DIY SWIR/NIR source from a halogen lamp

[_Wim_]

Although you don't really know the material of the coating so the thickness might be slightly different.

I know. also due to the changing angle of the coating vs the probe absolute thickness determination is hard.

Attached another test I ran today, with a reflectance probe directly on the reflector. This setup should also be better to determine absolute thickness of the film...

[_Wim_]

Looking for info on thin film measurement I realized there is a plugin for my spectrometer to do it directly...

2040 nm according to that. But it is still quite fiddly, and normally you are required to take a reference spectrum without the film first (using the same substrate). I used a first surface mirror instead. 

Anyway, it is not like I "need" to know the thickness of the film, but it fun using the spectrometer for a different kind of application.

[Andy Perrin]

Hi, this is my first post on the forum (I didn't see anywhere to introduce myself, although maybe I missed the thread, since this forum is gigantic).

I found this post while searching for a MWIR light source for my Agema Thermovision 470 MWIR camera, but I also have a cooled germanium-on-CMOS SWIR cam, the NoblePeak TriWave camera, which works from 350-1600nm or so (give or take if you push it a bit).

On the topic of the post, I recently got an Arcadia Deep Heat Projector bulb, which puts out copious amounts of light in NIR, SWIR, and MWIR (roughly 1000nm to 2500nm or so is the range, but I don't have an exact spectrum). The bulb is for keeping reptiles warm, but it works nicely for illumination in those bands.

Greetings to the community, and if there's a better place to make an intro, do tell me!

[_Wim_]

Hi, this is my first post on the forum (I didn't see anywhere to introduce myself, although maybe I missed the thread, since this forum is gigantic).

I found this post while searching for a MWIR light source for my Agema Thermovision 470 MWIR camera, but I also have a cooled germanium-on-CMOS SWIR cam, the NoblePeak TriWave camera, which works from 350-1600nm or so (give or take if you push it a bit).

On the topic of the post, I recently got an Arcadia Deep Heat Projector bulb, which puts out copious amounts of light in NIR, SWIR, and MWIR (roughly 1000nm to 2500nm or so is the range, but I don't have an exact spectrum). The bulb is for keeping reptiles warm, but it works nicely for illumination in those bands.

Greetings to the community, and if there's a better place to make an intro, do tell me!

Welcome to the forum! That is some very nice toys you got there. I am sure you will fit right in.

Good choice of forum section to post is, from your list above, it seems you are only still missing an "LWIR thermal camera" to cover the full spectrum...

[Ben321]

I'd be more interested in a DIY solution for a SWIR camera.

[DaJMasta]

Well when you figure out an InGaAs FPA homebrew it may be feasible 


In seriousness, though, if you get a NIR enhanced standard camera, you can see just a bit into the SWIR band.  I haven't checked, but I've got a camera I bought for NIR use based on the newer IMX 462 sensor, and it's got good enough NIR performance that if I put a RG1000 filter in front of it, it would still see a little of the um range of shorter SWIR waves - InGaAs sensors often start around 900nm, and it certainly has no trouble with that.  Would take some experimentation, and will likely never see to 1.5um or so, but you could get a little in the right band.

[Andy Perrin]

Silicon can see up to 1200nm and that is often regarded as part of SWIR (nobody is quite sure where SWIR begins or ends anyhow...different people say different things). By 1200nm Silicon becomes transparent, so the photons just zip right through without being captured. It’s possible to improve the sensitivity up to slightly higher than 1200 by designing the chip to make the light bounce several times inside each pixel, improving the absorption. Conventional cameras are not designed this way, however.

[_Wim_]

Silicon can see up to 1200nm and that is often regarded as part of SWIR (nobody is quite sure where SWIR begins or ends anyhow...different people say different things).

I have done a test here with a normal industrial camera to see how far it "sees" into SWIR: https://www.eevblog.com/forum/thermal-imaging/electrophysics-micronviewer-7290a-heat-imaging-test-and-inherent-display-lag/msg3481036/#msg3481036

[_Wim_]

InGaAs sensors often start around 900nm, and it certainly has no trouble with that.  Would take some experimentation, and will likely never see to 1.5um or so, but you could get a little in the right band.

InGaAs based camera's all seem to fetch very high prices, I have not been able to find an affordable solution. InGaAs line array can sometimes be bought offordable on Ebay. With some sort of scanning mirror in front maybe a full image can be constructed from it. On my "todo" list, but too many projects currently...

