Endoscope

Abstract

To provide an endoscope which can prevent reduction in an amount of illumination light and reduce the peak value of light intensity distribution to improve coagulation resistance of an in-vivo substance.SOLUTION: An illumination optical system 23 transmits illumination light from a light source 28 to the tip 17c of an insertion part via a light guide 27 to apply the illumination light to an observation portion. The illumination optical system 23 comprises: a first lens 41 positioned on the tip side of the light guide 27; and a second lens 42 located on the tip side of the first lens 41 with a fixed interval. The outer diameter of the second lens 42 is larger than that of the first lens 41 and is 2.1-3.0 mm.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an endoscope that emits illumination light from the distal end of an insertion portion. Background Art

[0002] Endoscopes are widely used in the medical field and the industrial field. An endoscope has an insertion portion that is inserted into a subject, and emits illumination light onto an observation target from the distal end of the insertion portion. The insertion portion of the endoscope is provided with a light guiding portion that guides illumination light supplied from a light source device to the distal end of the insertion portion. The inside of the subject can be observed by the light guiding portion guiding the illumination light and illuminating the observation target.

[0003] As the light guiding portion, it is general to include a light guide formed of an optical fiber bundle and an illumination optical system that emits illumination light to an observation site. The endoscopes described in Patent Documents 1 and 2 include an optical element having a light reflection function, and a three-plate illumination optical system combining two convex lenses. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Patent No. 5345171 Patent Document 2 International Publication No. 2017 / 130524 Summary of the Invention Problems to be Solved by the Invention

[0005] However, in the endoscopes described in the aforementioned Patent Documents 1 and 2, the intensity distribution at the light exit end is concentrated near the lens optical axis, and the peak value of light density increases, which may cause coagulation of in-vivo substances such as blood adhering to the lens surface. To avoid this phenomenon, it is necessary to reduce the amount of illumination light guided from the light source device. A reduction in the amount of illumination light may lead to insufficient performance, such as failure to achieve sufficient brightness in observation by the endoscope.

[0006] The present invention aims to provide an endoscope that can prevent a decrease in illumination light intensity and improve the coagulation resistance of biological substances by reducing the peak value of the light intensity distribution. [Means for solving the problem]

[0007] The endoscope of the present invention has an illumination optical system that transmits illumination light from a light source to the tip of the insertion section via a light guide, thereby irradiating the observation site from the tip. The illumination optical system comprises a first lens and a second lens, the outer diameter of the second lens being larger than the outer diameter of the first lens, and being 2.1 mm or more and 3.0 mm or less. The first lens is located on the tip side of the light guide. The second lens is positioned on the tip side of the first lens at a constant distance.

[0008] The outer diameter of the second lens is preferably 1.4 times or more the outer diameter of the first lens. The first lens is preferably a convex lens. The first lens is preferably a biconvex lens.

[0009] The second lens is preferably a convex lens. The second lens is preferably a convex-flat lens with a convex shape at the light incident end and a flat shape at the light exit end.

[0010] When the outer diameter of the second lens is D and the radius of curvature at the light incident end of the second lens is R, it is preferable that the second lens satisfies the following condition: 1.48 ≤ D / R.

[0011] It is preferable that an optical element having a light-reflecting function is placed between the light guide and the first lens. The optical element preferably has a light-entering end facing the light guide, an outer periphery having a light-reflecting function, and a convex-shaped light-emitting end. The optical element preferably has a total internal reflection function. The optical element preferably consists of a core and a cladding.

[0012] The endoscope of the present invention has an illumination optical system that transmits illumination light from a light source to the tip of the insertion section via a light guide, thereby irradiating the observation site from the tip. The illumination optical system comprises an optical element and a first lens, the outer diameter of the first lens being larger than the outer diameter of the optical element and being 2.1 mm or more and 3.0 mm or less. The optical element has a light incident end facing the light guide and an outer periphery having a light reflection function. The first lens is positioned on the tip side of the optical element at a constant distance.

[0013] The outer diameter of the first lens is preferably 1.4 times or more the outer diameter of the optical element. The first lens is preferably a concave lens. The first lens is preferably a concave-flat lens with a concave shape at the light incident end and a flat shape at the light exit end.

[0014] When the outer diameter of the first lens is D and the radius of curvature at the light incident end of the first lens is R, it is preferable that the first lens satisfies the following condition: 2.80 ≤ D / R.

[0015] The optical element preferably has a total internal reflection function. The optical element preferably consists of a core and a cladding. [Effects of the Invention]

[0016] According to the present invention, it is possible to prevent a decrease in illumination light intensity and to improve solidification resistance by reducing the peak value of the light intensity distribution. [Brief explanation of the drawing]

