Single focal length lens and optical apparatus using the same
A single focal length lens includes an aperture stop and first through fourth lens units having, respectively, negative refractive power, positive refractive power, negative refractive power, and positive refractive power. Positions of the first, second, and fourth lens units are fixed. When focusing from an object at infinity to an object at a short distance, the third lens unit moves toward the image side. Conditional expressions (1), (2), and (3) are satisfied: −5< f 1/ f<− 0.5 (1), −10< f 3/ f<− 1 (2), and 0.5< f 12/ f <1 (3), where f1 denotes a focal length of the first lens unit, f denotes a focal length of an overall single focal length lens system when focusing to an object at infinity, f3 denotes a focal length of the third lens unit, and f12 denotes a combined focal length of the first and second lens units.
1. A single focal length lens comprising, in order from an object side to an image side:
a first lens unit having a negative refractive power;
an aperture stop;
a second lens unit having a positive refractive power;
a third lens unit having a negative refractive power; and
a fourth lens unit having a positive refractive power,
wherein:
the single focal length lens does not include a lens unit other than the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit,
a position of the first lens unit, a position of the second lens unit, and a position of the fourth lens unit are relatively fixed in the single focal length lens, and a position of the third lens unit is relatively moveable in the single focal length lens,
at a time of focusing from an object at infinity to an object at a short distance, the third lens unit moves toward the image side,
the following conditional expressions (1), (2), and (3) are satisfied:
−5< f 1/ f<− 0.5 (1),
−10< f 3/ f<− 1 (2), and
0.5< f 12/ f< 1 (3),
where f1 denotes a focal length of the first lens unit, f denotes a focal length of an overall single focal length lens system at the time of focusing to an object at infinity, f3 denotes a focal length of the third lens unit, and f12 denotes a combined focal length of the first lens unit and the second lens unit,
the first lens unit includes an object-side sub lens unit and an image-side sub lens unit,
an air lens having a biconvex shape is formed between the object-side sub lens unit and the image-side sub lens unit,
the object-side sub lens unit has a negative refractive power, and includes at least two negative lenses nearest to object, and
the image-side sub lens unit includes, in order from the object side, at least one negative lens and at least one positive lens.
2. The single focal length lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
0.05< Dm/St< 1 (5)
where Dm denotes a maximum variable air space from among variable air spaces in the single focal length lens, and St denotes a maximum diameter of the aperture stop.
3. The single focal length lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
0.2< DA/DL< 1 (6)
where DA denotes a sum of air spaces between a lens surface nearest to the object of the single focal length lens and a lens surface nearest to an image of the single focal length lens, and DL denotes a sum of lens thicknesses between the lens surface nearest to the object of the single focal length lens and the lens surface nearest to the image of the single focal length lens.
4. An optical apparatus, comprising:
a single focal length lens according to claim 1 ; and
an image pickup element which is disposed on the image side of the single focal length lens,
wherein the image pickup element has an image pickup surface, and converts an image formed on the image pickup surface by the single focal length lens to an electric signal.
5. An optical apparatus, comprising:
a single focal length lens according to claim 1 ; and
a display element which is disposed on the image side of the single focal length lens,
wherein the display element has a display surface, and an image displayed on the display surface is projected toward the object side by the single focal length lens.
6. A single focal length lens comprising, in order from an object side to an image side:
a first lens unit having a negative refractive power;
an aperture stop;
a second lens unit having a positive refractive power;
a third lens unit having a negative refractive power; and
a fourth lens unit having a positive refractive power,
wherein:
the single focal length lens does not include a lens unit other than the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit,
a position of the first lens unit, a position of the second lens unit, and a position of the fourth lens unit are relatively fixed in the single focal length lens, and a position of the third lens unit is relatively moveable in the single focal length lens,
at a time of focusing from an object at infinity to an object at a short distance, the third lens unit moves toward the image side,
the following conditional expressions (1), (2), and (3) are satisfied:
−5< f 1/ f<− 0.5 (1),
−10< f 3/ f<− 1 (2), and
0.5< f 12/ f< 1 (3),
where f1 denotes a focal length of the first lens unit, f denotes a focal length of an overall single focal length lens system at the time of focusing to an object at infinity, f3 denotes a focal length of the third lens unit, and f12 denotes a combined focal length of the first lens unit and the second lens unit,
the second lens unit includes in order from the object side, a first sub lens unit, a second sub lens unit, and a third sub lens unit,
the second lens unit does not include a sub lens unit other than the first sub lens unit, the second sub lens unit, and the third sub lens unit,
the first sub lens unit has a positive refractive power, and includes at least two positive lenses,
the second sub lens unit has a negative refractive power, and includes at least one negative lens,
the third sub lens unit has a positive refractive power, and includes at least one positive lens, and
at least one of the positive lenses in the second lens unit satisfies the following conditional expression (4):
80< vd 2 p< 96 (4)
where vd2p denotes an Abbe number for said at least one of the positive lenses in the second lens unit.
