JP2002074729A - Optical pickup device, information reproducing device, and information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably maintain the emitted light intensity of a light source and also to obtain superior reproduced signals by making the polarization direction of the light from the light source orthogonally cross that of the return light when the return light from a light probe side generating a minute spot is made incident on the light source. SOLUTION: With a polarization converting element 8, the polarization direction of the light emitted from the light source 4 is controlled to orthogonally cross that of the return light which is reflected by a recording medium 1 and which returns to the light source 4 side through the optical probe 7. Consequently, interference of light inside the light source 4 is reduced, so that the light returning from the recording medium 1 to the light source 4 passes through without hardly affecting the emitted light intensity of the light source 4. Accordingly, the emitted light intensity of the light source 4 is stably maintained and, the light passing through this light source 4 is received by a photodetector 9 arranged in the rear side of the light source 4, thereby obtaing satisfactory reproducing signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup device, an information reproducing device, and an information recording / reproducing device.

[0002]

2. Description of the Related Art In an optical memory device currently in practical use, a laser beam of a plane wave is condensed to a diffraction limit by an objective lens and irradiated to a recording medium to apply thermal and magnetic modulation to the recording layer. While the information is recorded as recording bits, the information is reproduced by detecting the intensity or polarization of the reflected light modulated by the recording bits. In such an information recording / reproducing method, the recording density on the recording medium is almost determined by the laser wavelength. Therefore, in order to cope with the recent increase in the amount of information surrounding information devices such as computers, the diffraction limit is limited. There is a demand for a large-capacity optical memory that achieves a recording density exceeding the above.

As a promising next-generation large-capacity optical memory, a so-called so-called information recording / reproducing that uses near-field light that sharpens the tip of an optical fiber into a conical shape and exudes from the tip is known. There is a proposal of a near-field optical memory (for example, OPTRONICS (1994) No. 12 P116 to P119 “Application to high-density optical memory”).

FIG. 16 shows the above proposed example utilizing the principle of the near-field optical memory. The emitted light from the laser light source 101 is
Fiber probe 104 via lenses 102 and 103
After being incident into the core 105 (106 is a clad), the light propagates through the fiber probe 104 to reach a sharply pointed tip 107, and an evanescent field (near field) near the tip 107. To form When the distal end portion 107 of the fiber probe 104 is brought close to a recording medium (magneto-optical recording medium) 108 to a distance of about the wavelength of the laser light source 101 or less, the fiber probe 104
From the recording medium 108 to the recording layer in the recording medium 108, and the recording layer is heated. At this time, when the recording layer reaches the Curie point or higher, the magnetization changes and information is recorded.
For reading the recorded information, the polarization change of the light transmitted through the recording medium 108 is converted into a light intensity signal via a lens 109 and a polarizing plate 110, and this is converted into a light detector (photomultiplier tube) 111.
This is performed by detecting at.

According to such an optical memory, if the sharpness of the distal end 107 of the fiber probe 104 is improved, it is possible to exceed the resolution due to the diffraction limit of light, and the recording density is 100 times or more that of the conventional optical memory. Is thought to be possible.

On the other hand, if high-density recording becomes possible, a large amount of information will be recorded on one recording medium. Therefore, the data access speed and the reproduction speed must be improved at the same time. Inconvenient. In order to realize such high-speed operation, it is necessary to reduce the size and weight of an optical pickup device for recording and reproducing data.

A conventional example for realizing this is disclosed in Japanese Patent Application Laid-Open No. 9-282704.
FIG. 17 shows the outline. In this conventional example, first, the light of the semiconductor laser 121 is directly introduced into the optical fiber 122. Then, the return light from the optical fiber 122 whose intensity has been modulated by the interaction with the recording bit is introduced into the semiconductor laser 121 again. At this time, the semiconductor laser 121
When the photodetector 123 is disposed behind the light source, the light intensity incident on the photodetector 123 is modulated according to the recording bit. Therefore, if this is used as a reproduction signal, information on the recording medium can be read. As shown in FIG. 17, the semiconductor laser 121 and the optical fiber 12
2 and the photodetector 123 are integrated on a semiconductor substrate 124, thereby realizing a small and lightweight optical pickup device.

[0008]

However, in the system for detecting the transmitted light from the recording medium 108 as shown in FIG. 16, the two-sided system for recording information on both sides of the recording medium 108 and increasing the storage capacity is not applicable. Cannot be applied.

In order to realize the double-sided system, it is necessary to reproduce the data by detecting the reflected light from the recording medium with a fiber probe. However, at this time, as shown in FIG. 17, in the method of introducing the reflected light from the recording medium into the semiconductor laser 121, it is difficult to obtain a good reproduction signal due to the influence of the oscillation noise of the semiconductor laser 121 and the like.

Therefore, the present invention basically relates to a method for realizing a small and light-weight device by adopting a configuration in which reflected light from a recording medium is introduced into a light source such as a semiconductor laser.
An object of the present invention is to provide an optical pickup device, an information reproducing device, and an information recording / reproducing device capable of obtaining a good reproduction signal.

