Illumination optical system for endoscopes, optical adapter for endoscopes

Abstract

To provide an illumination optical system for endoscope that can diffuse illumination light only in a predetermined direction with less light distribution unevenness without reducing a light amount of the illumination light in a visual field.SOLUTION: A light transmission optical member 51 for endoscope includes: an incident surface 51c provided at a distal end portion 11 of an insertion section 5, on which light is made incident as incident light from a proximal end side of the insertion section 5; and emission surfaces 51a and 51b for emitting the light as illumination light. The emission surfaces 51a and 51b each include a diffusing section DS which diffuses the emitted light. The diffusing section DS includes a plurality of convex-shaped sections UF extending in a predetermined direction OC on the emission surfaces 51a and 51b. Each of the convex-shaped sections UF includes: a slope section IP1 having an angle θa with respect to the emission surfaces 51a and 51b, and totally reflecting the incident light; and a slope section IP2 having an angle θb smaller than the angle θa with respect to the emission surfaces 51a and 51b and transmitting and emitting reflected light totally reflected on the slope section IP1 and the incident light.SELECTED DRAWING: Figure 15

Description

[Technical field]

[0001] The present invention relates to an illumination optical system for an endoscope, an optical adapter for an endoscope, and To In particular, an illumination optical system for an endoscope that diffuses emitted light, and an optical adapter for an endoscope To Regarding. [Background technology]

[0002] Endoscopes are widely used in industrial and medical fields. An endoscope has an insertion section and emits illumination light from the tip of the insertion section. Reflected light of the illumination light from a subject is received by an observation window, and an image of the subject is obtained by capturing an image of the subject inside the subject.

[0003] Endoscopes include endoscopes for direct viewing, endoscopes for side viewing, etc. In order to uniformly irradiate an object with illumination light, a diffusion element having a diffusion surface that diffuses light is often provided in an illumination optical system.

[0004] For example, Japanese Patent Application Laid-Open Publication No. 2019-69043 proposes an endoscope illumination optical system that uses a U-shaped prism to reduce the amount of light that is not totally reflected and leaks to the outside, thereby improving the transmission efficiency of illumination light. In the endoscope proposed in this proposal, a diffusion element having a diffusion surface is provided to diffuse the illumination light emitted from the U-shaped prism evenly in all directions, i.e., in two-dimensional directions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-69043 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when using a diffusion element that diffuses light evenly in two dimensions, there is a problem in that the illumination light is diffused, for example, outside the field of view of the endoscopic image displayed on the monitor, reducing the amount of light within the field of view.

[0007] For example, the above-mentioned U-prism has a reflective surface that is tilted so that the light is directed toward the exit surface. Since the distribution of the illumination light reflected by the reflective surface is not isotropic, if a diffusion element is placed on the exit side of the U-prism, the total amount of light within the field of view will be reduced.

[0008] Also, in order to diffuse light in a one-dimensional direction corresponding to the horizontal direction of the screen in accordance with the shape of the horizontally long monitor screen on which the endoscopic image is displayed, a diffusion element having an uneven surface with a cross-sectional shape of, for example, a triangular shape can be provided on the illumination light output side. However, simply using a diffusion element having an uneven surface with a cross-sectional shape such as a triangular shape causes a problem in that the return light reflected by the uneven surface of the diffusion element increases, reducing the amount of light.

[0009] Fig. 27 is a diagram for explaining the reduction in the amount of light in a diffusion element having an uneven surface with a trapezoidal cross-sectional shape. Fig. 27 shows a cross section of a part of the uneven surface. As shown in Fig. 27, incident light R1 shown by a dashed line is refracted at the slope of the uneven surface of the diffusion element DE and is emitted as outgoing light R1E, ​​while incident light R2 shown by a dashed line is totally reflected by the uneven surface of the diffusion element DE and becomes return light R2E.

[0010] Therefore, the present invention provides an endoscope illumination optical system and an endoscope optical adapter capable of diffusing illumination light only in a predetermined direction with little unevenness in light distribution without reducing the amount of illumination light in the field of view. Ta The purpose is to provide. [Means for solving the problem]

[0011] An illumination optical system for an endoscope according to one aspect of the present invention is an illumination optical system for an endoscope having an insertion portion to be inserted into a subject, the illumination optical system comprising an optical element provided at a tip portion of the insertion portion and having an incident surface into which light is incident from a base end side of the insertion portion as incident light, and an exit surface from which the light is emitted as exit light, the exit surface having a diffusion section which diffuses the exit light, the diffusion section having a plurality of convex sections extending along a predetermined direction on the exit surface, each of the convex sections comprising a total reflection surface which has a first angle with respect to the exit surface and which totally reflects the incident light, and a transmission surface which has a second angle with respect to the exit surface smaller than the first angle and which transmits and emits the reflected light totally reflected by the total reflection surface and the incident light. When a depth of a first groove formed by two adjacent total reflection surfaces is Ha and a depth of a second groove formed by two adjacent transmission surfaces is Hb, the relational expression Ha≧Hb is satisfied, and when a length of the total reflection surface in the longitudinal direction is a and a length of the transmission surface in the longitudinal direction is b, the relational expression a≦b is satisfied when the side surface of the convex portion is viewed from a direction perpendicular to the longitudinal axis of the insertion portion.

[0012] An optical adapter for an endoscope according to one aspect of the present invention is an optical adapter that can be attached to a tip portion of an insertion portion of an endoscope having an insertion portion to be inserted into a subject, the optical adapter comprising: an optical element provided at the tip portion and having an entrance surface into which light is incident from a base end side of the insertion portion as incident light and an exit surface from which the light is exited as exit light; and an illumination window through which the exit light from the exit surface of the optical element is exited, the exit surface having a diffusion section that diffuses the exit light, the diffusion section having a plurality of convex sections extending along a predetermined direction on the exit surface, each of the convex sections having a total reflection surface that has a first angle with respect to the exit surface and that totally reflects the incident light, and a transmission surface that has a second angle with respect to the exit surface that is smaller than the first angle and that transmits and exits the reflected light totally reflected by the total reflection surface and the incident light. wherein, when a depth of a first groove formed by two adjacent total reflection surfaces is Ha and a depth of a second groove formed by two adjacent transmission surfaces is Hb, a relational expression of Ha≧Hb is satisfied; and, when a length of the total reflection surface in the longitudinal direction is a and a length of the transmission surface in the longitudinal direction is b, a relational expression of a≦b is satisfied when a side surface of the convex portion is viewed from a direction perpendicular to the longitudinal axis of the insertion portion. . Effect of the Invention

[0014] According to the present invention, an illumination optical system for an endoscope and an optical adapter for an endoscope are provided that can diffuse illumination light only in a predetermined direction with little unevenness in light distribution without reducing the amount of illumination light in the field of view. Ta It can be achieved. [Brief description of the drawings]

