5 ms·

Making a DIY text laser projector

173 points by atomlib 8y ago

Vrpe 8y ago
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?
- frabert 8y ago
  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.
  - MarkSummer 8y ago
    ...or what frabert said much more succinctly :)
    - Vrpe 8y ago
      Both are good :)
  - squarefoot 8y ago
    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.
- MarkSummer 8y ago
  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 https://en.m.wikipedia.org/wiki/Dichroic_prism 2. https://en.m.wikipedia.org/wiki/Dichroic_filter https://en.m.wikipedia.org/wiki/Dichroic_filter
  - pjc50 8y ago
    Hmm. That sounds like maintaining the alignment of the three beams would be a total nightmare.
    - dekhn 8y ago
      it's funny, we're building this set up (https://github.com/PRNicovich/NicoLase 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"
    - jbay808 8y ago
      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.
- sandworm101 8y ago
  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.
  - rolph 8y ago
    if the 3 beams were miniaturized as in surface mount diodes: these for example http://www.excelitas.com/Pages/Product/Surface-Mount-Laser.aspx 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.
    - cr0sh 8y ago
      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/mechanical-television-primer/2463/26 http://dci-forum.com/back-roots-tv-history-beginning/24/mech...
      - Animats 8y ago
        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.
        8y ago
kgwxd 8y ago
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.
- sigwinch28 8y ago
  Here's a standup maths video about that projector: https://www.youtube.com/watch?v=FkHjG759ABY https://www.youtube.com/watch?v=FkHjG759ABY
- bloopernova 8y ago
  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.
  - stevekemp 8y ago
    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.
gdubs 8y ago
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.
- plussed_reader 8y ago
  The post indicates the builder went with a raster approach to the projection.
  - gdubs 8y ago
    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.
sammycdubs 8y ago
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.
- sandworm101 8y ago
  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.
- astura 8y ago
  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-maximum-penalty-after-fan-who-allegedly-used-laser-pointer-on-tom-brady-gets-caught/ 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.
tdeck 8y ago
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 https://youtu.be/JKJ_hCDKJic
equalunique 8y ago
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...

173 points by atomlib 8y ago

Vrpe 8y ago

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?

frabert 8y ago
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.
- MarkSummer 8y ago
  ...or what frabert said much more succinctly :)
  - Vrpe 8y ago
    Both are good :)
- squarefoot 8y ago
  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.
MarkSummer 8y ago
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 https://en.m.wikipedia.org/wiki/Dichroic_prism 2. https://en.m.wikipedia.org/wiki/Dichroic_filter https://en.m.wikipedia.org/wiki/Dichroic_filter
- pjc50 8y ago
  Hmm. That sounds like maintaining the alignment of the three beams would be a total nightmare.
  - dekhn 8y ago
    it's funny, we're building this set up (https://github.com/PRNicovich/NicoLase 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"
  - jbay808 8y ago
    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.
sandworm101 8y ago
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.
- rolph 8y ago
  if the 3 beams were miniaturized as in surface mount diodes: these for example http://www.excelitas.com/Pages/Product/Surface-Mount-Laser.aspx 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.
  - cr0sh 8y ago
    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/mechanical-television-primer/2463/26 http://dci-forum.com/back-roots-tv-history-beginning/24/mech...
    - Animats 8y ago
      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.
      - 8y ago

kgwxd 8y ago

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.

sigwinch28 8y ago
Here's a standup maths video about that projector: https://www.youtube.com/watch?v=FkHjG759ABY https://www.youtube.com/watch?v=FkHjG759ABY
bloopernova 8y ago
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.
- stevekemp 8y ago
  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.

gdubs 8y ago

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.

plussed_reader 8y ago
The post indicates the builder went with a raster approach to the projection.
- gdubs 8y ago
  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.

sammycdubs 8y ago

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.

sandworm101 8y ago
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.
astura 8y ago
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-maximum-penalty-after-fan-who-allegedly-used-laser-pointer-on-tom-brady-gets-caught/ 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.

tdeck 8y ago

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 https://youtu.be/JKJ_hCDKJic

equalunique 8y ago

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...