CN117935467A - Large-range ultra-long-distance scanning type fire sensing system and method - Google Patents
Large-range ultra-long-distance scanning type fire sensing system and method Download PDFInfo
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Abstract
The invention provides a large-range long-distance scanning fire sensing system and a method, wherein the system consists of a high-light gain red/ultraviolet detector 1, a horizontal and vertical rotating mechanism 2, a rotating control circuit 3, a power supply circuit 4, an electromagnetic compatibility and protection circuit 5, a signal transmission circuit 6 and a high-light gain sensing and image signal processing circuit 7. The core signal processing component of the system is a high optical gain sensing and image signal processing circuit, so as to collect various high optical gain infrared/ultraviolet detector signals, collect image signals and infrared temperature measurement data of a camera, and complete various related calculations and analyses through an embedded processing chip. The method at least comprises the steps of signal gain rate of a high optical gain detector, convolution neural network calculation of image signals, fusion calculation of multi-characteristic signals and the like, and alarm decision and judgment are completed.
Description
Technical Field
The application relates to the technical field of emergency disaster prevention, in particular to a large-range long-distance scanning type fire sensing system and method.
Background
Most application objects of the space fire detection technology are industrial enterprises and civil commercial buildings, so that international and domestic product standards are limited to a short distance of 100m, but a large number of outdoor applications such as wood structure building groups (similar to ancient towns), forest grasslands, ports and the like are faced in practical application. In order to realize remote fire detection, the mainstream technical method in the years adopts an infrared thermal imaging camera and a visible light camera, and is matched with an AI deep learning algorithm, a pattern recognition method and the like to realize remote detection. However, when the infrared thermal imaging camera is used for identifying and judging a remote fire point, a great problem exists, namely that the camera is used for measuring temperature, when the temperature measurement precision is set for a certain specific distance, the temperature measurement precision can be greatly changed along with the distance change, particularly the temperature measurement precision is rapidly reduced along with the increase of the distance difference, and the distance is increased to a certain degree, so that the temperature measurement capability is lost. Therefore, when the alarm is used in a large range at a long distance, the most direct problem is that the false alarm rate is too high or the alarm is not given under the condition of long distance. There is therefore a need for a system that can reliably detect even a large range of remote conditions.
Disclosure of Invention
The invention aims to provide a large-range ultra-long-distance scanning type fire sensing system and a method thereof, which are used for solving the problems in the background technology.
In order to achieve the above purpose, the present invention provides the following technical solutions: the large-range long-distance scanning type fire sensing method is characterized by being applied to a large-range long-distance scanning type fire sensing system, wherein the large-range long-distance scanning type fire sensing system comprises a high-light gain infrared/ultraviolet detector (which can be used in combination with a visible light and/or infrared camera), a horizontal and vertical rotating mechanism, a rotating control circuit, a power supply circuit, an electromagnetic compatibility and protection circuit, a signal transmission circuit and a high-light gain sensing and image signal processing circuit.
Preferably, the high optical gain infrared/ultraviolet detector adopts a large-area spherical surface and a curved surface reflecting mirror to be matched with a proper infrared or ultraviolet sensor, so that characteristic spectrum radiation with a larger area is focused on a target surface or a (longitudinal cylindrical) sensing surface of the sensor, the high optical gain detector is formed, the response capacity of the sensor is increased by tens or hundreds of times, and the response distance of the detector is greatly increased.
Preferably, the effective area of the reflecting mirror of the high optical gain red/ultraviolet detector needs to be calculated according to the response spectrum range of the sensor, and the specific method comprises the following steps:
According to planck's law of radiation, the radiant power emitted outwards per unit wavelength interval per unit surface area around wavelength lambda,
I.e. spectral radiance mbλ, satisfies the following relationship with wavelength λ and temperature T:
Wherein the first radiation constant c1=2pi hc2= 8.7415 x108w·μm4/m2; a second radiation constant c2=hc/k= 1.43879 x104 μm·k, C is the speed of light in vacuum, c=3×108m/s; h is planck constant, h= 6.6256 x10-34 j·s; k is a boltzmann constant, k= 1.38054 x10-23J/K;
according to the law of spatial distribution of radiation-lambert cosine law, the radiation intensity is expressed as follows:
Wherein λ1 is the lower limit of the spectral band of the sensor response, λ2 is the upper limit of the spectral band of the sensor response, S is the effective reflecting surface area of the optical reflector, and θ (z) is the normal angle of the radiation source with a specific size on a certain distance radiation space;
In general, the minimum radiation intensity M min acceptable by the sensor can be measured by an instrument, and the minimum photosensitive area S min can be obtained according to the above formula, in many cases, the light of the reflecting mirror cannot be received by the target surface completely, so that the mirror surface form and the size of the reflecting mirror should be carefully designed to achieve the performance in practical design.
Preferably, the reflection area design of the high optical gain red/ultraviolet detector can be calculated by an equivalent method, firstly, the maximum response distance of a specific sensor to a certain standard radiation source under the condition of no optical gain can be easily obtained, the maximum response distance is indicated by D s, the photosurface or target surface of the sensor is indicated by A s, and according to the principle that the radiation intensity of electromagnetic waves decays with the square of the distance, if one wants to respond to the standard radiation source at the position of the distance D, the following formula can be approximately obtained;
where D is the distance that is expected to be responsive to the standard radiation source, A is the effective photosurface area for the standard radiation source that is satisfied at distance D, i.e., the specular surface area where the mirror is capable of reflecting light waves from the radiation source to the sensor target surface,
By the simple method, the effective mirror surface area required by the reflecting mirror can be calculated rapidly and effectively, so that the reflecting mirror can be designed conveniently.
