We describe studies on the scanning optical system for compact and inexpensive Canon laser beam printer (which we call LBP). Based on Canon's historically accumulated laser scanning optical technologies, our originally developed scanning optical system has the two functions of fθ-characteristic and deflection error compensation (we call the scanning optical system fθ-DEC), comprising a polygonal mirror scanner and toric lens as key components. As for the design, compactness and inexpensiveness of the fθ-DEC scanning optical system was investigated based on our theoretical and analytical study on fθ-lens for LBPs. On the manufacturing side, exclusive manufacturing equipment was developed for each of the above mentioned key components for effective mass production. In this paper, the theory, design, and manufacturing technologies for our fθ-DEC scanning optical system are presented. In addition, as an application example, Canon LBP-CX is introduced, where the above technologies have been integrated.