This paper proposes a method for estimating the omnidirectional distribution of the scene illuminant spectrum from images taken by a camera aimed at a mirrored ball. First, we introduce measuring systems using a RGB color camera and a mirrored ball placed at an arbitrary location in a natural scene for acquiring ambient light from any direction. Second, in order to estimate the direction from which light comes to the ball, we calibrate the measuring systems and determine a mapping between the image coordinates of the spherical ball and the directions of light rays in the world. An omnidirectional image representing the spatial distribution of ambient light sources is created in a polar coordinate system. Third, we present an algorithm for recovering the illuminant spectral power distribution from the image data at each pixel and the reflectance data of the mirrored ball. Finally, we execute an experiment in a natural environment with multiple light sources for examining the feasibility of the proposed method.
A study has been carried out on the effect of the optical density of inks on the specular reflectance of a printed surface. Samples of cyan, magenta, and yellow ink were printed with a liquid electrophotographic, an offset lithographic, and a thermal transfer printer. Specular reflectance was measured using a goniophotometric instrument to produce the bidirectional reflectance distribution function. The results clearly demonstrated that the amount of specular light reflected from a printed surface depends strongly on the optical density of the ink. A linear correlation was observed between the total amount of specular light reflected from the surface and the square of the transmittance of the ink layer. A highly transparent ink (e.g., yellow ink measured with red light) reflected approximately twice as much specular light than a highly absorbing ink (e.g., yellow with blue or cyan with red). It is suggested that specular reflections from surfaces below the ink layer can contribute significantly to overall specular reflectance of a printed image.
High throughput screening has been used to rapidly screen for chemical compounds in a biological assay. Until recently, many of the biological assays utilized simple biochemical techniques, the result of which could be interpreted in single or at most a few numerical values. That made it easy to evaluate, without bias, any unique chemical entities screened. However, with biological cells or tissue images, the information was qualitative or at best limited to simplified algorithms. Recently, it is now becoming possible to perform standardized assays and utilize complex image data to derive reproducible information which could be utilized to precisely quantify the efficacy of compounds. Much of this is possible due to the precise mathematical algorithms that are used to compute image data to derive information. This review will discuss some of the basic algorithms involving kernel operations that are commonly used and how they can be applied for any image or picture data.
Recently, the study of the colorization algorithm for monochrome still images has prospered. Considering actual applications, an extension to monochrome video becomes important. This paper proposes two colorization algorithms for monochrome image sequence without scene changing in video. In our approach, key frames in the image sequence are firstly colorized by a conventional colorization technique for still image. In the technique, a small number of color seeds are sown on the monochrome key frame, and color seeds are propagated spatially to remaining monochrome pixels. Then, each color in the colorized frame propagates to the next monochrome frame by extracting a displacement vector for each pixel between two frames. In this paper, the displacement vector is calculated by a simple block-matching algorithm, and color propagation to temporary direction is performed. So, in the proposed algorithm, video colorization can be realized by setting only some color seeds on key frames. Experimental results suggest a success of colorization for video by setting key frames for each 10 frames.
Traditional methods for patterning conductive materials, such as screen-printing and photolithography, are complex and time-consuming. In this paper, we successfully combined three processes: Self-assembly polyelectrolyte (SAP) surface treatment, microdispensing catalyst patterning on the substrate, and electroless plating to form metal circuits. Due to the porous structure, these polyelectrolyte membranes are of great benefit to the absorption of the catalyst used for metal deposition. Hence, the processes above can form excellent metal pattern for various substrates, for example, PET, Glass, PI, FR-4, etc. The result has been verified by IPC 6013 standard for flexible substrate. This study also developed an image analysis method to validate the reliability of this ink jet printed circuit. It included the steps of threshold setting, erosion operation, template calibration, filtering, and edge-enhancement. After image analysis, the line width was of 135 μm on the average and the standard deviation was of 3.5 μm. The maximum blurring rate of the edge of the line observed is within ±%.
