Complex sentence: He was head of the Computer Science Division from 1980 to 1983, since when he has worked extensively on computer graphics, geometric modelling, and on the development of computer aided design (CAD) tools for circuit designers, architects, and for mechanical engineers.
Split into simpler sentences: He was head of the Computer Science Division from 1980 to 1983. Since then he has worked extensively on computer graphics, geometric modelling, and on the development of computer aided design (CAD) tools for circuit designers, architects, and for mechanical engineers.