JP2020140197A5 - - Google Patents

Description

The converter lens according to the embodiment of the present invention has a negative refractive force as a whole, and by being arranged on the image side of the master lens, the focal distance of the entire system is longer than the focal distance of the master lens alone. The converter lens is composed of five or more lenses, and the five or more lenses are composed of a front group having a positive refractive force and a rear group having a negative refractive force. This is a lens group in which the combined refractive force is positively maximized when the refractive forces of the lenses are combined in order from the lens arranged on the object side toward the image side, and the focal distance of the front group is f1. The focal distance of the converter lens is EXT_f, the lateral magnification of the converter lens when placed on the image side of the master lens is β, and the optical axis from the lens surface on the most object side of the converter lens to the lens surface on the image side. When the upper distance is L, and the distance on the optical axis from the lens surface on the image side of the converter lens to the image surface when placed on the image side of the master lens is sk.
0.11 <f1 / (| EXT_f | × β) <0.34
1.00 <L / (sk × β) <4.00
It is characterized by satisfying the conditional expression.

Claims (13)

It is a converter lens that has a negative refractive power as a whole and is arranged on the image side of the master lens to make the focal length of the entire system longer than the focal length of the master lens alone.
The converter lens is composed of five or more lenses.
The five or more lenses consist of a front group of positive refractive power and a rear group of negative refractive power.
The front group is a lens group in which the combined refractive power is positively maximized when the refractive powers of the lenses are combined in order from the lens arranged on the object side toward the image side.
The focal distance of the front group is f1, the focal distance of the converter lens is EXT_f, the lateral magnification of the converter lens when placed on the image side of the master lens is β, and the lateral magnification of the converter lens is from the lens surface on the most object side of the converter lens. The distance on the optical axis to the lens surface on the image side is L, and the distance on the optical axis from the lens surface on the image side to the image surface of the converter lens when it is arranged on the image side of the master lens is sk. When
0.11 <f1 / (| EXT_f | × β) <0.34
1.00 <L / (sk × β) <4.00
A converter lens characterized by satisfying the conditional expression. The posterior group consists of a first subgroup and a second subgroup.
The second subgroup is a first junction lens having a positive refractive power as a whole including a positive lens and a negative lens, which is arranged on the most image side of the rear group, or a positive lens arranged on the most image side of the rear group. The converter lens according to claim 1, wherein the converter lens comprises a lens. When the focal length of the first subgroup is fa,
0.03 <fa / (| EXT_f | × β) <0.15
The converter lens according to claim 2, wherein the converter lens satisfies the conditional expression. The converter lens according to claim 2 or 3, wherein the first subgroup has a second junction lens including a positive lens and a negative lens. The converter lens according to claim 4, wherein the refractive index of at least one negative lens included in the second junction lens with respect to the d-line is 1.80 or more. When the focal length of the second subgroup is fb,
0.10 <fb / (| EXT_f | × β) <0.35
The converter lens according to any one of claims 2 to 5, wherein the converter lens satisfies the conditional expression. The distance on the optical axis from the lens surface on the most image side of the front group to the lens surface on the most object side of the rear group is d, and the most image side of the converter lens when arranged on the image side of the master lens. When the distance on the optical axis from the lens surface to the image surface is sk,
0.10 <d / sk <0.60
The converter lens according to any one of claims 1 to 6, wherein the converter lens satisfies the conditional expression. The radius of curvature of the nth lens surface from the object side of the converter lens is Rn, the refractive index of the medium on the light emitting side of the nth lens surface is N', and the refractive index of the medium on the light incident side of the nth lens surface is When the refractive index is N,
―0.20 ＜ ｜ EXT_f ｜ × Σ {(1 / N'-1 / N) / Rn} <0.20
The converter lens according to any one of claims 1 to 7, wherein the converter lens has a lens surface satisfying the conditional expression. When the radius of curvature of the object side surface of the lens closest to the image side of the converter lens is R1 and the radius of curvature of the image side surface is R2,
-3.0 <(R2 + R1) / (R2-R1) <-0.1
The converter lens according to any one of claims 1 to 8, wherein the converter lens satisfies the conditional expression. The converter lens according to any one of claims 1 to 9, wherein the front group comprises two or less lenses. The converter lens according to any one of claims 1 to 10, wherein the number of lenses constituting the rear group is larger than the number of lenses constituting the front group. An interchangeable lens comprising a master lens and the converter lens according to any one of claims 1 to 11. An image pickup apparatus comprising: a master lens, the converter lens according to any one of claims 1 to 12, and an image pickup element that receives an image formed by the master lens and the converter lens.