Patent ID: 7896460
Filing Date: 2011-03-01
Classification: B41J

Abstract:
1. A method for detecting intermittent, weak or missing jets of a printer having a row of nozzles, the method comprising: sensing a test pattern using a sensor, the test pattern having an array of dashes produced by the row of nozzles; generating a first response profile that represents a first cross section of the sensed test pattern, the first cross section extending in and being parallel with a process direction in which a print medium advances, the first response profile containing illumination level variations in the process direction; obtaining a first metric for the first response profile based on the illumination level variations in the process direction, the first metric being a phase of a set of minimum illumination levels in the first response profile, obtaining a difference between the first metric and a reference, the reference being a reference phase; and wherein obtaining the difference between the first metric and the reference comprises: