Automatic focusing of an imaging system

A method of determining an optimum focus position of an imaging system comprising:

• creating a set of images of an object at a plurality of different focus positions using the imaging system, wherein each image in the set is created at a different one of the plurality of focus positions, such that each image has an associated focus position;
• computing a density of edges for each image in the set;
• and
• determining the optimum focus position for the imaging system, the optimum focus position being the focus position associated with the image having a greatest computed edge density.

A method of determining a change in focus position of an imaging system comprising:

• creating a set of images of a first object using the imaging system, each image in the set being created at a different one of a plurality of focus positions, such that each image has an associated focus position, the first object being representative of a class of objects;
• selecting a reference image from the set of images of the first object, the selected reference image having an associated first focus position;
• creating an image of a second object at a second focus position using the imaging system, the second object being a member of the class of objects;
• comparing the image of the second object to images in the set of images of the first object to find a closest matching image, the closest matching image from the set having an associated third focus position;
• and
• determining a change in the second focus position to provide an optimum focus position for imaging the second object with the imaging system.

An imaging system having automatic focusing comprising:

• an imaging subsystem that images an object;
• a memory;
• a computer program stored in the memory;
• and
• a controller that executes the computer program and controls the imaging subsystem, wherein the computer program comprises instructions that, when executed by the controller, implement using an image of the object created by the imaging system to determine an optimum focus position.