JP2002304739A - Information reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce information recorded on a low-cost information recording medium having sufficient recording capacity. SOLUTION: The information recording medium 1 having an information recording part 10 wherein a plurality of phase diffraction gratings 20 are disposed with a two-dimensional pattern corresponding to the information to be recorded, is irradiated with linear laser beams emitted from a two-dimensional semiconductor laser array 71, then the diffracted light generated in the information recording part 10 is detected by a CCD array 76.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reproducing apparatus for reproducing information recorded on an information recording medium for recording information using a phase diffraction grating.

[0002]

2. Description of the Related Art Conventionally, as an information recording medium on which information is reproduced by irradiating light, for example, a CD is used.
-Optical disks such as ROMs are widely used. Although such an optical disk generally has a large storage capacity of several hundred MB to several GB, it needs to be driven to rotate when recording and reproducing information. There was a limit to miniaturization.

Also, optical disks such as CD-ROMs have the advantage that they can be manufactured at extremely low cost by mass production.
It is being distributed in large quantities as an appendix to books and magazines. However, in this way the CD-R
When distributing an OM, data of only a relatively small size of about several MB to several tens MB is often recorded. Therefore, the conventional optical disk is oversized depending on the size of the data to be recorded, and in view of the current state of being disposable in order to only record data of a small size, from the viewpoint of load on the natural environment. In some cases, it was used for undesirable purposes.

Therefore, a so-called optical card has been proposed and put into practical use as an information recording medium having a storage capacity of about several MB to several tens MB and smaller in size and more convenient than an optical disc.

As shown in FIG. 11, for example, an optical card has a signal recording layer 100 in which, for example, a chalcogenide-based phase-change recording material is formed in a thin film shape on a substrate formed in a size of several cm square. When recording and reproducing information, the signal recording layer 100 is irradiated with a light spot 101 obtained by condensing a laser beam. And light spot 1
01 is scanned, for example, as shown by arrow A in FIG.
By detecting a change in reflectance, the recording mark 102 formed on the signal recording layer 100 in accordance with the information to be recorded.
Is detected, and reproduction is performed. When information is recorded, the signal recording layer 100 changes its phase at the position of the light spot 101 by irradiating a laser beam modulated according to the information to be recorded with an output larger than that at the time of reproduction. Thus, a recording mark 102 is formed.

That is, in the optical card, information (digital data) to be recorded is recorded on the signal recording layer 100 as the recording mark 102. At the time of recording / reproduction, various encoding / coding methods such as NRZI are applied to digital data for the purpose of realizing error correction and high recording density.
Generally, decoding processing and various modulation / demodulation processing such as 8-10 modulation are performed.

[0007] Since an optical card performs recording and reproduction using a laser beam, it has a much larger storage capacity than a so-called magnetic card which has been widely used in credit cards and the like. It is possible. Therefore, for example, by recording deposit balance information, medical chart information, or personal information, it is expected to be used as a high-performance cash card in a financial institution or as a medical chart in a medical institution.

[0008] As a specific example of such an optical card, a write-once optical card and a reproducing apparatus therefor which can be produced relatively inexpensively because they are not preformatted are described in "K. Toyota et al. al., "A New Optical Card Req
uiring No Preformatting ", SPIE Vol.1316 Optical Dat
a Storage (1990), p. 345 ". In this example, a simple device configuration using a CCD array that scans in only one direction without a servo mechanism such as focus servo, tracking servo, or azimuth servo for a laser beam recording mark is described.

[0009]

By the way, in the conventional optical card, the laser beam applied to the signal recording layer causes the signal recording layer to undergo phase change, melting, evaporation, deformation, and the like. A recording mark is formed. Therefore, when a large number of optical cards having the same recording content are manufactured, it is necessary to individually record information on each optical card, and there has been a problem that productivity is significantly reduced.

In forming a recording mark, various printing techniques such as those used in an ink jet printer may be used. However, with the current printing technique, the recording mark is printed with a positional accuracy of about 20 μm or less. However, there is a problem that it is extremely difficult to realize a sufficient recording capacity because the recording is not easy.

Accordingly, the present invention has been made in view of the above-mentioned conventional circumstances, and has been developed to provide an information recording medium which not only has a sufficient recording capacity but can be manufactured in large quantities at low cost. It is an object of the present invention to provide an information reproducing apparatus for reproducing information recorded in a device.

[0012]

According to the information reproducing apparatus of the present invention, the light emitting element which emits a laser beam in a predetermined wavelength range is X-ray.
A two-dimensional semiconductor laser array provided in a plurality in the -Y direction, and a plurality of phase diffraction gratings in a two-dimensional pattern corresponding to information to be recorded by condensing laser light emitted from the two-dimensional semiconductor laser array. Irradiating means for irradiating the information recording section of the information recording medium provided on the substrate with an information recording section having a linear laser beam shape, and a laser beam irradiated by the irradiating means, Scanning means for scanning at a position of the information recording part in a direction substantially perpendicular to the length direction of the laser beam shape, and a straight line generated by diffracting the laser light scanned by the scanning means at the information recording part Having a light-receiving surface sufficient to receive the diffracted light in the shape of the light-emitting element, the light-receiving surface having an aspect ratio sufficient to receive the laser light emitted from each light-emitting element in the surface-emitting laser element. The light receiving elements are more disposed, and a CCD array for detecting a two-dimensional pattern of said information recording unit in each basic information unit by each of these light receiving elements.

