JPS63175231A - Driving device for optical element of optical pickup - Google Patents

Abstract

PURPOSE:To ensure the proper displacement of a movable part by increasing the gains of a control system including said movable part and a drive part in response to the temperature drop when the frequency of a position control signal is lower than the resonance frequency of the movable part. CONSTITUTION:The component having a frequency less than the resonance frequency f0 of a movable part 27 undergoes the division of pressure with the resistance of a resistor 51 and the series synthetic resistance of a resistor 57 and a thermistor 58 and supplied to an operational amplifier 52 for the focus error signal Et which is supplied to the amplifier 52 through a focus error signal processing part 50 with connection of a gain control circuit 56. That is, the resistance value of the thermistor 58 increases in accordance with the temperature drop and therefore the dividing ratio increases as the temperature drops for said component of the signal Et. Then the gains of said component of the signal Et are increased as the temperature drops through the amplifier 52. Thus the part 27 can have a proper displacement.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Field of industrial application B. Overview of the invention C. Prior art D. Problem to be solved by the invention E. Means for solving the problem F. , Fig. 2) G-2 Modification H Effect of the invention A Industrial application field The present invention relates to an objective lens in an optical pickup that writes information to or reads information from a recording medium using a light beam. The present invention relates to an optical element driving device for an optical pickup that moves an optical element such as the above in a predetermined direction.

B. Summary of the Invention The present invention provides an optical element such as an objective lens for optical pink-up, which writes information to or reads information from a recording medium by making a light beam incident on the recording medium. In an optical element drive device for an optical pickup that moves in a predetermined manner, a movable part made of synthetic resin that holds the optical element and can be displaced to move it in a predetermined direction is controlled in a predetermined position. A gain control unit is connected to the drive unit that is displaced by the signal, and the gain control unit controls the gain of the control system including the movable unit and the drive unit, such that the frequency of the position control signal is the resonant frequency of the movable unit. By increasing the temperature as the temperature decreases, it is possible to avoid a situation in which a movable part made of synthetic resin is unable to properly displace due to the influence of low temperatures. This is what I did.

C. Conventional Technology An optical disc player that uses a light beam to reproduce information from a disc as an information recording medium is equipped with an optical pickup that constitutes an optical system for reading information from recording tracks formed on the disc. It will be done.

Such optical pink-up can be realized, for example, as shown in a simplified manner in FIG.
For example, the disks D can be moved along the radial direction of the disk D (in the direction indicated by arrow A). Then, the laser beam emitted from the semiconductor laser 1 is diffracted by the grating 2 into three laser beams (in FIG. 3, for the sake of simplicity,
These three laser light beams are shown by one solid line), and each laser light beam enters the polarization beam splinter 3, passes through its analyzer surface 3a, and then enters the collimator lens 4. The three laser beams incident on the collimator lens 4 are collimated, then pass through the quarter-wave plate 5, enter the objective lens 6, and are focused by the objective lens 6. The light is made incident on disk D. At that time, the three laser beams are
They are arranged in such a relationship that they form a central beam and beams on both sides sandwiching the central beam, and the central beam is used for reading information recorded on the disk D and detecting the focus state on the recording surface of the disk D, and It is assumed that the beams on both sides are used to detect the tracking state of the center beam with respect to the recording track formed on the disk D. The three laser beams incident on the disk D are each reflected while being modulated by the recording tracks formed on the disk D, and are turned into reflected laser beams.

Note that in relation to the objective lens 6, a focus control drive coil 9F and a tracking control drive coil 9T are arranged.

Each of the three reflected laser beams from disk D is
It returns through the objective lens 6, is made into a parallel beam, and is again 17
Passes 4 wavelengths + Ii5. In this way, the three reflected laser beams that pass through the 174-wavelength plate 5, enter the disk D, are reflected by the disk D, and pass through the 174-wavelength plate 5 again pass through the polarizing beam splitter 3 and enter the disk. D
The polarization direction of each of the three laser beams incident on the laser beam is rotated by π/2.

