How to make a microscopic 3-D image.

This is essentially a bit of fun, but it can have a practical purpose as well.

3D images

I've always been fascinated by 3D photographs. Tricking your eyes so that one sees one image and the other sees an entirely different image, is clever. But then when your brain re-integrates those images to form a complete three dimensional structure just spins me out.


I was vacuuming the floor in the showroom the other day (we have the most wildly exciting jobs) when I found a tiny coil of swarf on the floor. Standing next to a saxon RST Researcher NM11-2000 stereo microscope, I began to wonder how might I take such a photo?

I fetched a saxon ScopePix phone adapter and attached my phone to one of the eyepieces. I had to remove the eyecup from the eyepiece to get the phone on straight. I focused carefully and took one photo through the right eyepiece. Then, without moving the sample, I swapped my phone to the left eyepiece and took  a second image.

I had a little trouble, as my phone's autofocus didn't quite nail the two images exactly the same. It seems that Apple doesn't quite know best.

Then I downloaded the two images onto my computer and combined them into one, with the image from the right eyepiece on the left, and the one from the left eyepiece on the right.

The photos

Have a look at the two images side-by side. Because the one on the left is the image taken from the right eyepiece, and the one on the right is from the left eyepiece, you're going to have to go a bit cross-eyed to integrate the images correctly. This is called "freeviewing".

It might take a bit of time to convince your eyes to focus at one distance and converge at a different distance, as they're not used to doing this.

This is what works for me. Put your finger on the screen between the two images, and then move it slowly towards your nose. Watch the finger as it move towards you. You'll notice in the background the two pictures split and become four, then the two in the middle will merge in the middle, so you'll see three. Now, without changing your cross-eyedness, concentrate on the middle image, drop your finger and refocus your eyes. Some people find this easy and some people find it frustratingly dfficult.

Aargh, nuts!

After the swarf photo, I did the same with a slightly larger subject, a nut off a 3mm bolt. Because it's larger than the swarf, the focus is much more critical, and the nut is almost too large for the field of view of the camera. You might find this one a little more difficult to integrate because the more critical depth of focus means there are larger out-of-focus areas in the photo.

There are practical applications for this type of thing. For example, we often see 3D views transmitted from Mars, and the museums are full of stereograms of flowers, insects and other specimens. For me, though, being able to create them is really a bit of a curio.