Zoom lens and imaging system incorporating it

摘要

The invention relates to a small-format yet high-performance two units or three units type zoom lens with a negative unit at the front, which has a zoom ratio of about 3, an angle of view of as wide as 60° at the wide-angle end and high image-formation capability, and is much less susceptible to chromatic blurring, with a compact lens barrel. The zoom lens comprises a first lens unit G 1 of negative refracting power and a second lens unit G 2 of positive power, wherein zooming is implemented by varying the space between the lens units. The first lens unit G 1 is made up of one negative lens L₁₁ and one positive lens L₁₂, two in all, and satisfies specific conditions with respect to their refractive index and Abbe constant.