The three reflected laser light beams whose polarization directions have been rotated by π/2 are incident on the collimator lens 4 , where they are made into a focused beam and incident on the polarizing beam splitter 3 . Then, each of the light beams is reflected by the analyzer surface 3a of the polarizing beam splitter 3, and guided to the light detection section 8 through the light receiving lens 7.

For example, as shown in FIG. 4, the photodetector 8 receives a central beam BC of the three reflected laser beams.
A photodetector 11 consisting of a photodetector element, and a photodetector 11
The photodetectors 12 and 13 are arranged to sandwich the beams Br and Be respectively. Then, the detection outputs from the four photodetection elements of the photodetector 11 and the detection outputs from each of the photodetectors 12 and 13 are supplied to the signal forming circuit 14, and the signal forming circuit 14 outputs the light. An information read signal SO corresponding to the information recorded on the recording track of the disk D, which is formed based on the detection outputs from the four photodetecting elements of the detector 11, and a focus of the central beam on the recording surface of the disk D. A focus error signal Ef corresponding to the state is obtained, and the photodetectors 12 and 13
A tracking error signal El corresponding to the tracking state of the central beam with respect to the recording trunk formed on the disk D is obtained based on the detection outputs from the respective ones.

The focus error signal Ef from the signal forming circuit 14 is supplied to the drive circuit 16 after being subjected to necessary processing such as phase compensation in the error signal processing section 15 . The drive circuit 16 obtains a drive signal Sf based on the focus error signal Ef and sends it to the focus control drive coil 9.
F to drive the focus control drive coil 9F, thereby moving the objective lens 6 in the direction along its leading axis, and ensuring that the focus state of the central beam on the recording surface of the disk D is appropriate. Control the position as much as possible. Similarly, the tire knocking error signal Et from the signal forming circuit 14 is also supplied to the drive circuit 18 after being subjected to necessary processing such as phase compensation in the error signal processing section 17. The drive circuit 18 obtains a drive signal 3t based on the tracking error signal Et, supplies it to the tracking control drive coil 9T, drives the tracking control drive coil 9T, and thereby controls the objective lens 6. , in a direction perpendicular to its leading axis, to control the position of the center beam so that the tracking state of the recording track formed on the disk D is appropriate.

In this way, a focus servo control system and a tracking servo control system related to the objective lens 6 are formed.

In an optical pickup that is operated with the focus servo control system and the tracking servo control system formed as described above, there is a section (hereinafter referred to as The two-wheel drive mechanism (referred to as a two-wheel drive mechanism) is configured as shown in FIG. 5, for example. The two-axis drive mechanism shown in FIG. 5 has a magnetic yoke member 20 made of a magnetic plate member, and the magnetic yoke member 20 has two pairs of opposing bent pieces 21a and 21b. A magnet 22 is fixed to each bent upright piece 21a.

Further, a movable connecting member 23 is attached to the magnetic yoke member 20 via a pair of pins protruding from the upper surface thereof, and a lens holding portion 24 to which the objective lens 6 is attached is attached to the movable connecting member 23. bobbin member 2 provided with
6 are connected.

Thereby, the bobbin member 26 is floatingly supported with respect to the magnetic yoke member 20 by the movable coupling member 23, and is supported in a direction along the optical axis of the objective lens 6 and perpendicular to the optical axis of the objective lens 6. It is designed so that it can be displaced in any direction. These movable connecting members 2
3 and the bobbin member 26 both support a movable part 27 that can hold the objective lens 6 and move the objective lens 6 in a direction along its optical axis and in a direction perpendicular to the optical axis. It consists of

The movable connecting member 23 and the bobbin member 26 that constitute the movable portion 27 are each integrally formed of synthetic resin. As shown in FIG. 6, the movable connecting member 23 has a fixed end portion 40 formed with a pair of through holes 40a into which a pair of bottles protruding from the upper surface side of the magnetic yoke member 20 are inserted, and A pair of parallel arm portions 42 whose one ends are connected to the upper and lower edges of the end portion 40 via a hinge portion 41 and are swingable in a direction along the optical axis of the objective lens 6; The upper end edge and the lower end edge are connected to each other end of the hinge part 43 via a hinge part 43.
4, the objective lens 6 has a distal end coupling portion 45 which is swingable in a direction perpendicular to the optical axis of the objective lens 6.

