JPS58105437A - Pickup device - Google Patents

Abstract

PURPOSE:To miniaturize a pickup device, by applying a technical means for the disposition of the optical path of a light beam as well as for the disposition between a focus controlling system and a track controlling system. CONSTITUTION:The magnetic driving force is generated from an electromagnetic driver A to move a solenoid coil 5d. Accordingly, the 2nd frame body 2 connected to the coil 5d slides within a sliding bearing 6. As a result, a focusing lens 11 within the body 2 moves vertically to the disk face to perform focusing control. On the other hand, the magnetic driving force is generated from an electromagnetic driver B. As a result, a solenoid coil 4d moves to press or absorb the side face of the 1st frame body 1, and therefore the body 1 turns right and left centering on a rotary bearing 3. Thus the lens 11 has an arc movement centering on the bearing 3, and the optical axis of the lens 11 can be vibrated vertically to the recording track. In addition, an elastic supporter 15 is set on the rotary shaft, and therefore the body 1 is supported by the bearing 3 from the lower side and by the supporter from the upper side, respectively. As a result, an arc movement is carried out smoothly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for recording information such as video and audio signals by optical means, by rotating the disk while irradiating a light beam onto the disk, thereby moving the information along the recording track where the information is stored. The present invention relates to a pickup device of an optical information reproducing apparatus that scans a light beam and reproduces information using modulation corresponding to recorded information received by the light beam on a recording track of a disk.

Recent information reproducing devices are now able to use extremely small semiconductor lasers instead of helium-neon tubes for the light beam generator, and they also control the direction of the light beam so that it does not deviate from the recording track. Progress has also been made in actively miniaturizing track control devices for controlling the recording speed and focus control devices for accurately determining the focal position of a light beam on a recording track. However, the degree of miniaturization is still insufficient for a pickup device that combines information reading with a drive device for track control and focus control. One of the reasons why it is difficult to miniaturize this pickup device is that the electromagnetic drive device, which is the drive source of the pickup for track control and focus control, has a structure that moves the entire pickup system. This is due to the fact that

In view of the above-mentioned problems, the present invention provides a new and useful optical pickup that makes it possible to downsize the entire device by making full use of technical means for the arrangement of the optical beam path and the arrangement of the focus control system and track control system. 1 to provide equipment
The target is

Hereinafter, the present invention will be explained in detail according to embodiments with reference to the drawings.

FIG. 1 is a perspective view of a pickup device showing one embodiment of the present invention. FIG. 2 is a layout diagram of optical components in the optical system of the pickup device shown in FIG. 1.

The optical system shown in FIG. 2 is arranged in a first frame 1 constituting a lens barrel of a pickup. This optical system includes a semiconductor laser stem 7 equipped with a semiconductor laser serving as a light source for light beam irradiation, a beam splitter 8 and a collimating lens 9 arranged on the light beam irradiation path, and a reflection prism 10 that bends the light beam toward the disk surface. , a converging lens 11 disposed to face the disk surface, and a photodetector 12 into which a modulated light beam reflected from the disk is incident from a beam splitter 8. The light emitted from the semiconductor laser passes through the beam splitter 8 and enters the collimating lens 9. The collimating lens turns the light into a parallel beam, the optical axis is bent by the reflecting prism IO, and the light is converged by the converging lens 11 to form a parallel beam of light on the disk. Irradiates onto the recording track. The reflected light from the disk becomes modulated light corresponding to the recorded information, passes through a converging lens 11, a reflecting prism 1O, a collimating lens 9, and a beam splitter 8, and the optical axis is bent by the beam splitter 8, and is detected by a photodetector 12. is,
The optical signal of the reflected light is replaced with an electrical signal.

Among the above optical systems, converging lens 1 for converging light beam irradiation
The optical components other than 1 are housed in the first frame 1, and the converging lens 11 is housed in the second frame 2 which is connected to the end of the first frame 1 in the direction of the disk surface. The second frame 2 is arranged so as to have a degree of freedom of movement in the direction of the disk surface relative to the first frame 1. That is, a slide bearing 6 is fixed to the end of the first frame l, and the second frame 2 is inserted into the slide bearing 6 and fixed so as to be slidable in the axial direction of the slide bearing 6. There is. Further, one end of a rectangular solenoid coil 5d is fixed to the outer peripheral surface of the second frame 2. The solenoid coil/l 15d is externally fitted to a soft iron yoke delay 5b which is stood in the center of the U-shaped soft iron yoke 5a, and forms an electromagnetic drive device A together with a permanent magnet 5C fixed to the soft iron yoke 5a. ing. Solenoid Koi/115
By energizing d, a magnetic driving force is generated in the electromagnetic drive device A, and this magnetic driving force moves the solenoid coil 5d.
The frame 2 also slides within the slide bearing 6 in conjunction with this, and focus control is performed by moving the converging lens 11 within the second frame 2 in a direction perpendicular to the disk surface.

