Illumination optical system and endoscope

Abstract

To provide a compact illumination optical system having a wide light distribution angle and excellent transmission efficiency, and to provide an endoscope equipped with the illumination optical system.SOLUTION: The illumination optical system is disposed at a distal end of a light guide of the endoscope. A first surface, which is a surface of the illumination optical system closest to the light guide, includes a plurality of annular grooves arranged concentrically around an optical axis of the illumination optical system. The groove has an inclined surface that narrows the groove width from the light guide side toward the irradiated body side. In the first surface, all surfaces perpendicular to the optical axis adjacent to the inclined surface of the groove portion are light diffusion surfaces. The light diffusion surface includes a first light diffusion surface between adjacent grooves. The illumination optical system satisfies a predetermined conditional expression.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Conventionally, illumination optical systems that are arranged at the tip of an insertion part of an endoscope and that illuminate a subject are known, for example, from the illumination optical systems described in Patent Documents 1 and 2 below. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-043620 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-244050 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for an illumination optical system that is compact, yet has a wide light distribution angle and good transmission efficiency.

[0005] The present disclosure provides an illumination optical system that is compact, yet has a wide light distribution angle and good transmission efficiency, and an endoscope equipped with this illumination optical system. [Means for solving the problem]

[0006] A first aspect of the present disclosure is an illumination optical system disposed at the tip of a light guide of an endoscope, wherein a first surface of the illumination optical system, which is the surface closest to the light guide, includes a plurality of annular grooves arranged concentrically around the optical axis of the illumination optical system, and the grooves have slopes that narrow the groove width from the light guide side to the illuminated body side, and all surfaces of the first surface that are perpendicular to the optical axis and adjacent to the slopes of the grooves are light diffusing surfaces, and the light diffusing surfaces include first light diffusing surfaces located between adjacent grooves, and when the radial length of the first light diffusing surface is C and the distance from the optical axis to the outermost diameter position of the outermost groove is A, 0.01 <C / A<0.3 (1) The conditional expression (1) expressed as follows is satisfied.

[0007] A second aspect of the present disclosure is the illumination optical system of the first aspect, wherein the light diffusing surface includes a second light diffusing surface adjacent to the outer diameter side slope of the outermost groove portion.

[0008] A third aspect of the present disclosure is an illumination optical system according to the second aspect, in which, when the radius of the illumination optical system is B, the distance in the direction of the optical axis from the second light diffusing surface to the intersection of the surface of the illumination optical system closest to the object to be illuminated and the optical axis is L, and the angle formed by the inclined surface on the outer diameter side of the outermost groove portion with a plane perpendicular to the optical axis is θ, 0.5<(BA) / (L×tanθ)<1.5 (2) Conditional expression (2) expressed as follows is satisfied.

[0009] A fourth aspect of the present disclosure provides an illumination optical system according to the second aspect, in which, when the distance in the direction of the optical axis from the second light diffusing surface to the intersection point between the surface of the illumination optical system closest to the object to be illuminated and the optical axis is L, and the distance in the direction of the optical axis from the deepest part of the groove portion closest to the optical axis to the intersection point is K, 0.5 <K / L<0.88 (3) Conditional expression (3) expressed as follows is satisfied.

[0010] A fifth aspect of the present disclosure provides an illumination optical system according to the second aspect, in which, when L is the distance in the direction of the optical axis from the second light diffusing surface to the intersection point between the surface of the illumination optical system closest to the object to be illuminated and the optical axis, K is the distance in the direction of the optical axis from the deepest part of the groove closest to the optical axis to the intersection point, and φ is the angle formed by the slope of the groove closest to the optical axis with a plane perpendicular to the optical axis, 0.104<(LK) / (A×tanφ)<0.4 (4) Conditional expression (4) expressed as follows is satisfied.

[0011] In a sixth aspect of the present disclosure, when the radius of the exit end surface of the light guide is G, 1 <G / A<1.8 (5) Conditional expression (5) expressed as follows is satisfied.

[0012] A seventh aspect of the present disclosure is an illumination optical system according to the first aspect, wherein, in the illumination optical system according to the first aspect, the angle formed by the inclined surface on the outer diameter side of the outermost groove portion and a plane perpendicular to the optical axis is defined as θ, the angle formed by the inclined surface on the optical axis side of the outermost groove portion and a plane perpendicular to the optical axis is defined as ω, and the units of θ and ω are degrees, 20<|ω-θ|<50 (6) Conditional expression (6) expressed as follows is satisfied.

[0013] An eighth aspect of the present disclosure is an illumination optical system according to the first aspect, wherein, when the radius of the illumination optical system is B, 1.2 Conditional expression (7) expressed as follows is satisfied.

[0014] A ninth aspect of the present disclosure is an endoscope including any one of the first to eighth illumination optical systems.

[0015] In this specification, the terms "consisting of" and "consisting of" are intended to mean that, in addition to the listed components, a lens having substantially no refractive power, optical elements other than lenses such as an aperture, a filter, and a cover glass, as well as a lens flange and a lens barrel, etc. may also be included. [Effects of the Invention]

