# Machine Vision

cancel
Showing results for
Did you mean:

Solved!
Go to solution

## Re: Detect dark 'needle' on light background (360°)

I'm not sure but you can try overlaying Gauge Indicator on to image and make the needle invisble.
Thanks
uday
Message 21 of 27
(3,094 Views)

## Re: Detect dark 'needle' on light background (360°)

Haha, it's funny that you mention it, because I (as an beginner) tried that and it worked, BUT it is far too inaccurate, is there an different solution?

Message 22 of 27
(3,090 Views)

## Re: Detect dark 'needle' on light background (360°)

never mind, It is not important anymore:)

Message 23 of 27
(2,994 Views)

## Re: Detect dark 'needle' on light background (360°)

Now it becomes interesting, the deviation is at some points too much, as well negative as positive. That's because of the resolution. Is it possible to increase the resolution, p.e., make from every pixel four??. (pixel overlap?)

Message 24 of 27
(2,977 Views)

## Re: Detect dark 'needle' on light background (360°)

It isn't the resolution.  It is more a perspective thing.  For accurate measurements, you need to be looking directly at the needle from a perpendicular position.  The needle has to be flat against the surface, and it needs to have the same shape in any position.  The lighting has to be good so there are no shadows.  I would not expect to get fantastic measurements from your setup, so it may be the best you can get.

Bruce

Bruce Ammons
Ammons Engineering
Message 25 of 27
(2,961 Views)

## Re: Detect dark 'needle' on light background (360°)

He gives at 8 points the correct value, at 12 oclock, 3, 6 and 9 amd between them, so the circle isnt really a circle, and thats because of the resolution, so it aint gonna be exact, but the higher the resolution the less the deviation. If I cant increase the resolution, I will try multiply the array with a handmade array as a filter. (Basicly I thougt that every pixel is a constant N degrees, but at some points (8) there are more pixels in the array), so the deviation is because of the calculation based on a constant index/degree
Message 26 of 27
(2,958 Views)

## Re: Detect dark 'needle' on light background (360°)

I did it!, I created an array (sine waveform) and added it to the other array to compensate the deviation, and it worked perfectly!:) The max deviation now is only 1 degree, thanks everyone for the responses

Message 27 of 27
(2,929 Views)