Security camera illumination and motion detection

Vortex12 wrote in news:dmrquiFsshhU1 @mid.individual.net:

Sounds a great idea - I have always been sceptical about the built in LEDs as they are bound to cause a haze as they illuminate dust particles close to the lens.

You have that much dust/muck in the air? Yerk. No need to wipe the washing line before hanging stuff out up here and one can only see ones breath when a diesel vehical has just driven past, assuming it's cold enough. Nothing in the air for the water vapour to condense onto. Built in IR is NFG if the camera is behind glass either, it blinds itself.

The little

You really want the external LEDs so you don't get the number plates burning out in the image.

These are stage/TV lighting gels, they tend to be fairly clear at IR, remember their real use is a few inches in front of say 2.5 kW halogen lamp. There is a lot of radiated heat if the gel absorbed much IR it would melt. Some gels do absorb IR and and they don't last long...

I had a play with layers of ND on it's own or in combination with layers of a few blues. Finally ended up with a few layers of a blue I don't know which one but something similar to Lee Filters 120 Deep Blue:

Virtually no transmission at visible red but then the transmission rapidly climbs. There is a reduction of the IR but almost complete elimination of the visible red glow, it doesn't catch your eye now. In fact even though I know where the iluminator is I have trouble seeing the glow.

Activate the IR lighting by a PIR motion sensor(s), which won't react to anything smaller than a small animal.

Owain

Actually it's more of tourquise than blue but without removing the filter from the illuminator and *attempting* to colour match against the PC screen that's as close as it's going to get.

The LDR in the illuminator turns it off but as that is also covered by the filter tends to turn it off late and on early. I really ought to cut some circles the same size as the glass and punch a hole in the middle to let full day light hit the LDR. That's another tuit for the stack...

The camera switches an IR filter in/out and to colour/monochrome based on light level. There is enough hysteresis to prevent chatter at marginal light levels.

I lied, found a bit lurking under the desk. Comparing against the computer screen the only one that it's really close to is:

"LED Filter CL119 on a Cool White LED (>6000K) gives a visual colour match to existing filter 119 Dark Blue on Tungsten (3200K)."

Think there are three layers of it in front of the iluminator.