[0017] [Figure 1] This is an external view of the endoscope system. [Figure 2] This is a perspective view of the endoscope system. [Figure 3] This is a cross-sectional view of the main part of the tip of the insertion section. [Figure 4] This is a disassembled perspective view of the tip section. [Figure 5] This is an explanatory diagram illustrating the dimensional relationships of the illumination optical system. [Figure 6]It is a graph showing light intensity distributions in a conventional illumination optical system and the illumination optical system of the present invention. [Figure 7] It is a graph showing light intensity distributions when the ratio between the outer diameter and the radius of curvature of a second lens is changed. [Figure 8] It is a graph obtained by extracting a part of the light intensity distribution of FIG. 7. [Figure 9] It is a cross-sectional view of essential parts of the distal end portion of an insertion section in a second embodiment. [Figure 10] It is an exploded perspective view of the distal end portion in the second embodiment. [Figure 11] It is an explanatory diagram for explaining the dimensional relationship of the illumination optical system in the second embodiment. [Figure 12] It is a graph showing light intensity distributions when the ratio between the outer diameter and the radius of curvature of a first lens in the second embodiment is changed. MODE FOR CARRYING OUT THE INVENTION

[0018] [First Embodiment] [Schematic Configuration of Endoscope System] As shown in FIG. 1, an endoscope system 10 includes an endoscope 12, a light source device 13, a processor device 14, a display 15, and a user interface 16. The endoscope 12 is optically and electrically connected to the light source device 13, and is electrically connected to the processor device 14.

[0019] [Schematic Configuration of Endoscope] As shown in FIG. 2, the endoscope 12 includes an insertion section 17 to be inserted into the body of a subject, an operation section 18 provided at a proximal end portion of the insertion section 17, a universal cable 19 provided to the operation section 18, and an endoscope-side connector 21 provided at an end of the universal cable 19. The endoscope 12 is detachably connected, via the endoscope-side connector 21, to a light source device-side connector 37 of the light source device 13.

[0020] The insertion section 17 is composed of a flexible section 17a, a curved section 17b, and a tip section 17c, which are arranged in sequence from the base end to the tip. By operating the angle knob 18a of the operating section 18, the curved section 17b bends. As a result, the tip section 17c faces the desired direction.

[0021] The universal cable 19 is a cable that integrates a light guide 27 (see Figure 3) that guides the illumination light emitted by the light source 28 (described later), a control line that controls the image sensor (not shown) provided at the tip 17c of the insertion section 17, a signal line that transmits the image signal output by the image sensor when an observation target illuminated by the illumination light is imaged, and power lines that supply power to various parts such as the image sensor.

[0022] [Outline configuration of the light source device and processor device] The processor unit 14 is electrically connected to the display 15 and the user interface 16. The display 15 outputs and displays the endoscopic image of the object being observed, or other information, processed by the processor unit 14.

[0023] The user interface 16 has a keyboard, mouse, touchpad, microphone, etc., and has the function to accept input operations such as function settings. The display 15 outputs and displays endoscopic images, whether video or still images.

[0024] Furthermore, the light source device 13 is electrically connected to the processor device 14, and the endoscope-side connector 21 of the endoscope 12 is connected to the processor device 14 via the light source device 13. The transmission and reception of image signals, etc., between the light source device 13 and the endoscope-side connector 21 is wireless. For this reason, the light source device 13 outputs the image signals, etc., transmitted and received wirelessly with the endoscope-side connector 21 to a signal transmission unit (not shown), which then transmits them to the processor device 14. In addition, the light source device 13 supplies power to the endoscope-side connector 21 to drive the imaging sensor, etc., and this power supply is also done wirelessly.

[0025] As shown in Figures 3 and 4, the light source device 13 comprises a light source 28 and a light source control unit 29. The light source 28 emits illumination light used to illuminate the object to be observed. The tip 17c of the endoscope 12 is provided with an illumination optical system 23, which will be described later. As described above, by connecting the endoscope-side connector 21 and the light source device-side connector 37, the light incident end 27a of the light guide 27 of the endoscope 12 faces the light source 28 of the light source device 13. As a result, illumination light from the light source 28 is transmitted to the tip 17c of the insertion section 17 via the light guide 27. This causes the illumination optical system 23 to irradiate the observation site with illumination light from the tip 17c.

[0026] The light source control unit 29 controls the light source 28. The light source 28 is, for example, a semiconductor light source composed of multiple color LEDs (Light Emitting Diodes). The light source control unit 29 controls the amount of illumination light emitted by turning the LEDs on / off and adjusting the LED drive current and drive voltage. Note that the semiconductor light source that makes up the light source 28 is not limited to LEDs; LDs (Laser Diodes) and other types may also be used. In the following, we will mainly describe the normal mode in which the light source 28 emits white light as illumination light.

[0027] The tip section 17a consists of a cylindrical tip section body 31, the aforementioned image sensor, objective optical system (not shown), and a pair of illumination optical systems 23 incorporated therein. The tip section body 31 is made of a hard resin or metal material. The tip surface 31a of the tip section body 31 is provided with an observation window 33, a pair of illumination windows 34, an air and water supply nozzle 35, and a forceps outlet 36 which serves as the outlet for the forceps channel.

[0028] The observation window 33 is for imaging the area to be observed, and the objective optical system is incorporated behind it, with a portion of it exposed. Behind the objective optical system, an image sensor is positioned, and this image sensor images the area to be observed through the objective optical system.

[0029] The illumination window 34 is for illuminating the area to be observed, and the illumination optical system 23 is incorporated behind it. The illumination optical system 23 distributes the illumination light emitted from the light guide 27 in a manner suitable for imaging, for example, so that the imaging area is uniformly illuminated. The pair of illumination windows 34 are provided on both sides of the observation window 33, but the number and arrangement of the illumination windows 34 can be changed as appropriate.

