Sunday, April 11, 2010

PLACE SANDWICH HERE: the camera

The original camera setup involved zip-tying t-slot aluminum to the microscope neck and positioning the camera based on a series of adjustments to the slot angles. There were a few issues with this setup. First, I didn't have any t-slot nuts, so it was always a pain to tighten things. I at first didn't have any t-slot L brackets either, but I had some nearly equivalent aluminum brackets, so that wasn't as big of a deal. Next, the small distances between the neck and the eyepiece really limited the flexibility in positioning the camera. It was very hard to position it accurately. Finally, the zip ties were only moderately stable, so if you hit it too hard, it would shift around.
The second setup I tried was to use a neck lamp as a flexible mount. It was abandoned because the camera was so much heavier than the light bulb that it caused it to sag. I took an old style fuse and ran a 1/4" bolt through it so it could mount to a camera. The camera isn't mounted to it here, but here I am disassembling it since I'm not going to use it anymore and bad things would happen if someone plugged in the lamp by mistake:

As the current setup is being upgraded for CNC control, the camera positioning will still remain manual since it doesn't need to be moved as the die is being scanned. Here is an overview of it:
Basically, this has two easy to position axis, which really help. The microscope eyepeice is on an angular axis and there is a linear slide that the camera is mounted on. Usually only minimal adjustment is needed with the t-slots, mostly for height. The slide was spring loaded to keep accurate positioning. When viewing the image manually, the eyepeice is swung around to the front of hte microscope where the neck is rather than at a 90 degree offset to standard orientation. This makes switching between manual and camera based viewing convenient.
Interesting to see the focal length as it relates to magnification. Here is 10X objective:

And here is 40X objective:


It looks like its touching, but its not. However, its very, very close. You can still get it out of focus by moving it closer. If you move it too close, the spring loaded objective lenses will move up rather than break. Here is what you see on the camera at 400X (more like 800X actually since we are zoomed in on the camera itself):
There is also a 100X objective, but I haven't looked into what it would take to use it. I believe I need to do something with immersion oil.
The original setup used an incandescent light. However, it only provided moderately acceptable light levels with the 40X objective. I recently bought a 500W halogen light that has really helped. However, its not very directional, so I installed a sandwich wrapper as a deflector to increase directionality to the sample and not blind the operator. As my friend Alex finished his lunch, he probably never thought about his burger wrapper again until he reads this. Little did he know it would become a critical ingredient in the camera setup after being banished to the gray cylinder labeled "TRASH."
Although it is festive, I'll probably replace it with some aluminum foil when I get a chance to go to the store or something.
This setup is pretty stable and I'm a lot happier with it over the previous one. It seems like a flexible mount would have been nice, but with the stability I've gained from the T-slot, this setup is probably best.
Thanks to Dane Kouttron (http://transistor-man.com/Index.html) for the pictures! Also thanks to Magesh Alagiriraj for lending me an SD card since mine died :(

2 comments:

  1. I bought a precision stepper-motor X-Y stage two years ago, with the idea in mind of doing the same thing, but I haven't yet purchased a microscope. What are you using? I want to extract metal-mask ROM code from chips made in the mid-1970s, and possibly try to reverse-engineer a netlist of a custom microprocessor from the same era. I expect that my chips use geometry no finer than 4 um. I'll be interested to see more of your results, and if you're interested, possibly collaborating with you.

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  2. Yes, I'm always looking for more people to collaborate with!
    There are two microscopes, each with its own CNC work in progress. The biological one, which I have a picture of, is mostly done. This uses bipolar stepper motors. That setup is only so-so though since I had to spring load one stage to the gear as it moves around. A more proper X-Y setup would be nice. Still, the stages work fine and I have a stack of cheap broken bipolar stepper drivers I got for free. I'm trying to test/swap parts to get them working. I have one working and with a little time I could probably get a second one. The computer in the background of some of my pictures has EMC2 (http://www.linuxcnc.org) installed on it from previous projects and is ready to go for CNC control.
    The inverted metallurgical microscope has a slightly different setup planned. It has two knobs on it that I can git a timing belt on really easily. I ordered some timing pulleys and just yesterday managed to find a pair of timing pulleys to stick on some motors. I have some large unipolar Precision Motion Controls (microstepping?) drivers. I used them before on several CNC projects. While they are way overkill, they should work fine and I have them lying around.
    With 4 um technology, you really don't need anything too precise. I can see 4 um tech pretty well even at 100X and it would take quite a few steps to move an entire camera field of view.
    For CNC picture taking, I'm trying to use libgphoto2. I've had some issues getting libgphoto2 to play nicely with my camera (Canon SD100). However, I can't turn off the flash when under computer control. My first solution was to simply cover the flash with electrical tape. However, an expected flash severely lowers the exposure time and results in dark pictures. I might contact the gphoto team or see if I can debug it myself.
    Unfortunately, I can't contact you through your profile, so send me an e-mail at [email protected] if you can so we can talk more.

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