JPS63247921A - Pickup position adjusting device - Google Patents

Abstract

PURPOSE:To always project a recording and reproducing laser beam perpendicularly to an information disk and to keep an interval between an objective lens and the information disk constant, by adjusting both the inclination and the interval of an optical pickup for the information disk. CONSTITUTION:A light emitting element 114 mounted on the optical pickup 14 is set so that a beam of light can be made incident and reflected on the information disk 13. The reflected light is detected by an optical detector 115 divided quarterly in a line shape. Assuming four optical detectors as (a), (b), (c), and (d) [the width of (b) and (c) are narrower than those of (a) and (b)], an output (a+b)-(c+d) is taken out by a differential amplifier, and is added on and driven by a motor 113 which rotates the pickup 14 centering a fulcrum at a driving circuit. Also, the output of the differential amplifier is added on a fulcrum moving motor 111 at the driving circuit, and the fulcrum is moved horizontally. In such a way, by adjusting both the inclination and the interval of the pickup 14 for the disk 13, it is possible always to project the laser beam perpendicularly to the disk 13 and to keep the interval between the objective lens and the disk 13 constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a pickup position adjustment device used in an optical video disk device that records and reproduces information using a loser beam.

(Prior Art) In a video disc device that reads signals from an information disc using a light beam, a width of 0.4 μm is provided on the information disc.

Information is engraved in a spiral or concentric pattern in the form of concavities and convexities with a length of 0.5 to 1.8 μm. To read this information, a laser beam is focused on a minute spot with a diameter of 1 μm using an objective lens, and the reflected light is guided through the objective lens to a light receiving element and extracted as an electrical signal.

By the way, the information disc used as the original video disc is made of PMMA resin with a diameter of 305I, so
Warpage may occur due to temperature, humidity, or pressure during molding, and when playing, the center hole of the information disk is clamped to a turntable and rotated, causing deflection due to its own weight.

When playing this information disc with the original pickup, the installation of the original pickup is adjusted so that the laser beam is irradiated perpendicularly to the information disc. However, if there is any bending or warping, the verticality must be adjusted at a certain position. However, if the optical pickup is moved in the radial direction, the laser beam will no longer be irradiated vertically, which will increase the beam spot diameter and cause a problem in which the S/N of the reproduced signal will deteriorate. there were.

To correct this, conventional methods detect the relative positional relationship between the optical pick-up and the information disk, that is, the inclination between the direction of incidence of the laser beam and the information disk, and tilt the optical pickup according to this tilt paddle to irradiate vertically. The so-called tilt servo method is used.

The conventional method is shown in Figure 5. The optical pickup 51 is mounted on a slider pace (line 5) that rotates around a fixed fulcrum 52.
3). Also, optical pickup 5]
Light emitted from a light emitting element 54 attached to the top surface is irradiated onto the information disk 55, the reflected light is detected by two photodetectors 56 and 57, and a motor 511 is used to balance the light. The lie 153 is tilted. As shown in the figure, when the optical pink-up is moved to the left (the moving mechanism is omitted) in order to reproduce a different radial position of the information disk 55 that is bent, for example, the outer periphery, the photodetector is similarly balanced. The base 53 is rotated and adjusted so that the light is irradiated vertically.

However, with this method, only the slope is adjusted, so
A problem arises in that the distance jllt58 between the objective lens of the optical pickup 51 and the information disk 55 changes depending on the relationship between the deflection or curvature of the information disk 55 and the fulcrum 52.

The position of the objective lens is kept constant through focusing control, but there is also an optimal control range, and if it deviates from this, it becomes unstable. Therefore, if the information disc is greatly bent or warped, there is a problem in that the reproduced signal deteriorates and the reproduced image becomes distorted.

(Problems to be Solved by the Invention) As mentioned above, the conventional tilt servo system for correcting warpage and deflection simply modifies the tilt only.
In some cases, the distance between the objective lens and the information disk changes. In particular, there were extremely serious problems in that warping and deflection were large, and when the focus servo was out of the control range, it became unstable and the reproduced image was distorted.

