Method and apparatus for calibrating a noncontact gauging sensor with respect to an external coordinate system
First Claim
1. A method for calibrating an arbitrarily oriented noncontact measurement sensor that is precalibrated and includes a structural light source and optical sensing means, with respect to an external coordinate system, the method comprising:
 using the structured light from the sensor to create a target lying simultaneously within a measuring zone of the sensor and a measuring zone of measuring means external to the sensor;
using the sensor to determine first spatial coordinates of the target expressed in terms of the sensor'"'"'s coordinate system;
using the external measuring means to determine second spatial coordinates of the target expressed in terms of the external coordinate system; and
transforming the first spatial coordinates into the coordinates expressed in terms of the external system using the first and second spatial coordinates of the target.
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Abstract
One or more noncontacting gauging sensors are calibrated to a common external coordinate system by providing each sensor to be calibrated with a target which can be simultaneously viewed by the sensor and an external measuring system for determining coordinates of the target in terms of the external coordinate system and in terms of the sensor coordinate system. With the resulting spatial coordinates of the target expressed in both frames of reference, transform matrix coefficients can be calculated, for example with a programmable computer, to calibrate each sensor to the preselected common external coordinate system.
55 Citations
38 Claims

1. A method for calibrating an arbitrarily oriented noncontact measurement sensor that is precalibrated and includes a structural light source and optical sensing means, with respect to an external coordinate system, the method comprising:

using the structured light from the sensor to create a target lying simultaneously within a measuring zone of the sensor and a measuring zone of measuring means external to the sensor; using the sensor to determine first spatial coordinates of the target expressed in terms of the sensor'"'"'s coordinate system; using the external measuring means to determine second spatial coordinates of the target expressed in terms of the external coordinate system; and transforming the first spatial coordinates into the coordinates expressed in terms of the external system using the first and second spatial coordinates of the target.  View Dependent Claims (2, 3, 4, 5, 6, 7, 8)


9. A method for calibrating an arbitrarily oriented optical gauging sensor with respect to an external coordinate system, the method comprising;

providing a target lying simultaneously within a measuring zone of the sensor and a measuring zone of measuring means external to the sensor; illuminating the target with a measuring light plane of a sensor optical source to generate at least three nonsymetrical illuminated points on the target; measuring coordinates of the at least three points with the sensor, the measured coordinates expressed in terms of the sensor coordinate system; measuring coordinates of the at least three points with the external measuring means, the measured coordinates expressed in terms of the external coordinate system; determining the mean value of each measured coordinate in the sensor coordinate system; determining the mean value of each measured coordinate in the external coordinate system; creating a sensor vector for each measured sensor coordinate point, each sensor vector extending from the sensor coordinate mean value point to a corresponding target point coordinate; creating an external vector for each measured external coordinate point, each external vector extending from the external coordinate mean value point to a corresponding target point coordinate; ordering pairs of sensor and external coordinates for all possible permutations thereof; for each permutation, using a least squares approximation to determine a mapping of sensor vectors into external coordinate vectors with acceptable orthogonality; and selecting the permutation resulting in the smallest transformation error.


10. Apparatus for calibrating an arbitrarily oriented noncontact measurement sensor that is precalibrated and includes a structured light source and optical sensing means, with respect to an external coordinate system comprising:

external measuring means; target means lying simultaneously within a measuring zone of the sensor and a measuring zone of the external measuring means and including radiant target points created by the interaction of the target means and the structured light emitted by the sensor; and transformation means coupled for receipt of radiant target point coordinate data relative to the target determined by both the sensor and the external measuring means, the transformation means operative to derive a transformation of sensor coordinate data into external coordinate data using the received target coordinate data from the sensor and the external measuring means.  View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)


22. In a noncontact optical measuring system having a plurality of optical sensors prepositioned with respect to a workpiece to be measured, each optical sensor having means for determining coordinates of points located within the sensor field of view with respect to a sensor coordinate system, an arrangement for calibrating any of the plurality of sensors with respect to an external coordinate system comprising:

external measuring means; target means releasably coupled to a sensor being calibrated, the target means carrying at least three nonsymetrically positioned target point generating elements operative upon illumination by the sensor to generate at least three corresponding illuminated target points simultaneously viewable by the sensor and the external measuring means, such that the sensor can determine coordinates of each target point in terms of the sensor coordinate system and the external measuring means can determine coordinates of each target point in terms of the external coordinate system; and transformation means coupled for receipt of sensor determined coordinate data and external measuring means determined coordinate data for the at least three target points, the transformation means operative to derive a matrix of transform coefficients effective to transform sensor coordinate measurement data into external coordinate measurement data, thereby calibrating a sensor with respect to the external coordinate system.  View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30)


31. A method of calibrating an arbitrarily oriented, precalibrated, noncontact measurement sensor with respect to an external coordinate system, the method comprising:

calibrating an independent external measuring system including a pair of theodolites relative to said external coordinate system; providing a target lying simultaneously within the measuring zone of the sensor and the measuring zone of the theodolites; using the sensor to determine first spatial coordinates of the target expressed in terms of the sensor'"'"'s coordinate system; using the theodolites to determine second spatial coordinates of the target expressed in terms of the external coordinate system; and transforming the first spatial coordinates into coordinates expressed in terms of the external coordinate system using the first and second spatial coordinates of the target.  View Dependent Claims (32)


33. Apparatus for calibrating an arbitrarily oriented, precalibrated, noncontact measurement sensor having a measuring zone, with respect to an external coordinate system, comprising:

an independent external measuring system including a pair of theodolites calibrated relative to said external coordinate system; target means lying simultaneously within the measuring zone of the sensor and the measuring zone of said theodolites; and transformation means coupled for receipt of coordinate data relative to the target determined by both the sensor and the external measuring means, the transformation means operative to derive a transformation of sensor coordinate data into external coordinate data using the received target coordinate data from the sensor and the external measuring means.  View Dependent Claims (34, 35, 36)


37. A method of calibrating an arbitrarily oriented, precalibrated, noncontact measurement sensor with respect to an external coordinate system, comprising the steps of:

calibrating an independent external measuring system relative to the external coordinate system; providing a target lying simultaneously within the measurement zone of the sensor and the measurement zone of the independent external measuring system; using the sensor to determine the spatial coordinates of the target in the sensor'"'"'s coordinate system; using the independent external measuring system to determine the translational position and rotational orientation of the target relative to the external coordinate system; using the data from the previous step to transform the spatial coordinates from the sensor'"'"'s coordinate system to the external coordinate system.  View Dependent Claims (38)

1 Specification