JPH0725863Y2 - Optical head for optical recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an optical recording capable of irradiating a recording medium with a laser beam to record information and reproducing the information from the recording medium using the laser beam. The present invention relates to a reproducing apparatus, and particularly to an optical head provided in the vicinity of a recording medium in this optical recording / reproducing apparatus and provided with an optical system such as a laser and an objective lens.

[Conventional technology]

The physical properties are changed by irradiating them with a laser beam, and the changes in the physical properties are read so that the changes in the physical properties can be read out. Various recording media having such characteristics have been proposed. However,
Many of these recording media usually have poor light resistance, and changes in their physical properties are easily erased by irradiation with a laser beam. Therefore, in an optical recording / reproducing apparatus that records and reproduces information by using such a recording medium, in other words, the information can be reproduced from the recording medium many times over a long period of time. In this way, the information recorded on the recording medium can be stored for as long as possible without being destroyed or erased by the irradiation of the laser beam, so that the laser or the laser beam has some light resistance during reproduction. It is necessary to take measures.

Therefore, conventionally, in an optical head in such an optical recording / reproducing apparatus, as shown in FIG. 6, for example, as shown in FIG. By switching to β as needed, the output of the laser beam is weakly suppressed to a constant value during reproduction.

[Problems to be solved]

However, in the optical head for the optical recording / reproducing apparatus of this type, even if the power of the lasing laser beam is adjusted by controlling the output on the semiconductor laser side,
Since the improvement measures for the peculiar light intensity distribution of the laser beam have been attached in a quiet manner, the light resistance measures are insufficient and pose a problem. That is, a laser beam bundle emitted from a semiconductor laser or the like usually has a Gaussian function type light intensity distribution as shown in FIG. 7, and therefore the central portion γ side of the laser beam bundle is located at the peripheral portion δ side. Since the light intensity is considerably higher than that of the semiconductor laser, even if the output of the semiconductor laser is weakened, when the central portion of the laser beam flux is irradiated to the recording portion of the recording medium, the destruction of that portion is large and the recording is performed. The existing information may be lost.

This invention has been made in view of the above-mentioned conventional problems, and its purpose is to prevent destruction of recorded information on a recording medium as much as possible even if information is reproduced many times over a long period of time. An object of the present invention is to provide an optical head for an optical recording / reproducing apparatus, which has failed to take good measures against light resistance of a recording medium.

[Means and Actions for Solving Problems]

That is, this invention is provided with an optical system such as a laser and an objective lens, irradiates a laser beam emitted from the laser to record information on a recording medium, and a tracking control unit or the like is used to track the information on the track of the recording medium. In an optical head for an optical recording / reproducing apparatus capable of irradiating a laser beam to reproduce information from a recorded portion on the track, the laser beam vibrated by the tracking control means during information reproduction is further superposed and vibrated. Therefore, a wobbling means for vibrating the laser beam with a constant amplitude and at least a frequency higher than the frequency by the tracking control means is provided, and the peripheral side of the laser beam is irradiated to the recording portion of the recording medium. In other words, the wobbling means is provided separately from the tracking control means. The laser beam applied to the recording medium at the time of reproduction is finely oscillated to the left and right with respect to the recording portion on the track by the wobbling means, so that the peripheral portion side avoiding the central portion side where the light intensity of the laser beam bundle is strong is recorded. To prevent the recorded information from being erased by preventing the destruction of the recorded portion due to the irradiation of the laser beam during reproduction, and thereby to prevent the recorded information from being erased, which enables the information to be reproduced many times over a long period of time.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an optical head for an optical recording / reproducing apparatus according to the present invention. The optical head is located on the optical path formed between the laser 1 and the objective lens 2 and directly below the objective lens 2. The wobbling means 4 is attached to the 45 ° mirror 3. The tracking control means and the like in this embodiment are constituted by an objective lens actuator (not shown), and the objective lens 2 and the 45 ° mirror 3 are slid by electromagnetic force to apply servo.

