Circle Detection Issues

[MachineVision]

@Steve_in_Denver

It’s a very fast lens (f1.4) which is great for light gathering, but such a large (small numerical) aperture will reduce your depth of field, so maybe that’s why you are having focusing problems (particularly if your object has some depth to it)

For depth I’m mainly only trying to get the top of the object in focus so depth isnt a huge concern as long as I can get the highest points of it in focus.

@Steve_in_Denver

I don’t see a minimum object distance in the specs for that lens, but in my experience 40mm would be very close. Most of the lenses I use have a MOD of 10cm or more. If I understand correctly you were having trouble focusing at 40mm distance with your wide angle (original) lens - this doesn’t surprise me. I also think you might have trouble at 40mm with the lens you ordered (again, I didn’t see that listed in the specs)

I’m not sure either, this is new to me as I thought this came down to just seeing more or less of the object / FOV when closer or further away from it I guess it does make sense that there should be a minimum distance that I guess will be determined when I receive it in a day or so.

@Steve_in_Denver

The 1.3MP lens might be fine for you, especially since you are using 720p resolution, but in my experience higher optical resolution is almost always better. First of all the manufacturers tend to overstate the optical resolution - maybe picking the central area of the lens for their test, and not telling you that it’s much worse at the edges. I use a 3MP sensor and can tell a significant difference between the 5MP lens we use for some products and the 12MP lens we use for others. They are similar FOV, but the 12MP lens produces a much better and more consistent image. It’s not just the optical resolution, it’s a better designed / more sophisticated lens. It’s also about 6x the cost ($25 vs $4 in volume)

Hmm I will have to see how bad it seems then, I understand this similar to running videos at 4k resolution even though you may have a 1080p monitor because you can still see a difference in quality.

@Steve_in_Denver

This is a secondary consideration, but you should keep it on your radar. The chief ray angle varies from lens to lens - roughly speaking it is the angle of incidence of the light on the sensor - this is important because sensors are designed to work with certain CRA ranges, and if you get a bad mismatch your image quality will suffer. I’m not an expert on it, but I think a mismatch will result in vignetting, color shifts and sharpness - probably affecting the perimeter more than the central part of the image.

Im not even going to act like I know what any of this means such as CRA ranges as I have no clue but sounds like a pain to deal with guess ill cross this road when the new one arrives and see how different it is again I’m shooting from the hip on this one.

@Steve_in_Denver

If you have trouble finding a lens that will focus at 40mm, consider moving the camera further away and either accepting the larger imaged area, or selecting a lens with an even longer focal length.

This is possible but would make the job time go up fairly a good amount as the Z axis (Up and Down) does not move very fast on the ender 3 v2 so having to position higher each time it plunges will drastically increase job times unless I can find a way to increase motor speeds for the Z axis without causing other problems which I’m positive there is just haven’t experimented with how fast I can actually make it go without problems.

@Steve_in_Denver

If I get a chance I will look through my lens library and see if I can recommend something. Are you able to change the mount on the camera? Is it a plastic mount with two mounting screws? 18mm spacing? 20? 22? I ask because the lenses I have used with a close focusing distance are M8 lenses, so they require a different mount.

I’m not 100% sure on the spacing of the mount holes at the moment but yes it does seem to use 2 screws with a plastic mount which, I was worried also it may not be long enough to use the 6mm lens with enough clearance to adjust it closer or further away from the sensor as I’m not familiar with how that works but just assuming I should have enough travel for it to work decently if not that will be the next part I invest in.

@Steve_in_Denver

Edit: The OV2710 appears to have a CRA of 23.6 deg (I didn’t see a CRA spec for the lens you ordered)

Why chief ray angle matters: https://www.opticsdan.com/post/__cra

I reviewed this but don’t 100% understand, it seems the only reason this would be problem is if the lens is offset from the sensor a fairly decent amount. In the diagram it seems as long as its lined up or centered reasonably CRA shouldn’t be a problem just based off that graphic alone.

I will also check out that AICO company may have to convince them I need to test some samples to get a few that may work for my need without having to put in a volume order kind of lame to do that but worth it for me if they’re as good as it sounds as the website I ordered from seems to be the only retailer online I found that doesn’t charge $150+ for a single lens… Sort of like EdmundOptics theirs seem ridiculously priced high but then again I’m no expert and they’re probably way more involved than I know about lenses.