JPH064882A - Optical pickup actuator - Google Patents

Abstract

PURPOSE:To detect the position of an optical pickup actuator without the increase in the number of shapes and wirings by detecting the position by means of a mirror provided on the upper side of a coil bobbin. CONSTITUTION:A mirror 21 is attached on the 45 deg. slope of the upper projection 19 of a coil bobbin 12, a light emitting diode 22 is fixed to a yoke base 11 just under the bobbin and a bisected photodiode 24 is fixed to the vertical surface of a case 23 so as to constitute a position detecting means. When an optical disk follows up a track, the mirror 21 moves as the coil bobbin 12 moves, a light beam from the light emitting diode 22 is reflected and the position of the converged beam on the bisected photodiode 24 is changed. By obtaining the difference of two outputs, the moving amount of the position of an objective lens 20 is detected and the difference is feedbacked to a tracking servo system so as to perform position control. Thus, the actuator is made thin without increasing the number of wirings.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup actuator used in an optical disk recording / reproducing apparatus, and more particularly to an optical pickup actuator equipped with an objective lens position detecting means.

[0002]

2. Description of the Related Art An optical pickup actuator is supported by a yoke base, a coil bobbin rotatably supported by the yoke base, and a focusing coil and a tracking coil provided on the coil bobbin, and a coil bobbin. It is composed of an objective lens and the like. Since the optical pickup needs to move between tracks at high speed for access and the like, it is required to prevent vibration of the objective lens and the like and have excellent track following property. For this reason, it has been conventionally proposed to provide the optical pickup actuator with position detecting means for detecting the amount of movement of the objective lens in the tracking direction.

3 (a) to 3 (c) schematically show an example of the structure of the position detecting means in the conventionally proposed optical pickup actuator. In these figures, 1 is a yoke base, 2
Is a coil bobbin, 3 is an objective lens fixed to the coil bobbin, and a shaft 4 of the coil bobbin is rotatably and slidably attached to the yoke base 1.

The position detecting means shown in FIG. 3 (a) is composed of a light emitting diode (LED) 5 which is laterally opposed to the yoke base 1.
And a two-divided photodiode 6 are provided, and a pin 7 protruding below the coil bobbin 2 is provided so as to block between them. An example in which this system is adopted is disclosed in, for example, Japanese Patent Laid-Open No. 3-256232. In the position detecting means shown in FIG. 3B, the light emitting diode 5 is provided on the lower surface of the coil bobbin 2, and the two-divided photodiode 6 facing the light emitting diode 5 is provided on the yoke base 1 to constitute the position detecting means. There is. An example in which this method is adopted is disclosed in, for example, Japanese Patent Laid-Open No. 3-176820.
In FIG. 3 (c), the light emitting diode 5 is provided on the side surface of the coil bobbin 2, and the two-divided photodiode 6 which is laterally opposed to the light emitting diode 5 is provided on the vertical surface of the yoke base 1 to form the position detecting means. There is.

[0005]

SUMMARY OF THE INVENTION These conventional optical pickup actuator construction methods include:
There were the following problems. In the method of FIG. 3 (a) or FIG. 3 (b), a certain space is provided between the coil bobbin and the yoke base to constitute the position detecting means,
The thickness of the actuator increases and it is difficult to reduce the thickness. In FIG. 3 (c), since the position detecting means is configured by using the side surface of the coil bobbin, it is possible to reduce the thickness, but on the other hand, the position detecting means increases the number of wires from the coil bobbin. There is. The present invention has been made in view of such circumstances, and an object thereof is to provide an optical pickup actuator having a position detecting means without increasing the thickness and the number of wires from the coil bobbin.

[0006]

An optical pickup actuator according to the present invention includes a yoke base, a coil bobbin rotatably supported by the yoke base and slidable in an axial direction, and a focus provided on the coil bobbin. And a tracking coil, and an objective lens fixed to the coil bobbin, and as the position detecting means of the objective lens, an obliquely downward direction is provided on the upper side surface opposite to the objective lens with respect to the axis of the coil bobbin. A mirror mounted facing the mirror, a light emitting element located directly below the mirror and fixed upward on the yoke base, and a vertical surface of a case connected to the yoke base mounted and irradiated by the light emitting element. A two-divided photodiode for detecting the light reflected by the mirror.

[0007]

According to the present invention, the position detecting means is constructed by utilizing the space on the side surface of the coil bobbin without increasing the thickness of the actuator. Further, a mirror is provided on the coil bobbin, and the number of wires from the coil bobbin does not increase due to the configuration of the position detecting means.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 (a) and 1 (b) are a plan view of an optical pickup actuator according to an embodiment of the present invention and its A--
It is an A'cross section figure. In the figure, 11 is a yoke base to which a shaft 13 of a coil bobbin 12 is attached so as to be rotatable and slidable in the axial direction. The outer yoke 1 is formed so as to sandwich the coil bobbin 12 integrally with the yoke base 11.
4 is formed, the inner yoke 15 and the magnet 16 are attached to the outer peripheral portion of the coil bobbin 12 so as to face the outer yoke 14, the focusing coil 18 is wound, and the tracking coils 17 are further provided at four positions outside thereof. Attached to form a magnetic circuit.

