Any compact mid-infrared sensors available? (DIY thermal imaging camera)
CuriousOne
Posts: 931
Hello.
I always wanted to have a thermal camera in household, but pricing for FLIR and similar others were always big thumb down for me. Recently, at surplus sale, I was able to acquire quite interesting product, which appears to be laboratory infrared sensor. It consists of two concentric mirror assembly with lens, which looks just like compact telescope. There's a set screw on the top, which appears to focus the system on various distances. There are also two worm drives, which are used to adjust X and Y coordinates of the focus point (They tilt the whole lens assembly left-right,up-down) In the focal point of 2nd mirror, the sensor was located. As I was told, this was plumbum sulphide sensor, which was damaged, due to high voltage applied to it. I've removed it, and it looks like old school leds, with metal case, but with stone-like (germanium?) lens on top. I've checked it with multimeter - it is shorted and no output from it. I took an 5mm infrared led, reduced it's dimensions with sandpaper, and inserted it into assembly. This is how I determined purpose of the front screw. So, assembly looks great, and when coupled with stepper motors, can be used as slow scan thermal imaging camera.
The main problem is, that I was not able to source PbS sensor small enough to fit into the existing assembly. The sensor in there is about 4mm in diameter and 8mm in length. All sensors from Melexis, teledyne judson, etc. appear to be at least 5mm in diameter, so they just won't fit into assembly. Maybe there are some other sensors,which may fit into that size?
I always wanted to have a thermal camera in household, but pricing for FLIR and similar others were always big thumb down for me. Recently, at surplus sale, I was able to acquire quite interesting product, which appears to be laboratory infrared sensor. It consists of two concentric mirror assembly with lens, which looks just like compact telescope. There's a set screw on the top, which appears to focus the system on various distances. There are also two worm drives, which are used to adjust X and Y coordinates of the focus point (They tilt the whole lens assembly left-right,up-down) In the focal point of 2nd mirror, the sensor was located. As I was told, this was plumbum sulphide sensor, which was damaged, due to high voltage applied to it. I've removed it, and it looks like old school leds, with metal case, but with stone-like (germanium?) lens on top. I've checked it with multimeter - it is shorted and no output from it. I took an 5mm infrared led, reduced it's dimensions with sandpaper, and inserted it into assembly. This is how I determined purpose of the front screw. So, assembly looks great, and when coupled with stepper motors, can be used as slow scan thermal imaging camera.
The main problem is, that I was not able to source PbS sensor small enough to fit into the existing assembly. The sensor in there is about 4mm in diameter and 8mm in length. All sensors from Melexis, teledyne judson, etc. appear to be at least 5mm in diameter, so they just won't fit into assembly. Maybe there are some other sensors,which may fit into that size?
Comments
http://www.aptina.com/products/features/low_light.jsp
http://www.teledyne-si.com/infrared_sensors/index.html
http://www.hamamatsu.com/us/en/index.html
http://www.digikey.com/product-highlights/us/en/panasonic-grid-eye/2108
Good question. Has anyone written an Object for this thing? I'm guessing it's just a matter of clocking the data into a Prop, but maybe there's more bit-banging involved. Most intriguing to me is that it doesn't seem to require an external lens to operate. True?
I wish I weren't so busy - this looks like something fun to play with.
Here's a link to a brochure: http://pewa.panasonic.com/assets/media/literature/PEWA-Grid-EYE-Brochure-2011.pdf
It's an i2c device, so I guess there's some protocol for banging out the data. Certainly above my pay grade, but if somebody here makes an object for it, I'd be happy to parasitize off the sweat of their more advanced brow.
Since I was not able to source proper sensor, I decided to build a servo control for my lens system. Also, just to start, I decided to buy some simple phototransistor, just to get the proof of my concept, whenever it works or not. Long story short, I've ordered servos, some phototransistors (OSRAM SFH-310 2/3), leds, etc. at digikey. The package promptly arrived, but when unpacked, I found that in the bag labeled "parallax standard servo" there were two 2000 megaohm resistors packed! This is my first case digi-key messing up with the order. I've contacted them quickly and they've sent servos next day, but they haven't arrived yet. Anyways, I have phototransistors, so I decided to build a receiver circuit for it. The book "BASIC Stamp, Second Edition: An Introduction to Microcontrollers" has a nice schematic for receiver with phototransistor "transfer data with laser pointer" chapter. It uses two ancient opamp ICs, about which even google does not knows, so I replaced them with LM358. I've tweaked scematics a bit, adding 2nd output, so I can also have analog on output, not only digital. Installed phototransistor into assembly and started experimenting.
I've faced two problems when experimenting:
1. Ambient light interference. While circuit has pot adjustment for ambient light compensation, fiddling with it each second is quite frightening. So, I definetly need some auto-compensation circuit, anyone got such?
2. Limited sensitivity of SFH310. Initially, I was quite happy with it - it picked up 20w halogen light bulb 30 feet away, but, due to working range, it is insensitive to body heat, warm objects and so on. A friend of mine lend me a mid-ir photodiode, made by german company (ROITHER?) which is really a little wonder- it detects sun position on the sky even in heavy rain and clouds! but, unfortunately, it is way too large, so won't fit into my assembly