Endoscope Lighting Device and Endoscope

Abstract

To suppress color irregularity in illumination light.SOLUTION: An illumination device for an endoscope includes: a light source part including a light emitting element for emitting excitation light and a fluorescent substance that is excited by the excitation light and emits fluorescent light, for radiating illumination light in which the excitation light and the fluorescent light are mixed; and a light distribution lens having an emission surface for emitting the illumination light made incident from the light source part. The emission surface includes a first emission surface and a second emission surface that are formed in different regions in the emission surface. In the illumination device for an endoscope, the thickness of the light emission element and the thickness of the fluorescent substance are regulated so that each of the excitation light and the fluorescent light radiated from the light source part at the same angle, and made incident on the distribution lens are emitted in roughly the same direction from the first emission surface or the second emission surface.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an endoscope illumination device and an endoscope.

Background Art

[0002] An endoscope without a light guide fiber is known. For example, Patent Document 1 describes a specific configuration of this type of endoscope.

[0003] The endoscope described in Patent Document 1 includes a light source chip for illuminating the body cavity at the tip of the insertion tube. Since it is not necessary to guide the illumination light supplied from the light source device to the tip of the insertion tube, a light guide fiber is not required.

[0004] The light source chip provided in this type of endoscope has, for example, a blue LED (Light Emitting Diode) and a phosphor (such as a phosphor that is excited by blue light and emits yellow light). The light source chip irradiates white light created by mixing blue light and yellow light.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] For example, in an endoscope for the large intestine, performance that enables imaging up to the back side of the folds of the large intestine is required. For this purpose, a light distribution lens that can distribute the illumination light from the light source chip over a wide range is necessary. However, when designing a light distribution lens so that the illumination light including a plurality of lights having different wavelengths (for example, blue light and yellow light) emitted from the light source chip can be distributed over a wide range, color unevenness of the illumination light increases, and color unevenness of the captured image increases.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide an endoscope illumination device capable of suppressing color unevenness of illumination light and an endoscope including such an endoscope illumination device. **Means for Solving the Problems**

[0008] An endoscope illumination device according to an embodiment of the present invention includes a light-emitting element that emits excitation light and a phosphor that is excited by the excitation light to emit fluorescence, and includes a light source unit that emits illumination light in which the excitation light and the fluorescence are mixed, and a light distribution lens having an emission surface that emits the illumination light incident from the light source unit. The emission surface includes a first emission surface and a second emission surface formed in different regions within the emission surface. In this endoscope illumination device, the thickness of the light-emitting element and the thickness of the phosphor are defined such that the excitation light and the fluorescence radiated from the light source unit at the same angle and incident on the light distribution lens are emitted from the first emission surface or the second emission surface in substantially the same direction.

[0009] The endoscope illumination device according to an embodiment of the present invention may be configured to include a support having an installation surface on which the light source unit is installed. In this case, the light source unit is configured such that the phosphor covers the light-emitting element. The thickness of the light-emitting element is the thickness from the first surface of the light-emitting element that contacts the installation surface to the second surface of the light-emitting element that is located on the side opposite to the first surface of the light-emitting element and faces the light distribution lens. The thickness of the phosphor is the thickness from the first surface of the phosphor that contacts the installation surface to the second surface of the phosphor that is located on the side opposite to the first surface of the phosphor and faces the light distribution lens. When the thickness of the light-emitting element is D1 and the thickness of the phosphor is D2, the endoscope illumination device according to an embodiment of the present invention may be configured to satisfy the following formula D2 / D1 ≦ 3.5 It is good also as a structure which satisfy | fills.

[0010] In one embodiment of the present invention, when the direction in which the support and the light source unit are arranged in order is the front direction and the direction orthogonal to the front direction is the side direction, the first emission surface is located, for example, in the front direction of the light source unit, and the second emission surface is located, for example, in the side direction of the light source unit. The emission surface includes, for example, a connection surface that connects the first emission surface and the second emission surface.

[0011] The connecting surface that connects the first emission surface and the second emission surface is formed as a curved surface, for example.

[0012] In one embodiment of the present invention, when the direction opposite to the forward direction is defined as the backward direction, the second emission surface may be formed to extend to the backward direction of the light source unit.

[0013] In one embodiment of the present invention, the light distribution lens has, for example, an incident surface facing the second surface, emits the illumination light incident on the incident surface from the emission surface, and a concave curved surface for expanding the light distribution angle of the illumination light is formed on the incident surface.

[0014] The concave curved surface formed on the incident surface of the light distribution lens includes, for example, a plurality of curved surfaces with different radii of curvature.

[0015] Among the above-mentioned plurality of curved surfaces, when the distance in the forward direction between the center of curvature of the first curved surface formed closest to the connecting surface and the center position of the light source unit is Z, the endoscopic illumination device according to one embodiment of the present invention has the following formula Z / D2≧0.1 and may be configured to satisfy this.

[0016] In the above, the first curved surface is formed, for example, at a position intersecting the line segment connecting the center position of the curved surface forming the connecting surface and the center position of the light source unit.

