Image forming optical system, projection type display device, and imaging apparatus

1 . An image forming optical system capable of forming an image on a conjugated plane on a reduction side as an intermediate image and re-forming the intermediate image as a magnified image on a conjugated plane on a magnification side, the image forming optical system comprising:

a first adjustment group that moves along an optical axis in adjusting an image formation position of a region of the magnified image including a farthest point from the optical axis; and

a second adjustment group that moves along the optical axis in adjusting an image formation position of a region of the magnified image including a nearest point from the optical axis,

wherein an optical element disposed closest to the magnification side is a lens,

the second adjustment group includes at least two lenses, has a positive refractive power as a whole, and is disposed closest to the reduction side, and

the first adjustment group is disposed closer to the magnification side than the intermediate image.

2 . The image forming optical system according to claim 1 ,

wherein the second adjustment group consists of two lenses,

at least one of the two lenses is a positive lens, and

assuming that an Abbe number of the positive lens based on a d line is vp, Conditional Expression (1) is satisfied, which is represented by

vp<45   (1).

3 . The image forming optical system according to claim 1 , wherein assuming that

a focal length of the first adjustment group is f1,

a composite focal length of a plurality of groups of the first adjustment group is f1 in a case where the first adjustment group consists of the plurality of groups that move by changing a spacing from adjacent groups during the adjustment,

a focal length of the second adjustment group is f2, and

a composite focal length of a plurality of groups of the second adjustment group is f2 in a case where the second adjustment group consists of the plurality of groups that move by changing a spacing from adjacent groups during the adjustment,

Conditional Expression (2) is satisfied, which is represented by

0.5<|f1/f2|<30   (2).

4 . The image forming optical system according to claim 1 , wherein assuming that

a paraxial lateral magnification of the first adjustment group is β1,

a composite paraxial lateral magnification of a plurality of groups of the first adjustment group is β1 in a case where the first adjustment group consists of the plurality of groups that move by changing a spacing from adjacent groups during the adjustment,

a composite paraxial lateral magnification of the entire optical system closer to the reduction side than the first adjustment group is β1r,

a paraxial lateral magnification of the second adjustment group is β2, and

a composite paraxial lateral magnification of a plurality of groups of the second adjustment group is β2 in a case where the second adjustment group consists of the plurality of groups that move by changing a spacing from adjacent groups during the adjustment,

Conditional Expression (3) is satisfied, which is represented by

0<|{(1−β1 2 )×β1 r 2 }/(1−β2 2 )|<0.5   (3).

5 . The image forming optical system according to claim 1 ,

wherein the image forming optical system consists of, in order from the magnification side to the reduction side, a first optical system and a second optical system with the intermediate image interposed therebetween, and

assuming that

a focal length of the first optical system is fU1, and

a focal length of the image forming optical system is fw,

where fU1 and fw are values at a wide angle end in a case where the image forming optical system is a variable magnification optical system,

Conditional Expression (4) is satisfied, which is represented by

1< fU 1/| fw|< 5   (4).

6 . The image forming optical system according to claim 1 , wherein assuming that

a back focal length of the image forming optical system at an air-equivalent distance is Bfw, and

a focal length of the image forming optical system is fw,

where Bfw and fw are values at a wide angle end in a case where the image forming optical system is a variable magnification optical system,

Conditional Expression (5) is satisfied, which is represented by

3.5< Bfw/|fw|   (5).

7 . The image forming optical system according to claim 1 , comprising three single lenses that have negative refractive powers, successively in order from a position closest to the magnification side to the reduction side.

8 . The image forming optical system according to claim 1 ,

wherein the image forming optical system is a variable magnification optical system, and

the image forming optical system includes at least two lens groups, of which spacings with adjacent groups change during magnification change, at a position closer to the reduction side than the intermediate image.

9 . The image forming optical system according to claim 1 , wherein the first adjustment group consists of two or fewer lenses.

