Wearable computers and head-mounted displays (HMDs) are in the press daily. Why now? While the basic technology has existed for decades, only recently have these devices become practical and desirable. Using consumer, professional, and “maker” devices, this exhibit demonstrates four challenges along the road to making a consumer wearable computer: power and heat, networking, mobile input, and displays. The groups of head-mounted displays shown here reflect product categories that developed as these challenges were addressed:
- virtual reality displays which seek to remove the user from reality
- portable video viewers for entertainment
- industrial systems designed to support work tasks
- early academic and maker systems that provide smartphone-like productivity and communication abilities for everyday use and
- current consumer devices that leverage modern miniaturized sensors and wireless mobile networks to provide services that are “there when you need it, gone when you don’t.”
POWER & HEAT
A Step Forward—Rechargeable Batteries
Power is the scarcest resource for most mobile electronics, and battery technology has improved slowly relative to developments in memory, disk storage, and wireless connection speeds. When creating a mobile device, a rule of thumb is to specify the largest battery the design might tolerate because, unlike most other computing technology, batteries are unlikely to improve during a normal 18-month product design cycle.
In the early 1990s, lead-acid gel cells and nickel-cadmium (NiCd) batteries were often used in mobile consumer electronics. By the late 1990s, lithium-ion (Li-ion) batteries significantly improved stored energy to weight ratios, leading to smaller cellular phones and small MP3 players.
Power-Sonic 12 V lead-acid gel cell battery (1995, $30)
Heavy lead-acid gel cells were used in many early wearable computers. The batteries are encapsulated to prevent leaking gas and fluids, making them safe to wear. Unlike some chemical batteries, lead-acid gel cells can be charged many times. This battery weighs 1.3 kg and stores 41 Wh of energy.
Sony lithium-ion camcorder battery and holder (1998, $150)
With a higher energy density to mass ratio and therefore better weight characteristics, rechargeable lithium-ion batteries have become popular for mobile consumer electronics, including wearables. This battery is a quarter of the weight (0.36 kg) for the same energy (48 Wh) as the Power-Sonic battery.
Most Li-ion batteries include microcontrollers to prevent fires caused by overcharging or shorting. Unfortunately, the cycle count, or the number of times a battery may be charged and discharged, is lower for a Li-ion battery than a lead-acid gel cell. Other promising technologies, such as rechargeable zinc-air batteries and fuel cells, have proven difficult to shrink to an appropriate size for on-body devices.
It is a surprisingly difficult challenge to create battery holders that can tolerate dropping and power connectors able to withstand snagging, such as a power cable on a doorknob. Here, soft Velcro® straps hold banana plug connectors in the Sony camcorder battery.
A Step Forward—Energy Scavengers
A developing approach to powering mobile consumer electronics is to scavenge energy from the user or the environment. With the growing popularity of cellular phones, several companies produce modern hand-wound generators, a concept similar to pre-World War II pedal-powered radios. Solar chargers have also become popular for campers. Perhaps in the future some on-body sensors will use the effect they are sensing to power themselves?
Nissho Electronics AladdinPower wind-up generator (2002, $40)
Squeezing the hand crank on this generator charges a cellular phone or the attached LED flashlight, which stores the energy in a supercapacitor. While supercapacitors have lower energy density than batteries, they are inexpensive and can charge quickly
RCA ultrasonic TV remote control (in the 1960s, it added 30 percent to the cost of a television)
This early television remote control demonstrates the harvesting of energy from the user interface instead of using batteries. The button pulls a hammer that strikes a metal rod tuned to resonate at a particular ultrasonic frequency. The television hears this tone and changes the channel. Ultrasonics were used for remote controls until infrared became popular in the early 1980s.
XTG Technology portable solar charger and battery (2010, $60)
Solar power is used to charge this USB battery, which in turn can provide extended power for on-body devices or the included LED flashlight.
A Step Forward—DC-DC Power Converters
One of the biggest improvements for small, mobile electronics was in the efficiency of 3 V and 5 V DC-DC power converters in the late 1990s. To be worn on the body, devices must not create too much heat. Yet, inefficient power systems often create significant excess heat.
In 1995, a device that required 10 W of power may have wasted 3 W as heat simply by converting the 12 V from a lead-acid gel cell to the 5 V required for the circuitry. By 2000, much smaller switching 10 W power converters only wasted 0.5 W, leading to longer battery life and smaller devices.
Datel UWR-5/3000-D5 converter (1995, $100)
This DC-DC converter can convert 12 V to 5 V at a maximum efficiency of 78 percent. At its peak current, it creates considerable heat.
Datel UNS-5/3-D12A converter (2000, $34)
Modern switching DC-DC converters can achieve over 98 percent efficiency, allowing the design of smaller wearables with cooler running temperatures.
