Thermal Cameras Are Being Outfitted to Detect Fever and Conduct Contact Tracing for COVID-19

Members in Spain and Switzerland are developing software for FLIR cameras and building their own versions to protect people’s privacy

4 min read
Researchers are using FLIR Systems thermal cameras paired with bcbTempScan software to do fever screenings.
IEEE Member Alejandro Kurtz de Grino tested the software in a FLIR camera. On the left is a thermal image of de Grino with a normal body temperature while on the right, the color red indicates elevated body temperature.
Photo: Alejandro Kurtz de Grino

THE INSTITUTE  Thermal imaging cameras, which use thermography, are a fast, contactless, and reliable method to detect a fever, a common symptom of COVID-19. Two IEEE members, one in Spain and the other in Switzerland, are working on separate projects that improve the technology used in these cameras so they can be used in places such as airports, hospitals, factories, office buildings, restaurants, and stores to provide fast individual screenings to help stop the spread of the virus.

IEEE Member Alejandro Kurtz de Grino a design and research engineer at software company BCB Informática y Control SL, in Madrid, is developing software that help the cameras meet technical standards required by the healthcare industry.

The thermal imaging camera that IEEE Fellow Touradj Ebrahimi is building also checks for elevated blood temperature but it can trace the person’s contacts. He also developed a cryptographic tool to ensure the privacy of the person whose temperature is being checked. Ebrahimi is a professor of multimedia signal processing at Ecole Polytechnique Fédérale de Lausanne, in Switzerland.

NEW SOFTWARE

De Grino says thermographic cameras used in the healthcare field must meet specific standards. For example, the screening technology must have a high thermal resolution and a measurement accuracy of +/- 0.5 ºC. Several manufacturers of these cameras are not following those requirements, he says, so his company is developing software for them that does.

“It wasn’t easy to develop a solution that met the requirements of the technical standard for fever screening using thermal cameras,” de Grino says.

The software will be tested in cameras made by FLIR Systems, a leading manufacturer of thermographic cameras. FLIR has several models that, when paired with his company’s bcbTempScan software, meet the international standards. The cameras have infrared temperature sensors and motorized focus, which are controlled by the software’s system operator. The temperature sensors detect electromagnetic waves from the person and the motorized focus allows the camera’s operator to zoom in and out.

The software uses GigE Vision and Genlcam, de Grino says. GigE Vision is an interface standard that can transmit high-speed video and related control data over an Ethernet connection. Genlcam is a common programming interface used for machine vision in cameras.

BcbTempScan is connected to the camera through a computer. When checking a person, the camera’s operator will see a detailed temperature pattern, called a thermogram and an alarm will sound if EBT is detected, de Grino says. The operator will then recommend to the person he or she be tested for COVID-19.

PROTECTING PRIVACY

The Pro-Cam infrared camera that Ebrahimi and his students built combines infrared, thermal, and visible light sensors while securing the visible light images.

“We designed and built a new type of connected camera with multiple sensors that can track people, also known as proximity or contact tracing, while protecting their privacy,” he says.

The cameras are made from off-the-shelf components and open software so they are less expensive than existing thermal cameras and can be easily built and installed. The team also created a custom enclosure to protect its components.

Using real-time streaming, Ebrahimi says the camera sends the images to a server and protects the anonymity of the individual in the scene by hiding the visible light images inside thermal images using a cryptographic tool called transmorphing.

A dedicated server records all the captured footage in a secure and anonymized way with the possibility for further analysis, visualization and eventual de-anonymization, he adds.

Ebrahimi says the camera is more accurate than current contact tracing methods that use smartphone positions, or Bluetooth discovery to determine the relative distance between devices. The Pro-Cam also doesn’t require individuals to carry a smartphone or install a contact-tracing app.

Also, these technologies pose various ethical challenges, including invasion of privacy. Ebrahimi says it will be possible to recover the person’s identity using cryptographic keys if consent is given or when the proper authorities make a request for the information.

