Illumination optical system and endoscope

Abstract

To provide an illumination optical system which is compact and has wide light distribution and excellent transmission efficiency, and to provide an endoscope equipped with the illumination optical system.SOLUTION: The illumination optical system includes a light guide of the endoscope and a diffusion plate that is disposed on an emission side of the light guide and diffuses light from the light guide. The diffusion plate includes a substrate and a diffusion surface provided on a surface of the substrate on the light guide side. The light diffusion angle distribution on the diffusion surface varies depending on the incident angle of light on the diffusion surface. The diffusion surface satisfies a conditional expression represented by 0.1 <φ a / φ b <0.7, where φ a is a half width at half maximum of the light diffusion angle distribution when the incident angle is equal to or greater than a predetermined threshold value, and φ b is a half width at half maximum of the light diffusion angle distribution when the incident angle is less than the threshold value.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] Patent Document 1 describes an illumination optical system for an endoscope that is provided in contact with the end face of a light guide at the tip of the insertion portion of the endoscope, and that has a diffusion plate that is provided on the end face of the light guide and diffuses light from the light guide.

[0003] Patent document 2 describes a diffuser plate used as a screen in display devices, beam shaping applications, or applications requiring light diffusion, which is recorded using a holographic technique and has the same diffusion properties across its entire surface, where there is no inherent or main optical axis in the diffuser plate body.

[0004] Patent Document 3 describes a hologram screen that displays an image by diffracting and scattering image light projected by an image projection device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7141540 specification [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-338312 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-294952 Summary of the Invention [Problem to be solved by the invention]

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

[0007] The present disclosure provides an illumination optical system that is compact, yet has a wide light distribution and good transmission efficiency, and an endoscope equipped with this illumination optical system. [Means for solving the problem]

[0008] One aspect of the technology disclosed herein is an illumination optical system including a light guide for an endoscope and a diffuser plate disposed on an exit side of the light guide and diffusing light from the light guide, wherein the diffuser plate includes a substrate and a diffuser surface provided on a surface of the substrate facing the light guide, and the light diffusion angle distribution on the diffuser surface varies depending on the angle of incidence of light onto the diffuser surface; 0.1<φa / φb<0.7 (1) The conditional expression (1) expressed by the following formula is satisfied. The symbols in the conditional expression are defined as follows: φa is the half-width at half maximum of the light diffusion angle distribution when the incident angle is equal to or greater than a predetermined threshold. φb is the half-width at half maximum of the light diffusion angle distribution when the incident angle is less than the threshold. φa and φb are expressed in degrees.

[0009] The illumination optical system of the above aspect preferably satisfies at least one of the following conditional expressions (2) to (7). The symbols in the conditional expressions are defined as follows: t is the thickness of the diffuser plate. H is the outermost radius of the diffuser plate. G is the radius of the light guide. θh is the threshold value. θh is expressed in degrees. N is the refractive index of the substrate at the d-line. φaq is the half width at ¼ of the maximum light intensity in the light diffusion angular distribution when the incident angle is equal to or greater than the threshold. φbq is the half width at ¼ of the maximum light intensity in the light diffusion angular distribution when the incident angle is less than the threshold. 0.4<(t / (HG))×tan(θh / N+φa)<2 (2) 0.1<(t / H)×tan(θh / N+φb)<1 (3) 0.3<(θh / N+φa) / (θh / N+φb)<1 (4) 3<φa-θh / N<10 (5) 0.5<φa / φaq<0.95 (6) 0.5<φb / φbq<0.95 (7)

[0010] In the illumination optical system of the above aspect, the light guide may be configured to include a light shield on the central axis.

