Patent Application
20070041302
The present invention relates to an information recording apparatus and an information recording/reproducing apparatus using a hologram.
In this type of apparatus using a hologram, upon the recording thereof, the record information is recorded as an interference pattern or fringe by performing two-dimensional spatial modulation of signal light, which is a laser beam or the like, and then irradiating a same point on the recording surface of a recording medium with the signal light, together with reference light. Upon the reproduction thereof, the record information is reproduced by irradiating the recording point with the reference light, and detecting transmitted light and reflected light, caused by the irradiation of the reference light, as signal light modulated in the same manner as the signal light in the recording. For example, a patent document 1 or a patent document 2 discloses a technology of a hologram recording/reproducing apparatus in which signal light that is a thick columnar or prism-like laser beam is irradiated to an entire two-dimensional spatial light modulator (or two-dimensional spatial modulator).
Moreover, there is also proposed a hologram recording/reproducing apparatus using a one-dimensional spatial light modulator (or one-dimensional spatial modulator).
Patent document 1: Japanese Patent Application Laid Open NO. Hei 10-91056
Patent document 2: Japanese Patent Publication NO. 3403068
However, in the hologram recording/reproducing apparatus disclosed in the above-mentioned patent document 1 or the like, the signal light is a thick prism-like laser beam, so that there is such a technical problem that the entire recording/reproducing apparatus including an optical system cannot be miniaturized or thinned.
On the other hand, if the two-dimensional spatial light modulator is miniaturized, a diffraction grating becomes narrow, to thereby increase the diffraction angle of higher-order light, so that there is no point to miniaturize the two-dimensional spatial light modulator. Namely, there is also such a technical problem that the two-dimensional spatial light modulator is essentially not suited for the miniaturization.
Moreover, even in the case of the recording/reproducing apparatus using the one-dimensional spatial light modulator, it is necessary to provide an optical system in which a disc-shaped recording medium, such as an optical disc, is irradiated with the signal light and the reference light, substantially in a normal direction with respect to the recording surface. Therefore, it is necessary to ensure the optical paths of the signal light and the reference light and an accommodation space for the information recording medium, at least within a housing, and there is such a technical problem that even in the case of the information recording/reproducing apparatus, it is essentially not suited for the miniaturization or the thinning.
In order to solve the above-mentioned conventional problems, it is therefore an object of the present invention to provide an information recording apparatus and an information recording/reproducing apparatus of a hologram type which can be miniaturized or thinned.
In order to solve the above-mentioned object, an information recording apparatus according to claim 1 of the present invention is an information recording apparatus for recording record information onto a recording medium having an optically recordable recording surface, provided with: a laser light source; a converting optical system for converting a laser beam emitted from the laser light source to a plate-like laser beam whose cross section extends linearly and for emitting the laser beam such that a direction extending linearly is along the recording surface; a one-dimensional spatial modulating device for performing one-dimensional spatial modulation in the direction extending linearly with respect to the plate-like laser beam, on the basis of the record information; a recording optical system for recording the record information onto the recording medium, by irradiating the recording surface with reference light based on the laser beam emitted from the laser light source while irradiating the recording surface with the spatial modulated plate-like laser beam as signal light; and a displacing device for displacing the recoding medium relative to the recording optical system such that irradiation positions of the signal light and the reference light are relatively displaced on the recording surface.
In order to solve the above-mentioned object, an information recording apparatus according to claim 10 of the present invention is an information recording/reproducing apparatus provided with: the information recording apparatus according to claim 1; a controlling device for making the one-dimensional spatial modulating device function as a shielding device for shielding the laser beam emitted from the laser light source; and a reproducing device for detecting interference light produced by transmission, diffraction, or reflection on the recording medium, caused by the reference light irradiated to the recording surface through the recording optical system, and reproducing the record information on the basis of the detected interference light.
These effects and other advantages of the present invention become more apparent from the following embodiments.
The information recording apparatus and the information recording/reproducing apparatus according to embodiments of the present invention will be explained.
The embodiment of the information recording apparatus of the present invention is an information recording apparatus for recording record information onto a recording medium having an optically recordable recording surface, provided with: a laser light source; a converting optical system for converting a laser beam emitted from the laser light source to a plate-like laser beam whose cross section extends linearly and for emitting the laser beam such that a direction extending linearly is along the recording surface; a one-dimensional spatial modulating device for performing one-dimensional spatial modulation in the direction extending linearly with respect to the plate-like laser beam, on the basis of the record information; a recording optical system for recording the record information onto the recording medium, by irradiating the recording surface with reference light based on the laser beam emitted from the laser light source while irradiating the recording surface with the spatial modulated plate-like laser beam as signal light; and a displacing device for displacing the recoding medium relative to the recording optical system such that irradiation positions of the signal light and the reference light are relatively displaced on the recording surface.
According to the embodiment of the information recording apparatus of the present invention, at first, the laser beam is emitted from the laser light source, such as a semiconductor laser and a gas laser, wherein the cross section of light flux spreads two-dimensionally, such as circular and oval, or the cross section is squashed in a particular direction, such as longitudinal and linear (e.g. straight line). The emitted laser beam is converted to the plate-like laser beam by the converting optical system including an expander or the like, and then inputted to the one-dimensional spatial modulating device. Then, on the one-dimensional spatial modulating device, one-dimensional spatial modulation is performed to the plate-like laser beam, in the direction thereof extending linearly, on the basis of the record information to be recorded. In other words, the spatial modulation is performed for each of the light flux portions which are aligned on the cross section of the light flux, which extends linearly, of the plate-like laser beam. Then, the recording surface is irradiated with the spatial modulated plate-like laser beam, as the signal light, by the recording optical system including an objective lens or the like. Together with this, the recording surface is irradiated by the recording optical system with the reference light based on the laser beam emitted from the laser light source, such as the reference light split from the laser beam and the reference light included in the plate-like laser beam, in the previous step of converting the laser beam to the plate-like leaser beam, for example.
While such a laser beam is modulated, the recording medium is relatively displaced by the displacing device, continuously, intermittently, or discontinuously. Namely, the recording medium is rotationally displaced or parallel-displaced, relative to the recording optical system or the like. In place of or in addition to this, the recording optical system or another recording system is displaced relative to the recording medium. Therefore, along with the displacement, it is possible to sequentially record the record information, as one portion of the interference pattern of the signal light and the reference light, into a desired position on the recording surface.
Particularly in the embodiment, after converted to the plate-like laser beam, the laser beam is spatial modulated, so that it is possible to perform the one-dimensional spatial modulation by using the one-dimensional spatial modulating device, in stead of the two-dimensional spatial modulating device which is generally used in the hologram recording. Moreover, the converting optical system emits the laser beam emitted from the laser light source such that the direction of the plate-like laser beam extending linearly is along the recording surface. For example, the laser beam is converted to the plate-like laser beam such that the flat surface of the plate-like laser beam is parallel to or substantially parallel to the recording surface. In this case, the laser light source and the converting optical system may be disposed such that even the optical path from the laser light source to the converting optical system is also is parallel to or substantially parallel to the recording surface, as well. In addition, the one-dimensional spatial modulating device and the recording optical system may be disposed such that even the optical path from the one-dimensional spatial modulating device to the recording optical system is also is parallel to or substantially parallel to the recording surface, as well. Therefore, it is possible to contain a space occupied by the optical path of the plate-like laser beam and a space occupied by the one-dimensional spatial modulating device for spatial-modulating the plate-like laser beam, in a space which spreads relatively thinly along the recording surface.
As a result, it is possible to dispose the laser light source, the converting optical system, the one-dimensional spatial modulating device, and the recording optical system of the present invention, in a relatively narrow space surrounding the recording medium which spreads flatly, such as an optical disc which can be hardly miniaturized or cannot be miniaturized, while the record information is modulated by using the one-dimensional spatial modulation, on a hologram recorder and a player or the like, for example. As result of this, it is possible to miniaturize and thin the entire information recording apparatus which include the space for containing the recording medium.
In one aspect of the embodiment of the information recording apparatus of the present invention, the recording optical system includes: a splitting optical system for splitting the laser beam emitted from the laser light source into the signal light and the reference light in a previous step of the converting optical system; and a combining optical system for combining the one-dimensional spatial modulated signal light and the reference light to a same optical path, in a subsequent step of the one-dimensional spatial modulating device.
According to this aspect, the laser beam emitted from the laser light source is split into the signal light and the reference light, by the splitting optical system, such as a beam splitter and a half mirror. After that, the signal light is modulated by the one-dimensional spatial modulating device as the plate-like laser beam, through the converting optical system. On the other hand, the reference light is not modulated without therethrough. Then, the one-dimensional spatial modulated signal light and the reference light are combined to the same optical path by the combining optical system, such as a coupling prism, and then, irradiated to the same recording position on the recording surface by the recording optical system. Therefore, it is possible to record the record information on the recording surface, by the interference of the one-dimensional spatial modulated signal light and the reference light.
Incidentally, it is also possible to dispose the splitting optical system between the converting optical system and the one-dimensional spatial modulating device.
Alternatively, in another aspect of the embodiment of the information recording apparatus of the present invention, the recording optical system further comprises a splitting optical system for splitting the laser beam emitted from the laser light source into the signal light and the reference light in a previous step of the converting optical system, and the one-dimensional spatial modulated signal light and the reference light are combined to a same optical path and irradiated to the recording surface.
According to this aspect, the laser beam emitted from the laser light source is split into the signal light and the reference light, by the splitting optical system, such as a beam splitter and a half mirror. After that, the signal light is modulated by the one-dimensional spatial modulating device as the plate-like laser beam, through the converting optical system. On the other hand, the reference light is not modulated without therethrough. Then, the one-dimensional spatial modulated signal light and the reference light are combined to the same optical path and irradiated onto the recording surface, by the recording optical system including a mirror, an object lens or the like, for example. Therefore, it is possible to record the record information on the recording surface, by the interference of the one-dimensional spatial modulated signal light and the reference light.
