JP2005003829A - Diffraction controller, hologram recording device, and method for hologram recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diffraction controller capable of reducing the interference of a diffracted light emitted from each diffraction control element, a hologram recording device, and a method for hologram recording. <P>SOLUTION: The diffraction controller is constituted of a plurality of diffraction control elements disposed so that emitted first-order diffracted lights do not interfere with each other. The zero-order diffracted lights of the diffracted lights emitted from the diffraction control elements are cast to the front of the diffraction control elements, so the zero-order diffracted lights emitted from each diffraction control element are hard to interfere. Since the first-order diffracted lights are emitted with an angle from the diffraction control elements, each of the first-order diffracted lights can interplay in some of the disposals of the diffraction control elements to cause interferences. By disposing the diffraction control elements in consideration of the emission direction of the first-order diffracted lights, the interferences by each of the diffracted lights emitted from the respective diffraction control elements can be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diffraction control device, a hologram recording device, and a hologram recording method for controlling light diffraction.
[0002]
[Prior art]
Hologram recording apparatuses that record data on a hologram recording medium have been developed. In the hologram recording apparatus, a spatial modulator having a plurality of pixels is used, and data is recorded on the hologram recording medium by independently controlling the plurality of pixels.
As the spatial modulator, a diffraction control device configured by arranging diffraction control elements that can control light diffraction independently of each other can be used. By representing bits 0 and 1 corresponding to the state of each diffraction control element, data of the number of bits corresponding to the number of diffraction control elements can be recorded on the hologram recording medium. Such a diffraction control device is also used in an image forming apparatus such as a printer (see Patent Documents 1 and 2).
[0003]
[Patent Document 1]
JP-A-9-174933
[Patent Document 2]
JP-A-9-220824
[0004]
[Problems to be solved by the invention]
However, when the diffracted lights emitted from the individual diffraction control elements constituting the diffraction control device interfere with each other, the data recorded on the hologram recording medium includes noise. Such noise may cause an error in data reading when data is reproduced from the hologram recording medium.
In view of the above, an object of the present invention is to provide a diffraction control device, a hologram recording device, and a hologram recording method that can reduce interference of diffracted light emitted from individual diffraction control elements.
[0005]
[Means for Solving the Problems]
A. In view of the above, the hologram diffraction control device according to the present invention controls the diffraction of incident light independently and emits them, and a plurality of diffraction control elements arranged so that the emitted first-order diffracted lights do not interfere with each other It is characterized by comprising.
Zero-order and first-order diffracted light is emitted from the diffraction control element. Of these, the 0th-order diffracted light is emitted in front of the diffraction control elements, and therefore the 0th-order diffracted lights from the respective diffraction control elements are unlikely to interfere with each other. Since the first-order diffracted light is emitted from the diffraction control element at an angle, depending on the arrangement of the diffraction control elements, there is a possibility that the first-order diffracted light crosses and causes interference. For this reason, by arranging the diffraction control elements in consideration of the emission direction of the first-order diffracted light, interference of the emitted light from each of the diffraction control elements can be prevented.
[0006]
Here, the plurality of diffraction control elements include a first phase element that imparts a phase to incident light, and a second phase element that imparts a phase to incident light independently of the first phase element. May be.
By controlling the second phase element independently of the first phase element, a phase difference is given to the outgoing light from the first and second phase elements, and the diffraction state of the light synthesized from the outgoing light is changed. Can be controlled. In this case, a third or more phase control element may be added.
[0007]
(1) The first and second phase elements are alternately arranged along a first axis, the plurality of diffraction control elements are arranged along a second axis, and the first and second phase elements are arranged. The absolute value of the angle formed by the axes may be 45 ° or more and 135 ° or less.
By arranging in this way, it is possible to prevent the diffracted lights from the diffraction control elements from interfering with each other.
[0008]
(2) Each of the first and second phase control elements can take various shapes, but as an example, it can have a substantially ribbon shape.
This shape is easy to create and drive. For example, when the ribbon is made of a conductive and elastic material (for example, a metal material), the ribbon is displaced by an electrostatic force based on the voltage applied to the ribbon, and the original state (shape) due to the elasticity of the ribbon. Can be restored. In this way, the first and second phase elements, and hence the diffraction control element, can be operated at a high speed (for example, about 1 μsec).
[0009]
(3) Each of the first and second phase elements may have a liquid crystal.
The light diffraction state can be controlled by changing the phase difference of light between the first and second phase elements using liquid crystal.
[0010]
B. The hologram recording apparatus according to the present invention includes a laser light source that emits laser light and the laser light emitted from the laser light source, and controls the diffraction of the incident laser light to emit the laser light. And a condensing element that condenses the diffracted light emitted from the diffraction control device onto a hologram recording medium.
By using a diffraction control device having a diffraction control element arranged in consideration of the emission direction of the first-order diffracted light, noise during data recording on the hologram recording medium can be reduced.
[0011]
(1) The hologram recording apparatus further includes a diffracted light component extraction element that is between the diffraction control device and the light condensing element and extracts a diffracted light component of a predetermined order from the diffracted light emitted from the diffraction control element. Also good.
By extracting a diffracted light component of a predetermined order from the diffracted light by the diffracted light component extracting element, the intensity of the diffracted light can be changed and data can be recorded on the hologram recording medium as the intensity of light.
