Puss in Boots

Puss... in Boots.
Crouching tiger, hidden Walken. Hypnotic, isn’t it?

If you’ve never seen Christopher Walken in Puss in Boots, add it to your queue right now. That’s him as Puss, craftily stalking a bird for supper.

Spoiler alert: it’s among the more terrible children’s films of 1988. But every scene that Walken is on screen is comic GENIUS.

I made the gif directly from Amazon video. They don’t implement freeze frame, but hey, it’s a web player. Time to fire up the JavaScript console!

(To all the jQuery haters in the audience: no, you don’t need jQuery to do this. But since Amazon thoughtfully included it on the page, why not use it?)

Open a browser console. Click on the console prompt but hover over a video to show the video controls. Then run the following:

jQuery('.playIcon').click(); setTimeout(function() { jQuery('.pausedIcon').click() }, 30);

Each time you run it in the console, the video advances one frame. Grab a screen shot and away you go.

All that glitters…

Gold particles on carbon at x50,000
Gold particles on carbon at x50,000

Here’s an image of a gold calibration target. To give you an idea of the scale, that line representing 100 nanometers is roughly the diameter of the HIV virus.

In other news, I posted wav2tiff to Github. I made the above image with Milly, an audio cable, a 10k resistor, and that script.

Megapixel images from an analog SEM

I recently posted my first batch of photos from Milly. While I am happy with her beam performance, I was dissatisfied with the digital photo quality.

Until now:

It's amazing what a difference a $0.50 cable and some math can make!
It’s amazing what a difference a cheap cable and some math can make! Click the image for full resolution.

The inset NTSC image was taken with a USB frame grabber on the CRT port. The bigger image was taken not with a $1k data acquisition module, but with an audio cable, a resistor, and a sound card.

Analog to digital

Milly is a JEOL JSM-6320F, an instrument from another era. That F is important. It means she uses a field emission gun rather than a thermionic filament (like Meryl). This gives you significantly more control over the beam current, and ultimately, brighter pictures at deeper magnification.

But Milly is predominantly an analog device.  While she sports “digital storage”, the on-board memory can only hold four frames, which are lost when the scope is powered off. There is a SCSI option for a 30MB hard drive, but I haven’t had any luck getting it to recognize a drive. According to one forum post I found from 1993, the files would be in an “obscure and difficult” format even if I could read them.

So to get digital photos from her, I could either take crappy pictures of the screen, or put a cheap NTSC frame grabber on her CRT mirror port (tip of the hat to Glen MacDonald from that same post for pointing out which port to use!)  This makes taking photos really easy, but it limits the resolution to NTSC (about 500 lines).

At first I took the second route, and ended up with a bunch of pretty (but tiny) screen captures. There had to be a better way.

Hard Copy

Her intended output device is a Polaroid camera attached to a CRT. You put in a sheet of film and set the scope to do a time exposure, and it scans the film one line at a time. The Polaroid adapter is the little black box on the right of the main console:

No school like the old school, I guess...
No school like the old school.

Even if I could find the proper film, I would end up with a useless hard copy. I would then need to scan it right back in so I can share it online. That way lies madness.

While the NTSC frame grabber can’t cope with the signal on the photo CRT, I could always sample it with a “scientific” data acquisition device. These modules are designed to minimize latency and artifacts, to produce the most accurate possible representation. This is critical for manufacturing and scientific applications, where a difference of a few nanometers can make or break a project. But if I just want nicer photos, the cost of these beasts ($1k and up) is out of the question.

Slow down there, pixel clock

According to the manual, the  film is scanned at up to 1940 lines of resolution, in a programmable period of up to 320 seconds. What would it take to sample that directly, assuming a 4:3 aspect ratio? Let’s do some pixel math:

1940 lines * 4/3 = 2587 pixels wide
1940 * 2587 * 1/320 fps = 15,684 pixels/second

Only 15.6 kHz? Really? A sound card can sample that a couple of times over at 24 bpp without breaking a sweat. Contrast that with NTSC and its 30 Hz refresh rate:

525 lines * 4/3 = 700 pixels wide
525 * 700 * 30 fps = 11,025,000 pixels/second

Even though it’s a much smaller frame, the 30 Hz refresh rate pushes the pixel clock up over 11 MHz. No way a sound card can keep up with that, which is why faster ADCs exist for video sampling.

Audio to Video

So I dug into the old box of audio cables and found a 3.5mm to RCA cable. I had a bunch left over from my bullet time camera rig project (one came free with each camera).

I connected the photo signal to the left channel and the horizontal sync signal to the right. I also added a couple of high-value resistors to limit the current and hopefully avoid damaging the scope. Then I hit the PHOTO button, and made a WAV file recording at 48 kHz.

