JPH0449926B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device that uses a reflecting mirror to change the direction of light, and in particular, a device that uses a piezoelectric element to excite the reflecting mirror by an electrical signal from the outside. By creating a standing wave there, both the direction of light deflection and the period of the standing wave can be controlled. The present invention relates to a light deflection device.

[Conventional technology]

Conventional light deflection devices include those using a rotating reflector system and a tuning fork.

The rotating reflector system mechanically rotates the reflector, and is characterized by a very simple structure and the ability to take a large deflection angle. However, on the other hand, since it is a mechanical drive system, it lacks durability and reliability. Further, the direction change frequency was at most several kHz or less.

A device for changing the direction of light using a tuning fork is, for example, disclosed in Japanese Patent Application Laid-Open No.
- As disclosed in Publication No. 117141 (vibrating device using a tuning fork), a reflecting mirror is attached to the tip of a tuning fork, and the tuning fork is excited by an electromagnet to resonate and vibrate the reflecting mirror attached to the tip. It changes the direction of the incident light while shaking it.

This method makes use of the physical properties inherent in the tuning fork, so it is more durable and reliable than the rotating reflector method, and can be used at high speeds (several hundred to several kilometres).
Hz).

Moreover, since it can have a large deflection angle, it is applied to various devices. However, in this direction changing device using a tuning fork, the tuning fork itself must be made to have high vibration in order to change the direction of light at a higher frequency (several + kHz or more). However, it has been impossible to make the tuning fork itself produce high vibrations due to physical and structural problems.

In addition, the Utility Model Application No. 1983-1999 disclosed a device in which a flexible reflecting mirror was vibrated by the vibration of a piezoelectric element.
A microfilm is known in which the contents of the specification and drawings attached to the application of No. 0593428 (Japanese Utility Model Publication No. 58-166620) are photographed. This idea deforms a cantilever-like flexible flat plate beam by displacement due to the expansion and contraction of a piezoelectric element, and changes the direction of the light beam. It was intended to be static, that is, to change slowly over time, and it was not possible to give the light beam high-speed vibrations (changes in direction) of several tens of kHz or more.

[Problem to be solved by the invention]

As mentioned above, in the case of the conventional light deflection device, the rotating reflector type has a simple structure and can obtain a large deflection angle, but because it is a mechanical drive method, it lacks durability and reliability. Moreover, it also had the disadvantage of a low light redirection frequency.

In the case of a light deflection device using a tuning fork, compared to a rotating reflector method, it utilizes the inherent physical properties of a tuning fork, so it is superior in reliability and durability, and the light deflection frequency ranges from several hundred to several kHz. Although it is quite fast,
If faster sampling is required, faster redirection of the light is required. This was not possible with conventional light redirecting devices. Furthermore, the light deflection device that uses a piezoelectric element to displace a flexible cantilever was also the same.

The present invention was made to overcome this situation, and in order to enable high-speed redirection that could not be achieved with conventional light redirection devices, it uses a piezoelectric element that vibrates through its thickness. It is an object of the present invention to provide an optical deflection device that utilizes a standing wave that is used as a vibration source of a reflecting mirror and deflects the direction by a standing wave generated in the reflecting mirror.

[Means to solve the problem]

In the present invention, thickness vibration (displacement) of a piezoelectric element is employed as a source of vibration (displacement). Here, thickness vibration means that the piezoelectric element sandwiched between the first electrode and the second electrode (installed on the top of the substrate)
The device vibrates in a direction perpendicular to the substrate due to an electric signal applied between the first and second electrodes.

One end of the reflecting mirror for light deflection is placed on the piezoelectric element in a cantilevered state, and the other end is left as a free end.
The thickness vibration introduces vibration into the reflecting mirror, causing standing waves in the reflecting mirror. A light beam is irradiated onto nodes of the standing wave to cause the light beam to change direction in response to fluctuations in the vibration of the standing wave.

The gist of the present invention will be explained based on FIG.
It is as follows.

A piezoelectric element 2 for applying an electric signal is placed on a substrate 1 having a first electrode 8 on its surface, and a second electrode 3 is provided above the piezoelectric element 2.

Then, one end of the reflecting mirror 4 is placed on the second electrode 3 so that the reflecting mirror 4 is in a cantilevered state, and the other end of the reflecting mirror 4 is left free.

Next, when an electric signal is applied to the piezoelectric element 2 via the first electrode 8, the piezoelectric element 2 vibrates, and eventually the reflecting mirror 4 fixed thereto vibrates.

