topic Re: Object length measurement in Machine Vision

Object length measurement

Pandiyan — Thu, 11 Aug 2011 06:26:10 GMT

hi friends

I have to work on vision based project to measure the length of the object.In this project camera position is not stable,and zooming also varied ,this case how to make accurate distance measurement.?

now I developed the edge detection method to measure distance between two points .but if zoom is changed ,its wont give proper value...

so pls tell me what steps I need to do..

expecting your replay.. 😕

Re: Object length measurement

BruceAmmons — Fri, 12 Aug 2011 00:39:32 GMT

It is impossible to measure something accurately if you are changing the zoom on the lens unless you have a reference included in the image that can be used for calibration. The only way to do it is to calibrate the image at known zoom positions and only use those positions.

The distance between the part and the camera is also an issue. If the distance is changing, the calibration factor changes just like the zoom. If the distance isn't fixed you need to calibrate at multiple distances and only place objects at those distances. The only way to make distance not matter is to use a telecentric lens.

Bruce

Re: Object length measurement

Pandiyan — Fri, 12 Aug 2011 04:19:26 GMT

Hi BRUCE Thanks for your reply.i am also suspect that.but now you clarified me .

Re: Object length measurement

CarlosOtiniano — Sun, 10 Nov 2013 20:25:56 GMT

I have been working for some time with high resolution Acama, with adequate lighting and digital zoom I can get 1mm menorahs measures, the automatic zoom was a problem but manually configure the vision assistant

Re: Object length measurement

CarlosOtiniano — Sun, 10 Nov 2013 20:26:40 GMT

if still not solved the problem you can measure distance passing an RGB image to 8bit and extract a color plane insert VERTICAL CLAMP IMAQ function MIN which will measure the minimum height of the piece analyzed, this function block can be located within the MACHINE VISION path / MEASURE DISTANCES