Intro: Get Your Laser Pointer 'Spot On'.
Check and adjust the alignment of your laser pointer or module.
This is a spin-off from another 'ible which is currently under construction. I bought a green laser pointer and took apart the 'easy bits' which in this model was only the focusing lens of the collimator. (The collimator is a pair of lenses which align the laser light from the diode into a parallel beam.) I then had the problem of getting the focusing 'spot on' again, and came up with this method.
To do this, you will need a fairly advanced camera with a zoom function and 'manual' mode.
Also a dark place, a couple of tripods (or other way of holding camera and laser steady) and a piece of matt black paper. Do not try this if you cannot manually set the aperture and speed on the camera as it will not work.
Step 1: Warnings Etc.
Firstly, the usual warnings :
Laser light can damage your eyesight permanently.
Avoid looking directly into the beam, even if it's reflected.
I'm showing how I aligned my pointer.
If you try doing yours and break it I'm not going to buy you a new one.
Your laser pointer may already be 'spot on' and this procedure may be totally unnecessary.
A quick word on 'tweaks' :
There is information on the internet for various power mods to laser pointers and modules. Some involve 'burning' a component, or 'turning a screw' to increase the power output. These mods are very likely to kill your laser immediately, or if they do work, will drastically shorten the life. My advice is do not try them unless you are willing to waste the pointer.
Step 2: Set Up Your Equipment
There is a ring at the 'business end' of most laser pointers which can be screwed off. If it's tight, wrap a turn of wide rubber band around it and try again. Don't use pliers as you will pretty certainly damage the pointer.
Underneath the screw end is a slotted ring. This can be turned, but may have some resistance. It is very rarely glued solid but if it doesn't move with reasonable effort, don't force it. I used long nosed pliers, but whatever you use, be very careful not to touch the lens.
If you have a bare module, the adjusting ring should already be visible.
Turning this ring adjusts the distance between the two lenses, and so the collimation.
Ensure the laser has relatively new batteries so the brightness of the laser doesn't change while you're setting it up. Also let the laser warm up to reach maximum power before you start.
Mount the camera and laser pointer on tripods. I used a rubber band to hold the pointer down. This has the advantage that if it doesn't have a locking 'on' switch, you can just twist it to turn it on.
Position a sheet of matt black paper at one end of the room; yourself, the camera and the laser at the other. The further the distance to the paper, the better. I was around 15 feet away.
Set the camera to fully manual mode. Ideally, show a grid of thirds in the viewfinder.
Turn on the laser, and point it at the matt black paper.
Set the zoom, aperture and speed to make the laser spot to fill around half the viewfinder screen (or as much as you can). Lock the focus. (I used f4 at 1/5th second.)
Step 3: Adjustment.
Turn the focusing ring half a turn one way and check the size of the spot in the viewfinder. You don't have to take a photo. The photos here were taken at half-turn intervals.
If the spot gets larger, go the other way.
Tweak until you've gone past the 'sweet spot' then reverse in smaller increments until you have the smallest spot possible.
The aperture and speed have to be set manually as any change to these will change the apparent size of the spot. In 'auto' mode, the camera would adjust to give a 'correctly' metered photo according to its settings.
Once you have found the best point, if the ring was feeling loose put a tiny bit of 'Pritt Stick' or other solid paper adhesive on your finger and very carefully work a bit into the gap. This will harden and lock the ring, but not permanently. Be very, very careful to keep this away from the lens.
Screw the end-cap back on, and your laser pointer is now Spot On.