- Dec 30, 2016
Can someone please explain the pros and cons between a 3x and 10x beam expander and what does a zoom able beam expander give you ?
3X:Can someone please explain the pros and cons between a 3x and 10x beam expander and what does a zoom able beam expander give you ?
Like what should be taken in account ?3X:
Pro: Expands beam by 3x, reduces divergence by 3x.
Con: Doesn't reduce divergence as much as a 10x.
Pro: Expands beam by 10x, reduces divergence by 10x.
Con: 3.3333...x fatter beam in the near field compared with a 3x. Likely physically bigger.
Zoomable = adjustable focus.
There's other things to take into account, not just expansion factor. Those things will vary based on which specific expander you use.
I get the part where the beam is expanded and over all the power is reduced but after refocusing the beam back to a point at lets say 5000 feet doesn't that bring the power back up at least some in that point at 5000 feet ?Expanders also reduce power out and the beam isn't as bright due to the power being spread out over a larger area. Regardless, has never bothered me, I prefer a lower divergence beam so I can see a spot on a cloud base 7,000 feet high. Many pointers won't do that because their divergence is too high and the power spreads out too much before it reaches the cloud. I've been able to see a spot on a cloud base as high as 12,000 feet with a 1 watt 532nm laser pointer expanded to 10X.
1x lol ya I didn't even think of that, Times one is just the same as it was to start with ! lolI have one of those and I never set it to 1X, didn't even realize it was advertised for 1-10X, always had it on maximum expansion. I don't know how it could really do 1x, that would mean the input beam is the same diameter as its output, no change. Is that even possible? If they advertise it as such, it must be, I didn't realize I could adjust it through that wide of a range. Theoretically, at 1X you will have no expansion and your divergence the same, but less power due to losses. However, the loss shouldn't be very much with that expander, nicely AR coated.
Edit: A beam expander, if adjustable, can be focused to a point to bring the power back into a smaller area, but the range of focus doesn't allow you to do that for long distances that I've ever seen. Unless you want to burn something a few feet away, they are normally focused to infinity, just like a regular laser collimator lens is focused to infinity so the light is as parallel as possible without a focal point, just goes on forever as parallel light without being focused to a point, except for the divergence, which causes it to spread. If a laser pointer has 1 mRad of full beam width divergence, every meter the beam travels it will expand by 1 millimeter wider.
oh I see mine is just a 200mm, I was just trying to see if I could make something very cool out of something that was just collecting dust and do so with no money or at least very little money, You know what I mean ?That might be something you can use, but I'd look for a 500mm telephoto lens on ebay, they can sometimes be found for twenty dollars. Only thing is, some of them have two lenses, one in the base and one on the end. If I find that, I like to remove the first lens and just leave the one in the end, or the objective lens in. Depending upon it's focal length this could cause a problem because the tube then might not be the correct length for mounting on your pointer with some kind of diameter adapter. I don't want that first lens in the tube because it adds loss and wasn't the correct focal length to use with a pointer anyway, not the one I had.
The longer focal length is better for use as an expander. Also, I have found if the beam is expanded to no more than 1/2 the diameter of the collimating lens, the splash won't show very much, if at all. In my experience those wings will appear if you fill up the entire objective lens using the NUBM44.
IIRC the 500mm telephoto lens I used had a 70mm diameter objective lens. I don't know if this same benefit would happen for smaller diameter lenses with the NUBM44 laser diode.
To get one of those to work as a beam expander, what I do is leave the G2 lens (or what ever lens you are using) in the pointer, and then defocus it so that only half the diameter of the objective lens in the telephoto unit is filled with beam, then adjust the telephoto lens to collimate the beam to infinity. It takes some juggling between the G2 focus, the distance the telephoto object lens is from it, but once things are set up right, I was able to get a fully collimated expanded beam without wings and use the telephoto lenses focus ring to adjust to infinity, or to focus close in to burn things.
Experimenting can be a big part of this hobby, it can be interesting messing around with different optics you have lying around. Especially if you're someone that learns by hands on experience. :beer:oh I see mine is just a 200mm, I was just trying to see if I could make something very cool out of something that was just collecting dust and do so with no money or at least very little money, You know what I mean ?
I'll get back to you on that if I get some extra time because right now I don't think the "effort" to "reward" ratio is high enough for that project right at this moment..... lolExperimenting can be a big part of this hobby, it can be interesting messing around with different optics you have lying around. Especially if you're someone that learns by hands on experience. :beer: