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Create staircase lens

  • 26 September 2023
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John.Hygelund
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Hello,

I would like to know if I can use the sequential ‘zone plate’ surface to construct a staircase lens* with variable zone radii. Below shows an example with equally spaced radii. It’s not clear if the ‘extra data file’ can be used to include individual radii (help screenshot below).

If the ‘zone plate’ surface won’t work, what would be suggested? Can the new composite surfaces be used to do this?

I’m currently using a phase surface (Binary 2) to define ideal behavior, but want to convert to physical surface so I can use POP to simulate the diffraction efficiency. 

 

 

* Staircase lens reference: https://opg.optica.org/ao/abstract.cfm?uri=ao-32-1-60

Thank you,

John

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Best answer by Mark.Nicholson 3 October 2023, 18:30

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Mark.Nicholson
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Looks good to me. The only thing you won’t get is TIR from the sides of the zone plate, or rays interacting at all with the sides of the plate. You’ll need non-sequential for that.

Mark.Nicholson
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Oh wait. The Zone plate lens will not let you define a radius per zone...it’s just the thickness of a flat plate that changes. 

There is a user-defined surface type called US_Multizone_Aspheric. This models a series of annular even aspheric zones. Each zone has a radius, conic even asphere coefficients to order 12, and a maximum radial aperture for the zone. Up to 20 concentric zones are supported. However, each zone is shifted so the surface is continuous across the zone boundaries, and you want a staircase. You may be able to modify the source code to provide this.

  • Mark

 

John.Hygelund
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@Mark.Nicholson , I haven’t made a user-defined surface before, but modification of the US_Multizone_Aspheric looks like it would be straitforward to modify. Thank you for the suggestion.

I was also thinking that I could make this surface using a grid sag. This approach wouldn’t be directly optimize-able, but it would be a good first test.

Another option would be to create the geometry in either the ‘Part Designer’ or external CAD program and import as a non-sequential object.

Any thoughts on these approaches?

I’ll pick back up on this in a few weeks, and provide an update on any progress.

Thank you,

John

Mark.Nicholson
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@John.Hygelund 

Try the hybrid NS route. You can easily make the staircase with Standard lens objects overlapping. That would be the five-minute approach 😎

  • Mark
Kevin Scales
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I think Mark’s last answer about using a non-sequential hybrid approach is going to work out the best. For POP, you’ll need to use rays to pass through the actual surfaces or object anyway, so the easiest approach is to use NSC for what it excels at - easy creation of complicated shapes.

Kevin Scales

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