JP3589784B2 - Control device for optical distortion element - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for a photostrictive element, and more particularly to a control device for a photostrictive element suitable for controlling the supply of energy to a photostrictive element which is a ferroelectric ceramic driven by being supplied with light energy.
[0002]
[Prior art]
In recent years, micromachines have been actively studied, but it is difficult to use a lead wire or the like when supplying energy to an actuator that drives the micromachine. Therefore, it is desired to supply energy to such an actuator from a distance in a non-contact manner and to precisely control it.
[0003]
PLZT ceramics (hereinafter referred to as PLZT): (Pb, La) (Zr, Ti) O ₃ is a ferroelectric ceramic having an “optical distortion effect” that expands when light is absorbed, and directly transmits light energy as an optical distortion element. It can be converted to mechanical energy.
[0004]
[Problems to be solved by the invention]
Thus, the PLZT can be irradiated with light and supplied with energy in a non-contact manner to control the driving of the PLZT, and it is expected that the PLZT is used as an actuator of a micromachine.
[0005]
Here, the responsiveness of PLZT, which is an optical distortion element, depends on the amount of energy per unit area (energy density) of the supplied light, and the responsiveness tends to improve as the energy density of the supplied light increases. There is.
In addition, the light energy absorbed by the photostrictive element is used not only for generating minute elongation by the photostrictive effect but also converted to thermal energy, and the temperature of the photostrictive element increases. Due to this heat, the residual polarization of the optical strain element is reduced, and the optical strain element contracts or expands due to thermal expansion. As a result, it becomes difficult to control the amount of expansion. The temperature of the optical distortion element increases as the energy density of the supplied light increases.
[0006]
When the optical strain element is used as an actuator of a micromachine, the size of the optical strain element must be reduced, and the heat capacity of the optical strain element itself becomes small, so that the influence of heat change of the element due to light irradiation increases. It is necessary to perform control in consideration of the rise and fall of the temperature of the element.
[0007]
Therefore, an object of the present invention is to provide a control device for an optical distortion element that can perform precise control in consideration of expansion of the optical distortion element due to heat when driving the optical distortion element.
[0008]
[Means for Solving the Problems]
Here, the factors of the expansion of the element when the light distortion element is irradiated with light are:
a. Elongation due to light distortion effect b. There are two types of elongation due to thermal effects, and it is known that the total amount of elongation of the photostrictive element is substantially equal to the sum of the above-mentioned elongation amount and b.
Inventors, the results of the experiments described below, the between the energy density E _d of the light irradiated to the two elongation of the Hikariibitsu element was found that there is a following relationship.
[0009]
▲ 1 ▼ total elongation by the optical distortion effects is independent of the energy density E _d of light. If the energy density of light is high, the speed of elongation only increases. That is, as shown in FIG. 3, when irradiation with light having energy densities E _d1 , E _d2 , and E _d3 (E _d1 > E _d2 > E _d3 ) is performed on the same optical distortion element, The amount of elongation converges to l _Smax .
[0010]
{Circle around (2)} As shown in FIG. 4, the elongation due to the thermal effect increases as the light energy density _Ed increases.
That is, the larger the energy density of light, the greater the amount of light energy converted to heat energy in the optical distortion element, the greater the temperature rise, and the greater the elongation due to thermal effects.
Therefore, when the energy density E _d of the light falls on the way radiation, lowered temperature of the optical strain element, the elongation amount according to the results thermal effect is reduced.
That is, the amount of elongation due to thermal influence can be controlled by adjusting the temperature of the element by some means.
[0011]
▲ 3 ▼ As shown in FIG. 5, the temperature of the element of the thermal equilibrium larger the energy density E _d is high.
In addition, as shown in FIG. 6, the elongation due to the optical distortion effect stops faster than the elongation due to the heat effect.
[0012]
From the above facts, the inventor stated, "In order to adjust the amount of elongation of the photostrictive element to an arbitrary value by controlling the light irradiation density, the elongation due to the photostriction effect reaches saturation, and only the elongation due to heat effect is obtained. Then, when the amount of elongation of the optical strain element reaches a desired value due to elongation due to thermal influence, the energy density of light may be reduced, so that the temperature does not change before and after switching. In this case, it is necessary to keep the amount of elongation due to thermal effects unchanged, that is, to keep the photostrictive element in a thermal equilibrium state even after reducing the energy density of light. "
[0013]
Here, the thermal equilibrium state means that the heat energy obtained by the photostrictive element by the irradiation light is equal to the heat energy emitted from the photostrictive element, and no temperature change occurs in the photostrictive element.
