Illumination optical system and endoscope

Abstract

The invention provides an illumination optical system which has a small structure, a wide light distribution angle and good transmission efficiency, and an endoscope provided with the illumination optical system. The illumination optical system is arranged at the front end of a light guide of an endoscope, is provided with only two or less lenses as lenses, and has a negative refractive power as a whole, and a first lens surface closest to the light guide side includes a concave surface at the center portion and a light diffusion surface closer to the radial outer side than the concave surface. The illumination optical system satisfies a predetermined conditional expression.

Description

Technical Field

[0001] The technology of the present invention relates to an illumination optical system and an endoscope. Background Art

[0002] Conventionally, as an illumination optical system that is disposed at the distal end portion of an insertion portion of an endoscope and is used to illuminate a subject, for example, illumination optical systems described in the following Patent Documents 1 to 3 are known.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 57-097508

[0004] Patent Document 2: Japanese Patent No. 3060245

[0005] Patent Document 3: Japanese Patent Application Laid-Open No. 5-142485 Summary of the invention

[0006] In recent years, there has been a demand for an illumination optical system that has a compact structure, a wide light distribution angle, and good transmission efficiency.

[0007] The present invention provides an illumination optical system with a small structure, a wide light distribution angle and good transmission efficiency, and an endoscope equipped with the illumination optical system.

[0008] The first illumination optical system of the present invention is arranged at the front end of the light guide of the endoscope, wherein only two or less lenses are provided as lenses, and the lens has negative optical power as a whole, and the first lens surface closest to the light guide includes a concave surface at the center and a light diffusion surface radially outward of the concave surface, and the absolute value of the paraxial curvature radius of the concave surface is set to R, the distance on the optical axis from the emission end surface of the light guide to the first lens surface is set to D, and the diameter of the emission end surface of the light guide is set to G,

[0009] Satisfies the conditional expression (1) expressed as follows:

[0010] [Formula 1]

[0011]

[0012] The second illumination optical system of the present invention is arranged at the front end of the light guide of the endoscope, wherein only two or less lenses are provided as lenses and the lens has negative optical power as a whole, the first lens surface closest to the light guide includes a concave surface at the center and a light diffusion surface radially outward of the concave surface, the absolute value of the paraxial curvature radius of the concave surface is set to R, the distance on the optical axis from the emission end surface of the light guide to the first lens surface is set to D, the diameter of the emission end surface of the light guide is set to G, and the focal length of the illumination optical system is set to f,

[0013] Satisfies the conditional expression (2) expressed as follows:

[0014] [Formula 2]

[0015]

[0016] Hereinafter, the first illumination optical system and the second illumination optical system of the present invention are collectively referred to as the illumination optical system of the present invention.

[0017] The illumination optical system of the present invention preferably satisfies the conditional expressions (3) and (4) represented as follows:

[0018] 0.2 < R / G < 0.6 (3)

[0019] [Formula 3]

[0020]

[0021] When the lens closest to the light guide has a core / clad structure in which the core is clad with a cladding, the diameter of the core in the direction perpendicular to the optical axis is set to C, and when the lens closest to the light guide does not have a core / clad structure, the outer diameter of the first lens surface is set to C,

[0022] The illumination optical system of the present invention preferably satisfies the conditional expressions (5) and (6) represented as follows:

[0023] 0.8 < C / G < 1.5 (5)

[0024] [Formula 4]

[0025]

[0026] When the distance on the optical axis from the first lens surface to the surface closest to the irradiated object is set to L, the focal length of the illumination optical system is set to f, when the lens closest to the light guide has a core / clad structure in which the core is clad with a cladding, the refractive index of the core with respect to the d line is set to Nd1, and when the lens closest to the light guide does not have a core / clad structure, the refractive index of the lens closest to the light guide with respect to the d line is set to Nd1,

[0027] The illumination optical system of the present invention preferably satisfies the conditional expression (7) represented as follows:

[0028] -1 < L / (Nd1 × f) < -0.22 (7).

[0029] The first illumination optical system of the present invention preferably satisfies the conditional expression (1-1) represented as follows:

[0030] [Formula 5]

[0031]

[0032] The second illumination optical system of the present invention preferably satisfies the conditional expression (2-1) represented as follows:

[0033] [Formula 6]

[0034]

[0035] The illumination optical system of the present invention preferably satisfies at least one of the following conditional expressions (3-1) and (4-1):

[0036] 0.3<R / G<0.5 (3-1)

[0037] [Formula 7]

[0038]

[0039] The illumination optical system of the present invention preferably satisfies at least one of the following conditional expressions (5-1) and (6-1):

[0040] 1.0<C / G<1.4 (5-1)

[0041] [Formula 8]

[0042]

[0043] The illumination optical system of the present invention preferably satisfies the conditional expression (7-1) represented by the following:

[0044] -0.5<L / (Nd1×f)<-0.21 (7-1).

[0045] The endoscope of the present invention includes the illumination optical system of the present invention.

[0046] In addition, the term "consisting of" or "including" in this specification means that in addition to the listed constituent elements, it may also include lenses that do not substantially have optical power, optical elements other than lenses such as apertures, filters, and cover glasses, as well as lens flanges, lens barrels, and the like.

[0047] "Single lens" refers to a single lens that is not bonded. The number of lenses mentioned above is the number of lenses that constitute the constituent elements. For example, the number of lenses in a bonded lens formed by bonding multiple single lenses of different materials is represented by the number of single lenses that constitute the bonded lens. However, a composite aspheric lens (i.e., a lens (e.g., a spherical lens) and a non-spherical film formed on the lens are integrated and function as a single aspheric lens as a whole) is used as a single lens and is not considered a bonded lens.

[0048] Unless otherwise specified, the sign of the optical power associated with the lens including the aspheric surface, the radius of curvature of the lens surface, and the shape of the lens surface are considered in the paraxial region. Regarding the sign of the radius of curvature, the radius of curvature of the surface of the shape of the convex surface toward the light guide side is set to positive, and the radius of curvature of the surface of the shape of the convex surface toward the irradiated body side is set to negative.

