South Pole Telescope Design
SPST183 uses a cold silicon lens as the final element.
Figure 1 - side view, all fields
Figure 2 - detail of Fig. 1.
Figure 3 - same as Fig. 2, but only central field
Figure 4 - Spot diagram.
Figure 5 - focal plane spot diagram
Figure 6 - distortion at focal plane
Figure 7 RMS wavefront error vs. field
Figure 8 - Polarization vs. pupil
Figure 9 - Point-spread function, off-axis field
Figure 10 - illumination of primary, central field
Figure 11 - illumination of primary, field 8
Figure 12 - illumination of primary, field 10.
Figure 13 - drawing of silicon lens. Something to worry about: it's much thicker in middle than edges, leading to "reverse apodization" of beam.