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US 6,618,494 B1Granted
Optical distortion correction in digital imaging
AssigneeWuestec Medical, Inc.
InventorsBarry A. Nonay, Cynthia G. Pachal
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Abstract
A system and method for digital x-ray imaging may correct distortion in a digital image by determining the cell size of a grid. A rotational correction may be applied to the cell to correct for distortion that might result from improper alignment between an imaging sensor used to capture the image and the image itself. Stretch factors for the pixels are calculated and applied to the cells of the grid to provide cells of consistent size. The calculated stretch factors may be applied to subsequent images to provide an efficient method for optical distortion correction.
Claims22
A method for optical distortion correction in a digital image, comprising the steps of:
- determining a size of a predetermined cell in said digital image, wherein said digital image is an image of a grid;
- applying a correction to said determined cell size to account for non-alignment between said grid and an imaging sensor utilized to capture said digital image, if said non-alignment exceeds a predetermined value;
- determining a plurality of sets of grid points of said grid;
- fitting each set of said plurality of sets of grid points to a selected polynomial to provide a plurality of equations for grid lines of said grid;
- and
- adjusting values of pixels of said digital image based on said plurality of equations for grid lines of said grid so that selected cells of said grid are of substantially the same size,
- wherein said determining said size of said predetermined cell comprises the substeps of:
- determining the distance between a first grid line in part forming said cell and a second grid line in part forming said cell utilizing a scan line, wherein said first and second grid lines are substantially parallel to each other, and said scan line is substantially orthogonal to said first and second grid lines,
- wherein said applying a correction step comprises the substeps of:
- determining a rotational angle between a third grid line of said predetermined cell and said scan line used to determine said cell size,
- wherein a corrected cell size is equal to said determined cell size times cos(theta), wherein theta is said determined rotational angle.
8 more elements
A method for optical distortion correction in a digital image, comprising the steps of:
- determining a size of a predetermined cell in said digital image, wherein said digital image is an image of a grid;
- applying a correction to said determined cell size to account for non-alignment between said grid and an imaging sensor utilized to capture said digital image, if said non-alignment exceeds a predetermined value;
- determining a plurality of sets of grid points of said grid;
- fitting each set of said plurality of sets of grid points to a selected polynomial to provide a plurality of equations for grid lines of said grid;
- and
- adjusting values of pixels of said digital image based on said plurality of equations for grid lines of said grid so that selected cells of said grid are of substantially the same size,
- wherein said plurality of equations for grid lines includes a plurality of equations for vertical grid lines and a plurality of equations for horizontal grid lines,
- wherein the number of said plurality of equations of said vertical grid lines is less than or equal to the width of said grid divided by the determined cell size,
- wherein said adjusting step comprises the substeps of:
- determining a vertical center of said image by dividing the width of said image by two;
- measuring the distance between a first vertical grid line and a second vertical grid line, wherein said first and second vertical grid lines are on either side of a third line passing through said vertical center, wherein said first vertical grid line, said second vertical grid line and said third line are substantially parallel to each other;
- and
- calculating a horizontal stretch factor value, wherein said horizontal stretch factor value is given by the equation:
- horizontal stretch factor value=desired cell size/measured distance.
11 more elements
A method for correcting distortion in a digital image, comprising the steps of:
- determining a plurality of stretch factors to be applied to pixels of said digital image, wherein each of said plurality of stretch factors is associated with a particular portion of said digital image;
- storing said plurality of stretch factors in a mapping file associated with a processor based system;
- and
- adjusting values of pixels of said digital image based on said stored values,
- wherein said determining a plurality of stretch factors step comprises the substeps of:
- determining a size of a preselected cell in a digital image of a grid;
- applying a correction to said determined cell size to account for non-alignment between said grid and an imaging sensor utilized to capture said digital image of said grid, if said non-alignment exceeds a predetermined value;
- determining a plurality of sets of grid points of said grid;
- and
- fitting each set of said plurality of sets of grid points to a selected polynomial to provide a plurality of equations for grid lines of said grid,
- wherein said plurality of equations for grid lines includes a plurality of equations for horizontal grid lines,
- wherein said determining a plurality of stretch factors step further comprises the substeps of:
- determining a horizontal center of said image by dividing a height of said image by two;
- measuring the distance between a first horizontal grid line and a second horizontal grid line, wherein said first and second horizontal grid lines are on either side of a third line passing through said horizontal center, wherein said first horizontal grid line, said second horizontal grid line and said third line are substantially parallel to each other;
- and
- calculating a stretch factor value of said plurality of stretch factor values, wherein said stretch factor value is given by the equation:
- stretch factor=desired cell size/measured distance.
14 more elements
Dependencies are inferred from the claim text.