Circle Detection Issues

[MachineVision]

@Steve_in_Denver

How did you get the calibration data? Is it a file the manufacturer provided, or something you generated from a calibration procedure. Frankly it’s not great, assuming the rows/columns of cartridges are linear in the world. It might not matter much, but it could be a source of error for your positioning system.

I used the circle grid calibration to get a calibration file which is noticeably better when looking at straight lines as with calibration the straight edges are straight but without they’re very obviously contoured.

@Steve_in_Denver

Get a different lens that is suitable for your sensor. The image circle for your sensor is fairly big (1/2.7" format) and there are a lot of good lenses that won’t fill the whole lens (or will have vignetting), so you might be stuck with a 1/3" format lens. Probably OK for your use case since (I think) you care about the central part of the image and not the edges. Depending on how far away the camera is (or can it be adjusted?) from the parts, you might consider getting a much narrower FOV lens and placing the camera further away. This will give you a better DOF so more can be in focus, if that’s a factor. You should be able to find a F2.0 or faster lens - I’m mentioning this because you said noise was a factor, so more light gathering might be good for you (Although since you can control the lighting and appear to have a sensor with good sensitivity, this probably shouldn’t be a big concern)

I do believe a smaller FOV will be beneficial as I am currently cropping just enough room from the frames to see the ROI I need which is a LOT smaller than what im currently getting.

@Steve_in_Denver

Get good intrinsic calibration for your camera.

Any references to this or tutorials id be willing to try, having it mounted to the machine seems to add a limitation to how accurate of a calibration I can get without removing it first, as I am limited to workspace area of the Ender 3 V2 I have it mounted to.

@Steve_in_Denver

1. You say the X,Y movements are pretty accurate, but I’d want to calibrate the camera (extrinsics) to the XY motion somehow. If you have calibrated intrinsics you can do something like:

• Put a single circle target in the machine bed somewhere, at the same height as the workpieces. Move (with the XY motion system) the camera over the circle so it is imaged with in various locations.
• Using the relative positions of the XY and the corresponding (accurately undistorted) image locations, compute a homography that maps between the two spaces. Basically you are using one fixed circle and your XY positioning system to create a calibration target with multiple points aligned to your XY control axes.
• Use this H to compute the motion you need so the detected circle ends up at a the desired location in the image.

This seems quite advanced but interesting currently I do not think I have much room to make this work especially with a full tray on the bed I am left with about 2" of movement space on any side of the tray. I was using the cartridge opening as a reference to MM per PX conversion which is working well and when I need to advance to the next one I use the previously stored variable to make the movement to the next one with GCode which is pretty accurate so far.

@Steve_in_Denver

What you want to achieve is totally doable, and you might be able to get away with something less involved, but I suspect you’ll have better success if you get a well calibrated system to work with.

Of course I believe this fully I am by no means a camera expert so I have little understanding of the actual technical side such as Focal lengths, Lenses and such but feel like this project may help me better understand these more than any YouTube video could. Which is the goal I love to learn by doing honestly I was going to order a set of M12 lenses as they go for fairly cheap and was recommended this may be the best way to just test and see what works for what I’m trying to get out of the camera. I’m not usually one for brute forcing parts usually I like to diagnose and figure out exactly what I need, but this seems to be more of a trial and error type of problem without a deep understanding of these parts.