Preferably, the high-light gain infrared/ultraviolet detector is used for fire detection, the selected light wave detection sensor needs to be sunlight blind, or fire and other light sources can be effectively distinguished through characteristic wave band comparison, for example, ultraviolet can adopt a 185-260 nm UVC wave band, infrared can adopt a 4.3 mu m narrow band wave band, and therefore rapid alarm can be guaranteed, and false alarm can be avoided.
Preferably, the high optical gain infrared/ultraviolet detector can obtain better convergence effect when adopting quadric surface reflecting mirror, but the angle of view at this moment is usually smaller, generally horizontal and vertical in the range of 6-15 ℃, can obtain wider view field when adopting spherical mirror, for example can reach more than 60 ° horizontally, vertical, but for spherical mirror, the effective optical gain reflection mirror area of a radiation source is only a certain zone, therefore need to measure and calculate the size of effective optical gain area according to the target surface size of sensor when carrying out the reflecting mirror design, in order to reach the anticipated detection distance, the sensor photosensitive target surface size and area that the detector adopts also have great influence to the design of reflecting mirror, for quadric surface mirror, the optimal sensor target surface should be columnar, this can obtain the biggest light receiving surface, when the sensor does not possess this condition, just need to measure and calculate the effective optical gain area of reflecting mirror according to the target surface size and distribution of sensor, simultaneously, the high optical gain infrared detector can be the same optical axis and the same optical axis of a sensor can be realized by the optical axis of a sensor, the infrared sensor can be placed on the same optical axis and the front of an ultraviolet sensor, the infrared sensor can realize the high optical gain is realized, the infrared optical gain can be realized simultaneously, and the infrared optical axis is focused on the same optical axis and the front of an ultraviolet sensor can be realized.
Preferably, the high optical gain red/ultraviolet detector may adopt a 45 ° angular mirror, 50% of incident light is projected onto a UVC ultraviolet or infrared high optical gain mirror along an optical axis through a spectroscope, and 50% of incident light is separated from the incident light in a 90 ° direction and projected onto an infrared or UVC ultraviolet high gain mirror, so that high gain amplification of infrared and ultraviolet is simultaneously realized, and further composite detection is realized.
Preferably, the optical signal acquisition of the large-range remote scanning fire sensing system can also have a composite mode that a high-light gain ultraviolet detector is combined with a high-light gain infrared detector, or the high-light gain ultraviolet detector is combined with an infrared camera, or a visible light camera is further combined, and the horizontal and vertical rotating mechanisms can drive different types of composite equipment to rotate at the same time so as to scan 360-degree airspace space.
Preferably, the horizontal and vertical rotating mechanism and the rotating control circuit mainly complete rotation, precision control and speed control in horizontal and vertical directions, the rotating control circuit is provided with an angle-measuring photoelectric code disc, the angle is 0.01-0.1 DEG in position precision, in practical application, the horizontal rotation speed depends on the horizontal field angle of a high-light gain infrared/ultraviolet detector or a camera, no matter single ultraviolet or infrared-ultraviolet combination or combination with the camera is adopted, the minimum field angle is taken as the upper limit of the rotation speed, and the upper limit of the rotation speed is alpha per second on the assumption that the angle is alpha; the vertical angle is intermittent, and the minimum value beta of the vertical field angle of the combined equipment is taken as a reference, and after one circle of 360-degree scanning rotation is completed horizontally, the next circle of dislocation scanning is carried out, and generally, a vertical rotation speed can be defined, wherein the rotation speed per second is not less than beta.
Preferably, the high optical gain sensing and image signal processing circuit may simultaneously receive image signals of multiple high optical gain detectors or infrared/visible light cameras, and simultaneously analyze and process the image signals, and the general processing method includes:
Calculating the periodic signal gain rate of the optical sensor, wherein I (t, gamma, theta) represents the optical signal of the current period t, I (t-1, gamma, theta) represents the optical signal of the current period t-1, and (gamma, theta) is a specific rotation angle position of each rotation period, and the signal gain rate is calculated as follows;
the image signal processing of the camera is divided into two types, wherein one type is an image analysis method, and a CNN convolutional neural network and image pattern recognition are generally adopted; for infrared video, temperature data or gray level data are extracted, and difference between two periods is carried out, so that the following calculation is carried out:
Wherein f (t, gamma, theta) represents the average value of calculation of the associated abnormal point values in the infrared frame image of the period t, f (t-1, gamma, theta) represents the average value of calculation of the associated abnormal point values in the infrared frame image of the period t-1, and the abnormal point data and the abnormal constant value in the infrared image are obtained according to the detected difference;
the fire judgment decision can be directly judged by adopting the indexes, and under the general condition, I (t, gamma, theta) is more than or equal to I th, delta I (t, gamma, theta) is more than 0 and delta I (t, gamma, theta) is more than or equal to delta I th, or f (t, gamma, theta) is more than or equal to f th, delta f (t, gamma, theta) is more than 0 and delta f (t, gamma, theta) is more than or equal to delta f th,
The calculated index is used as the input of a neural network, and the trained neural network is adopted to perform data fusion, so that the index is in the range of [0,1], the index can be used as an early warning signal when the index is between 0.7 and 0.8, and a fire alarm can be triggered when the index is above 0.9.
