Vision Sensor

National Instruments has done a lot of work in this area. Check 'em out.

It all depends on what you need to inspect.

One part at a time is generally better.

Most of the hard work is to be done in the lighting design, then everything is easier to analyse when your features stand out.

Take a look at Cognex if your needs are not too complicated.

Yes, I agree with checking out Cognex. They bought another visual sensing company out of Georgia several years back called, I believe DVT. Between the 2 brands they can provide alot of options. The DVT brand had more capability, but its one drawback vs. the Cognex brand was the more memory intensive the application the slower it worked.

It works on the principle of taking a snapshot of what you consider ideal, then allows you to put tolerance borders around the object to be inspected. As each part passes, it will compare to the ideal. In order to maintain speed, you can blank out parts of the object not needed and only keep what provides value in your inspections. The Cognex brand is less capable, but is not so affected by memory use.