How to create diffraction gratings from negative film

[Paddyster]

Hi,
I recently tried to create diffraction gratings using the negative film of a disposable camera. I designed them so the 'slits' were black and the rest was white so on the negative film the slits would be transparent and the rest would be opaque. It didn't work however. Does anybody have any tips on how to make this work?
Kind regards, Patrick.

 

[sophiecentaur]

Hi,
I recently tried to create diffraction gratings using the negative film of a disposable camera. I designed them so the 'slits' were black and the rest was white so on the negative film the slits would be transparent and the rest would be opaque. It didn't work however. Does anybody have any tips on how to make this work?
Kind regards, Patrick.

Photographic techniques work pretty well for producing some fine structures like integrated circuits. You say it didn't work but what were your results like?
The quality of the optics is relevant to image quality. Were your pictures well focussed? What was the grating design you were aiming at and what did the stripes on your film look like under a powerful lens? Colour film has a layer of 0.1mm or more.

 

[Paddyster]

results didn't work at all, I think the problem was I took the pictures too close with the flash on so there was a lot of glare and what not. Do you think if I done them again with no flash they would work? I don't know how focussed they were as I only got the negatives printed, the camera says stand 1m away for it to be fully focused but if i do that i get more than my diffraction grating design in the lens' sight. Would you recommend blowing the designs up so I can stand 1m away and only get that in?

 

[sophiecentaur]

Do you mean that you couldn't get a picture at all?
1. What was your original? Hand drawn or printed, perhaps?
2. Did you do some scale calculation, to find whet pitch to expect for the photographic grating?

It is quite a business to get a good photo of a flat image that needs to have exact proportions. Flash is a bad idea and multiple light sources placed around the original will avoid specular reflections. If you want to get a good result, the setup below would be ideal. Having the camera too near to the original can easily produce distortion and the grating would not have parallel lines.

Not easy, I'm afraid.
I suggest that you could try part of the surface of a CD or DVD as a good grating. People here on PF have reported some very convincing results.

 

[Andy Resnick]

Hi,
I recently tried to create diffraction gratings using the negative film of a disposable camera. I designed them so the 'slits' were black and the rest was white so on the negative film the slits would be transparent and the rest would be opaque. It didn't work however. Does anybody have any tips on how to make this work?
Kind regards, Patrick.

It's not simple; did you inspect the developed negative to see what the structure looked like?

I've used a similar test target to evaluate microscope objectives, this is a piece of exposed film-

https://www.edmundoptics.com/test-targets/resolution-test-targets/sinusoidal-targets/

Not sure how they were fabricated.

 

[Tom.G]

Also see:
https://www.edmundoptics.com/optics/gratings/#f=Categories_ss|167,29351_s|400 - 700,27776_s|500.0

Edit:
I just looked up the resolution of Kodak Color films. Resolution at 50% contrast ratio runs 20 to 30 lines per mm. Can't find my book on B/W film. Optical gratings start around 300 L/mm and for $$$ got to multiple thousands of L/mm.

 

[cosmik debris]

It's been a long time since I did this but I used a laser and two separate paths combined to get the diffraction pattern. I exposed a plate of Kodak 349F, which has a spatial frequency of thousands of cycles per millimetre. I guess 349F is long gone but I made lots of gratings this way.

Cheers

 

[sophiecentaur]

It's been a long time since I did this but I used a laser and two separate paths combined to get the diffraction pattern. I exposed a plate of Kodak 349F, which has a spatial frequency of thousands of cycles per millimetre. I guess 349F is long gone but I made lots of gratings this way.

Cheers

The film stock in a disposable camera doesn't support that sort of resolution. it will have a coarse grain and a high enough ISO speed to make up for a lens that's like the proverbial 'sucked boiled sweet'.