A fellow forum member highlighted the sale of some ISG Talisman fire fighting cameras and wondered whether Mike would do a teardown on one. Now Mike has already done a teardown of a Talisman, but it was the original Pevicon based unit and not the later BST based model. I have a number of the later BST based units so thought I would take some pictures of a chassis that I had lying around. Before anyone gets concerned about me tearing the chassis down, fear not, this is a spares donor chassis with a seized chopper wheel motor and another unknown fault in the electronics package. I have yet to look at this, or any of the other Talisman cameras tat I have as I just did not find the time. This is the first Talisman chassis that I have taken apart but the design uses some parts from Raytheon that are common to the E2V ARGUS 2 and I know that model well
A little about the ISG Talisman and its design.....
The original ISG Talisman thermal camera was built around the EEV Pyroelectric Vidicon tube and had a very similar electronics package to the EEV P4428 and its stable mates. Why this is so is a story for another day !
As technology moved on, Raytheon introduced the Barium Strontium Titanate (BST) high resolution staring array and its associated integration kit. The BST sensor die provides 320 x 240 pixels operating at high frame rates and is housed a ceramic package incorporating a heater to raise the die up to the required operating temperature of around 30 Celcius. The kit that Raytheon supplied to those companies wishing to use the BST staring array varied depending upon the customers needs. A common integration kit would contain the following parts:
1. Raytheon BST Sensor array
2. Raytheon Electronics package to drive the BST sensor and output image data
3. Chopper Wheel with associated motor and mounting frame
4. Chopper wheel optical sensor to position and RPM feedback
5. Integration Guide.
Some kits would also contain a Raytheon PCB for the BST sensor array and this connected to the supplied Electronics package to make integration simpler for some customers.
The company using the Raytheon BST kit could use it to easily create a thermal camera with just the addition of a suitable lens and power supply. The Raytheon electronics package will produce composite video in a fully automatic operating mode with no other image creation electronics required.
More advanced and capable thermal cameras were created by adding a combined lens and mechanical iris, camera control electronics and features such as video overlays, temperature measurement and visible light camera image merging with the thermal image. The Raytheon kit basically took care of the important image creation role and other additional features were just added around it. For this reason the Raytheon BST kit became very popular and appeared in many manufacturers products. Some manufacturers engaged Raytheon to supply complete thermal camera solutions and these use basically the same electronics design but on a different PCB layout to suit the application. Raytheon also produced their own line of complete, self contained BST thermal imaging cores, complete with lens assembly. These were the Raytheon Thermal Eye 300A and 300D cores. The 'D' version of the core had lower image noise content and improved performance over the 'A' model. The Cadillac DeVille night vision thermal camera is a Raytheon product based upon the Thermal Eye 300 series design. The Raytheon BST cores are to be found in may thermal imaging systems of the era in which they were produced. They appeared in pan tilt camera heads for vehicles (Law Enforcement) , Boats (Navigation & safety) plus perimeter security systems, both civilian and military. There is a mix of Raytheon BST Kit (OEM build) based products and those 'Manufacturers' that chose a Thermal Eye 300 series complete core for integration into their end product. The Thermal Eye 300 series was the easiest path to take but was not as versatile as the kit approach in terms of form factor or capabilities.
Fire Fighting is an area where thermal imaging has proved invaluable, both in terms of dynamic safety assessment by the officers on scene, and the rescue of casualties hidden in the dense smoke that the thermal camera can image through in many cases.
Fire fighting thermal cameras are a specialist product in terms of their design as they must be robust, waterproof and ergonomic whilst producing an adequate thermal image to assist the fire fighter in his tasks. A common consumer grade thermal camera design would not normally cope with the hostile environment of fire fighting. With this in mind, manufacturers of fire fighting thermal cameras looked to the Raytheon BST thermal imaging integration kit and complete cores. Some opted for the simple route of building a thermal camera around a Raytheon 300A or D core, whilst others carefully considered the features that they wanted to provide for the fire fighting brigades and also other uses, such as law enforcement and SAR duties beyond Fires. These manufacturers tended to go with the Raytheon BST kit and integrate it into their own custom lens, sensor board, control, image overlay and power systems. They were able to offer specialist features such as visible light camera image overlay, Pyrometer based scene temperature measurement and image Zoom. As they had designed all but the BST sensor and its associated electronics package, the design could be updated and modified to suite the market as and when required.
The ISG Talisman BST thermal camera is built using the Raytheon integration kit, as is the venerable EEV ARGUS 2. Both cameras were designed independently but both use the same BST sensor and associated electronics board. Beyond that, the designs do differ, as you would expect. Both have a similar lens specification and a mechanical IRIS that increases the cameras temperature imaging capability. The BST sensor has a relatively limited dynamic range but the IRIS compensates for this factor.
The Talisman was available with different options installed and, as we will see, the ISG designed control and features board is populated as required to provide the purchased feature set. The example that I have dismantled here is a basic model so there are many unpopulated pads on the control PCB.
OK, I think it time that we headed into the pictures. I may write more about the Talisman design later.
Fraser
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