Method of calibrating a three-dimensional optical measurement system
First Claim
1. A method for calibrating a three-dimensional optical measurement system, said method comprising the steps of:
- mechanically measuring three-dimensional coordinates at each of a plurality of points on a surface of a three-dimensional test calibration fixture;
placing said test calibration fixture into the field of view of said optical measurement system;
optically acquiring a set of data representing the phase at each of a plurality of pixels corresponding to said optical measurement system'"'"'s view of the surface of said test calibration fixture;
for both the mechanically measuring step and the optically acquiring step, calculating the intersection point of three faces on said surface to uniquely define an accurate correlation between three-dimensional coordinate position and measured phase at that location; and
using an optimization procedure, calculating parameters of said three-dimensional optical measurement system, so as to minimize the difference between intersection point coordinates calculated from the mechanically measuring step and intersection point coordinates calculated from the optically acquiring step; and
fixing said parameters based upon the results of the optimization procedure.
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Abstract
A method for measuring the contours (30) of a three-dimensional object (4); and a method for calibrating an optical system (2, 8). The object (4) is placed into the field of view of the optical system (2, 8). The optical system (2, 8) is activated to obtain a set of data giving a phase (xt) at each of a plurality of pixels corresponding to the object (4). The phases (xt) are unwrapped, e.g., by a method of ordered phase unwrapping. The unwrapped phases are converted into a set of three-dimensional coordinates (xs, ys, zs) of the object (4) for each of the pixels. These coordinates (xs, ys, zs) can be portrayed on a display of a computer (10). The method for calibrating the optical system (2, 8) shares several common steps with the above method. In addition, coordinates of a test calibration fixture (38, 46) are first mechanically measured. Following optical measurement of the calibration fixture (38, 46), an optimization procedure is used to minimize the difference between the mechanically measured coordinates (xm, ym, zm) and the coordinates (xs, ys, zs) calculated from the optical measurements. The optimization procedure in the calibration method fixes the intrinsic and extrinsic parameters of the optical system (2, 8). A blending method can be used to increase the dynamic range of the measured intensity. Phase shifting is performed by either a method of temporal phase shifting or a method of spatial phase shifting.
56 Citations
11 Claims
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1. A method for calibrating a three-dimensional optical measurement system, said method comprising the steps of:
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mechanically measuring three-dimensional coordinates at each of a plurality of points on a surface of a three-dimensional test calibration fixture; placing said test calibration fixture into the field of view of said optical measurement system; optically acquiring a set of data representing the phase at each of a plurality of pixels corresponding to said optical measurement system'"'"'s view of the surface of said test calibration fixture; for both the mechanically measuring step and the optically acquiring step, calculating the intersection point of three faces on said surface to uniquely define an accurate correlation between three-dimensional coordinate position and measured phase at that location; and using an optimization procedure, calculating parameters of said three-dimensional optical measurement system, so as to minimize the difference between intersection point coordinates calculated from the mechanically measuring step and intersection point coordinates calculated from the optically acquiring step; and fixing said parameters based upon the results of the optimization procedure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification