panel 103, the object light is added with information as a surface, and is incident on the hologram recording medium 104 made of lithium niobate crystal. The image of the information added by the liquid crystal panel 103 is as shown by 103a, and the image shown in FIG.
In a, for example, a white portion is digital data representing 1 and a black portion is digital data representing 0.

On the other hand, the reference light is transmitted by a mechanical scanner 105.
And is transmitted through the beam splitter 106 to enter the grating mirror 107. The reference light is a grating mirror 1
07, and is incident on the hologram recording medium 104 via the beam splitter 106 and the lens 108.

The object light and the reference light interfere with each other in the hologram recording medium 104, and the interference information is recorded in the hologram recording medium. The angle of incidence of the reference light on the hologram material is determined by the scanner 105.

At the time of reading information, the hologram recording medium 1 is supplied with the reference light at the same angle as when the information is recorded.
The object light is reproduced by irradiating the object light 04, and the reproduced object light is guided to the CCD 109. And CCD
Reference numeral 109 designates an object signal that is photoelectrically converted into an electric signal, and this signal is converted into digital data.

FIG. 11 shows another conventional hologram memory device. Information recording in the hologram memory device shown in FIG. 11 is performed as follows. Beam splitter 1
The reference light separated by 11 is used to deflect the reference light in the vertical direction and the horizontal direction, respectively.
6 (acousto-optic deflector acousto-optic element) and is incident on the hologram recording medium 114 at an incident angle that changes depending on the state of the AODs 115 and 116.

[0008] The object light passes through a frequency correcting AOD 112 for achieving frequency matching with reference light passing through the AODs 115 and 116, and then enters a liquid crystal panel 113 serving as a spatial light modulator. And information is added to the hologram recording medium 114. The object light interferes with the reference light in the hologram recording medium 114, and information is recorded on the hologram recording medium 114.

When reading information, AOD1
The reference beam is adjusted at the same angle as when the information to be read was recorded by adjusting
The object light is reproduced by being incident on the object 14, and the reproduced object light is photoelectrically converted by the CCD 117.

[0010]

However, the conventional hologram memory device has the following problems. That is, in the first and second conventional examples, no effective means for changing the incident positions of the object light and the reference light on the hologram recording medium is not provided. For this reason, the storage capacity of the hologram memory device depends only on the multiplex recording property of the hologram material, and the hologram memory device cannot fully utilize the inherently large storage capacity.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a hologram memory device capable of performing large-capacity recording without impairing the inherent high-speed accessibility of the hologram memory device.

[0012]

In order to achieve the above object, the present invention provides a hologram memory device which performs at least one of recording information on a hologram recording medium and reproducing information from the hologram recording medium. A plurality of optical elements whose directions can be changed are provided, and at least one of the object light and the reference light is guided to the hologram recording medium using the optical elements.

Further, according to the present invention, the plurality of optical elements are arranged so as to form at least one optical element row, and at least one of object light and reference light is guided in a direction along the optical element row. The optical element forming the optical element row is selectively displaced in the optical path of the guided object light or reference light, and the object light or the reference light is guided to the hologram recording medium by the displaced optical element.

Further, according to the present invention, the object light and the reference light are:
Each is guided to the same array of optical elements, and is guided to the hologram recording medium by a pair of optical elements selected from the array of optical elements.

Further, the present invention provides a hologram memory device for reproducing information from a hologram recording medium, a plurality of optical elements capable of changing the direction of light, and an image sensor on which the reproduced object light is incident. Wherein the reproduced object light is guided to the image sensor using the optical element.

Further, the present invention is characterized in that the optical element is a reflecting mirror.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment First, a first embodiment will be described. 1 to 6 are views showing a first embodiment of the present invention. In addition,
In order to facilitate understanding of the following description, an XYZ orthogonal coordinate system is set as shown in the lower left of FIG. 1, and description will be made with reference to this coordinate system as necessary. In FIG. 1, the Z axis extends in the direction normal to the paper surface, and the positive direction is the near side of the paper surface. The coordinate axes added to each figure correspond to the coordinate axes in FIG.

As shown in FIG. 1, the hologram memory device has a first micromirror having a plurality of micromirrors for switching the optical paths of the object light and the reference light and changing the incident angles of the object light and the reference light to the hologram material. Analog micromirror array device (hereinafter referred to as "AMD") 10
And a second A for switching the optical path of the reproduced object light.
MD20. The first AMD 10 and the second AMD 20 operate according to a command from a control device (not shown).

The first AMD 10 and the second AMD 2
The hologram recording medium 30 is disposed between the hologram recording medium 30 and the hologram recording medium 30.

As shown in FIG. 1, a hologram memory device includes a light source device 2 for generating light having good coherence, for example, a laser beam, and a laser beam emitted from the light source device 2 as an object beam and a reference beam. And a beam splitter 3 for separation.

