Illumination optical system and endoscope

Abstract

The present invention addresses the problem of providing: an illumination optical system that is compact, has a wide light distribution, and has good transmission efficiency; and an endoscope provided with the illumination optical system. The illumination optical system includes a light guide of an endoscope, and a diffusion plate disposed on an emission 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 light guide-side surface of the substrate. The light diffusion angle distribution on the diffusion surface varies depending on the angle of incidence of the light toward the diffusion surface. The diffusion surface satisfies the conditional expression represented by 0.1 < [phi] a / [phi] b < 0.7, where [phi] a is the full width at half maximum of the light diffusion angle distribution when the incident angle is equal to or greater than a preset threshold value, and [phi] b is the full width at half maximum of the light diffusion angle distribution when the incident angle is less than the threshold value.

Description

TECHNICAL FIELD

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

[0002] In Patent Literature 1, there is described an illumination optical system for an endoscope which is provided in contact with an end surface of a light guide at a distal end portion of an insertion portion of an endoscope, the illumination optical system for an endoscope having a diffusion plate which is provided at the end surface of the light guide and diffuses light from the light guide.

[0003] In Patent Literature 2, there is described a holographic diffusion plate which is a diffusion plate used as a screen in a display device, a light beam shaping use, or a use in which light diffusion is required, the holographic diffusion plate being recorded using a holographic method, there being no intrinsic or main optical axis in a diffusion plate main body, and the diffusion characteristics being the same on the entire surface.

[0004] In Patent Literature 3, there is described a holographic screen which displays an image by diffracting / scattering image light projected by an image projection device.

[0005] Patent Literature 1: Japanese Patent No. 7141540

[0006] Patent Literature 2: Japanese Patent Application Laid-Open No. 2000-338312

[0007] Patent Literature 3: Japanese Patent Application Laid-Open No. 2003-294952

[0008] In recent years, there is a demand for an illumination optical system which is small in structure, has wide light distribution, and has good transmission efficiency. SUMMARY

[0009] The present application provides an illumination optical system which is small in structure, has wide light distribution, and has good transmission efficiency, and an endoscope provided with the illumination optical system.

[0010] One mode of the technology of the present application is an illumination optical system which includes a light guide of an endoscope and a diffusion plate which is disposed on an emission side of the light guide and diffuses light from the light guide, wherein the diffusion plate includes a substrate and a diffusion surface which is provided on a surface of the substrate on the light guide side, a light diffusion angle distribution on the diffusion surface differs depending on an incident angle of light to the diffusion surface, and the illumination optical system satisfies a conditional expression (1) expressed by the following expression:

[0011] 0.1 < φa / φb < 0.7 (1).

[0012] The symbols in the conditional expression are defined as follows.

[0013] The half width at half maximum of the light diffusion angle distribution in the case where the incident angle is equal to or greater than a threshold value which is set in advance is set as φa.

[0014] A half value width at a value of ¼ of a maximum light amount in the light diffusion angle distribution in a case where the incident angle is equal to or greater than the threshold value is set to φaq.

[0015] Units of φa and φb are set to degrees.

[0016] The illumination optical system of the above-described aspect preferably satisfies at least one of the following conditional expressions (2) to (7).

[0017] Symbols in the conditional expressions are defined as follows.

[0018] A thickness of the diffusion plate is set to t.

[0019] A radius of an outermost diameter of the diffusion plate is set to H.

[0020] A radius of the light guide member is set to G.

[0021] The threshold value is set to θh.

[0022] A unit of θh is set to degrees.

[0023] A refractive index of the substrate at the d line is set to N.

[0024] A half value width at a value of ¼ of a maximum light amount in the light diffusion angle distribution in a case where the incident angle is equal to or greater than the threshold value is set to φaq.

[0025] A half value width at a value of ¼ of a maximum light amount in the light diffusion angle distribution in a case where the incident angle is less than the threshold value is set to φbq.

[0026] 0.4 < (t / (H-G)) × tan(θh / N+φa) < 2 (2)

[0027] 0.1 < (t / H) × tan(θh / N+φb) < 1 (3)

[0028] 0.3 < (θh / N+φa) / (θh / N+φb) < 1 (4)

[0029] 3 < φa-θh / N < 10 (5)

[0030] 0.5 < φa / φaq < 0.95 (6)

[0031] 0.5 < φb / φbq < 0.95 (7)

[0032] In the illumination optical system of the above-described aspect, the light guide member can be configured to include a light shielding member on the central axis.

[0033] Another aspect of the technology of the present application is an endoscope provided with the illumination optical system of the above-described aspect.

[0034] Effects of the Invention

[0035] According to the present application, it is possible to provide an illumination optical system which is small in structure, has wide light distribution, and has good transmission efficiency, and an endoscope provided with the same. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a sectional view showing a structure of an illumination optical system according to an embodiment.

[0037] Figure 2 is a diagram for explaining an action of a diffusion plate with respect to incident light above a threshold value.

[0038] Figure 3 is a diagram for explaining an action of a diffusion plate with respect to incident light below a threshold value.

[0039] Figure 4 is a diagram showing a light diffusion angle distribution of a diffusion surface of the illumination optical system of Figure 1

[0040] Figure 5 is a diagram showing a structure and an optical path of the illumination optical system of Figure 1

[0041] Figure 6 is a diagram showing a structure and an optical path of the illumination optical system of Figure 1

[0042] Figure 7 is a diagram showing a light distribution characteristic of the illumination optical system of

[0043] Figure 8 is a diagram showing a structure and an optical path of the illumination optical system of

[0044] Figure 9 is a diagram showing a structure and an optical path of the illumination optical system of

[0045] Figure 10 is a diagram showing a light distribution characteristic of the illumination optical system of

[0046] Figure 11 is a diagram showing a structure and an optical path of the illumination optical system of

[0047] Figure 12 is a diagram showing a structure and an optical path of the illumination optical system of

[0048] ​​​Figure 13 is a perspective view showing the schematic structure of the light guide of the illumination optical system of Example 3.