[0016] ​ According to the present disclosure, it is possible to provide an illumination optical system that is compact, yet has a wide light distribution angle and good transmission efficiency, and an endoscope equipped with this illumination optical system. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of the configuration of an illumination optical system according to an embodiment, corresponding to the illumination optical system of Example 1. FIG. [Figure 2] 2 is a diagram showing the configuration of the illumination optical system of FIG. 1 on a plane perpendicular to the optical axis. [Figure 3] 2 is a cross-sectional view showing the configuration and optical paths of the illumination optical system of FIG. 1. [Figure 4] FIG. 10 is a diagram for explaining a comparative example. [Figure 5] 2 is a diagram for explaining symbols in conditional expressions in the illumination optical system of FIG. 1. FIG. [Figure 6] 4 is a graph showing the light distribution characteristics of the illumination optical system of Example 1. [Figure 7] FIG. 10 is a cross-sectional view showing the configuration and optical paths of an illumination optical system according to a second embodiment. [Figure 8] FIG. 10 is a diagram showing the configuration of an illumination optical system of Example 2 on a plane perpendicular to the optical axis. [Figure 9] 10 is a graph showing the light distribution characteristics of the illumination optical system of Example 2. [Figure 10] FIG. 10 is a cross-sectional view showing the configuration and optical paths of an illumination optical system according to a third embodiment. [Figure 11] FIG. 10 is a diagram showing the configuration of an illumination optical system of Example 3 on a plane perpendicular to the optical axis. [Figure 12] 10 is a graph showing the light distribution characteristics of the illumination optical system of Example 3. [Figure 13] FIG. 10 is a cross-sectional view showing the configuration of an illumination optical system according to a fourth embodiment. [Figure 14] FIG. 10 is a cross-sectional view showing the configuration and optical paths of an illumination optical system according to a fourth embodiment. [Figure 15] FIG. 10 is a diagram showing the configuration of an illumination optical system of Example 4 on a plane perpendicular to the optical axis. [Figure 16]FIG. 10 is a diagram for explaining symbols in conditional expressions in the illumination optical system of Example 4. [Figure 17] 10 is a graph showing the light distribution characteristics of the illumination optical system of Example 4. [Figure 18] FIG. 10 is a cross-sectional view showing the configuration and optical paths of an illumination optical system according to a fifth embodiment. [Figure 19] FIG. 10 is a diagram showing the configuration of an illumination optical system of Example 5 on a plane perpendicular to the optical axis. [Figure 20] 10 is a graph showing the light distribution characteristics of the illumination optical system of Example 5. [Figure 21] FIG. 10 is a cross-sectional view showing the configuration and optical paths of an illumination optical system according to a sixth embodiment. [Figure 22] FIG. 13 is a diagram showing the configuration of an illumination optical system of Example 6 on a plane perpendicular to the optical axis. [Figure 23] 13 is a graph showing the light distribution characteristics of the illumination optical system of Example 6. [Figure 24] 1 is a schematic configuration diagram of an endoscope according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Fig. 1 shows the configuration of an illumination optical system 10 according to one embodiment of the present disclosure, taken along a cross section including an optical axis Z. The illumination optical system 10 shown in Fig. 1 corresponds to Example 1, which will be described later.

[0019] The illumination optical system 10 is an optical system arranged at the tip of a light guide 50 of an endoscope. The light guide 50 is made up of a bundle fiber in which multiple optical fibers are bundled, and outputs 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 50 and is emitted from the illumination optical system 10 to become illumination light. When the illumination optical system 10 is arranged at the tip of the insertion section of the endoscope, the illumination light illuminates an illuminated object (not shown) that is the object to be observed. FIG. 1 shows a cross-sectional view of the illumination optical system 10 including the optical axis Z, with the left side being the light source side and the right side being the illuminated object side.

[0020] Of the surfaces of the illumination optical system 10, the first surface 10a is the surface of the illumination optical system 10 closest to the light guide 50. The first surface 10a includes a plurality of annular grooves arranged concentrically around the optical axis Z. The grooves have slopes that narrow the groove width from the light guide side toward the illuminated object side. Figure 2 shows the configuration of the illumination optical system 10 in Figure 1 on a plane perpendicular to the optical axis Z as viewed from the illuminated object side.

[0021] As an example, the illumination optical system 10 shown in Figure 1 is composed of one optical element L1. However, the illumination optical system of the present disclosure may include multiple elements, and may also include an optical element without refractive power, such as a plane-parallel plate. The illumination optical system 10 in Figure 1 has a rotationally symmetric configuration with the optical axis Z as the axis of rotation. In Figure 1, to avoid cluttering the illustration, some reference numerals are omitted for parts below the optical axis Z.

[0022] As an example, the first surface 10a of the illumination optical system 10 in FIG. 1 includes three grooves 21, 22, and 23, arranged in this order from the optical axis side to the outer diameter side. Groove 21 on the optical axis has a V-shaped cross section and includes a slope 21a. Groove 22 has a substantially V-shaped cross section and includes a slope 22a on the outer diameter side and a slope 22b on the optical axis side. Groove 23 has a substantially V-shaped cross section and includes a slope 23a on the outer diameter side and a slope 23b on the optical axis side. Making each groove V-shaped or substantially V-shaped in a cross section including the optical axis Z is advantageous for widening the light distribution angle.

[0023] Hereinafter, for the sake of convenience, when there is no need to distinguish between the grooves 21, 22, and 23, they will be simply referred to as "grooves." Furthermore, when there is no need to distinguish between the inclined surfaces of the grooves, they will be simply referred to as "inclined surfaces."

[0024] Of the first surface 10a, all surfaces perpendicular to the optical axis Z that are adjacent to the slopes of the grooves are configured as light diffusing surfaces. Light rays that pass through the light diffusing surfaces are diffused and projected onto the illuminated object in a state where the light is widely spread. Therefore, the inclusion of a light diffusing surface on the first surface 10a is advantageous in widening the light distribution angle.

[0025] In the description of this specification, "perpendicular" refers not only to perfect perpendicularity but also to approximately perpendicularity that includes an error generally acceptable in the technical field to which the technology of the present disclosure belongs. Furthermore, the above "plane perpendicular to the optical axis Z" refers to the shape compared to the groove portion when viewed macroscopically, not microscopically.