[0015] [Figure 1]1 is a configuration diagram showing a configuration of an endoscope apparatus according to a first embodiment of the present invention. [Diagram 2] 1 is a perspective view of an optical adapter according to a first embodiment of the present invention; [Diagram 3] 1 is a plan view of an optical adapter as seen from a subject according to a first embodiment of the present invention. FIG. [Figure 4] 4 is a cross-sectional view of the optical adapter taken along line IV-IV in FIG. 3. [Diagram 5] 5 is a cross-sectional view of the optical adapter taken along line VV in FIG. 4. [Figure 6] 6 is a cross-sectional view of the optical adapter taken along line VI-VI in FIG. 3. [Figure 7] 1 is a perspective view of an imaging optical system and an illumination optical system in an optical adapter according to a first embodiment of the present invention; [Figure 8] 1 is a front view of an imaging optical system and an illumination optical system in an optical adapter according to a first embodiment of the present invention. [Figure 9] 2 is a right side view of the imaging optical system and the illumination optical system in the optical adapter according to the first embodiment of the present invention. FIG. [Figure 10] 1 is a perspective view of a light-transmitting optical member according to a first embodiment of the present invention. [Figure 11] 1 is a perspective view of one of two extending portions of a light transmission optical member according to a first embodiment of the present invention; [Figure 12] 2 is a perspective view of a diffusion portion of each extension portion of a light-transmitting optical member and an optical member arranged above a diffusion surface according to a first embodiment of the present invention. FIG. [Figure 13] 2 is a side view of the diffusion portion of each extension portion of the light-transmitting optical member and two optical members arranged above the diffusion surface according to the first embodiment of the present invention. FIG. [Figure 14] 3 is an enlarged side view of a portion of the diffusion portion of each extension portion of the light-transmission optical member and the optical member arranged above the diffusion surface according to the first embodiment of the present invention. FIG. [Figure 15] 3 is a cross-sectional view showing the cross-sectional shapes of a plurality of convex portions according to the first embodiment of the present invention. FIG. [Figure 16] 4 is a cross-sectional view of a triangular prism member, which is a minimum unit that defines the shapes of the two slope portions of each convex portion, according to the first embodiment of the present invention. FIG. [Figure 17] FIG. 2 is a diagram for explaining the cross-sectional shape of each convex portion according to the first embodiment of the present invention. [Figure 18] FIG. 2 is a diagram for explaining optical paths in a diffusion section according to the first embodiment of the present invention. [Figure 19] 10 is a diagram showing the light distribution of illumination light when the angle θa of the convex portion is 75 degrees and the angle θb is 20 degrees, according to a simulation performed by the applicant, in the first embodiment of the present invention. FIG. [Figure 20] FIG. 11 is a diagram showing the light distribution of illumination light when the angle θa of the convex portion is 80 degrees and the angle θb is 20 degrees, according to a simulation performed by the applicant, in accordance with the first embodiment of the present invention. [Figure 21] FIG. 11 is a cross-sectional view showing the cross-sectional shape of a diffusion part having a plurality of convex parts according to a first modified example of the first embodiment of the present invention. [Figure 22] 11 is a cross-sectional view showing the cross-sectional shape of a diffusion portion having a plurality of convex portions according to a second modified example of the first embodiment of the present invention. FIG. [Diagram 23] FIG. 11 is a cross-sectional view showing the cross-sectional shape of a diffusion part having a plurality of convex parts according to a fourth modified example of the first embodiment of the present invention. [Figure 24] FIG. 11 is a perspective view of a tip portion of an endoscope according to a second embodiment of the present invention. [Diagram 25] 13 is a plan view showing the arrangement of two optical elements and a rod lens in the tip portion according to the second embodiment of the present invention. FIG. [Figure 26] FIG. 13 is a plan view showing the arrangement of two optical elements and a rod lens in the tip portion according to the fourth modified example of the second embodiment of the present invention. [Figure 27] 1A and 1B are diagrams for explaining a reduction in the amount of light in a diffusion element having an uneven surface with a trapezoidal cross-sectional shape. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (First embodiment) (Configuration of the endoscope device)

[0017] FIG. 1 is a configuration diagram showing the configuration of an endoscope apparatus according to the present embodiment.

[0018] 1, an endoscope device 1 includes a device main body 2 equipped with functions such as a video processor, and an endoscope 3 connected to the device main body 2. The device main body 2 includes a display unit 4, such as a liquid crystal panel (LCD), on which an endoscopic image, an operation menu, etc. are displayed. The display unit 4 may be provided with a touch panel.

[0019] The endoscope 3 is configured to have an insertion section 5 as an endoscope insertion section to be inserted into a subject, an operation section 6 connected to the base end of the insertion section 5, and a universal cord 7 extending from the operation section 6. The endoscope 3 is detachable from the device body 2 via the universal cord 7.

[0020] The insertion section 5 is configured to have, in order from the distal end, a distal end portion 11, a bending portion 12, and a long flexible portion 13. The bending portion 12 is connected to the proximal end of the distal end portion 11, and is configured to be bendable, for example, in the up, down, left, and right directions. The flexible portion 13 is connected to the proximal end of the bending portion 12, and is flexible.

[0021] An imaging element 11x (FIG. 4), such as a CMOS image sensor, is built into the tip portion 11 of the insertion portion 5. The imaging element 11x receives incident light that is incident on an observation window (not shown) provided in the tip portion 11 of the insertion portion 5.

[0022] As shown by the arrow, a side-viewing optical adapter 10 can be detachably attached to the tip portion 11. By attaching the side-viewing optical adapter 10 to the tip portion 11, the endoscope 3 becomes a side-viewing endoscope. In other words, the optical adapter 10 can be attached to the tip portion 11 of the insertion portion 5 of the endoscope 3.

[0023] The operation unit 6 is provided with a bending joystick 6a for bending the bending portion 12 in the up, down, left and right directions. The user can bend the bending portion 12 in a desired direction by tilting the bending joystick 6a. In addition to the bending joystick 6a, the operation unit 6 is provided with various operation buttons such as buttons for instructing endoscope functions, for example, a freeze button, a bending lock button, and a recording instruction button.

[0024] If the display unit 4 is provided with a touch panel, the user may instruct the endoscope device 1 to perform various operations by operating the touch panel.

[0025] The display section 4 of the device body 2 displays an endoscopic image captured by an imaging element 11x (FIG. 4) of an imaging unit provided in the distal end section 11. Inside the device body 2, various circuits are provided, such as a control section (not shown) that performs image processing and various controls, and a recording device that records processed images in a memory (not shown). (Optical adapter configuration)

[0026] FIG. 2 is a perspective view of the optical adapter 10. FIG. 3 is a plan view of the optical adapter 10 as viewed from the subject side. FIG. 4 is a cross-sectional view of the optical adapter 10 taken along line IV-IV in FIG. 3. FIG. 5 is a cross-sectional view of the optical adapter 10 taken along line VV in FIG. 4. FIG. 6 is a cross-sectional view of the optical adapter 10 taken along line VI-VI in FIG. 3. FIG. 7 is a perspective view of the imaging optical system and the illumination optical system in the optical adapter 10. FIG. 8 is a front view of the imaging optical system and the illumination optical system in the optical adapter 10. FIG. 9 is a right side view of the imaging optical system and the illumination optical system in the optical adapter 10.

[0027] As shown by the two-dot chain line in FIG. 4, the tip 11 of the insertion portion 5 has a cylindrical tip rigid member 11a, and a male screw portion 11b is formed in a partial region R1 of the outer circumferential surface of the tip rigid member 11a.

[0028] The optical adapter 10 for side viewing has a cylindrical shape and has a cylindrical stop ring 10a on the base end side. The stop ring 10a is rotatable around the central axis O (here, the central axis of the tip portion 11) of the insertion portion 5 (hereinafter, referred to as axis O), and a female screw portion 10b that can be screwed into a male screw portion 11b is formed on the inner peripheral surface of the base end of the stop ring 10a. When the optical adapter 10 is attached to the tip portion 11, the axis O coincides with the central axis of the cylindrical optical adapter 10.

[0029] The optical adapter 10 can be attached and fixed to the tip portion 11 by inserting the tip rigid member 11a inside the stop ring 10a and rotating the stop ring 10a in a predetermined direction to screw the male screw portion 11b into the female screw portion 10b. When the stop ring 10a is rotated in a predetermined direction, the inward flange portion 10c provided at the tip portion of the stop ring 10a presses the step portion of the adapter body 31 of the optical adapter 10. As a result, the optical adapter 10 is firmly fixed to the tip portion 11.

[0030] Moreover, the optical adapter 10 can be removed from the tip portion 11 by rotating the retaining ring 10a in the direction opposite to the predetermined direction.

