The Company Behind the Samsung Galaxy S8 Iris Scanner

Princeton Identity on how it scored a major licensing deal for biometric security

3 min read
A user holds up a new Samsung Galaxy S8, to demonstrate the smartphone's iris scanning preview screen, which shows two circles that users can rely on as a guide to position their eyes..
Photo: Samsung

Last week, Samsung revealed its new smartphone, the Samsung Galaxy S8, which users can unlock with a quick glance. Since the big debut, we’ve learned that the iris scanner in the S8 comes from a little-known biometric security company in New Jersey called Princeton Identity.

CEO Mark Clifton says the company’s technology can produce an accurate scan in varying light conditions from arm’s length, even if the user isn’t standing completely still. Those features persuaded Samsung that iris scanners, which are already common in building security systems, were ready to be integrated into its popular line of smartphones.

“They became convinced that we were the real deal when we were able to show them iris recognition working outdoors in a sunny parking lot, when none of the other competitors could do that,” Clifton says.

Adding an iris scanner to a smartphone is a big decision, because it requires extra hardware and modifications to the body of the phone. Clifton estimates the total cost of adding this form of biometric security works out to be less than $5 per handset. That’s still a lot of money for an industry in which any manufacturer can build a smartphone, but few can do it profitably.  

If you look closely at the S8, there are three dots and one long dash right above the screen. The middle dot is the selfie camera and the thin slit is the proximity sensor, neither of which play a role in iris scanning.

The dot on the far left, however, is an LED that produces near-infrared light. And the dot on the far right is a camera equipped with a special filter that blocks most visible light but allows infrared waves to pass through.

To produce a scan, the LED emits infrared waves that penetrate just below the surface layer of the iris (the colored part of the eye) and reflect back to the infrared camera. This camera can then produce a high-contrast scan of the iris based on those reflections of infrared light from the eye. The proprietary piece of Princeton’s technology is the pattern of the pulse, or strobe, of the LED that produces the infrared light, and the design of the filter that blocks out visible light and yields the high-contrast scan.  

A user’s first scan captures about 250 points of reference from the iris, the part of the eye that includes a pair of muscles that dilate and constrict the pupil to let more or less light in. This compares favorably with the 20 to 70 points that a fingerprint sensor gathers. An iris scan may show the contours of muscles, the patterns of blood vessels, or other artifacts, such as strands or folds of tissue, within the iris. 

All of the information about those reference points is stored in a template in the phone’s “trust zone,” a specialized area of hardware where sensitive data is encrypted. When a user wants to unlock their phone, software compares the iris pattern in the latest scan to the pattern in the original template.   

Many of the elements within the iris are shaped during early development as well as by genetics, so even identical twins would have unique templates. For people who wear glasses, Princeton recommends users take them off to do their original scan, but Clifton says the iris scanner should generally work even with their glasses on.

Dr. Kevin Miller, a corneal surgeon who performs artificial iris transplants at the UCLA Stein Eye Institute, points out that the muscle contours of the iris change considerably based on lighting conditions and pupil dilation. And there are other factors that could produce errors in an iris scan over the course of a person’s lifetime.

“What happens if you're scanning somebody with diabetes and they have a little hemorrhage in the eye? Now that hemorrhage shows up on the scan and it's not going to recognize them,” he says. “There's issues like that with all these biometric methods.”

A user can create a new scan of their iris at any time. And the template that’s stored in the trust zone is a digital representation of the contrast points on their iris, rather than an actual image of the iris. Storing the image itself would create another security problem because, unlike passwords or credit card numbers, a person’s iris pattern can’t be revoked or updated.

Clifton says with their technology, the chances of producing a false positive are about 1 in 1.1 million for a scan of a single eye and 1 in 1.4 trillion for a scan of both eyes. "You do approach DNA-level type of accuracies with a duel-eye recognition,” Clifton says.

The company says they’ve also incorporated “liveness detection” into the scanner so that the iris scanner can’t be fooled by a photograph—a common problem for facial recognition technology—though Clifton wouldn’t say much about how this feature works.

Samsung actually debuted Princeton’s iris scanners in the Galaxy Note7, which had a brief run of sales in 2016 before a mass recall. The only change to the technology for the S8 appears to be cosmetic—this time, Samsung implemented a full color live preview mode with two circles on the screen to help users position their eyes. The ill-fated Note7 preview was in black and white. “Hopefully this will go much smoother,” Clifton says.

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The Inner Beauty of Basic Electronics

Open Circuits showcases the surprising complexity of passive components

5 min read
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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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