I ended up with a 50MB WAV file full of data.

I had to turn the gain way down to avoid clipping. Adding a potentiometer to tone down the input volume would probably be a good thing.

You might dig the sound, if you're into relentlessly repetitive industrial.
Ah, the sound of boron. You might dig it, if you’re into relentlessly repetitive unbalanced industrial music.

The next step was to turn it back into a picture. I used numpy, audiolabtifffile, and about 4 lines of python.

Here is the shot as captured with the NTSC frame grabber:

Boron x2200, NTSC quality.
Boron x2200, NTSC quality.

And here is my first attempt at wav2tiff:

My first attempt. Terrible, no?
My first attempt. Awful, isn’t it?

There are so many problems! The aspect ratio is wrong. The sync wanders all over the place. I’m missing half of the contrast depth. And what is all of that extra junk on the right?

Fortunately, these are all software problems. I added a few more lines of python, scaled and cropped it appropriately in Photoshop, and ended up with this:

Much, much better.
Ohai, boron!

Much cleaner! That’s a 3.4 megapixel image, scaled to fit on this web page. Click it to zoom all the way in.

I believe the black streaking effect is due to poor brightness and contrast settings. Since this is a time exposure, there is a lot more charge on the sample, making it brighter and a little overcharged. While the settings were fine for the NTSC fast scan, they’re too bright for a 320 second exposure.

You can see a similar effect on my earlier shots of pollen taken with the NTSC grabber. I think I simply need to turn the brightness down.

I’ll post more shots (and code) soon.

Big SEM: online

I recently got Milly the big SEM online. She had a ton off issues that I’ll chronicle in future posts. But rather than dwell on her past, let’s see what she can do.

Remember that 2mm stainless screw?  Here it is again, with my finger for scale:


And here is the gap between two threads, up close and personal:

Extreme closeup!

Here are some more samples. We’ll look at the stuff on the right-hand strip for now:

Eight samples for Milly. We'll look at the ones on the right for now.

They are (from top to bottom):

  1. Pollen from a random tree (not sure of the species). Those pods contain the pollen; the actual pollen is too small to see in that shot.
  2. dandelion seed. The SEM photos are of the bushy head and a single fiber.
  3. Highly ordered pyrolytic graphite (which we’ll skip for now)
  4. Crystalline boron


pollen, x450

pollen, x1200



Dandelion seed head



Dandelion seed fiber







Crystalline boron







I’m still learning how to use Milly as a camera (so many variables!) but I’m really pleased with this first batch of shots.

Getting better contrast on organics will be a lot easier once I get the sputter coater online. There are a bunch more photos (including hematite and more) in the gallery.


Laser HV repair

I’m in the process of upgrading the brain in the laser from a cheap (and recently deceased) Chinese special to a new design based on the open source Lasersaur. More on that later.

I was right in the middle of testing my new design when the laser suddenly stopped firing. Apparently it was time for the HV supply to pack it in. The cause? A dead thermistor.

Can you spot the trouble?
Can you spot the trouble?

It looks like this one was being used to limit the inrush current at the bridge rectifier. Apparently it died a sudden and spectacular death.

I took a look around the shop and happened to find an old junked server supply with a very similar looking thermistor in it.

Could this part do the job?
Could this part do the job?

After finding the datasheets for the dead 5D-13 and the spare 15SP M005, it turned out that they were largely compatible.

5 Ohms at 25C is good enough for me.
5 Ohms at 25C is good enough for me.

So I swapped in the 15SP and fired up the supply.

The question is, do we have a charge?
But more importantly, did we get a charge?

Success! We have sparks. Now to reinstall it and resume robot brain surgery.

The real question is, why did it fail? I think some research into the switching frequency of the Lasersaur and the capability of this cheap supply are in order.

Tomorrow we bake

Milly is coming along nicely.

I believe we’re over the vacuum difficulties. She’s buzzing along at a nice deep vacuum in the SPEC, INT, and GUN chambers. Last night the computer finally booted up without the dreaded CHECK VACUUM alert.

Finally, a new and excitingly different error message!
Finally, a new and excitingly different error message!

Next up will be an extended 30 hour bake session to try to revive the emitter. I don’t trust her to run the heater unattended, so I’ll be staying over at the shop to keep an eye on things.

This is the specimen chamber pressure. The gun is all the way down to 5e-11, pre-bake!
This is the specimen chamber pressure. The gun is all the way down to 5e-11 kPa, pre-bake!

Keep your fingers crossed. With any luck I might have some images to post on Sunday evening!