My guess is that the mirror is not flat enough. I tested a thin mirror which was flexing a little bit and it gave a fuzzy double reflection.
Seems odd to me that it makes such a clear double-image though. On a first surface, I've have thought that to be impossible for one reason or another.
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Maybe the targets on the old collimators were smaller than 24mm? In that case yes a 10x eyepiece could work. @ic-racer could check his to see. I got the 20x from Ritcher autocollimator manual.
I suspect you can just use a test lens. As you know, the pattern stays in the middle of the eyepiece no matter the orientation of the test lens.Here's a place of concern and could be where this project dies; figuring out how to calibrate the autocollimators to align the target and graticle. Have you seen any examples of ways to mount lens elements (in this case, the target and the entire eyepiece mount, I guess) that lets you push them around in 2 dimensions while keeping the axes parallel?
Do you know what is the reasoning behind the 10x/2x rule for the lenses? I know that the reflection from film on slow wide angles get very dim. Maybe it's about matching the pupil diameter rather that focal length. Because a longer focal length will better simulate infinity (I think).
Here's a place of concern and could be where this project dies; figuring out how to calibrate the autocollimators to align the target and graticle. Have you seen any examples of ways to mount lens elements (in this case, the target and the entire eyepiece mount, I guess) that lets you push them around in 2 dimensions while keeping the axes parallel?
The target is demagnified onto the film plane by the ratio of the focal lengths of the lens under test to the collimating lens. That is if there is a 24mm diameter target, a 50mm lens under test, and a 250mm collimating lens, the image of the target on the film plane will be diameter = 24 * 50/250 = 4.8 mm. There's probably some good reason to keep this from getting too small, and certainly to keep it from getting too large - if the demagnification was 1 you'd start to get close to overfilling the film gate.
Any focal length lens would be able to simulate infinity (produce a collimated beam), but because the collimator is a simple lens, one wants it to be fairly slow to keep its own aberrations from mattering. For ex if the collimator were a focal length 250mm lens of about 40mm diameter (basically a +4 closeup lens), its own focal ratio is 250/40 = 6.25. And the edge of the 24mm target is 12mm off-axis from the collimating lens 250mm away, so it's nearly on axis, which means that the curvature of field or other aberrations of the collimating lens will be small. OTOH, if the collimating lens is very long focal length, the device gets uncomfortably large.
Just to mention again, what a fantastic project you are very talented!
I suspect you are an Engineer, and I'm just someone that can break things, but this might be a source of failure if the device topples or someone leans on it.
Thank you. I'm actually not a an engineer, but I do have a diploma in electronics engineering. The mechanical is all self-taught.
The comment in #33 above was assuming the device was 3d printed in some polymer. Will this be metal?
I was actually imagining you collimator done up in resin like this. I had JLC3DP print these in resin and they are absolutly fantastic. But you probably know much more about it than myself. I do have one of your light meters. Those are 3d printed, yes?
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You know if you put some indicators of distance from the center, you can use your collimator to quantify lens sharpness at center and edges.
Myth Busted: Minox I Holds Its Own Against Minox III
Have you ever wondered how the image quality of the very first Minox camera, the Riga Minox (Minox I), compares to its successor, the Minox A (Minox II/III)? During the last months I dived deep into a fascinating investigation to answer exactly that question! To do this, I directly compared...www.photrio.com
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