2 replies to this topic

[topcode]

I am once again making a thread about one of my kinda dumb ideas that will go not very far. Except unlike with a DMD[which I still want to do, but cant find a suitable one], I actually found all the stuff I need for this, and have bought it already. So I don't have any excuses.
So, this is what I've got. Slits are about 175 um wide, I think around .6mm tall.


Two different versions, I will use the squared edge one for this, not sure about what use I will eventually have for the round edge one. As you can see, 4 of the 5 slits overlap, which is not good. For the spacing horizontally, I will be using some prisms to squish it down into a roughly straight line after the focal plane. So the slits will be spaced apart like this on the sky, letting me get the spectra of objects further away in the sky simultaneously, but close together and narrow in the image sensor. The bottom one doesn't need to be blocked, but only 2 of the top 4 can be used at a time, so I need a way to block them selectively, without interfering with the other ones.

[TOMDEY]

Cool --- spectroscopy?!  "How to reversably block off slits in a very small array of slits?"

 

Yeah... that's pretty small. Believe it or not... I addressed a similar challenge in the field with half a dozen anxious techs and scientists looking over my shoulder. We had a tiny clear slit (on fused silica substrate) 150µm x 1500µm that I needed to opaque around its edge without ruining the reticule. I used Kodak Opaque Black Retouching Fluid and an ultra fine paint brush while looking through the stereo microscope. Took three tries before I got it done to our satisfaction. The advantage of the fluid is that it's water soluble, entirely opaque, benign... and comes off with a moistened Q-tip. If your slits are on a glass substrate (?) it would be quite easy to block out any ones without interfering with the others. It takes a very steady hand. We were always doing "micro surgery" on hardware in the field and in the optics labs. Handling spider webs... similar trickery --- Real spider webs! I actually carried an actual spider around in a little box to make fresh silk when needed. This sort of stuff is covered in some detail... especially in the old optics literature. Ummm... custom metrology reticules were one of my specialties. Couple of related images from an old white-paper probably some SPIE or OSA convention. I was immersed in that academic and applied optics back then.  Tom

 

PS: That precision fused silica substrate is 2 inches across.

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[topcode]

Cool --- spectroscopy?!  "How to reversably block off slits in a very small array of slits?"

 

Yeah... that's pretty small. Believe it or not... I addressed a similar challenge in the field with half a dozen anxious techs and scientists looking over my shoulder. We had a tiny clear slit (on fused silica substrate) 150µm x 1500µm that I needed to opaque around its edge without ruining the reticule. I used Kodak Opaque Black Retouching Fluid and an ultra fine paint brush while looking through the stereo microscope. Took three tries before I got it done to our satisfaction. The advantage of the fluid is that it's water soluble, entirely opaque, benign... and comes off with a moistened Q-tip. If your slits are on a glass substrate (?) it would be quite easy to block out any ones without interfering with the others. It takes a very steady hand. We were always doing "micro surgery" on hardware in the field and in the optics labs. Handling spider webs... similar trickery --- Real spider webs! I actually carried an actual spider around in a little box to make fresh silk when needed. This sort of stuff is covered in some detail... especially in the old optics literature. Ummm... custom metrology reticules were one of my specialties. Couple of related images from an old white-paper probably some SPIE or OSA convention. I was immersed in that academic and applied optics back then.  Tom

 

PS: That precision fused silica substrate is 2 inches across.

my horrible spelling strikes once again. I'm pretty sure it is on a glass substrate, though you can never really be sure with a strange optical device from surplus shed(if anyone else for some reason wants to do this too, here's a link), so I might go and see if I can find some of that stuff on ebay.

Edited by topcode, 11 February 2025 - 11:42 PM.