Thermal Camera - Affordable Raytheon Night Vision thermal camera unit.

[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

[Fraser]

Raytheon cutaway image of the Cadillac Deville camera attached.

This is the early Type 1 version that was replaced by my Type 2 design. The two are very similar in content however.

The camera lens appears to be a simple two element design.

Aurora

[Fraser]

CORRECTION:

I have been doing some research on the label that provides DOM details.

I read mine wrong 

My camera was built on the year 2000 so it is 15 years old and not 8 as previously stated.

The DOM format on the label is : DOM: YY:MM:DD

It is definitely the later Type 2 (Type B in some references), so has the later sealed objective assembly and removable filter holder.

Apologies for any confusion caused

Aurora 

[Fraser]

A little picture gallery of horror.....Raytheon cameras with stone damage 

Note: the old and new versions of the camera are represented here. The older type 1 camera has an oval lens barrel and fixed filter holder, whilst the later type 2 has the circular barrel and the removable filter holder.

Most of the cameras shown in these images would have serious corrosion of the Germanium lens. The damage to my lens 'filter' was relatively minor when compared to what commonly occurs to these cameras on the road.

Aurora

[Fraser]

Some images from and old ebay auction showing some parts of the older Type 1 camera.

Note the different lens structure and that the Objective lens sits further forward than on the later Type 2 camera.  There is a red cross on the objective shown in the picture as the seller had shattered the lens whilst trying to polish off the surface corrosion 

The Type 1 lens assembly is not sealed beyond the front filter holder. If the filter is broken, and water can enter, the PCB gets wet and serious corrosion occurs to many components, including the BST sensor. Such water ingress usually renders the camera scrap.

The chopper wheel and its associated motor are missing from the pictures. Also note the signs of corrosion inside the case rear and on the rear of the PCB. This combined with a heavily corroded objective lens tells the story of a camera that has suffered water ingress through a shattered filter. This would be a camera to avoid. It sold for less than $40 as parts.

Aurora

[Fraser]

I have just searched out some pictures that I took of my Raytheon 300A camera.

It is a very different design to the Type 2 Cadillac Deville unit as you can see. If appears to be more like the older Cadillac Deville Type 1 shown in the previous post.

Note the appearance of the chopper wheel when not degraded and the mask broken. The spiral mask is clearly visible.

Aurora

[poot36]

Since this is a car camera what would be the temperature difference detection ability?  Ie can it tell the difference between a 20°C object and a 21°C object or is the resolution like a 5°C difference?  Would this camera with an appropriate lense be good for looking at PCBs?  Sorry if these questions seem stupid but I only have a general knowledge of thermal cameras.

[Fraser]

Well another Ex Cadillac Deville Raytheon thermal camera has just arrived, fresh from a car scrap yard in San Antonio, Texas 

Initial impressions are very good. The camera has an intact stone protection window and has its loom present so I now have the correct connectors etc. No damage visible on the camera exterior either. Not had a chance to inspect the internals yet but the worst I expect to find will be a a degraded chopper wheel membrane that I can easily repair.

To repair the previous Raytheon camera I will be attaching 12 Micron thick Polyolefin film and shrinking it tight before either spraying the spiral onto it in graphite or adhering a thin thermally opaque plastic spiral to the strong Polyolefin support film. The film will prevent flapping of the spiral mask when spinning.

Pictures of the latest arrival attached.

The cost was a very reasonable $200 considering its excellent physical condition. The OEM Germanium stone guard window costs $400 alone as a replacement part, and it is often broken on used cameras.

Aurora

[Fraser]

I have managed to find some specs on the Raytheon camera. It is actually better than I had stated. The thermal differentiation capability is 0.1C at 30C ambient and the BST FPA refresh rate is 60fps. Not bad.

Aurora

[Hescohar]

Hi,

I am new at this forum so any imperfections in my posting I appologize beforehand.

I was wondering if you ever came to rebuild the chopper disk for the camera?
I have the same problem with mine and would like to try repairing it.Not being a electronics technician I do not understand all you are saying about the material to use.
The objective for me is to ad the camera to my collection of night vision gear and/or install and use it on occasion on one of my vehicles.

Har

[Fraser]

Hi Har,

I put the repair of the chopper wheel on hold whilst focussing on other priorities, but I can detail my intended repair process and thoughts behind it.

Thanks to a very nice chap in the Thermal. camera industry I now know more about the design of the chopper wheel. My thanks to him for this help.

1. A chopper wheel is needed to create a change across the BST array. The sweep of the chopper wheels opaque section effectively resets the detector elements ready for the next image capture.
2. The chopper wheel used in the Raytheon cameras has a semi opaque spiral applied to the surface of a thermally transparent film. This spiral is the part that 'resets' the BST detectors to a nominal level.
3. The spiral is semi opaque and not totally opaque in order to improve the dynamic range of the BST core. It is created using a pattern of dots rather than 100% coverage.
4. The chopper wheel is turned by a DC motor that is driven by a speed control loop that synchronises the speed with the cameras read out electronics. A small slot in the edge of the chopper wheel aligns with an IR beam break detector as the wheel rpm and position trigger.

My proposed repair of the broken chopper wheel film is as follows.....

1. The film that is used for the shutter wheel substrate must offer good transmission of thermal energy and so it is very thin. It is actually a very thin heat shrink film, so once applied and glued in place, it may be gently heated to ensure that it is taught across the frame. I recommend 12.5 or 15 micron Polyolefin shrink film used in the food and product wrapping industry. Some CD and DVD boxes often come wrapped in this film. It is non stretchy and shrinks with the heat from a hair dryer. CD and DVD wrapping that is stretchy is not the right stuff. I bought new film on eBay. It is also used for secondary glazing use.