[0026] The light diffusing surface is a surface that has the function of diffusing light. The light diffusing surface may be a roughened surface having fine irregularities, for example, a surface that has been subjected to a graining treatment by polishing. The light diffusing surface may also be a surface provided with a layer containing a substance having a light diffusing function, such as glass beads. The surface roughness of the light diffusing surface having fine irregularities can typically be several μm or less in arithmetic mean roughness Ra, and is preferably 0.3 to 0.7 μm.

[0027] In the example of FIG. 1 , a light diffusing surface 31 is formed between adjacent groove portions 21 and 22 adjacent to slopes 21a and 22b, and a light diffusing surface 32 is formed between adjacent groove portions 22 and 23 adjacent to slopes 22a and 23b. A light diffusing surface 33 is also formed on the outer diameter side adjacent to slope 23a of the outermost groove portion 23. The light diffusing surfaces 31 and 32 are an example of a first light diffusing surface of the technology disclosed herein. The light diffusing surface 33 is an example of a second light diffusing surface of the technology disclosed herein. Hereinafter, for convenience of explanation, when it is not necessary to distinguish between the light diffusing surfaces 31, 32, and 33, they will be simply referred to as "light diffusing surfaces."

[0028] Figure 3 shows the optical paths of the illumination optical system 10 of Figure 1 having the above configuration using solid lines and dashed dotted lines. Figure 3 shows the state of light rays when multiple light rays emitted from multiple points on the exit end surface of the light guide 50 are incident on the illumination optical system 10. As shown in Figure 3, the illumination optical system 10 of Figure 1 achieves a wide light distribution angle.

[0029] The effects of the illumination optical system 10 of this example will be described in detail below. By providing the grooves with the above-mentioned slopes, the light rays emitted from the light guide 50 can be emitted from the illumination optical system 10 as light rays with a large divergence angle. In the illumination optical system 10X made up of a negative lens of the comparative example shown in FIG. 4, which will be described later, the divergence angle of the light rays emitted from near the center of the light guide 50 is small. In contrast, in the illumination optical system 10 of this example, even the light rays emitted from near the center of the light guide 50 can be emitted from the illumination optical system 10 as light rays with a large divergence angle.

[0030] In this example, by providing multiple annular grooves, the thickness of the illumination optical system 10 in the optical axis direction can be made thinner than the configuration described in Patent Document 2. Furthermore, by providing multiple annular grooves, the area of ​​the grooves on the first surface 10a can be reduced, which is advantageous for making the illumination optical system 10 thinner. Note that in this example, even if the area of ​​the grooves is reduced, a wide light distribution angle can be maintained because a light diffusing surface is provided. In particular, in this example, the light diffusing surface 33 is provided adjacent to the slope 23a of the outermost groove 23, so a wide light distribution angle can be maintained even if the area of ​​the grooves is reduced. As described above, the illumination optical system 10 of this example can achieve both compactness and a wide light distribution angle.

[0031] Furthermore, because this example has a light diffusion surface between the grooves, it is advantageous in that it reduces uneven light distribution while widening the light distribution angle, as described below. The exit end surface of the light guide 50, which is made of a bundle fiber, includes dark and bright areas because the non-emitting cladding, the gaps between the fibers, and the emitting cores are arranged on the same plane. If an image of the exit end surface of this light guide 50 were to be formed on the illuminated object, a bright and dark pattern would be projected onto the illuminated object, resulting in significant uneven light distribution. If the projected image of this bright and dark pattern were too clear, it could interfere with observation of the illuminated object. In this regard, this example, which has a light diffusion surface, can diffuse light rays, thereby suppressing the projection of the bright and dark pattern on the illuminated object and thereby suppressing uneven light distribution.

[0032] FIG. 4 shows, as a comparative example, the state of light rays in an illumination optical system 10X when the illumination optical system 10 in FIG. 1 is replaced with a lens L1X that has neither a groove nor a light diffusion surface. The lens L1X in FIG. 4 is a negative lens with a concave surface facing the light guide. In the example in FIG. 4, the divergence angle of light rays emitted from near the center of the light guide 50 tends to be small, and the divergence angle of the light rays tends to increase as the emission position moves from the center toward the outer diameter. In this configuration, if the outer diameter of the lens L1X is reduced to achieve compactness, there is a risk that light rays with large emission angles will be blocked. In other words, in the example in FIG. 4, it is difficult to achieve both compactness and a wide light distribution angle.

[0033] Furthermore, since the lens L1X, which does not have a light diffusing surface, only slightly diffuses the light, the light is projected onto the illuminated object with a small spread. Therefore, in the illumination optical system 10X, it is difficult to maintain a wide light distribution angle compared to the illumination optical system 10 of this example, and a projected image of a light and dark pattern caused by the dark and bright portions of the light guide 50 described above will be generated on the illuminated object, increasing the possibility of uneven light distribution.

[0034] Furthermore, because light from a light guide actually has a divergence angle, light leakage may occur when light emitted from a position near the outer periphery of the light guide's exit end face passes through the concave surface of lens L1X. To achieve compactness, the diameter of the concave surface of lens L1X is sometimes configured to be equal to the diameter of the light guide's exit end face, and this configuration is prone to light leakage. Light leakage reduces the light transmission efficiency. In contrast, the illumination optical system 10 of this example shown in FIG. 1 has a light diffusing surface 33 adjacent to the slope 23a of the groove portion 23 on the outermost diameter side, thereby suppressing the reduction in light transmission efficiency caused by the light leakage.

[0035] Next, preferred and possible configurations for the conditional expressions will be described. In the following description of the conditional expressions, to avoid redundant explanation, the same symbols are used for elements with the same definitions, and some of the duplicated explanations of the symbols will be omitted. In the following description of the conditional expressions, the light diffusion surface between adjacent grooves will be referred to as the first light diffusion surface, and the light diffusion surface adjacent to the outer diameter side slope of the outermost groove will be referred to as the second light diffusion surface.

