JPS63146230A - 2-head optical disk device - Google Patents

Abstract

PURPOSE:To shorten a recording time by providing the titled device with a 1st arm whose one end is pivoted to a 1st head and the other end is pivoted to a movable member, and a 2nd arm whose one end is pivoted to a 2nd head and the other end is pivoted to the movable member, then making the 1st and 2nd arms the same in length. CONSTITUTION:A 1st arm 44R has the same length as a 2nd arm 44L and both ends of each are equal in pivoting position and interval. Therefore, 1st and 2nd heads 20R and 20L move close to or away from each other on the same radius of a recording medium 12 via a link mechanism when a bobbin 42 is moved toward a 2nd straight line after drive of a linear motor. Then the light spot sent from the head 20L scans the same information track on the medium 12 with a delay of a half round against the light spot sent from the head 20R. Thus it is possible for a postscript type recording medium to reproduce the recorded data by the head 20L to confirm whether the data is recorded correctly or not right after the data is recorded by the head 20R. Then the recording and reproducing actions are simultaneously performed in a simple way.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a two-head optical disk device, and more particularly to a two-head optical disk device that can be applied to an optical disk device that uses a write-once optical disk, an erasable magneto-optical disk, etc. be.

(Prior Art) An optical disk device is known that records and reproduces information by irradiating a light spot onto concentric information tracks of a disk-shaped recording medium through an objective lens. In a conventional optical disk device, only a single so-called head is provided, which has an objective lens and scans a light spot on an information track.

Therefore, for example, when the recording medium is a write-once optical disc, in the process of recording, the recorded data must be reproduced (verified) after recording to confirm that it has been recorded correctly. If the number of records is so large that it spans several tracks, the head must be returned from the position after recording ends to the information track position at the beginning of recording during the verify operation, which causes the problem that it takes a long time to record information. be.

(Objective) Therefore, an object of the present invention is to provide a two-head optical disc device that can reduce recording time.

(Structure) In order to achieve the above object, the present invention provides an optical disc device including a first head having an objective lens and scanning a light spot on an information track, and a first head with respect to the center of a recording medium. A second head is set at a symmetrical position to the head, and the first head and the second head are placed on a first straight line connecting the first head, the second head, and the center of the recording medium, respectively.
head guide means for guiding the head of the recording medium, movable member guide means for guiding the movable member on a second straight line passing through the center of the recording medium and perpendicular to the first straight line, driving means for the movable member; A first arm having the other end pivotally connected to the movable member, and a second arm having one end pivotally connected to the second head and the other end to the movable member, the first arm and The second arm is characterized by having the same length.

A detailed description will be given below based on one embodiment of the present invention.

First, optical pickup in an optical disc device will be explained.

In FIG. 4, the light beam emitted from the semiconductor laser 2 is converted into parallel light by the coupling lens 4, and travels through the polarizing beam splitter 6, the 1/4 wavelength plate 8, and the objective lens 10, and then travels through the disk-shaped recording medium 12. The light is focused on the top as a light spot with a diameter of about 1 μm. The reflected light from the recording medium 12 travels backward through the objective lens 10, the 1/4 wavelength plate 8, and the polarizing beam splitter 6 in this order.

The light is focused by the condensing lens 14 and sent to the light receiving element 1 for track detection.
A part of the luminous flux is irradiated onto 6. Track detection and optical information detection are performed by this track detection light receiving element 16, and the remaining light beam is received by a focus detection light receiving element 18 placed at the convergence point of this reflected light beam, and focus detection is performed. It will be done.

The principle of focus detection will be explained with reference to FIG. Recording medium 12
When the light-receiving element 18 moves away (Fig. 6(b)) or approaches it (Fig. 6(C)) than when in focus (Fig. 6(a)) due to surface contact, etc., the two-divided element A of the light-receiving element 18 , B changes. Therefore, the focal point is detected by electrically detecting the difference between the outputs of elements A and B.

Then, the two-dimensional actuator is driven by this detected focus signal to move the objective lens 1o in the optical axis direction, so that the focus signal is always zero, that is, the light spot is on the recording medium 1.
Control is performed so that the focus is on 2.

Next, the principle of track detection will be explained with reference to FIGS. 7 to 9.

On the recording medium 12, information tracks 50 called, for example, pregrooves are formed in a concentric shape (including a spiral shape). Track detection is performed by detecting the symmetry of the far field image of the reflected light beam with respect to the center of the rack, based on the phase difference of the reflected light due to the optical distance between the tracks.

In other words, when the light spot focused on the recording medium 12 shifts from the information track and the light enters the edge of the track, which has a phase difference of about π/2 with respect to the part between the track grooves, it is reflected. In the far-field image of the light beam, a region of high light intensity moves in the direction in which the light spot is shifted from the normal position shown in FIG. 7, as shown in FIGS. 8 and 9. Therefore, this change in light intensity is detected by the track detection light receiving element 16 shown in FIG.
Detected by two divided elements C and D that constitute pixel C
, D, the tracking control signal can be obtained. Note that the reference numeral 56 in FIG. 5 indicates a reflected light beam.

Incidentally, regarding the signal strength, in FIG. 7, C=D, and in FIG. 8, when CD<O1100, CD>o.

Therefore, with this detected tracking control signal,
A two-dimensional actuator is driven to move the objective lens 10, and the light spot is controlled so as to always follow the information track as shown in FIG.

Further, by detecting the sum of the outputs of the element C9D of the track detection light receiving element 16, the strength of the reflected light is detected and the information recorded on the recording medium 12 is read.

Information is recorded on the information track by changing the amount of light emitted from the semiconductor laser 2, for example, and recording the recording medium 1 with strong light.
This is done by forming a small hole called a pit on the top of the hole.

In conventional optical disk devices, only one optical pickup with such a configuration is provided, but as shown in FIGS.
In the embodiment shown in the figure, two are provided.

In FIG. 1, the reference numeral 20R indicates a first head, and as shown in FIG. It is. The objective lens IOR is supported so as to be movable in the focusing direction and the tracking direction via a two-dimensional actuator 26R. 6 In addition, immovable members outside the first head 20R include a semiconductor laser 2R, a coupling lens 4R, a light condensing lens 14
R, track detection light receiving element 16R1, focus detection light receiving element 188, etc. are provided.

A recording medium 12 is provided above the first head 20R so as to be rotatable about its center O.

With this configuration, the diverging light emitted from the semiconductor laser 2R is made into parallel light by the coupling lens 4R, passes through the polarizing beam splitter 6R and the 1/4 wavelength plate 8R, and is turned upward by the prism 22R, and is sent to the objective lens IOH.
The light is then focused onto the recording medium 12 by the lens. The reflected light is transmitted through the objective lens IOR, the prism 22R, the quarter-wave plate 8R, and the polarizing beam splitter 6H.
The light travels backward in this order, is changed course by the prism 24R, reaches the condensing lens 14, and is condensed by the lens onto the focus detection light receiving element 18H.

A second head 20L is set at a position symmetrical to the first head 20R with respect to the center O of the recording medium 12. The same members as those provided on the first head 20R are also provided on the second head 20L in the same arrangement. Listing the names of the main components in Fig. 1 are: polarizing beam splitter 61. 1/4 wavelength plate 8L.
, prism 22L, objective lens 10L, prism 2, etc.

Also, on the immovable members outside the second head 20L, as in the first head 20R, there are a semiconductor laser 2L, a coupling lens 4L, a focus detection element 18L, a track detection element 16L, and a condenser lens 1. etc. are provided.

Here, if the line connecting each center of the objective lenses IOR and IOL and the center O of the recording medium 12 is called a first straight line 52, then
Two guide rails 28. parallel to this first straight line 52.
30 is a provision.

The first head 20R is movably supported by a guide rail 28.30 via a bearing 32.34.

Similarly, the second head 20L has a bearing 36°38
It is movably supported on guide rails 28, 30 via.

Thus, the objective lenses 10R910L on each head can both be guided and moved on the first straight line 52. Therefore, the guide rails 28, 30, bearings 32, 34, 36° 38, etc. constitute head guiding means.

Here, it is assumed that the optical axis directions of the coupling lenses 4R, 4L and the condensing lens 14R, 1 female are set parallel to the first straight line.

Next, assuming a second straight line 54 passing through the center 0 of the recording medium 12 and perpendicular to the first straight line 52, a rod-shaped magnet 40 corresponding to the stator of the near motor is immovable on this second straight line 54. It is set up like this.