[0011] Another aspect of the technique of the present disclosure is an endoscope including the illumination optical system of the above aspect. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide an illumination optical system that is compact, yet has a wide light distribution and good transmission efficiency, and an endoscope equipped with this illumination optical system. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing the configuration of an illumination optical system according to an embodiment, which corresponds to the illumination optical system of Example 1. FIG. [Figure 2] 10A and 10B are diagrams for explaining the action of a diffuser plate on incident light equal to or greater than a threshold value. [Figure 3] 10A and 10B are diagrams for explaining the effect of a diffuser plate on incident light below a threshold value. [Figure 4] 2 is a diagram showing the light diffusion angle distribution on the diffusion surface of the illumination optical system of FIG. 1. [Figure 5] 2 is a diagram showing the configuration and optical path of the illumination optical system of FIG. 1 when the angle of incidence is equal to or greater than a threshold value. [Figure 6] 2 is a diagram showing the configuration of the illumination optical system of FIG. 1 and the optical path when the angle of incidence is less than a threshold value. [Figure 7] FIG. 3 is a diagram showing the light distribution characteristics of the illumination optical system of Example 1. [Figure 8] 10 is a diagram showing the configuration of an illumination optical system and optical paths according to a second embodiment when the angle of incidence is equal to or greater than a threshold value. FIG. [Figure 9] 10 is a diagram showing the configuration and optical paths of an illumination optical system according to a second embodiment when the angle of incidence is less than a threshold value. FIG. [Figure 10] FIG. 10 is a diagram illustrating the light distribution characteristics of the illumination optical system of Example 2. [Figure 11] 10 is a diagram showing the configuration of an illumination optical system and optical paths according to a third embodiment when the angle of incidence is equal to or greater than a threshold value. FIG. [Figure 12]10 is a diagram showing the configuration and optical paths of an illumination optical system according to a third embodiment when the angle of incidence is less than a threshold value. FIG. [Figure 13] FIG. 10 is a perspective view showing a schematic configuration of a light guide of an illumination optical system according to a third embodiment. [Figure 14] FIG. 10 is a diagram illustrating the light distribution characteristics of the illumination optical system of Example 3. [Figure 15] 10 is a diagram showing the configuration of an illumination optical system and optical paths according to a fourth embodiment when the angle of incidence is equal to or greater than a threshold value. FIG. [Figure 16] 10 is a diagram showing the configuration and optical paths of an illumination optical system according to a fourth embodiment when the angle of incidence is less than a threshold value. FIG. [Figure 17] FIG. 10 is a diagram showing the light distribution characteristics of the illumination optical system of Example 4. [Figure 18] 10 is a diagram showing the configuration of an illumination optical system and optical paths according to a fifth embodiment when the angle of incidence is equal to or greater than a threshold value. FIG. [Figure 19] 10 is a diagram showing the configuration and optical paths of an illumination optical system according to a fifth embodiment when the angle of incidence is less than a threshold value. FIG. [Figure 20] 13 is a diagram showing the light diffusion angle distribution on the diffusion surface of the illumination optical system of Example 5. FIG. [Figure 21] FIG. 10 is a diagram showing the light distribution characteristics of the illumination optical system of Example 5. [Figure 22] 13 is a diagram showing the configuration of an illumination optical system and optical paths according to a sixth embodiment when the angle of incidence is equal to or greater than a threshold value. FIG. [Figure 23] 13 is a diagram showing the configuration and optical paths of an illumination optical system according to a sixth embodiment when the angle of incidence is less than a threshold value. FIG. [Figure 24] FIG. 13 is a diagram showing the light distribution characteristics of the illumination optical system of Example 6. [Figure 25] 1 is a schematic configuration diagram of an endoscope according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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.

[0015] The illumination optical system 10 includes a light guide 2 of the endoscope and a diffuser plate 4 that is arranged on the exit side of the light guide 2 and diffuses light from the light guide 2. The light guide 2 is composed of a bundle fiber in which multiple optical fibers 3 are bundled. The diffuser plate 4 includes a substrate 6 and a diffusing surface 8 that is provided on the surface of the substrate 6 that faces the light guide. The diffusing surface 8 is the surface of the diffuser plate 4 that is closest to the light guide. The diffuser plate 4 is arranged so that the diffusing surface 8 is in close contact with or near the tip of the light guide 2.

[0016] Light emitted from a light source (not shown) passes through the light guide 2 and enters the diffusing surface 8 of the diffuser plate 4, where it is diffused and passes through the substrate 6 before being emitted from the diffuser plate 4 to become illumination light. When the diffuser plate 4 is disposed at the tip of the insertion portion of the endoscope, the illumination light illuminates an illuminated object (not shown) that is the observation target. In Fig. 1, the left side is the light source side and the right side is the illuminated object side.

[0017] The diffuser 4 is configured so that the light diffusion angle distribution on the diffuser surface 8 varies depending on the angle of incidence of light on the diffuser surface 8. The "angle of incidence of light on the diffuser surface 8" is the angle between the incident light and a line perpendicular to the diffuser surface 8. The "light diffusion angular distribution" is the angular distribution of diffused light. The light diffusion angular distribution will be explained later with an example.

[0018] The diffuser 4 is configured so that the light diffusion angle distribution on the diffuser surface 8 varies depending on whether a predetermined threshold value for the angle of incidence is crossed. Schematically, the angle width of the light diffusion angle distribution on the diffuser surface 8 is small for incident light whose angle of incidence on the diffuser surface 8 is equal to or greater than the threshold value, and the angle width of the light diffusion angle distribution on the diffuser surface 8 is large for incident light whose angle of incidence is less than the threshold value.

[0019] The above-described configuration of the diffusing surface 8 will be described with reference to FIGS. 2 and 3. FIGS. 2 and 3 are conceptual diagrams for explanation. FIG. 2 shows incident light 21 incident on the diffusing surface 8 at an incident angle θ1 equal to or greater than the threshold, and the resulting diffused light 23 obtained by diffusing the incident light 21 on the diffusing surface 8. FIG. 3 shows incident light 22 incident on the diffusing surface 8 at an incident angle θ2 less than the threshold, and the resulting diffused light 24 obtained by diffusing the incident light 22 on the diffusing surface 8. That is, when the threshold is θh, θ1≧θh and θ2<θh. The divergence angle of the diffused light 23 shown in FIG. 2 is smaller than the divergence angle of the diffused light 24 shown in FIG. 3. Configuring the diffusing surface 8 in this manner facilitates both a wide light distribution and compactness, and also facilitates increasing the thickness of the diffuser plate 4.

