JP2001184697A - Reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reproducing device capable of efficiently detecting the modulated reflection light of a near field light radiated to a recording medium. SOLUTION: This reproducing device 1 is provided with a probe 40 for radiating a near field light to a recording medium 9, and a photodetection portion 45 for detecting a light 48 obtained by modulating the radiated near field light at the recording medium 9. This probe 40 is arranged such that the main axis MP of the radiated near field light is inclined by an angle α with respect to a vertical line VL to the recording surface 9a of the recording medium 9. In addition, the photodetection portion 45 is arranged such that the main axis SP of detected sensitivity is inclined by an angle β with respect to the vertical line VL to the recording surface 9a of the recording medium 9. The inclination angles α and β are approximately equal to each other. Thus, the modulated reflection light 48 of the near field light radiated to the recording medium 9 is efficiently detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus using near-field light, and more particularly, to a reproducing apparatus for detecting modulated reflected light of near-field light on a recording medium.

[0002]

2. Description of the Related Art A reproducing apparatus capable of reproducing information recorded in a size smaller than the wavelength of light by using near-field light which is not restricted by the "light diffraction limit" has been receiving attention.

As the above-mentioned reproducing apparatus, near-field light generated from the tip of a probe is radiated to an optical recording medium, and modulated light (modulated reflected light) of the near-field light radiated to the optical recording medium by a condensing optical system separate from the probe. A reproducing apparatus that collects and detects (propagating light) is known. In this reproducing apparatus, the probe is arranged along a perpendicular line of the recording surface of the optical recording medium, and the irradiation angle of the near-field light is perpendicular to the recording surface of the optical recording medium.

[0004]

However, in the above-described reproducing apparatus, the probe is arranged along the perpendicular to the surface of the optical recording medium, so that the condensing optical system needs to be arranged at an angle from the perpendicular to the surface of the recording medium. However, since a considerable portion of the modulated reflected light from the recording medium is vignetted by the probe, there is a limitation in improving the detection efficiency of the modulated reflected light.

Further, when the probe is arranged along a perpendicular line on the surface of the recording medium, if the tip of the probe is coated with metal, the optical recording medium is not connected to the probe when the optical recording medium is irradiated with near-field light. Multiple reflections of the modulated reflected light occur with the surface of the recording medium, which may cause a loss of linearity between the recording state of the optical recording medium and the reproduced signal.

The present invention has been made in view of the above problems, and has as its object to provide a reproducing apparatus capable of efficiently detecting modulated reflected light of near-field light applied to a recording medium.

[0007]

According to a first aspect of the present invention, there is provided a reproducing apparatus for reproducing information recorded on a recording medium by irradiating near-field light, comprising: (B) near-field light generating means for irradiating the main axis of the near-field light at a first inclination angle in a predetermined direction with respect to a perpendicular to the recording surface of the recording medium; And detecting means for detecting the modulated reflected light of the near-field light applied to the recording medium.

According to a second aspect of the present invention, in the reproducing apparatus according to the first aspect of the present invention, the detecting means tilts a main axis of detection sensitivity in a direction substantially opposite to the predetermined direction with respect to the perpendicular by a second inclination. The modulated reflected light of the near-field light is detected at an angle.

According to a third aspect of the present invention, in the reproducing apparatus according to the second aspect, the first inclination angle and the second inclination angle are substantially equal.

According to a fourth aspect of the present invention, in the reproducing apparatus according to the third aspect, an absolute value of a difference between the first inclination angle and the second inclination angle is 5 degrees or less.

According to a fifth aspect of the present invention, in the reproducing apparatus according to any one of the first to fourth aspects,
(c) moving means for integrally moving the near-field light generating means and the detecting means relative to the recording medium in a direction substantially perpendicular to the recording medium.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Main Configuration of Reproducing Apparatus> FIG.
FIG. 1 is a diagram illustrating a main configuration of a playback device 1 according to an embodiment of the present invention. The reproducing apparatus 1 reads (reproduces) a signal from / to a recording surface 9a of the recording medium 9 and a rotation mechanism unit 2 that rotates the recording medium 9 about a rotation axis RC while holding the recording medium 9 such as an optical disk. And a reproducing unit 3.
Further, the reproducing apparatus 1 includes a light supply unit 6 for supplying light used for reproduction, a controller 7 for supplying a drive control signal to the rotation mechanism unit 2, the reproduction unit 3, and the light supply unit 6, and a recording medium 9 Signal processing unit 8 for processing a reproduction signal read from
And

The rotation mechanism section 2 includes a rotation drive section 21 and a rotation member 22. The rotation drive section 21 rotates the rotation member 22 based on a drive control signal given from the controller 7.
Is rotated around the rotation axis RC. The rotating member 22 has a structure for holding the detachable disk-shaped recording medium 9 at a predetermined position, and performs a rotating operation integrally with the loaded recording medium 9.