More specifically, the present invention provides a method in which the polarization direction of light emitted from a light source and the polarization direction when return light from an optical probe that generates a minute spot enters the light source are orthogonal to each other. In addition, the present invention provides an optical pickup device, an information reproducing device, and an information recording / reproducing device capable of maintaining a stable light emission intensity of a light source and obtaining a good reproduction signal.

Further, the present invention achieves the above-mentioned object by further reducing the size and weight of the optical pickup device.

In order to achieve the above object, according to the present invention, of the light emitted behind the light source, only the light from the optical probe can be selectively detected and a good reproduced signal can be obtained. Provided are an optical pickup device, an information reproducing device, and an information recording / reproducing device.

In order to achieve the above object, the present invention is directed to a situation in which the relationship between the drive voltage or the drive current and the emission intensity changes due to the deterioration of the light source with time or a change in temperature. The present invention provides an optical pickup device, an information reproducing device, and an information recording / reproducing device that can obtain a stable reproduction signal by monitoring the light emission intensity of a light source and using the feedback as a feedback signal to control the light emission intensity of the light source to be constant.

According to the present invention, in order to achieve the above object, when the optical probe is caused to scan close to the recording medium, the gap between the optical probe and the recording medium is always kept constant, thereby achieving a stable operation. Provided are an optical pickup device, an information reproducing device, and an information recording / reproducing device capable of performing a recording or reproducing operation.

Further, in order to realize the above object, the present invention is applicable to a case where the optical probe moves up and down due to a surface runout or the like generated when the recording medium is rotated.
Provided are an optical pickup device, an information reproducing device, and an information recording / reproducing device capable of always maintaining a constant distance between an optical probe and an objective lens and performing a stable recording / reproducing operation.

Further, according to the present invention, in order to realize the above object, when an optical probe is scanned on a recording medium, an optical system member such as a light source other than the optical probe and a photodetector follows the movement of the optical probe. An optical pickup device, an information reproducing device, and an information recording / reproducing device capable of performing a stable recording / reproducing operation in such a manner.

Further, according to the present invention, in order to achieve the above object, the light emitted from the semiconductor laser is not perfectly linearly polarized light,
Provided is an information reproducing apparatus capable of obtaining a good reproduction signal while maintaining a constant light emission intensity of a semiconductor laser even in a case where interference with return light from an optical probe occurs inside a semiconductor laser.

[0019]

According to the first aspect of the present invention, there is provided an optical pickup device for irradiating a light source and light supplied from the light source onto a recording medium by narrowing the light to a region having a size equal to or smaller than the light source wavelength. A probe, an objective lens for condensing light supplied from the light source and making the light incident on the optical probe, and a polarization of light emitted from the light source disposed on an optical path between the optical probe and the light source A polarization conversion element that makes a direction orthogonal to a polarization direction of light reflected by the recording medium and returned to the light source side through the optical probe, and light that is disposed on an optical path behind the light source and heads rearward from the light source. And a photodetector that receives light.

Therefore, the polarization direction of the light emitted from the light source and the polarization direction of the light reflected by the recording medium and returning to the light source side via the optical probe are converted by the polarization conversion element so as to be orthogonal to each other. When the light emission intensity of the light source is kept stable because the light interference of the light source is reduced and the light reflected by the recording medium and returned to the light source side via the optical probe is transmitted without substantially affecting the light emission intensity of the light source. At the same time, the light transmitted through the light source is received by the photodetector arranged behind the light source, whereby a good reproduction signal can be obtained.

According to a second aspect of the present invention, in the optical pickup device according to the first aspect, the polarization conversion element is a Faraday element.

Accordingly, in realizing the optical pickup device according to the first aspect, the rotation angle of polarized light can be controlled by using a Faraday element as the polarization conversion element.

According to a third aspect of the present invention, in the optical pickup device of the first aspect, the polarization conversion element is a 波長 wavelength plate with respect to the wavelength of the light source.

Therefore, in realizing the optical pickup device according to the first aspect, by using a quarter-wave plate as the polarization conversion element, the optical path is very short because the volume is small as compared with the case of the Faraday element or the like. , Which is advantageous for reducing the size and weight of the entire optical pickup device.

According to a fourth aspect of the present invention, in the optical pickup device of the first, second or third aspect, a polarizing element is provided on an optical path between the light source and the photodetector.

Accordingly, the light emitted backward from the light source includes light emitted by the light source itself and light reflected by the recording medium and transmitted through the light source through the optical probe and emitted backward. Since the light exists, only the light reflected from the recording medium by the polarizing element and passing through the optical probe is extracted by using the difference in the polarization direction and detected by the photodetector, thereby improving the S / N of the reproduced signal. Can be.

According to a fifth aspect of the present invention, in the optical pickup device of the fourth aspect, the polarizing element is divided into regions so as to transmit light having different polarization directions, and the light receiving surface of the photodetector is the light receiving surface. The region is divided so as to receive light from each divided region of the polarizing element.

Therefore, even in a situation where the relationship between the drive voltage or the drive current and the emission intensity changes due to the deterioration of the light source with time or the temperature change, the region-divided polarizing element and photodetector can be used. By using in combination,
Both the light emission intensity of the light source and the reflected light intensity from the recording medium can be monitored at the same time. Therefore, while reproducing the recorded information, the light emission intensity of the light source is monitored, and the light emission intensity of the light source is used as a feedback signal. Is controlled so that a stable reproduction signal can be obtained.

