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LAN_403

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Mon Apr 27 2009, 06:16PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Thanks for the kind words guys, and I have more good news!
1. As a part of a class I am taking at UCSB, I am designing a microprocessor based control system that will have a set of galvos (or possible orthogonal spinning mirrors like I used last time) and color control to allow easily projecting multicolor geometric shapes (will be done in early june)
2. I have ordered parts and hope to machine a new case for the second revision that will have proper dichroic mirrors to combine the beams, and some fresh, high quality uv curing adhesive to hold the optics in place which will hopefully keep the beams co-aligned a bit better (hope to get it built in late june)

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Wed May 27 2009, 05:45AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I figure its been long enough I should give you an update:
*The controller hardware wise is now just about done, and I am working on an enclosure to finish it off. I have simple code written to control everything, but am planning to let a user upload custom programs (ie, lists of coordinates/color values) that can be selected on the vfd.
*The laser head and galvos are now working in unison (abut somewhat haphazardly since the enclosure is still being built)
*It projected its first full color image! (well at least the only one that had more than one color at a time)

kilovolt

Fri May 29 2009, 05:00PM

Registered Member #2018 Joined: Tue Mar 10 2009, 09:56AM
Location: Switzerland
Posts: 74

Very nice work! Especially the full color range of the second picture looks awesome indeed! Well done

Regards kilovolt

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Tue Jun 02 2009, 05:06AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I am just about ready to call this project done, although if I have time tomorrow I am going to build up the rest of the case (although the wires-everywhere-held-together-with-double-sided- tape look seems to be in these days around campus...).

That said, I made a poster with an overview of the system:

But since the poster is not all that informative...

Overview
This project started out as a curiosity, and quest to build a whitelight laser for a reasonable budget (estimated cost for the laser source is $100). I then chose to use it for a project class (ECE 94R at UCSB) and added set of galvanometers and a controller for the system based on an Arduino microprocessor. The project has probably 200hrs of work in it (150 for the various revisions of the rgb source and 50 for the electrical design and programming), and about $300 in parts that went into it (about $150 in laser diodes--only $60 worth of which are in the final system, $100 for the microprocessor and lcd, $30 for the galvanometers, and $20 in odds and ends).

Design
The design of the projector is highly modularized, and can be easily broken down into the RGB source, Galvanometers, Controller, and Software.

RGB Source:
The RGB source was the hardest of this project to create, and I spent about 2 years working on it on and off. The concept is simple--take red, green, and blue laser diodes, and use dichroic mirrors to combine them into a single beam, which would be sent to the galvanometers.

1243915933 56 FT22477 Rgb System Optics 2

In practice, as the rest of this thread shows, this was not so easy. In order to keep the beams coincident, which is absolutely necessary for proper color mixing, they must be all kept aligned in the x/y/z axis to within about .05" or so, and 0.03mRad in pitch/yaw. This second figure is much harder (that is .1" over 30ft), and is a result of the fact that the divergence of the laser beam is on the order of .2mRad so to keep the beams at least somewhat coincident .03mRad is the max error you can use. To put that in perspective, if one of the edges of the 1/4" square mirrors moves 1/15,000th of an inch, the beam will not be aligned anymore.
That said, to get around this problem I machined a pocket in a 2" square by 1" thick aluminum, and use uv curing epoxy to hold the optics in place:

(for more photos of the system, see the post made on 4-20)
The lasers themselves would be to costly to buy from a laser manufacture, so alternate sources of the lasers were found. For the red laser, I used the 650nm laser diode found in a high speed DVD-burner, for the blue laser I decided that the violet laser found in a blu-ray or hd-dvd burner would suffice, and for the green I used a dpss module extracted from a 50mw hand held laser pointer.

Galvanometers:
The purpose of the galvanometers is to position the beam, which allows arbitrary shapes to be 'drawn' using the laser source. Due to cost restrictions, I used a set of stepper motors for the galvanometers. One of the windings was fed with a dc bias which acts as a 'spring' holding the mirror at 45 degrees, and the other winding is fed a signal from the Arduino which will rotate the shaft some angle proportional to the input current. Mounted on the shaft is a mirror, which deflects the beam at some angle, proportional to the rotation of the shaft. Two of these are placed orthogonally, which allows the beam to be positioned at any x,y coordinate on the surface the projector is pointing at, with a scan angle of about 30 degrees (60degrees total scan). However, due to the large momentum of the motors, and lack of feedback, the scan speed is limited to about 1000points/second, and only simple shapes which can easily be represented by a combination of sine and cosine--circles, stars, etc.

