AA sensor filter question

[summerwind4]

sorry if this has been discussed here before, but is the AA filter that is mounted to the CMOS sensor made of glass or plastic?

[CyberDyneSystems]

I thinks it's glass.. what's on the outside.. that gets cleaned is glass anyway.
But I'm not sure if that is the AA filter or another layer of glass over the AA....

Either way.. I'm pretty sure it's glass. Given the conditions the cameras are exposed to.. I would think that any form of polymer would be susceptible to coloration over the long term.

[summerwind4]

thank you for the answer.
i had read somewhere that someone said they damaged it because it was plastic.
your answer makes sense

[summerwind4]

here is a bit of info from another discussion.
this is cut and pasted from an ongoing discussion................be careful of cleaning your sensor.
************************************************** *********************************************
The IR filter is a multilevel dielectric cut off filter on the front side.
The UV filter is a multilayer cut off filter on the back side.

The AA (blur) filter is made up of two layers of a birefringent material both orrented 45 degrees WRT the sensor pixels and both having 1/4 wavelength of differential delay between the polarized and non-polarized component paths.

I believe that both of these birefringent layers are made of calcite, although other birefringent materials are possible.

--
Mitch

and,
Information such as this is easy enough to come across if you are willing to take the time to rumage through hundreds/thousands of hits on Google and have a vocabulary on the subject mater at hand. About 6 months ago I spend 5 hours one night doing such specifically looking at AA filter technology and ran into what I regurgatated.

The only thing I am not 100% sure about is the word 'dielectric' on the IR part of the filter.

On the UV part of the filter the UV filter does not need a quick transition from pass band to stop band because the sensor itself is not very sensitive to UV past 350nm.

On the IR side one needs a rather steep transition from stop band to pass band, a transition fast enough to make simple filters not perform well enough. The sensor itself is sensitive into the 2 micron range (at least) so the filter has to do all the work. Do I need to remind everyone about the 'little' mishap a few years ago when it was discovered that video cameras without an IR filter could see through womens clothings.....

In addition dielectric filters are quite hard as coatings go, improving the life of the coating with respect to cleanings.

--
Mitch

[robertwgross]

The only thing I am not 100% sure about is the word 'dielectric' on the IR part of the filter.

In addition dielectric filters are quite hard as coatings go, improving the life of the coating with respect to cleanings.


Dielectric means it is an electrical insulator, not an electrical conductor.

Not all dielectric coatings have to be hard, either. Fortunately, these are.

---Bob Gross---

[summerwind4]

the reason i want to know is because obviously i will want to clean it once in a while.
not knowing exactly what i'm touching is not very reasurring.

[drisley]

I have never touched my 20D sensor to clean it since I got it 10 months ago.
I just use the Giotto Rocket Blower, and I have no spots at all, down to F22.
This method works well too.
http://194.100.88.243/petteri/pont/How_to/a_Brush_Your_Sensor/a_Brush_Your_Sensor.html