[0049] The "focal length" used in the conditional expression is the paraxial focal length. Unless otherwise specified, the "distance on the optical axis" used in the conditional expression is the geometric distance. The value used in the conditional expression is the value when the d line (wavelength 587.56nm (nanometer)) is used as a reference.

[0050] Effects of the Invention

[0051] According to the present invention, it is possible to provide an illumination optical system having a compact structure, a wide light distribution angle, and good transmission efficiency, and an endoscope including the illumination optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The diagram corresponds to the illumination optical system of Example 1 and is a cross-sectional view showing the structure of the illumination optical system according to one embodiment.

[0053] Figure 2 This is a diagram for explaining a light diffusion surface.

[0054] Figure 3 This is a diagram for explaining a light diffusion surface.

[0055] Figure 4 It is a diagram for explaining a comparative example which does not have a light diffusion surface.

[0056] Figure 5 This is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 1.

[0057] Figure 6 This is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 1.

[0058] Figure 7 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 2.

[0059] Figure 8 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 2.

[0060] Fig. 9 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 3.

[0061] Fig.10 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 3.

[0062] Fig.11 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 4.

[0063] Fig.12 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 4.

[0064] Fig.13 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 5.

[0065] Fig.14 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 5.

[0066] Fig.15 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 6.

[0067] Fig.16 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 6.

[0068] Fig.17 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 7.

[0069] Fig.18 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 7.

[0070] Fig.19 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 8.

[0071] Fig. 20 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 8.

[0072] Fig.21 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 9.

[0073] Fig. 22 It is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 9.

[0074] Fig.23 This is a schematic structural diagram of an endoscope according to one embodiment.

[0075] Explanation of symbols

[0076] 3-light guide, 3a~3d-area, 10, 10X-illumination optical system, 20, 20X-lens surface, 20a-concave surface, 20b-light diffusion surface, 22-core, 24-cladding, 100-endoscope, 102-operating part, 104-insertion part, 106-universal cord, 107-flexible part, 108-bending part, 109-bending operation knob, 110-front end part, C-diameter of core, D-distance on the optical axis from the emission end face of the light guide to the first lens face, G-diameter of the emission end face of the light guide, L-distance on the optical axis from the first lens face to the face closest to the irradiated body, L1, L1X, L2-lens, Obj-object plane, PP-parallel plane plate, Z-optical axis. DETAILED DESCRIPTION

[0077] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 It is a cross-sectional view showing the structure of an illumination optical system 10 according to one embodiment of the present invention. Figure 1 The illustrated illumination optical system 10 corresponds to Example 1 described later.

[0078] The illumination optical system 10 is an optical system disposed at the front end of the light guide 3 of the endoscope. The light guide 3 is composed of a bundle of optical fibers in which a plurality of optical fibers are bundled together, and emits light emitted from a light source (not shown) to the illumination optical system 10. That is, the light emitted from the light source enters the illumination optical system 10 via the light guide 3, and is emitted from the illumination optical system 10 to become illumination light. When the illumination optical system 10 is disposed at the front end of the insertion portion of the endoscope, the illumination light illuminates an irradiated object (not shown) serving as an observation object. Figure 1 , a cross-sectional view including the optical axis Z is shown, with the left side being the light source side and the right side being the illuminated object side.

[0079] The illumination optical system 10 of the present invention has only two or less lenses as lenses, and has negative optical power as a whole. Here, the two or less lenses of the illumination optical system 10 may be a joined lens formed by joining two lenses. By setting the number of lenses of the illumination optical system 10 to be two or less and configuring it to have negative optical power as a whole, it is easy to achieve miniaturization and expand the light distribution angle. As an example, Figure 1 The illumination optical system 10 shown is composed of one negative lens L1. Alternatively, the illumination optical system 10 may include an optical component having no optical power, such as a plane-parallel plate.

[0080] In the illumination optical system 10, the first lens surface 20 closest to the light guide 3 includes a concave surface 20a at the center and a light diffusion surface 20b radially outward from the concave surface 20a. By using the concave surface 20a as the center of the first lens surface 20, it is easy to achieve miniaturization and expand the light distribution angle. By arranging the light diffusion surface 20b at a position radially outward from the concave surface 20a of the first lens surface 20, it is easy to improve the light transmission efficiency and maintain a wide light distribution angle (details will be described later). The light diffusion surface 20b is formed by, for example, grinding the surface of the lens.

[0081] In the illumination optical system 10, the lens closest to the optical waveguide 3 may be a lens having a core / cladding structure in which a core 22 is covered with a cladding 24 (a so-called lens composed of a single optical fiber). According to the core / cladding structure, light incident on the boundary surface between the core 22 and the cladding 24 having different refractive indices is totally reflected and directed toward the periphery of the field of view on the opposite side. Therefore, even if the light is refracted by the concave surface 20a or diffused by the light diffusion surface 20b, it is possible to suppress light leakage from the periphery of the lens. Furthermore, in the case where the lens surface on the side opposite to the concave surface 20a is chamfered, light passing through the chamfered portion is sometimes absorbed, but by utilizing total reflection based on the core / cladding structure, it is possible to avoid light passing through the chamfered portion. That is, by making the lens closest to the optical waveguide 3 have a core / cladding structure, the light transmission efficiency can be improved.

[0082] As an example, Figure 1 The lens L1 shown has a core / cladding structure including a core 22 and a cladding 24. Figure 1 , the boundary between the core 22 and the cladding 24 is illustrated by a dotted line. On the first lens surface 20 closest to the light guide 3, a concave surface 20a is formed on the core 22. The light diffusion surface 20b is formed across the core 22 and the cladding 24. In addition, the light diffusion surface 20b may be formed only on the core 22 and not on the cladding 24, for example.