Incidentally, it is also possible to dispose the splitting optical system between the converting optical system and the one-dimensional spatial modulating device.
In an aspect related to the splitting optical system, it may be constructed such that the splitting optical system splits the reference light such that the optical path of the reference light and the plate-like laser beam are located side-by-side as viewed from the recording surface.
By such construction, it is possible to contain not only the space occupied by the optical path of the plate-like laser beam, but also the space occupied by the optical path of the split reference light, in the space which spreads relatively thinly along the recording surface. Therefore, it is possible to miniaturize and thin the entire information recording apparatus while a hologram optical system for splitting the reference light from signal light is adopted.
Alternatively, in another aspect of the embodiment of the information recording apparatus of the present invention, the reference light is emitted from the laser light source, together with the signal light, and irradiated to the recording surface through the converting optical system, the one-dimensional spatial modulating device, and the recording optical system.
According to this aspect, by virtue of a so-called “self-coupling method”, it is possible to record the information on the recording surface, by the interference of the signal light and the reference light included in the same laser beam. More specifically, for example, the reference light corresponds to light which mainly contains a brightness component of the one-dimensional spatial modulated laser beam, and the signal light corresponds to light which mainly contains a phase component of the one-dimensional spatial modulated laser beam. The recording surface is irradiated with the reference light and the signal light, as one combined light.
In another aspect of the embodiment of the information recording apparatus of the present invention, the information recording apparatus is further provided with an irradiation angle changing device capable of relatively changing irradiation angles of the signal light and the reference light with respect to the recording surface.
According to this aspect, by virtue of a so-called “angle multiplexing method”, it is possible to record a plurality of record information, by changing an irradiation angle at the same position on the recording surface. Therefore, it is extremely useful in increasing a recording density. Particularly in the case of the angle multiplexing method, it is only necessary to perform the recording with an inclination of the irradiation angle by 1 degree or less, or a tenth of a degree or less. Therefore, even if the plate-like laser beam is inclined to a certain degree from a position parallel to the recording surface because of the inclination of the irradiation angle, the degree of the inclination is minor, and yet it cannot be said that the plate-like laser beam is out of the position along the recording surface. In other words, even if the angle multiplexing is performed, such a unique effect of the embodiment is sufficiently maintained that the information recording apparatus can be miniaturized and thinned, as described above.
Incidentally, in the embodiment, it is possible to adopt not only the angle multiplexing but also various methods related to the hologram recording, such as a “frequency multiplexing method”. Moreover, it is also possible to adopt the multiplexing method in which the inclination is performed not in the radial direction but in the normal direction.
In another aspect of the embodiment of the information recording apparatus of the present invention, at least one portion of the laser light source, the converting optical system, the one-dimensional spatial modulating device, and the recording optical system disposed in a same plane located along the recording surface.
According to this aspect, the plane on which at least one portion of the laser light source, the converting optical system, the one-dimensional spatial modulating device, and the recording optical system is disposed is along the recording surface, as in the plate-like laser beam, so that it is possible to contain the constitutional elements in the space which spreads relatively thinly along the recording surface. Therefore, it is possible to miniaturize and thin the entire information recording apparatus.
In another aspect of the embodiment of the information recording apparatus of the present invention, the recording optical system includes a mirror device for changing the one-dimensional spatial modulated plate-like laser beam which travels along the recording surface, to travel in a direction crossing the recording surface.
According to this aspect, the plate-like laser beam which travels along the recording surface is changed by the mirror device included in the recording optical system, to travel in the direction crossing the recording surface. Then, it is irradiated onto the recording surface through another optical element, such as an object lens, for example. Therefore, it is possible to prevent the recording optical system from being unnecessarily thicken in the direction crossing the recording surface.
In another aspect of the embodiment of the information recording apparatus of the present invention, at least one of the converting optical system, the one-dimensional spatial modulating device, and the recording optical system includes an optical element in which a cross section crossing a traveling direction of the plate-like laser beam is in a longitudinal shape, extending along the recording surface in accordance with a cross section of light flux, which extends linearly, of the plate-like laser beam.
According to this aspect, various optical elements, such as a cylindrical lens, a spatial light modulator, a mirror, a half mirror, and a prism, included in the converting optical system, the one-dimensional spatial modulating device, and the recording optical system are in a longitudinal shape, extending in accordance with the cross section of light flux extending linearly of the incident plate-like laser beam. Therefore, without using an unnecessarily large optical element, it is possible to miniaturize and thin the entire information recording apparatus, by using the longitudinal shaped optical element which has a flat shape along the recording surface and which can function, necessarily and sufficiently, with respect to the plate-like laser beam.
