Hewlett-packard Company

Hewlett-packard Development Company, L.P.

Konica Corporation

Jeffrey L Trask

Brian E Hoffmann

Hiroyuki Honda

Marcus A Smith

Kenji Sato

Qian Lin

Yukio Okamoto

Gary Lee Vondran, Jr

David Alan Johnson

Steve A Jacob

Richard Lee Swantner

Kenneth Eugene Heath

George Bernhard Clifton

Richard H Benear

Mikihiko Takada

James A Kazakoff

David S Pitou

Rulon Gregory Esplin

Andrew LeVake

Rulon G Esplin

Marcus A La Barre

Roger D Archibald

A method for printing images on at least one substrate using an apparatus having a plurality of print modes, wherein at least one of the print modes is a monochrome printing mode and another of the print modes is a color printing mode, the method comprising: printing a first portion of the images in a first of the print modes; determining whether the images being printed in the first mode meet a predetermined criteria; switching the apparatus into a second of the print modes when the images then being printed in the first print mode meet the predetermined criteria; and printing a second portion of the images using the apparatus in the second of the print modes after the switching.

Printing device and method for switching between monochrome and color modes

According to one embodiment, a scanning system includes a first light source configured to emit a first light beam, a second light source configured to emit a second light beam, a first sensor configured to detect a position of at least one of the first and the second light beams with respect to a photoconductor, a second sensor configured to provide positional information of a transfer system, and a control system coupled with the first sensor and the second sensor and configured to select one of the first light source and the second light source to form a first scan line of a latent image on the photoconductor responsive to output of the first sensor and the second sensor.

Scanning system

Methods and arrangements are provided to apply trapping techniques to print image data prior to printing. The trapping techniques employ a trapping process that is designed to detect edges between different color regions that are susceptible to gap/halo formation due to registration errors. The trapping process selectively modifies the print image data associated with the color regions near the edge to provide an overlap of color planes that significantly reduces the potential for gap/halo formation in the subsequently printed image. The trapping process buffers an array of print image data, categorizes the print image data in the array by color, detects if an edge exists in the array based on the categorized colors, and selectively modifies print image data associated with the edge based on neighboring print image data. The modified print image data can then be used to print out the image.

Trapping methods and arrangements for use in printing color images

A system provides a halftone image having reduced moire patterns by applying a screen function of the type having a first function exhibiting symmetry about a point and a second function exhibiting symmetry about a line. In a progression of tone levels, such a screen function creates first dots, then lines, then dots. For example, a screen function may include the sum of a first function of the type (1&minus;cos(pi*(x&plus;y))*cos(pi*(y&minus;x))) and a second function being a piecewise linear function of x, where &lcub;x,y&rcub; is a coordinate location in a unit cell mapped to a halftone cell mapped to the image pixel grid. In other embodiments, a unit cell is defined on the grid by a vector. The vector has a component along an axis of the grid. The component has a noninteger length. Unit cells of the type so defined implement rational tangent angles not possible with conventional halftone cells.

System providing hybrid halftone

A color mapping scheme is provided which enables a K-only black point while minimizing interpolator image artifacts. Specifically, a system and method of reducing image artifacts for a color imaging device include implementing a color map so that no C, M or Y color value that is used in defining the black point is produced, except at the black point. The system and method further include implementing a halftone ramp so that: (i) a halftone pattern is selected to provide no rendering for any C, M or Y color value that is used in defining the black point, and (ii) a halftone pattern is selected to provide a full rendering for any K color value that is used in defining the black point. The color map is also implemented so that no C, M or Y color value that is used in defining the black point is obtained as a result of interpolation, except for at the black point.

