This photograph shows a side-view of the original military night-sight, which is actually a periscope system for armored vehicles.
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MK4 Intensified Camera |
The MK4 intensified camera was conceived as a direct result of one of the principal short-comings of the MK3, namely the image reversal. The MK4 does not suffer from this problem, and is also a far superior concept. If you have not read about MK2 and MK3, please do. It will make the following description much easier to understand.
The original sight
The MK4 (like MK3), is an attempt to produce an intensified camera with the absolute minimum of effort, and to this end, it is built using the body and main lens of a military night vision periscope. The MK4 is however a significant improvement over the MK3, utilising more of the original housing.
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This photograph shows a side-view of the original military night-sight, which is actually a periscope system for armored vehicles. |
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The modifications
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This photograph shows the night sight face cushion and eyepiece assembly prior to modification. |
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The night sight shown above was partially dismantled by removing the face cushion, this allows access to the eyepiece.
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This photograph shows the night sight with face cushion removed. You can see the 6 screws which secure the (heated) eyepiece screen to the rear of the housing. |
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Next, the last 3 lens elements are removed from the eyepiece housing. These lenses are large pieces of glass, retained by 4 screws and some metal clips. After these parts have been removed, a large empty space is created inside the eyepiece housing. This is where the CCD (PCB camera) will be mounted. Two new pieces of metal are now required.
The first is a bracket which is fitted inside the eyepiece housing to retain the prism in place. This function was previously performed by a combination of metal clips and the original lenses. The prism is required, and must be secured.
The second is a panel which fits across the eyepiece housing aperture. This panel is drilled to accept the video output connector (BNC), and to mount the CCD (PCB camera).
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This photograph shows the new prism retaining bracket fitted in place. It is clear that a sizeable space has been created, and this is where the PCB camera will now live. The new cover panel is also shown, with the PCB camera and BNC video connector Fitted in place. The PCB camera is fitted with an 8mm lens. Please see the MK2 camera description for a discussion of PCB cameras and lenses. The MK4 concept as shown here can use a 6mm or 8mm (preferred) lens. |
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Once the components are mounted and the PCB camera lens has been adjusted, the new cover plate can be secured in position using the 6 original eyepiece cover screw positions.
The completed camera
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This photograph shows the completed camera. The whole init is powered by 24V via the original power connector. The video output connector (BNC) can be seen at the rear. The completed camera is very robust, and "tidy". |
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Results
The results are excellent, with clear views in almost any lighting condition. Easy capture of meteor trails down to magnitude ~7.0, and excellent night scene views.
Unlike the MK3, the MK4 provides images that are the right way around without resorting to a fancy PCB camera or any other trickery.
As with the MK3, the fixed length lens (actually 66mm) is a serious limitation compared to the flexibility of the MK2 camera with it's interchangeable lenses. For some applications this doesn't matter, but if you would like the flexibility this could be a problem. There is no simple way to provide an adjustable focal length on this unit. If you need this feature, look again at the MK2!
The MK4 camera does have considerable benefits. It is VERY robust, and could easily be sealed for a fully weather-proof end result.
Conclusions
The MK4 is a big improvement over the MK3, and while it requires two new items of metalwork, it is also very simple to build. However, if your application would benefit from interchangeable lenses, it's back to the MK2!
