Higher resolution (but inexpensive) "microscope" camera

[mikeselectricstuff]

on all but the smallest boards, its going to need more than one picture to be able to look at the entire board, to spot issues, it strikes me that it may be more cost effective and a whole lot easier to have an array of low cost USB cameras, than to have one that moves around...

Yes or rotate the board while it passes the camera, could be an option.
If time is critical combine it with another step in the process like after loading it in the flying probe tester or exiting the reflow oven.

I figure a Panel of up to A4 size could be imaged by 12 USB ( 4 x 3 ) cameras very cost effectively. I imagine them being around 200mm above the pcb..  The cameras are cheap ( 20-30 USD in china ).

AIUI it's hard to use multiple USB cameras as they all have the same IDs, if nothing else they may enumerate in different orders.

[Kjelt]

I figure a Panel of up to A4 size could be....... 

About that, the rest of the process including the endmilling/breaking of the pcb's is than not captured.

[Smallsmt]

We started talking about a cheap system first.
So the microscope cameras are really great now and the first step is a manual inspection where a person is moving the PCB under Kamera and deciding it's good or bad.
Next step is to do a PC software to do the job of the operator.
And finally the PCB need to get moved automatically ore a multi camera system do the job.

But first it need a base system.

[mrpackethead]

AIUI it's hard to use multiple USB cameras as they all have the same IDs, if nothing else they may enumerate in different orders.

That can be quite a challenge!

[forrestc]

Back ontopic, will one picture tell the whole story?
As could be seen in Daves $500 camera video the tombstoned cap could not be identified from a single picture from above. 
You need at least one more picture from an angle, better a few different angles.

It really depends on what you are looking for.   

I've seen various tools where a 3d map is built either with stereo cameras or often with focus stacking.  Or some combination thereof.   Then you can 'see' any tombstoned components just because they are thicker on one end.

For what I would look for, a lot of it would show up with an adequate resolution short from above.   Incorrect resistors.  Missing parts.  Bridges, and so on. 

The top view is sort of the low hanging fruit which will get a lot of the way toward usable.   Beyond that you do need angles and/or 3d views, with 3d seeming to be fairly common anymore since with a good 3d AOI system you can even estimate solder fillet volume.