On the issue of classification of inspection and search equipment

Inspection equipment is of crucial importance in the activities of police officers, as equipment ensuring security at federal checkpoints, during the inspection of citizens and their belongings at transport hubs, in cases of inspection of citizens at the entrance to places of mass events, etc. In this regard, in Article 13 of the Federal Law "On Police", the relevant rights are assigned to police officers.

 The search technique is used in the investigation of crimes, to detect lost or intentionally hidden objects that can become material evidence of illegal acts, during operational search activities, such as: surveillance; examination of objects and documents; inspection of premises, buildings, structures, terrain areas and vehicles; control of postal items, telegraphic and other messages.

Since some devices can be used both for inspection and for search, for the purposes of this work it is advisable to combine them under one name inspection and search equipment (DPT).

Currently, the DPT is being actively improved, there are devices operating on new physical principles of detection, its capabilities for detecting various materials are expanding. A sufficiently large variety of DPT raises the question of its classification, for example, when considering the relevant topic in the educational process, drafting regulatory legal acts, compiling catalogs of DPT. The ideal classification should be compact (contain as few groups as possible), with clearly formulated classification features (classifiers), promising, that is, allowing you to group inspection and search devices not only existing at present, but also those that will be developed in the future according to certain characteristics.

The classification of DPT has already been superficially considered by the author in ^[1], however, the format of its presentation did not allow for a deeper analysis of classification features. The main task of this work is to develop a classification of DPT based on its physical principles of action, a secondary one is to improve classifiers of other types, for example, those specified in ^[2,3].

In the materials of scientific conferences held by FGKU NPO "Special Equipment and Communications" of the Ministry of Internal Affairs of Russia in 2016 and 2019 ^[4,5] there is a fairly wide list of DPT. Analysis of the capabilities of its various samples gives the following types of detectable objects:

                         - metal objects;

                         - flammable, explosive substances;

                         - narcotic drugs, psychotropic substances or their precursors;

                         - weapons, ammunition, ammunition cartridges;

                         - radioactive materials;

                         - living biological objects;

                         - criminal burials;

                         - semiconductor devices;

                         - sources of radio waves;

                         - optical devices;

                         - acoustic signals from biological objects and clock mechanisms;

                         - cavities and voids in solid media;

                         - biological substances;

                         - heat-contrast objects.

It should be noted that during the inspection, the task is to detect an even wider list of items included in the list of dangerous substances and items listed in the order ^[6]. However, not all of these objects and substances can be quickly detected by technical means.

Choosing the type of object you are looking for as a classifier for individual devices will be quite acceptable and characterizes them well, for example, for metal detectors. But there are drawbacks in this approach: firstly, the list of classes turns out to be quite voluminous; secondly, devices of different physical principles of operation and different names can be used to detect the same object. For example, a person hiding by thermal contrast can be detected by a thermal imager, by a shadow image – by X–ray equipment, by body movement and breathing behind opaque walls - by a radio wave radar detector. Since the same device can be used to detect various desired objects, a natural question arises about the correctness of assigning the device to a particular group.

In principle, the above classifier is quite understandable, revealing the purpose of individual PDT samples, but not talking about the principle of their operation. Let's consider other classifiers that allow us to divide PDT into groups.  

One of the traditional ones used for grouping different types of equipment is such a classification feature as the design of the device, expressed in the ability to move it. According to this classifier , the TPD is divided into funds:

1) stationary, non-movable during work, designed to work at a certain point;

2) movable, which can be freely moved and used during movement and stops. The latter, in turn, based on the method of movement, can be divided into:

– mobile, transportable. The most common: automobile (transported), moved by cars;  airmobile, moved by unmanned aircraft; as well as electric vehicles, moved on the ground on a remotely controlled mobile platform;

– wearable, human-movable. The most compact of them relate to hand-held (portable) products used both for inspection and for locating the location of the desired items. Wearable devices made structurally in such a way that they can be used covertly belong to the concealed ones.

It should be noted that the classifier "movability" is too general, allowing you to divide the inspection and search equipment into very large groups, in addition, almost any inspection and search tool can be implemented in each type of design.

Another fairly general classifier is the ability of DPT to affect the environment. Samples of equipment that affect the environment with their radiation are active. They use the principle of location, scanning the environment with various fields and radiation.

Devices that do not affect the environment, do not emit anything, work as radiation receivers that record changes in the parameters of the sensitive element of the device are passive.

Next, let's consider another classifier – the principle of operation of the DPT, which is supported by the content of the definition of technical means of inspection, given in GOST R 55249-2012. Technical means of passenger inspection are hardware and complexes operating on various physical principles designed for the inspection of people ^[7].

To explain the division into groups of DPT according to the physical principle of operation, we will give the names of individual types of devices that relate to each class name proposed below. A link will be given to some devices, where you can learn more about its principle of operation.    

The technique of the mechanical principle of action. This group includes fairly simple products that allow you to detect the desired objects due to mechanical contact with them. These are probes, sieves, trawls, drills, rakes.

The technique of magnetic and magnetometric principle of action. This group includes search magnets capable of attracting ferromagnetic materials due to their magnetic properties. Magnetometric devices capable of detecting ferromagnetic materials by fixing changes in the Earth's magnetic field can also be included in this group. 

