Infrared Cameras -- Do they use a Lens to Focus?

In summary: Why the OP didn't bother, I don't know. I guess it's easier to have us do the work for him.I don't understand all that stuff. Can IR be focused? Or are its properties too different?In summary, an IR camera lens must transmit IR light in order to focus the radiation. Most materials used for visible light block the far IR, so a lens for IR imaging must be made from specially selected materials. Since the refractive index, and so the focal length of a lens, is a function of wavelength, the focal point for IR will be in a slightly different place to that for visible light.
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LightningInAJar
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TL;DR Summary
Do IR cameras need a lens?
Can infrared cameras focus IR radiation as a visible light camera focuses visible light? I think IR doesn't pass through glass well? What are these germanium lens about? I don't think my Flir IR camera has a lens.
 
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@LightningInAJar, your question brought back a FLIR project and the fun of minimum resolution for crack detection, but Teledyne FLIR has this 'selecting a lens' primer that notes the physical configuration for the IR aspect which may help with your enquiry.
 
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I don't understand all that stuff. Can IR be focused? Or are its properties too different?
 
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LightningInAJar said:
I don't understand all that stuff.
All what stuff? Can you please make it a habit to quote the post that you are commenting on? And indicate that you have actually read any links suggested to you by saying what you do and do not understand in each? Lordy.
 
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IR can be focussed, just like other light, but a lens for IR imaging must transmit IR light. Most materials used for visible light block the far IR. That is why the lens for IR must be made from specially selected materials.

Since the refractive index, and so the focal length of a lens, is a function of wavelength, the focal point for IR will be in a slightly different place to that for visible light.
 
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LightningInAJar said:
I don't understand all that stuff. Can IR be focused? Or are its properties too different?
Ir is light. What's the problem?

My Seek Thermal camera has a lens and manual focus.
 
  • #9
LightningInAJar said:
I don't understand all that stuff. Can IR be focused? Or are its properties too different?
It all depends on which wavelength of IR you are interested in. In the 'old days' of film cameras, many of them had an alternative focus / distance setting so that you could use IR film 'blind'. So, in principle, it's fine - especially when you realize that many solid state sensors are so sensitive to IR that they have an IR filter stuck on the front of them. A bit more loss in the lens shouldn't affect results too much.
Saying you "don't understand all that stuff" is a shame. Most PF members use the forum to increase their understanding. If you want to do a successful technical project then. you may need to take on a significant amount of new stuff. It's quite rare to 'just get things to work' without some knowledge and you don't need to know the whole lot.
 
  • #10
Baluncore said:
IR can be focussed, just like other light, but a lens for IR imaging must transmit IR light. Most materials used for visible light block the far IR. That is why the lens for IR must be made from specially selected materials.

Since the refractive index, and so the focal length of a lens, is a function of wavelength, the focal point for IR will be in a slightly different place to that for visible light.
Thank you. This is what I wanted to understand. Wasn't sure if IR had different properties from visible light or if any material could focus as optical glass can, but outside the visible spectrum.
 
  • #11
LightningInAJar said:
if any material could focus as optical glass can, but outside the visible spectrum.
If you want a good focussing action over a wide bandwidth then you could do worse than using a paraboloid reflector with a metallic surface. The biggest optical and IR telescopes all use this method and so do radio telescopes, of course. Despite passing through most materials, X Rays can also be focussed with a metallic reflector - the only difference is that reflection only works at very oblique angles. An X Ray scope works this way (a highly 'offset' reflector)

A massive advantage of a reflector is that the geometry works exactly the same way for all wavelengths - no chromatic aberration to bother about.
 
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1. What is the purpose of a lens in an infrared camera?

A lens in an infrared camera is used to focus the infrared light onto the camera's sensor. This allows the camera to capture clear and detailed images of the infrared spectrum.

2. How does a lens in an infrared camera differ from a lens in a regular camera?

The lens in an infrared camera is designed specifically to focus infrared light, which has a longer wavelength than visible light. This means that the lens must be made of materials that are transparent to infrared light, such as germanium or silicon. Regular camera lenses are designed to focus visible light, which has a shorter wavelength.

3. Can you adjust the focus of an infrared camera?

Yes, most infrared cameras have adjustable focus settings that allow you to manually focus the lens to capture clear images. Some cameras also have autofocus capabilities.

4. Are there different types of lenses used in infrared cameras?

Yes, there are different types of lenses used in infrared cameras depending on the specific application. Some common types include fixed focus lenses, zoom lenses, and macro lenses. Each type of lens has different capabilities and is used for different purposes.

5. Do all infrared cameras use lenses to focus?

No, not all infrared cameras use lenses to focus. Some cameras, such as thermal imaging cameras, use a different method called "refocusing" to capture images. These cameras do not have a traditional lens, but instead use a special detector to measure the infrared radiation emitted by objects.

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