Single focus optical system and optical apparatus using the same

1. A single-focus optical system which forms a conjugate relationship between a conjugate point on an enlargement side at a long distance and a conjugate point on a reduction side at a short distance, comprising in order from the enlargement side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a positive refractive power, wherein

a lens component is one of a single lens and a cemented lens, and

the first lens unit includes an enlargement-side lens component having a negative refractive power which is disposed closest to the enlargement side, and a reduction-side lens component which is disposed closest to the reduction side, and

a shape of the reduction-side lens component is a meniscus shape having a convex surface directed toward the enlargement side, and

the second lens unit includes in order from the enlargement side, a cemented lens of a meniscus shape having a convex surface directed toward the reduction side, and a plurality of positive lens components, and

the plurality of positive lens components includes all the positive lens components that are adjacent, and

the cemented lens in the second lens unit includes in order from the enlargement side, a negative lens and a positive lens, and

the third lens unit includes a negative lens component closest to the enlargement side, and

all air spaces in the first lens unit and all air spaces in the second lens unit are constant at the time of focusing.

2. The single-focus optical system according to claim 1 , wherein the enlargement-side lens component in the first lens unit is a negative single lens.

3. The single-focus optical system according to claim 2 , wherein the following conditional expression (1) is satisfied:

0.75< SF 11 <3.5  (1)

where,

SF 11 =(R F11 +R R11 )/(R F11 −R R11 ), and here

R F11 denotes a radius of curvature of an enlargement-side surface of the enlargement-side lens component, and

R R11 denotes a radius of curvature of a reduction-side surface of the enlargement-side lens component.

4. The single-focus optical system according to claim 1 , wherein the first lens unit includes a positive lens.

5. The single-focus optical system according to claim 1 , wherein:

the second lens unit includes a reduction-side positive lens component closest to the reduction side, and

the reduction-side lens component is a single lens.

6. The single-focus optical system according to claim 5 , wherein in a rectangular coordinate system in which a horizontal axis is let to be Nd 2PR and a vertical axis is let to be vd 2PR , when a straight line represented by Nd 2PR =α×vd 2PR +β 2PR , where, α=−0.01, Nd 2PR and vd 2PR for the reduction-side positive lens component are included in both of an area determined by a straight line when a lower limit value of a range of the following conditional expression (11) is β 2PR =2.25, and an area determined by the following conditional expressions (12) and (13):

2.25≤β 2PR   (11),

1.40< Nd 2PR   (12), and

35< vd 2PR   (13)

where,

Nd 2PR denotes a refractive index of the reduction-side positive lens component, and

vd 2PR denotes Abbe number for the reduction-side positive lens component.

7. The single-focus optical system according to claim 1 , wherein all of the plurality of positive lens components are single lenses.

8. The single-focus optical system according to claim 1 , wherein:

the third lens unit includes in order from the enlargement side, a first sub-unit, a second sub-unit, and a third sub-unit, and

the first sub-unit includes only one negative lens component, and

the second sub-unit includes only one positive lens component, and

the third sub-unit includes a negative lens, and

all air spaces in the third sub-unit are constant at the time of focusing.

9. The single-focus optical system according to claim 1 , wherein the following conditional expression (2) is satisfied:

1.4< SF 12 <15  (2)

where,

SF 12 =(R F12 +R R12 )/(R F12 −R R12 ), and here

R F12 denotes a radius of curvature of an enlargement-side surface of the reduction-side lens component, and

R R12 denotes a radius of curvature of a reduction-side surface of the reduction-side lens component.

10. The single-focus optical system according to claim 1 , wherein the following conditional expression (3) is satisfied:

−15< SF 21 <−2.0  (3)

where,

SF 21 =(R F21 +R R21 )/(R F21 −R R21 ), and here

R F21 denotes a radius of curvature of an enlargement-side surface of the cemented lens in the second lens unit, and

R R21 denotes a radius of curvature of a reduction-side surface of the cemented lens in the second lens unit.

11. The single-focus optical system according to claim 1 , wherein the following conditional expression (7) is satisfied:

−1.5<Φ 1 /Φ 23 <0.2  (7)

where,

Φ 1 denotes a refractive power of the first lens unit, and

Φ 23 denotes a combined refractive power of the second lens unit and the third lens unit at the time of focusing to an object at infinity.

12. The single-focus optical system according to claim 1 , wherein the following conditional expression (8) is satisfied:

−1.5<Φ 1 /Φ 2 <0.2  (8)

where,

Φ 1 denotes a refractive power of the first lens unit, and

Φ 2 denotes a refractive power of the second lens unit.

13. The single-focus optical system according to claim 1 , wherein:

the first lens unit includes an enlargement-side lens component closest to the enlargement side, and

the following conditional expression (A) is satisfied:

0< f/e N1F <2  (A)

where,

f denotes a focal length of the overall single-focus optical system at the time of focusing to an object at infinity, and

e N1F denotes a maximum effective aperture of the enlargement-side lens component in the first lens unit.