[0036] It is preferable that the illumination optical system 10 satisfy the following conditional expression (1). Here, the radial length of the first light diffusing surface is defined as C. The distance from the optical axis Z to the outermost diameter of the outermost groove is defined as A. The radial direction is perpendicular to the optical axis Z. If there are multiple first light diffusing surfaces, the average radial length of these multiple first light diffusing surfaces is defined as C. FIG. 5 shows a partial enlargement of the illumination optical system 10 of FIG. 1, illustrating the length C and distance A as examples. Some reference numerals are omitted in FIG. 5. By ensuring that the corresponding value of conditional expression (1) is not equal to or less than the lower limit, the divergence angle of the emitted light can be increased, making it easier to ensure a wide light distribution angle. By ensuring that the corresponding value of conditional expression (1) is not equal to or greater than the upper limit, miniaturization is facilitated and light transmission efficiency is improved. 0.01 <C / A<0.3 (1)

[0037] In order to obtain better characteristics, the lower limit of conditional expression (1) should preferably be set to 0.015, more preferably 0.02, and even more preferably 0.025. In order to obtain better characteristics, the upper limit of conditional expression (1) should preferably be set to 0.25, more preferably 0.2, and even more preferably 0.15.

[0038] It is preferable that the illumination optical system 10 satisfy the following conditional expression (2). Here, the radius of the illumination optical system 10 is defined as B. The distance in the direction of the optical axis Z from the second light diffusing surface to the intersection of the surface 10b of the illumination optical system 10 closest to the object to be illuminated and the optical axis Z is defined as L. The angle formed by the inclined surface on the outer diameter side of the outermost groove portion and a plane perpendicular to the optical axis Z is defined as θ. θ is an acute angle, not an obtuse angle. As an example, FIG. 5 shows the radius B, distance L, and angle θ. Ensuring that the corresponding value of conditional expression (2) is not equal to or less than the lower limit is advantageous for improving the light transmission efficiency. Ensuring that the corresponding value of conditional expression (2) is not equal to or greater than the upper limit can increase the divergence angle of the emitted light, making it easier to ensure a wide light distribution angle. 0.5<(BA) / (L×tanθ)<1.5 (2)

[0039] In order to obtain better characteristics, the lower limit of conditional expression (2) should preferably be set to 0.53, more preferably 0.56, and even more preferably 0.6.In order to obtain better characteristics, the upper limit of conditional expression (2) should preferably be set to 1.35, more preferably 1.25, and even more preferably 1.1.

[0040] It is preferable that the illumination optical system 10 satisfy the following conditional expression (3). Here, K is the distance in the direction of the optical axis Z from the deepest part of the groove closest to the optical axis Z to the intersection of the surface 10b of the illumination optical system 10 closest to the object to be illuminated and the optical axis Z. Note that if a groove is located on the optical axis, the groove located on the optical axis is the groove closest to the optical axis Z. As an example, FIG. 5 shows the above-mentioned deepest part 21c and the distance K. In the example of FIG. 5, the deepest part 21c is located on the optical axis. By ensuring that the value corresponding to conditional expression (3) is not equal to or less than the lower limit, the thickness does not become too thin, and therefore cracks are less likely to occur. By ensuring that the value corresponding to conditional expression (3) is not equal to or greater than the upper limit, the light intensity near the center can be prevented from becoming too high compared to other parts, making it easier to uniformize the light intensity distribution of the illumination light emitted from the illumination optical system 10. 0.5 <K / L<0.88 (3)

[0041] In order to obtain better characteristics, the lower limit of conditional expression (3) should preferably be set to 0.53, more preferably 0.57, and even more preferably 0.6.In order to obtain better characteristics, the upper limit of conditional expression (3) should preferably be set to 0.85, more preferably 0.82, and even more preferably 0.8.

[0042] If the angle formed by the inclined surface of the groove portion closest to the optical axis Z and the plane perpendicular to the optical axis Z is φ, it is preferable that the illumination optical system 10 satisfies the following conditional expression (4). φ is an acute angle, not an obtuse angle. As an example, FIG. 5 shows the above angle φ. By ensuring that the corresponding value of conditional expression (4) is not equal to or less than the lower limit, it is possible to prevent the light intensity near the center from becoming too high compared to other parts, making it easier to homogenize the light intensity distribution of the illumination light emitted from the illumination optical system 10. By ensuring that the corresponding value of conditional expression (4) is not equal to or greater than the upper limit, the thickness does not become too thin, making it less likely to crack. 0.104<(LK) / (A×tanφ)<0.4 (4)

[0043] In order to obtain better characteristics, the lower limit of conditional expression (4) should preferably be set to 0.11, more preferably 0.12, and even more preferably 0.13. In order to obtain better characteristics, the upper limit of conditional expression (4) should preferably be set to 0.37, more preferably 0.33, and even more preferably 0.3.

[0044] When the radius of the exit end surface of the light guide is G, it is preferable that the illumination optical system 10 satisfy the following conditional expression (5). As an example, the above radius G is shown in FIG. 1. By ensuring that the corresponding value of conditional expression (5) is not equal to or smaller than the lower limit, miniaturization becomes easier and it is advantageous for improving the light transmission efficiency. By ensuring that the corresponding value of conditional expression (5) is not equal to or larger than the upper limit, the divergence angle of the exiting light can be increased, making it easier to ensure a wide light distribution angle. 1 <G / A<1.8 (5)

[0045] In order to obtain better characteristics, the lower limit of conditional expression (5) should preferably be set to 1.06, more preferably 1.08, and even more preferably 1.1.In order to obtain better characteristics, the upper limit of conditional expression (5) should preferably be set to 1.7, more preferably 1.6, and even more preferably 1.45.

