The goal of this exercise is to convert from surface #1 to #6 to equivalent non-sequential components and place a non-sequential detector object at the location of the current image plane (surface #7).  We will also place a non-sequential source that represents the beam on-axis in object space. This will let us confirm that the converted system works correctly.

After the conversion, ZEMAX will create a Non-Sequential Surface in the Lens Data Editor containing all the non-sequential components, thus making the system "mixed mode" (non sequential with ports). In a mixed mode system, rays are traced sequentially outside the non-sequential group (outside the Non-Sequential Surface type) and non-sequentially inside.

Now, the concept of a "Stop surface" only applies to sequential ray tracing. This is because in sequential ray-tracing rays are aimed initially at the entrance pupil, which is the image of the stop, or at the stop itself. Therefore, only a sequential surface can be set as the system Stop. The Stop surface must precede the non-sequential segment of the design.

In the Cooke triplet example, the Stop surface is embedded in the system. Consequently, we need to move the current stop location to a dummy inserted before the first lens we want to convert.

Also, the all semi-diameter should be fixed (“U” next to the semi-diameter) before converting to a non-sequential design. The Semi-Diameter values in this file are by default fixed.

Insert a dummy surface prior to current surface #1.



Set the dummy surface as the stop in the Surface Property window. To open the surface property window, double click on the "type" column of the dummy surface.



After clicking “OK”, the Lens Data Editor will display“STO” next to the dummy surface indicating that the surface is a stop.