Found original part?

[deathproof]

Yup! Those were the two I was watching all right.

Like I said, I'm glad I didn't bid against you.  Make sure you post photos and stuff when you get them

There will be more, I'm sure.

Coming from the UK, I imagine they'll take a week or two minimum. Which is fine, because by then maybe I'll have a little more money to spend on the wheels and actually get more done on the base.

[Paul6700]

Wow, amazing find! Now I have to upgrade Treadwell's lenses.

[Lichtbringer]

You´re on a better start than me - i need to start a Treadwell.

[savagecreature]

Since it's our birthday and all, I figured I'd go ahead and post the Treadwell eye files.  I know more data will become available and the models will become more accurate, but there are people who aren't that concerned about 100% accuracy who might find these useful.  They were based on Lichtbringer's wonderful photographs and measurements, so they're not just guess work.

The model is printed in two pieces, a front and a back, so that they can be printed without supports, then glued together. I've done tests  with good results.  They look like this:

The files can be found in our files section, or you can click
Here

Let us know if you use them and how they work for you

[savagecreature]

I recently acquired a couple of Paterson Slide viewers without the internal focus lenses that were used for the treadwell eyes.
(I'm going to do other things with them that I'll tell people more about when I actually start doing it.)

On a lark, I printed one of my 3D focus lenses to see how well it would fit where it's supposed to go in the device.  I just had to share my results.

The one on the left is my lens (the yellow part) and the one on the right is a photo I collected while researching the slide viewer showing the factory part.

Mine was engineered from the photos that lichtbringer so generously provided. Though it's not absolutely perfect, I was shocked to discover that it's surprisingingly close! 

I can't wait to get my own lenses so I can correct the errors and make it a perfect match.

[kresty]

We expected nothing less of you savage Of course it fits! Fun that they used the same housing, what a difference a single lens can make!

I guess one wouldn't need the inner lens for the original security camera that started this thread, but what are you going to use it for?

[Dyne]

The glass lens is pretty massive, and i have no idea ho to measure the curve.

After several months of illness- and politics-induced loss of motivation, a 3d printer that I thought was broken, and just time getting away from me, I'm finally back to working on (aka "starting") my Treadwell build.  Printed out savage's STL, and I was reminded about the lens question.

It's pretty obvious that the outer face of this lens (as used on Treadwell) is convex, but I can't tell from the photos whether the inner face is flat, convex, or concave.   Whatever the case, it's not difficult to measure the curvature of a simple spherical lens, which is what this probably is.  As implied by the name, a spherical lens is just a slice of a sphere.

The simplest case is a plano-convex lens (the back face of the lens is flat).  We've all seen edge-on cross sections of this type of lens.  It's basically a rectangle with one edge curved outward (I put a line between the rectangular section and the curved section):


The part that we care most about for modeling purposes is the lighter blue section.  As you might guess, that bit is just a slice out of a circle.  It's bordered by an arc (curved line on top) and a chord (the horizontal line between the two sections).  The radius of the arc is equal to the radius of the circle it comes from, which in turn is equal to the radius of the sphere that the lens comes from.

To get the radius of the arc, you need two measurements:

• W is the green horizontal line.  It's the length of the chord ... or in other words, the diameter of the lens.  Since this particular lens is likely not a full disc shape, but instead squared off to fit into its holder, I'd suggest measuring at its widest diameter (i.e. across the square from "corner" to "corner").
  
• H is the small purple vertical line.  It's the height of the arc, aka the distance that the lens protrudes out from the point where you measured the diameter.  Alternately, if you know the maximum thickness of the lens, you can subtract the height of the darker rectangle (which we'd eventually want to know anyway).
  

Once you have H and W, you just use this formula:

( (W^2) / (8H) ) + (H/2)

For a lens with diameter of 60 mm and an H of 5 mm, this would work out as ( 3600 / 40 ) + 2.5, or a sphere of radius 92.5 millimeters.  Once you know that, you can take measurements like the thickness of that darker rectangle, then reproduce the lens in CAD :



I measured that sketch in Fusion 360, and the width of the resulting lens shape is indeed exactly 60 mm.


A biconvex lens -- both faces are convex -- isn't much worse.  It's just two of the above, back-to-back.  There's a good chance that this sort of lens is symmetrical, both faces having identical curvature.  But it is possible that they aren't the same.  The curvature of the inner face probably doesn't matter much unless you want to take screen accuracy to an extreme.



A meniscus lens (one face convex, the other concave, like eyeglasses) can be treated like two convex lenses pointing in the same direction, but the one on the concave side subtracts material from the lens rather than adding to it.



If someone can give me the relevant measurements, I can try my hand at modeling the thing.  At the very least one could print a mockup, sand it smooth, and paint it black.

[kresty]

Interesting... transparent filament wouldn't work as a lens, but it might be an interesting effect (ends up kinda frosted, at least with ABS). It could also be illuminated then.

[Dyne]

Interesting... transparent filament wouldn't work as a lens, but it might be an interesting effect (ends up kinda frosted, at least with ABS).  It could also be illuminated then.

True, it wouldn't be fully transparent. Frosted could be useful if you wanted the look of, say, 327-T from Clone wars.

My interest is primarily getting something to test fit with.  I think a model would be useful beyond that, though.

Just off the top of my head, you could possibly use the file on a CNC mill to shape a piece of clear acrylic, then polish it.  Or use a piece of milled wood as a blank for vacuum forming a part, similar to the BB-8 Radar Eye.  Or print a mold to cast the lens in clear resin.

[savagecreature]

Interesting... transparent filament wouldn't work as a lens, but it might be an interesting effect (ends up kinda frosted, at least with ABS).  It could also be illuminated then.

True, it wouldn't be fully transparent.  Frosted could be useful if you wanted the look of, say, 327-T from Clone wars.

My interest is primarily getting something to test fit with.  I think a model would be useful beyond that, though.

Just off the top of my head, you could possibly use the file on a CNC mill to shape a piece of clear acrylic, then polish it.  Or use a piece of milled wood as a blank for vacuum forming a part, similar to the BB-8 Radar Eye.  Or print a mold to cast the lens in clear resin.

Dyne, I hope you're not offended, but I had a couple of minutes this evening so I threw the lens model together. You're more than welcome to redo it if it's not to your liking.  I also included the retaining ring that is glued in behind it to hold it in place. I also discovered that the frame has recesses in it to accommodate the curvature of the lens in the front. I cut the recesses, but there were errors I will have to correct. I'll fix it and get those posted soon, too.

The lens and retaining ring can be found in the files secion, here.