As an example of the diffracted light component extraction element, a combination of a convex lens and a slit can be considered. With this combination, for example, it is possible to simply extract the 0th-order diffracted light by removing the first-order or higher-order diffracted light components.
[0012]
(2) The hologram recording device splits the laser light emitted from the laser light source into first and second light, and makes the first light incident on the diffraction control device, and the light splitting A second condensing element that condenses the second light emitted from the element at a position where the laser light emitted from the condensing element on the hologram recording medium is condensed. Good.
The laser light emitted from the laser light source is divided into a reference light that does not pass through the diffraction control device and a signal light that passes through the diffraction control device, and both are condensed on the hologram recording medium. Interference fringes between reference light and signal light can be recorded.
An example of the light splitting element is a half mirror.
[0013]
(3) The hologram recording apparatus applies a light shielding element that shields the first light emitted from the light splitting element, and a laser beam condensed on the hologram recording medium by the second light collecting element. And a light receiving element that receives light emitted from the hologram recording medium.
A signal corresponding to the data recorded from the hologram recording medium by blocking the signal light emitted from the light splitting element from reaching the hologram recording medium so that only the reference light reaches the hologram recording medium. Generate light. The recorded data can be reproduced by reading the generated signal light with the light receiving element.
This light receiving element preferably corresponds to the diffraction control device that originally generated the signal. For example, when the diffraction control device is composed of diffraction control elements arranged one-dimensionally, it is preferable that the diffraction control device is composed of individual light receiving elements arranged correspondingly.
[0014]
C. The hologram recording method according to the present invention is performed by a diffraction control device having a plurality of diffraction control elements arranged so that light diffraction is controlled independently and emitted, and the emitted first-order diffracted light does not interfere with each other. A diffraction step for diffracting the laser light, and a condensing step for condensing the diffracted light diffracted in the diffraction step onto a hologram recording medium.
By performing hologram recording using a diffraction control device having a diffraction control element arranged in consideration of the emission direction of the first-order diffracted light, noise recorded on the hologram recording medium can be reduced.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic diagram showing a hologram recording apparatus 100 according to the first embodiment of the present invention. FIG. 2 is a schematic diagram showing a state in which the hologram recording apparatus 100 is viewed from the X-axis direction of FIG.
As shown in FIGS. 1 and 2, the hologram recording apparatus 100 includes a laser light source 10, a one-dimensional beam expander 20, a half mirror 30, a one-dimensional diffraction control device 40, a slit element 50, a one-dimensional light receiving element 60, It is composed of a cylindrical lens 71 and convex lenses 81 to 85, and records and reproduces information on the hologram recording medium M.
[0016]
(Internal configuration of the one-dimensional diffraction control device 40)
First, the one-dimensional diffraction control device 40 will be described.
FIG. 3 is a top view illustrating a state in which the one-dimensional diffraction control device 40 is viewed from above.
4 and 5 are a side view and a front view, respectively, showing the state of the one-dimensional diffraction control device 40 as viewed from the side and the front. 4A and 4B show two states (OFF, ON) of the diffraction control element 41, respectively. FIG. 5 schematically shows the operation state of the ribbon 42.
The one-dimensional diffraction control device 40 includes a plurality of diffraction control elements 41 arranged in the Y direction. The diffraction control element 41 diffracts incident light and emits it as diffracted light, and can control the diffraction state independently of each other.
[0017]
The diffraction control element 41 includes six ribbons 42, an insulating film 43 facing the ribbon 42, and a counter electrode 44, and is configured on a substrate 45. Six ribbons 42 are driven up and down every other ribbon. By applying a voltage between the ribbon 42 and the counter electrode 44, an electrostatic force is generated during this time, and the ribbon 42 is attracted to the counter electrode 44 (ON state: FIGS. 4B and 5B). reference). When the voltage applied between the ribbon 42 and the counter electrode 44 is removed, the ribbon 42 returns to the original state by the elastic force of the ribbon 42 (OFF state: see FIGS. 4A and 5A). ).
For example, the ribbon 42 may have a width of several μm, a length of about 100 μm, and a distance d of several hundred nm. At this time, the operation time of the ribbon 42 can be about 1 μs.
[0018]
Consider a case in which laser light is vertically incident on the one-dimensional diffraction control device 40 (diffraction control element 41). As shown in FIG. 5A, if the six ribbons 42 of the diffraction control element 41 are on the same plane (OFF state), the laser light is reflected vertically as it is, and only the 0th-order diffracted light is generated. On the other hand, as shown in FIG. 5B, when every other ribbon 42 is lowered (ON state), the first-order diffracted light is also generated in addition to the zero-order diffracted light reflected vertically. The intensity of the second or higher order diffracted light is small and therefore neglected.
At this time, the ratio of the 0th-order diffracted light and the 1st-order diffracted light from the one-dimensional diffraction control device 40 is determined by the distance d between the lowered ribbon 42 and the unfallen ribbon 42, and the distance d is λ / 4 (λ: laser light). ), Only the first-order diffracted light is emitted. That is, the 0th-order diffracted light from the lowered ribbon 42 and the 0th-order diffracted light from the ribbon 42 that has not fallen cancel each other out, and the intensity becomes 0, leaving only the 1st-order diffracted light (2 as described above). Ignore ingredients above and below).
