JPS6132336Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a light detection device using a pyroelectric polymer film.

Piezoelectric polymer materials such as polyvinylidene fluoride are known to have pyroelectric properties. By utilizing the pyroelectricity of such a polymer material and using it as a photoelectric conversion element, a photodetecting device can be constructed. That is, the pyroelectric polymer film can be used to configure detection devices such as fire alarms and intrusion detectors, as well as detection elements of optical calorimeters for measuring the output of laser light.
In particular, a pyroelectric polymer film is useful as a high-output optical calorimeter with little dependence on beam diameter because a large-area element with a uniform pyroelectric distribution can be obtained. A photoelectric conversion element made of such a polymer material is obtained by polarizing a polar material such as polyvinylidene fluoride under a DC voltage. A photoelectric conversion element made of a polymer film is stretched and attached to a frame to constitute a photodetector. When light is incident on such a device, the photoelectric conversion element outputs an electrical output corresponding to the incident light, and a light measurement or light detection operation is performed.

However, since the photoelectric conversion element has piezoelectricity, when the photoelectric conversion element vibrates due to external sound, wind, etc., an output voltage is generated along with this vibration. Therefore, such disturbances cause malfunctions and measurement errors. In order to prevent such disturbances, it is conceivable to place the photoelectric conversion element in a disturbance-prevented room, but the disturbance prevention room is naturally divided into two by the conversion element, and the absorption of incident light energy causes the disturbance to be divided into two. It has been found that a temperature difference occurs between the disturbance prevention chambers, and a pressure difference occurs between the two chambers when the disturbance prevention chamber is sealed, and the piezoelectric effect caused by this pressure also causes a large noise.

The present invention was developed in view of these problems, and is a photodetector that uses a pyroelectric polymer film as a light receiving element. A first disturbance prevention chamber is provided, and a second disturbance prevention chamber is provided on the back side of the light receiving element, which also serves as a shield case if necessary.
The present invention relates to a photodetecting device characterized in that a communication portion is formed in each of the second disturbance prevention chamber and communicated with the outside. Therefore, vibrations and electrical noise can be prevented by the first and second disturbance prevention chambers. Furthermore, since both disturbance prevention chambers are communicated with the outside, it is possible to eliminate the pressure difference between the two disturbance prevention chambers, and deformation of the light receiving element due to the pressure difference can be prevented. When the second disturbance prevention chamber also serves as a shield case, the back plate of the second disturbance prevention chamber is made of a conductive material, or a conductive layer is formed on one surface of the back plate, and this back plate is made of a conductive material. Alternatively, it is preferable that the conductor layer and the electrode facing the first disturbance prevention chamber of the light receiving element be electrically connected to form a shield case.

The present invention will be described below with reference to the drawings, with reference to the illustrated embodiments. In this embodiment, the present invention is applied to an optical calorimeter for laser light. This calorimeter, as shown in Figures 1 and 2,
Pyroelectric polymer film 1 constituting a photoelectric conversion element
A pair of rings 2 and 3 clamp the peripheral edge of the film 1 from the front and back to hold it in a stretched state, and a transparent protection plate 4 is attached to the front side of the ring 2 to protect the polymer film 1. and a back plate 5 attached to the back side of the ring 3.

The pyroelectric polymer film 1 used in this example is, for example, a polymer containing a highly polar monomer such as vinyl fluoride, vinylidene fluoride, trifluoroethylene, or fluorochlorovinylidene, or a copolymer. It may be a polarized polymer or a composition mainly composed of these polymers or copolymers. Among these, monopolymers or copolymers containing 50 mol % or more of vinylidene fluoride are particularly preferred because they have extremely high pyroelectricity.
Furthermore, polymer films consisting of compositions containing vinylidene fluoride polymers or copolymers as a main component, mixed with PZT or other inorganic ferroelectric materials can also be used because they have high pyroelectric properties. becomes.

When such a pyroelectric polymer film 1 is used as a photoelectric conversion element of a detector, electrodes 6, 7 are attached to both sides of the film. The electrode 6 on the light incident side is an infrared absorbing electrode made of a metal conductor electrode coated with a light absorbing film such as gold black or carbon paint, or a transparent electrode made of a transparent conductor such as tin oxide or indium oxide, or an extremely thin film of gold, nickel, or the like that can transmit light. Furthermore, the electrode 6 on the incident side is formed over the entire surface of the polymer film 1, that is, extending to its peripheral portion. If necessary, this electrode 6 is electrically connected to the conductive ring 2 described later to form a part of the shield case.