On the optical path of the object light, a beam expander 4 for expanding the object light into parallel light having a predetermined sectional area, and a digital micromirror array device (hereinafter, referred to as a spatial light modulator for adding information to the object light) And a Fourier transform lens 6 a for focusing the object light in each recording medium element of the hologram recording medium 30.

The DMD 5 is a product of TI
(Texas Instrument Incorporated). The addition of information to the object light by the DMD 5 is performed by oscillating each micromirror constituting the DMD 5, and a part of the object light having a predetermined width is converted by the micromirror oriented in the first direction into the light of the Fourier transform lens 6 a. This is performed by deflecting the remaining part of the object light in a direction that does not enter the Fourier transform lens 6 by a micromirror that reflects in the axial direction and faces in the second direction. When the object light is reflected in different directions as described above, the object light incident on the Fourier transform lens 6a is reflected by the Fourier transform lens 6a.
Projected onto a plane perpendicular to the optical axis of the image 103a, a projection image similar to the image 103a (see FIG. 10) described in the related art can be obtained. Thus, information can be added to the object light by the DMD 5.

As a spatial light modulator for adding information to object light, a liquid crystal panel as described in the prior art may be used. In this case, the DMD 5 shown in FIG. 1 may be replaced with a normal reflecting mirror, and the liquid crystal panel may be disposed between the reflecting mirror and the beam expander 3.

On the other hand, mirrors (normal reflecting mirrors) 7a and 7b and a collimator lens 8 are sequentially provided on the optical path of the reference light. The collimator lens 8 expands the reference light and adjusts it to parallel light having a predetermined sectional area.

Further, on the optical path of the object light reproduced at the time of reading information, a Fourier transform lens 6b, a mirror 7c, and a CC as an example of a photoelectric conversion element are provided.
D9 (image sensor) is sequentially provided.

Next, the first AMD 10 and the second AM
D20 will be described in detail.

As shown in FIG. 2A, the first AMD 1
0 denotes a micromirror row (optical element row) A including a plurality of micromirrors (optical elements) 28 arranged at equal intervals in the object light incident direction, that is, the X-axis direction, and a reference light incident direction, that is, X Micromirror row B composed of a plurality of micromirrors 28 arranged at equal intervals along the axial direction
And

Between the micromirror row A and the micromirror row B, a plurality of micromirror rows C comprising a plurality of micromirrors 22 arranged at equal intervals in the Y-axis direction are provided.

The micromirror rows C are provided corresponding to the respective micromirrors 28 constituting the micromirror rows A and B, and the micromirror rows A and B are formed on an extension of the micromirror row C. Micro mirror 2
8 is located.

As shown in FIG. 2A, when the micromirrors 22 constituting each micromirror row C are viewed as a whole, the micromirrors 22 are arranged at equal intervals in the X-axis direction and at the Y-axis. Also in the direction, they are arranged in a matrix on the rectangular substrate 21 at equal intervals.

Therefore, the micromirrors 22 and 28 constituting each of the micromirror rows A, B and C are arranged in a matrix when viewed as a whole.
They are arranged at equal intervals in both the axial direction and the Y-axis direction.

The micromirrors 22 constituting the micromirror row C are provided so as to be swingable about an axis parallel to the X axis. The micromirrors 28 forming the micromirror row A are rotated about an axis rotated by 45 degrees with respect to the X axis, and the micromirrors 28 forming the micromirror row B are rotated 45 degrees with respect to the X axis. Each is provided so as to be swingable about an axis.

As shown in FIG. 2C, the second AMD 20 differs from the first AMD 10 only in that the second AMD 20 does not have the micromirror row A, and is otherwise identical to the first AMD 10. It has a configuration. That is, the second AMD2
The micromirrors 0 are arranged at exactly the same X coordinate and Y coordinate positions as the micromirrors of the first AMD 10. That is, when the micro mirror array B is removed from the first AMD 10 shown in FIG. 2A and the micro mirror array B is turned upside down, the AMD 20 shown in FIG. 2C is obtained.

Next, the hologram recording medium 30 will be described. As shown in FIG. 2B, the hologram recording medium 3
Numeral 0 has a rectangular plate-shaped substrate 30a and a plurality of recording medium elements 31 provided on the substrate 30a and made of a hologram material such as a lithium niobate crystal or a photopolymer.

The recording medium elements 31 are arranged at equal intervals along the Y-axis direction and at equal intervals along the X-axis direction.
Each recording medium element row D constituted by a plurality of recording medium elements 31 and extending in the Y-axis direction is located immediately above any one of the micro mirror rows C of the AMD 10.

The configuration of the hologram recording medium 30 is not limited to the above-mentioned configuration, and the hologram recording medium 30 may be made of one hologram material.

Further, as shown in FIG.
The pitch p of the micromirror 22 in the Y-axis direction is equal to the pitch p of the micromirror 22 in the Y-axis direction. Further, each recording medium element 31 is arranged at the same pitch p as the micromirror 22 and at a position shifted from the micromirror 22 by a half pitch (1 / 2p).

