Wearable Computing

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

- 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.”

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.

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?

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.

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.

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.

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.

What use were mobile head-mounted displays to the average consumer before 2008? Very few digital devices provided a way of feeding an image to an external display. In an attempt to reach consumers, head-mounted display (HMD) manufacturers designed lighter-weight headsets intended primarily for watching videos while stationary, such as during a flight, on a train, or at home.



When Apple’s video iPod was released in 2005, HMD manufacturers had a popular mobile system with which to interface. These systems avoid the eyestrain of 3D viewing by opting instead for a 2D experience. Mobile video viewers used displays originally designed for camcorder viewfinders or video projectors. Wearable computing academics and makers adopted these viewers and often adapted them for their mobile needs by removing the display for one eye. They used messaging, mobile navigation, restaurant reviews, email and web search on their wearables before smart phones became prevalent in 2008. Today, similar video viewers are often self-contained or wireless, using microSD cards to play stored movies or using WiFi to connect to a video player.

Instead of immersing the user, one-eyed HUDs designed for industrial, military, and medical purposes often provide brief, intermittent assistance while the user is performing another primary task. For example, an anesthesiologist in the operating room may use a HUD to glance at the patient’s vital signs while looking at his face for signs of hypoxia (lack of oxygen). A soldier may refer to a display to determine his location on a map, or a worker in a warehouse may view a diagram showing which part to pick next for an order.



These “microinteractions” last a few seconds and require a device that is faster to access than a smartphone, which averages about 20 seconds simply to unlock and navigate. Like the dashboard of a car, a user glances at it and is quickly back to the task at hand. What tasks would consumers desire if they had similarly fast access to a computer?

A handful of makers and academics began designing wearable computers to be used as part of their everyday lives in the early- to mid-1990s. Instead of focused, work-related duties, these devices were used for more personal tasks: email, messaging, music, note-taking, photography, and scheduling. The MIT Wearable Computing Project established a “living lab” where advocates explored a wearable computing lifestyle in a community of users. Collaboration with designers led to wearable computing fashion shows, where the importance of fashion for devices on the body became clear. A community led by Carnegie Mellon University, Georgia Tech, and MIT established wearable computing as its own academic field and encouraged makers to participate.

Wearable computers have been mainstream since the late 1990s; digital music players, wireless earphones, fitness and sports devices, wristwatches, and body-mountable cameras have been commonly available for many years. However, with reliable digital networks, cloud services, low-power processors, plastic optics, and miniaturization, general purpose HUD-based wearables can be designed as fashionable packages and marketed to the general consumer. The popularity of smart phones has helped create a market by acquainting the consumer with desirable mobile services as well driving innovation in small, low-power components.