According to a sixth aspect of the present invention, in the optical pickup device of the fourth aspect, the polarizing element is a polarization hologram element that transmits or diffracts the incident light in accordance with the polarization direction of the incident light. The light receiving surface is divided into regions so as to separate and receive the transmitted light and the diffracted light by the polarization hologram element.

Therefore, even in a situation in which the relationship between the drive voltage or the drive current and the emission intensity changes due to the deterioration of the light source with time or a change in temperature, the light in which the polarization hologram element and the light receiving surface are divided into regions is obtained. By using the detector in combination, it is possible to monitor both the light emission intensity of the light source and the reflected light intensity from the recording medium at the same time, and thus monitor the light emission intensity of the light source while reproducing recorded information. By using this as a feedback signal to control the light emission intensity of the light source to be constant, a stable reproduction signal can be obtained.

[0031] The invention according to claim 7 is the invention according to claims 1 to 6.
In the optical pickup device according to any one of the above, the optical probe has a slider structure which is held by an arm and slides on the recording medium.

Therefore, when the optical probe is scanned close to the recording medium, the optical probe has a slider structure which slides on the recording medium while being held by the arm, so that the gap between the optical probe and the recording medium is always constant. , And a stable reproduction operation or the like can be performed.

According to an eighth aspect of the present invention, in the optical pickup device according to the seventh aspect, the objective lens is integrated with the optical probe.

Therefore, even when the optical probe moves up and down due to surface deflection caused when the recording medium is rotated, since the objective lens is integrated with the optical probe, the optical probe and the objective lens are integrated. Can always be kept constant, and a stable reproduction operation or the like can be performed.

According to a ninth aspect of the present invention, in the optical pickup device of the eighth aspect, the light source, the polarization conversion element, and the photodetector are arranged on the arm that holds the optical probe having a slider structure. .

Accordingly, since the positional relationship between the optical probe and the objective lens and other optical systems such as the light source, the polarization conversion element, and the photodetector is always kept constant through the arm, scanning is performed on the recording medium. In addition to enabling a stable reproduction operation and the like, the optical probe, the objective lens, and other optical systems such as a light source, a polarization conversion element, and a photodetector are configured on a single arm. Miniaturization is realized.

An information reproducing apparatus according to a tenth aspect of the present invention provides:
10. A near-field light or a propagating light on a region having a size equal to or less than a light source wavelength on the recording medium by a driving source for rotating and driving the recording medium and an optical probe approaching the recording medium. The optical pickup device according to any one of the above.

Therefore, since the optical pickup device according to any one of the first to ninth aspects is provided, a method for realizing a small size and light weight by introducing a reflected light from a recording medium to a light source is provided. A good reproduction signal having a high S / N can be obtained.

According to an eleventh aspect of the present invention, in the information reproducing apparatus according to the tenth aspect, the light source is a semiconductor laser, and a high-speed intensity modulating means for high-speed intensity-modulating the semiconductor laser to emit light.

Therefore, the case where the light emitted from the semiconductor laser as the light source is not perfectly linearly polarized light and interferes with the return light from the optical probe (that is, the reflected light from the recording medium) inside the semiconductor laser. In this case, even when the intensity of a specific mode is temporarily reduced by return light, the intensity can be maintained at a constant level as a whole by causing the semiconductor laser to perform high-speed intensity modulation to emit light and perform a reproducing operation. As a result, a stable signal can be obtained in data reproduction.

According to a twelfth aspect of the present invention, there is provided an information recording / reproducing apparatus, wherein a drive source for rotating and driving a recordable recording medium and an optical probe approaching the recording medium have a size less than a light source wavelength on the recording medium. The optical pickup device according to any one of claims 1 to 9, which irradiates near-field light or propagating light to the region (1).

Accordingly, since the optical pickup device according to any one of claims 1 to 9 is provided, a method for realizing a compact and lightweight system by introducing reflected light from a recording medium into a light source is provided. A good reproduction signal having a high S / N can be obtained, and the recording operation can be performed without any trouble.

According to a thirteenth aspect of the present invention, in the information recording / reproducing apparatus according to the twelfth aspect, the light source is a semiconductor laser, and comprises a high-speed intensity modulation means for performing high-speed intensity modulation on the semiconductor laser to emit light during reproduction.

Accordingly, the case where the light emitted from the semiconductor laser as the light source is not perfectly linearly polarized light and interferes with the return light from the optical probe (ie, the reflected light from the recording medium) inside the semiconductor laser. In this case, even when the intensity of a specific mode is temporarily reduced by return light, the intensity can be maintained at a constant level as a whole by causing the semiconductor laser to perform high-speed intensity modulation to emit light and perform a reproducing operation. As a result, a stable signal can be obtained in data reproduction.

[0045]

FIG. 1 shows a first embodiment of the present invention.
A description will be given with reference to FIG. FIG. 1 shows a schematic configuration example of an optical memory device to which the present embodiment is applied. The optical memory device may be a read-only information reproducing device or a recordable information recording / reproducing device. The optical memory device generally includes a spindle motor 2 as a drive source for driving the recording medium 1 to rotate, and an optical pickup for irradiating one side of the recording medium 1 to be driven for reproduction or recording with light. And the device 3.

