So after considerable deliberation I purchased a 500 mW RGB laser used in video projectors and light shows, with a pair of blue, green and infrared safety goggles.
RGB lasers create a white beam consisting of red, green and blue lasers that are combined using a couple of dichroic mirrors (I did an experiment with a dichroic prism previously here).
Before firing it up I researched laser safety to calculate the amount of energy that would enter your pupil if the beam entered a night adapted pupil, with the line generator spread at various distances. I also joined the PhotonLexicon forum, which was worthwhile because the first advice was to ensure you don’t mount any flat surfaced optics (eg filters or line generator) perpendicular to the beam because the reflection can fry itself – always mount them at an angle…
So I went about designing an enclosure so that the line generator could be rotated and the beam can be masked off to reduce the possibility of catching your eye in stray beams. Another necessity is an interlock switch so that the laser can’t be switched on without the optics in place.
I needed to see why the beam was so inconsistent and on closer inspection I found the colours weren’t exactly
Making a Powell Lens line expander:With the help of Graham Stabler and Tim Stephens from Oxford Hackspace looked into making my own Powell lens line expander – Graham cut out some blanks in perspex and using 1500 grit sandpaper and brasso which I polished on a couple of blocks of wood.
That’s as far as I have got.
Next stage – polish a new blank with up to 2000 grit wet sandpaper followed by aluminium oxide polish finish using a polishing jig made on aluminium blocks.
Then hopefully we’ll have a precision polished lens with a more consistent line.
Next step is to integrate a beam controller to reduce the beam intensity to safe levels using pulsed width modulation (PWM) and RGB colour adjusters to make it as close as possible to white.