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A System for Automatic Calibration of Multiple Printers

IP.com Disclosure Number: IPCOM000013624D
Original Publication Date: 2000-Apr-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Abstract

Described is a system for automatic calibration of multiple printers. Each printer is equipped with an automatic densitometer or similar measurement device. The system causes the printers to measure the current engine behavior, receives the measurements asynchronously and updates the grayscale correction curves as necessary. A tagging scheme is employed to enable the system to identify the origin and context of each asynchronous measurement, so that the right curve can be updated. A typical embodiment of the system consistes of a print server and a number of bilevel printers attached to the servers using local area network. The printers are equipped with automatic optical measuring devices, such as densitometers. For printers that use multiple engines (commonly one for each side of the paper), one measuring device is provided for each engine. Each measuring device continously monitors a predetermined location on each output page. If a predefined pattern is detected, the measurement device takes a set of measurements (typically of optical density) and reports it to the server via the network. The pattern causing the measurements to be generated is a set of patches, typically generated on the server and sent to the printer as a print job (measurement job). Due to the spooling and printer uptime factors, the delay between sending such a measurement job to the printer and receiving the measurements is unpredictable. Multiple measurement jobs can also be sent to each printer, since each halftone screen must be calibrated separately. In such a case, there is often no guarantee of the order in which the jobs are printed and measured, and consequently no guarantee that the measurements will be received in a particular order.

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A System for Automatic Calibration of Multiple Printers

   Described is a system for automatic calibration of multiple printers. Each
printer is equipped with an automatic densitometer or similar measurement device.
The system causes the printers to measure the current engine behavior, receives
the measurements asynchronously and updates the grayscale correction curves as
necessary. A tagging scheme is employed to enable the system to identify the
origin and context of each asynchronous measurement, so that the right curve can
be updated.

A typical embodiment of the system consistes of a print server and a number of
bilevel printers attached to the servers using local area network. The printers
are equipped with automatic optical measuring devices, such as densitometers. For
printers that use multiple engines (commonly one for each side of the paper), one
measuring device is provided for each engine.

Each measuring device continously monitors a predetermined location on each
output page. If a predefined pattern is detected, the measurement device takes a
set of measurements (typically of optical density) and reports it to the server
via the network. The pattern causing the measurements to be generated is a set of
patches, typically generated on the server and sent to the printer as a print job
(measurement job).

Due to the spooling and printer uptime factors, the delay between sending such a
measurement job to the printer and receiving the measurements is unpredictable.
Multiple measurement jobs can also be sent to each printer, since each halftone
screen must be calibrated separately. In such a case, there is often no guarantee
of the order in which the jobs are...