[0019]
The diffracted light in the ON state of the diffraction control element 41 is light in which diffracted lights having a half-wave phase shift from each other from the lowered ribbon 42 and the unfallen ribbon 42 are mixed. That is, each of the ribbons 42 can be considered as a phase element that can change the phase of diffracted light diffracted from each of the ribbons 42.
[0020]
As described above, each of the diffraction control elements 41 constituting the one-dimensional diffraction control device 40 independently takes two diffraction states (OFF: only the 0th-order diffracted light, ON: only the first-order diffracted light), so that the number of pixels ( The number of bits of data corresponding to the number of diffraction control elements 41) can be expressed. For example, 1088 bits of data can be expressed by arranging 1088 diffraction control elements 41.
[0021]
Here, the diffracted light emitted from each of the diffraction control elements 41 is considered.
FIG. 6 is a schematic diagram showing the state of the first-order diffracted light emitted from the one-dimensional diffraction control device 40. (A) and (B) represent the emission state of the first-order diffracted light viewed from the end face and front of the one-dimensional diffraction control device 40, respectively. Here, the ribbon 42 is arranged in the direction D1, the diffraction control element 41 is arranged in the direction D2 (coincident with the Y-axis direction), and the directions D1 and D2 are orthogonal to each other.
[0022]
First-order diffracted light L + 1, L-1 (L + 1: + 1st-order diffracted light, L-1: -1st-order diffracted light) is emitted from each of the diffraction control elements 41. At this time, the first-order diffracted light is emitted in a direction inclined by an angle ± θ (for example, ± 4 °) with respect to the arrangement direction D1 of the ribbon 42 (the sign of the angle θ is positive or negative of the first-order diffracted light (+ 1st order or −1st order). ), The arrangement direction D1 of the ribbons 42 is orthogonal to the arrangement direction D2 of the diffraction control elements 41, so that the first-order diffracted lights emitted from the respective diffraction control elements 41 are parallel to each other and do not intersect.
Further, since the 0th-order diffracted light L0 is emitted in the front direction of the diffraction control element 41, it is parallel to each other and does not intersect.
As a result, the diffracted lights emitted from the respective diffraction control elements 41 do not interfere with each other.
[0023]
Next, a reference example for comparison with the present embodiment will be described.
FIG. 7 is a reference schematic diagram showing the state of the first-order diffracted light emitted from the one-dimensional diffraction control device 40a which is a reference example of the one-dimensional diffraction control device 40. (A) and (B) respectively represent the emission state of the first-order diffracted light viewed from the side and front of the one-dimensional diffraction control device 40a.
In this reference example, the arrangement direction D1 of the ribbons 42 and the arrangement direction D2 of the diffraction control elements 41 are the same. For this reason, the + 1st order diffracted light L + 1 and the −1st order diffracted light L−1 emitted from the adjacent diffraction control elements 41 are emitted in directions intersecting each other. As a result, there is a possibility that the first-order diffracted lights emitted from the respective diffraction control elements 41 interfere with each other.
[0024]
Next, a modification of this embodiment will be described.
FIG. 8 is a schematic diagram showing a one-dimensional diffraction control device 40b which is a first modification of the one-dimensional diffraction control device 40. As shown in FIG.
Here, the angle θ formed by the arrangement direction D1 of the ribbons 42 and the arrangement direction D2 of the diffraction control elements 41 is 45 °. For this reason, the first-order diffracted lights (L + 1, L−1) emitted from the respective diffraction control elements 41 are parallel to each other and do not intersect. As a result, the first-order diffracted lights emitted from the respective diffraction control elements 41 do not interfere with each other.
[0025]
This is not limited to the case where the angle θ is 45 °. If the absolute value of the angle θ is in the range of 45 ° or more and 135 ° or less, the interference between the first-order diffracted lights emitted from the respective diffraction control elements 41 is prevented. Similarly, it can be prevented. The case where the angle θ is 90 ° corresponds to the one-dimensional diffraction control device 40, and it can be seen that the one-dimensional diffraction control device 40 is further generalized.
[0026]
FIG. 9 is a schematic diagram showing a one-dimensional diffraction control device 40b which is a second modification of the one-dimensional diffraction control device 40. As shown in FIG. Here, electrodes 46 for supplying electricity to the diffraction control element 41 and, consequently, the ribbon 42 are arranged on both side surfaces of the diffraction control element 41. Thus, an electric supply mechanism such as the electrode 46 may be formed on the same plane as the diffraction control element 41.
[0027]
The operation of the one-dimensional diffraction control device 40 (diffraction control element 41) when the laser light is directly incident has been described above. The operation principle is that the laser light is incident on the one-dimensional diffraction control device 40 obliquely. Is basically the same. However, since the optical path length difference is shorter at oblique incidence than at normal incidence, only the first-order diffracted light is emitted when the interval d is approximately (λ / 4) / cos θ (θ is a one-dimensional diffraction control device). 40).
[0028]
(Other components)
Hereinafter, components other than the one-dimensional diffraction control device 40 will be described.
The laser light source 10 is a light source that emits laser light.
