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The single mirror interferometric MEMS display is a full-color, daylight-visible, video-rate reflective display with high brightness that consumes power only during content updates. It consists of an array of identical pixels each of which can produce a continuous range of colors through precise analog positioning of one moving element, a mirror. Electrostatic actuation is driven with an integrated active-matrix backplane of indium-gallium-zinc oxide thin-film transistors. Displays of 384 × 384 pixels built on a surface micromachining process on glass substrates have been demonstrated on both 6-in wafers and Gen 4.5 panels (730 mm × 920 mm) showing good yield and uniformity.

In the above paper [1] , Figs. 1 – 3 , 10 , 15 , 28 , and 30 – 31 were inadvertently printed in black and white. The color figures are as follows.

In this paper, a QR code is presented with a dual resolution structure. It contains a high resolution layer that is coded in luminance and is in consistency with the conventional QR code, and a low resolution layer providing additional error checking information, that is coded in chrominance and is robust to blurring. The proposed QR code is compatible to its underlying conventional black and white barcode as it can be read by their decoders. Its advantage is additional reliability when a color decoder is used. In particular, it enhances the decoding accuracy for devices such as mobile devices for barcodes printed in small sizes.

A method is provided for embedding a UV fluorescent watermark in a color halftone image printed on paper. The described method implements two different strategies to halftone a watermark region and a background region. One strategy uses dot-on-dot halftoning to maximize the usage of black ink and minimize ink dispersion, while the other strategy uses successive-filling halftoning to maximize ink dispersion. An accurate color look-up-table (LUT) is built to directly transform the colorant values for one halftoning strategy to the colorant values for the other strategy. With the color transformation applied on one region, the binary outputs in both watermark and background regions halftoned with different strategies exhibit similar color appearance under normal lighting condition. However, under UV illumination, due to the fluorescent effect caused by different paper coverages in two regions, the embedded watermark becomes clearly visible.

A halftone configuration is presented that utilizes three or four rotated hexagonal screens, or more precisely, screens with hexagonally tiled clusters, for moire-free color printing. Halftone designers consider many options to deliver a screen with desirable characteristics, and often must settle for less than desirable results. The present method presents a new option with several beneficial properties compared to conventional square-cell-based screens. Hexagonal screens can appear to have smoother texture. Due to differences in packing geometry and touch point geometry, hexagons have the potential to possess different tone reproduction characteristics, which may be favorable for some marking processes. A fourth screen (e.g., yellow) can be included moire-free, thereby avoiding problems associated with stochastic solutions for yellow. We also present a corresponding parametrically controlled hexagonal halftone spot function that allows for optimization of dot touch points and provides compact growth. The optimized touch points can prevent a tone reproduction bump, while the compact growth throughout the gray range ensures maximum stability. Examples are provided.

While diffraction-pattern sampling has been widely applied in the classification of patterns, still its usage has been limited somewhat by the need to devise rather sophisticated algorithms. In this paper we describe sorting or classification of a variety of patterns with commercially available neural-network software together with the ring-wedge photodetector to supply optical transform data for the input neurons. With this combination of neural networks and diffraction-pattern sampling it is no longer necessary to write specialized software. The training and testing methodology is carried out for this new system, and excellent results are obtained for sorting thumbprints. In sorting thumbprints the neural network can be trained for orientation-independent or wide-scale size-independent classifications by use of ring-only or wedge-only input neurons, respectively. Separate experiments are described for the sorting of particulates. Again, these are cases in which writing appropriate software based on diffraction theory would be extremely difficult. Two interesting novel neural networks are obtained: one is for real-time control of a submicrometer colloidal suspension of CdS, and the second is for concentration measurements of 2.02-µm polyvinyltoulene spheres in methyl alcohol. Widespread new applications are predicted for this hybrid system that combines diffraction-pattern sampling and the neural network.

Color printer calibration is always performed in the presence of noise. A major part of this noise is due to the spatial non-uniformity of the printer. In many cases, the spatial non-uniformity does not repeat the same pattern page by page. Some calibration techniques use randomizing the locations of patches and averaging a large numbers of measurements to reduce the noise. Since the non-uniformity is a kind of systematic errors, it should be estimated and corrected in a more effective way. This presentation describes a method to provide a more accurate color calibration/characterization result by estimating the spatial non-uniformity presented on the printed target page and applying a correction to the very same page itself. Instead of defining the noise in the color measurement space, e.g. the CIE Lab space, the new method specifies the noise in the printer-dependent color space, e.g. the CMY space. After the first-round color calibration, an inverse transform, from CIE Lab to CMY, is derived from measurements of the entire printed target. The noise dC, dM, or dY is determined as the difference between the original CMY values and the output of the inverse transform with the measured Lab values as the transform input. Since color patch locations are stochastically arranged, any "noticeable" spatial pattern of the noise is most likely due to the printer non-uniformity in the corresponding channel. The nonuniformity can be estimated by spatially smoothing the noise terms and the result can be subtracted from the original CMY input for a second-round calibration to achieve higher color accuracy.

Color printer calibration is the process of deriving correction functions for device CMYK signals, so that the device can be maintained with a fixed known characteristic color response. Since the colorimetric response of the printer can be a strong function of the halftone, the calibration process must be repeated for every halftone supported by the printer. The effort involved in the calibration process thus increases linearly with the number of halftoning methods. In the past few years, it has become common for high-end digital color printers to be equipped with a large number of halftones thus making the calibration process onerous . We propose a halftone independent method for correcting color (CMY/CMYK) printer drift. Our corrections are derived by measuring a small number of halftone independent fundamental binary patterns based on the 2×2 binary printer model by Wang et. al. Hence, the required measurements do not increase as more halftoning methods are added. The key novelty in our work is in identifying an invariant halftone correction factor (HCF) that exploits the knowledge of the relationship between the true printer response and the 2×2 predicted response for a given halftoning scheme. We evaluate our scheme both quantitatively and qualitatively against the printer color correction transform derived with the printer in its "default state". Results indicate that the proposed method is very successful in calibrating a printer across a wide variety of halftones.