Next, the configuration of the micro mirrors 22 and 28 and the drive mechanism that allows the micro mirrors 22 and 28 to swing freely will be described in detail.

The micromirrors 22 constituting the micromirror row C are formed by a technique such as depositing a reflective metal film on a plate-like member made of a conductive material.

As shown in FIG. 4, each micro mirror 22
Is a fulcrum member 2 provided on the substrate 21 and oriented in the X-axis direction.
5, and a pair of L-shaped beams 23 are connected to the micromirror 22.

The beams 23 have appropriate flexibility, and the end of each beam 23 opposite to the micromirror 22 is supported by a beam base 24 provided on the substrate 21. The micromirror 22 is connected to a power supply 27 via a beam base 24 and a beam 23 formed integrally with the micromirror 22.

An electrode 26 is formed on the substrate 21 below the first portion 22a of the micromirror, and the electrode 26 is also connected to a power supply 27.

The micromirror 22 having the driving mechanism configured as described above applies an appropriate voltage to the micromirror 22 and the electrode 26 by the power supply device 27 so that the first portion 22a of the micromirror 22 and the electrode 26 are connected. By applying a suction force or a repulsion force therebetween, it is possible to rotate around a tangent to the fulcrum member 25 as a rotation center.

That is, when the potential of the micromirror 22 and the potential of the electrode 26 are both 0, the micromirror 22 maintains a horizontal state as shown in FIG.

When voltages having different polarities are applied to the micromirror 22 and the electrode 26 by the power supply device 27, an attractive force acts between the first portion 22a of the micromirror 22 and the electrode 26. The micro-mirror 22 rotates about the tangent line to the fulcrum member 25 by the suction force.

In this case, along with the displacement of the micromirror 22, the longitudinal portion 23a of the beam 23 in the Z-axis direction bends downward. Then, the micromirror 22 stops at a position where the force for restoring the longitudinal portion 23a to the initial state (the state shown in FIG. 4) due to its elasticity and the suction force are balanced. Thus, the micro mirror 22
Takes an inclined state.

As understood from the above description,
The tilt angle of the micro mirror 22 is
Is determined by the balance between the electrostatic attraction force acting between the electrode 23 and the electrode 26 and the spring force of the beam 23.
By continuously changing the potential difference between the electrode 2 and the electrode 26, the tilt angle of the micromirror 22 can be changed continuously (in an analog manner) to an arbitrary angle.

When it is desired to rotate the micro mirror 22 in the reverse direction, the micro mirror 22 and the electrode 26
May be made the same in polarity. In this way, a repulsive force proportional to the magnitude of the voltage acts between the two, and the micromirror 22 can be inclined at an arbitrary angle in the direction opposite to the above.

The structure of the drive mechanism of the micromirror 22 is not limited to the structure shown in FIG. 4, but may be as shown in FIG. In this case, the micromirror 22 is supported by a pair of beams 23 extending in the X-axis direction from the pair of beam bases 24 provided across the micromirror 22 toward the micromirror 22. The tilt angle of the micromirror 22 is determined by the balance with the electrostatic attraction (or repulsion) force.

The micromirrors 28 constituting the micromirror row A and the micromirror row B are shown in FIG.
As schematically shown in (a), the second portion 22b side of the micromirror 22 is set at 4 degrees around a tangent to the fulcrum member 25.
It has a shape that is bent five times. FIG.
The coordinate axes shown in (a) relate to the micromirrors 28 constituting the micromirror row A of the AMD 10.

The micromirror 28 operates according to the same operating principle as the micromirror 22. When the potentials of the electrode 25 and the micromirror 28 are both 0, the second portion 22b of the micromirror 28 is 6
(A) is taken at a position indicated by the solid line (in a state of being inclined by 45 degrees with respect to the XY plane, hereinafter referred to as an “inclination state” or “inclination position”), and between the electrode 25 and the first portion 22 a of the micromirror 28. 6 (a) (a state perpendicular to the XY plane, hereinafter referred to as an "upright state" or "an upright position") by applying a suction force having an appropriate strength. Is available.

The micromirror 28 passes the object light traveling in the negative direction of the X-axis without entering the micromirror 28 when the micromirror 28 is in the inclined state, and the second part when the micromirror 28 is in the upright state. 22b is disposed with a relative positional relationship with the optical path of the object light traveling in the negative direction of the X axis so that the optical path of the object light can be reflected in the positive direction of the Y axis while blocking the optical path of the object light. ing.

The structure of the micromirror 28 is shown in FIG.
However, the present invention is not limited to the one shown in FIG.
The micro mirror 28 may be configured by providing the micro mirror 9. In this case, it is sufficient that the surface of the element 29 indicated by the reference numeral 29a has a function as a reflecting mirror.

Next, the operation of the present embodiment having the above configuration will be described.

First, the operation of writing information on the hologram recording medium 30 will be described.