The embodiment of the information recording/reproducing apparatus of the present invention is an information recording/reproducing apparatus provided with: the above-mentioned embodiment of the information recording apparatus of the present invention (including its various aspects); a controlling device for making the one-dimensional spatial modulating device function as a shielding device for shielding the laser beam emitted from the laser light source; and a reproducing device for detecting interference light produced by transmission, diffraction, or reflection on the recording medium, caused by the reference light irradiated to the recording surface through the recording optical system, and reproducing the record information on the basis of the detected interference light.
The embodiment of the information recording/reproducing apparatus of the present invention is provided with the above-mentioned embodiment of the information recording apparatus of the present invention. Thus, it is possible to dispose the laser light source, the converting optical system, the one-dimensional spatial modulating device, and the recording optical system of the present invention, in a relatively narrow space surrounding the recording medium which spreads in a plate-like way, on a hologram recorder and a player or the like, for example, and it is possible to miniaturize and thin the entire information recording/reproducing apparatus including an accommodation space for the recording medium.
These effects and other advantages of the present invention become more apparent from the following embodiments.
As explained above, according to the embodiment of the information recording apparatus of the present invention, the one-dimensional spatial modulation is performed by the one-dimensional spatial modulating device, and the laser beam is converted by the converting optical system to the plate-like laser beam such that the direction thereof extending linearly is along the recording surface. Thus, it is possible to miniaturize and thin the entire information recording apparatus including an accommodation space for the recording medium. Moreover, according to the embodiment of the information recording/reproducing apparatus of the present invention, the laser beam is converted by the converting optical system to the plate-like laser beam such that the direction thereof extending linearly is along the recording surface. Thus, it is possible to miniaturize and thin the entire information recording/reproducing apparatus including an accommodation space for the recording medium.
Hereinafter, a basic recording principle and a basic reproduction principle in the examples of the information recording/reproducing apparatus which uses the hologram of the present invention will be discussed, with reference to
At first, with reference to
The record information inputted from the exterior is once stored or held in a buffer 12, and then, transmitted to a formatter 11. The formatter 11 performs a necessary process, such as addition of an ECC (Error Correction Code), to the record information, generates data following a predetermined recording format, and supplies it to a modulator 9. The modulator 9 performs two types of modulation. One is the modulation of signal light performed by a one-dimensional spatial light modulator 3 described later, and the other is the modulation of laser light emitted from a laser light source 1. Incidentally, they will be discussed again later.
A laser optical system, which produces or generates recording light (signal light and reference light) and irradiating the disc 8 with it, is provided with: the laser light source 1; an expander 2; the one-dimensional spatial light modulator 3; a Fourier transform lens 4; an inverse Fourier transform lens 5; a light receiving element (or photo-detector) 6; a half mirror 14; a reflecting mirror 15; and a condensing lens 16. The disc 8 is disposed between the Fourier transform lens 4 and the inverse Fourier transform lens 5.
The laser beam emitted from the laser light source 1 is expanded by the expander 2 in size or width of the beam, and is split or divided into two series, i.e. the signal light and the reference light, by the half mirror 14. The laser beam transmitted through the half mirror 14 passes through the one-dimensional spatial light modulator 3, by which it is modulated in accordance with a pattern given by the modulator 9, and enters the Fourier transform lens 4. Moreover, the laser beam passes through the Fourier transform lens 4, by which it is irradiated onto the disc 8 as signal light Ls.
The other laser beam, split by the half mirror 14, is reflected by the reflecting mirror 15, and irradiated as reference light Lr onto the recording surface of the disc 8 through the condensing lens 16. On the recording surface of the disc 8, the signal light Ls and the reference light Lr are simultaneously irradiated to the same position on the disc 8. By this, the signal light Ls and the reference light Lr interfere with each other on the disc 8, to thereby produce an interference pattern or fringe, and the interference pattern is recorded as a Fourier image into the hologram medium.
On the other hand, upon the reproduction of the information, the signal light Ls is shielded or blocked so that the disc 8 is not irradiated, and the disc 8 is irradiated with only the reference light Lr which is the same as in the recording. The irradiated reference light Lr is diffracted by the interference pattern recorded on the disc 8, to thereby produce diffracted light. The diffracted light enters the light receiving element 6 through the inverse Fourier transform lens 5, and thus a reproduction signal is obtained. The reproduction signal is supplied to a reproducing processing system 20.
Next, with reference to
The laser light transmitted through the one-dimensional spatial light modulator 3 is irradiated onto the recording surface of the disc 8 by the Fourier transform lens 4. As shown in the figure, on the recording surface of the disc 8, there is formed a Fourier image F, including one O-order diffracted light L0 and two 1st-order diffracted lights L1. In the example of
In the present invention, the Fourier image F is recorded onto the disc 8 while the recording medium is relatively displaced relative to the recording optical system. In the example, the recording medium is the disc, so that by the rotation of the disc 8, the Fourier image F formed on the recording surface of the disc 8 is displaced in the tangential direction of the disc 8.
