PTZ lens window slowly "fogging" from the inside? (no humidity)

nicobar

Young grasshopper
Sep 5, 2019
46
9
New York City, NY
Hello,

I have two PTZ's DS-2DE4425IW-DE and one DS-2DE5432IW-AE out in the countryside, installed about 1 year apart from each other, 3, 2, 1 years ago.
I noticed that the daily images got progressively less clear with time, the oldest camera being the worst.
Upon close examination, it looks like the windows in front of the lenses are not as clear as they used to be: they look as if they are lightly "fogged" (sorry no pictures, I am not in the premises). Cameras are outdoor in the rain and the sun, I keep the windows clean, and the problem affects much more the daily images than the nightly ones, especially when the sun hits the lens, typical of an optical path less than clean.

I haven't disassembled them yet, but I can assert that:
1) it's not humidity from the inside, as it does not change with time/season/temperature and shows no droplets and it's very homogenous up to the edge of the window. It looks more like a very thin patina like something caused by fumes, or an acrylic cooked by the sun.
2) the window outside is clean.
3) no issues with the infrared leds, whose windows I also clean.

I first thought of plastic lens windows getting cooked by the sun with time, but tapping the fingernail on them they sound like they are made of thin glass (I hope they're glass, I may be wrong)

Before I disassemble the oldest camera to see what's going on, has anybody heard of this issue with these cameras?

If they are glass they could be probably cleaned. I am thinking maybe some lubricant or glue slowly outgasses and coats the windows from the inside (most optimistic scenarios as they can then be cleaned!)

IF they are acrylic, well I have a big problem, especially after only a couple years....out of warranty and Hikvision notoriously does not sell parts. Has anyone ever had the need to replace the lens windows of Hikvision PTZ's ?

Thank you all for reading
 
@guykuo, I think you're more "into" (literally) Dahua PTZ's but do you have thoughts on the OP's foggy sensor windows on his Hikvision PTZ's?