Therefore, this invention adjusts both the inclination and spacing of the optical pickup relative to the information disk so that the recording and reproducing laser beam is always irradiated perpendicularly to the information disk, no matter how much bending or warping the information disk has. It is an object of the present invention to provide a pickup position adjusting device which can maintain a constant distance between an objective lens and an information disk.

[Structure of the invention]

(Means for Solving the Problem) The present invention provides an optical pickup that emits a laser beam to read information from an information disk, a moving means for conveying the same in a radial direction, and a relative positional relationship between the optical pickup and the information disk, that is, an optical detection means for detecting the inclination and the interval; an inclination adjustment means having a fulcrum for adjusting the inclination of the optical pickup to yA; a sliding means for moving the fulcrum position according to the interval between the optical pickup and the information disk; The present invention is characterized in that it includes a drive means for driving the tilt adjustment means and the slide means using an output signal from the detection means.

(Function) The photodetector outputs an error signal corresponding to the relative inclination and spacing between the information disk and the optical pickup, and these two outputs are raised and lowered by rotating the optical pickup 9 around the fulcrum. By adding a moving mechanism and a second moving mechanism that slides the fulcrum position left and right, it is driven so that the error signal of the tilt and interval becomes zero, and the laser beam is always perpendicular to the information disk and the interval is adjusted. can be matched to the working distance of the objective lens. Therefore, it is possible to obtain a reproduced image with a good S/N ratio of the reproduced signal and no crosstalk from adjacent tracks.

(Example) Details of an example of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the mechanical configuration of an embodiment of the present invention. An information disk 13 is clamped to a main table 12 attached to a motor 11 and rotated.

Optical pickup 1 that reads signals from this information disk 13
4 is attached to a moving table 15 that moves in the radial direction. A rack 16 is attached to the moving table 15, and can be moved by rotating a binon 18 attached to a moving motor 17. A slit 19 is provided in the movable table 15 so that a fulcrum 110 fitted into the slit 19 can be moved.

This fulcrum portion 110 can be slid left and right by rotating the motor 111. In addition, the moving table 15
A screw structure 112 for moving it up and down is attached to the end of the fulcrum 11 by rotating a motor 113.
It can see-saw around 0. Further, a light emitting element 114 and a photodetector 115 are attached to the upper surface of the optical pickup 14, and thereby detect the inclination and distance of the optical pickup 14 with respect to the information disk 13.

FIG. 2 is a diagram showing the operating principle of the present invention. Information disc 1
3 is in a human state, the inclination and height of the optical pickup 14 attached to the moving table 15 are adjusted and the fulcrum 110
Assume that the reference line of the movable table 150 is located at B and the reference line of the moving table 150 is located at C. If the information disk 13 is tilted from this state to the state A', the optical pickup 14 is no longer vertical, so the movable table 15 rotates about the fulcrum B, and the reference line becomes CI. With only this, the optical pickup 14 will be perpendicular to the information disk 13, but the distances between the information disk and the objective lens are A, H, C.
The distance is different from that at 9 degrees.In order to keep this distance constant, the fulcrum B is moved to B'. Furthermore, at this time, the reference line C' also moves vertically in parallel and reaches the state of CI. In this way, the distance D' between the optical pickup 14 and the information disk 13 can always be made to match, and verticality can also be maintained. This series of movements can be performed simultaneously by using a photodetection means shown in FIG. 3 below.

FIG. 3 shows an embodiment of the inclination and interval detecting means of the present invention. As shown in (a), the light emitting element 114 mounted on the optical pickup 14 is arranged so that light is obliquely incident on the information disk 13 and is reflected. This reflected light is detected by a photodetector 115 divided into four lines. (
As shown in b), four photodetecting elements are arranged as a, b, cd (b
, c is narrower than a, d), then (a +
b) - (c + d) output is taken out by the differential amplifier 31 and applied to the motor 113 that rotates the optical pickup 14 around the fulcrum in the drive circuit 32 to drive it. Also, the differential amplifier 3
The three outputs (a+d) - (b+c) are applied to the fulcrum shifter 111 by the drive circuit 33 to move the fulcrum left and right.