[0083] refer to Figure 2 to Figure 4 , the light diffusion surface 20b will be described in detail. Figure 2 2 is a diagram showing the correspondence between the emission end surface of the light guide 3 and the radial position of the first lens surface 20. Figure 2 In FIG. 1 , as a comparative example, a lens surface 20X that is composed of only a concave surface and does not have a light diffusion surface is also illustrated. Figure 2 In the figure, for convenience of explanation, the emission end surface of the light guide 3 is divided into four regions 3a to 3d with equal areas. That is, the amount of light emitted from each of the regions 3a to 3d is the same.

[0084] As shown in the lens surface 20X of the comparative example, when the diameter of the concave surface is equal to or larger than the diameter of the emission end surface of the light guide 3, the light emitted from the area (for example, area 3d) outside the emission end surface of the light guide 3 diverges when passing through the concave surface, thereby causing light leakage. Regarding this light leakage, even if an attempt is made to suppress it using a core / cladding structure, a sufficient effect may not be obtained due to factors such as the spread angle of the light emitted from the light guide 3.

[0085] Furthermore, the depth of the concave surface changes more steeply toward the periphery, so the area through which light passes becomes larger. For example, of the area of ​​the lens surface 20X through which light emitted from the area 3a on the inner side of the emission end surface of the light guide 3 passes and the area of ​​the lens surface 20X through which light emitted from the area 3d on the outer side of the emission end surface of the light guide 3 passes, the latter becomes larger. Therefore, in the concave surface, the influence on the transmission efficiency due to light leakage and light absorption by the chamfered portion is greater in the periphery (for example, Figure 2 The portion shown in bold in the figure is larger than that in the center.

[0086] In the illumination optical system 10 according to the present embodiment, a light diffusion surface 20b is formed on a plane extending radially outward from the concave surface 20a on the first lens surface 20 closest to the light guide 3. That is, by forming the light diffusion surface 20b on the outer side of the outer peripheral portion of the concave surface 20a, which is a factor that easily causes a decrease in light transmission efficiency, a decrease in light transmission efficiency can be suppressed.

[0087] Figure 3 is emitted from the emission end face of the light guide 3 and incident on Figure 1 FIG. 2 is a diagram showing a light diffusion surface 20 b of the illumination optical system 10 and a state of light emitted from the illumination optical system 10 . Figure 4 for Figure 3 The comparative example is to assume that Figure 1 FIG. 1 is a diagram showing the state of light in the illumination optical system 10X when the lens L1 of the illumination optical system 10 is replaced with a lens L1X that does not have a light diffusion surface 20b. Figure 3 and Figure 4 In FIG. 1 , light rays incident on the lens L1 or the lens L1X from three points on the emission end surface of the light guide 3 are illustrated by solid lines, dashed lines, and dotted lines, respectively.

[0088] like Figure 3 As shown, the light passing through the light diffusion surface 20b is diffused and projected onto the object plane Obj in a state where the light spread is large. That is, the illumination optical system 10 according to this embodiment easily maintains a wide light distribution angle by diffusing the light using the light diffusion surface 20b.

[0089] Furthermore, by diffusing the light, it is possible to suppress the image of the emitting end face of the optical waveguide 3 from being imaged on the object plane Obj through the illumination optical system 10. In the emitting end face of the optical waveguide 3 composed of a bundle of optical fibers, since the non-luminous cladding and the gaps between the optical fibers and the luminous cores are arranged on the same plane, it includes dark parts and bright parts. If the image of the emitting end face of the optical waveguide 3 is imaged on the object plane Obj, the light and dark pattern (uneven light distribution) is projected onto the object plane Obj, and when the projected image is clear, it interferes with the observation of the object plane Obj (the irradiated object). As in the present embodiment, by diffusing the light using the light diffusion surface 20b, it is possible to suppress the generation of a projection image of a light and dark pattern on the object plane Obj.

[0090] On the other hand, Figure 4 As shown in FIG. 1 , in the lens L1X without the light diffusion surface 20b, it can be seen that the degree of diffusion of light is Figure 3 That is, in the lens L1X without the light diffusion surface 20b, it is difficult to maintain a wider light distribution angle than the illumination optical system 10 involved in this embodiment, and there is a high possibility that a projection image of a light and dark pattern (uneven light distribution) will be generated on the object surface Obj.

[0091] Next, the preferred structure and the achievable structure related to the conditional formula of the illumination optical system of the present invention are described. In addition, in the description related to the following conditional formula, the same symbols are used for the parts with the same definition, and the repeated description of some symbols is omitted in order to avoid redundant description. And, in order to avoid redundant description, the "illumination optical system of the present invention" is also referred to as "illumination optical system" in short.

[0092] When the absolute value of the paraxial radius of curvature of the concave surface 20a is set to R, the distance on the optical axis Z from the emission end face of the light guide 3 to the first lens surface 20 is set to D, and the diameter of the emission end face of the light guide 3 is set to G, the illumination optical system 10 preferably satisfies the following conditional formula (1). That is, when the vertex of the concave surface 20a is located on the optical axis Z, D refers to the interval on the optical axis Z from the emission end face of the light guide 3 to the vertex of the concave surface 20a. By preventing the corresponding value of the conditional formula (1) from becoming below the lower limit value, the concave surface 20a will not become too small, so the light distribution will not become too narrow, which is beneficial to the wide-angle light distribution. By preventing the corresponding value of the conditional formula (1) from becoming above the upper limit value, the concave surface 20a will not become too large, and the transmission efficiency will not be reduced too much, which is beneficial to improve the transmission efficiency. In order to obtain better characteristics, the illumination optical system 10 more preferably satisfies the following conditional formula (1-1).

[0093] [Formula 9]

[0094]

[0095] [Formula 10]

[0096]

[0097] When the focal length of the illumination optical system 10 is set to f, the illumination optical system 10 preferably satisfies the following conditional formula (2). By preventing the corresponding value of the conditional formula (2) from becoming less than the lower limit value, the concave surface 20a will not become too small, so the light distribution will not become too narrow, which is conducive to wide-angle light distribution. By preventing the corresponding value of the conditional formula (2) from becoming more than the upper limit value, the concave surface 20a will not become too large, and the transmission efficiency will not be reduced too much, which is conducive to improving the transmission efficiency. In order to obtain better characteristics, the illumination optical system 10 more preferably satisfies the following conditional formula (2-1).

