Millidoc

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Features

The millidoc / milliscope is a very useful device for inspecting and documenting small, but not microscopic, objects.

  •  ? to ~75x magnification on 15" monitor
  • Full HD video at 30 fps
  • Real time output to LCD monitor

ToDo:

  • 5 MP still photos
  • Recording to external HD or network fileserver
  • Audio recording for voice-over explanations
  • Stream over local network (for display via projector)
  • Stream online, e.g. ustream or own server
  • Automatic upload to Youtube / Vimeo / Flickr / your server
  • Total cost: Under ~$200

Magnification

When using a Durst 606 photo-enlarger, at maximum zoom a 4 mm object will approximately fill the width of the monitor. For a 15" monitor that is about 75x magnification. The exact magnifying power will vary depending on the photo-enlarger and the monitor.

Bill of materials

Summary of materials and Cost

Don't cheap out. Get a sandisk. 1 GB is enough though.
Consider getting a high quality microphone. Audio quality is super important.
  • Total: ~$175 + tax and shipping

Tools and minor materials

  • Box cutter or exacto knife
  • Wide clear packing tape
Though any wide tape will do
  • Hot glue gun and glue
  • Currugated plastic

Photo-enlarger

A photo-enlarger is a device used to project light through a photo-negative, magnifying the image onto photo-sensitive paper in order to create a large version of the photo. They are little-used nowadays and can be gotten for cheap or free. I've gotten them for between $0 and $50. If you're in the bay area good places to look for them are Urban Ore in Berkeley and the East Bay Center for Creative Re-use in Oakland, or of course Craigslist. I recommend getting a table-top model. Larger wall-mount units also exist but they are unwieldy and I have not yet attempted to modify one.

There seem to be two distinct designs when it comes to tabletop

photo-enlarger. One type has the magnifier mounted on a pole at a 90 degree angle to the table and another has it mounted at a somewhat smaller angle. The 90 degree angle model is preferable since you can zoom in and out without changing the relative position of the camera and

the object being studied. It is possible to modify the non-90-degree 

models to 90-degrees with the trade-off being that the camera will then be pointed at the object at an angle.

I have modified the following models so far:

  • Durst 606 (90 degree)
  • Omega C-700 (less than 90 degree)

You may come across photo-enlargers in less than perfect condition. You don't need a fully intact photo-enlarger. The only part of the optics you need is the final lens that is mounted right before the light leaves the photo-enlarger. You don't need any of the big magnifying-lense optics or mirrors. You don't need the the lightbulb or lightbulb-socket either. If the final lense is there and isn't too scratched up and the knobs for adjusting focus and zoom are working, then your photo-enlarger will be suitable for modification into a milliscope.

Lighting

The milliscope will need a light source. I recommend this cheap adjustable LED work lamp from Ikea:

Whatever you do, don't use a light-source with fluorescent bulbs as they will cause flickering and banding on the video.

Camera mode

These are the camera modes supported by the Raspberry Pi camera:

  • 2592×1944 1-15fps, video or stills mode, Full sensor full FOV, default stills capture
  • 1920×1080 1-30fps, video mode, 1080p30 cropped
  • 1296×972 1-42fps, video mode, 4:3 aspect binned full FOV. Used for stills preview in raspistill.
  • 1296×730 1-49fps, video mode, 16:9 aspect , binned, full FOV (width), used for 720p
  • 640×480 42.1-60fps, video mode, up to VGAp60 binned
  • 640×480 60.1-90fps, video mode, up to VGAp90 binned

<a rel="nofollow" class="external text" href="http://www.raspberrypi.org/new-camera-mode-released/">source</a>

The one you want to use for the milliscope is 1920x1080 at 30

fps. As you can see, it is cropped a cropped mode meaning that it gives us only a portion of the full image as seen by the camera. This is a good thing for two reasons:

  • It gives us a bit of extra zoom.
  • Unless you manage to remove all of the black plastic that used to hold the lens over the CCD the non-cropped modes will give you a view like you're looking down a tunnel with round black borders.

Technical notes

Intesting stuff

<a rel="nofollow" class="external free" href="https://github.com/monsieurpod/raspifpv">https://github.com/monsieurpod/raspifpv</a>

What I did

Installed raspian on sd-card and configured using built-in configurator.

Ran upgrade:

 aptitude update
 aptitude safe-upgrade

Used this guide for read-only root:

 <a rel="nofollow" class="external free" href="http://blog.pi3g.com/2014/04/make-raspbian-system-read-only/">http://blog.pi3g.com/2014/04/make-raspbian-system-read-only/</a>

Installed avahi:

 aptitude install avahi-daemon

Disabled bootclean autostart:

 update-rc.d checkroot-bootclean.sh disable

Added this script for re-mounting read-write:

#!/bin/sh
mount -o remount,rw /
/etc/init.d/triggerhappy stop
/etc/init.d/avahi-daemon stop
/etc/init.d/cron stop
/etc/init.d/rsyslog stop
/etc/init.d/dbus stop
ifdown eth0
umount /var
mount -o bind /var_org /var
umount /etc
mount -o bind /etc_org/ /etc
/etc/init.d/triggerhappy start
/etc/init.d/cron start
/etc/init.d/rsyslog start
/etc/init.d/dbus start
/etc/init.d/avahi-daemon start
ifup eth0

Ran clean:

 aptitude clean
 aptitude autoclean