The reproducing section 3 includes an optical head 4 and a driving mechanism 30 for driving the optical head 4.

The optical head 4 includes a probe 40 functioning as a near-field light generating means, a light detecting unit 45 spatially separated from the probe 40, a probe 40 and a recording medium 9.
And a distance detecting unit 5 for detecting a distance from the recording surface 9a. The probe 40, the light detection unit 45, and the distance detection unit 5 are fixed at predetermined positions inside the optical head 4, respectively, and are integrated with the recording medium 9 by the driving mechanism unit 30, that is, the probe 40 and the light detection unit. It can move while maintaining the inclination angle with the part 45.

FIG. 2 is a sectional view showing the structure of the probe 40 described above.

The probe 40 has an optical fiber 41 and a metal coating section 42.

The optical fiber 41 comprises a core portion 41a and a cladding portion 41b, and a tip portion 40a has a sharp shape. The tip portion 40a is formed by heating the optical fiber 41 and then pulling it.

The metal coating portion 42 is formed by evaporating aluminum around the tip 40a of the optical fiber 41 and applying a coating film. Further, the opening 43 is formed by chemically etching only the aluminum at the tip portion 40a. The diameter of this opening is about 100 n
m.

The probe 40 having such a configuration is as follows.
The laser light from the light supply unit 6 is incident on the light incident unit 40 b of the optical fiber 41, and near-field light NF is generated in the opening 43. The near-field light NF is transmitted from the opening 43 to the opening 4.
3 is light that is spatially distributed around a main axis MP in a direction perpendicular to the opening surface of No. 3.

FIG. 3 is a diagram for explaining the positional relationship between the probe 40 and the light detecting section 45.

The probe 40 is connected to the recording surface 9a of the recording medium 9.
Is perpendicular to the recording surface 9a (-
The arrangement is such that the main axis of the near-field light can be irradiated at an inclination angle α in the X) direction.

The light detecting section 45 includes a condenser lens 46 and a photodiode 47. The condenser lens 46 condenses the light 48 that has been modulated and reflected according to the information recorded on the recording medium 9. The photodiode 47 photoelectrically converts the light 48 condensed by the condenser lens 46 to generate an electric signal. Then, based on the electric signal, the light amount is calculated by the controller 7, and the information on the recording surface 9a of the recording medium 9 is read based on the magnitude of the light amount.

The light detecting section 45 tilts the main axis SP of the detection sensitivity by the tilt angle β in the (+ X) direction opposite to the tilt direction of the probe 40 with respect to the perpendicular VL on the recording surface 9 a of the recording medium 9. Thus, the arrangement is such that the modulated reflected light of the near-field light is detected. The main axis SP of the detection sensitivity corresponds to a vertical axis with respect to the detection surface of the photodiode 47 or an optical axis of the condenser lens 46. The inclination angle β of the detection sensitivity of the light detection unit 45 and the inclination angle α of the near-field light of the probe 40 are substantially equal.
The relationship between the inclination angles α and β will be described later in detail.

Returning to FIG. 1, another main configuration of the reproducing apparatus 1 will be described below.

The distance detecting section 5 includes light emitting sections 50, light receiving sections 51, and driving elements 52 and 59 for driving the probe 40.
And

The light irradiation section 50 has a laser light source 53 and a condenser lens 54. Note that the laser light source 53
A laser beam having a wavelength of 780 nm is generated. The laser light 55 generated by the laser light source 53 is
Irradiates the probe 40 via the. Here, the spot diameter of the irradiation light is set to be larger than the width of the probe 40 in the Y direction.

As described above, since the spot diameter of the irradiation light is larger than the width of the probe 40, the light 56 irradiated on the probe 40 has a shadow of the probe 40. The light 56 is divided into two parts in the Y direction via a condenser lens 57 by a photodiode 58 (58a, 58b).
Is photoelectrically converted to generate an electric signal. Then, based on the electric signal, the light amount is calculated by the controller 7.