The tip coupling portion 45 is adapted to fit into a notch 46 formed in the bobbin member 26 that holds the objective lens 6.

In addition to the lens holding part 24 to which the objective lens 6 is attached, the bobbin member 26 is attached to the parallel arm part of the movable coupling member 23 with the distal end coupling part 45 of the movable coupling member 23 fitted into the notch part 46. It has a pair of side plate members 47 that form a cavity into which 42 is loosely inserted. The lens holding portion 24 and the pair of side plate members 47 have two
A pair of opposing projections 48 and 49 are formed.

As shown in FIG. 5, between each pair of these two sets of opposing protrusions 48 and 49 is a focus control drive coil 9F wound in a cylindrical shape.

A tracking control drive coil 9T is disposed on the focus control drive coil 9F, and is insulated and in close contact with the focus control drive coil 9F so that its winding axis direction is orthogonal to the rotation axis direction of the focus control drive coil 9F. and is fixed to the bobbin member 26.

Then, in a state where the movable connecting member 23 and the bobbin member 26 formed as described above are connected to each other, the movable connecting member 23 is attached to the magnetic yoke member 20 via a pair of pins. The focus control drive coils 9F and the tracking control drive coils 9T are respectively attached to the bent upright pieces 21 provided on the magnetic yoke member 20.
b. In such a state, the bent upright pieces 21a and 21b and the magnet 22 act as a magnetic field forming section, and these bent upright pieces 21a and 21b and the magnet 22 act as a focus control drive coil 9F and a tracking control drive. Together with the coil 9T, it constitutes a focus control drive section and a trunking control drive section.

Under such a configuration, when the drive signal sr is supplied from the aforementioned drive circuit 16 to the pair of focus control drive coils 9F, each of the focus control drive coils 9f is activated by the above-described magnetic field forming section. In the generated magnetic field, an electromagnetic force is applied in a direction along the optical axis of the objective lens 6. Therefore, the bobbin member 26 to which the focus control drive coil 9F is fixed is moved in the direction along the optical axis of the objective lens 6 by the displacement of the parallel arm part 42 of the movable coupling member 23 accompanied by the bending of the hinge parts 41 and 43. As a result, the objective lens 6 is moved in the direction along its front axis by the drive signal S.
``It will be moved accordingly.

Further, when the drive signal SL is supplied from the drive circuit 18 to the tracking control drive coils 9T respectively attached to the pair of focus control drive coils 9F, each of the tracking control drive coils 9T is In the magnetic field formed by the magnetic field forming section, one side receives an electromagnetic force that causes it to be brought close to the magnet 22 facing it, and the other side is moved away from the ci stone 22 facing it. As a result, the bobbin member 26 to which the tracking control drive coil 9T is fixed via the focus control drive coil 9F is rotationally displaced as the hinge portion 44 of the movable connection member 23 is bent. The objective lens 6 is moved in a direction perpendicular to its front axis in response to a drive signal St.

D Problems to be Solved by the Invention In the above-mentioned two-shaft drive mechanism, the movable connecting member 23
In the movable part 27 composed of the and bobbin member 26,
The displacement system including the hinge parts 41 and 43 that contributes to the focus control operation and the displacement system including the hinge part 44 that contributes to the tracking control operation are modeled and considered, for example, as shown in FIG. I can get 5. In the model shown in Fig. 7, F is the external force 1M is the mold surface.

R is the viscous resistance and K is the spring constant. this house,
The spring constant is determined by the characteristics of the synthetic resin that is the material of the movable connecting member 23 and the bobbin member 26.

The equation of motion in such a model is + K x (t) (1)
becomes. When calculating the transfer function by Laplace transform of (112), G(S) =X(S) /F(S) =1/ (MS2 +R5+K) ・ ・ ・(
2). And the amplitude in equation (2) is G=
It is obtained as IC(jω)1 (where ω is the vibration angular frequency).

