US2021255422A1PendingUtilityA1

Rear converter lens and imaging apparatus

Assignee: FUJIFILM CORPPriority: Sep 15, 2017Filed: May 4, 2021Published: Aug 19, 2021

Est. expirySep 15, 2037(~11.1 yrs left)· nominal 20-yr term from priority

Inventors:Tetsuya Ori

G02B 15/12G02B 13/02G02B 9/30

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References

Claims

Abstract

The rear converter lens consists of, in order from an object side: a first lens group that has a positive refractive power; a second lens group that has a negative refractive power; and a third lens group that has a positive refractive power. The first lens group consists of a cemented lens in which a negative lens concave toward the image side and a positive lens convex toward the object side are cemented. The second lens group consists of a cemented lens in which a negative lens concave toward the image side, a positive lens convex toward both sides, and a negative lens concave toward the object side are cemented. The third lens group consists of a cemented lens in which a positive lens convex toward the object side and a negative lens are cemented. The rear converter lens satisfies predetermined Conditional Expressions (1) and (2).

Claims

exact text as granted — not AI-modified

What is claimed is: 
     
         1 . A rear converter lens that has a negative refractive power and is mounted on an image side of a master lens so as to make a focal length of a whole system including the master lens larger than a focal length of the master lens alone, the rear converter lens consisting of, in order from an object side:
 a first lens group that has a positive refractive power;   a second lens group that has a negative refractive power; and   a third lens group that has a positive refractive power,   wherein the first lens group consists of a negative lens and a positive lens in order from the object side,   wherein the second lens group consists of a cemented lens in which a negative lens concave toward both sides, a positive lens convex toward both sides, and a negative lens concave toward the object side are cemented in order from the object side,   wherein the third lens group includes, closest to the object side, a cemented lens in which a positive lens and a negative lens are cemented in order from the object side, a lens surface closest to an image side of the third lens group has a convex shape toward the image side.   
     
     
         2 . The rear converter lens according to  claim 1 ,
 wherein assuming that
 a focal length of the first lens group is f1, and 
 a focal length of the rear converter lens is fC, 
 Conditional Expressions (1) is satisfied,
   −1.4&lt; f 1/ fC&lt;− 0.5  (1).
 
 
   
     
     
         3 . The rear converter lens according to  claim 1 ,
 wherein assuming that
 a focal length of the second lens group is f2, and 
 a focal length of the rear converter lens is fC, 
 Conditional Expressions (2) is satisfied,
   0.2&lt; f 2/ fC&lt; 0.36  (2).
 
 
   
     
     
         4 . The rear converter lens according to  claim 1 ,
 wherein assuming that
 a focal length of the third lens group is f3, and 
 a focal length of the rear converter lens is fC, 
 Conditional Expression (3) is satisfied,
   −1.5&lt; f 3/ fC&lt;− 0.8  (3).
 
 
   
     
     
         5 . The rear converter lens according to  claim 1 ,
 wherein assuming that
 an Abbe number of the negative lens of the first lens group is ν1, and 
 an Abbe number of the positive lens of the first lens group is ν2, 
 Conditional Expression (4) is satisfied,
   12&lt;ν1−ν2&lt;45  (4).
 
 
   
     
     
         6 . The rear converter lens according to  claim 1 ,
 wherein the negative lens of the first lens group has a shape concave toward the image side.   
     
     
         7 . The rear converter lens according to  claim 6 ,
 wherein the negative lens of the first lens group has a meniscus shape concave toward the image side.   
     
     
         8 . The rear converter lens according to  claim 1 ,
 wherein the positive lens of the first lens group has a shape convex toward the object side.   
     
     
         9 . The rear converter lens according to  claim 8 ,
 wherein the positive lens of the first lens group has a shape convex toward both sides.   
     
     
         10 . The rear converter lens according to  claim 1 ,
 wherein the positive lens of the third lens group has a shape convex toward the object side.   
     
     
         11 . The rear converter lens according to  claim 10 ,
 wherein the positive lens of the third lens group has a shape convex toward both sides.   
     
     
         12 . The rear converter lens according to  claim 2 ,
 wherein Conditional Expression (1-1) is satisfied,
   −1.35&lt; f 1/ fC&lt;− 0.7  (1-1).
 
   
     
     
         13 . The rear converter lens according to  claim 3 ,
 wherein Conditional Expression (2-1) is satisfied,
   0.25&lt; f 2/ fC&lt; 0.35  (2-1).
 
   
     
     
         14 . The rear converter lens according to  claim 4 ,
 wherein Conditional Expression (3-1) is satisfied,
   −1.3&lt; f 3/ fC&lt;− 0.9  (3-1).
 
   
     
     
         15 . The rear converter lens according to  claim 5 ,
 wherein Conditional Expression (4-1) is satisfied,
   14&lt;ν1−ν2&lt;40  (4-1).
 
   
     
     
         16 . An imaging apparatus comprising the rear converter lens according to  claim 1 .

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