UA152063U - Laser sensor for early detection of fires - Google Patents

Abstract

The laser sensor for early detection of fires 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 and a matrix of light guides to a receiving optical system, the output of which is coupled to a receiving device, the output of which is connected to the input of an analog-to-digital converter, the output of which is connected to the input of an analyzing device. Additionally, the sensor contains an optical aperture, the input of which is optically coupled to a matrix of light guides, and the output of the aperture is coupled to the input of the optical receiving system, and a photodiode is used as a receiving device.

Description

A 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.

Also known is the aspiration smoke fire detector |2)|, 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.

A well-known analogue of the proposed useful model is a 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 beam expansion, the output of which is optically connected through a reflector to the input of a receiving device, the output of which is connected to input of the analog-to-digital converter, the output of which, in turn, is connected to the input of the analyzing device.

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 shortcoming of this sensor is the small depth of beam intensity modulation in the early stages of detecting fires that occur due to thermal disturbances, and as a result - the impossibility of their early detection.

The closest analogue of the proposed useful model is a laser sensor for the early detection of fires |5|, 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 through a reflector with the input of the 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, where a mirror is used as a light 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 to the input of the receiving device, in the role of which a device with a charge connection is used.

The disadvantage of the closest analogue is the discrepancy between the time constant of the charge-coupled device and the fluctuation spectrum of atmospheric turbulence. It is known that the spectrum of temporal fluctuations of atmospheric refractive index inhomogeneities is random and ranges from 0 Hz to 1 kHz. The characteristic time constant of the CCD is no more than 50 Hz, therefore, with "fast" changes in the refractive index, the change in the structure of the scattered radiation in the receiving plane (Fig. 1) will change so quickly that these changes will be averaged.

Thus, the real picture of the change in intensity distribution will be distorted, which will lead to a decrease in the probability of detecting fires.

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 a new set of features, the possibility of matching the spectrum of fluctuations of atmospheric heterogeneity and the time constant of the photodetector would be ensured.

To solve the given problem in a laser fire detector, which 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 through a reflector to the input of a receiving device, the output of which is connected to the input of an analog-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, an optical diaphragm, optically connected to it, a receiving optical system, the output of which is optically connected connected to the input of the receiving device, as such a photodiode is used.

The essence of the proposed useful model is explained by drawings (Fig. 1 - Fig. 3).

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

In fig. 2 shows the diffraction pattern in the receiving plane.

In fig. C shows the time spectrum of the current at the output of the photodetector.

The proposed laser sensor for the early detection of fires (see Fig. 1) contains: a semiconductor laser 1, a collimating optical system for beam expansion 2, a mirror 3, a matrix of light guides 4, an optical diaphragm 5, a receiving optical system 6, a photodiode 7, an analog-to-digital converter 8, analyzing device 9.

The output of the semiconductor laser 1 is optically connected to the input of the collimating optical system for beam expansion 2, the output of which through the mirror 3, the matrix of light guides 4, the optical diaphragm 5, is optically connected to the input of the receiving optical system 6, the output of which is optically connected to by the input of the photodiode 7, the output of which is connected to the input of the analog-to-digital converter 8, the output of which, in turn, is connected to the input of the analyzing device 9.

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, the optical diaphragm 5, and after passing through the diffraction process through the receiving optical system 6, a diffraction speckle pattern is formed in the receiving plane, which is a collection of light spots . The radiation that passed through the diaphragm into the receiving optical system 6 is detected by the photodetector 7. This signal is digitized by the analog-to-digital converter (ADC) 8 and analyzed using the analyzer 9.

In the absence of turbulent atmospheric disturbances due to a heat source (fire), the current at the output of the receiver 7 will have a constant value. When turbulence appears, the diffraction pattern, fig. 2, will randomly move in the receiving plane, each of the elements will have a trajectory similar to fig. 3.

The photodiode is a high-speed photodetector, so current changes will adequately correspond to the nature of the movement of the diffraction pattern without averaging, as was the case in the closest analogue.

A useful model provides early detection of fires due to the introduction of optical into the device

From the diaphragm, which ensures the creation of a variable light flow adequate to changes in atmospheric turbulence, as well as the use of a high-speed photodiode instead of a PZZ, due to which the spectrum of turbulence fluctuations is ensured to correspond to the time spectrum of the current at the output of the photodetector, which will increase the probability of early detection of fires.

Sources of information: 1 A. p. Mo. 593227 (USSR), 5088 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 Aspiratsionnyi dmmovoy pozharnyi izveshatel GABO. Technical description of ООО "Sensor Fire Detector System". - (Electronic resource | Mode of access to the resource: see 7Lllumm.mazpaot.gy/apisIev/5ui5ietvepvzog 4.PIt.

Z. Sharovar F.I. Comparative evaluation 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: per://dayu.zes.gy/daiymrrizpom/.stt ?gid-baria-173838roz-4851r-25. 4. Sharovar F.I. Method of early detection lit up. - M.: Stroyizdat. - 1988. - P. 78. 5. Laser sensor for early detection of fires. Utility model patent Mo 124616 dated 04/10/2018, Bull. Mo 7.

Claims (1)

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