Question

Surface sag map tilt?

  • 5 April 2024
  • 3 replies
  • 81 views

Hello 

I have a question on the tilt x and y values, in the text tap of the Surface Sag map.

When I create the OAP and try to extract the sag map, it shows certain values.

What does mean of tilt? Was the data in text tilted by displayed angle? (To have the center of sag map to be normal to projection angle?) If this means tilt, the aperture should be oval shape with cosine factor. 

 


3 replies

Userlevel 7
Badge +3

Can you post a screenshot of what you’re seeing?

I have attached a snapshot of the surface sag map data. This pertains to off-axis optics surface. I have highlighted the angle values in red underline.

Userlevel 5
Badge +1

Hi!  For off-axis coordinates in the sag map, the center of the sag map corresponds to the center of the aperture on the part, and the angles reported are chosen so that the sag map has zero tilt across the aperture.

You are correct that the aperture is not adjusted in the new, off-axis coordinate system.  We made that choice due to the way that apertures are defined in Zemax;  apertures are always applied in the Y-Z plane as defined by the local vertex of the surface and then projected onto the part, giving elliptical parts for steeply curved surfaces.  Optics tend to have circular substrates, though, so we chose not to adjust the off-axis sag map aperture away from circular.  

If you would like an elliptical aperture to appear in the off-axis sag map, just calculate the elliptical aperture shape and apply it to the surface using either the built-in elliptical aperture or the user-defined aperture, depending on how much accuracy you need.  Another option would be to oversize the starting aperture, retrieve the sag data, and apply a mask to it.

Best regards,

Erin

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