Skip to main content

Advantages of the new nonsequential Off-Axis Mirror object

  • September 23, 2021
  • 4 replies
  • 763 views

Forum|alt.badge.img+1

We’ve introduced an Off-Axis Mirror object in nonsequential mode.  It has some advantages for users:

  • The object has a coordinate system that is at the center of the off-axis part.  (See sketch below.)
  • This makes tolerancing and moving the part easier, because there’s no need to define motions with respect to the parent vertex.
  • It also means that the edges of the part’s substrate are perpendicular to the surface slope at the vertex.  This is more realistic for parts that are polished directly onto a blank (versus small parts that can be cut out of a parent part).
  • It is simpler to define the off-axis apertures.  The part supports native elliptical and rectangular apertures (including circular and square).
  • The object simplifies the nonsequential editor, since a Boolean is not required to define the aperture.

 

Definition of the off-axis coordinate system for the Off-Axis Mirror in nonsequential mode
A shaded model view of the Off-Axis Mirror object

 

Did this topic help you find an answer to your question?

4 replies

Mark.Nicholson
Luminary
Forum|alt.badge.img+3

Will there be a sequential equivalent?


Forum|alt.badge.img+1
  • Author
  • Zemax Staff
  • 51 replies
  • April 25, 2022

The sequential equivalent is the Off-Axis Conic Freeform.   This is an off-axis part with the vertex at the center of the geometric aperture, and sides parallel to the vertex.  The user just specifies the conic constant and the off-axis distance.  It’s handy!

Jose Sasian at the University of Arizona did this work and helped with implementation:

Dmitry Reshidko, Jose Sasian, "A method for the design of unsymmetrical optical systems using freeform surfaces," Proc. SPIE 10590, International Optical Design Conference 2017, 105900V (27 November 2017); https://doi.org/10.1117/12.2285134

 

We’ve gotten a lot of enthusiasm from users about the nonsequential Off-Axis Mirror so far.  They especially appreciate that we have implemented User-Defined Apertures (UDAs) for the part.  In the telescope world, there’s no such thing as a standard mirror shape, because you have to trim the part around the beam to reduce mass and size.

 


Mark.Nicholson
Luminary
Forum|alt.badge.img+3

Is that in the code now? Wow, sorry I missed it!


Forum|alt.badge.img

I had the same question as Mark.  It would be useful to have the off-axis conic freeform extended to include the even radial asphere terms (r^4,r^6,r^8, etc.)--for the same ease of use in tolerancing as with conics.  Or potentially have a way to use the convert asphere tool to include converting to off-axis conic freeform.  I was hoping that the user-defined tolerance operands would do this, but that is not how they are constructed.

Assuming that I haven’t missed this capability somewhere, is there a graceful way of implementing a tilt tolerance on an off-axis even asphere?  I’m hoping not to have to figure out a brute-force method.

 


Reply


Cookie policy

We use cookies to enhance and personalize your experience. If you accept you agree to our full cookie policy. Learn more about our cookies.

 
Cookie settings