[0098] [Formula 11]

[0099]

[0100] [Formula 12]

[0101]

[0102] The illumination optical system 10 preferably satisfies the following conditional formula (3). By preventing the corresponding value of the conditional formula (3) from becoming below the lower limit, the light will not diverge too much, so that it is possible to suppress the leakage of light from the periphery, thereby suppressing the reduction of the transmission efficiency. By preventing the corresponding value of the conditional formula (3) from becoming above the upper limit, the light distribution will not become too narrow, which is conducive to the wide-angle light distribution. In order to obtain better characteristics, the illumination optical system 10 more preferably satisfies the following conditional formula (3-1).

[0103] 0.2<R / G<0.6 (3)

[0104] 0.3<R / G<0.5 (3-1)

[0105] The illumination optical system 10 preferably satisfies the following conditional formula (4). By preventing the corresponding value of the conditional formula (4) from becoming below the lower limit, the light will not diverge too much, so that it is possible to suppress the leakage of light from the periphery, thereby suppressing the reduction of the transmission efficiency. By preventing the corresponding value of the conditional formula (4) from becoming above the upper limit, the light distribution will not become too narrow, which is conducive to the wide-angle light distribution. In order to obtain better characteristics, the illumination optical system 10 more preferably satisfies the following conditional formula (4-1).

[0106] [Formula 13]

[0107]

[0108] [Formula 14]

[0109]

[0110] The illumination optical system 10 preferably satisfies the following conditional expression (5). In conditional expression (5) and conditional expression (6) described later, when the lens L1 closest to the light guide 3 has a core / cladding structure, the diameter of the core 22 in the direction perpendicular to the optical axis Z is set to C. On the other hand, when the lens L1 closest to the light guide 3 does not have a core / cladding structure, the outer diameter of the first lens surface 20 is set to C. By preventing the corresponding value of conditional expression (5) from becoming less than the lower limit value, the outer diameter of the lens L1 does not become too small, so that light leakage from the periphery can be suppressed and light can pass through sufficiently, thereby suppressing a reduction in transmission efficiency. By preventing the corresponding value of conditional expression (5) from becoming more than the upper limit value, the outer diameter of the lens L1 does not become too large, which is conducive to miniaturization. In order to obtain better characteristics, the illumination optical system 10 more preferably satisfies the following conditional expression (5-1).

[0111] 0.8<C / G<1.5 (5)

[0112] 1.0<C / G<1.4 (5-1)

[0113] The illumination optical system 10 preferably satisfies the following conditional formula (6). By preventing the corresponding value of the conditional formula (6) from becoming less than the lower limit, the outer diameter of the lens L1 does not become too large, which is conducive to miniaturization. By preventing the corresponding value of the conditional formula (6) from becoming more than the upper limit, the outer diameter of the lens L1 does not become too small, so it is possible to suppress the leakage of light from the periphery and allow it to pass through sufficiently, thereby suppressing the reduction of transmission efficiency. In order to obtain better characteristics, the illumination optical system 10 more preferably satisfies the following conditional formula (6-1).

[0114] [Formula 15]

[0115]

[0116] [Formula 16]

[0117]

[0118] When the distance on the optical axis Z from the first lens surface 20 to the surface closest to the irradiated body is set to L, and when the lens L1 closest to the light guide 3 has a core / cladding structure, the refractive index of the core 22 with respect to the d-line is set to Nd1, and when the lens L1 closest to the light guide 3 does not have a core / cladding structure, the refractive index of the lens L1 closest to the light guide with respect to the d-line is set to Nd1, the illumination optical system 10 preferably satisfies the following conditional formula (7). That is, L refers to the thickness of the illumination optical system 10 as a whole on the optical axis Z. By preventing the corresponding value of the conditional formula (7) from becoming below the lower limit value, the center thickness of the illumination optical system 10 will not become too large, which is conducive to miniaturization. By preventing the corresponding value of the conditional formula (7) from becoming above the upper limit value, the center thickness of the illumination optical system 10 will not become too small, so the lens is not easily broken. In order to obtain better characteristics, the illumination optical system 10 more preferably satisfies the following conditional formula (7-1).

[0119] -1<L / (Nd1×f)<-0.22 (7)

[0120] -0.5<L / (Nd1×f)<-0.21 (7-1)

[0121] The above-mentioned preferred structures and achievable structures including the structures related to the conditional expressions can be arbitrarily combined, and are preferably appropriately and selectively adopted according to the required specifications.

[0122] As an example, a preferred embodiment of the illumination optical system of the present invention is an illumination optical system arranged at the front end of a light guide of an endoscope, wherein only two or less lenses are provided as lenses and the system has negative optical focal length as a whole, and the first lens surface closest to the light guide side includes a concave surface at the center and a light diffusion surface radially outward of the concave surface, and the above-mentioned conditional formula (1) is satisfied.

[0123] As another example, a preferred embodiment of the illumination optical system of the present invention is an illumination optical system arranged at the front end of a light guide of an endoscope, wherein only two or less lenses are provided as lenses and the system has negative optical focal length as a whole, and the first lens surface closest to the light guide side includes a concave surface at the center and a light diffusion surface radially outward of the concave surface, and the above-mentioned conditional formula (2) is satisfied.

[0124] Next, embodiments of the illumination optical system of the present invention are described with reference to the accompanying drawings. In addition, the reference symbols marked on each lens in the cross-sectional view of each embodiment are used independently in each embodiment to avoid complicating the description and drawings due to the increase in the number of digits of the reference symbols. Therefore, even if the drawings of different embodiments are marked with common reference symbols, they are not necessarily common structures.

