JPH0740364B2 - Optical pickup - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical pickup used for recording and reproducing signals on an optical disc.

[Prior Art and Problems to be Solved by the Invention] Various pickups have been proposed for recording and reproducing signals of optical discs such as audio discs, video discs, and data discs.

For example, there is one shown in FIG. This optical pickup detects a focus error signal by the critical angle method.

The light beam emitted from the light source 1 is collimated by the collimator lens 2 and then enters the polarizing prism 3 and is reflected by the polarizing film 4 before reaching the reflecting surface 5. Then, the parallel light flux totally reflected in the right angle direction on the reflecting surface 5 is converged by the objective lens 7 through the quarter-wave plate 6 and is focused on the optical disc 8 as a light spot having a diameter of about 1 μm.
The objective lens 7 is supported in an objective lens actuator 9 including a magnet, a yoke, a coil, and the like so as to be movable in the two axial directions of the optical axis and the radial direction of the optical disc 8 orthogonal to the optical axis. Two
The focus servo and the tracking servo are performed so that the light spot is driven in the axial direction and follows the center of the track of the optical disk 8 in the focused state. The reflected light of the light spot on the optical disk 8 follows the same optical path as the outward path up to the polarizing film 4, but in the returning path, the polarization direction is orthogonal to the outgoing polarization direction due to the action of the 1/4 wavelength plate 6 Through. The return light from the optical disk 8 that has passed through the polarizing film 4 passes through the critical angle prism 10 and a photodetector.
It is incident on 11. The critical angle prism 10 has such an optical property that the incident angle of the return light from the optical disk 8 with respect to the optical axis is substantially the critical angle, and the optical detector reflects the return light to the photodetector 11. It is incident. Further, the photodetector 11 has four light receiving areas which are divided into two in the radial direction and the tangential direction of the optical disk 8, and a data signal, a focus error signal and a tracking error signal are obtained from the outputs of these light receiving areas. Has become.

The applicant of the present application discloses a conventional technique relating to the optical pickup having the above structure, for example, in Japanese Patent Laid-Open No. 55-146636.

However, the tracking servo mechanism of the objective lens actuator having the above-described structure has a configuration in which the tracking error signal is fed back only during the normal recording / reproducing operation. Therefore, for example, the pickup carriage is moved during high-speed access, but when the carriage is accelerated or decelerated, a parallel force is generated in the driving direction of the carriage, and unnecessary vibration occurs in a spring or the like that supports the objective lens so that it can move in the tracking direction. To do. This unnecessary vibration may cause problems such as deterioration of positioning accuracy, disabling of servo control, and delay of access time.

Japanese Patent Laid-Open No. 58-26331 discloses a conventional optical head configured to detect the position of an objective lens by using a capacitance type non-contact type micro displacement detection probe so that tracking tracking control can be always closed loop control. The technology of is proposed.

However, in this conventional technique, since a capacitance type detection sensor is used, a linear analyzer is required to linearize the output signal, and the large sensor diameter reduces the size and weight of the optical pickup. It wasn't suitable. In addition, there is a risk of being affected by electromagnetic noise from the outside.

Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 57-94942, an optical type of tracking control is performed by rotating a mirror for reflecting a light beam from a light source toward an objective lens by a predetermined angle by an actuator. In order to eliminate unnecessary vibration that occurs in the mirror during high-speed access, the angular pickup uses an angular position detection device to correct the tilt angle of the mirror during access.

However, it is necessary to open a certain distance between the position detecting light source provided at the position detecting position of the prior art and the mirror. Further, in order to detect the tilt angle of the mirror by the light flux from this light source, it is necessary to irradiate a relatively large light spot on this mirror. When this light spot becomes large, the light receiving element that receives the reflected light receives it. The area will also have to be increased. As a result, the size of the device is increased and the structure is complicated. Further, Japanese Patent Application Laid-Open No. 55-153138 describes a structure in which a detecting portion formed of a through hole is provided in a lens holding member, and a light emitting element and a light receiving element are fixed to a base so as to sandwich the detecting portion. However, the configuration in which the through hole is provided in the lens holding member has a drawback that the lens holding member becomes large and heavy.