The electrode 7 formed on the surface of the polymer film 1 opposite to the incident side may be an extremely thin film of nickel, aluminum, or the like. Further, this electrode 7 is not formed on the entire surface of the ordinary film 1, but a predetermined gap is formed between it and the ring 3. Therefore, this electrode 7 is not electrically connected to the ring 3, but instead is connected to an input terminal of a voltmeter 11 via a lead wire 8, a connector 9, and a shielded wire 10. However, if at least the surface of the ring 3 in contact with the film 1 is an insulator, the electrode 7
and ring 3 may be in contact with each other.

The pair of rings 2 and 3 have a size of, for example, 100 mm, and are usually made of conductive metal. Steps 12 and 13 are formed on the opposing surfaces of these rings 2 and 3, respectively, and the peripheral edge of the polymer film 1 is clamped at these steps 12 and 13. ing. Note that instead of the step, the ring may have a slight inclination that becomes thinner toward the inside, or there may be no step or inclination. In this way, the film 1 is held stretched by the frame 14 formed by the rings 2 and 3. Frame 1
A transparent protective plate 4 attached to the front of the film 4 allows laser light to pass through, protects the film 1, and prevents noise caused by air vibrations, and is designed to prevent noise from external noise and wind. This prevents the film 1 from vibrating and producing an output voltage due to piezoelectric action. The protection plate 4 may be made of a material such as polyethylene, silicon, germanium, sapphire, polyvinylidene fluoride, or the like.

With this protection plate 4 and ring 2,
A first disturbance prevention chamber 16 is formed on the front side of the film 1. This first disturbance prevention chamber 16 is communicated with the outside. That is, the ring 2 has three grooves 17 formed on its front surface in the circumferential direction at intervals of, for example, 120 degrees, and the grooves 17 extend in the radial direction of the ring 2. Therefore, there is a groove 17 between the ring 2 and the protection plate 4.
A communication section is formed by the first disturbance prevention chamber 1.
6 communicates with the outside. Therefore, this disturbance prevention chamber 1
The pressure inside 6 will be maintained at a pressure equal to atmospheric pressure. Although the protection plate 4 is bonded to the ring 2, it is also possible to provide another ring outside the ring 2 and sandwich the protection plate 4 between the ring 2 and this other ring.

If a shield is required, the back plate 5 attached to the back side of the frame 14 is made of a conductive metal, or has a conductive layer formed on one surface thereof, and is in contact with the back side of the ring 3, for example, and is fastened with screws. are combined. Therefore, the back plate 5 is electrically connected to the electrode 6 on the incident side of the polymer film 1 via the rings 2 and 3. Furthermore, a small hole 15 is formed in the back plate 5;
The lead wire 8 passes through it. A connector 9 is attached to the outer surface of the back plate 5 around the small hole 15, and its negative terminal is directly electrically connected to the back plate 5. Therefore, this negative terminal constitutes a ground line. Also, this back plate 5 is the film 1 mentioned above.
The film 1 faces the back surface of the film 1 with a predetermined distance therebetween. Note that this back plate 5 may be formed integrally with the ring 3.

A second disturbance prevention chamber 18 is formed on the back side of the film 1 by the back plate 5 and the ring 3. This second disturbance prevention chamber 18 is also communicated with the outside. That is, the ring 3 has three grooves 19 formed along the circumferential direction on the back surface thereof, for example, at intervals of 120 degrees, and these grooves 19 are formed to extend in the radial direction of the ring 3. . Therefore, a communication section is formed between the ring 3 and the back plate 5 by the groove 19, and the second disturbance prevention chamber 18 is also communicated with the outside. Therefore, the pressure within the second disturbance prevention chamber 18 is also maintained at a pressure equal to the atmospheric pressure, which is also equal to the pressure in the first disturbance prevention chamber 16.

For example, when the rings 2 and 3 are made of perforated plates such as sintered metal, the grooves 17 and 19 provided in the first and second disturbance prevention chambers 16 and 18 can be regarded as the holes in the perforated plates. can. Furthermore, it is not essential that the 18 disturbance prevention chambers be shielded, and may be omitted in devices used in rooms with little electrical noise.

