JPH01211244A - Optical pickup - Google Patents

Abstract

PURPOSE:To miniaturize a device by providing an objective lens position sensor consisting of a light emitting element and a light receiving element as a fixing member side. CONSTITUTION:On a substrate 37, the light emitting element 38 which emits a light beam for detecting the lens position of an objective lens 22 in a direction of a reflecting part 21e, and the light receiving elements 39 and 40 which receive the light beam reflected on the reflecting part 21e are provided, and the objective lens position sensor S is constituted of those elements (38-40) and the reflecting part 21e. And when a lens holder 21 is located at a neutral point, the light beam emitted from the light emitting element 38 is reflected on the reflecting part 21e, and the light beam is made incident uniformly on the light receiving elements 39 and 40. When the holder 21 is turned from the neutral point even a little, a difference is generated in incident light quantities on the elements 39 and 40, therefore, it is possible to recognize the turn of the lens 22 in which direction and in what degree.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical pickup used for compact discs, video discs, optical memory discs capable of both recording and playback, etc. The present invention relates to an optical pickup having an objective lens position sensor that detects the position of an objective lens.

(Background of the Invention) Optical disks are expected to be put to practical use as memories with the characteristics of high density and large capacity. Furthermore, high-speed access is required for optical pickups that read and write information on optical disks that have the feature of high density and large capacity.

When an optical pickup is accessed at high speed, a large acceleration is applied to the optical pickup. Therefore, even if the optical pickup stops after access, the objective lens, which is supported within the optical pickup via a support member (damper), will experience lateral displacement and vibration, making it impossible to quickly shift to stable tracking. There is. For this reason, a positive sensor for an objective lens is provided in an optical pickup to perform control to suppress lateral shift and silk movement.

Next, an example of an optical pickup having a conventional position sensor will be described with reference to the drawings. FIG. 6 is a perspective view of the structure of a conventional example, FIG. 7 is a cross-sectional view of FIG. 6, and FIG. 8 is a block diagram of the lens position sensor shown in FIG.

In the figure, the disk is placed at the top.

Reference numeral 1 denotes a lens holder which is a movable part and is provided with an objective lens 2 for converging laser light onto the disk. A casing coil 3 is wound around the side surface of the lens holder 1. Reference numeral 4 denotes a magnetic substrate serving as a fixed portion, and a shaft 5 is erected on the substrate 4. The lens holder is fitted onto the shaft 5 so as to be movable in the axial direction (focusing direction) of the shaft 5 on the fixed portion side and rotatable relative to the shaft 5 (tracking direction). The lens holder 1 is provided with a first through hole 1a and a second through hole 1b. The inner yoke 6 and the second inner yoke 7 are fitted into each other. 8 is the first yoke 6 via the lens holder 1
A first magnet 9 is provided on the substrate 4 to face the second yoke 7 via the lens holder 1, and is magnetized in the horizontal direction. A second magnet whose orientation is horizontal. A first outer yoke 10 is provided on the first magnet 8 on the opposite lens holder 1 side, and a second outer yoke 11 is provided on the second magnet 9 on the opposite lens holder 1 side, respectively, on the substrate 4. There is.

Also, the tracking coil 1 is attached to the focusing coil 3.
2.13, 14.15 (tracking coil 13.1
4.15 (not shown) is provided. Further, as shown in FIG. 7, one end of the lens holder 1 is supported by a projection 4a provided on the substrate 4 via a damper 16 which is a support portion. and the first magnet 8. first outer yoke 10
．． A first magnetic circuit is formed by the substrate 4 and the first inner yoke 6, and a magnetic field is generated between the first magnet 8 and the first inner yoke 6. Also, the second magnet 9. Second outer yoke 1
1. A second magnetic circuit is formed by the substrate 4 and the second inner yoke 7, and a magnetic field is generated between the second magnet 9 and the second inner yoke 7.

A light shielding pin 17 is provided protruding from the lower part of the lens holder 1. Further, on the substrate 4, a light emitting diode 18 which is a light emitting element and a two-part photodiode 19 which is a light receiving element are provided so as to sandwich the light shielding pin 17. and,
These light shielding pins 17° light emitting diode 18. The two-split photodiode 19 constitutes a lens position sensor.