[0020] As an example, the diffusion surface 8 may be configured using a holographic diffusion plate. Holographic diffusion plates can be formed by conventionally known methods. For example, holographic diffusion plates can be formed using a sol-gel method. Specifically, a solution (sol) containing SiO2, which is the material for the holographic diffusion plate, is prepared, coated on a substrate, and then gelled. A master (mold) capable of transferring a surface relief structure designed by a computer-generated hologram is pressed against the gelled coating, and the coating is heated and hardened to form a holographic diffusion plate.

[0021] Alternatively, the diffusing surface 8 may be formed on one surface of the substrate 6. The diffusing surface 8 may be configured to be made of a film-like hologram element. A conventionally known method can be used to form the film-like hologram element. For example, the film-like hologram element can be formed by recording a diffusing body on a photosensitive member using an exposure optical system.

[0022] For example, glass can be used as the substrate 6. If it is desired to increase the strength, the substrate 6 may be made of sapphire glass.

[0023] As an example, Fig. 4 shows the light diffusion angle distribution of diffused light on the diffusing surface 8 of Fig. 1. As shown in Fig. 4, the light diffusion angle distribution can be expressed with the diffusion angle φ on the horizontal axis and the light amount on the vertical axis. Fig. 4 shows an example where the threshold is 12 degrees. In Fig. 4, the light diffusion angle distribution when the incident angle is equal to or greater than the threshold is shown by a dashed line, and the light diffusion angle distribution when the incident angle is less than the threshold is shown by a solid line.

[0024] FIG. 4 also shows, as an example, angles φa, φb, φaq, and φbq, which are defined as follows: φa is the half-width at half maximum of the light diffusion angle distribution when the incident angle is equal to or greater than a threshold. φb is the half-width at half maximum of the light diffusion angle distribution when the incident angle is less than a threshold. φaq is the half-width at 1 / 4 of the maximum light intensity in the light diffusion angle distribution when the incident angle is equal to or greater than a threshold. φbq is the half-width at 1 / 4 of the maximum light intensity in the light diffusion angle distribution when the incident angle is less than a threshold.

[0025] The illumination optical system 10 of this embodiment is configured to satisfy the following conditional expression (1) regarding the above φa and φb. Ensuring that the corresponding value of conditional expression (1) does not become equal to or less than the lower limit thereof is advantageous for ensuring a wide light distribution. Ensuring that the corresponding value of conditional expression (1) does not become equal to or greater than the upper limit thereof is advantageous for maintaining good transmission efficiency. This is based on the following reason. The outer peripheral surface of the diffuser plate 4 is often configured to have an adhesive or the like applied to prevent components from falling off. In this configuration, light incident on the outer peripheral surface is absorbed by the adhesive or the like, and the light transmission efficiency (amount of emitted light / amount of incident light) decreases accordingly. Ensuring that the corresponding value of conditional expression (1) does not become equal to or greater than the upper limit thereof reduces light absorption on the outer peripheral surface, which is advantageous for maintaining good transmission efficiency. 0.1<φa / φb<0.7 (1)

[0026] In order to obtain better characteristics, the lower limit of conditional expression (1) is more preferably set to 0.2, even more preferably to 0.25, and even more preferably to 0.3. In order to obtain better characteristics, the upper limit of conditional expression (1) is more preferably set to 0.65, even more preferably to 0.6, and even more preferably to 0.55. For example, it is preferable that the illumination optical system 10 satisfies the following conditional expression (1-1), more preferably the following conditional expression (1-2), and even more preferably the following conditional expression (1-3). 0.2<φa / φb<0.65 (1-1) 0.25<φa / φb<0.6 (1-2) 0.3<φa / φb<0.55 (1-3)

[0027] The configuration and optical path of a diffuser 4 that satisfies conditional expression (1) and has the light diffusion angle distribution shown in FIG. 4 are shown in FIGS. 5 and 6. In FIG. 5, the optical path when the incident angle is equal to or greater than the threshold value θh is shown by a solid line and a dashed-dotted line. In FIG. 6, the optical path when the incident angle is less than the threshold value θh is shown by a solid line and a dashed-dotted line.

[0028] As shown in Figures 5 and 6, this embodiment makes it possible to achieve a wide light distribution. Furthermore, as the thickness of a diffuser plate decreases, it becomes more susceptible to cracking, raising concerns about durability. However, the configuration of this embodiment is advantageous in that it allows the thickness of the diffuser plate to be increased while achieving both high light transmission efficiency and compactness. This point will be explained below with reference to the technology described in Patent Document 1.