2. The film needs to be made opaque in the correct pattern in order to form the required chopper function. I cannot reproduce the semi opaque pattern so would use spray paint to create the pattern.

3. The spiral on the original chopper wheel is know as a Fibonacci Spiral and needs to be created using a paper mask over the wheel. This can be created using a computer image of the spiral, resized to fit the wheel frame. The area to be painted is then cut out with a craft knife.

4. The spiral mask needs to be applied to the wheel in the correct orientation with reference to the timing notch (presumed but not confirmed). The orientation of the remains of the original spiral will show correct spiral positioning.

5. The spray paint is applied in several light passes to avoid over application of paint and migration into the 'clear' areas of the chopper wheel.

Alternative approach.......

1. The chopper wheel needs to create a spiral chopper for the BST array. This may be created using a coated film or using a solid spiral driven by the motor.

2. A solid spiral chopper may be made from very thin FR4 PCB material or thin plaricard used in modelling.

3. A paper template is created with a computer and the sprawl is cut out of the chosen material with a craft knife.

4. The solid chopper spiral may then be glued to the original chopper wheel game to provide it with rigidity. The indexing slot must not be obscured,

5. Balancing of the complete chopper wheel will be needed to correct for the uneven weight distribution caused by the solid spiral material. The counterweights can be plastic or metal and moved around the wheels edge or centre until minimum vibration occurs. Failure to do this will lead to vibration and long term damage to the precision motor bearings.

New Chopper wheel availability..........

I will not have to carry out this work now as I have managed to purchase a replacement new Raytheon chopper wheel. I regret I cannot provide my source of the chopper wheel at this time. If more chopper wheels become available, I will advise here.

Fraser

[Fraser]

To aid those wanting to make their own replacement chopper wheel I have taken some photos of the wheel fitted to my spare Raytheon core. As it is not totally opaque, the spiral is hard to photograph but you can see the spiral shape and the alignment with the indexing slot.

Fraser

[Fraser]

Chopper wheel

[Fraser]

Close up of chopper wheel dots that form the semi-opaque spiral.

The spiral shape is common on the internet as it is a mathematical shape.

Fraser

[Hescohar]

Hi,
Thanks Fraser for your great explanation,

Those are very interesting ideas about rebuilding/making a chopper disk.I had some similar ideas,though not thought through in detail yet.

Rather then using the original disk and removing the old mask I think I could make a new supporting disk out of some suitable material.
Then covering it with a mask made from a suitable material.

If I understand you right,the spiral may not need to be semi opaque,it could even be totally blocking heat energy?

When I find time and motivation I maybe making a few different styles of chopperdisk to test.


Har

[Fraser]

Hi,

Yes, the chopper can be totally opaque to thermal energy and the camera will still work. The semi opaque coating was to improve dynamic range but for general use I would expect the BST sensor to work fine with a DIY opaque chopper wheel. Remember the timing slot at the outer edge though.

Fraser

[Bill W]

The physics are similar to the older Pevicon tube cameras, which had a solid / open chopper spiral made of thin FR4 fibreglass.

The concept is to provide an edge that follows the scan up the sensor, so the relationship to the notch is indeed crucial Fraser.

The inner diameter is the distance from axis to the nearest part of the active sensor area, the outer diameter is from axis to furthest active part of the sensor area.  Do not forget to allow for the field blanking. 

That said it is not so critical on shape or you would start to worry about the support struts.  However greater inaccuracy would lose some sensitivity or create variations if some pixels did not have a full period of exposure / full blanking between each readout.

There have been a few other chopper wheel designs too....
'Windmill' - the motor axis is off to the side rather than above / below so that has a slower castellated / windmill blade.
'Conical' - folded up spiral onto a conical surface to reduce the frontal diameter.
'Multiple spiral' - turning slower, and some even had optical elements in the clear sections to perform microscanning.  By taking the four (IIRC) separate open images it was possible to create the effect of a higher resolution sensor.

Bill

www.fire-tics.co.uk

[Fraser]

Great information. Thanks Bill 

[Hescohar]

Hi Fraser and Bill,

With your information I went checking out different plastic packaging materials,most I tested were indeed transparant for IR energy.
I used a Flir Lepton in a Flytron camerabody for this.I made a handheld viewer for it with the viewfinder out of an old videocamera.
It is hold together with a crude cardboard construction and use an USB battery for power supply.Off course its accuracy is nill,but it is a usefull tester.
My idea at the moment is buying a piece of the same material they use for IR movement detectors and cut the disk from that and then spraypaint the spiral on to it.
I already found a company selling it,but have yet to ask if they would sell me a small piece rather then industrial amounts.
Maybe next week I'll find some time to continue this project and make up a chopper disk.I wouldn't turn down an original disk though if one might pop up.

Bill,nice link to explore,I have one of the camera's listed for many years, but knew nothing about its history other then that it came from the German navy while most that are around in Holland(were I live) are ex Dutch navy off course.

Have a nice day.
Harald

[Bill W]

The image below is of the EEV P4428 shutter wheel and lens to illustrate the 'solid' version

Bill

www.fire-tics.co.uk

[Fraser]

Bill,

We're the solid chopper wheels dynamically balanced to reduce vibration or was the balance achieved during design of the wheels shape ? (Even weight distribution)

Fraser