Chapter 10 - Small-Screen Interfaces

Abstract

The use of small screens as a tool for displaying dynamic information is becoming ubiquitous. Displays include very simple screens as seen on clocks, microwaves, and alarm systems. Small-screen design primarily makes use of the visual system. Questions in small-screen design often center on how small data elements can be displayed so that they are properly seen or recognized. To gain a deeper understanding of the answers to these questions, a brief background of light, eye anatomy, and the sensitivity and acuity of the eye are required. Light is described by its wavelength and intensity. The subjective or psychological correlate to wavelength is color. The color that people see is their perception of the light's wavelength. As light rays enter the eye, they pass through the cornea, the pupil, and the lens to ultimately fall on the retina. The cornea and the lens refract the light so that images come into focus on the retina. The iris controls the amount of light entering the eye by dilating or constricting the size of the pupil. The sensitivity of the eye to light is heavily dependent on the wavelength of the light. The smallest detail the eye is capable of resolving at a particular distance is known as the minimum visual acuity. Visual acuity of an object depends on its size and its distance from the viewer. A small object that is very close may appear larger than a large object that is far away. The distinguishing feature of an object's size, therefore, is the size the object projects on the retina, also known as its visual angle.