Aberration Evaluation
Use the Aberration Evaluation () derived values node to compute a list of Zernike coefficients for Zernike polynomials that correspond to various types of monochromatic aberration that arise when electromagnetic rays are focused by a system of lenses and mirrors. An Intersection Point 3D dataset (see Intersection Point 2D and Intersection Point 3D) pointing to a Ray (Dataset) dataset must be used. The dataset must point to an instance of the Geometrical Optics interface in which the optical path length is computed. To add this node, right-click the Derived Values node or any Evaluation Group node and choose Aberration Evaluation from the More Derived Values menu.
In addition, in the Settings window for the Intersection Point 3D dataset, Hemisphere must be selected from the Surface type list. The Center of the hemisphere corresponds to the focus and the Axis direction points from the focus toward the center of the exit pupil in the focusing system.
The Aberration Evaluation derived values node is available with the Ray Optics Module.
Filters
Use the options in the Filters section to exclude some rays from the calculation of the Zernike coefficients.
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Select the Filter by wavelength check box to exclude all rays except those of a specified vacuum wavelength. If this check box is selected, enter a Wavelength (default: 632.8 nm) and a Tolerance (default: 1 nm). If the difference between the specified wavelength and the vacuum wavelength of a ray exceeds this tolerance, then the ray will be ignored.
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Select the Filter by release feature index check box to exclude all rays except those released by a specific physics feature. Then enter an integer value for the index; the default is 1. This field is 1-indexed, meaning that 1 corresponds to the first ray release feature, 2 is the second ray release feature, and so on.
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Select the Filter by number of reflections check box to include rays only if they have reflected a specified number of times. Then enter an integer for the number of reflections; the default is 0. For this option to work correctly, it is necessary to select the Count reflections check box in the settings for the Geometrical Optics interface, before running the study.
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Select the Filter by additional logical expression check box to include rays if they satisfy another user-defined expression. The expression is considered to be true if it returns a nonzero value. The default expression is 1, which would cause all rays to be included.
Zernike Coefficient Calculation
The optical path difference among all rays that pass through the exit pupil is computed. Then a linear least-squares fit is used to express the optical path difference as a linear combination of a standard set of orthogonal polynomials on the unit circle, called Zernike polynomials. The polynomials are scaled by the coefficients that are computed by the least-squares fit, called the Zernike coefficients.
Select the Length unit in which the Zernike coefficients will be given. The default is the micron (μm). This input is disabled if the model is dimensionless.
Select an option from the Maximum polynomial order list: 2, 3, 4, or 5 (the default).
A list of Zernike polynomials and their derivation, properties, and references are included in the Ray Optics Modeling chapter of the Ray Optics Module User’s Guide.