The requirements for color technology in the general office are reviewed. The two most salient factors driving the requirements for color are the information explosion and the virtually negligible growth in white collar productivity in the recent past. Accordingly, the business requirement upon color technology is that it be utilized in an effective and efficient manner to increase office productivity. Recent research on productivity and growth has moved beyond the classical two factor productivity model of labor and capital to explicitly include knowledge as a third and vital factor. Documents are agents of knowledge in the general office. Documents articulate, express, disseminate, and communicate knowledge. The central question addressed here is how can color, in conjunction with other techniques such as graphics and document design, improve the growth of knowledge? The central thesis is that the effective use of color to convert information into knowledge is one of the most powerful ways to increase office productivity. Material on the value of color is reviewed. This material is related to the role of documents. Document services are the way in which users access and utilize color technology. The requirements for color technology are then defined against the services taxonomy.
Image noise, tone reproduction, color reproduction, fine line reproduction, and OHP performance are the most important characteristics for a high quality color copier. Technologies enabling such quality are use of fine toner, halftone algorithm to ensure good highlight reproduction, soft roll fuser with good release performance, smooth surface and high thermal conductivity, white and smooth paper, and selection of a coating material for the surface layer of the OHP sheets. These technologies are integrated in the Fuji Xerox `A- Color' product. Utilizing 7 micrometers color toner, `A-Color' can make very high quality color copies.
The human visual system has evolved with a sophisticated set of mechanisms to produce stable perceptions of object colors across changes in illumination. This phenomenon is typically referred to as chromatic adaptation or color constancy. When viewing scenes or hard-copy reproductions, it is generally assumed that one adapts almost completely to the color and luminance of the prevailing light source. This is likely not the case when soft-copy image displays are viewed. Differences in the degree of chromatic adaptation to hard-copy and soft- copy displays point to two types of chromatic-adaptation mechanisms: sensory and cognitive. Sensory mechanisms are those that act automatically in response to the stimulus, such as retinal gain control. Cognitive mechanisms are those that rely on observers' knowledge of scene content. A series of experiments that measured the spatial, temporal, and chromatic properties of chromatic-adaptation mechanisms are reviewed and a mathematical model for predicting these chromatic adaptation effects is briefly described along with some practical recommendations, based on psychophysical experiments, on how to approach these problems in typical cross-media color reproduction situations.
Despite the proven ability of color to enhance scientific and technical communication, many designers and their teachers strongly avoid chromatic color. They can overcome their reluctance and use color effectively if they understand how color works, respect the limitations of color, and apply it in ways compatible with communications objectives and human perception.
The first thermal paper technology was developed in the 1930s. Since then, thermal recording systems have branched into two main groups, two-component systems and heat-transfer systems. In the 1960s, the leuco dye system was developed by NCR. This type of system has been used mainly in thermal recording systems. The leuco dye system however has some drawbacks such as poor image stability and an artificial texture. In a recent development, a compound with an epoxy functional group was added to the thermal sensitive layer of a leuco dye thermal paper to obtain good stability. A special overcoat layer gives the product the texture of plain paper. In addition to this product, other special thermal papers have been developed, such as two-color thermal paper, IR readable thermal paper, high resolution thermal paper, and translucent thermal paper.
Aluminum can be anodized to form a microporous surface film consisting of uniform cylindrical pores normal to the substrate. This film may be engineered to permit detachment from its aluminum substrate, allowing the transfer of the film to a secondary substrate for printing. The film pores can act as vertical receivers of the toners and inks used in non-impact printing, thereby limiting in-plane spreading. If the film is formed on foil of a gauge compatible with printer media handling systems, the image and oxide may be transferred after printing. The use of such films for non-impact printing applications is proposed.
Ink-jet printers (IJ) were developed in the early 1980s and recently, their use has spread in the fields of business applications and computer graphics. IJs feature a faster printing speed than a thermal transfer printer. The printing quality of IJs has been improved to 400 DPI. It is said that even 600 DPI can be realized. Accordingly, almost the same level of printing quality as that of a laser beam printer (LBP) is possible. A compact model requires space of less than 50% of an LBP and smaller power consumption also should expand the demand of IJs for business application. In addition, with the extension of computer graphics, IJ color printers have been increasing remarkably lately. IJs have many advantages compared with the conventional electro photographic system. In the use of color ink-jet printers, an image quality is important and it is influenced by the applied ink and paper. In this connection, the recent trends are explained.
