Endoscope lighting device

Abstract

To provide an illumination device for an endoscope with an objective having a great angle of view, particularly an angle of view greater than 180°.SOLUTION: An endoscope tip comprises an objective for imaging a field of view and an illumination device for illuminating the field of view. The objective has an angle of view greater than 180°, and the illumination device is arranged around the objective in a plan view. The illumination device includes a transparent cap from which the illumination light is emitted into the field of view. The illumination device includes one or more light emitting devices that emits emission light. With respect to one of the light emitting devices, a centroid of an angular distribution of the emission light is located in a direction tilted away from the optical axis, or a reflective surface reflects at least the emission light in a direction further away from the direction of the optical axis than a direction in which the emission light is incident on the reflective surface.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The present invention relates to an illumination device for an endoscope. In particular, the present invention relates to an illumination device for an endoscope comprising an objective lens having a large angle of view, particularly an angle of view greater than 180°.

Background Art

[0002] The illumination system of an endoscope can include a plurality of LEDs arranged around the objective lens. The light-emitting elements are typically arranged in a plane perpendicular to the optical axis of the objective lens, and the light-emitting elements are configured to emit light parallel to the optical axis. More precisely, the center of gravity of the angular distribution of the radiation is located in the direction of the optical axis. The light of the LED passes through the transparent cap and then illuminates the field of view. The transparent cap bounds the illumination device towards the object space including the field of view of the objective lens.

Summary of the Invention

Problems to be Solved by the Invention

[0003] It is desirable that the field of view of the objective lens of an endoscope equipped with an imaging system be illuminated as uniformly as possible, as shown by the hatched area in FIG. 1 with respect to an angle of view of 180°. When the objective lens has an angle of view greater than 180° and the LED is a Lambert emitter that emits light directly towards the transparent cap in the direction of the optical axis, as shown in FIG. 2, it is not possible to achieve substantially uniform illumination of the field of view. In FIG. 2, the solid line indicates the radiation field of the Lambert emitter.

Means for Solving the Problems

[0004] An objective lens for imaging the field of view, An illumination device for illuminating the field of view with illumination light, Comprising, The objective lens has an optical axis, The objective lens has an angle of view greater than 180°, The illumination device is arranged around the objective lens in a plan view along the optical axis, The lighting device includes a transparent cap that emits the illumination light into the viewing field. The lighting device includes one or more light-emitting elements that are light-emitting diodes configured to emit light from respective light-emitting surfaces. The lighting device satisfies the following conditions, namely The lighting device includes a reflective surface that reflects at least a part of the light emitted from at least one of the light-emitting elements in a direction that is further away from the optical axis than the direction of incidence of at least the part of the at least one of the light emitted from the at least one of the light-emitting elements onto the reflective surface. and the light-emitting elements are attached to a plane perpendicular to the optical axis, the reflective surface is disposed between the plane perpendicular to the optical axis in a direction parallel to the optical axis and the tip of the objective lens. An endoscope tip or a capsule endoscope is provided.

Advantages of the Invention

[0005] Approximately uniform illumination of the viewing field of the objective lens is achieved by the lighting device, even when the angle of view is greater than 180°. "Approximately uniform" means that the light intensity across the entire angle of view is between 50% and 100% of the maximum light intensity (preferably between 75% and 100% of the maximum light intensity). Furthermore, some embodiments are relatively simple and space-saving. Optionally, in some cases (possibly when minimal refraction in the transparent cap is negligible), the optical refraction element can be omitted, which simplifies manufacturing and thus increases cost-effectiveness.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0007] FIG. 3 shows an example of an endoscope tip 10 in which an objective lens 1 (preferably a wide-angle objective lens having an angle of view exceeding 180°) is disposed. The optical axis 11 of the objective lens 1 may extend parallel to the axis of symmetry of the endoscope tip 10. In particular, the optical axis 11 of the objective lens 1 may be the same as the axis of symmetry of the endoscope tip 10, or may be offset from the axis of symmetry of the endoscope tip 10. However, the optical axis 11 may be inclined with respect to the axis of symmetry of the endoscope tip 10 as shown in the example of FIG. 3.