However, since the reflecting mirror 4 is supported on one side, that is, in a cantilevered state, a standing wave is generated in response to an excited electric signal.

Therefore, the direction of the light reflected by the standing wave generated on the surface of the reflecting mirror 4 can be changed and controlled.

〔Example〕

FIG. 1 is a structural diagram showing an embodiment of a light deflection device (also referred to as a light deflection device or light deflector) using standing waves according to the present invention. FIG. 2 is an operational diagram of the light deflection device, and parts having the same functions as those in FIG. 1 are given the same reference numerals.

The symbols shown in FIG. 1 and FIG. 2 will be explained below.

1 indicates a substrate on which electrodes can be formed, and 2 indicates a piezoelectric element. 3 indicates a second electrode provided on the top of the piezoelectric element 2. Reference numeral 4 indicates a reflecting mirror having one end (one end) supported on the second electrode 3 and the other end free, that is, cantilevered. Since the reflecting mirror 4 itself vibrates and generates standing waves, a thin cover glass coated with aluminum is used. 5
8 indicates an AC power supply for supplying voltage to the piezoelectric element 2, and 8 indicates a first electrode on a substrate (also simply referred to as a substrate) 1 on which an electrode can be formed. Is this board 1 made of conductive aluminum, copper, etc.?
It is made by gold plating or forming a thin metal film on a substrate. 6 indicates a first lead wire for connecting the first electrode 8 on the substrate 1 and the power source 5, and 7 indicates a second lead wire for connecting the second electrode 3 and the power source 5. show. 9 shows the entire light deflection device. When the piezoelectric element 2 excited by the AC power source 5 vibrates, the reflecting mirror 4 vibrates. However, since the reflecting mirror 4 is supported on one side, that is, fixed in a cantilevered state, standing waves are generated in the reflecting mirror 4 due to vibration.

Hereinafter, the operation of the light redirecting device according to the present invention will be described in a second manner.
This will be explained using FIGS. a, b, FIGS. 3, 4, and 5 a, b. FIGS. 2a and 2b show the light deflection device 9.
FIG. In this figure, by applying an electric signal between the second electrode 3 on the top of the piezoelectric element 2 and the first electrode 8 on the substrate 1, the piezoelectric element 2 itself repeatedly expands and contracts in response to the electric signal. . Therefore, the vibration is transmitted to the reflecting mirror 4 fixed to the top of the piezoelectric element 2. Since the reflecting mirror 4 is supported on one side, that is, cantilevered, and the piezoelectric element 2 expands and contracts at high speed (several hundred kHz), standing waves are generated in the reflecting mirror 4. This standing wave periodically repeats the states shown in FIG. 2 a and b as a function of time. Therefore, the angular direction of the reflecting surface of the reflecting mirror 4 changes with respect to the incident light that enters from a certain direction. This results in a light deflection device in which the incident angle changes over time and the direction of the light reflected by the mirror surface of the reflecting mirror 4 changes. The deflection angle in this light deflection device is proportional to the inclination (π×A/λ) of the mirror surface of the reflecting mirror 4. Therefore, it can be said that it depends on the amplitude. Here, A is the amplitude of the difference between the maximum and minimum points of vibration of the mirror surface, and λ is the wavelength of the wave generated on the reflecting mirror 4. From this, if the amplitude can be increased, the deflection angle of the light can also be increased.

In addition, in the present invention, since the piezoelectric element 2 is used as the vibration source of the reflecting mirror 4, a conventional light deflection device (tuning fork,
Much faster (several hundred kHz) than rotating reflectors, etc.)
It is possible to change direction. Furthermore, it is superior in reliability and durability compared to mechanical drive systems. Further, by changing the frequency of the electric signal applied to the piezoelectric element 2, it is also possible to control the period of changing direction of the light with the electric signal.

Figure 3 shows the experimental results of the actually prototype light deflection device. In the figure, the vertical axis represents the output from the photomultiplier, that is, the standardized intensity of light, and the horizontal axis represents the distance displaced from the center of the light.

In this case, as shown in FIG. 5a, the scanning method was to run a pinhole receiving changing direction light (changed direction light) in the y direction and detect it with a photomultiplier. Here, the graph a shown in Fig. 3 is the voltage value of the DC component from the photomultiplier, and the
The graph b shown in the figure is the amplitude value of the AC component from the photomal. From these two graphs a and b, it can be seen that the prototype light deflection device deflects the light by 80 μm.

