Bright relay optical system, and optical system for rigid endoscope and rigid endoscope using the same
A relay optical system includes an object-side lens which is disposed nearest to an object, an image-side lens which is disposed nearest to an image, and a cemented lens having a positive refractive power. The object-side lens has a positive refractive power and is disposed such that a convex surface is directed toward an object side. The image-side lens has a positive refractive power and is disposed such that a convex surface is directed toward an image side. A plurality of the cemented lenses is disposed between the object-side lens and the image side lens and the following conditional expression (1) is satisfied: 0.04< Gce/Drel <0.4 (1) where, Gce denotes the smallest of intervals of adjacent cemented lenses, and Drel denotes a distance from an object plane up to an image plane of the relay optical system.
1. A relay optical system, comprising:
an object-side lens which is disposed nearest to an object;
an image-side lens which is disposed nearest to an image; and
a cemented lens having a positive refractive power,
wherein:
the object-side lens has a positive refractive power and is disposed such that a convex surface is directed toward an object side,
the image-side lens has a positive refractive power, and is disposed such that a convex surface is directed toward an image side,
a plurality of the cemented lenses are disposed between the object-side lens and the image-side lens,
a diffractive optical element is disposed between the object-side lens and the image-side lens, and
the following conditional expression (1) is satisfied:
0.04< Gce/Drel< 0.4 (1)
where,
Gce denotes a smallest interval of intervals of adjacent cemented lenses, and
Drel denotes a distance from an object plane up to an image plane of the relay optical system.
2. The relay optical system according to claim 1 , wherein the following conditional expression (6) is satisfied:
0.05< Dcd/Drel< 0.30 (6)
where,
Dcd denotes a distance from a cemented surface up to a diffractive surface, and
Drel denotes a distance from the object plane up to the image plane of the relay optical system, and
the cemented surface is a cemented surface of the cemented lens which is positioned nearest to the diffractive optical element.
3. The relay optical system according to claim 1 , wherein the following conditional expression (7) is satisfied:
0.2<(OBH+IH)/Φ doe <1.2 (7)
where,
Φdoe denotes a light-ray effective diameter of the diffractive optical element,
OBH denotes a maximum object height, and
IH denotes a maximum image height.
4. The relay optical system according to claim 1 , wherein the following conditional expression (8) is satisfied:
0.3<FL doe /( doe× 100)<15 (8)
where,
FLdoe denotes a focal length of the diffractive optical element, and
Φdoe denotes a light-ray effective diameter of the diffractive optical element.
5. The relay optical system according to claim 1 , wherein:
the plurality of cemented lenses is disposed in an optical path of the relay optical system, which is formed by an object-side optical path and an image-side optical path,
a lens surface positioned nearest to the image in the object-side optical path is a surface which is convex toward the image side, and
a lens surface positioned nearest to the object in the image-side optical path is a surface which is convex toward the object side.
6. The relay optical system according to claim 1 , wherein the following conditional expression (9) is satisfied:
1<FL ce/Gce <20 (9)
where,
FLce denotes an average value of focal lengths of the adjacent cemented lenses.
7. An image relay unit, comprising:
a plurality of relay optical systems,
wherein at least one relay optical system of the plurality of relay optical systems is the relay optical system according to claim 1 .
8. An image relay unit, comprising:
one or more predetermined relay optical systems; and
a plurality of relay optical systems consisting of lenses,
wherein:
a number of the plurality of relay optical systems consisting of lenses is larger than a number of the one or more predetermined relay optical systems, and
the one or more predetermined relay optical system is the relay optical system according to claim 1 , and
the following conditional expression (10) is satisfied:
0.05<NAI×FL doe/Dreall <1.5 (10)
where,
NAI denotes an image-side numerical aperture of the relay optical system,
FLdoe denotes a focal length of the diffractive optical element, and
Dreall denotes a distance from the object plane up to an image plane of the image relay unit.
9. An optical system for rigid endoscope, comprising:
an objective optical system; and
an image relay unit which is disposed on an image side of the objective optical system,
wherein the image relay unit is the image relay unit according to claim 7 .
