A-to-D conversion from paper records with a desktop scanner and a microcomputer

A novel method for digitizing signals contained in paper records is presented. This method is based on the use of an inexpensive optical scanner to translate the image on paper into a binary, bit map data structure. Several algorithms which recognize the signal line in the bit map and translate it into a series of numbers which are equivalent to the output of electronic analog-to-digital converters are described. The method was validated by comparison both with idealized test patterns of varying frequency content and with electronically digitized pressure and pressure time derivative tracings from chronically instrumented dogs. The root mean square error for the physiological signals was 3.5-3.9% of peak-to-peak full scale, corresponding to roughly 50% more than the thickness of the signal line on the paper.