JPH0376725B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a light deflection device, and in particular uses a piezoelectric element to vibrate a reflecting mirror in response to an external electric signal to deflect and vibrate light. A light deflector that can control both the period and the period of the tuning fork is attached to the free end of the tuning fork. several KHz)
This invention relates to a voltage-controllable double-direction device for light that enables double-direction of light by combining the following.

[Conventional technology]

Conventionally, a device for changing the direction of light using a tuning fork is disclosed in, for example, Japanese Patent Application Laid-Open No. 117141/1983 (Vibrating device using a tuning fork).
As disclosed in , a reflecting mirror was attached to the free end of the tuning fork, the tuning fork was caused to resonate by an electromagnet, and the light reflected by the reflecting mirror was deflected.

FIG. 6 is a diagram showing its structure, and the part surrounded by dotted lines shows a light deflection device 40 using a tuning fork.

In this figure, 12 is a U-shaped tuning fork (hereinafter also simply referred to as a tuning fork), 41 is a reflector attached to the free end of the tuning fork, 13 is a balancer attached to the other free end of the tuning fork, and 14 is a tuning fork. 15 is an excitation magnetic head for exciting the tuning fork.

Here, the mass of the reflector 41 is equal to the mass of the balancer 13, and the center of gravity of the reflector 41 and the balancer 13 is substantially located within the plane of symmetry of the U-shaped tuning fork 12, which includes both legs of the tuning fork 12, and It must be arranged substantially symmetrically about the centerline of the tuning fork 12 in the plane of symmetry. Furthermore, asymmetry in the position of the center of gravity is a major cause of lowering the Q of the natural vibration of the vibration system, and because it increases the number of vibration modes (multi-mode), it may not produce any vibration at all, or it may reduce the natural vibration in the local part of the device. It causes the induction.

Further, the balance 13 can be provided with a groove for adjusting the center of gravity depending on the material and shape of the reflecting mirror 41. The pick-up magnetic head 14 and the excitation magnetic head 15 have cores 16 and 16', respectively.
and coils 17, 17' wound around the cores 16, 16'. Since the current is supplied, the pickup magnetic head 14 becomes a magnet. Therefore, if the tuning fork 12 vibrates even slightly, the gap between the core 16 of the magnetic head 14 and the leg of the tuning fork 12 will change, and the magnetic resistance will change. Therefore, the density of magnetic lines of force running through the core 16 changes, and an alternating current corresponding to the vibration of the tuning fork 12 is induced in the coil 17. This induced alternating current is branched by a drive circuit 50, one is amplified by an amplifier 52, and further, in order to make the vibration of the tuning fork 12 constant, it is sent to the excitation magnetic head 15 via a drive voltage adjustment circuit 53. is applied as a driving voltage. In addition, in order to keep the vibration of the tuning fork 12 at a constant amplitude, the other one is amplified by an amplifier 54 and passed through a full-wave rectifier circuit 55 and a low-frequency amplifier 56 to produce an output corresponding to the absolute value of the alternating current. . The drive voltage adjustment circuit 53 automatically adjusts the drive voltage so that when this output increases beyond a predetermined value, the drive voltage decreases.
In this way, the tuning fork 12 is excited at its natural frequency and at the automatically adjusted driving voltage, so that vibrations with a high Q and stable amplitude can be obtained as is.

[Problem that the invention seeks to solve]

However, the device described above that uses a tuning fork to deflect light,
Due to physical and structural problems with tuning forks, light cannot be deflected at high speeds (several tens of KHz or higher). For this reason, there is a limit to the speed at which light can be redirected using only a tuning fork, and there is also a limit to the number of sampling times when measuring an object with light.

Therefore, in this invention, in order to overcome the limitation of high-speed direction changing in the conventional tuning fork-based light turning device, the reflecting mirror that was conventionally installed at one free end of the tuning fork is replaced with a reflecting mirror using a piezoelectric element. The vibration caused by the piezoelectric element (several hundred KHz) is further added to the vibration caused by the tuning fork (several hundred to several KHz), and the reflected light on the reflecting mirror is replaced with a light deflector that can vibrate. It is assumed that the light can be double-directed,
The present invention aims to provide a voltage-controllable dual-direction device for light that dramatically increases the number of sampling times when measuring an object.

[Means for solving problems]

This invention first involves placing a substrate on a substrate having a conductive portion on its surface so that electrodes can be formed.
The first and second piezoelectric elements are installed in a separated manner, for example, so that their piezoelectric axes are opposite, and the first and second piezoelectric elements
First and second electrodes are provided on top of the piezoelectric element, respectively, and then a reflecting mirror having an electrode on the back side and a mirror surface on the front side is placed in contact with the first and second electrodes. , a voltage-controllable light deflector having a structure in which the first and second piezoelectric elements are placed so as to bridge each other is used.

Next, this voltage-controllable light deflector is attached to one free end of the tuning fork, and voltage control is performed to superimpose the vibrations caused by the tuning fork and the vibrations caused by the first and second piezoelectric elements to deflect the light. It is intended to be a possible double-direction device for light.

〔Example〕

FIG. 1 is a structural diagram showing an embodiment of a voltage-controllable double-direction device for light according to the present invention.

In this figure, 10 indicates a light deflector, 12 indicates a tuning fork (in this embodiment, a U-shaped tuning fork is used), and 13 indicates a balancer. The balancer 13 and the light deflector 10 have the same mass, and the center of gravity of the light deflector 10 and the center of gravity of the balancer 13 are substantially located within the symmetry plane of the tuning fork 12 that includes both legs of the tuning fork 12. Moreover, they are arranged substantially symmetrically with respect to the center line of the tuning fork 12 that lies within the plane of symmetry.

14 indicates a magnetic head for pickup; 15
indicates the excitation magnetic head. The pickup magnetic head 14 and the excitation magnetic head 15 constitute an excitation device for exciting the tuning fork 12. 1
6 and 16' indicate the cores of the pickup magnetic head 14 and the excitation magnetic head 15, respectively;
7 and 17' indicate coils wound around cores 16 and 16', respectively. 20 is a double light diversion device.

Further, FIG. 2 is a structural diagram showing an embodiment of the light deflector 10 which is a component of the double light deflection device shown in FIG.

In this figure, 1 indicates a substrate on which electrodes can be formed,
2 indicates a first piezoelectric element, and 3 indicates a second piezoelectric element. In this embodiment, the main vibration axes (piezoelectric axes) of the first piezoelectric element 2 and the second piezoelectric element 3 are in opposite directions. 4 indicates a first electrode provided on the top of the first piezoelectric element 2, and 5 indicates a second electrode provided on the top of the second piezoelectric element 3. Reference numeral 6 denotes a reflecting mirror that is provided in contact with the first electrode 4 and the second electrode 5, respectively, and placed so as to bridge the first piezoelectric element 2 and the second piezoelectric element 3. show. Reference numeral 7 indicates a power source for supplying voltage to the first piezoelectric element 2 and the second piezoelectric element 3, and reference numeral 11 indicates an electrode on the substrate 1 on which an electrode can be formed (also referred to simply as an electrode or an electrode of the substrate). It shows. For this electrode, the substrate 1 is made of conductive material such as Al or Cu.
It is made by plating the substrate with Au or by forming a thin metal film. 62 indicates a first lead wire for connecting the electrode 11 on the substrate 1 and the power source 7, 61 indicates an electrode of the reflecting mirror provided on the back surface of the reflecting mirror 6,
Reference numeral 63 indicates a second lead wire for connecting the electrode 61 of the reflecting mirror and the power source 7.

With this structure, the first and second piezoelectric elements 2 and 3 excited by the power source 7 vibrate, eventually causing the reflecting mirror 6 to vibrate. On the other hand, as shown in FIG. 1, the tuning fork 12 is vibrated by the excitation magnetic head 15 and the pickup magnetic head 14, and the light reflected by the reflecting mirror 6 is double deflected.

[Effect]

Hereinafter, the operation of the voltage-controllable double-direction device for light according to the present invention will be explained with reference to FIGS. 3a and 3b, FIGS. 4, 5, 8, and 9.

3a and 3b are diagrams showing the operation of the light deflector 10. FIG. In this figure, since the piezoelectric axes of the first and second piezoelectric elements 2 and 3 face in opposite directions, when an electric signal is applied between the first and second electrodes 4 and 5, the The phases of the vibrations of the first and second piezoelectric elements 2 and 3 are opposite to each other. As a result, the reflecting mirror 6 fixed to the first and second electrodes 4 and 5 above the first and second piezoelectric elements 2 and 3 performs a seesaw movement, and the direction of the light reflected by the mirror surface changes. It becomes a light deflector.

Since this light deflector 10 uses the first and second piezoelectric elements 2 and 3 as the vibration source of the reflecting mirror 6,
Much faster (several hundred kHz) than conventional light deflectors
It is possible to change direction. Furthermore, by changing the frequency of the electrical signals applied to the first and second piezoelectric elements 2 and 3, the vibration frequency of the reflecting mirror 6 can be varied, so the period of redirection of the light can be controlled by the electrical signals. In Figures 3a and b, 31 is a laser beam;
Reference numeral 2 indicates a doubly deflected laser beam, and reference numeral 61 indicates an electrode of a reflecting mirror.

FIG. 4 is a diagram showing the operation of the double light deflection device 20 in which the light deflector 10 is attached to one free end of the tuning fork 12. This double light deflection device 20 vibrates the tuning fork 12 using the exciting magnetic head 15 and the pickup magnetic head 14 to greatly deflect the light reflected by the reflecting mirror, and further performs the operation described in FIG. The light deflector 10 can deflect light at high speed. In other words, it is possible to provide a dual light deflection device in which the tuning fork 12 moves the light over a wide range, and the light deflector 10 moves the light at high speed. FIG. 4 is exaggerated for ease of understanding. It is clear from this figure that the deflection angle of the light changes due to the vibration of the tuning fork 12.

FIG. 5 shows a double-direction device 20 for light as described above.
FIG. 2 is a diagram showing a configuration when applied to a laser outer diameter measuring machine. When the laser light 31 enters the light double deflection device 20, the laser light 31 is doubly deflected and reflected as the double deflected laser light 32.
Then, the double-directed laser beam 32 is turned into parallel light by the lens 21, the beam waist is positioned at the position of the object to be measured 22, and the beam is focused on the photodetector 24 by the lens 23. With such a configuration, the number of samplings performed when the laser beam 32 traverses the object to be measured is significantly increased, and measurement accuracy is improved.

FIG. 9 is a diagram showing experimental results regarding an actually prototype light deflector. The vertical axis shows the output from the photomultiplier, that is, the standardized intensity of light, and the horizontal axis shows the distance displaced from the center of the light.

Here, the upper graph is the voltage value of the DC component from the photomul, and the lower graph is the voltage value of the DC component from the photomul.
This is the amplitude value of the AC component. From these two graphs,
It can be seen that the prototype light deflector deflects the light by 50 μm.

Therefore, when the amount of actual displacement of the piezoelectric element was calculated using FIGS. 3a and 3b and FIG. 8, in the experiment, a deflection of W=50 μm was obtained at a distance of L=65 cm. Therefore, the turning angle θ is θ=tan ⁻¹ (W/2/L)≒0.0022°.

Therefore, the distance l between the first and second piezoelectric elements is 3.8
From mm, the displacement d is d=l×tanθ≒1460 Å.

Assuming that the displacement amounts of the first and second piezoelectric elements are equal, one piezoelectric element vibrates with an amplitude of 1460 Å. This value of 1460 Å is sufficiently smaller than the value of 1 μm for ordinary piezoelectric elements that vibrate at several hundred KHz, and is sufficiently small even when considering the absorption of vibration by the conductive adhesive that bonds the piezoelectric element and the reflector. it is conceivable that. Conversely, this means that a larger deflection angle can be obtained by improving the adhesion between the piezoelectric element and the reflecting mirror, or by optimizing the frequency of the electrical signal applied to the piezoelectric element.

In addition, as another embodiment of the light deflector, even if the piezoelectric axes of the first and second piezoelectric elements are oriented in the same direction, the reflecting mirror may have a curvature as shown in FIG. Therefore, it is possible to change the direction of the light, and without being limited to the above-described structure, a method in which the piezoelectric axes are oriented in the same direction may also be adopted. Figure 7 is exaggerated for ease of understanding, and the symbols used are the same as in Figures 2 and 3, and it is clear that the deflection angle of light changes due to the vibration of the piezoelectric element. It is. Furthermore, by changing the curvature of the reflecting mirror, the direction change can be changed non-linearly, for example.

