Night Vision

The eerie green magic of the night
 

Well everyone's seen it in the movies: the green images from a pair of night vision goggles. The ability to see in the dark has never been overrated in my opinion - just think how useful would be, and how it would change the way we work if we could.

There are in fact two types of night vision devices... thermal cameras and image intensifier devices. The latter is what we shall explore here at Penguin's Lab!

 

 


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
Some properties of generation 0 - IV tubes

Image intensification is the process of taking light that enters through the objective lens and amplifying it tens of thousands of times.

Image intensifier tubes (or night vision tubes) are classified into different generations. The earliest models are generation zero, while the latest (at the time of writing) are generation IV, which are currently only available in the military.

Generation 0 image intensifier

When I first went around scrounging for an image intensifier, anything better than a generation zero was 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 (2000VAC) to power it , shown here is the tube with a blue LED torch to demonstrate that it works.


Gen zero tube responding to light input

Gen zero tube mounted with IR source

Generation zero tubes require a separate source of infrared light (invisible to the human eye) in order to see anything.

For this, I obtained 30 IR LEDs and hooked them up in an array to form an IR beam. 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.

It works! Quite well in fact. The range is very limited though - about 20m. But hey, what do you expect from something made in the 1970's.

My camera couldn't seem to focus on the screen, but nevertheless this is clearly a toy kangaroo in the dark.

The case turned out to be really uncomfortable seeing as it was rectangular.

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 as the power supply.

 

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, which is why the window appears saturated.

All in all, I don't think this tube was such a bad investment. I imagine this device would be incredibly useful for observation of night wildlife in conjunction with a few IR torches.

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 I plucked up the courage to acquire a generation I image intensifier.

The night vision tube arrived quickly. The two flying leads attached to it were not helpful, and it turns out that the RED striped cable was not the positive lead, and before I figured this out I had wondered whether it was dead on arrival.

Upon power-up, a beautiful green display appeared. Nice!


Gen I image intensifier tube

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

The objective lens is from my old generation zero setup, which is screwed into a hole in the end cap which was drilled a tad small then carefully expanded with a round file. In hindsight it would have been nice to use a thread tapper.

This is the eyepiece and on/off switch. The eyepiece lens was actually salvaged from an old scanner - it was mounted in front of the scanner CCD as a focussing lens. Here I've wrapped it in several layers of masking tape so that it fits snugly inside a modified PVC adaptor tube.

On the other side of the cap, you can see the PVC tube which houses the eyepiece, and the on/off switch contacts.

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.

Cutting and filing the main PVC tube to size was extremely important, as one end had to be exactly the right distance from the the eyepiece, and the other from the phosphor screen on the intensifier tube.

Here is a look inside the almost completed night vision device. A 3V CR123A lithium battery is connected permanently using solder. The image intensifier draws only about 40 microamps, and so the battery should virtually last forever.
Last step - a plastic eyepiece was placed over the eyepiece tube. Perfect fit. Immediately the device looked a lot more proffessional than a bunch of PVC scrap ends!

The completed Generation I night vision device!

Well, the camera was chucking a fit once again and wasn't able to focus on the screen through the eyepiece. Just bear in mind that in reality the intensified images are crystal clear.

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

 

 

 

 

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