JPH0412878B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a sensor device equipped with a dark field warning device and a length measuring device or a speed detecting device. BACKGROUND ART Conventionally, so-called dark field alarm devices that utilize infrared rays have been used as devices for monitoring darkness such as night security. In other words, the infrared rays emitted from the light emitting part are received by a light receiving part far away, and if something breaks between the light emitting part and the light receiving part, the light receiving part detects this, or the infrared rays emitted from the light emitting part are detected by the light receiving part. A light receiving unit detects the infrared rays that are reflected by an object and issues an alarm. In this dark field alarm device, a GaAs light emitting diode is generally used as the light emitting part, and the wavelength
Near-infrared light of around 1 μm is used. Also,
For example, pyroelectric materials such as PbTiO ₃ , PbS,
Infrared light guiding materials such as InSb are used, but
This is protected inside a light receiving window made of germanium, silicon, etc., and infrared rays pass through this light receiving window and reach the infrared sensor. On the other hand, as a device for measuring the distance to a distant object or moving object, there is a pulse radar that emits microwaves, captures reflected waves from the object, and calculates the distance from the phase of the reflected waves. Further, as a device for detecting a moving object or its moving speed, there is a Doppler effect using electromagnetic waves or ultrasonic waves, that is, a Doppler radar that calculates the speed from the amount of frequency change of reflected waves. However, with the recent advances in laser technology, especially the development of carbon dioxide lasers that are highly energy efficient and can produce large outputs from several tens of watts to several tens of kilowatts,
Pulse radar and Doppler radar using far infrared rays with a wavelength of 10.6 μm have been devised. Problems to be Solved by the Invention It would be very effective if the dark field alarm device was equipped with the length measurement function of a pulse radar or the speed detection function of a Doppler radar. However,
By adding these functions, multiple openings are created in the device, and if the device becomes larger, there will be restrictions on where and how it can be installed, and it will also become difficult to move the device. Problems also arise. Therefore, dark field alarm, length measurement or speed detection,
It is desired to realize a compact sensor device that has all the functions of detecting a moving object, but to achieve this, it is necessary to have a single opening in the sensor device and to
A near-infrared sensor for dark-field alarm and a microwave or far-infrared sensor for length measurement, speed detection, or moving object detection are installed, and a near-infrared sensor with a wavelength of about 1 μm for dark-field alarm is installed through the window provided in the opening. It is necessary to emit or receive infrared rays and microwaves or far infrared rays for length measurement, speed detection, and moving object detection. Further, the use of electromagnetic waves (light and radio waves) of different wavelengths for different measurements is also necessary in order to prevent interference between measurement electromagnetic waves. However, germanium and silicon, which were the materials for the light receiving window of conventional dark-field alarm devices, cannot
The transmittance is high in the near infrared region (wavelength 0.76 to 2.5 μm) including 1 μm, but the transmittance is low in the far infrared region (wavelength 2.5 μm or more) including the carbon dioxide laser wavelength of 10.6 μm.
It also has a transmission spectrum that makes it difficult to pass through the microwave range. Therefore, if a light-receiving window made of germanium or silicon is used, most of the energy of the microwave and carbon dioxide laser light will be absorbed by the light-receiving window. Therefore, the energy captured by the microwave sensor and the far-infrared sensor is small, making it difficult to perform highly sensitive length measurement, speed detection, or moving object detection. Therefore, an object of the present invention is to provide a new sensor device equipped with a dark field alarm function and a length measurement or speed detection/moving object detection function, which enables highly sensitive measurement and detection. Our goal is to provide window materials. Means for Solving the Problems According to the first feature of the present invention, an infrared sensor has a first wavelength range in the infrared region as the highest sensitivity wavelength, and a second wavelength region in the microwave region has the highest sensitivity wavelength. A sensor device equipped with a microwave sensor having a sensitivity wavelength has an opening and a window plate provided in the opening, and the window plate is made of ZnS that transmits infrared rays and microwaves. The thickness of the window plate is approximately equal to an integral multiple of half the wavelength of the microwave used in the microwave sensor in the window plate, and the infrared sensor and the microwave sensor are each It is installed inside the opening. According to a second feature of the present invention, the infrared sensor has a maximum sensitivity wavelength in a first wavelength region in the infrared region, and a maximum sensitivity wavelength in a second wavelength region different from the first wavelength region in the infrared region. A sensor device equipped with a carbon gas laser light sensor includes: 1
and a window plate provided in the opening, the window plate is made of ZnS that transmits infrared rays, and the infrared sensor and the carbon gas laser light sensor are respectively located in the opening. is installed inside. Effect By configuring in this way, the wavelength is 1 μm.
