  The PFS is a multi-object spectrograph fed by 2394 fibers at the prime focus
of Subaru telescope. Since the F/# at the prime focus is too fast for the
spectrograph, we designed a small concave-plano negative lens to be attached to
the tip of each fiber that converts the telescope beam (F/2.2) to F/2.8. We
optimized the lens to maximize the number of rays that can be confined inside
F/2.8 while maintaining a 1.28 magnification. The microlenses are manufactured
by glass molding, and an ultra-broadband AR coating (<1.5% for lambda=0.38-1.26
um) will be applied to the front surface.
