Making a DIY text laser projector

Here's a standup maths video about that projector:

https://www.youtube.com/watch?v=FkHjG759ABY

Well, thank you for the unexpected nostalgia-gasm.

As a certain set of divorced absentee fathers are wont to do, my father would show up every 18 to 24 months, shower me with gifts, then disappear again in a puff of Ferrari exhaust. Those gifts would always be slightly off from what I wanted, usually reflecting his own tastes rather than what a 10 year old might want. One such time I got a Vectrex, I was the only kid who had one and as such it didn't really get much use beyond my brother and I. The cheapo ZX Spectrum 48k got much more use because I could swap games with friends, use hardware with their systems, etc etc. (Other items he'd buy me throughout the years: a Yamaha SHS10 keytar rather than a full size keyboard I requested. An expensive SLR camera whose lens drank batteries when I asked for clothes. An Atari ST that wasn't the same as the other kids' STs in a way I don't remember, but it couldn't do everything their machines could. All this sounds like I'm horrifically entitled and bitter; I was, back then. He's dead now, and my anger has been swamped by sad regret)

But the Vectrex and its vector graphics was pretty amazing. Razor sharp lines at a time when most systems struggled to do CGA. But I remember the games being repetitive and limited by the single colour screen.

Unfortunately, no.

This project was done as a raster display, not a vector display. Well done work, but not what you want for vector Asteroids.

If you wanted to DIY a laser vector Asteroids, you'll need to build your own galvo system in some manner. Google around for "DIY Laser Galvos" - you'll find a few people who have done it. Note: It isn't simple, nor easy. In fact, it'd probably be cheaper to buy some second-hand galvos off ebay than the time and cost to build it yourself. It would depend on whether you are more interested in DIY-ing the laser game, or if you are interested in learning how to build a laser light vector scanning system from scratch.

It's kinda the same question when people learn how "simple" it is to build their own CO2 laser - they think "Yes, now I can build a cheap laser cutter!"

But if you look into the forums about homemade laser building, every single one will advise you against that path, because it is a foolhardy thing to do - you will end up spending way more money for way less of a result than if you simply purchased the laser cutter (or at least the tube and such) outright, pre-built. Because building a laser is not as easy as it looks.

Same here. So weigh what it is you are trying to do and learn; maybe it would be worth it to you - and the game is really secondary.

That said - check out this instructable (and be sure to expand and read ALL of the comments - I mention something in there that may potentially be possible):

https://www.instructables.com/id/Moving-Things-With-Printed-...

IOW - there may be a way to make a very cheap capacitive feedback "galvo" using custom etched quadrature magnetic positioning PCBs. I think the concept is sound, but the question would be "throw" of the laser, and speed, and whether ringing/overshoot of the mass could be controlled using such a system...

There's issues with doing this with a laser.

The vector display used on Asteroids actually steered the beam to form each individual line, and could do it fast enough to draw all the objects on the screen at a decent refresh rate. Steering the electron beam is fast because that is all electronic.

If you wanted to do a laser vector display, that's difficult because you'd be physically moving something (the laser or the mirror). Doing that fast is super difficult.

You could create a laser raster display (as in the linked blog post), but that won't look or work the same as a vector display.

In principle, yes. In practice, it's painful. I built a vector laser projector back in the 80s when lasers were huge and my XY galvanometer probably cost $1000, but my college was paying for it, so why not? I drove the thing with a Fairlight CMI, onto which I painstakingly drew the parametric equations of X and Y with a light pen. (Nowadays I'd write a program to do that bit for me.) The biggest problem -- other than the cost -- was the fact that the galvos are not perfect: They exhibit lag and resonance at certain frequencies, so you have to cancel all that out and overdrive them in particular ways. This is probably easier today than then, and it can be done more easily with closed-loop feedback than the open-loop way I did it, but it looked amazing.

This. Lasers do damage. Worse yet, that damage (blind spots) often goes unnoticed for years. Then one day you want to be a pilot, finally get a proper vision field test, and are rejected.

Indeed... someone is facing criminal charges for pointing a laser pointer at a football player.

https://www.cbssports.com/nfl/news/report-chiefs-pushing-for...

>According to ESPN's Adam Schefter, who cited league sources in his report, not only has the fan been banned from Arrowhead Stadium for life, he'll also be charged by the Kansas City district attorney. Schefter reported that Kansas City police only wanted to cite the man with disorderly conduct, but the Chiefs are pushing for "the harshest penalty possible" as they try to deter fans from using laser pointers in the future.

The post indicates the builder went with a raster approach to the projection.

You could use three lasers (rgb) and merge their beams using a set of dichroic mirrors, then use the resulting beam as if it was your red laser. The control logic then switches the three lasers instead of only one.

Sure, rather easily in fact. You just need three laser diodes (Red, Green, and Blue), each pointed into the appropriate side of an RGB dichroic optical combiner cube. The cube redirects each of the three beams, combining them into a single beam emitted out of the remaining side (1) (the prisms can also function in reverse to split collimated a white light into constituent RGB components).

In lieu of a cube, you could use three (R,G,B) dichroic notch reflectors (mirrors) (2) and combine the lasers 'manually', but the cubes are nice because you don't have to build a mount for the I individual mirrors.

You can either scavenge a cube or dichroic mirrors from an old standard projector, or pick them up online for a few bucks. After that, just place the combined beam in the same path at the red laser shown in this example set-up, modulate the three lasers according to an image's RGB intensity values (you can separate an image frame into three RGB frames using openCV), and there you go.

Tangentially, the basic idea of scanning a laser to form an image is what underpins the Virtual Retinal Display (VRD) - a head up display technology developed at the Univ. of Washington and later attempted to be commercialized by Magic Leap (ML) for Augmented Reality eyewear. Even though ML hasn't panned out, I still see the VRD as a very viable path forward for high resolution/field of view AR displays.

1. https://en.m.wikipedia.org/wiki/Dichroic_prism

2. https://en.m.wikipedia.org/wiki/Dichroic_filter

Combining multiple beams into a single white beam is an answer, but is horribly inefficient. A better (ie brighter) approach is to scan with multiple beams, overlaying them as necessary to create various colors. It would be more complex (3x moving parts, more alignment) but the net result would be faster scanning and a greater percentage of laser time being used.