Finally there has been some progress with LaserLine, just in time for EOH. Last Thursday night I had a chance to get EasyLaseUSB support hacked in to our ILDAInspector program; allowing me to display ILDA frames and sequences on the oscilloscope.

First ILDA Test Frame output on EasyLase USB from my Mac.

I posted some additional videos and photos at http://www.acm.uiuc.edu/~hagedorn/EasyLase/

This represents good progress toward LaserLine 2.0’s core objectives. More information about what those objectives are, and how we’re progressing is available at our Trac site.

I’ll be spending whatever free time I have over the next couple of weeks implementing the optical position-detector system on the galvos (I finally gave up on the RF-PD) and fixing bugs in the EasyLaseUSB driver for Mac OS X. It is close, but still occasionally hangs; and that needs to be fixed completely. Engineering Open House is approaching quickly; so are due dates for assignments…

I am somewhat, perhaps to an unhealthy degree, frightened of adhesive. Not of it’s contents, or it’s consistency; it’s texture or it’s smell, but of the permanentness of it. While I understand there are somethings that are worth making permanent, the assembly of an experimental galvanometer is by no means one of those things. I question both my ability to line up the parts without smearing the epoxy, and their placement. Perhaps the dimensions won’t even be correct!

Alas I am afforded a bit of consolation in the opportunity to “dry-fit” the components of the galvo project before committing to final assembly. No thermal epoxy or cyanoacrylate, no worries when things need adjustment. I seized the opportunity and have included a number of pictures (inside this post) demonstrating the details of the assemblies, as they finally resemble something that will actually work.
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A few weeks ago the most adorable little Päckchen arrived on my doorstep from Germany. Inside was the EasyLase USB interface by JM Laser. The EasyLase is a USB device that has a 25-pin ILDA compatible DB-25 connector to output analog signals for laser projectors. It incorporates 12-bit DACs for the X-Y channels for superior resolution.

Above: Interface, first output on Oscilloscope

In testing so far, it seems like it is going to be great, but there is plenty of coding to do yet to achieve the greatest performance. The card has plenty to give, and extra features like DMX512 In/Out–one less thing I need to buy!

Thus far, because the projector isn’t quite finished yet, I’ve been testing with a Tektronix 2440 Oscilloscope. My friend Sean helped code a 3d Torus(QuickTime video) demo. It worked quite well, but I’m still having trouble with FTDI’s D2XX driver for OS X version 0.1.0, perhaps the next version will solve some of the problems I’m having. Specifically, read and write calls are hanging when I know they shouldn’t.

A while back I had the pleasure of speaking with a gentleman named Craig from the ECE Machine shop here at my university. I had the opportunity to talk to him because I was picking up some parts that he had machined for me out of solid aluminum!

I consider them stunning.

Key features include all-aluminum construction for optimal heat-dissipation as well as strategically placed mounting holes for circuitry or additional heatsinks. The should also provide flexible mounting surfaces for the galvos. It will be necessary to use thermal epoxy to glue the coils to the surface for maximum thermal conduction.

I really anticipate these will provide high-performance platforms for the rest of the components.

I am providing CAD drawings of the Base and Side parts in PDF format if you’d like to make them yourself as well. If you’ve like them in an editable format, just let me know.

Over the past couple of months a number of specialized components have arrived for the laser scanner. I shall summarize where to purchase them here.

1. Ball Bearings - 2×6x2.5 Hybrid Ceramic/Stainless Steel Ball Bearings from VXB for $4.95/each.
   These bearings are designed to be especially “smooth” and have an ABEC-5 rating. In searching for bearings, I learned that all is not contained in the ABEC rating, and the ceramic properties of these bearings provides greater smoothness; though they are not rated for extremely high lateral loads. This is not a problem with a couple-gram rotor. Perhaps less expensive bearings would be adequate, however this is a vital component so it was probably worth it.
2. Mirrors - small and thin first surface mirrors off of eBay.
3. Set Screw Collars - 2mm Metric Set Screw Collars model MC-02 manufactured by Climax Metal Products. Purchased at Fastenal for $1.04/each available only in the (especially cool looking) Black Oxide Finish.
4. Machined Galvo Frames! You’re going to have to come up with something for these…

Left to right: US quarter dollar coin, bearing, mirror, and collar.