The one-dimensional beam expander 20 is configured by combining a plano-concave lens 21 having a semi-elliptical prism-shaped depression and an elliptic cylindrical lens 22 and expanding the beam diameter of incident light in a one-dimensional direction (Y direction). It is an optical element. By passing through the one-dimensional beam expander 20, the beam shape of the laser light emitted from the laser light source 10 is converted from a substantially circular shape to a substantially elliptic shape. As shown in FIG. 2, this conversion is performed to irradiate the entire diffraction control element 41 arranged in the Y direction of the one-dimensional diffraction control device 40 with a light beam.
The half mirror 30 is an optical element that branches incident light into two lights.
The cylindrical lens 71 is an optical element for collecting an incident light beam in the X direction. This condensing is performed in order to make the laser beam correspond to the size of the one-dimensional diffraction control device 40 in the X direction.
[0029]
The convex lens 81 is an optical element for forming a diffraction spectrum of diffracted light emitted from the one-dimensional diffraction control device 40.
The slit element 50 is disposed in the vicinity of the focal point of the convex lens 81, and removes the first-order or higher-order diffracted light component of the diffracted light emitted from the one-dimensional diffraction control device 40 (in other words, extracts the 0th-order diffracted light component). ). A slit 51 (opening) is formed in the slit element 50 along the Y direction. The reason why the slit 51 is along the Y direction is that it corresponds to the arrangement direction of the diffraction control elements 41. As shown in FIG. 10, in the slit 51, the zero-order diffracted light L0 passes through the slit 51, but the first-order diffracted light L1 (including both positive and negative first-order diffracted lights L + 1 and L-1) cannot pass through the slit 51 and is slit. It is shielded by the element 50. This is because, as described above, the 1st-order diffracted light L1 is emitted with an angle ± θ inclined with respect to the 0th-order diffracted light L1 (the sign of the angle θ is positive or negative of the 1st-order diffracted light (+ 1st order or −1st order). )).
[0030]
The convex lens 82 is an optical element for converting light emitted from the slit element 50 into substantially parallel light.
The convex lens 83 is an optical element for condensing the substantially parallel light emitted from the convex lens 82 onto the hologram recording medium M.
Here, the reason why the convex lenses 82 and 83 and the two lenses are used is that the diffraction spectrum itself of the diffracted light from which the first-order diffracted light is removed by the slit 51 is recorded on the hologram recording medium M.
[0031]
When only one of the convex lenses 82 and 83 is used, the diffracted light is Fourier transformed only once, and what is recorded on the hologram recording medium M is a real image of the one-dimensional diffraction control device 40. In this real image, since the first-order diffraction component is removed from the diffracted light by the slit element 50, the pixels in which the ribbons 42 are aligned (FIG. 5A) are bright, and every other ribbon 42 moves up and down. The pixel (FIG. 5B) is dark. In the present embodiment, the diffraction spectrum itself of the diffracted light is recorded on the hologram recording medium M by using the convex lenses 82 and 83.
Note that the recording of data on the hologram recording medium M can be performed by either the diffraction spectrum itself from the one-dimensional diffraction control device 40 or its real image.
[0032]
The convex lens 84 is an optical element for condensing the light emitted from the half mirror 30 in the X negative direction on the hologram recording medium M. The light emitted from the convex lens 84 is applied to the same portion of the hologram recording medium M as the light emitted from the convex lens 83 to form interference fringes (light brightness and darkness).
[0033]
The hologram recording medium M is a recording medium that records interference fringes due to light emitted from the convex lenses 83 and 84 as a change in refractive index. As a constituent material of the hologram recording medium M, any material can be used regardless of whether it is an organic material or an inorganic material as long as the refractive index changes according to the intensity of light.
[0034]
As an inorganic material, for example, lithium niobate (LiNbO ₃ The photorefractive material whose refractive index changes according to the exposure amount by the electro-optic effect such as) can be used.
As the organic material, for example, a photopolymerization type photopolymer can be used. In the photopolymerization type photopolymer, in the initial state, monomers are uniformly dispersed in the matrix polymer. When this is irradiated with light, the monomer is polymerized at the exposed portion. And the refractive index of the part changes as it polymerizes.
As described above, by changing the refractive index of the hologram recording medium M according to the exposure amount, interference fringes generated by the interference between the reference light and the signal light can be recorded on the hologram recording medium M as a change in the refractive index.
[0035]
The convex lens 85 is an optical element for condensing the reproduction light when reproducing the recording from the hologram recording medium M on the one-dimensional light receiving element 60.
The one-dimensional light receiving element 60 has a plurality of light receiving elements arranged in the Y direction, receives the reproduction light emitted from the convex lens 83, and outputs a signal corresponding to the intensity of the received light. In the one-dimensional light receiving element 60, the light receiving elements are one-dimensionally arranged in the Y direction corresponding to the diffraction control element 41 of the one-dimensional diffraction control device 40.
However, instead of the one-dimensional light receiving element 60, it is also possible to use a two-dimensional (planar) arrangement of a plurality of light receiving elements.
[0036]
(Operation of Hologram Recording Device 100)
A. Data recording on the hologram recording medium M (see FIGS. 1 and 2)
The laser light emitted from the laser light source 10 is divided into two lights (reference light and signal light) by the half mirror 30 after the beam diameter is expanded in the Y direction by the one-dimensional beam expander 20.