Particles dispersed in a hydrocarbon liquid become charged by the addition of a charge director, a hydrocarbon soluble ionic surfactant, which aggregates into inverse micelles in non-polar media. This effect is utilized in liquid electrostatic developers for imagewise particle deposition which enables electrostatic printing. The charge director micelles ionize to form both positive and negative micelles which can compete with particles of the same sign for image charge during the image development process. Several techniques are available for the measurement of particle charges. These include methods by which particles are electrophoretically developed and the transient current monitored, one method where micelle counter ions are stripped from the particles by fluid flow, and particle charge can be related to particle mobility which can be measured by a number of techniques. All of these methods have some utility but their effectiveness will depend on how well they account for all of the charged species in the particle dispersion and other factors which effect charge on the particle. In this report a discussion of the influence of micelle ionization and the affect applied field have on the charge of particles is presented and how these phenomena might impact the measurement of the particle charge.
Since the first jetting of ink, that is solid at room temperature, in 1979 solid ink technology has offered the promise of revolutionizing on-demand printing. With the successful introduction of a number of products during the last 18 months, solid ink is on the verge of realizing this promise. In principle solid ink jetting is simple: melt the ink and jet it as a liquid; in practice there are many factors critical to the containment, ejection, and formulation of phase change inks. These factors have influenced the development of the drive portion of the ink jet print head with all commercial applications using a piezoelectric drive. These factors have also spawned a great deal of work in innovative ink delivery systems that bring ink to the print head in a solid form. The most important feature of the technology has been the quality of the resulting image and the independence of the substrate on this image quality. Solid ink also has the unique feature of easily producing small spot sizes. As a result, the gray scale levels and high resolution can increase to keep pace with improvements in competing technologies and demands from the marketplace. Though Dataproducts (and its predecessor Exxon Printing Systems) were the first to develop solid ink technology, through various license agreements, products using solid ink have been introduced from a number of printer companies. Through this collection of products, solid ink provides the enabling technology to bring the office of the 1990s into the color era.
I am going to describe a computer program which we use to develop and predict the actuator and pressure wave forms used to energize Xaar's ink jet printheads. In addition to precise control of drop ejection, the main theme of the paper is acoustic wave cancellation, i.e., the removal of residual energy in ink channels following drop ejection.
A predictive model for multi-colored halftone prints has been developed for inkjet printing. This model is based on the `n-modified' Neugebauer equations. For each substrate, the optimal value of n is determined through the optimization of gray levels prediction. Ink jet printing properties are taken into account by describing the shape of dots on grids. Overlapping of dots increases the number of `stackings' that can be obtained and contribute to the color of the pixel: for three inks, 27 stackings are used to describe the pixels. The colors of these stackings are measured on solid print patches. The model has been used to predict halftone color prints on different substrates such as plastic films, metal plates, and several varieties of paper. Its accuracy is estimated for each substrate with color test patches. The color differences (Delta) E between our predictions and measurements are given. The results demonstrate the importance of the parameter n and of the position of dots.
The piezo-electric pusher technology used in the Dataproducts Jolt solid-ink jet color printer is described. Present performance and limitations on the performance are discussed. This technology is well suited for the higher print quality and throughput required for future solid ink printers. To meet these requirements, some improvements in printhead performance and changes in jet array architecture that may be needed are outlined. Areas for performance improvements include range of dot size, dot shape, dot reproducibility, placement accuracy, and drop emission frequency. Limiting characteristics such as instabilities, cross-talk between channels, spurious or satellite drop emission, jet velocity, and ink ligament dynamics are described in terms of how the performance limits could be extended. Experiments and mathematical modeling work that have improved our understanding of the basic operation of the pusher jet are described and the ultimate physical limits explored.
There are stages in the refinement of new imaging processes where the use of unique test equipment and study tools is required to isolate problems related to performance and fabrication steps. A juncture had been reached in the Xerox thermal ink jet program where an evaluation of the printing device for both electrical function and print quality prior to final packaging was required. Nondestructive testing is necessary so that these printing devices can be tested repeatedly and subsequently packaged by mounting them onto a substrate with appropriate circuit boards, wire bonds, and ink manifolds to form finished thermal ink jet printheads. This paper describes test equipment which has been designed to electrically test, print test, and fully evaluate imaging properties of unpackaged thermal ink jet printing devices. The use of this test equipment and related testing procedures has accelerated process development times significantly and is playing a key role in quality control functions in the product manufacturing environment. Test equipment, techniques and results are discussed.
