Digitizer having flat tablet with magnetic shield plate

摘要

A digitizer for determining coordinate value of a point designated on a given two-dimensional coordinate plane. A pointing instrument is manually operable to designate a point on the given two-dimensional coordinate plane of a tablet. The tablet includes a flat sensor defining the given two-dimensional coordinate plane and operative for transmitting magnetic signal between the flat sensor and the pointing instrument disposed thereon to detect the designated point to thereby produce a detection signal, and a shielding plate disposed under the flat sensor to magnetically shield the flat sensor. The shielding plate is composed of silicon steel containing 4.0 to 7.0 weight % of silicon. A processing circuit is connected to the flat sensor for processing the detection signal to determine the coordinate value of the designated point.