Abstract: A charged particle beam apparatus in which a beam of charged particles emitted from a beam source is focussed on a target in a predetermined size and shape through a plurality of aperture members. Each of the aperture members is combined with a respective deflecting unit which effects a two-dimensional scan with the charged particle beam in response to a scan signal supplied thereto. The center axis of the aperture formed in the aperture member is arithmetically determined on the basis of time-based variation in the quantity of the charged particles trapped by the aperture member during the scan operation. Further, deviation of the arithmetically determined center axis of the aperture from a reference axis is determined. The aperture member is slided on a plane extending perpendicularly to the center axis of the aperture to cancel out the deviation.

Abstract: After a slide glass having blood smeared thereon has been mounted on a movable stage of a microscope, the stage is moved to position a view field of the microscope to the center of the slide glass. Then, the stage is moved in one direction along the length of the slide glass. The view field of the microscope moves as the stage is moved so that red blood corpuscle densities on the smear are measured sequentially along the length of the slide glass. Based on the measurement a computer determines an optimum test area on the smear for the recognition of white blood corpuscles and the stage is moved to a start position of the optimum test area by an instruction from the computer. Thereafter, a normal stage scan operation for detecting the white blood corpuscles is carried out and the detected white blood corpuscles are automatically classified.