JPH04211217A - Optical deflector - Google Patents

Abstract

PURPOSE:To realize wide ranging two-dimensional optical scanning by constituting an optical polarizer simply at low cost. CONSTITUTION:The first vibrator 20 which has a reflecting mirror 1 and can rotate with span band parts 2a and 2b setting as its axis and the second vibrator 21 which can rotate with span band parts 4a and 4b setting as its axis are superposed on a board 6 so that respective rotation axes can cross at right angles to each other, and voltage is impressed respectively between electrodes 10a and 10b of the first vibrator 20 and an electrode 15 of the second vibrator 21 and between the electrode 15 of the second vibrator 21 and electrodes 11a and 11b on the board 6. Thereby, two-dimensional optical scanning by the use of electrostatic force can be realized by small electric power consumption.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflector suitable for use in optical scanning of optical equipment such as electrophotographic copying machines, image forming devices of laser printers, or tracking servos of magnetic storage devices.

0002

2. Description of the Related Art Conventionally, a galvanometer mirror is known in which a reflecting mirror is attached to a span band and integrally formed, and the mirror is driven by electrostatic force (if necessary, for example, IBM J. "R&D" VOL. 24, P.631,19
(See 1980). FIG. 11 shows such a conventional device. In the figure, 61 is a vibrator formed integrally with span bands 62a, 62b and a reflecting mirror 63 from a silicon plate, and 64 is a glass substrate. The reflecting mirror 63 is in contact with the protrusion 65 of the substrate 64 at its center, but a certain gap is ensured by recesses 66 on the left and right sides thereof. 67a and 67b are electrodes provided on the substrate 64, and by applying a voltage from the outside between one electrode and the mirror 63 by an appropriate means, the mirror 63 is attracted by electrostatic attraction and tilted. , the light hitting the mirror 63 is scanned as shown by the arrow in FIG. 11(b). In other words, when the mirror 63 tilts left and right by each φ,
The light will swing by 2φ in total.

Compared to electromagnetically driven devices, this device does not require an external magnetic field such as a permanent magnet, and only requires a pair of driving electrodes facing the mirror, so it has the advantage that the device can be made smaller in size. be. However, since a pair of span bands are placed against the mirror and rotated around the span band axis, only linear (one-directional, one-dimensional) scanning is possible, and in order to make two-dimensional scanning possible, a feed mechanism is required. The problem is that it is required separately. On the other hand, there is an optical deflector that supports a reflecting mirror on all sides with piezoelectric bimorphs and can perform two-dimensional scanning, that is, scanning any point on the surface. FIG. 12 shows an example of this type of device. If you need details, please refer to "Micromachining and Micromechanics" published by the Institute of Electrical Engineers of Japan's Industrial Measurement and Control Conference on October 27, 1989.
．． See 71.

FIG. 13 is a cross-sectional view for explaining its function. That is, the piezoelectric bimorph 72 has a structure in which a central metal plate 73 is sandwiched between piezoelectric elements 74 having the same shape on both sides. A divided electrode 75 is provided on the surface of this piezoelectric element 74.
a, 75b and a full-surface electrode 75c are provided, and are polarized in the direction of the arrow in the figure. Further, the polarization directions of the two piezoelectric elements are opposite to each other as shown by the arrows in the figure. When a voltage V is applied to the metal plate and the electrodes as shown in FIG. 5B, the piezoelectric bimorph is deformed as shown by the broken line in FIG. Since this device has a piezoelectric bimorph arranged in two orthogonal axes, it is possible to swing the beam two-dimensionally with one actuator. It has the characteristics of greatly simplifying the structure, reducing the size, and reducing the cost.

