Spectral color management requires inversion of printer spectral characterizations and necessarily involves the concept of spectral gamut mapping. A printer was spectrally characterized and the spectra were transformed to an interim connection space (ICS), a spectral description space with low dimensionality useful for building lookup tables (LUTs) of feasible sizes. LabPQR is the ICS used. It has separate dimensions describing colorimetry (CIELAB) and a spectrum's metameric black difference from a standard metamer (PQR). The relationship between digital value and LabPQR was inverted using a single stage objective function combining colorimetric and spectral criteria. The objective function's colorimetric criterion minimized CIEDE2000 under chosen conditions and its spectral criterion minimized Euclidian distance in PQR coordinates. A weight series was performed to find the optimal trade-off between colorimetric and spectral error. A 1:50 weighting ratio, CIEDE2000 to PQR difference, was deemed best. For the GretagMacbeth ColorChecker, the proposed single stage objective function showed equivalent levels of the performance to a full 31-dimensional unmodified spectra approach, resulting in an average RMS error of 4.18% and an average CIEDE2000 of 0.03. The single stage objective function for spectral gamut mapping using LabPQR proved to be promising for spectral reproduction.
This article proposes a new algorithm for coloring a monochrome image. Recently, a few effective colorization algorithms have been proposed. Those algorithms can colorize monochrome images by giving them some color hints, and they work well as an intuitive impression. However, a realistic colorization in detail was difficult to achieve by those algorithms because they have not been constructed based on any physical model. They formulate a colorization process as a pixel-based digital signal processing. This article aims at developing a realistic colorization technique by considering a physical reflection model. We focus on the well-known dichromatic reflection model and try to colorize monochrome images by utilizing a property of diffuse-only reflection components. We demonstrate that high quality colorizations of still images may be obtained from a small number of color seeds given by a user.
A soft proofing display that can serve as a trustworthy replacement of the hardcopy contract proof is a long anticipated missing element in the all–digital workflow of the graphic arts industry. We describe a novel approach of spectral color reproduction on screen, which combines a specially designed multi-primary projection display and spectral data processing, and discuss its application for soft proofing. The feasibility of this concept is shown, and the results of a realized system are described and analyzed. In addition, other possible configurations are simulated. The results show that the system provides a very close simulation of the print process and to the appearance and color of the printed page.
In the bilevel halftoning technique using a stochastic screen, an input image value is thresholded by a corresponding screen value (threshold) to represent two printable output levels, i.e. black and white. This halftoning method can be easily extended to multilevel halftoning (multitoning) by scaling the threshold before thresholding. However, if a general transformation function is used for the scaling of the threshold, banding artifacts can appear due to similar dot distributions near the printable output levels, thus resulting in discontinuity in the smooth tone transition region. Accordingly, in order to reduce such banding artifacts, this paper proposes a multitoning method that arranges the gray-level distribution by controlling the blending proportion of the adjacent output pixels based on improved threshold scaling functions. The proposed method consists of two thresholding processes to print the majority pixels and the adjacent output pixels. For input pixels within the neighborhood of the printable output levels, the majority pixels are first placed according to the point-wise comparison result between the fixed input value and the corresponding threshold value that is scaled by a general threshold scaling function. This allows the proportion of majority pixels to be controlled using the fixed input value. The adjacent output pixels are introduced to preserve a gray-level balance near the printable output levels based on the comparison result between the input value and the corresponding threshold value that is scaled by an improved threshold scaling function. The gray-level distribution across the banding regions is affected by two control factors of the improved threshold scaling function that control the blending point of the adjacent output pixels. To prove that the improved threshold scaling function, with specific factor values, could achieve a smoother visual transition, several observers investigated the gray-level distribution around the printable output levels. The experimental results confirmed that the proposed method was able to reduce the banding artifacts in both gray and color images and a better color reproduction was produced.
A procedure for the calibration of a micro–goniophotometer is described that enables the analysis of gloss data in terms of the underlying optical properties of the glossy material. Calibration studies are described and calibration procedures are presented, along with a discussion of accuracy and precision characteristics of the current instrument. Examples of analytical applications are described in which the utility of the calibrated device is demonstrated. These examples demonstrate analytical protocols capable of distinguishing between the effects of two key optical constants (n and κ) and the angular distribution of surface facets. In addition, by calibrating the device in separate red, green, and blue bands of light, measurements can provide information relevant to chromatic changes in optical constants and the effects of sublayer specular contributions to gloss. This work is intended provide a tool for imaging scientists concerned with the effects of material properties on the gloss of printed materials. Future work will address the instrumental measurement of appearance attributes of gloss.