Controller:
The controller for the project is electrically quite simple, and most of the grunt work is done in a microprocessor. The hardware timer modules in the Arduino microprocessor are used to generate 5 PWM modulated signals, 3 of which are used to control the laser intensities and 2 are used for the galvanometers. To actually drive the laser diodes a constant current source based on a LM317 voltage regulator is used, and a small mosfet is put in parallel with the laser diode--such that with the mosfet is it will divert current from the laser and blank the laser. The mosfets are driven directly from the PWM outputs of the Arduino, and as a result the lasers are actually being pulse width modulated. However due to the fast PWM outputs of the Arduino (32KHz) and slow scan speeds, this effect is not noticeable in the scanned images. Similarly, to drive the galvanometers, the PWM output from the Arduino is fed through a small amplifier (actually designed for driving mosfets), which is then fed to the galvanometer. Through careful biasing of the galvanometers, it is possible to get both a positive and negative scan angle using this technique, and due to the high momentum of the galvanometers they effectively filter the PWM signal and respond quite linearly.
The microprocessor is an Atmel ATMega328, which has the Arduino bootloader and code written using the Arduino IDE, which controls all of the components of the projector. Due to the limited storage available on the Arduino, an Atmel DataFlash chip was added, which allows about 50 programs that have 4000 points in them (about 4s of continuous scanning) to be stored. Finally, a 4x20 character LCD and simple up/down/select user interface was added to allow programs to be easily selected. Finally, there is a manual mode where the Arduino simply accepts coordinates from an external computer over a RS-232 compliant serial port, which allows for longer and more complex programs to be displayed.

Firmware:
The firmware for the projector is written in a Wiring based program language (the Arduino language), which while not my first choice is what the class was based on. The main loop in the code reads coordinates from the DataFlash and updates the galvanometers and lasers accordingly, then waits a period of time defined by a 5th coordinate saved in DataFlash. Additionally, there a program selector logic, which displays each program's name on the LCD display, and allows the user to scroll through them using an up/down pushbutton. Additionally, there is a random mode which uses a simple random generator, based on a multiply-with-carry random number generator, which displays pseudo-random abstract shapes, a manual mode which projects coordinates received from an external computer via a serial port, or a test mode which displays a simple circle made up of several colors.

The test pattern (projected on a piece of paper because my camera cannot see the 405nm on a non-florescing surface) and the random data.

Conclusions:
All considered, I learned a lot in making this project, and definitely have plans for a rev 4 (although probably not any time soon). I encourage you to try a project like this, however it is not something that you can throw together in a weekend and have a really decent working project. I really enjoyed the construction process, and the projected images are amazing. The pictures really do not do it justice, the color gamut obtained using 405nm and 650nm is incredible, and computer monitors simply cannot display the range of colors this thing produces. Especially the random mode is very mesmerizing, and it can fill half a room with ever changing patterns of brightly colored lines. I hope you enjoyed reading about it!

c4r0

Tue Jun 02 2009, 08:48AM

Registered Member #151 Joined: Sun Feb 12 2006, 02:53PM
Location: Poland
Posts: 153

That's simply awsome! Where did you get the dichros from? Looks like they are from some optical drives, although on the other hand if you have such lab you certainly have also great dichros :P I have a lot of different dichros harvested from DVD writers but found only one that works quite good for combining 532nm and 650nm. And how do you think is it possible to align all the optics without such sophisticated mechanics like yours or adjustable holders? I set up a quick and dirty RGY laser projector on Saturday. It's so cool that I want to try RGB with 405nm laser now

Youtube:

c4r0

Sun Jun 21 2009, 01:47PM

Registered Member #151 Joined: Sun Feb 12 2006, 02:53PM
Location: Poland
Posts: 153

Hello

Inspired by your project Peter I also built an RGB laser this weekend and it works quite well. I used dichros from HD DVD and DVD drives, not perfect (especially for green) but works. And BTW do you study at UCSB (I just noticed a logo on the poster)? I'm going to SB on Friday

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Sun Jun 21 2009, 10:27PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

That looks great! I am glad the project inspired at least one person

Also, I bought some proper dichroic mirrors that I am going to dice up to the proper size, if you are interested I could probably sell a set of r/g/b dichros for about $10 a piece or $20 for the set.

Can't wait to see it working with the projector!

And yes, i do go to UCSB, but i am not there over the summer. If you look hard enough you should be able to find my poster in harold frank or engineering 2 somewhere, but I am not sure where they put them up or if they are still up.

Conundrum

Sat Aug 08 2009, 03:49PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

hell yeah :) i'll buy a few if they work as described.

btw if its any help I just purchased a load more indium and bismuth metal, so if anyone or ... wants some more low melting point alloy PM me. I am happy to accept swaps as am currently short of several parts including piezoelectric transformers and large area (phone type?) piezo sounders.

c4r0

Fri Oct 02 2009, 09:41PM

Registered Member #151 Joined: Sun Feb 12 2006, 02:53PM
Location: Poland
Posts: 153

Hi again!

I just have to show it to you guys! I have a flu for a few days so I'm sitting home and trying to not be bored - I finished my RGB laser today. I made a 3-channel LD driver and a wooden casing for the optics and hooked it up to my galvos. It works really well, much better than I thought it would!

The only bad thing is that there are different LDs currents setting for white color for eye and camera, so I have to tune it every time I want to take some nice pics or enjoy the effects with naked eye

..., does your dichros sell offer still stand?

And BTW I spent July in Santa Barbara, haven't seen your poster but I've been on a few parties on del playa! Oh yeah

MRacerxdl

Fri Oct 02 2009, 10:23PM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

WoW thats impressive, I little curious:
The photo shows the laser at air, as like was some smoke or something so, but it doesnt seens to be smoke there. Is there effect visible with naked eye?

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