1. A charged-particle-beam optical system for projecting an image of an object onto a sample, the system comprising: (a) first and second projection lenses for projecting an image of the object onto the sample using a charged particle beam propagating along a trajectory through the first and second projection lenses, the object being situated at an object position, and the sample being situated at an image position; and (b) a deflector system configured and situated so as to deflect the trajectory of the charged particle beam such that a second-order derivative of the deflected trajectory is substantially constant through most of an object-side region extending from the object position to a crossover image point located between the object position and the image position, and substantially constant through most of an image-side region extending from the crossover image point to the image position.