[0125] [Example 1]

[0126] A cross-sectional view of the structure of the illumination optical system of Example 1 is shown in FIG. Figure 1 The illustration method is as described above, so some repeated descriptions are omitted here. The illumination optical system of Example 1 is composed of a negative lens L1. The first lens surface closest to the light guide 3 includes a concave surface at the center and a light diffusion surface radially outward of the concave surface. The lens I1 has a core / cladding structure. The above is an overview of the illumination optical system of Example 1.

[0127] For the illumination optical system of Example 1, basic lens data are shown in Table 1, and specifications are shown in Table 2. The table of basic lens data is as follows. The Sn column shows the surface number when the surface closest to the light guide side is set as the first surface and the number increases by 1 as it moves toward the irradiated body side. The R column shows the radius of curvature of each surface. The D column shows the surface spacing on the optical axis between each surface and the surface adjacent to its irradiated body side. The Nd column shows the refractive index of each lens with respect to the d-line. The vd column shows the Abbe number of each lens based on the d-line. For lenses with a core / cladding structure, the refractive index Nd and the Abbe number vd are recorded for the core and cladding, respectively.

[0128] In Table 2, the diameter H of the concave surface in the first lens surface, the diameter G of the emission end surface of the light guide, the diameter C of the fiber core in the direction perpendicular to the optical axis Z in the lens L1, the maximum outer diameter Cm of the illumination optical system and the focal length f of the illumination optical system are shown based on the d line.

[0129] In the data of each table, millimeters are used as the unit of length, but since the optical system can be used even if it is scaled up or scaled down, other appropriate units can also be used. In addition, in each table shown below, the values ​​rounded to a preset number of digits are recorded.

[0130] [Table 1]

[0131] Example 1

[0132]

[0133] [Table 2]

[0134] Example 1

[0135] H 0.612 G 0.85 C 0.96 Cm 1.20 f -0.484

[0136] exist Figure 5 and Figure 6 2 is a cross-sectional view showing the structure and optical path of the illumination optical system of Example 1. Figure 5 and Figure 6 The optical path shown in is the optical path of the light when a plurality of light rays emitted from a plurality of points on the emission end surface of the light guide 3 enter the illumination optical system. Figure 5 The light path of the light incident on the concave surface is shown in Figure 6 The optical path of the light incident on the light diffusion surface is shown in FIG. Figure 5 and Figure 6 In the diagram, the sectional view is shown in the same way as Figure 1 The same, so repeated description is omitted here.

[0137] Unless otherwise specified, the symbols, meanings, recording methods, and graphical representation methods of each data related to the above-mentioned embodiment 1 are also the same in the following embodiments, and therefore, repeated descriptions are omitted below.

[0138] [Example 2]

[0139] exist Figure 7 and Figure 8 A cross-sectional view showing the structure and optical path of the illumination optical system of Example 2 is shown in FIG. Figure 7 The light path of the light incident on the concave surface is shown in Figure 8 The optical path of the light incident on the light diffusion surface is shown in . The illumination optical system of Example 2 has the same structure as the outline of the illumination optical system of Example 1. For the illumination optical system of Example 2, basic lens data are shown in Table 3, and specifications are shown in Table 4.

[0140] [Table 3]

[0141] Example 2

[0142]

[0143] [Table 4]

[0144] Example 2

[0145] H 0.612 G 0.85 C 1.11 Cm 1.20 f 0.484

[0146] [Example 3]

[0147] exist Fig. 9 and Fig.10 A cross-sectional view showing the structure and optical path of the illumination optical system of Example 3 is shown in FIG. Fig. 9 The light path of the light incident on the concave surface is shown in Fig.10 The optical path of the light incident on the light diffusion surface is shown in . The illumination optical system of Example 3 has the same structure as the outline of the illumination optical system of Example 1. For the illumination optical system of Example 3, basic lens data are shown in Table 5, and specifications are shown in Table 6.

[0148] [Table 5]

[0149] Example 3

[0150]

[0151] [Table 6]

[0152] Example 3

[0153] H 0.612 G 0.85 C 1.00 Cm 1.20 f -0.689

[0154] [Example 4]

[0155] exist Fig.11 and Fig.12 A cross-sectional view showing the structure and optical path of the illumination optical system of Example 4 is shown in FIG. Fig.11 The light path of the light incident on the concave surface is shown in Fig.12 The optical path of the light incident on the light diffusion surface is shown in . The illumination optical system of Example 4 includes a negative lens L1 and a parallel plane plate PP without optical focal length in sequence from the light guide 3 side to the irradiated body side. The first lens surface closest to the light guide 3 side includes a concave surface in the center and a light diffusion surface radially outward of the concave surface. Lens L1 has a core / cladding structure. For the illumination optical system of Example 4, basic lens data are shown in Table 7, and specifications are shown in Table 8. In Table 7, the row where Sn is 3 records the data of the bonding agent for bonding lens L1 and parallel plane plate PP.

[0156] [Table 7]

[0157] Example 4

[0158]

[0159] [Table 8]

[0160] Example 4

[0161] H 0.693 G 0.85 C 0.96 Cm 1.20 f -0.538

[0162] [Example 5]

[0163] exist Fig.13 and Fig.14 A cross-sectional view showing the structure and optical path of the illumination optical system of Example 5 is shown in FIG. Fig.13 The light path of the light incident on the concave surface is shown in Fig.14The optical path of the light incident on the light diffusion surface is shown in . The illumination optical system of Example 5 includes a negative lens L1 and a negative lens L2 in sequence from the light guide 3 side toward the irradiated body side, and the lens L1 is bonded to the lens L2. The first lens surface closest to the light guide 3 side includes a concave surface in the center portion and a light diffusion surface radially outward of the concave surface. Lens L1 has a core / cladding structure. In addition, lens L2 does not have a core / cladding structure. For the illumination optical system of Example 5, the basic lens data is shown in Table 9, and the specifications are shown in Table 10. In Table 9, the data of the bonding agent bonding lens L1 and lens L2 are recorded in the row where Sn is 3.