The optical pickup device 3 includes a semiconductor laser 4 as a light source for emitting light toward the recording medium 1 side, a collimating lens 5 for collimating the light, an objective lens 6, and an objective lens 6. An optical probe 7 for guiding the emitted light to the recording medium 1 side, a semiconductor laser 4 and an optical probe 7
(More specifically, the collimating lens 5
A Faraday element 8 as a polarization conversion element which is arranged on the optical path between the objective lenses 6 and rotates the polarization direction of light passing therethrough by 45 °, and behind the semiconductor laser 4 (optical probe 7)
(A side opposite to the side) and a photodetector 9 of a photodiode arranged on the optical path.

The Faraday element 8 includes magnets 11 and 12 provided on both sides of the magneto-optical element 10 as shown in FIG.
With this configuration, a magnetic field is generated by the lines of magnetic force as indicated by arrows, and the rotation angle of polarized light can be set according to the strength of the applied magnetic field. In the present embodiment, the polarization direction is set to be rotated by 45 ° as described above.

The optical probe 7 has, for example, a core 14 and a clad 15 in the center of a flat casing 13 as shown in FIG.
The core 14 and the cladding 15 other than the opening 16A are formed of a metal film made of a metal material such as gold or aluminum. An optical probe 7A configured to be covered with a light-receiving plate 17 and an optical probe 7B formed by forming a light-shielding plate 19 having a frustum-shaped opening 16B in a glass plate 18 as shown in FIG. 4 are used. Even at the leading end, a minute opening 16 for irradiating the recording medium 1 with light energy is provided. This minute opening 1
The size of 6 differs depending on the form of the light energy applied to the recording medium 1. In the case of the method of applying the light energy in the form mainly including the propagating light, it is set to be about the wavelength of the light source light or more. In the case of a method of irradiating light energy in a form containing evanescent light (near-field light) as a main component, it is formed smaller than the wavelength of the light source light used.

The operation in such a configuration will be described. Laser light (linearly polarized light) emitted from the semiconductor laser 4
Are converted into parallel light by the collimating lens 5 and guided to the Faraday element 8. By passing through the Faraday element 8, the parallel light has its polarization direction rotated by 45 °,
After that, the light is condensed by the objective lens 6 and is incident on the optical probe 7 arranged close to the recording medium 1. The light radiated to the recording medium 1 as the propagating light or the near-field light from the minute opening 16 of the optical probe 7 is modulated by the recording information on the recording medium 1 and simultaneously reflected and reflected again by the optical probe 7. Is taken in.

For example, when the recording information is formed on the recording medium 1 by a change in reflectance, the intensity of the reflected light is modulated according to the recording information. The reflected light modulated in this way returns to the semiconductor laser 4 side again through the objective lens 6 and the Faraday element 8. At this time,
When passing through the Faraday element 8, the polarization direction is further increased by 45.
The light emitted from the semiconductor laser 4 is converted into a direction orthogonal to the polarization direction. Thus, the semiconductor laser 4
Since the light orthogonal to the polarization direction of the light oscillating does not cause interference, it is transmitted to the rear of the semiconductor laser 4 without substantially affecting the emission intensity of the semiconductor laser 4. And the recording medium 1
The light intensity reflecting this recorded information is detected by a photodetector 9 disposed on the rear side of the semiconductor laser 4.

Therefore, if the signal from the photodetector 9 is monitored while rotating the recording medium 1 by the motor 2, the information on the recording medium 1 can be sequentially read. on the other hand,
When a recording medium 1 on which recording information can be written, such as a recording medium using a phase change recording material, is used, the light emission intensity of the semiconductor laser 4 is modulated according to the information to be recorded. The recording can be performed for this.

A second embodiment of the present invention will be described with reference to FIG. The same parts as those described in the above-described embodiments are denoted by the same reference numerals, and description thereof is omitted (the same applies to each of the following embodiments).

In this embodiment, instead of the Faraday element 8, a quarter-wave plate 20 is used as a polarization conversion element,
It is provided on the optical path between the six.

In such a configuration, the semiconductor laser 4
The laser light (linearly polarized light) emitted from the optical probe 7 is converted into circularly polarized light by passing through the 波長 wavelength plate 20 and is condensed on the optical probe 7. The return light from the optical probe 7 side reflected by the recording medium 1 is again converted from circularly polarized light to linearly polarized light by passing through the 波長 wavelength plate 20 again. The direction is orthogonal to the polarization direction of the light emitted by the semiconductor laser 4.

Therefore, as in the case of the above-described embodiment, even if the return light from the optical probe 7 enters the semiconductor laser 4, it is transmitted backward without substantially interfering with the output light. If the photodetector 9 is arranged behind the semiconductor laser 4, a light intensity signal corresponding to the recorded information can be detected. The optical system using the quarter-wave plate 20 as in the present embodiment can be configured with an optical path that is much shorter than the case where the Faraday element 8 is used, so that the entire optical pickup device 3 is reduced in size. be able to.

