Projection device and projection system

1. A projection device configured to magnify and project, on a screen, an image displayed at an image display element, the projection device comprising:

a dioptric system including at least one positive lens and at least one negative lens; and

a reflection optical system having at least one reflection optical element, wherein

the at least one positive lens and the at least one negative lens satisfy conditional expressions (1)-(3):

−6< dnT,   (1)

70<ν d,   (2)

BF/Y< 4.0,  (3)

dnT denotes a temperature coefficient of a relative refractive index at a D line in a range of 40 to 60 degrees,

νd denotes an Abbe number,

BF denotes a distance from an intersection between a surface including the image display element and the optical axis, to a vertex of an image display element side surface of a lens closest to the image display element,

Y denotes a maximum value of a distance between the optical axis and an end portion of an image forming unit, and

the optical axis is an axis shared by a plurality of axisymmetric lenses of the dioptric system.

2. The projection device according to claim 1 , wherein

the dioptric system further includes an aperture stop,

the at least one positive lens is disposed closer to an image display element side than the aperture stop is, and

the at least one negative lens is disposed closer to a magnification side than the aperture stop is to the magnification side.

3. The projection device according to claim 1 , wherein the at least one positive lens and the at least one negative lens are included in a lens group including a lens having the highest temperature at a time of displaying a white image.

4. The projection device according to claim 1 , wherein the at least one positive lens and the at least one negative lens are included in a lens group closest to the image display element side.

5. The projection device according to claim 1 , wherein the at least one positive lens and the at least one negative lens are included in a group not moved at a time of focusing.

6. The projection device according to claim 1 , wherein

the dioptric system includes a resin lens, and

the resin lens is included in a lens group having the lowest temperature at a time of displaying a white image.

7. The projection device according to claim 1 , wherein the dioptric system and the reflection optical system together operate as a non-telecentric optical system.

8. A projection system, comprising:

the projection device according to claim 1 ; and

the screen satisfying the conditional expression (4):

TR< 0.30,  (4)

wherein TR denotes a ratio of a distance to the screen from an intersection between the reflection optical element and an optical axis of the dioptric system, to a lateral width of the screen.

9. A projection device configured to magnify and project, on a screen, an image displayed at an image display element, comprising:

a dioptric system including at least one cemented lens; and

a reflection optical system having a reflection optical element including at least one magnification, wherein

the cemented lens includes at least one positive lens and at least one negative lens satisfying conditional expressions (5)-(8):

4< dnTP,   (5)

0.61<θ gFP,   (6)

3< dnTN,   (7)

0.59<θ gFN,   (8)

dnTP denotes a temperature coefficient of a relative refractive index in an e line in a range of 40 to 60 degrees of the positive lens,

θgFP denotes a partial dispersion ratio in a g line and an F line of the positive lens,

dnTN denotes a temperature coefficient of a relative refractive index in the e line in a range of 40 to 60 degrees of the negative lens,

θgFN denotes a partial dispersion ratio of the negative lens, and

θgF denotes a partial dispersion ratio expressed by expression (9):

θ gF =( Ng−NF )/( NF−NC ),  (9)

where

Ng denotes a refractive index relative to the g line,

NF denotes a refractive index relative to the F line, and

NC denotes a refractive index relative to a C line.

10. The projection device according to claim 9 , wherein

the dioptric system further includes an aperture stop, and

the cemented lens is disposed closer to a magnification side than the aperture stop is to the magnification side.

11. The projection device according to claim 9 , wherein the cemented lens is included in a lens group including the aperture stop.

12. The projection device according to claim 9 , wherein the cemented lens is included in a lens group on a side closest to the image display element.

13. The projection device according to claim 9 , wherein the cemented lens is included in a lens group which is not moved at the time of focusing.

14. The projection device according to claim 9 , wherein

the dioptric further includes at least one resin lens PL included in a lens group which is moved at the time of focusing, the at least one resin lens PL satisfying the conditional expressions (10) and (11):

| P 40 d ( h )− P 20 d ( h )|× FP <0.02,  (10)

| h|< 0.85× D,   (11)

h denotes a height from the optical axis A, the optical axis A being an axis shared by a plurality of axisymmetric lenses of the dioptric system,

D denotes a distance between the optical axis A and a point where a distance from the optical axis A becomes largest out of intersections between a reduction-side lens surface and a beam,

FP denotes a paraxial focal length of the resin lens,

P40d(h) denotes a magnification when temperature at a height h from the optical axis A is 40 degrees, and

P20d(h) denotes a magnification when temperature at height h from the optical axis A is 20 degrees.

15. The projection device according to claim 14 , wherein the resin lens PL is included in a lens group which is moved at the time of focusing.

16. The projection device according to claim 9 , wherein the reflection optical element is a concave mirror and has a free-form surface.

17. The projection device according to claim 9 , wherein the conditional expression (12) is satisfied:

BF/Y< 4.0,  (12)

BF denotes a distance from an intersection between a surface including the image display element and the optical axis A, to a vertex of an image display element side surface of a lens closest to the image display element, and

Y denotes a maximum value of a distance between the optical axis and an end portion of an image forming unit, and the optical axis A is an axis shared by a plurality of axisymmetric lenses of the dioptric system.

18. The projection device according to claim 9 , wherein the dioptric system and the reflection optical system together operate as a non-telecentric optical system.

19. A projection system, comprising:

the projection device according to claim 9 ; and

the screen satisfying the conditional expression (13):

TR< 0.30,  (13)

wherein TR denotes a ratio of a distance to the screen from an intersection between the reflection optical element and the optical axis A of the dioptric system, to a lateral width of the screen.

20. A projection device configured to magnify and project, on a screen, an image displayed at an image display element, comprising:

a dioptric system including at least one cemented lens; and

a reflection optical system having a reflection optical element including at least one magnification, wherein

the cemented lens includes at least one positive lens and at least one negative lens satisfying conditional expressions (14)-(16):

4< dnTP,   (14)

0.61<θ gFP,   (15)

3< dnTN,   (16)

dnTP denotes a temperature coefficient of a relative refractive index in an e line in a range of 40 to 60 degrees of the positive lens,

θgFP denotes a partial dispersion ratio in a g line and an F line of the positive lens,

dnTN denotes a temperature coefficient of a relative refractive index in the e line in a range of 40 to 60 degrees of the negative lens, and

θgF denotes a partial dispersion ratio expressed by expression (17):

θ gF =( Ng−NF )/( NF−NC ),  (17)

where

Ng denotes a refractive index relative to the g line,

NF denotes a refractive index relative to the F line, and

NC denotes a refractive index relative to a C line.