Kortum P. (ed.) HCI Beyond the GUI. Design for Haptic, Speech, Olfactory, and Other Nontraditional Interfaces
Подождите немного. Документ загружается.
10.2.1 Display Technologies
Today, LCD technology can be broken into two major categories: active- and passive-
matrix displays. Passive-matrix displays work by rapidly activating corresponding rows
or columns of the display sequentially to update the screen with new images. The tech-
nology is called “passive” because each pixel must retain its state between refreshes
without an electrical charge. Passive-matrix screens require less power and are less
costly to manufacture than active-matrix displays, but as the resolution of the display
increases, the response time and the contrast of the passive display become worse.
Active-matrix LCDs employ an individual transistor for each screen pixel.
Active-matrix displays use more power because each transistor requires a steady
electric charge to maintain or update its state. However, because each pixel is
controlled separately, active-matrix displays are typically brighter, sharper, and
have a faster response time than passive screens.
Both active and passive LCD technologies can be used in color or mono-
chrome displays. Monochrome displays use less power, have higher contrast,
and cost less to manufacture than color displays (Wright & Samei, 2004). Obvi-
ously, color LCDs provide a richer and more compelling graphical user interface
(GUI) and are typically more desired by users.
While LCD screens are the primary display technology in use today in small-
screen devices, other technologies are in common use depending on the device’s
application. The simplest display technology is the vacuum fluorescent display
(VFD). VFDs are used in microwave ovens, home theater components, and other
consumer electronic devices that do not require complex user interfaces. VFDs
emit very bright light, are very high contrast, and are inexpensive to manufacture.
The downside is that a single VFD screen element can only display a single color
at a time and is too slow for more complex computer-like interfaces. VFD displays
are frequently designed in a segmented fashion with relatively large segments
(compared to LCD or CRT pixels), thus limiting the range of shapes that can be
created. Figure 10.4 shows a close-up of a VCR’s segmented VFD display.
FIGURE
10.4
Close-up of a vacuum fluorescent display.
VFDs have been adapted to display dynamic data by breaking down the segments
into individual pixels.
Source:
From Wikipedia.org, 2007.
10 Small-Screen Interfaces
312
Another straightforward technology that has blossomed into a viable display
modality is the light-emitting diode (LED). From the single LED light that tells
you that your smoke alarm is receiving power to fiber-optic light pipes that allow
for high-resolution LED displays, the LED has evolved into an extremely useful
display technology. LEDs use a very small amount of power, and have a long life
span and quick response times. Figure 10.5 shows a car-parking assistant that tells
the user how far away he or she is from backing into objects by displaying the
distance on an LED display.
One of the most exciting developments in display t echnology is the organic
LED (OLED) display. Organic dyes are deposited on a layer of glass or plastic
that emits light when excited by electrons. OLED displays have great potential
as a display technology because they r equire litt le power, produce a bright
picture, and can be made very thin. The major disadvantage of current imple-
mentations of OLED displays is the short life span of the organic materials
used (current implementations are limited to a maximum of 10,000 hours).
If this limitation can be overcome, OLED displays may quickly overtake the
LCD as the primary di splay technology. Commercial implementati ons of OLED
technology are already becoming available; Figure 10.6 shows a Samsung
OLED watch.
An additional benefit of OLED displays is that the entire screen may be made
flexible. Electronic paper (also called e-paper) is an OLED display technology
designed to look and act like printed paper but with the ability to display dynami-
cally changing data. The key difference between e-paper technology and other
displays is that no power is needed to keep pixels on the screen (a technique
known as image stability); power is only needed to change the picture on the dis-
play. The image stability properties of e-paper mean that these displays require
very little power to operate over long periods of time.
FIGURE
10.5
Car-parking assistant with an LED display.
The number on the display is the distance the user is from any objects behind
him.
Source:
From Alibaba.com, 2007.
10.2 Technology of the Interface
313
10.2.2 Screen Size, Resolution, and Dots per Inch
Screens are defined by both their physical size and their resolution (the number of pix-
els they can display). Physical screen size is measured in inches by diagonal length.
Typical displays use a ratio of horizontal to vertical size of 4:3. Newer, so-called
“wide-screen” displays, use a 16:9 ratio, and other less common ratios (e.g., 3:2, 5:4,
or 16:10) are employed depending on the application or device (Figure 10.7).
