JPS6158879B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sensor used in crime prevention, disaster prevention systems, etc.

PVF ₂ (polyvinylidene fluoride) of about 30μm
If the film is stretched (stretched) by about 3 times by applying tension in one direction at a temperature of 80°C to 100°C, then bored, and thinner metal films are deposited on both sides of the film as electrodes, This thin film of PVF ₂ is known to be used as an excellent acoustic transducer.
For example, products that apply this to microphones and high-frequency speakers are commercially available. It has also been revealed that the PVF ₂ film surface subjected to the same treatment has excellent properties in terms of the so-called electroless effect, which generates a polarization voltage on the film surface due to temperature changes when the temperature changes due to infrared irradiation. It is being done.

On the other hand, in the field of crime prevention and disaster prevention detection systems, μCPu
Nowadays, microcomputers (microcomputers) have developed, and although the processing units have various processing capabilities, the input side detectors have not made much progress since before, so the current situation is that they suffer from a high false alarm rate. is expected to appear.

The present invention attempts to provide a crime prevention and disaster prevention sensor that meets these demands. Examples thereof will be described below. In Fig. 1, 1 is a storage case made of a conductor such as Al and has a shielding effect, 2 is an insulator made of Delrin or other material that is easy to process, and 3 is a receiving case which will be described later from the opening of the storage case 1. This is a spacer inserted so that the sensitive film 4 is kept at a certain distance, and is made of a conductive material. 4 is a thin film of PVF ₂ ;
This thin film has thinner metal films deposited as electrodes on both sides, and the polarization voltage generated on both sides of the PVF ₂ is extracted to the outside through this deposited film. In this case, the deposited film is preferably one that is stable against the environment, such as Al, Ni or NiCr. 5
is a fixing material that fixes the membrane surface of PVF _2. It is conductive and also serves as a lead to take out the voltage generated on the back side of the electrode. Here, it is assumed to be elastic in order to hold down the membrane surface. 6 is a small printed circuit board, on which a conductive fixing member 5 is fixed in the center, and at the same time, an amplifier 10 and an output lead wire 12, which will be described later, are fixed thereon. Reference numeral 7 denotes a set screw that passes through the fixing member 5 and the printed circuit board 6, and is tightened by an eyelet 9 with a lug and a tap so that the fixing member 5 and the printed circuit board 6 are integrated. 8 is a washer, and 10 is an amplifier consisting of a FET for signal amplification (in this case, it also serves as impedance conversion).The gate is connected to the lug of the center screw, and the drain and source are taken out as leads. 11 is the back cover, and 12 is its lead. Reference numeral 13 denotes a window material through which light enters, and is constructed using a plastic film or the like to improve transmission characteristics of infrared light and to suppress attenuation of acoustic energy.

That is, according to this sensor, infrared rays and acoustic energy are transmitted through the window material 13 and applied to the thin film 4. Since this thin film 4 performs photoelectric conversion and acoustic-electrical conversion, an electric signal corresponding to incident information can be obtained.
After being amplified by an amplifier 10, it is output.

As it is sensitive to both infrared rays and sound pressure, it is useful as a crime prevention sensor for monitoring indoor rooms late at night, and it outputs infrared radiation from the body temperature of an intruder and acoustic output when footsteps or other noises are emitted. You can receive both. In addition, in the event of a fire or the like, there is an even greater infrared input, so a greater output can be obtained, and at the same time, the acoustic output that occurs when something burns can be obtained.

FIG. 2 shows a processing circuit that identifies infrared input and sound pressure input from the output of the sensor in FIG. In FIG. 2, 21 is a sensor that detects infrared rays and acoustic energy, converts it into an electrical signal, and outputs it, 22 is a preamplifier that amplifies the output signal of the sensor 21, and 23 is a preamplifier that amplifies the output signal of the preamplifier 22. Filter to extract 50Hz signal, 24
25 is an amplifier that amplifies the output signal of filter 23; 26 is an amplifier that amplifies the output signal of filter 24; 27 is an infrared signal output terminal; 28 is an output terminal for audio signals.

