Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



How to attach a Powell lens to a laser pointer?

Joined
Jan 15, 2021
Messages
15
Points
3
As described in my intro post ("Hello from Massachusetts"), I'm interested in doing laser-stimulated fluorescence photography and I'm trying to assemble a setup.

My requirements are:
- Battery-powered 405nm laser pointer (or module, if a pointer is impractical to attach the lens to) in the 150-300mW range.
- Powell lens with a 30 degree fan angle attached to the above laser. Somehow.
- [ETA] As little fabrication as possible since I live in a small studio apartment and even drilling stuff is difficult with no place to put a workbench.

Also desireable but not strictly necessary:
- A way to decrease the beam power.

The problem is that I have no experience with lasers really, so I am not sure how one goes about attaching the lens to the laser, especially an odd-looking thing like a Powell lens. ThorLabs has some nice Powell lenses and I've found many other sellers, so obtaining the lens doesn't look hard. For the laser, portability is very important (this is likely to be used to photograph graffiti in abandoned houses and the like, which may require a hike) so I need things to be light and self-contained as much as possible. So I think a laser pointer is preferable, and I can carry the batteries separately for safety.

I haven't settled on a pointer yet but I was thinking strongly of the JetLasers PL-E Pro 405nm Violet Laser at 300mW, or possibly the Mini at 150mW (but the Pro seems to allow power adjustment?). And probably the Thorlabs 30 degree Powell lens if I can figure out how to attach it! All help much appreciated.
 
Last edited:



RA_pierce

Well-known member
Joined
Sep 16, 2007
Messages
3,540
Points
113
A simple adapter that holds the lens and fits over the pointer will work fine.
The design of the adapter depends on the lens design.
Edmund Optics has powell lenses that have a circular profile which will be easier to mount into an adapter turned on a lathe.
I see that Thorlabs' powell lenses have a square profile. I've attached a quick sketch of my idea to this post.
You can secure the lens in place with a few dabs of epoxy applied to the non-optical sides of the lens or also with nylon-tipped set screws so as not to mar or crack the optic.

Depending on the centering of the laser beam relative to the aperture, it may be necessary implement some way to adjust the position of the powell lens to ensure ideal alignment, but this is probably not critical for your purposes.

You could even get fancy and have some holes drilled into the front face of the adapter to glue in some small neodymium magnets in 3 or 4 locations. This will allow you to easily attach/detach additional gadgets (of course these would be designed to be magnetic as well) to the aperture for further manipulating the beam (like reducing power).

For decreasing the power of the laser:
This can be achieved by modulating the power to the laser diode or by placing an optic in the beam path that attenuates the output.
The optical method is perhaps cheaper than the electronics method but can be tricky.
The electronic method will allow greater control and reduces the number of fiddly optics you need to worry about but will require some self-assembly or out-sourcing the work since a ready-made product that meets your needs may not exist off-the shelf (others might know different).

I'll comment on the optical method since I'm not very knowledgeable when it comes to electronic engineering.
Because the power density of a laser can be very high, the beam can destroy or distort many types of beam attenuators (like neutral density filters or photographic polarizing filters). It will be important to either select an optic that can withstand the power density of your laser or expand the beam so that the power density is reduced.
A stack of weak ND filters may work better than a single strong one, since less light will be absorbed by each filter - effectively dispersing the beam little by little and minimizing the thermal distortion at each filter. I don't know if this will work in practice.
There are other possibilities but I won't discuss them in this post since it's long already.
 

Attachments

  • powellLensAdapter.png
    powellLensAdapter.png
    121.5 KB · Views: 12
Joined
Jan 15, 2021
Messages
15
Points
3
First, thanks!

Going to the practical: Where would I get such an adapter? I don't have access any fabrication facilities at all, and even simple stuff like drilling is hard in my tiny studio apartment. If you can buy them then that would be perfect. (Side note: you have the Powell lens facing the wrong way. Apparently the sharp point goes towards the laser and the flat part is towards the outside world.)

With regard to power, definitely I could put a filter on there, but I would rather just buy a laser that already has an electronic means of decreasing the output. If I put a filter on it, either it will get hot in the case of absorption glass or potentially reflect back at the laser (bad!!) with a dichroic filter.

I guess what I'm really looking for is something that uses as much off-the-shelf pieces as possible. If I really have to I may be able to build some kind of adapter, but that's kinda my last resort.

BTW, sorry for not linking the Thorlabs - apparently there is something that prevents n00bs from posting links, or I would have saved you the Google.
 

RA_pierce

Well-known member
Joined
Sep 16, 2007
Messages
3,540
Points
113
Going to the practical: Where would I get such an adapter? I don't have access any fabrication facilities at all, and even simple stuff like drilling is hard in my tiny studio apartment. If you can buy them then that would be perfect.
There are some members of this forum that do custom machining. You can try contacting one of them. Unfortunately I don't know who is actively taking commissions these days. Lifetime17 may be able to help you.
Otherwise, if you opt for the last resort, you could probably make something like this out of PVC pipe, glue, and bits of things from the local hardware store. It won't look as nice but if it gets the job done, well that's just fine, right?
(Side note: you have the Powell lens facing the wrong way. Apparently the sharp point goes towards the laser and the flat part is towards the outside world.)
Oops. Now I know...
I guess what I'm really looking for is something that uses as much off-the-shelf pieces as possible. If I really have to I may be able to build some kind of adapter, but that's kinda my last resort.
Yeah I hear you... I'm not familiar with off-the-shelf lasers so hopefully someone can chime in and tell us if there is a 405 nm laser with built-in power modes.

