JPH04343318A - Torsional vibrator - Google Patents

Abstract

PURPOSE:To provide the torsional vibrator of a thin type which can be driven by a low voltage and at a high speed, and by which a large deflection angle is obtained. CONSTITUTION:The torsional vibrator is provided with a sheet-like plate member 1 having a first and a second movable electrodes of a comb-teeth shape laminated through an insulating film, holding members 3a, 3b joined to the plate member 1 and a substrate 7 on a shaft passing through the centroid of this plate member 1, and fixed electrodes 5a, 5b (5b is omitted from showing it in the figure) of a comb-teeth shape, which are engaged to comb teeth of the plate member 1 and have sufficient thickness, comparing with the plate member 1, and by impressing a voltage between a first and a second movable electrodes and the fixed electrodes 5a, 5b, the plate member 1 becomes rotatable in the periphery of the holding members 3a, 3b.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torsional vibrator that can be applied to optical scanning of optical equipment.

0002

[Prior Art] Conventionally, as an element of this type, for example, there is an optical scanning element (optical deflector) which is electromagnetically driven by attaching a reflecting mirror and a driving coil to a span band. The disadvantage is that it is difficult to miniaturize because it requires assembly. As one method for solving this drawback, it is known that the span band and the reflection mirror are integrally formed. FIG. 7 shows such a device, for example, IBM “R&D” VOL.
．． 24, p631, '80. In the figure, 21 is a spun band 22a made from a silicon plate.
, 22b and a reflecting mirror 23 are integrally formed,
24 is a glass substrate. The reflective mirror 23 is in contact with the protrusion 25 of the substrate 24 at its center, but a constant gap is maintained between the left and right sides by the depressions 26. 27a,
Reference numeral 27b denotes an electrode provided on the substrate 24. By applying a voltage from the outside between one electrode and the mirror 23 by an appropriate means, the mirror 23 is attracted by electrostatic attraction and tilted. The light that hits will be scanned as shown by the arrow in FIG. 7(b). In other words, when the mirror 23 is tilted left and right by φ, the light is deflected by 2φ.

[0003] Such a device can be easily miniaturized by simply installing electrodes with a certain gap in order to drive the reflecting mirror, but the deflection angle of the reflecting mirror is determined by the distance between the gaps. . In order to increase the deflection angle of this reflecting mirror, it is necessary to deepen the recess and increase the gap distance, but in order to obtain a constant electrostatic attraction, a voltage proportional to the square of the gap distance must be applied. Therefore, there is a problem that it is difficult to achieve both an increase in the deflection angle and low voltage driving. Therefore, the applicant proposed a device as shown in Figure 8 (hereinafter also referred to as the proposed device).
are doing. In addition, the same figure (a) is a perspective view, and the same figure (b) is the sectional view. As shown in FIG. 3A, this device includes a frame 36 made of an insulating material, a fixed electrode 35 made of a silicon substrate 37 bonded to the frame, a plate member 31, a beam 33 as a holding member, and a movable part. The fixing material 34 is integrally formed by a photo-etching process, and the torsional vibrator 3
It constitutes 0. Furthermore, as shown in FIG. 3(B), the plate member 31 is pushed up by the support member 38, and a step X is provided by leaving a slight overlap between the movable electrode 32 and the fixed electrode 35, so that one fixed electrode 35 and the movable electrode 32 By applying a voltage between them, the reflective mirror 31A installed on the plate member 31 is rotated about the support member 38. In this way, the driving force is obtained from the comb-teeth electrode with steps, making it compact and lightweight.Moreover, by increasing the step, the deflection angle can be increased, and furthermore, by increasing the number of comb-teeth, it is possible to drive at a low voltage. becomes possible.

0004

[Problem to be Solved by the Invention] However, in order to increase the swing angle of such a device, it is necessary to thicken the plate member, which increases the moment of inertia around the rotation axis and lowers the frequency. Therefore, there is a problem that there is a limit to the improvement of optical scanning speed. Therefore, an object of the present invention is to provide a device that can be driven at a lower voltage and at higher speed than the proposed device, is thinner, and can obtain a larger deflection angle.

[0005]

[Means for Solving the Problems] In order to solve the problems, the present invention provides a plate-like member having at its ends first and second comb-shaped movable electrodes formed with an insulating film sandwiched therebetween; The present invention is characterized in that it includes a pair of holding members that connect the plate-like member to a fixed substrate, and a fixed electrode having comb teeth that mesh with the comb teeth formed on the plate-like member. Further, the fixed electrode is characterized in that one or more fixed electrodes having the same comb teeth are stacked on top of each other.

