JPS61294642A - Driving device for optical system - Google Patents

Abstract

PURPOSE:To prevent a lens holder from moving unnecessarily by detecting the quantity of displacement between the conductor plate and fixed electrode plate of the lens holder when the lens holder is driven and applying a feedback signal based upon the quantity of displacement to a recording and reading part. CONSTITUTION:When the lens holder A rotates according to a tracking signal from an amplifier 13, either of variable capacitors 31 and 32 varies in capacity continuously, but when a current flows to the bridge circuit consisting of variable capacitors 31 and 32 and resistances 26 and 27, the current flowing through the bridge circuit varies and the output voltage between terminals 24 and 28 varies. Consequently, the voltage outputted from the bridge circuit is amplified by an amplifier 25 and led out from an output terminal 14. Then, the output voltage at the output terminal 14 is inputted to the amplifier 13 and inputted to an actuator 5 through a feedback circuit 33 to control the driving of an objective 6 at right angles to the optical axis, thereby preventing the lens holder from moving unnecessarily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical system driving device, and more specifically, the present invention relates to an optical system driving device that controls the driving of a lens holder by electrical means and adjusts the position of the lens holder. The present invention relates to Nishi-Ku's optical system drive device.

[Conventional technology]

In recent years, optical information recording and reproducing devices using recording media such as optical disks have become popular as devices that write or read information using optical means.

The optical system drive device used in such an optical information recording/reproducing device is driven electromagnetically by passing a current through a coil body disposed at a predetermined distance from a magnet provided on a lens holder.

In this optical system drive device, an optical system such as an objective lens is also provided on the lens holder at a position where the support axis of the lens holder and the optical axis are parallel, and the optical information recording medium is irradiated with light generated by the light source. .

The light reflected by the surface of the optical information recording medium enters the optical system again and is converted into an electrical signal by the photoelectric conversion means, and the lens holder is driven in accordance with the electrical signal. It has become.

[Problem that the invention seeks to solve]

Correction of the position in such a lens driving device is performed according to the amount (change) of current flowing through the coil.

However, if the lens holder is moved at high speed in the rotational direction by the driving force from the coil, the lens holder may move more than necessary due to acceleration, etc., making it impossible to control the position quickly and accurately.

[Means for solving problems]

The present invention was made in view of this problem, and in order to prevent the lens holder from moving more than necessary when driving the lens holder, the amount of displacement between the conductive plate and the fixed electrode plate is adjusted when the lens holder is driven. The object of the present invention is to provide an optical system driving device that detects the amount of displacement and applies a feedback signal to the recording/reading section based on the amount of displacement to adjust the position.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical system driving device of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a diagram showing an example in which the present invention is applied to an optical information recording/reproducing device.

In the figure, reference numeral 1 denotes an optical head, and the optical head 1 converts Raded light generated from a Raded generator 2 into a collimator V lens 3. The beam passes through a beam sinter 4 consisting of a triangular prism, is held by an actuator 5, and is focused onto a medium surface 7 of an optical information recording medium in a switch shape by an objective lens 6-.

The actuator 5 is an actuator for adjusting the position of the objective lens 6, and moves the objective lens 6 according to a focus control signal or a tracking control signal to direct the light from the radar generator 2 onto the medium surface 7. Accurately focus light on the track. The radar light that has been reflected and optically modulated by the medium surface 7 enters the beam sinter 4 again.

Then, the laser beam reflected in the horizontal direction (-C> with respect to the medium surface 7) by the beam sinter 4 is reflected by three prisms.
When incident on the configured beam splitter 9, it is optically split into three optical paths 10 & p10b*10c, and these split reflected light components are sent to each photoelectric converter 11a, flb, lie. is input and converted into an electrical signal.

Among the reflected light components, the central optical path component 10b is connected to the photoelectric converter 1.
1b, focus detection is performed using a well-known method such as the beam size method, amplified by an amplifier 12, and sent to the actuator 5 as a focus control signal.
The objective lens 6 is moved in the axial direction.

Of the reflected light components, both end optical path components 10a.

