Cameras
The current approach is to design for 3 separate cameras
- Downwards facing camera on placement head
- Fiducial mark detection on pcb
- Placed part inspection (?)
- teaching
- Upwards facing camera on table
- Nozzle facing camera on placement head
- Orientation of small components
Each camera will interface to the controlling PC via USB2, allowing the computer to process the video easily.
Lighting
By controlling the lighting conditions on the part, the job of computer recognition can be made easier. removing shadowing from the image is a useful first step, however by using polarized light and polarizing filters, it should be possible to detect only reflective surfaces in the image, producing bright spots where the component leads are. These can then be used for part orientation.
One other use of controlled lighting is to illuminate the part from multiple directions, and use the resultant shadow images to detect missing balls on bga parts.
Prototyping
The current prototype camera suggestion is as follows:
Logitech Web cam pro 9000
- cheap, abundant, easy to modify
- reasonable image quality
- prior art for modifying with different lenses
Initial tests have been done with this camera and a cheap led ring light from ebay, with reasonable results.