% Example of spherical aberation% Set the options for ploting of the optics/raytracingopt_ops.plotrays=1; % plot the individual raysopt_ops.plotpaus=0; % do not pause after each  ray intersectionopt_ops.plotRT = 0; % do not ``drawnow'' after each ray intersection% build the optical system as specified in opt.exmploptelements = opt_build('opt_single_lens2.exmpl');% make a default rayray = opt_ray;%make 100 paralell rays with random displacement in y-z planenr_rays = 18;clrs = jet(9);for ray_i = 2:nr_rays,    fi_of_i = atan(2/20-ray_i/100);    rays(ray_i) = ray;  rays(ray_i).r = [-20 0 2-4*ray_i/20];  %rays(ray_i).e = [cos(fi_of_i) 0 sin(fi_of_i)];  rays(ray_i).e = [1 0 0];  rays(ray_i).color = clrs(abs(ray_i-10)+1,:); % color is line color for                                   % plotting of rays  end%subplot(2,2,1)% plot the optical systemopt_plotoptics(optelements);hold on% trace all rays[opt_screen] = opt_trace(optelements,rays,opt_ops);view(0,90)% $$$ subplot(2,2,2)% $$$ % Last element should be a screen, which stores the image.% $$$ imagesc(opt_screen(end).img)% $$$ axis([245 265 245 265])% $$$ % $$$ subplot(2,2,3)% $$$ ray.r = [-3 -1 0];% $$$ opt_plotoptics(optelements);% $$$ hold on% $$$ [opt_screen] = opt_trace(optelements,ray,opt_ops);% $$$ view(-15,75)