[0049] Figure 14 is a graph showing the light distribution characteristics of the illumination optical system of Example 3.

[0050] Figure 15 is a graph showing the structure and the light path of the illumination optical system of Example 4 in the case where the incident angle is equal to or greater than a threshold value.

[0051] Figure 16 is a graph showing the structure and the light path of the illumination optical system of Example 4 in the case where the incident angle is less than a threshold value.

[0052] Figure 17 is a graph showing the light distribution characteristics of the illumination optical system of Example 4.

[0053] Figure 18 is a graph showing the structure and the light path of the illumination optical system of Example 5 in the case where the incident angle is equal to or greater than a threshold value.

[0054] Figure 19 is a graph showing the structure and the light path of the illumination optical system of Example 5 in the case where the incident angle is less than a threshold value.

[0055] Figure 20 is a graph showing the light diffusion angle distribution of the diffusion surface of the illumination optical system of Example 5.

[0056] Figure 21 is a graph showing the light distribution characteristics of the illumination optical system of Example 5.

[0057] Figure 22 is a graph showing the structure and the light path of the illumination optical system of Example 6 in the case where the incident angle is equal to or greater than a threshold value.

[0058] Figure 23 is a graph showing the structure and the light path of the illumination optical system of Example 6 in the case where the incident angle is less than a threshold value.

[0059] Figure 24 is a graph showing the light distribution characteristics of the illumination optical system of Example 6.

[0060] Figure 25 is a schematic configuration view of an endoscope according to an embodiment.

[0061] Symbol explanation

[0062] 2, 302 - light guide, 3 - optical fiber, 4, 204, 504, 604 - diffusing plate, 6, 206 - substrate, 8, 508 - diffusing 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 - general-purpose cord, 107 - soft section, 108 - bending section, 109 - bending operation knob, 110 - tip section, 303 - wedge-shaped body, G - radius, H - radius, t - thickness, Z - optical axis, θ1, θ2 - angle of incidence, φa, φb - half-width at half-maximum, φaq, φbq - half-width at 1 / 4 of maximum light amount. DETAILED DESCRIPTION

[0063] Hereinafter, an embodiment of the present application will be described in detail with reference to the drawings. Figure 1 A cross-sectional structure of an illumination optical system 10 including an optical axis Z according to an embodiment of the present application is shown in FIG. 1. Figure 1 The illumination optical system 10 shown corresponds to Example 1 described later.

[0064] The illumination optical system 10 includes a light guide 2 of an endoscope and a diffusing plate 4 disposed on an emission side of the light guide 2 and diffusing light from the light guide 2. The light guide 2 is constituted by a bundle of optical fibers in which a plurality of optical fibers 3 are bundled together. The diffusing plate 4 includes a substrate 6 and a diffusing surface 8 provided on a light guide side surface of the substrate 6. The diffusing surface 8 is a surface of the diffusing plate 4 closest to the light guide side. The diffusing plate 4 is disposed so that the diffusing surface 8 is in close contact with or close to the tip of the light guide 2.

[0065] Light emitted from a light source (not shown) is incident on the diffusing surface 8 of the diffusing plate 4 via the light guide 2, diffused by the diffusing surface 8, and transmitted through the substrate 6, and then emitted from the diffusing plate 4 to become illumination light. In a case where the diffusing plate 4 is disposed on the tip section of the insertion section of the endoscope, the above-described illumination light illuminates an irradiated body (not shown) as an observation object. In a case where the diffusing plate 4 is disposed on the tip section of the insertion section of the endoscope, the above-described illumination light illuminates an irradiated body (not shown) as an observation object. Figure 1 In FIG. 1, the left side is the light source side, and the right side is the irradiated body side.

[0066] The diffusing plate 4 is configured so that the light diffusion angle distribution on the diffusing surface 8 differs depending on the angle of incidence of light on the diffusing surface 8. In addition, the "angle of incidence of light on the diffusing surface 8" is the angle formed by a line perpendicular to the diffusing surface 8 and the incident light. Also, the "light diffusion angle distribution" is the angle distribution of diffused light. The light diffusion angle distribution will be described later by way of example.

[0067] The diffusion plate 4 is configured so that the light diffusion angle distribution on the diffusion surface 8 differs with a threshold value set in advance for the incident angle. In short, it is configured so that the angle width of the light diffusion angle distribution on the diffusion surface 8 is small for incident light whose incident angle with respect to the diffusion surface 8 is equal to or greater than the threshold value, and the angle width of the light diffusion angle distribution on the diffusion surface 8 becomes large for incident light whose incident angle is less than the threshold value.

[0068] Reference Figure 2 and Figure 3 The above structure of the diffusion surface 8 will be described. Figure 2 and Figure 3 is an explanatory conceptual diagram. Figure 2 The manner in which incident light 21 incident to the diffusion surface 8 at an incident angle θ1 equal to or greater than the threshold value and the diffusion light 23 diffused on the diffusion surface 8 from the incident light 21 is shown in Figure 3 The manner in which incident light 22 incident to the diffusion surface 8 at an incident angle θ2 less than the threshold value and the diffusion light 24 diffused on the diffusion surface 8 from the incident light 22 is shown in. That is, in the case where the threshold value is set to θh, θ1 ≥ θh, and θ2 < θh. Figure 2 The divergence angle of the diffusion light 23 shown in is smaller than Figure 3 The divergence angle of the diffusion light 24 shown in. By configuring the diffusion surface 8 in this manner, it is easy to achieve both wide light distribution and miniaturization, and it is easy to increase the thickness of the diffusion plate 4.