In such a configuration, when a laser beam is incident on the polymer film 1 from the outside through the transparent protection plate 4, the pair of electrodes 6, 7 of the film 1 is caused by the pyroelectricity of the polymer film 1. A voltage corresponding to the intensity of the laser beam is generated between the two. Since electrode 6 is held at ground potential, this output voltage is taken out by electrode 7 and supplied to voltmeter 11 via lead wire 8, connector 9 and shielded wire 10, where the output voltage is Measurements are taken.

Moreover, according to the calorimeter of this embodiment, since the first disturbance prevention chamber 16 is provided on the front side of the polymer film 1, this prevention chamber 16 prevents noise from external noise and wind. Vibrations are no longer transmitted to the film 1. Therefore, the film 1 does not produce an output voltage due to piezoelectric action due to vibration, and the intensity of the laser beam can be measured without being affected by disturbance noise such as sound or wind. Further, the first disturbance chamber 16 and the second disturbance chamber 18 are communicated with the outside through communication portions consisting of grooves 17 and 19, respectively, so that both the disturbance chambers 16 and 18 are both at atmospheric pressure. The pressure will be equal. In other words, even if light is incident on the incident surface of the film 1 and the temperature of the incident surface increases, both disturbance chambers 16,
There is no pressure difference between the two. Therefore, the film 1 is not deformed due to the pressure difference between the two chambers 16 and 18, and no output voltage is generated due to piezoelectric action. Therefore, more accurate measurements are possible.

Further, according to the calorimeter of this embodiment, the electrode 6 on the incident side of the polymer film 1, the frame body 14 consisting of a pair of rings 2 and 3, and the back plate 5 are electrically connected to each other. Thus, the second disturbance chamber 18 constitutes a shield case. Therefore, even if electrical noise is generated from, for example, an external commercial AC power source, a laser oscillator, an amplifier, etc., this noise is blocked by the shield case and does not act on the electrode 7 on the back surface of the polymer film 1. There's nothing to do. Therefore, highly reliable and accurate measurements are possible without affecting the measured values due to these electrical noises. In addition, since this shield case is composed of the electrode 6 of the polymer film 1, the frame 14, and the back plate 5, there is no need to provide a separate case, making the meter with a shield function compact. Can be provided. Note that since the communication portion formed by the groove portion 19 of the ring 3 is relatively small, there is hardly any decrease in the shielding effect.

Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the technical idea of the present invention.

For example, the above embodiment relates to a laser beam calorimeter, but the present invention is applicable to a fire alarm,
It is also possible to apply it to a light detection device such as an intrusion detector.

In the above embodiment, the back plate is made of a conductive metal, but a non-conductive back plate may be used with a conductive layer formed on its surface.

Further, in the above embodiment, the grooves 17 and 19 are provided in the rings 2 and 3, respectively, to form a communication section, but instead of the grooves 17 and 19, the rings 2 and 3 are provided with grooves 17 and 19, respectively.
A single or a plurality of through holes extending in the radial direction may be formed in each of the holes, or a through hole may be formed in the window frame or back plate of the entrance window to serve as a communication portion. In some cases, the shield hole may be bent to further improve the effect of preventing disturbances, although the structure is somewhat complicated.

As is clear from the above, according to the present invention, the first disturbance prevention chamber can prevent disturbance noise caused by sound and vibrations caused by wind, etc., and the second disturbance prevention chamber can also serve as a shield case. In some cases, electrical noise can be further prevented, and the pressure difference between the two chambers can be eliminated by the communication portions provided in the first and second disturbance prevention chambers, thereby preventing disturbance noise caused by the pressure difference. Therefore, it is possible to detect light or measure the intensity of light more accurately and without malfunction.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a laser beam calorimeter according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of the same meter. In the symbols used in the drawings, 1...polymer film, 4...transparent protection plate, 16...first disturbance prevention chamber, 17...groove, 18...second disturbance prevention chamber, 19... ...Mizobe.

Claims (1)

[Scope of utility model registration request] In a photodetecting device using a pyroelectric polymer film as a light receiving element, a first disturbance prevention chamber having a light incident window made of a transparent plate is provided on the light receiving surface side of the light receiving element, and a first disturbance prevention chamber having a light incident window made of a transparent plate is provided on the back side of the light receiving element. is the second
What is claimed is: 1. A photodetecting device characterized in that a disturbance prevention chamber is provided, and communication portions are formed in each of the first and second disturbance prevention chambers to communicate with the outside.