The technique of the induction principle of action. This group includes devices whose principle of operation is crucial to the phenomenon of electromagnetic induction. For example, pulsed, eddy current, induction metal detectors ^[8].The technique of the optical principle of action.

 Optical radiation, in addition to visible radiation perceived by the human eye, includes infrared and ultraviolet radiation ^[9]. Accordingly, it is advisable to divide the DPT of the optical principle of operation into visual devices (using the visual visible range), infrared and ultraviolet devices. 

Examples: visual devices (endoscopes, boroscopes, videoscopes (tele-endoscopes), inspection mirrors, video camera detection devices, inspection television complexes); infrared devices (thermal imagers, devices for detecting optical devices operating in the infrared range, both passive and active, for example pulse-phase ^[10]; ultraviolet devices (ultraviolet lanterns for the detection of luminescent substances, vision devices in the ultraviolet range of the type "Cayman-1" ^[11]).

In the same group there will be devices using several types of optical radiation, multispectral and multispectral. As well as devices, the basis of the principle of operation of which are spectrometric methods.

Products using Raman scattering of light for identification can also be identified in this group, for example, lidar for remote detection of explosives using a complex method of Raman spectroscopy and laser-induced fluorescence ^[12].

The technique of the radio wave principle of action. An important characteristic of this group of devices is the frequency of operation of the antenna unit or search element, which determines the depth of penetration of the probing signal into the covering medium: the higher the frequency of radio waves, the less their penetration into the covering medium. Therefore, it is advisable to divide the devices of this group by the frequency range of their operation into:

– megahertz (radar metal detectors (in such devices, the parameters of the electromagnetic signal reflected from a metal object are estimated) ^{[8, p.16]}, deep GPR ^[13]);

– gigahertz (active devices: nonlinear locators, ground-penetrating radars for concrete structures, wall imagers; passive devices: field indicators, frequency meters, search receivers used to identify and localize various types of radio transmitting devices in radiation mode).

– terahertz (passive terahertz complexes and terahertz scanners for inspection ^[14]).

The technique of the acoustic principle of operation allows you to detect the desired object by the acoustic vibrations created by it. It is divided into products of the sound and ultrasonic range. The first type includes devices for detecting living beings in vehicles. For example, the product "Lavender-M" is used to detect a person in motor transport by the acoustic vibrations created by him, up to the heartbeat.

An example of an ultrasound device is an ultrasound tomograph, which serves to search for inhomogeneities, cavities in concrete walls. 

The means of the chemical principle of action make it possible to detect narcotic and explosive substances, traces of blood, etc. by the method of color chemical reactions. For example, a set of analytical tests of the CASPER series ^{[15, 16]}.

The technique of the X-ray principle of action uses the penetrating capabilities of electromagnetic radiation of the X-ray range. It can be divided into a scanning one (built on the technology of backscattered X-ray radiation (ORRI)), that is, capable of perceiving X-rays reflected from an object. And conventional X-ray equipment of direct transmission, built according to the traditional scheme. In any case, the detection of the concealed object is formed due to its difference in density from the hiding medium.

The technique of the nuclear-molecular principle of action. It is advisable to include products in this group whose principle of operation is implemented using processes and characteristic features of substances existing at the level of the atomic nucleus.

These are devices for detecting radioactive substances by gamma radiation. Also devices for detecting explosives by registering secondary radiation of neutrons and gamma quanta obtained as a result of irradiation of the examined medium by a stream of fast neutrons created by an isotope source. Devices using magneto-molecular resonance (the Alpha-6 product, a device for detecting and determining explosives and narcotic substances, which detects a molecular frequency identical to the recognition card located in the device ^[17]). There are also products using the nuclear quadrupole resonance method, which allows not only to detect, but also to identify individual chemical compounds ^[18].

Technique of the combined principle of action

In this group it makes sense to place devices using 2 or more different operating principles. Examples: portable combined inspection detector "Anchor-4E" ^[19], detecting electric, magnetic and acoustic fields; metal detector combined with a nonlinear locator (EH-MD product) ^[20].

Technique of other principles of action This includes devices that are not included in the previous groups, using unique physical principles of action, which are difficult to classify.

For example, the LQtest product. The device uses the technology of quasi-static field tomography. The device measures the gradient of the drop in the intensity of the electric field created by the device in the sample under study. This indicator is significantly higher for ethanol, acetone, gasoline and other flammable liquids than for non-flammable ones, such as water, which makes it possible to successfully separate them into flammable and non-flammable liquids ^[21]. 

Perhaps, gas-analytical devices should be included in this group: drift spectrometers and gas chromatographs. For example, the Sled-N device, which uses the method of combining gas chromatography with ion mobility spectrometry ^[22].

So, the proposed system of classifiers in general and the developed classification system according to the physical principle of operation of the DPT in particular can be applied to the overwhelming number of samples of the considered technique and allows them to be characterized sufficiently fully.

The enumeration of all classifying features in relation to a specific product allows us to fully characterize not only its purpose and design, but also the principle of operation, in order to form a single conceptual apparatus in the subject area.