[0069] As an example, the diffusion surface 8 can be configured using a holographic diffusion plate. As a method of forming the holographic diffusion plate, a method known in the art can be used. For example, the holographic diffusion plate can be formed using a sol-gel method. Specifically, a solution (sol) containing SiO2, which is a material of the holographic diffusion plate, is prepared and applied to a substrate, and then gelled, and in a state in which a master (mold) capable of transferring a surface relief structure designed by computer-synthesized hologram is pressed against the gelled applied film, the applied film is heated to cure it, whereby the holographic diffusion plate can be formed.

[0070] Alternatively, the diffusion surface 8 can be formed on one face of the substrate 6. The diffusion surface 8 can be configured by a thin-film holographic element. As a method of forming the thin-film holographic element, a method known in the art can be used. For example, the thin-film holographic element can be formed by recording a diffuser on a photosensitive member using an exposure optical system.

[0071] As the substrate 6, for example, glass can be used. In the case where it is desired to further improve the strength, the substrate 6 can be configured by sapphire glass.

[0072] As an example, the light diffusion angle distribution of the diffusion light in the diffusion surface 8 of Figure 4 is shown in Figure 1 . As shown in Figure 4As shown, the light diffusion angle distribution can be represented by setting the horizontal axis as the diffusion angle φ and the vertical axis as the light intensity. Figure 4 As an example, a threshold of 12 degrees is shown. Figure 4 In the diagram, dashed lines represent the light diffusion angle distribution when the incident angle is above the threshold, and solid lines represent the light diffusion angle distribution when the incident angle is below the threshold.

[0073] exist Figure 4 As an example, the following definitions are also shown: angles φa, φb, φaq, and φbq. φa is the half-height and half-width of the light diffuse angle distribution when the incident angle is above the threshold. φb is the half-height and half-width of the light diffuse angle distribution when the incident angle is below the threshold. φaq is the half-width at 1 / 4 of the maximum light intensity in the light diffuse angle distribution when the incident angle is above the threshold. φbq is the half-width at 1 / 4 of the maximum light intensity in the light diffuse angle distribution when the incident angle is below the threshold.

[0074] The illumination optical system 10 of this embodiment is configured to satisfy the following conditional expression (1) regarding φa and φb. By ensuring that the corresponding value of conditional expression (1) is not below the lower limit, it is beneficial to ensure a wide light distribution. By ensuring that the corresponding value of conditional expression (1) is not above the upper limit, it is beneficial to maintain good transmission efficiency. This is based on the following situation. In order to prevent parts from falling off, the outer peripheral surface of the diffuser plate 4 is often coated with adhesive or the like. In this structure, the light incident on the outer peripheral surface is absorbed by the adhesive or the like, and correspondingly, the light transmission efficiency (emitted light amount / incident light amount) decreases. By ensuring that the corresponding value of conditional expression (1) is not above the upper limit, the absorption of light on the outer peripheral surface can be reduced, thus helping to maintain good transmission efficiency.

[0075] 0.1 < φa / φb < 0.7 (1)

[0076] To obtain better characteristics, the lower limit of condition (1) is more preferably set to 0.2, further preferably 0.25, and even more preferably 0.3. To obtain better characteristics, the upper limit of condition (1) is more preferably set to 0.65, further preferably 0.6, and even more preferably 0.55. For example, the illumination optical system 10 preferably satisfies the following condition (1-1), more preferably satisfies the following condition (1-2), and even more preferably satisfies the following condition (1-3).

[0077] 0.2 < φa / φb < 0.65 (1-1)

[0078] 0.25 < φa / φb < 0.6 (1-2)

[0079] 0.3 < φa / φb < 0.55 (1-3)

[0080] A diffusing plate 4 that satisfies the conditional expression (1) and has a light diffusion angle distribution of Figure 4 The structure and light path of the diffusing plate 4 that satisfies the conditional expression (1) and has a light diffusion angle distribution of Figure 5 and Figure 6 In Figure 5 , the light path in the case where the incident angle is equal to or greater than the threshold value θh is indicated by a solid line and a single-dot chain line. In Figure 6 , the light path in the case where the incident angle is less than the threshold value θh is indicated by a solid line and a single-dot chain line.

[0081] As shown in Figure 5 and Figure 6 , according to the present embodiment, wide light distribution can be achieved. Also, if the thickness of the diffusing plate is made thin, it becomes easy to break, thereby causing concern in terms of durability; but by being configured as in the present embodiment, it is advantageous to achieve high light transmission efficiency and miniaturization while increasing the thickness of the diffusing plate. In this regard, the technology described in Patent Literature 1 is referred to, and the following is described.

[0082] In Patent Literature 1, a lighting optical system is proposed that has a diffusing plate provided to the end surface of a light guide member, and by satisfying t / L≤1.6, it is possible to prevent a decrease in the utilization efficiency of light. In Patent Literature 1, t is the thickness in the direction perpendicular to the emission surface of the diffusing plate, and L is the shortest distance between the edge of the emission surface of the diffusing plate and the edge of the end surface of the light guide member in the in-plane direction of the emission surface. If the t / L≤1.6 expression of Patent Literature 1 is followed, if L is decreased in order to miniaturize, t also needs to be decreased. In Patent Literature 1, there is a description of an embodiment in which t=0.2 mm (millimeters), but as the thickness of the diffusing plate that is disposed to the distal end of an endoscope, there is a risk of easy breakage with a thickness of 0.2 mm (millimeters). Also, the light diffusion angle distribution of the diffusing plate of Patent Literature 1 is uniform regardless of the incident angle. In contrast, in the lighting optical system 10 of the present embodiment, the light diffusion angle distribution on the diffusing surface 8 is made different according to the incident angle, so it is possible to maintain high light transmission efficiency while increasing the thickness of the diffusing plate 4, and it is possible to achieve miniaturization and wide light distribution.