14. The single-focus optical system according to claim 1 , further comprising:

an aperture stop, wherein the following conditional expression (B) is satisfied:

0<( f/e AS )/ Fno< 2  (B)

where,

f denotes a focal length of the overall single-focus optical system at the time of focusing to an object at infinity,

e AS denotes a maximum diameter of the aperture stop, and

Fno denotes an F-number for the overall single-focus optical system at the time of focusing to an object at infinity.

15. The single-focus optical system according to claim 1 , wherein the following conditional expression (C) is satisfied:

0< T air _ max Σd≤ 0.27  (C)

where,

T air _ max is a largest axial air space in the range from a surface positioned closest to the enlargement side to a surface positioned closest to the reduction side in the single-focus optical system, and

Σd is an axial distance from the surface positioned closest to the enlargement side to the surface positioned closest to the reduction side in the single-focus optical system.

16. An optical apparatus, comprising:

an optical system; and

an image pickup element which is disposed on a reduction side, wherein:

the image pickup element has an image pickup surface, and converts an image formed on the image pickup surface by the optical system to an electric signal, and

the optical system is the single-focus optical system according to claim 1 .

17. An optical apparatus, comprising:

an optical system; and

a display element which is disposed on a reduction side, wherein:

the display element has a display surface, and

an image displayed on the display surface is projected on the enlargement side by the optical system, and

the optical system is the single-focus optical system according to claim 1 .

18. The single-focus optical system according to claim 1 , wherein the enlargement-side lens component in the first lens unit has a meniscus shape with a convex surface directed toward the enlargement side.

19. The single-focus optical system according to claim 1 , wherein a refractive power of a combined system of all the lenses on the enlargement side of the reduction-side lens component in the first lens unit are negative.

20. The single-focus optical system according to claim 1 , further comprising:

a positive lens which is disposed on the enlargement side of the cemented lens in the second lens unit.

21. A single-focus optical system which forms a conjugate relationship between a conjugate point on an enlargement side at a long distance and a conjugate point on a reduction side at a short distance, comprising in order from the enlargement side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a positive refractive power, wherein

a lens component is one of a single lens and a cemented lens, and

the first lens unit includes a reduction-side lens component closest to the reduction side, and

a shape of the reduction-side lens component is a meniscus shape having a convex surface directed toward the enlargement side, and

the reduction-side lens component is a cemented lens, and

the reduction-side lens component includes in order from the enlargement side, a positive lens and a negative lens, and

the second lens unit includes in order from the enlargement side, a cemented lens of a meniscus shape having a convex surface directed toward the reduction side, and a plurality of positive lens components, and

the plurality of positive lens components includes all the positive lens components that are adjacent, and

the cemented lens in the second lens unit includes in order from the enlargement side, a negative lens and a positive lens, and

the third lens unit includes a negative lens component closest to the enlargement side, and

all air spaces in the first lens unit and all air spaces in the second lens unit are constant at the time of focusing.

22. A single-focus optical system which forms a conjugate relationship between a conjugate point on an enlargement side at a long distance and a conjugate point on a reduction side at a short distance, comprising in order from the enlargement side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a positive refractive power, wherein

a lens component is one of a single lens and a cemented lens, and

the first lens unit includes a reduction-side lens component closest to the reduction side, and

a shape of the reduction-side lens component is a meniscus shape having a convex surface directed toward the enlargement side, and

the second lens unit includes in order from the enlargement side, a cemented lens of a meniscus shape having a convex surface directed toward the reduction side, and a plurality of positive lens components, and

the plurality of positive lens components includes all the positive lens components that are adjacent, and

the cemented lens in the second lens unit includes in order from the enlargement side, a negative lens and a positive lens, and

the third lens unit includes a negative lens component closest to the enlargement side, and

all air spaces in the first lens unit and all air spaces in the second lens unit are constant at the time of focusing, and

the third lens unit includes in order from the enlargement side, a first sub-unit, a second sub-unit, and a third sub-unit, and

the first sub-unit includes only one negative lens component, and

the second sub-unit includes only one positive lens component.

23. The single-focus optical system according to claim 22 , wherein from among the air spaces in the third lens unit, only an air space between the first sub-unit and the second sub-unit varies at the time of focusing.

24. The single-focus optical system according to claim 23 , wherein:

the second sub-unit includes only a positive lens component, and

the third sub-unit includes in order from the enlargement side, a positive lens, a negative lens, and a positive lens.

25. The single-focus optical system according to claim 22 , wherein from among air spaces in the third lens unit, only an air space between the first sub-unit and the second sub-unit, and an air space between the second sub-unit and the third sub-unit vary at the time of focusing.

26. The single-focus optical system according to claim 25 , wherein:

the second sub-unit includes only a positive lens component, and

the third sub-unit includes in order from the enlargement side, a negative lens and a positive lens.

27. The single-focus optical system according to claim 22 , wherein the third sub-unit is fixed at the time of focusing.

28. The single-focus optical system according to claim 22 , wherein a shape of the negative lens component in the first sub-unit is a meniscus shape having a concave surface directed toward the reduction side.

