TheWaterbug,
Yes the 50um pixels are huge compared to modern 12um pixels and your 17um pixels. The 50um pixels are more forgiving of lens resolution and this is why I mentioned that your higher resolution, smaller pixel size, microbolometer may discover the limits of your elderly lenses optical performance. That said, such is likely not that much of an issue in normal use, but if studying the best performance of a microbolometer, the lens limitations could poison the tests results.
If you research the history of BST and Microbolometer thermal sensor arrays, you will see that BST was a very promising technology that enabled portable thermal imaging equipment to be produced without the need for coolers or thermionic PEVICON tubes. The BST thermal pixel has an unfortunate characteristic though…. it detects the change in its illumination so if an FPA of BST pixels stares at a static thermal scene, the scene image fades away ! Any thermal movement in the scene will be immediately visible though. This effect was used for such things as people counters to ignore static areas of a scene. For thermal cameras it was necessary to incorporate a chopper wheel between the BST FPA and the lens. This requires the BST camera lens to have enough back focus distance in order to place the spinning chopper wheel behind it. The requirement for a mechanical spinning chopper wheel was part of the move against BST technology. There was also the issue of a BST FPA not being being able to produce an output that could be calibrated for temperature measurement (though efforts were made to create such a capability). It ended up with BST and the ‘new’ Microbolometer FPA technology competing for development funding from the US DoD. The Microbolometer technology won that competition and BST faded into history through lack of development funding.
Raytheon were the manufacturer of BST FPA’s and they provided kits of parts as well as complete cores and cameras. The pixel size never progressed below 50um in their released product range. It would surely have reduced with further development, and BST technology had much to offer. In comparison, Early Microbolometer FPA’s were tricky beasts when it came to taming their less desirable characteristics. Once DoD funding was removed from the BST FPA development program, Raytheon concentrated on Microbolometer FPA development. They produced the very advanced (for its time) 160 x 120 pixel A-Si Microbolometer that was released in the well known Raytheon Thermal Eye 2000AS core. The rest is History.
Fraser
Home
Help
Search
Login
Register
