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 acquiring a plurality of images in a pick and place machine, the method comprising: 
 resetting photosites of a photosensitive array;    acquiring a first image on the photosites;    transferring the first image to a non-photosensitive area of the array;    resetting the photosites of the photosensitive array to clear the first image; and    generating a controlled exposure to acquire a second image before the first image is read completely from the non-photosensitive area of the array.    
     
     
         2 . The method of  claim 1 , wherein transferring the first image to the non-photosensitive area includes transferring the first image to vertical registers of an interline transfer CCD array.  
     
     
         3 . The method of  claim 1 , wherein transferring the first image to the non-photosensitive area includes transferring the first image to a storage area of a frame transfer CCD array.  
     
     
         4 . The method of  claim 1 , wherein the first and second images are smaller than the size of an imaging area of the array.  
     
     
         5 . The method of  claim 4 , and further comprising positioning the photosensitive array at an angle relative to an optical axis providing the first and second images.  
     
     
         6 . The method of  claim 1 , wherein generating a controlled exposure of the second image includes obstructing all light from falling upon the photosensitive array after an integration period of the second image has elapsed.  
     
     
         7 . The method of  claim 6 , wherein obstructing all light includes causing an electronically controlled optical shutter to enter a closed state thereby preventing light from passing therethrough.  
     
     
         8 . The method of  claim 1 , and further comprising: 
 hindering illumination not within a selected wavelength band from falling upon the photosensitive array; and    wherein generating the controlled exposure includes providing illumination within the selected wavelength band upon a placement location for a selected exposure time.    
     
     
         9 . A method of acquiring a plurality of images of a placement location in a pick and place machine, the method comprising: 
 resetting photosites of a first photosensitive array;    acquiring a first image on the photosites of the first photosensitive array;    resetting photosites of a second photosensitive array; and    acquiring a second image on the photosites of the second photosensitive array;    wherein the first and second arrays acquire images sequentially through common optics.    
     
     
         10 . The method of  claim 9 , wherein the first and second photosensitive arrays acquire images based on substantially monochromatic illumination.