JP2000111410A - Fire detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fire detector which can distinguish and detect a frame from an abnormality at a stage of a spark before generation of the flame in a short time and can monitor a state of the site as an infrared image. SOLUTION: Images of two wavelengths are formed at different positions on an infrared image pickup element 7 by a two-wavelength-separating mirror 2, a band pass filter 6 and a lens 3. A luminance signal of each pixel exceeding a preliminarily set luminance is compared and operated at a fire outbreak- judging circuit 14, whereby a flame and an abnormal high temperature part before the outbreak is distinguished and detected. An alarm is raised and moreover, the band pass filter is switched to a long wavelength pass filter, thereby enabling a state of the site to be confirmed by an infrared image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire detector which detects a fire and issues an alarm.

[0002]

2. Description of the Related Art Conventionally, heat detectors, smoke detectors, and flame detectors have been used as fire detectors.

A heat-sensitive fire detector detects a fire by detecting a rise in temperature of the fire itself, and a smoke-detection fire detector detects a fire by detecting the concentration of smoke generated by the fire. The flame detection type fire detector detects ultraviolet rays or infrared rays emitted by a flame generated by a fire.

[0004]

Since the conventional fire detector has the above operating principle, the heat detection type smoke detector and the smoke detection type fire detector have a detectable temperature rise after the occurrence of a fire. Or, there is a problem that it takes time to reach the smoke density, and the flame detection type fire detector has a problem that detection is early after the flame is generated, but it is not possible to detect abnormalities until the flame is generated . Therefore, in any of the methods, the fire has already progressed at the time of detecting the fire, and it is necessary to spray water immediately with a sprinkler or the like. Therefore, there is a problem that it is difficult to minimize damage by initial fire extinguishing. Furthermore, since the situation of the site cannot be monitored with a conventional fire detector, it is necessary to provide a TV camera or the like separately.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can detect a flame in a short period of time by distinguishing between the detection of a flame and the abnormality at the stage of the fire before the flame is generated. It is an object of the present invention to provide a fire detector capable of monitoring the situation at a site as an image.

[0006]

According to a first aspect of the present invention, there is provided a fire detector that separates infrared light into two wavelengths.
A lens for condensing and imaging the wavelength-separated infrared light,
An infrared imaging element for detecting an infrared image formed by the lens, a band-pass filter disposed between the lens and the infrared imaging element, and extracting pixels having a predetermined brightness or higher from a detection signal of the infrared imaging element It comprises a bright spot extraction processing circuit and a fire determination circuit that determines whether or not the bright spot extracted by the bright spot extraction processing circuit has a fire and issues an alarm.

A fire detector according to a second aspect of the present invention provides a two-wavelength separating means for separating infrared light into two wavelengths, a lens for condensing and imaging the wavelength-separated infrared light, and an infrared image formed by the lens. An infrared imaging element for detection, a band transmission filter, a long wavelength transmission filter, a filter switch disposed between the lens and the infrared imaging element for switching between the band transmission filter and the long wavelength transmission filter, and detection of the infrared imaging element A bright spot extraction processing circuit that extracts pixels having a luminance equal to or higher than a predetermined luminance from a signal, a fire determination circuit that determines whether or not a bright spot extracted by the bright spot extraction processing circuit has fired and issues an alarm, and an infrared imaging element And a means for converting the output of the above to a video signal.

A fire detector according to a third aspect of the present invention includes a wedge-type two-wavelength separating mirror as two-wavelength separating means.

A fire detector according to a fourth aspect of the present invention includes a two-wavelength separating mirror as a two-wavelength separating means, which is constituted by a parallel plate type two-wavelength separating plate and a flat mirror.

A fire detector according to a fifth aspect of the present invention has an infrared ray of 3.5 to 4.0 μm and a wavelength of 4.15 to 4.5 μ as two wavelengths.
m.

