JPS61285424A - Optical beam deflector - Google Patents

Abstract

PURPOSE:To obtain a comparatively large displaced variable quantity by fixing respective base ends of bimorph type piezo-electric elements on a base board so that respective terminals are displaced in the contacting/separating direction with/from the base board and supporting a reflection mirror to reflect an optical beam by the mirror. CONSTITUTION:Three projection parts 11-13 are formed on one side surface of the cylindrical base board 10 having 15mm inner diameter and 25mm outer diameter and made of metal such as SUS and titanium. Respective base ends of the bimorph type piezo-electric elements 21-23 are fixed on the projection parts 11-13 with a bonding agent. The elements 21-23 are shaped like circular arcs and respective leading ends are extended in the circumferential direction of the base board 10 so as to be displaced. One electrode plate of the elements 21-23 is connected to terminals 41-43 through lead wires 31-33 and the other electrode plate is connected to the conductive part of the base board. The conductive part is connected to a terminal through a lead wire 34 and three corner parts 51-53 of an optical beam reflecting mirror 50 shaped like a regular triangle are supported by the respective leading end parts of the elements 21-23 through flexible members.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light beam deflector that deflects a light beam such as a laser beam to a predetermined angle, and particularly relates to an improvement in an actuator that drives and controls the angle of a reflecting mirror.

[Conventional technology]

Laser inspection equipment for fine patterns such as LSI.

A light beam deflector used in a laser character drawing device, a laser microscope, etc. requires a scanner that scans a laser light beam in the X-Y direction. As an actuator for driving the reflecting mirror fl1m in this scanner,
Piezoelectric actuators using piezoelectric elements are being researched.

FIG. 3 is a perspective view showing an example of a conventional piezoelectric actuator that has been researched and developed to date. In Figure 3, 1
is a base, and on this base 1, four laminated piezoelectric elements 2a to 2d are arranged so as to be located at each corner of a square. Each of the tip portions of four meters 3a to 3d of a reflecting mirror 3 is coupled to the upper end of each of these laminated piezoelectric elements 2a to 2d.

In the piezoelectric actuator having the above configuration, when voltages with opposite polarities are simultaneously applied to the stacked piezoelectric elements 2b and 2d while no voltage is applied to the stacked piezoelectric elements 2a and 2C, the reflecting mirror 3 is centered around the X axis. Rotate to. Further, contrary to the above, when a voltage of opposite polarity is applied to the laminated piezoelectric elements 2a and 2c while no voltage is applied to the laminated piezoelectric elements 2b and 2d, the reflecting mirror 3 rotates around the Y axis. . In this way, the voltage applied to the laminated piezoelectric elements 2a to 2d is appropriately controlled, and the upper ends of the laminated piezoelectric elements 2a to 2d are expanded and contracted in the vertical direction as shown by the arrows, thereby controlling the angle of the reflecting mirror 3 to be sequentially changed. As a result, the laser beam is deflected by the reflecting mirror 3, and XY scanning is performed. Note that since the laminated piezoelectric elements 2a to 2d are formed of lead zirconate titanate (PZT), which is a ferroelectric material, they have so-called hysteresis characteristics. Therefore, when the above piezoelectric actuator is put into practical use, it is necessary to configure a closed-loop system with a high-precision position sensor, and adjust the applied voltage based on the signal from the sensor to avoid the effects of hysteresis. Size needs to be controlled. As a means to solve the above-mentioned problem of hysteresis, it is possible to use electrostrictive elements that do not have hysteresis characteristics instead of the laminated piezoelectric elements 2a to 2d. However, as shown by curve A and 8 in FIG. 4, the electrostrictive element has significantly poorer temperature characteristics than the piezoelectric element. For this reason, special temperature compensation means must be provided, making it difficult to put it into practical use.

[Problem that the invention seeks to solve]

The piezoelectric actuator described above has advantages over other types of actuators, such as: ■ High-speed response is possible; ■ Random scanning is easy; ■ The structure is compact and lightweight. be. However, there were the following problems to be solved.