[0017] The light distribution lens is formed in an annular shape. When the radius of curvature of the curved surface forming the connecting surface is Re and the radius of curvature of the first curved surface is R1, In at least a partial angular range of the annularly formed light distribution lens, the endoscopic illumination device according to one embodiment of the present invention has the following formula Re / R1≦1.6 and may be configured to satisfy this.

[0018] For example, in at least the above-mentioned partial angular range, the curved surface forming the connecting surface is located in the forward direction of the light source unit.

[0019] In one embodiment of the present invention, the light distribution angle of the illumination light is, for example, 180° or more.

[0020] The illumination light emitted from the light source unit is, for example, white light.

[0021] An endoscope according to one embodiment of the present invention includes an insertion tube, an imaging unit provided at the distal end of the insertion tube, and the above-described endoscope illumination device provided around the imaging unit. The light distribution lens is formed in an annular shape so as to surround the imaging unit. A plurality of light source units are arranged at intervals around the imaging unit.

Effects of the Invention

[0022] According to one embodiment of the present invention, there are provided an endoscope illumination device capable of suppressing color unevenness of illumination light and an endoscope including such an endoscope illumination device.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8A

Figure 8B

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13A

Figure 13B

Figure 13C

Figure 14

Mode for Carrying Out the Invention

[0024] Hereinafter, an endoscope illumination device and an endoscope according to an embodiment of the present invention will be described with reference to the drawings.

[0025] FIG. 1 is an external view of an endoscope 1 according to an embodiment of the present invention. As shown in FIG. 1, the endoscope 1 includes an insertion tube 2, an operation unit 3, a universal tube 4, and a connector unit 5.

[0026] The insertion tube 2 is a portion to be inserted into the body cavity and includes a flexible portion 20, a bending portion 21, and a distal end portion 22. The distal end portion 22 is connected to the distal end of the flexible portion 20 via the bending portion 21. The proximal end of the flexible portion 20 is connected to the operation unit 3 via a cylindrical connection portion 23.

[0027] The universal tube 4 has one end connected to the operation part 3 and is formed to extend in a direction different from that of the insertion tube 2. The connector part 5 is connected to the other end of the universal tube 4.

[0028] On the operation part 3 held by the operator, operation members for performing various operations are provided. The operation part 3 includes, as operation members, a bending operation knob 30, a plurality of operation buttons 31, and the like.

[0029] The bending operation knob 30 is connected to the bending part 21 by a wire (not shown) passed through the inside of the connecting part 23 and the flexible part 20. The bending part 21 bends in two directions orthogonal to each other within the axial cross-section by the operation of the bending operation knob 30. Thereby, the direction of the distal end part 22 inserted into the body cavity is changed.

[0030] FIG. 2A is an external perspective view of the distal end part 22. FIG. 2B is a view in the direction of the arrow B corresponding to FIG. 2A. As shown in FIGS. 2A and 2B, the optical axis direction of the objective lens 25 is defined as the Z direction, and the two directions orthogonal to the Z direction and orthogonal to each other are defined as the X and Y directions, respectively.

[0031] As shown in FIGS. 2A and 2B, the distal end part 22 is formed in an elliptical shape, and the tip projects in a substantially conical shape.

[0032] FIG. 3 is a view showing the internal structure of the distal end part 22. The cross-section shown in FIG. 3 is the YZ cross-section of the distal end part 22.

[0033] An imaging part for imaging the inside of the body cavity is provided in the distal end part 22. The imaging part includes an imaging element 6 and an objective lens 25.

[0034] The imaging element 6 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a CCD (Charge Coupled Device) image sensor, or the like. Further, the objective lens 25 is a wide-angle lens.

[0035] The imaging unit including the imaging device 6 and the objective lens 25 is configured to be capable of imaging with a field of view of 180° (±90°) or more. In FIG. 3, the two-dot chain line indicates the imaging field of the imaging unit.

[0036] The endoscope illumination device according to the present embodiment is provided around the imaging unit and includes a light distribution cap 26 and a light source chip 27.

[0037] The light distribution cap 26 is an example of a light distribution lens having a light emitting surface for emitting illumination light incident from the light source unit. The light distribution cap 26 includes a cap-shaped lens portion 26a and a cylindrical lens portion 26b.

[0038] The cap-shaped lens portion 26a is formed in a cap shape that closes the tip of the tip portion 22, and is also formed in an annular shape so as to surround the imaging unit.

[0039] Incidentally, the light distribution cap 26 has a shape in which the cap-shaped lens portion 26a extends radially outward from the peripheral edge portion of the objective lens 25 to the outside of the tip portion 22 and is continuous with the cylindrical lens portion 26b that forms a part of the side wall of the tip portion 22 through a curved surface portion (described later).

[0040] An annular substrate 28 surrounding the imaging unit is provided inside the tip portion 22. A plurality of light source chips 27 are arranged on the upper surface 28a of the substrate 28 at intervals around the imaging unit. In FIG. 2B, as an example, seven light source chips 27 are arranged.

[0041] The light source chip 27 is an example of a light source unit. The substrate 28 is an example of a support having an installation surface (upper surface 28a) on which the light source unit is installed.