The reference light passes through the convex lens 84 and is collected on the hologram recording medium M.
[0037]
The signal light is converged in the X direction by the cylindrical lens 71 and enters the one-dimensional diffraction control device 40. As described above, each of the diffraction control elements 41 independently takes two diffraction states (OFF: only the 0th-order diffracted light, ON: only the first-order diffracted light), so that the entire one-dimensional diffraction control device 40 has a diffraction control element. The number of bits corresponding to 41 (for example, 1088 bits when the number of diffraction control elements 41 is 1088) can be expressed. Here, the diffracted lights emitted from the respective diffraction control elements 41 are emitted without interfering with each other.
[0038]
The diffracted light diffracted by the one-dimensional diffraction control device 40 is converged by the convex lens 81 and passes through the slit element 50, so that two intensities (bright and dark) corresponding to two diffraction states (OFF and ON) are obtained. Take. That is, ON and OFF of the diffraction control element 41 can be made to correspond to bits 1 and 0.
The diffracted light whose diffraction state has been converted into intensity is condensed on the hologram recording medium M via the convex lenses 82 and 83. At this time, since the reference light and the signal light are condensed at substantially the same location of the hologram recording medium M, an interference fringe is formed on the hologram recording medium M, and the refractive index of the hologram recording medium M corresponds to the interference fringe. Change. Since the diffracted lights emitted from the respective diffraction control elements 41 do not interfere with each other, noise can be prevented from being mixed into the data recorded on the hologram recording medium M.
[0039]
As described above, the refractive index distribution of the hologram recording medium M is formed corresponding to each binary state of the diffraction control elements 41 of the one-dimensional diffraction control device 40, and data can be recorded on the hologram recording medium M. Become. For example, when there are 1088 diffraction control elements 41, 1088-bit data is recorded by exposing the hologram recording medium M once using the one-dimensional diffraction control device 40.
[0040]
The hologram recording medium M is exposed to the hologram recording medium M a plurality of times by shifting the condensing location and the incident angle of the reference light and the signal light, whereby data having a bit number that is a multiple of the number of the diffraction control elements 41 is stored in the hologram recording medium M. Can record. That is, when the number of ON / OFF diffraction control elements 41 of the diffraction control element 41 is n and the number of exposures is m, n · m-bit data can be recorded on the hologram recording medium M. Since the diffracted lights emitted from the respective diffraction control elements 41 do not interfere with each other, noise can be prevented from being mixed into the data recorded on the hologram recording medium M.
[0041]
In the above, the diffracted light diffracted by the one-dimensional diffraction control device 40 is converted into light contrast (strong and weak) by the convex lens 81 and the slit element 50. On the other hand, it is also possible to perform recording on the hologram recording medium M without using the convex lens 81 and the slit element 50.
Also in this case, since the diffracted light emitted from each of the diffraction control elements 41 does not interfere with each other, noise is prevented from being mixed into the data recorded on the hologram recording medium M. Since the first-order diffracted light is directly used for recording without blocking, the advantage that the diffracted lights emitted from the respective diffraction control elements 41 do not interfere with each other can be further enjoyed.
[0042]
B. Reproduction of data from hologram recording medium M
FIG. 11 is a schematic diagram showing a state in which data is reproduced from the hologram recording medium M using the hologram recording apparatus 100.
In order to reproduce data from the hologram recording medium M, the signal light is blocked by the shielding plate 90 out of the two lights (reference light and signal light) emitted from the laser light source 10 and divided by the half mirror 30, Only the reference light passes through the convex lens 85 and is condensed on the hologram recording medium M. In order to prevent the light reflected from the shielding plate 90 from being mixed into the reference light and causing noise, for example, the shielding plate 90 is preferably slightly inclined with respect to the incident light. Further, if a normal mirror is used instead of the half mirror 30, the shielding plate 90 becomes unnecessary.
The reference light incident on the hologram recording medium M is diffracted by the refractive index distribution in the hologram recording medium M, and signal light is generated. The generated signal light is emitted from the extension of the traveling direction of the recording signal light that has entered the signal light during recording on the hologram recording medium M. The reproduced signal light is converged by the convex lens 85 and is incident on the one-dimensional light receiving element 60. Data recorded in the hologram recording medium M can be reproduced as the intensity of light received by each light receiving element of the one-dimensional light receiving element 60.
[0043]
(Second Embodiment)
Next, a hologram recording apparatus 200 according to the second embodiment of the present invention will be described.
The configuration of the hologram recording apparatus 200 is obtained by changing the one-dimensional diffraction control apparatus 40 shown in FIG. 1 to a one-dimensional diffraction control apparatus 240, and the entire illustration is omitted.
[0044]
FIG. 12 is a front view illustrating a state in which the one-dimensional diffraction control device 240 is viewed from the front. FIG. 13 is a diagram illustrating a state in which the one-dimensional diffraction control device 240 is viewed from the end surface. 13A and 13B correspond to OFF / ON of the diffraction control element 241 respectively. The one-dimensional diffraction control device 240 is configured by arranging diffraction control elements 241, and the diffraction control element 241 is configured by arranging phase elements 242. Liquid crystal 243 is sealed in the phase element 242, and the phase of light passing through the phase element 242 is controlled by changing the direction of liquid crystal molecules by an electric field.