[0008] The lighting device is attached around the objective lens 1 in a plan view of the distal end of the endoscope tip. For example, it may be directly attached around the objective lens 1, or may be disposed away from the objective lens 1. The lighting device may be rotationally symmetric. When the lighting device is rotationally symmetric, its axis of rotation is preferably (but not necessarily) the same as the optical axis 11 of the objective lens 1.

[0009] Hereinafter, the present invention will be described with respect to an endoscope tip 10 in which the objective lens 1 is symmetrically attached with respect to the axis of the endoscope tip 10 and the lighting is rotationally symmetrically attached around the optical axis of the objective lens 1. However, the present invention is not limited to this specific configuration as described above.

[0010] FIG. 4 shows an endoscope tip according to the prior art. An objective lens having an angle of view exceeding 180° is disposed at the endoscope tip. The angle of view (“optical system aperture angle”) is shown in FIG. 5. Due to the large aperture angle of the optical system, the objective lens should be located at the tip of the endoscope, and all other components (endoscope cap, lighting) are lowered behind the objective lens so as not to appear in the field of view.

[0011] The distal end of the endoscope can further include a camera for capturing an image of the field of view captured by the objective lens. The camera can have, for example, a CCD chip or a CMOS chip as a sensor. Instead of the camera, the distal end of the endoscope may include a part of a relay optical system that guides the image captured by the objective lens to the proximal end of the endoscope.

[0012] The distal end of the endoscope further includes an illumination device for illuminating the field of view of the objective lens (or the object space including the field of view). The illumination device is equipped with an LED that illuminates the object space through a transparent cap (endoscope cap). The cap is transparent when its transparency is at least 75%, preferably at least 90%, more preferably at least 95% for all wavelengths emitted at an intensity of at least 50% of the maximum intensity of the LED as a function of wavelength. The cap must not be colorable. That is, the difference in transparency at different wavelengths must be 20% or less, preferably 10% or less. Also, when the LED emits light of wavelengths outside the visible range (400 nm to 800 nm), the above conditions apply to the wavelengths in the visible range and do not apply to the wavelengths outside the visible range.

[0013] Since the refractive power of the cap acts essentially like a plane parallel plate, it is typically small. The refractive power may vary locally. For example, the maximum local refractive power may be 2 dpt (2 m-1), preferably 1 dpt (1 m-1), even more preferably 0.5 dpt (0.5 m-1). However, in some examples of the present invention, the cap can be configured as a lens having a refractive power that directs the illumination light to a predetermined region of the field of view.

[0014] The LEDs can all be of the same type or of different types. For example, two different types can be used to illuminate the object space in two different colors. In this case, each individual type of LED should preferably be mounted rotationally symmetrically about the optical axis of the objective lens. An example of this is shown in FIG. 7 in a plan view.

[0015] All LEDs may be controllable individually or in groups. "Controllable" means that at least the LEDs can be switched on and off. In some examples, the intensity and / or color of the emitted light can also be controlled.

[0016] Figure 6 shows the emission angle of the LED illumination at the distal end of the endoscope of FIG. 4 according to the prior art. In this case, the emission angle of the LED illumination is such that the field of view of the objective lens is not illuminated or not sufficiently illuminated at the edge. This means that the large angular field of the objective lens is (almost) useless. The emission angle indicates the range in which the light intensity is at least 50% of the maximum intensity (at the same distance from the LED). Figure 8 shows the radiation pattern corresponding to FIG. 6. All the illustrated radiation patterns are radiation patterns with respect to the optical axis of the objective lens. In all the illustrated radiation patterns, the total illumination is normalized to 100%.

[0017] As shown in FIG. 9, it is possible to attempt to mount a plurality of LEDs of the same type adjacent to each other radially. However, this does not change the emission angle (C = A), and thus a part of the outer field of view remains unilluminated. Figure 10 shows the corresponding radiation pattern that is qualitatively not different from the radiation pattern shown in FIG. 8. In principle, even if a plurality of LEDs each radiating light parallel to the optical axis of the objective lens are mounted radially, it only corresponds to an enlargement of the light emitting surface of each individual LED.