[0042] The illumination light emitted from the light source chip 27 is emitted to the outside through the light distribution cap 26 and illuminates the imaging field of the imaging unit.

[0043] To illuminate a wide imaging field of view, the light distribution cap 26 is designed to distribute the illumination light from the light source chip 27 over a wide range. In FIG. 3, the dashed line indicates the light distribution range by the light distribution cap 26. The light distribution angle of the illumination light by the light distribution cap 26 is, for example, 180° (±90°) or more.

[0044] The light source chip 27 includes a light emitting element that emits excitation light, and a phosphor that is excited by the excitation light to emit fluorescence. The light source chip 27 is configured such that the phosphor covers the light emitting element, and emits illumination light in which the excitation light and the fluorescence are mixed.

[0045] In the present embodiment, the light emitting element is a blue LED (see reference numeral 27b in FIG. 4 described later). The phosphor is a yellow phosphor (see reference numeral 27y in FIG. 4 described later) that is excited by blue light to emit yellow light. The light source chip 27 emits white light created by mixing blue light and yellow light.

[0046] The configuration of the light source chip 27 that emits white light is not limited to the above. The light source chip 27 may be configured to include a blue LED, a red phosphor, and a green phosphor, or may be configured to include an ultraviolet LED, a blue phosphor, a green phosphor, and a red phosphor.

[0047] FIG. 12 is a diagram showing the light distribution characteristics of a blue LED and a yellow phosphor. In FIG. 12, the symbol Ib indicates the light distribution characteristics of the blue LED, and the symbol Iy indicates the light distribution characteristics of the yellow phosphor.

[0048] The light distribution characteristics of both the blue LED and the yellow phosphor are such that the intensity of the light emitted at an angle θ from the light emitting surface is COSθ times the intensity of the light emitted perpendicularly, that is, Lambertian light distribution.

[0049] Consider the case where the light source chip 27 is disposed at the center of a sphere and the inner surface of the sphere that is sufficiently distant from the light source chip 27 is illuminated by the light source chip 27.

[0050] In this case, the point on the sphere in the 0° light distribution angle direction is illuminated by the light with intensity Ib_0 emitted from the blue LED at a light distribution angle of 0° and the light with intensity Iy_0 emitted from the yellow phosphor at a light distribution angle of 0°. The light intensity ratio Ib_0 / Iy_0 is set so that the illumination light illuminating the point on the sphere in the 0° light distribution angle direction becomes white.

[0051] Also, the point on the sphere in the θ light distribution angle direction is illuminated by the light with intensity Ib_θ emitted from the blue LED at a light distribution angle of θ and the light with intensity Iy_θ emitted from the yellow phosphor at a light distribution angle of θ. The light intensity ratio Ib_θ / Iy_θ is set so that the illumination light illuminating the point on the sphere in the θ light distribution angle direction becomes white.

[0052] That is, the light source chip 27 is set to have the characteristic that the intensity ratio Ib_0 / Iy_0 and the intensity ratio Ib_θ / Iy_θ are substantially the same so that a wide range can be illuminated with white light.

[0053] FIGS. 13A to 13C are schematic views showing the positional relationship between the light distribution cap 26 and the light source chip 27. As shown in FIGS. 13A to 13C, the light source chip 27 includes a blue LED 27b and a yellow phosphor 27y. The blue light emitted from the blue LED 27b is denoted as "blue light Lb", and the yellow light emitted from the yellow phosphor 27y is denoted as "yellow light Ly".

[0054] As shown in FIGS. 13A to 13C, the blue light Lb at each angle emitted from the blue LED 27b and the yellow light Ly at each angle emitted from the yellow phosphor 27y are incident on the light distribution cap 26 and are emitted to the outside from the light emitting surface of the light distribution cap 26.

[0055] FIG. 13A shows blue light Lb and yellow light Ly radiated at an angle close to perpendicular to the light emitting surfaces of blue LED 27b and yellow phosphor 27y. Such blue light Lb and yellow light Ly pass through substantially the same position of light distribution cap 26. Therefore, the light ray angles of blue light Lb and yellow light Ly when emitted from light distribution cap 26 are substantially the same, illuminating substantially the same area on the irradiated surface. Accordingly, the intensity ratio Ib_θ / Iy_θ becomes a value close to the intensity ratio Ib_0 / Iy_0, and the illuminated surface is illuminated in substantially white color.

[0056] FIG. 13B shows blue light Lb and yellow light Ly radiated at an angle not close to perpendicular (e.g., 45°) to the light emitting surfaces of blue LED 27b and yellow phosphor 27y. Such blue light Lb and yellow light Ly pass through relatively distant positions of light distribution cap 26. Therefore, the light ray angles of blue light Lb and yellow light Ly when emitted from light distribution cap 26 are greatly different, illuminating different areas on the irradiated surface. The area on the irradiated surface where blue light Lb reaches is illuminated in a bluish color, and the area on the irradiated surface where yellow light Ly reaches is illuminated in a yellowish color.