By comparing the amount of light detected by each of the photodiodes 58a and 58b, the light
The position of the probe 40 in the Y direction can be detected in the form of a relative position with respect to the zero position.

In the distance detection, the driving element 52 applies a small vibration in the Y direction to the probe 40. The frequency of this vibration is approximately equal to the resonance frequency of
At kHz, the amplitude is 50 nm. When approaching the vibrating probe 40 to the recording medium 9, the amplitude and phase of the vibration of the probe 40 change when the distance between the two approaches within a certain range. It is said that this is due to the influence of the adsorbed water on the surface of the recording medium 9, and under this influence, the amplitude gradually decreases and the phase shifts as compared with the initial position where the distance between them is large. This allows
The relative distance between the probe 40 and the recording medium 9 can be detected by detecting the amplitude change or the phase shift through the two-division photodiode 58. By performing feedback to the drive element 59 in the Z direction of the probe 40 based on the detected relative position, position control can be performed to make the distance between the two coincide with the target value. The lower end of the probe 40 and the recording surface 9 of the recording medium 9
The distance to a is controlled to about 20 nm.

The driving mechanism section 30 includes a holding member 31 for holding the optical head 4 and an optical head driving section 32 for driving the optical head 4.

The holding member 31 is configured so as to be able to advance and retreat in the direction of the rotation axis RC of the recording medium 9 by the optical head driving section 32, and the controller 7 is provided with the optical head driving section 32. By providing the drive control signal, the position of the optical head 4, that is, the position of the probe 40 with respect to the recording medium 9 is controlled. Note that the drive mechanism of the optical head 4 does not need to be configured to advance and retreat in the direction of the rotation axis RC of the recording medium 9, and to swing the holding member of a predetermined length in the direction of the rotation axis RC. It may be a mechanism for operating.

The light supply unit 6 includes a laser light source 61 and an optical coupling unit 62 for optically coupling the laser light source 61 and the probe 40.

The laser light source 61 is composed of Ar having a wavelength of 514 nm.
An ion laser beam is generated. Note that a small light source such as a semiconductor laser may be used as the laser light source 61.
The light emitted from the laser light source 61 is
And the recording medium 9 is radiated to the recording medium 9 as near-field light.

The light coupling section 62 has a collimator lens 63 and a condenser lens 64. Collimator lens 63
Has a function of converting the light emitted from the laser light source 61 into parallel light, and the condenser lens 64 condenses the parallel light guided from the collimator lens 63 on the light incident portion 40 b of the optical fiber 41. The light transmitted through the optical fiber 41 is transmitted to the recording surface 9 a of the recording medium 9 by the opening 43.
Is formed and projected.

The signal processing unit 8 has a function of receiving read data (reproduced data) detected by the optical head 4 via the controller 7 and outputting the data to another data processing device.

<Relationship between Inclination Angles α and β> The inventor of the present invention proposes that the inclination angle α of the main axis MP of the near-field light in the probe 40 and the inclination angle of the main axis SP of the detection sensitivity in the light detection unit 45 described above. An experiment on β was performed.

FIG. 4 is an experimental result showing the relationship between the detected light amount and the inclination angle β of the main axis MP of the detection sensitivity in the light detection section 45. 4A shows a case where the inclination angle α of the principal axis of the near-field light in the probe 40 is 30 °, and FIG. 4B shows an inclination angle α = 30 degrees of the principal axis of the near-field light in the probe 40. 15 ° is shown.

As shown in FIG. 4A, when the inclination angle α of the near-field light in the probe 40 is 30 °, the amount of detected light is maximum when the inclination angle β is 30 °. Also,
In the range of the inclination angle β = 25 ° to 35 °, the superiority of the light amount detection is particularly recognized. This is presumably because the specular reflection component is detected with a certain degree of directivity even in the modulated reflection light of the near-field light, similarly to the propagation light such as visible light.

As shown in FIG. 4B, when the inclination angle α of the near-field light at the probe 40 is 15 °,
When the inclination angle β = 15 °, the detected light amount is maximum.
Further, in the range of the inclination angle β = 10 ° to 20 °, the superiority of the light amount detection is particularly recognized.

From these experimental results, regarding the inclination angles α and β with respect to the probe 40 and the light detection section 45, | α−
It is desirable that β | <5 °. Furthermore, it is understood that it is preferable that the inclination angle α = β is substantially satisfied.

In order to prevent the lateral width of the optical head 4 from becoming too large, the inclination angles α and β are preferably, for example, 45 ° or less.

