I have noticed that a lot of cheap non-focusable laser pointers seem to have relatively low divergence, so the dot stays pretty much the same size over all distances. I have one focusable laser, and I can never seem to get its divergence quite as good as the cheap ones. Now, it is 405nm, and I am aware that due to the wavelength, the dot appears to be much larger than it really is at long distances. However, I still notice that to someone standing close to the dot, it still gets bigger.
Some possible reasons for this:
1. I'm just not very good at focusing.
2. The threads of the adjustable lens aren't fine enough, making it difficult to focus accurately and hold the same position for a long time.
3. There is something about the optics or construction of fixed-focus lasers that collimates better than my adjustable lens possibly can.
I have a hunch that #3 is at least part of the reason, and that in general there is a tradeoff: when you get an adjustable focus laser, you can get it pretty well collimated but not quite as good as a typical fixed focus laser. I haven't read anything that mentions this, so I might just be crazy. Can anyone confirm this, or give another explanation?
Thanks
Some possible reasons for this:
1. I'm just not very good at focusing.
2. The threads of the adjustable lens aren't fine enough, making it difficult to focus accurately and hold the same position for a long time.
3. There is something about the optics or construction of fixed-focus lasers that collimates better than my adjustable lens possibly can.
I have a hunch that #3 is at least part of the reason, and that in general there is a tradeoff: when you get an adjustable focus laser, you can get it pretty well collimated but not quite as good as a typical fixed focus laser. I haven't read anything that mentions this, so I might just be crazy. Can anyone confirm this, or give another explanation?
Thanks