Imaging optical system and optical apparatus including the same
An imaging optical system includes a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, a fourth lens unit, and a fifth lens unit, and the first lens unit includes a first negative lens and a first cemented lens, the second lens unit includes a second cemented lens and one or more positive lens components, the third lens unit includes one or more positive lens components and a third cemented lens, and the first cemented lens includes a negative lens closest to the reduction side and has a concave surface facing the reduction side, the second cemented lens has a positive refractive power and has a concave surface facing the enlargement side, the third cemented lens has a positive refractive power and has a negative lens on the reduction side.
1. An imaging optical system configured to form a conjugate relation between a conjugate point on an enlargement side having a long distance and a conjugate point on a reduction side having a short distance,
the imaging optical system 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;
a third lens unit having a positive refractive power;
a fourth lens unit; and
a fifth lens unit,
wherein
an aperture stop is included in the second lens unit,
the first lens unit includes a first negative lens positioned closest to the enlargement side and a first cemented lens positioned closest to a reduction side,
the second lens unit includes, in order from the enlargement side, a second cemented lens and at least one positive lens component,
the third lens unit includes, in order from the enlargement side, at least one positive lens component and a third cemented lens,
the lens component is a lens block in which an enlargement-side surface and a reduction-side surface alone are in contact with air in an optical path,
the first cemented lens includes a negative lens closest to a reduction side and has a surface closest to the reduction side having a concave surface facing the reduction side,
the second cemented lens has a positive refractive power and has a surface closest to the enlargement side having a concave surface facing the enlargement side, and
the third cemented lens includes a positive refractive power and has a negative lens on the reduction side.
2. The imaging optical system according to claim 1 , wherein
following Conditional Expression (1) is satisfied:
0.1< M 5 _ 3G /M 5 _ 4G <5 (1)
where
M 5 _ 3G is a lateral magnification of the third lens unit at a time of focusing to an object at infinity; and
M 5 _ 4G is a lateral magnification of the fourth lens unit at the time of focusing to the object at infinity.
3. The imaging optical system according to claim 1 , wherein
following Conditional Expression (2) is satisfied:
−10<( R 2GF +R 2GR )/( R 2GF −R 2GR )<−0.1 (2),
where
R 2GF is a paraxial radius of curvature of a surface positioned closest to the enlargement side in the second lens unit; and
R 2GR is a paraxial radius of curvature of a surface positioned closest to the reduction side in the second lens unit.
4. The imaging optical system according to claim 1 , wherein
first positive lens positioned closest to the second cemented lens is included, and
following Conditional Expression (3) is satisfied:
0.001<( R P1F +R P1R )/( R P1F −R P1R )<5 (3)
where
R P1F is a paraxial radius of curvature of an enlargement-side surface of the first positive lens; and
R P1R is a paraxial radius of curvature of a reduction-side surface of the first positive lens.
5. The imaging optical system according to claim 1 , wherein an air space in a range from the third lens unit to the fifth lens unit changes at a time of focusing.
6. The imaging optical system according to claim 1 , wherein
following Conditional Expression (4) below is satisfied:
−8<( R 5GF +R 5GR )/( R 5GF −R 5GR )<−0.1 (4)
where
R 5GF is a paraxial radius of curvature of a surface positioned closest to the enlargement side in the fifth lens unit; and
R 5GR is a paraxial radius of curvature of a surface positioned closest to the reduction side in the fifth lens unit.
7. The imaging optical system according to claim 1 , wherein
the fourth lens unit includes one lens,
the one lens is a second positive lens, and
following Conditional Expression (5) is satisfied:
0.01<( R P2F +R P2R )/( R P2F −R P2R )<2 (5),
where
R P2F is a paraxial radius of curvature of an enlargement-side surface of the second positive lens; and
R P2R is a paraxial radius of curvature of a reduction-side surface of the second positive lens.
8. The imaging optical system according to claim 1 , wherein the first negative lens is a meniscus lens.
9. The imaging optical system according to claim 1 , wherein
following Conditional Expression (6) is satisfied:
0.1<( R N1F +R N1R )/( R N1F −R N1R )<6 (6)
where
R N1F is a paraxial radius of curvature of an enlargement-side surface of the first negative lens; and
R N1R is a paraxial radius of curvature of a reduction-side surface of the first negative lens.
10. The imaging optical system according to claim 1 , wherein
the third lens unit includes a negative lens component closer to the reduction side than the third cemented lens is,
the fourth lens unit has a positive refractive power and includes a positive lens component, and
the fifth lens unit has a negative refractive power and includes a negative lens component.
11. The imaging optical system according to claim 1 , wherein
following Conditional Expression (7) is satisfied:
0.1< D 3G /D 4G <4.5 (7),
where
D 3G is an amount of movement of the third lens unit at a time of focusing; and
D 4G is an amount of movement of the fourth lens unit at the time of focusing.
12. The imaging optical system according to claim 1 , wherein
the third lens unit comprises, in order from the enlargement side, the positive lens component, the third cemented lens, and a negative lens component,
the third cemented lens comprises, in order from the enlargement side, a positive lens and the negative lens, and
a shape of the negative lens component in the third lens unit is a biconcave shape.
13. The imaging optical system according to claim 1 , wherein
following Conditional Expression (A) is satisfied:
0< f/e N1F <2 (A),
where
f is a focal length of the imaging optical system as a whole at a time of focusing to an object at infinity; and
e N1F is a maximum effective aperture of an enlargement-side surface of the first negative lens.
14. The imaging optical system according to claim 1 , wherein
following Conditional Expression (3) is satisfied:
0<( f/e AS )/ Fno< 2 (B),
where
f is a focal length of the imaging optical system as a whole at a time of focusing to an object focusing at infinity;
e AS is a maximum diameter of the aperture stop; and
Fno is an F-number of the imaging optical system as a whole at the time of focusing to the object focusing at infinity.
15. The imaging optical system according to claim 1 , wherein
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 a range from a surface positioned closest to the enlargement side to a surface positioned closest to the reduction side in the imaging 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 imaging optical system.
16. An optical apparatus comprising:
an optical system; and
an image pickup element arranged 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 into an electrical signal, and
the optical system is the imaging optical system of claim 1 .
17. An optical apparatus comprising:
an optical system; and
a display element arranged on a reduction side,
wherein
the display element has a display surface,
an image displayed on the display surface is projected toward an enlargement side by the optical system, and
the optical system is the imaging optical system of claim 1 .
18. The imaging optical system according to claim 1 , wherein
at a time of focusing,
a distance between the second lens unit and the third lens unit,
a distance between the third lens unit and the fourth lens unit, and
a distance between the fourth lens unit and the fifth lens unit change.
19. The imaging optical system according to claim 1 , wherein
the aperture stop is arranged closest to the reduction side in the second lens unit,
the fourth lens unit comprises one lens component, and
the fifth lens unit comprises one lens component.
20. The imaging optical system according to claim 1 , wherein
at a time of focusing,
the third lens unit moves, and
a distance between the third lens unit and the fourth lens unit and
a distance between the fourth lens unit and the fifth lens unit change.