Next, with reference to
In the condition that the disc 8 stays still, the Fourier image F as shown in
The hologram mark shown in
One of the modulation in the two directions is modulation by the grating structure 3a of the one-dimensional spatial light modulator 3. In this example, the 8-bit one-dimensional spatial light modulator 3 as shown in
In addition to this, in the example, the modulation using a hologram mark length is preformed by controlling whether to irradiate or not the laser beam (i.e. ON/OFF of the laser light source 1) in the recording direction, i.e. in the H direction, in
In the example of
Next, with reference to
Next, with reference to
Namely, the hologram recording is performed in the present invention, so that it is possible to multiplex and record different information into the same position on the recording medium, by changing a recording condition. For example,
Moreover, the above-mentioned example shows the case where the axial direction of the Fourier image (i.e. the direction of a straight line formed of the 0-order light and the 1st-order) is 90 degrees to the rotational direction of the disc (i.e. 0 degree to the V direction which is the radial direction of the disc); however, it is possible to shift the axial direction of the Fourier image from the radial direction of the disc and to record the information.
In the case of the disc-shaped recording medium, damage, such as a scratch, caused while a user treats the disc or the like, is caused in the radial direction of the disc in relatively many cases.
It is also possible to use a cylindrical lens for the expander 2 and the Fourier transform lens 4.
The recording/reproducing apparatus shown in
Moreover, the recording/reproducing apparatus shown in
As described above, the above-mentioned example and another example is constructed such that it is possible to distinguish the pattern of the reproduction light even if the Fourier image is displaced, relatively to the recording medium, by performing the spatial modulation of the Fourier image only in a direction different from the displacement direction of the recording medium and by recording the information. Thus, it is unnecessary to stop the recording medium upon the recording/reproduction of the information, to thereby improve a random access performance. Moreover, it is possible to increase a recording capacity, by modulating the information by using the mark information even in the displacement direction of the recording medium.
Moreover, in the above-mentioned example, the hologram disc is exemplified as the recording medium. The application of the present invention, however, is not limited to the disc-shaped recording medium, and can be applied to recording medium in various shapes, such as a card-type recording medium.
Next, the recording/reproducing apparatus for the card type recording medium will be discussed, as another example of the present invention.
In
Specifically, as shown in
Next, the recording/reproducing apparatus which uses self-coupling will be explained as another example of the present invention, with reference to
Namely, in the above-mentioned example, the laser beam from the laser light source is split to produce the signal light and the reference light. However, the present invention can be also applied to the case where the 0-order light and the higher-order light are allowed to interfere with each other, by using the fact that the laser light is not split but transmitted through the spatial light modulator, to produce the 0-order light which mainly has the brightness component and the higher-order light which has the phase component.
In
On the other hand, the recording medium 110 is movably held by a movable stage 60. The movable stage 60 is controlled by a not-illustrated controller, and displaces the recording medium 110 upon the recording and reproduction of the information.
The beam expander BX expands the diameter of the light beam 112 transmitted through the shutter SHs to produce parallel light, and enters it perpendicularly to the one-dimensional spatial light modulator 103. As in the example shown in
Next, with reference to
Upon reproduction, as shown in
Moreover, the example is explained by using ±1st-order light, however, both the plus 1st-order light and the minus 1st-order light have the same characteristics, so that the same effect can be obtained, even with only one 1st-order light.
Next, a detailed explanation will be given to an optically relative positional relationship in reality between constitutional elements within the optical system of the recording/reproducing apparatus in the first example of the present invention and the disc, with reference to
In
Incidentally, the reflection type recording/reproducing apparatus in the first example is one specific example of the recording/reproducing apparatus of the present invention.
As shown in
The various optical components are accommodated or included in a not-illustrated case or housing of the optical system 19-1, as shown in
Next, with reference to
At first, the operation upon the recording of the information will be explained.
Upon the recording of the information, the laser beam emitted in the X axis direction from the laser light source 1 is split into two series by the half mirror 14A. Namely, one laser beam is the signal light Ls which is subsequently modulated by the one-dimensional spatial light modulator 3, and the other laser beam is the reference light Lr which is combined with the signal light Ls, in order to record the interference pattern onto the disc 8. In other words, the half mirror 14A serves as a splitting or dividing optical system for splitting the emitted laser beam into the signal light Ls and the reference light Lr. The signal light Ls transmitted through the half mirror 14A in the X axis direction is emitted to the expander 2. The signal light Ls transmitted through the expander 2 is converted from the prism-like laser beam to the lamellate or plate-like laser beam, and its width is expanded. Namely, it is converted to the “plate-like laser beam” of the present invention. In other words, the expander 2 serves as a converting optical system for converting the laser beam emitted from the laser light source 1, to the plate-like laser beam in which the cross section of light flux extends linearly. Hereinafter, the plane defined by the signal light Ls is referred to as a “signal light plane Hs”, as occasion demands. Particularly in the present invention, the optical system is disposed such that the signal light plane Hs is located along the plane of the disc 8; for example, such that the signal light plane Hs is located in parallel with the plane (recording surface) of the disc 8. This plate-like signal light Ls is entered to the collimator lens 18 and converted from the plate-like diffused light to the plate-like parallel light. This signal light Ls which has been converted to the parallel light is one-dimensional-spatial-modulated by the one-dimensional spatial light modulator 3. The one-dimensional spatial light modulator 3 serves as a one-dimensional spatial modulating device for performing one-dimensional spatial modulation in a direction extending linearly (e.g. in a direction extending based on a shape of a straight line) with respect to the plate-like laser beam.