[0005]

However, such an optical deflector capable of biaxial scanning also has the following problems. The first problem is that since the same mirror is driven by two-axis bimorphs, mutual interference occurs. That is,
If an attempt is made to increase the tilt of the mirror by driving one axis, twisting occurs in the bimorph on the other axis, which acts as a force that suppresses the tilt, making it impossible to obtain the desired deflection angle. The second problem is that an offset in the deflection angle occurs due to the initial twist of the reflecting mirror, which affects the deflection angle and increases errors when setting the deflection angle. In other words, the reflection mirror is not horizontal due to distortions and residual stress in each part and distortion during assembly.For this reason, the inclination of the reflection mirror has traditionally been adjusted mechanically, but the overall size As the value becomes smaller, it becomes difficult to obtain that precision. In addition, since the amplitude is open-loop control that only controls the voltage that drives the reflection mirror, the deflection angle is affected by changes in the driving force due to changes in the piezoelectric constant due to changes in the ambient temperature, increasing the error. It is.

[0006]

[Means for Solving the Problems] In order to solve the first problem, two vibrators each consisting of a movable part and a pair of span bands are used, and the first vibrator has a span band in between. Two first electrodes are provided, and a second electrode is provided on the entire surface of the second vibrator.
The first and second electrodes are installed on the movable part of the second vibrator so that the first and second electrodes face each other with an appropriate distance therebetween, and the axes of the two sets of span bands are orthogonal to each other. Then, the second vibrator on which the first vibrator is mounted is placed on a substrate having two third electrodes that are symmetrical with respect to the axis of each span band, so that the electrodes face each other and maintain an appropriate spacing. Fix it. Note that the reflection mirror is installed on the movable part of the first vibrator. In addition, in order to solve the second problem, the two electrodes provided on the first vibrator and the substrate are further divided into two, four each are provided, and the drive electrode and the static Capacitance detection electrodes, means for calculating their output values, and voltage applying means for applying a voltage to the drive electrodes based on the results of the calculations are provided.

[0007]

[Operation] When a voltage is applied between one electrode of the first vibrator and the electrode of the second vibrator, a rotational moment is generated around the span band of the first vibrator, and the reflecting mirror rotates. Further, when a voltage is applied between the electrode of the second vibrator and one electrode on the substrate, a rotational moment is generated around the span band of the second vibrator, and the fixed portion of the reflecting mirror rotates. Since the span bands of the first and second vibrators are perpendicular to each other, the reflecting mirror can be rotated around each axis, allowing two-dimensional optical scanning. In this scanning method, the two axes are completely independent, so they do not interfere with each other, and since the scanning method is driven by electrostatic force generated between each movable part and the electrode facing it, the member that holds the mirror The length may be small, and the external dimensions can be reduced. Furthermore, the capacitances of the two pairs of first and third electrodes, which are provided symmetrically with respect to the rotation centers of the first and second vibrators, are It is determined by the spacing between the three electrodes, and when the vibrator is tilted, the capacitance of one increases and that of the other decreases. Therefore, by detecting these two capacitances and controlling (adjusting) the voltage distribution on the left and right sides of the driving electrodes arranged symmetrically with respect to the axis so that the ratio becomes "1", the above-mentioned intervals will be equal on the left and right sides. , the oscillator is kept horizontal. Similarly, when swinging by an arbitrary angle, the capacitance ratio can be set and the voltage applied to the first and third driving electrodes can be controlled. Since this control can be performed completely independently of the first and second vibrators, it is possible to perform optical scanning to any point on a plane.

[0008]

Embodiment FIG. 1 is a structural diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram showing the back side of a first vibrator, and FIG. 3 is a sectional view showing the cross section of FIG. In FIG. 1, 20 is a first vibrator;
First movable part 3 and a pair of span bands 2 that hold it
a, 2b and a frame 12 for fixing the span band, and is integrally formed of an insulating material such as SiO2, glass, or resin. As shown in FIG. 2, electrodes 10a and 10b, which are divided into two parts symmetrically across the axis of the span band, are joined to the back surface of the first movable part 3, and each electrode is connected to the frame body through the span band. The lead wires are connected by pulling out and bonding as shown in Figure 3 (A). Note that a mirror 1 for reflecting light is provided on the electrode surface of the first movable part.
Set up.

