Since a general rotationally symmetric lens system cannot make a concave lens creating a negative aberration, neither chromatic nor spherical aberration can be compensated by optimizing the configuration of the electric and magnetic fields in the electron optics presented in Fig. 1. Chromatic aberration is inherently generated by the energy dispersion of the emitted electrons, and this restricts the practical resolution of the system. Our previous study demonstrates that the initial energy dispersion of emitted electrons from an nc-Si ballistic emitter is innately small (approximately 2 eV at RT and 500 meV at 100 K),11,13,14 and thus, the chromatic aberration can be sufficiently optimized by making the energy distribution as close to monochromatic as possible. In this regard, we are improving the physical properties of nc-Si itself, as well as exploring other potential schemes such as operating the emitter at a lower temperature, which has been demonstrated to significantly reduce energy spread of the emitted electrons.11,13,14 On the other hand, spherical aberration should be compensated on a reduced image projected by the telecentric reduction lens system in order to improve the practical resolution. It can be corrected by controlling each of the driving voltages in the picture cells of the integrated LSI, so that the spatial distribution of the emitted beamlets’ energy can be adjusted to compensate for the spherical aberration and be balanced on the projected image. At present, we are studying how to incorporate such a function into the next design of the LSI.