(1) Laminated piezoelectric elements 2a to 2d have a voltage of 500 [V]
, 100 [&] voltage is applied, and only a deflection angle of about E'-F 5.6 [m, ra(l) can be obtained, which has the disadvantage that the deflection angle is relatively small. As shown by lines C and D in Figure 5, laminated piezoelectric elements generally have smaller displacements with respect to applied voltage than bimorph piezoelectric elements.The characteristics in Figure 4 are obtained when hysteresis is compensated for in a closed loop. belongs to.

(2) The displacement force generated by a laminated piezoelectric element is much larger than that of a bimorph piezoelectric element or the like. However, the object to be driven is the relatively light reflecting mirror 3.

Therefore, a very large displacement force is not required.

Laminated piezoelectric elements are suitable for actuators that require large torques, such as X-Y stages, but they are suitable for use in actuators for optical beam scanners that require large amounts of displacement. The force is too excessive and not appropriate. In other words, it cannot be said that the characteristics of the laminated piezoelectric element are effectively utilized, and there is a problem that there is a large amount of waste.

(3) The multilayer piezoelectric elements 2a to 2d require complicated processes such as stacking a large number of thin piezoelectric ceramics and connecting the stacked piezoelectric ceramics in parallel using lead wires, resulting in high costs. There is a drawback.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light beam deflector equipped with a piezoelectric actuator that can obtain a large deflection angle, perform efficient drive control, and can be manufactured at low cost.

[Means for solving problems]

The present invention is characterized by taking the following measures in order to solve the above problems and achieve the objects.

That is, in the light beam deflector of the present invention, each base end of a bimorph piezoelectric element is fixed on a base, and each tip of the bimorph piezoelectric element is movable in a direction toward and away from the base. The present invention is characterized in that a piezoelectric actuator is provided so that a reflecting mirror is supported by each tip of these bimorph piezoelectric elements, and a light beam is reflected by the reflecting mirror.

[Effect]

By taking such measures, a relatively large amount of displacement can be easily obtained, and the displacement force of the bimorph piezoelectric element has a magnitude just suitable for driving the reflecting mirror. 4. Also, there is no need for a stacking process as in the case of using a stacked piezoelectric element, and the parallel connection process is also significantly simplified.

〔Example〕

FIGS. 1(a) to (C) are diagrams showing the configuration of main parts of an embodiment of the present invention, in which (a) is a perspective view of a piezoelectric actuator in a light beam deflector, and (b) is a diagram of the above-mentioned piezoelectric actuator. FIG. 3 is a plan view of the piezoelectric actuator seen from directly above, and FIG.

In Fig. 1 (a) to (C), 10 is made of metal such as SUS or titanium, resin such as acrylic or epoxy, ceramics such as silicon nitride or alumina, etc., with an inner diameter of 15 mm and an outer diameter of 25 mm. It is a base having an annular shape with a limit φ, and three protrusions 11 to 13 are provided on the negative side surface thereof. Note that when the base 10 is formed of a non-conductive material, a conductive film is formed on its surface by means such as plating, so that at least a portion thereof is provided with a conductive part. The respective base ends of bimorph piezoelectric elements 21 to 23 are adhesively fixed to the projections 11 to 13 using an adhesive such as epoxy resin. The bimorph piezoelectric elements 21 to 23 have an arc shape, and each tip portion extends along the circumferential direction of the base 10, and the tip extends toward and away from one side of the base 10. It is provided so that it can be displaced. One electrode plate of each of the bimorph piezoelectric elements 21 to 23 is connected to terminals 41 to 43 via lead wires 31 to 33, respectively, and each other electrode plate is connected to a conductive part of the base 1o. . The conductive portion is connected to a terminal 44 via a lead wire 34. Reference numeral 50 denotes a reflection mirror for reflecting a light beam in the form of an equilateral triangle, and three corners 51 to 53 are supported at the tips of the bimorph piezoelectric elements 21 to 23, respectively.

