Printer colour reference system

Abstract

A test apparatus comprising a portable reference element having colour and spectrophotometrically neutral gray elements of predetermined hues and saturations, and a digital software file provides identical colour and spectrophotometrically neutral grayscale data which, when printed or otherwise reproduced accurately, may be compared with the test colours and grayscale provided by the portable reference element, enabling appropriate adjustments to be made to the printer as required.

Claims

1. An apparatus for use in evaluating the accuracy of reproduction of printing devices and comprising: a primary reference element having an reference array of colour and grayscale elements of predetermined values, including four typical flesh tones and six highly saturated primary and secondary colors, and a rainbow of colours wherein the colours increase in wavelength uniformly through the human visible spectrum, typically from 400 to 700 nm, and gray tones sequentially from black to white in ever increasing brightness; and, a second element comprising a digital software file of said reference array, which, when reproduced by a printing system, optimized to reproduce colours accurately, produces a print that matches the colours and grayscale array of said reference element.

2. The apparatus for use in evaluating the accuracy of reproduction of printing devices as claimed in claim 1 wherein the individual colour and grayscale elements comprising said primary reference element and digital software file arrays radiate from a central point within said array of colour and grayscale elements.

3. The apparatus for use in evaluating the accuracy of reproduction of printing devices as claimed in claim 2 wherein said reference element is circular.

4. The apparatus for use in evaluating the accuracy of reproduction of printing devices as claimed in claim 2 wherein said reference element is oval.

5. The apparatus for use in evaluating the accuracy of reproduction of printing devices as claimed in claim 2 wherein said reference element is rectangular.

6. The apparatus for use in evaluating the accuracy of reproduction of printing devices as claimed in claim 2 wherein said primary reference and second digital software file elements are isosceles triangles radiating from a central point.

7. The apparatus for use in evaluating the accuracy of reproduction of printing devices as claimed in claim 1 wherein the individual colours and gray tones within said reference element arrays are blended to produce a step-less rainbow of colours and gray tones, said step-less rainbow of colours increasing in wavelength uniformly through the human visible spectrum, from 400 to 700 nm.

8. The apparatus for use in evaluating the accuracy of reproduction of printing devices as claimed in claims 1 wherein said reference image elements are arranged randomly.

9. The apparatus for use in evaluating the accuracy of reproduction of printing devices as claimed in claim 2, wherein said reference element has a hole in the centre.

10. A method of optimising the colour reproduction of a colour printer of the type having colour controls, and comprising the steps of: providing a reference image panel showing a plurality of colour segments and a plurality of gray tone segments, said segments arranged in a pattern and defining a centre, and said reference panel having an opening at said centre, making a print image of a secondary image from said printer using a secondary reference software file; comparing said secondary image with said reference image to identify any discrepancies between the colour segments and gray tone segments of said reference image, and said printed image; and, adjusting said controls of said printer to eliminate said discrepancies.

11. The method of optimising the colour reproduction of a colour printer of the type having colour controls as claimed in claim 10 wherein the primary reference panel has an opening centred in the centre of the primary reference image and including the step of placing the printed image behind the primary reference panel with the printed image centred in the opening in the panel, and comparing the primary reference image with the printed image.

12. the method of optimising the colour reproduction of a colour printer of the type having colour controls, as claimed in claim 11 and including the step of adjusting the printer to correct any discrepancies between the primary reference image and the printed image.

Description

IN THE DRAWINGS

[0026] FIG. 1 Is a Front elevation view of one embodiment of the primary reference image element;

[0027] FIG. 2 is a Front elevation of the primary reference image element superimposed over an image printed from the secondary digital file, showing errors;

[0028] FIG. 3 is a Front elevation of the primary reference image element superimposed over an image printed from the secondary digital file, after correcting the printer to match with the primary reference image element; and,

[0029] FIG. 4 is a schematic illustration of a printer connected to computer, to which the digital file is uploaded.

DESCRIPTION OF A PREFERRED EMBODIMENT

[0030] Referring to FIGS. 1-3

[0031] FIG. 1. Shows the primary reference element 1. typically a round disk, which comprises a panel showing a multiplicity of colour segments 2. encompassing the human visible spectrum, from approximately 400 to 700 nm, and a number of spectrophotometrically neutral gray tone segments 3. ranging from black to white. In a preferred embodiment, the centre of the primary reference element is open at 4. to facilitate centring. It will be understood that there could be a much larger number of smaller segments.

[0032] Preferably the segments are shaped as isosceles triangles, as shown, in this embodiment

[0033] The secondary reference element comprises a digital software file, (not shown), which may be saved on any suitable storage media, such as a USB flash drive, etc 18 (FIG. 4).

[0034] The digital software file comprises a digital reference image element with colour and gray scale segments identical to the primary reference image element 1

[0035] This digital software file is uploaded into for example a computer 20, connected to a printer 22 (FIG. 4).

[0036] A monitor 24 shows the image from the digital software file.

[0037] In operation, an operator prints an image from printer 22 of the digital reference pattern, onto any suitable medium such as a clean paper sheet 26, for example. The operator then compares the accuracy of the segments of the printed image with the segments of the primary reference element 1. The printer is then adjusted to compensate for differences 6. in brightness; contrast, gamma, chroma precision and other aspects of image reproduction as are well known in the trade. Different printer manufacturers offer more or less adjustment which is often performed with a sliding scale. The rainbow arrangement of the colours on the reference pattern makes it easy to determine the printer colour to be adjusted. If red is looking too orange, cyan should be increased or yellow decreased. If red is looking too magenta, yellow should be increased or magenta decreased, and so on.

[0038] FIG. 3. Illustrates a printer that reproducing colour accurately. There should be no discernible difference between an accurately printed image 7., from the printer, and the primary reference image element 1

[0039] The foregoing is a description of a preferred embodiment of the invention which is given here by way of example only. The invention is not to be taken as limited to any of the specific features as described, but comprehends all such variations thereof as come within the appended claims.