[0046] It is preferable that the illumination optical system 10 satisfy the following conditional expression (6). Here, ω is the angle formed by the optical axis-side slope of the outermost groove portion and a plane perpendicular to the optical axis Z. The units of θ and ω are degrees. ω is an acute angle, not an obtuse angle. As an example, FIG. 5 shows the above angle ω. By ensuring that the corresponding value of conditional expression (6) is not equal to or less than the lower limit, it is possible to prevent the light intensity near the center from becoming too high compared to other parts, making it easier to homogenize the light intensity distribution of the illumination light emitted from the illumination optical system 10. By ensuring that the corresponding value of conditional expression (6) is not equal to or greater than the upper limit, it is advantageous for improving the light transmission efficiency. 20<|ω-θ|<50 (6)

[0047] In order to obtain better characteristics, it is more preferable that the lower limit of conditional expression (6) be set to 21, even more preferably to 22, and even more preferably to 24. In order to obtain better characteristics, it is more preferable that the upper limit of conditional expression (6) be set to 48, even more preferably to 46, and even more preferably to 44.

[0048] It is preferable that the illumination optical system 10 satisfies the following conditional expression (7). By ensuring that the corresponding value of conditional expression (7) is not equal to or smaller than the lower limit, miniaturization becomes easier and is advantageous for improving light transmission efficiency. By ensuring that the corresponding value of conditional expression (7) is not equal to or larger than the upper limit, the spread angle of the emitted light can be increased, making it easier to ensure a wide light distribution angle. 1.2

[0049] ​In order to obtain better characteristics, the lower limit of conditional expression (7) should preferably be set to 1.35, more preferably 1.45, and even more preferably 1.55.In order to obtain better characteristics, the upper limit of conditional expression (7) should preferably be set to 2.3, more preferably 2.15, and even more preferably 2.

[0050] The above-described preferred and possible configurations, including those relating to the conditional expressions, can be arbitrarily combined within a range that does not contradict each other, and it is preferable that they be selectively adopted as appropriate according to the required specifications.

[0051] As an example, a preferred embodiment of the illumination optical system of the present disclosure is an illumination optical system arranged at the tip of a light guide of an endoscope, wherein a first surface of the illumination optical system, which is the surface closest to the light guide, includes a plurality of annular grooves arranged concentrically around the optical axis Z of the illumination optical system, and the grooves have slopes that narrow the groove width from the light guide side to the illuminated body side, and all surfaces of the first surface that are perpendicular to the optical axis Z and adjacent to the slopes of the grooves are light diffusing surfaces, and the light diffusing surfaces include first light diffusing surfaces located between adjacent grooves, and the illumination optical system satisfies the above conditional formula (1).

[0052] Next, examples of the illumination optical system of the present disclosure will be described with reference to the drawings. Note that the reference symbols assigned to the optical elements in the drawings of each example are used independently for each example to avoid cluttering the explanation and drawings due to an increase in the number of digits in the reference symbols. Therefore, even if common reference symbols are assigned in drawings of different examples, this does not necessarily mean that the optical elements share the same configuration.

[0053] [Example 1] The configuration of the illumination optical system of Example 1 is shown in FIGS. 1 and 2, and the optical path of the illumination optical system of Example 1 is shown in FIG. 3. The illustration methods are as described above, so some overlapping explanations will be omitted here. The illumination optical system of Example 1 is composed of a single optical element L1. The first surface 10a closest to the light guide 50 includes grooves 21, 22, and 23 and light diffusion surfaces 31, 32, and 33. The grooves 21, 22, and 23 are annular grooves arranged concentrically around the optical axis Z, and have a V-shaped or approximately V-shaped cross section including the optical axis Z. The groove 21 has a slope 21a. The groove 22 has a slope 22a on the outer diameter side and a slope 22b on the optical axis side. The groove 23 has a slope 23a on the outer diameter side and a slope 23b on the optical axis side. A light diffusing surface 31 is provided between groove portion 21 and groove portion 22, a light diffusing surface 32 is provided between groove portion 22 and groove portion 23, and a light diffusing surface 33 is provided on the outer diameter side adjacent to groove portion 23. Light diffusing surfaces 31, 32, and 33 are surfaces perpendicular to optical axis Z, and light diffusing surfaces 31, 32, and 33 are positioned at the same position in the optical axis direction. This completes the overview of the illumination optical system of Example 1. In the illumination optical system of Example 1, in a cross section including optical axis Z, groove portion 21 has an apex angle near its deepest portion, and grooves 22 and 23 have acute-angle shapes near their deepest portions.

[0054] Table 1 shows the construction data and Table 2 shows the specifications of the illumination optical system of Example 1. The construction data table is written as follows: The Sn column indicates the surface numbers assigned in order from the light guide side toward the illuminated object side. However, because the first surface 10a includes a light diffusing surface and grooves, the light diffusing surface and the deepest part of the grooves are listed as separate surfaces in the table for convenience. The surface numbered 1 corresponds to the light diffusing surfaces 31, 32, and 33. The surface numbered 2 corresponds to the deepest part 21c of the groove 21 on the optical axis (see Figure 5). In an illumination optical system consisting of one optical element L1, the surface numbered 3 corresponds to the surface 10b of the illumination optical system closest to the illuminated object. The R column indicates the radius of curvature of each surface other than surface numbers 1 and 2. The D column indicates the surface distance in the optical axis direction between each surface and the next surface on the illuminated object side. The Nd column shows the refractive index for the d-line (wavelength 587.56 nm (nanometers)). The νd column shows the Abbe number based on the d-line.