On the other hand, the reference light Lr emitted in the Z axis direction by the half mirror 14A is reflected by the reflecting mirror 15B in the X axis direction, and is entered to the half mirror 14B disposed below the light receiving element 6 (hereinafter refer to
The signal light Ls modulated by the one-dimensional spatial light modulator 3 and the above-mentioned reference light Lr are combined on the half mirror 14C to the same optical path, and are entered to the reflecting mirror 15A in the X axis direction (refer to
Next, the operation upon the reproduction of the information will be discussed.
Upon the reproduction of the information, at first, the one-dimensional spatial light modulator 3 is used as a shutter to shield or block the signal light Ls in order not to transmit it. Then, only the reference light Lr with the same characteristics as in the recording, specifically, with the same wavelength, amplitude, or light intensity or the like, is irradiated to the disc 8 in the Z axis direction, on the same optical path as in the recording. The irradiated reference light Lr is diffracted by the interference pattern recorded within the disc 8, to thereby produce diffracted light (reproduction light) Lk. The diffracted light Lk is reflected by the reflective layer or the like within the disc 8, for example, and passes through the same optical path as the approach route. Specifically, the diffracted light Lk is transmitted through the objective lens 17A, and is reflected by the reflecting mirror 15A in the minus X axis direction. Then, it is reflected by the half mirror 14C in the Z axis direction, and is transmitted through the half mirror 14B, and thus it is entered to the light receiving element 6 (refer to
As described above, in the first example, it is possible to change the prism-like laser beam to be plate-like, by using the one-dimensional spatial light modulator instead of the two-dimensional spatial light modulator. Moreover, the optical system is disposed so as to maintain the positional relationship that the plate-like laser beam which expands in the optical system 19-1, i.e. the signal light plane Hs, faces the plane of the disc 8 in a parallel relationship, for example. As a result, it is possible to further miniaturize and thin the entire information recording/reproducing apparatus, including the both the space which accommodates the disc 8 and the optical system 19-1.
Incidentally, in the first example, the reference light Lr passes through the upper part of the constitutional element, such as the one-dimensional spatial light modulator 3. This space is in a range of the thickness of the objective lens 17A, and an upper side space in which the objective lens 17A is not located in the optical system 19-1 is used, so that it is possible to realize the simplification, miniaturization and thinning of the entire optical system 19-1.
Next, a detailed explanation will be given to an optically relative positional relationship in reality between constitutional elements within the optical system of the recording/reproducing apparatus in the second example of the present invention and the disc, with reference to
Incidentally, in explaining the second example with reference to
As shown in
Next, with reference to
Upon the recording of the information, the laser beam emitted in the X axis direction from the laser light source 1 is split into two series of the signal light Ls and the reference light Lr by the half mirror 14A, as in the first example.
At first, the optical path of the signal light Ls transmitted through the half mirror 14A in the X axis direction is the same as that in the first example, except that the signal light Ls is not transmitted through the half mirror 14C and is transmitted through not the objective lens 17A which is a cylindrical lens but the simple objective lens 17B. Particularly in the present invention, the optical system is disposed so as to maintain the positional relationship that the signal light plane Hs faces the plane of the disc 8 in a parallel relationship, for example.
On the other hand, the reference light Lr emitted by the half mirror 14A in the Y axis direction is reflected by the reflecting mirror 15C in the X axis direction and is entered to the reflecting mirror 15D. The reference light Lr is reflected by the reflecting mirror 15D in the minus Y axis direction, and is entered to the reflecting mirror 15E. The reference light Lr is reflected by the reflecting mirror 15E toward the objective lens 17B disposed in the Z axis direction, and is transmitted through the objective lens 17B.
Consequently, the signal light Ls modulated by the one-dimensional spatial light modulator 3 is transmitted through one area of the objective lens 17B, and is irradiated to the disc 8 at an irradiation angle Θ1 from the normal of the disc 8, i.e. from the minus Z axis direction. The reference light Lr is also transmitted through another area of the objective lens 17B through the plurality of reflecting mirrors 15C, 15D, and 15E, as described above, and is irradiated to the disc 8 at an irradiation angle Θ2 from the normal of the disc 8. As described above, the signal light Ls and the reference light Lr are transmitted through the different axes, i.e. the different optical paths, of the same objective lens 17B, and separately focused or converged, and simultaneously irradiated to the same position on the disc 8. By this, the signal light Ls and the reference light Lr interfere with each other on the disc 8, to thereby generate the interference pattern having a grating vector with the irradiation angles Θ1 and Θ2 and wavelength λ of the signal light Ls and the reference light Lr as parameters. The interference pattern is recorded into the hologram medium within the disc 8 as the Fourier image.