[0057] That is, in the case of FIG. 13B, since the color unevenness of the illumination light is large, color unevenness occurs in the captured image.

[0058] FIG. 13C shows blue light Lb and yellow light Ly (blue light Lb emitted at light distribution angle θ and yellow light Ly emitted at light distribution angle θ') radiated at different angles with respect to the light emitting surfaces of blue LED 27b and yellow phosphor 27y.

[0059] As shown in FIG. 13C, among the blue light Lb and yellow light Ly emitted at different light distribution angles, there are those where the light ray angles when emitted from light distribution cap 26 are substantially the same, illuminating substantially the same area on the irradiated surface. However, the intensity ratio becomes Ib_θ / Iy_θ', which is different from Ib_0 / Iy_0. Therefore, the area on the irradiated surface is illuminated in a bluish color or a yellowish color.

[0060] Depending on the shape of the incident surface and the emission surface of the light distribution cap 26, the difference in the light beam angles between the blue light Lb and the yellow phosphor 27y after passing through the light distribution cap 26 may increase, resulting in increased color unevenness, or the difference in the light beam angles may decrease, resulting in reduced color unevenness. Further, in order to make the light distribution angle of the illumination light 180° or more, as shown in FIGS. 13A to 13C, when the incident surface and the emission surface of the light distribution cap 26 are formed into a complex shape, the light beam angles of the blue light Lb and the yellow phosphor 27y after passing through the light distribution cap 26 change complexly. Therefore, color unevenness of the illumination light is likely to occur.

[0061] As a result of intensive studies, the inventor has found that the deviation in the emission positions of the blue LED 27b and the yellow phosphor 27y in the height direction is one of the factors causing color unevenness in the illumination light.

[0062] Therefore, in the present embodiment, by appropriately setting the emission position of the blue LED 27b and the emission position of the yellow phosphor 27y (in other words, appropriately defining the thickness of the blue LED 27b and the thickness of the yellow phosphor 27y), color unevenness is less likely to occur in a wide range within the irradiated surface.

[0063] Specifically, in the endoscopic illumination device according to the present embodiment, the blue light Lb and the yellow light Ly radiated from the light source chip 27 at the same angle and incident on the light distribution cap 26 are respectively emitted from the first emission surface (for example, the emission surface 126a of the cap-shaped lens portion 26a) or the second emission surface (for example, the emission surface 126b of the cylindrical lens portion 26b) in substantially the same direction, and the thickness of the blue LED 27b and the thickness of the yellow phosphor 27y are defined.

[0064] FIG. 14 is a diagram showing color unevenness of illumination light. In FIG. 14, reference symbol C indicates an example of an image when the inner surface of a sphere at a certain distance from the distal end portion of the endoscope is imaged. In FIG. 14, reference symbol E1 indicates the RGB intensity distribution on line D of the image example C imaged by a conventional endoscope. In FIG. 14, reference symbol E2 indicates the RGB intensity distribution on line D of the image example C imaged by the endoscope 1 according to the present embodiment.

[0065] As can be seen by comparing the intensity distributions E1 and E2, in the endoscope 1 according to the present embodiment, color unevenness in the captured image is suppressed as compared with the conventional case.

[0066] FIG. 4 is a schematic internal structure diagram of the distal end portion 22 for explaining each element of the endoscope illumination device according to the present embodiment. FIG. 5 is an enlarged view showing a part of FIG. 4 in an enlarged manner.

[0067] Reference sign D1 indicates the thickness of the blue LED 27b. The thickness D1 of the blue LED 27b is the thickness from the bottom surface of the blue LED 27b (an example of the first surface of the light emitting element) that contacts the upper surface 28a of the substrate 28 to the light emitting surface of the blue LED 27b (an example of the second surface of the light emitting element) that is located on the side opposite to the bottom surface and faces the light distribution cap 26.

[0068] Reference sign D2 indicates the thickness of the yellow phosphor 27y. The thickness D2 of the yellow phosphor 27y is the thickness from the bottom surface of the yellow phosphor 27y (an example of the first surface of the phosphor) that contacts the upper surface 28a of the substrate 28 to the light emitting surface of the yellow phosphor 27y (an example of the second surface of the phosphor) that is located on the side opposite to the bottom surface and faces the light distribution cap 26.

[0069] The inner surface of the light distribution cap 26 is an incident surface on which the blue light Lb and the yellow light Ly are incident. As shown in FIGS. 4 and 5, the incident surface of the light distribution cap 26 includes, in a cross-sectional view, a concave curved surface portion 226a and an inner peripheral portion 226b parallel to the light emitting surface 126b of the cylindrical lens portion 26b.

[0070] The incident surface (at least the curved surface portion 226a) of the light distribution cap 26 is located to face the light emitting surfaces of the blue LED 27b and the yellow phosphor 27y. The curved surface portion 226a is formed in a concave shape in order to expand the light distribution angle of the illumination light.

[0071] The curved surface portion 226a includes a plurality of curved surfaces having different radii of curvature. The curved surface portion 226a is composed of two curved surfaces in a partial angular range of the annularly formed light distribution cap 26 and is composed of three curved surfaces in other angular ranges.

