An optical system includes a diffractive optical element and a refractive optical
element. The diffractive optical element corrects a chromatic aberration flare
component of wavelengths other than a predetermined wavelength (a design wavelength)
remaining in the refractive optical element by means of an aspherical component
given by the grating pitch of a diffraction grating included in a diffractive portion
of the diffractive optical element. In addition, a refractive portion of the diffractive
optical element is adapted to correct an aberration component as a composite of
the aberration component of the design standard wavelength shifted by the correction
and the aberration component of the design standard wavelength of the refractive
optical element.