Introduction of security inspection x-ray machine imaging principle

Security X-ray machine is a kind of security equipment that we are all familiar with, but few people understand the imaging principle of security X-ray machine. This article will introduce the imaging principle of security inspection x-ray machine.

Security inspection x-ray machine imaging principle

The security inspection X-ray machine is mainly composed of X-ray tube and X-ray machine power supply and control circuit. The X-ray tube is composed of cathode filament (Cathod), anode target (Anode) and vacuum glass tube It is a high-voltage power supply and a filament power supply. The filament power supply is used to heat the filament. The high-voltage output terminals of the high-voltage power supply are located at both ends of the cathode filament and the anode target, respectively. Form a high-speed electron flow.

Three methods of generating X-rays in the principle of X-ray imaging of security inspection can generate X-rays: Bremsstrahlung, electron capture, and internal conversion. The mechanism of X-rays generated by X-ray machines belongs to bremsstrahlung.

In the principle of X-ray imaging of security inspection, X-ray was discovered by Professor Roentgen in Germany in 1895. This kind of radiation emitted by the vacuum tube can penetrate the object. The energy in the electromagnetic spectrum is stronger than that of visible light, the wavelength is shorter, and the frequency is higher. Similar radiations include cosmic rays and X-ray. To produce X-Ray, you must have an X-ray tube, and the basic structure of the X-ray tube must have:

1. Cathode filament (Cathod);

2. Anode (Anode);

3. Evacuated glass envelope;

4. Of course, there must be power supply.

The X-ray generation procedure is to first turn on the power, pass the step-down transformer, and heat the X-ray tube filament to generate free electrons and gather them near the cathode. When the step-up transformer provides high-voltage electricity to the two poles of the X-ray tube, the potential difference between the cathode and the anode increases sharply, and the free electrons in the active state are strongly attracted to make the bundled electrons travel from the cathode to the anode at high speed. , Striking the anode tungsten target atomic structure. At this time, energy conversion occurs, in which about 1% or less of the energy forms an X-ray, and the remaining 99% or more is converted into thermal energy. The former is mainly emitted by the X-ray tube window, and the latter is distributed by the heat dissipation facility to provide the corresponding feedback signal. The pulse width modulation technology is used for closed-loop control. The operating frequency is about 30KHZ. The voltage and current are closed-loop adjusted, and there is overvoltage Flow protection.

The security inspection machine is completed by sending the checked baggage into the track-type channel by means of a conveyor belt. After the baggage enters the passage, it will block the light barrier signal and the detection signal will be sent to the control unit to trigger the ray source to emit the X-ray beam. A very narrow fan-shaped X-ray beam passing through the collimator penetrates the luggage items on the conveyor belt and falls onto the dual-energy detector. The high-efficiency semiconductor detector converts the received X-rays into electrical signals. These very weak current signals It is directly quantified and transmitted to the industrial control computer for further processing through the universal serial bus. After complex operations and imaging processing, high-quality images are obtained.

These are the introduction of security inspection x-ray machine imaging principles. Only after understanding can you better use security inspection x-ray machine in practice, so as to better use security to protect people's safety.