I already did this using a laser pointer without a collimation lens together with a telescope without an eye piece and it worked, I just had laser far enough away from the objective lens so that the spot was big enough to cover close to 80 percent of the lens and it worked, but I did have to use the telescopes focus adjustment (in and out slider) to tune it to the low divergence sweet spot otherwise known as infinity.
I was able to do this using just one lens instead of the four used in a normal laser and expander coupling due to the following:
After removing my el cheapo 70mw 532nm lasers internal expander lens as well as its output or collimation lens (which together are an internal expander, something all of the 532nm lasers I've seen have) the beam spread out fairly fast directly out of the crystal, but
not as fast as it does if I left the expander lens on the crystal (for some telescopes, you might need to leave that expander lens on, depending on the characteristics of the laser and the length of the tube). Without any other lenses between the internal crystal and the output, I then coupled the laser to a 900mm long telescope (without an eye piece lens). The telescopes tube was just long enough to allow the lasers beam to expand enough in size to cover most of the 60mm objective lens, because of this I did not need the eye piece or an expander lens. The laser was just small enough to fit inside the tube where the eye piece would have been and when I took it outside and pointed it into the night sky, it produced a lovely low divergence fat beam on the output.
Below, photo of the lenses found inside my cheap 70mw laser pointer; collimation lens, expander lens and crystal assembly. Every DPSS pumped 532nm laser I've seen has a mini-beam expander built into it to reduce the divergence, these lenses are made from cheap plastic.
From this, I believe I reduced the divergence the same as if I had used a beam expander, but
without the loss of an expander lens in the laser itself, the lasers collimation lens as well as without the additional expander lens on the input of a normal expander (or eye piece of a telescope), this reduced the number of lenses by three, only needing one. From all of this, I really didn't have a beam expander at all, I just let the lasers beam expand to close to 50mm before collimation with a 60mm lens to reduce the divergence that way, but I had to use a long tube to do it.
The Lightning Stalker: I'd like to understand you regarding the possibility of the expanding laser light being at too high of an angle for the lens to be able to collimate the light properly. I can understand the glass can only bend the light so much for a given thickness, is that the limiting factor and because of this, there is a maximum angle which can be used with any given lens ?
If he doesn't answer, could someone please help explain this to me, can I really have too high of an angle from a concave lens for a PCX lens to be able to collimate the energy?
I've spent about an hour trying to write this post so it could be easily understood, damn! Here's a picture of another telescope I found for three bucks at a thrift store where I did the same thing, but with this pointer, I left it's expander lens glued onto the crystal holder, just removing the collimation lens and the beam expanded enough to cover most of the objective lens making a nice little beam expander, compared to the 900mm FL one I have. The opening where the eye piece would have been was just large enough to allow me to insert the head of my 70mw laser pointer into the tube (eight dollar laser on ebay, search 8000m 532nm).
Below is a photo of the 900mm FL telescope I wrote about above, in this photo I have my 175mw LaserGlow pointer taped to it without an eye piece but I do have two expander lenses in series between it and the telescope. There is no way I would modify my nice Aries pointer! The photo of the lens next to it is a concave lens I bought on ebay cheap, used two of them to get the laser beam to expand enough.
Here's a photo of the 900mm FL telescope showing its fat beam outside at night during a light drizzle, the green spot you see at the end of the beam is the base of a cloud the beam was hitting.
