Advanced surface color quality assessment in paper-based full-color 3d printing

Color 3D printing allows for 3D-printed parts to represent 3D objects more realistically, but its surface color quality evaluation lacks comprehensive objective verification considering printing materials. In this study, a unique test model was designed and printed using eco-friendly and vivid paper-based full-color 3D printing as an example. By measuring the chromaticity, roughness, glossiness, and whiteness properties of 3D-printed surfaces and by acquiring images of their main viewing surfaces, this work skillfully explores the correlation between the color representation of a paper-based 3D-printed coloring layer and its attached underneath blank layer. Quantitative analysis was performed using ΔE*ab, feature similarity index measure of color image (FSIMc), and improved color-image-difference (iCID) values. The experimental results show that a color difference on color-printed surfaces exhibits a high linear correlation trend with its FSIMc metric and iCID metric. The qualitative analysis of microscopic imaging and the quantitative analysis of the above three surface properties corroborate the prediction of the linear correlation between color difference and image-based metrics. This study can provide inspiration for the development of computational coloring materials for additive manufacturing

Dynamically Tunable Plasmonic Structural Color

Functional surfaces which can control light across the electromagnetic spectrum are highly desirable. With the aid of advanced modeling and fabrication techniques, researchers have demonstrated surfaces with near arbitrary tailoring of reflected/transmitted amplitude, phase and polarization - the applications for which are diverse as light itself. These systems often comprise of structured metals and dielectrics that, when combined, manifest resonances dependent on structural dimensions. This attribute provides a convenient and direct path to arbitrarily engineer the surface\u27s optical characteristics across many electromagnetic regimes. But while many of these plasmonic systems struggle to compete with the efficiency of pre-existing technologies, the ability to tune plamsonic structures post-fabrication is a distinct advantage which may lead to novel devices. In this work, I will summarize fundamental and applied aspects of tunable plasmonic systems as applied to the visible and infrared regimes. I will demonstrate how liquid crystal may be used to dynamically and reversibly tune the plasmonic resonances of metallic surfaces on a millisecond time scale. For the visible, this results in dynamic color-changing surfaces capable of covering the entire RGB color space and which is compatible with active addressing schemes. I will then show the application of these concepts to infrared absorbers through the use of liquid crystal and phase change materials. The later of these devices can find use in infrared data/image encoding, thermal management and camouflage. Together, these works explore the limits of tunable plasmonic systems and the novel devices they might lead to

New software for comparing the color gamuts generated by printing technologies

In the color industry, it is vital to know the color gamut of a given device. Several tools for visualizing and comparing color gamuts are available but they each have some drawbacks. Therefore, the aim of this work was to develop and validate new software for comparing the color gamuts generated by printing devices; we also developed an automated color measurement system. The software simultaneously represents the gamuts in the 3D CIELAB space. It also calculates the Gamut Comparison Index and the volume using two algorithms (Convex Hull and Alpha Shapes). To evaluate the performance of our software, we first compared the results it obtained for the color gamuts with those from other comparison methods such as representation in the CIE 1931 chromaticity diagram or other color spaces. Next, we used Interactive Color Correction in 3 Dimensions (ICC3D) software to compare the gamut representations and volumes. Our software allowed us to identify differences between color gamuts that were not discriminated by other methods. This new software will enable the study and comparison of gamuts generated by different printing technologies and using different printing substrates, International Color Consortium profiles, inks, and light sources, thereby helping to achieve high quality color images.Optics Group (FQM151, University of Granada)University of Granada (pre-doctoral contract, Training Programme for Research Staff, FPU)Funding for open access charge: University of Granada/CBU

Multispectral photography for earth resources

A guide for producing accurate multispectral results for earth resource applications is presented along with theoretical and analytical concepts of color and multispectral photography. Topics discussed include: capabilities and limitations of color and color infrared films; image color measurements; methods of relating ground phenomena to film density and color measurement; sensitometry; considerations in the selection of multispectral cameras and components; and mission planning

