JPH0430578Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wobbler for swinging a beam spot in order to obtain a tracking signal in an optical reproducing device.

[Prior Art] When reproducing information recorded on an optical disk, it is necessary for a beam to accurately track a track. Among the methods for obtaining tracking control signals for this purpose, there is a wobbling method. This is a method in which the beam spot is slightly oscillated left and right with respect to the track in order to detect tracking errors.As a result, the carrier wave of the output of the photodetector undergoes amplitude modulation, so its envelope is detected and an appropriate When processed, a DC signal corresponding to the tracking deviation is obtained, and this DC signal is used as the tracking control signal.

FIG. 3 shows a wobbler installed in the optical path of the beam to swing the beam and a drive circuit for the wobbler. In the figure, 1 is the base and base 1
One end of the vibrating member 2 is fixed to. 3 is a mirror, 4 is a drive piezoelectric element, and 5 is a detection piezoelectric element, each of which is attached to the vibrating member 2. The wobbler 10 is configured as described above. 6 is a high gain amplifier whose output voltage is applied to the driving piezoelectric element 4.
The driving piezoelectric element 4 is vibrated in a transverse mode. The vibration is transmitted to the mirror 3 via the vibrating member 2.
Since the mirror 3 is vibrated, the beam irradiated onto the mirror 3 is oscillated and reflected, resulting in a wobbling effect. Further, since the vibration causes the detection piezoelectric element 5 to also vibrate, the detection piezoelectric element 5 generates a voltage according to the vibration. This voltage is fed back to the amplifier 6 to form a closed loop oscillation circuit, so that the oscillation is sustained. FIG. 4 shows the transmission characteristics from the drive piezoelectric element 4 to the vibration member 2 and the detection piezoelectric element 5. ₁ in the diagram,
Since the amplitude peaks at the resonance frequencies ₂ , ₃ , ..., the oscillation circuit oscillates at one of these resonance frequencies. The frequency at which the beam is oscillated needs to be higher than the frequency band of the tracking servo circuit, so usually the second-order resonance frequency ₂
I'm trying to make it oscillate.

[Problem that the invention attempts to solve]

As described above, even if the wobbler 10 is configured to oscillate at the secondary resonance frequency ₂ , it may oscillate at another resonance frequency. The amplitude peak at the third-order or higher resonance frequency is relatively small, so oscillation at this frequency is rare, but the magnitude of the resonance frequency peak changes due to variations in the attachment position of the piezoelectric element or mirror, etc. Next resonant frequency
₁ often oscillates.

FIG. 5 shows the vibration state of the vibrating member 2 in the second-order mode when a voltage at the second-order resonance frequency is applied to the drive piezoelectric element 4. In FIG. 5A, the upper part of the vibrating member 2 is expanded and the lower part is contracted. FIG. 5B shows a case where the supply voltage is in reverse phase, and the upper part of the vibrating member 2 is contracted and the lower part is expanded. In this way, even when the driving piezoelectric element 4 is expanded, for example, a part of the vibrating member 2 is in a contracted state, so there is a problem that the driving force of the driving piezoelectric element 4 is not effectively acting on the vibrating member 2. .

The present invention aims to ensure that the vibrating member 2 vibrates at the secondary resonance frequency and to improve the efficiency of the driving force.

[Means to solve the problem]

This invention uses a vibrating member with one end fixed to the base.
When attaching the detection voltage element, mirror, and drive piezoelectric element, the drive piezoelectric element is divided into two parts. When these two divided drive piezoelectric elements are polarized in opposite directions, the same phase voltage is supplied to both elements. Furthermore, when two divided driving piezoelectric elements having the same polarization direction are used, voltages of opposite phases are supplied to each other. By doing this, when one of the two-split driving piezoelectric elements expands, the other one contracts, so that the vibration state matches the second-order mode of the vibrating member.

〔Example〕

FIG. 1 shows an embodiment of the wobbler of the present invention.