The resolution of the display also plays an important role in the amount of
information that can be presented on screen. Dots per inch (DPI) (also called
pixels per inch) is a measure of the number of pixels in each square inch of the
display. The higher the DPI value, the denser the pixels are in the display and thus
the better the visual quality of the display. A typical DPI value for a computer
screen is 72, but newer screens are already exceeding 200 in density.
Another more common measurement of resolution is the number of horizon-
tal and vertical pixels the screen is capable of displaying. Small-screen device reso-
lutions can range from as low as 16 16 pixels for watch displays and other
FIGURE
10.6
Commercial implementation of OLED.
The Samsung GPRS Class 10 Watch Phone uses an OLED display.
Source:
From
Engadget.com, 2004; courtesy Samsung.
10 Small-Screen Interfaces
314
similar very small screens, to 800 600 pixels (SVGA) found in some high-end
devices (like the Motion LS800 Tablet PC). Newer devices are continually pushing
this limit for higher-resolution displays. Various resolution standards are shown in
Table 10.1.
10.2.3 Input Technologies
It is difficult to design for small-screen devices without considering how informa-
tion is inputted to the device. The design of the display interface is heavily
TABLE 10.1 Standard Small-Screen Resolutions
Name Aspect Ratio Resolution
QQVGA 4:3 160 120
QCIF 1.22:1 176 144
QCIFþ 4:5 176 220
QVGA 4:3 320 240
CGA 16:5 640 200
EGA 64:35 640 350
VGA 4:3 640 480
SVGA 4:3 800 600
XGA 4:3 1024 768
FIGURE
10.7
Four common aspect ratios.
Typical displays use a ratio of 4:3.
Source:
From Cambridgeincolour.com, 2007.
10.2 Technology of the Interface
315
dependent on the data entry method. In fact, human data input for small-screen
devices is arguably the biggest challenge facing device designers. Today, the
QWERTY keyboard and mouse are the ubiquitous input devices for the PC; how-
ever, the small size of today’s mobile devices requires different input techniques.
For mobile phones the standard telephone keypad (known as the dual-tone
multifrequency, or DTMF, keypad) is a standard input device. For entering num-
bers, the DTMF keypad is fast and effective, but for alphabetic textual input, it is
slow and inefficient. The most common method of textual input is called multitap
entry. It requires the user to press the number key that represents a particular let-
ter a number of times in order to produce the desired character. For example,
pressing the 2 key three times would produce the letter C. Clearly this method
requires several times more effort than a typical computer keyboard. Figure 10.8
shows the edgy DTMF keypad on a Motorola RAZR phone.
Several methods of predictive text input have been developed to overcome
the limitations of the DTMF keyboard, including the T9, SureType, and iTap (to
name only a few). Generally these technologies rely on dictionary completion,
meaning that words are guessed from a dictionary based on the keys pressed. In
the T9 system the user presses the number key representing the letters in the
word (once for each letter). The software then guesses the most appropriate word
based on dictionary matches of the letters entered. If the word is not correct, the
user is given the option of cycling through other words that match the keys
FIGURE
10.8
DTMF keypad for the Motorola RAZR.
This model has a five-way rocker, two softkeys, and four hardkeys.
Source:
From
Wikimedia.org, 2007; courtesy Motorola.
10 Small-Screen Interfaces
316
pressed. While predictive techniques are faster than multitap input, they are still
slow in comparison with a standard computer QWERTY keyboard. A recent con-
test between a champion predictive-text phone user and a 93-year-old telegraph
operator found that Morse code was a faster text entry method than predictive text
(Engadget.com, 2005).
Even the small QWERTY keyboards employed in some phones tend to make the
phone volume too large to be desirable for some consumers. The need for smaller
form factors has led to the exploration of different input technologies. Techniques
such as the Palm’s handwriting recognition software and virtual soft keyboards
(which display a QWERTY keyboard on a touch-sensitive screen) have been imple-
mented. However, Western consumers have not taken to these new input styles en
masse due to their limited input speed and poor accuracy rates (Bohan, 2000).
It is clear that a full QWERTY keyboard is a quick and usable input device,
so companies like Lumio have developed projection keyboards. The projection
keyboard (like the one shown in Figure 10.9) is a device that projects light in
the shape of a regular keyboard onto a flat surface. The user interacts with it by
virtually pressing the keys on the surface. Based on which light beams are broken,
the device can tell which keys are being “pressed.” So far, few commercial devices
use the projection keyboard, but as the technology matures it will no doubt be
integrated into more devices.