The operation of this photodetector will be explained in FIG. (a) is when the information disk 13 is tilted or far away from the optical pickup 14, (b) is when the information disk 13 and optical pickup 14 are perpendicular and at the correct distance, and (C) is when the information disk 13 is is tilted oppositely to the optical pickup 14 or is located close to it. Here, when in state (b), (a+b)-(c+d) and (a+
Adjust the circuit so that d)-(b+c) becomes zero. In case (a), the light beam 42 is shifted to the right with respect to the center line 41 of the photodetector, so if you rotate the moving table so that (a+b)-(c-1-d) becomes zero, , the position of the light beam 42 moves to the left and comes to the center 41 of the photodetector. However, in this case, the size of the light beam 42 is larger than that in the state (b), so (a+a)-(b+c
The size of the light beam 42 is adjusted so that ) becomes zero. This makes it possible to keep the spacing constant. (C
), the behavior is opposite to what was described above, but it still works (
It can be controlled so that state b) is achieved.

〔Effect of the invention〕

According to the present invention, the inclination and spacing between the information disk and the optical pickup are automatically adjusted at the same time, so even if the information disk is deflected or warped, the laser beam for signal reading can be irradiated accurately and vertically. Moreover, since the information disk can be placed within the working distance of the objective lens, the laser beam can be focused to the minimum. For this reason,
8/N of the reproduced signal can be maximized, crosstalk with adjacent tracks is reduced, and deterioration of the reproduced image can be eliminated. Furthermore, it is no longer necessary to widen the dynamic range of focusing in the optical pickup, making it easier to design the optical pickup, and making it possible to use smaller and cheaper optical pickups.

This becomes even more important when the beam spot size is reduced in response to the recent trend toward higher density recording. That is,
In order to further narrow down the beam spot size, it is necessary to shorten the wavelength of the laser beam or increase the NA of the objective lens, but this will reduce the depth of focus and increase the accuracy of the allowable tefocus value. Must. It is also necessary to increase the perpendicularity with which the laser beam is irradiated onto the information disk. Such a tilt and spacing adjustment device is expensive and unavoidable.

Since the structure of the present invention requires only one fulcrum for movement in two directions, it can be realized with a mechanically simple configuration.

Also, even if the turntable surface that fixes the information disk is not installed completely parallel to the original pickup movement direction,
Since the movement of the optical pickup can be adjusted so that it is parallel to the information disk, optimal operation is always possible even if the tolerances of the mechanism are tight.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a diagram showing the operating principle of the invention, FIG. 3 is a diagram showing an embodiment of the position detection means of the invention, and FIG. 4 is a diagram showing an embodiment of the position detection means of the invention. FIG. 5, which is a diagram showing the operation of the position detecting means of the present invention, is a diagram showing a conventional method. 11, 17.111.113 ...Motor 1
2... Turntable 13... Information disk 14... Optical pickup 15... Moving table 19... Slit 110...
...Fully point 114...Light emitting element 115...Photodetector

Claims (1)

[Claims] An optical pickup that irradiates an information medium with a light beam and receives reflected light or transmitted light from the information medium to record and reproduce information signals; and a moving means that transports the pickup so as to record and reproduce information signals at different locations on the information medium. a photodetection means for detecting changes in the inclination and distance between the optical pickup and the information medium; an inclination adjusting means for adjusting the inclination of the optical pickup around a fulcrum; A pickup position characterized by comprising a slide means for moving the position of the light spot according to an interval, and a drive means for driving the tilt adjustment means and the slide means according to an output signal from the light detection means. Adjustment device.