[0072] As shown in FIGS. 4 and 5, the first curved surface connected to the inner peripheral portion 226b is formed with a radius of curvature R1 and within an angular range indicated by the sign A1. The second curved surface connected to the first curved surface is formed with a radius of curvature R2 and within an angular range indicated by the sign A2. The third curved surface connected to the second curved surface is formed with a radius of curvature R3 and within an angular range indicated by the sign A3. As shown in FIG. 5, for the sake of convenience, the first curved surface, the second curved surface, and the third curved surface are respectively labeled with signs CS1, CS2, and CS3.

[0073] In FIGS. 4 and 5, the curved surface portion 226a shows a shape composed of three curved surfaces. In the case where the curved surface portion 226a has a shape composed of two curved surfaces, the first curved surface CS1 is formed within the angular range A1, and the second curved surface CS2 is formed within the angular ranges A2 and A3.

[0074] The outer surface of the light distribution cap 26 is an emission surface from which the blue light Lb and the yellow light Ly incident on the incident surface are emitted. The light distribution cap 26 includes a first emission surface and a second emission surface formed in different regions within the emission surface. More specifically, the emission surface of the light distribution cap 26 includes the emission surface 126a of the cap-shaped lens portion 26a, the emission surface 126b of the cylindrical lens portion 26b, and an emission surface 126c (an example of a connection surface) that connects the emission surface 126a and the emission surface 126b.

[0075] The emission surface 126b of the cylindrical lens portion 26b is formed to extend in the Z direction. In contrast, the emission surface 126a of the cap-shaped lens portion 26a is formed at an angle with respect to the Z direction. In FIGS. 4 and 5, the sign Ae indicates the angle formed between the emission surface 126a and the emission surface 126b.

[0076] The emission surface 126c is formed of a curved surface with a radius of curvature Re.

[0077] When the direction in which the substrate 28 and the light source chip 27 are arranged in sequence is defined as the forward direction (in FIG. 4, the upward direction and the Z direction), and the direction orthogonal to the forward direction is defined as the side direction (in FIG. 4, the horizontal direction and the Y direction), the emission surface 126a, which is an example of the first emission surface, is located in the forward direction of the light source chip 27, and the emission surface 126b, which is an example of the second emission surface, is located in the side direction of the light source chip 27.

[0078] When the direction opposite to the forward direction is defined as the rear direction (the downward direction and the Z direction in FIG. 4), the emission surface 126b, which is an example of the second emission surface, is formed to extend to the rear of the light source chip 27.

[0079] In FIGS. 4 and 5, the line segment LS connects the center position of the emission surface 126c and the center position of the light source chip 27. The first curved surface CS1 is formed at a position intersecting the line segment LS. Incidentally, the first curved surface CS1 is formed closest to the emission surface 126c, which is an example of the connection surface, among the plurality of curved surfaces forming the curved surface portion 226a.

[0080] In FIGS. 4 and 5, the distance Y1 indicates the distance in the Y direction from the central axis of the light distribution cap 26 (which coincides with the optical axis of the objective lens 25) to the emission surface 126b of the cylindrical lens portion 26b.

[0081] In FIGS. 4 and 5, the distance Y2 indicates the distance in the Y direction from the central axis of the light distribution cap 26 to the inner peripheral portion 226b of the light distribution cap 26.

[0082] In FIGS. 4 and 5, the distance Y3 indicates the distance in the Y direction from the central axis of the light distribution cap 26 to the center position of the light source chip 27.

[0083] In FIGS. 4 and 5, the distance Z1 indicates the distance in the Z direction from the bottom surface of the light source chip 27 (in other words, the bottom surface of the blue LED 27b or the bottom surface of the yellow phosphor 27y or the upper surface 28a of the substrate 28) to the front end surface of the light distribution cap 26.

[0084] In FIGS. 4 and 5, the distance Z2 indicates the distance in the Z direction from the bottom surface of the light source chip 27 to the boundary position between the curved surface portion 226a and the inner peripheral portion 226b.

[0085] In FIGS. 4 and 5, the distance Z3 indicates the distance in the Z direction from the bottom surface of the light source chip 27 to the boundary position between the emission surface 126b and the emission surface 126c.

[0086] In FIGS. 4 and 5, the distance Z4 indicates the distance in the Z direction from the bottom surface of the light source chip 27 to the center position of the light source chip 27.

[0087] Quantification of color unevenness of illumination light will be described. FIG. 6 shows an illumination model for quantifying color unevenness of illumination light. In the illumination model shown in FIG. 6, the tip 22 is disposed at the center of the sphere, and the inner surface of the sphere sufficiently distant from the tip 22 is illuminated with illumination light. In this illumination model, the Z-axis direction is set to 0° and the Y-axis direction is set to 90°.

[0088] When the amount of blue light Lb incident on a certain angular position on the spherical surface is B and the amount of yellow light Ly incident on the same angular position is Y, the ratio of the amount of light B / the amount of light Y indicates the ratio of the amount of blue light Lb to the amount of yellow light Ly at the above angular position. The ratio of the amount of light B / the amount of light Y is an index value indicating the color tone of illumination light obtained by mixing blue light Lb and yellow light Ly having different wavelengths. Hereinafter, this index value will be referred to as "index value I".

