UA148977U - LASER SENSOR OF EARLY FIRE DETECTION - Google Patents

Abstract

The laser sensor of early detection of fires contains a semiconductor laser, a collimating optical system for beam expansion, a grating of reflectors, a receiving optical system, a device with a charge connection, an analog-to-digital converter, an analyzing device. Additionally introduced a light divider, a mirror, a second receiving optical system, a second device with a charge connection, a second analog-to-digital converter.

Description

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

A well-known aspiration smoke fire detector |1|, 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. The disadvantage of the sensor is low immunity and the possibility of false alarms due to the high noise level of the optical amplifier.

A known laser fire detector (2, C), 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 expanding the beam, the output of which is optically connected to the input of the receiving device through a reflector, output 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 initial 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 a laser fire detector is the small depth of beam intensity modulation in the early stages of fire detection, which occurs due to thermal disturbances, and as a result - a low level of the signal/noise ratio during detection and a high level of false alarms, that is, low immunity.

The closest analogue of the useful model is the selected laser sensor for early detection of fires |4).

This laser sensor for early detection of fires contains a semiconductor laser, a collimating optical system for beam expansion, a reflector array, a receiving optical system, a charge-coupled device, an analog-to-digital converter, analyzing

From the device. The output of the laser is optically connected to the input of a collimating optical system for beam expansion, the output of which is optically connected through a reflector array to the input of a receiving optical system, the output of which is optically connected to the input of a charge-coupled device, the output of which is connected to the input analog-to-digital converter, the output of which, in turn, is connected to the input of the analyzing device.

The peculiarity of the operation of this device is that it is based on shifts of scattered radiation in the receiving plane due to the passage of the beam through the phase inhomogeneities of the air caused by thermal disturbances created by ignition at its initial stage. The greater the level of ignition, the greater the level of emerging air phase inhomogeneities and the greater the amplitude of chaotic deviations of scattered radiation observed in the receiving plane. The dispersion (SCA) of the deviations is compared with the threshold and a decision is made about the occurrence of ignition.

However, the vibrations of the object with the SVP applied to it also lead to angular shifts of the diffraction pattern in the receiving plane. A set of microprisms on a surface that is tilted relative to the front of the incident wave can be considered a kind of two-dimensional Michelson echelon, the diffraction patterns on which are well known and consist in the fact that the diffraction orders deviate by an amount equal to twice the angle of deviation of the surface from the front of the incident wave. This approach is described in more detail in (5) and confirmed by the results of mathematical modeling |bЭІ. The estimation of the amplitude of these oscillations shows that its magnitude (units of angular minutes) is comparable to the magnitude of angular oscillations of the local maximum caused by atmospheric turbulence, which complicates the detection and analysis of thermal disturbances in the presence of vibrations.

Thus, the disadvantage of the known device is low immunity due to the influence of vibrations.

The basis of a useful model is the task of creating a laser sensor for early detection of fires, in which the possibility of eliminating the influence of vibrations on the operation of the sensor would be ensured.

Fluctuations in the index of refraction of air, created by the source of ignition, are random. They will be uncorrelated in regions of space, the distance between which is greater than the spatial correlation radius. Let's create two probing beams and direct them to the SVP (see drawing).

The shift of the local maximum in the diffraction pattern, which is created by the first beam, 60 is due to two factors:

And in - Vo zhussthu tyu

The first component is caused by the influence of atmospheric inhomogeneities, and the second - by surface vibrations. Similarly, it can be written for the second probing beam.

The components due to air fluctuations are different and statistically independent in the two channels, and the components due to surface vibrations will be the same in both channels if the rays are directed to one point on the surface. Numerical data on the amount of deviation in each channel are determined with the frequency of the frame scan. When they are subtracted, the component caused by vibrations disappears: aku Sh Yaku Shchi u -Vhu

Then the elements of the array of data should be raised to the second power, averaged and the variance (SKE) should be calculated: hud) hu (sponge) what

The component turns to zero, because the random deviations in the channels are independent, sign-changing and have an average value equal to zero. Thus, the result of the calculations characterizes only the level of fluctuations of the refractive index due to the heating of the air by the ignition source and is not subject to the influence of the interfering vibrations of the surface.

