diff --git a/private/simple_optim_fitness.m b/private/simple_optim_fitness.m
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+% Copyright 2018 
+% Open University (Katrine Rogers - k.s.rogers@open.ac.uk)
+% University of Southampton (Edward Rogers - etr@orc.soton.ac.uk)
+
+% Defines function to be optimised
+
+% Note fwhm_target is in terms of number of lambdas
+function IR = simple_optim_fitness(b, phi1, phi2, x, lambda, fwhm_target, ind, ind_red)
+
+f =  b*phi1 + phi2;
+I = abs(f).^2;
+w = calc_fwhm_simple(I(1:ind),x,ind_red)/lambda;   % So that w is in terms of no of lambdas
+
+if w>fwhm_target
+    IR = 1e8*w;
+else
+    IR = calc_IR(I,ind);
+end