| 摘要 |
Charged-particle-beam optical systems are disclosed exhibiting reduced aberrations. Such a system comprises a symmetric magnetic doublet type projection lens system and deflectors. An imaginary Z-axis is superimposed on the optical axis with an origin at an image-crossover point. Excitation of the deflectors and lenses is controlled by a controller so that the ratio of G1(Z) to G2(-MxZ) is substantially equal to the ratio of (-M) to 1 (i.e., G1(Z):G2(-MxZ)=(-M):1), and the deflection trajectory of the charged-particle beam intersects with the optical axis at a crossover Zc, where M is the magnification of the lens system, G1(Z) is the distribution of the deflective magnetic field formed on the object side of the crossover, and G2(Z) is the distribution of the deflective magnetic field formed on the image side of the crossover.
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