Method for scanning the surface of an object
First Claim
1. A method of digitising a surface of a workpiece comprising the steps of:
- scanning the surface with a probe to produce a digitised coordinate data signal representing coordinates of a plurality of points on the workpiece surface; and
filtering said coordinate data signal to reject portions of said coordinate data signal representing some of said points, wherein the filtering step comprises the steps of;
selecting portions of said coordinate data signal representing first, second and third points, produced in that order, on the surface,creating a vector extending from the first point through the third point,determining whether said vector lies within a predetermined tolerance distance from the second point, andremoving the portion representing the second point from said coordinate data signal to reject the second point if said vector lies within said tolerance distance.
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Accused Products
Abstract
A workpiece surface 30 is digitized by scanning it with the stylus 8 of a scanning probe 5. Digitized coordinate data for many points P1-P6 on the workpiece surface are subjected to a filtering algorithm, in order to remove redundant data when the surface is relatively flat or planar. Top and bottom tolerance vectors TV0,BV0 are defined, starting from a first point P1 and lying at a given tolerance h above and below a second point P2. Next, a direct vector DV1 is defined between the point P1 and a third point P3. If the vector DV1 lies outside the tolerance band between the vectors TV0 and BV0, then point P2 is deemed to be required and is not filtered out. Otherwise, the data for point P2 is deemed to be redundant and is rejected. In this case, new tolerance vectors TV1 and BV1 are now defined, starting from point P1 and passing within a tolerance h above and below point P3. From the four vectors TV0,TV1,BV0,BV1, a pair of vectors TVn,BVn is selected for a further iteration of the process, based upon which of these vectors lies closest to the vector DV1.
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Citations
25 Claims
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1. A method of digitising a surface of a workpiece comprising the steps of:
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scanning the surface with a probe to produce a digitised coordinate data signal representing coordinates of a plurality of points on the workpiece surface; and filtering said coordinate data signal to reject portions of said coordinate data signal representing some of said points, wherein the filtering step comprises the steps of; selecting portions of said coordinate data signal representing first, second and third points, produced in that order, on the surface, creating a vector extending from the first point through the third point, determining whether said vector lies within a predetermined tolerance distance from the second point, and removing the portion representing the second point from said coordinate data signal to reject the second point if said vector lies within said tolerance distance. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 19)
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9. A method of filtering a digitised coordinate data signal representing coordinates of a plurality of points on a surface of a workpiece, to filter portions of said coordinate data signal representing some of the points, comprising the steps of:
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scanning the surface of the workpiece with a probe to generate the coordinate data signal, selecting portions of said coordinate data signal representing first, second and third points, produced in that order, on the surface, creating a vector extending from the first point through the third point, determining whether said vector lies within a predetermined tolerance distance from the second point, and filtering the portion representing the second point from said coordinate data signal to reject the second point if said vector lies within said tolerance distance. - View Dependent Claims (10, 11, 12, 13, 14, 20)
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15. A method for filtering a data signal generated by scanning the surface of a workpiece, comprising the steps of:
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scanning the surface with a probe; generating a data signal comprising a plurality of point position data signals, each point position data signal indicative of a position of a point of the surface relative to a predetermined coordinate system; filtering the data signal to remove redundant ones of the plurality of point position data signals to form a filtered data signal; and storing the filtered data signal in a memory device; wherein the filtering step comprises the steps of; selecting a point corresponding to one of the plurality of point position data signals as a base point, selecting another point corresponding to another of the plurality of point position data signals as a test point, selecting another point corresponding to another of the plurality of point position data signals as a current point, the base, test and current points located in that order on the workpiece surface, generating a test vector extending from the base point through the current point, determining if the test vector lies within a selected tolerance distance extending from the test point, and filtering the point position data signal corresponding to the test point from the data signal as one of the redundant ones of the plurality of point position data signals when the test vector lies within the tolerance distance. - View Dependent Claims (16, 17)
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18. A method for filtering a data signal generated by scanning the surface of a workpiece, comprising the steps of:
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placing the workpiece within a measuring space of a machine having a probe and a plurality of axis measuring devices, each axis measuring device generating a coordinate signal indicating a distance of the surface from an origin position along an independent axis; scanning the surface with the probe; generating a data signal comprising a plurality of point position data signals, each point position data signal indicative of a position of a point of the surface relative to a predetermined coordinate system and comprising a plurality of the coordinate signals from the plurality of axis measuring devices; filtering the data signal to remove redundant ones of the plurality of point position data signals to form a filtered data signal; and storing the filtered data signal in a memory device; wherein the filtering step comprises the steps of; selecting a point corresponding to one of the plurality of point position data signals as a base point, selecting another point corresponding to another of the plurality of point position data signals as a test point, selecting another point corresponding to another of the plurality of point position data signals as a current point, the base, test and current points located in that order on the workpiece surface, generating a test vector extending from the base point through the current point, determining if the test vector lies within a selected tolerance distance extending from the test point, and filtering the point position data signal corresponding to the test point from the data signal as one of the redundant ones of the plurality of point position data signals when the test vector lies within the tolerance distance.
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21. A method of digitizing a surface of a workpiece, comprising the steps of:
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scanning the surface with a probe to produce a digitized coordinate data signal representing coordinates of a plurality of points on the workpiece surface; and filtering said coordinate data signal to reject portions of said coordinate data signal representing some of said points, wherein the filtering step selects portions of said coordinate data signal representing respective points on the workpiece surface in consecutive order and comprises steps of; (a) selecting portions of said coordinate data signal which represent first and second points on the surface, in that order, the first point being defined as a base point and the second point as a test point; (b) creating a tolerance band which is defined in dependence on the base and test points; (c) selecting a next portion from said coordinate data signal which represents a next point on the surface, said next point defined as a current point; (d) determining whether the current point lies within said tolerance band; (e) removing the portion of said coordinate data signal representing the test point and redefining the current point as a new test point if the current point does lie within said tolerance band, and redefining the test point as a new base point and the current point as a new test point if the current point does not lie within said tolerance band; and (f) repeating steps (b) through (e) for the remaining portions of said coordinate data signal, using points as redefined in step (e). - View Dependent Claims (22, 23, 24, 25)
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Specification