JPH01109536A - Angle fine adjusting mechanism - Google Patents

Abstract

PURPOSE:To obtain an angle fine adjusting mechanism to be able to maintain a neutral point under zero voltage by equipping the title device with a movable block supported with two laminating-type piezoelectric actuators, which are position-adjustable symmetrically to the middle line of a fixed block, and two rigid thin band plates. CONSTITUTION:Two laminating-type piezoelectric actuators 2 and 3 are arranged in parallel in their expanding direction, and while a fixed block 4 is provided at an interval (d) between each of the actuators and the block 4, a movable block 5 is provided, which is press-contacted on the other edge of the device, at symmetrical positions to the medium line of each block, two rigid thin band plates 7 and 8, which can expand minutely, are linked to the fixed block 4 and the movable block 5. Since the actuators 2 and 3 are held so that the interval (d) between the block 4 and each of them can be adjusted with push screws 9 and 10, the actuators 2 and 3 can set the initial angle (the angle to be the neutral point) and can accurately fine-adjust angles alpha and betato correspond to the difference in voltage to be impressed.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an angle control mechanism, and in particular to a fine angle adjustment mechanism suitable for use in controlling the light spot position of a two-beam optical head. In order to provide a mechanism for finely adjusting the angle of a laminated piezoelectric actuator that can be maintained at a constant angle, two laminated piezoelectric actuators are arranged in parallel in the direction of expansion and contraction, and a fixing block is provided at one end of the laminated piezoelectric actuator with a gap therebetween. At the same time, a movable block is provided that presses against the other end,
In a plane including the central axes of each of the laminated piezoelectric actuators, two microstretchable rigid thin strip plates facing each other in symmetrical positions with respect to the median line of each of the central axes are connected to the fixed block and the movable block. The fixing block is provided with a push screw that can adjust the gap and holds the laminated piezoelectric actuator.

[Industrial application field]

The present invention relates to an angle control mechanism, and particularly to an angle fine adjustment mechanism suitable for use in controlling the light spot position of a two-beam optical head.

The optical head of modern optical disk devices has a recording beam for recording information on a recording medium, and a beam that checks whether the recorded information is accurately recorded immediately after recording to confirm the authenticity of the recording. A two-beam system has been adopted in which recording and playback are performed simultaneously using a playback beam that performs checking, and it is desired to develop a means for fine adjustment to accurately control the positions of two light spots on the same track. .

[Conventional technology]

A piece of piezoelectric material obtained by molding and sintering metal oxide powder such as ternary zircon/lead titanate powder using a powder metallurgy method is shaped into an appropriate shape.

A magnetic element that is processed into a size, has metal electrodes closely attached to two opposing surfaces for the purpose of polarization and driving, and applies a DC high voltage between these two electrodes to create residual polarization and residual strain inside. A so-called ceramic laminated piezoelectric actuator made of laminated layers is widely used as an actuator for precision fine adjustment equipment.

The ferroelectric crystal that constitutes the piezoelectric ceramic has dipole efficiency, and its direction is constant. In this sintered body, the sintering axis is statistically distributed in all directions in the sintered state, but when a high DC voltage is applied to it, the direction of the dipoles is aligned in the direction of the electric field, and the crystal as a whole is aligned in the direction of the electric field. It stretches in the direction and contracts in the perpendicular direction. This state remains fixed inside the crystal even if the external electric field is removed. This is called residual polarization. When an alternating electric field is applied from the outside to an element body with residual polarization, the element body expands and contracts in the polarization direction according to the magnitude of the electric field, and this displacement is used for precise fine adjustment.

[Problem that the invention seeks to solve]

A laminated piezoelectric actuator can be expanded in its polarization direction by applying a voltage, but has the disadvantage that it cannot be contracted by applying a voltage of opposite polarity.

Therefore, when you want to make fine adjustments in both directions based on a certain neutral point, such as when adjusting the angle, the neutral point must be set at a place where a certain voltage is applied, and when no voltage is applied, it will be biased to one side, and the machine The disadvantage is that it is not possible to maintain a neutral point.

The present invention has been made in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a fine angle adjustment mechanism for a laminated piezoelectric actuator that can maintain a neutral point at zero voltage.

