Minimal cooling worth it? - Page 1
Forum section: electronics / general

author: Moose850
author_rank: Newbie
timestamp: October 13, 2024, 07:46:26 am
content: I have a hikvision 640 res IP camera that I have mated a 150mm f1 lens to and set up for remote control and focus.I have a few hikvision thermal cameras. I do astrophotography and have a few cooled deep space cameras. They work great cooled to 0 degrees.I have some Peltier modules and I was wondering it might improve the uncooled LWIR image if the camera guts were cooled a little. Not talking about pyramiding on the sensor. Just keeping the entire internals of the camera cooler than ambient since I have the room for a couple modules with heat sinks and a fan inside of the 5 inch tube the camera internals now reside in.Maybe cool things to a low temp above freezing.Is it worth the trouble if power is not an issue?

author: Fraser
author_rank: Super Contributor
timestamp: October 13, 2024, 01:37:03 pm
content: Sadly cooling a microbolometer based thermal imaging camera is somewhat different to cooling CCD imaging sensors and associated electronics. As you may be aware, cooled thermal cameras exist, but they are very different detector technology to that found in a microbolometer based camera. I seem to recall one forum member experimenting with cooling a Seek Thermal camera dongle and seeing some improvement in image noise, but the Seek Thermal cameras of that time were very noisy beasts and not typical of the better microbolometer based cameras of the time.I will try to keep my explanation as short as possible.A microbolometer array is really just an array of variable resistance elements that change their resistance when exposed to heating or cooling. They are passive devices but will have some internal thermal noise present. The microbolometers are read using a Read Out IC and this is an active device that most certainly adds some noise to the signal that appears at its output. The ROIC feeds its output to an analogue to Digital converter ready for processing by the video processor in the camera. The ADC can add noise to the signal path. Manufacturers of microbolometers are continually trying to reduce the amount of noise introduced to the signal and they have been successful in doing so. Video processing then cleans up the somewhat ugly thermal image and presents it to the user. There are still things like column “noise’” sometimes visible as this is caused by tolerances in the actual hardware inside the microbolometer ROIC.The microbolometer is normally operated in thermal equilibrium mode when not temperature stabilised. This means that the microbolometer die self heats itself to a point of thermal equilibrium and the host electronics package monitors the die temperature. It also monitors ambient temperature and lens/FFC flag temperature. The manufacturer knows that the microbolometer die temperature will vary with changes in ambient temperature so correction tables are used to maintain measurement calibration. The nominal microbolometer die thermal equilibrium temperature is around +30 Celsius with an ambient of around +20 Celsius. The manufacturer chooses an ambient temperature and resultant microbolometer die temperature at which to carry out the cameras NUC, dead pixel and measurement calibrations. The ambient temperature is sometimes stated in the calibration certificates. As the camera moves away from the temperature at which it was calibrated, the electronics package firmware routines track the changes in ambient, FFC flag and microbolometer die temperatures. Calculations take place to maintain measurement accuracy and attempt to maintain optimal operation of the camera. If you artificially cool a thermal imaging microbolometer, complete imaging core or a whole thermal camera, you are driving the unit away from the temperature at which it was optimised during the factory calibration. This can lead to degraded performance, depending upon the quality of the camera.Temperature controlled microbolometer based cameras do exist. They contain a microbolometer that has a Peltier module attached to the rear of the microbolometer array inside the vacuum of the module. The Microbolometer die is held at a specific operating temperature by a combination of the Peltier module and its thermo-electric element controller. This is a closed circuit control system that maintains the preset microbolometer die temperature no matter what ambient temperature the camera finds itself in (within reason of course!) It may be of interest to note that these temperature controlled microbolometers are not operated at very low die temperatures. Doing so would take a lot of power as the Peltier fights against ambient temperature and ROIC self generated heat. A die temperature set point close to the natural thermal equilibrium point of the die is usually chosen. The Peltier module is then only tweaking the microbolometer die temperature a little at normal ambient temperatures. If there had been significant performance gains when cooling the microbolometer die to lower than ambient temperature, I feel sure that this avenue of performance improvement would have been investigated and would be present in microbolometer science cameras that care little about power consumption.For low noise astronomy, a photon collection type detector array may be the better choice, but sadly that is the realm of cooled detector arrays operating at 77K (-196 Celsius) and those cameras are expensive.Hope this helpsFraser

