JPH01287525A - Deflecting or scanning device - Google Patents

Abstract

PURPOSE:To switch an optical path or scan light by simple constitution with high accuracy by setting the reflecting surfaces of two plane reflecting mirrors opposite each other, and displacing one reflecting mirror by a displacement generating means to and away from the other reflecting mirror. CONSTITUTION:When light is reflected repeatedly between a couple of reflecting surfaces 4 and 5 and one reflecting surface 5 is displaced to or from the other reflecting surface 4, the optical path of light which exits by being reflected finally by the reflecting surface 5 is increased in displacement quantity according to the number of times of reflection between the reflecting surfaces 4 and 5. At this time, only the increasing operation is obtained corresponding to the displacement quantity of the reflecting surface 5 and the deflection of the angle of incidence of the light which is incident first on the reflecting surface 4 is not increased. For the purpose, a piezoelectric element 10 which has high accuracy even if its displacement stroke is small is used as a displacement driving means which displaces the reflecting surface 5 to deflect and scan light with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to electromagnetic waves, particularly light deflection or scanning devices, and is not limited to any particular product field, but is applicable to fields and devices that utilize electromagnetic waves, light, etc. The present invention is particularly useful as a deflection or scanning device that performs optical path changing or light scanning at high speed, with high precision, and with excellent reproducibility.

BACKGROUND OF THE INVENTION In fields that utilize light, there arises a need to selectively switch the optical path of a light beam. Moreover, the positioning accuracy for switching the optical path is sufficiently high, and once the optical path has been switched to a certain position, there are cases where it is necessary to continue stably maintaining one position of the optical path.

Conventionally, in response to such a request, it has been proposed to switch the optical path by changing the attitude of the reflecting mirror using, for example, a galvanometer. This is intended to switch the optical path of the reflected light from the reflecting mirror to a desired path position by rotating the reflecting mirror using a galvanometer. Although this method has the characteristic of being able to rotate the reflecting mirror over a fairly wide angle, as is well known,
Due to the low rigidity of the galvanometer, the posture of the reflector is extremely susceptible to external vibrations, making it difficult to maintain a highly stable optical path.

A galvanometer may also be used as a light scanning device by vibrating a reflecting mirror. It is obvious that this case is also easily affected by external vibrations for the reasons mentioned above, but in addition, since this case constitutes a typical spring/mass vibration system, especially from the viewpoint of natural vibration. Since then, there have been many practical problems. In other words, regarding the scanning speed, scanning frequency, mass of the reflecting mirror, etc.
This results in various restrictions.

Another possible method for switching the optical path is to control the attitude of the reflecting mirror using a rotary actuator, such as a pulse motor. However, this method has drawbacks, such as the fact that the pulse motor itself and its drive circuit are expensive, and the device becomes larger.

Further, the rotation angle per pulse of a pulse motor is usually limited to about 0.2 degrees, even if it is small, and it cannot be said that it has sufficient resolution to perform precise attitude control. Of course, this rotation angle per 1 pulse can be further reduced by coupling to a special drive circuit or a suitable gear train, but in that case, the equipment would be more expensive,
It becomes complicated.

A method using a piezoelectric element has been proposed as a smaller deflection device or scanning device with high resolution. The figure is from the magazine "Electronic Ceramics" in 1987.
This is a deflection or scanning device published on page 44 of the April issue.

In the figure, a reflecting mirror 50 is fixed to a fixed boss 51,
The fixed boss 51 is attached to the housing 53 via a leaf spring 52. Then, by displacing one end of the fixed boss 51 by the piezoelectric element 54, the reflecting mirror 50 performs a minute rotational movement about the fulcrum of the center rod 55.

In this way, the reflecting mirror 50 is vibrated or the resting position of the reflecting mirror 50 is controlled to scan or deflect light. Further, 56 is a steel ball.

The laminated piezoelectric element used in this conventional example has excellent characteristics as a high-precision actuator, such as being able to easily control the amount of expansion and contraction with high precision, being able to drive at a high frequency, and generating large force. It is. Therefore, in this conventional example, although it is possible to deflect or scan light with high precision, the amount of expansion and contraction of the piezoelectric element itself is small, several tens of μm, and the angle of the reflecting mirror is only 0.5 μm. The position can only be changed within a range of degrees, which is too small for practical use.

As mentioned above, in the past, optical paths can be switched or light can be scanned with a simple configuration and with high precision.
There were no reliable deflection or scanning devices. The present invention solves this conventional problem.

Means for Solving the Problems The means for solving the above-mentioned surface problems is to make the reflecting surfaces of two plane reflecting mirrors face each other, and to move one reflecting mirror to the other by means of a displacement generating means. The mirror ζ is displaced, and light is multiple-reflected between a pair of reflective surfaces configured in this manner.

Effects The effects of the above means are as follows. That is, when light is multiple-reflected between a pair of reflective surfaces configured as described above and one reflective surface is displaced relative to the other, the light is finally reflected from the reflective surface and output. The optical path of the incoming light is changed in accordance with the number of reflections between the reflecting surfaces so that the amount of displacement is amplified. Furthermore, this amplification effect acts only on the amount of displacement of the reflecting surface, and does not amplify, for example, the fluctuation in the incident angle of the incident light that first enters the reflecting surface. Since such an excellent amplification effect can be obtained, the above-mentioned problem of the conventional method can be solved by using a high-precision drive means, such as a piezoelectric element, with a small displacement stroke as the displacement drive means for displacing the reflective surface. It is.

Embodiment FIG. 1 shows the configuration of essential parts of an embodiment of the present invention. First, the configuration and basic characteristics will be explained.

Reference numerals 1 and 2 denote a pair of plane reflecting mirrors whose reflecting surfaces 4.5 face each other, and the reflecting surface 5jL2 is bonded to the thick metal plate 11. The metal plate 11 has a leaf spring 8 at one end 7 thereof.
It is attached to a housing 6b which is substantially integral with the housing 6a to which the reflecting mirror l is fixed. The end lOb of the laminated piezoelectric element 10 is fixed to a housing 6c that is substantially integral with the housing 6a. By applying a voltage between both ends lOa and 10b of the electrical element lO, the end 10a expands and contracts in the direction of arrow A. This amount of expansion and contraction is magnified by the displacement magnification mechanism 12 and transmitted to the reflecting mirror 2. The displacement magnifying mechanism 12 is rotatably supported by a support shaft 14, and two points of action 15.1 are provided from the support shaft 14.
It has an enlargement ratio according to the distance ratio up to 6. Reference numeral 17 denotes a tension spring that biases the reflecting mirror in the direction of arrow B.

As is well known, by changing the DC voltage value applied to both ends 10a and 10b of the piezoelectric element 10, the amount of expansion and contraction in the stacking direction (in the direction of the arrow in the figure) can be precisely controlled. and,
This amount of expansion and contraction is transmitted to the end 9 of the reflecting mirror 2, and due to this displacement, the reflecting mirror 2 performs an arcuate motion with the bending portion 8a of the leaf spring as the center of rotation. Due to this arcuate movement, the intersection angle between reflecting mirror 1 and reflecting mirror 2 (as shown in Figure 1, when both are in a parallel state, the intersection angle is 0) changes by a value almost equal to the rotation angle of reflecting SN2. do.

Now, the functions of the apparatus of this embodiment configured as described above will be explained in detail below.

In FIG. 2, a light beam A 20 is incident on the device shown in FIG. This shows the state in which the beam is emitted. The reflecting mirror 2 in a state displaced by the small angle α by the piezoelectric element 10 is shown by a broken line. The emitted light beam at this time is indicated by a broken line 21b. Now, if the number of reflections on the reflecting mirror 2 is n, then the beams 21a and 21b
The angle β between the two is β=2(n-1)α (1), and β is obtained by amplifying α according to the number of reflections n. Therefore, if n is increased appropriately as required, β will also be increased, and in practice, clearly separated and different optical paths can be obtained.

In other words, the optical path is switched.

Moreover, since the above-mentioned α is extremely precisely controlled by the piezoelectric element, this switching of the optical path can also be performed with high precision.

Next, the excellent basic characteristics of the present invention will be explained.

An important point in principle is that equation (1) does not include the beam incidence angle γ (see FIG. 2). This means that in the device of the present invention, only the angular displacement of the reflecting mirror appears as an enlarged angular displacement of the emitted light beam. In other words, this means that the present invention has the essentially important feature that the deviation of the incident angle γ does not appear magnified. Since the present invention has this essential and excellent feature in principle, it is possible to perform highly accurate and stable control.