7. A single focal length lens comprising, in order from an object side to an image side:
a first lens unit having a negative refractive power;
an aperture stop;
a second lens unit having a positive refractive power;
a third lens unit having a negative refractive power; and
a fourth lens unit having a positive refractive power,
wherein:
the single focal length lens does not include a lens unit other than the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit,
a position of the first lens unit, a position of the second lens unit, and a position of the fourth lens unit are relatively fixed in the single focal length lens, and a position of the third lens unit is relatively moveable in the single focal length lens,
at a time of focusing from an object at infinity to an object at a short distance, the third lens unit moves toward the image side,
the following conditional expressions (1), (2), and (3) are satisfied:
−5< f 1/ f<− 0.5 (1),
−10< f 3/ f<− 1 (2), and
0.5< f 12/ f< 1 (3),
where f1 denotes a focal length of the first lens unit, f denotes a focal length of an overall single focal length lens system at the time of focusing to an object at infinity, f3 denotes a focal length of the third lens unit, and f12 denotes a combined focal length of the first lens unit and the second lens unit, and
the following conditional expressions (7) and (8) are satisfied:
60°<2ω<190° (7), and
0.8 <FNOm< 1.4 (8),
where ω denotes a half angle of view at the time of focusing to an object at infinity, and FNOm denotes a minimum F-number at the time of focusing to an object at infinity.
8. A single focal length lens comprising, in order from an object side to an image side:
a first lens unit having a negative refractive power;
an aperture stop;
a second lens unit having a positive refractive power;
a third lens unit having a negative refractive power; and
a fourth lens unit having a positive refractive power,
wherein:
the single focal length lens does not include a lens unit other than the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit,
a position of the first lens unit, a position of the second lens unit, and a position of the fourth lens unit are relatively fixed in the single focal length lens, and a position of the third lens unit is relatively moveable in the single focal length lens,
at a time of focusing from an object at infinity to an object at a short distance, the third lens unit moves toward the image side,
the first lens unit includes an object-side sub lens unit and an image-side sub lens unit,
an air lens having a biconvex shape is formed between the object-side sub lens unit and the image-side sub lens unit,
the object-side sub lens unit has a negative refractive power, and includes at least two negative lenses nearest to an object,
the image-side sub lens unit includes, in order from the object side, at least one negative lens and at least one positive lens,
the second lens unit includes in order from the object side, at least two positive lenses, at least one negative lens, and at least one positive lens, and
at least one of the positive lenses in the second lens unit satisfies the following conditional expression (4):
80< vd 2 p< 96 (4)
where vd2p denotes an Abbe number for said at least one of the positive lenses in the second lens unit.
9. The single focal length lens according to claim 8 , wherein the following conditional expression (3) is satisfied:
0.5< f 12/ f< 1 (3)
where f12 denotes a combined focal length of the first lens unit and the second lens unit, and f denotes a focal length of an overall single focal length lens system at the time of focusing to an object at infinity.
10. The single focal length lens according to claim 8 , wherein the following conditional expression (5) is satisfied:
0.05< Dm/St< 1 (5)
where Dm denotes a maximum variable air space from among variable air spaces in the single focal length lens, and St denotes a maximum diameter of the aperture stop.
11. The single focal length lens according to claim 8 , wherein the following conditional expression (6) is satisfied:
0.2< DA/DL< 1 (6)
where DA denotes a sum of air spaces between a lens surface nearest to the object of the single focal length lens and a lens surface nearest to an image of the single focal length lens, and DL denotes a sum of lens thicknesses between the lens surface nearest to the object of the single focal length lens and the lens surface nearest to the image of the single focal length lens.
12. The single focal length lens according to claim 8 , wherein the following conditional expressions (7) and (8) are satisfied:
60°<2ω<190° (7), and
0.8 <FNOm< 1.4 (8)
where ω denotes a half angle of view at the time of focusing to an object at infinity, and FNOm denotes a minimum F-number at the time of focusing to an object at infinity.
13. A single focal length lens comprising, in order from a magnification side to a reduction side:
a first lens unit having a negative refractive power;
an aperture stop;
a second lens unit having a positive refractive power;
a third lens unit having a negative refractive power; and
a fourth lens unit having a positive refractive power;
wherein:
the single focal length lens does not include a lens unit other than the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit,
the first lens unit, the second lens unit, and the fourth lens unit are relatively fixed in the single focal length lens, and the third lens unit is relatively moveable in the single focal length lens,
at a time of focusing, the third lens unit moves,
the first lens unit includes a magnification-side sub lens unit and a reduction-side sub lens unit,
an air lens having a biconvex shape is formed between the magnification-side sub lens unit and the reduction-side sub lens unit,
the magnification-side sub lens unit has a negative refractive power, and includes at least two negative lenses on the farthest magnification side,
the reduction-side sub lens unit includes, in order from the magnification side, at least one negative lens and at least one positive lens,
the second lens unit includes, in order from the magnification side, at least two positive lenses, at least one negative lens, and at least one positive lens, and
at least one of the positive lenses in the second lens unit satisfies the following conditional expression (4):
80< vd 2 p< 96 (4)
where vd2p denotes an Abbe number for said at least one of the positive lenses in the second lens unit.
14. The single focal length lens according to claim 13 , wherein the following conditional expression (5) is satisfied:
0.05< Dm/St< 1 (5)
where Dm denotes a maximum variable air space from among variable air spaces in the single focal length lens, and St denotes a maximum diameter of the aperture stop.
15. An optical apparatus, comprising:
a single focal length lens according to claim 13 ; and
an image pickup element which is disposed on an image side of the single focal length lens,
wherein the image pickup element has an image pickup surface, and converts an image formed on the image pickup surface by the single focal length lens to an electric signal.