JPH02289928A - Recorded information reader - Google Patents

Abstract

PURPOSE:To allow the exact detection and removal of crosstalks by controlling a relative angle according to the output difference of a pair of light receiving means which receive the reflected light by the recording surface of emitted light. CONSTITUTION:The emitted light from a light emitting element 23 is reflected by the recorded picture of a disk 11 while the light diffuses when the disk and an optical axis 31 are perpendicular. The light receiving elements 24a, 24b are evenly irradiated with this light. The orthogonal relation of the disk and the optical axis 31 deviates when the disk 11 is deformed to a circular conical shape. The reflected light is then made incident only to the light receiving element 24b and a tilting motor 27 is driven by the differential output of a differential amplifier 25, by which an optical head unit 12 is turned around a revolving shaft 14 and, therefore, tilting servo is executed. The generation of a difference in the quantity of the received light between a pair of the light receiving elements 24a and 24b is only in the case in which the disk surface is inclined in the radial direction of the disk. The detection of crosstalks is thus always exactly executed.

Description

Detailed Description of the Invention Technical Field The present invention relates to an optical recorded information reading device, and more particularly to an optical recording device having a servo system that maintains an orthogonal relationship between the optical axis of a recorded information reading light beam and the recording surface of a recording medium. It relates to an information reading device.

BACKGROUND ART When the angle between the optical axis of the optical beam for reading recorded information and the recording disk as a recording medium deviates from a right angle, information from adjacent recording tracks leaks, resulting in a so-called crosstalk phenomenon. . There are various reasons why the angle between the two may deviate from the orthogonal relationship, but for example, the recording disk may become umbrella-shaped due to changes over time, or the disk rotation axis may become tilted due to changes in the shape of the deck of the playback device. The occurrence of crosstalk is inevitable because it is a problem that occurs after the product is shipped.

Therefore, a servo system is provided that electrically detects the crosstalk and always accurately maintains the orthogonal relationship between the optical axis of the light beam and the recording disk to reduce the crosstalk. Such a technique is disclosed in detail in Japanese Patent Application Laid-Open No. 186237/1983. This example is applied to a playback device for a recording disc recorded using the CLV (Constant Linear Velocity) method, and in a recording disc using the CAV (Constant Angular Velocity) method, the synchronization signal recording section spans all recording tracks. The crosses 1 and 1 are detected by utilizing the fact that they are arranged on the same radius line, whereas in the CLV method they are not aligned on the same radius line.

That is, in the CLV system, the amount of crosstalk is detected by detecting leakage components of synchronization signal information of adjacent tracks, and the optical axis of the reading light beam is tilted so as to eliminate this amount.

Such a method has disadvantages such as that the electric circuit for crosstalk detection is complicated and expensive, and that it is limited to the CLV method and cannot be applied to the CAV method.

SUMMARY OF THE INVENTION The present invention has been made to eliminate the drawbacks of the above-mentioned conventional devices. It is an object of the present invention to provide a recorded information reading device having a function of accurately detecting the relative angle between a pickup light beam and a recording surface without being affected by the above.

The relative angle detection means in the recorded information reading device according to the present invention includes a light emitting means in which emitted light is irradiated toward the recording surface;
On a plane perpendicular to the optical axis of the emitted light, a pair of emitted light beams are arranged at symmetrical positions with respect to the light emitting means on a predetermined line perpendicular to the recording track, and receive the emitted light from the recording surface of the emitted light. This configuration includes a light receiving means.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention, and the recording disk 11 is shown as being tilted with respect to the horizontal line due to deformation. An optical head unit 12 for optically reading recorded information on the recording disk is provided, and this is rotatably supported by a support portion +A' 13 around a rotation shaft 14. This support member is the slider 1
5, and this slider 15 is for moving the head unit 12 in the radial direction of the disk 11. For example, the pinion gear 17 is adapted to engage with a rack portion 16 formed in a part of the slider 5, and the pinion gear 17 is driven by the slider motor 8.
The movement of the slider 5 in the disk radial direction is controlled by the drive of the slider 5.

