摘要:
A hybrid halftone cell selection method enables selection of gray levels in halftone printing algorithms to minimize the effects of noise resulting in nonuniformities, such as, for example, halftone banding. The method requires selection of hybrid halftone cells possessing structures wherein the total number of gray pixels are limited. The number of gray pixels having any given intermediate reflectance level in any halftone cell is also limited. The cell selection method thus reduces the number of TRC gray steps to some minimum required number by eliminating the most noise sensitive cells (i.e. those cells having the highest percentage of gray level pixels). The intermediate reflectance values of the gray pixels in the selected cells are then selected to produce uniform gray steps and reduce variability in the TRC.
摘要:
A pulsed imaging Raster Output Scanner utilizes pulse width modulation in conjunction with spatial filtering to form three exposure levels at the surface of a recording medium, one of the levels associated with a specific color.
摘要:
A multi-beam laser ROS print system is described which is adapted to minimize banding in output prints. Multiple beams from a laser source are separated by a distance which causes the beam to scan consecutive lines in a non-consecutive scan; e.g., according to a particular beam interlacing sequence. It has been found that as a general proposition, banding decreases with increasing interlacing orders and, furhter, that once a print system error frequency, or another frequency of interest has been identified, there are a number of interlacing orders, each an optimum value, which can be introduced to reduce banding which would ordinarily result from the particular frequency error.
摘要:
A printing system employing a raster output scanning device is compensated for the effects of motion of the medium upon which an image is being printed. An amplitude transmittance spatial filter is positioned either in an exit pupil of the "slow scan" optics of the system or in the first Fourier transform plane of a lens positioned between the scanning device and the recording medium. Several preferred transmittance functions are provided.
摘要:
The methods and apparatus of this invention model and reconstruct binarized images. A grayscale image is modeled using a template matching approach. Each binarized grayscale image value is characterized by a unique set of templates which are rotations of each other. The set of templates allows construction of a look-up table between patterns and grayscale values. The look-up table is provided with a limited number of entries. As a result, the number of entries in the look-up table is reduced. The look-up table thus obtained is used for reconstructing the original grayscale image from the binarized image. The generated image quality is good in comparison with conventional methods. The process may be applied to various halftoning processes including error-diffusion processes.
摘要:
A method and apparatus for automating the design of morphological or template-based filters for print quality enhancement. A plurality of different phase, but same resolution, subsampled images are generated from training documents. Statistical data derived therefrom is then employed in an automated process to generate filters. The filters may be used for resolution enhancement and/or conversion of bitmap images. Furthermore, the statistical data is used to produce filters that are intended to not only optimize image structure, but image density as well.
摘要:
A multiple diode laser array used in a ROS scanning system is modified to reduce the effects of undesirable spatial exposure variation at the surface of certain type of layered, semi-transparent photoreceptors. The spatial absorption variation is later manifested as a "plywooding" pattern formed on output prints derived from the exposed photoreceptor. The laser array is modified to form a merged scanning beam at the photoreceptor surface of two or more diode outputs, each output operating at a different wavelength than the other. In one embodiment, a plurality of diodes, each at a different wavelength, are sequentially addressed, and an image of each diode is scanned across the photoreceptor which results in an exposure distribution that would be similar to that formed by an incoherent beam.
摘要:
In an electronic printer which utilizes an image write bar, a control circuit is provided to compensate for the effects of vibration in a rotating photoconductive member, typically a photoreceptor drum. In one embodiment an encoder is positioned so as to detect spatial displacements of indicia affixed to the photoconductor surface, Correction signals are generated and sent to control circuits which adjust the on/off timing of the write bar operation and/or the intensity of the image bar output. This adjustment results in compensation for the effects of photoconductor vibration.
摘要:
A document feeder is provided for presenting documents to the platen of a copier for copying with a vacuum belt platen transport system having document transporting belts movable under a substantially planar vaccum plenum backing. Also included is a vacuum system for applying a partial vacuum to a document sheet being transported by the movable belts over the platen. Show-through and show-around problems are reduced by optically mtching the belts and the plenum backing. In the preferred embodiment, the background surface is slightly roughend and made to be approximately 92% reflective to light during image exposure. The belts are composed of a urethane material which is approximately 16% transmissive but provides a 91% reflectance when moving along the plenum surface.
摘要:
A gradient index lens array having improved stray light characteristics is enabled by coating the surfaces of the fibers comprising the array with a low transmittance, low viscosity material. The index of this material is matched to that of the fiber surface to prevent Fresnel reflection. The interstitial areas of the lens array comprises a light absorbing material. In another embodiment, stray light caused by light scattering at the end faces of the lens array is reduced by masking the end face with a mask having apertures overlying the fiber faces. The mask apertures have slightly smaller diameters to mask out the rough outer edge of the fibers.