The reflection plate 244 is an optical element for reflecting incident light incident on the diffraction control element 241.
[0045]
As shown in FIG. 12, in the OFF state of the diffraction control element 241, since the phases of the light reflected by the phase element 242 are the same, the light Lout0 that passes through the diffraction control element 241 becomes 0th-order diffracted light (FIG. 13 ( A)). In contrast, when the diffraction control element 241 is in the ON state, the phases of the light reflected by the phase element 242 are alternately different by λ / 2. Therefore, the light Lout1 that passes through the diffraction control element 241 becomes first-order diffracted light (FIG. 13B).
Specifically, a fixed phase element 242a in which no electric field is applied to the liquid crystal 243 and a variable phase element 242b in which an electric field is applied to the liquid crystal 243 are alternately arranged, and the diffraction control element 241 is turned on. The orientation of the molecules of the liquid crystal 243 of the phase element 242b changes, and the phase difference from the adjacent phase element 242a becomes λ / 2.
[0046]
The arrangement of the diffraction control elements 241 and the phase elements 242 in the one-dimensional diffraction control device 240 is essentially the same as that of the one-dimensional diffraction control device 40 shown in FIG. The one-dimensional diffraction control device 40 controls the phase by moving the ribbon 42 up and down, and the one-dimensional diffraction control device 240 controls the phase by changing the orientation of the liquid crystal 243 molecules. Common in controlling the state. For this reason, interference of diffracted light from each of the diffraction control elements 241 of the one-dimensional diffraction control device 240 is prevented for the same reason as in the case of the one-dimensional diffraction control device 40.
Similar to the one-dimensional diffraction control device 40, the one-dimensional diffraction control device 240 can employ an arrangement as shown in FIG. 8 to prevent interference of diffracted light from each of the diffraction control elements 241.
Since the basic operation of the hologram recording apparatus 200 is not essentially different from that of the hologram recording apparatus 100, description thereof is omitted.
[0047]
(Third embodiment)
FIG. 14 is a schematic diagram showing a hologram recording apparatus 300 according to the third embodiment of the present invention.
As shown in FIG. 14, the hologram recording apparatus 300 includes a laser light source 10, a one-dimensional beam expander 20, a one-dimensional diffraction controller 40, a one-dimensional light receiving element 60, a cylindrical lens 71, convex lenses 381, 382, and 83. And recording and reproducing information to and from the hologram recording medium M.
In the hologram recording apparatus 300, the half mirror 30 is not disposed. That is, information is recorded on and reproduced from the hologram recording medium M using interference between diffracted lights emitted from the same diffraction control element 41 of the one-dimensional diffraction control device 40 without using reference light.
[0048]
The convex lens 381 is an optical element for converting light emitted from the one-dimensional diffraction control device 40 into substantially parallel light.
The convex lens 382 is an optical element for condensing the substantially parallel light emitted from the convex lens 382 on the hologram recording medium M.
The convex lenses 381 and 382 use lenses having the same focal length f, and the distance Le between the convex lenses 381 and 382 is twice the focal length f (Le = 2 * f). Further, the convex lenses 381, 382, the one-dimensional diffraction control device 40, and the hologram recording medium M are arranged so as to be point-symmetric with respect to the middle point A of the convex lenses 381, 382. This is because the interference light emitted from the one-dimensional diffraction control device 40 is condensed at a target position on the hologram recording medium M.
[0049]
Here, it is preferable that both convex lenses 381 and 382 are telecentric lenses. It becomes easy to collect the diffracted light emitted from the one-dimensional diffraction control device 40 at a symmetrical position on the hologram recording medium M.
The telecentric lens is a lens in which the principal ray is parallel to the optical axis on the one-dimensional diffraction control device 40 side with the convex lens 381 and on the hologram recording medium M side with the convex lens 382. In order to realize a telecentric lens, for example, a pinhole may be disposed at the midpoint A of the convex lenses 381 and 382, that is, the focal position of the convex lenses 81 and 82.
[0050]
FIGS. 15 and 16 are schematic diagrams showing the state of diffracted light traveling from the one-dimensional diffraction control device 40 to the hologram recording medium M when the diffraction control element 41 is in the ON state and the OFF state, respectively.
As shown in FIG. 15, when the diffraction control element 41 is in the ON state, the + 1st order diffracted light L + 1 and the −1st order diffracted light L-1 are emitted from the diffraction control element 41. As described above, each of the diffracted lights has an emission angle θ of ± 4 °, for example. These diffracted lights pass through the convex lenses 381 and 382 and are condensed on the hologram recording medium M. Interference fringes are formed and recorded on the hologram recording medium M by the interference of the ± first-order diffracted beams.
[0051]
In the case where the convex lenses 381 and 382 are telecentric lenses, the condensing position of the diffracted light on the hologram recording medium M is symmetric with the output position from the one-dimensional diffraction control device 40. That is, recording on the area of the hologram recording medium M is performed in accordance with the size of the one-dimensional diffraction control device 40.
On the other hand, as shown in FIG. 16, when the diffraction control element 41 is in the OFF state, only the 0th-order diffracted light L0 is emitted from the diffraction control element 41. The diffracted light passes through the convex lenses 381 and 382 and is condensed on the hologram recording medium M. At this time, since the single light is condensed, no interference fringes are formed or recorded on the hologram recording medium M.
