Products > Thermal Imaging

Thermal Camera - Affordable Raytheon Night Vision thermal camera unit.

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Fraser:
Hi Thermal Camera Fans.

I have just taken delivery of another thermal camera for my collection  :)

This time it is a Raytheon unit that was designed for the Cadillac DeVille automobile. It was a very expensive option that provided night vision enhancement. It uses a Raytheon thermal camera feeding a HUD on the windscreen in front of the driver. It apparently worked very well.

These units are appearing on ebay as the Car Wrecker Yards recognise them as having value on the secondary market. Fortunately the originally high asking prices now seem to be dropping. My unit came from a wreckers yard for $100.

The camera is monochrome only, fully automatic, and employs a 320x240 BST staring array. The frame rate, IIRC, is 30fps. The unit requires only 12V to 14V to operate and the output is Composite NTSC. Couldn't be simpler   :-+

My unit has a cracked front 'filter'. It isn't really a filter at all, it is a Germanium window stone protector that sits in front of the objective to protect it. Sadly automotive conditions are hazardous for such a camera and stones have a habit of smashing the protector quite often.  A later modification employed a small wire grille in front of the camera to afford it greater protection. My camera is a 2007 2000 model that has a replaceable front 'filter' so I could fit a new one. I do not need it in my application so the broken 'filter' will be removed.

Sadly a camera that has had a broken front 'filter' for a prolonged period of time can suffer water ingress that corrodes the germanium lens that sits behind it. We shall have to see if that is the case with mine. If it is corroded, it may still work OK, or I can fit one of my spare Raytheon lenses to it.

This is an 'early days' post to advise that I will be opening this camera to inspect it so you will see her insides soon. I have just given her a quick clean to remove the road dirt and she is in very good condition. The Germanium lens condition will be the most likely issue with this camera.

In the pictures you will see an AA cell to provide a size reference. these cameras are not that small ! It is the same size as the Raytheon 300A but with additional bracketry on 3 corners.The camera is weathertight, even if the front filter is broken. Very early versions of this camera (Circa 2001) were not weathertight in such circumstances.

I will add to this thread as and when I work on this unusual camera.

Aurora

Fraser:
Lens protector removal......

This version of the camera is the later incarnation of the Raytheon unit and has removable 'filter' holder.

To remove the filter, and its associated thermostatically controlled heater assembly, requires only the removal of one plastic rivet and then a 1/4 turn anti clockwise twist of the filter holder. The filter holder can then be lifted away from the camera.

Once removed from the camera, the 'filter' may be simply lifted away from the heated ring against which it is normally held by the cameras neoprene sealing ring. It is a very simple job to replace the filter.

The moment of truth came as I lifted the filter housing away from the camera...... was the Objective trashed or had it survived ? The news was good  :) The objective is in better condition than some of the lenses on my fire brigade cameras and they still seem to function OK.

Some gentle cleaning with IPA on soft cotton wool removed much of the dirt that had entered through the small hole in the 'filter'. There is still a mild 'tide' mark' where water has collected over time, but this may still be removable and it is at the edge of the lens and so likely of little consequence.

This camera is in far better condition than I had expected. I am very pleased with it for $100  :)

I will be opening the casing next as I need to inspect it for any water ingress. There should not be any problems here as the lens assembly is fully sealed at the objective and the rear shell is also 'o' ring sealed.

The smashed 'filter' is not going to waste. It is a Germanium window and at least one piece is big enough for use in experiments or as a lens protector for a small lenses camera. Cutting it down to the required size could be interesting though !

Aurora

Towger:
Can't wait to see it working.
A fully wife approved purchase I take it!  You should extend that garage and open the world's first night vision/thermal camera museum.

SeanB:
Frasier, if that cracked lens cover is Ge have you considered trying to make a few poor transistors out of the pieces? Might be a good thing to try, using some alloy from a cracked peltier element as the alloying metal, or reduce some antacid to get metallic bismuth metal.

At least here you have a good working unit, an improvement over your last one by a really good margin.