Imaging device and method for implementing a color map with K-only black point while reducing interpolator artifacts

A test page, system, and method are used to set a color density level of a laser printer, by producing a dot gain test pattern. The laser printer has at least one primary color. The dot gain test pattern is self-indicating and thus requires no external reference in order to determine a correct color density level. A preferred embodiment of the dot gain test pattern includes (a) a stable pattern having a color density which is stable with respect to changes in the laser printer operating conditions, and (b) a sensitive pattern having a color density which is sensitive to changes in the operating conditions, wherein the sensitive pattern in reference to the stable pattern indicates the density level of the laser printer for the at least one primary color. Additionally, in a preferred embodiment, the stable pattern includes a uniform coarse dot pattern, and the sensitive pattern includes a gradient of fine dot densities, the gradient printed adjacent to the coarse dot pattern, wherein a correct density level of the laser printer for the at least one primary color is indicated when a mid-spectrum area of the fine dot gradient appears to blend into the coarse dot pattern.

Self-indicating test page for use in setting density level and color

A print apparatus performs a halftoning action on a raster pixel image. The print apparatus includes a super-pixel data base for storing plural n.times.n superpixels, each superpixel corresponding to a subset (or 'bucket') of gray level pixel values. The method comprises the steps of: logically tiling a dither matrix across the raster pixel image and outputting a threshold value which, logically and positionally corresponds to a given image pixel value. The given image pixel value is then quantized into a selected bucket of pixel values which encompass the given image pixel value. A proportionality value is then determined which identifies the relative position of the given image pixel value within the selected bucket of pixel values. The outputted threshold value is then compared to the determined proportionality value, and the selected bucket number is incremented to a next sequential bucket number if the proportionality value exceeds the threshold value. A superpixel is next selected that is identified by the selected bucket number or the next sequential bucket number, as the case may be. A superpixel includes plural halftone pixel values and the method selects one of those halftone pixel values that is positioned at a location determinable from the coordinates of the given image pixel value. The selected halftone pixel value from the superpixel is then passed to the print engine of the printer for rendering. The method of the invention is carried out, preferably, by an application specific integrated circuit so as to enable high speed halftoning of the raster image.

Resolution enhancement procedure and apparatus for a color laser printer

A lockout mechanism for preventing an operator from filling a toner hopper in an electrographic printing device until the hopper is at least empty enough to accept the entire contents of a toner cartridge. An interlock mechanism takes advantage of the already existing selector shaft to selectively de-activate lockout members in response to a low toner level transducer. The printing device includes a plurality of tones hoppers. Each provided with a lockout member which is pivotable between a locked out position and a refill position. The locked out position has the lockout members interfering with a connection between toner cartridges and the top of toner hoppers. The lockout members are held in their locked out positions by cam follower members, which are slidable between an upward locked out position and a downward refill position. The slider member interacts with the cam follower members, via follower pins and notches, to lock the cam follower members in their upwards position or to allow them to move down against the selector cams.

Toner hopper lockout mechanism

Fine pulse width modulation (PWM) adjustments in the output of a laser printer are accomplished by receiving values from a bit map and modifying the values in accordance with values in a lookup table (LUT). The lookup table is subdivided into a plurality of blocks, and a selection of the blocks is made in accordance with external values. This allows the output of a pulse width modulation circuit to be adjusted to a precision that is greater than that afforded by the bit size of the values from the bit map. The use of plural blocks in the lookup table permits adjustments in the output of the pulse width modulation circuit in accordance with external factors such as relative humidity, sensitivity of an optical photoreceptor, and developer life.

Adjustment of dot size for laser imagers

A software/firmware based method for determining gray level values to be assigned to a binary pixel image initially creates a linked list of templates, each template associated with a gray level value to be assigned to an image pixel value. Each template may include a central pixel value and plural neighbor pixel values or just plural neighbor values. However, each template is a listing of entries of template pixel values that are generally arranged in increasing concentric circles about the central pixel value. Each template entry includes a field for a template pixel value, a field for a template pixel address and a link field for a next template entry, in the event of a non-match determination between the associated template pixel value and an image pixel value. The method selects an image pixel window from the binary image and compares a central image pixel in the window with a logically, correspondingly located template pixel value. If a match is found, a next image pixel is compared against a next template entry to determine if a match occurs. This procedure continues, assuming matches are found, until all entries in the template have been tested and found to match, in which case, the central pixel of the image pixel window is changed in accordance with the gray level value associated with the matching template. If, at any time, a non-match occurs, the procedure moves to a linked template entry and the comparison procedure continues in another template. The invention enables a binary search to be executed which identifies a matching template (if any) after considering, on the average, between 5 to 10 entries.