[0089] The index value I changes according to the angular position. This indicates that color unevenness of illumination light occurs on the irradiated surface. The larger the index value I (that is, the ratio of the amount of light B / the amount of light Y), the bluer the illumination light. The smaller the index value I, the yellower the illumination light.

[0090] FIG. 7 shows the relationship between the angular position (in other words, the light distribution angle (°)) and the index value I. In FIG. 7, the vertical axis indicates the index value I, and the horizontal axis indicates the light distribution angle (°). In the example of FIG. 7, the index value I at the light distribution angle 0° (position on the Z axis) is normalized to 1. The illumination optical system formed by the endoscope illumination device is generally rotationally symmetric with respect to the axis of the light distribution angle 0°. Therefore, in FIG. 7, only the index value I of the positive light distribution angle is shown.

[0091] In FIG. 7, the solid line connects from the light distribution angle 0° to 124° at a 4° pitch, and the broken line is an approximation of this solid line by a quadratic equation.

[0092] Let the PV (Peak-to-valley) of the deviation of the solid line with respect to the approximate line (dashed line) be Pva, and the PV of the approximate line be Pvb. In this embodiment, the value obtained by adding Pva to the value obtained by dividing Pvb by 2 (that is, Pva+(Pvb / 2)) is defined as the "color unevenness evaluation value" for quantitatively evaluating color unevenness.

[0093] The smaller the color unevenness evaluation value, the smaller the color difference of the illumination light, that is, the color unevenness, across the entire light distribution angle. Note that the human eye has a higher tolerance for gradually changing color unevenness compared to rapidly changing color unevenness (in other words, it is less likely to perceive color unevenness if the change is gradual). In accordance with such characteristics of the human eye, in the above formula for defining the color unevenness evaluation value, the value Pvb corresponding to gradual color unevenness is divided by 2, while the value Pva corresponding to rapid color unevenness is not divided.

[0094] In this embodiment, the allowable color unevenness evaluation value is set to 0.5 or less. Note that a color unevenness evaluation value of 0.4 or less is more desirable. Further, a color unevenness evaluation value of 0.3 or less is even more desirable.

[0095] As described above, in this embodiment, in order to suppress color unevenness of the illumination light over a wide range within the irradiated surface, the blue light Lb and the yellow light Ly radiated from the light source chip 27 at the same angle and incident on the light distribution cap 26 are respectively emitted from the first emission surface (as an example, the emission surface 126a of the cap-shaped lens portion 26a) or the second emission surface (as an example, the emission surface 126b of the cylindrical lens portion 26b) in substantially the same direction. The thickness of the blue LED 27b and the thickness of the yellow phosphor 27y are defined.

[0096] As a more specific example, the thickness D1 of the blue LED 27b and the thickness D2 of the yellow phosphor 27y satisfy the following formula (1) D2 / D1≦3.5···(1) are satisfied.

[0097] When the thicknesses of the blue LED 27b and the yellow phosphor 27y are made the same, color unevenness of the illumination light can be suppressed to a small extent. However, in order to efficiently make the excitation light from the blue LED 27b enter the yellow phosphor 27y, it is necessary to configure the light source chip 27 such that the yellow phosphor 27y covers the blue LED 27b. Therefore, it is difficult to make the thicknesses of the blue LED 27b and the yellow phosphor 27y the same.

[0098] On the other hand, since the blue LED 27b and the yellow phosphor 27y also have a certain size in the width and depth directions (for example, the X and Y directions orthogonal to the Z direction in FIG. 4) orthogonal to the thickness direction, color unevenness on the irradiated surface is also averaged to a certain extent.

[0099] In consideration of these, the above formula (1) is defined. By satisfying the above formula (1), it becomes easy to suppress the color unevenness evaluation value to 0.5 or less, and it is easy to favorably suppress the color unevenness of the illumination light (see Numerical Examples 1 to 56 described later).

[0100] Here, the degree of color unevenness of the illumination light also varies depending on the shape of the inner surface (incident surface) and the outer surface (emitting surface) of the light distribution cap 26.

[0101] For example, as described above, the emitting surface 126c of the light distribution cap 26 is formed as a curved surface. Since the emitting surface 126c connects the emitting surfaces 126a and 126b of the light distribution cap 26, it does not become a gentle curved surface. The smaller the radius of curvature (the more acute the curved surface), the easier it is for the refraction angle to change depending on the light passing position. Therefore, the emitting surface 126c is likely to be a factor causing color unevenness of the illumination light. However, in the present embodiment, by satisfying the above formula (1), even if the emitting surface of the light distribution cap 26 has a shape with a local curved surface (emitting surface 126c), the color unevenness of the illumination light can be favorably suppressed.

