About

About
The aperture is supposed to be the only element of the system diaphragming light rays. It is characterized by its position and its size. It can be located in the object space, in the image space or in an intermediate space.

The aperture location is selected in the Aperture position cell containing the following selection list :

- surface identifier - the aperture is located on a surface of the system,
- telecentric in the object space - the aperture is at infinity in the object space,
- telecentric in the image space - the aperture is at infinity in the image space.


The aperture size can be defined by different means proposed in the type column :

- Object NA - numerical aperture in the object space,
- Image F/# - working paraxial F_number,
- Aperture diameter - diameter defined on the surface declared as the aperture,
- Half angle - half aperture angle in the object space.


The aperture can be laterally shifted. This means that its center can be placed away from the center of the surface designated as the aperture (if any) or from the Z axis of the coordinate system in the related space if it is specified as telecentric.

The shift can be defined by an angle or a decenter in the Center shift cell. The shift values are defined in the X shift and Y shift cells. They are considered either as rotations or decenters depending on the selected type of shift and are described with more details in the related "tutorial".