Body Scanners: Do Airports Use Infrared Technology?

Airport body scanners use a variety of technologies to detect objects on or inside a person's body without physical contact or the removal of clothing. One such technology is infrared thermal conductivity scanning, which uses slight temperature differences on the surface of clothing to detect foreign objects. This method does not use electromagnetic radiation to penetrate the body or clothing and instead relies on thermal conductivity, which is based on the ability of contraband hidden under clothing to heat or cool the surface of the clothing faster than the skin surface.

Millimeter wave scanners use non-ionising radiation to detect objects

Millimeter wave scanners emit a special type of microwave, a form of electromagnetic radiation, that bounces off the skin and any concealed solid or liquid objects, and then returns to the machine's receivers. The machine then uses this data to construct a 3D image, which is displayed on a remote monitor for analysis. This allows security personnel to identify any potential threats without physically contacting or invading the privacy of the individual being scanned.

The non-ionising radiation used by millimeter wave scanners is much larger in wavelength than X-rays and has far less energy. This means it does not have the ability to alter biological molecules or cause cancer, making it safer than other types of radiation. However, the health risks posed by these machines are still being studied, and the evidence is mixed.

Millimeter wave scanners are particularly useful for detecting non-metallic objects, which cannot be detected by traditional metal detectors. They can also detect objects hidden underneath clothing, making them ideal for security screening. The scanners emit very low levels of radiation, similar to that produced by a cell phone, and are considered safe for use on humans.

In addition to security applications, millimeter wave scanners can also be used for 3D physical measurement of body shape in fields such as apparel design, prosthetic devices design, and ergonomics.

Backscatter X-ray scanners use low-dose radiation to detect objects

Backscatter X-ray scanners are a type of full-body scanner that uses low-dose radiation to detect objects on or inside a person's body. This technology is designed to detect both metallic and non-metallic objects, including weapons, explosives, and other contraband items that may pose a security risk. The use of backscatter X-ray technology in airport security emerged in the 1990s and gained traction after the events of 9/11, but it has also sparked concerns and controversies around privacy and health risks.

Backscatter X-ray machines operate by emitting low-energy X-rays that bounce off the surface of the skin and are reflected back to the machine. This radiation is a form of ionizing radiation, which can break chemical bonds and is considered carcinogenic even in small doses. However, the dose received from a backscatter scan is typically between 0.05 and 0.1 μSv, which is comparable to the radiation exposure during two minutes of flying or about an hour of background radiation. While there are concerns about potential health risks, especially for frequent flyers, radiation safety authorities have stated that there is no specific evidence that full-body scans are unsafe.

One of the main concerns with backscatter X-ray scanners is the potential invasion of privacy. These machines create an image of the person's body, which some critics have likened to a virtual strip search. To address this issue, airports have implemented Automated Target Recognition software that replaces the anatomical image with a cartoon-like representation, indicating areas of concern without exposing personal details. Additionally, privacy measures are in place to ensure that images are not stored or recorded without consent.

While backscatter X-ray scanners have been widely used, some countries, including those in North America and Europe, have started to discontinue their use in favor of millimeter-wave scanners, which use non-ionizing radiation and are considered less invasive. Millimeter-wave scanners use radio waves to create a 3D image of the person, detecting objects without exposing the details of the body. This technology also offers faster scanning times and improved accuracy, reducing the need for physical pat-downs.

In summary, backscatter X-ray scanners use low-dose radiation to detect objects, and while they have been a common tool for airport security, there are ongoing debates about their safety and privacy implications. As a result, the aviation industry is continuously evolving, with some airports adopting alternative technologies, such as millimeter-wave scanners, to enhance security and improve the passenger experience.

Transmission X-ray scanners use higher-dose radiation to detect objects

Transmission X-ray scanners are a type of full-body scanner that uses higher-dose radiation to detect objects. They are designed to detect objects hidden not only under clothes but also inside the human body, such as in body cavities. This makes them particularly useful in correctional institutions for detecting contraband, such as drugs carried by drug couriers in their stomachs.

The way these scanners work is by using penetrating radiation that passes through the human body and is then captured by a detector or array of detectors. This technology allows for the detection of objects that may be hidden inside an individual's body, which is not possible with other types of scanners such as backscatter X-ray scanners or millimeter-wave scanners.

The radiation dosage received from transmission X-ray scanners is typically not higher than 0.25 μSv, which is regulated by the American radiation safety standard for personal search systems using gamma or X-ray radiation. This is still a relatively low dose, but it is higher than the dosage from backscatter X-ray scanners, which is usually between 0.05 and 0.1 μSv. Due to concerns about the safety of backscatter X-ray scanners, multiple countries have banned their usage.

