Determining touch or hover behaviour of an object interacting with a touch screen, using off-axis parabolic mirror

摘要

The position and/or orientation of an object 2, located in an interaction volume 1 which is delimited by an interaction surface â such as a touch screen or interactive whiteboard 12 â and by a height above that surface, is determined by reflecting radiation from the object to a camera 5 via a mirror arrangement 7 comprising one or more sections, at least one of these being an off-axis concave, substantially parabolic mirror element, arranged so that the focal point of the elements is located at the aperture of the camera, with its axis parallel with the interaction surface. The use of a parabolic mirror means that the height dimension of the volume is magnified by a constant value, allowing more accurate determination of touch or hover behaviour, combined with positional information to give feedback to the computer system. The camera and/or the mirror may be provided with coatings that filter light to enhance signal-to-noise ratio. The arrangement may use natural light, or be provided with specific illumination. The apparatus may be mounted in a single housing.