Simple yet complex idea - suggestions needed

Single lens manual-focus with Arduino

I would like to manually control the movement of a lens inside a lens barrel, supported by two retaining rings on either side. This could easily be achieved by using a spanner wrench that fits the retaining rings on either end and in turn the spanner wrenches are controlled by a motor (stepper for precision).

Problem, how would I engage the spanner wrench (with gears for stepper control) with the retaining rings ? Even if I do accomplish that, how would I control the positions of each retaining ring as to not exceed the travel length (which is obviously not preferable).

With all these ideas in mind, I believe Arduino would be the best approach to manually focus (manually move the lens up and down its housing).

Any suggestions or previously done (similar) ideas from anyone ?

Thanks for reading.

This is a mechanical/optical problem not electronic or arduino.

Common optical requirement.

Optics are not easy or cheap for a one off.

Edmunds scientific could be a scource of (very expensive) optics that could do this.

Mass market devices like cameras do this very cheaply if you can find the right camera to hack.

If you describe your requirement in more detail (what the end idea is ) its possible that someone may know a solution.

If you already have the lens assembly post a pic, perhaps you could have a ring cog type component printed on a makerbot.

I wonder if it would be possible to rotate the focus ring on a camera with a large belt - perhaps an O-ring - driven from a very small pulley on a motor shaft. It would probably slip at the limits thus preventing mechanical damage to the lens.

...R

Typically you would either use two limit switches or one 'home' switch and software to limit the movement in the other direction. With two limit switches you can connect them in series (NC) or parallel (NO) to use one input pin for both. Test the limit switches on every step. With a home switch you start by running the motor until the home switch is activated. Then count steps from there to make sure you don't exceed the limits of motion. Re-check the home position occasionally to correct for any lost/skipped steps.

If its a smooth ring perhaps something like a rubber pinch wheel would do the trick.

Robin2:
I wonder if it would be possible to rotate the focus ring on a camera with a large belt - perhaps an O-ring - driven from a very small pulley on a motor shaft. It would probably slip at the limits thus preventing mechanical damage to the lens.

...R

Considering a lens in a lens barrel supported by 2 retaining rings on its either side, I would have to design a mechanism (retaining ring lock-gear) that would engage the retaining rings on either end first. Second step would be to move in either direction. As Johnwasser mentions the limits or travel range can be calculated precisely or even better if we know the sweet spot of the lens position in the barrel the travel range can be reduced and hence the optical component can be safe.

But the initial step which is actually a mechanical problem would be how to lock the mechanism onto the retaining ring. Again this is a mechanical problem.

optoabhi:
Considering a lens in a lens barrel supported by 2 retaining rings on its either side, I would have to design a mechanism (retaining ring lock-gear) that would engage the retaining rings on either end first. Second step would be to move in either direction. As Johnwasser mentions the limits or travel range can be calculated precisely or even better if we know the sweet spot of the lens position in the barrel the travel range can be reduced and hence the optical component can be safe.

But the initial step which is actually a mechanical problem would be how to lock the mechanism onto the retaining ring. Again this is a mechanical problem.

I think that means NO

…R

optoabhi:
Considering a lens in a lens barrel supported by 2 retaining rings on its either side, I would have to design a

I think i understand , this is a hollow internally screwed barrel ? As seen on fixed focus devices ?

Normally for this sort of thing a second tube would be used to slide within , in and out.

Why do you want to move a lens inside a lens tube in the first place? What optical system are you building?

What is the product being used for, might help people come up with something, but I rekon hacking the way a camera lens is driven would be a better idea if that is what you are going to use

I think a mechanical adapter would have to be developed first. Can a spanner wrench remain attached to the retaining rings when adjustments are not being made? How do you know when the retaining rings are properly adjusted?

A spanner wrench will fall off if you dont keep pressure against it. I sense XY problem.

liudr:
A spanner wrench will fall off if you dont keep pressure against it. I sense XY problem.

Ever hear of hot glue? 8) My question is will the spanner wrench interfere with the lens operation if it remains in place on the retaining ring.

Hi,
Can you post a picture of the lens assembly please?

Thanks.. Tom... :slight_smile:

zoomkat:
Ever hear of hot glue? 8) My question is will the spanner wrench interfere with the lens operation if it remains in place on the retaining ring.