10c is received by the photoelectric converters 11a and lie, and the difference between these output signals is amplified by the amplifier 13 and sent to the actuator 5 as a tracking control signal. direction).

By sending the focus control signal and the tracking control signal to the actuator 5 in this manner, the position of the objective lens 6 in the optical axis direction and in the direction perpendicular thereto is corrected.

Note that an information signal is also detected from the photoelectric converter 11b that receives the central optical path component 10b, and this information signal can be taken out from the HF signal output terminal B.

Next, a detailed explanation will be given based on the explanatory diagram of FIG. 2 of the 7-cut 5ft evaporator of the above embodiment.

The lens holder is made of an insulating disc with a certain thickness, and is movable in the axial or rotational direction via a bearing 16 on a support shaft 15. A semicircular conductor plate 17 is attached so as to be carried around with the holding figure.

Further, the insulator section A1 of the lens holder is equipped with an objective lens 6, and the Rede light emitted from the light source is reflected by the medium surface 7 so as to pass through the objective lens 6, and the light is modulated as shown in FIG. The signal passes through the objective lens 6 again and is converted into an electric signal by the charging converters 11a to 11ie.

Furthermore, the lens holder A has two magnets a, for example, on its outer peripheral surface.
(b) is attached, and coils (c) and (d) are placed at positions separated by a predetermined distance from the magnets (a) and (l).

And a magnet, b, and a coil, c, provided on the lens holder A,
Due to the interaction between the current flowing through the coils d and the magnetic field formed by the current ``C'', the current flowing through the coils e and d is controlled in accordance with the tracking control signal from the amplifier 13 shown in FIG.

The tW objective lens 6 can be moved in the axial direction of the support shaft 15 by a drive mechanism (not shown) in response to the aforementioned focus control signal.

In addition, a fixed electrode plate of 1g is placed at a predetermined distance from the lens holder.
, 19 and fixed electrode plates 20, 21 are arranged. The fixed electrode plates 18 and 19 and the fixed electrode plates 20 and 21 are flat plates having a quarter circular shape, and are attached to the support shaft 15 with insulators 22 and 23 interposed therebetween. Therefore, as described above, when the lens holder rotates in response to the tracking control signal, the rotation angle of the conductor plate 170 relative to each fixed electrode plate changes. The waiting fixed electrode plate and the conductor plate 17 function in the same manner as a so-called variable capacitor.

Next, the position control circuit network of the lens holder A will be described in detail.

In this network, the fixed plates 1B, 19 are connected via terminals 24 to the input side of the amplifier 250, and the fixed plates 20.2
1 is connected to the power supply 30 and to a terminal 28 via resistors 26 and 27, and the terminal 28 is connected to the input side of the amplifier 25.

Here, resistors 26 and 27 are defining resistors that are set to a predetermined resistance value during adjustment. Also, the resistor 29 is connected to the support shaft 15.
It is inserted between the terminal 28 and the terminal 28, and is designed to function as an insulation resistance.

Next, referring to FIGS. 3 and 4, the feedback signal detection source 11! I will explain about it.

Figure 3 schematically shows the positional relationship between the conductor plate and each polar plate in the Akti island eta of Figure 2. (a)
(b) is a plan view and a survey map, respectively.

Here, the conductor plate 17 is connected to fixed electrode plates 18 and 19 and fixed electrode plate 2.
0 and 21, the capacitance changes as the lens holder rotates, and constitutes a variable capacitance type angle sensor that detects the rotation angle θ.

For example, when the conductor plate 17 is rotated from angle θ=0 to θ with respect to each electrode plate, the direct product of the conductor portion of the conductor plate 17 with respect to the electrode plate is reduced by the rotation angle of the conductor plate 170.

Next, based on K in FIG. 3(b), how the capacitance changes when changing the position between the conductor plate and each electrode plate will be explained using a mathematical formula.

In FIG. 3(b), the fixed electrode plate 16 and the fixed electrode plate 18
The capacitance between the fixed electrode plates with the conductor plate 14 placed between them is C1, and the insulating part A1 of the lens holder is placed between the fixed electrode plates 17 and 19. If the capacitance between the fixed electrode plates is C2, the total capacitance between the fixed electrode plates is C1+02.

