JP3639282B2 - Information recording / reproducing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an information recording / reproducing apparatus, and more particularly, to an information recording / reproducing apparatus that records and reproduces information by irradiating a recording medium with evanescent light.
[0002]
[Prior art]
In an information recording / reproducing apparatus that records and / or reproduces information by irradiating light onto a recording medium, a method called high-density recording / reproduction that exceeds the diffraction limit of light is a localized method called evanescent light. A method using electromagnetic waves is known.
[0003]
In a known information recording / reproducing apparatus using evanescent light, light from a laser light source is made into a substantially parallel light flux and incident on an objective lens, and light passing through the objective lens is incident on a minute spherical evanescent light generating lens. Thus, evanescent light is generated, and this is tunneled and irradiated to a recording medium disposed in the vicinity of the evanescent light generating lens.
[0004]
The evanescent light generating lens is mounted on a flying slider similar to that used in a magnetic head of a magnetic disk device (HDD: hard disk device), and between the flying slider and the recording medium as the recording medium rotates at high speed. The generated dynamic pressure is controlled so as to maintain a substantially constant small gap of several tens to 100 nm with respect to the recording medium.
[0005]
However, in such a configuration, it is inevitable that the gap between the evanescent light generating lens and the recording medium is fluctuated due to surface vibration of the recording medium accompanying the rotation of the recording medium or vibration due to disturbance. Such a change in the gap between the evanescent light generating lens and the recording medium causes a change in the intensity of light tunneling from the evanescent light generating lens to the recording medium. This change in tunneling light intensity impairs the uniformity of the recording bit (pit, mark, etc.) shape during recording on the recording medium, and jitter due to a change in the reproduction signal amplitude during reproduction from the recording medium. This is undesirable because it causes an increase in
[0006]
[Problems to be solved by the invention]
As described above, the conventional information recording / reproducing apparatus using evanescent light has a problem that good recording and reproduction cannot be expected due to a change in the gap between the evanescent light generating lens and the recording medium.
[0007]
The present invention provides information that enables high-density and good recording and reproduction by minimizing the gap change between the evanescent light generating lens and the recording medium, or by compensating for the change in tunneling light intensity due to the gap change. An object is to provide a recording / reproducing apparatus.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is an information recording / reproducing apparatus that irradiates a recording medium with light and records and / or reproduces information, and is reflected on the surface of the evanescent light generating lens facing the recording medium. The gap between the evanescent light generating lens and the recording medium is monitored from the intensity of the return light, and feedback control is performed so that the intensity of the light tunneling to the recording medium of the evanescent light is constant with respect to the gap change. The main point is to do so.
[0009]
That is, an information recording / reproducing apparatus according to the present invention includes a light source that emits light, an objective lens that receives the light emitted from the light source, and a light that is provided facing the recording medium and passes through the objective lens. An evanescent light generating lens that receives the evanescent light, detecting means for detecting the intensity of light reflected by the surface of the evanescent light generating lens facing the recording medium, and light intensity detected by the detecting means And control means for controlling the intensity of light incident on the evanescent light lens so that the intensity of light evanescent light tunneling to the recording medium becomes substantially constant.
[0010]
Here, the control means for controlling the intensity of the light incident on the evanescent light lens has a light modulation element for intensity-modulating the light emitted from the light source, and the light intensity detected by the detection means. By controlling based on the above, the intensity of light incident on the evanescent light lens is controlled.
[0011]
When a semiconductor laser is used as the light source, the control means for controlling the intensity of light incident on the evanescent light lens controls the driving current of the semiconductor laser based on the light intensity detected by the detection means. Thus, the configuration may be such that the intensity of light incident on the evanescent light lens is controlled.
[0012]
As described above, in the present invention, the change in the gap between the evanescent light generating lens and the recording medium is compensated by controlling the intensity of the incident light to the evanescent light generating lens, thereby achieving uniform recording bit shape during recording. During playback, it is possible to perform good recording and playback without increasing jitter due to changes in the playback signal amplitude.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a configuration of an information recording / reproducing apparatus according to the first embodiment of the present invention. This embodiment is an example in which the present invention is applied to an information recording / reproducing apparatus using a typical SIL (Solid Imersion Lens) as an evanescent light generating lens.
[0014]
The recording medium 11 is, for example, a magneto-optical disk, a phase change optical disk, or an optical disk master having a photoresist layer, and is rotated by a spindle motor 12 during recording / reproduction. A laser beam emitted from a semiconductor laser (LD) 14 driven by a drive current supplied from an LD driver 13 is converted into a parallel light beam by a collimator lens (not shown), and then transmitted through a beam splitter 15 to be reflected by a reflection mirror. 16 is guided to the movable optical system 17.
