| 摘要 |
An optical analogue probe (9) is used on a co-ordinate measuring machine (1). Prior to use, it is datumed to compensate for any misalignment of the angle ( theta ) of its measurement axis (12A) from each of the machine's axes (X,Y,Z). Trigger points (D2,D3) are defined near opposite ends of the probe's measurement range (MR). A first set of machine X,Y,Z co-ordinates of at least four points (40) on a test sphere (38) are taken at one probe trigger point (D2). A corresponding set of co-ordinates for another four points (44) are taken at the other trigger point (D3). For each set of co-ordinates, a calculation is made of the center of the sphere, giving respective center points (42,46). The vector between these center points (42,46) is parallel to the measurement axis (12A) of the probe (9). From this vector, direction cosines are calculated for correcting the probe output to give X,Y and Z values.
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