[0014]
Hereinafter, the experiment will be briefly described.
The above experiment is described in detail in a previous patent application (Japanese Patent Application No. 7-251430) relating to the invention of the present inventor.
[0015]
〔sample〕
The photostrictive element, PLZT, which is the sample 15, is a ferroelectric substance having a perovskite structure having a composition of La: Zr: Ti = 3: 52: 48.
Further, as shown in FIG. 7, the sample 15 was cut into a length t = 14.5 mm, a width w = 6 mm, and a thickness d = 3.3 mm, and the surface of t × w (14.5 mm × 6 mm) was irradiated with light. Irradiated surface. Further, electrodes 21 were provided on both sides of w × d (6 mm × 3.3 mm) by baking Ag, and an electric field of 10 kV / cm (indicated by arrow P) in silicon oil at 150 ° C. in the t (14.5 mm) direction. And a polarization treatment was performed for 40 minutes.
[0016]
(Heating test)
Sample 15 was directly heated in an electric furnace, and the expansion and contraction of sample 15 due to heat in the polarization direction (t = 14.5 mm direction) was measured.
[0017]
(Light irradiation test)
In this experiment, a 500 W ultra-high pressure mercury lamp was used as a light source, and parallel light having a central wavelength of 365 nm and a bandwidth of 6 nm was perpendicularly applied to a sample formed by PLZT, which is a photostrictive piezoelectric element, using an infrared cut filter and two band-pass filters. Irradiation.
[0018]
Here, the reason why the center wavelength is set to 365 nm is based on a report that the optical distortion effect appears best for this PLZT (K. Uchino et al., Photostrictive effect in (Pb, La) (Zr, Ti) O _3. Ferroelectrics, 64, pp. 199-208. (1985))
[0019]
The elongation of the sample was measured using an electric micrometer, and displayed on a xy plotter and a data display device such as a personal computer.
[0020]
The temperature of the sample was measured with an infrared non-contact thermometer (radiation thermometer). Incidentally, the energy density of the light was measured in two conditions was ^{50mW / cm 2, 120mW / cm} 2.
[0021]
From the results of the above experiments, it has been found that the PLZT result sample has the above tendency.
[0022]
Based on the above results, the following means have been adopted in the present invention in order to solve the above problems.
[0023]
In the present invention, means for solving the above-mentioned problems include a light source 2 for irradiating light to a photostrictive element 1 that produces a photostrictive effect, and an illumination optical system for projecting light from the light source 2 onto the photostrictive element 1. 3, a temperature measuring means 4 for measuring the temperature of the optical distortion element, and a control means 5 for controlling the amount of light projected on the optical distortion element 1. When the amount of elongation of the optical strain element 1 obtained by adding the amount of expansion of the optical strain element due to thermal influence after the expansion of the strain element 1 has stopped reaches a desired value, the temperature of the optical strain element 1 changes before and after switching. caused not to lower the energy density E _d of light to be irradiated to Hikariibitsu element 1 as a control apparatus for an optical strain element switched.
[0024]
The control device for an optical strain element according to the present invention has an elongation amount measuring means 6 for measuring the elongation amount of the optical strain element 1, and the control means 5 determines whether the measured value of the elongation amount measuring means 6 is the elongation of the optical strain element. There can be made to switch when it becomes a desired value, the light to be irradiated to the optical distortion device 1 the energy density E _d.
[0025]
Further, the control device for a photostrictive element according to the present invention has a memory 7 for storing the temperature of the photostrictive element 1 before light irradiation, and the control means 5 stops the expansion of the photostrictive element 1 due to the photostrictive effect. Thereafter, when the elongation of the optical strain element reaches a desired value, a temperature difference ΔT between the temperature of the optical strain element 1 measured by the temperature measuring means 4 and the temperature stored in the memory 7 is obtained. From the difference ΔT, it is possible to determine an energy density at which a temperature change does not occur in the optical distortion element before and after switching.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a control device for a photostrictive element according to the present invention will be described.