The information reproducing apparatus according to the present invention configured as described above has a very simple configuration in which a laser beam having a linear laser beam shape is scanned by an information recording unit to detect a diffracted beam. The information recorded on the information recording medium according to the present invention can be reproduced. Also,
The information recording unit is irradiated with linear laser light emitted from the two-dimensional semiconductor laser array, and diffracted light is detected by a CCD array having a plurality of light receiving elements having a sufficient aspect ratio. It is possible to easily detect the two-dimensional pattern with high accuracy.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an information reproducing apparatus to which the present invention is applied will be described in detail with reference to the drawings. Hereinafter, an information recording medium 1 as shown in FIG. 1 will be described as one configuration example of an information recording medium for reproducing an information signal using an information reproducing apparatus to which the present invention is applied.

As shown in FIG. 1, the information recording medium 1 has a phase diffraction grating formed in a two-dimensional pattern in accordance with information to be recorded on a substrate 2 which is formed of, for example, various resin materials into a substantially flat plate shape. Information recording sheet 3 and reflection film 4 for improving the reflectivity of laser light emitted during reproduction of information
And a protective film 5 for protecting the information recording sheet 3 and the reflective film 4
Are sequentially laminated.

When reproducing information, the information recording medium 1 is irradiated with laser light from the protective film 5 side to the information recording sheet 3, and diffracted light generated by the phase diffraction grating formed on the information recording sheet 3. Is detected, the recorded information is reproduced.

Although FIG. 1 shows only the main part of the information recording medium 1, the information recording medium 1
In addition to the configuration shown in FIG. 1, for example, various exterior materials may be provided for the purpose of improving handling convenience, mechanical durability, and resistance to environmental changes.

The substrate 2 has a shape similar to that of a general magnetic card that has been widely used in the past. For example, the length is 50 mm and 80 mm, respectively, and the thickness is about 0.1 mm. Can be. However, the shape and material of the substrate 2 are not particularly limited.
For example, the size and thickness may be the same as that of office paper set to a predetermined standard (for example, A4, A5, B4, etc.). On the substrate 2, an image such as a photograph or a character is printed, or another sheet on which the image is printed is laminated on a surface (back surface) opposite to the side on which the information recording sheet 3 is laminated. May be.

The substrate 2 is provided for the purpose of ensuring convenience of handling and mechanical durability in the information recording medium 1, and if these are sufficiently ensured, the substrate 2 has flexibility. It may be. Information recording sheet 3
When the substrate itself satisfies these objects, the substrate 2 can be omitted. In the information recording medium 1, the substrate 2
Is unnecessary, the information recording sheet 3 also functions as the substrate 2. However, in consideration of the fact that the information recording medium 1 is fed and moved relative to the optical system at the time of reproducing information by an information reproducing apparatus described later, the overall thickness is 0.2 mm to 0.5 mm.
mm. As a result, the positioning can be performed with high accuracy, and the reproducing operation can be reliably performed.

In the information recording sheet 3, a plurality of phase diffraction gratings are formed on one main surface in a two-dimensional pattern according to an information signal to be recorded. The information recording sheet 3 is made of various resin materials such as polycarbonate and has a thickness of 0.1 m.
It is formed in a sheet shape with a thickness of about m, and a groove-like uneven pattern 3a constituting each phase diffraction grating is formed. The uneven pattern 3a can be transferred and formed on the information recording sheet 3 with high accuracy and low cost by using various stamping techniques as described later.

The reflection film 4 is made of, for example, Al, Au, Cu,
It is formed of a metal material such as Ag to have a thickness of about 50 nm. Since the information recording medium 1 includes the reflection film 4, it is possible to improve the reflectance of the laser light and output the diffracted light with a sufficient light intensity and light modulation. In the information recording medium 1, if the information recording sheet 3 itself has a sufficient reflectance, the reflective film 4 can be omitted.

It is desirable that the reflection film 4 is made of an organic material. The organic material that can be used as the reflection film 4 is:
A material capable of obtaining a refractive index of 0 or more, for example, an organic material having a high refractive index in the wavelength region of laser light, such as a cyanine-based organic dye material, can be used. In the information recording medium 1, by forming the reflective film 4 with an organic material, the load on the environment can be reduced when the information recording medium 1 is discarded by burning or the like.
In addition, resources can be easily recycled.

In the information recording medium 1, the refractive index of the light transmitting layer (the protective film 5 in this example) through which the laser beam passes before reaching the information recording sheet 3 is about 1.5. In this case, the reflectivity of the light transmitting layer with respect to the laser beam is about 4%.
% Or more must be secured. Therefore, the reflection film 4
Is formed of an organic material, when the refractive index of the organic material is n ₀ and the wavelength of the laser beam is λ, the film thickness of the reflective film 4 is set to around λ / n ₀ , High reflectivity can be obtained. Note that the organic material does not necessarily need to have a light-transmitting property with respect to the laser light.
The material and the film thickness may be selected in consideration of the complex refractive index instead of the refractive index in the above.

The protective film 5 is laminated for the purpose of protecting the information recording sheet 3 and the reflective film 4, and is formed in a thin film of a material which transmits laser light. The information recording medium 1 does not need to directly protect the information recording sheet 3 and the reflection film 4 by, for example, providing an exterior material, or the information recording sheet 3 and the reflection film 4 have sufficient environmental resistance characteristics. For example, the protective film 5 can be unnecessary.