[0029] Patent Document 1 proposes an illumination optical system that includes a diffuser plate attached to the end face of a light guide, and that satisfies the relationship t / L≦1.6 to prevent a decrease in light utilization efficiency. In Patent Document 1, t is the thickness of the diffuser plate in the direction perpendicular to the exit surface, and L is the shortest distance between the edge of the exit surface of the diffuser plate and the edge of the end face of the light guide in the in-plane direction of the exit surface. According to the formula t / L≦1.6 in Patent Document 1, if L is reduced to achieve compactness, t must also be reduced. Patent Document 1 describes an example in which t = 0.2 mm (millimeters), but a thickness of 0.2 mm for a diffuser plate placed at the tip of an endoscope may be susceptible to breakage. Furthermore, the diffusion angle distribution of the diffuser plate in Patent Document 1 is uniform and independent of the incident angle. In contrast, in the illumination optical system 10 of this embodiment, the light diffusion angle distribution on the diffusion surface 8 varies depending on the angle of incidence, so it is possible to maintain high light transmission efficiency while increasing the thickness of the diffusion plate 4, and also to achieve compactness and wide light distribution.

[0030] It is preferable that the illumination optical system 10 of this embodiment further satisfies the following conditional expression (6) regarding the above φa and φaq. By ensuring that the corresponding value of conditional expression (6) is not equal to or less than the lower limit, it is possible to reduce the absorption of light on the outer peripheral surface caused by the adhesive, etc., as described above, which is advantageous for maintaining good transmission efficiency. By ensuring that the corresponding value of conditional expression (6) is not equal to or greater than the upper limit, it is advantageous for ensuring a wide light distribution. 0.5<φa / φaq<0.95 (6)

[0031] In order to obtain better characteristics, the lower limit of conditional expression (6) is more preferably set to 0.6, even more preferably to 0.7, and even more preferably to 0.8. In order to obtain even better characteristics, the upper limit of conditional expression (6) is more preferably set to 0.94, even more preferably to 0.93, and even more preferably to 0.92. For example, it is preferable that the illumination optical system 10 satisfies the following conditional expression (6-1), more preferably the following conditional expression (6-2), and even more preferably the following conditional expression (6-3): 0.6<φa / φaq<0.94 (6-1) 0.7<φa / φaq<0.93 (6-2) 0.8<φa / φaq<0.92 (6-3)

[0032] It is preferable that the illumination optical system 10 of this embodiment further satisfies the following conditional expression (7) regarding the above φb and φbq. By ensuring that the corresponding value of conditional expression (7) is not equal to or less than the lower limit, it is possible to reduce the absorption of light on the outer peripheral surface caused by the adhesive, etc., as described above, which is advantageous for maintaining good transmission efficiency. By ensuring that the corresponding value of conditional expression (7) is not equal to or greater than the upper limit, it is advantageous for ensuring a wide light distribution. 0.5<φb / φbq<0.95 (7)

[0033] In order to obtain better characteristics, the lower limit of conditional expression (7) is more preferably set to 0.6, even more preferably to 0.7, and even more preferably to 0.8. In order to obtain even better characteristics, the upper limit of conditional expression (7) is more preferably set to 0.94, even more preferably to 0.93, and even more preferably to 0.92. For example, it is preferable that the illumination optical system 10 satisfies the following conditional expression (7-1), more preferably the following conditional expression (7-2), and even more preferably the following conditional expression (7-3): 0.6<φb / φbq<0.94 (7-1) 0.7<φb / φbq<0.93 (7-2) 0.8<φb / φbq<0.92 (7-3)

[0034] Other preferable conditional expressions for the illumination optical system 10 of this embodiment are listed below. To avoid redundant explanation, the same symbols are used for elements with the same definitions, and duplicate explanations of symbols are omitted. In the following conditional expressions, all angles are in degrees.

[0035] The illumination optical system 10 preferably satisfies the following conditional expression (2). Here, t denotes the thickness of the diffuser plate 4. H denotes the radius of the outermost diameter of the diffuser plate 4. G denotes the radius of the light guide 2. θh denotes the threshold value. θh is expressed in degrees. N denotes the refractive index of the substrate 6 at the d-line. In the diffuser plate 4 shown in FIG. 1, the thickness of the diffusing surface 8 is configured to be very small, allowing the thickness of the substrate 6 to be approximated as the thickness of the diffuser plate 4. As an example, FIG. 1 shows the above-mentioned t, H, and G. Ensuring that the corresponding value of conditional expression (2) is not equal to or less than the lower limit is advantageous for ensuring a wide light distribution or for improving durability by increasing the thickness of the diffuser plate 4. Ensuring that the corresponding value of conditional expression (2) is not equal to or greater than the upper limit is advantageous for maintaining good transmission efficiency by reducing light absorption on the outer peripheral surface caused by the adhesive, etc. 0.4<(t / (HG))×tan(θh / N+φa)<2 (2)