[0102] As described above, the emission surface 126b, which is an example of the second emission surface, is formed to extend rearward of the light source chip 27. When the emission surface 126b is formed to extend rearward of the light source chip 27, the emission range of the illumination light from the light distribution cap 26 expands. Therefore, such a configuration leads to an increase in the light distribution angle of the illumination light, while it can also be a factor causing color unevenness of the illumination light. However, in the present embodiment, by satisfying the above formula (1), even when the emission surface 126b is formed to extend rearward of the light source chip 27, the color unevenness of the illumination light is well suppressed.

[0103] As described above, the incident surface of the light distribution cap 26 includes the curved surface portion 226a formed in a concave shape. In order to expand the light distribution angle of the illumination light, the smaller the radius of curvature of the curved surface portion 226a (the steeper the curved surface), the easier it is for the refraction angle to change depending on the light passing position. Therefore, the curved surface portion 226a is likely to be a factor causing color unevenness of the illumination light. However, in the present embodiment, by satisfying the above formula (1), even when the radius of curvature of the curved surface portion 226a is small, the color unevenness of the illumination light is easily suppressed.

[0104] As described above, the curved surface portion 226a includes a plurality of curved surfaces with different radii of curvature. By forming the curved surface portion 226a with a plurality of curved surfaces having different radii of curvature, it is possible to suppress the color unevenness of the illumination light while expanding the light distribution angle of the illumination light.

[0105] When the distance in the Z direction between the center of curvature of the first curved surface CS1 and the center position of the light source chip 27 (more specifically, the distance obtained by subtracting the distance Z4 from the distance Z2) is Z, the endoscopic illumination device according to the present embodiment has the following formula (2) Z / D2≧0.1···(2) It may be configured to satisfy. Note that the distance Z takes a negative value when the distance Z4 is longer than the distance Z2.

[0106] By satisfying the above formula (2), it becomes easy to suppress the color unevenness evaluation value to 0.4 or less, and the color unevenness of the illumination light is easily suppressed well (see Numerical Examples 5 to 44 described later).

[0107] FIG. 8A shows a cross-section of the light distribution cap 26 and the light source chip 27 included in the Y1-Y1 line cross-section of FIG. 2B. FIG. 8B shows a cross-section of the light distribution cap 26 and the light source chip 27 included in the X1-X1 line cross-section of FIG. 2B.

[0108] The annularly formed light distribution cap 26 has an emission surface 126c positioned in the forward direction of the light source chip 27 in some angular ranges (see FIG. 8A), and the emission surface 126c is positioned in the backward direction of the light source chip 27 in other angular ranges (see FIG. 8B).

[0109] In the angular range where the emission surface 126c is positioned in the forward direction of the light source chip 27, the endoscopic illumination device according to the present embodiment has the following formula (3) Re / R1 ≦ 1.6 ··· (3) It may be configured to satisfy.

[0110] By satisfying the above formula (3), it becomes easier to suppress the color unevenness evaluation value to 0.3 or less, and it is easier to suppress the color unevenness of the illumination light well (see Numerical Examples 45 to 56 described later).

[0111] Next, specific numerical examples will be shown.

[0112] Table 1 shows the parameter values of the endoscopic illumination devices according to Numerical Examples 1 to 4.

[0113] (Table 1) TIFF0007709943000001.tif145161

[0114] FIG. 9 is a graph showing the relationship between the color unevenness evaluation value and formula (1) in Numerical Examples 1 to 4. In FIG. 9, the vertical axis represents the color unevenness evaluation value, and the horizontal axis represents the value of D2 / D1.

[0115] As shown in Table 1, in Numerical Examples 1 to 2, the value of D2 / D1 exceeds 3.5. As a result, the color unevenness evaluation value exceeds 0.5. On the other hand, in Numerical Examples 3 to 4, the value of D2 / D1 is 3.5 or less. As a result, the color unevenness evaluation value is 0.5 or less.

[0116] As described above, in Numerical Examples 3 to 4, it can be seen that by appropriately defining the thickness D1 of the blue LED 27b and the thickness D2 of the yellow phosphor 27y, unevenness in the color of the illumination light is well suppressed.

[0117] Tables 2A to 2D show the parameter values of the endoscope illumination device according to Numerical Examples 5 to 44. Note that in any of Numerical Examples 5 to 44, the value of D2 / D1 is 3.0.

[0118] (Table 2A) TIFF0007709943000002.tif144163

[0119] (Table 2B) TIFF0007709943000003.tif141164

[0120] (Table 2C) TIFF0007709943000004.tif142163

[0121] (Table 2D) TIFF0007709943000005.tif119161

[0122] FIG. 10 is a graph showing the relationship between the unevenness evaluation value in Numerical Examples 5 to 44 and Equation (2). In FIG. 10, the vertical axis represents the unevenness evaluation value, and the horizontal axis represents the value of Z / D2.

[0123] As shown in FIG. 10, when the value of Z / D2 is 0.1 or more, the unevenness evaluation value is 0.4 or less in most of the numerical examples. That is, it can be seen that by satisfying Equation (2), unevenness in the color of the illumination light is well suppressed.

[0124] Tables 3A to 3B show the parameter values of the endoscope illumination device according to Numerical Examples 45 to 56. Note that in any of Numerical Examples 45 to 56, the value of D2 / D1 is 3.0.

