Patent ID: 8837053
Filing Date: 2014-09-16
Classification: G02B

Abstract:
1. A zoom lens comprising: an aperture diaphragm; and a plurality of lens units including a negative lens unit arranged on a light incident side of the aperture diaphragm, the zoom lens being configured to make variable a focal length by changing an interval among the plurality of lens units, wherein the negative lens unit includes a negative lens having a radial type refractive index distribution and a concave surface on the light incident side, and wherein the negative lens has a wavelength dispersion distribution in which a difference per unit thickness between a power for a F-line and a power for a C-line in a refractive index distribution of a gradient-index defined by the following expression is positive on an optical axis of the zoom lens, and the difference per unit thickness monotonously decreases as a distance from the optical axis increases: where a value Δ∂φ where N