[0052]
In the hologram recording apparatus 300, the diffraction control elements 41 are arranged so as to prevent interference of diffracted light between different diffraction control elements 41 of the one-dimensional diffraction control apparatus 40, as in the hologram recording apparatus 100. It is.
[0053]
(Operation of Hologram Recording Device 300)
A. Recording of data on the hologram recording medium M (see FIG. 14)
The laser light emitted from the laser light source 10 is expanded in the Y direction by the one-dimensional beam expander 20, converged in the X direction by the cylindrical lens 71, and enters the one-dimensional diffraction control device 40. At this time, the laser light emitted from the laser light source 10 itself functions as signal light, and recording is performed on the hologram recording medium M only with this signal light, and no separate reference light is required (the laser light is half-lighted). It is not necessary to divide into reference light and signal light with a mirror or the like).
Each of the diffraction control elements 41 constituting the one-dimensional diffraction control device 40 independently takes two diffraction states (OFF: only 0th-order diffracted light, ON: only positive and negative first-order diffracted light), so that the number of pixels (diffraction control element) 41 bits) of data can be expressed (for example, ON: 1 and OFF: 0 are set).
[0054]
The diffracted light diffracted by the one-dimensional diffraction control device 40 is condensed on the hologram recording medium M via the convex lenses 381 and 382. The diffracted light at this time differs depending on the ON / OFF state of the diffraction control element 41.
In the ON state, the diffracted light includes positive and negative first-order diffracted light components, and the first-order diffracted light interferes on the hologram recording medium M, and interference fringes are formed on the hologram recording medium M. Then, the refractive index of the hologram recording medium M changes corresponding to the formed interference fringes.
On the other hand, in the OFF state, since the diffracted light includes only the 0th-order diffracted light component, the formation of interference fringes on the hologram recording medium M and the change in the refractive index due to the interference fringes do not occur.
As described above, the refractive index distribution of the hologram recording medium M is formed (or not formed) corresponding to the two states (ON and OFF) of each of the diffraction control elements 41 of the one-dimensional diffraction control device 40. (Data recording). Here, since the interference lights emitted from the different diffraction control elements 41 do not interfere with each other, the data recorded on the hologram recording medium M has low noise.
[0055]
B. Reproduction of data from hologram recording medium M
FIG. 17 is a schematic diagram showing a state where data is reproduced from the hologram recording medium M using the hologram recording apparatus 300.
In order to reproduce data from the hologram recording medium M, only one of the positive and negative first-order diffracted light incident on the hologram recording medium M at the time of recording may be incident on the hologram recording medium M on which data is recorded. For this purpose, all the diffraction control elements 41 of the one-dimensional diffraction control device 40 are turned on to generate positive and negative first-order diffracted light and extract only one of them.
[0056]
As shown in FIG. 17, a slit element 350 is disposed between the convex lenses 381 and 382. In the slit element 350, a slit 351 (opening) along the Y direction is formed. The slit 351 along the X direction corresponds to the arrangement direction of the diffraction control elements 41. However, as shown in FIG. 18, the central axis of the slit 351 is arranged so as to be deviated in the X positive direction from the optical axis. As a result, the positive first-order diffracted light L + 1 passes through the opening, but the negative first-order diffracted light L-1 is blocked by the slit element 350. In this way, only the positive first-order diffracted light L + 1 as the reference light reaches the hologram recording medium M.
[0057]
The reference light incident on the hologram recording medium M is diffracted by the refractive index distribution formed in the hologram recording medium M, and signal light is generated. The generated signal light is emitted from the extension of the traveling direction of the negative first-order diffracted light incident upon recording on the hologram recording medium M. The reproduced signal light is converged by the convex lens 83 and is incident on the one-dimensional light receiving element 60 (the convex lens 83 and the one-dimensional light receiving element 60 are arranged in the direction of about −4 ° of the hologram recording medium M).
In this way, data recorded in the hologram recording medium M can be reproduced as the intensity of light received by each light receiving element of the one-dimensional light receiving element 60.
[0058]
Here, the slit 351 of the slit element 350 is arranged in the Y negative direction so that only negative first-order diffracted light is allowed to pass, and the hologram recording medium M can be reproduced using this. At this time, positive first-order diffracted light for data reproduction is generated from the hologram recording medium M, and the convex lens 83 and the one-dimensional light receiving element 60 are arranged in the direction of about + 4 ° of the hologram recording medium M, so that one-dimensional light reception is performed. Data can be reproduced using the element 60.
As described above, it is possible to reproduce data from the hologram recording medium M by adding the slit element 350 to the hologram recording apparatus 300 and turning on all the diffraction control elements 41. That is, the hologram recording apparatus 300 can be used for both recording and reproduction.
Note that data can be reproduced from the hologram recording medium M only by incident the laser light from the laser light source 10 on the hologram recording medium M at + 4 ° or −4 °. However, at this time, it is difficult to perform recording and reproduction with the same apparatus.
[0059]
(Other embodiments)
Embodiments of the present invention are not limited to the above-described embodiments, and can be expanded and modified. The expanded and modified embodiments are also included in the technical scope of the present invention.
For example, the present invention can be applied regardless of the presence or absence of a slit.
