Endoscope illuminating optical system
The endoscope illuminating optical system includes a transparent resin member, and a lighting member which outputs illumination light. The transparent resin member has a through hole in which an image sensor is disposed, a non-through hole in which the lighting member is disposed, an internal optical surface which is formed at an interior of the transparent resin member by the non-through hole, and an outer surface from which the illumination light incident on the transparent resin member via the internal optical surface, is emerged toward an object. The outer surface has a curved-surface area through which the illumination light passes, and the curved-surface area has a boundary with the through hole. In the curved-surface area, a displacement of each point of the curved-surface area from the boundary occurs in a direction away from the object.
1. An endoscope illuminating optical system, comprising:
a transparent resin member; and
a lighting member which outputs illumination light,
wherein:
the transparent resin member has:
a through hole in which an image sensor is disposed,
a non-through hole in which the lighting member is disposed,
an internal optical surface which is formed at an interior of the transparent resin member by the non-through hole, and
an outer surface from which the illumination light incident on the transparent resin member via the internal optical surface emerges toward an object,
the outer surface has a curved-surface area through which the illumination light passes,
the curved-surface area has a boundary with the through hole,
in the curved-surface area, a displacement of each point of the curved-surface area from the boundary occurs in a direction away from the object,
a shape of the curved-surface area in a cross section defined by a plane including a central axis of the through hole is a shape such that an angle of inclination at each point in the curved-surface area increases in accordance with an increase in distance away from the central axis, and
the following conditional expressions (1) and (2) are satisfied:
0.02<Ziax/Ds<0.08 (1), and
10°<Aiax<35° (2)
where,
Ziax denotes a distance from a predetermined position to the boundary, as measured along the central axis, and here
the predetermined position is a position at which an axis, which passes through a center of gravity of the internal optical surface and is parallel to the central axis, intersects the curved-surface area, and
regarding the sign, either positive or negative, of the distance, the distance is let to be positive when the boundary is positioned on an object side of the predetermined position,
Ds denotes a maximum outer diameter of the transparent resin member, and
Aiax denotes an angle of inclination at the predetermined position for a cross-sectional shape of the curved-surface area in a cross-section defined by a plane including the central axis and the predetermined position, and here
the angle of inclination is an angle made by a tangent to the cross-sectional shape and an axis perpendicular to the central axis.
2. The endoscope illuminating optical system according to claim 1 , wherein:
a plurality of the non-through holes are provided,
a plurality of the lighting members are provided,
each of the plurality of lighting members is disposed in a respective one of the plurality of non-through holes, and
at least two non-through holes from among the plurality of non-through holes are formed to be mirror-symmetric with respect to at least one of the cross-sections defined by a plane including the central axis.
3. The endoscope illuminating optical system according to claim 1 , wherein:
the shape of the curved-surface area is axisymmetric having an axis of symmetry near the central axis, and is definable by a function expression in which a distance from the axis of symmetry is let to be a variable, and
the following conditional expressions (3) and (4) are satisfied:
0.15< Z [L]/Z[Ds/ 2]<0.55 (3), and
0.4< A[L]/A[Ds/ 2]<0.8 (4)
where,
Z [r] denotes a function expressing a displacement at a point on the curved-surface area, separated away only by a distance r from the axis of symmetry, and here
the displacement is a distance from a point on the curved-surface area to the boundary, as measured along the central axis,
A [r] denotes a function expressing an angle of inclination based on a differential coefficient of Z [r] at the point on the curved-surface area, separated apart only by the distance r from the axis of symmetry, and
L denotes a distance from the axis of symmetry to the center of gravity of the internal optical surface.
4. The endoscope illuminating optical system according to claim 1 , wherein:
the curved-surface area is one of a spherical surface and an aspheric surface having an axis of symmetry near the central axis, and
the following conditional expression (5) is satisfied:
0.55<Roax/Ds<2 (5)
where,
Roax denotes an absolute value of a radius of curvature at a central portion of the one of the spherical surface and the aspheric surface.
5. The endoscope illuminating optical system according to claim 1 , wherein the lighting member comprises one of a light guide and a light emitter.