Do your homework and google what a lens tube spanner wrench is :smiley:
Besides hot glue, I've also heard of duct (duck) tape, elbow grease and WD40. Unfortunately none of them help optics projects. I wish OP posts some sort of schematics etc. I've been doing optics for decades and I suspect the OP is just looking for something else.

liudr:
Do your homework and google what a lens tube spanner wrench is :smiley:
Besides hot glue, I've also heard of duct (duck) tape, elbow grease and WD40. Unfortunately none of them help optics projects. I wish OP posts some sort of schematics etc. I've been doing optics for decades and I suspect the OP is just looking for something else.

Looks like most are the usual spanner wrench for a ring with two holes which a wrench of various designs with two pins that fit into the two holes. If this is not the type spanner wrench, please be specific as to what you are talking about. Also please answer the question I asked if the lens ring can still function with a spanner wrench engaged in the ring. The "'I've been doing optics for decades" would indicate you should be able to answer the questions.

https://www.google.com/search?q=lens+tube+spanner+wrench&num=100&lr=&source=lnms&tbm=isch&sa=X&ved=0ahUKEwin6tCp5p7KAhVGLyYKHTp4DfMQ_AUICSgC&biw=1124&bih=615&dpr=0.95

1] "My question is will the spanner wrench interfere with the lens operation if it remains in place on the retaining ring." - zoomkat

Ans: This is something to be investigated using optics simulation software like zemax, if like you said a spanner wrench which is a part of the assembly can be used then depending on the design of the spanner wrench it should be investigated if it interferes with the aperture or cause stray light excess. I will work on a analysis once I get back to my system.

2] Can you post a picture of the lens assembly please? - TomGeorge

Ans: https://www.thorlabs.com/thorproduct.cfm?partnumber=LMR05 [Here you go, click on CAD PDF to open the drawing with dimensions and other details]

3] liudr - I wish OP posts some sort of schematics etc.

Ans: What schematics in specific ? Also why would I want to move the lens with a precision inside its barrel; to adjust the focal length (with a very precise movement) so that the blue spectrum is more focussed with respect to red. (PS: I am an optics engineer, the challenge is purely opto-mechanics and would like to experiment with Arduino)

zoomkat:
Looks like most are the usual spanner wrench for a ring with two holes which a wrench of various designs with two pins that fit into the two holes. If this is not the type spanner wrench, please be specific as to what you are talking about. Also please answer the question I asked if the lens ring can still function with a spanner wrench engaged in the ring. The "'I've been doing optics for decades" would indicate you should be able to answer the questions.

https://www.google.com/search?q=lens+tube+spanner+wrench&num=100&lr=&source=lnms&tbm=isch&sa=X&ved=0ahUKEwin6tCp5p7KAhVGLyYKHTp4DfMQ_AUICSgC&biw=1124&bih=615&dpr=0.95

Third image, two typical designs, a tube and the adjustable ones with two pins. Neither will stay in place like an adjustable wrench and are both trick to motorize. You almost have to add a spring tension system to replace a hand, in both case (tensioning system or hand) the optical path is blocked.

optoabhi:
3] liudr - I wish OP posts some sort of schematics etc.

Ans: What schematics in specific ? Also why would I want to move the lens with a precision inside its barrel; to adjust the focal length (with a very precise movement) so that the blue spectrum is more focussed with respect to red. (PS: I am an optics engineer, the challenge is purely opto-mechanics and would like to experiment with Arduino)

What is the reason of moving a part that are in a tube that is designed to secure the part against any movement in the first place? If you need to adjust focal length, why not moving the whole lens tube with a linear stage driven by a motorized actuator? Too expensive? Find a way to move without spend a lot of money? It's hard. If you are concerned with light leaking into your system due to lens tube movement or else, say it up front. Post a picture of your system. Optics is mostly mechanics anyway. So without a good picture of the mechanics, there is little anyone can help. Plus, how much total distance and how much precision for the movement? Are you using a CCD down stream of the lens? I'm simplifying what might be your system since you're not saying a word about it. Why not motorize that ccd etc. instead? You can still seal the system with a CCD inside a lens tube and an actuator or piezo actuator pushing the ccd from inside the lens tube with the back end sealed.

optoabhi:
Ans: https://www.thorlabs.com/thorproduct.cfm?partnumber=LMR05 [Here you go, click on CAD PDF to open the drawing with dimensions and other details]

That is helpful.

I would suggest that if you want to use that mounting arrangement that the mount is attached to a precision linear positioning stage which an arduino can control.
They can be expensive.
How much movement is required in terms of mm not wavelengths. ?