FIG. 4 shows the results of an experiment conducted to observe the wave state of the reflecting mirror of a prototype light deflection device.
In the figure, the vertical axis shows the output from the photomultiplier, that is, the standardized intensity of light, and the horizontal axis shows the distance the laser spot moves on the reflecting mirror. In this case, as shown in FIG. 5B, the scanning method was to scan the reflecting mirror 4 in the y direction and detect the light whose direction was changed by a direction changing device using a photomultiplier. The graph in Figure 4 shows the AC component, and what can be said from this is that it depicts periodic waves and that the phases at adjacent peaks are reversed. These results show that standing waves are occurring on the reflecting mirror, and the wavelength of the waves can also be measured. From the results of this experiment, the wavelength of the standing wave on the reflecting mirror of the prototype light deflection device was 1395 mm.

FIG. 6a shows a configuration in which the light deflection device 9 as described above is applied to an optical spectrum analyzer. When the light 30 is incident on a diffraction grating 10 for separating light into a certain range of spectral light, the light is separated and diffracted into a certain spectrum of light. The diffracted light 31 passes through the slit 11 and enters the reflecting mirror of the light deflection device 9, and by applying an electric signal to the light deflection device 9, the spectral light 31 is deflected. The deflected spectral light 32 passes through the slit 12 and a photodetector 13 measures the intensity of the spectral light 32. FIG. 6b shows a configuration in which the light deflection device is applied to an angle sensor.

Light 33 emitted from the laser oscillator 14 kept horizontally
enters the reflecting mirror of the light deflection device 9, and by applying an electric signal to the light deflection device 9, the laser beam is deflected. The deflected light 34 enters the mirror surface 15 along the object whose angle is to be measured, is reflected again by the mirror surface 15, and is detected by the photodetector array 17. The angle of incidence on the mirror surface 15, that is, the angle of incidence, changes rapidly depending on time, and sampling is possible, and the angle can be determined from the deflection angle of the light deflection device.

Furthermore, the light deflection device of the present invention can increase the deflection angle in proportion to the amplitude generated in the reflecting mirror, and the higher the frequency applied to the piezoelectric element, the shorter the wavelength. Therefore, the deflection angle of the light becomes large, and the deflection angle is ultimately proportional to the frequency. Therefore, when precisely measuring spectral light in a certain range separated by the diffraction grating of an optical spectrum analyzer, the light diffracted by the conventional diffraction grating can be used with the light deflection device of the present invention. With this change in direction, repeated measurements became possible. Further, this light redirecting device can be used not only as an optical spectrum analyzer but also as an optical spectrum analyzer.

〔Effect of the invention〕

As explained above, the light direction changing device of the present invention is configured to change the direction of light using a piezoelectric element whose vibration can be controlled by an electric signal and a standing wave of a reflecting mirror caused by the vibration. High frequency (several hundred k
Hz), it became possible to change direction. Furthermore, the direction of change in direction can now be controlled by electrical signals. Therefore, since it is possible to obtain modulation of an optical signal by high frequency, it can be widely used for optical measurement.

[Brief explanation of drawings]

FIG. 1 is a structural diagram showing an embodiment of a light deflection device using standing waves of the present invention, and FIGS. 2a and 2b are diagrams showing the operating state of the present invention. Figure 3 is a waveform diagram showing the output from the photomul in the experiment, Figure 4 is a waveform diagram showing the standing wave of the reflecting mirror, and Figures 5a and b are waveform diagrams showing the output from the photomultiplier in the experiment.
A diagram showing the scanning method in Fig. 4 is shown in Fig. 6.
Figures a and b show configuration diagrams when the light deflection device is applied to an analyzer and a sensor, respectively. In the figure, 1 is a substrate, 2 is a piezoelectric element, 3 is a second electrode, 4 is a reflecting mirror, 5 is a power source, 6 is a first lead wire, and 7 is a second lead wire.

Claims (1)

[Scope of Claims] 1. A substrate 1 having a first electrode 8 on its surface; installed on the first electrode, having a second electrode 3 on top thereof, and having a structure between the first and second electrodes; a piezoelectric element 2 that is displaced in a direction perpendicular to the substrate by an electric signal applied to the piezoelectric element; one end is placed on the top of the piezoelectric element, the other end is free, and a standing wave is generated by the displacement of the piezoelectric element; an optical modulation system using standing waves, comprising: a vibrating reflecting mirror 4 configured to generate a vibration; and means for inputting light to be deflected toward the position of a node of the standing wave generated on the reflecting mirror. direction equipment.