For the development of new ink jet printing (IJP) technology, instead of traditional processes, such as spinning, screen printing, photolithography, and laser printing, used for semiconductor and display fields, what are the obstacles to mass production? IJP is an ideal technology for fabricating material layering on a specific substrate that needs to be patterned. However, the line width presence often conflicts with the thin film requirement, i.e., to obtain a better line edge quality, the overlap distance of drops needs to be tuned closer and this results in greater thickness, which deteriorates the electronic performance. Besides, sometimes the image resolution for a metal circuit will be expected to fall within a tunable region, up to ±3 μm for a high level IC carrier board, in order to correct the image deterioration caused during the prior layering process. Those process needs are hard to achieve because of the innate characteristics of IJP transfer into the raster image data format. This paper proposes a novel image trimming method to transfer an original image to a trimmed image, based on the spreading factor between the liquid-solid interface and the assumption of linear superposition for drop-to-drop overlapping, as well as a versatile filtering function built-in as an auxiliary look-up table to modulate layer thickness. In detail, the trimming method included the procedure of pattern identification and location, image separation, seamless image merging, image boundary compensation, image trimming on spreading factor, and image reconstruction. The filtering method included the local characteristic of boundary inspection with a defined correcting function and varied filtering pattern applied to the inner field of boundary. The test pattern found that the circuit was satisfactory in terms of thickness and line width, according to expectation.
Corona charging of organic photoreceptors (OPCs) has been characterized by the measurement of the time-dependent charging current. With this experimental technique, we have investigated the quantity and the dynamics of charging for times greater than the charger time constant (∼0.08 s). With a generic near-infrared sensitive OPC, we observe significant depletion of trapped charge during corona charging. The trapped charge sources are light exposure prior to charging as well as thermal generation with an activation energy of ∼1 eV. In addition, exposure during charging, with the corona-emitted light, produces a steady-state offset current. An OPC sensitive to visible light exhibited much less trapped charge, and thermal charge generation did not occur. This methodology provides a means of quantifying these effects and understanding the interactions of the OPC with the charging and exposure systems in an electrophotographic printer.
The influence of toner shape on the toner performance was investigated. Toner particles were thermally or mechanically modified to make variations in shape from irregular to quasispherical shape. In addition to the typical developing characteristics such as transfer efficiency, the developing characteristics were investigated by observing the degree of toner contamination on the developing roller with an electron microscope and measuring the charge of the toner particles on the developing roller on continued development. It was found that the surface of the developing roller was gradually contaminated to form an additional thin film made of toner materials after a long run developing process. This contamination played a major role in the decrease of the toner charge, especially in the late part of the cartridge life. The degree of contamination was found to be dependent critically on the toner shape and the structure of the toner surface. Both thermal and mechanical modifications worked to reduce the contamination, thus improving the lifetime of toner performance.
A study has been carried out on photoluminescence (PL) and photoluminescence excitation (PLE) of unsensitized and reduction sensitized cubic and octahedral AgBr emulsions. It has been determined that the PL spectra of cubic and octahedral micro<?xpp hyph?>crystals differ. This difference is explained by the formation of polyhalogenoargentate complex anions (PHACA) during the synthesis of octahedral microcrystals. These PHACA adsorb on the microcrystal surface, resulting in appearance of PL bands which are not observed for cubic microcrystals. PHACA can be transformed, after capturing an electron from a reducing agent, into negatively charged fragments, which are efficient hole traps. It is found that Agl-2 and AgBrl- complexes, which can be formed during the synthesis of nominally pure AgBr octahedral microcrystals, play an important role in reduction sensitization. The PLE spectra of the 550 and 590 nm PL bands, which appear upon reduction sensitization of octahedral AgBr microcrystals, have maxima at 3.75 and 2.80 eV for the 550 nm band and 3.81 and 2.88 eV for the 590 nm band. The energy difference between these PLE maxima corresponds to the energy of the spin-orbit splitting in the iodine atom ground state. This leads to the conclusion that the negatively charged fragments responsible for the 550 and 590 nm PL bands contain iodide ions. Finally, our results show that the AgBr emulsion PL consists not only of micro–crystal PL but also of the emission due to impurity centers formed in gelatin during synthesis of AgBr microcrystals.