[0125] (Table 3A) TIFF0007709943000006.tif141164

[0126] (Table 3B) TIFF0007709943000007.tif142154

[0127] Figure 11 is a graph showing the relationship between the color unevenness evaluation values in Numerical Examples 45 to 56 and Equation (3). In Figure 11, the vertical axis represents the color unevenness evaluation value, and the horizontal axis represents the value of Re / R1.

[0128] As shown in Figure 11, when the value of Re / R1 is 1.6 or less, the color unevenness evaluation value is 0.3 or less. That is, it can be seen that by satisfying Equation (3), the color unevenness of the illumination light is well suppressed.

[0129] The above is the description of the exemplary embodiments of the present invention. The embodiments of the present invention are not limited to those described above, and various modifications are possible within the scope of the technical idea of the present invention. For example, the content obtained by appropriately combining the embodiments explicitly exemplified in the specification or obvious embodiments is also included in the embodiments of the present invention.

Description of Reference Numerals

[0130] 1: Endoscope 2: Insertion tube 3: Operation section 4: Universal tube 5: Connector section 6: Image pickup element 20: Flexible section 21: Curved section 22: Tip section 23: Connection section 25: Objective lens 26: Light distribution cap 27: Light source chip 27b: Blue LED 27y: Yellow phosphor 28: Substrate 30: Curvature operation knob 31: Operation button

Claims

1. A light source unit including a light emitting element that emits excitation light, and a phosphor that is excited by the excitation light to emit fluorescence, and radiating illumination light in which the excitation light and the fluorescence are mixed; A light distribution lens having an emission surface that emits the illumination light incident from the light source unit. The emission surface includes a first emission surface and a second emission surface formed in different regions within the emission surface. The thickness of the light emitting element and the thickness of the phosphor are defined such that the excitation light and the fluorescence, which are radiated from the light source unit at the same angle and incident on the light distribution lens, are emitted from the first emission surface or the second emission surface in substantially the same direction. An endoscope illumination device.

2. A support having an installation surface on which the light source unit is installed; The light source unit is configured such that the phosphor covers the light emitting element; The thickness of the light emitting element is the thickness from a first surface of the light emitting element that contacts the installation surface to a second surface of the light emitting element that is located on the side opposite to the first surface of the light emitting element and faces the light distribution lens. The thickness of the phosphor is the thickness from a first surface of the phosphor that contacts the installation surface to a second surface of the phosphor that is located on the side opposite to the first surface of the phosphor and faces the light distribution lens. When the thickness of the light emitting element is D1 and the thickness of the phosphor is D2, the following formula D2 / D1 ≤ 3.5 is satisfied. The endoscope illumination device according to claim 1.

3. When the direction in which the support and the light source unit are arranged in order is the front direction and the direction orthogonal to the front direction is the side direction, The first emission surface is located in the front direction of the light source unit. The second emission surface is located in the side direction of the light source unit. The emission surface includes a connection surface that connects the first emission surface and the second emission surface. The endoscope illumination device according to claim 2.

4. The connection surface is formed as a curved surface. The endoscope illumination device according to claim 3.

5. When the direction opposite to the front direction is the rear direction, The second emission surface is formed to extend to the rear direction of the light source unit. The endoscope illumination device according to claim 3.

6. The light distribution lens Has an incident surface facing the second surface, Emits the illumination light incident on the incident surface from the emission surface, A concave curved surface for expanding the light distribution angle of the illumination light is formed on the incident surface. The endoscope illumination device according to claim 4.

7. The concave curved surface includes a plurality of curved surfaces having different radii of curvature. The endoscope illumination device according to claim 6.

8. When the distance in the forward direction between the center of curvature of the first curved surface formed closest to the connection surface among the plurality of curved surfaces and the center position of the light source unit is Z, the following formula Z / D2 ≥ 0.1 is satisfied, The endoscope illumination device according to claim 7.

9. The first curved surface is formed at a position intersecting a line segment connecting the center position of the curved surface forming the connection surface and the center position of the light source unit, The endoscope illumination device according to claim 8.

10. When the light distribution lens is formed in a ring shape, the radius of curvature of the curved surface forming the connection surface is Re, and the radius of curvature of the first curved surface is R1, In at least a partial angular range of the ring-shaped light distribution lens, the following formula Re / R1 ≤ 1.6 is satisfied, The endoscope illumination device according to claim 8.

11. In at least the partial angular range, the curved surface forming the connection surface is located in the forward direction of the light source unit, The endoscope illumination device according to claim 10.

12. The light distribution angle of the illumination light is 180° or more, The endoscope illumination device according to claim 1.

13. The illumination light is white light, The endoscope illumination device according to claim 1.

14. An insertion tube, An imaging unit provided at the tip of the insertion tube, An endoscope illumination device according to any one of claims 1 to 13 provided around the imaging unit, and The light distribution lens is formed in a ring shape so as to surround the imaging unit, The light source units are arranged in a plurality at intervals around the imaging unit. Endoscope

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