Drawings
FIG. 1 is a schematic diagram of a large-scale remote scanning fire sensing system according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a high optical gain infrared and ultraviolet composite detection system according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a system for combining infrared and visible cameras with high optical gain infrared/ultraviolet detectors according to an embodiment of the present application;
FIG. 4 is an exemplary diagram of a curved surface and a spherical optical mirror of a high optical gain red/ultraviolet detector according to an embodiment of the present application;
FIG. 5 is a diagram illustrating a design example of a coaxial dual-mirror optical system of a high optical gain red and ultraviolet composite detector according to an embodiment of the present application;
FIG. 6 is a diagram illustrating a design example of a vertical axis dual-mirror optical system of a high optical gain red and ultraviolet composite detector according to an embodiment of the present application;
FIG. 7 is a flow chart of control, calculation and alarm decisions for a large-scale remote scanning fire sensing system according to an embodiment of the present application.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the application provides a large-range long-distance scanning type fire sensing system structure diagram, which is shown in fig. 1. The large-range long-distance scanning fire sensing system comprises a high optical gain infrared/ultraviolet detector 1, a horizontal and vertical rotating mechanism 2, a rotating control circuit 3, a power supply circuit 4, an electromagnetic compatibility and protection circuit 5, a signal transmission circuit 6 and a high optical gain sensing and image signal processing circuit 7. The high optical gain infrared/ultraviolet detector consists of an infrared or ultraviolet sensor, a high optical gain optical reflector, a sensor position adjusting mechanism and a driving control and signal acquisition circuit. The horizontal and vertical rotation mechanism 2 mainly comprises a horizontal rotation control motor, a horizontal rotation transmission mechanism, a vertical rotation motor, a vertical rotation transmission mechanism, a (horizontal and vertical) angle sensor, a (horizontal 0 degree starting position and a vertical 0 degree position) limit switch and the like. The rotation control circuit 3 mainly comprises a rotation control chip, a motor driving circuit, an overload protection circuit and the like. The horizontal and vertical rotating mechanism 2 is matched with the rotating control circuit 3, so that continuous control of horizontal rotation and vertical rotation can be realized, and the rotating speed is controlled to meet the requirement of scanning perception. The power supply circuit 4 mainly comprises an input power supply voltage stabilizing and isolating circuit, a multi-voltage-class power supply sorting circuit and the like, and can rotate a motor to supply power on one hand and output various voltage-class power supplies for different components or circuits on the other hand. The electromagnetic compatibility and protection circuit 5 mainly plays roles in internal and external protection and isolation, and comprises circuits and treatment measures such as surge protection, sensing disturbance protection, electromagnetic field radiation disturbance protection, static electricity protection and the like. The signal transmission circuit 6 mainly comprises an Ethernet transmission circuit, a 5G or other wireless transmission circuit, an alarm signal relay passive contact signal output circuit and the like. The high-light gain sensing and image signal processing circuit 7 is a core component of the whole system, is usually designed by adopting an embedded multi-ARM high-end processing chip, mainly completes acquisition, analysis and calculation of high-light gain detector signals and infrared or visible light video image signals, and performs data fusion processing on various types of characteristic signals which are primarily analyzed to form a fire probability index, wherein the index is usually in the range of {0,1 }.
Fig. 2 provides a schematic diagram of a high optical gain infrared and ultraviolet composite scanning detection type system. Because each sensor always has its advantages and disadvantages, for example, a uv c sensor of 185-260 nm, it is advantageous to be solar blind, substantially unaffected by sunlight, but it is affected by electric welding or lightning, while an infrared sensor of a specific band range (this may be chosen according to the detection target, for example, a range of 4.0 μm to 5.0 μm) may avoid the effect of lightning, but may be affected by sunlight. In order to ensure high sensitivity and high reliability of detection, two relatively independent high optical gain detectors may be mounted side by side on the horizontal and vertical rotating mechanism 2, as shown in fig. 2, fig. 2 (a) is a schematic front view of the high optical gain infrared and ultraviolet composite scanning detection system, and fig. 2 (b) is a schematic side view of the high optical gain infrared and ultraviolet composite scanning detection system. For such a system, the high optical gain sensing and image signal processing circuit 7 mainly processes the signals of the high optical gain infrared and ultraviolet detectors, and by compounding and fusing the infrared and ultraviolet signal processing results, higher reliability is achieved.
Fig. 3 provides a schematic diagram of a high optical gain red/ultraviolet detector and infrared/visible camera combination system. The advantage of the high-gain infrared/ultraviolet detector is that reliable remote detection can be realized, but the high-gain infrared/ultraviolet detector is mainly aimed at flame detection, and the situation of an accident area cannot be visually observed by a user, so as to form a system with higher practical value, in this embodiment, an infrared variable view field camera and a visible variable view field camera are respectively hung on two sides of the high-gain infrared/ultraviolet detector, as shown in fig. 3, fig. 3 (a) and fig. 3 (b) are front and side schematic views of a high-gain infrared/ultraviolet detector and infrared/visible camera composite system. For such a system, the high optical gain sensing and image signal processing circuit 7 processes the signals of the high optical gain infrared or ultraviolet detector on the one hand, and simultaneously processes the image signals of the infrared and visible light cameras on the other hand, and combines and fuses the red/ultraviolet signal processing results with the image signal processing results to achieve higher reliability, and meanwhile, the system also has the capability of detecting smoke through the image signals and also has the capability of providing video image observation and monitoring for the attendees under the alarm condition.