Oh, BTW, It's cool to see someone else on here that's into fluorescence photography.
I use LEDs, since they are easier to obtain in wavelengths below 400 nm (doesn't show up on the camera sensor). My subjects tend to be more of the natural kind as you may be able to see from my profile picture. Welcome! 🍻
 
Joined
Jan 15, 2021
Messages
15
Points
3
Thanks, I will look around to see if I can find a way to do it off-the-shelf first, and then I will get in touch with Lifetime17 if that falls through. I know Thorlabs has some of its own mounting solutions but they charge the earth and I also don't know if the sizes match the laser. Do you have any idea what kind of front threads lasers usually have? I keep seeing the phrases "G2" and so on but I don't know what that means exactly. I'd love to make a screw-on solution.

Regarding fluorescence photography, I've been doing LEDs for years with flowers and so forth for exactly the reason you said, but I finally hit a project where I realized that I have to be ~15ft/5m or more away and doing it with LEDs wasn't gonna cut it.
 

RA_pierce

Well-known member
Joined
Sep 16, 2007
Messages
3,540
Points
113
"G-2" refers to a short focal length aspheric collimator. It is typically mounted in a brass thingy with m9x0.5 threads.
The threads fit the heatsink most commonly used for mounting diodes.
The dimensions of the adapter will need to be tailored to the specific laser pointer you end up purchasing if you go with the "slip-on" design i sketched up.

It may be possible to integrate the Powell lens in a more compact way depending on the size of the lens. I think the ones from Edmund are like 9mm diameter. Without knowing which laser you plan to use, it'll be hard to recommend specific mounting possibilities.

Have you been able to find a regular cylindrical lens with a long focal length that would approximate the 30° fan angle you want?
If you could, it might substantially reduce the cost of this project.
 

Encap

Well-known member
Joined
May 14, 2011
Messages
6,059
Points
113
Have a look at "405nm line lasers" on eBay--there are several 100mw, 200mW and 300mW versions available that accomplish the same fanning out to create a line that a Powell lens would do. Some might have provision to adjust the driver output All you would need is a battery pack to power same in AC adapter is not possible to use. See: https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=405nm+line+laser&_sacat=0

What you want exactly does not exist--no demand, need, or call for same--is an extreme unique situation need niche
 
Joined
Jan 15, 2021
Messages
15
Points
3
"G-2" refers to a short focal length aspheric collimator. It is typically mounted in a brass thingy with m9x0.5 threads.
The threads fit the heatsink most commonly used for mounting diodes.
The dimensions of the adapter will need to be tailored to the specific laser pointer you end up purchasing if you go with the "slip-on" design i sketched up.
For the laser, assume it's the JetLasers PL-E Pro 405nm Violet Laser at 300mW. I would prefer to have the adapter screw in rather than slip on, but if it can only be done via slip-on then so be it. I noticed that the PL-E Pro seems to already have a beam expander that screws on, so I know it must have a thread in front. If I can determine what that thread is (m9x0.5??) then I can work from there.

Have you been able to find a regular cylindrical lens with a long focal length that would approximate the 30° fan angle you want?
If you could, it might substantially reduce the cost of this project.
Re the cylindrical lens -- my current laser that I posted about in the Welcome thread has one of those, and it gets dimmer near the edges, which is not what I want for photography. Powell lenses by definition don't do that, which is how I ended up on the board here.

Have a look at "405nm line lasers" on eBay--[snip]

What you want exactly does not exist--no demand, need, or call for same--is an extreme unique situation need niche
Encap, I have one of those eBay lasers from my first attempt, got disappointed, started trying to put together something better. I get that a Powell lens adapter doesn't exist exactly, but I think I can come up with something involving multiple pieces that will screw together. If I can work out what the front threads are then I can start to assemble the pieces.
 
Last edited:

Encap

Well-known member
Joined
May 14, 2011
Messages
6,059
Points
113
For the laser, assume it's the JetLasers PL-E Pro 405nm Violet Laser at 300mW. I would prefer to have the adapter screw in rather than slip on, but if it can only be done via slip-on then so be it. I noticed that the PL-E Pro seems to already have a beam expander that screws on, so I know it must have a thread in front. If I can determine what that thread is (m9x0.5??) then I can work from there.
You can look at the Jetlasers 10X beam expander schematics here --they show the adapter thread sizes -- it has it's own adapter that allows percise positioning of the BE to center align the input lens over the beam as well----maybe all you need is the adapter and to fashion something that will allow you to mount a Powell lens on the BE adaptor.
Have a look here at photos of the adapter: https://laserpointerforums.com/threads/jet-lasers-beam-expander-adapter.102567/
-- you can also email Gray at Jestlasers and ask questions, see beam expander schematics here https://www.jetlasers.org/index.php?id_product=15&controller=product
Email: jetlasers@gmail.com put attention Gray in the subject line.
 
Last edited:




Top