JPH0757281A - Biaxial actuator - Google Patents

Abstract

PURPOSE:To assure the accuracy of reading performance of information even at the time of low temp. by providing the biaxial actuator with a temp. detecting means for a lens holder and a control means for the servo signals to be applied to at least either of a focusing coil and a tracking coil. CONSTITUTION:This biaxial actuator has the focusing coil 30 and the tracking coil 28 and operates to move a lens 26 relative to the focusing direction FCS and tracking direction TRK of an automatic information memory medium. The temp. detecting means 60 detects the temp. of the objective lens holder 24 and a coil driving means 76 applies the servo signals S3, S4 to at least either of the focusing coil 30 and the tracking coil 28. A gain controller 70 of the control means controls the servo signals S3, S4 to be applied to at least either of the focusing coil 30 and the tracking coil 28 from the coil driving means 76. As a result, the temp. of the lens under low-temp. service environment is raised.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a biaxial actuator for reading information from a rotation information recording medium of an optical disk device.

[0002]

2. Description of the Related Art A biaxial actuator of an optical pickup has an objective lens for reading information from a rotation information recording medium of an optical disc device, that is, an optical disc.
In order for this objective lens to follow the warp and surface deflection of the disc, the eccentricity of the disc, and the meandering of the track,
The objective lens can be moved in the focus direction and the tracking direction.

[0003]

The objective lens is fixed to the holder with an adhesive. When this type of optical pickup is used in a low temperature environment, the adhesive becomes hard. Because of this, the objective lens is distorted at low temperatures,
There is a problem that the optical characteristics of the objective lens are deteriorated and the performance of reading the information from the optical disc of the objective lens is deteriorated when the biaxial actuator is operated at a low temperature.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a biaxial actuator capable of ensuring the information reading performance even at low temperatures.

[0005]

According to the present invention, there is provided a biaxial actuator which comprises a focus coil and a tracking coil, and which moves a lens in the focus direction and the tracking direction of a rotation information storage medium. There is a temperature detecting means for detecting a temperature, a driving means for applying a servo signal to at least one of the focus coil and the tracking coil, and based on the detected temperature, the driving means outputs the focus coil and the tracking coil. And a control means for controlling the servo signal given to at least one of the two.

In the present invention, preferably, the temperature detecting means detects the temperature of the holder holding the lens.

Further, in the present invention, it is preferable that the driving means, when the detected temperature is equal to or lower than a predetermined temperature, control the signal for controlling the frequency outside the frequency band of the servo signal by the focus. At least one of the coil and the tracking coil is provided.

Further, in the present invention, preferably, when at least one of the operation of moving the lens in the focus direction and the operation of moving the lens in the tracking direction is being performed, the driving means outputs the servo signal. A control signal outside the frequency band is applied to at least one of the focus coil and the tracking coil.

[0009]

Function: The temperature is detected by the temperature detecting means. The drive means gives a servo signal to at least one of the focus coil and the tracking coil. Based on the detected temperature, the control unit controls the servo signal applied from the drive unit to at least one of the focus coil and the tracking coil, thereby raising the temperature of the lens under the low temperature use environment.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the examples described below are suitable specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

FIG. 1 is a perspective view showing a preferred embodiment of the biaxial actuator of the present invention. In FIG. 1, the biaxial actuator A has a base 20. The base 20 includes a fixing portion 22. The biaxial actuator shown in FIG. 1 is provided in an optical disk device. The optical disc device is, for example, a compact disc device or a magneto-optical disc device. As shown in FIG. 2, the biaxial actuator A is arranged so as to face an optical disc D such as a compact disc.

An objective lens 26 is fixed to the objective lens holder 24, preferably with an adhesive. For example, the objective lens 26 is made of acrylic, for example. The objective lens holder 24 is provided with a tracking coil 28 and a focus coil 30. The objective lens holder 24 is elastically supported by the suspension 32 with respect to the fixed portion 22.

The suspension 32 has a structure as shown in FIGS. The suspension 32
For example, it can be made of a highly elastic resin or metal. The suspension 32 is provided with four tracking hinges 40 and 42 and four focus hinges 50, 52, 54 and 56 in the illustrated example.

As shown in FIG. 1, the tracking hinge 4
0 and 44 are fixed to the fixed portion 22 of FIG. The tracking hinges 42 and 46 are fixed to the objective lens holder 24 on the movable part side.

For the tracking coil 28 of FIG.
By supplying a current that is the servo signal S3, a force is generated between the magnet and the yoke (not shown), and the objective lens holder 24 is moved in the tracking direction TR of FIG.
A tracking movement operation can be performed on the fixed portion 22 along K.