Note that the corner portions 51 to 53 and the tip of the bimorph piezoelectric element 21 are not firmly connected and fixed, but are connected via a flexible member such as silicone rubber.

Figure 2 (a) and (b) show bimorph type piezoelectric elements 21 to 23.
FIG. 3 is a side view showing an example of the structure. (a) is a diagram showing a bimorph type piezoelectric element 60 having a parallel structure. This bimorph type piezoelectric element 60 is made by bonding piezoelectric ceramics 61 and 62 so that the polarization directions face the same direction as shown by the arrows, and connecting the electrode plate 63 on the bonded surface to the terminal T1 corresponding to the terminals 41 to 43. , the respective electrode plates 64 and 65 on the non-bonded surface side are short-circuited and connected to the terminal T2 corresponding to the terminal 44.

(b) is a diagram showing the structure of a bimorph type piezoelectric element 70 having a series structure. This bimorph type piezoelectric element 70 has a pair of piezoelectric ceramics 71 and 72 bonded so that their polarization directions are opposite as shown by the arrows, and one electrode plate 74 on the non-bonded side corresponds to the terminals 41 to 43. The other electrode plate 75 is connected to the terminal T1, and the other electrode plate 75 is connected to the terminal T1 corresponding to the terminal 44.
Connected to 2. In order to ensure mechanical strength,
Actually, between piezoelectric ceramics 61.62 and 71.
In many cases, a reinforcing material such as a thin metal plate is sandwiched between the parts 72. In addition to the above, piezoelectric ceramics and non-piezoelectric ceramics such as metals and plastics are joined together,
Connect the electrode plates on both sides of the piezoelectric ceramic to terminals T1. There is also a structure connected to T2.

Bimorph type piezoelectric element 6 with parallel structure shown in FIG. 2(a)
0 and the bimorph type piezoelectric element 70 having a series structure shown in FIG. 3(b), (a) is more suitable when obtaining a large amount of displacement by applying a voltage. Therefore, in the following explanation of this embodiment, the case will be explained assuming that (a) is used.

The displacement amount ΔX of the bimorph piezoelectric element 6o and the generated displacement force ΔF are: Δx−3℃2 ・d31−V/12 (1) ΔF
=36t-Vd31 ・E/4j2= (2) However,
E: Young's modulus, J2: length of bimorph piezoelectric element, t
: Thickness of the bimorph piezoelectric element.

For comparison, the displacement amount ΔX of the laminated piezoelectric element and the generated displacement force ΔF are shown as follows: Δx-n-d33-V (3) ΔF-8-E
627° C. (4) where Δ2: displacement amount of the two-layer piezoelectric element.

As can be seen from the comparison of equations (1) and (3) above, the displacement of the laminated piezoelectric element is unrelated to the size and shape;
The displacement of the bimorph piezoelectric element is the dimensions (length a1 thickness t)
depends on the size of Therefore, in the case of a bimorph type piezoelectric element, it is possible to obtain a relatively large displacement depending on the shape.

For example, if the length 2 is increased and the thickness t is decreased, the displacement ΔX
can be made larger. However, in this case, as can be seen from equation (2), the generated displacement force ΔF becomes smaller. Therefore, the dimensions and shape of the bimorph piezoelectric element 60 are set so that the displacement amount ΔX is maximum within a range where the displacement force ΔF has a size that does not cause any problem in driving the reflecting mirror 50 shown in FIG. do it.

