Auto focus function for vision inspection system

A vision inspection system comprising:

• a platform supporting parts for inspection at an inspection zone, wherein the parts include a first subset of parts and a second subset of parts;
• an inspection station positioned adjacent the platform, the inspection station including an imaging device to image the parts on the platform, wherein the first and second subsets of parts are imaged at different times, the first subset of parts being imaged during a calibration mode, the second subset of parts being imaged during a normal operation mode;
• and
• a vision inspection controller receiving images from the imaging device, the vision inspection controller including an auto focus module for orienting the imaging device relative to the inspection zone, the auto focus module comprising:
• one or more processors configured to move the imaging device to a first working distance from the inspection zone;
• one or more processors configured to capture a first image of one of the parts in the first subset of parts at the first working distance;
• one or more processors configured to calculate a first image contrast score of pixel values of the first image;
• one or more processors configured to move the imaging device to a second working distance from the inspection zone;
• one or more processors configured to capture a second image of one of the parts in the first subset of parts at the second working distance;
• one or more processors configured to calculate a second image contrast score of pixel values of the second image;
• and
• one or more processors configured to compare the first image contrast score and the second image contrast score to determine which has a higher image contrast score;
• and
• wherein the inspection station operates the imaging device at an imaging working distance equal to the working distance associated with the higher image contrast score to image the second subset of the parts only at the imaging working distance after the imaging working distance is determined.

A method of inspecting parts including a first subset of parts and a second subset of parts imaged at different times, the first subset of parts being imaged during a calibration mode, the second subset of parts being imaged during a normal operation mode, the method comprising:

• moving an imaging device to a first working distance from an inspection zone;
• capturing a first image of one of the parts in the first subset of parts at the first working distance;
• calculating a first image contrast score of pixel values of the first image;
• moving the imaging device to a second working distance from the inspection zone;
• capturing a second image of one of the parts in the first subset of parts at the second working distance;
• calculating a second image contrast score of pixel values of the second image;
• comparing the first image contrast score and the second image contrast score to determine which has a higher image contrast score value;
• and
• operating the imaging device at an imaging working distance equal to the working distance associated with the higher image contrast score value to image the second subset of the parts only at the imaging working distance after the imaging working distance is determined.