A third embodiment of the present invention will be described with reference to FIG. This embodiment focuses on the fact that the polarization directions of two lights emitted backward from the semiconductor laser 4 are orthogonal to each other, and by arranging the polarization element 21 on the optical path between the semiconductor laser 4 and the photodetector 9. Only signals from the optical probe 7 (original signals on the recording medium 1) are detected. That is, the light emitted backward from the semiconductor laser 4 includes the light emitted by the laser oscillation of the semiconductor laser 4 itself emitted backward and the light returned from the optical probe 7 side passing through the semiconductor laser 4. Two components including light emitted backward are included. Even if the light intensity obtained by adding both lights is detected by the photodetector 9, a signal reflecting the recorded information can be obtained. However, if the light oscillated by the semiconductor laser 4 itself can be removed, the light from the optical probe 7 side can be removed. Since only the signal can be extracted, the S / N of the reproduced signal can be improved. For this reason, a polarizing element 21 is added.

The light emitted from the semiconductor laser 4 is reflected by the recording medium 1 via the optical probe 7 and returns to the semiconductor laser 4 via the optical probe 7 again, as in the above-described embodiment. This return light passes through the semiconductor laser 4 and is emitted from the back together with the light emitted by the semiconductor laser 4 itself. At this time, the polarization directions of these two lights emitted to the rear of the semiconductor laser 4 are orthogonal to each other, so that only the linearly polarized light in a specific direction is transmitted on the optical path between the semiconductor laser 4 and the photodetector 9. By arranging the element 21, only light returning from the optical probe 7 can be guided to the photodetector 9. Therefore, the semiconductor laser 4
An unnecessary optical signal radiated backward is removed, and the S / N of the reproduced signal can be improved.

FIGS. 7 and 8 show a fourth embodiment of the present invention.
It will be described based on. In the present embodiment, both the emission intensity of the semiconductor laser 4 and the intensity of the reflected light from the recording medium 1 can be detected by using the polarization element 22 and the photodetector 23 divided into regions. is there.

That is, the polarizing element 22 provided in place of the polarizing element 21 is divided into a central area A and a peripheral area B as shown in FIG. 8A, and these areas A and B are mutually separated. It is configured to transmit orthogonal linearly polarized light. The photodetector 23 provided in place of the photodetector 9 has a light receiving surface 24 divided into a central region C and a peripheral region D corresponding to the division of the polarizing element 22 as shown in FIG. The central area C receives light transmitted through the central area A,
Peripheral region D is associated so as to receive light transmitted through peripheral region B.

More specifically, for example, the reproduced signal light returning from the optical probe 7 side is applied to the central area C of the photodetector 23.
In order to detect the light radiated backward by the semiconductor laser 4 itself in the peripheral region D of the photodetector 23, the center of the polarization element 22 with respect to the polarization direction of the light radiated backward by the semiconductor laser 4 itself. The polarization element 22 may be arranged so that the polarization direction of the region A (the polarization direction that can transmit the polarization element 22) is orthogonal and the peripheral region B is parallel.

According to such a configuration, while reproducing recorded information based on the output of the central area C of the photodetector 23, the emission intensity of the semiconductor laser 4 is simultaneously output to the output of the peripheral area D of the photodetector 23. It can be monitored based on this. Therefore, even in a situation where the relationship between the drive current and the emission intensity changes due to the deterioration of the semiconductor laser 4 with time or a temperature change, the monitor signal obtained from the peripheral area D of the photodetector 23 is used as a feedback signal. By controlling the drive current of the laser 4, the light emission intensity can be kept constant, whereby a stable reproduction signal can be obtained.

FIGS. 9 and 1 show a fifth embodiment of the present invention.
Description will be made based on 0. In this embodiment, a polarization hologram element 25 for transmitting or diffracting according to the polarization direction of incident light and a photodetector 26 in which a light receiving surface 26a is divided into regions.
By using this, both the emission intensity of the semiconductor laser 4 and the intensity of the reflected light from the recording medium 1 can be detected. 27 is a lens.

The polarization hologram element 25 provided in place of the polarization element 21 has a single-period diffraction grating structure on the entire surface, for example, as shown in FIG. 10A, and a polarization component parallel to the direction in which the gratings are arranged. Is transmitted as it is, and a polarized light component perpendicular thereto generates diffracted light (mainly ± 1st-order diffracted light). The light receiving surface 26a of the photodetector 26 provided in place of the photodetector 9 has a region A for receiving light transmitted through the polarization hologram element 25 and a polarization hologram element 25.
Is divided into three regions B and regions B on both sides for receiving the light diffracted by the above.

Therefore, when the polarization hologram element 25 is arranged at the position shown in FIG. 9 so that the direction in which the gratings are arranged is perpendicular to the polarization direction of the light emitted from the semiconductor laser 4, the semiconductor laser 4 emits backward. The light intensity of the light is detected by the region B of the photodetector 26 by diffraction.
On the other hand, light from the optical probe 7 side is
5 and its light intensity is detected by the region A of the photodetector 26.

According to such a configuration, while reproducing the recorded information based on the output of the area A of the photodetector 26,
At the same time, the emission intensity of the semiconductor laser 4 can be monitored based on the output of the photodetector 26 in the region B.
Therefore, even in a situation where the relationship between the drive current and the emission intensity changes due to the deterioration of the semiconductor laser 4 with time or a temperature change, the monitor signal obtained from the peripheral area D of the photodetector 23 is used as a feedback signal. By controlling the drive current of the laser 4, the light emission intensity can be kept constant, whereby a stable reproduction signal can be obtained.