[0015]
The movable optical system 17 includes a reflection mirror 18, a reflection mirror 19, an objective lens 20, and an SIL 21 that is an evanescent light generation lens as main optical elements, and the SIL 21 is mounted on the flying slider 22. The flying slider 22 is supported at the distal end of the suspension arm 23, and the base end of the suspension arm 23 is supported by the rotary actuator 24. The suspension arm 23 is rotated in the radial direction of the recording medium 11 by the rotary actuator 24 at the time of recording / reproducing, thereby performing track seek and tracking.
[0016]
In the middle of the suspension arm 23, an SIL driving actuator 25 is provided. The SIL driving actuator 25 is constituted by, for example, an actuator using a piezoelectric element, more specifically, a laminated piezoelectric actuator or a bimorph actuator. The SIL driving actuator 25 is mounted on the floating slider 22 at the distal end of the suspension arm 23 by being driven by the actuator driver 30 to move the suspension arm 23 up and down with the base end side supported by the rotary actuator 24 as a fulcrum. The SIL 21 is moved up and down, that is, moved in the thickness direction of the recording medium 11. As a result, the gap between the SIL 21 and the recording medium 11 changes.
[0017]
As described above, the laser light emitted from the semiconductor laser 14 and guided to the movable optical system 17 by the collimator lens 14, the beam splitter 15, and the reflection mirror 16 is sequentially guided by the reflection mirror 18 and the reflection mirror 19 to be objective lens 20. And is focused here to form a thin beam, and then enters the SIL 21. The laser light incident on the SIL 21 forms a minute spot of evanescent light on the lower surface of the flying slider 22 facing the recording medium. The evanescent light spot is tunneled to the recording medium 11 when the gap between the SIL 21 and the recording medium 11 is ½ or less of the wavelength of the semiconductor laser 14, for example, 100 nm or less.
[0018]
On the other hand, the light that has not been tunneled to the recording medium 11 is reflected by the bottom surface of the SIL 21 and returns to the reverse path of the incident light. This is called return light. That is, the return light reflected by the bottom surface of the SIL 21 passes through the objective lens 20, the reflection mirror 19, the reflection mirror 18, and the reflection mirror 16 in order and enters the beam splitter 15. The return light incident on the beam splitter 15 is reflected here to separate the incident light from the semiconductor laser 14 from the optical path, and is guided to the photodetector 27 by the condenser lens 26.
[0019]
The photodetector 27 is, for example, a divided photodetector in which the light receiving surface is divided into a plurality of regions (four regions as an example), and an output signal from each region is input to the analog arithmetic circuit 28. In the analog arithmetic circuit 28, a reproduction signal, tracking servo, tracking error signal for focus servo and focus error signal are generated, and a return light intensity signal described later is generated. The focus servo here is an operation for controlling the position of the SIL 21 in order to form a light spot at a predetermined position on the lower surface of the SIL 21.
[0020]
FIG. 2 shows changes in the tunneling light intensity (evanescent light intensity) of the evanescent light with respect to the gap change between the SIL 21 and the recording medium 11 and changes in the return light intensity detected by the photodetector 21. However, in FIG. 2, the gap between the SIL 21 and the recording medium 11 is G, the wavelength (light source wavelength) of the semiconductor laser 14 is λ, G / λ is on the horizontal axis, and the light intensity of tunneling light and return light is on the vertical axis. . It can be seen that the tunneling light intensity of the evanescent light decreases as the gap increases, whereas the return light intensity increases as the gap increases.
[0021]
According to this embodiment, the gap between the SIL 21 and the recording medium 11 is kept substantially constant. Specifically, in this embodiment, the output signal of the photodetector 27 in which the light receiving surface is divided into a plurality of regions is guided to the analog arithmetic circuit 28, where, for example, the output signals of the plurality of regions are similar to the reproduction signal. A return light intensity signal is generated by taking the sum or taking out the output signal of a specific region. This return light intensity signal is input to the servo control circuit 29, and the servo control circuit 29 controls the SIL driving actuator 25 via the actuator driver 30 so that the return light intensity becomes constant, thereby recording the SIL 21 and the recording light. The gap between the media 11 is maintained almost constant.
[0022]
As described above, according to the present embodiment, the gap between the SIL 21 and the recording medium 11 can be kept substantially constant, so that a change in the tunneling light intensity of the evanescent light can be suppressed, and high density and stable good recording can be achieved. Playback can be performed.
[0023]
For example, when a phase change optical disk that performs recording using the phase change between the amorphous and crystalline phases of the recording film is used as the recording medium 11, information is recorded by using the drive current of the semiconductor laser 14. By modulating according to the binary signal (recording signal) to be recorded, the tunneling light intensity of the evanescent light is also modulated according to the recording signal, so that a phase change mark is formed on the recording film of the phase change optical disk as the recording medium 11. It is done by being formed. Here, according to the present embodiment, by keeping the gap between the SIL 21 and the recording medium 11 substantially constant, the tunneling light intensity when the recording signal is 0 can be kept substantially constant. It is possible to avoid a change in the shape of the phase change mark due to a factor and to perform good recording.