〔Effect of the invention〕

As explained above, the voltage-controllable dual-direction device for light of the present invention has a configuration using two piezoelectric elements whose vibrations can be controlled by electrical signals and a reflecting mirror that changes the direction of light. The light deflector is combined with a tuning fork installed at one free end, making it possible to vibrate in a double manner. Although it vibrates at a high speed, it is difficult to increase the angle of displacement of the light, and the characteristic of a deflector using a tuning fork, which allows the angle of displacement of light to be large, but the vibration period is long, combine to make it difficult to increase the angle of displacement of the light. It is possible to widely displace the light with the redirection function, and to partially redirect the light at high speed with the high-speed redirection function.

For this reason, the deflection period is partially very short compared to laser outer diameter measuring machines and laser thickness measuring machines that use only a tuning fork. This measuring device can significantly increase the number of samplings per unit time compared to conventional devices, which improves averaging accuracy. It is also advantageous for objects to be measured that move at high speed.

[Brief explanation of drawings]

Fig. 1 is a structural diagram of a voltage-controllable dual light deflection device of the present invention, Fig. 2 is a diagram showing the structure of the light deflector of Fig. FIG. 4 is a diagram showing the operation of the deflector (first embodiment); FIG. 4 is a diagram showing the operation of the voltage-controllable dual light deflection device of the present invention;
FIG. 5 is a block diagram showing one embodiment of the voltage-controllable double-direction device for light according to the present invention;
The figure is a structural diagram showing a light deflection device using a tuning fork, FIG. 7 is a diagram showing the operation of the light deflector (second embodiment), and FIG. FIG. 9 is a diagram showing the state of light deflection when the deflector (first embodiment) is actually operated, and FIG. 9 is a waveform diagram showing the output from the photomultiplier in the experiment shown in FIG. In the figure, 1 is a substrate, 2 is a first piezoelectric element, 3 is a second piezoelectric element, 4 is a first electrode, 5 is a second electrode, 6 is a reflecting mirror, 10 is a light deflector, 11 is an electrode, 12 is a tuning fork (U-shaped tuning fork), 13 is a balancer,
14 and 15 are excitation devices (magnetic head for pickup, magnetic head for excitation), 16 and 16' are cores, 1
7 and 17' are coils, 50 is a drive circuit, 51 is a constant current generation circuit, 52 and 54 are amplifiers, 53 is a drive voltage adjustment circuit, 55 is a full-wave rectifier circuit, and 56 is a low-frequency wave generator.

Claims (1)

[Claims] 1. A tuning fork 12; a light deflector 10 attached to the free end of one leg of the tuning fork and deflecting light by voltage control; and a light deflector 10 attached to the free end of the other leg of the tuning fork; installed,
and has a mass substantially equal to the mass of the light deflector, and its center of gravity and the center of gravity of the light deflector substantially lie within a plane of symmetry of the tuning fork that includes both legs of the tuning fork, Moreover, the balancer 13 is arranged substantially symmetrically with respect to the center line of the tuning fork in the plane of symmetry.
and; excitation devices 14 and 15 for exciting the tuning fork.
A voltage-controllable double-direction device for light with 2. The light deflector comprises a substrate 1 having an electrode 11 on its surface; first and second piezoelectric elements 2 and 3 installed separately on the electrode 11; first and second electrodes 4 and 5 respectively provided on the top of the piezoelectric element; having an electrode on the back side and a mirror surface on the front side, maintaining contact with the first and second electrodes; While the first and second
A reflecting mirror 6 placed so as to bridge the piezoelectric elements of
A voltage-controllable double-direction device for light according to claim 1, characterized in that it comprises: 3. A voltage controllable light according to claim 1, characterized in that the second piezoelectric element of the light deflector has a piezoelectric axis oriented oppositely to that of the first piezoelectric element. double diversion device. 4 the reflective mirror of the light deflector has a curvature;
2. The voltage-controllable double-direction device for light according to claim 1, wherein the first piezoelectric element and the second piezoelectric element have their piezoelectric axes in the same direction.