Like the first vibrator 20, the second vibrator 21 is composed of a second movable part 4, span bands 4a, 4b, and a frame 13, and a recess 14 is formed in the second movable part 4. , a second electrode 15 is bonded to the entire surface of the vibrator on the back surface thereof. Moreover, the first vibrator 20 is
The span band and the second span band are perpendicular to each other, and the recess 1
The protrusions 4c of 4 are joined to the first movable part 3 so as to be in contact with each other at the center of rotation, and the first movable part 3 is connected to the first span band 2a.
, 2b serves as a fulcrum when rotating around the center. Further, a third electrode 11a, 11b which is divided into two parts is bonded on the substrate 6 made of an insulating material, and a glass plate is placed on top of the third electrode 11a, 11b.
An insulating layer 16 is coated with ceramic or resin, and a spacer 17 having an appropriate height to form a recess is bonded thereon (see FIG. 3(b)). The second vibrator on which the first vibrator is mounted is joined to the spacer 17 of the substrate 6 so that the protrusion of the spacer recess 9 contacts the rotation center of the second movable part, and the second movable part is connected to the second movable part. It serves as a fulcrum when rotating around the span band. Note that the third electrode divided into two is arranged symmetrically with respect to the second span band, and the deflection angles of the first movable part and the second movable part are determined by the heights of the recesses 9 and 14, respectively. It looks like this. Further, the second electrode is grounded and has a zero potential.

[0010] Here, its operation will be explained. First, in a first electrode having two electrodes, when the potential of the electrode 10a is higher than the potential of the electrode 10b, a moment is applied due to the electrostatic attraction acting between the first span band 2a and the first span band 2b. is twisted and rotates in the direction of the arrow in Fig. 3(a). Similarly, in the third electrode, when the potential of the electrode 11a is higher than the potential of the electrode 11b, the second span band 4 receives a moment due to the electrostatic attraction acting between it and the second electrode.
a and 4b are twisted and rotated in the direction of the arrow in FIG. 3(b). Therefore, the reflecting mirror rotates around the first and second span bands in accordance with the voltage applied to each of the two electrodes of the first and third electrodes, thereby enabling optical scanning of a two-dimensional plane. .

FIG. 4 is a structural diagram showing an embodiment using a piezoelectric bimorph. In the same figure, 39 is the first vibrator,
It is constructed by bonding piezoelectric elements 32 and 34 to a metal plate 33. A second vibrator 31 is composed of piezoelectric elements 35 and 37 and a metal plate 36. The vibrators 39 and 31 are perpendicular to each other, and the movable part 3 has a concave portion to maintain an appropriate interval.
8, and the second vibrator is used with both ends fixed. Each piezoelectric element of the first and second vibrators is provided with electrodes and polarized in the same way as in the case of FIG. 13(A), so when voltage Vx is applied as shown in FIG.
It rotates in the x direction and in the arrow θy direction when voltage Vy is applied. Therefore, the reflecting mirror 30 has x-axis,
It rotates completely independently about the y-axis, allowing two-dimensional optical scanning.

FIG. 5 shows another embodiment of the invention. The small and lightweight torsional vibrator 20 as described above is fixed to a galvanometer mirror 40 consisting of ligaments 42a, 42b and a coil 43 placed within an external magnetic field by permanent magnets 41a, 41b. In this case, the rotation axis of the torsional oscillator 20 is
installed perpendicular to the axis. The galvanometer mirror 40 corresponds to the second vibrator in FIG. 1 here. In addition, as the torsional vibrator 20, instead of the span band shown in FIG.
It is also possible to use one using a letter-shaped beam, as shown in Figure 5.
shows this example. In such a configuration, scanning in the Y-axis direction is performed by applying voltage to two electrodes provided on the torsional vibrator 20 to generate an electric field, and rotating the movable plate (reflection mirror) using the electrostatic force. This is done by Scanning in the X-axis direction is performed by passing a current through the coil 43 to generate a force in a direction perpendicular to the magnetic field proportional to the current, and rotating the galvano mirror 40. In this way, by using a magnetic field and an electric field for scanning (driving) in each axis direction, there is no interference as shown in Fig. 12 or 13 when scanning each axis, and the driving can be done completely independently of each other, making it compact and low cost. It becomes possible to obtain a two-dimensional optical deflector that has good controllability and can scan over a wide range. It is of course possible to reverse the configurations of the first and second vibrators, that is, to make the first vibrator a galvano-mirror type and to make the second vibrator an electrostatic drive type.