In the information recording medium 1 according to the present embodiment, the information recording sheet 3 is irradiated with laser light from the protective film 5 side, and the protective film 5 has a function as a light transmitting layer. are doing. For this reason, the protective film 5 needs to have sufficient translucency for laser light. However, for example, when the information recording medium 1 is configured to irradiate laser light from the substrate 2 side, the substrate 2 serves as a light transmitting layer,
It is important to have sufficient translucency. In this case, the protective film 5 does not need to have translucency.

Next, how information is recorded on the information recording medium 1 configured as described above will be described.

In the information recording medium 1, as shown in FIG.
A plurality of phase diffraction gratings are arranged in a two-dimensional pattern according to the information to be recorded by the concavo-convex pattern 3a formed on the information recording sheet 3, and the region where the phase diffraction gratings are arranged is used as a whole for information recording. The unit 10 is constituted.
FIG. 2 is a plan view of the main surface of the information recording medium 1 as viewed from the side irradiated with the laser beam, and is a schematic diagram showing a part of the two-dimensional pattern omitted.

In the area of the information recording section 10, a first control information recording section 11 and a second control information recording section 12 as areas where various kinds of control information are recorded in a band-like area, And a data recording unit 13 as an area in which is recorded. A plurality of first control information recording units 11 are set in parallel with each other at predetermined intervals, and a second control information recording unit 12 is disposed in a direction orthogonal to the first control information recording unit 11 in a predetermined direction. Are set in parallel at intervals of. A lattice-shaped internal area constituted by the first control information recording unit 11 and the second control information recording unit 12 is set as a data recording unit 13. Will be recorded.

The control information recorded in the first control information recording unit 11 and the second control information recording unit 12 is, for example, when the information is reproduced by irradiating a laser beam.
It is desirable to record information indicating the irradiation position and scanning position of the laser light. Thereby, the information reproducing apparatus that reproduces the information recorded on the information recording medium 1 can detect the irradiation position and the scanning position of the laser light, irradiate the laser light to the center of each phase diffraction grating, It becomes easy to scan the laser beam along the row of the phase diffraction grating,
Good reproduction output characteristics can be obtained by reliably detecting diffracted light.

It is desirable that the information indicating the irradiation position and the scanning position of the laser beam be recorded at least at two or more positions in the area of the information recording section 10. Thereby, the inclination of the information recording medium 1 with respect to the optical system in the information reproducing apparatus (that is, the inclination of the information recording unit 10), the amount of deviation, and the like can be reliably detected.

Further, as the control information, information indicating the timing at which the information reproducing apparatus emits a pulse of laser light can be recorded. Thereby, in the information reproducing apparatus, by detecting the control information, the laser light can be pulse-emitted at the position of each phase grating or the position corresponding to the row of the phase grating, and the irradiation power of the laser light can be reduced. It is possible to adjust or reduce crosstalk between adjacent phase diffraction gratings. The information indicating the timing may be information directly indicating a pulse emission cycle or the like.
For example, the information may be such that “0” and “1” appear alternately along the scanning direction of the laser beam. In this case, an output signal obtained by scanning the laser beam in accordance with this information has a waveform as shown in FIG. 3, for example, and the pulse emission timing can be calculated from the cycle of this waveform.

The control information may indicate address information in a data recording section. Thereby, the information recording medium 1 can easily reproduce specific information from the information recorded in the information recording unit 10.

More specifically, as the information recording section 10, for example, the arrangement of the phase diffraction gratings in the direction in which the first control information recording section 11 is set (the horizontal direction in FIG. 2) is referred to as "track". Then, as the first control information recording unit 11, a track number is recorded in the header part, and “0” is recorded.
And a recording pattern in which “1” appears alternately is recorded every other track for three tracks. Thus, for example, when the information reproducing apparatus detects one track at a time using laser light having a linear laser beam shape, a shift that occurs when scanning is performed in a direction orthogonal to the track is detected. It becomes easier.

For example, the first control information recording unit 11
Alternatively, the second control information recording unit 12 may record position information in the scanning direction of the laser beam, information including a synchronization signal for detecting “unevenness” in the scanning speed, and the like.

By the way, the information recorded in the first control information recording unit 11, the second control information recording unit 12, and the data recording unit 13 is, as shown in FIG.
It is recorded by a planar pattern in which a plurality of phase diffraction gratings 20 are arranged, that is, a two-dimensional pattern. The phase diffraction grating 20 is formed by forming several grooves as one set by the concave / convex pattern 3 a formed on the main surface of the information recording sheet 3. In the area of the information recording unit 10, for example, a portion where the phase diffraction grating 20 is formed is set as a value “1”, and a portion where the phase diffraction grating 20 is not formed is set as a value “0”. ing. In the information recording medium 1, since a plurality of patterns are formed in the area in the information recording section 10 in a pattern corresponding to the information recorded by the phase diffraction grating 20, digital data of "0" and "1" is formed. Information is recorded. That is, in the information recording medium 1, the phase diffraction grating 20 functions as a basic information unit, which is the smallest constituent element indicating information.

