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Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2002-Jan-23

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Jerrold Pine


There are two distinct lighting techniques employed for Robotic Vision Assisted Placement. A component is either backlit to perform analysis of its silhouette, or frontlit to perform analysis of some feature of interest. Ideally, the background for silhouette analysis should be as close to pure white to provide maximum contrast with a dark silhouette. The background for frontlit com- ponents should be as close to pure black to provide maxi- mum contrast with white frontlit features. In current fac- tory implementations, vacuum tips configured with backlighting have white diffusers to provide maximum contrast. These tips have terrible contrast when used for frontlighting. An obvious solution is to employ a tool changer and switch between tips designed for backlighting or frontlighting. The additional cost and cycletime does not justify this type of implementation. A more elegant approach is to divide the spectral response of the cam- era (4OOnm-1OOOnm) in half and use half the spectrum for frontlighting and half the spectrum for backlighting. Ifan optical longpaas lilter (>7OOnm) is placed behind the vacuum tip and IR light sources are placed behind it, the IR passing through the tilter when the backlights are illuminated will appear pure white. If a florescent light source (<7OOnm) is used for 6ontlighting the tip, the back- ground appears pure black. The result is perfect frontlighting and perfect backlighting that provides max- imum imaging contrast.