Upon the reproduction of the information, the one-dimensional spatial light modulator 3 is used as a shutter to shield or block the signal light Ls in order not to transmit it. Then, only the reference light Lr with the same characteristics as in the recording, specifically, with the same wavelength, amplitude, or light intensity or the like, is irradiated to the disc 8 on the same optical path as in the recording. The irradiated reference light Lr is diffracted by the interference pattern having the grating vector which is recorded within the disc 8, to thereby produce the diffracted light (reproduction light) Lk. The diffracted light Lk is emitted from the disc 8 at a diffracted light emitting angle Θ3 which is uniquely determined from the grating vector. The diffracted light Lk is transmitted through the objective lens 17B, and is entered to the light receiving element 6. In this manner, a reproduction signal is obtained on the light receiving element 6, and this reproduction signal is supplied to the reproduction processing system.
As described above, in the second example, as opposed to the first example, it is possible to simplify the constitutional elements of the optical system 19-2, by using not the cylindrical lens but a simple lens which does not need a high performance, for the objective lens 17B. Then, the signal light Ls and the reference light Lr are not combined on the half mirror but transmitted through the different areas of the objective lens 17B, and combined on the plane of the disc 8. This is how the interference pattern, i.e. the Fourier image, is recorded in a photosensitive material, such as a hologram medium, within the disc 8.
Moreover, in the second example, as in the first example, it is possible to change the prism-like laser beam to be plate-like, by using the one-dimensional spatial light modulator. Moreover, the optical system is disposed so as to maintain the positional relationship that the signal light plane Hs faces the plane of the disc 8 in a parallel relationship, for example. Thus, it is possible to further miniaturize and thin the entire optical system 19-2.
Moreover, in the second example, the reference light Lr is transmitted such that optical path of the reference light Lr and constitutional elements (e.g. the one-dimensional spatial light modulator 3 and so on) are located side by side. As a result of this, it is possible to miniaturize and thin the entire optical system 19-2.
Next, a detailed explanation will be given to an optically relative positional relationship in reality between constitutional elements within the optical system of the recording/reproducing apparatus in the third example of the present invention and the disc, with reference to
Incidentally, in explaining the third example with reference to
As shown in
Upon the recording of the information, the laser beam emitted in the X axis direction from the laser light source 1 is the signal light Ls which is subsequently modulated by the one-dimensional spatial light modulator 3. The signal light Ls is emitted toward the expander 2, and the signal light Ls transmitted through the expander 2 is converted from the prism-like laser beam to the laser beam having the signal light plane Hs. This plate-like signal light Ls is entered to the collimator lens and converted from the diffused light to the parallel light. This signal light Ls which has been converted to the parallel light is modulated by the one-dimensional spatial light modulator 3. The signal light Ls is focused by passing through the objective lens 17B, and is irradiated to the disc 8. In the example, the incident light processing device R is located on the opposite side to a side where the disc 8 is irradiated. The incident light processing device R has a function of splitting the signal light Ls irradiated to the disc 8, into the 0-order light and the higher-order light, and returning one portion of light to the inside of the disc 8. Specifically, the incident light processing device R is provided with: the 0-order light reflecting device RR for reflecting only the 0-order light of the signal light Ls to the inside of the disc 8; and the higher-order light transmitting portion T for defining the range thereof and transmitting the higher-order light. The 0-order light reflecting device RR reflects the 0-order light of the signal light Ls to the inside of the disc 8. The 0-order light, reflected by the 0-order light reflecting device RR to the inside of the disc 8, and the irradiated higher-order light interfere with each other, and thus, the interference pattern, i.e. the Fourier image, is recorded in a photosensitive material, such as a hologram medium, within the disc 8. By the principle of this self-coupling, it is unnecessary to split the laser beam from the laser light source to thereby produce the reference light, as in the first and second examples explained with reference to
In particular, with respect to an aspect of the self-coupling, in addition to the aspect of the example in which the 0-order light is reflected and the higher-order light is transmitted, it may be an aspect in which the 0-order light is transmitted, absorbed, scattered, or polarized, and the higher-order light is reflected.
