Figure 6.

DQE measurements with the decelerator-CCD system. (a) A series of measurements of DQE vs spatial frequency with various microscope and decelerator voltage combinations. The corrected net voltage difference is given. (b) A summary of the DQE dependence on voltage, for two spatial frequencies; the upper curves (each curve representing a different microscope voltage) are for low frequencies, around 0.05 Nyquist, while the lower curves are for half-Nyquist frequency (0.25 on the graph at the left). The essential point is that the DQE improves from 0.08 at 300 kV to 0.4—i.e., by a factor of 5—at the midfrequencies, and a factor of 2 at the low frequencies.