Near-infrared rays can be sensed by an infrared sensor, and microwave or far-infrared rays can be sensed by a microwave sensor or a sensor for carbon dioxide laser light, respectively. Therefore, the infrared sensor enables dark field monitoring, and the microwave sensor or carbon dioxide laser light sensor enables length measurement, moving body detection, and speed detection. In order to provide these two functions as a compact sensor device, a window material that allows light to pass from near infrared to far infrared or microwave is important. Almost no materials were known that allow far infrared rays to pass, particularly wavelengths around 10.6 μm, and also allow microwaves to pass through. From our actual measurements, ZnS is
This is the first material to be confirmed to efficiently transmit everything from near-infrared rays to microwaves. Figure 3 shows the transmission spectrum of a 6 mm thick ZnS plate in the infrared region. As is clear from this figure, ZnS has a wavelength of approximately
It transmits infrared rays shorter than 15 μm, and exhibits particularly high transmittance around the 10.6 μm wavelength of carbon dioxide laser light. Table 1 also shows the frequencies of ZnS plates with three different thicknesses.
Shows microwave characteristics for 6GHz and 12GHz.
Here, ε _r is the relative dielectric constant, and tan δ is the loss coefficient of the dielectric constant. In this way, it can be seen that the ZnS plates of various thicknesses have a small loss coefficient in each frequency band, that is, the lost energy is small, so that microwaves are efficiently transmitted.

[Table] Also, the wavelength λ of the microwave used in ZnS
The diameter is from several mm to several tens of mm, and is used for opening windows.
Since the thickness is almost the same as that of the ZnS plate, the phenomenon of interference cannot be ignored. That is, in Fig. 4, ZnS
The microwave incident on the plate is reflected by a reflected wave 31 at the upper surface 35.
, and the waves transmitted through this upper surface 35 pass through the lower surface 3
4 and returns as a reflected wave 32. Therefore, the combined reflected wave 33 by the ZnS plate is represented by the sum of the reflected waves 31 and 32. Now, top surface 3
As is well known, the reflection coefficients at 5 and the lower surface 34 are inverted in phase and have equal amplitudes and opposite phases, so the condition for minimizing the combined reflected wave 33 due to interference is the propagation distance between the reflected waves 31 and 32. The difference between is an integer multiple of the wavelength and is given by the following equation. 2d=nλ...(1) However, d: Thickness of ZnS plate λ: Wavelength of microwave in ZnS n: Integer Therefore, from equation (1), thickness d of ZnS plate is The ZnS plate transmits microwaves most efficiently when the wavelength is an integral number n times half of the wavelength λ. Note that similar conditions can be obtained in an analysis that takes into account multiple reflections within the ZnS plate. When the half wavelength λ/2 of microwaves in ZnS at frequencies of 6 GHz and 12 GHz is determined using the relative permittivity ε _r , they are approximately 9.0 mm and 4.5 mm, respectively, and the sample thicknesses in Table 1 are 9.0 mm, 18.0 mm, 26.9 mm is set to a value that satisfies equation (1). Note that the infrared transmission spectrum does not change much due to a change in the thickness d of the ZnS plate. Therefore
The thickness d of the ZnS plate is determined by the frequency f of the microwave used. That is, when carbon dioxide laser light is used for length measurement or moving object detection, the thickness d of the ZnS plate may be any value. Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. Embodiment 1 FIG. 1 is a configuration diagram of an opening of a sensor device according to an embodiment of the present invention. Window 1 is made of ZnS, transmits infrared rays and microwaves, and protects infrared sensor 2 and microwave sensor 3. And its thickness is about 9.0mm. A charge-coupled device (CCD) was used as the infrared sensor 2. The holder 4 is a member for supporting the window 1.
