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Surface-Based Sequential Ray Tracing

Sequential ray tracing is surface-based, i.e. optical components are described by a list of surfaces. This is in distinction to non-sequential ray tracing, which as implemented in Zemax is a 3D volume object based representation.

What this means is that in sequential mode, an optical component is built up of independent surfaces. A singlet lens, for example, is comprised of two surfaces: the front and back face. The specific details of each face is defined by the surface type.

The most common surface type is the standard surface, which is a conic asphere. This is used to represent spherical surfaces, elliptical surfaces, parabolic surfaces etc. Another common surface type is the diffraction grating surface. This has all the properties of the standard surface, plus it can be defined to add a diffractive property as well. Another common surface is the even asphere surface, which has the properties of the standard surface, which has the properties of the standard surface but which also allows radial polynomials of power r², r⁴, r⁶ etc to be added. This is very useful for controlling spherical and higher-order spherical aberration.

This surface-based approach makes it easy to give any optical surface the shape or diffractive properties needed for a specific application. All surfaces are parametric, which means they are defined by an underlying equation. This makes it easy to optimize the properties of a given surface for a specific application, and to tolerance it to examine what the effects of manufacturing defects are.

Zemax supports more than 60 surface types, including many sag (surface shape) types, phase, diffractive, Zernike, grid (tabular data), NURBS, hologram and more. There is also a capability to write your own surface types for rare cases where you need a surface type that Zemax does not support natively.

Related Information:
Zemax SE Surface Types
Zemax EE Surface Types

Once a surface is defined, apertures, scattering, tilt/decenters and other properties can be added via the surface properties dialog box.

The surface properties dialog

Related Knowledge Base articles:
Exploring Sequential Mode in Zemax