[0083] The lighting optical system 10 of the present embodiment preferably further satisfies the following conditional expression (6) with respect to the above-described φa and φaq. By making the corresponding value of the conditional expression (6) not be below the lower limit value, it is possible to reduce the absorption of light on the outer peripheral surface caused by the above-described adhesive or the like, so it is advantageous to maintain good transmission efficiency. By making the corresponding value of the conditional expression (6) not be above the upper limit value, it is advantageous to ensure wide light distribution.

[0084] 0.5 < φa / φaq < 0.95 (6)

[0085] To obtain better characteristics, the lower limit value of conditional expression (6) is more preferably set to 0.6, further preferably to 0.7, and still further preferably to 0.8. To obtain better characteristics, the upper limit value of conditional expression (6) is more preferably set to 0.94, further preferably to 0.93, and still further preferably to 0.92. For example, the illumination optical system 10 preferably satisfies the following conditional expression (6-1), more preferably satisfies the following conditional expression (6-2), and further preferably satisfies the following conditional expression (6-3).

[0086] 0.6 < φa / φaq < 0.94 (6-1)

[0087] 0.7 < φa / φaq < 0.93 (6-2)

[0088] 0.8 < φa / φaq < 0.92 (6-3)

[0089] The illumination optical system 10 of the present embodiment preferably further satisfies the following conditional expression (7) with respect to the above φb and φbq. By making the corresponding value of conditional expression (7) not be lower than the lower limit value, it is possible to reduce the absorption of light on the outer peripheral surface caused by the above adhesive or the like, and thus it is advantageous to maintain a good transmittance efficiency. By making the corresponding value of conditional expression (7) not be higher than the upper limit value, it is advantageous to ensure a wide distribution of light.

[0090] 0.5 < φb / φbq < 0.95 (7)

[0091] To obtain better characteristics, the lower limit value of conditional expression (7) is more preferably set to 0.6, further preferably to 0.7, and still further preferably to 0.8. To obtain better characteristics, the upper limit value of conditional expression (7) is more preferably set to 0.94, further preferably to 0.93, and still further preferably to 0.92. For example, the illumination optical system 10 preferably satisfies the following conditional expression (7-1), more preferably satisfies the following conditional expression (7-2), and further preferably satisfies the following conditional expression (7-3).

[0092] 0.6 < φb / φbq < 0.94 (7-1)

[0093] 0.7 < φb / φbq < 0.93 (7-2)

[0094] 0.8 < φb / φbq < 0.92 (7-3)

[0095] The following describes other preferred conditional expressions in the illumination optical system 10 of the present embodiment. Hereinafter, to avoid lengthy description, the same symbols are used for the same defined parts, and the repeated description of the symbols is omitted. In the following conditional expressions, the unit of the angle is degree.

[0096] The illumination optical system 10 preferably satisfies the following conditional expression (2). Here, the thickness of the diffusion plate 4 is set to t. The radius of the outermost diameter of the diffusion plate 4 is set to H. The radius of the light guide member 2 is set to G. The threshold value is set to θh. The unit of θh is degrees. The refractive index of the substrate 6 under the d-line is set to N. In Figure 1 In the example of the diffusion plate 4, the thickness of the diffusion surface 8 is made very small, and the thickness of the substrate 6 can be approximated to the thickness of the diffusion plate 4. As an example, t, H, and G are shown in Figure 1 By making the corresponding value of the conditional expression (2) not less than the lower limit value, it is advantageous to secure a wide distribution of light, or the thickness of the diffusion plate 4 can be increased, and thus it is advantageous to improve durability. By making the corresponding value of the conditional expression (2) not more than the upper limit value, the absorption of light on the outer peripheral surface caused by the above-mentioned adhesive or the like can be reduced, and thus it is advantageous to maintain a good transmission efficiency.

[0097] 0.4 < (t / (H-G)) x tan(θh / N+φa) < 2 (2)

[0098] In order to obtain better characteristics, the lower limit value of the conditional expression (2) is more preferably set to 0.47, further preferably to 0.5, and more further preferably to 0.58. In order to obtain better characteristics, the upper limit value of the conditional expression (2) is more preferably set to 1.7, further preferably to 1.5, and more further preferably to 1.2. For example, the illumination optical system 10 preferably satisfies the following conditional expression (2-1), more preferably the following conditional expression (2-2), and further preferably the following conditional expression (2-3).

[0099] 0.47 < (t / (H-G)) x tan(θh / N+φa) < 1.7 (2-1)

[0100] 0.5 < (t / (H-G)) x tan(θh / N+φa) < 1.5 (2-2)

[0101] 0.58 < (t / (H-G)) x tan(θh / N+φa) < 1.2 (2-3)

[0102] The illumination optical system 10 preferably satisfies the following conditional expression (3). By making the corresponding value of the conditional expression (3) not less than the lower limit value, it is advantageous to secure a wide distribution of light, or the thickness of the diffusion plate 4 can be increased, and thus it is advantageous to improve durability. By making the corresponding value of the conditional expression (3) not more than the upper limit value, the absorption of light on the outer peripheral surface caused by the above-mentioned adhesive or the like can be reduced, and thus it is advantageous to maintain a good transmission efficiency.

[0103] 0.1 < (t / H) x tan(θh / N+φb) < 1 (3)

[0104] In order to obtain more favorable characteristics, the lower limit value of conditional expression (3) is more preferably set to 0.15, further preferably to 0.25, and still further preferably to 0.3. In order to obtain more favorable characteristics, the upper limit value of conditional expression (3) is more preferably set to 0.9, further preferably to 0.8, and still further preferably to 0.7. For example, the illumination optical system 10 preferably satisfies the following conditional expression (3-1), more preferably satisfies the following conditional expression (3-2), and further preferably satisfies the following conditional expression (3-3).

