infra red filter

[AJH]

I've been playing with a cheap 12V wireless camera as a means of identifying flytippers. It works well enough in daylight and it has some leds around the lens which are switched by a daylight sensor. Trouble is this gives a visible red glow.

So I need to disable the leds and provide ir light from another source, all triggered by a pir to conserve battery (I'll leave it all set up in a parked car so power is not a big problem.

I'm wondering if a 12V spotlight run at reduced voltage with an ir filter in front would work and still appear black? If so where can I get a filter?

I seem top recall skipweasel did some experiments with cameras in the dark?

AJH

[George]

My experience of messing about with cameras that have IR leds around the camera is that they are too close to the lense of the camera and either it blackens out the centre of the image or has a white hazed halo effect.

Cover the the IR leds with blu-tac and construct an IR board as described here and dont have it to near the camera. The more leds you have the it will radiate IR.

quarter of the way down the page

[Skipweasel]

Let me know how large the lamp is and I'll post you some filter material. The very nice people at Lee Filters sent me an acre of free samples, so it'd be churlish not to share it about. Oh, and I'll need and address, of course!

[LiveCat]

You can buy plastic IR-pass filter sheets from suppliers such as

suspect that the IR ELDs that give off a visible red glow are the 880nm type. Could you try replacing the camera's LEDs with some 950nm types ?

[Mike Harrison]

That is probably the best bet - you can certainly get IR LEDs that are completely invisible to the eye

[meow2222]

Black camera film is the standard cheap IR filter. Filament lamps run on half voltage or less produce almost nowt but IR

NT

[AJH]

So this would be true of 12V 55W halogen headlights too??

AJH

[AJH]

I was looking to using a 12V car headlight or spotlight.

This reply to: address is valid, please send me an e-mail and I'll reply with my home address.

AJH

[AJH]

Given that the light being at the camera is probably not a good idea I'll first try a filter then look at making a couple of ir illuminating boards, as George suggests, but my prowess with a soldering iron leaves a lot to be desired.

AJH

[George]

In that case. :-) this is cheap to say the least.

[John]

In article , AJH writes

Do you want the light to be "visible" or truly "black"?

Many security cameras have a visible red light near them to act as a deterrent although most of the light is infra red. What are you trying to achieve?

P.S. I understood that under-running halogen led to the bulb blackening quite quickly.

[geoff]

In message , Mike Harrison writes

how do you know where they are, then ?

[AJH]

Live cat suggested 880nm leds are visible and 950nm ones invisible to naked eye. Now I'm confused...

AJH

[AJH]

truly black so as not to draw attention to them

AJH

[George]

This artical says it all.

[Dave Liquorice]

850nm, which IIRTTC may still produce a dull red glow. 950nm should be completely invisible.

[George]

It might but its within the boundries of IR,800 is the start of the IR spectrum.

Nothing wrong with the HK power sellers,Ive bought off three different ones,takes a while for the stuff to come through but they do deliver.

[Andy Burns]

Wait until the flytippers start using night-vision goggles to take advantage of the workplace illumination you've provided for them.

[meow2222]

Is it really a challenge to reduce V of these high temp bulbs a bit further to get black?

NT

[AJH]

I'm taking on board that halogens may not like reduced voltage.

I assume the problem is that whilst running a normal filament, at low voltage, will shift its spectrum it will still be a broad spectrum with still some visible light, hence the need to put an ir filter in front. Thanks to Skipweasel I'll be able to give this a try. The power required may still be too much of a drain and ir (950nm) leds may be the way to go, of course a filter in front of 850nm leds may also work.

I'm also aware that the light will show with a scanner (lcd display on a camera, cheap image intensifier etc) and that villains will be using methods to detect ir light. So there is good reason not to have the ir source at the camera and to trigger it with a pir switch.

AJH