10 . An image forming optical system capable of forming an image on a conjugated plane on a reduction side as an intermediate image and re-forming the intermediate image as a magnified image on a conjugated plane on a magnification side, the image forming optical system comprising:

a first adjustment group that moves along an optical axis in adjusting an image formation position of a region of the magnified image including a farthest point from the optical axis; and

a second adjustment group that moves along the optical axis in adjusting an image formation position of a region of the magnified image including a nearest point from the optical axis,

wherein an optical element disposed closest to the magnification side is a lens,

the second adjustment group includes at least one positive lens, has a positive refractive power as a whole, and is disposed closest to the reduction side,

assuming that an Abbe number of the positive lens based on a d line is vp, Conditional Expression (1) is satisfied, which is represented by

vp<45   (1), and

the first adjustment group is disposed to the magnification side than the intermediate image.

11 . The image forming optical system according to claim 10 , wherein assuming that

a focal length of the first adjustment group is f1,

a composite focal length of a plurality of groups of the first adjustment group is f1 in a case where the first adjustment group consists of the plurality of groups that move by changing a spacing from adjacent groups during the adjustment,

a focal length of the second adjustment group is f2, and

a composite focal length of a plurality of groups of the second adjustment group is f2 in a case where the second adjustment group consists of the plurality of groups that move by changing a spacing from adjacent groups during the adjustment,

Conditional Expression (2) is satisfied, which is represented by

0.5<|f1/f2|<30   (2).

12 . The image forming optical system according to claim 10 , wherein assuming that

a paraxial lateral magnification of the first adjustment group is β1,

a composite paraxial lateral magnification of a plurality of groups of the first adjustment group is β1 in a case where the first adjustment group consists of the plurality of groups that move by changing a spacing from adjacent groups during the adjustment,

a composite paraxial lateral magnification of the entire optical system closer to the reduction side than the first adjustment group is β1r,

a paraxial lateral magnification of the second adjustment group is (β2, and

a composite paraxial lateral magnification of a plurality of groups of the second adjustment group is β2 in a case where the second adjustment group consists of the plurality of groups that move by changing a spacing from adjacent groups during the adjustment,

Conditional Expression (3) is satisfied, which is represented by

0<|{(1−β1 2 )×β1 r 2 }/(1−β2 2 )|<0.5   (3).

13 . The image forming optical system according to claim 10 ,

wherein the image forming optical system consists of, in order from a magnification side to a reduction side, a first optical system and a second optical system with the intermediate image interposed therebetween, and

assuming that

a focal length of the first optical system is fU1, and

a focal length of the image forming optical system is fw,

where fU1 and fw are values at a wide angle end in a case where the image forming optical system is a variable magnification optical system,

Conditional Expression (4) is satisfied, which is represented by

1< fU 1/| fw|< 5   (4).

14 . The image forming optical system according to claim 10 , wherein assuming that

a back focal length of the image forming optical system at an air-equivalent distance is Bfw, and

a focal length of the image forming optical system is fw,

where Bfw and fw are values at a wide angle end in a case where the image forming optical system is a variable magnification optical system,

Conditional Expression (5) is satisfied, which is represented by

3.5< Bfw/|fw|   (5).

15 . The image forming optical system according to claim 10 , comprising three single lenses that have negative refractive powers, successively in order from a position closest to the magnification side to the reduction side.

16 . The image forming optical system according to claim 10 ,

wherein the image forming optical system is a variable magnification optical system, and

the image forming optical system includes at least two lens groups, of which spacings with adjacent groups change during magnification change, at a position closer to the reduction side than the intermediate image.

17 . The image forming optical system according to claim 10 , wherein the first adjustment group consists of two or fewer lenses.

18 . A projection type display device comprising:

a light valve that outputs an optical image; and

the image forming optical system according to claim 1 ,

wherein the image forming optical system projects the optical image, which is output from the light valve, on a screen.

19 . An imaging apparatus comprising the image forming optical system according to claim 1 .