Upon the reproduction of the information, the one-dimensional spatial light modulator 3 is used as a fully opened shutter not to shield or block the reference light Lr, so the reference light Lr emitted in the X axis direction from the laser light source 1 is not modulated by the one-dimensional spatial light modulator 3. Then, only the reference light Lr with the same characteristics as in the recording, specifically, with the same wavelength, amplitude, or light intensity or the like, is irradiated to the disc 8 on the same optical path as in the recording. The irradiated reference light Lr is diffracted by the interference pattern having the grating vector which is recorded within the disc 8, to thereby produce the diffracted light (reproduction light) Lk. The diffracted light Lk is reflected by the reflective layer or the like within the disc 8, for example, and passes through the same optical path as the approach route. Specifically, the diffracted light Lk is transmitted through the objective lens 17B, is reflected by the half mirror 14D in the minus Z axis direction, and is entered to the light receiving element 6. In this manner, a reproduction signal is obtained on the light receiving element 6, and this reproduction signal is supplied to the reproduction processing system.
As described above, in the third example, as in the first and second examples, it is possible to change the prism-like laser beam to be plate-like, by using the one-dimensional spatial light modulator. Moreover, the optical system is disposed so as to maintain the positional relationship that the signal light plane Hs faces the plane of the disc 8 in a parallel relationship, for example. Thus, it is possible to further miniaturize and thin the entire optical system 19-3.
Moreover, the self-coupling is used in the third example, so that the optical path splitting or dividing element, such as the half mirror, is not required, which allows less optical components or the like. Thus, it is possible to simplify, miniaturize, and thin the entire optical system 19-3.
Next, a detailed explanation will be given to an optically relative positional relationship in reality between constitutional elements within the optical system of the recording/reproducing apparatus in the fourth example of the present invention and the disc, with reference to
Incidentally, in explaining the fourth example with reference to
In the fourth example, the third example is further developed to realize the recording by the “angle multiplexing”. Here, the angle multiplexing in the example is a technology of (i) multiplexing and recording the different record information into the same area and (ii) reproducing them, by relatively changing the irradiation angles of the reference light and the signal light with respect to the surface of the hologram recording medium.
In the fourth example, in order to realize the angle multiplexing, as new constitutional elements added to the constitutional elements in the third example, there are provided with: an optical system board 19A; and a motor 19B. On the top surface of the optical system board 19A, there are provided the expander 2, the collimator lens 18, and the one-dimensional spatial light modulator 3, which constitute an optical system 19-4. One side of the optical system board 19A is a spindle 19C parallel to the X axis. If the motor 19B is driven, the optical system board 19A and the signal light plane Hs which expands in the optical system 19-4 can be inclined by 1 degree or less, such as several tenth of a degree, with respect to the disc plane. Thus, it is possible to change the irradiation angle of the signal light Ls or the reference light Lr with respect to the plane of the disc 8, to thereby realize the recording by the angle multiplexing. Incidentally, the change in the irradiation angle necessary to realize the angle multiplexing is determined from the thickness of the disc 8. For example, by changing the irradiation angle stepwise by several tenth of a degree, it is possible to repeatedly record many pieces of record information, such as a dozen to several tens, into the same point on the recording surface.
The operations upon the recording and the reproduction in the fourth example are the same as in the third example.
Particularly, even in the fourth example, the positional relationship that the signal light plane Hs faces the disc plane is maintained.
Incidentally, the “irradiation angle changing device” of the present invention may relatively change the irradiation angle of the signal light Ls or the reference light Lr with respect to the disc plane. For example, the irradiation angle changing device may be constructed to change the angle and the arrangement with respect to the optical path on the laser light source 1, the half mirror 14A, the expander 2, the collimator 18, and the one-dimensional spatial light modulator 3, which constitute the optical system 19-4. Alternatively, an optical element exclusive for changing the irradiating angel of the signal light Ls or the reference light Lr may be additionally provided for the optical system. Alternatively, in place of or in addition to this, it may be constructed to mechanically change the holding angle of the disc 8. Moreover, in addition to the angle multiplexing in the radial direction, the angle multiplexing in another direction, such as the normal direction, can be also performed.
As described above, in the fourth example, as in the first, second, and third examples, it is possible to change the prism-like laser beam to be plate-like, by using the one-dimensional spatial light modulator. Moreover, the optical system is disposed so as to maintain the positional relationship that the signal light plane Hs faces the plane of the disc 8 in a parallel relationship, for example. Thus, it is possible to further miniaturize and thin the entire optical system 19-4.
Moreover, the self-coupling is used in the fourth example, so that the optical path splitting or dividing element, such as the half mirror, is not required, which allows less optical components or the like. Thus, it is possible to simplify, miniaturize, and thin the entire optical system 19-4.
In the present invention, various changes may be made, if desired, without departing from the essence or spirit of the invention which can be read from the claims and the entire specification. The information recording apparatus and the information recording/reproducing apparatus of a hologram type, all of which involves such changes, are also intended to be within the technical scope of the present invention.
The information recording apparatus and the information recording/reproducing apparatus of the present invention can be applied to an information recording apparatus and an information recording/reproducing apparatus which use a hologram.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-330575 | Sep 2003 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/13737 | 9/21/2004 | WO | 6/26/2006 |
