Correction of chromatic aberration in hybrid objectives

In this paper two hybrid objectives of three-elements are presented. In one of the objectives one lens is made from fluorite and in the other one - from special glass. Both have corrected chromatic aberration in the wavelength range 0.435 mum < lambda < 0.852 mum. For both the objectives spherochromatic aberration is calculated and maximum aperture angle is estimated. The imaging quality obtained is compared to that of typical apochromatic objectives: refractive and hybrid ones built without use of special glasses.