As a result of an experiment using infrared rays with a wavelength of about 1 μm and microwaves of 6 GHz from a GaAs light emitting diode, it was found that an object 100 meters away can be detected by an infrared sensor at night, and this distance of 100 meters can be measured by microwave sensor 3. was completed. Embodiment 2 FIG. 2 is a configuration diagram of an opening in a second embodiment. In this second embodiment, a carbon dioxide laser light sensor 5 is installed in place of the microwave sensor 3 in the embodiment shown in FIG. The carbon dioxide laser light sensor 5 has particularly high sensitivity around a wavelength of 10.6 μm. As a result of an experiment using infrared laser light with a wavelength of 10.6 μm from a carbon dioxide laser and infrared light with a wavelength of about 1 μm from a GaAs light emitting diode, the infrared sensor 2 sensed an object about 100 meters away at night, and this 100 meter distance was detected by carbon dioxide. It was possible to measure using the gas laser light sensor 5. In the first and second embodiments described above, distance was measured using microwaves or carbon dioxide laser light, but similar effects can be obtained by detecting speed or moving objects. In the above embodiment, a GaAs light emitting diode was used for the infrared sensor for dark field alarm, but an InP light emitting diode, a GaSb light emitting diode,
It is also possible to use light emitting diodes with different emission wavelengths, such as CdSnP ₂ light emitting diodes. Furthermore, microwaves used for distance measurement, etc.
Although the Hz band is used, other wavelength ranges can also be used. However, as the wavelength of microwaves becomes longer,
Since the thickness of the window panel must be increased, the attenuation will also increase accordingly. Therefore, the microwave to be used is determined within a range that does not make the window plate too thick. In addition, far-infrared lasers used for distance measurement, etc. are not limited to carbon dioxide lasers, but also include N ₂ O, CN, NH ₃
Gas lasers such as PbSnSeTe and PbSnSSe
Semiconductor lasers such as can also be used. Furthermore, in one of the above embodiments, near-infrared light is used for dark-field alarm and far-infrared light is used for distance measurement, etc., but by reversing this, far-infrared light is used for dark-field alarm. Outside light may be used, and near-infrared light may be used for distance measurement, etc. Effects of the Invention As explained above, according to the present invention, a compact sensor device has a function of not only a dark field alarm but also a function of measuring and detecting the distance to an object or the speed of a moving object with high sensitivity. Realized. Therefore, it would be very effective to apply the sensor device according to the present invention to a nighttime dark field alarm device for building management, etc.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the aperture of a sensor device according to one embodiment of the present invention, FIG. 2 is a block diagram of another embodiment, FIG. 3 is a transmission spectrum of ZnS, and FIG.
FIG. 2 is a diagram illustrating microwave interference caused by a ZnS plate. (Main reference numbers), 1...Window, 2...Infrared sensor, 3...Microwave sensor, 4...Holder, 5...Sensor for carbon dioxide laser light.

Claims (1)

[Claims] 1. A sensor comprising an infrared sensor whose highest sensitivity wavelength is a first wavelength range in the infrared range, and a microwave sensor whose highest sensitivity wavelength is a second wavelength range in the microwave range. The device has one opening and a window plate provided in the opening, the window plate is made of ZnS that transmits infrared rays and microwaves, and the thickness of the window plate is as follows: The value is approximately equal to an integral multiple of half the wavelength of the microwave used in the window plate, and the infrared sensor and the microwave sensor are each installed inside the opening. sensor device. 2.Equipped with an infrared sensor whose highest sensitivity wavelength is a first wavelength range in the infrared range, and a carbon gas laser light sensor whose highest sensitivity wavelength is a second wavelength range different from the first wavelength range in the infrared range. The sensor device has one opening and a window plate provided in the opening, the window plate is made of ZnS that transmits infrared rays, and the window plate is made of ZnS that transmits infrared rays, and the window plate is made of ZnS that transmits infrared rays. A sensor device characterized in that a sensor is installed inside each of the openings.