UA124616U - LASER SENSOR FOR EARLY FLAMMING - Google Patents

Abstract

Laser sensor for early detection of fires has a semiconductor laser, the output of which is optically coupled to the input of a oscillating optical system for beam expansion, the output of which through the reflector is optically connected to the input of a receiving device whose output is connected to the input of an analog-to-digital converter whose output in turn connected to the input of the analyzer. A mirror and a fiber optic matrix were used as a reflector, after which an optically coupled receiving optical system was introduced, the output of which was optically coupled to the input of a receiving device, as a charger device.

Description

The proposed useful model belongs to the field of security and fire alarm systems and can be used for early detection of fires.

A known fire detector |1|, which contains a radiation source and a photodetector. To determine the fact of ignition, light radiation scattered on smoke particles is used, which is detected by a photodetector, and if the threshold is exceeded with an increased concentration of smoke particles, a fire warning signal is issued.

The disadvantage of the known device is the impossibility of early detection of fires, because the power of radiation scattered on particles at a low concentration of particles is very low.

An aspirating smoke fire detector is also known, which contains a laser diode, an optical amplifier and a photodiode. Light radiation scattered on smoke particles detected by a photodiode is also used to determine the fact of ignition, and if the threshold is exceeded with an increased concentration of smoke particles, a fire warning signal is issued.

The optical amplifier allows you to increase the power of laser radiation by directing it to the photodiode, and thus increase the sensitivity of the sensor. But the disadvantage of the known sensor is also the impossibility of early fire detection, if the concentration of smoke particles is not yet high, although there are already thermal disturbances in the air caused by the fire.

The closest analog to the proposed useful model is a laser fire sensor |4|, which reacts to the appearance of thermal disturbances and contains a semiconductor laser, the output of which is optically connected to the input of a collimating optical system for beam expansion, the output of which is optically connected to the input through a reflector receiving device, the output of which is connected to the input of the analog-to-digital converter, the output of which, in turn, is connected to the input of the analyzing device.

Moreover, the reflector is made in the form of a reflective system with three mutually perpendicular faces, and the receiving device is a photoreceiver based on a photodiode.

At the early stage of the occurrence of fires, thermal disturbances appear, which lead to modulation of the initially uniform distribution of the intensity of the laser beam. The magnitude of the variable component is a measure of emerging thermal disturbances and is used to detect fires.

The disadvantage of the laser fire detector, which is taken as the closest analogue, is the small depth of modulation of the beam intensity in the early stages of detecting fires that occur due to thermal disturbances, and as a result - the impossibility of their early detection.

The basis of a useful model is the task of creating a laser sensor for early detection of fires as a fire alarm sensor, in which, due to the creation of a new set of features, the possibility of early detection of fires would be ensured.

To solve the given problem in the laser fire detector |4), which contains a semiconductor laser, the output of which is optically connected to the input of a collimating optical system for expanding the beam, the output of which through a reflector is optically connected to the input of a receiving device, the output of which is connected to the input of the analog-to-digital converter, the output of which, in turn, is connected to the input of the analyzing device, according to a useful model, a mirror is used as a reflector, after which a matrix of light guides is additionally introduced, the receiving optical system is optically connected to it, the output of which is optically connected connected to the input of the receiving device, in which a device with a charge connection is used.

The presence of thermal air disturbances is manifested in angular fluctuations of local maxima of the spatially inhomogeneous distribution of laser radiation intensity, which can be registered when projecting the diagram of the radiation scattered by the fiber optic matrix onto the photosensitive platform of the device with charge coupling. Thus, it is possible to detect fires early by measuring the spatial coordinates of local maxima.

The essence of the proposed useful model is explained by drawings (Fig. 1 - Fig. 4).

In fig. 1 shows the structural diagram of the proposed laser sensor for early detection of fires.

Fig. 2 shows the scattering diagram of laser radiation on a grid of reflectors.

In fig. C shows the characteristic trajectory of the movement of the local maximum in the sensitive plane of the device with charge coupling.

In fig. 4 presents a graph of the dependence of the root mean square deviation of the displacement of the position of the local maximum on the value of the intensity of the heat source.

The proposed laser sensor for the early detection of fires (see Fig. 1) contains: a semiconductor laser 1, a collimating optical system for expanding the beam 2, a mirror 3,

light guide matrix 4, receiving optical system 5, charge coupling device 6, analog-to-digital converter 7, analyzing device 8. The output of the laser 1 is optically connected to the input of the collimating optical system for beam expansion 2, the output of which is through the mirror 3, fiber optic matrix 4, optically connected to the input of the receiving optical system 5, the output of which is optically connected to the input of the device with charge coupling 6, the output of which is connected to the input of the analog-to-digital converter 7, the output of which, in turn, is connected to the input of the analyzing device 8.