Reflective displays that rely on ambient light as opposed to an internal light source have been making inroads for a variety of important applications, especially those involving mobility where power usage must be aggressively controlled. The underlying color rendering strategies for both reflective and emissive displays have largely been the same, combining three fixed, primary color subpixels to compose the rich gamut that users expect. The result, for reflective color displays, is unfavorable brightness/gamut performance since each of the color subpixels absorbs roughly 2/3 of the incident white light. We demonstrate a new technology that we call the single mirror interferometric display that overcomes such limitations with pixels whose reflectance properties can tune through a continuum of colors, including high contrast black and white reflectance states. We use an effect that we call interferometric absorption in which a thin absorbing metal layer in front of a highly reflective mirror surface selectively absorbs different colors, depending on the gap that separates the two. The gap is controlled by electrostatic actuation in a relatively simple micro-electro-mechanical-system structure. We describe this elegant and powerful color rendering principle and present experimental results for the basic pixel device as well as early system demonstrations.

Glossmark technology is a halftone-based digital imaging process to embed visible watermarks into xerographic color prints. The gloss of a xerographic print depends not only on surface roughness of paper and toner, but also on the microscopic structure created by the halftone process. The surface relief of a halftone image can be treated as a two-dimensional phase grating. The shape, or profile, of the surface relief determines the reflected pattern of the illumination. A strong angular differential gloss can be obtained by employing two anisotropic halftone screens in the halftone process. A careful design of these screens enables embedding Glossmark images while maintaining the high quality of the color reproduction. The printing process, that simultaneously creates high quality primary and Glossmark images in a single step, requires neither special equipment nor special paper or toner. Glossmark images, shown in a high contrast of gloss, provide a perfect simulation of the traditional paper watermarks, while their digital implementation makes it easy to embed variable data as digital watermarks into individual documents.

A new technique for design of stochastic screens is proposed that produces screens that are robust against mis-registration in multi-pass printing. Conventional stochastic screens are designed through an optimization process that minimizes low-frequency structure in halftone images under the assumption that the placement of pixels is accurate. In inkjet printing, however, a page is often printed in multiple passes to allow for better drying of inks and to minimize appearance of a head signature. Any potential mis-registration between the passes is typically not comprehended in the conventional stochastic screen design process. The mis-registration between the passes can therefore cause significantly increased graininess (low-frequency structure) in printed images produced with stochastic screens even though the corresponding electronic bitmaps are free from low-frequency structure. In this paper, we propose modifications to the stochastic screen design process that take the two pass printing into account and produce halftones that are robust to inter-pass mis-registration errors. This allows reduced tolerances and alignment requirements in manufacturing that translate to lower cost. The proposed technique works by modifying the screen design process to ensure that a majority of the minority pixels are concentrated in a single pass, which provides improved robustness to mis-registration between the passes. Experimental results demonstrate that the proposed design technique performs significantly better than conventional stochastic screens in the presence of mis-registration errors.

In color reproduction, the most troublesome moire pattern is the second-order moire, or the three-color moire, usually produced by mixing of cyan, magenta and black halftone outputs. A classical 3-color zero-moire solution is using three identical cluster halftone screens with different rotations: 15, 45 and 75°, respectively. However, for most digital printing devices, the size and shape of halftone screens are constrained by the "digital grid", which defines the locations of printed dots; and therefore, an exact 15 or 75° rotation of a cluster screen is impossible. Although there are many alternative approaches for moire-free color halftoning, most of them only provide approximate solutions and/or have a tendency to generate additional artifacts associated with halftone outputs. The difficulty to achieve moire-free color halftoning is greatly relieved by using non-orthogonal halftone screens, i.e., screens in general parallelogram shapes. In this paper, a general condition for 3-color zero-moire solutions is derived. A procedure using integer equations to search moire-free solutions for different applications is also described.

In most existing color reproduction systems, color correction is performed in an open-looped fashion. For multiple generation color copying, color fidelity cannot be guaranteed as the errors introduced in color correction may accumulate. In this paper, we propose a method of solving the error accumulation problem by embedding color information as invisible digital watermark in hardcopies. When the hardcopy is scanned, the embedded information can be retrieved to provide real-time calibration. As the method is close-looped in nature, it may reduce error accumulation and improve color fidelity, particularly when copies go through multiple generation reproduction.

We present a stochastically seeded, clustered halftoning method with parametric control of dot shapes as well as seed placement adaption to local image structure. While the literature on other randomly structured screens (blue noise, green noise, and stochastic halftoning) is quite extensive, there is very little discussion on optimization of dot shape for robustness or preferred tile appearance. The parametric control presented here can enable an imaging engineer to optimize robustness for a given printing system. The halftoning method that we introduce defines dot centers as seeds that are placed typically in a random, high spatial frequency configuration. Spot functions are defined about these randomly placed seeds, where the spot function allows control of dot cluster growth, touch points, cluster angle, and eccentricity. The spot function can also be applied to regular and irregular polygonal halftone tiling. The adaptability of the seed placement provided by the halftoning method allows for better edge rendition than conventional isotropic methods and enables the implementation of data-embedding techniques. The resulting monochromatic screens can be seamlessly integrated with novel successive filling techniques in order to provide dot-off-dot vector halftoning capabilities.