The same parts in FIG. 1 as in FIG. 3 are given the same symbols, and their explanation will be omitted. The difference between FIG. 1 and FIG. 3 is that a first driving piezoelectric element 11 and a second driving piezoelectric element 12 are used instead of the driving piezoelectric element 4 in FIG. 3. Here, the first and second driving piezoelectric elements 11 and 12 are those having polarization directions opposite to each other. The amplifier 6 supplies the first and second driving piezoelectric elements 11 and 12 with voltages that are in phase with each other, but the polarization directions of the first and second driving piezoelectric elements 11 and 12 are opposite to each other. When one expands, the other contracts. This driving force is applied to the vibrating member 2, so if, for example, the first driving piezoelectric element 11 expands and the second driving piezoelectric element 12 contracts, the upper part of the vibrating member 2 from the center will expand, The lower part contracts and vibrates in the second mode. Therefore, the amplifier 6 outputs a voltage at the second-order resonance frequency ₂ shown in FIG. 4 to ensure vibration in the second-order mode. Therefore, the transfer characteristic from the first or second drive piezoelectric element 11 or 12 to the detection piezoelectric element 5 becomes as shown in FIG. 2, and the peak at the resonance frequency ₂ becomes extremely large.

Further, since the upward or downward expansion or contraction of the vibrating member 2 coincides with the expansion or contraction of the first or second drive piezoelectric element, the first and second drive piezoelectric elements 11 and 12 are driven. The force will effectively act on the vibrating member 2.

In the above example, the first and second driving piezoelectric elements 1
Although 1 and 12 were used with opposite polarization directions, they may also be used with the same polarization direction. However, in this case, the first and second driving piezoelectric elements 11
and 12 are applied with voltages of opposite phases to each other.

FIG. 6 shows another embodiment, in which 13 is a driving piezoelectric element. This drive piezoelectric element 13 is different from the piezoelectric element itself divided into two parts as in each of the above-mentioned examples. , 13b
divides the device into an upper half and a lower half.
If the upper and lower halves of the element are polarized in opposite directions, apply a voltage of the same phase, and if they are polarized in the same direction, apply a voltage of opposite phase to produce the same result as in the above example. can be made to work.

[Effect of idea]

In the wobrator of the present invention, the driving piezoelectric element is divided into two as described above, and when one expands, the other contracts, so that the vibration state of the second mode of the vibrating member and the driving force match. , the efficiency of the driving force is increased and the vibrating member can be reliably vibrated at the secondary resonance frequency.

[Brief explanation of the drawing]

Figure 1 shows the wobbler of the present invention and its drive circuit, Figure 2 shows the transmission characteristics of the wobrator of the present invention,
Figure 3 shows a conventional wobbler and its drive circuit, Figure 4 shows the transmission characteristics of the conventional wobrator, Figure 5 shows the vibration state of the second-order mode of the vibrating member of the wobrator, and Figure 6a shows another embodiment of the present invention. FIG. 6b is a side view of an exemplary wobbler, and FIG. 6b is a front view thereof. 1... Base, 2... Vibration member, 3... Mirror,
5... piezoelectric element for detection, 10... wobbler,
11, 12...First and second driving piezoelectric elements.

Claims (1)

[Claims for Utility Model Registration] (1) A vibrating member having one end fixed to a base, a first driving piezoelectric element, and b a second driving piezoelectric element having a polarization direction opposite to that of the first driving piezoelectric element. A wobbler comprising: a driving piezoelectric element, c a detection piezoelectric element, and d a mirror, each element being attached thereto, and in-phase voltages being supplied to the first and second driving piezoelectric elements, respectively. (2) Utility model registration claim 1, characterized in that the first and second driving piezoelectric elements have the same polarization direction and supply voltages of opposite phases to each other.
The wobbler described in section. (3) The wobbler according to claim 1 or 2, wherein the first and second driving piezoelectric elements are formed of a single element that communicates with each other.