Electrophotography, as an original invention, was just another way to make a copy. Its development into a continuous process made it historic. As with any technology, the evolution proceeded along several fronts, in particular the advancement of enabling components including stimulation and sponsorship of research in related scientific disciplines, development of technology and engineering solutions, and expansion of the market while satisfying existing demand. The evolution, driven by customer and market requirements, has followed the paradigm of any other technology-based appliance: growth in performance and reliability and reduction in size and cost, ultimately enabling the transition all the way from highly functional centralized machines to personal devices. Besides this traditional evolution, xerography expanded when it could link with other technologies. The most dramatic breakthroughs that led to rapid market expansion occurred when digital electronics enabled printing and image processing, and the proliferation of personal computers launched a robust color creation and hardcopy market. The electrophotography industry was prepared for this opportunity and made possible desktop publishing, distributed printing, and recently, color copying and printing with acceptable color fidelity. What early indicators signaled the evolutionary paths, and the divergences, electrophotography would take? In this paper, we examine the history, including relevant publications, to find such indicators. Current literature is also considered in that light.
The primary objective of this work is to develop computing capabilities to enable computational prototyping as a complementary and parallel path to the hardware product development process. The evolution of a systems approach, capturing aspects of information generation, processing, visualization, transfer, and reuse, within a sharable, multimedia, electronic environment, is crucial to the integrated design process of the future. We discuss a general computing environment to support the multi-level (process-device-material) simulations of xerographic subsystems. This environment features: distributed computing, concurrent processing, network sharable information and tools, a visual programming interface, dynamic computing and visualization, and interactive steering. We describe the implementation of the testbed environment and the mathematical simulations, from first principles, of the charging, imaging, and development subsystems. Generic algorithms developed for these subsystems are discussed. Interactive steering of dynamical solutions and browsing of visual data are emphasized. A model for multi-level simulation is proposed to support the decision making process. A visual programming interface is used to encapsulate the simulation and visualization tools as modules which can then be visually assembled into dataflow networks on Unix workstations. Mathematical formulations, parallel computing on clusters of workstations, and their use in interactive sessions are detailed.
The `toner jumping method' is proposed to more simply conduct the non-impact printing process in electrophotography. To clarify the fundamental functions of this method, in this paper, the jumping behavior of toner is studied by simulating with the aid of a personal computer. To control the locus and distribution of toner from a magnet roller electrode to the paper on the back electrode, the mesh electrode is assumed to be inserted at the middle of the roller and back electrode. Between the magnet roller electrode and the back electrode the higher dc voltage is applied compared with the mesh electrode against the roller electrode. The locus and distribution of toner reaching the paper are simulated changing the applied voltage in each raw's and column's direction of mesh electrode. It is assumed to be possible to control the jumping behavior of toner from magnet roller to paper. As a result, the role of the mesh electrode in the `toner jumping method' on the quality of image in the non-impact printing process is suggested.
The utilization of air entrainment for transport and control of charge deposition in ionographic printing is investigated numerically. The geometries considered can be thought of as a charge generation region followed by an air entrainment region followed by an ion projection region. The air entrainment region provides a zone in the ion flow path where moderate electrode voltages can be applied to achieve stable and accurate control and modulation of the ion current levels. Results of the numerical simulations showing effects of air flow and modulation voltage on ion trajectories are presented.
This theoretical and experimental investigation studies the corona induced oscillation of a wire located near a ground plane. The corona is created by a high, positive dc, potential difference between the wire and the plane. The motion of 1.5 and 3.5 mil inch diameter wires is optically measured. The effects of voltage, mechanical tension, spacing, and several other primary operating parameters are explored experimentally. Neutral stability curves are determined. A theoretical model of the wire motion is presented. The model considers the high voltage driver circuitry, the conduction of current through air and the wire dynamics. The wire motion is obtained numerically. The model is linearized and a stability analysis is performed. The constraints on the operating parameters that are necessary for stable equilibrium are discussed. The results are compared to measured data.
