A simple, compact optical system is provided that includes a transmissive optical
element and a HOE but that nevertheless does not require an extra optical element
for the correction of chromatic aberration. The HOE is designed to have diffractive
efficiency for each of R, G, and B light beams and have different focal lengths
for those light beams so as to correct the longitudinal chromatic aberration produced
by a rectangular parallelepiped prism. This eliminates the need for an extra means
for correcting the chromatic aberration produced by the prism. The HOE may be designed
to exhibit different angles of diffraction for the R, G, and B light beams so as
to correct the chromatic aberration produced perpendicularly to the optical axis
by a wedge-shaped prism.