A sixth embodiment of the present invention will be described with reference to FIGS. The present embodiment particularly relates to the structure of the optical probe 7. That is, in order to allow the optical probe 7 to slide on the recording medium 1 while approaching the recording medium 1, the optical probe 7 itself is configured as a slider structure. As shown in FIG. 11, a pad 2 for sliding on the recording medium 1 is provided on the flat substrate 28 of the optical probe 7.
9 is provided, which functions as a slider. Further, a minute opening 16 necessary for the optical probe 7 is formed in a pad 29 portion as shown in FIG.

On the other hand, as shown in FIG. 12, the entire optical probe 7 having a slider structure (a flat substrate 28) is mounted on a position controlling arm 31 via a suspension 30, and the recording medium 1 is By moving the arm 31 while rotating the optical probe 2, the optical probe 7 can slide and scan an arbitrary position on the recording medium 1.

The other configuration of the optical pickup device 3 is the same as, for example, the case shown in FIG.
By operating this while rotating it, a series of information recorded on the recording medium 1 can be read and the information can be written.
At this time, since the optical probe 7 has a slider structure that slides on the recording medium 1 by the pad 29, the recording medium 1
Since the distance from the camera is always kept constant, a stable recording / reproducing operation can be performed.

A seventh embodiment of the present invention will be described with reference to FIG. First, when the optical probe 7 is held via the suspension 30 as in the case of the above-described sixth embodiment, the objective lens 6 and the optical probe 7 are moved due to surface deflection when the recording medium 1 rotates. 7, the intensity of light emitted from the optical probe 7 to the recording medium 1 fluctuates, and the reproduction signal becomes unstable. Therefore, in the present embodiment, the positional relationship between the objective lens 6 and the optical probe 7 is always maintained by integrating the objective lens 6 with the optical probe 7 having a slider structure based on the sixth embodiment. It is intended to keep it constant.

Therefore, according to the present embodiment, even when the optical probe 7 moves up and down due to a surface runout that occurs when the recording medium 1 is rotated, the objective lens 6 Since they are integrated, the distance between the optical probe 7 and the objective lens 6 can always be kept constant, and a stable reproduction operation and the like can be performed. At this time, the objective lens 6 and other optical systems below the quarter-wave plate 20 are not integrated, but are coupled by parallel light as shown in FIG. Accordingly, even when the optical probe 7 having the slider structure and the objective lens 6 move up and down, no optical effect appears. Therefore, even when the recording medium 1 is rotated, a stable recording / reproducing operation can be performed.

An eighth embodiment of the present invention will be described with reference to FIG. This embodiment is based on the above-described seventh embodiment, and a quarter-wave plate is provided on an arm 31 for scanning the recording medium 1 while holding the optical probe 7 and the objective lens 6 having a slider structure. 20, a collimating lens 5, a semiconductor laser 4, a polarizing element 21, and a photodetector 9 are integrally mounted. 32 is a reflection mirror. As a result, the other optical systems can always follow the operation of scanning the optical probe 7.

According to such a configuration, when scanning the recording medium 1 by moving the arm 31, the optical probe 7
Since the positional relationship between the optical system and other optical systems is always kept constant, stable recording / reproducing operations can be performed and at the same time, the size of the entire apparatus can be reduced.

A ninth embodiment of the present invention will be described with reference to FIG. In the present embodiment, a driving circuit of the semiconductor laser 4 during the reproducing operation is devised.

Generally, the light emitted from the semiconductor laser 4 is not completely linearly polarized light. Therefore, in the configuration shown in FIG. 1, the light emitted from the semiconductor laser 4 and the return light from the optical probe 7 are used. It is difficult to prevent the semiconductor laser 4 from interfering with the semiconductor laser 4 at all.

Therefore, in the present embodiment, the driving circuit for the semiconductor laser 4 is provided with the high-speed intensity modulation means 33,
At the time of reproduction, the intensity of the semiconductor laser 4 is modulated at high speed. The high-speed intensity modulating means 33 is configured by connecting a DC power supply 34 for supplying a DC current to the semiconductor laser 4 and an AC power supply 35 for supplying an AC current in parallel. Is performed. The modulation frequency determined by the AC power supply 35 is determined by the optical path length between the semiconductor laser 4 and the recording medium 1, the data reproduction speed, and the like. For example, if the optical path length is about several cm, the intensity may be modulated at a frequency of about several hundred MHz.

As described above, the semiconductor laser 4 is oscillated in a plurality of modes by high-speed intensity modulation of the semiconductor laser 4, and the intensity of the specific mode is temporarily reduced by the return light from the optical probe 7 side. Even if it does, the strength can be kept constant as a whole. Therefore, a stable signal can be obtained in data reproduction.