29. The single-focus optical system according to claim 22 , wherein:

the third sub-unit includes a negative lens, and

the negative lens and a positive lens which is adjacent to the negative lens are cemented.

30. The single-focus optical system according to claim 22 , wherein the following conditional expression (5) is satisfied:

0.80< SF 31 <4.0  (5)

where,

SF 31 =(R F31 +R R31 )/(R F31 −R R31 ), and here

R F31 denotes a radius of curvature of an enlargement-side surface of the negative lens component in the first sub-unit, and

R R31 denotes a radius of curvature of a reduction-side surface of the negative lens component in the first sub-unit.

31. The single-focus optical system according to claim 30 , wherein the following conditional expression (6) is satisfied:

−0.4< SF 32 <1.6  (6)

where,

SF 32 =(R F32 +R R32 )/(R F32 −R R32 ), and here

R F32 denotes a radius of curvature of an enlargement-side surface of the positive lens component in the second sub-unit, and

R R32 denotes a radius of curvature of a reduction-side surface of the positive lens component in the second sub-unit.

32. The single-focus optical system according to claim 22 , wherein:

a negative lens component in the first sub-unit is a single lens, and

in a rectangular coordinate system in which a horizontal axis is let to be Nd 3NF and a vertical axis is let to be vd 3NF , when a straight line represented by Nd 3NF =α×vd 3NF +β 3NF , where, α=−0.01, Nd 3NF and vd 3NF for the negative lens component in the first sub-unit are included in both of an area determined by a straight line when a lower limit value of a range of the following conditional expression (14) is β 3NF =2.15, and an area determined by the following conditional expressions (15) and (16):

2.15≤β 3NF   (14),

1.45< Nd 3NF   (15), and

25< vd 3NF   (16)

where,

Nd 3NF denotes a refractive index of the negative lens component in the first sub-unit, and

vd 3NF denotes Abbe number for the negative lens component in the first sub-unit.

33. A single-focus optical system which forms a conjugate relationship between a conjugate point on an enlargement side at a long distance and a conjugate point on a reduction side at a short distance, comprising in order from the enlargement side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a positive refractive power, wherein

a lens component is one of a single lens and a cemented lens, and

the first lens unit includes a reduction-side lens component closest to the reduction side, and

a shape of the reduction-side lens component is a meniscus shape having a convex surface directed toward the enlargement side, and

the second lens unit includes in order from the enlargement side, a cemented lens of a meniscus shape having a convex surface directed toward the reduction side, and a plurality of positive lens components, and

the plurality of positive lens components includes all the positive lens components that are adjacent, and

the plurality of positive lens components includes a front-side positive lens component which is positioned closest to the enlargement side, and a rear-side positive lens component which is positioned closest to the reduction side, and

the cemented lens in the second lens unit includes in order from the enlargement side, a negative lens and a positive lens, and

the third lens unit includes a negative lens component closest to the enlargement side, and

all air spaces in the first lens unit and all air spaces in the second lens unit are constant at the time of focusing, and

the following conditional expression (4) is satisfied:

0.10< SF 22 −SF 23 <7.0  (4)

where,

SF 22 =(R F22 +R R22 )/(R F22 −R R22 ), and

SF 23 =(R F23 +R R23 )/(R F23 −R R23 ), and here

R F22 denotes a radius of curvature of an enlargement-side surface of the front-side positive lens component,

R R22 denotes a radius of curvature of a reduction-side surface of the front-side positive lens component,

R F23 denotes a radius of curvature of an enlargement-side surface of the rear-side positive lens component, and

R R23 denotes a radius of curvature of a reduction-side surface of the rear-side positive lens component.

34. A single-focus optical system which forms a conjugate relationship between a conjugate point on an enlargement side at a long distance and a conjugate point on a reduction side at a short distance, comprising in order from the enlargement side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a positive refractive power, wherein

a lens component is one of a single lens and a cemented lens, and

the first lens unit includes a reduction-side lens component closest to the reduction side, and

a shape of the reduction-side lens component is a meniscus shape having a convex surface directed toward the enlargement side, and

the second lens unit includes in order from the enlargement side, a cemented lens of a meniscus shape having a convex surface directed toward the reduction side, and a plurality of positive lens components, and

the plurality of positive lens components includes all the positive lens components that are adjacent, and

the cemented lens in the second lens unit includes in order from the enlargement side, a negative lens and a positive lens, and

the third lens unit includes a negative lens component closest to the enlargement side, and

all air spaces in the first lens unit and all air spaces in the second lens unit are constant at the time of focusing, and

the following conditional expressions (9) and (10) are satisfied:

0.50<Φ 23 ×f< 1.6  (9), and

0.012 (1/mm)<Φ 2p /N< 0.035 (1/mm)  (10)

where,

Φ 23 denotes a combined refractive power of the second lens unit and the third lens unit at the time of focusing to an object at infinity,

f denotes a focal length of the overall single-focus optical system at the time of focusing to an object at infinity,

Φ 2p denotes a combined refractive power of the plurality of positive lens components, and

N denotes the number (N≥2) of positive lens components in the plurality of positive lens components.