As schematically shown in FIG. 5, the phase diffraction grating 20 has, for example, a region having a length L of 7 μm square.
A plurality of stripe-shaped grooves having a line width b of about 1 μm are formed in parallel with each other with a pitch p of about several μm. Also, the depth d of this groove is
Assuming that the wavelength of the laser beam is λ and the refractive index of the light transmitting layer is n, λ
When / 4n, the degree of modulation when the laser beam is diffracted can be maximized. However, in practice, a Gaussian distribution is generated in the light intensity of the laser beam in the light spot. Therefore, if the half width of the Gaussian distribution is set to an effective light intensity, the depth d of the groove becomes 2/4 of λ / 4n. Times, ie, λ / 2n
Even in the case where it is less than or equal to about, a sufficient degree of modulation can be obtained. More specifically, the depth d of the groove is set to λ / 8n ~
It is desirable to set it in the range of λ / 2n.

The pitch p of the grooves in the phase diffraction grating 20 is determined by the diffraction angle of the diffracted light. m-th order (m =
0, ± 1, ± 2, the diffraction angle theta _m of diffracted light, ...) can be calculated by Equation 1 below.

Θ _m = sin ⁻¹ (mλ / p) (Equation 1) Accordingly, the numerical aperture of the objective lens used for focusing the laser beam when reproducing the information recording medium 1 is set to NA.
Assuming that (= sin θ ₀ ), the groove pitch p needs to satisfy the following expression 2.

P <λ / NA (Equation 2) Therefore, for example, in the case where reproduction is performed by a laser beam having a wavelength of 500 nm using an objective lens having an NA of 0.1, the groove pitch p Must be at least about 5 μm or less. Here, in the information recording medium 1, since the concavo-convex pattern 3a constituting the phase diffraction grating 20 can be formed with high accuracy by various stamping techniques, the groove shape of the phase diffraction grating 20 is set to several nm to several tens nm. Can be easily realized with the precision of Therefore, good reproduction characteristics can be ensured without using laser light having a small wavelength λ or using an objective lens having a large numerical aperture NA.

That is, the information recording medium 1 has a wavelength of, for example, 650 nm or 755 which has been widely used in the past.
a laser oscillation element that emits light of about nm
Can be reliably reproduced using an objective lens of about 0.2, which can contribute to realizing an information reproducing apparatus at extremely low cost.

In the information recording medium 1, the size of the phase diffraction grating 20 as a basic information unit, that is, the area occupied by one phase diffraction grating 20 in the information recording section 10 is desirably 100 μm ² or less. . This corresponds to a case where the phase diffraction grating 20 has a square shape and the length L of one side is 10 μm or less. If the occupied area exceeds 100 μm ² , it does not conform to the concept of the present invention that realizes a low-cost information recording medium having the same size and recording capacity as an optical card conventionally used. In order to secure a sufficient storage capacity, the size of the information recording unit 10 becomes large,
When the size is about the same as that of an optical card, a sufficient recording capacity cannot be achieved.

Next, as an information reproducing apparatus for reproducing the information recorded on the information recording medium 1, an information reproducing apparatus 70 as shown in FIG. 6 will be described as an example.

As shown in FIG. 6, the information reproducing device 70
A two-dimensional semiconductor laser array 71 that emits laser light having a wavelength of 780 nm at an optical output of 1 mW is provided as a light source. In this two-dimensional semiconductor laser array 71, the spread angle (intensity 1 / e ⁻² ) of the emitted laser light is 50 ° in the vertical direction and 20 ° in the horizontal direction with respect to the bonding surface to the device.
It has been.

A first cylindrical lens 72, a beam splitter 73, and a second cylindrical lens 74 are sequentially arranged on the optical axis of the laser light emitted from the two-dimensional semiconductor laser array 71. I have. Also,
The position where the laser light transmitted through the second cylindrical lens 74 is irradiated is located on the information recording section 10 of the information recording medium 1.
Is attached. Then, of the diffracted light generated by irradiating the information recording unit 10 with the laser light, the zero-order diffracted light is again incident on the beam splitter 73 via the second cylindrical lens 74.

The beam splitter 73 includes the information recording unit 10
And reflects the diffracted light in a direction orthogonal to the optical axis of the laser light emitted from the two-dimensional semiconductor laser array 71. Further, the information reproducing device 70 includes a third cylindrical lens 75 and a C light beam on the optical path of the diffracted light reflected by the beam splitter 73.
CD arrays 76 are sequentially arranged.

The information reproducing apparatus 70 includes a scanning mechanism (not shown) for scanning the information recording section 10 of the information recording medium 1 with a laser beam. As the scanning mechanism, for example, a mechanism that makes the information recording unit 10 of the information recording medium 1 relatively movable with respect to the irradiation position of the laser beam can be realized by combining mechanical members.
On the optical path of the laser light, for example, a galvanometer mirror,
By providing various optical elements such as a hologram element and a mirror array, a scanning mechanism can be realized.

In the information reproducing apparatus 70, for example, the irradiation position (information reading position) of the laser beam is the same as that of a conventional card type recording medium reading apparatus widely used such as a card reader. By manually moving the information recording medium 1 relative to
The information recording unit 10 may be moved with respect to the irradiation position of the laser beam, so that the information recording unit 10 scans the laser beam.

The information reproducing apparatus 70 is provided with a control section for controlling the operation of each section, a signal processing section for performing various kinds of signal processing on the signal output from the CCD array 76, and the like. The control unit and the signal processing unit can be realized by, for example, a control circuit or an arithmetic circuit configured by combining various semiconductor elements, and can be appropriately designed according to a desired device operation or signal processing. Therefore, detailed description here is omitted.