When reproducing the information recorded on the recording medium 5 shown in FIG. 2, the wobbling means 4 records the information on the laser beam emitted toward the recording medium 5 with a constant amplitude and a constant frequency. It is for vibrating in a direction orthogonal to the recording portion 7 on the track 6. And
As shown in FIGS. 3 (a) and 3 (b), the wobbling means 4 of this embodiment has a casing 8 on the objective lens actuator side in which a pair of left and right laminated ceramic piezoelectric elements are fixed to the back side of the 45 ° mirror 3. As shown in FIG. 4, these monolithic ceramic piezoelectric elements are operated with their phases shifted by a half wavelength. In the wobbling means 4 of this embodiment, the operation of each laminated ceramic piezoelectric element is about three times as high as the frequency of tracking servo, for example, 60.
It is designed to vibrate at around KHz. Further, in the wobbling means 4 of this embodiment, a laser beam having a weak power is used, and the wobbling means 4 vibrates at a constant amplitude so that a region having a weak light intensity on the peripheral side of the laser beam is irradiated to the recording portion 7. For example, when the radius of the laser beam bundle during reproduction is set to about 1 μm, the oscillation width A of the laser beam by the wobbling means 4 is set to about 0.5.
The optical intensity of the laser beam applied to the recording portion 7 is suppressed to about 1/5 of that of the central portion of the laser beam (see FIG. 5).

Incidentally, the wobbling means 4 of this embodiment is not particularly limited to that of the above-mentioned embodiment, and servo is applied by using, for example, the slide type objective lens actuator or the mirror rotation type tracking actuator of this embodiment. In this case, it is of course possible to use an electromagnetic drive type actuator instead of the monolithic ceramic piezoelectric element so that the laser beam is vibrated.

Therefore, according to the optical head for the optical recording / reproducing apparatus in this embodiment, the laser beam is applied to the recording portion 7 while vibrating the recording portion 7 by the tracking servo by the objective lens actuator (not shown) during reproduction.
The 45 ° mirror 3 is vibrated at a frequency of about 3 times that of the tracking servo and at a constant amplitude by the laminated ceramic piezoelectric element fixed to the laser beam. The peripheral portion side of is irradiated onto the recording portion 7. In this way, each recording portion 7 of the recording medium 5 is irradiated with a laser beam having a weak light intensity during reproduction.

〔effect〕

As described above, according to the optical head for an optical recording / reproducing apparatus of the present invention, the wobbling means finely vibrates the laser beam at a constant frequency and a constant amplitude during reproduction. The peripheral part of the laser beam bundle is irradiated to the recording part of, so that there is no fear that the recorded information will be erased in a short period of time, and it is possible to reproduce the information many times over a long period of time. The effect is extremely large.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic structure of an optical head for an optical recording / reproducing apparatus according to the present invention, and FIG. 2 is a case where a recording portion is irradiated with a laser beam by the optical head for an optical recording / reproducing apparatus according to the present invention. Explanatory diagram showing the state of FIG. 3, FIG.
FIGS. 4 (b) and 4 (b) are a schematic plan view and a schematic cross-sectional view, respectively, showing the mounting state of the wobbling means according to the present invention, and FIG. 4 is an explanatory view for explaining the operation timing when the wobbling means according to the present invention is operated, and FIG. FIG. 6 is an explanatory view showing a change in light intensity when a laser beam vibrates by the wobbling means according to the present invention, and FIG. 6 shows laser output when information is recorded and reproduced by an optical head for a conventional optical recording / reproducing apparatus. FIG. 7 is a graph showing the characteristics of the recording medium at that time, and FIG. 7 is a graph showing the light intensity distribution of the laser beam. 1 ... Laser, 2 ... Objective lens, 5 ... Recording medium, 7
…… Recording part, 4 …… Wobbling means, 3 …… (45
°) Mirror.

Claims (1)

[Scope of utility model registration request] 1. An optical system such as a laser and an objective lens is provided,
Information is recorded on the recording medium by irradiating the laser beam emitted from the laser, and information is reproduced from the recording portion on the track by irradiating the track of the recording medium with the laser beam by the tracking control means or the like. In an optical head for an optical recording / reproducing apparatus that can be performed, in order to further oscillate the laser beam vibrated by the tracking control unit at the time of information reproduction, the laser beam has a constant amplitude and at least by the tracking control unit. A wobbling means for vibrating at a frequency equal to or higher than a frequency is provided, and the peripheral side of the laser beam is configured to irradiate the recording portion of the recording medium.
A pair of the wobbling means is provided on both ends of the back surface of the mirror installed in a part of the optical path from the laser to the objective lens, and is configured to operate by shifting the phase by a half wavelength from each other. The optical head for an optical recording / reproducing apparatus is characterized in that the frequency when the laser beam is vibrated is three times or more the frequency when the tracking control means is activated to vibrate the laser beam. .