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# Tolerancing Irregularity of a Binary 2 surface type

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Is there a way to tolerance irregularity on a 'Binary 2' surface type?

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Best answer by Allie 18 June 2020, 20:01

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Userlevel 6
+2

Hi Jennifer,

We typically recommend one of two options for tolerancing irregularity on a Binary 2 surface:

1. Use TPAR to directly tolerance the Binary 2 parameters. This would probably require an external calculation of the RMS error you want to see using the Binary 2 sag equation as given in the Help System file The Setup Tab...Editors Group (Setup Tab)...Lens Data Editor...Sequential Surfaces (lens data editor)...Binary 2 (sequential surfaces, lens data editor). This would be a similar method to how TEZI applies across a Zernike Standard Sag surface.

2. Use a Zernike Fringe Phase surface to apply irregularity. The Knowledgebase article 'Tolerancing surface irregularity using a phase surface' discusses how this phase surface can be used to apply A(B/C) irregularity, as given by ISO 10110 standards. Additionally, the author of this KBA - Erin Elliott - presented this topic at a recent OpticsTalk. The forum thread for that talk is found here: OpticsTalks: Tolerancing A (B/C) Irregularity per ISO. It contains the relevant slides and code.

Since you are already using Zernike terms to apply the irregularity, I think the second option will be best. If you continue to see 0% contribution on your tolerance report after working through these tutorials, let us know! It might be a good idea for us to get a look at the file in that case.

Best,

Allie

Userlevel 4
+1

The Binary 2 surface has the same sag shape as an even asphere, but it does not support the use of irregularity operands directly. You could try to have a Binary 2 surface with no thickness or material but with sag parameters exactly matching a subsequent supported surface like Standard or Even Asphere. A pickup solve in this case, though usually discouraged, would be appropriate as the surfaces represent a single physical surface and should change in unison.

Hi Kevin, thank you for the reply. Before I read your response I had tried something similar to what you suggested, but in reverse. However, the change in criterion shown in the tolerancing run output was zero, so it appears that the tolerance I applied was effectively ignored. I used a Zernike Fringe Sag surface with zero thickness (but still with the same lens material) immediately followed by the Binary 2 surface. The Binary 2 surface had pickups for radius, conic, and aspheric terms to the Zernike surface. In the tolerance data editor I used TPAR to apply a tolerance to parameter 25 of the Zernike surface which is Z11 for spherical aberration. So, I tried to apply spherical aberration to the Binary 2 surface, but it appears to have had no effect. Note that by using the Zernike Fringe Sag surface it is easy to compute the coefficient values needed to apply a specific amount of aberration. Tolerancing aspheric or binary coefficients directly does not allow for a straightforward conversion to the amount of error applied (as far as I know). That is why I did not put the Zernike surface after the Binary 2, with pickups to the Binary 2. Any other suggestions?