A bobbin 42 as a movable member is fitted into the magnet 40 so as to be movable on a second straight line 54 .

Thus, the magnet 40 constitutes movable member guiding means,
A linear motor constituted by a combination of a bobbin 42 and a magnet 40 also functions as a means for driving a movable member.

The first arm 20R and the bobbin 42 are the first arm 44R.
The second arm 20L and bobbin 42 are the second arm 4.
They are each connected by 4L. Specifically, one end of the first arm 44R is pivotally connected to the negative part of the bobbin 42 by a pin P, and the other end is pivotally connected to the first head 20R by a pin P.

Similarly, one end of the second arm 44L is connected to a part of the bobbin 42 by a pin P, and the other end is connected to the second head 20 by a pin P.
Each is pivotally connected to L.

Here, the first arm 44R and the second arm 44L have the same length, and the intervals between the pivot positions at both ends thereof are the same.

Therefore, when the linear motor is driven to move the bobbin 42 in the second straight direction, the first head 20R and the second head 20L move toward or away from each other on the same radius of the recording medium 12 due to the link mechanism. move in the direction. Therefore, the light spot from the second head 20L is different from the light spot from the first head 20R on the recording medium 12.
The same information track above will be scanned with a delay of half a rotation.

Therefore, in a write-once type recording medium, after recording with the first head 20R, the recorded data is immediately reproduced with the second head 20L (
It becomes possible to confirm whether or not recording has been performed correctly by verifying the recorded data, which simplifies immediate recording and reproduction, and significantly reduces the time required to complete the recording operation compared to the prior art.

Furthermore, if the recording medium 12 is an erasable disk such as a magneto-optical disk, information is erased by applying strong light similar to recording, but when recording after erasing information,
The light spot must scan the same information track twice, which also takes time.

In this case as well, the first head 20R erases the information and the second head 20R erases the information.
If the head 20L is used for recording, data over several tracks can be recorded at once.

Furthermore, if the amount of data that can be recorded at one time is limited to one track or less, the information can be erased using the first head 2OR,
Record with the second head 20L, then write again with the first head 20R.
In general, two-head optical disk drives have the above-mentioned effects, but simply arranging two optical pickup units requires a large device. Therefore, the cost will also increase.

Point 1: This example focuses on the fact that even if the two heads do not necessarily move independently, if they can always seek to the same radial position, the same time-saving effect can be obtained, and one driving means drives the two heads at the same time. I decided to do so.

In the embodiment shown in FIG. 1, if the reflective surface of the prism 24L is changed to guide one reflected light to the prism 24R, the condenser lens 1 and the track detection light receiving element 16
L, members such as the focus detection light receiving element 18L are omitted, and these functions are replaced by a condensing lens 14R.

Track detection light receiving element 16R1 Focus detection light receiving element 1
It is possible to reduce the number of members by replacing them with 8R or the like.

(Effects) According to the present invention, it is possible to achieve high-speed operation with a small size and low cost, and to shorten the recording time, which is advantageous.

[Brief explanation of the drawing]

FIG. 1 is a front view of essential parts of a two-head optical disk device according to an embodiment of the present invention, FIG. 2 is a side view of the same as the above figure, and FIG. 4 is a diagram explaining the general configuration of the optical pickup, FIG. 5 is a diagram illustrating the light receiving element for track detection, and FIG.
This figure is a diagram explaining the principle of focus detection, and FIGS. 7 to 9 are diagrams each explaining the principle of track detection.

Claims (1)

[Claims] Concentric information tracks of a disc-shaped recording medium,
Record information by shining a light spot through an objective lens.
An optical disc device that performs playback includes a first head that has an objective lens and scans a light spot on an information track, and a second head that is set at a position symmetrical to the first head with respect to the center of the recording medium. , a head guide means for guiding the first head and the second head on a first straight line connecting the first head and the second head and the center of the recording medium, and a first straight line passing through the center of the recording medium. A movable member guide means for guiding the movable member on a second straight line perpendicular to the straight line, a movable member driving means, and a first arm pivotally connected at one end to the first head and at the other end to the movable member. and a second arm having one end pivotally connected to the second head and the other end pivotally connected to the movable member, the first arm and the second arm having the same length.