[0030] The illumination optical system 23 is inserted into and assembled in a lens mounting hole 38 formed in the tip body 31. The lens mounting hole 38 extends from the tip surface 31a toward the base end along the optical axis PL of the illumination optical system 23, and the opening on the tip surface 31a serves as the illumination window 34. The lens mounting hole 38 is formed with a stepped shape in which the outer diameter at the tip end is larger than the outer diameter at the base end, in accordance with the lens barrel 43, which will be described later.

[0031] Furthermore, the tip body 31 has a light guide mounting hole 39 connected to the lens mounting hole 38, into which the light guide 27 is fitted. Both the lens mounting hole 38 and the light guide mounting hole 39 are circular in cross-section and are formed coaxially.

[0032] The illumination optical system 23 consists of an optical element 40, a first lens 41, a second lens 42, a lens barrel 43, and a spacer 44. The illumination optical system 23 is inserted into the lens mounting hole 38 in the following order: lens barrel 43 with the optical element 40 fixed, first lens 41, spacer 44, and second lens 42.

[0033] The lens barrel 43 holds the optical element 40, the first lens 41, and the second lens 42. By fitting the lens barrel 43 into the lens mounting hole 38, the optical element 40, the first lens 41, and the second lens 42 are fixed to the tip body 31. As a result, the optical element 40, the first lens 41, and the second lens 42 are positioned on the tip side of the light guide 27.

[0034] The inner circumferential surface of the lens barrel 43 has, in order from the base end to the tip end, a first inner diameter portion 43A, a second inner diameter portion 43B, and a third inner diameter portion 43C. The inner diameter of the first inner diameter portion 43A is the same as the outer diameter of the optical element 40, and the inner diameter of the second inner diameter portion 43B is larger than the inner diameter of the first inner diameter portion 43A and the outer diameter of the optical element 40. As a result, light rays emitted from the periphery of the surface 40a and traveling approximately parallel to the optical axis PL enter the first lens 41 without being obstructed.

[0035] The inner diameter of the second inner diameter section 43B is slightly larger than the inner diameter of the first inner diameter section 43A, and is the same as the outer diameter of the first lens 41. That is, the outer diameter of the first lens 41 is slightly larger than the outer diameter of the optical element 40. As a result, the first lens 41 does not enter the first inner diameter section 43A, but is held in the second inner diameter section 43B. In other words, the lens barrel 43 functions as a spacer, defining the distance between the optical element 40 and the first lens 41. As a result, the first lens 41 is positioned towards the front end of the optical element 40, maintaining a constant distance from the optical element 40.

[0036] The inner diameter of the third inner diameter portion 43C is larger than the inner diameter of the second inner diameter portion 43B and is the same as the outer diameter of the second lens 42. That is, the outer diameter of the second lens 42 is larger than the outer diameter of the first lens 41. The spacer 44 is ring-shaped and has the same outer diameter as the outer diameter of the first lens 41. The spacer 44 is placed between the first lens 41 and the second lens 42. In this way, the spacer 44 defines the distance between the first lens 41 and the second lens 42. That is, the second lens 42 is positioned on the tip side of the first lens 41 while maintaining a constant distance.

[0037] On the other hand, the outer surface of the lens barrel 43 has a first outer diameter portion 43D and a second outer diameter portion 43E, in order from the base end to the tip end. As described above, the outer diameter of the first lens 41 is slightly larger than the outer diameter of the optical element 40, and the outer diameter of the second lens 42 is larger than the outer diameter of the first lens 41. Therefore, the outer diameter of the first outer diameter portion 43D is one size larger (by the thickness of the lens barrel 43) than the outer diameter of the optical element 40, and the outer diameter of the second outer diameter portion 43E is one size larger than the outer diameter of the second lens 42. In other words, the outer surface of the lens barrel 43 has a stepped shape because the outer diameter of the second outer diameter portion 43E is larger than the outer diameter of the first outer diameter portion 43D.

[0038] The optical element 40 is a roughly cylindrical rod lens composed of a core 46a, which is a central component, and a cladding 46b formed around the core 46a. The cladding 46b has a lower refractive index than the core 46a. This optical element 40 is a convex lens, and more specifically, the surface 40a on the light incident end side facing the light guide 27 is flat, while the surface 40b on the opposite light emission end side (illumination window side) is convex, thus providing it with the function of a plano-convex lens.

[0039] Furthermore, due to the difference in refractive index between the core 46a and the cladding 46b, the optical element 40, like an optical fiber, reflects light incident on surface 40a within itself and guides it to surface 40b, thus having a light-reflecting function on its outer periphery. The optical element 40 may be composed of multiple components combined to have equivalent functions. For example, the optical element 40 may have a reflective surface formed on the outer periphery of a plano-convex lens, and may have a total internal reflection function that reflects all light incident on the plano-convex lens.

[0040] The lens barrel 43 holds the optical element 40 inside and also functions as a spacer to keep the first lens 41 spaced at a constant distance from the optical element 40. The optical element 40 is fixed inside the lens barrel 43 so that there is no step between its surface 40a and the end of the lens barrel 43 on the light guide 27 side, and is inserted into the lens mounting hole 38 together with the lens barrel 43.

