Charged particle beam apparatus and control method for charged particle beam apparatus

A charged particle beam apparatus for scanning a specimen with a charged particle beam and acquiring a scan image, the charged particle beam apparatus comprising:

• an optical system comprising a pulse mechanism for illuminating the specimen with pulses of the charged particle beam, and a deflector that deflects the charged particle beam and scans the specimen with the deflected charged particle beam;
• and
• a control unit configured to control the optical system,
• wherein the control unit controls the optical system so as to satisfy T=n×t (n is a natural number), where T represents a dwell time of the charged particle beam in each pixel of the scan image, and t represents a cycle of pulses of the charged particle beam,
• the control unit receives specification of an illumination dose of the charged particle beam to the specimen,
• the control unit determines a ratio w/t, where w represents an illumination time of the charged particle beam to the specimen in one cycle, based on the specified illumination dose, and
• the control unit operates the pulse mechanism based on the ratio w/t.