First, a control device (not shown) is as shown in FIG.
For example, in the micromirror row A of the first AMD 10 shown in FIG.
Is in an upright state, and the other micromirrors 28 are in an inclined state. Similarly, with respect to the micro mirror array B of the AMD 10, only the central micro mirror 28 is in the upright state. That is, one micromirror is selectively displaced from a plurality of micromirrors constituting the micromirror rows A and B, respectively.

Next, laser light is emitted from the light source device 2, and the laser light is separated by the beam splitter 3 into object light and reference light.

The object light is the beam expander 4
And enters the DMD 5. The DMD 5 adds information to the object light and reflects the object light in the negative X-axis direction. Then, the object light enters the space between the hologram recording medium 30 and the first AMD 10.

The reference light is sequentially reflected by the mirrors 7a and 7b, turned in the negative direction of the X-axis, and then adjusted by the collimator lens 8 into parallel light having a predetermined width. The light enters the space between the first AMD 10 and the first AMD 10.

The object light that enters the space and travels in the negative direction of the X-axis passes by the first and second micromirrors from the right of the micromirror row A in FIG. Incident on the central micromirror 28 displaced so as to be located in the object light path, and is reflected by the micromirror 28 in the positive Y-axis direction.

As a result, the object light is shifted from the center (third from the right).
It follows along the micromirror row C). Similarly, the reference light is also used for the central micromirror 28.
, And travels in the negative Y-axis direction along the central micromirror row C like the object light. The subsequent operation will be described with reference to FIG.

As shown in FIG. 3, when the micromirrors 28 of the micromirror rows A and B of the AMD 10 are displaced, the control device (not shown) The micro mirrors 22, 22 adjacent to each other are displaced. That is, a pair of micromirrors of the plurality of micromirrors constituting the micromirror row C are selectively displaced.

In this example, for example, the second micromirror 22 from the right of the micromirror row C of the AMD 10 shown in FIG. 3 is rotated clockwise by an angle α (hereinafter referred to as “inclination state”). The third micromirror 22 is rotated counterclockwise by an angle β to be in an inclined state. The other micromirrors 22 are in a horizontal state (a state parallel to the XY plane). Note that the second AMD in a state inclined at an angle α in FIG.
The 20 micromirrors 22 may be in a horizontal state.

As can be understood from the following description, the relationship between the angle α and the angle β is such that the object light and the reference light reflected by the micromirror 22 in the inclined state intersect in the recording medium element 31. Set in relationship.

The micromirrors 28 in the micromirror row A
The object light reflected by the mirror and traveling in the Y-axis positive direction forms an optical path close to the reflection surface of the micromirror 22 in the horizontal state, and forms the micromirror 22 in the horizontal state.
Slightly above, and is incident on the micromirror 22 in an inclined state. Micro mirror 22 on which object light is incident
Reflects the object light obliquely upward and guides it to the hologram recording medium element 31.

The reference light also passes slightly above the horizontal micromirror 22 like the object light, is reflected by the micromirror 22 inclined at an angle β, and is guided to the hologram recording medium element 31.

The object light and the reference light interfere with each other in the hologram recording medium element 31, and the hologram recording medium element 3
1, information is recorded.

In the present embodiment, as described above, the inclination angle of the micromirror 22 can be changed continuously, so that the angle β of the micromirror 22 that reflects the reference light is changed. By continuously changing the hologram material, multiple information can be written to the same portion of the recording medium element 31 without changing the angle α of the micromirror 22 that reflects the object light by utilizing the multiple recording property of the hologram material. .

In this case, the incident position of the reference light on the recording medium element 31 is slightly shifted, but this does not cause any problem. This is because the object light is light that passes through the Fourier transform optical system (Fourier transform lens 6a) and is focused in a region that can be regarded as a point of the recording medium element 31, whereas the reference light is a predetermined light shaped by the collimator lens 8. This is because interference between the object light and the reference light occurs as long as the irradiation area of the reference light to the recording medium element 31 includes the irradiation area of the object light.

In this embodiment, when the recording medium element 31 to be recorded is changed, the optical path length between the Fourier transform lens 6a and the selected recording medium element 31 changes. For this reason, the width of the object beam at the time of incidence on the recording medium element 31 differs depending on which recording medium element 31 is incident. From the viewpoint of improving the recording density that minimizes such fluctuations in the width of the object light, use of a Fourier transform lens 6a having a focal length long enough to neglect the influence of the change in the optical path length described above is used. Is preferred. Alternatively, the AMD 10 and the hologram recording medium 30 may be replaced as in a second embodiment described later.
And a lens array for correction may be inserted between them. However, since the recording is possible even if the object light is not accurately focused in the recording medium element 31, the above-described improvement is not necessarily required.

In this embodiment, the angle α and the angle β of the micromirror are appropriately changed under the condition that the condition that the reflected object light and reference light intersect within the recording medium element 31 is satisfied. Information can be written to various portions of one recording medium element 31.

