JP2008145586A5 - - Google Patents

Claims (14)

In order from the object side to the image side, the image side surface is composed of a negative refractive power front group including a lens portion in which three or more concave lenses are continuously arranged, and a positive refractive power rear group. that an optical system, one lens that make up the lens portion has a first aspheric surface on the image side, the object side than the aperture stop a image side of the first aspherical the lens disposed a second aspheric, the opening angle of the first aspheric surface when the theta,
119 ° <θ <180 °
An optical system characterized by satisfying the following conditions. The optical system according to claim 1, wherein the second aspheric surface is provided by a lens constituting the lens unit. Wherein the first aspherical surface, an optical system according to claim 1 or 2, characterized in that over the heart or RaAmane sides of the lens negative refractive power has a shape becomes weak. It said second aspheric surface, a lens optical system of claim 1, 2 or 3, characterized in that over the heart or RaAmane sides a negative refractive power becomes stronger shape. The optical system according to claim 1, wherein the rear group moves on an optical axis to perform focusing. 6. The optical system according to claim 1, wherein the lens unit includes two negative lenses having a concave surface on the image side and a meniscus shape. The front lens group from the object side to the third counting of the optical system of any one of claims 1 6, wherein the image side is a negative lens of meniscus shape concave. When the curvature radii of the object-side and image-side surfaces of the most object-side lens of the front group are R11 and R12, respectively.
3.30 <(R11 + R12) / (R11-R12) <6.70
The optical system according to claim 1, wherein the following condition is satisfied. When the focal lengths of the front group and the rear group are ff and fb, respectively, and the focal length of the entire system is fw,
1.62 <| ff / fw | <7.98
2.06 <fb / fw <2.7
The optical system according to claim 1, wherein the following condition is satisfied. The optical system has a lens on the image side of the aperture stop, the combined refractive power of all of the lens disposed on the object side of the aperture stop, all than aperture stop is disposed on the image side The optical system according to claim 1, wherein the combined refractive power of the lenses is positive. D _{AS is} the aspheric amount of the first aspheric surface from the reference spherical surface defined by the surface apex of the first aspheric surface and the effective end of the first aspheric surface, and the focal length of the optical system is fw. And when
0.09 <D _AS /fw<0.22
The optical system according to claim 1, wherein the following condition is satisfied. 12. An image pickup apparatus comprising: the optical system according to claim 1; and an image pickup element that receives an image formed by the optical system. When the diagonal length of the imaging surface of the imaging device is IMG, the distance from the first lens surface counted from the object side of the optical system to the imaging surface is L, and the back focus is Sk ′,
2.75 <L / IMG <3.25
0.90 <Sk '/ IMG <1.25
The imaging apparatus according to claim 11, wherein the following condition is satisfied. An incident point when the most off-axis chief ray is incident on the first aspheric surface is R _xa , and a point symmetric with respect to the optical axis of the incident point R _xa is R _xb, and the surface apex of the first aspheric surface And the aspherical amount from the reference spherical surface defined by the points R _xa and R _xb is D _ASS and the focal length of the optical system is fw,
0.07 <D _ASS /fw<0.2
The imaging apparatus according to claim 12, wherein the following condition is satisfied.