[0006]

[Operation] When a voltage is applied between two movable electrodes and a fixed electrode, an electrostatic force is applied perpendicularly outward to each other on the surfaces of the two movable electrodes according to the potential difference between them and the fixed electrode. By setting the potential difference between one electrode and the fixed electrode to be larger than the potential difference between the plate-shaped member and the fixed electrode, the plate-like member is rotated about the holding member by the vertical outward torque generated on the other electrode. The electrostatic force acting on one electrode is the same in the opposing comb-shaped fixed electrodes, so by increasing the thickness of the fixed electrode, the deflection angle can be increased by that amount, and the electrostatic force is Since it acts on the comb teeth of the movable electrode, by increasing the number of comb teeth, it becomes possible to drive at a low voltage.

[0007]

[Embodiment] Fig. 1 is a perspective view showing an embodiment of this invention, and Fig. 2
is its A sectional view. In this embodiment, a movable member (plate-like member) 1 constituting a torsional vibrator 10, a pair of holding members 3a, 3b, and fixed electrodes 5a, 5b (note that the electrode 5b is not shown) are integrally formed from a single silicon wafer by a photo-etching process and bonded to the glass substrate 7, and then the fixed electrodes 5a, 5b are separated from other members by etching or mechanical means to insulate them. In the etching process of the silicon wafer, an SiO2 insulating film 11 and aluminum (Al), which will become the second electrode 12 (see FIG. 2), are deposited on the surface of the plate member 1 by sputtering, and masks are applied to the front and back sides. Then, the outer shape of the torsional vibrator 10 is etched from the front side, and the thickness of the torsional vibrator 10 is etched from the back side. Holding members 3a and 3b are plate-like members 1
Since there is an appropriate gap D between the movable electrode 4 and the fixed electrode 5, the plate member 1 can rotate around the holding members 3a and 3b. can.

In such a configuration, when a voltage as shown in FIG. 2 is applied between the fixed electrode 5a and the first movable electrode 13 and the second movable electrode 12 which form part of the plate member 1,
The first and second electrodes have vertical and outward electrostatic force f1,
f2 works respectively. This force f represents the dielectric constant of air as ε, the length of the electrode as L, and the potential difference between each movable electrode and the fixed electrode as V.
If the distance between the fixed electrode and the movable electrode is D, then f=ε・L
・Represented by V2 /2D. Therefore, for example, if the potential of the second movable electrode is set to be the same as that of the fixed electrode, f2 ≒0, and f=f1 - f2 ≒f1 ≒ε・L・V2/2D. When composed of comb teeth,
A driving force of 2nf can be obtained. A similar force can be obtained by applying a voltage to the other fixed electrode, and the plate member rotates by a certain angle φ around the support, so if a reflecting mirror is installed on the plate member, the light of 2φ will be Scanning can be performed.

In this way, the movable electrode and the fixed electrode are formed in a comb-teeth shape, and the movable electrode is configured to move by a distance equal to the thickness of the opposing fixed electrode, so that the plate-like member has appropriate rigidity. Since it does not matter how thin it is, the moment of inertia can be reduced and the resonant frequency can be set high. Further, by increasing the depth of silicon etching from the back surface, the deflection angle can be increased, and furthermore, by increasing the number of comb teeth, low voltage driving becomes possible. In addition, here, the holding member 3
Although a and 3b are straight lines, any shape may be used as long as it can support the plate member and has torsional rigidity. Also,
The material constituting the torsional vibrator is not limited to silicon, but any material that can be processed in a similar manner may be used. Furthermore, if two electrodes are formed on the plate-like member, the torsional vibrator itself can be made into an insulator.

FIG. 4 is a perspective view showing another embodiment of the present invention, and FIG. 5 is a sectional view taken along line B thereof. As shown in Figure 4, 10
1 shows a torsional vibrator consisting of the plate member 1, first fixed electrode 5a, substrate 7, etc. explained in FIG. 1, on which second fixed electrodes 15a and 15b having the same shape as the first fixed electrode are aligned. , to join. Since the second fixed electrodes 15a and 15b must be electrically connected only to the corresponding first fixed electrodes 5a and 5b, the connecting portions 17a to 17d must be etched or machined to insulate them from the other electrodes. Separate by physical means. As shown in FIG. 5, the movable electrode 4a is located at the center of the first fixed electrode 5a and the second fixed electrode 15a.