Clearly, textual input is not the only way in which users input data to their
devices. For many years, hardkeys have been used in devices from microwaves
FIGURE
10.9
Simulation of a projection keyboard.
This one is in use on a Windows Mobile device.
Source:
From Roeder-Johnson.
com, 2007; courtesy Cayerta, Inc.
10.2 Technology of the Interface
317
and watches to phones and media devices. A hardkey is a dedicated button that
when pressed activates one or more functions within the device. A similar tech-
nology is the softkey, which is a dedicated button with a software-determined
label. The softkey performs context-sensitive actions based on the state of the soft-
ware, and is very common in mobile phones. A popular trend in small-screen
devices is the use of touch-sensitive screens. Recently the touch screen has
become a more viable input option because of both the reduction in production
cost and the improved sensitivity of the screens themselves. There is a good
reason why keyboards have not been replaced by touch screens in larger devices;
tactile feedback is an important part of the input experience. This limitation of
feedback has hampered the development of touch screens until recently, when
improved sensitivity and responsive interfaces have made the touch screen a
reasonable input technology.
Other common input devices include the click wheel used in t he popular
iPod, the four- and five-way rocker used in a large number of phones, the track
wheel used in BlackBerries, a nd the joystick used i n phones a nd media devices.
As yet no ideal al l-around input devi ce has been discovered. When determining
a device’s input technology, the hardware should be designed in cooperation
with t he software so that the primary use cases of the device are made easy
and efficient.
10.3
CURRENT IMPLEMENTATIONS
OF THE INTERFACE
Small-screen interfaces have become a pervasive part of today’s society. From the
simple digital watch to in-car displays, almost everyone interacts with small-
screen devices on a regular basis. Despite the prevalence of these devices, their
complexity and usability vary widely across the spectrum of implementations.
Diversity of hardware aside, several trends can be seen throughout the industry:
a continued reduction in the size of devices, increasing computing power within
the device, growing software and user interface complexity and the enhanced
convergence of features.
10.3.1 Mobile Phones
In many ways, mobile phones are responsible for today’s explosive proliferation of
small-screen, handheld communication devices. In 2005, worldwide mobile phone
sales were estimated at more than 825 million units sold (Gohring, 2006). This
massive market has driven manufacturing costs of small-screen devices down to
a level where they are accessible to new user groups. The reduction in the cost
of parts has also made other small devices more cost-effective to manufacture.
10 Small-Screen Interfaces
318
Typically mobile phones are smaller, less feature filled, and less costly than
their larger PDA cousins. Mobile phones in the past usually performed a limited
number of key functionalities such as making phone calls, writing short message
service (SMS) messages, and managing contacts. Screens on mobile phones are
found in both monochrome and color but tend to be lower resolution and tend
to have simpler and more straightforward software interaction design than PCs.
Newer phones follow the trend toward more features: camera integration, video
playback, high-resolution screens, and multiple displays, to name a few.
10.3.2 Smart Phones and Personal Digital Assistants
Not only do users want smaller devices, they also want devices that have advanced
technological and networking capabilities (Sarker & Wells, 2003). Nokia’s Series
60–based devices allow users to perform a nearly unlimited number of tasks pre-
viously only available in full-blown PCs. According to the promotional material
for the Nokia N95, “It’s GPS. It’s a photo studio. It’s a mobile disco. It’s the World
Wide Web. It’s anything you want it to be” (s60.com, 2007). The combination of
improved battery technology, miniaturization of components, and a seemingly
endless number of new hardware and software features are making small-screen
devices into true portable PCs.
The downside of increased technological complexity, generally, is a reduction
in usability. This is true of many of the cutting-edge small-screen devices. How-
ever, improved integration of features is making it easier for users to understand
and even manage the complexities of multimedia data. The Research In Motion
(RIM) BlackBerry Pearl keeps the user in control of his or her busy life by
providing simple but effective filters for e-mail, integration of instant messaging,
and the ability to easily synchronize the device with a PC. Despite the complexity
of the underlying technology, usability-focused PDAs like the Blackberry can
provide an easy-to-use integrated computing experience.
