Information about the environment is always obtained through sensors. To understand the handling of perceptual information, we must first start with an understanding of the types and properties of sensors and the nature of data they produce.

Types of Sensors

In general, a sensor is a device that measures a physical quantity and converts it into a signal that a human or a machine can use. Whether the sensor is human-made or from nature does not matter. Sensors for sound and light have been the most important for multimedia computing during the past decades because audio and video are best for communicating information for the tasks humans typically perform with or without a computer. That is, most people prefer to communicate through sound, and light serves illustrative purposes, supplementing the need for language-based description of a state of the world. New or different tasks might use different sensors, however. For example, in real-world dating (as opposed to current implementations of online dating), communication occurs on many other levels, such as scent, touch, and taste (e.g., when kissing). Artificial sensors are therefore invented as you read this chapter. Let’s start with a rough taxonomy of current sensors interesting to multimedia computing.