A Step Forward
Consumer WiFi (802.11) and digital cellular networks are widespread today, but early wearable computers had to be mostly self-contained. By 1996, Cellular Digital Packet Data (CDPD) radios might have provided effective speeds of 9600 baud. In 1999, universities began to deploy campus-wide WiFi, but otherwise open access points were rare.
Until the advent of smartphones in the late 2000s, mobile “cloud computing” was seldom used by consumers. In 2014, digital cellular networks are fast and have low latency—basic requirements for wearable computing consumer experiences that leverage the cloud.
Other networks play key roles for mobile devices as well: GPS provides positioning; Bluetooth wirelessly connects devices on- and near-body; and USB provides both wired networking and power. Over time, these systems have become smaller with lower power requirements, allowing them to be embedded successfully in wearable computers.
IEEE 802.11 Wavelan PCMCIA card (1997, $295)
While power-hungry, WiFi provides wearable computers a high-speed connection to the “cloud.” Free WiFi hotspots started becoming commonplace after the year 2000.
Garmin GPS 35-LVS (2001, $200)
In 2000, Selective Availability was turned off, improving the accuracy of civilian Global Positioning Systems from 100 m to 20 m. Only in the last five years, however, have embedded GPS receiver chips been able to acquire their position quickly and become sensitive enough to connect through cars, wooden houses, and foliage.
Xerox PARC/Olivetti Research Laboratory Active Badge location system (1992, research prototype from the collection of Keith Edwards)
The Active Badge emitted infrared signals that allowed receivers in the infrastructure to detect where a user was in a building. While not commonly thought of as a network, this system was a forerunner of many similar local area systems.
LG Tone Pro headset (2014, $70)
The LG Tone Pro is a pair of Bluetooth wireless stereo earphones. The IEEE 802.15 Wireless Personal Area Network (WPAN) standards can be traced to the IEEE Ad Hoc “Wearables” Standards Committee led by Richard Braley at FedEx in 1997. Bluetooth is described under 802.15.1, and ZigBee uses the 802.15.4 layers. While the basic Bluetooth technology was invented in 1994, it was not until the 2002 1.1 specification that it became stable and popular. A major step forward was the recent introduction of Bluetooth Low Energy wireless technology, which improves many of the power consumption and device speed-of-discovery problems that have limited Bluetooth’s usefulness for wearable devices.
Metricom Inc. Ricochet wireless modem (1997, $350)
Starting in the mid-1990s, Metricom Inc. provided wireless Internet service for customers in select cities with a wireless mesh network of radios mounted on street lamps. Originally intended to serve utility companies, these radios served as repeaters for packets of data at rates up to 128 kilobits per second, which was a more satisfying speed than most dial-up connections at the time. The service predated most WiFi and digital cellular networks and was surprisingly affordable. Due to the bankruptcy of the company, most of the service was shut down in 2001.
A Step Forward
Desktop interfaces are inappropriate when a user is on-the-go. They require significant manual attention to control a mouse and significant visual attention to track the pointer on the screen. Instead, on-the-go interfaces might use gross gestures and key verbal phrases for input and audio, bold graphics or haptics for feedback. A notable interface problem is text entry. While speech recognition has improved significantly, it is inappropriate in meetings and many other social situations.
Mini-QWERTY keyboards, such as the Blackberry, and virtual keyboards require significant hand-eye coordination. Chording input systems such as the Twiddler and the Chorder shown here are fast and best used without visual attention, but they require training. The Half Keyboard employs a more familiar, flat, desktop QWERTY keyboard layout for touch-typing with one hand, but a user chords with the spacebar to achieve the full alphabet.
Twiddler 1 (1991, $200) & Twiddler 2 (2001, $219)
The Twiddler 1 is a chording input system enabling mobile touch-typing at nearly desktop speeds. The letters A to H have their own buttons, while I to Z are chorded using “shift” buttons. It also includes a tilt sensor-based mouse. The Twiddler 2 uses an isometric joystick for the mouse and offers PS/2 or USB for the interface with the computer. In 2008, the Twiddler 2.1 switched to an eight-way joystick. Coupled with a head-up display (HUD), a user can take detailed notes in the classroom, while having a face-to-face conversation, or while brainstorming during a walk.
Twiddler 3, model and prototypes shown (2014, $199 projected)
The upcoming Twiddler 3 chording input system will connect via Bluetooth or USB. It is smaller and adds separate mouse buttons (previous versions used the A, E, and Space keys modally as mouse buttons). Displayed are 3D printouts of early prototypes of the new device and an SLA model of the final plastics.