The present invention has been made in view of the above circumstances, for example,
An object of the present invention is to provide an optical pickup that can detect a displacement position of an objective lens with respect to a base (stationary member), which occurs during high-speed access, with a very simple structure and with high accuracy, and that can be reduced in size and weight.

[Means and Actions for Solving Problems] In order to solve the above problems, the optical pickup according to the present invention reads information on a recording medium in which information is recorded in a track shape, and therefore a lens is used for the recording medium. In an optical pickup that is driven in a direction parallel to the medium surface and transverse to an information track, a movable piece that blocks light is arranged on a lens holding member to which the lens is fixed, and the movable piece is sandwiched. The light emitting element and the light receiving element having at least one dividing line are fixed to a base, and the movable piece is arranged substantially symmetrically with respect to an imaginary plane including the optical axis of the light beam emitted from the light emitting element and the dividing line. Outputs from a first light receiving region and a second light receiving region divided by the dividing line in the light receiving element (referred to as an arrangement in a stationary state in which the movable piece is not operating) It is characterized in that it has configured to compare the signals.

Embodiments Embodiments according to the present invention will be specifically described below with reference to the drawings.

1 to 5 relate to a first embodiment of the present invention. FIG. 1 is a sectional view of an objective lens actuator portion of an optical pickup, FIG. 2 is a top view of FIG. 1, and FIG. FIG. 1 is a perspective view of the position detecting member of FIG. 1, FIG. 4 is an explanatory view of the principle of position detection of the objective lens, and FIG. 5 is a view showing detection output characteristics with respect to the position of the objective lens.

In these drawings, reference numeral 21 is an objective lens actuator 21 of the optical pickup. This actuator 21
The outer frame 22 of is formed in a cylindrical shape with both ends open,
A permanent magnet 23 having a rectangular cross section and an annular shape as a whole is fixedly provided at a substantially central portion inside the outer frame 22. or,
The two poles of the permanent magnet 23 have a rectangular cross section and an L shape.
Y-shaped yokes 24a and 24b, which are formed in a ring shape, are fixedly provided. A gap is formed between the yokes 24a and 24b, and the yokes 24a and 24b and the permanent magnet 23 form a magnetic circuit. Further, in the outer frame 22, a holding cylinder 25
Is provided. The holding tube 25 has a substantially tubular middle tubular portion 25a with both ends open, and a coil holding tubular portion 25b that is integrally formed on the outside of the middle tubular portion 25a in a concentric tubular shape and has one end side (upper end side) opened. It is formed from and. The coil holding tubular portion 25b
A focusing voice coil 26 is wound around the outer periphery of the. The coil holding cylinder portion 25b around which the focusing voice coil 26 is wound is placed in and out of a gap formed by the yokes 24a and 24b at one end (upper side) opening side thereof so that the voice coil 26 faces the permanent magnet 23. It is freely inserted. The holding cylinder 25 has a spiral spring for focusing made of an elastic material whose periphery is held in a space 27 arranged above the yoke 24a at the upper end of the middle cylinder 25a.
It is attached to the outer frame 22 by 28a. Also, the holding cylinder 2
5 is attached to the outer frame 22 by the same focusing spiral spring 28a whose periphery is held by a spacer 29 arranged at the lower end side of the outer frame 22 on the lower end side of the middle tubular portion 25a. . That is, the holding cylinder 25 is supported by the outer frame 22 by the focusing spiral springs 28a and 28b so as to be displaceable in the axial direction (optical axis direction F) thereof. A yoke holding frame 30 is mounted inside the outer frame 22 above the focusing spiral spring 28a, and the yoke holding frame 30 is formed in a rod shape.
And a pair of firsts arranged parallel to the tracking direction T
And the second fixed yokes 31a, 31b and the first and second fixed yokes.
A pair of first and second permanent magnets 32a, 32b connected to both ends of the fixed yokes 31a, 31b are provided. Tracking coils 33a and 33b are wound around the central portions of the first and second fixed yokes 31a and 31b. First and second windings around which the tracking coils 33a and 33b are wound
An objective lens 34 is arranged between the fixed yokes 31a and 31b. The objective lens 34 is attached to the lens holding frame 35 with the optical axis direction thereof oriented toward the central axis direction of the outer frame 22.
On the outer side of the lens holding frame 35, a magnetic member 36 formed so as to face the tracking coils 33a and 33b is fitted. A gap is formed between the lens holding frame 35 and the magnetic member 36, and the objective lens is placed in this gap.
One ends of the leaf springs 37, 37 for tracking which are composed of a pair of elastic members for driving 34 in a tracking direction T orthogonal to the optical axis are inserted and fixed. The other end of the tracking leaf springs 37, 37 is inserted through the holding cylinder 25 and is fixed inside the lower end of the holding cylinder 25.
That is, the objective lens 34 is supported by the holding cylinder 25 via the tracking leaf springs 37, 37 and is displaceable in the tracking direction T.

On the other hand, a light receiving element fixing member 38 is attached to the inner surface side of the first fixed yoke 31a near the first (or second) permanent magnet 32a, and the light receiving element 39 is fixed to the fixing member 38. . The light receiving element 39 has light receiving regions 39a and 39b divided into two in the tracking direction. In addition, the light receiving element 3
The second fixed yoke 31b facing the 9 includes a light emitting element fixing member.
A light emitting element 41 is fixed to the fixing member 40. A position detecting member 42 is fixed to the lens holding frame 35 to which the objective lens 34 is attached. The position detecting member 42 is made of a plate material or the like and has an annular mounting portion 43.
And a detecting portion 44 that is elongated from a part of the mounting portion 43 and is bent at a right angle on the end side thereof.
The position detecting member 42 is arranged so that the detecting portion 44 is located at the center of the optical axis connecting the light emitting element 41 and the light receiving element 39, and the mounting portion 43 is fitted to the lens holding frame 35. Installed. Incidentally, the light receiving regions 39a, 39 of the light receiving element 39
A tracking current proportional to the output difference signal of the amount of received light detected in b flows in the tracking coils 33a and 33b.

In such a configuration, when a focus error signal current is passed through the voice coil 26 during normal recording / reproduction, a force acts on the holding tube 25, and the objective coil 34 is moved in the focusing direction F due to the bending deformation of the focusing spiral springs 28a, 28b. Displace. In addition, when the tracking error signal current is passed through the tracking coils 33a and 33b, the tracking leaf spring 3
Due to the bending deformation of 7,37, the objective lens 34 is displaced in the tracking direction T.

Next, when the objective lens 34 moves in the tracking direction T due to a high-speed access operation or the like, the position detecting member 42 is displaced along with the movement, and the detecting unit 44 causes the light emitting element 41 to move.
The light amount distribution emitted from the light receiving element 39 is changed. When the objective lens 34 is not displaced, if the optical axis of the light emitting element 41 and the dividing line in the tracking direction of the light receiving element 39 are aligned with the center of the detecting section 44, the light receiving element 39 is divided into two parts. The output voltage difference between the light receiving regions 39a and 39b is 0. Further, when the objective lens 34 is displaced, the light amount distribution becomes proportional to the displacement of the detecting section 44, and as shown in FIG. 5, the output voltage difference between the light receiving regions 39a and 39b of the light receiving element 39 is different from that of the position of the objective lens 34. Proportional to displacement. A current proportional to this output voltage difference is fed back so as to flow to the tracking coils 33a and 33b to form a servo system closed loop, and the displacement of the objective lens 34 in the tracking direction T is 0.
The position is controlled to be held. Therefore, it is possible to prevent unnecessary vibration of the objective lens that occurs during high-speed access.

In this embodiment, since the detector 44 that moves together with the objective lens 34 is arranged between the light emitting element 41 and the light receiving element 39, the output signal to be detected can be made linear, and the size and weight can be reduced. be able to.

FIG. 6 is a perspective view of a position detecting member portion according to the second embodiment of the present invention.

