Mad scientists wanted to build laser-based vector HUD

[Rococo Modem Basilisk]

I've been running variants of this design around in my head for something like two years, but I haven't drawn schematics on the computer until now. The general idea is that you have a rotating laser (yaw) and a rotating mirror (pitch), then maybe some lenses and something to draw on. If you build it small enough, you can probably drive it with stepper motors and make a (VERY LOUD) monochrome vector graphics display on the inside of a pair of sunglasses. Build it bigger and you can project it on a wall or something.



I have too little blood in my caffeine system currently, and don't trust my math, so I won't post my code for determining the position of points based on the rotation of the two pivots and the distance between the pivot and the {mirror,laser source}. If you have mirrors, steppers, laser diodes, and too much free time, feel free to play around with the design. I don't have the cash to build a prototype (though it is sure cheaper than a MyVu). If you happen to have a red laser, a green laser, and a blue laser (plus, again, lots of free time and some more lenses) you can probably build a colour version capable of displaying both primary and secondary colours of light (plus white), but that requires more optics experience and probably more maths than I am aware of.

[Rococo Modem Basilisk]

Probably. Not sure. The main problem with just using plain DC motors is that they don't stop when you tell them to. I know for sure that floppy drives have usable steppers for this project. Scavenged servos from remote control cars/planes/whatever are also good. But, if you can drive it accurately, it's probably okay. (I'm not sure if a cdrom motor is just a DC motor for spinning the disk and a couple solenoids for moving the laser around on one axis -- in which case, it would not be suitable).

[Faust]

While a stepper has very smooth motion, getting one with a fast enough response to actually properly generate what you need you might need something expensive.

[Rococo Modem Basilisk]

The original design (as of N years ago) had DC motors and bumpers. As long as the timing is reliable, you can probably turn the laser on and off while the thing is going. I just didn't think the timing would be reliable. A variant was kind of a pseudo-raster (two motors set to go back and forth out of phase, with the speed of one being N times the speed of the other, N being the number of rows, and the only thing being controlled is the laser) -- but that should probably be far less efficient, and one of the goals was to be able to automate particular types of things by memorizing the path (it was initially for a cheap augmented reality rig, so having a dedicated micro capable of remembering a series of paths and going through them on the command of another micro would be VERY useful since all the chips involved were planned to be AT90S8515s or something).

[Doktor Howl]

Gonna be big.  And pricey.

This stunner thing is very simple by comparison, and is still costing an arm and a leg, and more time than I thought.

[Rococo Modem Basilisk]

I'm kinda lost as to how this would work out cheaper, as surely you'd need an arduino or knock off, at least to drive em? right?

Initially, I was planning to use an AVR -- specifically, an AT90S8515 (which I have two of, and which sold for something like $5, and more like $2 if you order ten at once). Currently, that line is being phased out, and they suggest the ATMEGA8515 (same pinout, twice the flash memory, twice the speed, slightly cheaper last I checked) instead. The arduino would probably be overkill for this project. If you managed to scavenge all the other parts (including gearboxes, lenses, whatever) a stereoscopic HUD of this type would cost you about $20 (three ATMEGA8515 chips plus shipping -- one for each eye, and one to keep they eyes synced up. Might actually be less, since you might trigger free shipping).

That said, mechanics isn't my thing, nor is optics, so appropriate motors and lenses may be super-expensive or super-rare. I was told that the steppers out of a floppy drive would be suitable for the project by an otherwise reliable source, but that was several years ago and I didn't have any schematics to show.

Edit: The programmer for an ATMEGA8515 (if you use a parallel port) is a couple capacitors, a resistor, a breadboard, and a 555 timer, iirc. There's a gnu toolchain for compiling code for that arch. I never got around to actually using either of my AVR chips, but in theory they shouldn't be particularly expensive.

[Template]

Stepper motors might be overkill-you're just moving a mirror.  You could probably use a speaker and a light weight mirror to point the light ray wherever.

[Rococo Modem Basilisk]

You could probably use a pivot and a solenoid as well, and just keep the solenoid moving in and out at the appropriate rate. However, I don't know where to scavenge solenoids.

How would you do it with a speaker, by the way?

[Doktor Howl]

Note:  This project will never get done.

It's an interesting thought experiment.

[Rococo Modem Basilisk]

You are probably right. It took me three years to draw the damned thing up.

[Doktor Howl]

You are probably right. It took me three years to draw the damned thing up.

Now all you have to do is buy the hardware, and build it.

And like I said, that simple-ass stunner I'm working on is taking more time and money than I expected, by a long shot.

[Rococo Modem Basilisk]

Well, buy the hardware, built it, and write the code to make it into something other than a doorstop

[Doktor Howl]

Well, buy the hardware, built it, and write the code to make it into something other than a doorstop

Wait.  The code isn't even written?

Do you at least have the logic worked out?

[Rococo Modem Basilisk]

It's trig. Other than accounting for the radius of the axles, it's one line of C code in a loop.

[Bella]

You could probably use a pivot and a solenoid as well, and just keep the solenoid moving in and out at the appropriate rate. However, I don't know where to scavenge solenoids.

How would you do it with a speaker, by the way?

You can scavenge solenoids from car starters in auto junk yards, from battery operated clocks and, I believe, from old disk drives. And also from my brother's garage if you're willing to travel to Utah for one.