Partially immersed lightpipe

  • 7 March 2022
  • 1 reply

Hi all.
I want to make a model as shown below. 
A beam whose wavelength is 532 nm is incident to the light pipe placed vertically to the bottom. 
The exit port of the light pipe and the detector are immersed in the water.
Even though the water is rolled by some vibrations, the light would not be refracted because the tip of the pipe is under the moving surface.   



So, I configured like attached zemax model.
The rolling water was simplified to a simple wedge.
However, as you see the Layout, the rays are refracted at the surface of the rolling water. It is the wrong result. And if the beam is tilted a little, it has to be refracted at the tip of the pipe, not at the surface of the water.

Could you please solve this simple problem?



Best answer by David 7 March 2022, 20:08

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Userlevel 6
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Hi Taeshin,

The reason rays refract at the water is the overlap rule. In non-sequential, if there is an overlap between objects then the region of the overlap is defined by the object that occurs last in the non-sequential component editor. In your design, the volume defining the water occurs last, so the ray encounters water at the edge of the wedge.

In the attached file, I made the cylinder occur after the wedge. Now the cylinder defines the overlap so the pipe penetrates the wedge.

To make this easier for me to do I changed the reference of all objects to global. I also changed the source orientation so we can see that the ray is guided by TIRs in the pipe, when surrounded by air, but does not TIR when the pipe is surrounded by water, Then we see a split. (This of course depends on the angle of the ray.)

I attach a ZAR of the modified design. (Note that you may occasionally see geometry errors with this design, but they occur in ray segments with little power.)