[0077]

According to the optical pickup device of the present invention, the polarization direction of the light emitted from the light source and the polarization direction of the light reflected by the recording medium and returning to the light source side via the optical probe are converted. Since the light is converted orthogonally by the element, the interference of light inside the light source is reduced, and the light reflected by the recording medium and returned to the light source side via the optical probe is transmitted without substantially affecting the light emission intensity of the light source. Therefore, the emission intensity of the light source is kept stable, and at the same time, a good reproduction signal can be obtained by receiving the light transmitted through the light source by the photodetector arranged behind the light source.

According to the second aspect of the present invention, in realizing the optical pickup device according to the first aspect, the rotation angle of polarized light can be controlled by using a Faraday element as a polarization conversion element.

According to the third aspect of the present invention, in realizing the optical pickup device of the first aspect, by using a quarter-wave plate as a polarization conversion element, compared with the case of using a Faraday element or the like, Since the volume is small, it can be configured with a very short optical path, which is advantageous for reducing the size and weight of the entire optical pickup device.

According to the invention described in claim 4, according to claim 1,
4. In the optical pickup device described in 2 or 3, the light emitted backward from the light source includes light emitted by the light source itself and light reflected by the recording medium and transmitted through the light source through the optical probe to the rear. Since there is light to be emitted, only the light reflected by the polarizing element by the recording medium and passing through the optical probe is extracted by using the difference in the polarization direction and detected by the photodetector, so that the S / S of the reproduced signal is obtained. N can be improved.

According to the fifth aspect of the present invention, in the optical pickup device according to the fourth aspect, the relationship between the drive voltage or the drive current and the emission intensity changes due to the deterioration of the light source with time or the temperature change. Even in such situations,
By using the polarizing element and the photodetector in which the regions are divided in combination, it is possible to monitor both the light emission intensity of the light source and the reflected light intensity from the recording medium at the same time. By monitoring the light emission intensity of the light source and using this as a feedback signal to control the light emission intensity of the light source to be constant, a stable reproduction signal can be obtained.

According to the sixth aspect of the present invention, in the optical pickup device according to the fourth aspect, the relationship between the drive voltage or the drive current and the emission intensity changes due to the deterioration of the light source with time or the temperature change. Even in such situations,
By using a polarization hologram element and a photodetector having a light-receiving surface divided into regions, it is possible to monitor both the light emission intensity of the light source and the light intensity reflected from the recording medium at the same time. A stable reproduction signal can be obtained by monitoring the light emission intensity of the light source while performing reproduction and performing control to make the light emission intensity of the light source constant using this as a feedback signal.

According to the seventh aspect of the present invention, in the optical pickup device according to any one of the first to sixth aspects, when the optical probe is scanned close to the recording medium, the optical probe is held by the arm. Since the slider has a slider structure that slides on the recording medium, the gap between the optical probe and the recording medium can always be kept constant, and a stable reproduction operation and the like can be performed.

According to the eighth aspect of the present invention, in the optical pickup device according to the seventh aspect, even when the optical probe moves up and down due to surface deflection or the like generated when the recording medium is rotated, Since the objective lens is integrated with the optical probe, the distance between the optical probe and the objective lens can always be kept constant, and a stable reproduction operation and the like can be performed.

According to the ninth aspect of the present invention, in the optical pickup device of the eighth aspect, the positional relationship between the optical probe and the objective lens and other optical systems such as a light source, a polarization conversion element, and a photodetector is determined. Since the scanning on the recording medium is always kept constant through the arm, stable reproduction operation and the like can be performed.In addition, the optical probe, the objective lens, and other light sources, the polarization conversion element, the photodetector, etc. Since the optical system is configured to be mounted on one arm, the size of the entire apparatus can be reduced.

According to a tenth aspect of the present invention, since the information reproducing apparatus includes the optical pickup device according to any one of the first to ninth aspects, the light source reflects reflected light from the recording medium. As a result, a good reproduction signal having a high S / N ratio can be obtained with respect to a method for realizing a reduction in size and weight.

According to the eleventh aspect, in the first aspect,
In the information reproducing apparatus described in No. 0, even when the light emitted from the semiconductor laser as the light source is not perfectly linearly polarized light and interferes with the return light from the optical probe inside the semiconductor laser, the semiconductor laser can operate at high speed. By performing the reproduction operation by modulating the intensity and emitting light, even if the intensity of a specific mode temporarily decreases due to the return light, the overall intensity can be maintained at a constant level. , A stable signal is obtained.

According to the twelfth aspect of the present invention, there is provided an information recording / reproducing apparatus comprising the optical pickup device according to any one of the first to ninth aspects. As a result, with respect to a method for realizing a reduction in size and weight, a good reproduction signal having a high S / N can be obtained, and a recording operation can be performed without any trouble.

According to the thirteenth aspect of the present invention, the first aspect
2. In the information recording / reproducing apparatus described in 2, the light emitted by the semiconductor laser as the light source is not perfectly linearly polarized light, and interferes with the return light from the optical probe (that is, the reflected light from the recording medium) inside the semiconductor laser. Even in such a case, by causing the semiconductor laser to perform high-speed intensity modulation to emit light and perform a reproducing operation, even if the intensity of a specific mode is temporarily reduced by return light,
As a whole, the intensity can be kept constant, and a stable signal can be obtained in data reproduction.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical memory device according to a first embodiment of the present invention.

FIG. 2 is a sectional structural view showing the Faraday element portion in an enlarged manner.

