What is a laser projector?

‘Alex. What was that thing in your wedding speech?’

Three months ago, I had a pretty out of the blue idea. I was thinking about my then upcoming wedding and wanted to do something a bit different. I had been playing around with an old oscilloscope (more on that in a later post). I’d long known it is possible to draw pictures on an oscilloscope screen but had no idea how to do it. A bit of searching around online and I discovered it was possible to draw similar images with a laser. I decided I was going to figure out how to do it to make my groom’s speech a bit different!

The result is far from perfect: the coding is absolutely awful, the wiring is a bird’s nest and many people have done a far better job. But, considering I had no idea how to code, and knew very little about electronics when I started, I am damn proud of the thing.

So what is it?

Take a laser pointer and shine it on a wall. You get a dot. Now imagine waving the laser beam repeatedly sideways really fast. Since your eyes can’t keep up with it, you’ll see a line on the wall. That is basically what a laser projector is. It is simply a collection of bits and pieces which move a laser beam around very fast to create an image. I like to think of it as a very fast version of connect the dots – just move the laser between a collection of points and you’ll get an image formed of the lines between the points.

Of course, for the image to stay visible you need to ‘draw’ it over and over again very quickly. Once you stop moving the laser beam around, you are left with just a dot again!

Things I didn’t know

Three months ago, I knew I wanted to build one of these but I needed to figure out the following:

• How do I move the beam around? I knew this would require coding, which I am terrible at.
• When I figure out how to move the beam, how do I draw a line?  A circle? A curve?
• How do I make 3D images?
• How do I make images move?
• What sort of laser did I need? I knew very little about lasers.
• How fast do I need to move the beam?
• Will it work in a room that isn’t pitch black?
• How am I going to power it?
• Is it safe? This was the most important question. This project ended up using mains voltage so I had to be extremely careful and do my research.
• What else did I need to know? I had 3 months to learn how to build it. If I got delayed too much, it wouldn’t be ready for the wedding. Was I wasting my time?

Thanks to a copious amount of googling, I managed to answer all the above questions and I’ll be sharing the answers over the next few weeks.

For reasons I’ll go into later, the images made by the projector are difficult to photograph or video, but I’ll do my best and get some pictures and hopefully some videos up too.

Oh, by the way, I built the projector in secret. The only other person who knew about it was my best man. So, it is pretty exciting to finally be able to tell everyone about it!

Alex