A normal feed signal generating section 20 is provided which detects a DC component included in an error signal from a tracking error signal generator (not shown) and generates a normal feed signal for the slider, and also performs address search of recorded information and so-called scanning. A high-speed feed signal generating section 21 is provided that generates a high-speed feed signal for the slider during operation. The outputs of these two signal generators are supplied to the driver 9 via the adder 22 to rotate the slider motor 8.

A light emitting element 23 and light receiving elements 24a and 24b are mounted on the head unit 12 in order to detect the tilt of the disk 11, and the light receiving outputs a and b of the light receiving elements 24a and 24b are input to a differential amplifier 25 and the difference is calculated. Output C is driver 26
The tilt motor 27 is driven via. A male threaded portion 28 connected to the rotation shaft of the tilt motor 27 and a female threaded portion provided on a part of the optical head unit 12 are screwed together, and as the motor 27 rotates, the optical head unit 12 is designed to be inclined at an arbitrary angle of inclination. The rotation axis that forms the center of inclination at this time is the support member 1
It becomes the axis 14 of 3.

Note that the spring S wound around the male threaded portion 28
is to prevent puck rush.

FIG. 2 is a perspective view of the optical head unit 12.
is the objective lens. A recorded information reading light beam emitted from a laser light source inside the unit 12 is focused onto the recording surface of the recording disk 11 by this objective lens. The center of this objective lens 29 is located at the point where the optical axis 31 of the light beam and the rotation axis 14 intersect.

In order to control the movement of the two objective lenses in a direction parallel to the optical axis 31 so that the light beam always converges on the recording surface, a so-called focus actuator 30 is provided, which is controlled by a magnetic circuit or Consists of coils, etc.

A straight line passing through the center of the objective lens 29 and the center of the light emitting element 23 is approximately parallel to the tangential direction of the recording I/rack during reproduction, and is preferably the convergence point of the light beam when reading recorded information, that is, the information detection point. The light emitting element 23 is placed at a position that illuminates the recording material preceding the point, and neither the emitted light from this light emitting element nor its reflected light passes through the objective lens 29. .

In addition, the optical axis 31 of the recorded information reading light beam and the light emitting element 2
The target axes from No. 3 are parallel to each other, and there is no problem in treating them as the same.

FIG. 3 is a diagram showing the details of the structure of the light emitting element 23 and the light receiving elements 24a, 24b that detect the disc tilt.
At ω, the light receiving element 24 is placed on the base 32 by shifting the light source position higher.
Direct incidence to a and 24b is avoided. In addition, in the figure, each element is mounted on the same plane, and the light emitting element 2
A cylindrical light shielding portion 33 is provided around the light receiving element 3 to prevent the light from directly entering the light receiving element. These figures《a》,
You may use any structure of (mountain).

FIG. 4 also shows the light emitting element 23 and the light receiving elements 24a, 24.
It is a top view which shows the positional relationship of b. As shown in FIG. 2, in a plane perpendicular to the optical axis 31 of the pickup light beam (top surface of the unit 12), on a straight line 32 parallel to a direction perpendicular to a recording track (not shown) (radial direction of the recording disk). The light receiving elements 24a and 24b are arranged so as to have a symmetrical positional relationship with respect to the light emitting element 23.

The operation of the present invention with the above configuration will be explained using FIGS. 5 to 7. FIG. 5 (ω to (C) is a diagram showing the reflection state of the luminous flux emitted from the light emitting element 23 according to the inclination of the disk, and FIG. 6 (a) to (C) are diagrams showing the reflection state, respectively. It is a diagram seen from the disk side.

In addition, FIG. 7 shows the outputs a and b of each light receiving element 24a and 24b.
and the output C of the differential amplifier 25 according to the inclination of the disk, where the peaks in FIG.
The outputs of 4a and 24b are also connected to the same figure (C) or the differential amplifier 2.
This shows the output of No. 5. Points A, B, and C in FIG. 7 correspond to the states (a), peaks), and (C) in FIGS. 5 and 6, respectively, and point B indicates that the disk is horizontal and the disk is This is a case where the optical axis 31 and the optical axis 31 are perpendicular.

When such a vertical relationship exists, the light emitted from the light emitting element 23 is reflected on the recording surface of the disk 1 while diverging, and is evenly irradiated onto the light receiving elements 24a and 24b. Therefore, the output levels of both elements are equal, and the output level of the differential amplifier 25 is zero.