From this equation (3), the following amplitude values can be obtained.

When ω=0, G=1/K (4)
- When /M- for ~β, that is, the resonance angular frequency ω. When, G=1/R-JM/K...
(5) ω〉ω. When #1/Mω2... (6) From the above (4), (51 and (6) equations, the change of G with respect to ω is as shown in Fig. 8, and G is ω 〉ω.

then -12dB10c without being affected by K
Asymptotic to the change of t, and ω≦ω. If so, it changes depending on K.

Here, as described above, K is determined by the characteristics of the synthetic resin that is the material of the movable connecting member 23 and bobbin member 26 that constitute the movable part 27, and therefore takes a larger value as the temperature decreases.

Therefore, G is ω≦ω. , it will take a smaller value as the temperature decreases.

As a result, the hinge parts 41 and 4 contributing to the focus control operation in the movable part 27 of the two-axis drive mechanism as shown in FIG. 5, which is modeled as shown in FIG.
The sensitivity (T
) - frequency (f) characteristics are shown in Fig. 9 as follows: high temperature is represented by a dashed line Th, room temperature is represented by a solid line Tn, and low temperature is represented by a broken line TJ. f is the resonant frequency fo of the movable part 27 (fo=ω(1/2
In a higher range, the sensitivity T is not affected by temperature changes (in Figure 9, the dashed line Th and the solid line Tn
and broken line T1), the frequency f is the movable part 2
In the range below the resonance frequency r0 of No. 7, the sensitivity T decreases as the temperature decreases.

In this way, the displacement system including the hinge parts 41 and 43 that contribute to the focus control operation in the movable part 27, and
The sensitivity T of each of the displacement systems including the hinge part 44 that contributes to the tracking control operation is determined by the frequency f of the movable part 27.
The resonant frequency f. In the following cases, as the temperature decreases, the low-frequency sensitivity decreases at low temperatures in the focus servo control system and tracking servo control system as shown in Figure 4, which are provided for optical pink-up. will be done.

As a result, when the optical pickup is operated at relatively low temperatures, if external vibrations are applied to the two-axis drive mechanism, out-of-focus or out-of-tracking conditions can easily occur, even if the vibrations are relatively mild. In addition, the amount of displacement of the displacement system including the hinge parts 41 and 43 that contributes to the focus control operation in the movable part 27 may be small, so that, for example, the focus retracting operation may not be performed normally. Otherwise, the amount of displacement of the displacement system including the hinge section 44 that contributes to the tracking control operation in the movable section 27 will be small, resulting in inconveniences such as the track jump operation not being performed properly. Become.

In view of the above, the present invention provides an optical pickup that includes or reads information by inputting a light beam onto a recording medium, and is capable of holding an optical element such as an objective lens and displacing it in a predetermined direction. taken as a thing,
A movable part made of synthetic resin and a drive part that displaces the movable part with a predetermined position control signal based on an error signal obtained depending on the state of a light beam incident on a recording medium through an optical element, for example. In preparation, the optical pickup is operated at a relatively low temperature.
To provide an optical element driving device for an optical pickup, which can avoid a situation where a movable part cannot be properly displaced due to the influence of low temperature even when the frequency of a position control signal is lower than the resonant frequency of the movable part. The purpose is to

E Means for Solving the Problems In order to achieve the above-mentioned object, an optical element driving device for an optical pickup according to the present invention is made of synthetic resin, and holds an optical element in an optical pickup and moves it in a predetermined direction. A movable part that can be displaced to move the movable part to a position, a drive part that causes the movable part to be displaced by a predetermined position control signal, and a gain control part connected to the drive part, the gain control part comprising: The gain of the control system including the movable part and the drive part is increased in response to a decrease in temperature when the frequency of the position control signal is equal to or lower than the resonant frequency of the movable part.