The proposed laser sensor for early fire detection works as follows.

With the help of a collimating optical system to expand the beam 2, the radiation of the semiconductor laser 1 is applied to the mirror 3, passes through the matrix of light guides 4 and after passing through the diffraction process through the receiving optical system 5 is directed to the sensitive plane of the device with charge coupling 6. The receiving optical system 5 is intended for reduction of the spatial scale of scattered laser radiation to a value corresponding to the size of the sensitive plane of the device with charge coupling 6. In the absence of thermal disturbances, the position of a separate local maximum in the diffraction pattern is unchanged, and when a heat source appears on the beam propagation path, chaotic angular displacements appear local maximum. Spatial (angular) fluctuations of local maxima are recorded by the photosensitive platform of the device with a charge connection.

Since the magnitude of the angular displacement of the local maximum is proportional to the degree of thermal disturbances (Fig. 4), changes in this value lead to early detection of fires.

The advantages of the proposed laser sensor for the early detection of fires can be justified by comparing the possibility of detecting small thermal disturbances formed by the center of fires at their early stage and determined by the value of the structural constant 2 -17 fluctuations of the refractive index Sp 5107 cm s

When using the prototype device, the dispersion of fluctuations of the logarithm of amplitude 7 is measured; A modulated light wave, which is determined by the ratio

I - 03 С 6 "1 and at a wavelength of А-0.533μm and a track length of 10 m has a value of 44107. Accordingly, the root mean square deviation of the amplitude level is equal to 6.3-10-. Since the existing receivers of light radiation have a linear range of light characteristics

Of no more than 2-3 orders of magnitude, it is not possible to record such small relative changes in the signal amplitude.

When using the proposed sensor, the measurements are carried out using a charge-coupled device characterized, for example, by a size of 5 x 5 mm with a total number of pixels of 106. This means that the linear size of one pixel is equal to 0.5-10-6 m, and its angular size at a distance of 10 m is equal to 0.5-106 radians.

The value of the dispersion of the angular displacements of the Roos diagram before the reflection on the grid of reflectors is determined by the ratio | according to and at the values of -2 sa -5107cm Z r-0m Z and 409. radii; Their x Y-Zmm is also equal to 0.5-106 radians, which means that it can be registered.

The width of a separate maximum in the scattering diagram due to changing the size of the illuminated grating can also be selected in such a way that the angular size of the local maximum becomes the corresponding angular displacement due to atmospheric turbulence.

Thus, small relative changes in the intensity of the light beam in ? Prototype devices cannot be registered with small C values. which are characteristic of the early stages of fires, while small deviations of the scattering diagram under the same conditions can be registered using the proposed sensor.

The technical result consists in the possibility of early detection of fires due to the replacement of the reflector with a mirror and a matrix of light guides, the introduction of a receiving optical system, as well as the replacement of a photoreceptor based on a photodiode with a charge-coupled device.

Sources of information: 1. A.b. Mo. 593227 (USSR), 2088 17/10. Dymovoy sensor / F.I. Sharovar, V.A. Tolykin, V.A.

Shakirov. - Application 27.07.76; published 15.02.78; Bul. Mo 6-2 p. 2. Aspiration fire detector (OR. Technical description 000 "Sensor Fire Detector System". -I (Electronic resource) Mode of access to the resource: per. 7Lymly mazpaoti.gy/apisiez/5uzietvzepsog 4.piIt.

WITH.

Sharovar F.M.

Comparative assessment of the effectiveness of the application of thermal maximum, differential and smoke fire detectors. // Fire-fighting and rescue equipment. -Me4.- 2006. - (Electronic resource|. - Mode of access to the resource: NEr://dayu.zes.gy/dayurrivNpom.stt ?gia-beria-173836roz-4v81r-a25. 4. Sharovar F.Y.

The early detection method is lit. - M.: Stroyizdat. - 1988. - P. 78-

Claims (1)

FORMULATION OF THE USEFUL MODEL A laser sensor for the early detection of fires, which contains a semiconductor laser, the output of which is optically coupled to the input of a collimating optical system for beam expansion, the output of which is optically coupled through a reflector to the input of a receiving device, the output of which is connected to the input of an analog-diff converter, the output of which, in turn, is connected to the input of the analyzing device, which is characterized by the fact that a mirror and a matrix of light guides are used as a reflector, after which a receiving optical system optically connected to it is additionally introduced, the output of which is optically connected to the input receiving device, as a device with a charging connection is used. 2 ich CHU x x shko x yayu and o N et h ri - x Z ! 5! min 7 - Fig. 1 i u yakh S v v nn nn i M i V v V y p p sho nn.- PShn Z her shi OK V V vn be v o pn I i i fr nn ZNNNNYA v I Ne i o v i : shi a I Ts Ts Ts Shts g Fig. 2