Sciencemadness Discussion Board

Removing coating in photo lenses

pneumatician - 28-11-2019 at 18:14

Hi, I think with HCL is enought to remove the optical coating in photo lenses. Any info, real practical experiences... I want to try this with a yashica of around 1970 fixed lense and maybe last Bronica lenses, the PE verion.

DavidJR - 29-11-2019 at 13:11

Why do you want to remove the coatings?

pneumatician - 30-11-2019 at 11:39

the coating block near all UV light, so obviously I want to capture some in this range of vibration. The native UV lenses are very expensive.

http://www.ultravioletphotography.com/content/index.php/topi...

http://www.tochigi-nikon.co.jp/en/products/lens/uv.htm

Well, I can use a much more old camera like this:

:)



untitled.bmp - 1.7MB

G-Coupled - 30-11-2019 at 16:01

Interesting - can you get some cheapo modern 35mm lenses to practice this on first? I suppose one could always get a UV lens filter if one wanted to block UV using the stripped lenses later on.

It was some kind of Flouride salt that was used for anti-glare coatings, can't think offhand what was used specifically for blocking UV.

I wish you good luck with it, anyway - what are you using UV imaging for?

Sulaiman - 30-11-2019 at 17:37

I have zero experience of uv photoghraphy but I'm curious
..what is your uv source / what wavelengths will you be using ?

I ask because based on some recent reading;

this article may interest you http://www.savazzi.net/photography/35mmuv.html

all glasses have a transmission spectrum
soda-lime glass will pass most of the uva spectrum
borosilicate (BK7 optical glass) will pass uva and some of the uvb spectrum
sapphire will pass uva, uvb and most of the uvc spectrum
quartz will pass uva, uvb and uvc

all glasses attenuate transmitted light,
so the less glass used the more light will pass through

all glasses have dispersion
... different wavelengths will have different focal lengths

so ideally you want an achromatic quartz lens,
more realistic would be a reasonably long focal length single sapphire lens,
e.g. https://www.ebay.co.uk/itm/Lens-Sapphire-Plano-convex-FL-150...
if you are only interested in near uva then see the article that I pointed to above.

you will also probably want to use a uv-pass filter to block visible light.

I hope that you succeed and post some photo's here for us to see.

BromicAcid - 30-11-2019 at 22:39

I went through this site, found a lens that fit and went with it:

https://kolarivision.com/uv-photography-lens-compatibility/

I was able to pick it up used for $60.

I have tried to remove the coating on the lens of a compact camera, I used a dremel with a buffer tool and polishing compound, it was a mes but did seem to remove the coating.

wg48temp9 - 1-12-2019 at 00:20

Quote: Originally posted by pneumatician  
Hi, I think with HCL is enought to remove the optical coating in photo lenses. Any info, real practical experiences... I want to try this with a yashica of around 1970 fixed lense and maybe last Bronica lenses, the PE verion.


I would expect the removal method to depend on what the coating is made from. If its MgF2 according to the patent below it can be removed with an alkali soak followed by nitric acid.
Attachment: removing-MgF2-US2536075.pdf (456kB)
This file has been downloaded 397 times

pneumatician - 8-12-2019 at 11:29

Quote: Originally posted by G-Coupled  
Interesting - can you get some cheapo modern 35mm lenses to practice this on first? I suppose one could always get a UV lens filter if one wanted to block UV using the stripped lenses later on.

It was some kind of Flouride salt that was used for anti-glare coatings, can't think offhand what was used specifically for blocking UV.

I wish you good luck with it, anyway - what are you using UV imaging for?


To capture Little Green Men :)

well is not a good tool to have at hand to see in other "realities"? like the predator hunter ETE?

well, no tool exist? to start on and with a potentiometer change the "light" emitted in steps of 5, 10, 15... nm. If visible light is from 400 to 700nm... A tool to see from 700 to 14000 nm in infrared and from 1 to 399nm in UV is no a good tool? :)

This, apart from expensive is ridiculous, beyond for what was designed

https://spexforensics.com/products/forensic-light-sources


Many problems start to capture UV light, because with photo film beyond 320nm the gelatin start to absorbs the UV light :( the glass of lenses from 300nm.

Inclusive with lenses like this only they can capture up to 180nm

https://www.ultravioletphotography.com/content/index.php/top...

of course, test are necessary, every brand maybe or sure use a particular coating...

pneumatician - 8-12-2019 at 11:42

Quote: Originally posted by Sulaiman  
I have zero experience of uv photoghraphy but I'm curious
..what is your uv source / what wavelengths will you be using ?

I ask because based on some recent reading;

this article may interest you http://www.savazzi.net/photography/35mmuv.html

all glasses have a transmission spectrum
soda-lime glass will pass most of the uva spectrum
borosilicate (BK7 optical glass) will pass uva and some of the uvb spectrum
sapphire will pass uva, uvb and most of the uvc spectrum
quartz will pass uva, uvb and uvc

all glasses attenuate transmitted light,
so the less glass used the more light will pass through

all glasses have dispersion
... different wavelengths will have different focal lengths

so ideally you want an achromatic quartz lens,
more realistic would be a reasonably long focal length single sapphire lens,
e.g. https://www.ebay.co.uk/itm/Lens-Sapphire-Plano-convex-FL-150...
if you are only interested in near uva then see the article that I pointed to above.

you will also probably want to use a uv-pass filter to block visible light.