[0041] The inner diameter of the light guide mounting hole 39 is slightly smaller (for example, by about 0.1 mm) than that of the lens mounting hole 38. By forming these mounting holes 38 and 39, which have different diameters, coaxially connected, a contact surface 48 is formed at the boundary between the lens mounting hole 38 and the light guide mounting hole 39, surrounding the light guide mounting hole 39. The light guide side edge of the lens barrel 43 abuts against this contact surface 48 and is locked in place, thereby positioning the lens barrel 43 and the optical element 40 it holds. The lens barrel 43 is fixed to the lens mounting hole 38, for example, by curing a thermosetting resin applied between its outer surface and the inner surface of the lens mounting hole 38.

[0042] The light guide 27 has an outer diameter that is approximately the same as the inner diameter of the light guide mounting hole 39, and also approximately the same as the outer diameter of the optical element 40. The light guide 27 is fitted into the light guide mounting hole 39 and fixed in place with its light-emitting end 27b in close contact with the surface 40a of the optical element 40. This ensures that the outer diameter of the optical element 40 does not increase, while all of the illumination light emitted from the light-emitting end 27b is incident on the surface 40a of the optical element 40.

[0043] In the optical element 40, the region of the surface 40a where effective light is incident is the core 46a, and the diameter of this core 46a is slightly smaller than the outer diameter of the optical element 40. For this reason, the outer diameter of the light guide 27 may be made slightly smaller than the outer diameter of the optical element 40 to match the diameter of the core 46a.

[0044] The first lens 41 is a convex lens, specifically a biconvex lens in which both the light-entering surface 41a and the light-exiting surface 41b are convex. The second lens 42 is a convex lens, specifically a convex-planar lens in which the light-entering surface 42a is convex and the light-exiting surface 42b is planar, with surface 42b being exposed from the illumination window 34. By configuring the illumination optical system 23 in this way, the illumination light is diffused and the imaging area is uniformly illuminated.

[0045] Furthermore, in order to apply thermosetting resin to the outer surfaces of the lens barrel 43 and the second lens 42 and the inner surface of the lens mounting hole 38, the lens barrel 43 and the second lens 42 are made slightly smaller (for example, about 10 μm) than the inner diameter of the lens mounting hole 38. Alternatively, grooves for the thermosetting resin may be formed on the outer surfaces of the lens barrel 43 and the second lens 42 or on the inner surface of the lens mounting hole 38.

[0046] Figure 5 shows the dimensional relationship between the first lens 41 and the second lens 42. As mentioned above, the outer diameter D12 of the second lens 42 is larger than the outer diameter D11 of the first lens 41. The outer diameter D12 of the second lens 42 is 2.1 mm or more and 3.0 mm or less. In the example shown in Figure 5, the outer diameter D12 of the second lens 42 is 2.5 mm, the outer diameter D11 of the first lens 41 is 1.7 mm, the radius of curvature R12 of the surface 42a (incident side) of the second lens 42 is 1.588 mm, the thickness of the second lens 42 is 2.20 mm, the radii of curvature of the surfaces 41a and 41b of the first lens 41 is 1.728 mm, and the radius of curvature of the surface 40b (exit side) of the optical element 40 is 1.728 mm.

[0047] The following explains the reason for defining the outer diameter D12 of the second lens 42 as described above, referring to the graph shown in Figure 6. The light intensity distribution ID0 shown by the dashed line in Figure 6 shows the light intensity distribution when the second lens is assumed to have the same dimensions as the second lens constituting a three-element illumination optical system in a conventional endoscope. In this case, the outer diameter of the second lens is 1.7 mm, and the diameter of the light-emitting end excluding the chamfered portion is 1.5 mm.

[0048] In the graph shown in Figure 6, the horizontal axis represents the radius r from the optical axis PL, and the vertical axis represents the light intensity LI of the second lens at the position of radius r. Furthermore, the light intensity LI is expressed using relative intensity; for example, the peak value LIP of the light intensity distribution ID0 is set to 1.0, and the light intensities other than the peak value are expressed as ratios to the peak value. Light intensity is the density of the luminous flux within a unit solid angle.

[0049] As is evident from the light intensity distribution ID0, when using a conventional second lens as shown in Figure 6, the light intensity is concentrated near the lens optical axis, and the peak value LIP protrudes significantly. Therefore, such lenses may cause coagulation of biological substances such as blood that adhere to the lens surface.

[0050] When the tip of an endoscope is immersed in blood using an illumination optical system consisting of a lens with light intensity distribution ID0, and illumination light from light source 28 is shone for 2 minutes, the areas where the light intensity exceeds the blood coagulation initiation point OP, indicated by the dashed line, are the areas where blood coagulation occurs. The criterion for determining blood coagulation is that blood coagulation has occurred when the change in light intensity falls below 50 percent. It can be seen that areas where the light intensity distribution ID0 is 0.62 times or more the peak value are the blood coagulation initiation points OP.