[0018] Figure 11 shows the endoscopic tip according to the first embodiment of the present invention. This endoscopic tip exactly corresponds to the endoscopic tip of FIG. 4, except that the LED emits light at a finite angle from the optical axis of the objective lens instead of emitting light parallel to the optical axis of the objective lens. The finite angle may be, for example, within the range of 5° to 85°, 5° to 80°, 10° to 85°, or 10° to 80°, preferably within the range of 5° to 50°, and even more preferably within the range of 10° to 45°. The finite angle is different from 0° and 90°.

[0019] Therefore, the LED is attached to a surface inclined with respect to the surface perpendicular to the optical axis. The angle of inclination of the surface corresponds to the change in the emission angle of the lighting device and can be selected according to the desired emission characteristics. The surface can be formed by a frustum of a cone that can be used, for example, instead of the flat mounting surface for the LED according to FIG. 4. Preferably (but not necessarily), the axis of the frustum of the cone coincides with the optical axis of the objective lens.

[0020] Furthermore, according to FIG. 11, since the LED is attached to the frustum surface, it is closer to the distal end. However, this is not essential. For example, instead of the frustum surface, it is also possible to arrange a trough on the LED mounting surface of FIG. 4 so that the center of the LED emission surface is located at the same height as in FIG. 4 in the direction of the optical axis.

[0021] Figure 12 shows the components of the endoscopic tip of FIG. 11 in a cross-sectional view (left side) and a plan view (right side). The plan view exactly corresponds to the plan view of the endoscopic tip of FIG. 4, and in the cross-section, only the frustum of the cone for attaching the LED is different from the cross-section of the endoscopic tip of FIG. 4.

[0022] Figure 13 shows the emission angle of the illumination of the endoscopic tip of FIG. 11 corresponding to the figure of FIG. 6 and the opening angle of the objective lens. As can be seen, the outer region of the field of view of the endoscope is now substantially better illuminated. Figure 14 shows the corresponding radiation pattern. The illumination is still sufficient even at an angular field of view exceeding 180°.

[0023] Figures 15 to 18 show a second embodiment of the present invention. Figures 15 to 18 respectively correspond to Figures 11 to 14. In contrast to the first embodiment, in the second embodiment, the LED is again mounted on a plane perpendicular to the optical axis, as in Figure 4. However, the endoscope tip has, in addition to the endoscope tip of Figure 4, a ring mirror attached around the objective lens. Preferably, the ring mirror is rotationally symmetric about the optical axis of the objective lens as the axis of rotation. The reflecting surface of the ring mirror faces the LED and is inclined at a finite angle with respect to the optical axis. For example, the angle of inclination may be in the range of 20° to 70° with respect to the optical axis. Thereby, a part of the radiation is reflected to the outer region of the field of view, and thus, as seen in Figures 17 and 18, sufficient illumination is achieved in the outer region of the field of view, particularly at an angle of view exceeding 180°.

[0024] The ring mirror should preferably be mounted so as not to cause additional shading in addition to the shading by the objective lens. This means that the protrusion of the ring mirror should be determined according to the height in the optical axis direction where the ring mirror is mounted.

[0025] The ring mirror preferably reflects the emitted light from the LED that is shaded by the objective lens at the endoscope tip of Figure 4 and thus does not contribute, or only slightly contributes, to the illumination of the object space. Thereby, the utilization of light is improved and the energy consumption and heat generation are reduced.

[0026] This is shown in Figures 19 and 20. Figure 19 shows an endoscope tip (without a transparent cap) according to the prior art in which a part of the emitted light from the LED is shaded by the objective lens. In contrast, according to the second embodiment, as shown in Figure 20, the shaded light is reflected to the outer field of view by the ring mirror. The central shading remains unchanged.

[0027] The mirror surface of the ring mirror can form a frustum of a cone surface on which no optical refractive power acts in the optical axis direction. However, in some embodiments of the present invention, it may be advantageous for the ring mirror to apply an optical refractive power in the direction of the optical axis and direct light to a specific region of the field of view. In such a case, in the cross-sections of FIGS. 15, 16, 17, and 20, the mirror surface is curved. The mirror surface of the ring mirror can generally even have an arbitrary shape. Preferably (but not necessarily), the axis of the frustum of the cone coincides with the optical axis of the objective lens.

