Achromatic lens system and optical apparatus

An achromatic lens system comprising:

• a resin lens having positive refractive power;
• a diffractive optical element;
• and
• a resin lens having negative refractive power;
• they being cemented with each other, and having positive refractive power as a whole,
• the diffractive optical element being constructed by cementing two diffractive element members made of different optical materials with each other, and
• the cemented surface thereof being a diffractive optical surface on which grooves of a diffraction grating are formed,
• wherein the two diffractive element members composing the diffractive optical element are different with each other, and at least one of them is made of an ultraviolet curing resin material, and
• wherein the following conditional expressions are satisfied:
• nd1≦1.54
• 0.0145≦nF1−nC1
• 1.55≦nd2
• nF2−nC2≦0.013
• where nd1 denotes a refractive index of a material of the diffractive element member having a lower refractive index and a smaller Abbe number among the two diffractive element members of the diffractive optical element at d-line (wavelength λ=587.562 nm), nF1 denotes a refractive index of a material of the diffractive element member having a lower refractive index and a smaller Abbe number among the two diffractive element members of the diffractive optical element at F-line (wavelength λ=486.133 nm), nC1 denotes a refractive index of a material of the diffractive element member having a lower refractive index and a smaller Abbe number among the two diffractive element members of the diffractive optical element at C-line (wavelength λ=656.273 nm), nd2 denotes a refractive index of a material of the diffractive element member having a higher refractive index and a larger Abbe number among the two diffractive element members of the diffractive optical element at d-line (wavelength λ=587.562 nm), nF2 denotes a refractive index of a material of the diffractive element member having a higher refractive index and a larger Abbe number among the two diffractive element members of the diffractive optical element at F-line (wavelength λ=486.133 nm), and nC2 denotes a refractive index of a material of the diffractive element member having a higher refractive index and a larger Abbe number among the two diffractive element members of the diffractive optical element at C-line (wavelength λ=656.273 nm).