As shown in FIG. 7, the two-dimensional semiconductor laser array 71 has a plurality of light emitting elements 81 arranged on a substrate 80 in a plane along the X and Y directions shown in FIG. The electrodes for supplying a current to each light emitting element 81 are formed in a matrix in the X direction and the Y direction. That is, from each light emitting element 81, an X electrode 82 extending in the X direction and a Y electrode 83 extending in the Y direction are drawn out. Then, X electrodes 82 and Y electrodes 83 drawn from each light emitting element 81 are grouped by a predetermined number and connected to a plurality of X terminals 84 and Y terminals 85, respectively. In addition, the two-dimensional semiconductor laser array 71
Among the plurality of X terminals 84 and Y terminals 85,
By selecting a predetermined set of terminals and applying a voltage,
The laser light is emitted from the light emitting element 81 formed at the position where the selected X terminal 85 and Y terminal 86 intersect.

Such a two-dimensional semiconductor laser array 71
Is a VCSEL (Vertical-CavitySurface-Emitting La
ser), for example, "IEEE PHOTONICS TECH
NOLOGY LETTERS, Vol. 11, No. 12, Dec 1999 "and the like.

In this example, the two-dimensional semiconductor laser array 71 is arranged such that the light emitting elements 8 are arranged in a positional relationship as shown in FIG.
It is assumed that a plurality of 1s are provided. That is, the two-dimensional semiconductor laser array 71 has a Y surface on the main surface of the substrate 80.
A plurality of sets of a plurality of light emitting elements 81 arranged in the X direction while being shifted by a predetermined amount in the direction are arranged in the Y direction. Specifically, for example, four light emitting elements 81 are arranged at a pitch of 28 μm in the X direction, and these four light emitting elements 8
1 are arranged at a pitch (shift amount) of 7 μm in the Y direction. Then, four light emitting elements 8 arranged in the X direction
1 are repeatedly arranged in the Y direction.
2048 light emitting elements 81 are arranged in the direction. The light emitting elements 81 are arranged at a predetermined pitch (7 μm) in the Y direction.

In the two-dimensional semiconductor laser array 71, since the light emitting elements 81 are arranged at a pitch of 7 μm in the Y direction, the arrangement positions do not overlap in the X direction. Therefore, as described later, by using the CCD array 76 having a plurality of light receiving elements having a sufficient aspect ratio, it is possible to easily realize the detection of the laser light emitted from each light emitting element 81 at one time. .
Therefore, it is possible to realize a high-speed reading operation with a simple configuration without having to perform complicated operation control such as, for example, sequentially emitting the light emitting elements 81.

The information reproducing apparatus 70 is not limited to using the two-dimensional semiconductor laser array 71 in which the light emitting elements 81 are arranged in a positional relationship as shown in FIG. Various two-dimensional semiconductor laser arrays arranged in a plurality in the −Y direction can be used. Further, the wiring of each light receiving element 81 is not limited to being arranged in a matrix. The information reproducing apparatus 70 includes a two-dimensional semiconductor laser array in which a plurality of light emitting elements are provided, so that each laser beam emitted from each light emitting element can be used for the information recording medium 1.
Irradiate the information recording unit 10 at a time to read a large amount of information substantially simultaneously. Therefore, a high-speed reproduction operation can be realized with an extremely simple device configuration.

The two-dimensional semiconductor laser array 71 is
The laser beam emitted from each light emitting element 81 is disposed in the information reproducing device 70 so as to irradiate the information recording unit 10 of the information recording medium 1 as a linear laser beam shape as a whole. That is, in the information reproducing apparatus 70, as shown in FIG. 8, the light emitting elements 81 of the two-dimensional semiconductor laser array 71 are arranged more in the Y direction than in the X direction. The laser beam emitted from the laser array 71 has a linear laser beam shape long in the Y direction in FIG. 8 as a whole.

In the two-dimensional semiconductor laser array 71 configured as described above, by appropriately selecting the X terminal 84 and the Y terminal 85 and applying a voltage, the light emitting element 81 is selected and a laser beam is emitted. Is easy. In particular,
For example, a laser light is sequentially emitted from each light emitting element 81, or a laser light is sequentially emitted for each light emitting element 81 in a predetermined group, and the light emitting pattern of the entire two-dimensional semiconductor laser array 71 is arbitrarily set. It is easy to set.

Therefore, each light emitting element 81 can emit light with an optimal light emitting pattern according to the two-dimensional pattern formed in the information recording section 10. Therefore, for example, even when the phase diffraction grating 20 forming the two-dimensional pattern of the information recording unit 10 is formed at a high density,
Laser light can be reliably irradiated to each phase diffraction grating 20, and diffracted light from these phase diffraction gratings 20 can be obtained.

When a two-dimensional semiconductor laser array 71 in which a plurality of light emitting elements 81 are arranged in a positional relationship as shown in FIG. 8 is used, a complicated light emitting pattern as described above is adopted. No need. That is, by using a two-dimensional semiconductor laser array 71 in which the arrangement positions of the light emitting elements 81 do not overlap in the Y direction and a CCD array including a plurality of light receiving elements having a sufficient aspect ratio as described later, The laser light emitted simultaneously from each light emitting element 81 of the two-dimensional laser array 71 can be received at once, and a high-speed reading operation can be realized with a simple configuration.

Further, the two-dimensional semiconductor laser array 71
Since the plurality of light emitting elements 81 are arranged at a predetermined pitch in both the X direction and the Y direction, these light emitting elements 8
Even when a drive circuit or a component member is formed around 1, the distance between the portions that actually emit laser light can be made closer in the Y direction. Therefore, for example, it is possible to improve the resolution in the Y direction (that is, the length direction of the linear laser light) in the drawing, and to increase the density of the phase diffraction grating 20 formed in the information recording unit 10. Even so, the diffracted light from these phase diffraction gratings 20 can be obtained with high accuracy.