The high light gain red/ultraviolet detector and/or the camera with different forms are/is mounted on a horizontal and vertical rotating mechanism, and the mechanism can drive the components to rotate at the same time so as to scan 360-degree airspace space. The horizontal and vertical rotating mechanisms and the rotating control circuit are matched to mainly complete rotation, precision control and speed control in the horizontal and vertical directions, the rotating control circuit is provided with an angle measuring photoelectric coded disc, and the angle is 0.05-0.01 degree in position precision. In practical applications, the horizontal rotation speed depends on the horizontal angle of view of the high-light gain infrared/ultraviolet detector or the camera, and whether single ultraviolet or infrared-ultraviolet combination or combination with the camera is adopted, the minimum angle of view is taken as the upper limit of the rotation speed, and if the angle is alpha, the upper limit of the rotation speed is alpha per second; the vertical angle is intermittent, and the minimum value beta of the vertical field angle of the combined equipment is taken as a reference, and after one circle of 360-degree scanning rotation is completed horizontally, the next circle of dislocation scanning is carried out, and generally, a vertical rotation speed can be defined, wherein the rotation speed is not more than beta per second. Therefore, the whole rotating mechanism drives the carried component to realize the scanning of the whole 360-degree airspace in a Z-shaped spiral mode.
The rotating mechanism used in fig. 2 and 3 may be a cradle head type or a ball turntable type. The cloud deck mode has poor wind resistance, and the ball turntable mode is more stable. However, the specific selection needs to be uniformly considered according to the use environment and the economy. The system has better robustness to the influence of shaking caused by wind, and the cradle head can be preferentially used as long as the positioning precision allows.
When the accurate positioning is needed, once an alarm signal appears in the system, the system can be finely adjusted by controlling the horizontal direction and the vertical direction of the rotating mechanism, when the signal output of the detector is strongest, the position coordinate of the fire point can be calculated only by combining the horizontal angle and the vertical angle of the rotating platform and the topographic altitude distribution according to the installation altitude of the system, namely, the fire point is indicated to be on the central optical axis of the high-light gain infrared/ultraviolet detector.
FIG. 4 is an exemplary diagram providing a high optical gain red/ultraviolet detector quadric and spherical optical mirror. Generally, the photosurface or target surface of the ultraviolet or infrared sensor is usually smaller, the sensors with small target surfaces are mainly used in the traditional detector, the electric signals output by the sensors are mainly driven by the optical signals directly received by the target surface, and the visible signals are usually smaller. Or more direct results are that the detection distance of the traditional detector is often relatively close, taking the traditional ultraviolet flame detector as an example, the alcohol fire detection distance of 0.1m 2 can only reach about 25m, the n-heptane fire detection distance of 0.1m 2 can only reach about 45m, and the detection distance is enough for the application of the general industry and the building field, but the difference is far. The basic idea of the high optical gain infrared/ultraviolet detector is to focus much larger radiation energy on the photosensitive surface or target surface of the sensor through an optical reflector, so that the response capacity and the response distance of the sensor are greatly improved through an optical gain method. Most concave mirrors have a certain condensing effect, such as a parabolic concave mirror, a quadric concave mirror, a spherical concave mirror or an elliptical concave mirror. The parabolic concave mirror as shown in fig. 4 (a) can focus the light radiation with a certain angle range, which is injected from the outside, onto the photosensitive surface of the sensor, and the focusing capability of the parabolic or quadric concave mirror is relatively strong, but there is a problem that the angle of view is relatively small (e.g., the angle of view is greater than 6-15 degrees in the figure). While the spherical concave mirror of fig. 4 (b) can focus light radiation with a larger angle (for example, the view angle of 34 ° x2=68° in the figure), it is difficult to focus the light on a point due to the spherical aberration problem of the spherical mirror, and in practical application, for a sensor with a specific photosurface, light focusing with different incident angles has different spherical areas acting on the sensor, and consideration needs to be given when calculating an effective reflection surface. According to the invention, the large-area spherical surface and the curved surface concave reflecting mirror are adopted to be matched with a proper infrared or ultraviolet sensor, so that the characteristic spectrum radiation with a larger area is focused on the photosensitive surface or the target surface of the sensor, a high optical gain effect is formed, and the response capacity of the sensor is increased by tens or hundreds of times, so that the response distance of the detector is greatly increased.
In practical application, the high optical gain red/ultraviolet detector needs to design the effective area of the reflecting mirror, and needs to calculate according to the response spectrum range of the sensor, and the method specifically comprises the following steps:
According to planck's law of radiation, the power of radiation emitted outwards per unit wavelength interval per unit surface area around wavelength λ, i.e. spectral radiance M bλ, satisfies the following relationship with wavelength λ and temperature T:
Wherein the first radiation constant C 1＝2πhc2＝8.7415×108W·μm4/m2; the second radiation constant C 2＝hc/k＝1.43879×104 μm.K. c is the speed of light in vacuum, c=3×10 8 m/s; h is planck constant, h= 6.6256 × -- 34 j·s; k is a boltzmann constant, k= 1.38054 ×10 --23 J/K.
According to the law of spatial distribution of radiation-lambert cosine law, the radiation intensity is expressed as follows:
Wherein λ1 is the lower limit of the spectral band of the sensor response, λ2 is the upper limit of the spectral band of the sensor response, S is the effective reflecting surface area of the optical reflector, and θ (m) is the normal angle of the radiation source with a specific size in a certain distance radiation space.