FIG. 6 shows a modification of FIG. 5. This has a torsional vibrator 20, a coil 43 placed in an external magnetic field, and ligaments 42a, 42b placed directly on an insulating substrate 45 made of glass or the like. This glass substrate 45 may be any insulating substrate with good moldability. Note that 44a and 44b indicate electrodes. By doing so, assembly is simple and cost-effective, and the moment of inertia around the ligament can be lowered, making it possible to obtain a two-dimensional optical deflector with a high torsional resonance frequency and good responsiveness.

FIG. 7 shows another modification of FIG. 5. This is because the first vibrator of the first vibrator 39 and the second vibrator 31 shown in FIG. 45, the first vibrator 39
is driven by applying a voltage, and the second vibrator is driven by a magnetic field. Note that also in this case, the configurations of the first and second vibrators can be reversed.

Next, an embodiment in which the deflection angle is adjusted will be described. FIG. 8 shows the structure of the optical deflector, FIG. 9 shows the electrode structure of the first vibrator, and FIG. 10 shows the overall structure including the adjustment and control circuits. In this case, it is necessary to further divide the symmetrically arranged first and third electrodes to provide drive electrodes and detection electrodes symmetrically. That is, as shown in FIG. 9, the first driving electrode 1 is symmetrically arranged with respect to the first span bands 2a and 2b on the first vibrator 20.
0a, 10b and the first detection electrodes 10c, 10d are joined, and as shown in FIG.
11b and the third detection electrodes 11c and 11d are joined. Note that the other configurations are completely the same as in FIG. 1. 56,5
7, 58, and 59 are as shown in FIG. 10 (a) and (b),
A capacitance detector between the first electrodes 10c, 10d and the second electrode 15 and between the second electrode 15 and the third electrodes 11c, 11d outputs a voltage according to the capacitance value. 52
, 53 is an arithmetic unit that calculates the ratio of the left and right outputs, 54
, 55 is the first driving electrode 10 based on this calculation result.
a, 10b and the third drive electrodes 11a, 11b, and 51X, 51Y are the arithmetic unit 5.
This is a setting device for giving a deflection angle setting signal for the reflecting mirror to 2 and 53, and is set by an external device.

[0016] Its operation will be explained. Now, when the distances between the first detection electrodes 10c, 10d and the second electrode 15 are equal, their capacitances are also equal, and there is no difference in the detection values of the detectors 56, 57. Here, the first movable part is shown in FIG.
When tilted as shown by the broken line, the distance between the first electrodes 10d becomes narrower, and the capacitance increases, causing a difference in the detection values of the detectors 56 and 57. The voltage of the first electrode 10b is adjusted (controlled) to be lowered and the voltage of the electrode 10a is increased. This is the same when controlling the deflection angle; if a control signal is applied from the outside according to the difference in capacitance according to the deflection angle, the voltage output ratio of the detectors 56 and 57, that is, the amplitude can be controlled. It turns out. Since the second vibrator can be controlled in exactly the same way, optical scanning can be performed at any point on the two-dimensional plane.