[0024]
On the other hand, when reproducing the information recorded on the phase change optical disk, which is the recording medium 11, reflected light by the evanescent light irradiated on the recording medium 11 is detected by the photodetector 27, and a plurality of areas of the photodetector 27 are detected. A reproduction signal is obtained by obtaining the sum of the output signals by the analog arithmetic circuit 28. Even in this case, by keeping the gap between the SIL 21 and the recording medium 11 substantially constant, the intensity of the tunneling light when the recording signal is 0 can be kept substantially constant. Therefore, good reproduction with little jitter becomes possible.
[0025]
(Second Embodiment)
FIG. 3 is a diagram showing a configuration of an information recording / reproducing apparatus according to the second embodiment of the present invention. Hereinafter, the same parts as those in FIG. 1 are denoted by the same reference numerals, and differences from the first embodiment will be described.
[0026]
In the present embodiment, as shown in FIG. 3, the SIL driving actuator 25, the servo circuit 29, and the actuator driver 30 in FIG. 1 are removed, and instead, one of the light modulation elements is provided on the light emitting side of the semiconductor laser 14. An acousto-optic modulation element (AOM) 31 is arranged. Further, the return light intensity signal output from the analog arithmetic circuit 28 is input to the servo circuit 32, and the servo optical circuit 32 controls the acoustooptic modulator 31 so that the return light intensity becomes substantially constant. The intensity of laser light emitted from the laser 14, that is, the intensity of light incident on the SIL 21 is controlled.
[0027]
Next, control for keeping the tunneling light intensity constant in this embodiment will be described with reference to FIG.
4 shows the change in the tunneling light intensity of the evanescent light with respect to the change in the gap between the SIL 21 and the recording medium 11 and the change in the return light intensity detected by the photodetector 27 as in FIG. The gap between the media 11 is G, the wavelength of the semiconductor laser 14 is λ, G / λ is dimensionless along the horizontal axis, and the light intensity of the tunneling light and return light is along the vertical axis. The tunneling light intensity of evanescent light decreases as the gap increases, whereas the return light intensity conversely increases as the gap increases, as in FIG.
[0028]
Assuming that the incident light intensity to the SIL 21 is II, the tunneling light intensity changes with respect to G / λ according to the characteristic (1) and the return light intensity changes according to the characteristic (3). In order to set the tunneling light intensity to a desired value, for example, I _T1 , the gap of the SIL 21 with respect to the recording medium 11 must be set to G ₁ . Although it is impossible to directly observe the tunneling light intensity, when viewed from the observable return light intensity, the return light intensity when the gap is G ₁ is I _M1 . In other words, the tunneling light intensity I _T1 can be measured by I _T1 = II−I _M1 .
[0029]
Since the flying slider 22 vibrates up and down as the recording medium 11 rotates, the gap between the S1L 21 supported by the recording medium 11 and the recording medium 11 changes, and the tunneling light intensity also changes. That is, when the gap is set to G ₁ and the gap changes by ΔG to G ₂ due to vibration, the tunneling light intensity becomes I _T2 .
[0030]
Therefore, in this embodiment, the intensity of the tunneling light to the recording medium 11 is controlled by changing the intensity of the incident light to the SIL 21 from II to II × k. k is a coefficient. When the incident light intensity is II, the return light intensity detected under the gap G ₁ is I _M1 , and unless the incident light intensity remains II, the return light intensity under the gap G ₂ is I _Since it becomes _M2 , the tunneling light intensity I _{T 2} can be measured by I _{T 2} = (II−I _{M 2} ). Therefore, (II-I _{M 2)} is (II-I _M1) and such that, k = the original incident light intensity _{II (II-I M 2)} / (II-I M1) II multiplied by comprising coefficients By making xk a new incident light intensity, the tunneling light intensity can always be kept constant (I _T1 ).
[0031]
That is, when the incident light intensity on the SIL 21 is changed from II to II × k, the tunneling light intensity changes according to the characteristic (2) and the return light intensity changes according to the characteristic (4) with respect to G / λ. At this time, the return light intensity under the gap G ₂ is I _{M 2} and the tunneling light intensity is I _T1 .
[0032]
In order to realize the above-described control specifically, the return light intensity I _M1 when the incident light intensity is II is obtained in the servo circuit 32 and held in the memory, and the gap between the SIL 21 and the recording medium 11 is determined. When the return light intensity changes to I _{M 2} due to the change, the coefficient k is obtained by k = (II−I _{M 2} ) / (II−I _M1 ), and the incident light intensity is expressed as II × k. Control is sufficient.