[0027]
[First Embodiment]
1 and 2 show an embodiment of a control device for a photostrictive element according to the present invention. This embodiment corresponds to claims 1, 2 and 3 above.
The control device for a photostrictive element according to the present embodiment uses the above-described PLZT as a photostrictive element used as an actuator, and, as shown in FIG. An illumination optical system 3 for projecting light from the light source 2 onto the optical distortion element 1; a radiation thermometer 4 as a temperature measuring means for measuring the temperature of the optical distortion element 1; It comprises a control means 5 for controlling the amount of light, an electric micrometer 6 as an elongation amount measuring means, and a memory 7 for storing the temperature of the optical strain element 1 before light irradiation.
[0028]
The light source 2 uses an ultra-high pressure mercury lamp having the above-described filter. Further, other light sources, for example, an ultraviolet laser or the like can be used. Further, it is possible to use a light source in another wavelength range based on a difference in type of the optical distortion element 1 or the like.
The illumination optical system 3 is an optical system including a lens, an optical fiber, and the like, and irradiates light to the optical distortion element 1.
[0029]
After the elongation of the optical strain element 1 due to the optical distortion effect is stopped, the control means 5 irradiates the optical distortion element with the measured value of the electric micrometer 6 when the elongation of the optical distortion element becomes a desired value. It reduces the energy density of light. The switching is performed by switching the energy density of light so that the temperature of the optical distortion element does not change before and after the switching.
[0030]
In this example, the control unit 5 controls the light amount of the light source by changing the voltage of the power supplied to the light source 2 and controlling the power consumption of the light source.
[0031]
The control device 5 controls the optical distortion element 1 in the following procedure.
First, from the start of irradiation, light irradiation is continued at an energy density _Ed1 as shown in FIG. At this time, the temperature T ₀ of the optical distortion element immediately before the start of irradiation is measured and stored in the memory 7.
[0032]
Elongation by light distortion effect by light irradiation of the energy density E _d1, as shown in FIG. 2 (1), it stops at a relatively early time t _1. The elongation occurring at this time is equal to the sum of the elongation l _SMAX due to the optical distortion effect and the elongation l _H1 due to the thermal influence, as shown in FIG.
[0033]
Thereafter, light irradiation is continued at the energy density E _d1 , and when the amount of elongation of the optical strain element 1 reaches a desired elongation (l _SMAX + l _H2 ) as measured by the electric micrometer 7, the energy is reduced to the light energy density E _d2 .
[0034]
The energy density E _d2 of the light is a temperature difference ΔT between the temperature of the optical strain element measured by the radiation thermometer 4 at that time and the temperature T ₀ of the optical strain element before light irradiation stored in the memory 7 (ie, (The measured temperature of the optical strain element 1 became T ₀ + ΔT).
That is, the switch to light energy density E _d3 such that the temperature of the optical strain element in this case when thermal equilibrium is T _{0 +} ΔT.
[0035]
As shown in FIG. 4, the values of the set energy densities are various energy densities (energy densities _Ed1 , _Ed2 , and _Ed3 ( _Ed1 > _Ed2 > _Ed3 ) are shown in FIG. 4). Is preliminarily measured for the elongation due to the thermal influence on the optical distortion element, and this value is stored as a table in the control means 5 to obtain the energy density E _{d3 at} which the amount of elongation due to the heat to maintain the optical strain element is obtained. Good.
[0036]
Thus, elongation due to thermal effects, elongation due to thermal effects because the thermal equilibrium state is maintained in the temperature change ΔT becomes be kept l _H2.
Further, elongation due to light distortion effects are independent of the energy density of light energy density of the irradiation light does not affect the amount of elongation down from E _d1 to E _d3.
Similarly, when the desired amount of elongation is l _smax + l _H3 , E _d1 is reduced to E _d2 .
[0037]
As described above, in order to adjust the amount of elongation of the optical strain element to an arbitrary value, after the elongation due to the optical distortion effect ends, the elongation due to heat influences, and then the elongation due to heat influence, Is reduced to a desired value, the energy density of the light is reduced. At this time, the temperature does not change before and after the switching, and the amount of elongation due to the heat does not change, that is, the energy density of the light is reduced. After that, the elongation of the element can be controlled to a desired value by controlling the optical distortion element so as to keep it in a thermal equilibrium state.
