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Making a "flexible" fibreoptic laser pointer Answered

Dear knowledgeable people

I am looking to put together a laser pointer connected to a some sort of a fibreoptic cable to allow a clean projection of the beam at the end of the cable. I have looked at visual detector devices but are they suitable in giving a "clean" and focused beam that can project for at least few metres? The other limitation is that I am looking to work with a class II laser to make it as safe as possible (sneaky kids etc..). If a VFD is not suitable for this purpose how can you connect a simple laser pointer to the cable (?possible ?practical).

Finally is the green laser more focused by its nature?

Many thanks in advance!!!!

Discussions

1
Orngrimm
Orngrimm

10 days ago

color has nothing to do with focusability per se...
The challenge is more that with different frequencies, you will need different materials for focussing it. Google "Chromatic aberration" if you want to know more.
However, normally a simple PC-Lens is sufficient for DIY-projects thou...

A bigger problem i see is with the fiber itself: Laser is by itself phase-synchronised and veeeeerry narrow angular at the exit. These properties may be lost thru a fiber as the individual strands for sure are not the same lengts and perfectly parallel: they always crisscross a bit if not super expensive and non-flexible (Hand-laid and lengt-adapted fiberpacks exist, but expect 10'000$+ per custom pack).
Also, as the ends of the fibers arent a lens by itself, you end up with a lot more spread than you put into the fiber with the laser.
So with a common fiber, you only keep one specific property of a laser: Almost single-chromatic: Almost only one single frequency.
If this is enough, i would suggest looking into a strong LED with optic to feed your fiber. Could be much more powerfull and simpler to handle:
LED --> Optic --> Fiber --> Optic --> Target

0
dreissawi
dreissawi

Reply 9 days ago

Hello and thanks for your time on answering my question. I think I am able to follow the main concepts you discussed above. I know I should have been more specific but I did not want to confuse things. I am a general surgeon specialised in key hole (laparoscopic) surgery and was thinking about a simple research project where you simply introduce the fibreoptic cable through a key hole port (about 5mm tube allowing instrument access into the abdomen). The concept is to act as an internal laser pointer and aid in surgical training, for example guiding a trainee surgeon to cut through a very specific tissue targey rather than the senior surgeon taking over.

Not rocket science and probably only of interest/use in the context of a research project. So I am sure you would imagine that the projection is only ever needed over a very short distance within the abdomen.

0
Orngrimm
Orngrimm

Reply 9 days ago

Oh! Very interesting! Working in the medical field (injection and infusion systems for self-medication + Insulin reatment with Pump and applicators) in the Device development, this is really cool.
Question: Does the abdoemen get inflated so you have space there? Otherwhise i dont see a laserpointer and optical feeds really happening in all the "goo" ;)

Back to the topic: So, if i try to estimate a bit, the range from the end of the fiber to the target is maybe max 20cm?
As the laser has a large angle of spread once it exits the fiber, something like half way down website https://www.olympus-lifescience.com.cn/en/microsc... Search for "top-hat", its just above.
As inherently, you will have a focal point after the optics, a simple "twist to adjust" might be enough to move the focal point back and forth (Far and close).
Could be accieved by having a non-twistable outer tube and a rotatable inner tube. The rotation runs the lens in a thread slightly back and forth, adjusting the focal point of the lens-pack.

But as normally in our field, a DIY-Version is a bit "frowned uppon"... https://www.toptica.com/products/wavemeters-laser... may give you a good starting point for commercial products.
Or SF280SMA-B @ www.sintec.sg/products/Fiber/1397.html also may be a good choice / starting point...
Also, found a nice video of a part from OZ Optics in use. May be worth asking them for a sample? ;)

A good yield from google should be possible from the terms "Adjustable Laser fiber collimator" :)




1
Erientes
Erientes

10 days ago

What's the practical problem you are facing? Are you trying to measure a discontinuation of a laser beam onto a sensor or st? Why must the laser pointer be flexible? It would really help if there is some more context (at least for me). Anyways, maybe this helps?


I'm not an experts on lasers, but common sense tells me that for focus the bottleneck would likely be the lens. I won't see how wavelength would influence that.

0
dreissawi
dreissawi

Reply 9 days ago

Thanks Erientes for taking time to answer my question. I know I should
have been more specific but I did not want to confuse things. I am a
general surgeon specialised in key hole (laparoscopic) surgery and was
thinking about a simple research project where you simply introduce the
fibreoptic cable through a key hole port (about 5mm tube allowing
instrument access into the abdomen). The concept is to act as an
internal laser pointer and aid in surgical training, for example guiding
a trainee surgeon to cut through a very specific tissue targey rather
than the senior surgeon taking over.

Not rocket science and
probably only of interest/use in the context of a research project. So I
am sure you would imagine that the projection is only ever needed over a
very short distance within the abdomen.

0
Downunder35m
Downunder35m

Reply 9 days ago

Ahhh....
See, now we have some concept to go with :)
In theory you would only need any fibre optics cable suitable for visible light.
Even a salvage "UFO lamp" would do if the fibres are long enough.
Problem is that normal FO cables are not actually designed to work as you need them to.
Buy the cheapest "cables" you can find for an optical audio connection on an amplifier - should be only a few bucks.
Get a connector port for it as well to act as a coupling to you laser - makes aligning it easier.

You will get a certain amount of scatter and beam expansion.
How much depends on how well you aligned the laser to the cable - if in doubt mount them fixed and fully horizonatlly - then adjust one side until you get the beam right onto the cable area - does not matter much if the cable is much thinner than your laser beam.
In case what you see is enough, make it a permanent thing.

If the beam quality is too shitty consider adding a tiny glass plate, like used for microscope specimen holders to cover the drop.
These pens with the UV glue to repair plastics offer a good enough clearness to glue the plate onto the input and output ends of the cable - this will prevent bad scatter a bit.
If the beam goes big at a too short distance you might be lost though as this is usually due to how the beam is reflected inside the cable.

The only way I know how to get a more or less usable output on a hobby level would be to make a polishing rig for the cable.
But even with that it is a true pain to do so....