Digital IR thermometer in parabolic mirror focus for directional sensing - Page 1
Forum section: electronics / projects

author: eneuro
author_rank: Super Contributor
timestamp: October 02, 2014, 10:03:38 am
content: Hello,In one of my projects I'd like to try detect directional temperatures changes from some bigget area (not dot spots) by using some kind of mechanical gimbal pointing Infrared sensor (thermometer) put in the focus of small parabolic mirror (diameter 0.100 meter max) automaticaly into preprogrammed direction and sense reflected IR radiation to estimate temperature in this direction.I'm thinking aboutMLX90614 Digital, plug & play, infrared thermometer in a TO-canwhile according its datasheetMLX90614 Datasheet (PDF)and product info it fit my main requirements:QuoteThis feature might be quite usefull too in some use cases:QuoteAt the price avaiable from my local electronics store for around 13$ for 25+ units it looks very interesting while I don't need detect temperatures higher than 90*C, but his thing can work at temperatures below 0*C which is fine, so this MELEXIS MLX90614ESF-DAA-000-TU by one of the Europe suppliers might fit my needs while it has I2C interface too, so it has everything I need for prototype design and testing using any MCU even DIP8 Atmel.Did you experienced any issues or traps with this MLX90614 digital IR thermomener sensor?My first concern in my design is reflective mirror-for IR it has to be polished and 90%-100% reflective or any curved metal polished surface (anodized aluminium ) maybe could quite nice reflect IR when we put this sensor in the focus of 0.100 meter (10cm/4inch) in diameter parabolic mirror shaped to get as many directional IR as possible?

author: ir-30thz
author_rank: Newbie
timestamp: April 03, 2025, 10:50:03 am
content: I have used the MLX90614 with a 10 inch parabolic reflector made of silvered aluminium and also with a larger 18 inch reflector made from aluminium. Both work very well as a part of a 30THz communication system. I did not take any special measures to ensure a high polish on the reflector surfaces. I was not interested in measuring exact temperatures as I was looking at hot sources which were several hundred yards away - just whether I could detect a signal or not.

author: coppercone2
author_rank: Super Contributor
timestamp: April 03, 2025, 11:48:57 am
content: The difficulty is in the reflector. These types of reflectors are actually chemically polished and also probobly made with PVDHowever, IR cares ALOT less then visible lightI am happy to see more people interested in THz, it felt like I was the only one for a long time lol (at least, the only non funded person)https://www.finishing.com/307/36.shtml

author: coppercone2
author_rank: Super Contributor
timestamp: April 03, 2025, 11:52:59 am
content: as for IR, get a thermal camera, and look at how different surfaces look like. I found brushed steel looked like a mirrorBut at some level it always has an effect. But it makes your testing ALOT easier when it works 70% of the way on something that's bearly finishedThink about how for VHF, your reflector looks like a net...

author: DaJMasta
author_rank: Super Contributor
timestamp: April 04, 2025, 12:40:14 am
content: Does it have to be reflected? Standard IR thermometers use a lens, often built into the the housing if the sensor itself, and it would certainly be convenient to not have to make it.Otherwise, a optical mirror for your focal length should work alright - normal coatings are not necessarily helpful, but will probably get you 70-80% reflectance (and the wider light collection area) with standard aluminum mirrors, so something like a small telescope mirror could be an option, some can be under 100mm.Alternatively, if you know what band your sensor is picking up, you could probably pick up a small germanium of ZnSe lens that, with a mount, could give you wider collection area and some focusing into a smaller sensor.