Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Patent
1996-10-01
1998-05-12
Reinhart, Mark J.
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
247251, 247232, B41J 247
Patent
active
057513260
DESCRIPTION:
BRIEF SUMMARY
INTRODUCTION
This invention relates generally to the art of colour printing, and in particular, to a process of automatic colour separation whereby an extended print density range may be achieved.
BACKGROUND OF THE INVENTION
Current methods of colour separation for colour printing involve the use of four colours to reproduce an original colour print or transparency. The standard four colours used are cyan, magenta, yellow and black (CMYK).
Such methods of printing have been in operation since the early part of the twentieth century and have permitted the reproduction on paper of an original colour image, although with limited colour range and saturation for matching colours in the reproduction to the original.
Unfortunately, saturated colours such as deep reds, greens and blues cannot be reproduced satisfactorily due to the limited print range of four colour process.
In recent years, there has been a strong demand for up to seven colour separations, in order to reproduce as closely as possible the colours in the original. This is a time-consuming task in which originals are scanned in the traditional CMYK method on a colour separation scanner.
Electronic colour data generated is then sent to a colour retouching system and colour masked to "create" additional special colours, ie. red, green and blue, to produce seven colour separations.
This process relies heavily upon the skill of the operator and the power of the colour retouching system to interpret the amount of colour required in each particular area of the new colour separations, to match closely to the colours in the original. It is not uncommon to make several attempts at matching the colours in the original during the course of this process, which involves intensive use of labour and materials.
SUMMARY OF THE INVENTION
According to a first aspect, the present invention provides a method of producing colour separations for a printing process wherein an image source is scanned one or more times to produce a plurality of data channels each of which provides a representation of one colour separation of the image source, the data provided by each channel being restricted to represent a printable tone density range, and the channels being separated into two groups, a first providing separation data representing a base image and comprising a compressed representation of the density range of the image source, and the second providing separation data representing a saturation image and substantially comprising a representation of the density range data lost from the first data set as a result of tone compression to a printable density range.
According to a second aspect the present invention provides a method of producing colour separations for a printing process comprising the steps of: scanning parameters to produce data representing a first set of colour separations of the image, each having a printable density range, the separations being capable of reproducing the image with a tone density range within a printable density range; saturated colours in the image source; a second set of colour separations of the image also having a printable density range and carrying saturation colour information not recorded in the first set of data; and data.
According to a third aspect the present invention provides a colour separation scanner comprising an image source mounting means, illumination means arranged to illuminate an image source mounted on the mounting means, optical separation means arranged to separate light components reflected from or transmitted through the image source into a plurality of colour components, detection means arranged to detect each of the plurality of colour components and to convert each component into an electrical colour signal, and signal processing means arranged to convert each colour signal into a compressed colour signal representing a colour separation having a printable tonal range wherein the processing means is arranged to produce two types of colour signals a first of which represents a print density range of 0-100
REFERENCES:
patent: 4613897 (1986-09-01), Stansfield
patent: 4614967 (1986-09-01), Sayanagi
patent: 4774567 (1988-09-01), Stansfield et al.
patent: 5099260 (1992-03-01), Sato et al.
patent: 5130786 (1992-07-01), Murata et al.
Opaltone International Limited
Reinhart Mark J.
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