[0055] Table 2 shows the values ​​used in the above-mentioned conditional expressions, as well as the values ​​of angles α1 and β1 shown in FIG. 5. α1 is the angle between the inclined surface 22a on the outer diameter side of the groove 22 and a plane perpendicular to the optical axis Z. β1 is the angle between the inclined surface 22b on the optical axis side of the groove 22 and a plane perpendicular to the optical axis Z. FIG. 6 shows a graph of the light distribution characteristics of the illumination optical system of Example 1. In FIG. 6, the horizontal axis represents the angle from the optical axis Z, and the vertical axis represents the radiant intensity. The half angles at half maximum of the graph in FIG. 6 are shown in the bottom column of Table 2.

[0056] In the data in each table, millimeters are used as the unit of length and degrees as the unit of angle, but since the optical system can be used with proportional magnification or reduction, other appropriate units can also be used. Also, in each table below, values ​​are listed rounded to a predetermined number of decimal places.

[0057] [Table 1]

[0058] [Table 2]

[0059] The symbols, meanings, notation and illustration methods of each data item related to the above-mentioned Example 1 are basically the same in the following Examples unless otherwise specified, and therefore, redundant explanations will be omitted below.

[0060] [Example 2] Fig. 7 shows a cross-sectional view illustrating the configuration and optical path of the illumination optical system of Example 2. Fig. 8 shows the configuration of the illumination optical system of Example 2 on a plane perpendicular to the optical axis Z as viewed from the illuminated object side. The illumination optical system of Example 2 has a configuration similar to the outline of the illumination optical system of Example 1. In Fig. 7, some reference numerals are omitted to avoid cluttering the drawing. In the illumination optical system of Example 2, the grooves 21, 22, and 23 have a shape with a curvature near their deepest portions.

[0061] Regarding the illumination optical system of Example 2, construction data is shown in Table 3, specifications are shown in Table 4, and a graph of light distribution characteristics is shown in FIG.

[0062] [Table 3]

[0063] [Table 4]

[0064] [Example 3] FIG. 10 is a cross-sectional view showing the configuration and optical path of the illumination optical system of Example 3. FIG. 11 shows the configuration of the illumination optical system of Example 3 in a plane perpendicular to the optical axis Z as viewed from the illuminated object side. The illumination optical system of Example 3 has a configuration similar to that of the illumination optical system of Example 1. In FIG. 10, some reference numerals are omitted to avoid complication. The shape of the deepest portion of each groove in the illumination optical system of Example 3 is similar to that of the illumination optical system of Example 1. The illumination optical system of Example 3 differs from the illumination optical system of Example 1 in that the outer diameter of the light diffusing surface 33 is smaller than that of Example 1 and a step L1a is formed on the outer diameter side of the light diffusing surface 33. The surface perpendicular to the optical axis Z, which includes the step L1a, is not adjacent to the groove and is not a light diffusing surface.

[0065] Regarding the illumination optical system of Example 3, construction data is shown in Table 5, specifications are shown in Table 6, and a graph of light distribution characteristics is shown in FIG.

[0066] [Table 5]

[0067] [Table 6]

[0068] [Example 4] Fig. 13 shows the configuration of the illumination optical system of Example 4. Fig. 14 shows the configuration of the illumination optical system of Example 4 on a plane perpendicular to the optical axis Z as viewed from the illuminated object side. Fig. 15 shows a cross-sectional view showing the configuration and optical path of the illumination optical system of Example 4. Fig. 16 shows a partially enlarged view of the illumination optical system of Example 4.

[0069] The illumination optical system of Example 4 includes one optical element L1 and one plane-parallel plate PP. The first surface 10a, which is the surface of the illumination optical system closest to the light guide 50, includes grooves 21, 22, 23, and 24 and light diffusing surfaces 31, 32, 33, and 34. The grooves 21, 22, 23, and 24 are annular grooves arranged concentrically around the optical axis Z, and have a V-shaped or approximately V-shaped cross section including the optical axis Z. The groove 21 has a slope 21a. The groove 22 has a slope 22a on the outer diameter side and a slope 22b on the optical axis side. The groove 23 has a slope 23a on the outer diameter side and a slope 23b on the optical axis side. The groove 24 has a slope 24a on the outer diameter side and a slope 24b on the optical axis side. Between groove portion 21 and groove portion 22, a light diffusing surface 31 is formed adjacent to slope 21a and slope 22b. Between groove portion 22 and groove portion 23, a light diffusing surface 32 is formed adjacent to slope 22a and slope 23b. Between groove portion 23 and groove portion 24, a light diffusing surface 33 is formed adjacent to slope 23a and slope 24b. A light diffusing surface 34 is formed on the outer diameter side adjacent to slope 24a of groove portion 24 on the outermost diameter side. The light diffusing surfaces 31, 32, 33, and 34 are surfaces perpendicular to the optical axis Z, and the positions of the light diffusing surfaces 31, 32, 33, and 34 in the optical axis direction are the same. This completes the overview of the illumination optical system of Example 4. In Example 4, the light diffusing surfaces 31, 32, and 33 are first light diffusing surfaces, and the light diffusing surface 34 is a second light diffusing surface. In the illumination optical system of Example 4, in a cross section including the optical axis Z, the groove 21 has an apex angle near its deepest portion 21c (see FIG. 16), and the grooves 22, 23, 24 have acute-angled shapes near their deepest portions.

[0070] Table 7 lists the construction data for the illumination optical system of Example 4, Table 8 lists its specifications, and FIG. 17 shows a graph of its light distribution characteristics. In an illumination optical system consisting of one optical element L1 and one plane-parallel plate PP, the surface with surface number 4 corresponds to the surface 10b of the illumination optical system closest to the illuminated object. Table 8 lists the values ​​used in the above-mentioned conditional expressions and the values ​​of angles α1, β1, α2, and β2 shown in FIG. 16. α1 is the angle between the outer diameter side inclined surface 22a of groove 22 and a plane perpendicular to the optical axis Z. β1 is the angle between the optical axis side inclined surface 22b of groove 22 and a plane perpendicular to the optical axis Z. α2 is the angle between the outer diameter side inclined surface 23a of groove 23 and a plane perpendicular to the optical axis Z. β2 is the angle between the optical axis side inclined surface 23b of groove 23 and a plane perpendicular to the optical axis Z.

