RU2489804C2 - Optical-electronic system for remote aerial radiological survey - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: invention provides an optical-electronic system which enables to measure density of fluorescence radiance in the UV spectral range, arising from ionisation of atmospheric nitrogen, and converting the obtained information to a visual image of distribution of levels of radioactive contamination on the underlying surface.

EFFECT: faster aerial radiological survey of an area due to shorter flight time of the aircraft and high reliability of instrument measurement data.

3 cl, 2 dwg

Description

Usage: conducting airborne radiation reconnaissance of the terrain (VRRM) in the interests of ensuring radiation protection of military units.

The essence of the invention lies in the development of an optical-electronic complex for remote sensitized Raman spectroscopy using the remote sensing method, which measures the fluorescence energy density in the UV spectral range arising from atmospheric nitrogen ionization and converts the received information into a visible image of the distribution of levels of radioactive contamination on the underlying surface.

EFFECT: increased operational efficiency of SRM and reliability of instrumental measurement data by reducing the flight time of the aircraft and obtaining a panoramic image of the distribution of levels of radioactive contamination on the ground.

The invention relates to the field of research on the development and creation of technical means for equipping a military radiation reconnaissance system.

Analysis of the status of the issue and the relevance of the invention.

The main drawback inherent in the existing military equipment for conducting SRRM is the local method used to obtain data on the parameters of radiation fields, based on the registration of direct gamma radiation at a point of radioactively contaminated area (REM) located under the aircraft (LA) at the time of measurement.

The algorithms used to process the incoming information used are not able to take into account all random and systematic errors caused by the uneven distribution of radioactive contamination resulting from natural atmospheric turbulence, the influence of the terrain, separation of radionuclides, etc. Correspondingly, the results obtained during the SRMM are the averaged characteristics of the REE parameters for a large area and the assessment based on them (forecasting the doses of radiation exposure to military personnel operating in the REE zones) will always be of low reliability.

Although aerial reconnaissance is one of the most efficient means of obtaining data on the extent and extent of radioactive contamination, its implementation consists in long-haul flights of aircraft over the contaminated area using the “tacking” method, i.e. along parallel lines located at a relatively small distance from each other to ensure the necessary density of control points. At the same time, an increase in the operational efficiency of conducting BPM by the local method is possible only by increasing the distance between the tacks of the span of the aircraft, which entails a decrease in the density of control points and, as a result, a significant decrease in the reliability of the assessment of RO.

These and other negative factors lead to a significant error in determining the extent and levels of radioactivity in the pollution zones, and since the magnitude of radiation losses in a particular pollution zone is proportional to its area, and ultimately to an increase in errors in decision-making on radiation protection of troops.

The author proposes the creation of a technical means of conducting BPM, the principle of which is based on the remote sensing method, in particular, the registration of atmospheric nitrogen fluorescence under the influence of AI. Maintaining VRRM using a device based on this method allows you to more quickly solve the tasks, since it does not require a long flight time by obtaining a panoramic image of the terrain over a large area.

Description of the invention.

The method of remote detection of radioactive objects based on the registration of the brightness field of the UV-fluorescence of atmospheric nitrogen under the influence of ionizing radiation has been known for a long time [1].

The experimental fluorescence spectrum of air nitrogen under the action of AI is shown in Figure 1. The data presented show that nitrogen fluoresces most intensively at wavelengths of 315.9 nm, 337.1 nm and 357.7 nm. It is known that in this case, the fluorescence yield linearly depends on the dose rate (MD) of ionizing radiation.

This method is already used to solve ground-based radiation reconnaissance tasks, in particular, it has been implemented in various types of equipment for the remote detection of ionizing radiation sources (III) for special equipment of the RBF defense troops [2]. The use of these samples for solving PP problems has not been further developed, in view of the low efficiency of their use on horizontal paths, where the influence of direct solar UV radiation is very large. However, when conducting reconnaissance from vertical scan paths (with aircraft), the effect of direct UV radiation will be significantly lower.

Thus, the essence of the invention lies in the practical possibility of obtaining a photo-television image of radioactive contamination of the underlying earth's surface according to the corresponding gradations of UV illumination in the informative range of atmospheric nitrogen fluorescence radiation. This device is an optical-electronic complex (hereinafter referred to as a complex) of aerial photo-television reconnaissance scanning the underlying surface in the UV range with transmission bands on the above nitrogen fluorescence lines and allowing to obtain a panoramic REM image in real time. Pollution zones, in this case, can be represented as a projection of the spatial-brightness structure of the atmosphere glowing in the UV region onto the underlying surface. The values of the energy brightness for any point of this projection will depend on the absorbed energy of ionizing radiation (AI) in the atmosphere above the underlying surface and, therefore, the REM image in the UV range can be “graded” in radiation levels.