[0051] To avoid the coagulation of biological substances such as blood adhering to the lens surface, it is necessary to reduce the peak value of the light intensity distribution. The peak value of the light intensity distribution is inversely proportional to the area of ​​the light-emitting edge. In other words, increasing the area of ​​the light-emitting edge lowers the peak value. Therefore, if the outer diameter of the light-emitting edge (excluding the chamfered portion) of the second lens 42 is D120 and the peak value of the light density is LIP, then the following equation (1) should be satisfied. LIP=(1.5) 2 (D120) 2 ≤0.62···(1) From equation (1), D120 is 1.9 mm or more. Considering the chamfered portion of the outer edge of the lens (0.1 mm on each side), the outer diameter D12 of the second lens 42 is D120 + 0.2 mm, which means the outer diameter D12 is 2.1 mm or more. Furthermore, considering the outer diameter of the tip 17c of the endoscope 12 and the internal space, the outer diameter D12 of the second lens 42 is limited to 3.0 mm. For these reasons, the outer diameter of the second lens 42 is set to be between 2.1 mm and 3.0 mm.

[0052] The solid line in Figure 6, representing the light intensity distribution ID1, shows the distribution when the outer diameter of the second lens 42 is between 2.1 mm and 3.0 mm. As shown in this light intensity distribution ID1, the peak value of the light density decreases, and the entire light intensity distribution ID1 is below the blood coagulation initiation point OP.

[0053] Furthermore, the outer diameter D12 of the second lens 42 is 1.4 times or more the outer diameter D11 of the first lens 41. This is because, in terms of transmission efficiency and processing accuracy, the first lens 41 needs to have an outer diameter D11 that is at least equal to or greater than that of the optical element 40, and the optical element 40 needs to have an outer diameter of 1.5 mm or more. Therefore, in order to make the outer diameter D11 of the first lens 41 1.5 mm or more, and furthermore, as mentioned above, to make the outer diameter D12 of the second lens 42 2.1 mm or more, the condition that the outer diameter D12 of the second lens 42 is 1.4 times or more the outer diameter D11 of the first lens 41 is necessary.

[0054] Furthermore, if the outer diameter of the second lens 42 is D12 and the radius of curvature on the light incident end of the second lens 42 is R12, then the second lens 42 is given by the following equation (2) 1.48 ≤ D12 / R12···(2) This satisfies equation (2). The reason why this equation (2) is satisfied is explained below. Increasing the outer diameter R2 of the second lens 42 reduces D12 / R12, and the illumination distribution becomes narrower (the light intensity at the periphery decreases).

[0055] The light intensity distributions ID11 to ID13 shown in Figure 7 represent the light intensity distribution when the outer diameter R2 of the second lens 42 is changed, with the horizontal axis representing the beam angle LDA and the vertical axis representing the light intensity LI as a ratio to the beam angle. Figure 8 shows the portion of light intensity distributions ID11 to ID13 where the beam angle is between 40° and 80°. Note that the light intensity is relative intensity; for example, the peak value of each light intensity distribution is set to 1.0, and the light intensity other than the peak value is expressed as a ratio to the peak value. Light intensity is the density of the luminous flux within a unit solid angle. Light intensity distribution ID11 shows the case where D12 / R12 is 1.25, light intensity distribution ID12 shows the case where D12 / R12 is 1.48, and light intensity distribution ID13 shows the case where D12 / R12 is 1.57.

[0056] With light intensity distribution ID12 and ID13, the illumination distribution is almost the same; that is, there is no difference in light intensity even in the peripheral areas (beam angle of 40° or more). In contrast, with light intensity distribution ID11 and ID12, the illumination distribution of ID11 is narrower, and the light intensity in the peripheral areas (beam angle of 40° or more) is lower. Therefore, in the case of light intensity distribution ID11, where D12 / R12 is less than 1.48, the peripheral areas of the screen in the image captured by the endoscope 12 become dark. On the other hand, in the case of light intensity distribution ID12 and ID13, where D12 / R12 is 1.48 or higher, as described above, the peripheral areas of the screen in the image captured by the endoscope 12 become brighter.

[0057] As described above, in this embodiment, the outer diameter D12 of the second lens 42 is larger than the outer diameter D11 of the first lens 41, and is set to be between 2.1 mm and 3.0 mm. Therefore, the peak value of light intensity can be reduced, improving the coagulation resistance of biological substances. Furthermore, by lowering the peak value of light intensity, illumination light can be transmitted without reducing the amount of illumination light guided from the light source device, so sufficient brightness can be obtained for observation with the endoscope 12. In addition, since the outer diameter D12 of the second lens 42 is 1.4 times or more the outer diameter D11 of the first lens 41, the peak value of light intensity can be reduced even more reliably.

[0058] Furthermore, by simply increasing the outer diameter of the second lens 42, the optical elements 40 and the first lens 41 can be those of a conventional illumination optical system, thus suppressing cost increases. Except for the outer diameter of the second lens 42, the basic optical performance, such as lens light transmittance and illumination distribution, can be designed to be equivalent to that of a conventional illumination optical system, allowing it to be used without performance degradation.

[0059] Furthermore, by ensuring that the outer diameter D12 and radius of curvature R12 of the second lens 42 satisfy 1.48 ≤ D12 / R12, a decrease in light intensity at the periphery can be prevented. Therefore, the peripheral areas of the image captured by the endoscope 12 become sufficiently bright, providing a good observation environment.