Completely Offtopic

I highly recommend the following guide for people new to IRC and the unicies:

A Guide to Efficiently Using Irssi and Screen

I’ve been in a bunch of IRC channels lately, including #laserfreak on irc.wiredirc.net, a german channel discussing laser tech, and a bunch of other channels around UIUC.

I spent quite a while building the prototypes. They include the cheap bearings I bought at the hobby store, a steel axle, and the N50 cylindrical magnets.

The acrylic models gave me a good idea of the tolerances involved, but it was clear I needed more precision. I used the dremel to finish the prototypes, drilling holes, and tapping some of them for 2mm screws. Unfortunately my drilling was not precise enough for production work.

I never install the coils more than just for test-fit in the acrylic prototypes. Amplifiers would be needed before any performance testing would be possible anyway. Eventually the prototypes proved useful in demonstrating design to the machinists that would build the aluminum pieces for the final version.

Electricity can be scary. As can be lasers. When working with high voltage and lasers always be sure to post appropriate warning signs. “But what if I don’t have the appropriate warning signs,” you plead. (Of course you are asking this, because of course you are commonly working with these, and other sorts of dangerous things…) The answer is simple. Make your own by following these simple steps:

1. Find appropriate warning sign on Google Images
2. Re-implement graphics in Adobe Illustrator
3. Mask, X-acto, and paint; repeat for each color

I followed this procedure exactly and produced a great warning sign for the power supply mentioned in a previous post.

I recommend using a good german font, like one from the Din Schrift family, and being careful with the masking. I covered the box in masking tape, printed my design, and taped the printed template. Next I used an X-acto knife to cut out areas of exposure for a given color. I repeated for each additional color, layering as I went.

Speaking of Power Supplies…

Every summer I spend way too much on eBay. Case in point:

Its a Power Designs TP 343B triple output power supply. Extremely well built on the outside, surprisingly modern on the inside, with ICs and such. I’m quite happy with my first real lab power supply. There will be at least one more post about summer eBay purchases within the next few weeks. I can make this guarantee because I have already made the purchase.

LGK-7630

I started working with lasers in 2003 when I bought the above Siemens LGK-7630 HeNe laser off eBay for like $15.00. It was lots of fun; rated at 6.0mw; manufactured in march of 1984, and tested 6.4mw (according to a sticker) in 1986; apparently removed from an old Xerox product of some sort.

Shortly after getting my second laser, the Argon Ion one, the power supply on the Helium-Neon failed catastrophically. This isn’t such a surprise for a $15.00 laser, but I couldn’t find a suitable replacement at a reasonable cost for a long time. Having the JDSU 2214 around made it even less of a priority.

Fast forward to 2006; development on LaserLine and the galvanometers is getting serious, so I need an easy to operate beam that I can switch on and off with no fuss so I can focus on development of the scanning hardware and software. No maintenance; instant on, quiet operation. Perfect.

Power Supply

Meredith Instruments (via eBay) happened to have a Melles Griot 05-LPM-948-065 Power Supply at just the right price. It does somewhere between 1.85 and 2.45 KV at 6.5ma; quite reasonable for the 15″ LGK-7630 tube (well, the enclosure is 15″, I’m guessing the tube is 13″ or 14″).

A quick trip to Fry’s provided me with some parts for the enclosure; other parts were found in my basement. Plenty of Dremel work was required for the IEC power plug and 1A breaker, but they look nice. Now I just need a source for a key switch, because it is a class IIIb laser, being above 5mw. Black paint should really make it look better too.

Beam Profile

The beam profile on the HeNe is so much rounder and consistent than any laser pointer I’ve ever used. (The dimmer 2nd beam in the top picture is laser pointer to which I was comparing beam profiles.) The picture below illustrates the quality Gaussian profile, but also illustrates the noise around the outside. I’m thinking much of it can be attributed to a dirty external surface of the OC. Pretty good for 22 years though…