International
Tables for
Crystallography
Volume B
Reciprocal space
Edited by U. Shmueli

International Tables for Crystallography (2010). Vol. B, ch. 2.5, p. 305   | 1 | 2 |

Figure 2.5.2.3 

J. M. Cowleya
[Figure 2.5.2.3]
Figure 2.5.2.3

The functions [\chi (U)], the phase factor for the transfer function of a lens given by equation (2.5.2.33)[link], and [\sin \chi (U)] for the Scherzer optimum defocus condition, relevant for weak phase objects, for which the minimum value of [\chi (U)] is [-2\pi /3].