| 摘要 |
The imaging optical system of the invention is built up of, in order from its object side, the first lens group G1 having positive refracting power, the stop S, the second lens group G2 having positive refracting power, and the third lens group G3 having negative refracting power. The first lens group G1 comprises a cemented lens consisting of the first lens L1 and the second lens L2. The second lens group G2 comprises the third lens L3. The third lens group G3 comprises the fourth lens L4. The second lens L3 has an object-side surface that is concave on its object side both on and off the optical axis, and an image-side surface being an aspheric surface that is convex on its object side on the optical axis and has one or more off-axis inflection points. |
