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Homemade Night Vision Scope

A deer in pitch dark as seen through the scope.

Here's something I've always wanted to make. A night vision system.

The finished unit

The main part of the scope, the image intensifier tube, is an ex-military unit and comes from a WW2 tank periscope. This was aquired through a seller on ebay for an un-beatable price of £35.


Image intensifier tube	Rear view screen	Imaging screen

The specs for this tube (8079HP) are:

- 1st generation tube with integral HV power supply (around 6kV I think)

- 3-6V DC power supplied via an outer ring and a terminal on the side of the unit

- 18.5CM Long, 6.25CM Diameter

All that is really needed to make a night vision scope with this tube is a suitable lense. A little research on the internet led me to believe a 35mm camera lense would be perfect for the job. A quick trip to the local junk, I mean antique shop, and I had my perfect lense. Well, nearly perfect, the lense I used is a Raynox 2.8/35mm (wide angle) which produces a "fish eye" like view, which I personally think is more usable, but as you will see, we are not stuck with this lense as I made it so that the user can attach other lenses at a later date.

Lense Spec:

Front lense:

- Raynox 2.8/35mm

- F stop 2.8-22 (Adjustable focal length)

- Adjustable iris (amount of light entering the image intensifier)

- Thread fitting (important to be able to change lenses at a later stage)

Rear lense:

- Plastic Jewellers eye piece, the type used by stamp collectors etc.

Overall case dimensions:

- Main image intensifier housing: 230mm long by 75mm wide

- IR Led lense: 25mm

- Total length inc perspex casing (3mmx2): 270mm

- Total length of entire system (above plus eye piece/lenses): 310mm

- Total system weight (inc batteries): >500g

System power:

- 4x AAA bateries (6V). Using these should provide a run time in the 10's of hours, as the insifier tube draws only a few milliamp.

Construction:

The image intensifier is mounted within an 80mm plastic drainpipe tube that has been cut down the middle and 5mm taken off the sides to form a 75mm diameter tube, 230mm long. This creates a nice tight fit that holds the tube in place. The ends of the tube a capped with twto perspex plates cut in a squshed number 8 shape. (pictures will explain this better). A hole of 75mm in diameter is cut in the larger of the 8 shaped perspex, and a smaller 25mm diameter hole is cut in the smaller 8 shaped perspex.

A plastic tube of 25mm in diameter is inserted parrallel to the image intensifier tube with a length of 270mm. This houses the 4 AAA batteries and the control electronics (see below for details).

The end perspex plates are held to the 75mm plastic tube by 4 right angle aluminium brackets, 2 at each end. These are bolted through from the outside and sit inside the tube.

A hole in the front of the perspex plates is drilled at 30mm and carefully filled out until the 35mm lense threads iteself into the perspex. The lense is then tightend down on to the perspex plate. A small cardboard tube (toilet roll) is cut to size to fit between the front lense and the image intensifier to block light from entering from anywhere we don't want it to.

A small hole of around 20mm is drilled in the rear perspex plate to allow the eye piece (which is of conical shape) to be clamped between the perspex plate and the back of the image intensifier (which has a rubber ring). A small amount of superglue is added to the eye piece and the hole cut in the perspex to hold it in place.

A small reflective led lense is fitted to the front of the smaller tube and a 5mm infra-red led is mounted to the middle. This lense was scanvenged from an old (very old) television remote control. The led is any old standard IR led. You could even use a standard bulb and put a red/ir lense in front of that.

The batteries and control circuits fit inside the smaller plastic tube. One end has the ir led reflector and the other has a bottle cap with an o-ring around the inside that press fits on to the plastic tube. A small switch is mounted to the bottle cap to function as the on/off for the tube and ir led.

The ldr is mounted behind the front perspex plate next to the main camera lense using copper wire and glue.

The control circuits:

To make a simple night vision scope, no control circuits are neccessary, but I decided to add additional control over the tubes intensity and protection against too much or accidental light exposure. (if you didn't already no, any stray light, even a small battery powered light, can permanently damage the image intensifier by causing screen burn on the cathode ray screen)

So, my solution to help eliminate this problem was to use a simple op-amp circuit to only allow the image intensifier to function when an ldr senses that it was below a specified light level. See the diagram below for details.

Click to Enlarge

The insifier tube brightness can be adjusted by the potentiometer, as shown in the diagram above. The safety cut out sensitivty can also be adjusted via the potentiometer, as shown in the diagram.

The safety cut out should protect the tube from most bright light sources, but just bear in mind that you can damage the tube from prolonged exposure to bright lights. You'll know when you've done it because you'll have a permanent image of that light source burned into the green phosphor screen.

Things to do with this project:

- Get a pair of these for binocular night vision!

- Use the nightvision system together with a telescope for an un-paralleled view of the night sky.

- Use nightvision with a camera for nighttime survellience.

- Go walking with friends in the night, don't take torches and don't let them know that you have a night vision scope with you, play hide and seek with an unfair advantage ;-)