[0031] As shown in FIGS. 2 and 3, an observation window 22 for side viewing and two illumination windows 23a, 23b are provided on either side of the observation window 22 on the side surface of the tip end of the optical adapter 10.

[0032] 3, when viewed from the front, the observation window 22 has a partially circular shape with two straight line portions 22a cut on both sides along the axis O. Two illumination windows 23a, 23b are disposed adjacent to the two straight line portions 22a of the observation window 22. The observation window 22 takes in light from the sides of the tip portion 11 of the insertion section 5.

[0033] When viewed from the front, each of the illumination windows 23a and 23b has an elongated shape extending parallel to the axis O, and as shown in FIG. 3, is a substantially rectangular shape with the four corners chamfered.

[0034] As shown in Fig. 4, a cover member 32 is fixed to the adapter body 31 of the optical adapter 10 so as to cover the tip surface of the adapter body 31. The cover member 32 has a cylindrical shape with a closed tip side. The cylindrical adapter body 31 is arranged so as to fit inside the cylindrical member 33. The cylindrical member 33 is fixed to the adapter body 31 by a fixing means such as a screw (not shown). The cylindrical member 33 is arranged so as to fit inside the cylindrical cover member 32. The cover member 32 is fixed to the cylindrical member 33 by a fixing means such as a screw (not shown).

[0035] The cover member 32 and the cylindrical member 33 each have openings 32a, 33a formed by being cut out along the direction of the axis O so as to pass through a position a predetermined distance away in the outer diameter direction from the axis O. The observation window 22 and the two illumination windows 23a, 23b are disposed in the two openings 32a, 33a formed in the cover member 32 and the cylindrical member 33.

[0036] A plano-concave lens 41 is positioned in the observation window 22 by a positioning portion 42 and is fixed to the adapter body 31, the cover member 32, and the cylindrical member 33 with an adhesive. The front surface of the plano-concave lens 41 is flat, and the back surface is concave. The positioning portion 42 is formed by a part of the adapter body 31.

[0037] On the rear surface of the plano-concave lens 41, a prism portion 43 consisting of two prisms 43a and 43b is disposed.

[0038] The adapter body 31 is formed with a cylindrical hole 31a parallel to the axis O. A lens portion 44 consisting of two lenses 44a, 44b aligned along the central axis O1 of the hole 31a is disposed on the base end side of the prism portion 43 and fixed in the hole 31a of the adapter body 31 with an adhesive. A cover glass 45 is disposed on the base end side of the lens portion 44 and fixed in the hole 31a of the adapter body 31 with an adhesive.

[0039] The joint surface of the two prisms 43a and 43b constitutes a reflecting surface that reflects the light from the plano-concave lens 41 toward the lens section 44. This reflecting surface can be made of a metal film or a multi-layer film. Specifically, the reflecting surface can be formed by coating with a metal such as aluminum. The reflecting surface may be configured to simply direct the total reflected light toward the lens section 44 without performing processing such as coating. Therefore, the prism section 43 is fixed to the adapter body 31 by an adhesive so that the traveling direction of the light from the plano-concave lens 41 is changed by 90 degrees and output toward the lens section 44. The plano-concave lens 41, the prism section 43, the lens section 44, the cover glass 45, and a group of lenses in the tip section 11 (not shown) constitute the observation optical system of the endoscope 3. The optical axes of the prism section 43 and the lens section 44 do not coincide with the axis O.

[0040] As described above, the plano-concave lens 41, prism portion 43, lens portion 44, and cover glass 45 of the optical adapter 10 constitute an observation optical system that emits light taken in through the observation window 22 from the distal end side to the proximal end side along the longitudinal axis of the distal end portion 11. An aperture stop 47 is disposed on the proximal end side of the prism portion 43.

[0041] 6 to 9, in the illumination window 23a, two optical members 23a1 and 23a2 stacked in a direction perpendicular to the axis O are positioned by a positioning portion 42 and fixed to the adapter body 31, the cover member 32, and the cylindrical member 33 by an adhesive. The two optical members 23a1 and 23a2 are bonded together by an optical adhesive. The optical adhesive may be, for example, a resin adhesive that is hardened by exposure to ultraviolet light.

[0042] Similar to the illumination window 23a, the illumination window 23b has two optical members 23b1 and 23b2 stacked in a direction perpendicular to the axis O, positioned by a positioning portion 42 and fixed to the adapter body 31, the cover member 32, and the cylindrical member 33 by adhesive. The two optical members 23b1 and 23b2 are bonded together by an optical adhesive. The illumination windows 23a and 23b emit illumination light to the sides of the tip portion 11.

[0043] The optical members 23a1 and 23b1 are elongated, plate-shaped glass members. The optical members 23a2 and 23b2 have a diffusion surface (indicated by dotted lines in Figs. 6, 8, and 9) that is a ground glass-like rough surface on the surface facing the optical members 23a1 and 23b1. The rough diffusion surface diffuses light isotropically (randomly). This can further eliminate uneven light distribution. The optical members 23a2 and 23b2 are bonded to the optical members 23a1 and 23b1 on their diffusion surface side with an optical adhesive that has a different refractive index from the optical members 23a1 and 23b1 and the optical members 23a2 and 23b2, respectively, and light is scattered by each diffusion surface.

[0044] In addition, the grained surface of the glass component has a large refractive index difference and is too diffuse at the surface in contact with air, causing the light distribution to be too wide. Therefore, in order to reduce the diffusion angle of the grain and reduce the amount of speckling, the glass components are bonded together with an optical adhesive with a refractive index of 1.52 or 1.56 (in this example, the refractive index of glass is 1.8).

[0045] Furthermore, if the aforementioned grained surface or the diffusion structure described below are exposed to air, the grained surface may be scratched or liquid droplets may adhere to the surface when the endoscope 3 is used, causing changes in the optical characteristics. Therefore, by using the optical members 23a1 and 23b1 as cover glass, scratches and the like can be prevented.

[0046] Since the surfaces of the cover member 32 and the openings 32a, 33a of the cylindrical member 33, the plano-concave lens 41 and the two optical members 23a1, 23b1 are flat, the optical adapter 10 has a flat portion 10p formed by these flat surfaces and parallel to the axis O.

[0047] Illumination light is emitted from the illumination windows 23a and 23b in a direction LD perpendicular to the axis O (hereinafter, referred to as the illumination direction LD).

[0048] A hole 31b for the rod lens 46 is formed in the adapter body 31 along the axis O. The center of the hole 31b does not coincide with the axis O, and the hole 31b is formed in the adapter body 31 offset from the axis O in the outer diameter direction. The rod lens 46 is inserted into the hole 31b and fixed to the adapter body 31 by adhesive or the like. Therefore, the cross-sectional shape of the hole 31b approximately coincides with the outer diameter shape of the rod lens 46. As shown in FIG. 5, the cross-sectional shape of the rod lens 46 perpendicular to the axis O is flat, the surface 46a on the axis O side is flat, and the surface 46b on the outer diameter side is a partial cylindrical shape protruding in the outer diameter direction.

[0049] 4, a light guide 11y for illumination light is inserted into the insertion portion 5. The tip surface of the light guide 11y is disposed facing the back surface of an illumination window (not shown) of the tip portion 11. The rod lens 46 is disposed in the optical adapter 10 so that the illumination window (not shown) of the tip portion 11 faces the base end surface of the rod lens 46 when the optical adapter 10 is attached to the tip portion 11.

[0050] A light transmitting optical member 51 is disposed on the tip side of the tip surface of the rod lens 46 and is fixed to the adapter body 31 by adhesive or the like.

[0051] The illumination windows 23a, 23b, the light-transmitting optical member 51, and the rod lens 46 constitute an endoscope illumination optical system for the endoscope 3 having an insertion portion 5 that is inserted into a subject.

