IR-light focusing and collimation

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In summary, Bryan thinks that using an IR-sensitive CCD to collimate an IR beam would be the best solution.
  • #1
TechSpec
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HI, I am thinking of how can i focus and make a home made collimation to an IR beam.

I have a lens and an IR-led mounted to a center of a focal point. But its hard to collimate the beam properly without visual sight to IR.

B/w-video cams are usually lit with a series of IR leds to have enough light to have a clear view, so that could be one solution, but i have only color-cam :( . Are these color cams also sensitive to IR ? What other possibilities there might be to do the job?

TechSpec
 
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  • #2
I used to collimate IR in my FTIR instrument by placing a temperature-sensitive LCD film in the path at the focal point. The temperature-sensitive LCD film is of the type used in 'mood rings'. It was black at room temperature and became blue then green and ultimately yellow at its extreme range. This was fairly intense IR from a globar. Your IR LED may not be intense enough to accomplish this.

You can use an IR-sensitive photodiode to do this as well. Place the photodiode exactly in the path you wish to focus upon and then adjust the focus to maximize the signal obtained from the photodiode. A voltmeter should do the trick. You may have to mask the diode to allow only the response from a small spot to be measured.
 
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  • #3
Please excuse me, but what are we talking about? Are we discussing ways of turning a telescope into an infrared camera? Or are we talking about producing infrared photons as a sort of laser?

- Bryan
 
  • #4
kanzure said:
Please excuse me, but what are we talking about? Are we discussing ways of turning a telescope into an infrared camera? Or are we talking about producing infrared photons as a sort of laser?

- Bryan

I was referring to focusing an IR beam generated by an IR diode. I don't believe that would apply to a laser or a telescope. My reference to an FTIR is to a Fourier transform infrared spectrometer used to measure the infrared spectrum of a laboratory sample using a very intense source or the type of IR beam used to measure the position of something like the IR beam in an intrusion alarm system.

My idea is to place an IR photodiode in the path of the IR beam and then focus the beam to a minimum spot size. This can be done with one or more IR photodiodiodes (different sizes/areas) and an appropriate mask(s). If the surface of the IR photodiode is large relative to the collimated spot, the response voltage will not change appreciably if the slightly defocussed IR spot is approximately the same size as the IR photodiode. Thus the mask. This reduces the IR sensitive area of the photodiode and allows for a more dynamic response near optimum focus.

If you are trying to collimate a telescope in the IR range, I think you will have to mount an IR-sensitive CCD at the focal point of the telescope and observe the image.
 
  • #5
Hi, first of all, i made a simple illustrating picture what i was thinking. I put a file into here:Link

The purpose is not just focus the beam into a spot, but focus it to an area of a size of that lens, about 30mm. Thatway the beam would be similar size on all of its lenght.

That photodiode came to my mind, but then i only know the strenght of a one spot, i don't know is the area of illumination circular or not, or is its strenght equal on the whole area. Offcourse i could move the sensor to check the area on a certain points. The focus is important, but also the shape is important, it should be round, not oval or stretched. Offcourse certain tolerances must be accepted.

Hmmmm.. Thats why i thought i should use cameras so i could see live picture and instantly see how my adjustments takes effect.

Now i remember, that my friend has a infrared viewing device, it has a capability to view infrared images as it has its own diodes to do the extra light. It is similar like this Meade unit:
http://www.meade.com/nightview/index.html [Broken]
What do you think of using that to do collimation and focusing?

TechSpec
 
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  • #6
The simplest solution would probabbly be to put a visible LED in place, locate it to the best spot for focus, mark that spot, and replace with IR LED.
If your Cam has night vision, it will see IR (my brother found this out accidentally by pointing the remote at the TV while the Camera sat on top of it, filming himself).
 
  • #7
What you need to do is to paint a target with an IR reflective pigment (http://news.thomasnet.com/fullstory/474510/1303) and visualize it with a camera set on night vision or low light illumination. Many digital cameras have this feature (my Sony digital camera does). It is probably better to buy an IR photodiode that has the lens integral to its construction and arrange a series of these so that the 'hot' spot is near the center of vision at the distance you are going for.
 
  • #8
LURCH said:
The simplest solution would probabbly be to put a visible LED in place, locate it to the best spot for focus, mark that spot, and replace with IR LED.
If your Cam has night vision, it will see IR (my brother found this out accidentally by pointing the remote at the TV while the Camera sat on top of it, filming himself).

Visible led should have exactly the same radiation pattern and the housing to get the equal results between these two diodes. And because the IR has a different focal point than a visual light, the result would not be the same.

TechSpec
 
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  • #9
If this is a very near infrared Silicon diode 905-920nm then the easiest way is to use a simple B+W tv camera.
 
  • #10
I just red that a digital camera is a very sensitive to IR, but this is blocked away with internal filtering. If its not filtered, IR can cause unsharp images as it has a different focal point on lenses than visual light :
http://www.naturfotograf.com/UV_IR_rev07.html

On that link above, they removed IR filtering to make a powerful IR photographing device from a camera.

Has anyone seen a spectral response curves for digital cam's ?? I am using 850-880nm leds.TechSpec
 
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  • #11
For a black and white TV camera without an IR filter the response curve is basically that of silicon so should be better than 10% at 850-880.
Even with the IR filter in place, in a dark room a camera with autogain would be enough to focus an 850nm IR-LED. Security cameras generally don't have IR filters.
 

1. What is IR-light focusing and collimation?

IR-light focusing and collimation is the process of directing and shaping infrared (IR) light beams to a specific area or point. This is typically done using lenses, mirrors, or other optical components to manipulate the direction and convergence of the light.

2. Why is it important in scientific research?

IR-light focusing and collimation is important in scientific research as it allows for precise control and manipulation of IR light, which is commonly used in various analytical techniques such as spectroscopy, microscopy, and imaging. It also enables scientists to study and understand the properties and behavior of IR light in different materials and environments.

3. What are some common methods for IR-light focusing and collimation?

Some common methods for IR-light focusing and collimation include using lenses with different curvatures and focal lengths, using mirrors to reflect and redirect the light, and using optical fibers to guide the light to a specific location. Adaptive optics, which use deformable mirrors to correct for any distortions in the light, are also commonly used for precise focusing and collimation.

4. How does the wavelength of IR light affect focusing and collimation?

The wavelength of IR light plays a crucial role in focusing and collimation as it determines the properties of the light, such as its direction, convergence, and diffraction. Shorter wavelengths, such as those in the near-infrared range, are easier to focus and collimate compared to longer wavelengths, which can be more challenging due to their tendency to diffract and spread out.

5. What are some challenges in IR-light focusing and collimation?

Some challenges in IR-light focusing and collimation include the tendency of IR light to diffract and lose coherence, making it difficult to achieve precise and efficient focusing. Thermal effects, such as heat-induced changes in the refractive index of materials, can also affect the performance of optical components used for IR-light focusing and collimation. Additionally, the design and alignment of optical systems for IR-light focusing and collimation can be complex and require specialized knowledge and expertise.

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