Software-based procedure and apparatus for enhancement of a gray level

Since the first cleaning member 24g scrapes off the foreign materials adhered to the corona charging electrode, and following that, the second cleaning member 24h wipes off the scraped foreign materials, the layered foreign materials firmly adhered on the corona charging electrode 22 is removed. Accordingly, image formation in electrophotographic apparatus or the like is suitably carried out, and image quality deterioration of the recorded image is suppressed.

Corona charging apparatus

A binary pixel bitmap image is converted to a multi-bit gray level pixel image at a level of resolution that is reproducible by a laser printer. An edge smoothing procedure is employed by the laser printer and comprises the steps of: deriving from font contours of the image, a binary pixel bitmap of the image at a higher level of resolution than is output by the laser printer; logically stepping an m.times.n pixel window across pixel groups of the higher resolution binary pixel bitmap and, at each step, determining a count of pixels of one binary kind that are present within the pixel window; converting each count of pixels to a corresponding modulation signal; and controlling a laser in the laser printer in accordance with each modulation signal so that an edge smoothed gray level image is produced at the printer's level of output resolution.

Software-based procedure for conversion of a scalable font character

A lockout mechanism for preventing an operator from filling a toner hopper in an electrographic printing device until the hopper is at least empty enough to accept the entire contents of a toner cartridge. An interlock mechanism takes advantage of the already existing selector shaft to selectively de-activate lockout members in response to a low toner level transducer. Each hopper is provided with a lockout member which is pivotable between a locked out position and a refill position. The locked out position has the lockout members interfering with a connection between toner cartridges and the top of toner hoppers. The lockout members are held in their locked out positions by cam follower members, which are slidable between an upward locked out position and a downward refill position. The slider member interacts with the cam follower members, via follower pins and notches, to lock the cam follower members in their upwards position or to allow them to move down against the selector cams.

A multi-color, electrostatic, laser printing system employs a method for enhancing color representations at boundaries of pixels with different colors. The system employs a charged electrostatic surface that is selectively discharged by application of a modulated laser beam. The system performs the steps of: identifying a pixel of a first color that bounds a pixel of a second color, the first color being a secondary color; decreasing applied laser power to the electrostatic surface at the secondary color pixel site in the process of applying underprint and overprint toners to produce the secondary color; and inhibiting the decrease of applied laser power when applying the overprint toner if the second color pixel is a primary color that is the same as the color of the overprint toner of the secondary color pixel. A similar inhibition action occurs when an isolated primary color pixel or a thin pixel line is found so as to assure proper development.

Color boundary enhancement in a multi-color electrostatic printer

A printer produces single and double sided images in correct page order using identically oriented sheets. An imprinting path is provided with mechanisms for transferring an image to one side of the sheet. The printer also has a sheet side reversing path that communicates with the imprinting path, and an output path. The printer includes first and second direction reversing paths that communicate with the imprinting path, the first direction reversing path further communicating with the sheet-side reversing path and the second direction reversing path communicating with the output path. A path selection apparatus is operable, when the printer is to imprint a double-sided image, to direct a sheet initially to the first direction reversing path after an image has been imprinted on one side thereof, and to direct the sheet to a second path after a second image has been imprinted on a second side thereof, whereby the sheet is directed to the output path after the second imprinting operation.

Growing community of inventors

Boise, ID, United States of America

Jeffrey L Trask