Flat panel displays such as liquid crystal displays (LCD) are well known. Such displays are used extensively for visual display in applications such as car dashboards, instrumentation panels, household devices, sign-posts, etc. Liquid crystal arrays (LCA) are used for displays such as computer display monitors, TV monitors and projection devices. In PCT application PCT/EP91/00065 liquid crystal devices are proposed for use in an improved transparency viewing apparatus.
The general need for improved human interfaces in the direct activation of apparatus is well known, and various types of touch screens are available. Such touch screens include apparatus based on infra-red detection and on piezo-electric, ultrasonic, resistive and other technologies.
Known combinations of flat panel displays and touch screens suffer from disadvantages of bulkiness, complexity and high cost resulting from the need to provide two separate systems, one for display and another for detection.