Refractive multispectral objective lens system and methods of selecting optical materials therefor

A method of selecting optical materials for an optical system having a first lens system and a second lens system, the first lens system comprising a first optical material and the second lens system comprising a second optical material, to provide correction of chromatic aberration of the optical system in first, second and third wavelength bands, the method comprising:

• providing a first set of values indicative of chromatic aberration of the optical system in the first wavelength band, the first set of values corresponding to potential combinations of first and second optical materials determined from a set of optical materials;
• providing a second set of values indicative of chromatic aberration of the optical system in the second wavelength band, the second set of values corresponding to said potential combinations of first and second optical materials;
• providing a third set of values indicative of an optical power of the first lens system and a fourth set of values indicative of an optical power of the second lens system, the third and fourth sets of values corresponding to said potential combinations of first and second optical materials, the third and fourth sets of values being generated in accordance with correction of chromatic aberration in the third wavelength band;
• comparing pairs of values from the first and second sets of values for said potential combinations of the first and second optical materials;
• comparing pairs of values from the third and fourth sets of values for said potential combinations of the first and second optical materials;
• and
• making a choice for the first and second optical materials based upon the comparison of pairs of values from the first and second sets of values for said potential combinations of the first and second optical materials and based upon the comparison of pairs of values from the third and fourth sets of values for said potential combinations of the first and second optical materials.