Focus control is to determine the focal position of the light beam converged and irradiated onto the recording track of the disk from the converging lens 11. In order to determine the focal position, only the solenoid coil 5d, the second frame 2, and the converging lens 11 are used. Since the distance between the disk and the converging lens 11 can be set appropriately by moving it up and down, the mass to be moved is much smaller than in the conventional method in which the entire lens barrel is moved up and down. can be sufficiently miniaturized.

A rotary bearing 8 is disposed near the center of the bottom surface of the first frame 1 and whose axis is a straight line 14 that passes through its center of gravity and is perpendicular to the bottom surface of the first frame l. Further, a solenoid carp/L/4d and a bobbin 4e are fixed to the side surface near one end of the first frame 1. The solenoid coil/L/4d forms the shadow of the electromagnetic drive device Bt together with a soft iron yoke 4a, a soft iron yoke delay) 4b, and a permanent magnet 4C. By energizing the solenoid coil /l/4d, a magnetic driving force is generated in the electromagnetic drive device B, and this magnetic driving force causes the solenoid coil 1v4d to move in the direction of suppressing or attracting the side surface of the first frame 1. , the first frame 1 rotates in the left-right direction around the rotation bearing 8, and therefore the converging lens 11 moves in an arc around the rotation bearing 8 as the rotation axis. The optical axis of the converging lens 11 can be vibrated perpendicularly to the recording track by making the tangential direction of the arc, which is the locus of the arcuate motion, perpendicular to the direction of the recording track on the disk surface. As a result, this arcuate motion makes it possible to perform track control in which the light beam accurately follows the recording track even against surface wobbling and the like that occur when the disk rotates at high speed. The energization of the solenoids /'4d and 5d may be carried out by a conventionally known method that detects when the light beam is out of position or out of focus with respect to the recording track, and is controlled by the detection signal.

Now, as described above, the equation of motion in which the first frame 1 performs a circular motion with the rotation axis being a straight line passing through its center of gravity and perpendicular to the bottom surface, and which follows the N equation, is determined. For the sake of simplicity, the first frame 1 is assumed to be a rectangular parallelepiped 13 having a length of 21 and uniform sides a and b as shown in FIG. 3.

The equation of motion according to the circular motion with the rotation axis being the straight line 14 passing through the center of gravity of the rectangular parallelepiped 18 and perpendicular to the bottom surface is given by the following equation.

dω I −= l F ・−・・・・・・・・・・・・・
·········(1)t Here, ■ is the moment of inertia of the rectangular parallelepiped 18, ω is the angular velocity of the circular arc motion, and F is the force acting on the rectangular parallelepiped. Cuboid 1
Let X be the displacement in the tangential direction of the arcuate trajectory at the tip of 8, and when the displacement of ~X is sufficiently small, let the deflection angle of the rectangular parallelepiped 18 be φ, then φ=−・−・・・・・・・・・・・・・・・−・・・・・・・・・
・・・・・・・・・・・・−・・・・・・(2)

The angular velocity ω is dφ ω=□・・−・・・・・・・・・・・・・・・・・・
......(3) Given by d and t.

Substituting equation (2) into equation (3), we get becomes.

(1) 2K Substituting the equation (4) yields. The moment of inertia of a rectangular parallelepiped 13 having length 21% and sides a and b of the end face with the rotation axis being a straight line 14 passing through its center of gravity and perpendicular to the bottom face is expressed as follows. Here, %M is the mass of the rectangular parallelepiped.

By substituting equation (5) into equation (6), we get the following. The equation of motion to be followed when the entire rectangular parallelepiped 18 is vibrated for track control is as follows. Assuming that the purpose is to compare equations (7) and (8), equation (7) becomes. Comparing equations (8) and (9), equation (9) is essentially an equation of motion where the mass is one-eighth.