A fire detector according to a sixth aspect of the present invention is a fire detector that transmits infrared rays of 8 μm or more as a long wavelength transmission filter.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing Embodiment 1 of the present invention. In the figure, 1
Is an incident infrared ray, 2 is a wedge-type two-wavelength separating mirror, 3 is a lens, 4 is a first infrared ray reflected on the front surface of the wedge-type two-wavelength separating mirror 2, and 5 is reflected on a back surface of the two-wavelength separating mirror 2. The second infrared ray, 6 is a band-pass filter, 7
Is an infrared imaging element, 8 is an element driving circuit, 9 is a timing generation circuit, 10 is a preamplifier, 11 is an AD conversion circuit,
2 is a correction processing circuit, 13 is a bright spot extraction processing circuit, 14 is a fire determination circuit, 15 is a first alarm, and 16 is a second alarm.

FIG. 2 is a graph showing the irradiance of infrared rays received by the fire detector from the fire source. The infrared rays in the 4.15 to 4.5 μm band are emitted from the flame by the resonance radiation of carbon dioxide in the combustion component. From the previous abnormally high temperature object of, for example, 1000 ° C., infrared rays in a wide wavelength range enter the fire detector. Comparing the infrared irradiance with a wavelength of 3.5 to 4.0 μm and the infrared irradiance with a wavelength of 4.15 to 4.5 μm,
In a flame, the infrared irradiance at a wavelength of 4.15 to 4.5 μm is larger than the infrared irradiance at a wavelength of 3.5 to 4.0 μm, and for an object at 1000 ° C., the infrared irradiance at a wavelength of 3.5 to 4.0 μm is longer. It is characterized by being larger than the infrared irradiance of 4.15 to 4.5 μm. Therefore, the incident infrared ray 1 is changed to a wavelength of 3.5 to 4.0 μm and a wavelength of 4.15 to 4.0 μm.
If the infrared rays are separated into 4.5 μm infrared rays and detected by the infrared ray image sensor 7, the flame and the abnormally high temperature object can be distinguished.

FIG. 3 is a diagram showing an optical path of infrared light reflected on the front and back surfaces of the wedge type two-wavelength separating mirror 2 according to the first embodiment of the present invention.
Is an optical thin film filter that reflects infrared light having a wavelength of 4.0 μm or less and transmits infrared light having a wavelength of 4.15 μm or more, and the back surface is a reflective surface provided with a metal reflective film. The first infrared ray 4 of 4.0 μm or less reflected on the front surface is output at a reflection angle θ equal to the incident angle θ, but the reflection angle θ of the second infrared ray 5 having a wavelength of 4.15 μm or more reflected on the back surface. _Two
Is given by equation (1). θ ₂ = sin ⁻¹ (n · sin
(Sin ^-1 (sin θ / n) + 2ω)) (1)
ω is the apex angle of the wedge type two-wavelength separating mirror 2 and n is the refractive index. FIG. 4 shows the vertical angle and the second angle when the incident angle is 45 ° using silicon as the material of the wedge type two-wavelength separating mirror 2.
Is a graph showing the relationship between the reflection angle θ ₂ of the infrared ray 5 and the vertical angle of 0.094 °, the reflection angle is 45.9 °, and the viewing angle of one pixel of the infrared imaging element 7 is 0.1 °. If the first
Of the infrared ray 4 and the second infrared ray 5
An image is formed at the position where the pixel is shifted. FIG. 5 is a diagram showing signals of the infrared imaging element 7 when an image of a high-luminance object is captured, and shows that a high-luminance signal appears at a position shifted by 9 pixels.