Further, by supplying a current which is the servo signal S4 to the focus coil 30 of FIG.
A force is generated between the magnet (not shown) and the yoke, and the objective lens holder 24 moves in the focus direction FCS.
A focus movement operation can be performed with respect to the fixed portion 22 along.

The tracking movement operation and the focus movement operation of the objective lens holder 24 are performed on the fixed portion 22 via the suspension 32.

In FIG. 1, the objective lens holder 24 is provided with a temperature sensor 60. Temperature sensor 60
Is preferably adapted to directly detect the temperature of the objective lens holder 24. This temperature sensor 60 can employ, for example, a transistor, a diode, or the like. This temperature sensor 60, as shown in FIG.
The temperature information signal SF from the temperature sensor 60 is connected to the gain controller 70 which is a control means, and is supplied to the gain controller 70.

Focus information, tracking information, an RF signal and the like from the light receiving portion H are input to the RF amplifier 72. The focus information and the tracking information are processed by the servo signal processor (SSP) 74. The servo signal processor 74 includes a phase compensation circuit for tracking servo and focus servo.

When a transistor is used for the temperature sensor 60, for example, it has a negative temperature characteristic, and its base-emitter voltage VBE has a negative temperature characteristic of -2 mV / ° C. That is, by the gain controller 70 knowing the base-emitter voltage VBE of the temperature sensor 60, the temperature of the objective lens holder 24 or the objective lens 26 itself corresponding to the negative base-emitter voltage VBE is known. Is able to.

The processing signal S1 from the servo signal processor 74 drives the coil driving means (driver) 76, so that the servo signals S3 and S4 are appropriately supplied to the focus coil 30 and the tracking coil 28, respectively.
Can be washed away.

The temperature detected by the temperature sensor 60 is a predetermined temperature, for example, 5 °, as shown in FIG.
The temperature information signal SF is turned on in a low temperature use environment of C or lower.
The signal is input to the gain controller 70 as a signal. On the other hand, when the temperature detected by the temperature sensor 60 is higher than a predetermined temperature, for example, 5 ° C., as illustrated in FIG. 3, the temperature information signal SF is input to the gain controller 70 as an OFF signal.

The gain controller 70 outputs a control signal S2 to the coil driving means 76 side based on the temperature information signal SF which is an ON signal or an OFF signal. Processed signal S1 output from the servo signal processor 74
Is controlled to the + side by the control signal S2 which is this ON signal. When the processing signal S1 is controlled by the control signal S2 in this way, the coil driving means 76 causes the servo signal S
A control signal for controlling at least one of the values of 3 and S4 is issued to cause a larger amount of current to flow through at least one of the focus coil 30 and the tracking coil 28 to generate heat. On the other hand, the processing signal S1 output from the servo signal processor 74 is not controlled by the control signal S2 which is an OFF signal.

In this way, the coil driving means 76 is
Based on the detected temperature, the servo signals S3 and S4 corresponding to the focus coil 30 and the tracking coil 28, respectively.
At least one of them can be controlled.

Next, a method for ensuring the information reading performance of the objective lens 26 at a low temperature in the above embodiment will be described. In FIG. 2, when the biaxial actuator A is in a low temperature use environment and the temperature detected by the temperature sensor 60 is equal to or lower than a predetermined temperature, the temperature information signal S as an ON signal is obtained.
F is input to the gain controller 70. As a result, the coil driving means 76 sends the servo signal S3 or S4, which is a larger current, to at least one of the focus coil 30 and the tracking coil 28, preferably the coil that is more likely to generate heat.

As a result, at least one of the focus coil 30 and the tracking coil 28 generates heat. Due to this heat generation, the objective lens holder 24 also called a bobbin is heated, and the heat is transferred to the objective lens 26 via the objective lens holder 24, and the objective lens 26 is heated.

If the focus coil 30 is not provided with the servo signal S3, the tracking coil 2
In the case where the servo signal S4 is not given to 8, that is, when the objective lens holder 24 is in a completely stationary state in which neither focus movement operation nor tracking movement operation is performed, the coil driving means 76 normally operates. The control signal within the frequency band of the servo signals SS3, S4 being used or the control signal outside the frequency band is supplied to the focus coil 30 and the tracking coil 2.
It gives to at least one of 8.

On the other hand, if the objective lens holder 24 is in the focus direction FCS or the tracking direction TRK.
Of at least one of the focus coil 30 and the tracking coil 28 from the coil driving means 76 for controlling the servo signals S3 and S4 used outside the frequency band. The temperature of the objective lens holder 24 and the objective lens 26 is raised by giving a servo signal.