Next, the operation of the above configuration will be explained. When a current is applied to the focusing coil 3, an electromagnetic force acts on the focusing coil 3, and the lens holder 1 moves in the direction of arrow X in FIG. 1, thereby performing focusing. Further, when a current is applied to the tracking coils 12 to 15, an electromagnetic force acts on the tracking coils, and the lens holder 1 moves in the direction of arrow θ (tracking direction) in FIG. 6, thereby performing tracking. Then, when the current flowing through the focusing coil 3 and tracking coils 12 to 15 is cut off,
The elasticity of the damper 16 causes the lens holder 1 to return to the neutral point.

Next, the principle of the lens position sensor will be explained. When the lens holder 1 is at the neutral point, the light shielding pin 17 of the lens position sensor blocks the light beam emitted from the light emitting diode 18, so that the light beam does not reach the two-split photodiode 19. However, if the lens holder 1 rotates even slightly from the neutral point, the light beam emitted from the light emitting diode 18 will hit one of the light-receiving surfaces of the two-split photodiode 19, and the lens holder 1 will rotate in which direction. It is now possible to detect if it is moving. During access, the signals from this lens position sensor are used to
15 to electrically lock the lens holder 1,
This is designed to prevent lateral displacement and vibration after access.

(Problems to be Solved by the Invention) In the conventional example with the above configuration, the lens position sensor is provided below the lens holder 1, so there is a problem that the height of the optical pickup becomes high and the device becomes large. .

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical pickup that can be miniaturized.

(Means for Solving the Problems) The present invention for solving the above problems includes a movable member having an objective lens, and a fixed member connected to the movable member via support means that movably supports the movable member. In the optical pickup that reads and/or writes information by irradiating a laser beam from a light emitting source onto a recording medium through the objective lens, the optical pickup is provided on the fixed member side, and the objective lens is provided on the fixed member side. a light emitting element that emits a light beam for lens position detection; a reflecting section that is provided on the side opposite to the support section of the movable section and reflects the light beam; and a reflecting section that is provided on the fixed member side and that is caused by the reflecting section. The present invention is characterized by having an objective lens position sensor including a light receiving element that receives the reflected light beam.

(Function) In the optical pickup of the present invention, the laser beam from the light emitting element is irradiated onto the recording medium via the objective lens,
Information is read and/or written. and,
A light beam for detecting the lens position of the objective lens is emitted from a light emitting element of the objective lens position sensor provided on the fixed member side. This light beam is reflected by the reflection section provided on the side opposite to the support section of the movable section, and strikes the light receiving element provided on the fixed member side. )'l Tfru.

(Example) Next, one embodiment of the present invention will be described using the drawings.

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
3 is a front view of the lens position sensor board in FIG. 1, FIG. 4 is an explanatory diagram of the light shielding plate in FIG. 1, and FIG. 5 is an explanation of the control circuit of the optical pickup in FIG. 1. It is a diagram.

First, in FIG. 1, the disk is arranged perpendicularly to the plane of the paper. , 21 is a lens holder which is a movable part provided with an objective lens 22 for converging laser light onto the disk. The lens holder 21 has a substantially cylindrical shape.
It consists of a lens holder 21a and a plate-shaped upper lens holder 21b attached to the top surface of the lower lens holder 21a and provided with the objective lens 22.

A focusing coil 23 is wound around the side surface of the lower lens holder 21a. Reference numeral 24 denotes a magnetic substrate serving as a fixed portion, and a shaft 25 is erected on the substrate 24.

