Machine Vision Inspection System and Method for Performing High-Speed Focus Height Measurement Operations

A machine vision inspection system configurable to collect a stack of images of a workpiece at a plurality of Z heights in order to measure Z heights based on a best focus height for a plurality of sub-regions of a region of interest, the machine vision inspection system comprising:

• an imaging system comprising a variable focal length lens electronically controllable to vary the focus position of the imaging system;
• and
• an illumination source configurable to illuminate a workpiece with strobed illumination in a field of view of the imaging system, wherein:
• the machine vision inspection system comprises a control portion configured to:
• periodically modulate a focus position of the variable focal length lens over a plurality of positions along a Z-height direction proximate to the workpiece;
• and
• collect an image stack comprising respective images focused at respective Z heights, wherein each image of the image stack corresponds to an instance of strobed illumination timed to correspond with a phase of the periodically modulated focus position corresponding to a Z height within the image stack, and
• the machine vision inspection system is configurable to:
• determine a region of interest within a field of view for focus height measurement operations;
• and
• determine a Z-height measurement for at least one portion of the region of interest based on analyzing the image stack to determine a Z height corresponding to a best focus position for the at least one portion of the region of interest.