Test Targets 3.0: A Collaborative effort exploring the use of scientific methods for color imaging and process control

Test Targets 3.0 focuses on the integration and analysis of a number of input devices, color image renderings with the use of a robust CTP system and a full-fledged web offset press … The first section is a collection of test forms … The second section is a compilation of color management practices by the class. – p. v

Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 314)

This bibliography lists 139 reports, articles, and other documents introduced into the NASA scientific and technical information system in August, 1988

A New framework for an electrophotographic printer model

Digital halftoning is a printing technology that creates the illusion of continuous tone images for printing devices such as electrophotographic printers that can only produce a limited number of tone levels. Digital halftoning works because the human visual system has limited spatial resolution which blurs the printed dots of the halftone image, creating the gray sensation of a continuous tone image. Because the printing process is imperfect it introduces distortions to the halftone image. The quality of the printed image depends, among other factors, on the complex interactions between the halftone image, the printer characteristics, the colorant, and the printing substrate. Printer models are used to assist in the development of new types of halftone algorithms that are designed to withstand the effects of printer distortions. For example, model-based halftone algorithms optimize the halftone image through an iterative process that integrates a printer model within the algorithm. The two main goals of a printer model are to provide accurate estimates of the tone and of the spatial characteristics of the printed halftone pattern. Various classes of printer models, from simple tone calibrations, to complex mechanistic models, have been reported in the literature. Existing models have one or more of the following limiting factors: they only predict tone reproduction, they depend on the halftone pattern, they require complex calibrations or complex calculations, they are printer specific, they reproduce unrealistic dot structures, and they are unable to adapt responses to new data. The two research objectives of this dissertation are (1) to introduce a new framework for printer modeling and (2) to demonstrate the feasibility of such a framework in building an electrophotographic printer model. The proposed framework introduces the concept of modeling a printer as a texture transformation machine. The basic premise is that modeling the texture differences between the output printed images and the input images encompasses all printing distortions. The feasibility of the framework was tested with a case study modeling a monotone electrophotographic printer. The printer model was implemented as a bank of feed-forward neural networks, each one specialized in modeling a group of textural features of the printed halftone pattern. The textural features were obtained using a parametric representation of texture developed from a multiresolution decomposition proposed by other researchers. The textural properties of halftone patterns were analyzed and the key texture parameters to be modeled by the bank were identified. Guidelines for the multiresolution texture decomposition and the model operational parameters and operational limits were established. A method for the selection of training sets based on the morphological properties of the halftone patterns was also developed. The model is fast and has the capability to continue to learn with additional training. The model can be easily implemented because it only requires a calibrated scanner. The model was tested with halftone patterns representing a range of spatial characteristics found in halftoning. Results show that the model provides accurate predictions for the tone and the spatial characteristics when modeling halftone patterns individually and it provides close approximations when modeling multiple halftone patterns simultaneously. The success of the model justifies continued research of this new printer model framework

N-colour separation methods for accurate reproduction of spot colours

In packaging, spot colours are used to print key information like brand logos and elements for which the colour accuracy is critical. The present study investigates methods to aid the accurate reproduction of these spot colours with the n-colour printing process. Typical n-colour printing systems consist of supplementary inks in addition to the usual CMYK inks. Adding these inks to the traditional CMYK set increases the attainable colour gamut, but the added complexity creates several challenges in generating suitable colour separations for rendering colour images. In this project, the n-colour separation is achieved by the use of additional sectors for intermediate inks. Each sector contains four inks with the achromatic ink (black) common to all sectors. This allows the extension of the principles of the CMYK printing process to these additional sectors. The methods developed in this study can be generalised to any number of inks. The project explores various aspects of the n-colour printing process including the forward characterisation methods, gamut prediction of the n-colour process and the inverse characterisation to calculate the n-colour separation for target spot colours. The scope of the study covers different printing technologies including lithographic offset, flexographic, thermal sublimation and inkjet printing. A new method is proposed to characterise the printing devices. This method, the spot colour overprint (SCOP) model, was evaluated for the n-colour printing process with different printing technologies. In addition, a set of real-world spot colours were converted to n-colour separations and printed with the 7-colour printing process to evaluate against the original spot colours. The results show that the proposed methods can be effectively used to replace the spot coloured inks with the n-colour printing process. This can save significant material, time and costs in the packaging industry

The preservation and conservation of ink jet and electrophotographic printed materials

This research project has investigated the light fastness of ink jet and electrophotographic printed materials by the means of an extensive accelerated and natural ageing test programme. The effect of visible radiation of different wavebands on the deterioration of a selection of ink jet printed materials has also been assessed. The findings of the research indicate that all of the ink jet printed materials tested are sensitive to light and should not therefore, be put on permanent display. Most of the ink jet printed samples exhibited greater light sensitivity to the shorter wavelengths of the visible spectrum, than the longer wavelengths, with damage decreasing as wavelength increases. This relationship was not evident with the cyan and blue printed samples, which showed that their light sensitivity was determined by the spectral absorption characteristics of the printed patch. Some of the ink jet printed materials produced erratic fading rates on exposure to light. This phenomenon was attributed to either the occurrence of photochromism or the disintegration of the dye particles in the ink, but further testing needs to be conducted to gain a better understanding of this reaction. Other factors also influenced the light fastness of the ink jet materials, such as the type of paper employed for printing, ink concentration and ink combination. The electrophotographic printed materials were found to be more stable to light, although the yellow toner from some of the systems would show noticeable fading after approximately 65 to 325 years on permanent display (at 50 lux for eight hours per day). A range of basic conservation treatments was also been investigated and the results indicated that ink jet print materials are very sensitive to all forms of aqueous treatments. Finally, thermal/dark ageing has been performed on the digital printed papers employed in this investigation. The conclusion is that all of the papers are prone to yellowing in storage

Aeronautical engineering: A continuing bibliography with indexes (supplement 218)

This bibliography lists 469 reports, articles, and other documents introduced into the NASA scientific and technical information system in September, 1987

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 381)

This bibliography lists 89 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during Nov. 1993. Subject coverage includes: aerospace medicine and physiology, life support systems and man/system technology, protective clothing, exobiology and extraterrestrial life, planetary biology, and flight crew behavior and performance

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 188, January 1979

This bibliography lists 230 reports, articles, and other documents introduced into the NASA scientific and technical information system in December 1978