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Meritoids (merit function contributions)

This page summarizes the available meritoids and their controls. For controls common to all meritoids, see the Merit function editor page.

If the title of the meritoid description is a hyperlink, it will take you to a page with more detailed information.

Lens performance

RMS Optical Path Difference
Root-mean-square (RMS) optical path difference (OPD) for a specified field point. Use several of these meritoids to control the OPD across the field.
RMS Spot Size
Root-mean-square (RMS) spot size in x, y, or radial direction, for a specified field point. Use several of these meritoids to control the spot size across the field.

Construction properties

Total Track
This meritoid calculates the total track, which is defined as the distance between the first glass surface and the image surface.
Petzval Sum
This meritoid calculates the Petzval sum.
Edge Thickness
This meritoid lets you set targets or limits for the edge thickness of (all) glass elements in the design.
Glass Thickness
This meritoid lets you set targets or limits for the center thickness of (all) glass elements in the design.

Paraxial (first-order) properties

Back Focal Length
Focal point for a forward beam, as a distance from the last glass surface.
Focal Length
Also known as "Effective focal length". The focal length is the distance between the second principal point and the second principal focus. It is also equal to the ratio of the image decenter to the input angle, for the image of a star. This meritoid lets you display the focal length of the lens in any of a number of units. You specify a target value and a tolerance, from which the contribution to the merit function is calculated in the usual way.
Front Focal Length
Focal point for a reverse beam, as a distance from the first glass surface.

Third-order aberrations

Seidel Spherical Aberration
This meritoid calculates S1 defined as eight times the wavefront distortion due to Seidel (third-order) spherical aberration.
Seidel Coma
This meritoid calculates S2 defined as eight times the wavefront distortion due to Seidel (third-order) coma.
Seidel Astigmatism
This meritoid calculates S3 defined as eight times the wavefront distortion due to Seidel (third-order) astigmatism.
Seidel Field Curvature
This meritoid calculates S4 defined as eight times the wavefront distortion due to Seidel (third-order) field curvature.
Seidel Distortion
This meritoid calculates S5 defined as eight times the wavefront distortion due to Seidel (third-order) distortion.

First-order chromatic properties

Conrady Axial Color
This meritoid calculates C1, the Conrady "dee minus dee" coefficient for axial color. The range of wavelengths in the wave editor is used.
Conrady Lateral Color
This meritoid calculates C2, the Conrady "dee minus dee" coefficient for lateral color. The range of wavelengths in the wave editor is used.

Emitters

These stochastic meritoids rely on randomly generated rays. The meritoid contribution is therefore a fluctuating value. It is unlikely that the optimizer can be used with merit functions that employ stochastic meritoids. However, such merit functions can be used with the merit plot.

Emitter efficiency
This meritoid calculates the fraction of rays from a specified emitter that reach the image plane.

See also