[0105] 0.15 < (t / H) x tan(0h / N + φb) < 0.9 (3-1)

[0106] 0.25 < (t / H) x tan(0h / N + φb) < 0.8 (3-2)

[0107] 0.3 < (t / H) x tan(0h / N + φb) < 0.7 (3-3)

[0108] The illumination optical system 10 preferably satisfies the following conditional expression (4). By making the corresponding value of conditional expression (4) not be below the lower limit value, φa does not become too small, and thus it is favorable to maintain a wide distribution of light, or φb does not become too large, and thus it is favorable to maintain a favorable transmission efficiency. By making the corresponding value of conditional expression (4) not be above the upper limit value, the effect obtained by the dependence of the incident angle on the light diffusion angle distribution on the diffusion surface 8 can be effectively achieved, and thus it is favorable to ensure a wide distribution of light.

[0109] 0.3 < (0h / N + φa) / (0h / N + φb) < 1 (4)

[0110] In order to obtain more favorable characteristics, the lower limit value of conditional expression (4) is more preferably set to 0.34, further preferably to 0.37, and still further preferably to 0.4. In order to obtain more favorable characteristics, the upper limit value of conditional expression (4) is more preferably set to 0.9, further preferably to 0.8, and still further preferably to 0.7. For example, the illumination optical system 10 preferably satisfies the following conditional expression (4-1), more preferably satisfies the following conditional expression (4-2), and further preferably satisfies the following conditional expression (4-3).

[0111] 0.34 < (0h / N + φa) / (0h / N + φb) < 0.9 (4-1)

[0112] 0.37 < (0h / N + φa) / (0h / N + φb) < 0.8 (4-2)

[0113] 0.4 < (0h / N + φa) / (0h / N + φb) < 0.7 (4-3)

[0114] The illumination optical system 10 of the present embodiment preferably satisfies the following conditional expression (5). By making the corresponding value of the conditional expression (5) not less than the lower limit value, it is possible to prevent the intensity of the emitted light from the diffusion plate 4 near the optical axis from becoming too weak to cause the central portion of the observation field of view to become dark. By making the corresponding value of the conditional expression (5) not more than the upper limit value, it is possible to reduce the absorption of light on the outer peripheral surface caused by the above-described adhesive or the like, and thus it is advantageous to maintain a good transmittance efficiency.

[0115] 3 < φa- θh / N < 10 (5)

[0116] In order to obtain better characteristics, the lower limit value of the conditional expression (5) is more preferably set to 4, further preferably to 5, and still further preferably to 6. In order to obtain better characteristics, the upper limit value of the conditional expression (5) is more preferably set to 9, further preferably to 8.5, and still further preferably to 8. For example, the illumination optical system 10 preferably satisfies the following conditional expression (5-1), more preferably satisfies the following conditional expression (5-2), and further preferably satisfies the following conditional expression (5-3).

[0117] 4 < φa- θh / N < 9 (5-1)

[0118] 5 < φa- θh / N < 8.5 (5-2)

[0119] 6 < φa- θh / N < 8 (5-3)

[0120] In the above-described conditional expression (5), the prevention of the reduction in the intensity of the emitted light is described, but conversely, in the case where it is desired to suppress the intensity of the emitted light from the diffusion plate 4 near the optical axis from becoming too strong, a light shielding member can be provided on the central axis of the light guide member 2. Generally, on and near the optical axis, the light intensity of the illumination light is strong compared to positions farther from the optical axis toward the outer diameter side. In surgery using an endoscope, sometimes blood or the like is attached to the illumination window provided on the irradiated body side of the illumination optical system, and if the light intensity is too strong, the blood attached to the illumination window can be coagulated by the illumination light. By configuring the light guide member 2 to include a light shielding member on the central axis thereof, it is possible to reduce the light intensity on and near the optical axis, and thus it is easy to prevent the coagulation of the blood attached to the illumination window. In addition, the "central axis" includes not only the exact "center" but also a substantially center including an error generally allowed in the technical field to which the technology of the present application pertains.

[0121] Next, embodiments of the illumination optical system of the present application will be described with reference to the drawings. Embodiments 1 to 6 shown below each have a rotationally symmetrical structure with the optical axis Z as the rotation axis. In the description of the following embodiments, the same reference signs are attached to the same structures, and a part of the repeated description is omitted.

[0122] [Embodiment 1]

[0123] The structure of the illumination optical system 10 of Example 1 is shown in Figure 1 The structure is as described above, and thus a part of the repeated explanation is omitted here. The illumination optical system 10 includes the light guide 2 and the diffusion plate 4. The diffusion plate 4 includes the substrate 6 and the diffusion surface 8 provided to the surface of the substrate 6 on the light guide side. The threshold value of the incident angle of the diffusion surface 8 is 12 degrees. Figure 4 The light diffusion angle distribution on the diffusion surface 8 is shown in Figure 5 The light path in the case where the incident angle is equal to or greater than the threshold value is shown in Figure 6 The light path in the case where the incident angle is less than the threshold value is shown in Figure 4 , Figure 5 and Figure 6 The explanation of the above has been described above, and thus the repeated explanation is omitted here.

[0124] Figure 7 A graph of the light distribution characteristics of the emergent light from the illumination optical system 10 is shown in Figure 7 In Figure 7 , the horizontal axis is set to the angle with respect to the optical axis Z, and the vertical axis is set to the radiation intensity. The graphing method of this light distribution characteristics is also the same in the following examples. The half-value half-angle of the light distribution characteristics graph shown in is shown together with the values of the other examples in Table 1 described later.