Fraser:
My luck has run out on Thermal Camera purchases  :(

Nah, don't worry I am still pleased with my Raytheon camera  :) , buts it needs some work.
Read on.......

I have just separated the two halves of the case. As expected, there is an 'O' ring seal between the two that has done its job and kept dust and dirt out of the electronics. I am the first person to be inside this camera since it was put together....always a good start  :-+

As I separated the two halves a sad sight came into view ......

The chopper (shutter) wheel is totally trashed  :(  The Chopper wheel is basically a frame onto which is mounted a plastic material. The translucent plastic sheet is very thin and looks to be the same across its whole surface.....but it isn't  ;)  The plastic actually has a coating on it that forms a spiral mask on its surface. The BST array is scanned by this spiral and this is what provides the required change in state that the BST technology needs to work. Without the chopper wheel, the camera would work, but it would only see an object that is moving. Any objects that are stationary would fade into the background. Early Fire fighting cameras provide a switch to stop the chopper wheel as this provides an anti blur capability when sweeping a scene quickly for people.

The Chopper wheel on my Raytheon unit is shredded. The material used for the mask has deteriorated due to heat and age. It has split all over its surface and so will not perform well. It will likely disintegrate if I run the camera for long. An image is produced but you can hear the plastic scraping on the BST sensor....not a good idea !

The good news is that chopper wheels used to be made from thin FR4 PCB material. The required spiral is cut into the PCB and may be made reasonably easily. I shall have to make a copy of one of these chopper wheels that is fitted on my fire fighting BST cameras. I do have a Raytheon 300A camera, so I can use that units perfect chopper wheel to check the spiral dimensions etc.

Sadly this means the camera is out of service until I have the time and inclination to make a new chopper wheel. Sorry to those wanting to see the unit working. Sods law strikes again.

On with the disassembly.......

The Chopper wheel, its motor and the position sensor (for synchronisation) are attached to a cover plate that may be seen in the pictures. One four screws are removed, the cover plate may be lifted away and the two cables disconnected from the PCB that lies behind.

The PCB is fixed to the rear shell of the camera which also acts as a heat-sink. Most BST cameras have a fan mounted on the heat sink to maintain cooling. This camera does not need this as the exterior case is free air circulation cooled.To achieve a good thermal transfer between the heat sink and the BST sensor array, a special pad is used. It was not possible to separate the sensor from the heat sink without risking damage, so for the moment I have left the PCB in place.

The PCB looks to be of decent quality and design, as would be expected of a company like Raytheon.

Moving on to the lens assembly.....

The Objective lens is Germanium. The lens which projects the image onto the BST sensor appears to be some form of IR transparent plastic ! This was unexpected and I presume, part of a a cost reduction strategy.

The lens has no external focus ring and the reason was obvious once the rear of the lens was visible. The lens focus is set via a large plastic ring gear, driven via a smaller brass gear. The small brass gear is driven using an allen key focus adjustment tool. It is inserted through the rear of the camera and into the hex socket in the brass gear. The focus tube is sealed using an 'O' ring seal and large flat headed screw compressing it. The focus control is surprisingly complex for such a simple camera. The lens does look to be of decent design and quality but I am not dismantling that for the moment.

So, the lesson from this little tear-down is ......... do not buy one of these used Cadillac DeVille Raytheon cameras unless you are prepared to make a new chopper wheel. Mine is a 2007 2000  unit so it looks as if the plastic used in the chopper mask has a life of less than 8 15 years. I have heard other reports of trashed chopper wheels in these cameras. No other detail has previously been provided however. It is likely a common issue with the design. Thankfully such a failure is purely mechanical in nature and so a replacement can be fabricated. First draw a template on paper and then transfer it onto a piece of 0.4mm FR4 PCB, The PCB may be bonded to the chopper wheel frame after having removed the old plastic mask.

Once I have made up a new chopper wheel I will post the template on here. This will help others who have the same problem but maybe not enough plastic mask left to see the spiral dimensions.

This will be another enjoyable little project for me to sort out at some point in the future.

I attach pictures for your interest.

Aurora

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