[0164] [Table 9]

[0165] Example 5

[0166]

[0167] [Table 10]

[0168] Example 5

[0169] H 0.612 G 0.85 C 0.95 Cm 1.20 f -0.594

[0170] [Example 6]

[0171] exist Fig.15 and Fig.16 A cross-sectional view showing the structure and optical path of the illumination optical system of Example 6 is shown in FIG. Fig.15 The light path of the light incident on the concave surface is shown in Fig.16 The optical path of the light incident on the light diffusion surface is shown in . The illumination optical system of Example 6 is composed of a negative lens L1. The first lens surface closest to the light guide 3 includes a concave surface of an aspheric surface in the center portion and a light diffusion surface radially outward of the concave surface. For the illumination optical system of Example 6, basic lens data are shown in Table 11, specifications are shown in Table 12, and aspheric coefficients are shown in Table 13. In Example 6, lens L1 does not have a core / cladding structure, so the core diameter C is omitted in Table 12. In addition, the outer diameter Cn of the first lens surface is added to Table 12.

[0172] In the basic lens data, the surface number of the aspheric surface is marked with an *, and the value of the paraxial curvature radius is recorded in the column of the curvature radius of the aspheric surface. In Table 13, the surface number of the aspheric surface is shown in the Sn row, and the numerical values ​​of the aspheric coefficients of each aspheric surface are shown in the KA row and the Am row. The numerical values ​​of the aspheric coefficients in Table 13 are "E±n" (n: integer) means "×10 ±n KA and Am (m=4, 6, 8, ... 16) are aspherical coefficients in the aspherical formula represented by the following formula.

[0173] Zd=C×h2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+∑Am×h m

[0174] in,

[0175] Zd: Aspheric depth (the length of the perpendicular line from a point on the aspheric surface at height h to the plane perpendicular to the optical axis Z that is tangent to the vertex of the aspheric surface)

[0176] h: Height (distance from the optical axis Z to the lens surface)

[0177] C: The reciprocal of the paraxial radius of curvature

[0178] KA, Am: Aspheric coefficients

[0179] The ∑ of the aspherical form refers to the sum related to m.

[0180] [Table 11]

[0181] Example 6

[0182] Sn R D Nd vd 1 0.3100 2* 0.3250 0.2500 1.45850 67.82 3

[0183] [Table 12]

[0184] Example 6

[0185] H 0.615 G 0.85 Cn 0.93 Cm 1.20 f -0.709

[0186] [Table 13]

[0187] Example 6

[0188] Sn 2 K 1.00000000000E+00 A4 3.07853636918E+02 A6 3.41067643384E+04 A8 1.67354510031E+06 A10 4.05667742591E+07 A12 5.14838795038E+08 A14 3.29690809696E+09 A16 8.42936182912E+09

[0189] [Example 7]

[0190] exist Fig.17 and Fig.18 A cross-sectional view showing the structure and optical path of the illumination optical system of Example 7 is shown in FIG. Fig.17 The light path of the light incident on the concave surface is shown in Fig.18 The optical path of the light incident on the light diffusion surface is shown in . The illumination optical system of Example 7 has the same structure as the outline of the illumination optical system of Example 1. For the illumination optical system of Example 7, basic lens data are shown in Table 14, and specifications are shown in Table 15.

[0191] [Table 14]

[0192] Example 7

[0193]

[0194] [Table 15]

[0195] Example 7

[0196] H 0.681 G 0.85 C 0.96 Cm 1.20 f -0.524

[0197] [Example 8]

[0198] exist Fig.19 and Fig. 20 A cross-sectional view showing the structure and optical path of the illumination optical system of Example 8 is shown in FIG. Fig.19 The light path of the light incident on the concave surface is shown in Fig. 20 The optical path of the light incident on the light diffusion surface is shown in . The illumination optical system of Example 8 has the same structure as the outline of the illumination optical system of Example 1. For the illumination optical system of Example 8, basic lens data are shown in Table 16, and specifications are shown in Table 17.

[0199] [Table 16]

[0200] Example 8

[0201]

[0202] [Table 17]

[0203] Example 8

[0204] H 0.679 G 0.85 C 0.96 Cm 1.20 f -0.484

[0205] [Example 9]

[0206] exist Fig.21 and Fig. 22 A cross-sectional view showing the structure and optical path of the illumination optical system of Example 9 is shown in FIG. Fig.21 The light path of the light incident on the concave surface is shown in Fig. 22 The optical path of the light incident on the light diffusion surface is shown in . The illumination optical system of Example 9 has the same structure as the outline of the illumination optical system of Example 1. For the illumination optical system of Example 9, basic lens data are shown in Table 18, and specifications are shown in Table 19.

[0207] [Table 18]

[0208] Example 9

[0209]

[0210] [Table 19]

[0211] Example 9

[0212] H 0.635 G 0.85 C 0.96 Cm 1.20 f 0.484

[0213] Table 20 shows the corresponding values ​​of conditional expressions (1) to (7) of the illumination optical systems of Examples 1 to 9. The corresponding values ​​of the examples shown in Table 20 may be used as the upper limit or lower limit of the conditional expression to set a preferred range of the conditional expression.

[0214] [Table 20]

[0215]

[0216] According to the above data, the illumination optical character systems of Examples 1 to 9 are all small-sized structures with wide light distribution angles and good transmission efficiency.

[0217] Next, an endoscope according to an embodiment of the present invention will be described. Fig.23 Detailed description of the overall configuration of an endoscope according to an embodiment of the present invention is shown in FIG. Fig.23 The endoscope 100 shown mainly includes an operation section 102, an insertion section 104, and a universal cord 106 connected to a connector section (not shown). Most of the insertion section 104 is a flexible section 107 that is bent in an arbitrary direction along an insertion path, a bending section 108 is connected to the front end of the flexible section 107, and a front end section 110 is connected to the front end of the bending section 108. The bending section 108 is provided to direct the front end section 110 to a desired direction, and can be bent by turning a bending operation knob 109 provided on the operation section 102.