Furthermore, another fundamentally important feature of the present invention is that the present invention uses only a flat reflecting mirror as an optical component, and therefore, in principle, no optical aberrations occur. This feature is extremely useful since light deflection or scanning devices are used integrated into optical devices.

Now, the present example will be described in detail below along with specific numerical values.

The commercially available multilayer piezoelectric element 10 used in this example had a maximum applied voltage of 1000 V, and the tip portion 10a had approximately 70 μm.
A displacement amount of m can be obtained.

This displacement is then magnified approximately three times by the displacement magnifying mechanism 12 and transmitted to the reflecting mirror 2. As a result, the reflecting mirror 2 performs an arcuate motion with the bending portion 8a of the leaf spring as the center of rotation. The rotation angle of 042M2 obtained by this circular arc movement is the displacement amount transmitted from the enlarging mechanism 12 converted into an angle. That is, in FIG. 1, the distance from the bending part of the leaf spring, which is the center of rotation, to the point of action 16 is 5.
mm, and since the amount of displacement of the tip 10a of the piezoelectric element 10 is 70 μm, the rotation angle θ of the reflecting mirror is θ=0.
07mmX 3/5mm= 0-042(rad)=
It becomes 2.4 (deg). Then, this value is finally expanded to the value of β shown in equation (1). In this embodiment, n=6, so n=24 (degrees), which is a practically sufficient value for switching the optical path.

Next, the positioning accuracy of the reflecting mirror 2 will be described.

As mentioned above, the piezoelectric element 10 generates a displacement of about 70 μm when 1000 V is applied. This changes the applied voltage to Iv
This means that if controlled in units, an extremely high resolution of 0.07 μm can be obtained.

If we convert this into angular resolution using the same calculation as above, if n in equation (1) is 6, it will be 2.4X
It is 10-3 degrees, which is a high accuracy that poses no problem in practical use.

Next, the response performance of the piezoelectric element 10 will be explained. FIG. 3 shows the time required from applying a voltage to the piezoelectric element until the displacement of the piezoelectric element becomes stable. As shown in this characteristic, piezoelectric elements usually have a thickness of 100 to 200μ.
It has a response speed of about 1.5 seconds. Since the natural frequency of the laminated piezoelectric element is usually about 30 to 50 KHz, sufficiently high-speed positioning control is possible.

Furthermore, since the laminated piezoelectric element generates a force of several tens of kilograms, it is possible to reliably drive the reflecting mirror.

Further, the weight of the reflector is not substantially limited.

The characteristics of this example will be shown below with specific values.

FIG. 4 shows a measurement system for various characteristics of the device of this embodiment. A shows the device of the present example, and only the reflecting mirror 1.2 is drawn to make the figure easier to see. In FIG. 4, the reflecting mirror 2 is moved to three positions 2 by the piezoelectric element 10.
It is positioned at positions a, 2b, and 2c. 2a is a position where the displacement amount of the piezoelectric element 10 approximately corresponds to O, and 2c
is a position where the amount of displacement of the piezoelectric element 10 corresponds to 70 μm. 2b is exactly at the center position between 2a and 2c. For one incident laser beam 20, output beams 30a and 30b are generated corresponding to the three positions of reflection fjF2.
, 30c are obtained. In this case as well, in order to make the diagram easier to read, the state of light reflection between the reflective surfaces is omitted.

As mentioned above, the number of reflections in this example device is n = 6.
Therefore, the angle between the beams 30a and 30c is approximately 24 degrees.

The incident beam 20 is the beam after passing through the focusing lens system, and as shown in the figure, it is being focused towards the focusing point. 31a, 31b, and 31c are beam 3, respectively.
It is a two-dimensional CCD sensor provided so that the optical axis of each beam hits the focal point positions of 0a, 30b, and 30c at right angles. 32 and 33 are an arithmetic unit and a display device, respectively. As shown in FIG. 5, each CCD sensor is irradiated with a TEMes mode laser beam whose intensity distribution can be approximated by a normal distribution. This beam spans multiple pixels on each CCD sensor. For example, beam 30b
In other words, the optical axis of the beam 30b spans a plurality of pixels around the pixel as the center. The arithmetic unit 32 calculates a constant sampling time rr! for each CCD sensor. At intervals of one pixel, the pixel receiving the strongest laser intensity is determined from among the plurality of pixels, and the number of times each pixel has been subjected to such determination is accumulated and stored in memory.