The development of a compact, high image quality, and maintenance-free electrophotographic color printer suitable for personal computers, EWS, and so on has been demanded. Another important demand is for the development of an electrophotographic printer for which less replacement and less disposal of material is necessary. With this in mind, the authors have been developing a contact type mono-component nonmagnetic development system utilizing a soft and conductive development roller, and a simultaneous development and cleaning process in order to realize a still simpler printing process. In this process, the residual toner remaining on the photoreceptor at the transfer process is cleaned simultaneously by the same development unit, while the latent image is developed by the same unit. Miniaturization of the printer system has been realized and the disposal of the waste toner has become unnecessary, since there is no cleaning unit. The authors have also developed a color toner suitable for a contact type mono-component nonmagnetic development system and have applied it to a four- drum-tandem type color printer. This paper describes the principle of the simultaneous development and cleaning process and the development characteristics of the four-drum- tandem color printer utilizing the development system.
The breakdown mechanism of hydrogenated amorphous silicon (a-Si:H) has been investigated. It has been shown that the acceptance of the surface potential of an a-Si:H photoreceptor is very sensitive to the micro-roughness of the substrate surface. This is because the junction between the metal substrate (usually aluminum) and the blocking layer (p+ or n+ a-Si:H) is strongly affected by the micro-roughness of the substrate surface. A model is proposed to expound this phenomenon, which indicates that the existence of micro- defects on the substrate surface results in the bending of the metal-semiconductor junction at these defect positions; that is, the original parallel plane junction changes into a spherical abrupt junction. Compared to the former, the curved junction has a lower breakdown voltage, therefore, it will more easily break down at these defect positions during charging. An a-Si:H photoreceptor was prepared on the drum substrate half covered with a thin aluminum film to confirm the model. The experiment result was qualitatively in agreement with the analysis mentioned above. In addition, the effects of PVD-like deposition processes (e.g., high power or high argon diluted silane deposition) on the microstructure and breakdown of a-Si:H photoreceptors are reviewed.
Thermal dye diffusion printing is a non-impact printing process that generates color prints that rival photographs in quality. The process involves the transfer of dye from a color ribbon to a receiver under the influence of a thermal head. It is therefore a completely dry process totally under electronic control. Applications range from color proofing, through business presentations, medical imaging, etc., ultimately to photographic replacement.
Laser transfer of volatile dyes as a means of direct digital printing has been a demonstrated fact for well over a decade. The advantages of the direct laser imaging system are that the process is dry, instantaneous, completely free of chemicals or processing, and can be done in full daylight. Another advantage is that all the amplification in the system is electronic. This allows better control of the signal to noise ratio in the image, just by building better electronic circuits. Silver halide and electrostatic imaging systems show image development artifacts which are, in fact, manifestations of image noise. A high quality color proofing system is described which makes use of the inherent high quality of laser dye transfer imaging, recent advances in high power laser diodes, and a new donor-receiver media set.
We have developed a 300 dpi A4-size printer using the TDT method for desk-top publishing images including pictures and characters. This printer consists of an engine part and an interface part. They are connected through a VME (Versa Module Europe) bus. The engine part has density compensation for keeping high uniformity and works as a one line printer. The interface part includes SCSI and Centronics I/F with 1 or 4 color plane memories. The most useful function is that it can print any length of paper size, for example A4/A5 size, letter size, U.S. legal size, or any longer size for a panoramic image.
I would like to talk about the latest example of Dry Silver technology that has led to a new product based on dry silver chemistry, but is really quite different. It is a thermal film that has similar sensitometric characteristics as dry silver. This has been accomplished by adapting dry silver chemistry to a purely thermal reaction. This technology can produce densities up to about 4, with Dmin less than .05, and it can be accomplished in microseconds using thermal heads or laser diodes, as I describe. The chemistry is similar to that used in dry silver, but the film is not light sensitive, it responds only to heat. The reaction rate for the thermal development of silver images has been adjusted so that high density can be achieved in the times available with existing thermal heads. We use silver behenate, the main ingredient of dry silver, and the same resins, but some of the other chemistry is quite different.
This article explains the importance and use of the color control technique -- on the basis of colormetrics -- for the complete production line in order to produce economically high-quality multicolor prints. For this purpose, first a short survey on the printing technologies and on prepress is given with special consideration to the digital technique. On this basis, the quality of multicolor prints is explained and specified. The principles of colormetrics are only treated to the extent which is necessary for understanding the color control techniques and their measurement devices. Color control devices and systems, which are used in practice, are indicated. A detailed description is given of a special scanning spectrometer, how it is used in the printing technique and how it has been evaluated for pointing the way for quality measurement and control techniques for graphical products and systems. Special emphasis is put on the fundamental theoretical model for conversion of color values to production control settings. In summary, the colormetrics and color control techniques are presented as fundamental tools and components for the development of `color management systems,' as they are absolutely necessary for the calibration of several devices within the production line and for system integration.