[0060] [Second Embodiment] In the first embodiment described above, the illumination optical system 23 has a three-element configuration comprising an optical element 40, a first lens 41, and a second lens 42. However, the present invention is not limited to this, and in the second embodiment described below, the illumination optical system has a two-element configuration comprising an optical element and a first lens. Note that the same reference numerals are used for parts similar to those in the first embodiment, and their descriptions are omitted.

[0061] As shown in Figures 9 and 10, the illumination optical system 51 is inserted into and assembled in a lens mounting hole 38 formed in the tip body 31. The illumination optical system 51 consists of an optical element 53, a first lens 54, and a lens barrel 55. The illumination optical system 51 is inserted into the lens mounting hole 38 in the order of the lens barrel 55, to which the optical element 53 is fixed, and the first lens 54. That is, the illumination optical system 51 is located at the tip 17c of the insertion part 17, similar to the illumination optical system 23 in the first embodiment described above. Since illumination light from the light source 28 is transmitted to the tip 17c via the light guide 27, the illumination optical system 51 irradiates the observation area with illumination light from the tip 17c.

[0062] The lens barrel 55 holds the optical element 53 and the first lens 54. By fitting the lens barrel 55 into the lens mounting hole 38, the optical element 53 and the first lens 54 are fixed to the front body 31. As a result, the optical element 53 and the first lens 54 are positioned on the front side of the light guide 27.

[0063] The inner circumferential surface of the lens barrel 55 has a first inner diameter section 55A and a second inner diameter section 55B, in order from the base end to the tip end. The inner diameter of the first inner diameter section 55A is the same as the outer diameter of the optical element 53, and the inner diameter of the second inner diameter section 55B is larger than the inner diameter of the first inner diameter section 55A and the outer diameter of the optical element 53. As a result, light rays emitted from the periphery of the surface 53a and traveling approximately parallel to the optical axis PL enter the first lens 54 without being obstructed.

[0064] The inner diameter of the second inner diameter portion 55B is larger than the inner diameter of the first inner diameter portion 55A, and is the same as the outer diameter of the first lens 54. That is, the outer diameter of the first lens 54 is larger than the outer diameter of the optical element 53. As a result, the first lens 54 does not enter the first inner diameter portion 55A, but is held in the second inner diameter portion 55B.

[0065] On the other hand, the outer surface of the lens barrel 55 has a first outer diameter portion 55D and a second outer diameter portion 55E, in order from the base end to the tip end. As described above, the outer diameter of the first lens 41 is larger than the outer diameter of the optical element 40. Therefore, the outer diameter of the first outer diameter portion 55D is slightly larger (by the thickness of the lens barrel 55) than the outer diameter of the optical element 53, and the outer diameter of the second outer diameter portion 55E is slightly larger than the outer diameter of the first lens 54. In other words, the outer surface of the lens barrel 55 has a stepped shape because the outer diameter of the second outer diameter portion 55E is larger than the outer diameter of the first outer diameter portion 55D.

[0066] The optical element 53 is a substantially cylindrical rod lens, similar to the optical element 40 in the first embodiment described above, and is composed of a core 56a, which is a central component, and a cladding 56b formed around the core 56a. The cladding 46b has a lower refractive index than the core 46a. The optical element 53 has a flat surface 53a on the light incident end side facing the light guide 27, and a flat surface 53b on the opposite light emission end side (illumination window side).

[0067] Furthermore, similar to the optical element 40 in the first embodiment described above, the optical element 53 reflects light incident from surface 53a within itself and guides it to surface 53b, similar to an optical fiber, due to the difference in refractive index between the core 56a and the cladding 56b, and thus has a light reflection function on its outer periphery. The optical element 53 may also have a total internal reflection function that reflects all incident light.

[0068] The first lens 54 is a concave lens, specifically a concave-flat lens with a concave shape on the light-entering end surface 54a and a planar shape on the light-exiting end surface 54b, with surface 54b exposed from the illumination window 34. By configuring the illumination optical system 51 in this way, the illumination light is diffused, and the imaging area is uniformly illuminated.

[0069] Figure 11 shows the dimensional relationship between the optical element 53 and the first lens 54. As mentioned above, the outer diameter D21 of the first lens 54 is larger than the outer diameter D20 of the optical element 53. The outer diameter D21 of the first lens 54 is 2.1 mm or more and 3.0 mm or less. In the example shown in Figure 11, the outer diameter D21 of the first lens 54 is 2.5 mm, the outer diameter D20 of the optical element 53 is 1.5 mm, the radius of curvature R21 of the surface 54a (incident side) of the first lens 54 is 0.892 mm, and the thickness of the first lens 54 is 0.75 mm.

[0070] The reason for defining the outer diameter D21 of the first lens 54 as described above is the same as the reason for defining the outer diameter D12 of the second lens 42 in the first embodiment described above. In the first lens constituting a conventional two-element illumination optical system, the outer diameter was 1.7 mm, and the diameter of the light-emitting end excluding the chamfered portion was about 1.5 mm.