F Effect With this configuration, in the optical element driving device for optical pink-up according to the present invention, when the optical pickup is in the operating state, the control system formed including the movable part and the driving part, The gain for the position side 1ffl signal having a frequency equal to or lower than the resonant frequency of the movable part, that is, the low-frequency gain, is increased in accordance with the decrease in temperature by the action of the gain control part. Therefore, even when the optical pickup is operated at a relatively low temperature, the control system including the movable part and the drive part has appropriate low-frequency sensitivity, and the movable part is affected by the effects of the low temperature. This prevents a situation in which proper displacement cannot be achieved due to the impact.

G Example G-1 Configuration and operation of main parts (FIGS. 1 and 2) FIG. 1 shows the main parts of an example of an optical element driving device for optical pink-up according to the present invention. This example is applied to an optical pickup that reads information from the disk D, as shown in FIG. 3, to form a focus servo control system and a tracking servo control system. A two-wheel drive mechanism as shown in FIG. 5 is provided, which includes a movable portion 27 formed by a movable connecting member 23 and a bobbin member 26 as shown in FIG.

Therefore, the movable part 27 in the example shown in FIG.
As shown in FIG. 6, it is composed of a movable connecting member 23 and a bobbin member 26 made of synthetic resin, and holds the objective lens 6, and also moves the objective lens 6 in the direction along the optical axis and in the direction along the optical axis. It is said that it can be displaced to move in orthogonal directions. Further, the focus control drive coil 9F and the tracking control drive coil 9T in the example shown in FIG. 1 are attached to a movable part 27 that holds the objective lens 6, as shown in FIG.

In FIG. 1, a photodetector 8 is provided in an optical pickup as shown in FIG.
A photodetector 11 consisting of four photodetector elements that receives a photodetector, and a photodetector 11 that is arranged at a position sandwiching the photodetector 11 and receives beams Br and B on both sides.
It is equipped with photodetectors 12 and 13, each receiving 1.

Then, in the same way as in the circuit system shown in FIG. 4, the detection outputs from the four photodetecting elements of the photodetector 11,
Detection outputs from each of the photodetectors 12 and 13 are supplied to a signal forming circuit 14 .

In the signal forming circuit I4, based on the detection outputs from the four photodetecting elements of the photodetector 11, an information read signal SO corresponding to the information recorded on the recording track of the disk D is input to the disk D. A focus error signal E corresponding to the focus state of the central beam of the three laser beams on the recording surface of the disk D is formed,
Further, based on the detection outputs from each of the photodetectors 12 and 13, tracking and tracking of the center beam of the three laser beams incident on the disk D with respect to the recording trunk formed on the disk D are performed.
Error signals Et are formed, and each signal forming circuit 1
Sent from 4.

The focus error signal Ef from the signal forming circuit 14 is supplied to the focus error signal processing section 50. Then, in the focus error signal processing section 50, the focus error signal Ef is subjected to necessary processing such as phase compensation, and then output to an output terminal 53 via an operational amplifier 52. The signal is supplied to an amplifier circuit 55. The drive amplifier circuit 55 receives the focus signal obtained from the output terminal 53 of the focus error signal processing section 50.
Obtain a drive signal Sf based on the error signal Ef and send it to the focus control drive coil 9F connected to its output terminal.
and drives the focus control drive coil 9F, thereby moving the movable part 27 holding the objective lens 6.
The objective lens 6 is moved in a direction along the optical axis according to the drive signal Sf. That is, the focus error signal processing section 5
0° drive amplifier circuit 55. Focus control drive coil 9
A focus servo control system including F, a movable part 27, etc. is configured, and the focus
In the servo control system, the focus error signal Ef and the drive signal Sf obtained based on it serve as a position control signal for the movable part 27.

In the focus error signal processing unit 50, a resistor 51 having a resistance value of 100Ω, for example, is connected to the input end of the operational amplifier 52, and the resistance between the resistor 51 and the input end of the operational amplifier 52 is connected to the input end of the operational amplifier 52. A connection point is led out to terminal 54. A gain control circuit 56 is connected between the terminal 54 of the focus error signal processing section 50 and the connection point between the drive amplifier circuit 55 and the focus control drive coil 9F. The gain control [1 circuit 56 includes, for example, a thermistor 58 and a resistor 57 whose resistance value is 100Ω.
and a capacitor 59 whose capacitance value is O, IpF, for example, and which passes a signal having a frequency exceeding the resonant frequency f0 of the movable part 27, are connected in series. The thermistor 58 has a negative temperature coefficient, and has a characteristic that its resistance value increases as the temperature decreases.