[0125] [Example 2]

[0126] The structure and the light path in the cross section including the optical axis Z of the illumination optical system 210 of Example 2 are shown in Figure 8 and Figure 9 The light path in the case where the incident angle is equal to or greater than the threshold value is shown in Figure 8 , and the light path in the case where the incident angle is less than the threshold value is shown in Figure 9 . The illumination optical system 210 includes the light guide 2 and the diffusion plate 204. The diffusion plate 204 includes the substrate 206 and the diffusion surface 8 provided to the surface of the substrate 206 on the light guide side. The threshold value of the incident angle of the diffusion surface 8 is 12 degrees. The light diffusion angle distribution on the diffusion surface 8 is shown in Figure 4 . The thickness of the diffusion plate 204 of the illumination optical system 210 of Example 2 is smaller than the thickness of the diffusion plate 4 of the illumination optical system 10 of Example 1. Figure 10 A graph of the light distribution characteristics of the emergent light from the illumination optical system 210 is shown in

[0127] [Example 3]

[0128] The structure and the light path in the cross section including the optical axis Z of the illumination optical system 310 of Example 3 are shown in Figure 11 and Figure 12 .Figure 11 The light path in the case where the incident angle is equal to or greater than the threshold value is shown in FIG. 12. The light path in the case where the incident angle is less than the threshold value is shown in FIG. 13. The illumination optical system 310 includes the light guide member 302 and the diffusion plate 4. The diffusion plate 4 of the illumination optical system 310 has the same structure as the diffusion plate 4 of the illumination optical system 10. Figure 12 The light path in the case where the incident angle is equal to or greater than the threshold value is shown in FIG. 12. The light path in the case where the incident angle is less than the threshold value is shown in FIG. 13. The illumination optical system 310 includes the light guide member 302 and the diffusion plate 4. The diffusion plate 4 of the illumination optical system 310 has the same structure as the diffusion plate 4 of the illumination optical system 10.

[0129] A wedge-shaped body 303 as a light-blocking member is disposed on the central axis of the light guide member 302. Figure 13 A schematic perspective view of the light guide member 302 is shown in FIG. 14. The light guide member 302 includes the wedge-shaped body 303 disposed on the central axis and a plurality of optical fibers 3 disposed around the wedge-shaped body 303. In FIG. 14, the illustration of each of the optical fibers 3 around the wedge-shaped body 303 is omitted, and only the symbols are written. Figure 13 The wedge-shaped body 303 is composed of, for example, a steel wire made of metal. Figure 14 A graph showing the light distribution characteristics of the emergent light from the illumination optical system 310 is shown in FIG. 15.

[0130] [Example 4]

[0131] The structure and the light path in the cross section including the optical axis Z of the illumination optical system 410 of Example 4 are shown in FIGS. 18 and 19. In FIG. 18, the light path in the case where the incident angle is equal to or greater than the threshold value is shown, and in FIG. 19, the light path in the case where the incident angle is less than the threshold value is shown. The illumination optical system 410 includes the light guide member 302 and the diffusion plate 204. The diffusion plate 204 includes the substrate 206 and the diffusion surface 8 provided to the surface of the substrate 206 on the light guide member side. The threshold value of the incident angle of the diffusion surface 8 is 12 degrees. The light diffusion angle distribution on the diffusion surface 8 is shown in FIG. 20. The thickness of the diffusion plate 204 of the illumination optical system 410 of Example 4 is smaller than the thickness of the diffusion plate 4 of the illumination optical system 310 of Example 3. Figure 15 Figure 16 In FIG. 18, the light path in the case where the incident angle is equal to or greater than the threshold value is shown, and in FIG. 19, the light path in the case where the incident angle is less than the threshold value is shown. The illumination optical system 410 includes the light guide member 302 and the diffusion plate 204. The diffusion plate 204 includes the substrate 206 and the diffusion surface 8 provided to the surface of the substrate 206 on the light guide member side. The threshold value of the incident angle of the diffusion surface 8 is 12 degrees. The light diffusion angle distribution on the diffusion surface 8 is shown in FIG. 20. The thickness of the diffusion plate 204 of the illumination optical system 410 of Example 4 is smaller than the thickness of the diffusion plate 4 of the illumination optical system 310 of Example 3. Figure 15 The light path in the case where the incident angle is equal to or greater than the threshold value is shown in FIG. 12. The light path in the case where the incident angle is less than the threshold value is shown in FIG. 13. The illumination optical system 310 includes the light guide member 302 and the diffusion plate 4. The diffusion plate 4 of the illumination optical system 310 has the same structure as the diffusion plate 4 of the illumination optical system 10. Figure 16 The light path in the case where the incident angle is equal to or greater than the threshold value is shown in FIG. 12. The light path in the case where the incident angle is less than the threshold value is shown in FIG. 13. The illumination optical system 310 includes the light guide member 302 and the diffusion plate 4. The diffusion plate 4 of the illumination optical system 310 has the same structure as the diffusion plate 4 of the illumination optical system 10. Figure 4 The light distribution characteristics of the emergent light from the illumination optical system 410 are shown in FIG. 21. Figure 17

[0132] [Example 5]

