Patent Number: 
Section: claims

1. A method of acquiring an image of a specimen comprising: (a) creating a charging map of said specimen including  (i) first scanning said specimen for applying a first dose of a particle beam and storing corresponding detected first pixel intensities;  (ii) second scanning said specimen applying a second dose of a particle beam greater than said first dose and storing corresponding detected second pixel intensities;  (iii) subtracting said first and second pixel intensities to form values indicating charging areas and non-charging areas; and  (b) selectively scanning said specimen based on said charging map after creating said charging map, to obtain an image of said specimen wherein charging areas are given a reduced dose of a particle beam relative to non-charging areas. 2. A method as recited in  claim 1  wherein said first scanning is performed more rapidly than said second scanning for achieving said greater second dose. claim 1 3. A method as recited in  claim 1  wherein a beam intensity of said second scanning is greater than a beam intensity of said first scanning for achieving said greater second dose. claim 1 4. A method as recited in  claim 1  wherein said selectively scanning includes a first plurality of scans wherein each said charging area determined by said charging map is irradiated by a beam only during a calculated percentage of said first plurality of scans. claim 1 5. The method as recited in  claim 1  wherein said non-charging areas are given a maximum dose of the particle beam. claim 1 6. The method as recited in  claim 1  wherein said particle beam is an electron beam. claim 1