STAGES OF DEVELOPMENT OF DOMESTIC INSPECTION EQUIPMENT.

STAGES OF DEVELOPMENT OF DOMESTIC INSPECTION EQUIPMENT..

ANTONOV Konstantin Anatolyevich,
ANDRYUSHIN Oleg Fedorovich, Doctor of Technical Sciences, Professor
AKHMATOV Alexander Pavlovich, Candidate of Technical Sciences

STAGES OF DEVELOPMENT OF DOMESTIC INSPECTION EQUIPMENT

The need to create inspection equipment arose after a series of terrorist attacks, the hijacking of aircraft and other vehicles, which resulted not only in material damage but also in human casualties. There was a need to control passengers, their hand luggage and baggage in order to prevent the possibility of carrying weapons, explosives and other items that could pose a danger.

In connection with this problem, all leading countries began work on creating effective inspection equipment and organizing its production.

In Russia, this problem arose in 1978, when, in preparation for the Moscow Olympics, it was discovered that the country's airports, which were supposed to receive guests and participants of the Olympics, were not equipped with means of protection against terrorist and other vandal acts.

In a relatively short time, according to the technical assignment of the civil aviation security service, a domestic company carried out a design development and ensured industrial production of the Luch-1 X-ray television introscopes, in which the formation of an X-ray image of the contents of inspected objects installed on a conveyor was carried out using synchronous rotation of X-ray generators and receivers. The installation of these X-ray television introscopes at Olympic airports made it possible to ensure the safe reception and then departure of foreign participants and guests of the 1980 Olympics.

After the Olympics, work on improving and developing technical means of inspection equipment continued. The task was set not only to increase the effectiveness of existing means and expand the conditions for their use, but also to find ways to create new means that would allow monitoring not only personal items and baggage carried, but also the owners of these items.

Given the breadth and diversity of means used to carry out terrorist and bandit actions, it became necessary to detect, along with standard firearms and bladed weapons, such as pistols, revolvers, TNT blocks, bayonet knives, Finnish knives and explosive caches, shooting pens, various sharpenings and other all sorts of shooting, piercing, cutting and exploding objects.

According to their tasks, inspection equipment is divided into three groups:

• X-ray television introscopes, allowing you to view the contents of hand luggage and baggage for the purpose of visually detecting dangerous objects on the TV monitor screen;
• stationary arched metal detectors that allow people passing through them to be checked for metal objects that are not presented for open visual inspection and are hidden in clothing. The presence of such objects is determined by sound and light signals;
• portable metal detectors that allow you to quickly determine the location of metal objects on a person or in any packaging, including mail, that in their size may correspond to objects that pose a danger.

These groups of inspection equipment, when used simultaneously, allow for effective control of the flow of objects being inspected.

X-ray television introscopes

The use of the Luch-1 X-ray television introscopes and its modification Luch-1M, which allows for the inspection of large-sized objects, has shown that mechanical scanning of the X-ray beam by rotating the X-ray generators and receivers has limited possibilities for improving their technical characteristics.

Therefore, from introscopes of the “Ray” type, domestic and foreign developers of inspection equipment have switched to the formation of an inspected image using the principle of a running beam. An X-ray generator with a wide cone-shaped radiation pattern, from which a narrow vertical fan-shaped pattern is cut out using a slit collimator, in this case does not rotate, but stands in one place. A vertically extended X-ray detector also stands in one place.

The inspection of the inspected object is carried out using the vertical movement of a point X-ray beam created by rotating a metal collimator disk with slits along the radius, with the simultaneous movement of the object on the conveyor in the horizontal direction.

The immobility of the X-ray generator and receiver made it possible to significantly improve such characteristics of the introscope as penetrating power and resolution.

Introscopes of this type of the Nadzor and Nadzor-1 series, due to the use of a point beam, created a low level of X-ray radiation, thereby ensuring safety for photo and film materials, magnetic tapes, disks, electronic components and medical preparations, and also allowing the inspection zone itself to be open, which gave the operator the opportunity to visually monitor objects undergoing inspection.

The Nadzor-1 introscope differs from the Nadzor introscope by a larger inspection zone and increased load capacity of the conveyor (up to 400 kg).

However, the throughput of the “Nadzor” series introscopes was relatively low due to the need for mechanical scanning, which limited the speed of passage of the X-ray beam through the inspected object, so further developments were carried out that allowed not only to increase the throughput of the introscope, but also to significantly improve its detection characteristics. This was achieved as a result of the creation of a multi-element semiconductor detector, which made it possible to abandon the use of a mechanical X-ray scanning system and switch to electronic scanning, which, in turn, increased the speed of scanning the inspected object by the X-ray beam, and therefore increased the speed of movement of the belt conveyor, and also reduced the inspection time and thereby increased the throughput of the introscope.