[0133] The structure and the light path in the cross section including the optical axis Z of the illumination optical system 510 of Example 5 are shown in FIGS. 24 and 25. In FIG. 24, the light path in the case where the incident angle is equal to or greater than the threshold value is shown, and in FIG. 25, the light path in the case where the incident angle is less than the threshold value is shown. The illumination optical system 510 includes the light guide member 302 and the diffusion plate 504. The diffusion plate 504 includes the substrate 6 and the diffusion surface 508 provided to the surface of the substrate 6 on the light guide member side. The threshold value θh of the incident angle of the diffusion surface 508 is 15 degrees. Figure 18 Figure 19 In FIG. 24, the light path in the case where the incident angle is equal to or greater than the threshold value is shown, and in FIG. 25, the light path in the case where the incident angle is less than the threshold value is shown. The illumination optical system 510 includes the light guide member 302 and the diffusion plate 504. The diffusion plate 504 includes the substrate 6 and the diffusion surface 508 provided to the surface of the substrate 6 on the light guide member side. The threshold value θh of the incident angle of the diffusion surface 508 is 15 degrees. Figure 18 The light path in the case where the incident angle is equal to or greater than the threshold value is shown in FIG. 12. The light path in the case where the incident angle is less than the threshold value is shown in FIG. 13. The illumination optical system 310 includes the light guide member 302 and the diffusion plate 4. The diffusion plate 4 of the illumination optical system 310 has the same structure as the diffusion plate 4 of the illumination optical system 10. Figure 19 The light path in the case where the incident angle is equal to or greater than the threshold value is shown in FIG. 12. The light path in the case where the incident angle is less than the threshold value is shown in FIG. 13. The illumination optical system 310 includes the light guide member 302 and the diffusion plate 4. The diffusion plate 4 of the illumination optical system 310 has the same structure as the diffusion plate 4 of the illumination optical system 10. Figure 20 ​​​The diagram shows the light diffusion angle distribution of diffused light on the diffuse surface 508. Figure 21 The graph shows the light distribution characteristics of the emitted light from the illumination optics system 510.

[0134] [Example 6]

[0135] The structure and optical path of the illumination optical system 610 of Embodiment 6 in a cross-section including the optical axis Z are shown. Figure 22 and Figure 23 .exist Figure 22 The diagram shows the optical path when the incident angle is above a threshold. Figure 23 The diagram illustrates the optical path when the incident angle is less than a 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 diffuser surface 508 disposed on the surface of the substrate 206 on the side of the light guide. The threshold angle θh of the incident angle of the diffuser surface 508 is 15 degrees. The light diffusion angle distribution on the diffuser surface 508 is shown in the diagram. Figure 20 The thickness of the diffuser plate 604 in the illumination optical system 610 of Example 6 is less than the thickness of the diffuser plate 504 in the illumination optical system 510 of Example 5. Figure 24 The graph shows the light distribution characteristics of the emitted light from the illumination optics system 610.

[0136] 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 conditional expressions, Table 1 also shows the values ​​described below. The Abbe number of the substrate based on the d-line is shown in the "v" row. The half-value and half-angle of the graph showing the light distribution characteristics of the emitted light from each illumination optical system are shown in the "Light Distribution Width" row. The diameter of the wedge 303 is shown in the "Wedge Diameter" row.

[0137] Furthermore, in the data of the tables in this specification, millimeters are used as the unit of length and degrees are used as the unit of angle. However, since the optical system can be used even when scaled up or down, other appropriate units can also be used. Also, the values ​​shown in each table are rounded to a predetermined number of decimal places.

[0138] [Table 1]

[0139]

[0140] Table 2 shows the corresponding values ​​of conditional expressions (1) to (7) for each illumination optical system of Examples 1 to 6. The values ​​shown in Table 2 can be used as upper or lower limits of the conditional expressions to set the preferred range of the conditional expressions.

[0141] [Table 2]

[0142]

[0143] As described above, each of the illumination optical systems of Embodiments 1 to 6 is small in size and has a wide distribution angle of light.

[0144] Next, an endoscope according to an embodiment of the present application will be described. In Figure 25 A schematic overall configuration of an endoscope according to an embodiment of the present application is shown in FIG. 1. Figure 25 The endoscope 100 shown in FIG. 1 mainly includes an operation section 102, an insertion section 104, and a general-purpose plug cord 106 connected to a connector section (not shown). A large portion of the insertion section 104 is a soft section 107 that is bent in any direction along an insertion path, a bending section 108 is connected to a front end of the soft section 107, and a front end section 110 is connected to a front end of the bending section 108. The bending section 108 is provided to direct the front end section 110 in a desired direction, and bending operation is possible by turning a bending operation knob 109 provided to the operation section 102.

[0145] A diffusing plate 4 according to an embodiment of the present application is provided inside a front end of the front end section 110. Also, a light guide 2 is provided inside the endoscope in such a manner that a front end of the light guide 2 opposes the diffusing plate 4. An illumination optical system 10 according to an embodiment of the present application is configured by including these light guide 2 and diffusing plate 4. Note that in Figure 25 In FIG. 1, the light guide 2 is omitted in part.

[0146] The above describes the technology of the present application with reference to the embodiments and examples, but the technology of the present application is not limited to the above-described embodiments and examples, and various modifications are possible. For example, the dimensions of the respective sections, the threshold value of the incident angle, the refractive index and Abbe number of the substrate, and the like are not limited to the values shown in the above-described examples, and other values are possible.

[0147] With regard to the above-described embodiments and examples, the following notes are further disclosed.

[0148] [Note 1]

[0149] An illumination optical system including a light guide of an endoscope and a diffusing plate disposed on an emission side of the light guide and diffusing light from the light guide, wherein

[0150] the diffusing plate includes a substrate and a diffusing surface provided to a surface of the substrate on the light guide side,

[0151] a distribution of a light diffusion angle on the diffusing surface differs depending on an incident angle of light to the diffusing surface,

[0152] a half value width of the distribution of the light diffusion angle in a case where the incident angle is equal to or greater than a threshold value set in advance is set to φa,

[0153] a half width of the light diffusion angle distribution when the incident angle is less than the threshold value is set to φb,

[0154] and units of φa and φb are set to degrees,

[0155] the illumination optical system satisfies a conditional expression (1) represented by the following expression:

[0156] 0.1 < φa / φb < 0.7 (1).

[0157] [Note 2]

[0158] The illumination optical system according to Note 1, wherein

[0159] in a case where a thickness of the diffusion plate is set to t,

[0160] a radius of an outermost diameter of the diffusion plate is set to H,

[0161] a radius of the light guide member is set to G,

[0162] the threshold value is set to θh,

[0163] a unit of θh is set to degrees,

[0164] and a refractive index of the substrate at a d line is set to N,

[0165] the illumination optical system satisfies a conditional expression (2) represented by the following expression:

[0166] 0.4 < (t / (H-G)) x tan(θh / N+φa) < 2 (2).