[0052] 7, light L1 from the subject enters the observation window 22 from the side of the optical adapter 10. The light L1 enters the plano-concave lens 41, is reflected by the prism portion 43, and exits toward the imaging optical system of the tip portion 11 through the lens portion 44 and the cover glass 45.

[0053] Light L2 emitted from the tip surface of the light guide 11y of the tip portion 11 is incident on the base end surface of the rod lens 46, enters the incident surface which is the base end surface of the light transmission optical member 51 from the tip surface of the rod lens 46, exits from the exit surface of the light transmission optical member 51, and is emitted to the side of the optical adapter 10 through the two illumination windows 23a, 23b. (Configuration of the light transmission optical member 51)

[0054] Next, the configuration of the light-transmitting optical member 51 of the illumination optical system will be described.

[0055] Fig. 10 is a perspective view of the light transmission optical member 51. Fig. 11 is a perspective view of one of two extending portions of the light transmission optical member 51. The configuration and operation of the light transmission optical member 51 of this embodiment are substantially the same as the configuration disclosed in JP 2019-69043 A, and therefore will be described briefly here, and only the configuration different from the configuration disclosed in that publication will be described briefly.

[0056] The light-transmitting optical member 51 is an optical member made of transparent glass or plastic and having a substantially U-shape when viewed from the axial direction O of the optical adapter 10, as shown in FIG.

[0057] The light transmission optical member 51 has a partial cylindrical portion 51X and two extending portions 51A and 51B extending from both circumferential ends of the partial cylindrical portion 51X. The above-mentioned prism portion 43 is disposed in the substantially U-shaped light transmission optical member 51 so as to be surrounded by the partial cylindrical portion 51X and the two extending portions 51A and 51B.

[0058] That is, the light transmission optical member 51 is a prism whose cross section, as viewed from the tip side of the longitudinal axis, is formed into a substantially U-shape or a partial shape of a substantially U-shape so that the observation optical system is disposed inside.

[0059] An exit surface 51a is formed on an end face of the extending portion 51A, and an exit surface 51b is formed on an end face of the extending portion 51B. Hereinafter, in the light transmission optical member 51, the direction in which the exit surfaces 51a, 51b of the extending portions 51A, 51B are located is also referred to as the upper direction.

[0060] Each of the emission surfaces 51a, 51b is provided with a diffusion section DS for diffusing light in a predetermined direction (in this embodiment, a direction parallel to the axis O). The diffusion section DS is formed using a molding technique. The diffusion section DS has a plurality of convex sections UF (FIGS. 12 and 13). The plurality of convex sections UF are formed on the emission surfaces 51a, 51b so as to extend along a direction perpendicular to the axis O. The diffusion section DS is formed at the same time as the light transmission optical member 51 is manufactured by molding using a mold. Therefore, the diffusion section DS can be formed by molding when the light transmission optical member 51 is manufactured, and therefore has good processability.

[0061] Alternatively, the diffusion portions DS may be provided on the extensions 51A and 51B by bonding a plate-like member having the diffusion portions DS to the emission surfaces 51a and 51b with an optical adhesive.

[0062] A flat surface 51a1 is formed on the tip side of the extending portion 51A, and a flat surface 51b1 is formed on the tip side of the extending portion 51B. A substantially U-shaped flat surface 51c is formed on the base end side of the light transmission optical member 51. A part of the flat surface 51c, i.e., the area facing the tip surface of the rod lens 46, is the light incidence surface.

[0063] That is, the light transmission optical member 51 is an illumination optical system and is provided at the tip portion 11 of the insertion portion 5. The light transmission optical member 51 is an optical element having a flat portion 51c as an incident surface and exit surfaces 51a, 51b that emit light as illumination light. The flat portion 51c is an incident surface on which light is incident at the base end side of the tip portion 11 along the longitudinal axis direction of the insertion portion 5. The exit surfaces 51a, 51b emit light as illumination light.

[0064] A recess 51U is formed on the tip side of the partial cylindrical portion 51X. The recess 51U is formed in a substantially V-shape when the light transmission optical member 51 is viewed from the subject on which the illumination light is applied. Two curved reflecting surfaces CS1 and CS2 are formed in the recess 51U of the light transmission optical member 51.

[0065] The two reflecting surfaces CS1 and CS2 are provided symmetrically with respect to a plane passing through the central axis of the tip portion 11. The two reflecting surfaces CS1 and CS2 are curved surfaces that have been given a reflective treatment such as an aluminum coating. Note that CS1 and CS2 may not be given a reflective treatment such as a coating, and the totally reflected light may simply be directed toward the exit surfaces 51a and 51b.

[0066] By providing two reflecting surfaces CS1 and CS2 in the recess 51U, the angle of incidence of the light reflected by the two reflecting surfaces CS1 and CS2 when it enters the outer peripheral surface of the light transmission optical member 51 can be made equal to or greater than the critical angle, so that almost all of the light from the light guide is totally reflected and reflected toward the two illumination windows, thereby improving the light transmission efficiency. (Configuration of the diffusion section DS)

[0067] Next, the diffusion portion DS of the light emitted from the substantially U-shaped light transmission optical member 51 will be described. Fig. 12 is a perspective view of the diffusion portion DS of each extension portion of the light transmission optical member 51 and the optical member arranged above the diffusion surface. Fig. 13 is a side view of the diffusion portion DS of each extension portion of the light transmission optical member 51 and two optical members arranged above the diffusion surface. Fig. 14 is an enlarged side view of the diffusion portion DS of each extension portion of the light transmission optical member 51 and a part of the optical member arranged above the diffusion surface.

[0068] The light transmitting optical member 51 is made of plastic and has a refractive index of 1.5. The optical members 23a2 and 23b2 are disposed above the emission surfaces 51a and 51b via an air gap g having a refractive index of 1. The optical members 23a1 and 23b1 are fixed in close contact with the upper sides of the optical members 23a2 and 23b2, respectively, by an optical adhesive (not shown). As shown in FIG. 13, the optical members 23a1 and 23b1 are bonded to the grained surfaces (indicated by dotted lines) of the optical members 23a2 and 23b2 by an optical adhesive (not shown). The optical members 23a1, 23b1, 23a2, and 23b2 are made of glass and have a refractive index of 1.8.

[0069] In addition, the grained surface of the glass component has a large refractive index difference and is too diffuse at the surface in contact with air, causing the light distribution to be too wide. Therefore, in order to reduce the diffusion angle of the grain and reduce the amount of speckling, the glass components are bonded together with an optical adhesive with a refractive index of 1.52 or 1.56 (in this example, the refractive index of glass is 1.8).

[0070] In the light transmission optical member 51 having a substantially U-shape, light incident on the flat portion 51c is reflected by two reflecting surfaces CS1 and CS2. The light reflected by the two curved reflecting surfaces CS1 and CS2 has a characteristic that it is widely diffused in a direction perpendicular to the axis O due to the shape of the reflecting surfaces, but is not widely diffused in a direction parallel to the axis O. Therefore, since the light is not diffused in a direction parallel to the axis O, uneven light distribution occurs. Even if a conventional diffusion element that diffuses light isotropically in two dimensions is used for a light transmission optical member having such light distribution characteristics, the uneven light distribution is not improved, and there is a problem that the diffusion element diffuses light outside the field of view, reducing the amount of light in the field of view.

[0071] Therefore, in this embodiment, in order to diffuse light in a direction parallel to the axis O, a diffusion section DS consisting of a plurality of convex sections UF formed along a direction perpendicular to the axis O is formed on the emission surfaces 51a, 51b of the extension sections 51A, 51B. Each diffusion section DS diffuses light along the axis O direction in each extension section 51A, 51B.