A known method and device for its implementation, which laid down the above principles. The closest prototype of the claimed complex is designed to observe the terrain image and simultaneously measure the reflection or radiation spectrum at its individual points [3]. Achievable technical result of the prototype is the ability to accurately measure spectral characteristics simultaneously with the measurement of the coordinates of the points of the object at which the spectral measurements are made.

The prototype block diagram includes an optical part, a matrix of a photosensitive charge-coupled device (FPSS) made with a control circuit, a video signal processing unit, a synchronization and control unit, an information conservation unit, a digital calculator and a control display, and the optical part includes a set of light filters for selection the corresponding part of the spectral zone, a reference object of reference white color (for channel calibration), a lens whose output is connected to the input of the video signal processing unit, and controlling second input - to the output of the block synchronization and control, wherein spetcvychislitelej output is connected to the control input of the display. The video spectrometer [3] contains for each spectral zone its own normalized beam-splitting television channel, in each channel the output of the video processing unit is connected to the corresponding input of the special calculator.

However, this prototype cannot be used to achieve the above stated technical result for the following reasons:

- the prototype does not allow to obtain a panoramic image of the distribution of the density of the energy brightness of fluorescence in the UV range, while providing the possibility of obtaining a photo-television image of the underlying surface with the measurement of the radiation spectrum of the visible range at its individual points;

- in the device [3] uses a set of normalized filters that allow you to work only in the visible range of the spectrum, which excludes their use for the UV range;

- there is no possibility of calibrating spectral channels by MD at a point on the earth's surface.

Obtaining a photographic television image of rare-earth metals in the UV range with an aircraft is a rather complicated task. The main interfering factor is the natural background of solar radiation in the range of 290-380 nm, which has a significant effect on the value of the minimum signal level coming from the detected radiation fields. In this case, the contribution of UV radiation reflected from the Earth’s surface is insignificant in comparison with direct solar radiation. In this regard, the placement of the complex on the aircraft has a significant advantage compared to the ground version, since, in this case, direct radiation from the upper half-space can be excluded to the maximum possible extent.

The contrast of the REM image will be determined by the excess of the fluorescence signal of the probed volume of the atmosphere over the REM attributable to the decomposition element in the field of view of the device over the signal of energy illumination from the rising radiation in the atmosphere and the noise of the receiving path. Therefore, the main step in the algorithm for detecting and detecting radioactive objects is the electronic-digital processing of the resulting image, while the characteristics of the image must be electronically controlled regardless of the characteristics of the object. Accordingly, to solve this problem, we proposed a complex based on a UV spectrometer with a tunable acousto-optical filter (AOF).

An acousto-optic filter is an optical filter whose selective properties are due to interaction with monochromatic, acoustic signals generated by light waves, the lengths of which, with sufficient accuracy, satisfy the Bragg condition. Such filters make it possible to isolate a sufficiently narrow range of light wavelengths from a wide spectrum of optical radiation with the possibility of moving them over the optical spectrum over a wide range. The action of AOF is based on the use of light diffraction by ultrasound (acousto-optical diffraction) in solids. The design of the AOF allows you to control the characteristics of optical radiation (amplitude, polarization, spectrum, composition of the light signal, etc.), as well as process information carried by a light or acoustic wave.

Thus, another close prototype of the claimed complex is an acousto-optical spectrometer of the visible and UV range [4]. However, this prototype is intended for conducting scientific research in laboratory conditions, where the use of differential spectroscopy methods is required, does not have a photo-television channel and cannot be used to obtain images of objects that are luminous and emitting in the UV range from an aircraft.

The claimed complex is characterized in that it uses a combination of tunable AOF with FPSS-matrix in one measuring electronic video path forming a photographic television image of UV illumination over a radioactively contaminated earth's surface in the AOF transmission spectral band for wavelengths of 315.9 nm, 337.1 nm and 357.7 nm characteristic of fluorescence of air nitrogen.

Video spectrometric systems based on tunable AOFs have greater functional flexibility than video spectrometers with a turret of optical spectral filters [3]. The absence of mechanical moving parts ensures their high speed (the tuning time from one spectral interval to another is several microseconds), which is especially important when performing spectrometry with aircraft.

As a photodetector in video spectrometers, matrices or FPSS lines are used.