Typically, the minimum response radiation intensity M min of the sensor can be measured by measuring with an instrument, and the minimum photosensitive area S min can be obtained according to the above formula. In many cases, the light from the mirror is not received entirely by the target surface, so that the mirror should be designed in detail in terms of its specular form and size to achieve performance.
For example, the parabolic mirror is adopted for design, the parabolic mirror has strong focusing capability, and the response wavelength range of the sensor is 4.0-5.0 μm, and the above expression can be expressed as:
according to the measurement result of the sensor, after M min is obtained, aiming at the flame with the sectional area of 1.0M 2, the effective area of a reflecting mirror with the effective area of about 0.06-0.1M 2 is required to be calculated to obtain S min, so that the purpose of detecting the distance of 7.5-10 Km is realized.
The high optical gain red/ultraviolet detector, the reflection area design can also be calculated by an equivalent method. The maximum response distance of a particular sensor from a standard radiation source without optical gain is readily available, given the designation D s, and the photosurface or target surface area of the sensor, designated a s. According to the principle that the radiation intensity of electromagnetic waves decays with the square of the distance and the principle that the effective area of a reflecting mirror reflects and converges radiation energy in direct proportion to the effective area of light receiving, if one wants to respond to a standard radiation source at the position of the distance D, the following formula can be approximately obtained:
Where D is the distance that is expected to be responsive to the standard radiation source, and A is the area of the photosurface that is responsive to the standard radiation source over a distance D, i.e., the area of the mirror that is capable of reflecting light waves from the radiation source to the target surface of the sensor.
By the simple method, the effective mirror surface area required by the reflecting mirror can be calculated rapidly and effectively, so that the reflecting mirror can be designed conveniently. Specific examples are as follows:
Assuming that for a flame of cross-sectional area 1m 2, the sensor direct photosurface is a s =1 mm×1mm, the corresponding distance to which it can respond is D s =100 m, if we want to respond equivalently to such a flame at a position of 5Km, then it is calculated as follows:
Therefore, the effective high optical gain area A is approximately 2500mm 2, and the effective reflection area of the designed high optical gain curved surface reflector is not smaller than A. Of course, under the condition of complex astronomical phenomena, the attenuation of light waves in different wave bands can be different, but the calculation result can be adopted to make proper adjustment to obtain the expected design sensitivity.
The high-light gain infrared/ultraviolet detector is used for detecting fire, and the selected light wave detection sensor needs to be sunlight blind or can effectively distinguish fire and other light/heat sources through characteristic wave band comparison. For example, ultraviolet can be in a 185-260 nm UVC band, and infrared can be in a 4.3 μm narrowband band. Therefore, the rapid alarm can be guaranteed, and false alarms can be avoided. In addition, the reliability can be improved under the condition that the response distance can be further improved through the composite use of the infrared detector and the ultraviolet detector.
The high optical gain red/ultraviolet detector of the invention can obtain better convergence effect when adopting a quadric reflector, but the angle of view at the moment is usually smaller, and is generally in the range of 6-15 degrees horizontally and vertically. When a spherical mirror is adopted, a wider view field can be obtained, for example, the view field can reach more than 60 degrees horizontally and vertically, but for the spherical mirror, the effective optical gain reflection area of one radiation source is only a certain zone, so that the size of the effective optical gain area needs to be calculated according to the target surface size of a sensor when the mirror is designed, and the expected detection distance is reached. Of course, the shape, size and area of the photosensitive target surface of the sensor adopted by the detector have great influence on the design of the reflecting mirror, and for various curved mirrors, the optimal sensor target surface shape is columnar, and the light receiving effect can be realized in the surrounding 360-degree range, so that the maximum light receiving surface is obtained. When the light-receiving target surface of the sensor is in a dot shape or other forms, the effective area of the reflecting mirror capable of reflecting and projecting onto the target surface is required to be designed according to the size of the target surface of the sensor, so that the effective high light gain effect is realized.
In addition to the composite detection of the two independent high-optical-gain infrared detectors and the ultraviolet detector in fig. 2, the high-optical-gain infrared-ultraviolet composite detector can also be formed by coaxially arranging a group of reflectors with different reflection bands and matching with ultraviolet and infrared sensors at different positions according to the mode of fig. 5. Specifically, two different types of reflectors are arranged back and forth, the front reflector 503 mainly reflects ultraviolet light 506 and converges on the light receiving surface of the ultraviolet sensor 504, and the front reflector can transmit infrared light 505. The infrared light 505 transmitted by the front mirror 503 is collected by the rear mirror 501 and projected onto the light receiving surface of the infrared sensor 502. The system thus designed requires the front mirror 503 to have infrared transmitting capability, and the optical axes of the front and rear mirrors to be coincident together so as to form the same angle of view. The advantage of this composite detection system is that it forms a consistent angular range of field of view, and the composite analysis of the red and ultraviolet sensor signals has a higher reliability, and the difficulty is that the fabrication of the front mirror 503 requires special materials to ensure that both the reflected and focused ultraviolet light and the transmitted infrared light are both reflected and concentrated.
An embodiment of a vertical axis dual-mirror optical system of another high optical gain infrared and ultraviolet composite detector of the invention is shown in fig. 6. The specific practice is that the optical axes of two reflecting mirrors in different forms are vertical, a beam splitter is added in the middle, 50% of incident light can be transmitted through the beam splitter, and 50% of incident light is vertically refracted to the 90-degree direction of the incident light axis, so that the arrangement scheme of fig. 6 can be adopted. The incident light rays comprise ultraviolet light 606 and infrared light 605, 50% of the light rays are continuously projected to the reflecting mirror 601 after passing through the spectroscope 607, wherein the infrared light rays in a specific wave band range are converged on the target surface of the infrared sensor 602; the other 50% of the light is refracted to 90 ° vertical direction and projected onto the mirror 603, where the UVC ultraviolet light is focused onto the target surface of the ultraviolet sensor 604.