The innate character of ink jet instability sometimes causes device defects in polymer light emitting diodes (PLED). This study develops an image-processing method to identify defects by methods such as filtering, color processing, background subtraction, dilation, etc. Based upon the defect information and the pre-built ink jet print head library, the amount of ink volume and the location to print on can be appropriately estimated to patch defects. In addition, an optimal printing route can be determined with a specially designed head driving waveform, consisting of pre-oscillations during motion intermission. By this methodology, a 60 pL sized drop from ink jet nozzles can approximately patch the PLED panel with pixel resolution of 240×73 μm, the QCIF standard. The results demonstrated good accuracy in landing while patching unfilled pixels. However, there are some satellite drop occurrences observed due to the sensitivity of image data threshold level setting. Overall, the confidence level of successful defect identification is larger than 95%. In this paper, an optimal repair route and a strategy about thin film morphology control were also discussed. These approaches are helpful to repair defects and, consequently, increase the yield rate for PLED or other applications by ink jet technology.
We develop a comprehensive procedure for characterizing the modulation transfer function (MTF) of a digital printer. Especially designed test pages consisting of a series of patches, each with a different one-dimensional (1D) sinusoidal modulation, enable measurement of the dependence of the MTF on spatial frequency, bias point, modulation amplitude, spatial direction of modulation, and direction of modulation in the color space. Constant tone patches also yield the extreme and center color values for the input modulation. After calibrating the scanner specifically for the direction of modulation in the color space, we spatially project the scanned test patches in the direction orthogonal to the modulation to obtain a 1D signal, and then project these sample points onto a line in the CIE L*a*b* color space between the extreme color values to obtain a perceptually relevant measure of the frequency response in a specific color direction. Appropriate normalization of the frequency response followed by compensation for the scanner MTF completes the procedure. For a specific inkjet printer using a dispersed-dot halftoning algorithm, we examine the impact of the above-mentioned parameters on the printer MTF, and obtain results that are consistent with the expected behavior of this combination of print mechanism and halftoning algorithm.
Previous studies on the banding mechanism have proposed various reduction methods for the electrophotographic process. The banding mechanism is generally caused by a vibration that is transmitted by the drive system and its resulting resonance. We analyzed the banding that occurred in a single-component contact development system, and it became evident that banding was caused by a self-excited vibration. The self-excited vibration model consists of the following elements: A spring element (the rubber layer of the development roller), a mass element (the development unit), and an exciting force (the friction between the development roller and the OPC drum). We also observed that the model's vibration frequency varies nonlinearly, an interesting characteristic caused by the nonlinear hardening properties of the spring. Since self-excited vibration can be prevented by stabilizing the system, we propose the use of appropriate damping components. We also statistically verified the banding reduction effect by conducting a quantitative analysis on the vibration intensity.
A model for charging of insulative materials has been developed which quantitatively links the surface chemistry of materials to their work functions, and to the triboelectric charge exchange charge in two-component developers. The proposed model fits within the standard high-density of states model for charging, but proposes bidirectional electron transfer from basic sites on one contacting material to acidic sites on the second contacting material, and equally, from the basic sites on the second material to acidic sites on the first. The result is an "effective" work function for the material surface, the average of the work functions of the surface acidic and basis sites. This model predicts that both surface work functions and negative toner charge increase linearly with the logarithm of the ratio of the toner acid/base constants, Ka/Kb, which can be experimentally measured by inverse gas chromatography. Charge exchange is zero when the toner and carrier acid-to-base constants are identical. The model implies that an insulator's surface Lewis base and acid functional groups are responsible for triboelectric charge exchange. The model can also be applied to insulator to metal charge exchange.
Inverse gas chromatography (IGC) has been applied to study the surface properties of developer materials, measuring acid, base, and dispersion interactions. Model carrier and toner particles were prepared, where the toner was blended with various nano-particulate metal oxide surface additives: Silica, titania, and alumina. Toner charging was determined with these surface additive formulations. IGC was used to characterize carrier and additive surface chemistry. Results from IGC were evaluated with respect to toner charge and to metal oxide work functions. A correlation was found between IGC-determined surface acid-base interaction parameters of the developer materials, and their work functions and triboelectric charge. Together, the IGC, work function, and charging results strongly support a work function model for developer charging, where the work function is determined by the acid and base properties of the developer components. Thus, as the ratio of the acid to base interaction parameters of the metal oxide surface additive increased, toner charge became more negative. The results are in quantitative agreement with the surface states charging model proposed in the companion paper in this series.