Further, by changing the combination of the micromirrors 22 in the inclined state among the micromirrors 22 constituting one micromirror row C (the nth micromirror 22 from the right side in FIG. n
+1 means that the combination with the micromirror 22 is changed. In this case, n is 1 to 4).
Information can be written to another recording medium element 31.

Further, the micromirrors 28 which are set upright from the micromirrors 28 of the micromirror rows A and B
Is selected, and the micromirror row C to which the object light and the reference light are guided is selected, so that information can be written to another recording medium element 31.

Next, the reproduction of the recorded information will be described. In this case, since the object light from the beam splitter 3 is not necessary for reading out information, it is prevented from reaching the hologram recording medium by an optical path blocking means (not shown).

When reading the information recorded on the recording medium element 31, the control unit (not shown) controls the first AM.
The micromirrors 22 and 28 of the D10 micromirror arrays B and C (the micromirrors 28 of the micromirror array A need not be adjusted) are set to the same state as when the information to be read is written, and read. The reference light may be applied to the position where the information is recorded at the same angle as the information recording. In FIG. 3, the micro mirror 22 displayed in a state of being inclined at the angle α may be in a horizontal state.

Then, the recording medium element 3 on which the reference light has entered
1 reproduces the object light at the same output angle 2α as the incident angle 2α of the object light at the time of information recording, and outputs the object light to the substrate 30.
It passes through the opening 32 formed in a.

This object light is the first AM that reflects the reference light.
The second A located just above the micromirror 22 of D10
The light enters the micro mirror 22 of the MD 20.

The micromirror 22 of the second AMD 20 on which the object light is incident is controlled in advance by a controller (not shown) at an angle α (this angle α is the inclination angle α of the micromirror 22 that guides the object light obliquely upward during information recording. Is the same as
The object light incident on the micromirror 22 is reflected in the positive Y-axis direction (horizontal direction).

The object light is the second A in the horizontal state.
An optical path close to the reflection surface of the micromirror 22 of the MD 20 is formed, and the micromirror 2 in a horizontal state is formed.
The micromirror 28 of the micromirror row A of the second AMD 20 that has passed slightly above the second
Incident on. The following operation will be described with reference to FIG.

As shown in FIG. 2C, the object light incident on the micromirror 28 of the second AMD 20 in the upright state is turned in the positive X-axis direction by the micromirror 28, and the micromirror 28 of the second AMD 20 is turned on. 1 from right of mirror row A
Micro-mirror 28 in the second and third tilted states
Hologram recording medium 30 and the second AMD
Then, the light is emitted toward the Fourier transform lens 6b.

The object light is collimated by the Fourier transform lens 6b, reflected by the mirror 7c, and enters the CCD 9.

On the imaging surface of the CCD 9, the DM
An object light equivalent to the object light immediately after passing through D5 is projected. The CCD 9 photoelectrically converts the image and transmits an image signal to a data converter (not shown). Then, the data conversion device converts the image signal into digital data.

As described above, according to the present embodiment, the selection of the recording medium element 31 to which information is written or reproduced can be selected only by changing the state of the micromirror constituting the micromirror array device. Is going. This micromirror has an extremely small mass per sheet. For this reason, the desired recording medium element 31 can be accessed very quickly.

Since the tilt angle of the micromirror can be changed in an analog manner by the balance between the electrostatic force and the spring force, the incident angle and the incident position of the object light and the reference light to the recording medium element 31 are set. Can be easily adjusted. Therefore, the recording capacity of the hologram memory device can be further increased.

In this embodiment, since the micromirrors of each AMD are arranged in a matrix, a wiring system for each micromirror (a wiring system for applying a voltage for driving the micromirrors is not provided). ) Can be divided into a vertical (Y-axis direction) sequence and a horizontal (X-axis direction) sequence so that a specific one micromirror can be designated by a combination of a vertical address and a horizontal address. is there. This can reduce the number of required wirings and simplify the electric circuit.

As can be understood from the above-described operation principle, the access time is constant regardless of which recording medium element 31 of the hologram recording medium 30 is accessed. Therefore, the capacity of the hologram recording medium can be easily increased.

That is, according to the present embodiment, it is possible to greatly increase the capacity of the hologram memory device without impairing the ultra-high-speed accessibility inherent in the hologram memory and without increasing the size of the entire device. it can.

In particular, according to this embodiment, the AMD 10, 2
0 and the hologram recording medium 30 are laminated in the vertical direction (Z-axis direction).
The distance between 0, 20, 30 can be very small. Therefore, by arranging the components constituting the hologram memory device at high density on the substrate 1 (see FIG. 1), it is thin (length in the Z-axis direction) and width (length in the X-axis and Y-axis directions). Hologram memory device having a small size can be obtained. Therefore, the hologram memory device according to the present embodiment can be used, for example, as a substitute for a hard disk device of a notebook personal computer. In addition, this hologram device memory device,
It can also be used as a cassette type ROM in which information is written in advance. For example, it can be used as a cassette-type ROM that stores map information of a car navigation system that requires enormous information.

