After looking at a few viewers and a couple sights I've seen something that seems to pop up in all of them but I can't figure out why....using the unit for little bit and then there is a ghost or shadow of a previously viewed scene in the viewer over the top of realtime views. Other times it looks like a shadow or shade pulled down that you can see through but no definition...kind of a cloud between you and the outside. I've seen them all do it and a simple recalibrate or reboot clears it out but that takes time. Is there some particular reason it occurs and can it be prevented? Hope the question is clear enough. The ATN guy at the shot show knew how to turn on the viewers but didn't seem to have any answers. The other vendors selling thermal didn't want to be bothered by those of us who weren't spending a few mil.
Thanks in advance.
Frank
Well, you really need an engineer to help you with this - and understand that the optical engineering associated with i^2, thermal, and light gathering lens systems are all different disciplines. It is not realistic to expect salespersons to know the answers to why these artifacts occur, versus what to do to use the controls provided to remedy them.
The technical phenomena behind the two artifacts (and they are two distinct artifacts) you describe, the ghosting and the clouding, are: drift and temporal response.
Uncooled thermal cores work by baselining a temperature gradient (across a sensor matrix) to a threshold and then using dynamic comparisons against the baseline to determine whether to display the corresponding OLED pixels as black body or white body.
As the thermal scope is being used from initial activation, it's ambient temperature slowly increases. This affects the baseline (described above) and skews the white body / black body algorithms, resulting in the hazing or clouding you describe - that is why many scopes require more frequent NUC in the period after startup. Abrupt changes in the ambient temperature from moving the scope between locations with different temperature and temperature conductivity (i.e. as modulated by humidity), or exposure to forced air (wind, air conditioning, heating, etc.) can also disrupt the measurement baseline and result in hazing / clouding of the thermal image displayed.
In regard to the ghosting, that is typically a result of fluctuations in the electrical current feeding the thermal core. Anything that affects the conductivity of the sensor elements can cause delays in the temporal response that may be displayed as slight phase shifting to prolonged "sticking" of images. I almost never encounter ghosting in the higher end thermal scopes, except when the power input wanes ... for example: with batteries reaching end of charge; or fluctuates: for example if connected to AC source and a power interruption or surge occurs. In a previous post, I demonstrated a portable, rechargeable DC battery power source for the FLIR T60 that provides consistent voltage and current feed, with large power reservoir (8 hours) for its small size ... as an APC or sorts, to minimize undesirable temporal response in the thermal core.
Hope this helps answer your questions.
IR-V
