In my opinion it is not VFP related question. If a selected camera is provided with a corresponding software (DLL or EXE), then you can use that software from VFP, VB, C++, Delphi -- whichever tool you choose.
Actually you have two issues: (1) how to trigger a camera (unless you want to take pictures every 5 seconds), and (2) how to pass a picture to your application.
My suggestion: it would be better to look for an existing hardware/software solution: camera and trigger device that can be connected to a database. There must be many of them on a market.