Remember that FOV/desired resolution dictates the required pixel res. of any vision system. If you want to simultaneously measure dimensions all over the part, the Field of view (FOV) is going to be a part size. My question to you is 'what is your desired FOV and what resolution do you desire'. A good vision engineer will tell you that most vision systems available to a great job when they are properly applied as most systems will do a poor job when improperly applied. Tell us exactly what you want to measure and we can give you some help. In vision systems, they will tell you Lighting, Lighting, Lightng, meaning that systems generally succeed or fail based on lighting or the misuse or optical lensing equipment. In general, Cognex Insight 1000, 2000 systems do well when used correctly. Dvt works well also. I like to keep my desired pixel size 1/1000 of my desired FOV. Most systems allow good subpixel measurements to .4-.1 subpixel distances. A 640 X 480 system therefore should be able to measure to a 1000th FOV and be @ .4-.6 pixel. Also remember that the color of your imaging lighting will limit your minimal resolution achievable. In general, the limits are 2.4 microns 96 microinches using Red light.
My quick and dirty recommendation is keep your measurements to 1/1000 of full view to avoid problems and very High-Tech tricks out of the equation. IPD has a new appliance based metrology system called igauge that looks very easy and nice to use. I saw in at a vision show in Nov. in San Jose and I have read some really good things about it. I will use most any of the existing brands out there; but, remember that some optical physics governs these systems and you have to play by the rules. Most of the $3000-$5000 systems will do what you want if you stay inside a few limits. I hope this helps.
