The Shop > Tools
Anybody build Dan Gelbart angled laser centre finder?
BaronJ:
Hi Guys,
Re lens for laser pointers et al.
All CD/DVD drives use a single lens about 5 mm in diameter to focus the laser inside, so that the disc can be read. In all the drives that I have played with the lens is easily removed and can be re-purposed for use with a laser pointer in order to focus the beam.
A Google search "focus laser pointer" came up with lots of hits for doing this, along with lots of warnings. I also discovered that in the UK at least there is a legal limit on laser power and class. It seems that 5 mw is the maximum for non industrial lasers.
Note that using a lens does not increase the power of a laser, it only concentrates the beam into a smaller area. This in turn increases the danger of eye damage, not only due to direct illumination, but also specular reflection, which will be more from shiny surfaces. I believe that some kinds of safety glasses used in engineering reduce the risk of eye damage from this cause. I haven't done any research into eye protection of this kind.
HTH.
Arbalist:
I don't have an old CD unit but I've seen these:
http://www.ebay.co.uk/itm/5-x-7mm-Collimating-Lens-Focusing-Lens-For-Laser-Diodes-/271604566954?pt=LH_DefaultDomain_3&hash=item3f3ce4cbaa
I've ordered a small unit and it says it's "Focusable" so I expect it's already got a lens in it.
Yes, as far as I am aware 5mw is the maximum here in the UK and maybe Europe as well.
I can see how important it is for a stationary laser but I'm not sure how small the dot really needs to be for a rotating laser. All the ones I've seen so far certainly weren't particularly small.
PekkaNF:
mine definately has a lense on it and it does have an effect. I think it has regulator in it, I was measuring current and it lits when voltage is over aabout 2,4V and at 3.00V it draws 19,6 mA. From 2,7 to 3 V current decreases lineary. So...I think it is close to 1mW "laser power" 10% or so?. Electrically it looks good, but I either need to get smaller unit or have a way to adjust it optically.
I should rig it onto something and spin it to see how does it work on garage environment (lighting etc...). maybe I need to get lower power unit.
Pekka
vtsteam:
I'm just kind of curious -- at the distances we're talking about, small spot size, and using lenses, etc., why does it have to be a laser?
Arbalist:
--- Quote from: PekkaNF on April 12, 2015, 09:28:35 AM ---I either need to get smaller unit or have a way to adjust it optically. Pekka
--- End quote ---
Do you mean the Dot is too big?
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