Second Embodiment Next, a second embodiment will be described. The second embodiment is different from the first embodiment in that a mirror that can be moved in parallel is provided in place of the micro mirror arrays A and B of the AMD, and that the AMD reproduces the object light, the reference light, and the reproduced light. The present embodiment is mainly different from the first embodiment in that a dedicated object light is provided for each object light and a point in which a means for performing optical path length correction is provided, and other configurations are substantially the same as those in the first embodiment. In the second embodiment, the same portions as those in the first embodiment are denoted by the same reference numerals, and overlapping description will be omitted.

In this embodiment, an XYZ coordinate system is set similarly to the first embodiment, and description will be made with reference to this coordinate system as necessary.

As shown in FIG. 7, the hologram memory device according to the second embodiment includes an AMD 40 and an AMD 50 attached to the lower substrate 1a, and an AMD 60 attached to the upper substrate 1b.

The AMDs 40, 50, and 60 are the micro mirror arrays A, B from the AMD 10 in the first embodiment.
Is substantially the same as that obtained by removing, and is constituted only by a plurality of micromirror rows C extending in the Y-axis direction. It is to be noted that the micro mirrors 22 are arranged in a matrix as a whole as in the first embodiment.

The micro mirror array C of the AMD 40
Are located on the same straight line as one of the micro mirror arrays C of the AMD 50.

The micromirrors 22 constituting the AMDs 40, 50 and 60 are different from the micromirrors 22 in the first embodiment in the length l1 and the length of the first portions 22b and the lengths of the second portions 22b of the micromirrors. Only the relationship with l2 is different, and the rest is the same as the first micromirror 22.
That is, the micro mirror 22 in the first embodiment
In the micromirror 22 of the second embodiment, l1 is set to a value larger than l1 while l1 and l2 have the same length.

By setting l2 to be larger than l1, when the micromirror 22 is displaced as shown in FIG. 8, the amount of displacement of the reflecting surface in the Z-axis direction can be increased. When only the micromirror 22 needs to be tilted in one direction as in the present embodiment, the object light and the micromirror 22 when the micromirror 22 is in a horizontal state are required in terms of miniaturization of the micromirror 22. And the inclination angle of the micromirror 22 required to displace the micromirror 22 into the optical path of the object light can be reduced, thereby reducing the load on the electrostatic drive mechanism. This is advantageous in that it can be performed.

A hologram recording medium 30 is provided substantially at the center between the upper substrate 1b and the lower substrate 1a. In the present embodiment, the hologram recording medium 30 is formed of one hologram material.

Micro movable mirrors 80a, 80b and 80c which are movable in the X-axis direction by a linear actuator (not shown) are provided at both ends of the lower substrate 1a and one end of the upper substrate 1b, respectively. Is provided. These movable mirrors play substantially the same role as the micro mirror arrays A and B in the first embodiment.

A Fourier transform lens array including a plurality of Fourier transform lenses 81 is provided between the movable mirror 80a and the AMD 40. The Fourier transform lenses 81 constituting this Fourier transform lens array are arranged along the X-axis direction, and the optical axis of each Fourier transform lens 81 is A
It is located on the extension of each micro mirror row C extending in the Y-axis direction of the MD 40.

Also, the movable mirror 80c and the AMD 6
Between 0 and 0, a Fourier transform lens array including a plurality of Fourier transform lenses 82 is provided. The Fourier transform lenses 82 constituting this Fourier transform lens array are also arranged along the X-axis direction, and the optical axis of each Fourier transform lens 82 is located on an extension of each micro mirror array C extending in the Y-axis direction of the AMD 60. ing.

The hologram recording medium 30 and the AMD4
Fresnel lens arrays 70 for performing optical path length correction are disposed between the lens array 0 and the AMD 60, respectively.
These Fresnel lens arrays 70 are AMD 40 and A
The MD 60 has a number of Fresnel lenses 71 corresponding to each micro mirror 22, and each Fresnel lens array 7.
0 Fresnel lens 71 is an AMD micro mirror 22
Are arranged in a matrix in the same manner as described above. Each Fresnel lens 71 has a corresponding Fourier transform lens 81
Alternatively, the Fourier transform lens 82 and the corresponding Fourier transform lens 6a or 6b constitute a Fourier transform optical system.

Next, the operation of the present embodiment having the above configuration will be described.

First, the operation of writing information on the hologram recording medium 30 will be described.

First, the control device (not shown) sets the movable mirror 80a to the specific micromirror rows C and Y of the AMD 40.
The movable mirror 80b is moved to a position so as to be aligned in a straight line along the axial direction, and the movable mirror 80b is moved to the micro mirror array C of the AMD 50 corresponding to the specific micro mirror array C of the AMD 40 (the specific micro mirror array C of the AMD 40). And the micromirror row C) of the AMD 50 aligned on the straight line along the Y-axis direction and the position to be aligned on the straight line along the Y-axis direction.