Transmission X-ray scanners are also designed to protect the privacy of individuals being scanned. The images produced by these scanners make it almost impossible to distinguish a person, and they also have software that can hide privacy issues. This addresses the concerns raised by passengers and advocates about the display of their naked bodies to screening agents, which has been called a violation of basic human rights and privacy.

In addition to their use in airports, transmission X-ray scanners are commonly used in correctional institutions. This is because they are the only devices capable of detecting metallic and non-metallic contraband hidden underneath clothing or inside body cavities. However, they are not widely used in airports nowadays due to the development of more advanced imaging technologies.

Passive infrared scanners detect natural radiation emitted by the body

Passive infrared scanners detect natural radiation emitted by the human body to locate objects worn or hidden on a person's body. This technology is often used in PIR-based motion detectors, such as burglar alarms and automatic lighting systems.

Passive infrared scanners work by detecting changes in the amount of infrared radiation impinging upon them. When an object, such as a person, passes in front of the background, the temperature at that point in the sensor's field of view will rise from room temperature to body temperature, and then back again. The sensor converts the resulting change in the incoming infrared radiation into a change in the output voltage, and this triggers the detection.

Passive infrared scanners can be designed with Fresnel lenses or mirror segments to focus the distant infrared energy onto the sensor surface. The number, shape, distribution, and sensitivity of these zones are determined by the lens and/or mirror, with manufacturers aiming to create the optimal sensitivity beam pattern for each application.

Passive infrared scanners are also used in automatic lighting applications, such as motion-sensitive lighting for security or practical uses. In security systems, PIR sensors typically control a small relay, which completes the circuit across electrical contacts connected to a detection input zone of a burglar alarm control panel.

Passive infrared scanners have also been implemented to measure the temperature of remote objects. In such circuits, a non-differential PIR output is used to evaluate the IR spectrum of a specific type of matter and obtain relatively accurate and precise temperature measurements.

In the context of airport security, passive infrared scanners can be used to detect forbidden objects concealed under a person's clothing. These devices do not expose the body to any additional radiation, completely ruling out health risks. For this reason, passive systems are generally preferred over active systems, which use artificial radiation to improve detection.

Active infrared scanners add artificial radiation to improve detection

Infrared thermography (IRT) is a technology that uses special materials to sense, convert, and then display infrared waves as electrical signals and digital images. IRT is used for defect detection due to its non-contact, efficient, and high-resolution methods, which enhance product quality and reliability.

Active IRT is a technique where the surface or interior of an object is excited in a controlled manner by a controlled heat source, causing a change in temperature. This change is recorded using an infrared thermal camera to obtain the dynamic response of the heat wave. Active IRT focuses on stimulating sources, heat transfer mechanisms, and image-processing algorithms.

Active IRT can be categorized into four types, depending on the type of heat source used:

• Pulsed thermography (PT): This technique uses a pulsed heat source, such as flash lamps or lasers, to emit heat pulses and disturb the thermal equilibrium of the specimen.
• Lock-in thermography (LT): This method subjects the specimen to a frequency-specified periodic thermal excitation and captures the surface heating using an infrared camera.
• Ultrasonically stimulated vibration thermography (UVT): UVT uses ultrasonic transducers to excite the specimen and generate localized heating through internal friction.
• Eddy current thermography (ECT): ECT uses external excitation to induce eddy currents inside the specimen, and an infrared camera captures the heat flow from the surface.

The choice of excitation heat source and waveform is critical in active IRT. Manipulating the amplitude, frequency, and duration of the heat source can enhance the accuracy and robustness of detection. Transient and static heat transfer methods are used, depending on whether the specimen is heated to a steady state before infrared data acquisition.

Active IRT offers several advantages over other technologies:

• Non-contact and non-invasive: It allows for the measurement of extremely hot objects or dangerous products without physical contact, keeping users safe.
• High-speed: Active IRT can scan both stationary and fast-moving targets quickly.
• Large-area coverage: It can examine large areas in a single test.
• Simple operation: It is easy to use and interpret.
• Wide range of inspection objects: Active IRT can be used on metallic, non-metallic, and composite materials.
• Radiation-free: Unlike X-ray imaging, IRT is safe for long-term and repeated use.

In conclusion, active IRT improves detection by adding artificial radiation to stimulate objects in a controlled manner, recording temperature changes with infrared thermal cameras, and employing image-processing algorithms to identify defects. This technique enhances defect detection in various industries, including electronics and renewable energy.

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