FIG. 3 is an enlarged sectional structural view showing an example of the optical probe.

FIG. 4 is an enlarged sectional view showing another example of the optical probe.

FIG. 5 is a schematic configuration diagram of an optical pickup device showing a second embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of an optical pickup device showing a third embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of an optical pickup device showing a fourth embodiment of the present invention.

FIG. 8A is a plan view of a polarizing element, and FIG. 8B is a plan view of a light receiving surface of a photodetector.

FIG. 9 is a schematic configuration diagram of an optical pickup device showing a fifth embodiment of the present invention.

FIG. 10A is a plan view of a hologram polarizing element,
(B) is a plan view of a light receiving surface of the photodetector.

FIG. 11 is a schematic configuration diagram of an optical pickup device showing a sixth embodiment of the present invention.

FIG. 12 is an enlarged schematic view showing the slider structure.

FIG. 13 is a schematic configuration diagram of an optical pickup device showing a seventh embodiment of the present invention.

FIG. 14 is a schematic configuration diagram of an optical pickup device showing an eighth embodiment of the present invention.

FIG. 15 is a circuit diagram showing a ninth embodiment of the present invention.

FIG. 16 is a schematic configuration diagram showing a configuration example of a conventional optical memory device.

FIG. 17 is a schematic perspective view showing a configuration example of a conventional optical pickup device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording medium 2 Drive source 3 Optical pickup device 4 Semiconductor laser, light source 6 Objective lens 7 Optical lobe 8 Faraday element, Polarization conversion element 9 Photodetector 16 Aperture 20 1/4 wavelength plate, Polarization conversion element 21, 22 Polarization element 23 Photodetector 25 hologram polarizing element, polarizing element 26 photodetector 31 arm 33 high-speed intensity modulation means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 5/32 G02B 5/32 G11B 7/125 G11B 7/125 C 7/13 7/13 H01S 5/0683 H01S 5/0683 // G12B 21/06 G12B 1/00 601C F term (reference) 2H049 BA02 BA07 BA08 BB03 BC21 CA01 CA05 CA08 CA11 CA15 CA17 5D119 AA11 AA12 AA20 AA22 BA01 CA06 DA01 DA05 EC35 FA05 HA14 JA30 JA32 JA35 MA05 MA06 AB27 AB28 AB30 BA04 EA12 EA22 GA02

Claims (13)

[Claims] 1. A light source, an optical probe for irradiating a light supplied from the light source to an area having a size equal to or less than the wavelength of the light source and irradiating the light on a recording medium, and condensing the light supplied from the light source, An objective lens to be incident on the optical probe; and a polarization direction of light emitted from the light source, which is disposed on an optical path between the optical probe and the light source, and the light source side reflected by the recording medium and reflected by the recording medium. An optical pickup device, comprising: a polarization conversion element that makes a polarization direction of light returning to the light orthogonal to the light source; and a photodetector that is disposed on an optical path behind the light source and receives light traveling rearward from the light source. 2. The optical pickup device according to claim 1, wherein said polarization conversion element is a Faraday element. 3. The polarization conversion device according to claim 1, wherein the polarization conversion element is 1 to a light source wavelength.
The optical pickup device according to claim 1, wherein the optical pickup device is a / 4 wavelength plate. 4. The optical pickup device according to claim 1, further comprising a polarizing element on an optical path between said light source and said photodetector. 5. The polarizing element is divided into regions so as to transmit light having different polarization directions, and a light receiving surface of the photodetector receives light from each of the divided regions of the polarizing element. The optical pickup device according to claim 4, wherein the optical pickup device is divided into regions. 6. The polarization hologram element, wherein the polarization element is a polarization hologram element that transmits or diffracts the incident light in accordance with the polarization direction, and a light receiving surface of the photodetector separates the transmitted light and the diffracted light by the polarization hologram element. 5. The optical pickup device according to claim 4, wherein the optical pickup device is divided into regions so as to receive light. 7. The optical pickup device according to claim 1, wherein the optical probe has a slider structure that slides on the recording medium while being held by an arm. 8. The optical pickup device according to claim 7, wherein the objective lens is integrated with the optical probe. 9. The optical pickup device according to claim 8, wherein the light source, the polarization conversion element, and the photodetector are arranged on the arm that holds the optical probe having a slider structure. 10. A drive source for rotating a recording medium, and an optical probe approaching the recording medium irradiates near-field light or propagation light to an area on the recording medium having a size equal to or less than a light source wavelength. An information reproducing apparatus comprising: the optical pickup device according to any one of 1 to 9; 11. The information reproducing apparatus according to claim 10, wherein said light source is a semiconductor laser, and said apparatus has a high-speed intensity modulation means for high-speed intensity modulation of said semiconductor laser to emit light. 12. A drive source for rotationally driving a recordable recording medium, and an optical probe approaching the recording medium irradiates a near-field light or a propagating light to a region having a size equal to or less than a light source wavelength on the recording medium. An information recording / reproducing apparatus comprising: the optical pickup device according to claim 1. 13. The information recording / reproducing apparatus according to claim 12, wherein the light source is a semiconductor laser, and a high-speed intensity modulating means for high-speed intensity-modulating the semiconductor laser to emit light during reproduction.