OPTICAL ACCESSORY ARRANGED TO CHANGE OPTICAL CHARACTERISTIC OF SHOOTING LENS

Abstract

An optical accessory having a high optical performance arranged to change an optical characteristic of a shooting lens and to be attached on the object side of a shooting lens is provided. The optical accessory FE is to be detachably attached to the object side of a master lens M and has at least one lens FE having a negative refractive power. The image-side surface r2 of the lens FE is designed to have an aspherical shape having a negative refractive power that decreases toward its periphery.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a lens according to a first embodiment at the wide-angle end.

FIG. 2 is a cross-sectional view of a master lens at the wide-angle end.

FIG. 3 shows aberrations of the master lens at the wide-angle end.

FIG. 4 shows aberrations in the first embodiment at the wide-angle end.

FIG. 5 is a cross-sectional view of a lens according to a second embodiment at the wide-angle end.

FIG. 6 shows aberrations in the second embodiment at the wide-angle end.

FIG. 7 is a cross-sectional view of a lens according to a third embodiment at the wide-angle end.

FIG. 8 shows aberrations in the third embodiment at the wide-angle end.

FIG. 9 is a cross-sectional view of a lens according to a fourth embodiment at the wide-angle end.

FIG. 10 shows aberrations in the fourth embodiment at the wide-angle end.

FIG. 11 is a cross-sectional view of a lens according to a fifth embodiment at the wide-angle end.

FIG. 12 shows aberrations in the fifth embodiment at the wide-angle end.

Claims

1. An optical accessory arranged to change an optical characteristic of a shooting lens and to be detachably attached to an object side of a shooting lens, wherein the optical accessory includes at least one lens FE having a negative refractive power, the image-side surface of the lens FE being an aspherical surface having a negative refractive power that decreases from the optical axis to its peripheral portion.

2. An optical accessory according to claim 1, wherein the following conditions are satisfied: 8.0×10−4<|Δ7/fe|<2.0×10−2,0.3<|Δ4/Δ7|0.65, and0.4<|Δ9/Δ7|<1.0,

3. An optical accessory according to claim 1, wherein the following conditions are satisfied: −1.5<SFa<0.2, andSFa=(r1+r2)/(r1−r2)

4. A shooting lens on which an optical accessory according to claim 1 is attached.

5. An image-pickup apparatus comprising an optical accessory according to claim 1 and a shooting lens on which the optical accessory is attached.