I hope that you succeed and post some photo's here for us to see.


I have the Sun like sourse and at this point a cheap chinese UV torch :)

well, lenses with mirrors are a kill all problems of light transmission, because calcium fluoride glass also have limitations...

Well guys, the last solution, of course beyond my hands at this point, are lenses of GAS, but if you can make a photo lens with GAS instead of pieces of GLASS, all gases transmit light =? :)

of course if any one want good results need to block with filters the rest of "light" like the Wratten 87...

[Edited on 8-12-2019 by pneumatician]

unionised - 8-12-2019 at 12:37

By far the commonest material for coating is MgF2- which is transparent to UV.

Sulaiman - 8-12-2019 at 19:24

You could consider a pinhole camera ?
https://en.wikipedia.org/wiki/Pinhole_camera

pneumatician - 12-12-2019 at 15:36

Quote: Originally posted by Sulaiman  
You could consider a pinhole camera ?
https://en.wikipedia.org/wiki/Pinhole_camera


a! of course, but this is more for "artistic" pics, than for a sci use.

well guys after I see here and there, the UV & IR photo tools public available are ridiculous and some expensive :) until 180nm in UV and under 1000nm in IR, beyond this you need to create new tools, maybe chemical, biological & mechanical.

For a reasonable price I can take IR shots in a mere 850nm, only 150nm beyond human eyes. Who know what is possible to see in the 2000, 5000, 10000, 14000 nm woaaaaa :)

Well maybe the big co. Zeiss, Canon, Nikon... are working with GAS lenses, because the GLASS lenses every generation are more bulky, expensive... for + or - the same optic quality and I think the R&D in glass lenses it's in a cul-de-sac.

Sulaiman - 12-12-2019 at 20:47

Quote: Originally posted by pneumatician  
For a reasonable price I can take IR shots in a mere 850nm, only 150nm beyond human eyes. Who know what is possible to see in the 2000, 5000, 10000, 14000 nm woaaaaa :)

for wavelengths between 1um and 10um silicon is transparent,
especially between 2.5 um and 8.5 um.
(silicon sensors stop responding at these wavelengths),
I used part of a silicon wafer as an i.r. pass filter for a commercial project.
The problem is that the energy of photons is low at longer wavelengths,
e.g. 2.5 um (2500nm) = 0.5 eV, 8 um = 0.155 eV
so low bandgap semiconductors are required,
and due to the large bandwidth (about 1014 Hz for the above example)
thermal noise becomes significant. https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise
So lens research is adequate, it is the sensor part that needs research.

wg48temp9 - 13-12-2019 at 09:27

In addition to the Johnson noise when image objects near ambient temperatures in IR the shot noise caused by the low number of arriving photons and thermal emissions from the the detector housing and even the lenses are major sources of noise.

The signal to shot noise ratio can be increased by collection more photons by increasing the numerical aperture of the optics or increasing integration (exposure) time.

The thermal emission from the detector housing and the detector thermal noise can be reduced by surrounding the detector with a cooled shield and cooling the detector. The shield has an entrance pupil such that the detector can only receive photons through the lens from the scene.

There are two types of detectors. One type detects the photons directly and the other bolometer type detects the changes in temperature when the IR photons absorbed.

Cooled shielded detector are used to achieve the best signal to noise ratio for use in military target detection systems and astronomical telescopes for example. Bolometer types can be low cost and are used in things like ear thermometers to IR imaging cameras for firemen.

Pitvipers us a bolometer type IR sensor in their pit that allegedly is capable of detector a 1mK change in temperature and it has no cooled shielding or detector. Its signal to noise ratio must be very low but it probably achieves the detection with combination averaging and signal processing.

One of the early imaging sensors imaged the IR onto a absorbing thin film. On the opposite side to the absorption it was arranged that a liquid would condense on it. The small changes in temperature of the film were made visible by changes in the condensation.

If you breath on a sheet of cling film stretched on a hoop a slight condensation will form and then evaporate. If the opposite side of the film is lightly touched with a finger after breathing on the film and image of your finger print appears in the condensation. Where the ridges of your finger print touch the film, the temperature is raised slightly which increases the evaporation at the point and makes the pattern visible. Unfortunately using a pinhole to image IR on the film is likely not to work as so little IR can get through the pin hole. It probably can be made to work with a IR lens. Cheapish uncorrected IR lens for CO2 lasers are available on ebay on occasions.

I once worked on a design for a fireman's helmet mounted IR imaging sensor. The design consisted of an array of pyroelectric sensors mounted on top of a silicon chip that read out the signal from the pyroelectric elements.
Pyroelectric materials are piezoelectric materials which when they expand due to a change temperature a significant electric polarisation occurs. That can be detected by contacts similar to the way piezoelectric microphones work. In order to produce a signal even when viewing an unchanging scene a rotating chopper wheel is used to blank off the IR signal at the frame rate.
With the sensitivity turn up it could easily see people or anything warmer or colder than the room temperature.


