How do I constrain the angular magnification of my system during optimization?

Synopsis

Method to constrain the angular magnification during optimization

Solution

The most direct way to constrain the system's angular magnification is by selecting the System Operand "amag" and entering the starting and ending surface range, the default is to evaluate the angular magnification over the entire system. The amag operand uses paraxial data and is very fast.

Open the Operands Data Editor (Optimize >> Operands)
Enter a Name (for example amag)
Enter the definition (AMAG(start,end,cfg) or AMAG for the defaults)
Change the MODE to Con from Min (to invoke the constraint)
Save the changes and evaluate the merit function.

An alternative approach is to calculate the ratio of the incident angle of the chief ray entering the system with the angle of the chief ray exiting the system if you wish to use real ray data.

For this method you need to define a field point (Optimize >> Error Function Tables >> Field Point Set) at full field. By default FPT 3 is already defined.
Define a ray (Optimize >> Error Function Tables >> Ray Set) entering the center of the aperture stop.
Add an operand as above but with a definition of "-RANG(3,1)/IANG(3,1,1,1)"

The ope output for a lens with both operands above defined may look like the following:

*OPERANDS OP MODE WGT NAME VALUE %CNTRB DEFINITIONO 1 C -- amag -4.998085 -- AMAG O 2 C 
-- amagr -4.842942 -- -RANG(3,1)/IANG(3,1,1,1) MIN RMS ERROR: --

Note that individual operand functions (i.e. "AMAG", "RANG" & "IANG") are not available in OSLO LT or OSLO Light, but a similar approach can be used in LT/Light in combination with an optimization CCL.