A Designer\u27s guide to the evaluation of digital proofs

Digital color proofs and pre-proofs are used by graphic artists and commercial printers throughout the prepress process. However the prepress process has undergone radical changes over the past decade due to the introduction of desk top publishing and desktop prepress. Alongside of the desktop publishing revo lution has come a multitude of new digital proofing technologies for use in this ever changing environment. Technologies including, but not limited to, liquid inkjet, dye sublimation, continuous inkjet, color laser, and thermal wax transfer printers have provided an entire range of color accuracy and price suitability to many of their users. However one needs to be able to understand the practical applications and limitations of these technologies to make a suitable choice for a specific prepress operation or design process. Therefore a handbook for the users of digital proofs has been created for their benefit. The underlying structure of this handbook is based on the following six chap ters. The first chapter, entitled Communicating with Prepress and the Attributes of Digital Proofing, contains multiple parts. Firstly, it contains information for the designer in regards to the advantages and disadvantages of all types of digital output devices. It discusses the advantages which digital output devices may or may not have over conventional proofing systems. Additionally, ideas such as the vantages and drawbacks of preproofers and proofers is elaborated upon. Information for this part of the chapter was obtained through questionnaires completed by, and interviews with print buyers, art directors, and production managers from advertising agencies and prepress providers in the Rochester area. More information for this section of the first chapter was obtained through various manufacturer\u27s literature, printing industry reports and various periodi cals. Chapter One also discusses ideas behind the application of color printers (preproofers) and digital proofers. These ideas address issues which pertain to the application of specific printing and proofing processes to specific phases of the creative and production processes. Additionally, discussions regarding proof ing costs, qualities, and production turnaround time may be found in this part of the first chapter. Information for this section of Chapter One was obtained through information found in printing and publishing related periodicals, as well as in manufacturers\u27 literature. Finally, the first chapter develops a system for the correction of digital preproofs and proofs. Multiple groups of ideas pertaining to the correction of digital output are discussed. Some of these include sections entitled Digital File Tracking and Identification, Evaluation of Design Elements, Evaluating Colors, Element Positioning, and Element Dimension Adjustments. Information for this part of the chapter was obtained through the evaluation of previously corrected digital con tract proofs and preproofs, as well as the interviews and questionnaires men tioned above. The second chapter, entitled Proofing Typography, displays the many different ways that printing and proofing technologies affect text type and display typog raphy. Using the CD-Rom included in the back of the book, one may view on screen how the following technologies affect type ranging from 3 points to 72 points in size: liquid inkjet, large format liquid inkjet, phase-change inkjet, ther mal wax transfer, dye sublimation, continuous inkjet, and dye ablation. Information and samples for this chapter were obtained through printing and proofing system manufacturers and advertising agencies in the Rochester area. The Color Primer and Chapter Three: Proofing for Imagery and Color, contain information for the designer which may be applied to proper evaluation of color on color prints and digital proofs. The Color Primer discusses subjects such as color space, the additive and subtractive color theories, and common color mea surement tools. Chapter Three then applies some of this knowledge in its discus sions of proper lighting conditions for viewing prints and proofs, and different human factors which influence the highly subjective evaluation of all digital color output. Information for this chapter was gathered using graphic arts and printing industry related periodicals and industry-wide books related to color and its reproduction. The fourth chapter, entitled Substrates and Digital Output, educates the design er about the effects on text, imagery, and graphics which occur when creating digital prints and proofs on a variety of papers. Various paper surfaces such as gloss, semi-gloss and matte surfaces are addressed. The affects of colored paper on imagery and graphics are also elaborated upon. Additionally, printing and proofing processes are discussed in regards to the substrates that they accept for output. Information for this chapter was gathered through manufacturers\u27 litera ture and various industry related books and periodical articles. The Proofing Process Supplement was created to familiarize the designer with all currently popular forms of digital output technology. The process supplement discusses the imaging processes used by the following digital output technolo gies: liquid inkjet, phase-change inkjet, thermal wax transfer, dye sublimation, continuous inkjet, and dye ablation. Additionally, the supplement contains brief explanations regarding screening technologies. Information for the process sup plement was gathered through manufacturers\u27 literature, interviews with pre press providers in the Rochester area, and interviews with technical representa tives from the manufacturers of devices which use the above digital, color out put technologies. Chapter Five, entitled Image Fidelity, simply illustrates how all of the current ly popular printing and proofing technologies affect graphics and imagery. Using the CD-Rom included with the guidebook, the reader may view magni fied and normal views of printing and proof sample imagery. Information noted by the reader in the proofing process supplement may then be actively applied when viewing these samples. Information and sample prints for the fifth chapter were gathered from several manufacturers and advertising agencies in the Rochester area. The sixth chapter, entitled The Acceptance of Digital Contract Proofing, discusses a new definition of the contract proof in regards to the evolution of digital proof ing. This chapter provides ideas for the designer, art director, and print buyer to realize when considering the use of digital contract proofing. Several questions are raised concerning what requirements a digital contract proof must fulfill depending upon the areas of its application and any agreements between the designer and prepress provider regarding their specific definition of a digital contract proof. Additionally, specific advantages of digital contract proofs, such as their ability to fingerprint a press and/or press run, are discussed. Finally, a discussion pertaining to the education of all users of digital proofing technolo gies is presented to aid the overall acceptance of digital contract proofing. Information for this chapter was obtained through the extensive interviews of leading technical and product oriented representatives from the manufacturers of currently used digital contract proofing systems. Many conclusions have been reached with the completion of this guidebook. In brief, the first and most prominent conclusion which may be reached states that the acceptance of digital contract proofing lies within the education of all designers, art directors and print buyers about digital printing and proofing technologies. As the use of digital contract proofing grows, education and inter est by all creative professionals will orient them towards their use of digital proofing systems. The next conclusion which has been reached is that the proper application of color printers and digital proofers is of major importance for the designer due to the added flexibility and rewards which result from the use of digital color out put devices throughout the creative and production processes. Another conclu sion which may be reached is that the display of proofing and printing process effects on text, graphics, and imagery serves to directly inform the creative pro fessional how these elements may be distorted by the utilized output device. Knowledge gained by the creative professional in regards to these effects helps to answer many questions regarding print or proof quality and proper output device application. Finally, additional knowledge gained by designers which pertains to proper viewing of all color output, color theories, color measurement, and proofing sub strates helps them to better communicate with those prepress and print professionals involved in the production process