author: Fraser
author_rank: Super Contributor
timestamp: October 13, 2024, 02:25:12 pm
content: Here is the experiment carried out by forum member Frenky. He cooled the casing of a Seek Thermal dongle camera. Be warned that these Seek Thermal dongles are well know for having quite noisy images and the cooling of the case may just be countering an issue with the design. Thermal contamination of the microbolometer by adjacent hot components, such as the video processor, can degrade thermal camera imaging performance and the seek Thermal cameras single PCB design may suffer from localised heating issues or even the camera getting too hot for best performance.https://www.eevblog.com/forum/thermal-imaging/seek-thermal-hardware-modification-to-improve-image-quality/25/Fraser

author: Fraser
author_rank: Super Contributor
timestamp: October 13, 2024, 02:29:04 pm
content: If using a thermal camera for astronomy, you may also wish to consider the effects of thermal radiation from the telescope/lens system that is illuminating the camera. Professional thermal telescopes incorporate cooling systems within the barrel.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: October 13, 2024, 02:34:56 pm
content: A couple of pictures showing a FLIR SC6000 cooled thermal camera mounted on the rear of a RC Optical Systems tracking telescope. The fan exhausts are visible in the sides of the barrel.https://www.rcopticalsystems.com/index.htmlThe Ritchey-Chrétien optical design…. Good from UV to LWIR…….https://www.rcopticalsystems.com/telescopes/index.htmlFraser

author: coppercone2
author_rank: Super Contributor
timestamp: October 13, 2024, 05:20:35 pm
content: I want to try it but dealing with humidity is really difficult, IMO it would require a re-housing into a special enclosure if you want a chance at reliability

author: Moose850
author_rank: Newbie
timestamp: October 13, 2024, 07:56:59 pm
content: Thank you very much Fraser for all of that information. I now understand. Very helpful and saved me some time for certain.I have not tried thermal astrophotography other than the moon which I probably need to try in the winter. I was thinking about making a plate to suspend the mirror in my 11" Schmidt Cassegrain telescope to eliminate the glass to see what it might do. Probably nothing too exciting.Thanks again!!

author: Fraser
author_rank: Super Contributor
timestamp: October 13, 2024, 08:22:43 pm
content: Moose850,,The Moon is a great test target when experimenting with thermal astrophotography. Sadly it acts as a very useful lesson in how limiting the relatively low resolution of a modern thermal imaging camera can be. The size of the pixels on the moons surface, even through quite a high magnification telescope are somewhat large ! When wishing to image more distant targets, life gets even more challenging, not just due to “pixel on target” limitations, but due to the better sensitivity needed in the telescope/camera system. Local thermal emitters such as the telescope itself can severely reduce the sensitivity of the system. If the moon is your primary interest, you can get decent thermal imagery without spending too much money.Fraser

author: Vipitis
author_rank: Frequent Contributor
timestamp: October 14, 2024, 01:00:55 am
content: I got a 640 module and 150mm f/1 lens around and wanted to do ground based observations since maybe 2016, when I joined here. I wonder what targets come into question beyond the moon? Maybe M42?

author: Fraser
author_rank: Super Contributor
timestamp: October 14, 2024, 12:32:24 pm
content: The problem with trying to image space targets with thermal imaging is the path losses that mean high sensitivity is needed in the imaging system. Highly sensitive thermal cameras are the order of the day but these can be blinded by their own optical system if it emits too much thermal energy. This is why some thermal astronomy telescopes have to be actively cooled to reduce the thermal contamination of the optical path. Noise is the other challenge for astronomers. We have been discussing microbolometer based thermal imaging systems here. Whilst these can image the moon due to its relatively large size and close proximity to Earth, more distant targets may illuminate far fewer thermal pixels and so become ‘lost’ in the microbolometers relatively noisy image. We need to also consider the negative effects of modern microbolometer camera video processing algorithms. These are configured to produce nice low noise images for the user but were not ‘tuned’ for small space targets. As such the noise reduction algorithms can actually hide the desired target from the user as it may be mistaken for ‘noise’. Operating a microbolometer based thermal camera in ‘RAW mode with image correction (NUC, dead pixel map and FFC) still active but no noise reduction algorithm active, might sound like a option but the image would be very noisy and hard to interpret by the human eye. Post processing of the image might be an option to reveal the desired details, but it might be better to use a dynamic noise reduction algorithm on the live image that is tuned to detect the space target as well as reduce spurious noise. Much like CCD visible light detector Astro photography, it is likely that the best imaging will only be produced when the camera and associated software is optimised for this specialist application. We will always be limited by the relatively low number of pixels on out thermal imaging sensor arrays. This may necessitate very large telescopes to provide a decent target energy and magnification for the sensor to use. Obtaining an image of a target that only occupies 1 pixel is never going to work well ! As stated single pixel targets could easily be ‘deleted’ by over zealous video processing algorithms. Determining the likelihood of imaging a particular target in space needs to begin with the telescopes IFOV. How much of the IFOV will the target fill ? You can then translate that to how many pixels on a particular sensor/detector will be illuminated by that particular target. The Moon can easily fill the IFOV of a decent optical system, but Saturn might still be too small for decent imagery using the same optical system. The Moon is also a relatively ‘Hot’ target thanks to its surface reflecting the energy of the a sun that illuminates it. I think there is a lot of fun to be had imaging the Moon, maybe the ISS or even the odd Space X rocket launch !Fraser

author: Fraser
author_rank: Super Contributor
timestamp: October 14, 2024, 12:34:54 pm
content: A useful read on telescope magnification…..https://skyandtelescope.org/astronomy-equipment/choosing-your-telescopes-magnification/Fraser

author: Fraser
author_rank: Super Contributor
timestamp: October 14, 2024, 12:38:03 pm
content: Another good read…. With thermal images !https://www.cloudynights.com/topic/843050-thermal-imaging-with-a-telescope/Fraser

author: Moose850
author_rank: Newbie
timestamp: October 14, 2024, 04:26:08 pm
content: ISS sounds like it would be fun. My deep space cooled 50mp camera does a great job of the moon even though it isn't meant for planetary pics.I got this first time trying to focus on the moon from the side of my house with my 150mm thermal lens 640 camera. Totally random. Same thing happened first time trying to get the sun with a solar telescope (not focused yet either and it needed one of the filter lenses replace it turns out), which is insanely coincidental. Not that much commercial jet traffic here. Plenty of fighter jets.

author: Fraser
author_rank: Super Contributor
timestamp: October 14, 2024, 07:38:47 pm
content: Great pictures

author: Bill W
author_rank: Super Contributor
timestamp: October 17, 2024, 11:15:32 am
content: Quote from: Vipitis on October 14, 2024, 01:00:55 amWith a similar setup (onto a F1G2 though) pretty much moon only.http://www.fire-tics.co.uk/project4/lenses.htmGetting a recent ULIS system behind the big lenses is in the 'to do' bin, behind lots of other things.If you point an 8-14um camera at the night sky, you get a temperature of somewhere around -50°C from the atmospheric emissions. I doubt anything apart from the sun and moon will be hot enough to give useable contrast. Also bear in mind the relatively large pixel field of view if thinking 'Venus is hot though'Bill

author: Vipitis
author_rank: Frequent Contributor
timestamp: October 17, 2024, 09:08:48 pm
content: here is some proof that mars and even stars are visible with uncooled sensors (they use a large telescope tho):https://arxiv.org/abs/1912.08276

author: JXstaystonight
author_rank: Contributor
timestamp: November 08, 2024, 08:53:22 am
content: Here’s a picture I saw at Raytron, taken of the moon. The details on the moon’s surface were truly stunning. I heard it was captured using a cooling core with a 40~825mm lens.

author: coppercone2
author_rank: Super Contributor
timestamp: November 08, 2024, 04:16:25 pm
content: are you sure that is not a prop from the twilight zone?It looks like a scary moon. I am almost expecting to see some zergs.