Colorimetric calibration is the process of producing colorimetrically correct data from a device. For the case of a scanner this would involve the process of converting scanner signals into signals which are related in a known way to some colorimetric standard. In the case of a printer, the process is reversed, the task at hand is to determine the printer signals necessary to produce a desired colorimetric signal. A common way of representing colors is by a three dimensional vector. This may be red, green, blue signals, CIE L*, a*, and b* values, or any one of a number of other coordinate systems. Colorimetric calibration can be viewed as the transformation of data in one 3-D space to data in another 3-D space. I present some research into the problem of visualizing the 3-D data used in the process of calibrating a printer. The visualizations are rendered onto a 2-D display, and include the rendering of 3-D gamuts, and vector spaces, and the ability to move around these 3-D spaces to examine details of the 3-D data set.
Essential elements of technology for analog off-press proofing are reviewed. They deal with the three steps of image capture, origin of color, and techniques to form the proof on a receptor. Silver Halide and Polymer Imaging Systems appear to be the most versatile media for image capture. Among physical imaging methods only electro-photography gained significant acceptance for analog proofing. The technologies have been combined in different ways for proofing applications resulting in a distinct pattern of performance with respect to color and density match, accuracy of registration, and dot gain. Future systems will probably evolve in the direction of higher productivity, higher resolution, and reduced environmental impact.
Accurate colorimetric scanning of a color image is absolutely essential for good color reproduction. This paper formulates the design of a set of three or more color scanning filters as an optimization problem. The optimization criterion is the measure of goodness which was developed in previous work. The method can be incorporated into any scanning system for which the colorimetric responses can be defined. The total system, including the lamps, light path, and sensor characteristics, is taken into account. Simulations and results from actual hardware demonstrate the utility of the method.
Color calibration for critical color proofing in the graphic arts is a two-fold process. The first step in the process is to select a technology that closely resembles the fundamental spectral behavior of colored pigments used in the printing industry. The second step in the process is to optimize the parameters by which the pre-press proof is made in order to achieve the best visual match between the proof and the printed image. In the case of digital proofing, there are two sets of parameters which generally can be optimized. The first set of parameters pertain to the densities and hence the colorimetric values of the solid primaries (YMCK) as well as secondaries (RGB) and tertiaries (3/C). The second set of parameters pertain to the tone response, and are generally in the form of one dimensional look-up tables. If the technology chosen is very dissimilar to the spectral properties of printing inks, it may be necessary to use 3 and 4 dimensional color transformation. While this approach can achieve good color matching results for one illuminant condition, it begins to negate the value of high resolution halftone proofing, since `false dots' begin to appear in the pre-press proof which do not occur in the halftone film.
Color calibration for critical color proofing in the graphic arts is a two-fold process. The first step in the process is to select a technology that closely resembles the fundamental spectral behavior of colored pigments used in the printing industry. The second step in the process is to optimize the parameters by which the pre-press proof is made in order to achieve the best visual match between the proof and the printed image. In the case of digital proofing, there are two sets of parameters which generally can be optimized. The first set of parameters pertain to the densities and hence the colorimethc values of the solid primaries (YMCK) as well as secondaries (RGB) and tertiaries (3/C). The second set of parameters pertain to the tone response, and are generally in the form of one dimensional look-up tables. If the technology chosen is very dissimilar to the spectral properties of printing inks, it may be necessary to use 3 and 4 dimensional color transformations. While this approach can achieve good color matching results for one illuminant condition, it begins to negate the value of high resolution halftone proofing, since "false dots" begin to appear in the pre-press proof which do not occur in the halftone film.
The halftone dot image formed on a Titanium Dioxide (TiO2) photoreceptor with liquid toner has high resolution and sufficient sharpness. We have applied these materials to the graphic arts industry in two ways: one is the application to a direct digital color proofing (DDCP) system, the other is to a direct digital plate printing (DDPP) system. In the DDPP system, dot image is directly recorded on a TiO2 photoreceptor (TiO2 press plate) without using dot film. The exposure light source is an He-Ne laser which is the same light source as that of the DDCP system. Therefore, a proofing image and color separation press plates are produced using the same apparatus and materials. In offset printing, a TiO2 press plate is capable of producing a high quality print. Dots on the paper have fine shape and uniform density distribution. The quality is little affected by the increase of fountain solution. The TiO2 press plate is also applicable to high quality color printing because of its consistent printing quality and high stability of plate size.
