Vignetting

Set and Clear Vignetting functions are available in System Explorer / Fields / Settings and in the Toolbar of the Field Data Editor, as shown below.

Set Vignetting Recomputes the vignetting factors for each field based upon the current lens data. Vignetting factors (VDX, VDY, VCX, VCY) are coefficients which describe the apparent entrance pupil size and location for different field positions. These vignetting factors should be left at zero if there is no vignetting in the system.  The factors are further described in "Conventions and Definitions" under "Vignetting factors". The set vignetting algorithm estimates the vignetting decenter and compression factors so that the four marginal rays in the top, bottom, left, and right edges of the pupil pass within the apertures of each surface. Only the primary wavelength is used.

Clear Vignetting Clears the vignetting factors back to the default values of zero.

The algorithm starts by launching a grid of rays through the pupil. At each surface with a surface aperture, the ray is tested to see if it passes within the specified aperture. All rays which pass all surfaces are then used to compute the unvignetted pupil centroid. The edge of the unvignetted pupil is then computed using an iterative method accurate to about 0.001%.

The algorithm may not work in all cases. For systems where the set vignetting algorithm fails, the vignetting factors will need to be adjusted manually. The accuracy of the set vignetting algorithm can be tested by tracing a few marginal rays.

See "Vignetting Factors" under "Conventions and Definitions"

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