The lens holder 21 is fitted onto the shaft 25 so that it can move in the axial direction (focusing direction) of the shaft 25 on the fixed part side and can rotate relative to the shaft 25 (tracking direction). The lower lens holder 21a has a first through hole 2IC.
and a second through hole 21d are drilled, and the first through hole 21
The first inner yoke 26 and the second inner yoke 27 provided on the substrate 24 are respectively larger than C and the second through hole 21d by I■. 28 is the first lens via the lens holder 21.
provided on the substrate 24 so as to face the yoke 26 of the
A first magnet whose magnetization direction is horizontal, 29 is a lens holder 21
The second magnet is provided on the substrate 24 so as to face the second yoke 27 via the magnet, and has a horizontal magnetization direction. 1st
A first outer yoke 30 is provided on the side of the magnet 28 opposite to the lens holder 21, and a second outer yoke 31 is provided on the side of the second magnet 29 opposite to the lens holder 21, respectively, on the substrate 24. Further, the focusing coil 23 is provided with four tracking coils (not shown) as in the conventional example. Further, as shown in FIG. 2, one end of the lens holder 21 is supported by a projection 24a provided on the substrate 24 via a damper 36 serving as a support means. and the first magnet 28. First outer yoke 30. A first magnetic circuit is formed by the substrate 24 and the first inner yoke 26, and the first magnet 2
A magnetic field is generated between the inner yoke 8 and the first inner yoke 26. Also, two second magnets, a second outer yoke 31. Substrate 24
and a second magnetic circuit is formed by the second inner yoke 27,
A magnetic field is generated between the two second magnets and the second inner yoke 27.

Anti-damper 36 (anti-support part) of upper lens holder 21b
A reflective portion 21e extending toward the substrate 24 is provided at the side end portion. On the substrate 24, as shown in FIG.
Lens position sensor board 3 facing reflection section 21e
7 is provided.

This lens position sensor board 37 includes a light emitting element (for example, an LED) 38 that emits a light beam for detecting the lens position of the objective lens 22 in the direction of the reflecting section 21e.
and two light receiving elements (for example, photodiodes) 39.4 that receive the light beam reflected by the reflecting section 21e.
0 is provided. These light emitting elements 38.
Light receiving element 39.40. The objective lens position sensor S is constituted by the reflecting section 21e.

Furthermore, as shown in FIG. 4, the lens position sensor board 37 has light beams other than the light emitting element 38 on the light receiving elements 39 and 40 (for example, stray light eclipsed by a part of the objective lens frame or lens holder). , stray light generated by reflection and diffraction on the recording medium) from entering the light shielding plate 41 is provided.

In FIG. 1, 42 is a terminal that supplies electricity to the focusing coil 23, and 43 is a terminal that supplies electricity to the tracking coil 43.

Further, in FIG. 3, 44 is the output terminal of the light receiving element 40, 45 is the output terminal of the light receiving element 39, and 46 is the light emitting element 38.
47 is a power supply terminal for the light emitting element 38 and the light receiving element 39
．． This is a common terminal with 40.

Next, the control circuit of the apparatus of this embodiment will be explained using FIG. In FIG. 5, 51 is a recording medium, 52 is a semiconductor laser that emits a laser beam, 53 is a beam splitter that separates the laser beam emitted from the semiconductor laser 52 and the laser beam reflected by the recording medium 51, and 54
is a two-part photodiode that receives the separated laser beam and outputs a tracking error signal. 55 is a CPU, 56 is an access mechanism system (radial feed mechanism) of the optical pickup, and 57 is an operational amplifier that performs calculations based on a signal from the CPtJ 55 or the objective lens position sensor S and provides a drive current to the access mechanism system 56. 5
Reference numeral 8 denotes a tracking mechanism system of the optical pickup, and 59 denotes an operational amplifier that performs calculations based on signals from the two-split photodiode 54 or the objective lens position sensor S and provides a drive current to the tracking mechanism system 56. Also, SW
is a switch that changes the output signal of the objective lens position sensor S.

Next, the operation of the above configuration will be explained. When a current is applied to the focusing coil 23, an electromagnetic force acts on the focusing coil 23, and the lens holder 21 moves in the direction of arrow X in FIG. 2, thereby performing focusing. Also,
When a current is applied to the tracking coil, an electromagnetic force acts on the tracking coil, and the lens holder 21 moves in the direction of arrow θ (tracking direction) in FIG. 1, thereby performing tracking. Then, when the current flowing through the focusing coil 3 and the tracking coil is cut off, the lens holder 21 returns to the neutral point due to the elasticity of the damper 36.

