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Making a DIY text laser projector (habr.com)
173 points by atomlib 11 days ago | hide | past | web | favorite | 31 comments





Someone recreated the arcade version of Astroids (vector graphics) using an expensive laser projector. Could something like this project pull that off on a smaller scale? It'd be like a DIY Vectrex, and it would be glorious.

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.


The Vextrex was a little repetitive, but the way they tried to make it colourful with the gel-overlays was kinda endearing.

I received one, as a cast-off gift from a richer cousin. But mostly I spent my time on the ZX Spectrum. More games to play, more coding to be done on it, and I spent hours hacking games for extra/infinite lives.


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...


That feels a lot more complicated than it needs to be.

Have you ever taken apart a mid-range camera with an electromechanical image stabilizer? It's a triangular plastic plate with a lens in the middle, a pin at one corner, and a couple of rare earth magnets at the other two. There are two voice coils mounted next to the plate to repel or attract the magnets, and a light spring to center the whole thing. Remarkably simple device, doing a remarkably similar job (modulo replacing the lens with a mirror if needs be).


Here's a standup maths video about that projector:

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


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.

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.


This is super cool, but I always get nervous about people messing around with lasers. This person seems to be somewhat safety conscious, but I worry they get treated as toys.

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.


If I could just string together several of these to get a vt100 terminal, then I could SSH in a room at night with all the lights turned off and have zero exposure to eye-straining blue light...

It can be hard to appreciate laser graphics unless you see them in real life. There’s a vividness to them that’s quite beautiful compared to rasterizd graphics.

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

Sure, I read it. The author discusses the trade offs, and the fact that they went with a raster approach in my mind doesn’t diminish this awesome project / post.

My point was simply that a generation of people who’ve never seen vector graphics in real life might be wondering what the big deal is. It’s worth trying to find an arcade where you can see an old working cabinet up close.


Here's a video of an earlier DIY laser-pointer projector. It's a bit tougher in appearance but still quite cool: https://youtu.be/JKJ_hCDKJic

Well layed out, my understanding of electrical engineering is a bit lackluster, but I appreciated the article nevertheless.

How hard would it be to self develop a multi color laser projector? How would it work?


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


Hmm. That sounds like maintaining the alignment of the three beams would be a total nightmare.

it's funny, we're building this set up (https://github.com/PRNicovich/NicoLase) in our lab for microscopy. From the docs:

"When aligning your laser launch, do not rush. This is not something to attempt late on a Friday afternoon in a free hour before heading to the pub. This is a task involving a great amount of precision and small, careful movements. There will be very little in the way of positive results until the task is nearly complete. Set aside up to a several hours to complete the alignment, especially on your first try"


You only have to do the alignment once, on the input to the combiner cube. Then you get a single output beam sent to the galvo.

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.

This, and then projecting the RGB beam from the rotating mirror fixed on the ceiling to a circular screen surrounding the user for full 360 degrees experience.

...or what frabert said much more succinctly :)

Both are good :)

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.

if the 3 beams were miniaturized as in surface mount diodes:

these for example

http://www.excelitas.com/Pages/Product/Surface-Mount-Laser.a...

and were carried or fibre coupled in a single "gimble?" there would not be duplication of moving carriage parts. a "trinitron like" emitter gun would be possible. moving a mirror as done by the author would also reduce the mass that would move at high speed while scanning across a large display field, it would then be a matter of timing a laser pulse of desired color to the desired position of the mirror set. a look at CRT television/display circuitry would be very inspirational, only in this case the color is emitted rather than stimulated by flouresence of a phosphor target.


Something to keep in mind is that mirror scanning for television is a very old technology, dating back to the beginnings of mechanically scanned TV:

http://dci-forum.com/back-roots-tv-history-beginning/24/mech...


Yes. There's a long history of ideas in this space. DLP projectors, with a MEMS mirror for each pixel, are one of the few successful examples. Any system where you illuminate only one pixel at a time flickers horribly, which is why this sort of thing is used for laser light shows and not much else.

- now if you can send the beam[s] through a tft display minus the backplate, and darken pixels you dont want to illuminate then scan the beam across the whole thing...This has a madmax or a maxheadroom sort of appeal to it.

i was trying to find the mems mirror around but couldnt , still looking for dead projectors to throw in the morgue of parts.


I do have wide streak of steampunk, i love retrotech, espescially when using junkyard parts and a few mailorder bits together.



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