A METHOD FOR APPLYING SPECTROPHOTOMETRY DATA TO DIGITAL IMAGES FOR VISUAL COMPARISON

DESCRIPTION:

The invention provides a methodology for digitally displaying a representation of a printed sheet versus a digitally displayed soft proof.

Back Ground of the Invention:

Traditionally hard copy proofs and soft proofs that are intended to represent the final printed colour, are supplied locally at press side or remotely to print buyers. These are intended to provide a visual guide for the printing press operator. These visual aids provide guidance for manual press adjustments, designed to get a more accurate colour match to the supplied proofing media; be it hard copy or soft proof.

Historically once a print job is started, the press operator must maintain control over the colour accuracy through constant measurement of the colour bar elements using some form of colour measurement instrumentation. Additionally he will use visual comparison between the printed materials and the provided pre press colour proof media.

In assessing the visual colour differences between the printed materials and the supplied pre press proof colour media, the press operator must attempt to interpret the colour differences, reflective properties of the hard copy proof, what remedial corrections to apply, while ignoring the mitigating differences between the subtractive reflective colour of the printed copy and the additive transmissive colour if a soft proof is used.

The above scenario often results in the need to extend a press run or reprint a job due' to colour variations at the start and throughout the press run. This results in needless waste in materials, time and additional expense to the press owner.

The proposed invention eliminates the currently required interpretation between subtracti::© colour and/or variation in additive colour media, thus providing faster and more accurate colour difference assessment.

Summary:

To overcome the disadvantages, the Invention displays a colour correct primary image adjacent to a secondary image modified with colour spectrophotometric data obtained by measuring a color bar printed onto the press sheets obtained from the press. The primary image data for individual print jobs are stored as files and transferred over a network connection to the file storage of the invention. The image data file matching a job to be printed is identified by it's file name and manually selected by the press operator. At this time the image colour data is transferred from the file storage to the memory of the computer, and may undergo a series of initial modifications to more accurately represent the expected colour to be printed on the press. The primary image ^■

data is displayed, and duplicated in memory to serve as the baseline for the secondary image to be modified using spectral colour data from the press sheet.

During the press run, a colour bar scanning device is used to scan a plurality of color patches printed onto a press sheet. These colour patches are arrayed in a line oriented perpendicular to the direction in which the sheets are delivered through the press. The color bar contains at least one solid patch for each ink, per ink key zone on the press, and may contain additional elements along its length of varying screen densities for each ink. The spectrophotometric data obtained from reading these elements are converted to a device independent colour space, such as CIELAB. The CIELAB color measurements represent the colour of the inks printed in varying density by the press printing units onto the press sheet. The density of ink transferred to the printed sheet by the plate on a press printing unit is determined by the density of photopolymer emulsion per unit area on the plate, and the thickness of the ink film transferred to this emulsion. Each inking unit is divided into a plurality of ink key zones across the width of the inking unit. An adjusting servo for each ink key on a printing unit controls the amount of ink delivered to the plate under the corresponding ink key zone.

The colormetric data for each ink on each inking zone on the press is applied to the secondary image data, which is segmented into zones that match the ink zones on the press. The secondary image is displayed adjacent to the primary image. The act of scanning press sheet colour bars printed during the course of the press run, permits the invention to dynamically update the secondary image for comparison to the ideal colour corrected primary image.

In the drawings, which form a part of this specification;

Figure 1 , is a schematic of the invention, including a press side computer work station, a soft proof display monitor, the scanning spectrophotometer, the press sheet, and the printing press.

Figure 2, is a schematic showing the press sheet and colour bar layout. Figure 3, a detailed illustration of the soft proofer display.

Detailed Description Of Preferred Embodiment:

Referring to Figure 1 , which is a schematic of the invention, including a press side computer work station (101), an application software display monitor (Display 1) (102), the soft proof display monitor (Display 2) (103), the primary image display area (111), the secondary image display area (112), the file storage location on hard drive (108), line memory location (114), the software for Process 1 (109), the software for Process 2 (110), the scanning spectrophotometer (104), the press sheet (105), the colour bar location (113), and the printing press (106); Figure 2, showing the press sheet and colour bar layout; and Figure 3, a detailed illustration of Display 2 (103).

The press side computer (101) automatically receives final imposition colour data via a network connection and allocates them to the storage location (108). The final imposed file can be in CIP/3 (.ppf), PDF, or other similar file formats.

Utilizing the Process 1 (109) User Interface which is located on Display 1 (102) the operator initiates a New Job, and selects the appropriate file from the File Storage Location (108).

Process 1 (109) transfers the file to Process 2 (110).

Process 2 (110) transfers the file to Line Memory (114), separates the file into colour layers, applies a colour correction modification representative of the final anticipated printed image.

The modified colour corrected image is displayed on Display 2 (103) at location (111). The press operator initiates the press run using press (106).

A printed sheet (105) is retrieved from the press (106) and positioned into the scanner (104) with colour bar (113) properly oriented into the scanner (104).

The scan is initiated using Process 1 (109) User Interface on Display 1 (102), or manually at the scanner (104).

The scanner (104) completes the scanning operation of each individual measurement element (116) comprising the colour bar (113), and transfer the spectrophotometric data to Process 1 (109).

Process 1 (109) takes the data for the individual color bar elements (116) and segments it uniformly into a format that equates directly to the number of ink keys (117) distributed across the width of the press (106).

This operation is repeated for all of the printing units that were originally designated in the pre press file.

Process 1 (109) sends the data to Process 2 (110).

Process 2 (110) loads a copy of the original pre press image file into line memory. This file is mathematically subdivided into segments that are representative of the ink key widths.

Process 2 (110) applies the ink key zone spectrophotometric data to the mathematically subdivided segments.

Process 2 (110) subsequently displays the modified image on Display 2 (103) at location (112).

The resulting dual display (111 , 112) allows the operator to objectively view the anticipated printed colour results (111) to a representation of what is actually being printed (112), without being hindered by the dissimilar media found in traditional proofing methods, whether they are printed hard copy or LCD displayed soft copy proofs.