Next, the principle of the objective lens position sensor S of this embodiment will be explained. When the lens holder 21 is at the neutral point,
The light beam emitted from the light emitting element 38 is reflected by the reflecting section 21e and evenly enters the light receiving elements 39 and 40. However, if the lens holder 21 is rotated even slightly from the neutral point, a difference will occur in the amount of light incident on the light receiving element 39,40, and a difference will occur in the voltage generated at the light receiving element 39,40.

Therefore, by looking at this voltage difference, the lens holder 2
1 (objective lens 22) is turned in which direction and by how much.

Next, the control of the apparatus of this embodiment will be explained using FIG. This figure shows the state at the time of access when the CPLJ 55 directly controls the access mechanism system. At this time,
A detection signal from the objective lens position sensor S is applied to an operational amplifier 59. The operating amplifier 59 is connected to the lens holder 2
In order to prevent lateral displacement and vibration after the first access, calculations are performed to electrically lock the tracking mechanism, and the tracking mechanism system is driven.

Next, when the switch SW is changed over, the normal state is established.

At this time, the detection signal of the objective lens position sensor S is applied to the operational amplifier 57. The operating amplifier 57 performs calculations such that the lens holder 21 is located at the neutral position, and drives the access mechanism system. Further, a detection signal from the two-split photodiode 54 is applied to an operational amplifier 59. The operational amplifier 59 calculates a tracking error signal based on the detection signal of the two-split photodiode 54, and drives the tracking mechanism system.

According to the above configuration, the reflecting part 21e of the objective lens position sensor S is provided so as to extend to the substrate 24 at the end of the lens holder 21, which is a movable part, on the side opposite to the supporting part.

Furthermore, since the light emitting element 38 and the light receiving elements 39 and 40 are provided so as to face the reflecting section 21e, the height of the optical pickup does not increase. In particular, when the apparatus of this embodiment is used for a 5.25-inch cartridge-type optical disk, it is effective because the objective lens position sensor is disposed in the dead space of the head window.

In addition, since the light shielding plate 41 is provided, light beams other than the light emitting element 38 (for example, stray light eclipsed by a part of the objective lens frame or lens holder, reflected or diffracted by the recording medium, (stray light generated by

(Effects of the Invention) As described above, according to the present invention, the objective lens position sensor is provided on the fixed member side, the light emitting element that emits a light beam for detecting the lens position of the objective lens, and the anti-support for the movable part. The optical pickup is made up of a reflecting part that is provided on the fixed member side and reflects the light beam, and a light receiving element that is provided on the fixed member side and receives the light beam reflected by the reflecting part, so that the device can be made more compact. can be realized.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
3 is a front view of the lens position sensor board in FIG. 1, FIG. 4 is an explanatory diagram of the light shielding plate in FIG. 1, and FIG. 5 is an explanation of the control circuit of the optical pickup in FIG. 1. 6 is a perspective view of the configuration of a conventional example, FIG. 7 is a sectional view of FIG. 6, and FIG. 8 is a configuration diagram of the lens position sensor in FIG. 6. 1.21... Lens holder 2.22... Objective lens 3.23... Focusing coil 4.24... Substrate 5.25... Axis 16.3
6...Damper 21e...Reflector 38...Light emitting element 39.40...Light receiving element Patent applicant
Konica Co., Ltd. Ceremony
Person Patent Attorney Fuji Ijima Jigai 1
Name No. 450 24 board No. 6 Fig. 7 Tube 8 Fig. 18 Light emitting diode

Claims (1)

[Scope of Claims] Consisting of a movable member having an objective lens, and a fixed member connected to the movable member via support means that movably supports the movable member, the laser beam from the light emitting source is emitted from the movable member. In an optical pickup that reads and/or writes information by illuminating a recording medium through the objective lens, the light emitting device is provided on the fixed member side and emits a light beam for detecting the lens position of the objective lens. a light receiving element provided on the fixed member side and receiving the light beam reflected by the reflecting part; An optical pickup characterized by having an objective lens position sensor.