South Pole Telescope Design
This model also has a shaped secondary. Addition of a sixth mirror allows better placement of dewar. Placement of chopper is precisely located at point where central ray of off-axis fields crosses the x = 0 plane. Image quality is good at 2 mm over entire 1 degree diameter field of view, but operation at shorter wavelengths has been sacrificed to improve quality of Lyot stop image.
Figure 1 - Side view, all fields.
Figure 2 - Side view, central field only
Figure 3 - Detail of Fig. 1 in vicinity of chopper. Quatinary is slightly convex.
Figure 4 - Detail of Fig. 2 near chopper.
Figure 5 - Detail of Fig. 1 near detector. As usual, Lyot stop is 160 mm diameter and silicon lens is 400 mm diameter.
Figure 6 - detail of Fig. 2 near detector.
Figure 7 - Spot diagram, with 2 mm wavelength Airy disks. This model is well-corrected at 2 mm wavelength, but smaller wavelengths have been sacrificed to improve quality of Lyot stop.
Figure 8 - rms wavefront error vs. field.
Figure 9 - Image plane