A direct single-layer negative-working phototackification system with application to 4-color half-tone proofing has been invented. It makes use of chemical amplification and is based on photo-induced microphase separation in an initially non-tacky miscible blend of acid-labile and tacky polymers. Factors which influence tack generation are discussed. The system has been sensitized both in the UV for conventional analog proofing and in the near-IR for digital proofing.
For our purposes, we needed colorimetric measurements or, better yet, spectral reflectance data. Our survey of commercially available instruments identified one spectrocolorimeter, the Hunter PICS (manufactured by Hunter Associates Laboratory, Inc.), which could be programmed to automatically measure the color (and spectral reflectance) of large numbers of samples on a proof sheet. After an evaluation of this instrument, which included measuring over 10,000 exhibits, it was decided that the unit did not fully meet our needs. This resulted in a decision to integrate another instrument, the Byk-Gardner Color Machine (manufactured by Byk-Gardner, Inc.), with an x-y positioning mechanism. This paper describes the design considerations used in the development of our color measurement system.
Rapid growth in internal drum image recording systems is fueling the resurgence of monofacet laser beam deflectors for high-resolution imaging applications. This paper reviews the image performance criteria required of laser beam scanning systems used for high-resolution graphic arts imaging applications and scanning system limitations that have previously hindered systems from achieving these imaging criteria. Also reviewed are previous monofacet deflector configurations and a new monofacet deflector that can be used with either laser or broadband light sources and is well-suited for both flat-field and internal drum imaging systems.
A highly sensitive register mark is formed by the moire pattern resulting from the overprinting of two screened patches. The two screened patches have slightly different screen frequencies so that when the two planes are in exact register a bright spot appears in the center of the register mark. When the two planes are misregistered, the bright spot is displaced by a gain factor times the misregister, where the gain factor is approximately equal to the size of the patch times the screen frequency (typically 10 to 20). The register mark indicates both the direction and degree of misregister. If the screen frequency were uniform throughout the patch, the mark could falsely indicate register when in fact the misregister was a multiple of exactly one dot. We warp the frequency of the screen pattern, with the center of the patch having a finer screen than the perimeter. A misregister of one dot or more does not produce a symmetrical bright spot in the center of the mark. Thus, the mark provides a positive indication of exact register. The range of sensitivity is nominally plus or minus half of a screen dot in both X and Y directions. It may, however, be extended by recognition of the frequency warped patterns resulting from larger misregistrations.
A hyperacuity laser imager utilizes gray source data and overscanned gray exposure to achieve fully saturated black and white image rendering on the photoreceptor at 4800 addressability in both the fast and the slow scan directions, while maintaining 400 lines per inch frequency response. Conventional laser printing techniques render bitmapped images at resolutions finer than required by the human visual system (for example, 600 to 1200 bits per inch) in an unsuccessful attempt to meet a related requirement for edge placement precision of text, line art, and halftones. This excessive bitmapped resolution is inefficient and cumbersome to maintain in a printing system and is still not nearly enough to satisfy the human visual system's need for edge precision. On the other hand, a hyperacuity imager has the edge precision necessary to satisfy the human visual system's needs, and trades off excessive resolution to do so. This paper examines the overscanned, gray exposure characteristics of the hyperacuity laser imager and how it can be viewed as a natural evolution of the current trends in laser printing technology. In addition, it establishes an order of magnitude relationship between addressability and frequency response for a hyperacuity imager, which is shown to significantly match the needs of the human visual system.
One of the major obstacles in raster graphics has been the artifacts due to aliasing in discrete sampling of continuous curves. These distortions may appear as `jaggie stair-case,' `edge ticks,' `roundup tips,' `squared corners,' and `filled ink-traps.' These distortions that occur in the higher spectrum of human vision create subtle unpleasant effects. Resolution enhancement technology employs a set of piecewise continuous rules to improve output quality by extrapolative prediction beyond traditional anti-aliasing algorithms. The first commercial version of this post processor has more than 200 rules capable of enhancing video streams on the fly. The enhanced print quality has an effect of more than doubling the perceived resolution in field print quality tests.
