Abstract: The invention concerns digitizing tablets in portable computers, wherein position of a stylus, located on the tablet, is computed. The invention corrects for various errors which creep into the computation, in order to produce a more accurate stylus position. The digitizing tablet has multiple sensors used to determine the stylus' position with respect to the digitizing tablet. Error signals are generated by measuring the sensors outputs when the stylus is not inducing a signal into the digitizing tablet. In one embodiment, these error signals are used to modify certain parameters used in calculating the stylus position.

Abstract: The invention concerns storage of correction tables for digitizing tablets. A digitizing tablet produces data indicative of position of a stylus. The data does not, in general, exactly indicate the position; errors exist. For example, a tablet may produce a data pair indicating a Cartesian position of (5.0, 6.0) when the position is actually (4.9, 6.1). Correction tables are used to correct the errors. These tables may be viewed as containing correct data for each possible pair of data produced by the tablet. Thus, in this example, a user would (a) receive (5.0, 6.0) from the tablet, (b) look up this data in the table, and (c) find that the actual position which corresponds to this data is (4.9, 6.1). The invention concerns compression of such tables, to reduce storage space.