[0071] [Table 7]

[0072] [Table 8]

[0073] [Example 5] Fig. 18 shows a cross-sectional view illustrating the configuration and optical path of the illumination optical system of Example 5. Fig. 19 shows the configuration of the illumination optical system of Example 5 on a plane perpendicular to the optical axis Z as viewed from the illuminated object side. The illumination optical system of Example 5 has a configuration similar to the outline of the illumination optical system of Example 4. In Fig. 18, some reference numerals are omitted to avoid cluttering the drawing. In the illumination optical system of Example 5, the grooves 21, 22, 23, and 24 have a shape with curvature near their deepest parts.

[0074] Regarding the illumination optical system of Example 5, construction data is shown in Table 9, specifications are shown in Table 10, and a graph of light distribution characteristics is shown in FIG.

[0075] [Table 9]

[0076] [Table 10]

[0077] [Example 6] FIG. 21 shows a cross-sectional view illustrating the configuration and optical path of the illumination optical system of Example 6. FIG. 22 shows the configuration of the illumination optical system of Example 6 on a plane perpendicular to the optical axis Z as viewed from the illuminated object side. The illumination optical system of Example 6 comprises one optical element L1 and one plane-parallel plate PP. The outer diameter of the optical element L1 is smaller than the outer diameter of the plane-parallel plate PP. The overall outer shape of the illumination optical system of Example 6 has a step, similar to the outer shape of the illumination optical system of Example 3. The surface of the optical element L1 of Example 6 facing the light guide 50 has the same general configuration as the surface of the optical element L1 of Example 3 facing the light guide 50. In FIG. 21, some reference numerals are omitted to avoid complication.

[0078] Regarding the illumination optical system of Example 6, construction data is shown in Table 11, specifications are shown in Table 12, and a graph of light distribution characteristics is shown in FIG.

[0079] [Table 11]

[0080] [Table 12]

[0081] Table 13 shows the corresponding values ​​of conditional expressions (1) to (7) for the illumination optical systems of Examples 1 to 6. The corresponding values ​​of the Examples shown in Table 13 may be used as the upper or lower limit values ​​for the conditional expressions to set preferred ranges for the conditional expressions.

[0082] [Table 13]

[0083] As described above, all of the illumination optical systems of Examples 1 to 6 are constructed to be small in size, yet have a wide light distribution angle and good transmission efficiency.

[0084] Next, an endoscope according to an embodiment of the present disclosure will be described. Fig. 24 shows a schematic overall configuration diagram of an endoscope according to an embodiment of the present disclosure. The endoscope 100 shown in Fig. 24 mainly includes an operation unit 102, an insertion unit 104, and a universal cord 106 connected to a connector unit (not shown). The majority of the insertion unit 104 is a flexible section 107 that can bend in any direction along the insertion path, and a bending section 108 is connected to the tip of the flexible section 107, and a tip unit 110 is connected to the tip of the bending section 108. The bending section 108 is provided to direct the tip unit 110 in a desired direction, and bending operation can be performed by turning a bending operation knob 109 provided on the operation unit 102.

[0085] An illumination optical system 10 according to an embodiment of the present disclosure is disposed at the inner tip of the tip portion 110. Fig. 24 shows a schematic illustration of the illumination optical system 10. Because the endoscope according to the present disclosure is equipped with an illumination optical system according to an embodiment of the present disclosure, it is possible to perform observation using good wide-angle illumination light while miniaturizing the tip portion of the insertion section 104.

[0086] Although the technology of the present disclosure has been described above using embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples and can be modified in various ways. For example, the thickness, interplanar spacing, refractive index, Abbe number, and the like of each component are not limited to the values ​​shown in the above examples and can take other values.

[0087] Although the above examples show an illumination optical system including three or four grooves, the number of grooves included in the illumination optical system may be different from that in the above examples in the technology of the present disclosure. The shape of the grooves can also be modified in various ways without departing from the technology of the present disclosure.

