Rotating chromatic range sensor system with calibration objects and method

A method for providing calibration data for correcting misalignment errors for a rotating chromatic range sensor configuration that is configured to direct a radial distance sensing beam along a radial direction relative to a rotation axis, and to rotate the radial distance sensing beam about the rotation axis, and focus different wavelengths at different distances along a measurement axis proximate to a workpiece surface to be measured, the method comprising:

• providing a cylindrical calibration object, the cylindrical calibration object comprising at least a first nominally cylindrical calibration surface having a central axis that extends along a Z direction;
• arranging the cylindrical calibration object in a relationship relative to the rotating chromatic range sensor configuration;
• operating the rotating chromatic range sensor configuration to provide a first set of cylindrical radial distance data acquired while rotating the radial distance sensing beam about the rotation axis at a first Z coordinate along the Z direction relative to the cylindrical calibration object, the cylindrical radial distance data referenced to a sensed rotational angle of the radial distance sensing beam about the rotation axis;
• processing the first set of cylindrical radial distance data referenced to the sensed rotation angle to determine a first set of cylindrical calibration data;
• providing a spherical calibration object, the spherical calibration object comprising a nominally spherical calibration surface, the nominally spherical calibration surface having a first plurality of surface portions;
• arranging the spherical calibration object in a relationship relative to the rotating chromatic range sensor configuration;
• operating the rotating chromatic range sensor configuration to provide, for the first plurality of surface portions, a corresponding set of spherical radial distance data acquired while rotating the radial distance sensing beam about the rotation axis with an optical pen of the rotating chromatic range sensor configuration approximately at a first nominal standoff distance from the spherical calibration object and for which the radial distance sensing beam is also moved along a scanning axis direction for acquiring the set of spherical radial distance data;
• processing each set of radial distance data corresponding to each respective sensed surface portion to determine a sensed closest surface point that is indicated to be closest to the optical pen of the rotating chromatic range sensor configuration;
• and
• determining spherical calibration data based at least in part on the sensed closest surface points corresponding to the plurality of surface portions.

A calibration system, comprising:

• a chromatic range sensor (CRS) configuration including a CRS optical probe;
• a cylindrical calibration object for providing cylindrical calibration data for correcting misalignment errors of the CRS optical probe, the cylindrical calibration object comprising at least a first nominally cylindrical calibration surface having a central axis that extends along a Z direction, wherein the CRS optical probe is configured to provide a first set of cylindrical radial distance data acquired while rotating the radial distance sensing beam about the rotation axis at a first Z coordinate along the Z direction relative to the cylindrical calibration object, the cylindrical radial distance data referenced to a sensed rotational angle of the radial distance sensing beam about the rotation axis, and for which the first set of cylindrical radial distance data referenced to the sensed rotation angle is processed to determine the cylindrical calibration data;
• a spherical calibration object for providing spherical calibration data for correcting misalignment errors of the CRS optical probe, the spherical calibration object comprising a nominally spherical calibration surface, wherein for a first plurality of surface portions on the nominally spherical calibration surface, for each surface portion the CRS optical probe is configured to provide a corresponding set of spherical radial distance data acquired while rotating the radial distance sensing beam about the rotation axis with the optical pen approximately at a first nominal standoff distance from the spherical calibration object and for which the optical pen is also moved along a scanning axis direction for acquiring the set of spherical radial distance data, and for which each set of radial distance data corresponding to each respective sensed surface portion is processed to determine a sensed closest surface point that is indicated to be closest to the optical pen, and for which the spherical calibration data is determined based at least in part on the sensed closest surface points corresponding to the plurality of surface portions;
• and
• a stage configured to position the cylindrical calibration object and the spherical calibration object with respect to the CRS optical probe.