According to a pattern input unit of the invention, when a pattern is written by hand on an absolute coordinate data output means, a decision will be made on whether a segment or two points must be formed by a decision means according to two absolute coordinates generated one after another therefrom, point or segment is displayed in sequence on a display means according to the decision result, thus displaying a pattern same as the pattern written by hand.

A coordinate position determining system and method includes a liquid crystal material separating first and second groups of conductors. The tablet is at least partially light transmissive, but may include a partially reflective layer. The first and second groups or conductors are sequentially scanned at different times. A wand adapted to be positioned against the tablet includes a light detector, and may also include a light source.

The present invention reduces overhead processing of a data processing system by storing a predetermined number of points corresponding to the position of a pointing device as it moves on a workpad or other touch sensitive input device. A predetermined number of points are stored in a buffer, wherein the predetermined number is dependent upon the type of pointing device (e.g., finger, stylus, etc.) used with the workpad. The stored points are periodically displayed or inked on a visual display at a rate of at least 20 times per second. As a result, the user moving the pointing device receives both tactile and visual feedback information similar to that provided by a pencil used to make markings on a piece of paper. An alternative embodiment provides a similar reduction of overhead associated with erasing graphical information displayed on the visual display.

A light pen system for use with a CRT scanning display pen system comprising: a hand-held light receiving assembly which is adapted to be pointed at a desired location on a CRT scanning display and to provide a light detection output indication indicating precisely an instant when light detection occurs and a horizontal line position signal synthesizer receiving at least one scan line address from the computer and being operative to generate horizontal line position information, based on the at least one scan line address, corresponding to the instant when light detection occurs. A light pen method is also provided.

A device for use with a raster display having associated therewith electromagnetic noise which includes signals related to at least one raster synchronization signal. The device includes: an electromagnetic radiation pick up device operative to receive the electromagnetic noise in a wireless manner, a filter receiving an output from the electromagnetic radiation pick up device for producing a reconstructed raster synchronization signal from the electromagnetic noise; and a correlator correlating an information signal with the reconstructed raster synchronization signal. The device may be a light pen, and one version detects scan lines within a cone extending from the tip thereof. The number of scan lines detected within the cone can be used to estimate the distance of the light pen from a computer screen. A light pen method is also provided.