[0017]

According to the present invention, two vibrators whose movable parts are rotatably vibrated by a driving means are used, and the whole of one vibrator is moved to the other movable part so that the centers of rotation of the two vibrators are orthogonal to each other. Since it is configured so that it is fixed to , it is possible to obtain independent deflection angles around two axes, which has the advantage that it can not only be made smaller but also that manufacturing costs can be kept low. Moreover, power consumption can be reduced by configuring it with a piezoelectric element or driving it with electrostatic force or electromagnetic force. Furthermore, if the deflection angle is controlled by detecting the angle of the two-axis movable part as the ratio of the capacitance on the left and right sides of the rotation center, the initial tilt of the reflecting mirror that occurs during manufacturing can be corrected without mechanical adjustment. This can be done relatively easily without increasing costs, and it is therefore possible to control the deflection angle with high precision.

[Brief explanation of the drawing]

FIG. 1 is an assembled configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an electrode structure of a first vibrator.

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

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

FIG. 5 is a perspective view showing still another embodiment of the present invention.

FIG. 6 is a perspective view showing a modification of FIG. 5;

7 is a perspective view showing another modification of FIG. 5. FIG.

FIG. 8 is an assembled configuration diagram showing another embodiment of the present invention.

9 is a configuration diagram showing the electrode structure of the first vibrator shown in FIG. 8. FIG.

FIG. 10 is an overall configuration diagram in which an adjustment and control circuit is added to the one shown in FIG. 8;

FIG. 11 is a configuration diagram showing a conventional example of an optical deflector capable of one-dimensional scanning.

FIG. 12 is a configuration diagram showing a conventional example of an optical deflector capable of two-dimensional scanning.

FIG. 13 is a cross-sectional view of FIG. 12;

[Explanation of symbols]

1 Reflection mirror 3 Movable part 4 Movable part 6 Board 9 Recessed part 2a Spun band 2b Spun band 4a Spun band 4b Spun band 4c Protrusion 12 Frame body 13 Frame body 14 Recess 15 Electrode 16 Insulating layer 17 Spacer 20 First oscillator 21 Second oscillator 30 Reflection mirror 31 Second oscillator 32 Piezoelectric element 33 Metal plate 34 Piezoelectric element 35 Piezoelectric element 36 Metal plate 37 Piezoelectric element 38 Movable part 39 First oscillator 40 Galvano mirror 43 Coil 45 Board 52 Arithmetic unit 53 Arithmetic unit 54 Voltage application section 55 Voltage application section 56 Detector 57 Detector 58 Detector 59 Detector 10a Electrode 10b Electrode 10c electrode 10d Electrode 11a Electrode 11b Electrode 11c Electrode 11d Electrode 41a Permanent magnet 41b Permanent magnet 42a Ligament 42b Ligament 44a Electrode 44b Electrode 51X Setting device 51Y Setting device

Claims (6)

[Claims] Claim 1: First and second vibrators each have a movable plate that rotates about one axis and a drive unit that drives the movable plate, and a reflective mirror is installed on the movable plate of the first vibrator, An optical deflector characterized in that a first vibrator is fixed to a movable plate of two vibrators such that the rotation axes of both vibrators are orthogonal to each other. 2. The optical deflector according to claim 1, wherein the movable plates of the first and second vibrators are driven by electrostatic force. 3. The optical deflector according to claim 1, wherein the movable plates of the first and second vibrators are constituted by piezoelectric elements and are driven by applying a voltage. 4. The optical deflector according to claim 1, wherein one of the movable plates of the first and second vibrators is driven by electrostatic force, and the other is driven by electromagnetic force. . 5. The movable plate according to claim 1, wherein one of the movable plates of the first and second vibrators is a piezoelectric element and is driven by applying a voltage, and the other is driven by electromagnetic force. optical deflector. 6. Detecting means for detecting capacitance, which is installed symmetrically about the respective rotational axes of the movable plates of the first and second vibrators, and calculating a ratio of the respective capacitance values. Claim 1 characterized in that the movable plate is provided with a calculation means and a voltage application means for applying a drive voltage according to the calculation result, so that the deflection angle of the movable plate with respect to the two rotation axes can be detected and adjusted. The optical deflector described in .