In ZEMAX, the position of EXIt Pupil is given relative to Image Plane. If you wish to measure the EXIT pupil position relative to the first surface, you can use EXPP and TTHI.
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For example, if your first surface is Surface 1 and the last surface (image surface) is 10, you could set ]+^;vc 1r
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TTHI with Surf1 = 1 and Surf2 = 10 and define EXPP in the merit function editor. Using SUMM to add the values retunred by these two operands you will be able to get the relative position of EXIT pupil to surface 1. m_{%tU;N
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