The display device 32 two-dimensionally displays the accumulated memory contents for each pixel of each CCD sensor.

6, 7, and 8, the sensor 31a,
A display example of the display device regarding 31b and 31c will be shown. This is data obtained when one cycle of positioning the reflecting mirror 2 in the order of 20a → 20b → 20c → 20a was repeated 10 times per second, that is, at lOH2, for about 15 minutes. In FIGS. 6 and 7, each rectangle represents one pixel on the CCD sensor, and its actual size is approximately 30 μm square. The numerical value displayed in the center of the rectangle is the aforementioned integrated value. Ru.

Furthermore, the numerical values at both upper corners of the rectangle represent the coordinate information of each pixel on the CCD sensor. In FIG. 4, the distance from the beam output end of the device of this embodiment to each CCD sensor is approximately 50 mm, and the repeatability of positioning of the reflecting mirror 2 in the device of this embodiment is based on the size of the pixels mentioned above. teeth,
This measurement example proves that the angle is highly accurate at least 0.8n+rad or less.

Furthermore, even when the above-mentioned positioning cycle of the reflecting mirror 2 was performed at 1 KHz, results completely similar to those described above were obtained.

In addition, since the present embodiment can operate at a high frequency in this way, it can also be used as an optical scanning device.

Furthermore, using the measuring device shown in FIG. 4, the temporal stability of positioning accuracy was investigated. That is, it was investigated how stably the beam center on the CCD sensor 31 remained stationary while the voltage applied to the piezoelectric element IO was maintained constant. As a result, in the environmental temperature range of 22 degrees to 33 degrees, 24 degrees
With time leaps, the positioning accuracy was about 2.4 mrad or less. This is a slight decrease in accuracy compared to the repeatability, but this seems to be largely due to the instability of the mode, output, etc. of the semiconductor laser itself.

However, it achieves sufficient accuracy for practical use.

In this embodiment, the anti-a1 mirror 2 was driven by a piezoelectric element via a displacement magnifying mechanism, but if the required displacement device is about 10 degrees, it can also be driven directly by a piezoelectric element. Of course it is possible.

Further, in the above explanation, light was used as an example, but it goes without saying that the above discussion also holds true for electromagnetic waves.

Effects of the Invention As explained above, the present invention has a simple configuration and can perform highly accurate and stable light deflection and scanning that could not be achieved conventionally.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a deflection or scanning device in an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the same device, and FIG.
A characteristic diagram of a piezoelectric element, FIG. 4 is a principle diagram of a characteristic measurement system according to an embodiment of the present invention, FIGS. 6 to 8 are diagrams showing actual measurement data of characteristics of the embodiment, and FIG. It is a block diagram of an example. l, 2-... Reflecting mirror, 3.4... Reflecting surface, 10...
Piezoelectric element. Name of agent: Patent attorney Toshio Nakao (1 person) 151f 1 Reflection Figure 2 Figure 3 Time (nsec) Figure 5 Halo of the Rat Figure 6 Figure 7 Figure 8 Figure 9 Procedure amendment % formula % 2 Relationship with the case of the person who makes the deviation of the name of the invention or the scanning device 3 Correction Patent application Address 1006 Kadoma, Kadoma City, Osaka Prefecture Name
(582) Matsushita Electric Industrial Co., Ltd. Representative Tani
Akio I 4 Agent 571 Address 1006 Oaza Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. Date 7 of the amendment order, "Principle Diagram," on page 16, line 18 of the detailed statement of amendments. ``Principle diagram,
Figure 5 is a diagram of the intensity distribution of the laser beam in TICMoo mode.''

Claims (3)

[Claims] (1) The reflecting surfaces of the two plane reflecting mirrors are made to face each other, and one reflecting mirror is displaced relative to the other reflecting mirror by a displacement generating means, and between the pair of reflecting surfaces configured in this way. A deflection or scanning device that deflects or scans electromagnetic waves by multiple reflections of electromagnetic waves. (2) A deflection or scanning device according to claim 1, comprising displacement generating means including a piezoelectric element. (3) Deflection or scanning according to claim 1 or 2, wherein the displaced reflecting mirror is displaced such that at least the intersection angle between that reflecting mirror and the other reflecting mirror changes. Device.