FIG. 6 shows a sectional view taken in a direction perpendicular to FIG. In the above configuration, for example, the first movable electrode 13
0 volt is applied to the second movable electrode 12, Vcc volt is applied to the fixed electrodes 5a and 15a, and Vcc volt is applied to the fixed electrode 5b.
, 15b, an electrostatic force proportional to the square of the potential difference with the fixed electrode is generated vertically outward on each surface of the first and second movable electrodes, so if only the total electrostatic force is shown. As shown by arrow F in the figure, completely equal torques are generated on the left and right sides of the movable electrode, thereby causing the torsional vibrator to rotate. fixed electrodes 5a, 15a and 5b,
If the voltage applied to 15b is reversed left and right, torque in the opposite direction will be generated. In this way, by bonding the second fixed electrode on top of the first fixed electrode, twice the torque can be obtained if the same voltage is applied as when not bonding, and from this, it is possible to obtain a large amplitude at a low voltage. It becomes possible to drive. Further, in this embodiment, the second fixed electrode is bonded above the first fixed electrode, but it may be bonded below, for example, between the first fixed electrode and the substrate.

[0012] Ratio of depth and width dug by etching,
In other words, the aspect ratio cannot be too large and is usually 2.
5, so in order to increase the efficiency of the drive unit, if the width of the comb teeth is reduced and the degree of integration is increased, that is, the number of comb teeth is increased, the etching depth from the back surface of the first fixed electrode becomes smaller.
The amplitude of the torsional oscillator was limited because the thickness could not be increased, but in this example, by joining the second fixed electrode, the thickness of the fixed electrode can be increased, so the amplitude can be further increased. Can be done. Similarly, by stacking several electrodes having the same shape as the second fixed electrode, it is possible to increase the amplitude of the vibrator several times.

[0013]

According to the present invention, two comb-shaped electrodes are laminated on a thin plate-like movable member with an insulating film interposed therebetween, and a holding member is bonded to the movable member and the substrate on an axis passing through the center of gravity of the movable member. A member and a fixed electrode that is sufficiently thick compared to the movable member that engages with the comb teeth are formed on the substrate, and the potential difference between the first electrode, the second electrode, and the fixed electrode is set to be large.
Since the movable electrode is driven by the difference in electrostatic force generated perpendicularly and outwardly to the electrode, the necessary driving force can be obtained within the opposing fixed electrode even if the movable electrode is thin. For this reason,
Since the moment of inertia of the torsional vibrator can be reduced and the resonance frequency can be set high, high-speed driving is possible. Further, by increasing the distance in the thickness direction of the fixed electrode, the deflection angle can be increased, and by increasing the number of comb teeth, the driving force can be increased, so there is an advantage that a large deflection angle can be easily obtained even at a low voltage. In addition, if the second fixed electrode is bonded onto the first fixed electrode, and the movable electrode is positioned at the center of the movable electrode to apply voltage to the left and right fixed electrodes, the torsional vibrator has two Since twice as much torque is generated, it is possible to obtain a large deflection angle with low voltage. Additionally, since the torque acting on the torsional oscillator becomes a couple with respect to the holding member, no force other than rotation acts on the supporting member, allowing stable optical scanning without vertical movement of the oscillator or surface distortion. becomes. Furthermore, the deflection angle can be increased by stacking several times as many layers.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the invention.

FIG. 2 is a sectional view of A in FIG. 1;

FIG. 3 is a cross-sectional view for explaining the operation of FIG. 1;

FIG. 4 is a perspective view showing another embodiment of the invention.

FIG. 5 is a sectional view of B in FIG. 4;

FIG. 6 is a cross-sectional view for explaining the operation of FIG. 4;

FIG. 7 is an explanatory diagram for explaining a conventional galvanometer mirror.

FIG. 8 is an explanatory diagram for explaining the proposed device.

[Explanation of symbols]

1 Movable member (plate-like member) 4. Movable electrode 7 Glass substrate 3a Holding member 3b Holding member 4a Movable electrode 4b Movable electrode 5a Fixed electrode 5b Fixed electrode 10 Torsional vibrator 11 Insulating film 12 Second movable electrode 13 Support member (first movable electrode) 15a Second fixed electrode 15b Second fixed electrode 17a Connection part 17b Connection part 17c Connection part 17d Connection part

Claims (2)

[Claims] [Claim 1] First and second electrodes formed with an insulating film sandwiched therebetween.
a plate-like member having comb-shaped movable electrodes at both ends; a pair of holding members that connect the plate-like member to a fixed substrate; and comb teeth that engage with the comb teeth formed on the plate-like member. A torsional vibrator comprising a fixed electrode. 2. The torsional vibrator according to claim 1, wherein one or more fixed electrodes having the same comb teeth are stacked on the fixed electrode.