Scanner as test print densitometer for compensating overall process drift and nonuniformity

An electrostatographic reproduction apparatus comprising:

• scanner means for scanning an original document to be copied and for generating signals representing a density characteristic of images on said document, said first signals representing density values from a first set of a first plural number of density values;
• an electrostatic recording member movable in a process direction;
• writer means for modulating charge on said member, said writer means including means for forming latent electrostatic images of a series of halftone step patterns of different densities, said writer means further including halftone rendering means for generating second signals representing halftone densities of superpixels to be recorded on a record member, said second signals representing density values from a second set of a second plural number of halftone density values that are fewer in number than said first plural number, the density values of said second set having a first corresponding relationship with density values from said first set;
• means for developing the latent images of the series of halftone step patterns;
• means for transferring developed images of the series of halftone step patterns to a record member;
• means responsive to rescanning of the record member having the series of halftone step patterns by the scanner means for generating adjustment signals for correcting for conditions in processing of an image, and
• said halftone rendering means being responsive to said adjustment signals to produce a second corresponding relationship between the halftone density values of said second set with the density values from the first set.

An electrostatographic reproduction method comprising:

• scanning an original document to be copied and generating first signals representing density characteristics of images on said document, said first signals representing density values from a first set of a first plural number of density values;
• moving an electrostatic recording member in a process direction;
• operating a writer in an image copying mode wherein the writer is responsive to said first signals for modulating charge on said member, said writer being operated in said copying mode to generate second signals representing halftone densities of superpixels to be recorded on a record member, said second signals representing density values from a second set of a second plural number of halftone density values that are fewer in number than said first plural number, the density values of said second set having a first corresponding relationship with density values from said first set;
• operating said writer in a calibration mode to form latent electrostatic images of a series of halftone step patterns of different densities on said recording member;
• developing the latent images of the series of halftone step patterns;
• transferring the developed images of the series of halftone step patterns to a second member;
• and
• scanning the record member having the series of halftone step patterns and generating adjustment signals for correcting for conditions in processing of an image, and in response to said adjustment signals producing a second corresponding relationship between the halftone density values of said second set with the density values from the first set.

An electrostatographic reproduction apparatus comprising:

• scanner means for scanning an original document to be copied and for generating signals representing a density characteristic of images on said document;
• an electrostatic recording member movable in a process direction;
• a test pattern generator for generating data signals representing a contone pattern;
• writer means, said writer means including a plurality of radiation-emitting recording elements, said writer means being responsive to said signals for modulating charge on said member to form a latent electrostatic image, said writer means also being responsive to signals for recording a contone pattern on the recording member;
• means for developing the latent image;
• means for transferring a developed image to a record member;
• and
• adjustment means responsive to rescanning of the record member by the scanner means for generating adjustment signals for correcting for nonuniformities in a direction transverse to said process direction, said adjustment means generating corrected multibit data signals and including means responsive to scanning of a contone step pattern by said scanner means for generating corrected exposure clock pulses, said adjustment means also including means responsive to scanning of a halftone step tablet by said scanner means for generating adjustment signals to a gamma correction look-up table and said writer means being responsive to said adjustment signals and said corrected clock pulses for generating corrected enablement times for recording by said recording elements.