[0036] In order to obtain better characteristics, the lower limit of conditional expression (2) is more preferably set to 0.47, even more preferably to 0.5, and even more preferably to 0.58. In order to obtain better characteristics, the upper limit of conditional expression (2) is more preferably set to 1.7, even more preferably to 1.5, and even more preferably to 1.2. For example, it is preferable that the illumination optical system 10 satisfies the following conditional expression (2-1), more preferably the following conditional expression (2-2), and even more preferably the following conditional expression (2-3): 0.47<(t / (HG))×tan(θh / N+φa)<1.7 (2-1) 0.5<(t / (HG))×tan(θh / N+φa)<1.5 (2-2) 0.58<(t / (HG))×tan(θh / N+φa)<1.2 (2-3)

[0037] It is preferable that the illumination optical system 10 satisfies the following conditional expression (3): By ensuring that the corresponding value of conditional expression (3) is not equal to or less than the lower limit, it is advantageous to ensure a wide light distribution, or to increase the thickness of the diffuser plate 4, which is advantageous for improving durability. By ensuring that the corresponding value of conditional expression (3) is not equal to or greater than the upper limit, it is possible to reduce light absorption on the outer peripheral surface caused by the adhesive, etc., as described above, which is advantageous for maintaining good transmission efficiency. 0.1<(t / H)×tan(θh / N+φb)<1 (3)

[0038] In order to obtain better characteristics, the lower limit of conditional expression (3) is more preferably set to 0.15, even more preferably to 0.25, and even more preferably to 0.3. In order to obtain better characteristics, the upper limit of conditional expression (3) is more preferably set to 0.9, even more preferably to 0.8, and even more preferably to 0.7. For example, it is preferable that illumination optical system 10 satisfies the following conditional expression (3-1), more preferably the following conditional expression (3-2), and even more preferably the following conditional expression (3-3). 0.15<(t / H)×tan(θh / N+φb)<0.9 (3-1) 0.25<(t / H)×tan(θh / N+φb)<0.8 (3-2) 0.3<(t / H)×tan(θh / N+φb)<0.7 (3-3)

[0039] It is preferable that the illumination optical system 10 satisfies the following conditional expression (4): By ensuring that the corresponding value of conditional expression (4) is not equal to or less than the lower limit, φa does not become too small, which is advantageous for maintaining a wide light distribution, or φb does not become too large, which is advantageous for maintaining good transmission efficiency. By ensuring that the corresponding value of conditional expression (4) is not equal to or greater than the upper limit, the effect obtained by the incident angle dependency of the light diffusion angular distribution on the diffusing surface 8 can be made effective, which is advantageous for ensuring a wide light distribution. 0.3<(θh / N+φa) / (θh / N+φb)<1 (4)

[0040] In order to obtain better characteristics, the lower limit of conditional expression (4) is more preferably set to 0.34, even more preferably to 0.37, and even more preferably to 0.4. In order to obtain even better characteristics, the upper limit of conditional expression (4) is more preferably set to 0.9, even more preferably to 0.8, and even more preferably to 0.7. For example, it is preferable that the illumination optical system 10 satisfies the following conditional expression (4-1), more preferably the following conditional expression (4-2), and even more preferably the following conditional expression (4-3): 0.34<(θh / N+φa) / (θh / N+φb)<0.9 (4-1) 0.37<(θh / N+φa) / (θh / N+φb)<0.8 (4-2) 0.4<(θh / N+φa) / (θh / N+φb)<0.7 (4-3)

[0041] It is preferable that the illumination optical system 10 of this embodiment satisfies the following conditional expression (5): By ensuring that the corresponding value of conditional expression (5) is not equal to or smaller than the lower limit, it is possible to prevent the intensity of the light emitted from the diffuser plate 4 near the optical axis from becoming too weak, causing the central part of the observation field to become dark. By ensuring that the corresponding value of conditional expression (5) is not equal to or larger than the upper limit, it is possible to reduce the absorption of light on the outer peripheral surface caused by the adhesive, etc., as described above, which is advantageous for maintaining good transmission efficiency. 3<φa-θh / N<10 (5)

[0042] In order to obtain better characteristics, it is more preferable that the lower limit of conditional expression (5) be set to 4, even more preferably to 5, and even more preferably to 6. In order to obtain even better characteristics, it is more preferable that the upper limit of conditional expression (5) be set to 9, even more preferably to 8.5, and even more preferably to 8. For example, it is preferable that the illumination optical system 10 satisfies the following conditional expression (5-1), it is more preferable that the illumination optical system 10 satisfies the following conditional expression (5-2), and it is even more preferable that the illumination optical system 10 satisfies the following conditional expression (5-3): 4<φa-θh / N<9 (5-1) 5<φa-θh / N<8.5 (5-2) 6<φa-θh / N<8 (5-3)

[0043] While the above conditional expression (5) describes preventing a decrease in the intensity of the emitted light, conversely, to prevent the intensity of the emitted light from the diffuser 4 near the optical axis from becoming too strong, a light shield may be disposed on the central axis of the light guide 2. Generally, the intensity of the illumination light is stronger on and near the optical axis than at positions further away from the optical axis. During endoscopic surgery, blood or other substances may adhere to the illumination window located on the subject side of the illumination optical system. If the light intensity is too strong, the blood adhering to the illumination window may coagulate due to the illumination light. By configuring the light guide 2 to include a light shield on its central axis, the light intensity on and near the optical axis can be reduced, making it easier to prevent coagulation of blood adhering to the illumination window. Note that the "center" in the above "on the central axis" refers not only to the exact center, but also to an approximate center that includes an error generally acceptable in the technical field to which the technology of the present disclosure pertains.

