Hello,
As a part of my research project, I am trying to create a 1mm(w)*3mm(l) rectangular (beam) of collimated light. I am using LED as a light source because I need a wavelength range of 300nm to 1100nm for my spectral calculations. I tried to collimate the light with the help of a parabolic mirror.
I could collimate the light for 10mm dia circular slits. The beam divergence is very small around these diameters. But when I try to pass the light through a 3mm*3mm vertical slit I can see that the beam divergence is very larger compared to the previous circular slit. A 9mm*9mm rectangular projection appeared on a projector which is around 100 cm away from the vertical slit.
There was a funny phenomenon when I tried to use a 1mm*3mm vertical slit. There were 2 bright lines on the projector screen with a gap between them. I used the same setup which I used for circular slits but I couldn't understand the reason behind this behaviour.
Ideally, I need 1mm*3mm rectangular collimated light with this setup (for over a distance of 100cm). But I would be happy if I can achieve at least a 3mm*9mm collimated light (beam).
I have attached the photos of the Light setup with a parabolic mirror. I would kindly request any information or solution that can help me to resolve this issue.
Many thanks in advance.
I would be happy to provide any further information.
Best regards,
Vayalthota Gopikishore
You are testing the aberrations (mainly coma) of the parabola with kind of a pinhole method. Google "angular dependent magnification", "reflector coma".
And you may try this : 10.1364/IODC.2017.ITh1A.1 and 10.1117/1.600832
regards,
Henning
(1) Any collimated light has a divergence that depends of light source size and collimator focal length. In this case there is no clear data about collimator divergence. For that you want to achieve your collimator should have divergence less than 6 mRads.
(2) When narrow slit is illuminated with collimated beam you can have diffraction effects that contribute to additional beam changes.
(A) You need to learn more about collimation and rearrange your set-up to get proper collimation.
(B) you need to study in more details diffraction effects to understand what is happening.
(C) you need to reconsider the purpose of your experiment and analyze how mentioned effects affect your purpose.
Good luck
Branko
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