measurement using VBAI

[Tikoy]

Good day to all,

 I am a newbie in Vision application. i just want to ask if it is possible to measure distance in an uneven surface with no telecentric lens. if it is possible, how can i do it with VBAI.

regards,

Tikoy

[PatJamSim]

Hello Tikoy,

If you are asking whether you can measure distance on a surface and take into account the roughness of the surface, then the answer is effectively no.  You would need a complex system with multiple lenses in order to get an accurate 3D image to measure that uneven surface, and even then, measurement would be difficult and potentially inaccurate.

If you are asking how to measure the straight-line distance between two points, then you can do this quite easily in VBAI.  You can use the Caliper or Geometry steps to measure distance.  Each step requires certain analysis to be performed on the image before taking measurements.  For example, you could use the Find Edges tool to locate two edges of a part, then calculate the distance between the edges.  Check out Chapter 3 of the NI VBAI Tutorial for more detailed instructions.

[Tikoy]

what i mean in the term uneven surface is that the surface of the unit under inspection has a slope and steep part (see attachment) <not actual drawing of the unit itself>

[Brad]

It would be helpful if you mentioned what part of that image you want to measure so we can understand how you go about doing it with Vision.

Thanks,

Brad

[CarlosOtiniano]

you can find some examples of vision in   https://decibel.ni.com/content/docs/DOC-31892

[ChristopheC]

To accurately make measurements in an image without using a telecentric lens, you might want to consider calibrating the image. By presenting a grid of dots, and calibrating the image using a distortion model, the calibration algorithm computes the distortion model associated with the lens. Subsequent measurements made on the image will take the distortion into account, and most functions such as the caliper will return results in calibrated units.

If you're planing to make are measurements, you will need to correct the image to get accurate results.

Check out the Calibrate Image Step Example.vbai.

[CarlosOtiniano]

is correct can calibrate the image to check the following links 

• http://www.ni.com/example/25897/en/
• http://zone.ni.com/reference/en-XX/help/370281P-01/imaqvision/imaq_correct_calibrated_image/
• http://books.google.com.pe/books?id=8tqeVwCyZJ4C&pg=PA265&lpg=PA265&dq=calibration+image+labview&sou...