Next, the operation of the fire detector according to the present invention will be described. An infrared ray 1 incident from a subject is first reflected by a wedge type two-wavelength separation mirror 2 having a wavelength of 4.0 μm or less.
Infrared ray 4 and second infrared ray 5 having a wavelength of 4.15 μm or more.
And is reflected separately. The first infrared ray 4 and the second infrared ray 5 which are separated and reflected are condensed and imaged on the infrared imaging element 7 by the lens 3 through the band transmission filter 6 which transmits infrared rays of 3.5 to 4.5 μm. Therefore, an infrared image having a wavelength of 3.5 to 4.0 μm and an infrared image having a wavelength of 4.15 to 4.5 μm are shifted on the infrared imaging element 7 by the number N of pixels corresponding to the angle determined by the vertex angle of the wedge. An image is superimposed and formed. The infrared imaging device 7 includes a timing generation circuit 9
The detection signal is output to the preamplifier 10 by applying a driving pulse by the element driving circuit 8 in accordance with the timing generated by the driving circuit. The output of the infrared imaging element 7 is amplified by a preamplifier 10 and converted into a digital signal by an AD amplifier circuit 11. The correction processing circuit 12 corrects the bias level variation based on the bias level variation data for each pixel acquired in advance, and sends the digital signal to the bright spot extraction processing circuit 13 and the fire determination circuit 14. The bright spot extraction processing circuit 13 detects that two pixels having a luminance equal to or higher than a preset luminance are present at an interval of N pixels as abnormal and detects a wavelength of 3.5.
If the infrared image of .about.4.0 .mu.m has a higher luminance than the infrared image of wavelengths of 4.15 .mu.
The alarm 15 of the second alarm 1
6 is output. Therefore, when the first alarm 15 is output, since the flame has not yet been generated, the guard or the manager can immediately rush to eliminate the abnormality at the stage of the fire type, and the second alarm 16 Is output, the fire extinguishing activity can be started by spraying water in the same manner as in the case of the conventional fire detector.

Embodiment 2 FIG. 6 is a block diagram showing Embodiment 2 of the present invention. In addition to Embodiment 1,
In addition to the bandpass filter 6, a long wavelength transmission filter 17 that transmits infrared rays of 8 μm or more is provided.
The band pass filter 6 and the long wavelength pass filter 17 can be switched and used in accordance with the filter switching signal 19 from the outside, and the digital video signal corrected by the correction processing circuit 12 is converted into an analog signal by the DA conversion circuit 20. This is output as a video signal 21.

Next, the operation of the fire detector according to the present invention will be described. As in the first embodiment, the band-pass filter 6 is used to distinguish and detect an abnormally high temperature portion before a flame or a fire, and a first alarm 15 or a second alarm 16 is output. The bandpass filter 6 is switched to the long-wavelength transmission filter 17 in accordance with an external filter switching signal 19 such as a guard or an administrator who receives the signal, thereby outputting an infrared image of 8 μm or more as the video signal 21. The infrared radiation amount of the room-temperature object at 8 μm or more is 3.5 to 4.0 μm band or 4.15 to 4.5 μm.
Since the amount of infrared radiation is 50 times or more than the m-band infrared radiation amount, it is possible to monitor the situation at the site which was not seen when the band-pass filter 6 is used, and to confirm the presence or absence of a person.

Embodiment 3 FIG. 7 is a block diagram showing a third embodiment of the present invention. In place of the wedge-type two-wavelength separating mirror 2 of the first embodiment, an infrared ray of 4.0 μm or less is reflected and an infrared ray of 4.15 μm or more is transmitted. Parallel plate type two-wavelength separation plate 22 and parallel plate type two-wavelength separation plate 2
2 and a flat mirror 23 that reflects infrared rays transmitted through the mirror 2.

FIG. 8 shows a case where the flat mirror 23 is replaced with the two-wavelength separation plate 22.
And the second infrared ray 5 is reflected at an angle shifted by twice the angle ω with respect to the first infrared ray 4 by disposing the second infrared ray 5 at an angle ω with respect to the first infrared ray 4. You can see that it works. The combination of the parallel-plate type two-wavelength separation plate 22 and the flat mirror 23 has an advantage that it is easier to manufacture than the wedge-type two-wavelength separation mirror 2.

Embodiment 4 FIG. 9 is a block diagram showing a fourth embodiment of the present invention. In place of the wedge-type two-wavelength separation mirror 2 of the second embodiment, an infrared ray of 4.0 μm or less is reflected and an infrared ray of 4.15 μm or more is transmitted. Parallel plate type two-wavelength separation plate 22 and parallel plate type two-wavelength separation plate 2
2 and a flat mirror 23 that reflects the infrared light transmitted through the light source 2 and has an advantage that the manufacture is easy as in the case of the third embodiment.