The advantages of combining tunable AOF with FPSS in one measuring video path are:

- a significant expansion of the dynamic range of measurements due to the operation of the AOF in the attenuator mode;

- full use of the capabilities of the optical system and the photosensitive surface of the FPSS due to the operation of the AOF in the optical shutter mode during personnel spectrometry;

- ensuring the same signal-to-noise ratio in the entire operating range due to the separate adjustment of the steepness of the transfer characteristic of the path in each spectral interval;

- the possibility of video spectrometry in the mode of time delay and integration, which significantly increases the signal-to-noise ratio and increases the accuracy of spectral measurements.

The video spectrometry algorithm is organized by an onboard microcomputer and includes sequential tuning of the spectral transmission band of the AOF, automatic correction of the unevenness of the spectral sensitivity and automatic regulation of the light FPSS mode, as well as the normalization of the output spectrometric data. Video spectrometry mode simplifies the task of geo-referencing spectrometric data in comparison with horizontal trace measurements.

In addition, along with the simple mode of video spectrometry considered, it is possible to implement a “background subtraction” mode and a selective (selective) mode, which has two stages. At the first stage, two-dimensional images of the studied surface fragment are formed in three to four spectral intervals, and from them, automatic identification of REM sections is performed. At the second stage, two-dimensional images are formed in a significantly larger number of spectral intervals, but only those image elements that correspond to the areas selected in the first stage are read.

In order to increase the distinguishability of rare-earth metals against the background of the underlying surface with an a priori indeterminate or changing spectral-energy characteristic (structure), it is advisable to use a spectrally adaptive television system (SATS) as a photo-television channel. In contrast to simple video spectrometers, SATS implements spectro-combined images. In this system, the process of spectral adaptation is reduced to the sequential implementation of the following steps:

- video spectrometry of the studied fragment;

- calculation of the contrast-spectral characteristics of the object-background (moreover, the spectrogram of the object can be set a priori);

- the formation of a spectrally-combined television image of a surface fragment.

The use of SATS is due to the need to increase the contrast of the luminous region above the rare-earth metals and the background at low levels of UV fluorescence radiation energy. Spectro-combined images are formed on the photosensitive surface of the FPSS sensor using one AOF, the spectral transmission characteristic of which is formed from the spectral ranges of fluorescence of atmospheric nitrogen and background. Image formation in the optical link of the SATS is preferable than in the electric path of multi-sensor television systems, since one AOF and one FPGA sensor are used, which increases the signal-to-noise ratio of the spectrally aligned image and significantly reduces the dimensions and weight of the optoelectronic link. In addition, this allows you to form a normal two-dimensional image of the object and obtain spectral information due to a tunable filter. Moreover, each picture can be taken at any wavelength, including all pictures can be taken only at one pre-selected wavelength. Such capabilities allow the storage of charges in the FPSS receiver in synchronism with the movement of the aircraft, exchanging the number of working spectral channels for radiometric accuracy.

Under real conditions, the background radiation flux, in addition to the influence of the solar zenith angle, will be subject to significant variations due to changes in the aerosol component of the atmosphere. Therefore, the brightness of the REM image will also change with the background radiation and, therefore, the dependence of the brightness of the REM image element on the radiation level above this element will be ambiguous. Therefore, when developing the complex, it should be possible to bind (calibrate) the brightness of the REM image to radiation levels. To solve this problem, it is advisable to use a position-sensitive gamma-ray telescope (PSHT).

A feature of the principle of operation of PCHT is the use of a position-sensitive detector (PSD) with a coding aperture [5]. The composition of the MAP is a polycrystalline scintillator located in a duralumin container with an optical window made of quartz glass, several optical fibers and a PMT. The coding aperture consists of a system of tungsten plates arranged in a horizontal plane in a specific order.

The principle of operation of the HRPGT is based on the analysis of successive images of the resulting code combinations formed during the passage of gamma radiation through a system of tungsten plates and characterizing the accuracy of the direction of the HRPG to a point in the terrain or object from which the radiation comes. The detector is protected from the influence of an external gamma background by means of flat lead plates.

The architecture of the main components of the claimed complex is illustrated by the block diagram shown in figure 2.

One of the most important channels of the complex is the electronic path, since it forms the output television image of the luminous region above the rare-earth metals and controls the operation of all subsystems and blocks.

It consists of a photo-television channel based on SATS 1, a channel for generating signal processing and visualization (FOVS) 2 and controller 3. The SATS channel includes an input optical unit (lens) 4, AOF 5, FPSS-matrix 6 made with the integrated electronic circuit of the photodetector. The FOVS channel includes input analog 7, digital 8, and output analog 9 blocks, as well as a video monitor 10. The control controller includes a logic circuit 11 and controls 12. A computer channel 13, including an on-board computer 14, a communication interface with a computer 15 and controls 16. A gamma-calibration channel 17, which allows preliminary calibration of the complex according to radiation levels on the ground using PCHT with a coding aperture 18 and processing unit 19 to obtain information about the MD of gamma radiation at specified points in the terrain.