[0072] As shown in Figs. 12 to 14, the diffusion section DS is formed with a plurality of convex portions UF formed on the emission surfaces 51a, 51b of the extension sections 51A, 51B. Specifically, the diffusion section DS has a plurality of convex portions UF extending linearly along a predetermined direction on the emission surfaces 51a, 51b. That is, each convex portion UF is formed so as to extend linearly along a direction OC perpendicular to the axis O on the emission surfaces 51a, 51b. As shown in Fig. 14, each convex portion UF has two inclined surface portions IP1 and two inclined surface portions IP2. Each convex portion UF has two convex portions P1, P2. As shown in Fig. 14, the inclined surface portion IP1 is a steep slope, and the inclined surface portion IP2 is a gentle slope having a smaller inclination angle than the inclined surface portion IP1.

[0073] The two protrusions P1, P2 of each protrusion UF are also formed to extend linearly along the direction OC. One of the two inclined surfaces IP1 and one of the two inclined surfaces IP2 form the protrusion P1, and the other of the two inclined surfaces IP1 and the other of the two inclined surfaces IP2 form the protrusion P2.

[0074] A groove G1 is formed by two inclined surfaces IP1 between two adjacent convex portions UF. A groove G2 is formed by two inclined surfaces IP2 that are plane-symmetrical with respect to the plane PP of each convex portion UF. The multiple grooves G1, G2 are arranged parallel to each other and alternately.

[0075] Fig. 15 is a cross-sectional view showing the cross-sectional shape of multiple convex portions UF. Fig. 15 shows a cross-section of a portion of the diffusion section DS when the emission surfaces 51a, 51b are viewed from the direction OC. As shown in Fig. 15, the inclined surfaces IP1 and IP2 of each convex portion P1 have angles θa and θb, respectively, with respect to a virtual plane RP parallel to the direction OC (i.e., a plane parallel to the emission surfaces 51a, 51b). The angle θb is smaller than the angle θa.

[0076] As described above, the protrusion P2 has a shape that is plane-symmetrical to the protrusion P1 with respect to the plane PP. Therefore, the inclined surfaces IP1 and IP2 of each protrusion P2 also have angles θa and θb, respectively, with respect to the imaginary plane RP that is parallel to the direction OC.

[0077] The shape of the convex portion UF will be described in detail. Fig. 16 is a cross-sectional view of a triangular prism member TM of a minimum unit MU that defines the shape of the two inclined surface portions IP1, IP2 of each convex portion UF. Fig. 17 is a diagram for explaining the cross-sectional shape of each convex portion UF.

[0078] The minimum unit MU has the shape of a triangular prism member TM having a triangular cross section as shown in Fig. 16. The shapes of the multiple protrusions P1, P2 are determined based on the shape of this minimum unit MU. As shown in Fig. 16, the triangular prism member TM having a triangular cross section has a bottom surface BS, a sloped surface SSa having an angle (interior angle) θa with respect to the bottom surface BS, and a sloped surface SSb having an angle (interior angle) θb with respect to the bottom surface BS. The shape of each protrusion UF is determined based on the shapes of these two sloped surfaces SSa, SSb.

[0079] As shown in Fig. 17, the shapes of the two protruding portions P1, P2 are determined based on the two sloped portions SSa and the two sloped portions SSb when the triangular prism member TM is symmetrical with respect to a plane PP that passes through a point on the sloped portion SSb, is parallel to the axis of the triangular prism member TM, and is perpendicular to the bottom portion BS. The sloped portions IP1 and IP2 that form the protruding portions P1, P2 respectively correspond to parts of the two sloped portions SSa, SSb of the triangular prism member TM.

[0080] The diffusion section DS is an uneven section formed by being disposed on the emission surfaces 51a, 51b as shown in FIG. 15. The uneven section is formed by disposing a plurality of convex portions UF at a predetermined interval d1 along an axial direction parallel to the axis O. Each convex portion UF has two convex portions P1, P2. The convex portions P1, P2 are formed by two inclined portions IP1, IP2. That is, the diffusion section DS has a shape by a plurality of convex portions UF disposed on the emission surfaces 51a, 51b of the extension portions 51A, 51B along an axial direction parallel to the axis O.

[0081] The joint JP between the inclined surfaces IP1 and IP2 of each of the projections P1 and P2 does not have to be sharp, and may have, for example, a rounded shape or a chamfered shape cut with multiple facets. (Diffusion and distribution of lighting light)

[0082] Next, the diffusion and light distribution of illumination light will be described.

[0083] 15, each convex portion UF has two inclined surfaces IP1 and IP2 that are plane-symmetric with respect to a plane PP perpendicular to the axis O. The convex portion P1 of each convex portion UF has a shape that is plane-symmetric with respect to the plane PP with respect to the convex portion P2. Since each convex portion UF has a shape that is plane-symmetric with respect to the plane PP, uneven light distribution in the left-right direction is prevented.

[0084] Fig. 18 is a diagram for explaining the optical path in the diffusion section DS. Light is incident toward the diffusion section DS, spreading at about 60°. As shown in Fig. 18, part of the light toward the diffusion section DS is totally reflected at the inclined surface IP1 of the convex portion P1, refracted at the inclined surface IP2, and becomes the outgoing light L1. Another part of the light toward the diffusion section DS is incident on the inclined surface IP2 of the convex portion P1, and becomes the outgoing light L2, refracted at the inclined surface IP2.

[0085] Further, another part of the light toward the diffusion section DS is totally reflected by the inclined surface IP1 of the convex portion P2, and refracts at the inclined surface IP2 to become the light L3 that is emitted. Another part of the light toward the diffusion section DS is incident on the inclined surface IP2 of the convex portion P2, and becomes the light L4 that is refracted at the inclined surface IP2 to become the light L4 that is emitted. As a result, the light L1, L2 and the light L3, L4 are emitted symmetrically with respect to the plane PP. Since each convex portion UF has two convex portions P1, P2, the emitted light is emitted with little unevenness in light distribution. If a diffusion element having an uneven surface with a triangular cross-sectional shape is simply used, a return light is generated as shown in FIG. 27, and the amount of light is reduced. However, by adopting a structure in which the diffusion section DS has a steep slope IP1 and a gentle slope IP2, the light can be emitted without generating a return light, and the amount of light can be prevented from decreasing.

[0086] 15, when the depths of the grooves G1 and G2 are Ha and Hb, respectively, and the lengths of the inclined surfaces IP1 and IP2 in the axial direction O as viewed from the direction OC are a and b, respectively, it is desirable to have the following relationship: Normally, incident light reaches the diffusion section DS with an angle of about 60°.

[0087] 60° <θa≦85° (1)

[0088] 0° <θb≦30° (2)

[0089] Ha ≧ Hb (3)

[0090] a≦b (4)

[0091] Equation (1) shows the relationship for total reflection of incident light at inclined surface portion IP1. Equation (2) shows the relationship for transmitting reflected light from inclined surface portion IP1 at inclined surface portion IP2. Equation (3) shows the relationship for transmitting a larger amount of reflected light from inclined surface portion IP1. Equation (4) shows the relationship for outputting reflected light from inclined surface portion IP1 from inclined surface portion IP2 with less loss. Equation (4) is also a relationship for adjusting the light distribution by changing the light intensity ratio between light L1 and L3 that is emitted at a large angle relative to plane PP and light L2 and L4 that is emitted at a small angle relative to plane PP.

[0092] That is, when viewed from a direction OC perpendicular to the axis O, the angle θa is an angle in the range of more than 60° and less than 85° with respect to the exit surfaces 51a, 51b, and the angle θb is an angle in the range of more than 0° and less than 30° with respect to the exit surfaces 51a, 51b.

[0093] Further, the depth Ha of the groove G1 formed by two adjacent inclined surface portions IP1 (total reflection surfaces) is deeper than the depth Hb of the groove G2 formed by two adjacent inclined surface portions IP2 (transmission surfaces).