[Means for solving problems]

FIG. 1 is a principle diagram of the angle fine adjustment mechanism 1 of the present invention. 2
The laminated piezoelectric actuators 2 and 3 are arranged in parallel in the direction of expansion and contraction, and a fixed block 4 is provided with a gap d between one end of the laminated piezoelectric actuator 2.3, and a movable block 5 is pressed against the other end. Two micro-expandable rigid thin strip plates 7.8 are provided, and are arranged in a plane including the central axis of each of the laminated piezoelectric actuators 2.3, facing each other at symmetrical positions with respect to the median line 6 of each of the central axes. is connected to the fixed block 4 and the movable block 5, and the fixed block 4 is provided with push screws 9.degree. 10 which can adjust the gap d and hold the laminated piezoelectric actuators 2 and 3.

[For production]

By adjusting the push screws 9 and 10, the initial angle of the movable surface 11 (the angle that becomes the neutral point) can be set.

When a voltage is applied to the laminated piezoelectric actuator 2 in this state, a displacement a1 corresponding to the voltage is generated around the position b0 against the tension of the rigid thin strip plate 7, and the movable surface 1
0 can be finely adjusted by angle α. Furthermore, when a voltage is applied to the laminated piezoelectric actuator 3, the displacement b corresponding to the voltage
1 is generated around the position a0 against the tension of the rigid thin strip plate 8, and the movable surface 11 can be finely adjusted by an angle β. Of course, if a voltage is applied to both the laminated piezoelectric actuators 2 and 3, a change in the angle of the movable surface corresponding to the difference in voltage can be obtained. The fine angle adjustment mechanism 1 is attached to a device using the mechanism of the present invention through a hole 12.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Note that, in order to make the explanation of the configuration and operation easier to understand, the same parts are given the same reference numerals throughout all the figures, and repeated explanation thereof will be omitted.

FIG. 1 shows a principle diagram of the angle fine adjustment mechanism of the present invention.

In the figure, the angle fine adjustment mechanism 1 includes two laminated piezoelectric elements 2 and 3 arranged in parallel in the expansion/contraction direction, a fixed block 4 provided at one end with a gap d in between, and a movable block 5 pressed against the other end. and two micro-stretchable rigid thin strip plates 7., which face each other at symmetrical positions with respect to the median line 6 of each central axis within a plane containing the central axis of each laminated piezoelectric actuator 2.3.
8 to the fixed block 4 and the movable block 5, a push screw 9 capable of adjusting the gap d to the fixed block 4, and holding the laminated piezoelectric actuator 2.3.
．． It consists of 10.

The fixed block 4 and the movable block 5 are rigid bodies that do not deform, and a rigid ribbon Fi7 connects the two blocks.

For example, a thin stainless steel plate having a thickness of 0.2 to 0.5 mm is used as the material 8. 9a and lOa, after initializing the laminated piezoelectric actuator 2.3 with push screws 9.10,
This is a lock nut for fixing. The end face of the movable block 5 is used as a movable surface 11 for finely adjusting the angle. The fine angle adjustment mechanism 1 is attached to a device using the mechanism of the present invention through a hole 12.

FIG. 2 shows a detailed illustration of the invention. This figure relates to a light spot position control mechanism for a preferred two-beam type optical head using the angle fine adjustment mechanism of the present invention. This optical head is an improved version of the one disclosed in Japanese Patent Application Laid-Open No. 60-101734, and has multiple light sources for reading, writing, erasing information, or checking for errors immediately after writing, and has angles formed by the optical axes of each light beam. This is an optical head for an optical disk device that is equipped with a mechanism that can adjust the position of each light spot on a recording medium by changing the optical axis angle of one or each of the following.

In the figure, a recording laser beam W modulated by recording information generated by a recording laser generator 14 passes through a collimating lens 15 and is deflected in the normal optical path direction by a recording beam deflector Fi 16, and is then deflected by a polarizing beam splitter on the optical path. 21 and the 174-wave plate 22 to reach the objective lens 23. The objective lens 23 focuses the incident recording laser beam W, sets its focus on a predetermined track of the optical recording medium 24, and records information.

On the other hand, the reproducing laser beam M generated by the reproducing laser generator 17 passes through the collimating lens 18, is deflected by the reproducing beam deflecting plate 19 in the normal optical path direction, and passes through the gicroic mirror 20 onto the optical path. The light passes through a polarizing beam splitter 21 and a 174-wave plate 22 and reaches an objective lens 23. Here, the objective lens 23 focuses the incident reproduction laser beam M and directs the focus onto the optical recording medium 2
irradiate according to a predetermined track.