[0033]
As described above, according to the present embodiment, the gap between the SIL 21 and the recording medium 11 is controlled by controlling the acousto-optic modulation element 31 to control the incident light intensity with respect to the change in the gap between the SIL 21 and the recording medium 11. It is possible to suppress a change in the tunneling light intensity of the evanescent light with respect to the change, and it is possible to perform stable recording and reproduction with a very high density.
[0034]
(Third embodiment)
FIG. 5 is a diagram showing a configuration of an information recording / reproducing apparatus according to the third embodiment of the present invention.
In the present embodiment, the return light intensity signal output from the analog arithmetic circuit 28 is input to the servo circuit 33, the LD driver 13 is controlled by the servo circuit 33, and the drive current (bias current) of the semiconductor laser 14 is controlled. Thus, the intensity of the laser light emitted from the semiconductor laser 14, that is, the intensity of the light incident on the SIL 21 is controlled.
[0035]
Therefore, this embodiment basically operates in the same manner as the second embodiment except for controlling the semiconductor laser 14 directly or controlling the acousto-optic modulator 31 inserted on the light emitting side of the semiconductor laser 14. Since it is the same, detailed description is abbreviate | omitted.
[0036]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.
For example, although the case where a phase change optical disk is used as a recording medium has been described in the above embodiment, the present invention can also be applied to a magneto-optical disk or an optical disk that records information as a pit string.
[0037]
Further, the present invention can be applied not only to a device having both recording and reproduction functions but also to a device having only one of recording and reproduction functions, for example, an apparatus for reproducing information recorded on a reproduction-only optical disc. Applicable to.
[0038]
In addition, the present invention is not an apparatus that directly uses evanescent light for recording or reproduction, and recording and reproduction are performed by magnetism, but the portion where recording / reproduction is performed is locally irradiated with light and heated. Thus, the present invention can be applied to a so-called optically assisted magnetic recording / reproducing apparatus that can perform good recording / reproducing even with a narrow track pitch of 0.2 μm, for example, while avoiding the influence of thermal disturbance.
[0039]
Furthermore, the present invention can also be applied to a master disk recording apparatus that records information by irradiating a light beam onto a photoresist layer of an optical disk master having a photoresist layer formed on a disk substrate.
[0040]
As another means for generating evanescent light, an optical fiber having a fine opening at the tip may be used instead of the combination of the objective lens and the evanescent light generating lens. The light source is not limited to a semiconductor laser, and a gas laser may be used.
[0041]
【The invention's effect】
As described above, according to the present invention, good recording with a uniform recording bit shape and excellent reproduction with no increase in jitter due to a change in the reproduction signal amplitude is achieved while using an evanescent light to achieve a high density. Can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an information recording / reproducing apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a gap and tunneling between an evanescent light generating lens and a recording medium in the information recording / reproducing apparatus according to the first embodiment. FIG. 3 is a diagram showing a relationship between light intensity and return light. FIG. 3 is a diagram showing a configuration of an information recording / reproducing apparatus according to a second embodiment of the present invention. FIG. 5 is a diagram for explaining the principle of keeping the tunneling light intensity constant with respect to a gap change between a generating lens and a recording medium. FIG. 5 is a diagram showing a configuration of an information recording / reproducing apparatus according to a third embodiment of the present invention. Explanation of]
DESCRIPTION OF SYMBOLS 11 ... Recording medium 13 ... LD driver 14 ... Semiconductor laser 20 ... Objective lens 21 ... SIL (Evanescent light generating lens)
25 ... SIL driving actuator 27 ... photodetector 28 ... analog arithmetic circuit 29 ... servo circuit 30 ... actuator driver 31 ... acousto-optic modulation elements 32, 33 ... servo circuit

Claims (3)

In an information recording / reproducing apparatus that performs at least one of recording and reproducing information by irradiating a recording medium with light,
A light source that emits light;
An objective lens into which the light emitted from the light source is incident;
An evanescent light generating lens provided facing the recording medium and generating evanescent light in response to light passing through the objective lens;
Detecting means for detecting the intensity of light reflected by the surface of the evanescent light generating lens facing the recording medium;
Control means for controlling the intensity of light incident on the evanescent light lens based on the light intensity detected by the detection means so that the intensity of the light tunneling to the recording medium of the evanescent light is substantially constant. An information recording / reproducing apparatus comprising: The control means includes a light modulation element that modulates the intensity of light emitted from the light source, and controls the light modulation element based on the light intensity detected by the detection means, whereby the evanescent light lens The information recording / reproducing apparatus according to claim 1, wherein the intensity of light incident on the head is controlled. The light source is a semiconductor laser;
The control means controls the intensity of light incident on the evanescent light lens by controlling the drive current of the semiconductor laser based on the light intensity detected by the detection means. 1. An information recording / reproducing apparatus according to 1.

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