Inspection THT components PCBA with light distortion

[dariogi888]

Hi,

I'm valuating the opportunity to perform a vision test on the THT components in our production line. I'm wondering if NI Vision is robust to tolerate the external light distortion ( we have closed vision machine ) . My main aim is to check the polarity and presence of THT components (capacitor, relay ..... ).

In the picture my idea. Is it possible to do with NI VISION?

 

Typical components to test

 

[1100fps]

Ambient light can wreak havoc on an inspection.  It might be possible to program around lighting changes, but it would be a tedious and time-consuming process, with a very high initial error rate as all possible failure modes are assessed and accounted for.

Assuming there is no way to control the ambient light environment there are a couple of approaches that help tremendously.

1) Wavelength filtering -  This approach uses a single-color light, and a matching filter on the camera.  By using a very narrow band pass filter, as much as 98% of ambient light can be eliminated from the camera view. This only works well with Monochrome images.  With AWI, and PCBs, this can add new challenges, as components and boards change color, but it's still easier to program around than random lighting changes.  Midwest Optical Systems will be happy to discuss your filter needs (I am not affiliated with them, they have just been a good supplier and have broad knowledge, and a good range of machine vision filters)

2) Strobing -  This is my favorite.  Companies like Advanced Illumination, and CCS sell lighting controllers that can limit the light output to a very short duration. In this case the camera shutter opens, sends a signal to the light control unit, which sends a pulse of light, and then the camera shutter closes.  This can happen in the range of a few microseconds.  With an exposure time of a few microseconds, it would be possible to do the inspection, in color, in broad daylight.  It's very repeatable and reliable.  The Advanced Illumination Strobe controller will actually overdrive LEDs when pulsed at short duration to maintain light output.  Other controllers may as well.

It's a guess that the part is stationary on the conveyor belt, however if the device under inspection is moving, then you need to take into account motion blur from long exposures, and registration.  The strobing option will eliminate motion blur.

Good luck, let me know if you have further questions.

[another_novice]

Building on the excellent reply from 1100fps, ambient light is a huge problem, regardless of whether you’re using NI Vision or any other machine vision software. Basically, it introduces a lot more variability into the images you’ll get from your camera.

If you can’t screen out the ambient, strobing, as 1100fps suggests, floods the scene with enough light to overwhelm it. It can also eliminate motion blur. However, strobing with visible light will likely irritate the heck out of anyone close by. For this reason you might want to go to IR lighting. In addition, IR plus an IR bandpass filter on the camera may cut down the impact of the building lights and perhaps that coming through the window too. (Note that it will also eliminate any color differences you may want to distinguish.)

Another point to consider is the type/direction of lighting you’re using. Your sketch suggests you’re going with brightfield, but have you considered what darkfield would do?