[0021]

According to the first, third, and fifth aspects of the present invention, images of different wavelength bands are shifted by a specific number of pixels to form an image on one infrared imaging element, thereby generating a flame and causing a fire. There is an effect that it is possible to distinguish and detect abnormal heat generation before.

According to the second, third and sixth aspects of the invention,
By forming images of different wavelength bands on a single infrared imaging device shifted by a specific number of pixels, it is possible to distinguish and detect the occurrence of flame and abnormal heat generation before a fire, and to change the band-pass filter to a long-wavelength filter. The effect is that the situation at the site can be monitored with an infrared image.

According to the fourth aspect of the present invention, the parallel plate type two-wavelength separation plate which can be easily manufactured and the flat plate mirror have the effect of performing the same function as the wedge type two-wavelength separation mirror.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a fire detector according to the present invention.

FIG. 2 is a graph of infrared irradiance to show the operation principle of the fire detector according to the present invention.

FIG. 3 is a diagram illustrating an operation of two-wavelength separation of the fire detector according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an operation of two-wavelength separation of the fire detector according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a state of image formation on the infrared imaging element 7 of the fire detector according to the first embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a fire detector according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a fire detector according to a third embodiment of the present invention.

FIG. 8 is a diagram illustrating an operation of two-wavelength separation of a fire detector according to a third embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a fourth embodiment of a fire detector according to the present invention.

[Explanation of symbols]

2 Wedge type two-wavelength separating mirror, 3 lens, 6 band transmission filter, 7 infrared imaging element, 11 AD conversion circuit, 13 bright spot extraction circuit, 14 fire determination circuit, 17
Long wavelength transmission filter, 20 DA conversion circuit, 22 parallel plate type 2 wavelength separation plate, 23 plate mirror.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G065 AA04 AA11 AB02 AB03 BA14 BA34 BB06 BB11 BB26 BB27 BC02 BC14 BC28 BC40 BD03 BD06 DA06 DA20 2G066 AA04 AC13 AC14 BA04 BA13 BA14 BA22 BA23 BA25 BC07 BC11 BC30 CA04 CA08 CA20

Claims (6)

[Claims] 1. A two-wavelength separating means for separating infrared light into two wavelengths, a lens for condensing and imaging the wavelength-separated infrared light, and an infrared imaging device for detecting an infrared image formed by the lens. A band-pass filter disposed between the lens and the infrared imaging device, a bright spot extraction processing circuit for extracting pixels having a brightness equal to or higher than a preset brightness from a detection signal of the infrared imaging device, and the bright spot extraction process A fire detection circuit for determining whether a bright spot extracted by the circuit has a fire and issuing an alarm. 2. A two-wavelength separating means for separating infrared light into two wavelengths, a lens for condensing and imaging the wavelength-separated infrared light, and an infrared imaging device for detecting an infrared image formed by the lens. A band-pass filter, a long-wavelength transmission filter, a filter switch disposed between the lens and the infrared imaging element to switch between the band-pass filter and the long-wavelength transmission filter, and a detection signal of the infrared imaging element. A bright spot extraction processing circuit for extracting pixels having a brightness equal to or higher than a predetermined brightness from the above; a fire determination circuit for determining whether or not the bright spot extracted by the bright spot extraction processing has fired and issuing an alarm; Means for converting the output of the element into a video signal. 3. The fire detector according to claim 1, wherein said two-wavelength separating means is a wedge-type two-wavelength separating mirror. 4. The fire detector according to claim 1, wherein said two-wavelength separating means is a combination of a parallel plate-type two-wavelength separating plate and a flat mirror. 5. The two wavelengths are 3.5 μm to 4.0 μm and 4.0 μm.
The fire detector according to claim 1, wherein the diameter of the fire detector is 15 to 4.5 μm. 6. The fire detector according to claim 2, wherein the long-wavelength transmission filter transmits infrared light having a wavelength of 8 μm or more.