In this way, by using circular arc motion as a driving method for the lens barrel necessary to vibrate the optical axis for track control, it is possible to substantially reduce the mass to be driven, and therefore the entire lens barrel can be reduced. Since the drive energy is less than that of a system that vibrates in the direction perpendicular to the track, the electromagnetic drive device B can be sufficiently miniaturized. In arc movement for track control, solenoid coil 1v5 of electromagnetic drive device A
Since d is rectangular and has a sufficient gap between it and the soft iron yoke 5b, it has a degree of freedom in the direction of circular arc movement and does not interfere with track control.

An elastic support 15 is disposed on the upper surface of the first frame 1 at a position corresponding to the rotation bearing 8, and the elastic support 15 supporting the first frame from the upper surface with its elastic force is made of copper. Metal spring materials such as beryllium alloy and phosphor bronze can also be used, but in this example, elastic rubber is used to form the elastic support 1.
5. Although metal spring materials are easy to process and provide reproducibility of spring characteristics, they have a small damping effect in absorbing vibration energy. On the other hand, in track control of a pickup device, the frequency characteristics of the drive system are required to be such that negative feedback is easily applied, and it is desirable to have a large damping effect. Although the elastic rubber plate is difficult to process, it has the advantage that it has a large damping effect and can be formed into any shape. Therefore, in this embodiment, this elastic rubber plate is formed into a rectangular parallelepiped shape. By arranging the elastic support 15 on the rotation axis, the first frame 1 is supported by the rotation bearing 3 from below and the elastic support 15 from above, making the arc movement smooth. Although the support body 15 deforms and applies a rotational return force to the first frame body 1, the amount of deformation at this time is less than when it is disposed at another position, and the life of the elastic support body 15 is extended. Furthermore, by forming the spring into a simple rectangular parallelepiped shape, processing becomes easier, and the spring constant can be calculated more accurately, improving the accuracy of specifications.

The elastic support 15 forms a return force in the opposite direction to the rotational force of the first frame 1 generated by the electromagnetic drive device B, thereby providing smooth servo control of the first frame 1. Gives agility.

As explained in detail above, in the present invention, focus control is performed by moving only the first frame, so the driving mass is small and it is possible to downsize the electromagnetic drive device for focus control, and track control is performed by moving only the first frame. Since the rotation axis is a straight line that passes through the center of gravity of the frame and is perpendicular to the bottom surface, it is an arcuate motion that can substantially reduce the driving mass, making it possible to downsize the electromagnetic drive device for track control. Therefore, the arcuate motion of the lens barrel is stabilized, and a highly reliable pick-up device that is compact as a whole can be constructed.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a pickup device showing one embodiment of the present invention. FIG. 2 is a layout diagram of an optical system used in the pickup device shown in FIG. 1. FIG. 8 is an explanatory diagram for analyzing and explaining the arc motion of the lens barrel for track control. , 1... First frame body 2... Second frame body
3...Rotating bearing 4a...Soft iron yoke 4b...Soft iron yoke grating 4c...Permanent magnet 4d...Solenoid coil 4e...Solenoid coil pobbin 5a
... Soft iron yoke 5b ... Soft iron yoke plate 5
c...Permanent magnet 5d...Solenoid carp/I/6
... Sliding bearing 7 ... Semiconductor laser stem 8.
...Beam splitter 9...Collimating lens 1
0... Reflection prism 11... Converging lens 12.
... Optical inspection device 15 ... Elastic support agent Patent attorney Aihiko Fukushi

Claims (1)

[Claims] 1. An optical system that irradiates a light beam along a recording track of a disk on which information is recorded and detects modulated light from the disk, and a focus control system that determines the focal position of the light beam. , a track control system for determining the irradiation position of the light beam, in the pickup device of the information reproducing apparatus, the focus control system controls the convergence irradiation section of the light beam disposed opposite to the disk. The track control system has a drive mechanism that moves the convergent irradiation section of the light beam in an arc in a direction substantially parallel to the surface of the disk, A pickup device characterized in that a support body having an elastic return force is specially provided at the rotation axis of motion. 2. The pickup device according to claim 1, wherein the axis of rotation of the circular arc motion is formed approximately in the vicinity of the center of gravity of the movable body having the convergent irradiation section of the light beam.