10. The optical system for rigid endoscope according to claim 9 , comprising:
an eyepiece optical system which is disposed on an image side of the image relay unit.
11. A rigid endoscope, comprising:
the optical system for rigid endoscope according to claim 9 ; and
an image pickup element which captures an image formed by the image relay unit.
12. A rigid endoscope, comprising:
the optical system for rigid endoscope according to claim 10 ; and
an illuminating unit for illuminating an object to be observed.
13. The rigid endoscope according to claim 11 , comprising:
an illuminating unit for illuminating an object to be observed.
14. A relay optical system, comprising:
an object-side lens which is disposed nearest to an object;
an image-side lens which is disposed nearest to an image; and
a cemented lens having a positive refractive power,
wherein:
the object-side lens has a positive refractive power and is disposed such that a convex surface is directed toward an object side,
the image-side lens has a positive refractive power, and is disposed such that a convex surface is directed toward an image side,
a plurality of the cemented lenses are disposed between the object-side lens and the image-side lens,
the following conditional expression (1) is satisfied:
0.04< Gce/Drel< 0.4 (1)
where,
Gce denotes a smallest interval of intervals of adjacent cemented lenses, and
Drel denotes a distance from an object plane up to an image plane of the relay optical system,
at least one cemented lens out of the plurality of cemented lenses includes three lenses,
a medium of each of the three lenses is different,
one of the three lenses is a first lens, and
in a rectangular coordinate system in which a horizontal axis is set to be vd LA and a vertical axis is set to be θgF LA ,
when a straight line expressed by θgF LA =α×vd LA +β LA is set, where α=−0.00163,
θgF LA and vd LA of a medium of the first lens are included in an area determined by following conditional expression (2) and conditional expression (3):
0.64<β LA (2)
vd LA <50 (3)
where,
θgF LA denotes a partial dispersion ratio (ng LA −nF LA )/(nF LA −nC LA ) of the medium of the first lens,
vd LA denotes Abbe number (nd LA −1)/(nF LA −nC LA ) for the medium of the first lens, and
nd LA , nC LA , nF LA , and ng LA denote refractive indices of the medium of the first lens for a d-line, a C-line, an F-line, and a g-line respectively.
15. The relay optical system according to claim 14 , wherein:
the cemented lens which includes the first lens, includes a second lens and an aspheric surface, and
the following conditional expressions (4) and (5) are satisfied:
1.4≤ nd LB ≤1.6 (4)
70≤ vd LB ≤100 (5)
where,
nd LB , nC LB , and nF LB denote refractive indices of the second lens for the d-line, the C-line, and the F-line respectively, and
vd LB denotes Abbe number (nd LB −1)/(nF LB −nC LB ) for a medium of the second lens.
16. A relay optical system, comprising:
an object-side lens which is disposed nearest to an object;
an image-side lens which is disposed nearest to an image; and
a cemented lens having a positive refractive power,
wherein:
the object-side lens has a positive refractive power and is disposed such that a convex surface is directed toward an object side,
the image-side lens has a positive refractive power, and is disposed such that a convex surface is directed toward an image side,
a plurality of the cemented lenses are disposed between the object-side lens and the image-side lens,
the following conditional expression (1) is satisfied:
0.04< Gce/Drel< 0.4 (1)
where,
Gce denotes a smallest interval of intervals of adjacent cemented lenses, and
Drel denotes a distance from an object plane up to an image plane of the relay optical system,
at least one cemented lens out of the plurality of cemented lenses includes two lenses,
a medium of each of the two lenses is different,
one of the two lenses is a second lens,
the cemented lens which includes the second lens has an aspheric surface, and
the following conditional expressions (4) and (5) are satisfied:
1.4≤ nd LB ≤1.6 (4)
70≤ vd LB ≤100 (5)
where,
nd LB , nC LB , and nF LB denote refractive indices of the second lens for a d-line, a C-line, and an F-line respectively, and
vd LB denotes Abbe number (nd LB −1)/(nF LB −nC LB ) for a medium of the second lens.