Night Vision

Seeing green images in the dark...

Well everyone's seen it in the movies: the green images from a pair of night vision goggles. And yes, they do exist by the way.

There are two types of night vision devices...Thermal imaging, and image intensifiers. Thermal imaging is the classic one with the guy holding the mug of coffee, and it tells you how hot something is.

Image intensification is the process of taking light that enters through the objective lens and amplifying it tens of thousands of times. This is the one I have, since thermal devices cost tens of thousands of dollars, money I don't have.

An exploded view of a generation II or higher night vision tube- Image courtesy of HowStuffWorks.

Gen	Properties
0	Needs separate source of infrared lighting
I	Moderate range in moonlight
II	Moderate range in starlight
III	Moderate range in absolute darkness
IV	Very long range in absolute darkness

Image intensifier tubes (or night vision tubes) are classified into different generations (abbrev. 'gen'). The earliest models are generation zero, while the latest are generation IV, which are only available to the military.

The old Generation 0 image intensifier

Anything more than a generation zero is stressful to the wallet, so naturally I went for a generation zero to see what it could do.

After making up a small high voltage power supply to power it (2000Vac), here is the tube with a blue LED torch to demonstrate that it works. The green spot is the illuminated section on the NV tube.

Generation zero tubes require a separate source of infrared light (invisible to the human eye) so that it can even see anything.

Oatley electronics supplied me with a IR illuminator kit. So I integrated the night vision tube and the IR illuminator into a custom case.

The top photo shows the NV tube sealed in a plastic case, which is mounted on top of the custom case, with the IR illuminator board mounted on the front of the case.

And a demonstration that it works. Very well in fact. Range is very limited though, about 20m. But hey what the hell do you expect from something made in the 1970's.

My camera doesn't agree with the focus length of the tube for some reason, but here's a picture of my toy kangaroo in the dark.

The case was really uncomfortable though, seeing as it was rectangular... So there was no way I was going to settle for that crappy setup.

After a bit of brain racking, I decided to modify an old cordless drill to accommodate the NV tube and power supply in it. That way I could use the original drill battery to power it too.

The top picture shows the new design. You can see the objective lens poking out, and drill battery attached on the bottom.

The picture to the left is a view of the other side, with a magnifying eyepiece mounted in front of the NV tube screen.

Here's a photo of our lounge room at night. I think the camera is cooperating with me now...

The outside lights are on, that's why the window is saturated.

The "newer" Generation I image intensifier

Eventually I got sick and tired of the need to lug around an IR illuminator every time I used the NVD, so a generation I image intensifier was bought off eBay.

The night vision tube arrived quickly as promised. The two flying leads attached to it were not helpful, and it turns out that the RED striped cable was not positive after all, and before I figured this out I had wondered whether it was dead on arrival. So, reversing polarity, I hooked up 3 volts the right way round (red=negative), and hey presto, a beautiful green display with no blemishes whatsoever. Pretty good.

The intensifier is mounted in a PVC tube with the objective and eyepiece lens screwed onto holes which are drilled into the PVC end caps.

The incomplete, original mounting for the tube [right]. There is an AA battery for scale. The objective lens is from my old generation zero setup, and it's screwed into a hole in the end cap which was drilled then carefully filed back.

This is the eyepiece and on/off switch. The eyepiece lens is actually salvaged off an old scanner, it was mounted in front of the scanner CCD to focus the images. Here I've wrapped it in several layers of masking tape so that it fits snugly inside a modified PVC adaptor tube. Cutting and filing the PVC to size is extremely laborious, as it has to be exactly the right distance from the the eyepiece, as well as from the phosphor screen on the intensifier.

On the other side of the cap, you can see the PVC tube which houses the eyepiece, and the switch contacts (wow... interesting eh?).

I found that the length of the original PVC tube was way too long, and the eyepiece lens could not focus on the phosphor screen from such a distance. So the PVC tube was cut down to size, and is now much shorter (and perhaps slightly cuter?).

Okay, a look inside the almost completed night vision device. A 3V CR123A lithium battery is connected permanently using solder. The image intensifier drains only about 40 microamps, and so the battery should virtually last forever.

Last step... an eye support or er.. plastic whatever thing is placed over the eyepiece tube. Perfect fit!

The completed Generation I night vision device!

Well, the camera is hating me again and isn't able to focus on the screen through the eyepiece. I guess it should work without the eyepiece, but I'll try that later. In reality the images are much clearer than this.

This is a shot looking at the bathroom sink and cupboard. You can see my reflection through the mirror on top.