By connecting such a gain control circuit 56, the operational amplifier 52 in the focus error signal processing section 50
Of the focus error signal Et supplied to the , the signal component having a frequency exceeding the resonant frequency f0 of the movable part 27 is divided by the resistance of the resistor 51 and the resistance of the resistor 57, and is then sent to the operational amplifier. 52, and has a frequency lower than the resonant frequency 10 of the movable part 27, the voltage is divided by the resistance of the resistor 51 and the series combination resistance of the resistor 57 and thermistor 5. and is applied to the input terminal of the operational amplifier 52. Therefore, the voltage division ratio of the signal component having a frequency exceeding the frequency f0 of the focus error signal processing unit 50 does not change, but the resistance value of the thermistor 58 increases as the temperature decreases, so that the frequency 10 of the focus error signal Et The partial pressure ratios for signal components having the following frequencies are assumed to increase as the temperature decreases.

Therefore, in the operational amplifier 52, the gain for the signal component having a frequency exceeding the frequency r0 of the focus error signal Et does not substantially change, but the gain for the signal component having a frequency exceeding the frequency r0 of the focus error signal EL does not change. Gains for signal components having frequencies below, that is, low-frequency gains, increase as the temperature decreases. For example, DC gain G
As shown in FIG. 2, dc increases relatively rapidly as the temperature t decreases. As a result, the focus error signal processing section 50. Drive amplification circuit 55° Resonance frequency f of the movable part 27 in the focus error signal in the focus servo control system including the drive coil 9F for focus control, the movable part 27, etc. Gains for signal components having frequencies below, that is, low-frequency gains, increase as the temperature decreases.

Therefore, when the optical pickup 7 is operated at a relatively low temperature, the spring constant of the movable part 27 made of synthetic resin becomes relatively large, and the low-frequency sensitivity tends to decrease. Even in the case where the low-frequency gain is large, the desired low-frequency sensitivity of the movable part 27 is maintained, and as a result, a state in which proper focus control is performed or proper focus is maintained. A state can be assumed in which a retracting operation is performed.

Further, the tracking error signal Et from the signal forming circuit 14 is supplied to a tracking error signal processing section 60. Then, in the I-rough king error signal processing section 60, the tracking error signal Et is subjected to necessary processing such as phase compensation, and then outputted to an output terminal 63 via an operational amplifier 62, and then connected to the output terminal 63. The signal is supplied to a drive amplifier circuit 65. The drive amplification circuit 65 obtains a drive signal St based on the tracking error signal EL obtained at the output terminal 63 of the tracking error signal processing section 60, and sends it to the tracking control drive coil 9T connected to its output terminal. and drives the tracking control drive coil 9T, whereby the objective lens 6
The movable part 27 holding the object is moved in a direction perpendicular to the optical axis of the objective lens 6 in accordance with the drive signal St. That is, the tracking error signal processing section 60. Drive amplifier circuit 65
, a tracking servo control system including a tracking control drive coil 9T, a movable part 27, etc. is configured, and in this tracking servo control system, a trunking error signal Et and a drive signal obtained based on the tracking servo control system are configured. St is a position control signal for the movable part 27.

In the tracking error signal processing section 60 as well, a resistor 61 is connected to the input end of the operational amplifier 62, and the connection point between the resistor 61 and the input end of the operational amplifier 62 is
It is led out to the terminal 64.

Then, the terminal 6 of the tracking error signal processing section 60
A gain control circuit 66 is connected between the drive amplifier circuit 4 and the connection point between the drive amplifier circuit 65 and the tracking control drive coil 9T. The gain control circuit 66 includes a resistor 67 and a capacitor 6 that allows a signal having a frequency exceeding the resonant frequency f0 of the thermistor 68 and the movable part 27 to pass therethrough.
9 are connected in parallel and connected in series. The thermistor 68 also has a negative temperature coefficient, and has a characteristic that its resistance value increases as the temperature decreases.