We quantitatively define a metric of image graininess and derive an analytic expression that relates toner number fluctuations in halftone dots to graininess. We then go on to define the random sequential adsorption (RSA) model, a simple model of particle deposition from which the statistics of development can be numerically calculated. Using the RSA model we find an analytic expression that gives the graininess as a function of toner size. The model is then extended to allow for the effect of a finite toner size distribution. We find that low graininess can be achieved for quite large toners, and the effect of finite size distributions on graininess is minor.
Perceptual characteristics of image noise vs its spatial frequency and colors were deduced from color hardcopy images. The following experiments were carried out: (1) A regular distribution random noise based on the Box & Mueller algorithm was generated. (2) Several noise patterns with a specific spatial frequency were prepared. (3) The noise patterns were superimposed on an arbitrary L*A*B* space of the original image. (4) Simulation prints were made on a xerographic color printer. (5) The prints were evaluated by noise perception tests. (6) Perception characteristics of the noise for spatial frequency were derived. The relationship between noise perception score and noise intensity was estimated on each noise pattern. The experimental results were compared with the visual response in display images. As a result, it has been found that the characteristics of visual perception vs noise intensity are non-linear and depend on the spatial frequency of the noise. The characteristics of image noise perception vs spatial frequency obtained by this experiment agree well with H. Sakata's VTF (Visual Transfer Function) according to Horst's experimental method in lightness space (L*). The magnitudes, however, do not agree with the noise perceptual characteristics in the display images as reported by Barstow. It is also shown that the noise perceptual characteristics in chromatic spaces (a*b*) have a wider band spatial frequency response than H. Sakata's VTF.
The United States Postal Service (USPS) desires quality inspection systems for the stamp manufacturing process to cover printing, finishing, and packaging activities. More than 50 billion stamps are printed in the U.S. annually by gravure, offset, and/or intaglio methods. Errors in stamp production waste resources and affect the cost of a stamp product. Typically, the printing industry has relied on human inspection, but speeds are becoming too high and work too tedious to support 100% inspection. It is clear that automated inspection is needed, but an assessment of the resolution and data rates was required before concept designs could be developed. An intensive research program was undertaken for the USPS to evaluate the feasibility of 100% inspection of postal stamp products and the potential for in-process quality control. Printing, finishing, and packaging preparations were examined to determine inspection requirements, identifying opportunities for inspection and process control, and determining commercial vendor capabilities that meet these requirements. The individual manufacturing problem areas, and some possible solutions, are identified.
This paper describes an under-compensated error diffusion algorithm that is intended for multi-level printing and copying. The new error diffusion algorithm is based on the fact that error calculations and feedback are less important in multi-level systems than in bi-level systems.
Coding for full-color still-image is standardized internationally by JPEG (Joint Photographic Experts Group). The coding method is used in wide area applications. In many cases, continuous-tone images are accompanied by characters. So improvements of JPEG coding by pre and post processing are investigated in mixed images. In this process, we use sharpening before JPEG coding as a pre-processing, and we use smoothing after JPEG coding as a post- processing. In both pre and post processing, the degree of emphasis is controlled by a weighting factor and the quality is compared between processed and unprocessed images. As a result of this process, it is confirmed that the processed image is better than an unprocessed image in quality.
The quantization of a graytone image results in the introduction of quantization noise. To influence the characteristics of the image, different types of constraints can be forced on the noise spectrum. These constraints may be used to adapt the image characteristics to a processing system or to the characteristics of the graytone image. Amplitude and phase can be controlled in different regions in the spectrum during the quantization, allowing an enhancement of details in the image. Moreover, it is of advantage to use oversampled spectra during the quantization, taking the fact into account that the finally printed or displayed image possesses a continuous spectrum. However, the realization of these spectral constraints is limited by two different mechanisms. An analysis of these mechanisms leads to a set of linear and a set of nonlinear equations. The restrictions they impose must be considered when choosing specific spectral constraints.
Ferroelectric liquid crystals based on the smectic C* phase have been shown to have fast electro-optic switching by many workers. The development of a video rate VGA display by Thorn EMI Central Research Laboratories has been recently reported. In this paper we report on the development of a ferroelectric technology for printing applications. We describe a printhead technology based on a ferroelectric liquid crystal shutter array. The feasibility of the technology has been demonstrated by building a 300 dpi printhead which has been incorporated into an Oce electrophotographic printer.