In parallel with this, a control device (not shown)
Any one of the micromirrors 22 constituting the micromirror row C of the AMD 40 is rotated by an angle α in the counterclockwise direction in FIG.
Further, one of the micromirrors 22 constituting the micromirror row C of the AMD 50 is rotated clockwise by an angle β in FIG. As shown in FIG. 7, when the n-th micro mirror from the right in the AMD 40 is rotated, the AM 40
Also in D50, the n-th micro mirror from the right is rotated.

Next, laser light is emitted from the light source device 2, and the laser light is separated by the beam splitter 3 into object light and reference light.

Of these, the object light is the beam expander 4
And enters the DMD 5. The DMD 5 adds information to the object light and reflects the object light in the negative X-axis direction. Then, the object light passes through the Fourier transform lens 6a,
The light enters the movable mirror 80a.

The object light is reflected by the movable mirror 80a in the positive Y-axis direction, and the micromirror 2 in a horizontal state is reflected.
2 above the micromirror 22 in an inclined state
Incident on.

The object light is reflected obliquely upward by the micro mirror 22, and enters the hologram recording medium 30 via the Fresnel lens 71.

Here, each Fresnel lens 71 of the Fresnel lens array 70 has a different focal length, and each Fresnel lens 71 converts the object light, which is parallel light added with information by the DMD 5, into a Fourier transform. In cooperation with the lens 6a and the Fourier transform lens 81, it has a function of always focusing within the hologram recording medium 30. That is, the focal length of each Fresnel lens 71 is determined according to the optical path length between the micromirror 22 of the corresponding AMD 40 and the Fourier transform lens 6a.
For this reason, the object light comes to be focused in the hologram recording medium 30, so that the hologram recording medium 3 has a higher density.
0 can record information.

On the other hand, the reference light is adjusted to a parallel light having a predetermined width by the collimator lens 8, and the movable mirror 80b
Incident on.

The reference light is reflected by the movable mirror 80b in the negative direction of the Y-axis, and the micromirror 2 in the horizontal state
2 above the micromirror 22 in an inclined state
Incident on. The object light is reflected obliquely upward by the micro mirror 22 and enters the hologram recording medium 30. The object light and the reference light are transmitted to the hologram recording medium 3.
0, the information is recorded on the hologram recording medium 30.

Next, a case where information is read will be described.

First, the movable mirror 80b and the AMD 50 are set to the same state as the state where the information is written.

Next, the movable mirror 80c is moved so as to be located at the same Y coordinate as the movable mirror 80a when the information was written. In addition, the n-th (n
Is the same as n indicating the number from the right of the micromirror 22 of the AMD 40 that is inclined when writing information.
(It is the same as the inclination angle of the micromirror 22 of D40)
Only in the counterclockwise direction to bring it into an inclined state (see FIG. 8).

Next, the reference light is made incident on the movable mirror 80b. Object light is not necessary for reading information,
An appropriate light path blocking means (not shown) provided on the light path of the object light prevents the light from entering the mirror 80a.

The reference light enters the hologram recording medium 30 via the mirror 80a and the micromirror 22 in the inclined state of the AMD 50, whereby the object light is reproduced.
The object light exits from the hologram recording medium 30 at an emission angle of 2α, and enters the micromirror 22 in the inclined state of the AMD 60 via the corresponding Fresnel lens 71 of the Fresnel lens array 70. The micro mirror 22 reflects the object light in the positive Y-axis direction, and the object light enters the movable mirror 80c via the corresponding Fourier transform lens 82.

The object light is reflected in the negative direction of the X-axis by the movable mirror 80c, is converted into parallel light by the Fourier transform lens 6b, and then enters the CCD 9.

On the imaging surface of the CCD 9, the DM
An object light equivalent to the object light immediately after passing through D5 is projected. The CCD 9 photoelectrically converts the image and transmits an image signal to a data converter (not shown). Then, the data conversion device converts the image signal into digital data.

In this case, the focal length of each Fresnel lens 71 of the upper Fresnel lens array 70 in FIG. 8 is equal to the focal length of the corresponding Fresnel lens 71 of the lower Fresnel lens array 70 in FIG. . For this reason,
Even when information is read from any position of the hologram recording medium 30, the object light passing through the Fresnel lens 71, the Fourier transform lens 82, and the Fourier transform lens 6b always enters the CCD 9 as perfect parallel light. Therefore, an image of the same size is always projected on the CCD 9. Therefore, the process of converting the signal from the CCD 9 into digital data can be performed more easily.

According to the second embodiment described above,
Operation and effect substantially the same as the operation and effect of the first embodiment can be obtained. Further, in the second embodiment, since the optical path length is corrected by the Fresnel lens array 70, higher density recording becomes possible. Further, at the time of reproduction, the conversion process from the image signal to the digital data can be performed more easily.

In the first and second embodiments described above, examples have been shown in which a reflecting mirror (micromirror) is exclusively used as an optical element for changing the directions of object light and reference light. It is not limited. That is, as a means for changing the direction of light, other optical elements arranged in an array may be used instead of the micromirrors 22 arranged in an array.

