A touch screen is a display that can detect the presence of touch within the display area. The use of touch screen improves productivity as it enhance the navigation of user interface elements. While traditional user interface requires users to activate control elements by using buttons, switches or movable objects, touch screen enabled users to directly manipulate control elements from the display. However the implementation touch screen to achieve the best results in terms of usability, and responsiveness is challenging. Wrong implementation of touch screen, will not only effect the usability, but make the device unpleasant to use.
In this section I’ll describe the case where touch screen made user interface, difficult to use rather than what it should be. Recently the trend of touch interface become a wide spread phenomena. We see cameras, cellphones, computers, gaming devices, etc. equipped with touch screen. Although we see successful cases for example the portable gaming device, Nintendo DS, which enable new ways of gaming experience through a touch screen. An iPhone which utilizes a mu
lti-touch technology, enabled a better way of navigation through scrolling, finger gestures. Now come to the area where the implementation of touch screen is not quite right.
1.1 Touch screen interface for tasks that require precision
Tasks that require precision like volume control, zooming control are better to implement with an interface that users can grab easily and receive p
hysical feedback for corrections. Figure 1 show an example when we overuse the touch screen. Notice that a zoom button is implemented as a UI element in the touch screen. The problem with this design is that users cannot get the feel of how much force requires to move the zoom level into a desired position. Often time users find the touch screen is too sensitive or too irresponsive. In a regular zoom button case, there is a distance between a pressed and unpressed state, which made it easy for one to operate with high level of precision. To improve this, we have to provide physical buttons for task which require precision and not overuse the touch screen. Many manufactures seems to understand this problem, and provide dedicate controls for this function. Figure 2. shows a proper combination of controls having a touch screen for selection with high degree of freedom and physical buttons for selection with fixed functionalities.
1.2 Touch screen interface with improper hardware technology
There are many types of touch screen technologies: resistive, surface acoustic wave, capacitive, infrared, etc. Each of these technology has its own advantages and disadvantages. For example resistive technology requires the use of force and works well with stylus. On the other hand, capacitive technology is highly sensitive and only accept finger touches. Figure 3 shows a phone that tries to combine both finger touches and stylus. The result is a torture user experience. Often times user will find that the system is irresponsive. Since the resistive type of touch screen require the use of force, when use with finger, one has to apply appropriate force to register a click. When a finger is place on top of the UI there is no feedback. Only when you really press it, the action is made. Also there is no way to avoid an unintended click since the action is already carried out. In the case of capacitive technology, we can detect the finger the moment it hits the screen surface. With this we can display a proper feedback.
1.3 Touch screen interface that lacks proper feedback
This one also concern issues in 1.2 but also discuss the design aspects of UI from the software point of view. In order to provide a good user experience, we always need to give a user the feedback so that he/she knows if the selection is correct or not. Figure 4. shows example of a typical selection screen found in ticket vending machine where many buttons are placed next to each other. In some places, machines do not provide visual feedback. For example (a) a user wish to choose D but accidentally press in the area in between D and E. With no visual feedback, the result can be ambiguous. Then (b), A user will then doubt about his selection which causes confusion. Since a touch screen provide no physical feedbacks like real objects, we have to provide visual feedbacks, sound feedbacks, or shake feedbacks to confirm the user. For example when press the button, the button has to change the look as if it is pressed as in (c) so that the user know right away which button was clicked.
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