Optical system and optical instrument, image pickup apparatus, and image pickup system using the same
View Patent ↗An optical system which forms an optical image on an image pickup element, comprising in order from an object side, a first lens unit having a positive refractive power, which includes a plurality of lenses, a stop, and a second lens unit which includes a plurality of lenses, wherein the first lens unit includes a first object-side lens which is disposed nearest to an object, and the second lens unit includes a second image-side lens which is disposed nearest to an image, and the first lens unit includes a negative lens, and a positive lens which is disposed on the object side of the negative lens, and the following conditional expressions are satisfied: β≦−1.1 (15) 0.08<NA (16) 1.0< WD/BF (19) 0.5<2×( WD ×tan(sin −1 NA)+ Y obj )/φ s <4.0 (20).
1. An optical system which forms an optical image on an image pickup element including a plurality of pixels arranged in rows two-dimensionally, which converts a light intensity to an electric signal, and a plurality of color filters disposed on the plurality of pixels respectively, comprising in order from an object side,
a first lens unit having a positive refractive power, which includes a plurality of lenses,
a stop, and
a second lens unit which includes a plurality of lenses, wherein
lens units which form the optical system include the first lens unit and the second lens unit, and
the first lens unit includes a first object-side lens which is disposed nearest to an object, and
the second lens unit includes a second image-side lens which is disposed nearest to an image, and
the first lens unit includes a negative lens, and a positive lens which is disposed on the object side of the negative lens, and
the following conditional expressions (15), (16), (19), and (20) are satisfied:
β≦−1.1 (15)
0.08<NA (16)
1.0 <WD/BF (19)
0.5<2×( WD ×tan(sin −1 NA)+ Y obj )/φ s <4.0 (20)
where,
β denotes an imaging magnification of the optical system,
NA denotes a numerical aperture on the object side of the optical system,
WD denotes a distance on an optical axis from the object up to an object-side surface of the first object-side lens,
BF denotes a distance on the optical axis from an image-side surface of the second image-side lens up to the image,
Y obj denotes a maximum object height, and
φ s denotes a diameter of the stop.
2. The optical system according to claim 1 , wherein
the first lens unit includes a first image-side lens which is disposed nearest to the image, and
the following conditional expression (31) is satisfied:
0.1 <L G1 /L G2 <1.5 (31)
where,
L G1 denotes a distance on the optical axis from the object-side surface of the first object-side lens up to an image-side surface of the first image-side lens, and
L G2 denotes a distance on the optical axis from an object-side surface of the second object-side lens up to an image side surface of the second image-side lens.
3. The optical system according to claim 2 , wherein the following conditional expression (25) is satisfied:
0.15 <D os /D oi <0.8 (25)
where,
D os denotes a distance on the optical axis from the object up to the stop, and
D oi denotes a distance on the optical axis from the object up to the image.
4. The optical system according to claim 3 , wherein the following conditional expression (23) is satisfied:
0.4 <L L /D oi (23)
where,
L L denotes a distance on the optical axis from the object-side surface of the first object-side lens up to the image-side surface of the second image-side lens, and
D oi denotes the distance on the optical axis from the object up to the image.
5. The optical system according to claim 4 , wherein the following conditional expression (34) is satisfied:
0.5 <D os /L G1 <4.0 (34)
where,
D os denotes the distance on the optical axis from the object up to the stop, and
L G1 denotes the distance on the optical axis from the object-side surface of the first object-side lens up to the image-side surface of the first image-side lens.
6. The optical system according to claim 5 , wherein the following conditional expression (21) is satisfied:
0.01 <D max /φ s <3.0 (21)
where,
D max denotes a maximum distance from among distances on the optical axis of adjacent lenses in the optical system, and
φ s denotes the diameter of the stop.
7. The optical system according to claim 6 , wherein the following conditional expression (56) is satisfied:
0.78 <L L /D oi +0.07 ×WD/BF (56)
where,
L L denotes the distance on the optical axis from the object-side surface of the first object-side lens up to the image-side surface of the second image-side lens,
D oi denotes the distance on the optical axis from the object up to the image,
WD denotes the distance on the optical axis from the object up to the object-side surface of the first object-side lens, and
BF denotes the distance on the optical axis from the image-side surface of the second image-side lens up to the image.
8. The optical system according to claim 7 , wherein the following conditional expression (57) is satisfied:
D os /L G1 −0.39 ×WD/BF< 1.8 (57)
where,
D os denotes the distance on the optical axis from the object up to the stop,
L G1 denotes the distance on the optical axis from the object-side surface of the first object-side lens up to the image-side surface of the first image-side lens,
WD denotes the distance on the optical axis from the object up to the object-side surface of the first object-side lens, and
BF denotes the distance on the optical axis from the image-side surface of the second image-side lens up to the image.
9. The optical system according to claim 8 , wherein the following conditional expression (27) is satisfied:
0 <BF/L L <0.4 (27)
where,
BF denotes the distance on the optical axis from the image-side surface of the second image-side lens up to the image, and
L L denotes the distance on the optical axis from the object-side surface of the first object-side lens up to the image-side surface of the second image-side lens.
10. The optical system according to claim 9 , wherein the following conditional expressions (35) and (36) are satisfied:
1.0 <D ENP /Y (35)
0 ≦CRA obj /CRA img <0.5 (36)
where,
D ENP denotes a distance on the optical axis from a position of an entrance pupil of the optical system up to the object-side surface of the first object-side lens,
Y denotes a maximum image height in an overall optical system,
CRA obj denotes a maximum angle from among of angles made by a principal ray that is incident on the first object-side lens, with the optical axis, and
CRA img denotes a maximum angle from among of angles made by a principal ray that is incident on an image plane, with the optical axis, and
an angle measured in a direction of clockwise rotation is let to be a negative angle, and an angle measured in a direction of counterclockwise rotation is let to be a positive angle.