[Ben321]

Well when you figure out an InGaAs FPA homebrew it may be feasible 

I was thinking more along the lines of motorized rotating hexagonal mirror in front of a pinhole and an InGaAs photo-diode. On the electronics side, a transimpedance amplifier for the photodiode, the output of which connected to my Picoscope USB oscilloscope. The computer then would be running my own custom software written with the Picoscope SDK, that actually pushes the scope to run faster than its rated maximum samplerate (up to 6.25 MSPS when it's rated for only up to 1 MSPS, and I have had some VERY GOOD results with this technique in other projects I've used it with). This data would not be displayed on the screen in the normal manner of oscilloscope software. Instead the raw samples would be saved directly to a file, for later viewing in a raw-image viewer type software (either the raw image data loader plugin for GIMP, or I could write my own raw image viewer software) to display the digitized signal from the photo-diode as an image.

Getting a pinhole isn't hard, but finding a motorized rotating mirror would be VERY hard. These are NOT off-the-shelf components. Every rotating mirror that I've EVER found in equipment I've disassembled, has been built SPECIFICALLY for the piece of equipment that I found it in. The rotating mirrors supermarket table-top barcode scanners are built for that specific piece of equipment. Same with the rotating mirrors in laser printers.

[DaJMasta]

Maybe something like a mirror galvanometer or pair of them would do?  They would be controllable (or variably oscillating), and if you're not concerned with a full-motion sort of framerate, they may be easier to deal with because you can configure the scanning yourself, though they are not so cheap with the required controllers.

Rotating mirrors may be difficult to find, but I think a lot of them could actually be usable if your form factor/placement/software is all configurable.  I thought about getting a flat mirror on a synchronized motor to make a linescan camera a full frame camera, and my trouble was trying to locate a mirror that was axially drilled for minimal image geometry processing - getting a suitable mirror you could attach to a collar for the motor would work, it would just need balancing and then some correction to the final image.  The technicalities of the optics are beyond my understanding, but you may also have trouble with lens convergence distance - unless you get a lens that gives you a fully collimated image to project on your mirror, you're going to need some careful focus adjustment or even lenses between mirror elements.

[_Wim_]

I was thinking more along the lines of motorized rotating hexagonal mirror in front of a pinhole and an InGaAs photo-diode. On the electronics side, a transimpedance amplifier for the photodiode, the output of which connected to my Picoscope USB oscilloscope.

Personally I would start from a linear array like this (https://www.benl.ebay.be/itm/284102443087), and move the array up and down itself behind a standard lens (so in essence imitating a rectangular sensor instead of a line sensor). This removes the whole complexity of the optics. These line arrays are relative easy to read out with a micro. Up down movement can be stepper controlled as it does not need to be that fast as your reading 256 or 512 pixels at a time.

[Ben321]

I was thinking more along the lines of motorized rotating hexagonal mirror in front of a pinhole and an InGaAs photo-diode. On the electronics side, a transimpedance amplifier for the photodiode, the output of which connected to my Picoscope USB oscilloscope.

Personally I would start from a linear array like this (https://www.benl.ebay.be/itm/284102443087), and move the array up and down itself behind a standard lens (so in essence imitating a rectangular sensor instead of a line sensor). This removes the whole complexity of the optics. These line arrays are relative easy to read out with a micro. Up down movement can be stepper controlled as it does not need to be that fast as your reading 256 or 512 pixels at a time.

What's the price of a linear array? A single InGaAs photodiode is already $80 from Edmund Optics. One place that was sellng a full rectangular array (suited for direct use in a camera) was selling that one InGaAs array chip (just the chip itself, and no optics or other electronics) for the huge price of $20000 (which is well over 90% of the cost of a fully functioning SWIR camera, so building one myself from such a component would not save much money). I can't imagine that a linear InGaAs array is not going to be cheap either. I'd guess it would still be somewhere around $800.

[_Wim_]

What's the price of a linear array? A single InGaAs photodiode is already $80 from Edmund Optics. One place that was sellng a full rectangular array (suited for direct use in a camera) was selling that one InGaAs array chip (just the chip itself, and no optics or other electronics) for the huge price of $20000 (which is well over 90% of the cost of a fully functioning SWIR camera, so building one myself from such a component would not save much money). I can't imagine that a linear InGaAs array is not going to be cheap either. I'd guess it would still be somewhere around $800.

New they are probably really expensive, but on Ebay they pop-up between 75 & 200$, which cannot be said for complete camera's unfortunately.

[ducatidragon916]

I know its been awhile on this topic, Have you had any luck with Converting the existing hardware on the S2000 Ocean Optics spectrum analyzers to USB etc? What if any information have you found on this? I know that they are boards that work on PCi slots which do the A/D conversions just wondering if you have had any luck reverse engineering on this?

[DaJMasta]

Not really in the scope of the original topic, but Ocean Optics made a USB adapter for the S2000, and a lot of the mainframes have it built in.  It's called the ADC1000-USB, and I think the original version was an ADC1000 with a second module but they eventually got integrated into a card.