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Color registration test patternRelated Patent Categories: Printing, Processes, Position Or AlignmentColor registration test pattern description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060191437, Color registration test pattern. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present embodiments relate generally processes of registering the printed images created from multiple single-array ink jet print heads. The present embodiments relate more particularly to an innovative method of visibly exposing and quantifying the amount of registration error, continuously, by means of the printed image itself. BACKGROUND OF THE INVENTION [0002] Continuous ink jet printing systems are known to be of use in the industry of high speed digital printing. In many installations a plurality of ink jet print heads are arranged inline over a web of paper to produce multi-color images in a single pass. In a typical printing system, to facilitate the digital printing process the ink jet print heads generate an array of micro-droplets of ink in the cross-web direction at a resolution of 300 drops per inch and at a rate of 100 Khz. The timing of the release of each cross-web pixel of droplets is computer synchronized to tachometer pulses received from the web transport system such that pixels will be released (printed) at a resolution of 300 or 600 drops per inch in the web travel direction. The tachometer pulses are also used to delay the printing of successive print heads such that the successive print head data will overlay (register) on top of the previous print head data; therefore, combining the two (or more) colors of ink from the print heads to achieve multi-color images. Inherently, this color-to-color registration process requires input from some expensive and complex electronic vision system or a system operator to observe the nominal registration error and then correct electronically as required to "zero" the average color-to-color registration error. [0003] In addition to the average color-to-color registration error adjustment, all web transport systems contain motor servo systems that create web speed fluctuations that result in web stretch (tension) variations which in turn equates to color-to-color registration error variation around the error average. Therefore, the need arises for good color-to-color registration measurement capability--certainly for operator ease of average adjustment but more importantly, for identifying and aiding in reducing the magnitude of error variations. [0004] Previous conventional art has led to the use of registration marks typically located at the comer(s) of each image. Marks have varied from simple lines, crosshairs, circles, or squares to combination crosshairs/circles, lines at various angles, chevron patterns, and others. While most of these approaches can be used to enable an operator to adequately adjust the average registration error near zero, the ability to use them to evaluate registration variation is marginal. Past procedures for evaluating color-to-color registration error variation in continuous ink jet printing systems utilized these marks at the corners of each image but in order to get just a minimal amount of data for statistical analysis a sample of at least 25 images would be necessary. The image registration marks would then have to be measured under magnification. At 12'' image spacing this yields registration error data for 25 pixels over of a span of 90,000 pixels--a sampling rate of about 0.03%. Additionally, multi-color text imaging printed under normal conditions has been observed to vary in registration error at multiple cycles per 12'' image. It is seen then that there is a need for a means of viewing registration error as the images are printed and at a sampling rate much greater than any error variation frequencies that may exist SUMMARY OF THE INVENTION [0005] A method for evaluating the stability of print module registration for a printer creates an innovative test pattern by forming two graphic images from two separate print modules. The graphic images include parallel graphic information and a desired intersection point. The graphic images are printed on by a pixel by pixel basis onto print media from the separate print modules. The resulting patterned image or test pattern is viewed to ascertain alignment based on the desired intersection point. [0006] Accordingly, the present embodiments provide the benefit of visibly exposing the amount of print color-to-color registration error continuously for as long as the test pattern images are being printed. The average error can, therefore, be readily discerned. More importantly, the error variation can be characterized. BRIEF DESCRIPTION OF THE DRAWINGS [0007] In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings, in which: [0008] FIG. 1 depicts a typical high-speed digital ink jet printing system usable with the embodied methods. [0009] FIG. 2 is an overall schematic of an embodiment of the method for evaluating the stability of print module registration for a printer entails forming at least two graphic images. [0010] FIG. 3 depicts a print version of a first graphic image usable in the invention [0011] FIG. 4 depicts a print version of a second graphic image usable in the invention. [0012] FIG. 5 depicts a printed version of an overlapped image with an index according to the invention. [0013] The present embodiments are detailed below with reference to the listed Figures. DETAILED DESCRIPTION OF THE INVENTION [0014] The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. [0015] The present embodiments provide a test pattern when printed with multiple ink jet printheads that visibly expose and quantify the actual in-track registration error of the two or more printheads. [0016] The pattern created by the embodied methods utilizes at least two printheads printing a repetitive stepping pattern. The first printhead prints the repetitive stepping pattern at a rate of one step per in-track pixel, or 600 lines per inch, at a cross-web width of 24 pixels, 300 lines per inch. The second printhead prints the same repetitive rate a solid single pixel line designed to overlay on top of the step pattern for the entire width of all steps. [0017] An intended overprint of the two patterns occurs at one of the 24 pixels wide steps. The overprint is identified in the step pattern by `tick` marks that are perpendicular to that step so as to visibly identify the zero error point. Each step extending in both directions from the zero steps is then identified by light `tick` marks and corresponds to one pixel of error step away from the zero steps or one half pixel of error relative to conventional 300 pixels per inch per. The resulting image from the printed pattern is a contrast between two colors with one of the colors viewed as a continuous band against the other. The center of the band relative to the stepped tracks is viewed as the actual registration error due to the design described above. [0018] The printed pattern effectively magnifies the registration error by a factor of at least 48, thereby making the error viewable on-the-fly or as printed images offline without the need of further magnification. [0019] A typical test pattern designed with this innovative method can repeat every eight pixels or 600 lines per inch, thereby giving viewable registration error data every fourth pixel over the entire image length, a sampling rate of 25%. Continue reading about Color registration test pattern... Full patent description for Color registration test pattern Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Color registration test pattern patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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