One example of such an optical element is a layer that changes the direction of light by changing the refractive index, for example, a Pockels effect or a Kerr effect.
ct), a layer whose refractive index is changed by the intensity of an electric field applied to an electrode provided in the vicinity of the layer, a layer made of a substance having a refractive index anisotropy, and specific substances such as KDP, ADP, and Li
Those having a layer made of NbO ₃ (lithium niobate) or the like can be used.

When such an optical element is used,
As shown in FIG. 9, by rotating the optical element in the reverse direction, the optical element is displaced so as to block the optical path of the object light (the same applies to the reference light; hereinafter, only the object light will be described). Then, the object light is made incident from the back surface of the optical element and emitted from the surface of the optical element.

When the above-mentioned optical element having a layer made of a substance having a refractive index anisotropy is used, the incident angle θ 1 of the object light to the optical element is changed to a small value so that the object light from the optical element can be changed. The light emission angle θ2 can be greatly changed. Therefore, the swing angle of the optical element required to change the incident position of the object light on the hologram recording medium by a predetermined amount can be reduced.
Therefore, the load on the drive mechanism of the optical element can be reduced.

When a layer having a layer whose refractive index is changed by the intensity of an electric field is used, the voltage applied to the layer is changed to change the refractive index so that the object light can be incident on the hologram recording medium. The corner can be changed. When such an optical element is used, it is not necessary to control the tilt angle of the optical element in order to change the incident position of the object light on the hologram recording medium. That is, the optical element only needs to be able to perform a digital operation, and does not need to perform an analog operation. Therefore, the load on the drive mechanism of the optical element can be reduced. In addition,
When such an optical element is used, an electrode may be provided on the side surface of the optical element to control the refractive index of the layer.

[0127]

As described above, according to the present invention,
It is possible to provide a compact hologram memory device that can perform large-capacity recording without impairing the inherent high-speed accessibility of the hologram memory device.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a hologram memory device according to the present invention.

FIG. 2 is a schematic plan view showing the configuration, positional relationship, and operation of a micromirror array device and a hologram recording medium.

FIG. 3 is a view showing a cross section taken along line III-III in FIG. 1,
FIG. 4 is a view showing the operation of the hologram memory device.

FIG. 4 is a perspective view showing a configuration of a micro mirror of a micro mirror array C and a driving mechanism thereof.

FIG. 5 is a perspective view showing another configuration of the micromirrors of the micromirror row C and its driving mechanism.

FIG. 6 is a perspective view showing a main part of the configuration of the micromirrors of the micromirror rows A and B.

FIG. 7 is a perspective view showing a hologram memory device according to a second embodiment of the present invention.

FIG. 8 is a side view from the X-axis direction showing the configuration and operation of the second embodiment.

FIG. 9 is a diagram showing a modification of an optical element that can be used in place of a micro mirror.

FIG. 10 is a diagram showing a conventional hologram memory device.

FIG. 11 is a diagram showing a conventional hologram memory device.

[Explanation of symbols]

 22, 28, 90 Optical element

Continuing from the front page (72) Inventor Hiroshi Shimura 1 Toshiba-cho, Komukai-shi, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba R & D Center (72) Inventor Hideyuki Nishizawa Toshiba-cho, Koyuki-ku, Kawasaki-shi, Kanagawa 1 Toshiba R & D Center, Inc. (72) Inventor Akiko Hirao, Komukai Toshiba Town, Yuki-ku, Kawasaki, Kanagawa 1 In Toshiba R & D Center, Inc. (72) Inventor Koichi Kondo, Kawasaki, Kanagawa 1 Komukai Toshiba-cho, Sachi-ku Toshiba R & D Center

Claims (5)

[Claims] 1. A hologram memory device for performing at least one of recording information on a hologram recording medium and reproducing information from the hologram recording medium, comprising a plurality of optical elements capable of changing the direction of light, A hologram memory device, wherein at least one of light and reference light is guided to a hologram recording medium using the optical element. 2. The plurality of optical elements are arranged so as to form at least one optical element row, and guide and guide at least one of object light and reference light in a direction along the optical element row. The optical element forming an optical element array is selectively displaced in the optical path of the object light or the reference light, and the object light or the reference light is guided to the hologram recording medium by the displaced optical element. Hologram memory device. 3. The hologram recording medium according to claim 2, wherein the object light and the reference light are respectively guided to the same optical element row, and respectively guided to a hologram recording medium by a pair of optical elements selected from the optical element row. 2. The hologram memory device according to claim 1. 4. A hologram memory device for reproducing information from a hologram recording medium, comprising: a plurality of optical elements capable of changing the direction of light; and an image sensor on which the reproduced object light is incident. A hologram memory device, wherein the reproduced object light is guided to the image sensor using the optical element. 5. The hologram memory device according to claim 1, wherein said optical element is a reflecting mirror.