[0218] The illumination optical system 10 according to the embodiment of the present invention is disposed at the inner front end of the front end portion 110. Fig.23 , the illumination optical system 10 is schematically shown. The endoscope of the present invention includes the illumination optical system according to the embodiment of the present invention, so that the distal end portion of the insertion portion 104 can be miniaturized and observation can be performed using wide-angle and good illumination light.

[0219] The above examples and embodiments are used to illustrate the technology of the present invention, but the technology of the present invention is not limited to the above examples and embodiments, and various modifications are possible. For example, the radius of curvature, surface spacing, refractive index, Abbe number, and aspheric coefficient of each lens are not limited to the values ​​shown in the above examples, and other values ​​can be used.

[0220] The following supplementary notes are further disclosed with respect to the above-mentioned embodiments and examples.

[0221] [Note 1]

[0222] An illumination optical system is arranged at the front end of a light guide of an endoscope, wherein:

[0223] The lens has only two or less lenses and has negative power as a whole.

[0224] The first lens surface closest to the light guide includes a concave surface at the center and a light diffusion surface radially outward of the concave surface.

[0225] The absolute value of the paraxial curvature radius of the concave surface is set to R,

[0226] The distance on the optical axis from the emission end surface of the light guide to the first lens surface is defined as D.

[0227] When the diameter of the emission end surface of the light guide is G,

[0228] Satisfies the conditional expression (1) expressed as follows:

[0229] [Formula 17]

[0230]

[0231] [Note 2]

[0232] According to the illumination optical system described in Supplementary Note 1, it satisfies the conditional expressions (3) and (4) expressed as follows:

[0233] 0.2<R / G<0.6 (3)

[0234] [Formula 18]

[0235]

[0236] [Note 3]

[0237] The illumination optical system according to Supplement 1 or 2, wherein:

[0238] When the lens closest to the light guide has a core / cladding structure in which a core is covered with a cladding, the diameter of the core in a direction perpendicular to the optical axis is set to C, and when the lens closest to the light guide does not have the core / cladding structure, the outer diameter of the first lens surface is set to C,

[0239] Satisfy the following conditional expressions (5) and (6):

[0240] 0.8<C / G<1.5 (5)

[0241] [Formula 19]

[0242]

[0243] [Note 4]

[0244] An illumination optical system according to any one of Supplementary Notes 1 to 3, wherein:

[0245] The distance on the optical axis from the first lens surface to the surface closest to the irradiated object is defined as L.

[0246] The focal length of the illumination optical system is set to f,

[0247] When the lens closest to the light guide has a core / cladding structure in which a core is covered with a cladding, the refractive index of the core with respect to the d-line is set to Nd1, and when the lens closest to the light guide does not have the core / cladding structure, the refractive index of the lens closest to the light guide with respect to the d-line is set to Nd1,

[0248] Satisfies the conditional expression (7) expressed as follows:

[0249] -1<L / (Nd1×f)<-0.22 (7).

[0250] [Note 5]

[0251] The illumination optical system according to any one of Supplementary Notes 1 to 4, which satisfies the conditional expression (1-1) represented by the following:

[0252] [Formula 20]

[0253]

[0254] [Note 6]

[0255] The illumination optical system according to Supplementary Note 2 satisfies at least one of the following conditional expressions (3-1) and (4-1):

[0256] 0.3<R / G<0.5 (3-1)

[0257] [Formula 21]

[0258]

[0259] [Note 7]

[0260] The illumination optical system according to Supplementary Note 3 satisfies at least one of the following conditional expressions (5-1) and (6-1):

[0261] 1.0<C / G<1.4 (5-1)

[0262] [Formula 22]

[0263]

[0264] [Note 8]

[0265] According to the illumination optical system described in Supplementary Note 4, it satisfies the conditional expression (7-1) represented by the following:

[0266] -0.5<L / (Nd1×f)<-0.21 (7-1).

[0267] [Note 9]

[0268] An illumination optical system is arranged at the front end of a light guide of an endoscope, wherein:

[0269] The lens has only two or less lenses and has negative power as a whole.

[0270] The first lens surface closest to the light guide includes a concave surface at the center and a light diffusion surface radially outward of the concave surface.

[0271] The absolute value of the paraxial curvature radius of the concave surface is set to R,

[0272] The distance on the optical axis from the emission end surface of the light guide to the first lens surface is defined as D.

[0273] The diameter of the emission end face of the light guide is set to G,

[0274] When the focal length of the illumination optical system is set to f,

[0275] Satisfies the conditional expression (2) expressed as follows:

[0276] [Formula 23]

[0277]

[0278] [Note 10]

[0279] According to Supplementary Note 9, the illumination optical system satisfies the following conditional expressions (3) and (4):

[0280] 0.2<R / G<0.6 (3)

[0281] [Formula 24]

[0282]

[0283] [Note 11]

[0284] The illumination optical system according to Supplement 9 or 10, wherein:

[0285] When the lens closest to the light guide has a core / cladding structure in which a core is covered with a cladding, the diameter of the core in a direction perpendicular to the optical axis is set to C, and when the lens closest to the light guide does not have the core / cladding structure, the outer diameter of the first lens surface is set to C,

[0286] Satisfy the following conditional expressions (5) and (6):

[0287] 0.8<C / G<1.5 (5)

[0288] [Formula 25]

[0289]

[0290] [Note 12]

[0291] An illumination optical system according to any one of Supplementary Notes 9 to 11, wherein:

[0292] The distance on the optical axis from the first lens surface to the surface closest to the irradiated object is defined as L.

[0293] The focal length of the illumination optical system is set to f,

[0294] When the lens closest to the light guide has a core / cladding structure in which a core is covered with a cladding, the refractive index of the core with respect to the d-line is set to Nd1, and when the lens closest to the light guide does not have the core / cladding structure, the refractive index of the lens closest to the light guide with respect to the d-line is set to Nd1,

[0295] Satisfies the conditional expression (7) expressed as follows:

[0296] -1<L / (Nd1×f)<-0.22 (7).