In addition, the transition to a multi-element semiconductor detector significantly increased the sensitivity and resolution of the system, and also made it possible to switch to computer methods of signal processing.

As a result of the work carried out, the Nadzor-2 X-ray television introscope was created, in which the registration of X-ray radiation that has passed through the inspected object is carried out by a multi-element detector containing semiconductor diodes that alternately register a narrow beam of X-ray radiation passing through the inspected object. The number of diodes is determined by the dimensions of the tunnel for passing baggage and the required image resolution.

The generator forms a fan-shaped X-ray beam diagram, wide in the vertical plane and narrow in the horizontal plane. The angle of the diagram in the vertical plane is determined by the selected maximum dimensions of the baggage being inspected. The presence of such a diagram requires closing the inspection zone with a tunnel, but allows for the inspection of objects up to 1.5 — 2 m in height and width and a length determined by the dimensions of the conveyor.

Further development of semiconductor detector technology made it possible to create a multi-element detector that records the soft (low-energy) component of the X-ray spectrum passing through the inspected object. The use of such a detector in an introscope as a second detector made it possible to create a color image of the internal contents of the inspected object, allowing the separation of the materials of objects located inside the object by color, depending on the effective atomic number of these materials, and thereby determine what kind of material it is.

Thus, in addition to the outline image of objects in the inspected object, it became possible to analyze information about the material of these objects, which significantly facilitated the recognition of objects and the determination of the degree of their danger.

The Nadzor-2M X-ray television introscope was created on the principle of spectral separation of the registered narrow X-ray beam that passed through the inspected object. In this introscope, in addition to color highlighting of objects in the inspected object, computer signal processing was introduced, which made it possible to implement negative and contour image modes, as well as to provide the ability to double and quadruple the size of any of the nine sections on the video monitoring device screen.

Recording information about inspected objects to a hard drive ensures that images of all objects are saved for a selected period of inspection time (for example, inspection of passengers' belongings when boarding a specific flight). This allows, if necessary, to repeatedly view an object that interests the inspection service.

The introscope “Nadzor-2M” allows for inspection of objects up to 70×50 cm high and wide with a conveyor length of 3 m.

The introscope “Nadzor-3” was created for inspection of larger objects up to 100×100 cm in size.

A number of domestic and foreign companies are engaged in the development of X-ray television introscopes, such as FSUE NPP Delta, Hyman (Germany), Kurt Mitterfelner (Germany), Rapiscan (England), G&G Astrophysics (USA), Metorex (Finland), Garrett (USA), CIA (Italy), NITs Okhrana (RF), SNPO Eleron (RF), Grotek (RF), NIIIN MNPO Spektr.

The X-ray inspection equipment created by the listed companies has similar technical characteristics and differs mainly in its external design, range of services, types of models intended for inspection of objects of various sizes and weights, as well as their price.

Standard technical characteristics of modern X-ray television introscopes are as follows:

1. Working voltage of X-ray generator 140 kV.
2. Current of X-ray generator 0.4 – 0.9 mA.
3. The radiation is recorded by a multi-element X-ray detector containing two groups of semiconductor diodes, the number of which is determined by the dimensions of the tunnel for passing baggage and the required image resolution; the signal is processed by a computer using the appropriate program, which allows:

• to separate objects in the inspected object with a color image on the TV monitor screen in colors depending on the effective atomic number Zeff. of the material of the objects;
• to present, if necessary, the image visible on the screen in black and white or negative form for a more detailed examination of the objects in the inspected object;
• magnify individual sections of the image in different sectors of the screen by 2, 4 or more times;
• call up images of objects that have passed inspection for repeated viewing and save up to 1000 images in the database to ensure the possibility of repeated viewing and analysis if necessary;
• optimize image sharpness and brightness.

1. Resolving characteristics of introscopes:

• diameter of the detected copper wire 0.1 – 0.15 mm;
• penetrating power up to 200 mm of steel;
• number of brightness levels 256.

1. Belt conveyor speed 20 cm/s.
2. The load capacity of the belt conveyor is determined by the tasks of a specific introscope model and can reach 400 kg or more.
3. All introscopes do not affect the photographic film located in the inspected object, with a sensitivity of up to 1600 ISO (33 DIN).

The block diagram of the X-ray television introscope is shown in Fig. 1.

The X-ray radiation required for the operation of the introscope is generated by an X-ray generator 1, equipped with an X-ray tube. To form a directed X-ray beam, narrow in the horizontal plane and fan-shaped in the vertical plane, a collimation and protection system 2 is used.