The structure of the tracking servo control system to which the gain control circuit 66 is connected is the gain control circuit 56 described above.
The configuration is the same as that of the focus servo control system connected to. Therefore, in the case of the trunking servo control system to which the gain control circuit 66 is connected, the same operation as in the case of the focus servo control system described above is performed, the same effects are obtained, and the temperature is relatively low. Even in the case where the optical pickup is operated and the spring constant of the movable part 27 made of synthetic resin becomes relatively large, the low-frequency sensitivity tends to decrease. By increasing the low-frequency gain, the desired low-frequency sensitivity in the movable part 27 is maintained, and thereby a state in which proper tracking control is performed or a state in which a proper trunk jump operation is performed is achieved. You will get it.

G-2 Modification In the above example, the objective lens 6 is held and driven, and is configured as both a focus servo control system and a tracking servo control system. The optical element driving device of such an optical pickup holds and drives the objective lens, and can constitute only either a focus servo control system or a trunking servo control system. Furthermore, it is also possible to adopt an embodiment in which optical elements other than the objective lens are held and driven.

Effects of the Invention H As is clear from the above explanation, the optical element driving device for an optical pickup according to the present invention allows a light beam to be incident on a recording medium to transfer information to or from the recording medium. A device made of synthetic resin that holds the optical element and can be displaced to move it in a predetermined direction in order to move the optical element such as an objective lens in an optical pickup that performs reading in a predetermined manner with respect to the recording medium. In order to displace the movable part, which has been set as In the case where the optical pink-up is activated, and as a result, the spring constant of the movable part made of synthetic resin becomes relatively large, and the low-frequency sensitivity tends to decrease. Also, the control system formed including the movable part and the driving part has appropriate low-frequency sensitivity,
This prevents a situation in which the movable part cannot be properly displaced due to the influence of low temperature.

Therefore, for example, when the objective lens is held and driven by the optical element driving device of the optical pickup according to the present invention, and a focus servo control system or a tracking servo control system is configured, Even when the optical pickup is operated at relatively low temperatures, the large low-frequency gain allows the desired position in the movable part, which can be displaced to hold and drive the objective lens. Low-frequency sensitivity is maintained, thereby achieving a state in which proper focus control or proper tracking control is performed, and furthermore, a state in which proper focus pull-in operation or proper track jump operation is performed. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a block connection diagram showing essential parts of an example of an optical element driving device for an optical pin tap according to the present invention, FIG. 2 is a characteristic diagram for explaining the operation of the example shown in FIG. 1, and FIG. is a simplified block diagram showing an example of an optical pickup, FIG. 4 is a block connection diagram showing a simplified control system configured for the optical pink-up shown in FIG. 3, and FIG. 5 is an example of a two-wheel drive mechanism. FIG. 6 is an exploded perspective view of the movable part used in the two-wheel drive mechanism shown in FIG. 5, FIGS. 7 and 8 are diagrams for explaining the movable part, and FIG. 5 is a characteristic diagram regarding the control system shown in FIG. 4. FIG. In the figure, 6 is an objective lens, 8 is a photodetector, 9F is a drive coil for focus control, 9T is a drive coil for tracking control, 14 is a signal forming circuit, 27 is a movable part, 50 is a focus error signal processing unit, 55 and 65 are drive amplifier circuits, 56 and 66 are gain 11 control circuits, 58 and 68 are thermistors, and 60 is a tracking error signal processing section. Figure 5 Moving part sickness 1 Figure 6 Figure 3 Figure 4

Claims (1)

[Scope of Claims] A movable part made of synthetic resin that holds an optical element in an optical pickup and can be displaced to move the optical element in a predetermined direction; A drive section that causes displacement in the movable section; and a gain of a control system connected to the drive section and formed including the movable section and the drive section, such that the frequency of the position control signal is equal to or lower than the resonant frequency of the movable section. An optical element driving device for an optical pickup, comprising: a gain control section that increases the gain according to a decrease in temperature.