[0094] As described above, each convex portion UF has an inclined surface IP1 and an inclined surface IP2 which are total reflection surfaces having an angle θa with respect to the exit surfaces 51a, 51b and totally reflecting the incident light. The inclined surface IP2 has an angle θb with respect to the exit surfaces 51a, 51b which is smaller than the angle θa, and is a transmission surface which transmits and emits the reflected light totally reflected by the inclined surface IP1 and the incident light directly incident on the inclined surface IP2.

[0095] Each convex portion UF has two convex portions P1, P2 formed by a total reflection surface and a transmission surface so as to be plane-symmetrical with respect to a plane (PP) that is perpendicular to the emission surfaces 51a, 51b and parallel to a predetermined direction.

[0096] According to simulations performed by the applicant, in a one-dimensional diffusion element having a diffusion section DS whose cross-sectional shape is an arrangement of multiple isosceles triangles, and each sloping surface of the diffusion element is at an angle of 10 degrees or 20 degrees to the base of the isosceles triangle, when light is incident from a direction perpendicular to the base, sufficient diffusion of the illumination light is not obtained.

[0097] In addition, according to simulations conducted by the applicant, in a one-dimensional diffusion element having a diffusion section DS whose cross-sectional shape is an arrangement of multiple isosceles triangles, and each sloping surface of the diffusion element is at an angle of 30 degrees, 40 degrees, 50 degrees or 60 degrees to the base of the isosceles triangle, when light is incident from a direction perpendicular to the base, reflection from the diffusion surface occurs, causing backlight to be generated and reducing the amount of light.

[0098] Furthermore, according to simulations performed by the applicant, in a one-dimensional diffusing element having a diffusing section DS whose cross-sectional shape is an arrangement of multiple isosceles triangles, and each diffusing element has an inclination of 70 degrees or 80 degrees to the base of the isosceles triangle, when light is incident from a direction perpendicular to the base, no return light is generated due to reflection on the diffusing surface, but uneven light distribution occurs.

[0099] In contrast, according to a simulation of the above-mentioned embodiment, when θa was 75 degrees and θb was 20 degrees, the illumination light was diffused in a specified direction, no return light was generated due to reflection at the diffusion section DS, and there was little unevenness in the light distribution.

[0100] Fig. 19 is a diagram showing the light distribution of the illumination light when the angle θa of the convex portion UF is 75 degrees and the angle θb is 20 degrees, according to a simulation performed by the applicant. As shown in Fig. 19, the central area CA is illuminated most brightly, but the peripheral area PA adjacent to the central area CA is also illuminated continuously and brightly. Since the illumination range of the illumination light is diffused only in a predetermined direction PO, it is diffused in a predetermined one-dimensional direction (the horizontal direction in Fig. 19) PO, and there is little unevenness in the light distribution. Therefore, for example, the illumination light can be emitted to match the field of view frame W (shown by a two-dot chain line) of the endoscope image displayed on a monitor.

[0101] Furthermore, according to a simulation of the diffusion section DS of the above-mentioned embodiment, even when the angle θa was 80 degrees and the angle θb was 20 degrees, diffusion was obtained in the specified direction (a direction parallel to the axis O), no return light was generated due to reflection at the diffusion section DS, and there was little unevenness in the light distribution.

[0102] Fig. 20 is a diagram showing the light distribution of illumination light when the angle θa of the convex portion UF is 80 degrees and the angle θb is 20 degrees, according to a simulation performed by the applicant. As shown in Fig. 20, the illumination range of the illumination light is diffused in a predetermined one-dimensional direction (the horizontal direction in Fig. 20) PO, and there is little unevenness in the light distribution.

[0103] Therefore, according to the above formulas (1) and (2), the amount of light is not reduced and the illumination light can be diffused in a predetermined direction. Also, according to the above formulas (3) and (4), the unevenness of the light distribution can be reduced.

[0104] As described above, according to the above-described embodiments, it is possible to provide an illumination optical system for an endoscope and an optical adapter for an endoscope that can diffuse illumination light in only a specified direction with little unevenness in light distribution without reducing the amount of illumination light within the field of view.

[0105] In the above-described embodiment, the endoscope 3 is for side viewing, emitting illumination light in a direction perpendicular to the longitudinal axis direction of the insertion portion 5 to observe the inside of the subject, but the above-described embodiment is also applicable to an oblique-viewing endoscope that emits illumination light in an oblique direction with respect to the axis O of the insertion portion 5 to observe the inside of the subject.

[0106] Next, a modified example will be described. (Variation 1)

[0107] In the above-described embodiment, in order to reduce uneven light distribution, each convex portion UF of the diffusion portion DS has convex portions P1, P2 that are plane-symmetrical with respect to the plane PP; however, the diffusion portion DS may have one convex portion for each convex portion, and multiple convex portions may be arranged, with the multiple convex portions being arranged plane-symmetrical.

[0108] Fig. 21 is a cross-sectional view showing the cross-sectional shape of a diffusion section having a plurality of convex portions UF1 according to Modification 1. Fig. 21 shows a cross section of a part of the diffusion section DS when the exit surfaces 51a, 51b are viewed from a direction OC.

[0109] In the first modification, each convex portion UF1 has inclined surface portions IP1 and IP2, and the multiple convex portions UF1 are formed on the emission surfaces 51a and 51b so as to extend linearly along a direction OC perpendicular to the axis O. Each convex portion UF1 has one convex portion P3. As shown in FIG. 21, each convex portion P3 is formed by one inclined surface portion IP1 and one inclined surface portion IP2.

[0110] Furthermore, halves of the multiple convex portions UF1 are arranged to be plane-symmetrical with respect to a plane PP1 perpendicular to the axis O. Halves of the multiple convex portions UF1 are arranged on the emission surfaces 51a and 51b to be plane-symmetrical with respect to the plane PP1 in FIG.

[0111] That is, some of the multiple convex portions UF1 are disposed on the emission surfaces 51a, 51b symmetrically with respect to the plane PP1 parallel to the direction OC perpendicular to the axis O with respect to other parts of the multiple convex portions UF1.

[0112] In this first modification, the above-mentioned formulas (1), (2), and (4) hold, but the following relationship (5) holds instead of the above-mentioned formula (3).

[0113] Ha = Hb (5)

[0114] The present modified example 1 can also provide the same effects as those of the above-described embodiment. (Variation 2)

[0115] In the above-mentioned variant example 1, in order to reduce uneven light distribution, the diffusion section DS has multiple convex portions UF1 that are plane-symmetrical with respect to a single plane PP1, but it may also have multiple convex portion groups, each of which has one convex portion and is made up of multiple convex portions arranged in plane symmetry.

[0116] Fig. 22 is a cross-sectional view showing the cross-sectional shape of a diffusion section having a plurality of convex portions UF1 according to Modification 2. Fig. 22 shows a cross section of a portion of the diffusion section DS when the emission surfaces 51a, 51b are viewed from the direction OC. Each convex portion UF1 of Modification 2 has the same shape as the convex portion UF1 of Modification 1.

[0117] 22, a plurality of (here, two) convex ridge portions UF1 are arranged so as to be plane-symmetrical with respect to a plane PP2 perpendicular to the axis O, and a plurality of convex ridge portion groups Gr1 each consisting of the plane-symmetrical plurality of (here, four) convex ridge portions UF1 are arranged on the emission surfaces 51a and 51b to form the diffusion portion DS. That is, the diffusion portion DS has a plurality of regions of the convex ridge portion groups Gr1.

[0118] In other words, there are provided a plurality of regions in which some of the multiple convex portions UF1 and other parts of the multiple convex portions UF1 are arranged on the emission surfaces 51a, 51b symmetrically with respect to a plane PP2 parallel to the direction OC.

[0119] In the present modified example 2, the above-mentioned formulas (1), (2), and (4) also hold, but the relationship of the above-mentioned formula (5) holds instead of the above-mentioned formula (3).