On the other hand, when the disk 1 is deformed into an umbrella shape as shown in FIGS. 5A and 5C, the orthogonal relationship between the disk and the optical axis 31 is blurred. For example, in the case of FIG. 5(a), the light receiving element 2
The reflected light is incident only on the light receiving element 24a, and its output level becomes maximum, and the output level of the light receiving element 24b becomes approximately zero. Therefore, the output level of the differential amplifier 25 is maximum at positive polarity. On the other hand, in the case shown in FIG. 5(C), the reflected light is incident only on the light-receiving probe 241), so the output of the differential amplifier 25 is at the maximum level of negative polarity.

Therefore, the output C of the differential amplifier 25 is a signal whose level and polarity change depending on the star deviated from the orthogonal relationship between the disk and the optical axis 31 and its direction. If we perform closed-loop tilt servo so that this differential output C becomes zero,
The optical axis 31 of the light beam can always be made perpendicular to the disk 11, making it possible to eliminate crosstalk.

Note that if the emitted light from the light emitting element 23 has an intensity distribution such as a Gaussian distribution, the slope of the output characteristic of the differential amplifier will increase and the detection sensitivity will increase. Selection becomes easier.

The differential output of the differential amplifier 25 drives the chill i motor 27 to move the optical head unit l 12 to the rotary unit 1.
Since it is rotated around 4, chill 1 servo is performed.

Further, to describe the advantages of the present invention with reference to FIG. 8, the disk surface is , there is an inclination in the radial direction and an inclination in the circumferential direction, and the distance between the disk surface and the reference surface always changes and is not constant.

Therefore, it is necessary to respond only to the angular change in the radial direction and not to the distance to the disk or the angular change in the circumferential direction. Figure 8 (J is the disk reflected light (dotted line) when the disk is tilted in the circumferential direction with respect to the reference surface.
The relationship between the light receiving elements 24a and 24b is shown, and the dash-dotted line represents the disc reflected light when the disc surface and the reference plane are parallel.

In this case, the reflected light changes from the dashed line to the dotted line, but since the changes in the amount of light received by the light receiving elements 24a and 24b are both equal, the output of the differential amplifier 25 for both received light outputs does not change.

Figure 8 shows the case where the distance between the disk surface and the reference surface changes while remaining parallel, and the reflected light shown by the dotted line changes as shown by the dashed line, but in this case too, both light receiving elements 24
Since the changes in both the light receiving signals a and 24b are equal, the output of the differential amplifier 25 does not change.

That is, a difference in the amount of light received by the pair of light receiving elements 24a, 24b occurs only when the disk surface is tilted in the radial direction of the disk, so crosstock can always be detected accurately.

Effects of the Invention According to the present invention, it is possible to detect angular changes only in the direction that affects crosstalk, and there is no effect on changes in angle or distance in other directions, so crosstalk can be detected accurately. and removal becomes possible. Furthermore, it is applicable to all discs of CAV format, CLV format, and other recording formats, and furthermore, it can be attached to a backup unit, so it can be miniaturized.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Fig. 2 is a perspective view of the pickup unit shown in Fig. 1, Fig. 3 is a side view showing an aspect of the tilt detector, and Fig. 4 is a plan view thereof. , 5th
8 to 8 are diagrams for explaining the detection operation of the tilt detection section of the apparatus shown in FIG. 1. Explanation of symbols of main parts 11... Disk 23... Light emitting elements 24a, 24b... Light receiving element

Claims (1)

[Claims] A recorded information reading device having an angle detection means for detecting a relative angle between an optical axis of a recorded information detection light beam and a recording surface of a recording medium, the angle detection means being configured to direct emitted light toward the recording surface. and the light emitting means irradiated with the emitted light, on a plane perpendicular to the optical axis of the emitted light, the light emitting means are arranged at symmetrical positions with respect to the light emitting means on a predetermined line in a direction perpendicular to the recording track of the recording medium. and a pair of light receiving means for receiving reflected light of the emitted light by the recording surface, and the relative angle is controlled according to a difference in output between the pair of light receiving means. reading device.