An objective lens 20 is fixed to the upper portion of the coil bobbin 12, and a projection 19 protruding laterally is formed at a position symmetrical to the objective lens 10 with the shaft 13 interposed therebetween. The projection 19 is a balance weight for the objective lens 20, and the side surface thereof is an inclined surface of 45 ° which is directed obliquely downward, and the mirror 21 is attached to this. That is, the optical axis of the mirror 21 is inclined downward at 45 °. The light emitting diode 2 is located directly below the mirror 21 and on the yoke base 11.
2 is fixed with the light emitting surface facing up. Further, a two-divided photodiode 24 for position detection is fixed to a vertical surface of the case 23 which is continuous with the yoke base 11. The light emitting diode 22, the mirror 21 and the two-divided photodiode 24 constitute a position detecting means. That is, the light emitted upward from the light emitting diode 22 and reflected laterally by the mirror 21 is detected by the two-divided photodiode 24.

When the track of the optical disk is made to follow by such an optical pickup actuator, the coil bobbin 12 and the objective lens 20 rotate about the axis 13. At this time, the mirror 21 moves as the coil bobbin 12 moves. The light beam emitted from the light emitting diode 22 is reflected by the mirror 21, and the focusing position on the two-divided photodiode 24 changes according to the movement of the mirror 21. Therefore, the position (movement amount) of the objective lens 20 in the tracking direction can be detected by taking the difference between the two outputs of the two-divided photodiode 24.
By feeding back this detection output to the tracking servo system, the tracking capability of tracking can be improved.

FIG. 2 shows an equivalent circuit configuration of a portion for performing the above-described objective lens position detection and servo system feedback control based on the detection. The light emitting diode 22 is connected in series with the transistor Q and the resistor R to form a light source circuit.
The base of the transistor Q is driven by the differential amplifier 31 whose one end receives the reference potential Vref. The two-divided photodiode 24 for position detection is equivalently connected as a series circuit of two photodiodes PD1 and PD2 as shown in the figure. The amplifier 32 takes the sum of the outputs of these two photodiodes PD1 and PD2. The output of the amplifier 32 is fed back to the amplifier 31 so that the sum of the outputs of the two photodiodes PD1 and PD2 is always kept constant. So that the transistor Q is controlled.

The differential amplifier 33 takes the difference between the outputs of the two photodiodes PD1 and PD2, and a position detection output is obtained at the output node N1 of this differential amplifier 33. That is, as described above, the magnitude relationship between the outputs of the two photodiodes PD1 and PD2 changes according to the movement of the coil bobbin 12, and this appears as a change in the output of the node N1. The detection output of the node N1 enters one input terminal of the differential amplifier 35 which drives the actuator drive circuit 36.

Two photodiodes PD3 and PD4
Is an optical disc (not shown) through the objective lens 20.
This is for detecting the tracking error by extracting the reflected light returning from the. The differential amplifier 34 takes the difference between the outputs of the two photodiodes PD3 and PD4, and a tracking error signal is obtained at the output node N2 of the differential amplifier 34. This output signal enters the other input of the differential amplifier 35.

In this way, an output signal corresponding to the displacement of the objective lens in the tracking direction is obtained at the position detection output node N1, and the tracking error detection output node N2 is obtained.
, A tracking error detection output obtained by superimposing the output obtained at the output node N1 is obtained. Then, these are canceled by the differential amplifier 35, the necessary tracking error detection output is input to the actuator drive circuit 36, and desired tracking control is performed.

According to this embodiment, the position detecting means of the objective lens is composed of the mirror 21 provided on the upper side surface of the coil bobbin 12, the light emitting diode 22 provided on the yoke base 11 side, and the divided photodiode 24. However, these can be arranged without increasing the thickness of the entire actuator, as shown in FIG. 3 (a) or (b) of the related art. Further, since the mirror attached to the coil bobbin 12 does not require wiring, the number of wirings from the coil bobbin 12 does not increase. Further, in the configuration of this embodiment, the projection 19 is arranged symmetrically with respect to the objective lens with respect to the axis 13 so that good weight balance can be achieved. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0016]

As described above, according to the present invention,
It is possible to obtain a thin optical pickup actuator without increasing the number of wires.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical pickup actuator according to an embodiment of the present invention.

FIG. 2 is a diagram showing an actuator control circuit configuration of the same embodiment.

FIG. 3 is a diagram showing a configuration example of a conventional optical pickup actuator.

[Explanation of symbols]

11 ... Yoke base, 12 ... Coil bobbin, 13 ... Shaft,
14 ... Outer yoke, 15 ... Inner yoke, 16 ... Magnet, 17 ...
Tracking coil, 18 ... Focusing coil, 1
9 ... Protrusion, 20 ... Objective lens, 21 ... Mirror, 22 ... Light emitting diode, 23 ... Case, 24 ... Two-division photodiode.

Claims (1)

[Claims] 1. A yoke base, a coil bobbin rotatably and axially slidably supported by the yoke base, a focusing coil and a tracking coil provided on the coil bobbin, and fixed to the coil bobbin. Objective lens, a mirror mounted obliquely downward on the upper side surface on the side opposite to the objective lens with respect to the axis of the coil bobbin, and positioned directly under the mirror and fixed upward on the yoke base. And a two-divided photodiode attached to a vertical surface of the case connected to the yoke base for detecting light emitted from the light emitting element and reflected by the mirror. Optical pickup actuator.