[0120] The second modification can also provide the same effects as those of the above-described embodiment. (Variation 3)

[0121] In the above-described example, the convex portion has parts on the exit surface that are plane-symmetric with respect to a specified plane, but it is not necessary for the convex portion to have plane-symmetric parts as long as the left and right light distribution is not significantly affected.

[0122] Specifically, the angle of the gently sloping surface portion IP2 may be changed, or the length b may be set to a different value for each convex portion. This makes it possible to reduce the unevenness of the light distribution on the left and right sides by appropriately designing the entire element, even if the arrangement of the convex portions is not plane symmetrical. Note that not only the angle and length of the gently sloping surface, but also the angle and length a of the steeply sloping surface portion IP1 may be changed as appropriate.

[0123] According to the third modification, the return light can be reduced and the amount of light can be increased. (Variation 4)

[0124] In the above-described first and second modifications, the plurality of convex portions have portions arranged in plane symmetry, but the plurality of convex portions do not have to be arranged in plane symmetry.

[0125] In this modification 4, the multiple convex portions UF1 are not arranged on the emission surfaces 51a and 51b so as to be plane-symmetrical with respect to the plane PP1 as shown in Fig. 21 of the above-mentioned modification 1. Therefore, in the case of this modification 4, the light distribution direction is biased in one direction.

[0126] Fig. 23 is a cross-sectional view showing the cross-sectional shape of a diffusion section having multiple convex portions UF1 according to Modification 4. Fig. 23 shows a cross section of a portion of the diffusion section DS when the emission surfaces 51a, 51b are viewed from the direction OC. Each convex portion UF1 of Modification 4 has the same shape as one side portion (the left side portion in Fig. 21) of the plane-symmetric multiple convex portions UF1 of Modification 1.

[0127] 23, a plurality of convex portions UF1 having the same cross-sectional shape are arranged on the emission surfaces 51a, 51b to form the diffusion portion DS. That is, the inclined surfaces IP1, IP2 of each convex portion UF1 have the same angle with respect to the imaginary plane RP parallel to the direction OC as the inclined surfaces IP1, IP2 of the other convex portions UF1.

[0128] In the fourth modified example, the above-mentioned formulas (1), (2), and (4) also hold, but the relationship in the above-mentioned formula (5) holds instead of the above-mentioned formula (3).

[0129] Therefore, the fourth modification is effective when it is desired to bias the light distribution in one direction, for example.

[0130] According to the fourth modification, the return light can be reduced and the amount of light can be increased.

[0131] In addition, in the present modified examples 1 to 4, each of the protrusions P1, P2, i.e., the joint JP between the inclined portions IP1 and IP2, does not have to be sharp, and may, for example, have a rounded shape or a chamfered shape cut with multiple facets. (Second embodiment)

[0132] The endoscopic device of the first embodiment is an endoscopic device for side viewing, whereas the endoscope of the endoscopic device of this embodiment is for direct viewing, emitting illumination light from an illumination window at the tip 11 forward along the longitudinal axis direction of the insertion portion 5.

[0133] The configuration of the endoscopic device of this embodiment is substantially the same as the configuration of the endoscopic device of the first embodiment, and therefore, in the configuration of the endoscopic device of this embodiment, the same components as those in the endoscopic device of the first embodiment are designated by the same symbols, and their descriptions are omitted; only the different configurations are described.

[0134] 24 is a perspective view of the tip portion 11A of the endoscope 3. An observation window 22x and an illumination window 23x are provided on a tip surface 11Aa of the tip portion 11A. Illumination light is emitted from the illumination window 23x, and the illumination light reflected from the subject is incident on the observation window 22x. The reflected light incident on the observation window 22x passes through an observation optical system (not shown) and is irradiated onto the imaging surface of the imaging element 11x.

[0135] The illumination window 23x has a shape extending in the horizontal direction SD in accordance with the shape of a rectangular endoscope image displayed on the monitor.

[0136] A light guide (not shown) that guides illumination light is inserted into the insertion portion 5. A partially cylindrical rod lens 46A is provided on the tip side of the light guide.

[0137] Fig. 25 is a plan view showing the arrangement of the two optical members 23A, 23B and the rod lens 46A in the tip portion 11A. Fig. 25 shows the arrangement of the two optical members 23A, 23B and the rod lens 46A when the tip portion 11A is viewed from above in the up-down direction UD perpendicular to the lateral direction SD. The entrance surface IS of the rod lens 46A and the exit surface on which the diffusion section DS is formed are parallel to each other.

[0138] For example, the rod lens 46A is made of plastic and has a refractive index of 1.5, and the optical members 23A and 23B are disposed with an air gap g having a refractive index of 1 therebetween. The optical member 23A is fixed in close contact with the optical member 23B by an optical adhesive (not shown). The rough surface (shown by a dotted line) of the optical member 23A is bonded to the optical member 23B by an optical adhesive (not shown). The optical members 23A and 23B are made of glass and have a refractive index of 1.8. Specifically, the refractive index of the optical adhesive may be 1.52 or 1.56, that is, a value smaller than that of the optical members 23A and 23B and larger than 1, which is the refractive index of air.

[0139] The tip surface of the rod lens 46A is provided with a diffusion section DS having a plurality of convex portions UF. The shape of the convex portions UF of the diffusion section DS is the same as that of the convex portions UF in the first embodiment, but may be the shape shown in the above-mentioned modified example 1 or modified example 2.

[0140] That is, the diffusion portion DS has a plurality of convex portions UF that extend linearly along a predetermined direction on the emission surface of the rod lens 46 A. The diffusion portion DS can be formed by molding when manufacturing the rod lens 46 A, and therefore has good processability.

[0141] Two glass optical members 23A and 23B are disposed on the tip surface side of the rod lens 46A with an air gap g between them. The optical members 23A and 23B are bonded and fixed with an optical adhesive (not shown). The surface of the optical member 23A on the optical member 23B side is provided with a grained surface (indicated by a dotted line) that has been processed to resemble ground glass.

[0142] Therefore, according to the above-described embodiment, it is possible to provide an illumination optical system for an endoscope and an optical adapter for an endoscope that can diffuse illumination light in only a specified direction with little unevenness in light distribution without reducing the amount of illumination light within the field of view.

[0143] It is also possible to provide a diffusion section DS on the incident surface IS side of rod lens 46A. In that case, however, when light passes through rod lens 46A and exits from the exit surface, the light that enters rod lens 46A leaks out from the side of rod lens 46A, reducing the amount of light exiting from the exit surface.

[0144] Furthermore, in Figures 24 and 25, the rod lens 46A as an optical element is arranged within the tip portion 11A of the insertion portion 5, but it may also be arranged within an optical adapter 10 that can be attached to the tip portion 11 of the insertion portion 5 shown in Figure 1. (Modification)

[0145] In the second embodiment described above, the rod lens 46A provided at the tip side of the light guide has a diffusion section DS, but it is also possible to arrange an optical element between the entrance surface on the base end side of the rod lens and the tip surface of the light guide, and have the diffusion section DS.

[0146] Fig. 26 is a plan view showing the arrangement of two optical elements and a rod lens in the tip portion according to a modified example of the second embodiment. Fig. 26 shows the arrangement of the two optical members 23A and 23B, the rod lens 46B, the optical element 52, and the light guide 11y1 when the tip portion 11A is viewed from above in the up-down direction UD perpendicular to the lateral direction SD. The incident surface IS of the rod lens 46B and the exit surface (where the diffusion section DS is formed) of the optical element 52 are parallel. The incident surface 52a of the optical element 52 and the tip surface of the light guide 11y1 are also parallel.

[0147] As shown in Fig. 26, the optical element 52 is disposed between the tip surface of the light guide 11y1 and the base end surface of the rod lens 46B. The optical element 52 is glass (or plastic) having a flat plate shape. The incident surface 52a of the optical element 52 has a flat surface, and the exit surface of the optical element 52 has a diffusion portion DS. The diffusion portion DS has a plurality of convex portions UF extending linearly along a predetermined direction on the exit surface of the optical element 52. As shown in Fig. 26, the convex portions UF have the same shape as the convex portions UF of the diffusion portion DS of the rod lens 46A in Fig. 25 described above.

