Lens Question for Design of an Infrared Spotlight

AI Thread Summary
The discussion focuses on designing an infrared spotlight to illuminate a distant object for a night vision camera. Key challenges include finding suitable optics that can work with off-the-shelf plastic lenses, as plastic generally lacks IR transparency. Participants suggest using LEDs with a narrow beam angle to minimize the need for optics and emphasize the importance of understanding the camera's sensitivity. There is a consensus that achieving effective illumination may require more powerful LEDs than initially considered. The conversation highlights the complexities of using plastic components in IR applications, particularly at 850 nm.
zlj06
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Hello All.

I'm working on a project to build an infrared spotlight which will hopefully light up a distant object so that I can see it on an IP enabled night vision camera. The lens problem seems very straight forward, but I could use some help. Per the attached diagram, I want to focus the light from an led (or cluster of LEDs) on an object that is 40m tall, 400m away. Ideally, I'd like the LEDs + Optics to be housed in a piece of PVC pipe less than 2m long. Whats the easiest way to do this with off the shelf cheap plastic lenses?

Thanks for the help...
 

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zlj06 said:
shelf cheap plastic lenses?
IR transparency and plastic are mutually exclusive.
 
I'm not an expert but I suspect you will need more power than that type of LED can produce. How sensitive is the camera? Perhaps start with that and work back?

Perhaps you could use LEDs that have a 6 degree beam angle? No optics needed then.
 
Bystander said:
IR transparency and plastic are mutually exclusive.

You might have to explain that. How do TV remote controls work if (at least some) plastic isn't IR transparent.
 
CWatters said:
You might have to explain that.
Just googled IR optics, and no plastic components.
 
zlj06 said:
Great call CW! That's a much easier solution. Digikey has some very narrow radiation angle LEDs, so I'll solder together a cluster of those first and give that a try. Thanks, Zach
Bystander said:
Just googled IR optics, and no plastic components.
The LED in question is in the near IR, at 850 nm. Aren't plastics typically transparent there?
 

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