In the last twenty years or so computers and other electronic equipment have become increasingly important for vision research. This is because they provide a flexible way to generate many kinds of stimuli which may be altered or adjusted in reply to an external input such as a subject's response. Although popular, these systems have many limitations from an engineering point of view and it is therefore important that the vision researcher should have good understanding of the way they work, what the potential problems and pitfalls are and how they may be minimised. It is also necessary to have a quantitative knowledge of the deficiencies so that the researcher can decide whether or not they are significant in the desired situation. In many cases, it is possible to augment a particular parameter of the system by trading it off against another, so an idea of relative priorities is needed too.

A basic system for vision research consists of a computer, which is often an IBM-type PC or MAC and a cathode ray tube (CRT) display monitor. The monitor may be the same one as that used to control the computer but is usually a separate and more fancy device that can be sited remotely; in a darkened room for example. In addition to the basic system, the user can add devices for capturing images from the real world such as ccd cameras or CD-ROMs, devices for producing hard copy such as laser printers, devices for producing special effects such as stereo glasses and devices for calibrating the system (very important). Video monitor configurations are not the only possible uses for computers in vision research but they are certainly the most popular and cause the most trouble so they are the ones we shall consider here. In this chapter we shall start by reviewing some of the fundamental aspects of using digital systems in an analog world and discuss a few of the engineering terms and concepts that are used by equipment designers and suppliers. After that, we will describe the principle of operation of some of the commonly used equipment and show how they can be used to generate different stimuli. Finally we will mention some of the other miscellaneous aspects not covered elsewhere. In order to keep things simple, the scope of the chapter is mainly confined to monochromatic stimuli and throughout, the approach will be largely non-mathematical and the reader referred to one of the many of the books available for a more rigorous discussion.

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