Optics: measuring and testing – By alignment in lateral direction
Reexamination Certificate
2000-12-15
2002-12-10
Le, Thien M. (Department: 2876)
Optics: measuring and testing
By alignment in lateral direction
C356S121000
Reexamination Certificate
active
06493083
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a digital rendering system and, more particularly, to an apparatus and improved method for measuring color registration and determining registration error in a multicolor marking platform.
BACKGROUND OF THE INVENTION
A digital rendering system renders a digital image, consisting of electronic pixel data, to a human readable version of the image. Digital rendering systems typically include: 1) an input section, sometimes referred to as an image input terminal (“IIT”) or a digital front end (“DFE”), 2) a controller, sometimes referred to as an electronic subsystem (“ESS”) or an image processing system (“IPS”), and 3) an output section, sometimes referred to as an image output terminal (“IOT”).
The input section either generates or translates one form of image data to digital image data that can be provided to the controller. The input section can be a scanner, individual computer, distributed computer network, electronic storage device, or any device capable of generating or storing the digital image. The controller processes the digital image data to create machine readable image data that is compatible with the output section. The controller also controls operations within the output section. The output section receives machine readable image data from the controller and produces a human readable version of the digital image. The output section can be a display device (e.g., cathode ray tube (“CRT”) monitor), marking platform (e.g., copier or printer), electronic storage device, or any device capable of producing a human readable image. For marking platforms, the output section is sometimes referred to as a print or marking engine. Again in reference to marking platforms, the human readable image is created by depositing marking material on a print page. The print page is often a single sheet of white paper, however, numerous other materials are available. Two technologies commonly used in marking platforms are ink marking and toner marking. Ink-jet printers and offset printing presses are common examples of platforms that implement ink marking technology. Marking platforms that use toner marking include electrophotographic printers, copiers, and multifunction peripherals. Toner marking is also known as electrophotographic marking.
Generally, electrophotographic marking employs a charge-retentive, photosensitive surface, known as a photoreceptor. The photoreceptor is a photoconductive region on the surface of a rotating drum or moving belt. The photoconductive region may only have one imaging region or there may be multiple imaging regions, particularly for the belt. The electrophotographic process begins by applying a uniform charge to the photoreceptor. In an imaging and exposing step, a light image representation of a desired output is focused on the photoreceptor and discharges specific areas of the surface to create a latent image. In a developing step, toner particles are applied to the latent image, forming a toner or developed image on the photoreceptor. This toner image is then transferred to a print page. The toner particles are heated to permanently affix the toner image to the print page. Finally, the photoreceptor passes through a cleaning step to prepare it for another electrophotographic cycle.
The electrophotographic marking process outlined above can be used to produce color as well as black and white (monochrome) images. Generally, color images are produced by repeating the electrophotographic process to print two or more different image layers or color image separations in superimposed registration on a single print page. Commonly, full color copying or printing is provided by subtractive combinations of cyan, magenta, and yellow toner. Such color mixing to produce a variety of colors is called process color separation. To produce black, a combination of equal amounts of cyan, magenta and yellow toner layers are mixed, or a fourth black color toner layer may be used as a substitute. To extend the color gamut of the process color output, as in high fidelity copiers or printers, additional colors of toner (e.g., red, green, blue, or a customer-selectable color) may be used in combination with the three or four color separations. Alternatively, where the additional colored toner is not mixed with the process colors, referred to as spot color separation, the additional toner image layer is used to set off certain portions of text or graphics in the composite full color image. Color images can also be produced with two colors, such as black and red, by a highlight color copier or printer. Highlight color copying or printing can use process color separation to produce images similar to halftone or gray-scaled images or spot color separation to produce images with the two colors unmixed.
A multicolor electrophotographic process may be accomplished by either a multiple pass or single pass marking engine. Marking platforms with a multiple pass marking engine require less hardware and are generally easier to implement than systems with a single pass marking engine. However, systems with a single pass marking engine provide much greater throughput.
A multiple pass marking engine uses multiple cycles of the electrophotographic process described above, one cycle for each color separation. During each cycle, a toner image layer for one color separation is formed on the photoreceptor and transferred to an intermediate substrate or to the print page. In the multiple pass architecture described, the composite color image is accumulated on the intermediate substrate or the print page in successive electrophotographic cycles. In the case where the image is accumulated on an intermediate substrate, the composite toner image is transferred to the print page and then fused. In the case where the composite toner image is accumulated on the print page, the composite toner image is fused after the last color separation is transferred. In an alternate multiple pass architecture, the composite color image is accumulated on the photoreceptor in multiple cycles and, after the last toner image layer is developed on the photoreceptor, the composite toner image is transferred and fused on the print page.
A single pass marking engine employs multiple charging, imaging and exposing, and developing devices, one set for each color separation. In the single pass architecture, each color separation device set sequentially applies a toner image layer to the photoreceptor. Within each color separation device set, the electrophotographic steps of charging, imaging and exposing, and developing occur as described above. The composite color image is accumulated on the photoreceptor in a single electrophotographic cycle in the single pass marking engine. The composite color image on the photoreceptor is then transferred and fused to the print page.
Another type of single pass marking engine, often referred to as a tandem architecture, employs multiple photoreceptors in addition to the components of the previously described single pass marking engine. In the tandem architecture, each color separation has a set of charging, imaging and exposing, developing, and photoreceptor devices. Additionally, an intermediate transfer belt in the tandem architecture accumulates the individual toner images in a composite image in a manner not unlike the single photoreceptor in the previously described single pass architecture. Each photoreceptor sequentially transfers a toner image layer to the image area on the intermediate transfer belt. The composite color image is accumulated on the intermediate transfer belt in a single electrophotographic cycle and then transferred and fused to the print page.
While the color imaging techniques described above are discussed primarily in reference to electrophotographic marking, they are also applicable to ink marking and any other type of marking platform that creates a composite multicolor image by combining multiple color separation layers. In multicolor marking platforms that form and transfer individual color
Dirkx Michael P.
Parisi Michael A.
Fay, Sharpe, Fagan Minnich and McKee, LLP
Le Thien M.
Xerox Corporation
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