<Operation of Reproducing Apparatus 1> The operation of the reproducing apparatus 1 having such a configuration is as follows.

First, the rotation drive unit 21 is activated to rotate the recording medium 9 about the rotation axis RC. Next, the rotating recording medium 9 is irradiated with near-field light having a tilted main axis MP from the probe 40 while maintaining an appropriate distance from the recording medium 9,
The modulated reflected light is photoelectrically converted in the light detection unit 45.
Then, the controller 7 calculates the amount of light based on the electric signal output of the light detector 45, thereby reproducing the information on the recording surface 9a.

According to the above operation, in the reproducing apparatus 1, since the main axis MP of the near-field light of the probe 40 and the main axis SP of the detection sensitivity of the photodetector 45 are arranged at an angle, the modulated reflected light can be efficiently detected. As a result, the SN ratio of the reproduced signal can be improved.

Even when the tip of the probe 40 is coated with a metal, the multiple reflection of the modulated reflected light mainly occurs in the direction perpendicular to the recording surface 9a of the recording medium 9, so that the main axis of the detection sensitivity is appropriate. The light detector that tilts to the right can detect the reproduced signal appropriately without detecting this multiple reflection.

<Modifications> When the recording medium is disk-shaped, the inclination direction of the probe 40 may be the radial direction (X) of the disk as in the above embodiment, or may be the circumferential direction of the disk ( Y). Further, the probe 40 is moved in the middle
Can also be tilted.

In the above embodiment, the main axis of the near-field light is inclined by inclining the lower half of the probe 40. However, in general, it is not the physical inclination of the near-field generating means, but the near-field light generated from it. Since the inclination of the main shaft is essential, the present invention may be realized by inclining the forming direction of the opening 43 at the distal end of the probe 40.

[0049]

As described above, according to the first to fourth aspects of the invention, the near-field light is irradiated with the main axis of the near-field light inclined with respect to the perpendicular to the recording surface of the recording medium. Modulated reflected light can be detected efficiently.

In particular, in the second aspect of the present invention, since the modulated reflected light of the near-field light is detected by tilting the main axis of the detection sensitivity, even if the tip of the near-field light generating means is coated with a metal, the modulated reflected light can be obtained. Modulated reflected light of near-field light can be detected without being affected by multiple reflection of light.

In the third and fourth aspects of the present invention, the first inclination angle and the second inclination angle are substantially equal.
The modulated reflected light of the near-field light can be particularly appropriately detected.

According to the fifth aspect of the present invention, since the near-field light generating means and the detecting means are integrally moved with respect to the recording medium, there is a possibility that the near-field light generating means or the detecting means may come into contact with the recording medium. Becomes lower.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a main configuration of a playback apparatus 1 according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a probe 40.

FIG. 3 is a diagram illustrating a positional relationship between a probe 40 and a light detection unit 45.

FIG. 4 is a diagram of an experimental result showing a relationship between an inclination angle β of a main axis MP of detection sensitivity in a light detection unit 45 and a detected light amount.

[Explanation of symbols]

 Reference Signs List 1 playback device 3 playback unit 4 optical head 5 distance detection unit 6 light supply unit 9a recording surface 40 probe 45 light detection unit NF near-field light MP near-field light main axis SP detection sensitivity main axis

Claims (5)

[Claims] 1. A reproducing apparatus for reproducing information recorded on a recording medium by irradiating a near-field light, wherein: (a) the near-field light is directed in a predetermined direction with respect to a perpendicular to a recording surface of the recording medium. And (b) spatially separate from the near-field light generating means, and modulating the near-field light applied to the recording medium. A reproducing apparatus, comprising: detecting means for detecting reflected light. 2. The near-field light according to claim 1, wherein the detection unit tilts a main axis of detection sensitivity by a second tilt angle in a direction substantially opposite to the predetermined direction with respect to the perpendicular. A reproducing apparatus characterized by detecting modulated reflected light. 3. The reproducing apparatus according to claim 2, wherein the first inclination angle and the second inclination angle are substantially equal. 4. The reproducing apparatus according to claim 3, wherein an absolute value of a difference between the first inclination angle and the second inclination angle is 5 degrees or less. 5. The reproducing apparatus according to claim 1, wherein (c) the near-field light generating means and the detecting means are integrated with each other, and the near-field light generating means and the detecting means are substantially perpendicular to the recording medium. A moving device for relatively moving in a direction.