[0060]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a diffraction control device, a hologram recording device, and a hologram recording method capable of reducing interference of diffracted light emitted from individual diffraction control elements.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a hologram recording apparatus according to a first embodiment of the present invention.
2 is a schematic diagram showing a state in which the hologram recording apparatus is viewed from the X-axis direction of FIG.
FIG. 3 is a top view illustrating a state where the one-dimensional diffraction control device illustrated in FIG. 1 is viewed from above.
4 is a top view showing a state of the one-dimensional diffraction control device shown in FIG. 1 as viewed from the side. FIG.
FIG. 5 is a front view illustrating a state in which the one-dimensional diffraction control device illustrated in FIG. 1 is viewed from the front.
FIG. 6 is a schematic diagram showing a state of first-order diffracted light emitted from a one-dimensional diffraction control device.
FIG. 7 is a reference schematic diagram showing a state of the first-order diffracted light emitted from the one-dimensional diffraction control apparatus as a reference example of the first embodiment.
FIG. 8 is a schematic diagram showing a one-dimensional diffraction control apparatus which is Modification 1 of the first embodiment.
FIG. 9 is a schematic diagram illustrating a one-dimensional diffraction control apparatus according to a second modification of the first embodiment.
FIG. 10 is a schematic diagram showing a state where the first-order diffracted light from the one-dimensional diffraction control device is blocked by a slit element.
FIG. 11 is a schematic diagram showing a state in which data is reproduced from a hologram recording medium using a hologram recording apparatus.
FIG. 12 is a front view illustrating a state in which a one-dimensional diffraction control apparatus of a hologram recording apparatus according to a second embodiment of the present invention is viewed from the front.
FIG. 13 is a diagram illustrating a state in which a one-dimensional diffraction control apparatus of a hologram recording apparatus according to a second embodiment of the present invention is viewed from an end surface.
FIG. 14 is a schematic diagram showing a hologram recording apparatus according to a third embodiment of the present invention.
FIG. 15 is a schematic diagram illustrating a state of diffracted light traveling from the one-dimensional diffraction control device to the hologram recording medium M when the diffraction control element is in an ON state.
FIG. 16 is a schematic diagram showing the state of diffracted light traveling from the one-dimensional diffraction control device to the hologram recording medium M when the diffraction control element is in an OFF state.
FIG. 17 is a schematic diagram showing a state in which data is reproduced from a hologram recording medium M using a hologram recording apparatus according to a third embodiment of the present invention.
FIG. 18 is a cross-sectional view showing the arrangement of slits in a hologram recording apparatus according to a third embodiment of the present invention.
[Explanation of symbols]
100 Hologram recording device
10 Laser light source
20 One-dimensional beam expander
21 Plano-concave lens
22 Cylindrical lens
30 half mirror
40 One-dimensional diffraction control device
41 Diffraction control element
42 Ribbon
43 Insulating film
44 Counter electrode
45 substrates
46 electrodes
50 Slit element
51 slit
60 One-dimensional light receiving element
71 Cylindrical lens
81-85 Convex lens
90 Shield plate

Claims (11)

A diffraction control device comprising: a plurality of diffraction control elements arranged so that diffraction of incident light is controlled independently and emitted, and the emitted first-order diffracted light does not interfere with each other. The plurality of diffraction control elements include: a first phase element that imparts a phase to incident light; and a second phase element that imparts a phase to incident light independently of the first phase element. The diffraction control device according to claim 1, wherein: The first and second phase elements are alternately disposed along a first axis, the plurality of diffraction control elements are disposed along a second axis, and are formed by the first and second axes. The diffraction control device according to claim 2, wherein an absolute value of the angle is 45 ° or more and 135 ° or less. The diffraction control device according to claim 2, wherein each of the first and second phase elements has a substantially ribbon shape. The diffraction control apparatus according to claim 4, wherein at least one of the first and second phase elements is displaced by an electrostatic force. The diffraction control apparatus according to claim 2, wherein each of the first and second phase elements includes a liquid crystal. A laser light source for emitting laser light;
The diffraction control device according to claim 1, wherein the laser light emitted from the laser light source is incident, and diffraction of the incident laser light is controlled and emitted.
And a condensing element for condensing the diffracted light emitted from the diffraction control device onto a hologram recording medium. The diffracted light component extracting element that is between the diffraction control device and the condensing element and extracts a diffracted light component of a predetermined order from the diffracted light emitted from the diffraction control device is further provided. Hologram recording device. A light splitting element that splits the laser light emitted from the laser light source into first and second light and makes the first light incident on the diffraction control device;
A second condensing element that condenses the second light emitted from the light splitting element at a location where the laser light emitted from the condensing element on the hologram recording medium is condensed. The hologram recording apparatus according to claim 7, wherein: A light shielding element that shields the first light emitted from the light splitting element;
And a light receiving element that receives light emitted from the hologram recording medium based on the laser light condensed on the hologram recording medium by the second light collecting element. 9. The hologram recording device according to 9. A diffraction step for diffracting the laser light by a diffraction control device having a plurality of diffraction control elements arranged so that the diffraction of the light is controlled independently and emitted so that the emitted first-order diffracted light does not interfere with each other; ,
And a condensing step of condensing the diffracted light diffracted in the diffraction step onto a hologram recording medium.

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