The structural coloration of textile materials using self-assembled silica nanoparticles

The work presented investigates how to produce structural colours on textile materials by applying a surface coating of silica nanoparticles (SNPs). Uniform SNPs with particle diameters in a controlled micron size range (207–350 nm) were synthesized using a Stöber-based solvent varying (SV) method which has been reported previously. Photonic crystals (PCs) were formed on the surface of a piece of textile fabric through a process of natural sedimentation self-assembly of the colloidal suspension containing uniform SNPs. Due to the uniformity and a particular diameter range of the prepared SNPs, structural colours were observed from the fabric surface due to the Bragg diffraction of white light with the ordered structure of the silica PCs. By varying the mean particle diameter, a wide range of spectral colours from red to blue were obtained. The comparison of structural colours on fabrics and on glasses suggests that a smooth substrate is critical when producing materials with high colour intensity and spatial uniformity. This work suggested a promising approach to colour textile materials without the need for traditional dyes and/or pigments

Computational Light Transport for Forward and Inverse Problems.

El transporte de luz computacional comprende todas las técnicas usadas para calcular el flujo de luz en una escena virtual. Su uso es ubicuo en distintas aplicaciones, desde entretenimiento y publicidad, hasta diseño de producto, ingeniería y arquitectura, incluyendo el generar datos validados para técnicas basadas en imagen por ordenador. Sin embargo, simular el transporte de luz de manera precisa es un proceso costoso. Como consecuencia, hay que establecer un balance entre la fidelidad de la simulación física y su coste computacional. Por ejemplo, es común asumir óptica geométrica o una velocidad de propagación de la luz infinita, o simplificar los modelos de reflectancia ignorando ciertos fenómenos. En esta tesis introducimos varias contribuciones a la simulación del transporte de luz, dirigidas tanto a mejorar la eficiencia del cálculo de la misma, como a expandir el rango de sus aplicaciones prácticas. Prestamos especial atención a remover la asunción de una velocidad de propagación infinita, generalizando el transporte de luz a su estado transitorio. Respecto a la mejora de eficiencia, presentamos un método para calcular el flujo de luz que incide directamente desde luminarias en un sistema de generación de imágenes por Monte Carlo, reduciendo significativamente la variancia de las imágenes resultantes usando el mismo tiempo de ejecución. Asimismo, introducimos una técnica basada en estimación de densidad en el estado transitorio, que permite reusar mejor las muestras temporales en un medio parcipativo. En el dominio de las aplicaciones, también introducimos dos nuevos usos del transporte de luz: Un modelo para simular un tipo especial de pigmentos gonicromáticos que exhiben apariencia perlescente, con el objetivo de proveer una forma de edición intuitiva para manufactura, y una técnica de imagen sin línea de visión directa usando información del tiempo de vuelo de la luz, construida sobre un modelo de propagación de la luz basado en ondas.<br /

High Dynamic Range (HDR) Display Perception

Displays have undergone a huge development in the last several decades. From cathode-ray tube (CRT), liquid crystal display (LCD), to organic light-emitting diode (OLED), even Q-OLED, the new configurations of the display bring more and more functions into industry and daily life. In the recent several years, high dynamic range (HDR) displays become popular. HDR displays usually refer to that the black level of the display is darker and the peak being brighter compared with the standard dynamic range (SDR) display. Traditionally, the peak luminance level can be used as the white in characterization and calibration. However, for HDR displays, the peak luminance is higher than the traditional diffuse white level. Exploration of the perceptual diffuse white in HDR image when presented in displays is proposed, which can be beneficial to the characterizing and the optimizing the usage of the HDR display. Moreover, in addition to the ``diffuse white , 3D color gamut volume can be calculated in some specific color appearance models. Calculation and modeling of the 3D color gamut volume can be very useful for display design and better characterizing display color reproduction capability. Furthermore, the perceptional color gamut volume can be measured through psychophysical experiments. Comparison between the perceptional color gamut volume and the theoretical 3D gamut volume calculations will reveal some insights for optimizing the usage of HDR displays. Another advantage of the HDR display is its darker black compared with the SDR display. Compared with the real black object, what level of black is `perfect\u27 enough in displays? Experiments were proposed and conducted to evaluate that if the HDR display is capable of showing ``perfect black for different types of background images/patterns. A glare-based model was proposed to predict the visual ``perfect black. Additionally, the dynamic range of human vision system is very large. However, the simultaneous dynamic range of human vision system is much smaller and is important for the fine tuning usage of HDR displays. The simultaneous dynamic range was measured directly for different stimulus sizes. Also, it was found that the simultaneous dynamic range was peak luminance level dependent. A mathematical model was proposed based on the experimental data to predict the simultaneous dynamic range. Also the spatial frequency effect of the target pattern on the simultaneous dynamic range was measured and modeled. The four different assessments about HDR displays perception would provide experimental data and models for a better understanding of HDR perception and tuning of the HDR display