The first cylindrical lens 72 converts the laser light emitted from the two-dimensional semiconductor laser array 71
The laser light converges in the width direction (short side direction) and is transmitted as a belt-shaped parallel laser light. In the information reproducing apparatus 70, the focal length of the first cylindrical lens 72 is 1
When it is 7 mm, the width of the laser beam is 6 mm by the first cylindrical lens 72.

The beam splitter 73 has a transmittance of 50% in the direction of the optical axis of the laser light emitted from the two-dimensional semiconductor laser array 71, and a reflectance of 5% in a direction orthogonal to this.
It has a half mirror which is 0%.

The second cylindrical lens 74 is
The lens surface is disposed in a direction parallel to the cylindrical lens 72 of FIG. 1, and the band-shaped parallel laser light transmitted through the beam splitter 73 is converged in the width direction of the laser light to record information on the information recording medium 1. The part 10 is irradiated with a linear laser beam shape. That is, the information reproducing apparatus 70 irradiates the plurality of phase diffraction gratings 20 arranged in the information recording unit 10 in a two-dimensional pattern with a laser beam having a linear laser beam shape, for example, to obtain a first laser beam. It is possible for the control information recording unit 11 to simultaneously irradiate a laser beam to the arrangement (track) of the phase diffraction gratings in the set direction (horizontal direction in FIG. 2).

The second cylindrical lens 74 is
In other words, it has a function as an objective lens, and corresponds to an objective lens having a numerical aperture NA of 0.15 when the focal length is 20 mm. In this case, the width of the laser beam having a linear laser beam shape is 6.5 μm on the information recording unit 10.

The laser beam applied to the information recording section 10 of the information recording medium 1 by the second cylindrical lens 74 is diffracted by the phase diffraction grating 20 provided in the information recording section 10, as shown in FIG. I do. In FIG. 9, a part of the information recording medium 1 is omitted and only the main part is shown.

Of the diffracted light generated at this time, the first-order diffracted light deviates from the opening of the second cylindrical lens 74,
Only the 0th-order diffracted light is incident on the second cylindrical lens 74. The second-order or higher-order diffracted light is reflected at the interface between the light transmitting layer and the outside, and does not exit the information recording medium 1 to the outside.

The 0th-order diffracted light that has entered the second cylindrical lens 74 in this manner is transmitted to the beam splitter 7.
The light is reflected by the third lens 3 and is incident on the third cylindrical lens 75. The third cylindrical lens 75 has a focal length of 20 mm, and has a laser beam (diffraction light).
Are converged in the width direction of the laser light, and the CCD array 7
6 is incident.

The CCD array 76 is a light receiving element in which a plurality of light receiving portions are continuously provided in the length direction (long side direction) of the incident linear laser light. The CCD array 76 shown in FIG.
As shown in FIG. 0, the light-receiving element 90 has a light-receiving surface 90 sufficient to receive linear diffracted light generated by diffraction in the information recording unit 10. A plurality of light receiving elements 91 each having an aspect ratio sufficient to receive the laser light emitted from 81 are provided. Each light receiving element 91 is illuminated with a light spot 92 which is returned by the laser beam emitted from each light emitting element 81 of the two-dimensional semiconductor laser array 71 being diffracted by the information recording unit 10. That is, a plurality of light spots 92 are applied to the light receiving elements 91 in a pattern corresponding to the pattern of the laser light emitted from the two-dimensional semiconductor laser array 71 on the light receiving surface 90 of the CCD array 76.

In the present embodiment, as the CCD array 76,
A light receiving portion having a light receiving portion in which the length of the incident linear laser light in the width direction (short side direction) is 200 μm and the length of the linear laser light in the length direction (long side direction) is 7 μm. 3000 elements 91 are continuously provided in the length direction of the laser beam, the data transfer rate is 5 MHz, and the light receiving sensitivity is 11
A light receiving element having V / lx / s was used. Then, the CCD array 76 detects the diffracted light generated by the phase diffraction grating 20 for one track provided in the information recording unit 10 at each light receiving unit.

Here, each of the light receiving elements 91 in the CCD array 76 has a length of 7 μm in the length direction (long side direction) of the incident linear laser light, and is the same as the diameter of the incident light spot. And the length in the width direction (short side direction) of the linear laser light is 200 μm,
It has a sufficient aspect ratio (aspect ratio). Therefore, it is not necessary to arrange each light receiving element 91 at a position corresponding to the arrangement pattern of the light emitting elements 81 arranged on the two-dimensional semiconductor laser array 71, and it is necessary to arrange the light receiving elements 91 according to the direction of the incident linear laser light. The overall orientation can be adjusted and arranged in the device.

In the information reproducing apparatus 70, the arrangement pitch of each light emitting element 81 in the two-dimensional semiconductor laser array 71 and the aspect ratio and arrangement pitch of each light receiving element 91 in the CCD array 76 May be appropriately set in consideration of the size and arrangement pitch of each phase diffraction grating 20 as a basic information unit, the beam diameter of laser light, the optical system provided in the information reproducing apparatus 70, and the like.

In the information reproducing apparatus 70, the light spots from all the light emitting elements 81 arranged in the two-dimensional semiconductor laser array 71 are detected by detecting the diffracted light by the CCD array 76 configured as described above. At the same time, and its light intensity can be detected.