A laser sensor for the early detection of fires, which contains a laser 1, the output of which is optically connected to the input of the light splitter 2, the first output of which is optically connected to the input of the first collimating optical system 4, the output of which is connected to the input of the reflector grid 5, and the output connected to the input of the first optical receiving system 6, the output of which is connected to the first receiving device with charge coupling 7, the output of which is connected to the input of the first analog-to-digital converter 8, the output of which is connected to the input of the analyzing device 13, the second output light splitter 2 is optically connected to the input of the mirror 3, the output of which is optically connected to the input of the second collimating optical system for beam expansion 9, the output of which is connected to the input of the reflector grid 5, and the output is connected to the input of the second optical receiving system 10, the output of which is connected to the second receiving device with a charging connection 11, the output of which is connected to the input of the second analog-to-digital converter 12, the output of which is connected to the input of the analyzing device 13.

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

The light stream created by the laser 1 is split into two beams that are separated in space by means of a beam splitter 2, the first beam is focused on the surface of the grid of reflectors 5 by means of the first collimating optical system 4. Due to diffraction on the set of reflectors in the receiving plane, a diffraction speckle is formed a picture that is a collection of light spots. Part of the radiation passes through the first optical receiving system 6 and is detected by the first receiving device with charge coupling 7. This signal is digitized by the analog-to-digital converter (ADC) 8 and analyzed using the analyzer 13.

The second beam with the help of the second collimating system 9 is focused on the surface of the grid of reflectors 5. Due to diffraction on the set of reflectors in the receiving plane, a diffraction speckle pattern is formed, which is a set of light spots. Part of the radiation passes through the second receiving optical system 10 and is detected by the photodetector 11. This signal is digitized by the analog-to-digital converter (ADC) 12 and analyzed using the analyzer 13.

In the analyzer 13, the signals are subtracted, raised to the second degree and averaged by means of software. Fluctuations will disappear due to vibrations, and dispersion will double due to turbulence.

The technical result that can be obtained when using the developed laser sensor for the early detection of fires is that an additional receiving channel is introduced, which is territorially dispersed relative to the main channel, and at the same time, due to a new set of features, the possibility of eliminating the influence of vibrations on the operation of the sensor will be ensured ( drawing).

The economic effect is a reduction in the probability of false alarms being issued by the sensor and, accordingly, a reduction in the number of calls to fire brigades.

Sources:

1. Aspiration demon fire alarm (OR.

Technical description 000 "System Sensor Fire Detectors". - (Electronic resource. - Mode of access to the resource: pErulimly mazpaot.gy/apisiez/5uvietvzepsog 4.pit.

2. Sharovar F.I.

Comparative evaluation of the effectiveness of the application of thermal maximum, differential and smoke fire detectors. // Fire-fighting and rescue equipment. - May 4. - 2006. - (Electronic resource). - Mode of access to the resource: NEr://dayu.zes.gy/daiurrivNpom.stt?gia-beria-173836roz-4v81r-a25.

3. Sharovar F.I.

Methods of early detection of a sunburned person. - M.: Stroyizdat. - 1988. - P. 78-83.

4. Laser sensor for early detection of fires.

Utility model patent No. 60240 dated 06/10/2011.

5. Dolya G.N., Katunin A.N., Kochyn A.V., Chudovskaya E.S.

About the interfering effect of vibrations on the operation of the sensor for detecting lit sources.

Management, navigation and communication systems. - 2009 - Issue 2(10) - P.89-91.

6. Dolya G.N., Chudovskaya E.S.

Mathematical modeling of the influence of vibrations on the operation of a television sensor of thermal atmospheric disturbances.

Bulletin of the Kherson National University.

Ex. 2(35). - Kherson: KhNTU, 2009. - P. 190-194.

Claims (1)

USEFUL MODEL FORMULA A laser sensor for the early detection of fires, which includes a semiconductor laser, a collimating optical system for beam expansion, a reflector array, a receiving optical system, a charge coupling device, an analog-to-digital converter, an analyzing device, the output of the laser being optically coupled to the input collimating optical system for expanding the beam, the output of the device with charge coupling 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, which is distinguished by the fact that a splitter, a mirror, a second receiving optical system are additionally introduced , the second device with charge coupling, the second analog-to-digital converter, and the output of the collimating optical system is optically connected to the input of the light splitter, the first output of which is connected to the input of the receiving optical system through the reflector grid, the second output of the light splitter through the mirror, the grid reflectors and the second receiving optical system emu is optically connected to the input of the second device with charge coupling, the output of which is connected to the input of the second analog-to-digital converter, the output of which is connected to the second input of the analyzer. N X Z KU she shi U No i st v : --