Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-07-24
2004-05-18
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
24
Reexamination Certificate
active
06736478
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the automatic determination of an image quality of a copy or picture obtained by a printing or print device or exposure device, especially for inkjet photo prints. Furthermore, the invention relates to a data carrier with a corresponding process in any desired programming language for the control of electrical or electronic functional devices for the realization of the process.
BACKGROUND ART
It is known in the prior art to use processes for the improvement of pictures. For example, the image quality can be improved by changing the color spectrum during the exposure or by brightening or darkening portions of a picture. It is also possible to carry out other quality improvements which some customers find pleasing.
While it is possible to improve the image quality of a picture, there is practically no possibility to generally define the concept of image quality and to make determinations in relation to such a generally valid definition of the image quality, such as that a color inkjet printer needs maintenance, another control software must be used, or the like.
Although the possibility exists for laser copiers or inkjet printers to carry out a correction and optimization printer internally by way of also printed patterns, this conventional testing and correction technology, however, does not lead to a more generally valid definition.
It is therefore in the prior art still a matter of experience and decision for an observer whether an image quality is sufficient, deserves improvement, or falls outside a tolerance interval. Thus, a picture can still be to one observers taste, while another already detects disturbing effects, such as, unpleasant graininess, unpleasant coalescence or a visible horizontal or vertical banding. Of course, color defects can be created, the contrast can be insufficient, and the like.
These totally different picture defects and further picture defects not mentioned here can occur in actual pictures and be noticed by some customers, while others do not recognize those defects. Correspondingly, an operator of a picture printer or photo exposer can be more discriminating or less, since the concept of the image quality itself is neither standardized nor set. The quality of image data in and of itself can also lead to deviations in the copies to be produced and can also lead to unfounded quality complaints. For example, digital image data can be deficient (for example, local resolution too low because of an insufficient number of pixels, or color depth insufficient) and the deficient image quality attributed to the photo printer, which principally has nothing to do with the deficient image quality, since it would definitely be in a position to produce better pictures, if it had correspondingly good data available. The software for the processing of image data can also create problems here so that it would be advantageous from this point of view to be able to better localize errors, for example, when a photo printer operates satisfactory, while the image data are or the image data processing is deficient.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide a process for automatic image quality determination to enable especially an objective, observer independent determination of an image quality.
It is a further object to provide a process which enables the detection of the necessity for maintenance or calibration of a photo printer and especially a color inkjet photo printer, or to better localize deficiencies within the individual stations of the picture production. Especially, deficiencies of the materials used, for example, paper, ink, toner, developing chemicals can be determined.
According to one aspect of the invention, the advantages achieved are based on the generation of a digital reference test chart or a set of digital reference test charts. Such reference test charts can be produced both directly digitally as well as by digitalization of corresponding originals. A photo printer, especially an inkjet photo printer or color inkjet photo printer, which is to be tested with respect to its image quality is provided with the digital form of the reference test chart for printout. A photo printer specific test chart print is hereby produced on the basis of the digital form of the reference test chart. The photo printer specific test chart print is scanned after printing. This scanned and therefore digital form of the photo printer specific test chart print is then compared with a digital form of the reference test chart. A quality parameter or a standardized quality value achieved by a photo printer and especially a color inkjet photo printer can then be calculated from the conformities and/or deviations based on the comparison between the reference test chart and the photo printer specific test chart print.
The reference test chart preferably includes several test patterns which specifically react to differentiable causes for deficient image quality, or such test patterns can be positioned on a set of reference test charts. The test patterns of the reference test chart can then be compared with the corresponding test patterns of the photo printer specific test chart print or the digitized image data thereof. The test patterns of the reference test chart are thereby preferably assigned optimum quality values. These are compared with actual quality values of a photo printer specific test pattern and the quality of the printouts or the image prints of a photo printer can be determined on the basis of deviations therebetween. Tolerance intervals can thereby be assigned to the photo printer specific test pattern or the reference test pattern, within which the corresponding quality deficiency is still acceptable. Beyond these threshold values or this tolerance interval, corresponding reactions can be initiated, such as the automatic scheduling of maintenance, the specific use of error correction software, the discontinued use of deficient materials consumed, or the like.
According to the present invention, it is especially possible to test the products of inkjet printers for the manufacture of customer specific copies by way of apparatus specific test prints. Preselected test patterns are thereby used, as mentioned above, and these printed test patterns are scanned or digitized for subsequent comparison with the digital reference test patterns. Image characteristics are thereby especially considered which can influence the image quality, especially such effects as banding, coalescence, color bleed, dot gain, image and color misregistration and image parameters such as graininess, uniformity, image sharpness (which means the contrast resolution behaviour) and color balance. These effects can be determined for each individual print color, but also for mixed colors.
The scanned apparatus specific test charts prints are evaluated using any desired image analysis method, especially already known image analysis methods, and specific parameters are determined which by comparison with the digital form of the reference test chart open up the possibility of determining an image quality value.
It is possible that the image quality so determined only insufficiently corresponds to the image quality perceived by a human, especially since the unweighted technical image quality determined so far is based on purely physical, which means especially directly measurable, parameters. It is specifically possible to also carry out weighting or acceptance tests with one or more test persons, in order to determine relevant tolerance intervals or their end values, which means in order to transform the unweighted, technical image quality into a perception aligned image quality.
A standardization is preferably also incorporated into the process according to the invention, in order to consider apparatus specific properties of apparatus which play a role in the process in accordance with the invention for image quality determination. For example, if a flatbed scanner with certain characteri
Franzke Dieter
Kohlbrenner Adrian
Kündig Armin
Corless Peter F.
Edwards & Angell LLP
Gordon Raquel Yvette
Gretag Imaging Trading AG
Jensen Steven M.
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