At this time, the aspect ratio of each light receiving element 91 of the CCD array 76 is expressed by the pitch in the X direction of the light emitting element 81 arranged in the two-dimensional semiconductor laser array 71 being p.
and _x, the number of light emitting elements 81 arranged in the X direction and _{n x,}
When the light spot diameter of the laser light emitted from each light emitting element 81 on each light receiving element is l, [p _x × n _x /
l] or more. Thereby, C
The CD array 76 can simultaneously receive light spots from all the light emitting elements 81 of the two-dimensional semiconductor laser array 71 by the respective light receiving elements 91 and simultaneously detect their light intensities. Reading operation can be realized.

It should be noted that the CCD array 71 is not particularly limited to the aspect ratio as described above, but may be used to receive laser light emitted from each light emitting element 81 in the two-dimensional semiconductor laser array 71, respectively. It is sufficient if a plurality of light receiving elements 91 having a sufficient aspect ratio are provided, and the light receiving elements 91 can detect the two-dimensional pattern of the information recording unit 10 for each basic information unit. Further, the light intensity of the light spot from each light emitting element 81 of the two-dimensional semiconductor laser array 71 is not limited to being detected all at the same time. For example, according to the light emission pattern of the two-dimensional semiconductor laser array 71, The detection may be performed with a predetermined time difference between the light receiving elements 91.

The information reproducing apparatus 70 constructed as described above
When reproducing information recorded on the information recording medium 1,
The information recording unit 10 converts the laser light into a linear laser beam shape.
, It is possible to detect the diffracted light generated in each phase diffraction grating 20 as a basic information unit for each track (simultaneously in the direction set by the first control information recording unit 11). ing. Then, the control unit controls the scanning mechanism to sequentially scan the laser beam in a direction substantially orthogonal to the length direction of the laser beam shape (the direction in which the second control information recording unit 12 is set). Thereby, a two-dimensional pattern in which the phase diffraction grating 20 is provided is detected, and recorded information is reproduced based on the detected two-dimensional pattern.

Therefore, the information reproducing apparatus 70 outputs the laser beam having a linear laser beam shape to the information recording section 10.
With a simple configuration that scans with and detects diffracted light,
The information recorded on the information recording medium 1 can be reproduced.

Incidentally, the spot size of the laser beam applied to the information recording unit 10 needs to be smaller than the size of each phase diffraction grating 20 as a basic information unit in the information recording unit 10. Here, considering the case of irradiating a normal circular light spot, the diameter of the Airy disk of this light spot can be represented by D, as shown in Expression 3 below.

D = 1.22λ / NA (Equation 3) Here, when the wavelength λ of the reproduction light is 780 nm and the numerical aperture NA of the objective lens is 0.15, the Airy disk diameter D is It is about 6.3 μm. Therefore, in the information reproducing apparatus 70 according to the present example, the width of the laser beam having a linear laser beam shape needs to be about 6.3 μm. In order to define the width of the laser light in this manner, the numerical aperture NA of the third cylindrical lens 75 functioning as an objective lens in the information reproducing apparatus 70 according to the present embodiment, and the laser emitted from the semiconductor laser oscillator 71 The wavelength λ of the light may be appropriately selected.

The focal depth Z of the laser beam with respect to the information recording unit 10 can be expressed by the following equation (4).

Z = ± λ / 2 (NA) ² (Equation 4) Accordingly, in the information reproducing apparatus 70 according to the present example, the wavelength λ of the laser beam and the wavelength of the second cylindrical lens 74 as the objective lens are determined. When the numerical aperture NA is set to a value sufficient to detect each of the phase diffraction gratings 20 formed in the information recording unit 10, the depth of focus Z can be set to, for example, about ± 17.3 μm. For this reason, the depth of focus Z can be set sufficiently larger than the depth d of the groove in the phase diffraction grating 20. The depth of focus Z is the depth d of the groove.
, It is not necessary to perform various servo controls such as a focus servo, and even if the information recording unit 10 is warped or inclined, it is possible to reliably perform two-dimensional servo control. Patterns can be detected.

In the information reproducing apparatus 70, when reproducing in this manner, the first control information recording section 11 and the second
It is desirable to acquire the control information recorded in the control information recording unit 12 of the above and to perform laser beam irradiation and scanning based on the control information. In particular,
The irradiation position and the scanning position are adjusted based on the information indicating the irradiation position and the scanning position of the laser light recorded as the control information, and the address information recorded as the control information is detected and the information to be reproduced is recorded. The position can be specified, and control can be performed so that this position is irradiated with laser light.

Alternatively, the timing at which the laser light is pulsed may be obtained from the control information, and scanning may be performed while the laser light is pulsed at this timing. This not only reduces crosstalk between vertically adjacent phase diffraction gratings 20 as compared with the case where the laser beam is continuously scanned by the information recording unit 10, but also reduces the laser beam irradiation. It is easy to appropriately control the power. As described above, the pulse width in the case where the laser light is pulsed can be set to, for example, 100 μs.

For example, based on the control information, the shift amount between each light receiving element 91 of the CCD array 76 and each phase diffraction grating 20 formed in the information recording section 10 is detected, and the CCD array is changed according to the detected shift amount. It is desirable to perform the address correction of the signal read from each light receiving unit in 76. This makes it possible to correct a minute shift in the scanning direction caused by the scanning of the laser light, and to detect the formation position of each phase diffraction grating 20 as a basic information unit with high accuracy. When such address correction is performed, for example, it can be realized by performing arithmetic processing by combining various semiconductor integrated circuits and the like.

[0082]

The information reproducing apparatus according to the present invention has a very simple structure in which a laser beam having a linear laser beam shape is scanned by an information recording section to detect diffracted light. Information recorded on such an information recording medium can be reproduced. In addition, a linear laser beam emitted from a two-dimensional semiconductor laser array is irradiated onto an information recording unit, and diffracted light is detected by a CCD array having a plurality of light receiving elements having a sufficient aspect ratio. It is possible to easily detect the recorded two-dimensional pattern with high accuracy. Therefore, not only is it possible to reproduce information recorded on the information recording medium according to the present invention, but also it is easy to simplify or eliminate the need for a servo mechanism for laser light. By simplifying, it is possible to reduce the cost and size of the entire apparatus.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical recording medium on which information is reproduced by an information reproducing apparatus to which the present invention is applied.

FIG. 2 is a schematic plan view showing a main surface of the information recording medium.

FIG. 3 is a schematic diagram showing an example of a waveform of an output signal obtained when scanning a main surface of the information recording medium with a laser beam.

FIG. 4 is an enlarged view of a main part showing a phase diffraction grating provided in the information recording medium.

FIG. 5 is a schematic diagram for explaining a structure of a phase diffraction grating provided in the information recording medium.

FIG. 6 is a schematic configuration diagram of an information reproducing apparatus shown as one configuration example to which the present invention is applied.

FIG. 7 is a schematic plan view showing a configuration example of a two-dimensional semiconductor laser array provided in the information reproducing apparatus.

FIG. 8 is a schematic diagram showing a positional relationship of light emitting elements in a two-dimensional semiconductor laser array provided in the information reproducing apparatus.

FIG. 9 is a schematic diagram used to explain how the information reproducing apparatus detects diffracted light from an information recording medium.

FIG. 10 is a schematic plan view showing one configuration example of a CCD array provided in the information reproducing apparatus.

FIG. 11 is a schematic diagram illustrating how information is reproduced in a conventional optical card.

[Explanation of symbols]

1 information recording medium, 2 substrates, 3 information recording sheets, 4
Reflective film, 5 protective film, 10 information recording section, 11 first
Control information recording unit, 12 second control information recording unit, 20
Diffraction grating, 70 information reproducing device, 71 two-dimensional semiconductor laser array, 72 first cylindrical lens, 7
3 Beam splitter, 74 2nd cylindrical lens, 75 3rd cylindrical lens, 76 CC
D array

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masanobu Yamamoto 6-35 Kita Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference) 5D090 AA03 BB02 BB16 CC04 DD01 DD05 EE18 LL01 LL05 5D119 AA01 AA40 BA02 BB01 DA05 FA10 KA03

Claims (5)

[Claims] 1. A two-dimensional semiconductor laser array in which a plurality of light-emitting elements that emit laser light in a predetermined wavelength range are arranged in the XY directions, and a laser light emitted from the two-dimensional semiconductor laser array is collected. A linear laser beam is applied to the information recording section of the information recording medium provided with an information recording section having a plurality of phase diffraction gratings arranged in a two-dimensional pattern corresponding to the information to be recorded on a substrate. Irradiating means for irradiating in a shape; scanning means for scanning a laser beam irradiated by the irradiating means at a position of the information recording section in a direction substantially orthogonal to a longitudinal direction of a laser beam shape; The laser beam scanned by the means has a light receiving surface sufficient to receive a linear diffracted light generated by diffracting the information in the information recording portion, and the light receiving surface is provided with each light emission in the two-dimensional semiconductor laser array. A plurality of light receiving elements having an aspect ratio sufficient to receive the laser beams emitted from the elements are arranged, and a CCD for detecting a two-dimensional pattern of the information recording unit for each basic information unit by each of the light receiving elements.
An information reproducing apparatus, comprising: an array. 2. The two-dimensional semiconductor laser array according to claim 1, wherein a plurality of sets of a plurality of light emitting elements arranged in the X direction while being shifted by a predetermined amount in the Y direction are arranged in the Y direction. The information reproducing apparatus according to claim 1, wherein Wherein the aspect ratio of each light receiving element of the CCD array, the pitch of the X direction of the light-emitting elements arranged in the two-dimensional semiconductor laser array and p _x, the number of light emitting elements arranged in the X direction and n _x, the diameter of the light spot on the light receiving elements of the laser light emitted from the light emitting element is taken as l, characterized in that there is a _{[p x × n x / l} ] or more claims Item 2. The information reproducing apparatus according to Item 1. 4. A shift amount between a basic information unit in the information recording unit and each light receiving unit in the CCD array, which is caused by scanning of the reproduction light, based on the diffracted light detected by the CCD array, 2. The information reproducing apparatus according to claim 1, further comprising address correction means for correcting an address of a signal read from each light receiving section of the CCD array in accordance with the detected amount of displacement. 5. A timing signal generating means for generating a timing signal according to a scanning speed of a reproduction light by said scanning means based on the diffracted light detected by said CCD array, wherein said irradiating means comprises: 2. The information according to claim 1, wherein the reproduction light is pulse-irradiated at a position corresponding to the center of each basic information unit in the two-dimensional pattern of the signal recording unit based on the timing signal generated by the generation unit. Playback device.