Vision builder camera calibration

[andreicb]

Hello,

I've setup a vision system composed of VBAI 2015 and a Basler Ace GigE camera.

I'm trying to measure length and width of 30 different products (in mm). The products are varying in height (from 20 mm to 150 mm), so they will appear closer to the camera. Also the products are coming on a conveyor and are mixed. A 30 mm height product can come, after that a 60 mm height product an so on. I did the camera calibration (with a grid) for a 20 mm products height image and it's working. What options do I have to keep the the same calibration for a product with a 150 mm in height. Or do I need to make more calibration let's say in increments of 5 mm ? 

[BruceAmmons]

If you are using a standard lens, the apparent size of the objects will change with height.  You would need to calibrate at each height, and identify the part before applying the calibration so you know which height to use.

I would suggest looking at a telecentric lens.  If you find one with the field of view you need and the depth of field to handle all the different heights, you will only need to calibrate at one height.  It will greatly simplify your programming, so the additional hardware cost would probably be worth it.

For example, Navitar has the MagniStar I-23723 lens with a 125x94mm FOV and 260mm DOF, assuming a 1/2" camera sensor.  That sounds like it would handle all your parts easily.  I am sure there are other options, but I found this first when I did a quick search.

Bruce