By doing so, the frequency band of the servo signals S3 and S4 used for the focus movement operation and the tracking movement operation, and the focus coil 30.
The frequency band of the control signal for heating at least one of the tracking coil 28 and the tracking coil 28 can be positively changed. Therefore, no malfunction occurs in the focus movement operation and the tracking movement operation of the objective lens 26.

When the objective lens holder 24 is stationary,
When a servo signal for control within the frequency band of the servo signals S3, S4 or a servo signal for control outside the frequency band is given, and the objective lens holder 24 is performing a servo operation for at least one of focus operation and tracking operation, By giving a servo signal (disturbance) outside the frequency band of the servo signals S3 and S4, the focus coil 30 and / or the tracking coil 28 to which the servo signal is given can be heated.

Due to the heat generated by this coil, heat is transmitted through the objective lens holder 24 and heats the objective lens 26. As the temperature of the objective lens rises, the distortion of the objective lens 26 disappears, and it is possible to prevent the deterioration of the optical reading characteristics of information under a low temperature use environment.

By improving the optical reading characteristics of the objective lens, the image forming performance originally possessed by the objective lens 26 can be secured and exhibited as designed. By the way, the frequency band of the servo signal in the focus moving operation and the tracking moving operation described above is, for example, D
It is in the range of C (direct current) to 1 kHz.

In this way, when the temperature of the objective lens 26 rises and exceeds the predetermined temperature of 5 ° C., the temperature information signal SF from the temperature sensor 60 of FIG. 2 is turned off.
Therefore, the processing signal S1 is not controlled, and therefore the heating servo signal is not applied from the coil driving means to the focus coil 30 and the tracking coil 28.

The present invention is not limited to the above embodiment. For example, the temperature sensor is not limited to a diode or the like. Further, the biaxial actuator of the present invention is an optical disc device, as long as it uses an optical pickup to record information on or reproduce information from a rotary information recording medium such as a compact disc or a magneto-optical disc. Can be widely applied.

In a low temperature environment, not only one of the focus coil and the tracking coil but also both the focus coil and the tracking coil may generate heat. The temperature sensor as the temperature detecting means can be arranged in a portion other than the objective lens holder.
In any case, this temperature sensor only needs to be able to detect the temperature around the objective lens or the temperature around the biaxial actuator. In addition, the temperature that determines the low temperature use environment is
Although it is 5 ° C. in the above-mentioned embodiment, it is not limited to this and other numerical values may be used.

[0036]

As described above, according to the present invention, the information reading performance can be ensured even at a low temperature. Therefore, the imaging performance of the lens can be exhibited.

[Brief description of drawings]

FIG. 1 is a perspective view showing a preferred embodiment of a biaxial actuator of the present invention.

FIG. 2 is a diagram showing the biaxial actuator of FIG. 1, a peripheral circuit thereof, and a part of a disk.

FIG. 3 shows that the gain controller is turned on at a predetermined temperature,
The figure which shows the example of OFF operation.

[Explanation of symbols]

 24 Objective Lens Holder 26 Objective Lens 60 Temperature Sensor 70 Gain Controller (Control Means) 72 RF Amplifier 74 Servo Signal Processor 76 Coil Drive Means (Drive Means) A 2 Axis Actuator S1 Processing Signal S2 Control Signals S3, S4 Servo Signals (Current)

Claims (4)

[Claims] 1. A biaxial actuator, comprising a focus coil and a tracking coil, for moving and operating a lens in the focus direction and the tracking direction of a rotation information storage medium, the temperature detecting means for detecting a temperature, and the focus coil. Drive means for applying a servo signal to at least one of the tracking coils, and control means for controlling the servo signal applied from the drive means to at least one of the focus coil and the tracking coil based on the detected temperature. , A two-axis actuator. 2. The biaxial actuator according to claim 1, wherein the temperature detecting means detects a temperature of a holder holding a lens. 3. The driving means is configured so that the detected temperature is
The biaxial actuator according to claim 1, wherein a signal for controlling a frequency outside the frequency band of the servo signal is applied to at least one of the focus coil and the tracking coil when the temperature is equal to or lower than a predetermined temperature. 4. When at least one of a movement operation of the lens in a focus direction and a movement operation in a tracking direction of the lens is being performed, the driving means outputs a control signal outside a frequency band of the servo signal to the control signal. The biaxial actuator according to claim 1, which is applied to at least one of a focus coil and the tracking coil.