This irradiated light is modulated by the information recorded on the track, becomes reflected light Z, is deflected through a 90 degree optical path via a 174 wavelength plate 22 and a polarizing beam splitter 21, passes through a filter 25, and is condensed. The light is focused by the lens 26,
The photodetector 27 is reached. The reflected light Z is converted into an electrical signal by the photodetector 27, and the information recorded on the optical recording medium 24 is reproduced.

The purpose of this reproducing process is to confirm the reliability of the information recorded on the optical recording medium immediately after recording. Therefore, the reproducing beam M is placed immediately after the focal point of the recording beam W on the same circumferential track. The focus needs to be located.

Here, the polarization plane of the polarization beam splitter 21 is set so that a portion of the recording laser beam W and reproduction laser beam M that pass through the polarization beam splitter 21 is deflected by 90 degrees in the opposite direction to the filter 25, and the polarization plane of the polarization beam splitter 21 is Laser light W
A condenser lens 28 condenses the recording laser beam M1 and the reproduction laser beam h1, and detects the light intensity of the recording laser beam M1 and the reproduction laser beam M1 condensed by the condenser lens 28, and generates a focal position signal of each laser beam. A two-light spot tracking error signal detection circuit 29 is provided which outputs the following.

The two-light spot trunk error signal detection circuit 29 determines the relative amount of track error for one of the two light spots, and controls the angle fine adjustment mechanism 1 via the control circuit 30 so as to set this track error amount to zero. and reproduce beam M
This is to correct the positional deviation.

FIG. 3 is a diagram for explaining the actual dimensions of the positional relationship of a plurality of light spots on a track. FIG. 3(a) shows the position of the light spot in the radial direction of the recording medium, and FIG. 3(b) shows the position of the light spot in the circumferential direction of the recording medium.

Assuming that the focal length of the objective lens 23 in both figures is 4 mm, and the angle formed by the optical axes of both beams in FIG.
．． 7 Xl0-3 degrees, Lt=0±0. O5l1m Fig. 3 (The angle formed by the optical axes of both beams at bl is θC9
Letting Lc be the distance between the two light spots, both normally take the following values within an error range of ±10%.

θc = 0.1 to 0.4 degrees, Lc = number - to number 10 - In this way, apart from the circumferential direction of the recording medium, alignment of both the angle and distance in the radial direction of the optical recording medium is possible with very high precision. Although necessary, if the reproducing beam deflection plate 19 is attached to the movable surface 11 of the angle fine adjustment mechanism 1, the recording beam W is fixed, and the incident angle of the reproducing beam M to the dichroic mirror 20 is adjusted by ml, this light can be adjusted. Axial angle difference is ±0.01
It is possible to accurately change the range of about 0.0001 degrees, and the beam spot position on the track can be controlled.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in addition to the many features of the laminated piezoelectric actuator, it can be maintained at a neutral point without applying voltage, so when there is a problem on the control side or when control is started. It is maintained close to the control point even when the power is turned on. Further, one of the drawbacks of the laminated piezoelectric actuator is that the control voltage is high, but the present invention has the advantage that the voltage required for control can be reduced to 1/2 or less.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the angle fine adjustment mechanism of the present invention, FIG. 2 is a detailed explanatory diagram of the present invention, and FIG. 3 is an explanatory diagram of the positional relationship of a plurality of light spots on a track. In Fig. 1, 2 and 3 are laminated piezoelectric actuators,
4 is a fixed block, 5 is a movable block, 6 is an intermediate line, 7
and 8 are rigid thin strip plates, 9 and 10 are push screws, and d is a gap, respectively. Summer □ 22 (Q) Kyuto 1 yū yū ban sā shun tb) Eki kanchu fuen kai ka sha-ra-t 7 j: q child is taught. ]
Figure 3

Claims (1)

[Claims] Two laminated piezoelectric actuators (2, 3) are arranged in parallel in the direction of expansion and contraction, and a fixed block ( 4), and a movable block (5) that is pressed into contact with the other end, and within a plane including the central axes of each of the laminated piezoelectric actuators (2, 3), on the midline (6) of each of the central axes. Two micro-stretchable rigid thin strip plates (7
, 8) to the fixed block (4) and the movable block (5).
, and the fixing block (4) is provided with push screws (9, 10) that are capable of adjusting the gap (d) and hold the laminated piezoelectric actuators (2, 3). Angle fine adjustment mechanism.