[0044] Next, examples of the illumination optical system of the present disclosure will be described with reference to the drawings. All of Examples 1 to 6 shown below have a rotationally symmetric configuration with the optical axis Z as the axis of rotation. In the following description of the examples, parts with the same configuration will be given the same reference numerals, and some overlapping explanations will be omitted.

[0045] [Example 1] The configuration of the illumination optical system 10 of Example 1 is shown in FIG. 1, and since the configuration is as described above, some of the duplicated explanation will be omitted here. The illumination optical system 10 includes a light guide 2 and a diffuser plate 4. The diffuser plate 4 includes a substrate 6 and a diffusing surface 8 provided on the surface of the substrate 6 facing the light guide. The threshold incident angle of the diffusing surface 8 is 12 degrees. FIG. 4 shows the light diffusion angle distribution on the diffusing surface 8. FIG. 5 shows the light path when the incident angle is equal to or greater than the threshold, and FIG. 6 shows the light path when the incident angle is less than the threshold. The explanations for FIGS. 4, 5, and 6 have been given above, so duplicated explanations will be omitted here.

[0046] Fig. 7 shows a graph of the light distribution characteristics of light emitted from illumination optical system 10. In Fig. 7, the horizontal axis represents the angle from optical axis Z, and the vertical axis represents radiant intensity. The method of illustrating this light distribution characteristic graph is the same in the examples described later. Various data for illumination optical system 10 of Example 1 and the half-angle at half maximum of the light distribution characteristic graph shown in Fig. 7 are summarized in Table 1 described later, along with values ​​for other examples.

[0047] [Example 2] 8 and 9 show the configuration and optical paths of an illumination optical system 210 of Example 2 at a cross section including the optical axis Z. FIG. 8 shows the optical paths when the incident angle is equal to or greater than a threshold, and FIG. 9 shows the optical paths when the incident angle is less than the threshold. The illumination optical system 210 includes a light guide 2 and a diffuser plate 204. The diffuser plate 204 includes a substrate 206 and a diffusing surface 8 provided on the surface of the substrate 206 facing the light guide. The threshold incident angle of the diffusing surface 8 is 12 degrees. The light diffusion angle distribution on the diffusing surface 8 is shown in FIG. 4. The thickness of the diffuser plate 204 of the illumination optical system 210 of Example 2 is smaller than the thickness of the diffuser plate 4 of the illumination optical system 10 of Example 1. FIG. 10 shows a graph of the light distribution characteristics of light emitted from the illumination optical system 210.

[0048] [Example 3] 11 and 12 show the configuration and optical paths of an illumination optical system 310 of Example 3 in a cross section including the optical axis Z. FIG. 11 shows the optical paths when the angle of incidence is equal to or greater than a threshold, and FIG. 12 shows the optical paths when the angle of incidence is less than the threshold. The illumination optical system 310 includes a light guide 302 and a diffuser plate 4. The diffuser plate 4 of the illumination optical system 310 has the same configuration as the diffuser plate 4 of the illumination optical system 10.

[0049] A wedge 303, which is a light shielding member, is disposed on the central axis of the light guide 302. FIG. 13 shows a schematic perspective view of the light guide 302. The light guide 302 includes the wedge 303 disposed on the central axis and a number of optical fibers 3 disposed around the wedge 303. In FIG. 13, the individual optical fibers 3 around the wedge 303 are not shown, and only the reference numerals are provided. The wedge 303 is made of, for example, a metal wire. FIG. 14 shows a graph of the light distribution characteristics of light emitted from the illumination optical system 310.

[0050] [Example 4] 15 and 16 show the configuration and optical paths of an illumination optical system 410 of Example 4 at a cross section including the optical axis Z. FIG. 15 shows the optical paths when the incident angle is equal to or greater than a threshold, and FIG. 16 shows the optical paths when the incident angle is less than the threshold. The illumination optical system 410 includes a light guide 302 and a diffuser plate 204. The diffuser plate 204 includes a substrate 206 and a diffusing surface 8 provided on the surface of the substrate 206 facing the light guide. The threshold incident angle of the diffusing surface 8 is 12 degrees. The light diffusion angle distribution on the diffusing surface 8 is shown in FIG. 4. The thickness of the diffuser plate 204 of the illumination optical system 410 of Example 4 is smaller than the thickness of the diffuser plate 4 of the illumination optical system 310 of Example 3. FIG. 17 shows a graph of the light distribution characteristics of light emitted from the illumination optical system 410.

