Patent ID: 6947179

Claim:
A method for measuring information loss, or conditional entropy, of a paper channel, said paper channel comprising: (a) a symbol input defining symbols to be printed; (b) a bitmap generator responsive to said symbol input to generate bitmaps representative of corresponding input symbols; (c) a printer responsive to said bitmap generator to print on a substrate symbol images substantially determined by said bitmaps; and (d) an imager to capture said images from said substrate and generate corresponding image signals, said method comprising the steps of: i) selecting a general, parametric, statistical model for said paper channel; ii) selecting a plurality of test bitmaps; iii) transmitting said test bitmaps through said paper channel to obtain a set of test image signals for each of said symbols, each of said sets containing at least one test image signal; iv) adjusting parameters of said model so that image signals predicted by said model for said set of test bitmaps substantially conform to said sets of test image signals, whereby a particular parameterization of said model substantially accurately describing said paper channel is obtained; and v) determining an estimate for the information loss of said channel in accordance with said particular parameterization.