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Troubleshooting of object (reflecting flat mirror) compound rotation in non-sequential mode

  • October 6, 2023
  • 1 reply
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JJiang

Dear community,

 

I have a 45-degree reflecting flat mirror in non-sequential mode, which simply changes the light path by 90 degrees, see below. When the “Tilt About Y” changed by 5 degrees, the reflected light was re-directed by 10 degrees. This is expected from fundamental geometric optics.

 

However, when the “Tilt About X” changed by 5 degrees, the light was re-directed (in the vertical direction, or along Y axis) by around 7 degrees, see below. So I didn’t see an expected 10-degree change here...

 

Could you please shine me some light on this issue? Some notes:

  • A .zar file was attached.
  • The ~7-degree change reminds me of a coefficient of 1/sqrt(2). I am not sure this comes from fundamental geometric optics or from my incorrect setup.
  • I checked the Y-coordinates of mirror vertices, which are the same as if 45-degree “Tilt About Y” absent. This is to double-check when something funny happens with compound rotation (matrices).
  • The local axis seems to be correct, see below.

 

Regards,

Jiang

Best answer by Kevin Scales

When you rotate a folding mirror in the direction it is already rotated, you do just add to that rotation and the beam is deviated by twice the total angle. But when you put both X and Y rotations in, the situation becomes a lot more complicated. Rotating a 90 degree folding mirror about the X axis does not just move the 90 degree bend to another orientation.

We have a tutorial on this topic. You can read it here: https://support.zemax.com/hc/en-us/articles/1500005576502-How-to-model-a-scanning-mirror

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Kevin Scales
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  • October 11, 2023

When you rotate a folding mirror in the direction it is already rotated, you do just add to that rotation and the beam is deviated by twice the total angle. But when you put both X and Y rotations in, the situation becomes a lot more complicated. Rotating a 90 degree folding mirror about the X axis does not just move the 90 degree bend to another orientation.

We have a tutorial on this topic. You can read it here: https://support.zemax.com/hc/en-us/articles/1500005576502-How-to-model-a-scanning-mirror


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