US 5,293,539 A · Method and apparatus for calibrating tone reproduction in a proofing system

Abstract

Apparatus and associated methods for providing accurate tone reproduction in an output image, specifically in terms of dot gain curve shape and scale, through a DDCP imaging chain (such as that implemented by a raster image processor (200), particularly a screening process (460) occurring therein, and a marking engine (130)) used in a direct digital color proofing (DDCP) system (100), based upon "Process" data (600) associated with that imaging chain and customer defined ("Aim") data (500). Specifically, monotonically interpolated, e.g. using monotone piecewise cubic interpolation, "Aim" and "Process" data for "all possible" inputs are determined from corresponding input "Aim" and "Process" data and then combined to yield a customized dot gain look-up table (460) that, for a given operating condition, reflects the "Aim" data modified by the inverse of the "Process" data, i.e. the latter reflecting the native dot gain characteristic of this imaging chain which occurs at that condition. Thereafter, incoming contone values for a proof image are routed through the look-up table to yield resulting modified values which, when subsequently printed by the DDCP imaging chain at that operating condition, will yield a proof image that exhibits only a desired "Aim" dot gain curve, without substantially any corruption, if at all, from the native dot gain characteristic of that chain. By obtaining and then interpolating appropriate "Process" and/or desired "Aim" data, for a common operating condition and then constructing a look-up table therefrom, the DDCP imaging chain can produce a proof image that, within physical limits occurring at that operating condition, will accurately exhibit only the desired "Aim" dot gain curve and hence the desired tone reproduction characteristic associated therewith.

Claims34

Dependent claims

Apparatus for generating, through an imaging system having a native tone reproduction characteristic, an output image that depicts an input image such that the output image is substantially free of corruption attributable to the native tone reproduction characteristic of the imaging system, said apparatus comprising:

means, responsive to first data values representing a desired tone reproduction characteristic of the input image that is to be reproduced at a specific operating condition of the imaging system and to second data values representing an actual tone reproduction characteristic of the imaging system obtained at said operating condition, for forming a table of values representing the first data values modified by an inverse function of the second data values;
means, responsive to incoming digitized values that collectively represent the input image for routing each of said digitized values through the table to produce a corresponding modified value therefor so as to form a plurality of modified values;
and
means for generating said output image in response to each of said modified values.

1 more element

A direct digital color proofing system for generating a color halftone proof image from incoming digitized pre-press continuous tone (contone) data for an input image, said system having means for processing the incoming pre-press contone data to yield screened halftone separation data representing halftone separations that are to collectively form the proof image, a marking engine for writing each of said halftone separations with proper registration so as to form said proof image, and control means connected to said processing means and said marking engine, wherein said processing means and said marking engine collectively form an imaging chain having a native dot gain characteristic and said system generates generating the proof image such that the proof image is substantially free of corruption attributable to the native dot gain characteristic, said system comprising:

means, responsive to first data values representing a desired dot gain characteristic of the input image and to second data values representing the native dot gain characteristic of the imaging chain, for forming a table of values representing the first data values modified by an inverse function of the second data values;
and
means, responsive to incoming digitized values that collectively represent each one of a plurality of continuous tone separations, for routing each of the digitized values through the table to produce a corresponding modified value therefor so as to form a plurality of modified values;
and
means for converting each of the modified values for each one of said separations into a corresponding halftone bit pattern so as to form a plurality of halftone bit patterns and applying each of said corresponding halftone bit patterns to said marking engine so as to write said one separation on a pre-defined media.

2 more elements

A method for generating, through an imaging system having a native tone reproduction characteristic, an output image that depicts an input image such that the output image is substantially free of corruption attributable to the native tone reproduction characteristic of the imaging system, said method comprising the steps of:

forming, in response to first data values representing a desired tone reproduction characteristic of the input image that is to be reproduced at a specific operating condition of the imaging system and to second data values representing an actual tone reproduction characteristic of the imaging system obtained at said operating condition, a table of values representing the first data values modified by an inverse function of the second data values;
routing each one of a plurality of digitized values that collectively represent the input image through the table to produce a corresponding modified value therefor so as to form a plurality of modified values;
and
generating the output image in response to each of the modified values.

1 more element

In a direct digital color proofing system for generating a color halftone proof image from incoming digitized pre-press continuous tone (contone) data for an input image, said system having a means for processing the incoming pre-press contone data to yield screened halftone separation data representing halftone separations that are to collectively form the proof image, a marking engine for writing each of said halftone separations with proper registration so as to form said proof image, and control means connected to said processing means and said marking engine, wherein said processing means and said marking engine collectively form an imaging chain having a native dot gain characteristic, a method for generating the proof image such that the proof image is substantially free of corruption attributable to the native dot gain characteristic, said method comprising the steps of:

forming, in response to first data values representing a desired dot gain characteristic of the input image and to second data values representing the native dot gain characteristic of the imaging chain, a table of values representing the first data values modified by an inverse function of the second data values;
and
routing each one of a plurality of incoming digitized values that collectively represent each one of a plurality of continuous tone separations through the table to produce a corresponding modified value therefor so as to form a plurality of modified values;
converting each of the modified values for each one of said separations into a corresponding halftone bit pattern so as to form a plurality of halftone bit patterns;
and
applying each of said corresponding halftone bit patterns to said marking engine so as to write said one separation on a pre-defined media.

3 more elements

Dependencies are inferred from the claim text.

Method and apparatus for calibrating tone reproduction in a proofing system

Life of this patent

Method and apparatus for calibrating tone reproduction in a proofing system

Life of this patent

Abstract

Claims34