[0088] The following additional notes are provided regarding the above embodiments and examples. [Appendix 1] An illumination optical system disposed at the tip of a light guide of an endoscope, a first surface, which is the surface of the illumination optical system closest to the light guide, includes a plurality of annular grooves arranged concentrically around an optical axis of the illumination optical system; the groove portion has a slope whose groove width narrows from the light guide side toward the illuminated body side, all of the first surfaces that are adjacent to the inclined surfaces of the grooves and perpendicular to the optical axis are light diffusing surfaces; the light diffusion surface includes a first light diffusion surface located between adjacent groove portions, The radial length of the first light diffusing surface is C, When the distance from the optical axis to the outermost diameter position of the outermost groove portion is A, 0.01 <C / A<0.3 (1) An illumination optical system that satisfies conditional expression (1) expressed as follows. [Appendix 2] 2. The illumination optical system according to claim 1, wherein the light diffusion surface includes a second light diffusion surface adjacent to the inclined surface on the outer diameter side of the groove portion on the outermost diameter side. [Appendix 3] The radius of the illumination optical system is B, L is the distance in the direction of the optical axis from the second light diffusing surface to the intersection point between the surface of the illumination optical system closest to the object to be illuminated and the optical axis, When the angle formed by the inclined surface on the outer diameter side of the outermost groove portion and a plane perpendicular to the optical axis is θ, 0.5<(BA) / (L×tanθ)<1.5 (2) 10. An illumination optical system according to claim 2, which satisfies conditional expression (2) expressed as follows: [Appendix 4] L is the distance in the direction of the optical axis from the second light diffusing surface to the intersection point between the surface of the illumination optical system closest to the object to be illuminated and the optical axis, When the distance in the direction of the optical axis from the deepest part of the groove portion closest to the optical axis to the intersection point is K, 0.5 <K / L<0.88 (3) 4. An illumination optical system according to claim 2, which satisfies conditional expression (3) shown below. [Appendix 5] L is the distance in the direction of the optical axis from the second light diffusing surface to the intersection point between the surface of the illumination optical system closest to the object to be illuminated and the optical axis, The distance in the direction of the optical axis from the deepest part of the groove portion closest to the optical axis to the intersection point is K, When the angle formed by the inclined surface of the groove portion closest to the optical axis and a plane perpendicular to the optical axis is φ, 0.104<(LK) / (A×tanφ)<0.4 (4) 5. An illumination optical system according to claim 2, which satisfies conditional expression (4) below. [Appendix 6] When the radius of the exit end face of the light guide is G, 1 <G / A<1.8 (5) 6. An illumination optical system according to claim 1, which satisfies conditional expression (5) below. [Appendix 7] θ is the angle formed by the inclined surface on the outer diameter side of the outermost groove portion and a plane perpendicular to the optical axis, The angle formed by the inclined surface of the outermost groove portion on the optical axis side and the plane perpendicular to the optical axis is ω, If the units of θ and ω are degrees, 20<|ω-θ|<50 (6) 7. An illumination optical system according to claim 1, which satisfies conditional expression (6) below. [Appendix 8] When the radius of the illumination optical system is B, 1.2 8. An illumination optical system according to any one of claims 1 to 7, which satisfies conditional expression (7) shown below. [Appendix 9] An endoscope comprising the illumination optical system according to any one of Supplementary Note 1 to Supplementary Note 8. [Explanation of symbols]

[0089] 10 Illumination optical system 10X illumination optics 10a 1st page 10b side 21, 22, 23, 24 Groove 21a, 21b, 22a, 22b, 23a, 23b, 24a, 24b Slopes 21c Deepest 31, 32, 33, 34 Light diffusion surface 50 Light Guide 100 Endoscope​ 102 Operation section 104 Insertion section 106 Universal Code 107 Soft part 108 Curved section 109 Curvature control knob 110 Tip A. Distance B radius C. Length G radius K distance L distance L1 optical element L1a step L1X Lens PP parallel plane plate Z optical axis α1, α2 angle β1, β2 angle θ angle φ angle ω angle

Claims

1. An illumination optical system disposed at the tip of a light guide of an endoscope, a first surface, which is the surface of the illumination optical system closest to the light guide, includes a plurality of annular grooves arranged concentrically around an optical axis of the illumination optical system; the groove portion has a slope whose groove width narrows from the light guide side toward the illuminated body side, all of the first surfaces that are adjacent to the inclined surfaces of the grooves and perpendicular to the optical axis are light diffusing surfaces; the light diffusion surface includes a first light diffusion surface located between adjacent groove portions, The radial length of the first light diffusing surface is C, When the distance from the optical axis to the outermost diameter position of the groove portion on the outermost diameter side is A, 0.01<C / A<0.3 (1) An illumination optical system that satisfies conditional expression (1) expressed as follows:

2. The illumination optical system according to claim 1 , wherein the light diffusing surface includes a second light diffusing surface adjacent to the inclined surface on the outer diameter side of the groove portion on the outermost diameter side.

3. The radius of the illumination optical system is B, L is the distance in the direction of the optical axis from the second light diffusing surface to the intersection point between the surface of the illumination optical system closest to the object to be illuminated and the optical axis; When the angle formed by the inclined surface on the outer diameter side of the outermost groove portion and a plane perpendicular to the optical axis is θ, 0.5<(B-A) / (L×tanθ)<1.5 (2) 3. The illumination optical system according to claim 2, which satisfies conditional expression (2) expressed as follows:

4. L is the distance in the direction of the optical axis from the second light diffusing surface to the intersection point between the surface of the illumination optical system closest to the object to be illuminated and the optical axis, When the distance in the direction of the optical axis from the deepest part of the groove portion closest to the optical axis to the intersection point is K, 0.5<K / L<0.88 (3) 3. The illumination optical system according to claim 2, which satisfies conditional expression (3) expressed as follows:

5. L is the distance in the direction of the optical axis from the second light diffusing surface to the intersection point between the surface of the illumination optical system closest to the object to be illuminated and the optical axis; The distance in the direction of the optical axis from the deepest part of the groove portion closest to the optical axis to the intersection point is K, When the angle formed by the inclined surface of the groove portion closest to the optical axis and a plane perpendicular to the optical axis is φ, 0.104<(L-K) / (A×tanφ)<0.4 (4) 3. The illumination optical system according to claim 2, which satisfies conditional expression (4) expressed as follows:

6. When the radius of the exit end face of the light guide is G, 1<G / A<1.8 (5) 2. The illumination optical system according to claim 1, which satisfies conditional expression (5) expressed as follows:

7. θ is the angle formed by the inclined surface on the outer diameter side of the outermost groove portion and a plane perpendicular to the optical axis, The angle formed by the inclined surface of the outermost groove portion on the optical axis side and the plane perpendicular to the optical axis is ω, If the units of θ and ω are degrees, 20<|ω−θ|<50 (6) 2. The illumination optical system according to claim 1, which satisfies conditional expression (6) expressed as follows:

8. When the radius of the illumination optical system is B, 1.2<B / A<2.5 (7) 2. The illumination optical system according to claim 1, which satisfies conditional expression (7) expressed as follows:

9. An endoscope comprising the illumination optical system according to any one of claims 1 to 8.

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