Surface profiling and imaging system including optical channels providing distance-dependent image offsets

A computer-implemented method for operating a surface profiling system, the method comprising:

• controlling a motion control portion of the surface profiling system to cause an optical imaging array of the surface profiling system to scan along a workpiece surface in a direction transverse to a first array axis, the surface profiling system comprising:
• an imaging detector array including at least one set of detector pixels arrayed along the direction of the first array axis;
• the optical imaging array which includes at least a first set of optical channels, wherein the first set of optical channels includes at least first and second optical channels and the optical channels in the first set are arrayed along the direction of the first array axis, each optical channel configured with its optical axis arranged transverse to the first array axis to input image light from a workpiece surface region of a workpiece surface located at an object distance along its optical axis in its field of view (FOV) and to transmit the image light to a plurality of pixels of the imaging detector array located in its imaged field of view (IFOV);
• and
• wherein:
• the detector pixels of the imaging detector array are arranged at a back imaging distance from the optical channels;
• each optical channel comprises a lens arrangement comprising a lens configured to provide an erect image in its IFOV for a workpiece surface located in its FOV and within a measuring range along the direction of the optical axes of the surface profiling system, for which the first optical channel has a first IFOV and a first FOV and comprises a first lens arrangement comprising a first lens configured to provide an erect image in the first IFOV for a workpiece surface located in the first FOV, and the second optical channel has a second IFOV and a second FOV and comprises a second lens arrangement comprising a second lens configured to provide an erect image in the second IFOV for a workpiece surface located in the second FOV, wherein the first lens arrangement does not include the second lens and the second lens arrangement does not include the first lens;
• the optical channels in the first set are configured in the optical imaging array to have overlapping FOVs and overlapping IFOVs, wherein:
• a workpiece surface point located in the measuring range is simultaneously imaged in at least the first and second overlapping IFOVs of the first and second optical channels;
• and
• when a surface point is located at a defined object reference distance from the the first and second optical channels in the measuring range, then the surface point is imaged by both the first and second optical channels at the same position along the imaging detector array as the surface point is imaged in each of the first and second overlapping IFOVs, and a surface point that is located at an object distance that is different than the object reference distance is imaged by the first optical channel at a first position and is imaged by the second optical channel at a second position, for which the first and second positions are different respective positions along the imaging detector array at least along the direction of the first array axis in each of the first and second overlapping IFOVs, for which the difference between the object distance and the object reference distance corresponds to an out of focus amount that produces the imaging of the surface point at the first and second positions along the imaging detector array and for which a difference between at least the first and second positions defines a respective image offset for the surface point;
• the method further comprising:
• controlling the motion control portion to move at least one of the workpiece surface relative to the optical imaging array or the optical imaging array relative to the workpiece surface so as to cause the optical imaging array to scan along the workpiece surface in a direction transverse to the first array axis to acquire image data for the workpiece surface region;
• acquiring image data provided by the imaging detector array while the optical imaging array scans along the workpiece surface in the direction transverse to the first array axis;
• analyzing the image data to determine the respective image offset for the surface point that is located at an object distance that is different than the object reference distance for which the difference between the object distance and the object reference distance corresponds to an out of focus amount that produces the imaging of the surface point at the different respective positions along the imaging detector array and for which the respective image offset is defined by the difference between at least the first and second respective positions at which the surface point is imaged along the imaging detector array;
• providing a surface height measurement coordinate for the surface point along the direction of the optical axes based at least in part on the determined respective image offset;
• analyzing the image data to determine respective image offsets for a plurality of additional surface points that are scanned by the optical imaging array along the workpiece surface in the direction transverse to the first array axis;
• and
• providing a surface height measurement coordinate for each of the plurality of additional surface points along the direction of the optical axes based at least in part on the determined respective image offsets.