DOLPi-UI – a diy near-UV / near-IR/ Thermal-IR /Polarization Imager

[prutchi]

Hi!

 

One more post for today. I developed the DOLPi-UI filter-wheel-based all-mode camera capable of working in the infrared-visible-ultraviolet range both for imaging and polarimetric analysis. I added a FLIR Lepton® module to extend the camera’s imaging capability (though not polarimetry) to the longwave IR (“thermal” IR).

 

DOLPi-UI is based on the Raspberry Pi NoIR camera, two servos, two filter wheels, a servo hat, and a Raspberry Pi 2.

 

The bandpass filter wheel is populated with the following filters:

1. Blank for full-spectrum imaging

2. IR bandstop (e.g. Schott BG-39 glass) for visible-range imaging

3. IR longpass at 680nm

4. IR longpass at 780nm

5. Infrared-supressed near-UV (stack of Schott UG-1 + BG-39 glass filters)

 

The polarization analyzer filter wheel is rotated by a 90⁰ servo. It is populated with the following filters:

1. Blank for non-polarized imaging

2. Wire-grid polarizer film at 0⁰

3. Wire-grid polarizer film at 90⁰

4. Wire-grid polarizer film at 45⁰

5. Wire-grid polarizer film at -45⁰

6. RH circular polarizer

7. LH circular polarizer

 

Very detailed construction and use instructions for the DOLPi-UI camera are available in the following whitepaper: DOLPi_Polarimetric_Camera_D_Prutchi_2015_v5. More details on the construction process are also available in my blog diyPhysics.com (including an iPhone based implementation of the DOLPi-EO polarimetric imager by one of the blog's readers).

 

This project was 5th-prize winner in the prestigious 2015 Hack-a-Day Prize!

 

Cheers,

 

David

www.UVIRimaging.com

www.diyPhysics.com

[Andrea B.]

David, this is quite interresting. I've had a fascination with the Raspberry Pi for quite some time now. But no actual time to play with one and develop any cool apps. So this is way neat to see!!

 

Do you have any images from this Imager to show us??

 

You might want to investigate the extensive amount of material we have on UVP about Filter Stacks. The preference for IR supression in UV capture these days seems to go to an S8612 filter.

 

[That of course reminds me just how far behind I am in collating all the references to Filter Stacks. Oh well.]

[prutchi]

Thanks Andrea!

 

Aware of the preferred stack thanks to the excellent postings on this blog. However, I used whatever I had in my collection, and the UG-1 + BG-39 give good enough results.

 

Programming the RasPi wasn't difficult at all. In fact, I now use it instead of PICs or Arduinos whenever I build one-of setups that are not constrained by the RasPi's size, power requirements, and cost. I highly recommend it.

 

One thing that DOLPi-UI is still missing is a nice GUI. I write spaghetti code, and the GUI-building modules are just too object-oriented for my aging brain. That said, I have to modify my code every time that I want to change the capture sequence. Since my submission to the Hackaday prize was all based on polarimetry, I neglected to capture and save representative UV/IR images. However, I'll take that up next and try to do some IR-VIS-UV multispectrals with it too.

 

By the way, there are amazing image processing toolboxes available for free that work under Python, so image processing in the RasPi is relatively easy. Some of these toolboxes easily rival Matlab!

 

Cheers,

 

David

[Andrea B.]

As an old Unix hacker I say GUIs be banned! Nothing wrong with a nice command line app.

Just kidding.....but I hear you about GUI-building modules. When they paid me for that stuff, I'd tackle it. But probably not now. "-)

 

I'm afraid if I got started with a RasPi I would then abandon the caretaking of my favorite website.

So cool to hear that there are those toolboxes you mentioned. I'd have so much fun!