The project wasn’t without its challenges, he says. Because low-cost infrared and thermal sensors have lower resolution and precision, the team had to combine three such sensors along with advanced image processing algorithms.

The team on a video callThe team from the Ecole Polytechnique Fédérale de Lausanne who worked on the Pro-Cam.Photo: Touradj Ebrahimi

“Even though everyone on the project worked remotely, they came up with the camera’s design from scratch and had it ready to build in 72 hours!” Ebrahimi says.

Three students will continue building other cameras as part of their senior project and will run trials on them from selected locations. Ebrahimi says further enhancements will include the ability to perform AI-based advanced video analytics, trace people between cameras, and merge with other proximity-tracing approaches such as those based on smart cameras.

This article appears in the September 2020 print issue as “Thermal Cameras’ New Role: Controlling COVID-19 Community Spread.”

Attention IEEE members: are you part of a team responding to the COVID-19 crisis? We want to hear from you! Wherever you are and whatever you are doing, if you are helping deal with the outbreak in some way, let us know. Send us accounts of anywhere from 200 to 800 words, or simply give us a rough idea of what you are doing and your contact information. Write to: k.pretz@ieee.org

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The Inner Beauty of Basic Electronics

Open Circuits showcases the surprising complexity of passive components

5 min read
Vertical
A photo of a high-stability film resistor with the letters "MIS" in yellow.
All photos by Eric Schlaepfer & Windell H. Oskay
Blue

Eric Schlaepfer was trying to fix a broken piece of test equipment when he came across the cause of the problem—a troubled tantalum capacitor. The component had somehow shorted out, and he wanted to know why. So he polished it down for a look inside. He never found the source of the short, but he and his collaborator, Windell H. Oskay, discovered something even better: a breathtaking hidden world inside electronics. What followed were hours and hours of polishing, cleaning, and photography that resulted in Open Circuits: The Inner Beauty of Electronic Components (No Starch Press, 2022), an excerpt of which follows. As the authors write, everything about these components is deliberately designed to meet specific technical needs, but that design leads to “accidental beauty: the emergent aesthetics of things you were never expected to see.”

From a book that spans the wide world of electronics, what we at IEEE Spectrum found surprisingly compelling were the insides of things we don’t spend much time thinking about, passive components. Transistors, LEDs, and other semiconductors may be where the action is, but the simple physics of resistors, capacitors, and inductors have their own sort of splendor.

High-Stability Film Resistor

A photo of a high-stability film resistor with the letters "MIS" in yellow.

All photos by Eric Schlaepfer & Windell H. Oskay

This high-stability film resistor, about 4 millimeters in diameter, is made in much the same way as its inexpensive carbon-film cousin, but with exacting precision. A ceramic rod is coated with a fine layer of resistive film (thin metal, metal oxide, or carbon) and then a perfectly uniform helical groove is machined into the film.

Instead of coating the resistor with an epoxy, it’s hermetically sealed in a lustrous little glass envelope. This makes the resistor more robust, ideal for specialized cases such as precision reference instrumentation, where long-term stability of the resistor is critical. The glass envelope provides better isolation against moisture and other environmental changes than standard coatings like epoxy.

15-Turn Trimmer Potentiometer

A photo of a blue chip
A photo of a blue chip on a circuit board.

It takes 15 rotations of an adjustment screw to move a 15-turn trimmer potentiometer from one end of its resistive range to the other. Circuits that need to be adjusted with fine resolution control use this type of trimmer pot instead of the single-turn variety.

The resistive element in this trimmer is a strip of cermet—a composite of ceramic and metal—silk-screened on a white ceramic substrate. Screen-printed metal links each end of the strip to the connecting wires. It’s a flattened, linear version of the horseshoe-shaped resistive element in single-turn trimmers.

Turning the adjustment screw moves a plastic slider along a track. The wiper is a spring finger, a spring-loaded metal contact, attached to the slider. It makes contact between a metal strip and the selected point on the strip of resistive film.

