Dual-resolution encoding system for high cyclic accuracy of print-medium advance in an inkjet printer
First Claim
1. Apparatus for controlling print-medium advance in a raster scanning device such as an inkjet printer;
- said apparatus comprising;
means for engaging and advancing such a print medium;
first position-monitoring means, coupled substantially directly to the engaging-and-advancing means, for providing a first electronic signal representing position of the engaging-and-advancing means;
means for providing a mechanical advantage, said mechanical-advantage means being coupled to the engaging-and-advancing means and having an element that moves in approximate correspondence with motion of the engaging-and-advancing means, but said element also having a mechanical advantage relative to the engaging-and-advancing means;
second position-monitoring means, coupled substantially directly to said element of the mechanical-advantage means, for providing a second electronic signal representing position of said element; and
digital electronic means for receiving the first and second electronic signals and combining them to obtain hybrid information representing position of the engaging-and-advancing means.
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Accused Products
Abstract
The invention uses two very inexpensive rotary encoders in combination--a close-coupled one (or more) for high accuracy, and a remote-coupled one for high resolution. High-accuracy information is then combined with high resolution information in a digital processing system to yield composite information that is high in both accuracy and resolution. This information can be used to establish image positioning on a print medium. The overall system cost is lower than with an equivalent single encoder. Insidious cyclical errors in the coupling system (gear train or the like) are removable without expensive high tolerances and assembly or test fixtures. Residual cyclical error due to eccentric mounting or other error in the direct-coupled encoder scale also can be substantially removed, if desired, by adding another one or more encoders reading that scale, and suitably combining the information about that scale from the different sensors. The information is combined in such a way that the systematic cyclical errors cancel--or are quantified for use in explicit correction.
79 Citations
17 Claims
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1. Apparatus for controlling print-medium advance in a raster scanning device such as an inkjet printer;
- said apparatus comprising;
means for engaging and advancing such a print medium; first position-monitoring means, coupled substantially directly to the engaging-and-advancing means, for providing a first electronic signal representing position of the engaging-and-advancing means; means for providing a mechanical advantage, said mechanical-advantage means being coupled to the engaging-and-advancing means and having an element that moves in approximate correspondence with motion of the engaging-and-advancing means, but said element also having a mechanical advantage relative to the engaging-and-advancing means; second position-monitoring means, coupled substantially directly to said element of the mechanical-advantage means, for providing a second electronic signal representing position of said element; and digital electronic means for receiving the first and second electronic signals and combining them to obtain hybrid information representing position of the engaging-and-advancing means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
- said apparatus comprising;
Specification