Pick and place machine with component placement inspection

Abstract

Improved component placement inspection and verification is performed by a pick and place machine. Improvements include stereovision imaging of the intended placement location; enhanced illumination to facilitate the provision of relatively high-power illumination in the restricted space near the placement nozzle(s); optics to allow image acquisition device to view the placement location from an angle relative to a plane of the placement location, thereby reducing the possibility of such images being obstructed by the component; techniques for rapidly acquiring images with commercially available CCD arrays such that acquisition of before and after images does not substantially impact system throughput; and image processing techniques to provide component inspection and verification information.

1 . A method of calibrating an off-axis image system in a pick and place machine, the method comprising: 
 placing a known target in an intended placement location;    acquiring an off-axis image of the known target;    determining initial positions of known artifacts on the known target from the acquired image; and    calculating a transformation matrix.    
     
     
         2 . The method of  claim 1 , and further comprising: 
 after the step of acquiring an off-axis image, presenting the known target at a different position along a z-axis;    acquiring at least one additional image of the known target at the different position; and    determining adjusted positions of known artifacts on the known target from the at least one additional image; and    comparing the initial positions to the adjusted positions to refine the transformation matrix.    
     
     
         3 . A method of calibrating a plurality of image acquisition devices in a pick and place machine, the method comprising: 
 placing a known target in an intended placement location;    acquiring an image of the known target with each image acquisition device;    determining positions of known artifacts on the known target from the acquired images; and    comparing the determined positions from each acquired image to calibrate for depth.