Here, as shown in Figure 3(b), the distance between each electrode plate is d
If l + d2 + d3, (1 = s in ε/(at-+-a3) ・Square (1)
Formula C2= gl-81/(ax+d2+a3)-song-・
(2) Formula here.

C is the dielectric constant in air C1 is the dielectric constant in the laminated layer including the insulating part S is the area of the conductor part Sl is the area of the insulating part.

Also, if the area between the fixed electrode plates is 82, then 5=s2(1
-(2θ/π)), ・・・・・・・・・(3) 2〇1=82(2i9/π) ・・・・・・：・・・(
4) The relational expression of Eq. is established.

Therefore, by substituting equations (3) and (4) into equations (1) and (2), we get C1,182(1-(2θ/π))/(
dl+aa)・・・・・・(5)2C2=l・52(2
θ/π)/(dl+d2+d3)...Equation (6) Therefore, the total capacitance C is (5), and according to Equation (6), C=
01+02 Next, if the electrostatic capacitance C3 when the rotation angle of the conductor plate 14 is set to θ=0, then C3= # 82/ d 1 + d 3 ...
...... Formula (8) and the rotation angle of the conductor plate 18 is 0.
=0 to θ, the amount of change in capacitance ΔC can be converted into a voltage using the bridge circuit shown in FIG.

The operation of this bridge circuit will be explained based on FIG.

When the lens holder A rotates, the variable condenser 31
Alternatively, the capacitance of one of the variable capacitors 32 changes continuously, but when current flows through the bridge circuit consisting of the variable capacitor 31, 32 and the resistor 26, 27, the current flowing through the bridge circuit changes. , terminal 24.
The output voltage between 28 and 28 changes. The voltage output from this sinking and bridge circuit is amplified by an amplifier 25, as shown in FIG. 2, and taken out from the output terminal 14.

Then, as shown in FIG. 1, the output voltage of the output terminal 14 is input to the amplifier 13, and the feedback circuit 33t-
and is input to the actuator 5 to control the driving of the objective lens 60 in a direction perpendicular to the optical axis.

In this way, the present invention applies emoticon feedback using a position sensor to the drive of the optical system.
Unnecessary movement of the optical system due to acceleration can be suppressed, and the position of the spot light can be controlled quickly and accurately.

In the embodiment, driving of the objective lens is illustrated, but the entire optical system including the light source and the like in addition to the objective lens may be configured to be driven.

〔Effect of the invention〕

As explained above, the present invention includes parallel polar plates arranged at a fixed position with respect to the support axis of an optical system holder, and a conductive plate that moves between the parallel polar plates as the optical system holder rotates. Since a capacitive variable type optical system position detection circuit is configured and the drive of the optical system is controlled by this detection signal, when the optical system holder is rotated, it may rotate more than necessary due to acceleration. This makes it possible to quickly and accurately control the position of the optical system.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment in which the present invention is applied to an optical information recording/reproducing device, FIG. 2 is a detailed explanatory diagram of the actuator of the embodiment in FIG. 1, and FIGS. 3(a) and (b) are Figure 1 is a diagram showing the W and principle of position detection in the embodiment, Figure 4 is a diagram showing the principle of position detection in the embodiment.
It is a figure which shows the bridge circuit comprised by the illustrated actuator. Explanation of the symbol '6...Objective lens, 15...Support shaft, A...Lens holder, 17...Conductor plate, 18, 19, 20.21
...Fixed electrode plate. Agent Patent Attorney Johei Yamashita Figure 1

Claims (1)

[Scope of Claims] An optical system holder that holds an optical system and is rotatable about a support axis parallel to the optical axis of the optical system, and an optical system holder that is rotated to move the optical system. an optical system driving device comprising: a parallel polar plate disposed at a fixed position with respect to the support shaft; and a conductive plate that moves between the parallel polar plates as the optical system holder rotates. An optical system driving device, characterized in that the position of the optical system is detected from the capacitance change between the parallel plates, and the driving means is controlled by the detected signal.