[0148] Light incident on incident surface 52a of optical element 52 is diffused and emitted from diffusion section DS, which is the emission section of optical element 52. The diffused light is reflected internally within rod lens 46B and travels in various directions, and is emitted in a divergent manner from emission surface OS of rod lens 46B.

[0149] The light emitted from the optical element 52 is diffused by the diffusion section DS so as to have a spread in the horizontal direction SD (the up-down direction in FIG. 26). However, because the rod lens 46B has a partially cylindrical shape, the light from the diffusion section DS is reflected inside the rod lens 46B in various directions other than the horizontal direction SD.

[0150] As a result, the light emitted from the exit surface of the rod lens 46B is diffused and emitted in various directions, not just in the lateral direction SD, so that the same effects as in the second embodiment described above can be obtained. (Third embodiment)

[0151] The first and second embodiments relate to a substantially U-shaped light-transmitting optical member 51 or rod lens 46A as an optical element used in an endoscope, but the optical element having the diffusion section DS described in the first and second embodiments can also be used in devices other than an endoscope device as an optical element that diffuses illumination light only in a specified direction with little unevenness in light distribution without reducing the amount of light in the field of view.

[0152] In the second and third embodiments, too, each of the protrusions P1, P2, and P3, i.e., the joint JP between the inclined portions IP1 and IP2, does not have to be sharp, and may, for example, have a rounded shape or a chamfered shape cut with multiple facets.

[0153] As described above, according to each of the above-mentioned embodiments, it is possible to provide an illumination optical system for an endoscope, an optical adapter for an endoscope, and an optical element that can diffuse illumination light in only a predetermined direction with little unevenness in light distribution without reducing the amount of illumination light within the field of view.

[0154] The present invention is not limited to the above-described embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0155] 1 endoscopic device, 2 device body, 3 endoscope, 4 display unit, 5 insertion unit, 6 operation unit, 6a curved joystick, 7 universal cord, 10 optical adapter, 10a ring, 10b female screw portion, 10c inward flange portion, 10p flat portion, 11, 11A tip portion, 11Aa tip surface, 11a tip rigid member, 11b male screw portion, 11x imaging element, 11y, 11y1 light guide, 12 curved portion, 13 flexible portion, 22 observation window, 22x observation window, 22a straight portion, 23x illumination window, 23A, 23B optical member, 23a illumination window, 23a1, 23a2 optical member, 23b illumination window, 23b1 optical member, 31 adapter body, 31a, 31b hole, 32 cover member, 32a Opening, 33 cylindrical member, 41 plano-concave lens, 42 positioning portion, 43 prism portion, 43a, 43b prism, 44 lens portion, 44a lens, 45 cover glass, 46, 46A, 46B rod lens, 46a, 46b surface, 51 light transmission optical member, 51A, 51B extension portion, 51B extension portion, 51U recess, 51X partial cylindrical portion, 51a exit surface, 51a1 flat portion, 51b exit surface, 51b1, 51c flat portion, 52 optical element, 52a entrance surface.

Claims

1. An illumination optical system for an endoscope having an insertion portion to be inserted into a subject, an optical element provided at a tip end of the insertion portion, the optical element having an incident surface through which light is incident as incident light from a base end side of the insertion portion, and an exit surface through which the light is exited as exit light; the exit surface has a diffusion portion that diffuses the exit light, the diffusion section has a plurality of convex sections extending along a predetermined direction on the exit surface, each of the convex sections having a total reflection surface that has a first angle with respect to the exit surface and totally reflects the incident light, and a transmission surface that has a second angle with respect to the exit surface that is smaller than the first angle and transmits the reflected light totally reflected by the total reflection surface and the incident light to be emitted; When the depth of the first groove formed by two adjacent total reflection surfaces is Ha, and the depth of the second groove formed by two adjacent transmission surfaces is Hb, Ha≧Hb The following relation is satisfied: When the side surface of the convex portion is viewed from a direction perpendicular to the longitudinal axis of the insertion portion, the length of the total reflection surface in the longitudinal axis direction is a, and the length of the transmission surface in the longitudinal axis direction is b. a≦b An illumination optical system for an endoscope that satisfies the following relational expression.

2. 2. The endoscope illumination optical system according to claim 1, wherein each of the convex portions has two convex portions formed by the total reflection surface and the transmission surface so as to be plane-symmetric with respect to a plane orthogonal to the emission surface and parallel to the predetermined direction.

3. 2. The endoscope illumination optical system according to claim 1, wherein, when viewed from the predetermined direction, the first angle is an angle in the range of 60° or more and 85° or less with respect to the exit surface, and the second angle is an angle in the range of more than 0° and 30° or less with respect to the exit surface.

4. 2 . The endoscope illumination optical system according to claim 1 , wherein a portion of the plurality of convex portions is disposed on the emission surface in plane symmetry with respect to a plane parallel to the predetermined direction with respect to another portion of the plurality of convex portions.

5. 2. The endoscope illumination optical system according to claim 1, wherein a plurality of regions are provided on the exit surface in which a portion of the plurality of convex portions and another portion of the plurality of convex portions are arranged symmetrically with respect to a plane parallel to the predetermined direction.

6. 2. The illumination optical system for an endoscope according to claim 1, wherein the illumination optical system for an endoscope is an illumination optical system for a direct vision, an oblique vision, or a side vision endoscope.

7. 7. The endoscope illumination optical system according to claim 6, wherein when the endoscope illumination optical system is an illumination optical system for direct vision, the optical element is a rod lens.

8. 7. The endoscope illumination optical system according to claim 6, wherein when the endoscope illumination optical system is the side-viewing illumination optical system, the optical element is a prism having a substantially U-shape or a part of a substantially U-shape and having two reflective surfaces that reflect the incident light.

9. a first optical member provided on the exit surface side of the optical element and having a grained surface on a surface opposite to the surface facing the exit surface; 2. The illumination optical system for an endoscope according to claim 1, further comprising: the first optical member and a second optical member bonded to the grained surface by an adhesive.

10. An optical adapter that can be attached to a tip end of an insertion portion of an endoscope having an insertion portion to be inserted into a subject, an optical element provided at the tip portion, the optical element having an incident surface through which light is incident as incident light from a base end side of the insertion portion, and an exit surface through which the light is emitted as exit light; an illumination window through which the emitted light from the emission surface of the optical element is emitted; having the exit surface has a diffusion portion that diffuses the exit light, the diffusion section has a plurality of convex portions extending along a predetermined direction on the emission surface, each convex portion has a total reflection surface that has a first angle with respect to the exit surface and totally reflects the incident light, and a transmission surface that has a second angle with respect to the exit surface that is smaller than the first angle and transmits the reflected light totally reflected by the total reflection surface and the incident light to be emitted; When the depth of the first groove formed by two adjacent total reflection surfaces is Ha, and the depth of the second groove formed by two adjacent transmission surfaces is Hb, Ha≧Hb The following relationship is satisfied: When the side surface of the convex portion is viewed from a direction perpendicular to the longitudinal axis of the insertion portion, the length of the total reflection surface in the longitudinal axis direction is a, and the length of the transmission surface in the longitudinal axis direction is b. a≦b An optical adapter for endoscopes that satisfies the relational expression.

11. The optical adaptor for an endoscope according to claim 10, wherein the outgoing light is emitted from the illumination window in a direction perpendicular to or oblique to a longitudinal axis direction of the insertion portion.

12. The optical adaptor for an endoscope according to claim 10 , wherein the emission light is emitted from the illumination window along a longitudinal axis direction of the insertion portion toward a front of the tip portion.

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