Stereo vision is the normal method to obtain the depth information from images. The problems encountered when applying well established algorithms to real time applications are due to the high computational load required. In this article, the authors address this issue by performing a region-based analysis which considers each pixel only once. Additionally, matching is carried out over statistical descriptors of the image regions. In this article, the authors present a new algorithm that has been specifically designed to solve some commonly observed problems which arise from other well known techniques. This algorithm was designed using a previous algorithm implemented by the authors. The complete analysis has been carried out over gray scale images. The results obtained from both real and synthetic images are presented in terms of matching quality and time consumption and are compared with other published results. Finally, a discussion of additional features related to the matching process is provided.

Multispectral systems allow the spectral and color characterization of objects using images obtained from several acquisition channels with different spectral sensitivities. Light sources based on light-emitting diodes have started to be used in multispectral systems, mainly to develop low-cost devices for the industry. In this study, the authors examine the variability of spectral power distribution according to the viewing angle of white and single color light-emitting diodes, which can have a significant impact on spectral and color accuracy. This must be taken into account if they are to be used in multispectral systems design. The spectrum drift according to the time of usage of white light-emitting diodes is also analyzed.

In this article, the authors propose a novel interpolation-based reversible data hiding algorithm for use with images that are encoded in the Joint Photographic Expert Group standard format. This algorithm is able to exactly recover the original coded quality of the image, once the hidden message has been extracted. The proposed algorithm embeds message data into discrete cosine transform blocks by calculating the difference values between the nonzero quantized AC coefficients and their interpolated counterparts and then shifting the histogram of those difference values. Simple linear interpolation is employed to exploit the correlation between the AC coefficients that are colocated across neighboring blocks for the purpose of creating hiding capacity for the insertion of data bits into the AC coefficients. The embedding of data is performed via the shifting of the histogram of interpolation differences. Our experimental results demonstrate that the proposed method not only provides an increased embedding capacity but also maintains a high image quality. Moreover, as an additional processing delay is not introduced and only simple arithmetic computations are involved, the proposed algorithm can operate in real time.

Security barcodes and other barcodes linked to on-line databases have become commonplace due to the increased availability of mobile phones equipped with high-quality cameras. In this article, the authors provide methods for quantifying the entropy of the embedded barcode data, assuming methods other than the standards-specified error-correcting code (ECC) approaches can be adopted. Higher entropy, which reduces the likelihood of a fraudulent agent being able to "guess" correct barcodes, is measured directly using a variety of novel algorithms and applied to large sets of barcodes. The authors data, however, show that removing ECC provides the additional advantage of increasing the entropy. Thus, all other settings (data payload size, printing technology, substrate used, etc.) being equal, eliminating the ECC increases the security of the information content for the barcodes (DataMatrix) tested.

In today's world of highly sophisticated technological crimes, criminals including counterfeiters, document forgers, and other parties interested in altering information have a low barrier of entry. To combat these crimes requires developing a level of forensic analysis to aid law enforcement agencies in tracing the origins of documents or materials in question. In this article, the authors use printer forensics in an effort to understand the effect of resolution and character selection on the accuracy of printer identification. Specifically, they use a multiclass ADABOOST classifier to determine which of six printers, representing several ink jet and laserjet models, were used to produce a subsequently scanned image. Their results, investigating six different English characters, show that classification accuracy continues to increase with scanning resolution up to 1200 pixels/in. The results are character dependent, suggesting that different characters may be used for different forensic purposes–printer model, cartridge, and individual printer identification as examples.

Wax-based electrophoretic rewritable media have been investigated since they potentially have good preservation characteristics. Reducing the thickness of rewritable media is critical for reducing the writing/erasing energy of wax-based rewritable media. The present study investigates the effect of rewritable media thickness. Samples of with dye concentrations of 0, 0.03, and, 0.07 wt. % and TiO2 concentrations of 2.5, 5, and 10 wt. % with respect to wax were prepared with media thicknesses of 0.05, 0.1, and 0.2 mm and their rewritable characteristics were evaluated. The Kubelka-Munk equation was applied to investigate the dependence of the reflection of the dyed side on the dye and TiO₂ concentrations and the absorption coefficient of the dye was estimated. It was found that a TiO₂ concentration of 5 wt. % and a dye concentration of 0.07 wt. % give suitable display characteristics for cells with thicknesses of 0.1-0.2 mm. A preliminary rewrite experiment was performed on an enlarged dot cell.

Externally added charge control agents (EA-CCAs) were prepared by means of a coacervation process. Spherical silica particles of 100 nm average diameter were coated with two kinds of charge control agents (CCAs); one was a polymer type P-1 and the other was a low molecular weight type P-2. Both of CCAs made remarkable contribution to toner charge. In a concentration range up to 0.2 μmol/g of CCA on toner, toner charge increased. From the relationship between the amount of EA-CCA on the toner and the tribocharge, P-2 was found more effective than P-1. It was estimated that 0.7 mol% of P-1 repeating units and 1.3 mol% of P-2 molecules contributed to toner charge, respectively. Calculation of the surface coverage of P-2 on spherical silica particles showed that the efficient concentration region of charge agreed with the 100% of surface coverage. The P-2 concentration was 0.02 μmol/g based on toner. This means that the CCA molecule has a great effect on tribocharge in small concentration.

The quality of a printed image is strongly influenced by the physical and the chemical interactions between the ink and the paper. Print quality can be evaluated either by objective measurements using instruments or by visual assessment studies involving panel of observers judging the final print. In this article, the print quality on commercial papers as well as on non-commercial papers with different amounts of salt for surface fixation has been studied. Perceived detail reproduction depends not only on sharp edge definition but also on the level of color saturation (Chroma). Color saturation and edge definition originate from two different ink and paper interaction processes. Color saturation is heavily dependent on ink penetration while edge definition correlates to ink spreading. In order to gain understanding of the performance of surface treatment by salt, large efforts have been put on splitting up of the increase in color saturation (Chroma) and improved edge definition. The printouts have been made with a desktop printer using pigmented inks. Cross section images have been taken with a light microscope to analyze the ink penetration depth. SEM analysis has been made to analyze the aggregation of the pigments on the surface. The print quality measurements have been both objective measurements such as print density and subjective image evaluation using a test panel of observers in a perceptual study. The perceptual study focused on detail reproduction, and efforts were made to separate the influence of the print density from the edge definition on the detail reproduction. The result from this study shows that an increased level of salt as surface fixation improves the detail reproduction due to aggregation of the pigments on the surface and that the ink penetration depth can be reduced by adding salt as surface fixation resulting in a higher print density.

The effects of corona discharge treatment (CDT) on ink drop impact and spreading on a coated polypropylene film substrate were investigated. Substrate surface energies were determined from static contact angles with water and ethylene glycol. The polar component increased with increasing CDT. Drops 39 μm in diameter of an acrylate-based UV-curable ink were printed on to the substrate, and the spreading process studied by high-speed photography. No changes occurred during the initial stages, but the wetting phase was shorter for higher doses of CDT. Drops spread further on substrates with low doses of CDT than with higher doses. White light interferometry was used to determine the final heights of drops after UV-curing. The height was significantly affected by CDT, with minimum height at low doses. The relationship was investigated between the static contact angle for large sessile drops and the equilibrium contact angle for printed drops after spreading. Contact angle measurements with millimeter-sized sessile drops of ink provide a reliable method to determine the effects of corona treatment on wetting by ink jet printed drops.