[Edited on 12/13/2019 by wg48temp9]

wg48temp9 - 13-12-2019 at 13:43

Lots of ZnSe and ZnS lens on ebay uk. The prices start at about £10 for a 20mm dia lens.

They are not corrected so the focus would vary with IR wavelength but I do not know how significant that would be.

That could also be used in an optical pyrometer for better stand off from the furnace.

ZnSe-lens.JPG - 53kB

There are also IR band pass filters with vis rejection. About £8 for a 10mm dia.

andy1988 - 13-12-2019 at 14:15

This is a neat detector design I was reading about.
Quote:
In research appearing online on November 25 in the journal Nature Materials, Duke researchers demonstrate a new type of broad-spectrum photodetector that can be implemented on a single chip, allowing it to capture a multispectral image in a few trillionths of a second and be produced for just tens of dollars. The technology is based on physics called plasmonics—the use of nanoscale physical phenomena to trap certain frequencies of light.

To accomplish this, Mikkelsen and her team fashioned silver cubes just a hundred nanometers wide and placed them on a transparent film only a few nanometers above a thin layer of gold. When light strikes the surface of a nanocube, it excites the silver's electrons, trapping the light's energy—but only at a specific frequency.

The size of the silver nanocubes and their distance from the base layer of gold determine that frequency, while the amount of light absorbed can be tuned by controlling the spacing between the nanoparticles. By precisely tailoring these sizes and spacings, researchers can make the system respond to any electromagnetic frequency they want.

To harness this fundamental physical phenomenon for a commercial hyperspectral camera, researchers would need to fashion a grid of tiny, individual detectors, each tuned to a different frequency of light, into a larger 'superpixel'.

In a step toward that end, the team demonstrates four individual photodetectors tailored to wavelengths between 750 and 1900 nanometers. The plasmonic metasurfaces absorb energy from specific frequencies of incoming light and heat up. The heat induces a change in the crystal structure of a thin layer of pyroelectric material called aluminium nitride sitting directly below them. That structural change creates a voltage, which is then read by a bottom layer of a silicon semiconductor contact that transmits the signal to a computer to analyze.


I hadn't yet looked at what the process they use to size and deposit these silver nanocubes, possibly do-able by an amateur?

wg48temp9 - 13-12-2019 at 15:51

Quote: Originally posted by andy1988  
This is a neat detector design I was reading about.

Quote:
In research appearing online on November 25 in the journal Nature Materials, Duke researchers demonstrate a new type of broad-spectrum photodetector that can be implemented on a single chip, allowing it to capture a multispectral image in a few trillionths of a second and be produced for just tens of dollars. The technology is based on physics called plasmonics—the use of nanoscale physical phenomena to trap certain frequencies of light.

To accomplish this, Mikkelsen and her team fashioned silver cubes just a hundred nanometers wide and placed them on a transparent film only a few nanometers above a thin layer of gold. When light strikes the surface of a nanocube, it excites the silver's electrons, trapping the light's energy—but only at a specific frequency.

The size of the silver nanocubes and their distance from the base layer of gold determine that frequency, while the amount of light absorbed can be tuned by controlling the spacing between the nanoparticles. By precisely tailoring these sizes and spacings, researchers can make the system respond to any electromagnetic frequency they want.

To harness this fundamental physical phenomenon for a commercial hyperspectral camera, researchers would need to fashion a grid of tiny, individual detectors, each tuned to a different frequency of light, into a larger 'superpixel'.

In a step toward that end, the team demonstrates four individual photodetectors tailored to wavelengths between 750 and 1900 nanometers. The plasmonic metasurfaces absorb energy from specific frequencies of incoming light and heat up. The heat induces a change in the crystal structure of a thin layer of pyroelectric material called aluminium nitride sitting directly below them. That structural change creates a voltage, which is then read by a bottom layer of a silicon semiconductor contact that transmits the signal to a computer to analyze.


I hadn't yet looked at what the process they use to size and deposit these silver nanocubes, possibly do-able by an amateur?


I would expect the array of cubes to be created by UV lithography and etching. Just generating the mask would be difficult.

Perhaps the mask could be written directly on to the photo-resit over a silver metal layer by scanning, using a UV DVD writing head with an added axis to give x y positioning. The whole thing driven by a micro controller.
Essentially micro 2D laser printing. Then develop the resit and etch the silver. But you still have to make a connection to them.

I like the idea of a micro 2D laser printer. Writing messages on the heads of pins would be fun.

pneumatician - 17-12-2019 at 10:26

this sound promising but at this moment I only want to work with films like orthocromatic film, blue "vision" expanded, so for UV.

Every digital sensor in cameras are industrial secret? and no public data is available, I think. + the sensor are blocked by law in IR and possible in UV (idiots) :)

Others films like the kodak 2495 are good for IR photo. well, some films are discontinued but chemical photo have a lot of enthusiasts :)

https://www.fotoimpex.com/films/