The high optical gain sensing and image signal processing circuit of the system can simultaneously receive the image signals of the multipath high optical gain detector or the infrared/visible light camera, and simultaneously analyze and process the image signals, and the general processing method comprises the following steps:
Calculating a periodic signal gain rate of the high optical gain detector, wherein I (t, gamma, theta) represents an optical signal at the moment of the current period t, I (t-1, gamma, theta) represents an optical signal at the moment of the previous period t, and (gamma, theta) is a specific rotation angle position of each rotation period, and the signal gain rate is calculated as follows:
the image signal processing of the camera is divided into two types, one is to adopt an image analysis method, a CNN convolutional neural network and image pattern recognition are usually adopted, and the calculation can often find a suspected smoke target or fire point information faster; for infrared video, temperature data or gray level data are extracted, two-period difference is carried out, and the signal gain rate is calculated as follows:
Wherein f (t, gamma, theta) represents the calculated average value of the associated temperature abnormal point values in the infrared frame image at the t moment of the current period angle (gamma, theta), and f (t-1, gamma, theta) represents the calculated average value of the corresponding associated point values in the infrared frame image at the t moment of the previous period. And obtaining data abnormal points and abnormal values in the infrared image according to the detection difference. In actual calculation, the image temperature data or gray level data of two periods are subjected to preliminary operation, when the signal gain rate is found to be larger than a certain threshold value, the system automatically performs association operation of abnormal points in the images of the two periods, and the association operation method can adopt a region growing method commonly used in image identification. In brief, a point with an abnormality in the image is found, the point is taken as a root, the connected points are checked in 8 directions until the abnormal point does not appear any more, and the grown point is the associated abnormal temperature point.
The fire judgment decision can be directly judged by adopting the indexes, and in general, I (t, gamma, theta) is more than or equal to I th, delta I (t, gamma, theta) is more than 0 and delta I (t, gamma, theta) is more than or equal to delta I th, or f (t, gamma, theta) is more than or equal to f th, delta f (t, gamma, theta) is more than 0 and delta f (t, gamma, theta) is more than or equal to delta f th.Ith、ΔIth、fth and delta f th are preset thresholds.
The calculated index is used as the input of a neural network, and the trained neural network is adopted to perform data fusion, so that the index is in a {0,1} interval, can be used as an early warning signal when the index is between 0.7 and 0.9, and can trigger fire alarm when the index is above 0.9. The neural network can be a simple BP neural network.
FIG. 6 is a flow chart of control, calculation and alarm decisions for a large-scale remote scanning fire sensing system according to an embodiment of the present invention.
Because the angle of view of the high-light gain reflector is limited, especially for ultra-long distance, the angle of view is only about 6 degrees, so the invention adopts the horizontal and vertical rotating mechanism to realize the fire early warning and monitoring of 360 degrees of airspace through the rotation of horizontal 360 degrees and vertical directions. Assuming that the horizontal/vertical minimum field angle of the high optical gain detector is α=β=6°, the horizontal rotation speed of the mechanism is not greater than 6 °/s, which is equivalent to 60s or more for one rotation, and if 60 ° angular coverage is achieved in the vertical direction of the airspace, 10 rotations are required for completing the full airspace scan, which is approximately 10 minutes.
As in the flowchart of fig. 6, the system first rotates according to a defined airspace scanning strategy. When the rotating mechanism is controlled to rotate, the horizontal rotating speed is smaller than or equal to alpha per second, the rotating angle beta is controlled in the vertical direction after one circle of scanning is finished, and the scanning is performed in a Z-shaped spiral mode. Where α is the minimum horizontal field angle for all high optical gain sensors or cameras and β is the minimum vertical field angle. For the design of the invention, the rotation position control precision reaches more than 0.05 DEG, which is enough to meet the detection requirement.
According to the flow, the horizontal and vertical rotating mechanisms are continuously driven in the horizontal direction, and in order to fully analyze and process possible fire information, the signal processing circuit acquires a group of high light gain ultraviolet detector signals at intervals of Deltat 1. Because the time required to rotate the horizontal angle α is 1s or less, the time interval Δt 1 can be less than 1/3s, for example 200ms. The data obtained is expressed as I uv (t, γ (t), θ (t)), (γ (t), θ (t)) is the position of the platform rotation angle at time t in each rotation period. The same processing method is also adopted for the high optical gain infrared detector signal, and related data I IR (t, gamma (t), theta (t)) of the time interval Deltat 2 is acquired. For infrared and/or visible light cameras, it is also only necessary to acquire f IR (t, γ (t), θ (t)) or f vis (t, γ (t), θ (t)) frame images
The acquired data are calculated according to a flow system, steady state values are mainly calculated and acquired for a high-light gain infrared/ultraviolet detector, and the system is mainly used for calculating the background values of image background and infrared temperature data/gray level data when a specific angle is acquired for a camera. The steady state value of the high light gain infrared ultraviolet detector can be obtained by adopting a weighted average method of the numerical values of the front scanning period and the back scanning period, and the calculation of the image background can be obtained by adopting a commonly used Gaussian model method or adopting a weighted average method.