Next, the operation of this embodiment will be explained.

In FIGS. 1 and 2, the storage case 1 attached to the measurement location is moved from the window material 13 to the sensitive membrane 4 when a person moves, a temperature change due to a fire, or a noise, voice, flame, etc. occurs. (Sensor 2 in Figure 2
1) detects these and converts them into electrical signals, which are amplified by the amplifier 10 (preamplifier 22 in FIG.
output to the outside. Among the outputs of the preamplifier 22, those from 1Hz to 50Hz are sent to the filter 23 and the amplifier 2.
5 to the processing unit 29, and the frequency is 50Hz to 10kHz.
is outputted to the processing section 29 via the filter 24 and the amplifier 26. When the voltage levels of the output signals of the amplifiers 25 and 26 are both above a predetermined value, the processing section 29 outputs an alarm signal from the alarm signal terminal 30.

In this alarm signal, when an illegal intruder occurs, a temperature change (about several Hz) due to body temperature is extracted by a filter 23, and an acoustic change (about 1 kHz) due to noise, voice, etc. is extracted by a filter 24. In addition, in the event of a fire, the temperature change (about several Hz) caused by the flame will affect the filter 24.
The filter 24 extracts the acoustic change (approximately 1 kHz) due to the natural burning sound (eg, "crackling, crackling" sound).

In this way, according to this embodiment, the sensors 4, 2
By separating the frequency components of the first output, the indoor situation can be identified from a distance. In particular, in the case of a fire, conventionally fires were detected only by the level of infrared output (temperature change), so the detection accuracy was improved by determining it as a "fire" only when there was a significant temperature change. .
However, in this embodiment, a "fire" is determined by the logical product of the infrared output level and the acoustic output level.
Therefore, even if the individual levels of the infrared output level and the acoustic output level are low and the sensitivity is high, there is a low probability that both levels will be falsely detected at the same time, resulting in a high overall density and fewer false alarms. Furthermore, in this embodiment, since the infrared output and the acoustic output are configured as one sensor, the crime prevention and disaster prevention sensor can be obtained at a lower cost and in a smaller space than when the acoustic output is obtained using a microphone.

As is clear from the above embodiments, the present invention converts external infrared rays and sound into electrical signals using polyvinylidene fluoride, and converts the infrared rays and sound into electrical signals by using the first and second filters to convert the infrared rays into 1Hz to 50Hz components corresponding to temperature change components. , separated into 50Hz to 10kHz components corresponding to acoustic components, and a processing unit determines that each of these signals is at a predetermined level or higher, and outputs an alarm signal when both are at a predetermined level or higher. Therefore, it has the effect of being highly sensitive, reducing false alarms, and being able to be implemented at low cost.

[Brief explanation of the drawing]

FIGS. 1A, 1B, and 1C are a top view, a front sectional view, and a side view of a security and disaster prevention sensor according to an embodiment of the present invention, respectively, and FIG. 2 is a block diagram of its processing circuit. 1... Storage case, 4... PVF ₂ thin film, 13
...Window material.

Claims (1)

[Claims] 1. A thin film of polyvinylidene fluoride housed in a case with a window that allows infrared rays and sound to pass through, metal electrodes attached to both sides of this polyvinylidene fluoride, and electrical signals obtained from the metal electrodes. Among them, 1Hz corresponds to the infrared temperature change component.
a first filter that passes only ~50 Hz components; a second filter that allows only 50 Hz to 10 KHz components that correspond to acoustic components to pass among the electrical signals obtained from the metal electrode; A crime prevention and disaster prevention sensor comprising: a processing unit that determines whether the output signal of the second filter is at a predetermined level or higher, and outputs an alarm signal when both of the output signals are at a predetermined level or higher.