Identifying an imaging failure mechanism in AMBER Sentinel infrared camera - Page 1
Forum section: electronics / general

author: DoubleG79
author_rank: Newbie
timestamp: January 20, 2025, 10:54:47 pm
content: I have recently acquired an operational AMBER Sentinel camera.However, the image quality is severely degraded when contrast is increased.This can be viewed when imaging a blank background:Any clues to a possible reason why the image fails at contrast? While low contrast can be used to get images the camera constantly applies an automatic correction resulting in a high, albeit smooth background level. For example a low contrast image of a coffee cup:Upon opening the camera up, there appears to be nothing damaged inside. The surfaces on either side of the NUC shutter appear to be clean and free of any residue.Upon a NUC, the shutter is used however this does not seem to fix the issue.It is not clear how to open the camera optics, especially without damaging it further. Perhaps there is something akin to residue or mold on either the sensor or lens? Does this kind of image ring any bells as a clear cause of something?Any help restoring the camera is greatly appreciated, but if the fix appears to be too involved, perhaps best to leave this camera as the working relic it currently is!

author: Fraser
author_rank: Super Contributor
timestamp: January 20, 2025, 11:17:03 pm
content: It looks to me like a camera that has lost its NUC table and dead pixel map. Can you locate the memory battery in the unit ? I suspect that you will find that it’s voltage has dropped below that needed to maintain the NUC and configuration memory. With the Radiance 1 this is corrected using the camera controller utility that creates a new NUC table and Dead Pixel map. I do not have a user manual for the Microbolometer based Sentinel camera so cannot advise how you can recreate the required data for normal operation. Sadly such configuration and calibration may have been a ‘return to service agent’ event.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: January 20, 2025, 11:47:04 pm
content: I just looked up the Sentinel specifications on the old Amber Infrared site.https://web.archive.org/web/19980211073715/http://www.amber-infrared.com/products/sentinel.htmlI see that Amber state a “Package life” of 10 years. This suggests to me the expected life of a common Lithium memory maintenance battery. The Lithium battery often lasts longer than 10 years, but expecting it to last 25+ years is asking a lot of it.The specifications also state that the microbolometer is thermoelectrically temperature stabilised. It would be worth checking the current draw of the camera at first power on to see if there is the classic higher current draw at start and gradual decrease as the Peltier module gets the microbolometer to the correct operating temperature. You can also monitor the power feed to the Peltier module within the microbolometer capsule. There should be a TEC somewhere on one of those PCB’s.Fraser

author: hap2001
author_rank: Regular Contributor
timestamp: January 22, 2025, 02:16:47 pm
content: I've never seen a TIC store it's calibration relying on battery, it's such an awful idea.Do many old cameras do that?

author: Fraser
author_rank: Super Contributor
timestamp: January 22, 2025, 03:24:25 pm
content: Thankfully, very few cameras store NUC and other crucial data in battery backed memory. I can only think of Amber and a Inframetrics (PM series) cameras being examples of such. Science cameras could use battery backed memory for calibration as they usually include a calibration utility so that the user can carry out their own calibration updates after a battery change. Why place the crucial data in battery backed memory rather than flash ? I do not know. The Amber Radiance 1 uses a PCMCIA linear flash card for its OS, yet stores calibration data in battery backed memory. That said, it uses a large BR123 Lithium Cell to power that volatile memory for many years.I do not know whether the Sentinel continued Ambers tradition of storing vital calibration data in battery backed memory, but it is a possibility. The Sentinel is a completely different technology to the Cooled Radiance 1 as it is Microbolometer based. That said, the design team for both cameras could have been the same.We shall have to see whether the OP updates this thread with news of whether a lithium memory backup battery is present in the Sentinel.A final thought…. If a manufacturer wants to “encourage” a customer equipment refresh at around 10 years…. a predicted 10 year life lithium battery supporting crucial calibration data makes some senseFraser

author: DoubleG79
author_rank: Newbie
timestamp: January 23, 2025, 10:32:20 pm
content: Unfortunately I could not find anything that resembles a battery on any of the boardsThere seems to be no way to access the microbolometer array for a look without breaking seals or somehow otherwise bonded metal which I am extremely reluctant to do!

author: Fraser
author_rank: Super Contributor
timestamp: January 24, 2025, 01:03:57 am
content: It is good news that the Amber Sentinel camera does not use a battery backed memory for calibration dataIn the images that you supplied, it is the unmasked dead pixels that concerns me. Whist a camera may gain a dead pixel or two over its operational life, the number showing in your images is unusual. Most are normally identified during the NUC process and added to the Dead Pixel map. This map is then used to hide the dead pixels using the pixel values around them to create a mask. The visibility of numerous dead pixels and unusual gradient pattern over the image that you supplied makes me think that your camera has lost its calibration data. (NUC and Dead Pixel Map). The use of a replacement image processor board that has not been calibrated with the microbolometer can also cause strange effects, though I think this possibility is less likely in this case.A bit of a mystery that is hard to solve without the camera being on the bench in front of me. Sorry I cannot be of more help to you.Fraser

author: Bill W
author_rank: Super Contributor
timestamp: January 25, 2025, 03:20:15 pm
content: Pure guesswork, but might it be a high-ish bit missing on the video AtoD - or equally from the correction table memory ?Look for 'floaty' data lines with a scope.Bill

author: DoubleG79
author_rank: Newbie
timestamp: February 02, 2025, 09:53:21 pm
content: There doesn't seem to be anything out of place with data lines, atleaston the ribbons connecting the bolometer board to the rest of the camera.However for the sake of finding something that looks strange and potentially related to resolving the camera's problems, upon completely disconnecting the bolometer board via its ribbonsand turning it on, I get as expected, the image that could be described as a paranormal horror movie trope (img2), but then, when performing a NUC on the disconnected camera, a "thumbprint" shaped image is outputted (attached).As Fraser noted above, there is still the presence of dead pixels even in this 'image' and the "thumbprint" correctly swaps with polarity.When the camera's power is cycled I have to re-calibrate to get the thumbprint back.