The coupling efficiency, of only about 2%, is reported in the geometric image analysis window.

We will optimize the image surface position (receiving fiber position) to maximize the coupling. The IMAE operand in the merit function editor reports the coupling efficiency at the image surface. Since there are more settings in the geometric image analysis than the number of available columns in the merit function editor, the IMAE operand uses the saved setting in the .CFG file. To store the desired geometric image analysis settings in the .CFG file, we need to click the Save button the settings window.

The IMAE operand will now report the correct coupling efficiency by using the saved settings. 

The value will be slightly different then what is reported in the geometric image analysis window, since the IMAE operand uses different random set of rays.

Since the thickness of surface #3 is already set as variable, all we need to do is to optimize the system by clicking on Tools...Optimization...Optimization and choosing the Othogonal Descent optimizer:

Look in the merit function editor, or update the geometric image analysis window and note that the new coupling efficiency is about 54%.