Ceramic Disc Capacitor

A cutaway of a Ceramic Disc Capacitor
A photo of a Ceramic Disc Capacitor

Capacitors are fundamental electronic components that store energy in the form of static electricity. They’re used in countless ways, including for bulk energy storage, to smooth out electronic signals, and as computer memory cells. The simplest capacitor consists of two parallel metal plates with a gap between them, but capacitors can take many forms so long as there are two conductive surfaces, called electrodes, separated by an insulator.

A ceramic disc capacitor is a low-cost capacitor that is frequently found in appliances and toys. Its insulator is a ceramic disc, and its two parallel plates are extremely thin metal coatings that are evaporated or sputtered onto the disc’s outer surfaces. Connecting wires are attached using solder, and the whole assembly is dipped into a porous coating material that dries hard and protects the capacitor from damage.

Film Capacitor

An image of a cut away of a capacitor
A photo of a green capacitor.

Film capacitors are frequently found in high-quality audio equipment, such as headphone amplifiers, record players, graphic equalizers, and radio tuners. Their key feature is that the dielectric material is a plastic film, such as polyester or polypropylene.

The metal electrodes of this film capacitor are vacuum-deposited on the surfaces of long strips of plastic film. After the leads are attached, the films are rolled up and dipped into an epoxy that binds the assembly together. Then the completed assembly is dipped in a tough outer coating and marked with its value.

Other types of film capacitors are made by stacking flat layers of metallized plastic film, rather than rolling up layers of film.

Dipped Tantalum Capacitor

A photo of a cutaway of a Dipped Tantalum Capacitor

At the core of this capacitor is a porous pellet of tantalum metal. The pellet is made from tantalum powder and sintered, or compressed at a high temperature, into a dense, spongelike solid.

Just like a kitchen sponge, the resulting pellet has a high surface area per unit volume. The pellet is then anodized, creating an insulating oxide layer with an equally high surface area. This process packs a lot of capacitance into a compact device, using spongelike geometry rather than the stacked or rolled layers that most other capacitors use.

The device’s positive terminal, or anode, is connected directly to the tantalum metal. The negative terminal, or cathode, is formed by a thin layer of conductive manganese dioxide coating the pellet.

Axial Inductor

An image of a cutaway of a Axial Inductor
A photo of a collection of cut wires

Inductors are fundamental electronic components that store energy in the form of a magnetic field. They’re used, for example, in some types of power supplies to convert between voltages by alternately storing and releasing energy. This energy-efficient design helps maximize the battery life of cellphones and other portable electronics.

Inductors typically consist of a coil of insulated wire wrapped around a core of magnetic material like iron or ferrite, a ceramic filled with iron oxide. Current flowing around the core produces a magnetic field that acts as a sort of flywheel for current, smoothing out changes in the current as it flows through the inductor.

This axial inductor has a number of turns of varnished copper wire wrapped around a ferrite form and soldered to copper leads on its two ends. It has several layers of protection: a clear varnish over the windings, a light-green coating around the solder joints, and a striking green outer coating to protect the whole component and provide a surface for the colorful stripes that indicate its inductance value.

Power Supply Transformer

A photo of a collection of cut wires
A photo of a yellow element on a circuit board.

This transformer has multiple sets of windings and is used in a power supply to create multiple output AC voltages from a single AC input such as a wall outlet.

The small wires nearer the center are “high impedance” turns of magnet wire. These windings carry a higher voltage but a lower current. They’re protected by several layers of tape, a copper-foil electrostatic shield, and more tape.

The outer “low impedance” windings are made with thicker insulated wire and fewer turns. They handle a lower voltage but a higher current.

All of the windings are wrapped around a black plastic bobbin. Two pieces of ferrite ceramic are bonded together to form the magnetic core at the heart of the transformer.

This article appears in the February 2023 print issue.

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