“Soft” and “hard” components of the X-ray beam that has passed through the controlled object 18, are recorded by a multichannel X-ray receiver 3, containing two groups of semiconductor detectors. Signals from the X-ray receiver are sent to the address block 4, where they are normalized and transmitted to the system unit 5 for further processing and image formation.

The introscope is controlled by the system unit through the address block and the optocoupler isolation block 7. Signals from the keyboard, control panel 8 and sensors 13? 16 the position of the controlled object installed on the belt conveyor 11, through the optocoupler isolation unit and the address block, are sent to the system unit. The image signal processed and formed by the system unit is sent to the television monitor 6, on the screen of which the image of the controlled object appears.

The TV monitor screen has an information line that displays the date and time of the inspection, as well as the number of objects that have been inspected. The “mode” column displays the selected image presentation type (black and white, color, lightening, etc., in accordance with the command selected on the control panel keyboard).

The information received from the X-ray receivers is recorded on the hard drive of the system unit. This allows for an unlimited viewing of the image of the monitored object on the TV monitor screen even after the X-ray radiation has been switched off, and, if necessary, to recall the image that has already been viewed for re-examination.

Connecting the introscope to the power supply network, monitoring the introscope's operating time, distributing the supply voltages and incoming control commands is carried out using the switching device 9. The introscope's operating life is monitored by the operating hour counter 10. The power supply unit 17 serves as a stabilized voltage supply for the low-voltage circuits of the introscope.

Fig. 1. Block diagram of an X-ray television introscope

Metal detectors

In addition to X-ray television introscopes, the group of technical means of inspection equipment includes stationary and portable (hand-held) metal detectors.

Metal detectors (metal detectors and metal detectors) are designed to search for metal-containing objects hidden in clothing, shoes or on the human body. They are used in airports, banks, government agencies, nuclear power plants, customs, enterprises, factories and other facilities.

By the method of inspection, metal detectors are divided into stationary and portable (hand-held).

Stationary metal detectors

Stationary metal detectors, as a rule, are structurally made in the form of a U-shaped collapsible arch.

The side posts, panels or columns of the arch contain the generator and receiving antenna systems. The posts are connected to each other at the installation site into a rigid structure using a jumper, which also serves as the body of the electronic unit.

The detection zone of the metal detector is located in the space between the generator and receiving antennas, therefore, at the checkpoint, the metal detector is installed so that during inspection, a person passes through the opening of the arch between its side posts.

The principle of operation of a stationary metal detector is based on recording changes in the mutual induction of the generator and receiving antennas, which occur when moving metal objects in the detection zone.

The operation of a stationary metal detector is as follows.

The electronic unit generates alternating current in the generator antenna, which is made in the form of an induction circuit, exciting a primary electromagnetic field in the controlled space. In the receiving antenna (also in the form of an induction circuit), signals are generated that represent the emf induced by the primary field. When a metal object is introduced into the detection zone, eddy currents are generated in the metal detector under the influence of the primary field, which induce a secondary emf in the receiving circuit. The total emf at the output of the receiving antenna changes, which is recorded by the electronic unit.

Various options for excitation of the primary field are used: harmonic, polyharmonic or pulse currents. Their frequency is in the range from 1 to 10 kHz.

The main technical characteristics of a stationary metal detector are: sensitivity, probability of correct detection, probability of false alarm, selectivity and compatibility with other devices of similar application.

Sensitivity is determined by the smallest size of an object that can be detected with a given probability. Since the emf at the output of the receiving antenna depends on several parameters of the object (size, shape, electrical conductivity, magnetic permeability), it is difficult to choose an exact measure that determines sensitivity. Therefore, in practice, approximate data on the volume of the object or its mass are used.

The block diagram of a stationary metal detector is shown in Fig. 2.

Radiating inductive system 2consists of four emitting coils (two ? emitting main channel and two ? compensating), which create a four-phase pulsed magnetic field in the detection zone. Generator 1 produces stable in time pulses of power supply of the emitting inductive system and pulses of signal sampling in the circuits of signal processing units of channels 1 and 2. Receiving inductive system 3consists of two coils. To achieve uniform sensitivity in the controlled area, the coils have the shape of double eights, offset relative to each other vertically and horizontally. Blocks 4, 5 for processing the signal of channels 1 and 2 are designed to amplify, convert and filter signals coming from the coils of the receiving inductive system.

The main and compensation signals of each channel have different polarity due to the phasing of the emitting coils. This allows the signal processing unit to add useful signals and cancel out common-mode interference. A useful signal is any change in the shape of the transient process when a metal object passes through the receiving and transmitting inductive systems of the metal detector. The total signal in the signal processing unit is amplified, filtered from interference and, after the signal module formation circuit, is fed to the indicator.

