UV dye bleaching

[LSRFAQ]

Try a solvent, a dye would have to be in a polymer base, and DMF or other strong solvents would possibly make quick work of it.

The strongest, most nasty stuff in a hardware store is the solvent based liquid or gel based paint removers for woodworkers. It tends to contain at least 3 nasty, strong, not for mere mortals, solvents. I've used it to strip some epoxies, so it might make fast work of a dyed lacquer used on optics.

Sounds like you need DPSS pulsed UV or nitrogen at 332 to degrade it.

Steve

 

[Bionic-Badger]

Some people have removed both using solvents and that works, but I also want to preserve the microlens arrays over the bayer filters if possible. Then again, the radiation might damage the lenses too, so I might need to remove them anyway.

From what you said before about damage to the CCD, I'm somewhat concerned about ionizing damage from UV-C radiation causing dark current defects. I don't know how much radiation is needed to cause that kind of defect though. Hopefully the webcam CCD will serve as a "canary in the mine" detecting any harmful effects before I apply the radiation to a more expensive camera.

 

[Benm]

I suppose it will be trial and error there.

Using solvens would be more crude really. It would take forever to find a mixture that could disslove the filter but leave the sensror unharmed, if its even possible at all.

 

[Benm]

So did he eventually succeed?

 

[LSRFAQ]

I suppose it will be trial and error there.

Using solvens would be more crude really. It would take forever to find a mixture that could disslove the filter but leave the sensror unharmed, if its even possible at all.

Nothing that is both organic and common is going to touch the glass, silicon, package or metal layers on the chip.

Steve

 

[Benm]

Thats a pretty bold statement. Some solvents will dissolve plastics like the bayer filter without harmng glass or even the sensor material. The trick is finding the correct mixtures really.

Things like acetone-chloroform can be very effective solvents for many plastics, but they will not dissolve glass at all. Its just a matter of making a mixture that is selective to whatever you wish to dissolve whilst leaving things you want to keep as they are.

 

[Bionic-Badger]

Well, initial results don't turn up anything with my germicidal lamp. It's hard to do a real qualitative analysis since this is a cheap webcam and I can't extract the raw bayer data from it.

Also, I only performed 15 minutes of exposure. I doubt if that was enough time to really affect anything. The experiment was cut short because the apparatus was getting pretty warm, and I did not have any ventilation for it because I taped up the edges to prevent any leaks. After the experiment I could smell fumes from the plastics and/or paints. I'm not sure if it was caused by the UV, or just the heat. Still, I'll need to come up with a better apparatus for exposing the CCD before doing longer exposures. Here's a picture of the ghetto rig:

At first I was afraid the 9W fluorescent shop light ballast wasn't quite compatible with the germicidal lamp and I'd need to buy one of those expensive UV ballasts. However, after about 5 minutes of flickering the mercury must have vaporized and the lamp finally assumed a constant glow. The ballast in the handle of the shop lamp did feel warm after the 15 minutes, so I wonder if it still needs a better ballast. Anyway, I'll try some other things later.

 

[Benm]

Don't worry about the ballast: the gas mixture and pressure is those germicadal tube is, afaik, idetical to that in normal fluorescent lights. The difference is the lack of fluorescent coating and the different tube material. Ballasts always run warm though, so they need a bit of ventilation.

As far as smells from the plastic goes: That box looks like its made of flexible plastic, perhaps pvc, but it will contain a good amount of plasticizers and fillers in any case. Expect some fumes and also the box becoming more brittle with exposure - plastics hate shortwave uv!

 

[Bionic-Badger]

I did put a ton of foil in that container where I had the lamp, so I expect most of the UV was absorbed by the inside container. It was probably eating away at the other plastics though, especially that spraypainted lid of the oatmeal container. I really do need a better arrangement for that though.

I'll next be trying it on a Logitech webcam I have here that I can read out the direct CFA data from. It also allows me to disable the auto exposure and such so that I get consistent measurement readings.

 

[Bionic-Badger]

Humm... I wonder too if this UV-C source will work at all. Those CCDs probably have a layer of glass over them, which is opaque to UV-C.

I finally received my 365nm LED, but am waiting on a power supply. Maybe that'll work since it's UVA.

 

[Benm]

I'm not sure what kind of glass or protection is used on the sensors, or how thick it is. Glass will dampen UVC significantly, but i can imagine that a protective layer would be so thin that at least a bit of it makes it through.