Fig. 4.

Resolution of glass plug system. (a) PSF characterization using 100 nm barium titanate crystals for the 40X 0.6 NA objective alone (red) and coupled to the plug with the correction collar optimized (black) indicates near diffraction-limited resolution in both cases. 1/e half widths are 105% and 110% of the diffraction-limited value, respectively. (b) Ray fans with NA = 0.6 for plug tilts of 0°, 2.5°, and 5° demonstrate loss of resolution for small tilts. (c) The square of the Strehl ratio versus plug tilt for NA = 0.6 (black), 0.45 (red), and 0.28 (blue). Lower NA systems are much less sensitive to tilt.