SWIR camera setup help

[Andy Perrin]

(All future questions will be added to this thread.)

 

Ok, so as previously noted, I'm trying to make a (relatively) cheap SWIR setup using a phosphor tube to up-convert 1500-1600nm IR to 850-1000nm, according to the tube's documentation. It's become clear that the way the setup is supposed to work is that the lens makes an image on the phosphor screen, and then the camera takes a picture of the screen. There is a focus ring on the phosphor tube that lets me bring the screen into focus.

 

I have my C-mount to NEX adapter and my tube, but what is very obvious is that the phosphor screen is far too close to the lens rear. I need some kind of spacer to make this setup work properly. (At the moment the lens does not focus at all.) Any advice on how one extends the M42-threaded tube to the appropriate length, and what that length should be? I am thinking that the flange focal distance is the proper length here?

 

[Andrea B.]

There are extension tubes of various widths which might help.

Or possibly a helicoid add-on which would permit variable extension.

 

How much extension do you think you might need??

 

wait a sec.....

Why isn't your NEX-to-Cmount adapter working?

Sony NEX flange focal distance is 18mm.

Typical C mount ffd is less than that at 17.526mm (according to various online sources).

So you do not need more extension. It might be that you have too much extension?

Does this adapter have any glass in it?

[Andy Perrin]

Andrea - the image is supposed to be in focus on the white screen shown in the photo above (where the phosphor is), not on the camera sensor. The tube's own optics handle getting the phosphor screen image to the camera. The C-mount is working perfectly for the tube. For example, this is how it looks to the camera at present:

 

The screen itself is in focus, but there is no image on the screen because the lens is not focusing on the screen properly (on the other side).

 

As for how much extension I might need, that is what I asked you guys!

[Andrea B.]

OK, so the lens must be at the proper distance from the phosphor layer. Got it. :D

What is the lens you will be using?

 

To extend a lens there are extension tubes, adapters and helicoids of varying lengths and mounts.

[Andy Perrin]

I have a 35mm Hanimar 3.5 (M42) that I would like to use?

[Andrea B.]

45.46mm.

 

What is the thread on the end of the phosphor tube? Is that an M42? If so then look on Ebay or on Fotodiox for an M42-M42 helicoid which will give you 45.46 mm of extension. I don't recall having ever seen an M42-to-M42 straight adapter but they may exist.

 

There is a 35-90mm heli on Ebay. This is a RANDOM pick. Please shop around for the best price. :D

36mm to 90mm M52 To M42 Lens Adjustable Focusing Helicoid Macro Tube Adapter

 

 

But I think I might instead stack two shorter helis? Again this is a random pick just for illustration. Not a recommendation.

Fotasy Pro M42(42mm) to M42 lens Focusing Helicoid Adapter, 15mm - 26mm

[Andy Perrin]

The end of the phosphor tube is a female M42 thread. My lens is male M42 thread. So I need something that goes female M42 on the lens side and male M42 on the phosphor tube side. Thanks for the links, I will have a look at those!

 

I'm thinking maybe I should try to find a straight M42-M42 that is a little under the 45.46mm and then put a helicoid on it to fine tune the distance.

[Andy Perrin]

This looks like it would do it:

https://www.amazon.com/gp/product/B01GC6B75C/ref=od_aui_detailpages00?ie=UTF8&psc=1

[Andrea B.]

That looks good. :D

 

With an adapter, tube, helicoid and lens, it is also quite possible you will need some extra support to prevent wobble. Like a beanbag or something?

[Andy Perrin]

Yeah. I'll figure out something. Thanks, Andrea!

[Andrea B.]

Andy, I was looking at this phosphor tube on Edmund Optics - just a bit pricey, yes?! It's very cool that you found one for so little. :D

I'm eager to see how it all works out.

[Andy Perrin]

Yeah, at $250 it seemed worth it, versus $2000! By the way, Edmund just slaps its brand name on it. Mine was branded CamIR or something, but it's the same tube (I confirmed with Edmund tech support). If you are looking for them, search for other names, like CamIR and Applied Scintillation.