In this embodiment, the position detecting member 51 has an annular mounting portion 52,
It is formed from a part of the mounting portion 52 and a detection portion 53 which is formed to extend horizontally in a slender shape. The position detecting member 51 is arranged such that the detecting portion 53 is located at the center of the optical axis connecting the light emitting element 54 and the light receiving element 55, which are fixed as in the first embodiment. The light receiving element 55 has light receiving regions 55a and 55b which are divided into two in the focusing direction F. Other configurations are the same as those in the first embodiment.

With such a configuration, when the objective lens 34 moves in the focusing direction F, the position of the objective lens 34 in the focusing direction F is set to the light receiving element 55 as in the first embodiment.
It is possible to control the focus direction F by detecting it as the output voltage difference.

In the above embodiment, the detecting portions 44, 53 of the position detecting members 42, 51 need only be fixed to the portion that moves together with the objective lens 34, and can be formed integrally or separately so that their shapes also block light, for example. The light blocking portion may also be formed in the window portion that transmits light. Further, the light emitting elements 41 and 54 and the light receiving elements 39 and 55 may be directly fixed to the fixed yokes 31a and 31b without using the fixing members 40 and 38, or may be fixed to the permanent magnet 32a (or 32b) and the like. Good. Furthermore, the structure of the objective lens actuator is not limited to that of the embodiment.

EFFECTS OF THE INVENTION The optical pickup of the present invention reads information on a recording medium in which information is recorded in a track shape, so that the lens is driven in a direction parallel to the medium surface of the recording medium and transverse to the information track. In the optical pickup described above, a movable piece that shields light is arranged on the lens holding member to which the lens is fixed (for example, the detection units 44 and 53 described in the above embodiments), and the light emitting element sandwiches the movable piece. And a light receiving element having at least one dividing line are fixed to a base, and the movable piece is arranged substantially symmetrically with respect to an imaginary plane including the optical axis of the light beam emitted from the light emitting element and the dividing line, A first light receiving region divided by the dividing line in the light receiving element (for example, the light receiving region described in the above embodiment)
39a) and the second light receiving area (for example, the light receiving area 39b described in the above embodiment) are configured to be compared with each other. There is an advantage that the displacement position can be detected with high accuracy.

[Brief description of drawings]

1 to 5 relate to a first embodiment of the present invention. FIG. 1 is a sectional view of an objective lens actuator portion of an optical pickup, FIG. 2 is a top view of FIG. 1, and FIG. FIG. 1 is a perspective view of the position detecting member, FIG. 4 is an explanatory view of the principle of objective lens position detection, FIG. 5 is a diagram showing detection output characteristics with respect to the position of the objective lens, and FIG. 6 is a second embodiment of the present invention. FIG. 7 is a perspective view of a position detecting member according to an example, and FIG. 7 is a principle explanatory diagram of an optical pickup according to a conventional example. 21 …… Objective lens actuator 25 …… Holding tube, 26 …… Voice coil 28a, 28b …… Focusing spiral spring 31a, 31b …… First and second fixed yokes 32a, 32b …… First and second permanent magnets 33a, 33b …… Tracking coil 34 …… Objective lens 35 …… Lens holding frame, 36 …… Magnetic member 37 …… Tracking leaf spring 39,55 …… Light receiving element 41,54 …… Light emitting element 42,51… … Position detection member 44,53 …… Detection section

Front page continuation (72) Inventor Shuji Fujisawa 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (72) Inventor Shunichi Orita 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optics Kogyo Co., Ltd. (72) Inventor Masaki Ninomiya 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (56) Reference JP-A-61-233305 (JP, A)

Claims (1)

[Claims] 1. An optical pickup in which a lens is driven in a direction parallel to a medium surface of the recording medium and across an information track in order to read information on a recording medium in which information is recorded in a track shape. A movable piece that blocks light is arranged on the lens holding member to which is fixed, and the light emitting element and the light receiving element having at least one dividing line are fixed to the base so as to sandwich the movable piece, and the light emitting element is further provided. The movable piece is arranged substantially symmetrically with respect to an imaginary plane including the optical axis of the light beam emitted from the light source and the dividing line, and a first light receiving region and a second light receiving region divided by the dividing line in the light receiving element are provided. An optical pickup characterized by being configured so as to compare signals output from the optical pickup.