[0051] [Example 5] 18 and 19 show the configuration and optical paths of an illumination optical system 510 of Example 5 at a cross section including the optical axis Z. FIG. 18 shows the optical paths when the incident angle is equal to or greater than a threshold, and FIG. 19 shows the optical paths when the incident angle is less than the threshold. The illumination optical system 510 includes a light guide 302 and a diffuser plate 504. The diffuser plate 504 includes a substrate 6 and a diffusing surface 508 provided on the surface of the substrate 6 facing the light guide. The threshold θh of the incident angle of the diffusing surface 508 is 15 degrees. FIG. 20 shows the light diffusion angle distribution of the diffused light on the diffusing surface 508. FIG. 21 shows a graph of the light distribution characteristics of light emitted from the illumination optical system 510.

[0052] [Example 6] 22 and 23 show the configuration and optical paths of an illumination optical system 610 of Example 6 at a cross section including the optical axis Z. FIG. 22 shows the optical paths when the incident angle is equal to or greater than a threshold, and FIG. 23 shows the optical paths when the incident angle is less than the threshold. The illumination optical system 610 includes a light guide 302 and a diffuser plate 604. The diffuser plate 604 includes a substrate 206 and a diffusing surface 508 provided on the surface of the substrate 206 facing the light guide. The threshold incident angle θh of the diffusing surface 508 is 15 degrees. The light diffusion angle distribution on the diffusing surface 508 is shown in FIG. 20. The thickness of the diffuser plate 604 of the illumination optical system 610 of Example 6 is smaller than the thickness of the diffuser plate 504 of the illumination optical system 510 of Example 5. FIG. 24 shows a graph of the light distribution characteristics of light emitted from the illumination optical system 610.

[0053] Table 1 shows various data for each of the illumination optical systems in Examples 1 to 6. In addition to the values ​​used in the above-mentioned conditional expressions, Table 1 also shows the following values. The "ν" row shows the Abbe number of the substrate based on the d-line. The "Light distribution width" row shows the half-angle at half maximum of the graph of the light distribution characteristics of the light emitted from each illumination optical system. The "Wedge diameter" row shows the diameter of the wedge 303.

[0054] In the data in each table in this specification, 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 enlargement or reduction, other appropriate units can also be used. Also, the values ​​shown in the data in each table are rounded to a predetermined number of decimal places.

[0055] [Table 1]

[0056] Table 2 shows the values ​​corresponding to conditional expressions (1) to (7) for each of the illumination optical systems in Examples 1 to 6. The values ​​in Table 2 may be used as the upper or lower limit values ​​for the conditional expressions to set preferred ranges for the conditional expressions.

[0057] [Table 2]

[0058] As described above, all of the illumination optical systems of Examples 1 to 6 have a wide light distribution angle while being constructed to be compact.

[0059] Next, an endoscope according to an embodiment of the present disclosure will be described. Fig. 25 shows a schematic overall configuration diagram of an endoscope according to an embodiment of the present disclosure. The endoscope 100 shown in Fig. 25 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. 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.

[0060] A diffuser plate 4 according to an embodiment of the present disclosure is disposed at the inner tip of the tip portion 110. Furthermore, the light guide 2 is disposed inside the endoscope so that the tip of the light guide 2 faces the diffuser plate 4. An illumination optical system 10 according to an embodiment of the present disclosure is configured to include the light guide 2 and the diffuser plate 4. Note that the light guide 2 is partially omitted from illustration in FIG. 25 .

[0061] 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 dimensions of each part, the threshold value of the incident angle, the refractive index and Abbe number of the substrate, etc. are not limited to the values ​​shown in the above examples and can take other values.