[0297] [Note 13]

[0298] According to Supplementary Note 9, the illumination optical system satisfies the conditional expression (2-1) represented as follows:

[0299] [Formula 26]

[0300]

[0301] [Note 14]

[0302] The illumination optical system according to Supplementary Note 10 satisfies at least one of the following conditional expressions (3-1) and (4-1):

[0303] 0.3<R / G<0.5(3-1)

[0304] [Formula 27]

[0305]

[0306] [Note 15]

[0307] The illumination optical system according to Supplementary Note 11 satisfies at least one of the following conditional expressions (5-1) and (6-1):

[0308] 1.0<C / G<1.4(5-1)

[0309] [Formula 28]

[0310]

[0311] [Note 16]

[0312] According to Supplementary Note 12, the illumination optical system satisfies the conditional expression (7-1) represented as follows:

[0313] -0.5<L / (Nd1×f)<-0.21 (7-1).

[0314] [Note 17]

[0315] An endoscope comprising the illumination optical system according to any one of Supplementary Notes 1 to 16.

Claims

1. An illumination optical system, which is arranged at the front end of a light guide of an endoscope, wherein: The lens has only two or less lenses and has negative power as a whole. The first lens surface closest to the light guide includes a concave surface at the center and a light diffusion surface radially outward of the concave surface. The absolute value of the paraxial curvature radius of the concave surface is set to R, The distance on the optical axis from the emission end surface of the light guide to the first lens surface is defined as D. When the diameter of the emission end surface of the light guide is G, Satisfies the conditional expression (1) expressed as follows: [Formula 1] 2. The illumination optical system according to claim 1, which satisfies conditional expressions (3) and (4) expressed as follows: 0.2 <R / G<0.6 (3) [Formula 2] 3. The illumination optical system according to claim 1 or 2, wherein: When the lens closest to the light guide has a core / cladding structure in which a core is covered with a cladding, the diameter of the core in a direction perpendicular to the optical axis is set to C, and when the lens closest to the light guide does not have the core / cladding structure, the outer diameter of the first lens surface is set to C, Satisfy the following conditional expressions (5) and (6): 0.8 <C / G<1.5 (5) [Formula 3] 4. The illumination optical system according to claim 1 or 2, wherein: The distance on the optical axis from the first lens surface to the surface closest to the irradiated object is defined as L. The focal length of the illumination optical system is set to f, When the lens closest to the light guide has a core / cladding structure in which a core is covered with a cladding, the refractive index of the core with respect to the d-line is set to Nd1, and when the lens closest to the light guide does not have the core / cladding structure, the refractive index of the lens closest to the light guide with respect to the d-line is set to Nd1, Satisfies the conditional expression (7) expressed as follows: -1 <L / (Ndl×f)<-0.22 (7)。 5. The illumination optical system according to claim 1, which satisfies the conditional expression (1-1) expressed as follows: [Formula 4] 6. The illumination optical system according to claim 2, which satisfies at least one of the conditional expressions (3-1) and (4-1) expressed as follows: 0.3 <R / G<0.5(3-1) [Formula 5] 7. The illumination optical system according to claim 3, which satisfies at least one of the conditional expressions (5-1) and (6-1) expressed as follows: 1.0 <C / G<1.4(5-1) [Formula 6] 8. The illumination optical system according to claim 4, which satisfies the conditional expression (7-1) expressed as follows: -0.5 <L / (Nd1×f)<-0.21(7-1)。 9. An illumination optical system, arranged at the front end of a light guide of an endoscope, wherein: The lens has only two or less lenses and has negative power as a whole. The first lens surface closest to the light guide includes a concave surface at the center and a light diffusion surface radially outward of the concave surface. The absolute value of the paraxial curvature radius of the concave surface is set to R, The distance on the optical axis from the emission end surface of the light guide to the first lens surface is defined as D. The diameter of the emission end face of the light guide is set to G, When the focal length of the illumination optical system is set to f, Satisfies the conditional expression (2) expressed as follows: [Formula 7] 10. The illumination optical system according to claim 9, which satisfies conditional expressions (3) and (4) expressed as follows: 0.2 <R / G<0.6 (3) [Formula 8] 11. The illumination optical system according to claim 9 or 10, wherein: When the lens closest to the light guide has a core / cladding structure in which a core is covered with a cladding, the diameter of the core in a direction perpendicular to the optical axis is set to C, and when the lens closest to the light guide does not have the core / cladding structure, the outer diameter of the first lens surface is set to C, Satisfy the following conditional expressions (5) and (6): 0.8 <C / G<1.5 (5) [Formula 9] 12. The illumination optical system according to claim 9 or 10, wherein: The distance on the optical axis from the first lens surface to the surface closest to the irradiated object is defined as L. The focal length of the illumination optical system is set to f, When the lens closest to the light guide has a core / cladding structure in which a core is covered with a cladding, the refractive index of the core with respect to the d-line is set to Nd1, and when the lens closest to the light guide does not have the core / cladding structure, the refractive index of the lens closest to the light guide with respect to the d-line is set to Nd1, Satisfies the conditional expression (7) expressed as follows: -1 <L / (Nd1×f)<-0.22 (7)。 13. The illumination optical system according to claim 9, which satisfies the conditional expression (2-1) expressed as follows: [Formula 10] 14. The illumination optical system according to claim 10, which satisfies at least one of the conditional expressions (3-1) and (4-1) expressed as follows: 0.3 <R / G<0.5(3-1) [Formula 11] 15. The illumination optical system according to claim 11, which satisfies at least one of the conditional expressions (5-1) and (6-1) expressed as follows: 1.0 <C / G<1.4(5-1) [Formula 12] 16. The illumination optical system according to claim 12, which satisfies the conditional expression (7-1) expressed as follows: -0.5 <L / (Nd1×f)<-0.21(7-1)。 17 . An endoscope comprising the illumination optical system according to claim 1 .

Images