[0028] In addition, in some embodiments of the present invention, at least a part of the bottom surface of the ring mirror and the outer shell of the objective lens adjacent to the bottom surface of the ring mirror are coated reflectively. As a result, the emitted light emerging from the LED at a flat angle can be directed to the outer field of view by multiple reflections on the outer shell of the objective lens and the bottom surface of the ring mirror. Thereby, the utilization of light is further improved.

[0029] For example, as shown in FIGS. 4 and 11, if the outer shell of the objective lens has a protrusion above the LED in the optical axis direction, a similar effect can be obtained without providing a ring mirror. According to the third embodiment of the present invention, both the bottom surface of the protrusion and at least a part of the outer shell of the objective lens below the protrusion and adjacent to the protrusion are coated reflectively to direct the light from the LED to the outer field of view.

[0030] In some embodiments of the present invention, (as shown in FIG. 11) the emission direction of the LED is tilted with respect to the optical axis of the objective lens, and (as shown in FIG. 15) the ring mirror is attached around the objective lens. In addition, as in the third embodiment, a part of the outer shell of the objective lens can also be coated reflectively. Thereby, the illumination of the outer field of view can be further improved.

[0031] Unless the outer shell of the objective lens is coated reflectively, the objective lens may be black so as to reflect hardly any light.

[0032] The reflecting surface can be formed, for example, of silver by a metal coating. Alternatively, when the space between the cap, the outer shell of the objective lens, and the mounting surface of the LED is filled with a transparent insulator, it is also possible to form the reflecting surface with another insulator having a lower refractive index. Further, in this case, the cap may be the same as the outer layer of the transparent insulator.

[0033] According to a fourth embodiment of the present invention, an optical refraction element is attached in the space between the LED and the cap in order to direct a part of the light to the outer field of view. For example, the optical refraction element can be directly located at the outer portion of the light emitting surface of the LED and can extend outward in a wedge-like shape in cross section. When the light from the LED appears from the wedge-shaped optical refraction element, the light is deflected outward toward the outer field of view.

[0034] The optical refraction element of the LED can be connected so as to form a frustum surface, and the axis of the frustum preferably (but not necessarily) coincides with the optical axis of the objective lens. It is also possible to combine the optical refraction element of the fourth embodiment with one or more of the first to third embodiments.

[0035] Figures 21 and 22 show the general principles according to some embodiments of the present invention. Each of Figures 21 and 22 shows a cross section of the (virtual or actual) endoscope tip portion in a plane extending by the optical axis 11 of the objective lens 1 and the light emission axis of at least one LED 2. The LED 2 emits (virtual or actual) light emission 20 symmetrically with respect to the light emission axis.

[0036] Figure 21 shows a virtual reference configuration corresponding to FIG. 4 according to the prior art. In the reference configuration, the LED 2 is arranged in a plane perpendicular to the optical axis 11 of the objective lens 1. The LED 2 emits (virtual) light emission 20 parallel to the direction of the optical axis 11. The (virtual) light emission 20 hits the transparent cap 6 directly, i.e., without being deflected by other components such as mirrors or optical refraction elements (lenses). There, the light is probably deflected and radiated as virtual illumination light 60 into the object space (or the field of view) of the objective lens 1. The virtual illumination light is based only on the light emission directly radiated from the LED 2 to the cap 6. The dashed lines indicate that the reference configuration is a virtual configuration.

[0037] The actual configurations according to some embodiments of the present invention are shown in FIG. 22 for comparison. The actual configuration differs from the reference configuration in that one or both of the following conditions are satisfied.

[0038] · The light emission 20 is emitted by the LED 2 that is not parallel to the optical axis 11.

[0039] · The (actual) illumination light 61 is at least partially based on the light emission deflected by the reflection or refraction element, rather than the light emission directly radiated from at least one LED 2 to the cap 6.

[0040] In other respects, the actual configuration in FIG. 21 is functionally identical to the virtual configuration in FIG. 22. In particular, the exit points of the respective light emission axes from the LED 2 are at the same position.

