XUV digital in-line holography using high-order harmonics

A step towards a successful implementation of timeresolved digital in-line holography with extreme ultraviolet radiation is presented. Ultrashort XUV pulses are produced as high-order harmonics of a femtosecond laser and a Schwarzschild objective is used to focus harmonic radiation at 38 nm and to produce a strongly divergent reference beam for holographic recording. Experimental holograms of thin wires are recorded and the objects reconstructed. Descriptions of the simulation and reconstruction theory and algorithms are also given. Spatial resolution of few hundreds of nm is potentially achievable, and micrometer resolution range is demonstrated.Comment: 8 pages, 8 figure

Halftone banding reduction for a class of electrophotographic systems - Part I: Characterization and modeling

This paper proposes new insights and methodologies that complement existing techniques for characterizing and modeling halftone banding, an artifact of periodic light and dark bands across a printed image perpendicular to the print direction, for a class of electrophotographic (EP) systems, which is commercially known as laser printers. For characterizing banding based on transmission error measurement, specific frequency-domain signal processing, i.e., order analysis, was applied to help identify possible disturbance sources with certain gear components. For characterizing banding based on absorptance measurement on printed images, it was pointed out that a good metric should incorporate appropriate nonlinear operator that characterizes the human visual system. This proposition was supported by simulation results obtained from a three-stage visual model. For modeling banding, a more comprehensive EP model was developed to include transmission parameters such as laser scanning frequency, gear dimension, and angular velocity. Simulation study was performed on the simplified version of the derived model, which demonstrated close correlation between halftone banding and transmission quality. This motivates control of the motor/gear transmission system for reducing banding artifact in EP processes. (c) 2008 Elsevier Ltd. All rights reserved

Naturalness and image quality : chroma and hue variation in color images of natural scenes

The relation between perceptual image quality and naturalness was investigated by varying the colorfulness and hue of color images of natural scenes. These variations were created by digitizing the images, subsequently determining their color point distributions in the CIELUV color space and finally multiplying either the chroma value of the hue angle of each pixel by a constant. During the chroma/hue-angle transformation the lightness and hue-angle/chroma value of each pixel were kept constant. Ten subjects rated quality and naturalness on numerical scales. The results show that both quality and naturalness deteriorate as soon as hues start to deviate from the ones in the original image. Chroma variation affected the impression of quality and naturalness to a lesser extent than did hue variation. In general, a linear relation was found between image quality and naturalness. For chroma variation, however, a small but systematic deviation could be observed. This deviation reflects the subjects' preference for more colorful but, at the same time, somewhat unnatural images

The RaPID Perceptual Image Description Method (RaPID)

This paper contains a general description of the RaPID (rapid perceptual image description) method, and the results of a series of experiments on the attribute sharpness. The method aims at a rapid and perceptually meaningful description and quantification of the primary factors of image quality. The purpose of the project is primarily to develop the main dimensions of image quality, but also to determine how they combine into overall image quality, and to develop perceptual models for the main dimensions. The result of the project will be a technique that can be used to evoke, quantify, analyze and interpret subjective reactions to the characteristics of imaging systems. A preliminary experiment was conducted on sharpness related attributes of images. The results showed that the five TV sets under study had to be evaluated on 11 different terms and that they combine into two independent attribute dimensions for natural or test images. If both types of images are considered simultaneously, the 'sharpness' space consists of at least 3 dimensions. Physical measurements were used to calculate sharpness related measures (MTFs, step responses, line width) and these were correlated with the subjective results

The RaPID Perceptual Image Description Method (RaPID)

This paper contains a general description of the RaPID (rapid perceptual image description) method, and the results of a series of experiments on the attribute sharpness. The method aims at a rapid and perceptually meaningful description and quantification of the primary factors of image quality. The purpose of the project is primarily to develop the main dimensions of image quality, but also to determine how they combine into overall image quality, and to develop perceptual models for the main dimensions. The result of the project will be a technique that can be used to evoke, quantify, analyze and interpret subjective reactions to the characteristics of imaging systems. A preliminary experiment was conducted on sharpness related attributes of images. The results showed that the five TV sets under study had to be evaluated on 11 different terms and that they combine into two independent attribute dimensions for natural or test images. If both types of images are considered simultaneously, the 'sharpness' space consists of at least 3 dimensions. Physical measurements were used to calculate sharpness related measures (MTFs, step responses, line width) and these were correlated with the subjective results