Chorder (mid-1990s, handmade by Greg Priest-Dorman)
Five- to seven-button chording keyboards have been a part of computing since the 1960s. Their relative simplicity, typing speed, and usability without visual attention allows them to be incorporated into a wearable system. At Vassar College, Greg Priest-Dorman fashioned this device for fast donning and doffing for use with his Herbert 1
Matias Half Keyboard (2001, $595)
The Half Keyboard leverages typists’ knowledge of the desktop QWERTY keyboard to quickly teach typing with one hand. When the spacebar is held down, the system mirrors the other side of the full-sized keyboard.
Ring trackball (unknown, $20)
Small trackballs and touchpads can be effective input devices while the user is moving, but tracking a small cursor on the screen requires significant visual attention. Using gross motion and audio feedback in lieu of a mouse pointer to control the interface allows the user to focus on the physical world.
Symbol WSS 1000 Wearable Computing System with RS 1 Ring Scanner (1998, $3500)
Symbol created a ring-based barcode scanner and forearm-mounted wearable computer to help workers more efficiently scan and inventory packages as they moved them. With previous systems, a worker would pick up a package, put it on a table, retrieve a “gun” scanner, scan the package, replace the scanner, and then move the package. With the ring scanner, a worker can scan the package as he reaches to move it. The system is a notable success, with variants still being sold by Motorola (which acquired Symbol) today.
Embroidered Textile Interfaces (2010, research prototypes from Georgia Tech)
Touch-sensitive interfaces use capacitive sensing and are created by embroidering conductive thread or screen-printing conductive ink in desired patterns such as buttons, rocker switches, pleats, menus and jog-wheels. While still not commonplace, e-textiles are beginning to be seen commercially in ski jackets and fashion accessories.
LilyPad Arduino toolkit, designed by Leah Buechley (2007, $25)
These microcontroller boards are designed to be sewn and help makers create interactive accessories and soft textile projects. Input from an accelerometer or light and temperature sensors can generate vibrations, LED lights or sound
VIRTUAL REALITY (VR) DISPLAYS
A Step Forward
In the late 1980s and early 1990s, the companies VPL Research and Virtual Research sparked popular imagination with virtual reality (VR) helmets. Unlike wearable computing displays that seek to augment the user’s experience in the everyday world, VR displays attempt to remove the user from reality, enclosing the user in high-fidelity, computer-controlled worlds. Beyond introducing the concept of a head-mounted display (HMD) to the public, these systems also helped focus attention on creating small displays and optics suitable for wearing.
Immersive systems feature large field-of-view displays, resulting in heavy headsets that are comfortable only for limited periods of time. These binocular systems sometimes have difficulty creating convincing illusions of 3D environments because only some depth cues can be simulated readily in a headset. Binocular disparity is a strong depth cue, and it may cause considerable conflict with other depth cues such as focus or vergence, leading to fatigue or simulator sickness. Early, heavy CRT technology has yielded to LCDs and recently OLEDs.
Virtual Research Flight Helmet (1991, $6000)
The Flight Helmet has a 100-degree diagonal field of view and a resolution of 240×120 pixels. It weighs 1.67 kg and uses 6.9 cm LCD screens with LEEP Systems’ wide angle optics to provide an immersive stereoscopic experience. Subsequent Virtual Research devices employed smaller lenses and a reduced field of view to save weight and cost. By 1994, the LCDs in the VR4 had twice the resolution at half the size. For its era, the Flight Helmet was competitively priced.
Philips Scuba VR Visor head-mounted display (1997, $299)
Weighing 544 g with an active-matrix LCD screen with a resolution of 263×230 pixels and a 50-degree diagonal field of view, the Scuba sold 55,000 units. While this technology was designed originally as a VR helmet for the Atari Jaguar home game system, it was sold and released by other companies without the head tracker, which Atari used only in its Missile Command game.
Oculus Rift Dev Kit 1 VR head-mounted display (2013, $300)
The commoditization of displays and motion sensors from smart phones has significantly improved the quality and reduced the cost for making VR devices. The Oculus Rift Dev Kit 1 has a 110-degree diagonal field of view with a 640×800 pixel resolution per eye, and it weighs 379 g plus a tethered control box. Approximately 60,000 of the first developer kits were sold. Very low latency head tracking and OLED technology are among the improvements featured in the new Dev Kit 2.
Nintendo Virtual Boy video game console (1995, $180)
The Virtual Boy provided an early, portable, 3D experience in an inexpensive package that included the full computing system in the device. As a table-mounted head display, the Virtual Boy has no possibility of head tracking or the freedom of motion available with most VR headsets. It uses Reflection Technology’s
scanning, mirror-style, monochromatic display in which a column of 224 LEDs is scanned across the eye with an oscillating mirror as the LEDs flash on and off, creating a 384×224 pixel resolution display with persistence of vision. It provides adjustments for focus and inter-eye distance. With over a million devices sold, the Virtual Boy introduced many consumers to immersive gameplay.