The next step in the flow is that the value of the high-light gain infrared/ultraviolet detector obtained at each t moment is differentiated from the steady state value to obtain the steady state variation, and meanwhile, the value of the signal gain rate can be obtained through the value operation of the t moment of the period and the t moment of the previous period. For an infrared camera and/or a visible light camera, a foreground image at the moment t can be obtained by calculating the difference between the image at the moment t and a background image, the pixel points in the foreground image are analyzed, and a connected target block diagram is cut out by adopting an image growth method. The value of the target block diagram is further calculated with the value at the time of the last period t, and the signal gain rate of the image temperature data or the gray data can be obtained. The system can also adopt CNN convolutional neural network to operate, namely directly taking a foreground image at the time t or an image at the time t as an input layer of the neural network, finally calculating fire similarity information, and adopting image calculation to simultaneously recognize and alarm smoke and flame.
In the actual flow operation, various related indexes and characteristic data (such as signal gain rate, steady state variation and the like) are acquired as much as possible, and the indexes and the data are subjected to secondary composite fusion calculation. The simplest fusion calculation method is to normalize each related index and then further weight and average to obtain the final judgment index. Further, using these feature data as input layers of the neural network, a judgment index may be further calculated, which falls within the interval of {0,1 }.
And for the result index of the composite fusion calculation, the system makes decisions and judges, and in the normal case, the index can trigger early warning when the index is between 0.7 and 0.9, and the fire alarm is started immediately after the index is more than 0.9.
Once the system confirms the fire alarm, the system can control the alarm relay to act and output an alarm signal, and meanwhile, the system sends alarm information, position information, video image information and the like to the management system through a wired network and a wireless network so as to be displayed by the monitoring system.
When the data calculation at the time t does not give an alarm, the system performs rotation control and data acquisition calculation at the next time, and the system is operated continuously.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. The large-range long-distance scanning type fire sensing method is characterized by being applied to a large-range long-distance scanning type fire sensing system, wherein the large-range long-distance scanning type fire sensing system comprises a high-light gain infrared/ultraviolet detector (which can be used in combination with a visible light and/or infrared camera), a horizontal and vertical rotating mechanism, a rotating control circuit, a power supply circuit, an electromagnetic compatibility and protection circuit, a signal transmission circuit and a high-light gain sensing and image signal processing circuit.
2. A method of large scale remote scanning fire sensing as defined in claim 1, wherein: according to the high-optical-gain infrared/ultraviolet detector, the large-area spherical surface and the curved surface reflecting mirror are adopted to be matched with a proper infrared or ultraviolet sensor, so that characteristic spectrum radiation with a larger area is focused on a target surface or a (longitudinal cylindrical) sensing surface of the sensor, the high-optical-gain detector is formed, the response capacity of the sensor is increased by tens or hundreds of times, and the response distance of the detector is greatly increased.
3. A method of large scale remote scanning fire sensing as defined in claim 1, wherein: the effective area of the reflecting mirror of the high-light gain red/ultraviolet detector needs to be calculated according to the response spectrum range of the sensor, and the method specifically comprises the following steps:
According to planck's law of radiation, the radiant power emitted outwards per unit wavelength interval per unit surface area around wavelength lambda,
I.e. spectral radiance mbλ, satisfies the following relationship with wavelength λ and temperature T:
Wherein the first radiation constant c1=2pi hc2= 8.7415 x108w·μm4/m2; a second radiation constant c2=hc/k= 1.43879 x104 μm·k, C is the speed of light in vacuum, c=3×108m/s; h is planck constant, h= 6.6256 x10-34 j·s; k is a boltzmann constant, k= 1.38054 x10-23J/K;
according to the law of spatial distribution of radiation-lambert cosine law, the radiation intensity is expressed as follows:
Wherein λ1 is the lower limit of the spectral band of the sensor response, λ2 is the upper limit of the spectral band of the sensor response, S is the effective reflecting surface area of the optical reflector, and θ (z) is the normal angle of the radiation source with a specific size on a certain distance radiation space;
In general, the minimum radiation intensity M min acceptable by the sensor can be measured by an instrument, and the minimum photosensitive area S min can be obtained according to the above formula, in many cases, the light of the reflecting mirror cannot be received by the target surface completely, so that the mirror surface form and the size of the reflecting mirror should be carefully designed to achieve the performance in practical design.
4. A method of large scale remote scanning fire sensing as defined in claim 1, wherein: the reflection mirror area design of the high-light gain red/ultraviolet detector can be calculated through an equivalent method, the maximum response distance of a specific sensor to a certain standard radiation source under the condition of no optical gain can be obtained easily, the maximum response distance is represented by D s, the light sensitive surface or target surface of the sensor is represented by A s, and according to the principle that the radiation intensity of electromagnetic waves decays with square times of the distance, if one wants to respond to the standard radiation source at the position of the distance D, the following formula can be obtained approximately;
where D is the distance that is expected to be responsive to the standard radiation source, A is the effective photosurface area for the standard radiation source that is satisfied at distance D, i.e., the specular surface area where the mirror is capable of reflecting light waves from the radiation source to the sensor target surface,
By the simple method, the effective mirror surface area required by the reflecting mirror can be calculated rapidly and effectively, so that the reflecting mirror can be designed conveniently.