[0071] In such a conventional first lens, the light intensity is concentrated near the optical axis of the lens, and the peak value protrudes significantly. Therefore, as with the first embodiment described above, it is clear that in order to avoid coagulation of biological substances, the peak value of the light intensity distribution should be reduced. The peak value of the light intensity distribution is inversely proportional to the area of ​​the light emission end. That is, increasing the area of ​​the light emission end will lower the peak value. So, if the outer diameter of the light emission end (excluding the chamfered portion) of the first lens 54 is D210 and the peak value of the light density is LIP, then it is sufficient to satisfy the following equation (3). LIP=(1.5) 2 (D210) 2 ≤0.62···(3) From equation (3), D210 is 1.9 mm or more. Considering the chamfered portion of the outer edge of the lens (0.1 mm on each side), the outer diameter D21 of the first lens 54 is D210 + 0.2 mm, which means the outer diameter D21 is 2.1 mm or more. Furthermore, considering the outer diameter of the tip 17c of the endoscope 12 and the internal space, the outer diameter D21 of the first lens 54 is limited to 3.0 mm. For the above reasons, the outer diameter of the first lens 54 is set to be between 2.1 mm and 3.0 mm.

[0072] Furthermore, the outer diameter D21 of the first lens 54 is 1.4 times or more the outer diameter D11 of the optical element 53. This is because, from the standpoint of transmission efficiency and processing accuracy, the optical element 53 must have an outer diameter of 1.5 mm or more. Therefore, in order to make the outer diameter D20 of the optical element 53 1.5 mm or more, and furthermore, as mentioned above, to make the outer diameter D21 of the first lens 54 2.1 mm or more, the condition that the outer diameter D21 of the first lens 54 is 1.4 times or more the outer diameter D11 of the first lens 41 is necessary.

[0073] Furthermore, if the outer diameter of the first lens 54 is D21 and the radius of curvature on the light incident end of the first lens 54 is R21, then the first lens 54 is given by the following equation (4) 2.80 ≤ D21 / R21···(4) It satisfies the condition. The reason why equation (4) is satisfied is explained below. Increasing the outer diameter R21 of the first lens 54 reduces D21 / R21, and the illumination distribution becomes narrower (the light intensity at the periphery decreases).

[0074] The light intensity distributions ID21 to ID23 shown in Figure 12 represent the light intensity distribution when the outer diameter R21 of the first lens 54 is changed. The horizontal axis represents the beam angle LDA, and the vertical axis represents the light intensity LI as a percentage of the beam angle. Note that the light intensity is relative intensity; for example, the peak value of each light intensity distribution is set to 1.0, and the light intensity other than the peak value is expressed as a ratio to the peak value. Light intensity is the density of the luminous flux within a unit solid angle. Light intensity distribution ID21 shows the case where D21 / R21 is 2.50, light intensity distribution ID22 shows the case where D21 / R21 is 2.63, and light intensity distribution ID23 shows the case where D21 / R21 is 2.80.

[0075] Between light intensity distribution ID22 and light intensity distribution ID23, the illumination distribution of light intensity distribution ID22 is narrower, and the light intensity in the peripheral area (beam angle of 40° or more) is lower. Furthermore, between light intensity distribution ID21 and light intensity distribution ID22, the illumination distribution of light intensity distribution ID21 is even narrower, and the light intensity in the peripheral area (beam angle of 40° or more) is even lower. Therefore, with light intensity distributions ID21 and ID22, where D21 / R21 is less than 2.80, the peripheral area of ​​the screen in the image captured by the endoscope 12 becomes dark. On the other hand, with light intensity distribution ID23, where D21 / R21 is 2.80 or more, as described above, the peripheral area of ​​the screen in the image captured by the endoscope 12 becomes brighter.

[0076] As described above, in this embodiment, the outer diameter D21 of the first lens 54 is larger than the outer diameter D20 of the optical element 53, and is set to be between 2.1 mm and 3.0 mm. Therefore, the peak value of light intensity can be reduced, improving the coagulation resistance of biological substances. Furthermore, by lowering the peak value of light intensity, illumination light can be transmitted without reducing the amount of illumination light guided from the light source device, so sufficient brightness can be obtained for observation with an endoscope. In addition, since the outer diameter D21 of the first lens 54 is 1.4 times or more the outer diameter D20 of the optical element 53, the peak value of light intensity can be reduced even more reliably.

[0077] Furthermore, by ensuring that the outer diameter D21 and radius of curvature R21 of the first lens 54 satisfy 2.80 ≤ D21 / R21, a decrease in light intensity in the peripheral areas can be prevented. Therefore, the peripheral areas of the image captured by the endoscope become sufficiently bright, providing a good observation environment.

[0078] In each of the embodiments described above, both of the pair of illumination optical systems are equipped with illumination optical systems 23 and 51, i.e., the second lens 42 and the first lens 54, which are enlarged in diameter. However, the present invention is not limited to this, and one of the illumination optical systems may be equipped with illumination optical systems 23 and 51, while the other may be equipped with a conventional illumination optical system using the second lens and the first lens. In this case, if a liquid is sprayed from the air / water supply nozzle 35 compared to the conventional illumination optical system using the second lens and the first lens, coagulation of biological substances can be made less likely.

