In sequential ZEMAX, everything is specified as a surface, and each surface can be given a surface aperture under the “Aperture” tab of the Surface Properties dialog.  Many of the applicable apertures are built-in functions, such as the Rectangular, Circular, Elliptical, and Floating apertures. 

In NSC, we treat the optical components as objects rather than surfaces.  Therefore, this general application of surface apertures does not exist.  However, some surface “objects” are available, and apertures may still be created within Non-Sequential (NS) mode. 

Some of the surface objects which exist in NS mode support user-defined apertures.  Those which support user defined apertures will activate the “Use Defined Aperture” option once selected from the “Type” pull down menu from within the Object Properties dialog:



Once this option is chosen, a user-defined aperture file may be chosen from the pull-down menu, a scale may be applied, or the file may be edited by clicking the “Edit Aperture File” button. 

User apertures may be used for a number of different purposes, but most often they are used to define off-axis sections of aspheric surfaces.  As an example, a rectangular, off-axis section of a parabolic mirror may be constructed using a Standard Surface with a Conic of -1, combined with a user defined aperture. 

The rectangle entity name for user defined apertures defines a rectangle centered on defined x and y coordinate which are relative to the local vertex of the parent surface.  The syntax is:

REC cx cy xhw yhw angle nx ny

where cx and cy are the x and y coordinates, and xhw and yhw are the widths of the rectangle in the x and y directions.  The angle parameter is defined in degrees, and may be used to rotate the angle clockwise to any desired position.  Nx and Ny (which are optional) define how many segments will be used to render the resulting surface.

As an example, creating the following UDA:

REC 0 10 3 3 0 50 50

and placing it on a parabolic surface (Standard Surface object with -1 Conic value), the following off axis parabolic mirror can be constructed:



For complete details on creating UDAs, please refer to the following section of the Editor’s Menu chapter in the ZEMAX User’s Guide:  “Lens Data > Surface properties aperture tab > User defined apertures and obscurations.”