Machine vision system utilizing autofocus and inspection processes

A method for operating a machine vision system,

• the machine vision system comprising:
• a vision components portion, comprising an optical assembly portion;
• a movement mechanism;
• and
• an inspection portion that is coupled to the optical assembly portion, comprising:
• a variable focal length (VFL) lens;
• a VFL lens controller configured to control the VFL lens to periodically modulate an optical power of the VFL lens over a range of optical powers at an operating frequency so as to periodically modulate a focus position of the inspection portion;
• an inspection portion light source which is configured to provide source light for illuminating a workpiece;
• an inspection portion objective lens having an optical axis and that is configured to input workpiece light arising from the workpiece, and to transmit the workpiece light along an imaging optical path that passes through the VFL lens, wherein the optical axis corresponds to a z-axis direction for which surface points on a surface of the workpiece have corresponding z-heights along the z-axis direction;
• and
• an inspection portion camera that is configured to receive the workpiece light transmitted by the VFL lens along the imaging optical path and to provide a corresponding workpiece image exposure;
• the method comprising:
• utilizing the vision components portion to perform an autofocus process which indicates z-heights of a plurality of sampling points SP on the surface of the workpiece for determining coarse surface profile data for the surface of the workpiece, and for which a sampling scan path SSP is followed;
• and
• utilizing the inspection portion to perform an inspection process, which comprises acquiring an extended depth of field (EDOF) image for each inspection point IP of a plurality of inspection points IP on the surface of the workpiece, and for which an inspection scan path ISP is followed which includes adjustments in relation to the distance between the inspection portion and the surface of the workpiece and is determined based at least in part on the coarse surface profile data from the autofocus process.

A metrology system, comprising:

• a vision components portion, comprising an optical assembly portion;
• a movement mechanism;
• an inspection portion that is coupled to the optical assembly portion, comprising:
• a variable focal length (VFL) lens;
• a VFL lens controller configured to control the VFL lens to periodically modulate an optical power of the VFL lens over a range of optical powers at an operating frequency so as to periodically modulate a focus position of the inspection portion;
• an inspection portion light source which is configured to provide source light for illuminating a workpiece;
• an inspection portion objective lens having an optical axis and that is configured to input workpiece light arising from the workpiece, and to transmit the workpiece light along an imaging optical path that passes through the VFL lens, wherein the optical axis corresponds to a z-axis direction for which surface points on a surface of the workpiece have corresponding z-heights along the z-axis direction;
• and
• an inspection portion camera that is configured to receive the workpiece light transmitted by the VFL lens along the imaging optical path and to provide a corresponding workpiece image exposure;
• a memory for storing programmed instructions;
• and
• one or more processors to execute the programmed instructions to perform operations including:
• utilizing the vision components portion to perform an autofocus process which indicates z-heights of a plurality of sampling points SP on the surface of the workpiece for determining coarse surface profile data for the surface of the workpiece, and for which a sampling scan path SSP is followed;
• and
• utilizing the inspection portion to perform an inspection process, which comprises acquiring an extended depth of field (EDOF) image for each inspection point IP of a plurality of inspection points IP on the surface of the workpiece, and for which an inspection scan path ISP is followed which includes adjustments in relation to the distance between the inspection portion and the surface of the workpiece and is determined based at least in part on the coarse surface profile data from the autofocus process.