5. A method of large scale remote scanning fire sensing as defined in claim 1, wherein: the high-light gain infrared/ultraviolet detector is used for fire detection, the selected light wave detection sensor needs to be sunlight blind, or fire and other light sources can be effectively distinguished through characteristic wave band comparison, for example, ultraviolet can adopt a 185-260 nm UVC wave band, infrared can adopt a 4.3 mu m narrow-band wave band, and therefore rapid alarm can be guaranteed, and false alarm can be avoided.
6. A method of large scale remote scanning fire sensing as defined in claim 1, wherein: the high-light gain infrared/ultraviolet detector can obtain better convergence effect when adopting quadric surface reflecting mirror, but the angle of view at this moment is usually smaller, generally horizontal and vertical in the range of 6-15 ℃, can obtain wider view field when adopting spherical mirror, for example can reach more than 60 DEG horizontally, vertical, but for spherical mirror, the effective light gain reflection mirror area of a radiation source is only a certain zone, therefore need to measure and calculate the size of effective light gain area according to the target surface size of the sensor when carrying out the reflecting mirror design, in order to reach the anticipated detection distance, of course, the sensor adopted by the detector sensitization target surface size and area also have great influence on the design of reflecting mirror, for quadric surface mirror, the optimal sensor target surface should be columnar, this can obtain the biggest light receiving surface, when the sensor does not possess this condition, just need to measure and calculate according to the effective light gain area of the target surface size and distribution reflecting mirror of sensor, simultaneously, the high-light gain infrared detector can be used for the same optical axis of a sensor and the same optical axis of a sensor, can realize the infrared light gain on the same optical axis and the same optical axis of a high-phase infrared sensor, and the infrared sensor can realize the simultaneous measurement and calculation of the infrared gain on the same optical axis, and the infrared sensor can realize the infrared gain on the same optical axis and the infrared.
7. A method of large scale remote scanning fire sensing as defined in claim 1, wherein: the high-light gain infrared/ultraviolet detector can adopt a 45-degree angle light mirror, 50% of incident light is projected onto a UVC ultraviolet or infrared high-light gain reflecting mirror along an optical axis through a spectroscope, 50% of incident light is separated from the incident light in the 90-degree direction and is projected onto the infrared or UVC ultraviolet high-gain reflecting mirror, and therefore high-gain amplification of infrared and ultraviolet is achieved simultaneously, and further composite detection is achieved.
8. A method of large scale remote scanning fire sensing as defined in claim 1, wherein: the optical signal acquisition of the large-range remote scanning fire sensing system can also be in a combined mode that a high-light gain ultraviolet detector is combined with a high-light gain infrared detector, or the high-light gain ultraviolet detector is combined with an infrared camera, or a visible light camera is further combined, and a horizontal rotating mechanism and a vertical rotating mechanism can drive different types of combined equipment to rotate at the same time so as to scan 360-degree airspace space.
9. A method of large scale remote scanning fire sensing as defined in claim 1, wherein: the horizontal and vertical rotating mechanism and the rotating control circuit mainly complete rotation, precision control and speed control in horizontal and vertical directions, the rotating control circuit is provided with an angle-measuring photoelectric coded disc, the angle is 0.01-0.1 DEG in position precision, in practical application, the horizontal rotating speed depends on the horizontal field angle of a high-light gain infrared/ultraviolet detector or a camera, no matter a single ultraviolet or infrared-ultraviolet compound or a compound with the camera is adopted, the minimum field angle is taken as the upper limit of the rotating speed, and the upper limit of the rotating speed is alpha per second on the assumption that the angle is alpha; the vertical angle is intermittent, and the minimum value beta of the vertical field angle of the combined equipment is taken as a reference, and after one circle of 360-degree scanning rotation is completed horizontally, the next circle of dislocation scanning is carried out, and generally, a vertical rotation speed can be defined, wherein the rotation speed per second is not less than beta.
10. A method of large scale remote scanning fire sensing as defined in claim 1, wherein: the high optical gain sensing and image signal processing circuit can simultaneously receive image signals of a plurality of paths of high optical gain detectors or infrared/visible light cameras, and simultaneously analyze and process the image signals, and the general processing method comprises the following steps:
Calculating the periodic signal gain rate of the optical sensor, wherein I (t, gamma, theta) represents the optical signal of the current period t, I (t-1, gamma, theta) represents the optical signal of the current period t-1, and (gamma, theta) is a specific rotation angle position of each rotation period, and the signal gain rate is calculated as follows;
the image signal processing of the camera is divided into two types, wherein one type is an image analysis method, and a CNN convolutional neural network and image pattern recognition are generally adopted; for infrared video, temperature data or gray level data are extracted, and difference between two periods is carried out, so that the following calculation is carried out:
Wherein f (t, gamma, theta) represents the average value of calculation of the associated abnormal point values in the infrared frame image of the period t, f (t-1, gamma, theta) represents the average value of calculation of the associated abnormal point values in the infrared frame image of the period t-1, and the abnormal point data and the abnormal constant value in the infrared image are obtained according to the detected difference;
The fire disaster judgment decision can be directly judged by adopting the indexes, I (t, gamma, theta) is more than or equal to I th, delta I (t, gamma, theta) is more than 0 and delta I (t, gamma, theta) is more than or equal to delta I th under the general condition, or f (t, gamma, theta) is more than or equal to f th, delta f (t, gamma, theta) is more than 0 and delta f (t, gamma, theta) is more than or equal to delta f th, the calculated indexes are used as the input of a neural network, and the trained neural network is adopted to conduct data fusion, so that the indexes can be used as early warning signals when the indexes are between 0.7 and 0.8, and fire alarm can be triggered when the indexes are above 0.9.
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