10.3.3 Digital Audio Players
In a 2003 study, Sarker and Wells found that reduced device size played a major
role in the adoption of mobile devices. Developments in hardware miniaturization
have allowed manufacturers to continue to reduce the form factors of small-
screen devices while increasing their computing power. The iPod is currently
one of the most popular mobile devices on the market with an estimated install
base of 40 million units (AppleInsider.com, 2006). The iPod Nano uses a touch-
sensitive click wheel, holds up to 8 gigabytes of music (or around 2,000 songs),
provides a vibrant color LCD display, and offers many different ways to enjoy
music. The Nano is barely bigger than a credit card at 3.5 in 1.6 in 0.26 in.
The iPod’s success makes it clear that users have a strong desire for small devices,
and the number of similar devices has skyrocketed.
10.3 Current Implementations of the Interface
319
10.3.4 Mobile Gaming Devices
Mobile gaming devices are another small-screen information appliance that has
found wide acceptance in the marketplace. While mobile gaming devices have
been around since the 1980s, newer devices play multiple games, have bigger
screens, and are packed with advanced features. The Nintendo DS Lite with its
two 3-in LCD screens, touch-screen input, four-way rocker, and WiFi connectivity
is a perfect example of a powerful computing device designed to be used by chil-
dren and adults. DS games seamlessly integrate the touch-screen interface into
play, encouraging an immersive interaction experience.
10.3.5 Scientific and Medical Equipment
Scientific equipment also employs small-screen technology to convey complex
information. Progress in screen technology has vastly improved the reliability
and accuracy of visual display–reliant scientific equipment. Small screens are
found in a myriad of scientific devices, including oximeters, signal analyzers, infu-
sion pumps, and oscilloscopes. For example, modern digital storage oscilloscopes
(DSOs) employ small color CRTs or LCDs to display detailed test data. The Tektronix
TDS 3052B shown in Figure 10.10 has an active-matrix VGA (640 480 pixel res-
olution) LCD screen, numerous hardkeys and softkeys, and an Ethernet network
interface, and can even connect to larger monitors.
Another area of prolific small-screen usage is consumer medical devices.
Modern thermometers, insulin pumps, glucose meters, and medical-alert devices
all make use of small-screen device technology. For example, glucose meters for
diabetics have advanced significantly in the past 10 years into digital devices that
FIGURE
10.10
Tektronix TDS 3052B LCD-based digital storage oscilloscope.
This device has an active-matrix VGA LCD screen and many other sophisticated
features. (Courtesy Tektronix, Inc.)
10 Small-Screen Interfaces
320
can display glucose levels within seconds of testing. The OneTouch Ultra meter
not on ly displays the detected glucose levels on a high-contrast monochrome
LCD screen, but also allows the user to keep track of exercise, health, and
medication by downloading the data fromthedevicetoaPC(Onetouch.ca,
2007).
10.3.6 Information Appliances
Devices like watches, microwaves, alarm clocks, cameras, stereo equipment, digi-
tal thermostats, and even exercise machines all make use of small screens. Donald
Norman, a leading expert in cognitive psychology and interface design, calls these
devices “information appliances,” devices that perform a limited number of func-
tions but carry out those functions in a simple and usable way (Norman, 1999).
The Logitech Harmony series of remote controls employs a small screen accom-
panied by a series of softkeys and hardkeys to perform task-based control over
even the most complicated home theater setups. The design of the Harmony
Remote mirrors how users actually interact with their home theater, allowing
the user to request simple tasks such as “Watch a movie” or “Watch TV.” Hidden
from the user, the Harmony intelligently performs a number of different actions
such as changing TV inputs and receiver inputs and turning devices on or off
(Logitech.com, 2007).
10.3.7 Media Center Interfaces
Small-screen devices share many design similarities with one particular large-
screen interface paradigm: the media center. Media center technology has evolved
out of the user’s need to control the various types of home theater media. Pro-
ducts like the Tivo Series 3, the Motorola 6200 s eries, and Microsoft’s Windows
XP Media Cen ter Editio n allow the user to watch television, watch recorded
shows, watch movies, and listen to music through a single integrated interface.
Even though televisions are far from “small screens,” the design guidelines used
for these devices are nearly identical to those used for small-screen devices
because the user sits a great distance f rom the display and the inter face must
be designed to accommodate the lower resolution of the majority of televisions
in today’s homes.
10.3.8 Hybrid Devices
The i ncreasing demand by users for simplicity has driven manufacturers of
small-screen devices to attempt combining various small-screen technologies
into hybrids. Typically these devices are not as robust or simple as dedicated
small-screen devices. However, due to their convenience, this is a rapidly
10.3 Current Implementations of the Interface
321