In the indicator 7The signals of the receiving channels are summed up, converted from analog signals into discrete signals and sent to a discrete LED level indicator and a sound signal generator with a duration proportional to the signal amplitude. The control unit 6 is used to turn the product on and off and adjust its sensitivity. The power supply 8 generates the voltages required for the operation of the electronic units of the product.

Modern stationary metal detectors have a sensitivity sufficient to register objects weighing from 10 g, and provide sensitivity adjustment for the purpose of tuning out objects of smaller size and weight than the search objects. The adjustment range is 40 dB (100 rad) and more, which approximately corresponds to the range of change in the size of real search objects. When preparing for work, the required sensitivity level is selected so that with maximum tuning out from smaller objects, the probability of detecting search objects is practically equal to 1. In this case, the probability of missing objects of smaller size and weight than the search objects is called selectivity.

Selectivity depends significantly on the homogeneity of the detection zone, which is characterized by the ratio of the maximum emf in the receiving antenna to the minimum in the entire arch opening when carrying the same object. The closer this ratio is to 1, the better the homogeneity and, therefore, the selectivity of the device.

The stationary metal detector has a fairly high noise immunity, which is ensured by the special design and configuration of the receiving antennas, as well as the circuit solutions of the electronic units. However, when working in conditions of intense electronic interference, for example, in airport conditions, false alarms are possible. To significantly improve noise immunity, the stationary metal detector includes an additional infrared (IR) channel, a channel for recording a person passing through the opening, and joint processing of signals from the main and IR channels.

Portable (hand-held) metal detectors

Portable (hand-held) metal detectors are used for the prompt search of metal objects hidden on the human body, in luggage, correspondence, etc. Structurally, the metal detector is made in the form of a portable dielectric housing, which contains a search element, electronic processing and indication units, and power elements. The search element is an induction circuit in the form of a rectangular, round or cylindrical coil.

The portable metal detector operates according to the following scheme.

The coil is included in the generator circuit. When a metal object appears near it, its inductance changes, which leads to a change in the generation parameters. These changes are recorded by the processing circuit and transmitted as a light or sound signal.

Fig. 2. Block diagram of a stationary metal detector

The generator frequency is usually in the range from 10 to 100 kHz. The electromagnetic field of the coil is quite weak and, just like in the stationary version of the metal detector, fully complies with sanitary and biological standards.

The block diagram of a portable (hand-held) metal detector is shown in Fig. 3.

Reference generator 1 generates electrical pulses with a repetition frequency of Fс. In the absence of a metal object in the electric field of the inductor coil, the measuring generator 2 generates electrical pulses with a repetition frequency of FP. The signals of the measuring and reference generators are fed to the mixer 3, after which, as a result of processing, a signal is generated in the form of pulses with a repetition frequency of F = FC – FP. The repetition rate is then converted into sawtooth pulses, the amplitude of which is inversely proportional to the repetition rate. The sawtooth pulses are fed to the input of the comparator 7, which forms a voltage drop used to trigger the sound signal generator 8. When the sound signal generator is triggered, the coincidence circuit 10 passes the sound generator signal to the power amplifier and speaker 11, which produces the output sound signal of the metal detector.

Until a metal object appears in the field of the inductance coil of the measuring generator, the amplitude of the sawtooth pulses is less than the comparator response threshold and sound signals are not generated.

When a metal object enters the field of action of the inductance coil, the frequency of pulses generated by the measuring generator changes, the amplitude of the sawtooth pulses increases and exceeds the comparator response threshold, the comparator starts the sound signal generator, the coincidence circuit begins to pass the sound generator signal and an audible signal appears at the output of the metal detector, indicating the presence of metal. To eliminate the influence of supply voltage fluctuations (battery power supply discharge 12), a voltage stabilizer 13 is introduced into the circuit.

Portable metal detectors are effectively used in combination with stationary ones. In this case, after passing through the stationary metal detector, if necessary, you can clarify the presence of search items by additionally checking the portable device.

Portable metal detectors from different companies differ in the selected forms, the introduction of additional service controls and operational characteristics with practically similar detection characteristics. The sensitivity of portable metal detectors is set in each specific case by manual adjustment.

Fig. 3. Block diagram of a portable (hand-held) metal detector

Domestic inspection equipment, with the same basic technical characteristics as foreign equipment, is inferior in design, but is more resistant to climatic conditions of operation in Russia and has a significantly lower cost. For introscopes — by 20? 25%, and for metal detectors — up to 50%. In addition, repair and maintenance of domestic equipment during the warranty and post-warranty periods is significantly cheaper than foreign equipment.

The intensification of international terrorism sets the task of further increasing the effectiveness of inspection equipment both in terms of improving the technical characteristics of existing equipment and in terms of finding ways to create promising devices based on new physical principles.

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