[0167] [Note 3]

[0168] The illumination optical system according to Note 1 or Note 2, wherein

[0169] in a case where a thickness of the diffusion plate is set to t,

[0170] a radius of an outermost diameter of the diffusion plate is set to H,

[0171] the threshold value is set to θh,

[0172] a unit of θh is set to degrees,

[0173] and a refractive index of the substrate at a d line is set to N,

[0174] the illumination optical system satisfies a conditional expression (3) represented by the following expression:

[0175] 0.1 < (t / H) x tan(θh / N+φb) < 1 (3).

[0176] [Note 4]

[0177] The illumination optical system according to any one of Note 1 to Note 3, in which

[0178] in a case where the threshold value is set to θh,

[0179] the unit of θh is set to degrees,

[0180] and the refractive index of the substrate at the d line is set to N,

[0181] the illumination optical system satisfies a conditional expression (4) represented by:

[0182] 0.3 < (θh / N + φa) / (θh / N + φb) < 1 (4).

[0183] [Note 5]

[0184] The illumination optical system according to any one of Note 1 to Note 4, in which

[0185] in a case where the threshold value is set to θh,

[0186] the unit of θh is set to degrees,

[0187] and the refractive index of the substrate at the d line is set to N,

[0188] the illumination optical system satisfies a conditional expression (5) represented by:

[0189] 3 < φa - θh / N < 10 (5).

[0190] [Note 6]

[0191] The illumination optical system according to any one of Note 1 to Note 5, in which

[0192] in a case where a half width at a value of 1 / 4 of the maximum light quantity in the light diffusion angle distribution in a case where the incident angle is the threshold value or more is set to φaq,

[0193] the illumination optical system satisfies a conditional expression (6) represented by:

[0194] 0.5 < φa / φaq < 0.95 (6).

[0195] [Note 7]

[0196] The illumination optical system according to any one of Note 1 to 6, in which

[0197] In a case where a half width at a value of 1 / 4 of a maximum light amount in the light diffusion angle distribution at the incidence angle smaller than the threshold value is set as φbq,

[0198] The illumination optical system satisfies a conditional expression (7) expressed by the following expression:

[0199] 0.5 < φb / φbq < 0.95 (7).

[0200] [Note 8]

[0201] The illumination optical system according to any one of Note 1 to Note 7, wherein

[0202] The light guide includes a light blocking member on the central axis.

[0203] [Note 9]

[0204] An endoscope provided with the illumination optical system according to any one of Note 1 to Note 8.

Claims

1. An illumination optical system comprising a light guide of an endoscope and a diffusion plate disposed on an emission side of the light guide and diffusing light from the light guide, wherein the diffusion plate comprises a substrate and a diffusion surface provided on a surface of the substrate on the light guide side, a light diffusion angle distribution on the diffusion surface differs depending on an incident angle of light to the diffusion surface, a half value width of the light diffusion angle distribution in a case where the incident angle is equal to or more than a threshold value that is set in advance is set to φa, a half value width of the light diffusion angle distribution in a case where the incident angle is less than the threshold value is set to φb, and units of φa and φb are set to degrees, the illumination optical system satisfies a conditional expression (1) represented by the following expression: 0.1 < φa / φb < 0.7 (1) when φa and φb are set to degrees.

2. The illumination optical system according to claim 1, wherein a thickness of the diffusion plate is set to t, a radius of an outermost diameter of the diffusion plate is set to H, a radius of the light guide is set to G, the threshold value is set to θh, a unit of θh is set to degrees, and a refractive index of the substrate at a d line is set to N, the illumination optical system satisfies a conditional expression (2) represented by the following expression: 0.4 < (t / (H-G)) x tan(θh / N+φa) < 2 (2) when φa and φb are set to degrees.

3. The illumination optical system according to claim 1 or 2, wherein a thickness of the diffusion plate is set to t, a radius of an outermost diameter of the diffusion plate is set to H, the threshold value is set to θh, a unit of θh is set to degrees, and a refractive index of the substrate at a d line is set to N, the illumination optical system satisfies a conditional expression (3) represented by the following expression: 0.1 < (t / H) x tan(θh / N+φb) < 1 (3) when φa and φb are set to degrees.

4. The illumination optical system according to claim 1 or 2, wherein the threshold value is set to θh, a unit of θh is set to degrees, and a refractive index of the substrate at a d line is set to N, the illumination optical system satisfies a conditional expression (4) represented by the following expression: 0.3 < (θh / N+φa) / (θh / N+φb) < 1 (4) when φa and φb are set to degrees.

5. The illumination optical system according to claim 1 or 2, wherein the threshold value is set to θh, a unit of θh is set to degrees, and a refractive index of the substrate at a d line is set to N, the illumination optical system satisfies a conditional expression (5) represented by the following expression: 3 < φa-θh / N < 10 (5) when φa and φb are set to degrees.

6. The illumination optical system according to claim 1 or 2, wherein a half width at a value of 1 / 4 of a maximum light amount in the light diffusion angle distribution in a case where the incident angle is equal to or more than the threshold value is set to φaq, the illumination optical system satisfies a conditional expression (6) represented by the following expression: 0.5 < φa / φaq < 0.95 (6) when φa and φb are set to degrees.

7. The illumination optical system according to claim 1 or 2, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In a case where a half width at a value of 1 / 4 of a maximum light amount in the light diffusion angle distribution at the incidence angle smaller than the threshold value is set as φbq, The illumination optical system satisfies a conditional expression (7) expressed by the following expression: 0.5 < φb / φbq < 0.95 (7).

8. The illumination optical system according to claim 1 or 2, wherein The light guide includes a light-blocking member on the central axis.

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

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