[0041] FIG. 22 shows an example in which the light emission 20 is emitted non-parallel to the optical axis. In addition, it is shown that there is a gap between the light emission 20 and the illumination light 61, so that the illumination light contains components other than the component directly emitted from the LED 2 to the cap 6.

[0042] As can be seen from FIG. 22, the actual illumination light 61 is directed in a direction further away from the optical axis than the virtual illumination light 60.

[0043] The arrow 20 representing the light emission of LED2 indicates the center of gravity of the angular distribution of the light emission. Typically, the light emission is symmetrically emitted around this center of gravity (e.g., a Lambert emitter). The arrows 60 and 61 representing the illumination light (virtual or real) indicate the centers of gravity of the angular distributions of the respective illumination lights. In general, the angular distribution of the illumination light is caused by the light shielding by the objective lens, and in the case of the real illumination light 61, it is probably also caused by components due to reflection or optical refraction or optical diffraction of the illumination light, and is not necessarily symmetric with respect to this arrow.

[0044] The LED is an example of a light-emitting element according to some embodiments of the present invention. Instead of the LED, for example, the output end of an optical waveguide can also be used. Also, some of the light-emitting elements may be LEDs, and other light-emitting elements may be the output ends of optical waveguides.

[0045] The objective lens is understood to mean a lens or lens system that images a scene onto an image plane, and possibly further optical elements. In particular, the objective lens continuously images the scene onto the image plane. This means that adjacent points in the scene are also adjacent in the image on the image plane. The angular field of view of the objective lens is greater than 180°. Preferably greater than 200°, more preferably greater than 220°, and even more preferably greater than 230°. Such an objective lens is described, for example, in European Patent Application No. 19187218.3. Typically, the endoscope tip includes a single objective lens.

[0046] The endoscope may be a rigid endoscope in which the proximal end of the endoscope tip is connected to a rigid tube. The endoscope may be a flexible endoscope in which the proximal end of the endoscope tip is connected to a flexible tube. Both the rigid tube and the flexible tube are called "shafts". The connection of the endoscope tip to the shaft can be made directly or indirectly via an angular element. The endoscope may be a freely floating endoscope (capsule endoscope) without a shaft. The endoscope (and thus, of course, the endoscope tip as well) may be suitable for insertion into a body cavity, such as a bronchoscope, a laryngoscope, or a colonoscope.

Claims

1. an objective lens for imaging the field of view; an illumination device for illuminating the field of view with illumination light; It is equipped with the objective lens has an optical axis; the objective lens has an angle of view greater than 180°; the illumination device is disposed around the objective lens in a plan view along the optical axis; the illumination device includes a transparent cap that emits the illumination light into the field of view; The lighting device includes light emitting devices configured to emit respective emissions from respective light emitting surfaces. one or more light emitting elements that are photodiodes; The illumination device includes a ring mirror having a truncated cone shape with a small diameter bottom surface and a large diameter top surface compared to the bottom surface, the ring mirror is disposed such that the bottom surface faces the light emitting element and the top surface faces the opposite side to the light emitting element; The lighting device satisfies the following conditions: the illumination device comprises a reflective surface, the reflective surface reflecting at least a portion of an emission of at least one of the light-emitting elements in a direction further away from a direction of the optical axis than a direction of incidence of the at least a portion of the emission of the at least one of the light-emitting elements on the reflective surface; Fulfilling The light emitting element is attached to a surface perpendicular to the optical axis, the reflecting surface is disposed between a surface perpendicular to the optical axis and a tip of the objective lens in a direction parallel to the optical axis, the reflecting surface is formed on the circumferential surface of the ring mirror, A bottom surface of the ring mirror and at least a portion of the outer shell of the objective lens adjacent the bottom surface of the ring mirror are reflectively coated. The tip of an endoscope or a capsule endoscope.

2. The endoscope tip or capsule endoscope according to claim 1 , wherein an axis of the ring mirror is the same as the optical axis.

3. the angular distribution of the illumination light in a plane including the optical axis includes an angular range greater than 90°; 3. An endoscope tip portion or a capsule endoscope according to claim 1 or 2.

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