[0038]
[Other embodiments]
In the above-described embodiment, the control unit 5 controls the light amount of the light source by changing the voltage of the power supplied to the light source 2 and controlling the power consumption of the light source.
However, the control method of the control means 5 may change the energy density of the light applied to the photostrictive element 1 by another means.
[0039]
That is, the position of the condenser lens (convex lens), which is an optical element constituting the illumination optical system, is moved back and forth with respect to the optical distortion element 1 by a linear motion mechanism or the like provided in the control means 5, so that the optical distortion element May be used to change the amount of light projected on the surface.
[0040]
The control means 5 changes the frequency, pulse width duty, or intensity of the pulsed light assuming that the light source 2 that irradiates the light to the light distortion element 1 irradiates the light with the pulsed light. The light quantity of the light projected on the light source 1 may be changed.
For example, the light source 2 initially changes the frequency of the supply light pulse, the pulse width of the supply light pulse, and the pulse intensity duty of the light pulse, or adjusts the amount of light applied to the light distortion element 1 by combining them. can do.
[0041]
Further, the control means 5 inserts an ND (Neutral Density Filter) filter 5 which is a filter for reducing the amount of incident light into the optical path of the illumination optical system 3, so that the light projected onto the optical distortion element 1 is reduced. The light amount may be changed.
[0042]
【The invention's effect】
As described above, according to the present invention, it is possible to precisely control the amount of expansion of the optical distortion element when driving the optical distortion element.
Therefore, when the optical distortion element is used as an actuator of a micromachine or the like, there is an effect that the drive control of the optical distortion element can be precisely performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a principle and a first embodiment of a control device for a photostrictive element according to the present invention.
FIG. 2 is a graph showing a control state of a control device for a photostrictive element according to the present invention, wherein (1) is an elongation amount of the element with respect to time, (2) is a temperature change of the element with respect to time, and (3) is a graph. FIG. 3 is a graph showing the energy density of light applied to the element with respect to time. FIG. 3 is a graph showing the elongation of the photostrictive element with respect to time during light irradiation.
FIG. 4 is a graph showing elongation of a photostrictive element due to thermal influence over time.
FIG. 5 is a graph showing a change in temperature with respect to an energy density of light emitted from a photostrictive element.
FIG. 6 is a graph showing a temperature change of a photostrictive element irradiated with light having different energy densities.
FIG. 7 is a perspective view showing PLZT used in the experiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical distortion element 2 Light source 3 Illumination optical system 4 Temperature measuring means 5 Control means 6 Expansion amount measuring means 7 Memory

Claims (3)

A light source (2) for irradiating light to a photostrictive element (1) that produces a photostrictive effect;
An illumination optical system (3) for projecting light from the light source (2) to the optical distortion element (1);
Temperature measuring means (4) for measuring the temperature of the optical strain element (1);
Control means (5) for controlling the amount of light projected on the optical distortion element (1),
The control means (5) determines that the expansion amount of the optical strain element (1) obtained by adding the expansion amount of the optical distortion element due to thermal expansion after the expansion of the optical distortion element (1) due to the optical distortion effect has stopped is a desired value. A control device for a photostrictive element that switches by lowering the energy density (E _d ) of light applied to the optical element (1) so that the temperature does not change in the photostrictive element before and after switching. An elongation amount measuring means (6) for measuring an elongation amount of the optical strain element (1);
When the elongation of the optical strain element reaches a desired value as measured by the elongation amount measuring means (6), the control means (5) controls the energy density (E _d ) of light applied to the optical element (1). The control device for an optical distortion element according to claim 1, wherein the control is performed. A memory (7) for storing the temperature of the photostrictive element (1) before light irradiation,
After the elongation of the optical distortion element (1) due to the optical distortion effect stops, when the elongation of the optical distortion element reaches a desired value, the control means (5) controls the light measured by the temperature measurement means (4). A temperature difference (ΔT) between the temperature of the distortion element (1) and the temperature stored in the memory (7) is obtained, and no temperature change occurs in the optical distortion element before and after switching based on the temperature difference (ΔT). 3. The control device for a photostrictive element according to claim 1, wherein the energy density is determined.

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