According to this embodiment configured in this way, FIG. 1(a)
- Each bimorph type piezoelectric element 21 to 23 shown in (C),
For example, no voltage is applied to the bimorph piezoelectric element 21,
When a voltage of +100 [V] is applied to the bimorph type piezoelectric element 22 and a voltage of -100 [V] is applied to the bimorph type piezoelectric element 23, a displacement of approximately 200 μl occurs in the bimorph type piezoelectric elements 22 and 23 in opposite directions. . As a result, the reflecting mirror 50 rotates around the broken line in FIG. 1(b), producing an inclination of θ as shown in FIG. 1(c). As a result, the deflection angle 20 [m, ra
dl is obtained. In this respect, in the case of a laminated piezoelectric element, 5
When a voltage of 00 [V] was applied to -r, a deflection angle of only about 5.6 [m, rad] was obtained, but the deflection angle was significantly improved.

By the way, in this embodiment, the bimorph type piezoelectric element 2
Since 1 to 23 are arcuate, there is an advantage that the entire piezoelectric element can be made smaller than when a linear bimorph piezoelectric element is used, even when the same bimorph length 2 is maintained. Three more bimorph piezoelectric elements 21 to 23
Since the reflecting mirror 50 is supported at three points, the reflecting mirror 50 can be stably supported, and the reflecting mirror 50 can be prevented from being distorted without applying a high-precision voltage. It has the advantage that it can be easily deflected in any direction.

Note that the present invention is not limited to the above embodiment. For example, although an arc-shaped bimorph piezoelectric element is shown, it is not necessarily limited to an arc-shaped one, and may be a straight-line one. Further, the number of bimorph type piezoelectric elements is not limited to three, but may be two or four or more, as long as they are plural.

Furthermore, the means for supporting the reflecting mirror, etc. can be modified as appropriate. It goes without saying that various other modifications can be made without departing from the gist of the present invention.

〔Effect of the invention〕

In the light beam deflector of the present invention, each base end of a bimorph piezoelectric element is fixed on a base, and each tip of the bimorph piezoelectric element is movable in a direction toward and away from the base. A piezoelectric actuator is provided so that a reflecting mirror is supported by each tip of these bimorph piezoelectric elements, and a light beam is reflected by the reflecting mirror.

Therefore, according to the present invention, a relatively large amount of displacement can be easily obtained, and the displacement force of the bimorph piezoelectric element has a magnitude just suitable for driving the reflecting mirror. Furthermore, the lamination process that is required when using a laminated piezoelectric element is completely unnecessary, and the parallel connection process is also significantly simplified.

As a result, it is possible to provide a light beam deflector equipped with a piezoelectric actuator that can obtain a large deflection angle, perform efficient drive control, and can be manufactured at low cost.

[Brief explanation of drawings]

FIGS. 1(a), (b), and (c) are diagrams showing the configuration of the main parts in an embodiment of the present invention, and FIGS. 2(a) and (b) are structural examples of the bimorph type piezoelectric element of the same embodiment. FIG. 3 is a perspective view showing the configuration of the conventional example, and FIGS. 4 and 5 are characteristic diagrams for explaining the problems of the conventional example. 1... Base, 2a to 2d... Laminated piezoelectric element, 3.
... Reflection mirror, 3a to 3d... Leg portion, 10... Base, 11 to 13... Projection, 21 to 23... Bimorph type piezoelectric element, 31 to 34... Lead wire, 41-4
4...Terminal, 50...Reflection mirror, 51-53...
・Corner part, 60... bimorph type piezoelectric element with parallel structure,
70...Series structured bimorph piezoelectric element, 61.6
2 and 71.72...piezoelectric ceramics, 63-6
5 and 73-75...electrode plate, T1. T2...terminal. Applicant's representative Patent attorney Atsushi Tsuboi Figure 1 °7 Figure 2 Figure 3 Figure 4 - OC Shijo 4L and (V) Figure 5

Claims (1)

[Claims] A base, bimorph piezoelectric elements each having its base end fixed on the base and disposed such that its tip end can be moved in a direction toward and away from the base, and the bimorph piezoelectric element A light beam deflector comprising a piezoelectric actuator comprising a reflecting mirror supported by each tip and provided to reflect a light beam.