The claimed complex works as follows:

The UV radiation stream enters the input optical unit 4 and then enters the AOF 5, where an ultrasonic wave creates a volume diffraction grating that selects the specified spectral components (wavelengths of 315.9 nm, 337.1 nm and 357.7 nm). The received signals are converted by the FPS matrix into a video signal, which is transmitted through analog block 7 to digital block 8, since in the general case the video signal generated by the photodetector cannot be directly fed to the monitor, since it has a number of specific features, the main of which is the need to isolate the difference REM spectral image in the UV fluorescence spectrum. Another feature of the video output signal is that additional processing is required to improve image quality at low light levels. The digital block 8 and two analog modules 7, 9 are designed to convert the video signal to the standard form in the FOVS channel. Thus, the input signal of channel 2 is the voltage of the video signals from output 1, and the output is the distribution of illumination on the screen of video monitor 10 and the digitized spectral images coming in to the on-board computer 14. The control controller 3, using the logic circuit 11 forms a system of commands 12 controlling individual modules 7, 8, 9, and also synchronizes the operation of blocks of the entire complex, including processes with placing radiance fluorescence densities in the UV range of the spectrum and the corresponding value of the terrain points in the MD. A gamma-calibration channel is used for this. 17. Calibration is carried out using at least two IRS with activities corresponding to the boundary values of the fluorescence energy density measured by the density complex. With the given flight parameters of the aircraft, the SPT is sent to the location point of one and the second III and the MD is measured. The processed information 19 in the form of an electric signal enters through the controller 3 into the FOVS channel, where it is assigned a certain value of the energy brightness obtained at the same point for the same flight parameters by the SATS channel 1. The values of the fluorescence energy brightness lying in the range measured by the complex are determined in accordance with the obtained linear dependence of the change in the intensity of UV light from the source of gamma radiation with minimal activity to the source with maximum activity. Directly in the process of conducting aerial radiation reconnaissance, the PSGT provides information on the level of radiation at the command of the logic circuit 11 for graduating the REM image at the selected point. Computer channel 13 carries out digital processing of video information, allows recording and reading video frames from FOVS channel blocks, combines the image of the underlying surface with the projection of pollution zones, and displays service information on the display screen 16.

List of sources used

1. Donahue T.M. Detection of high-altitude explosions by atmospheric fluorescence // TIIER, 1965, vol. 53, No. 12, p. 2293.

2. Explanatory note to the technical design for OCD, code "Antiknock": BUTI 201219.703ПЗ. - SPb .: GUDP SKB TNV, 2001 .-- 139 p.

3. A method for measuring the spectral characteristics of the reflection or radiation of an object at any point in its television image and a video spectrometer that implements this method in real or conventional time scale. Patent of the Russian Federation No. 2179375.

4. Acousto-optical spectrometer of the visible and UV range. - M.: NTTSUP. - Mhtml: fale: // D: \ Users \ User10 \ Acousto-optical devices.mht.

5. The study of the principles and methods of processing and transmitting information about the CBR situation obtained using orbital means: Research Report No. 5812 (final); Head A.Yu. Smartly; performers: S.N. Solovy [et al.]. - Volsk-18: military unit 61469, 2002 .-- 129 s.

Claims (3)

1. Optoelectronic complex for conducting aerial radiation reconnaissance of the area using the remote sensing method, characterized in that the composition of its elements includes a measuring video path with an acousto-optic filter and FPSS-matrix and a position-sensitive gamma-ray telescope, while the complex includes a logic circuit configured to comparing the brightness of fluorescence and the dose rate of gamma radiation. 2. The optical-electronic complex according to claim 1, characterized in that the design of the measuring video path uses a combination of a tunable acousto-optic filter with a FPSS matrix, forming a photo-television image of the brightness of the UV glow over a radioactively contaminated earth's surface in the spectral transmission zone of the acousto-optical filter for wavelengths 315 , 9 nm, 337.1 nm and 357.7 nm. 3. The optical-electronic complex according to claim 1, characterized in that it has a gamma calibration channel, including a position-sensitive gamma telescope with a coding aperture, which provides directional reception of gamma radiation from sources of ionizing radiation located on the underlying earth's surface, measurement dose rate and the formation of the received information into an electrical signal.

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