[0079] In the above embodiment, a medical endoscope was used as an example for explanation, but the present invention can also be applied to endoscopes used for other purposes, such as industrial applications. Furthermore, in the above embodiment, the light guide section is equipped with two illumination optical systems and a light guide, but it is not limited to this, and may be equipped with three or more illumination optical systems and a light guide. [Explanation of Symbols]

[0080] 10 Endoscopy Systems 12 Endoscopes 13 Light source device 14 Processor Unit 15 displays 16 User Interface 17 Insertion part 17a Soft part 17b Curved section 17c Tip 18 Control section 18a Angle knob 19 Universal Cable 21 Endoscope-side connector 22 Objective optical system 23, 51 Illumination optical system 27 Light Guide 27a Light entrance end 27b Light output end 28 light source 29 Light source control unit 31 Tip body 31a Tip surface 33 Observation window 34 Lighting window 35 Air and water supply nozzles 36 Forceps exit 37 Light source device side connector 38 lens mounting holes 39 Light guide mounting holes 40 optical elements 40a side 40b side 41. First lens 41a, 41b side 42. Second lens 42a, 42b side 43 Telescope Tube 43A First inner diameter section 43B 2nd inner diameter part 43C 3rd inner diameter part 43D 1st outer diameter section 43E 2nd outer diameter section 44 Spacers 46a core 46b Clad 48 Contact surface 51 Illumination optical system 53 Optical elements 53a, 53b side 54 First Lens 54a, 54b side 55 Telescope Tube 55A First inner diameter section 55B Second inner diameter section 55D 1st outer diameter section 55E 2nd outer diameter section 56a core 56b Clad D11, D12, D20, D21 Outer diameter R12, R21 radius of curvature r radius ID0, ID1, ID11, ID12, ID13, ID21, ID22, ID23 Light intensity distribution LDA beam angle LI light intensity LIP Peak Value OP (Optical Coagulation Point)

Claims

1. An endoscope having an illumination optical system that transmits illumination light from a light source to the tip of the insertion section via a light guide, thereby irradiating the observation site from the tip of the insertion section with the illumination light, The illumination optical system is The first lens located at the tip of the light guide, It comprises a second lens positioned at the tip of the first lens at a constant distance, The outer diameter of the second lens is It is larger than the outer diameter of the first lens, and is 2.1 mm or more and 3.0 mm or less. If the outer diameter of the light-emitting end of the second lens, excluding the chamfered portion, is D120, then the following formula (1.5) ２ / (D120) ２ ≦0.62 Satisfying the conditions, If the outer diameter of the second lens is D and the radius of curvature at the light incident end of the second lens is R, then the second lens is given by the following conditional equation 1.48 ≤ D / R An endoscope that meets the requirements.

2. An endoscope having an illumination optical system that transmits illumination light from a light source to the tip of the insertion section via a light guide, thereby irradiating the observation site from the tip of the insertion section with illumination light, The illumination optical system is The first lens located at the tip of the light guide, It comprises a second lens positioned at the tip of the first lens at a constant distance, The outer diameter of the second lens is It is larger than the outer diameter of the first lens, and is 2.1 mm or more and 3.0 mm or less. If the outer diameter of the light-emitting end of the second lens, excluding the chamfered portion, is D120, then the following formula (1.5) 2 / (D120) 2 ≦0.62 Satisfying the conditions, An endoscope in which an optical element having a light-reflecting function is arranged between the light guide and the first lens.

3. The endoscope according to claim 1 or 2, wherein the outer diameter of the second lens is 1.4 times or more the outer diameter of the first lens.

4. The endoscope according to claim 3, wherein the first lens is a convex lens.

5. The endoscope according to claim 4, wherein the first lens is a biconvex lens.

6. The endoscope according to claim 5, wherein the second lens is a convex lens.

7. The endoscope according to claim 6, wherein the second lens is a convex-flat lens having a convex shape at the light input end and a flat shape at the light output end.

8. The endoscope according to claim 2, wherein the optical element has an incident light end facing the light guide, an outer peripheral portion having a light reflection function, and a convex-shaped light emission end.

9. The endoscope according to claim 8, wherein the optical element has a total internal reflection function.

10. The endoscope according to claim 9, wherein the optical element comprises a core and a cladding.

11. An endoscope having an illumination optical system that transmits illumination light from a light source to the tip of the insertion section via a light guide, thereby irradiating the observation site from the tip of the insertion section with the illumination light, The illumination optical system is An optical element having an incident light end facing the light guide and an outer peripheral portion having a light reflection function, It comprises a first lens positioned at the tip of the optical element at a constant distance, The outer diameter of the first lens is, It is larger than the outer diameter of the optical element, and is 2.1 mm or more and 3.0 mm or less. If the outer diameter of the light-emitting end of the first lens, excluding the chamfered portion, is D210, then the following formula (1.5) ２ / (D210) ２ ≦0.62 Satisfying the conditions, When the outer diameter of the first lens is D and the radius of curvature at the light incident end of the first lens is R, the first lens is given by the following conditional equation 2.80 ≤ D / R An endoscope that meets the requirements.

12. The endoscope according to claim 11, wherein the outer diameter of the first lens is 1.4 times or more the outer diameter of the optical element.

13. The endoscope according to claim 12, wherein the first lens is a concave lens.

14. The endoscope according to claim 13, wherein the first lens is a concave-flat lens having a concave shape at the light incident end and a flat shape at the light exit end.

15. The endoscope according to claim 11, wherein the optical element has a total internal reflection function.

16. The endoscope according to claim 15, wherein the optical element comprises a core and a cladding.

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