[0062] The following additional notes are provided regarding the above embodiments and examples. [Appendix 1] An illumination optical system including a light guide for an endoscope and a diffuser plate disposed on an exit side of the light guide and diffusing light from the light guide, the diffusion plate includes a substrate and a diffusion surface provided on a surface of the substrate facing the light guide, the light diffusion angle distribution on the diffusion surface varies depending on the angle of incidence of light on the diffusion surface, a half width at half maximum of the light diffusion angle distribution when the incident angle is equal to or greater than a predetermined threshold value; a half-width at half maximum of the light diffusion angular distribution when the incident angle is less than the threshold value is defined as φb; If φa and φb are in degrees, 0.1<φa / φb<0.7 (1) An illumination optical system that satisfies conditional expression (1) expressed as follows. [Appendix 2] The thickness of the diffusion plate is t, The outermost radius of the diffusion plate is defined as H, The radius of the light guide is G, The threshold value is θh, The unit of θh is degrees, When the refractive index of the substrate at the d line is N, 0.4<(t / (HG))×tan(θh / N+φa)<2 (2) 10. An illumination optical system according to claim 1, which satisfies conditional expression (2) expressed as follows: [Appendix 3] The thickness of the diffusion plate is t, The outermost radius of the diffusion plate is defined as H, The threshold value is θh, The unit of θh is degrees, When the refractive index of the substrate at the d line is N, 0.1<(t / H)×tan(θh / N+φb)<1 (3) 10. The illumination optical system according to claim 1, wherein the illumination optical system satisfies conditional expression (3) shown below. [Appendix 4] The threshold value is θh, The unit of θh is degrees, When the refractive index of the substrate at the d line is N, 0.3<(θh / N+φa) / (θh / N+φb)<1 (4) 4. An illumination optical system according to claim 1, which satisfies conditional expression (4) below. [Appendix 5] The threshold value is θh, The unit of θh is degrees, When the refractive index of the substrate at the d line is N, 3<φa-θh / N<10 (5) 5. An illumination optical system according to claim 1, which satisfies conditional expression (5) below. [Appendix 6] When the incident angle is equal to or greater than the threshold value, the half width at 1 / 4 of the maximum light amount in the light diffusion angle distribution is φaq, 0.5<φa / φaq<0.95 (6) 6. An illumination optical system according to claim 1, which satisfies conditional expression (6) below. [Appendix 7] When the incident angle is less than the threshold value, the half width at 1 / 4 of the maximum light amount in the light diffusion angular distribution is φbq, 0.5<φb / φbq<0.95 (7) 7. An illumination optical system according to claim 1, which satisfies conditional expression (7) below. [Appendix 8] 8. The illumination optical system according to claim 1, wherein the light guide includes a light shield on a central axis thereof. [Appendix 9] An endoscope comprising the illumination optical system according to any one of Supplementary Note 1 to Supplementary Note 8. [Explanation of symbols]

[0063] 2, 302 Light Guide 3. Optical Fiber 4, 204, 504, 604 Diffuser 6, 206 board 8,508 Diffusion Surface 10, 210, 310, 410, 510, 610 Illumination optical system 21, 22 Incident light 23, 24 Diffused light 100 Endoscope 102 Operation section 104 Insertion section 106 Universal Code 107 Soft part 108 Curved section 109 Curvature control knob 110 Tip 303 Wedge G radius H radius t thickness Z optical axis θ1, θ2 incident angle φa, φb Half width at half maximum φaq, φbq Half width at 1 / 4 of maximum light intensity

Claims

1. An illumination optical system including a light guide for an endoscope and a diffuser plate disposed on an exit side of the light guide and diffusing light from the light guide, the diffusion plate includes a substrate and a diffusion surface provided on a surface of the substrate facing the light guide, the light diffusion angle distribution on the diffusion surface varies depending on the angle of incidence of light on the diffusion surface, a half width at half maximum of the light diffusion angular distribution when the incident angle is equal to or greater than a predetermined threshold value; a half-width at half maximum of the light diffusion angular distribution when the incident angle is less than the threshold value is defined as φb; When the units of φa and φb are degrees, 0.1<φa / φb<0.7 (1) An illumination optical system that satisfies conditional expression (1) expressed as follows:

2. The thickness of the diffusion plate is t, The outermost radius of the diffusion plate is defined as H, The radius of the light guide is G, The threshold value is θh, The unit of θh is degrees, When the refractive index of the substrate at the d line is N, 0.4<(t / (HG))×tan(θh / N+φa)<2 (2) 2. The illumination optical system according to claim 1, which satisfies conditional expression (2) expressed as follows:

3. The thickness of the diffusion plate is t, The outermost radius of the diffusion plate is defined as H, The threshold value is θh, The unit of θh is degrees, When the refractive index of the substrate at the d line is N, 0.1<(t / H)×tan(θh / N+φb)<1 (3) 2. The illumination optical system according to claim 1, which satisfies conditional expression (3) expressed as follows:

4. The threshold value is θh, The unit of θh is degrees, When the refractive index of the substrate at the d line is N, 0.3<(θh / N+φa) / (θh / N+φb)<1 (4) 2. The illumination optical system according to claim 1, which satisfies conditional expression (4) expressed as follows:

5. The threshold value is θh, The unit of θh is degrees, When the refractive index of the substrate at the d line is N, 3<φa-θh / N<10 (5) 2. The illumination optical system according to claim 1, which satisfies conditional expression (5) expressed as follows:

6. When the incident angle is equal to or greater than the threshold value, the half width at ¼ of the maximum light amount in the light diffusion angle distribution is φaq, 0.5<φa / φaq<0.95 (6) 2. The illumination optical system according to claim 1, which satisfies conditional expression (6) expressed as follows:

7. When the incident angle is less than the threshold value, the half width at ¼ of the maximum light amount in the light diffusion angle distribution is φbq, 0.5<φb / φbq<0.95 (7) 2. The illumination optical system according to claim 1, which satisfies conditional expression (7) expressed as follows:

8. The illumination optical system according to claim 1 , wherein the light guide includes a light shield on a central axis thereof.

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

Images