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Thin Holographic Video Display For Mobile Phones

Samsung video display aimed at putting holograms in our hands

3 min read
Photos taken of a full-color holographic movie.
Photos taken of a full-color holographic movie. Because the depths of all objects in the 3-D image are different, the sharpness of holographic objects changes as the camera focus changes. (Left) The camera is focused 0.1 meters behind the display; note the blurriness of the foreground. (Right) The camera is focused 0.35 meters in front of the display; note the blurriness of the background.
Photos: Samsung Advanced Institute of Technology

A thin holographic display could one day enable 4K 3-D videos on mobile devices as well as household and office electronics, Samsung researchers and their colleagues say.

Conventional holograms are photographs that, when illuminated, essentially act like 2D windows looking onto 3D scenes. The pixels of each hologram scatter light waves falling onto them, making the light waves interact with each other in ways that generate an image with the illusion of depth.

Holography creates static holograms by using laser beams to encode an image onto a recording medium such as a film or plate. By sending the coherent light from lasers through a device known as a spatial light modulator—which can actively manipulate features of light waves such as their amplitude or phase—scientists can instead produce holographic videos.

Holographic video displays create realistic 3-D images that people can view without feeling eye strain, unlike conventional 3-D displays that create the illusion of depth using 2-D images. However, creating a commercially viable holographic video display has proven challenging for a variety of reasons.

For starters, whereas static holograms can encode an extraordinary amount of data onto light-sensitive films, resulting in large images that can be viewed from a wide range of angles, holographic video displays are limited by pixel size and pixel number. They are, therefore, often limited to small images or narrow viewing angles. Previously, holographic video displays capable of full high-definition resolution could provide either a viewing angle of 0.25 degrees in a 10-inch display or 30 degrees in a 0.1-inch display.

Another issue has been the challenge of generating the coherent light needed for a holographic video display. It often requires complicated, bulky optics, making it difficult to do holography with slim flat-panel displays. What’s more, the extraordinary amount of data within holographic videos demands a huge amount of computing power.

The new slim-panel holographic video display from Samsung researchers and their colleagues. The overall thickness of the display parts (right) is just 1 centimeter.The new slim-panel holographic video display from Samsung researchers and their colleagues. The overall thickness of the display parts (right) is just 1 centimeter.Photo: Samsung Advanced Institute of Technology

But researchers at Samsung say they have developed a way to create a thin holographic video display that is viewable from a wide range of angles. The team detailed their findings online on 10 Nov. in the journal Nature Communications.

“I have confidence that we can make a holographic display as a product in the near future,” says study senior author Hong-Seok Lee, an optical engineer at the Samsung Advanced Institute of Technology in Suwon, South Korea.

A key feature of the new display is a special backlight equipped with a beam deflector that can tilt the angles of coherent light beams from laser diodes. This has expanded the viewing angle for the display 30-fold without increasing the number of pixels needed. Moreover, instead of using a bulky lens to gather scattered light from the display's pixels for viewing, the researchers used a relatively svelte geometric phase lens. The result, say the researchers, is that the display's optical components measure only 1 centimeter thick.

To generate high-quality holographic videos in real time, the Samsung team employed a number of methods to cut down the amount of computation needed. For example, they used as few bits as possible to represent each pixel and replaced complex mathematical operations with simple lookup tables.

All in all, the size of the prototype display is 10.1 inches, with a viewing angle of 15 degrees at a viewing distance of 1 meter. The single-chip holographic video processor they developed could perform roughly 140 billion operations per second to generate 4K-resolution holographic color images at a speed of 30 frames per second.

The researchers note that their holographic video processor is designed to be embedded in a smartphone application processor. They are now working to scale down the system to make it suitable for mobile phones.

“I think everybody wants to know when they can see it in everyday life,” Lee says. “I just can tell you that it will not take very long.”

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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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