JP6226207B2 - Endoscope - Google Patents

Description

The present invention relates to an endoscope having an endoscopic lens unit.

  2. Description of the Related Art Conventionally, endoscopes for imaging the inside of a human body, equipment, or structure are widely used in the medical field or the industrial field. As this type of endoscope, there is an electronic endoscope in which an image pickup unit including an image pickup lens and an image pickup element is mounted in an insertion portion inserted into an observation target. In an electronic endoscope, light from an imaging region is imaged on an imaging surface of an imaging element by an imaging lens, and the imaging light is converted into an electrical signal by the imaging element, and an external image processing device is connected via a signal cable. Etc. as a video signal. In endoscopes, for the purpose of expanding the range of observation objects, reducing the burden on the subject, simplifying the structure, reducing costs, etc., miniaturization of the insertion part has been cited as an issue, and in electronic endoscopes, It is important to further reduce the size and diameter of the tip including the imaging unit.

  For example, in Patent Document 1, in order to reduce the size of an optical device such as an endoscope, a plano-concave lens is provided on the image sensor side of the lens unit, and the flat portion of the plano-concave lens is projected from the end of the lens barrel. An imaging mechanism and an endoscope fixed to a cover member that covers the surface of the imaging element are disclosed. Further, Patent Document 2 discloses an endoscope objective lens having three lens groups that can reduce distortion by using only a spherical lens in an endoscope objective lens and realize cost reduction.

JP 2013-200377 A Japanese Patent No. 3426378

  The imaging unit of an electronic endoscope normally performs focus adjustment between the imaging lens and the imaging surface of the imaging device using a frame (tip rigid portion) that holds a lens barrel that houses the imaging lens and the imaging device. It has a configuration. In the configuration of the conventional imaging lens, when it is intended to realize excellent optical performance, the back focus becomes long, and it is necessary to secure a predetermined distance from the final surface of the imaging lens to the cover member surface of the imaging element. For this reason, it has been difficult to realize a structure in which the imaging lens and the imaging element are fixed with an adhesive or the like for the purpose of downsizing. In the endoscope objective lens described in Patent Document 2, the total optical length is about 6.51 to 7.22 mm, the back focus is about 0.70 to 0.87 mm, and the back focus is long with respect to the total optical length. Therefore, the imaging lens and the imaging element cannot be fixed without using a frame or the like. In addition, the imaging mechanism described in Patent Document 1 is configured to fix the plane of the final surface on the imaging element side to the cover member of the imaging element. However, since there is no refractive power on the final surface, It cannot contribute to the convergence and the reduction of aberration of the optical system. For this reason, it has been difficult to obtain desired optical performance while reducing the size of the imaging lens.

The present invention aims to provide a endoscope inner an imaging lens and an imaging device and can be realized a structure for fixing with an adhesive or the like.

The present invention includes a lens barrel, a front lens group and a rear lens group housed in the lens barrel, an image sensor whose imaging surface is covered with a cover glass, an imaging side final surface of the rear lens group, and the mirror a surface consisting of an imaging side end surface of the cylinder, interposed between the objective side surface of the cover glass of the image sensor, they are fixed, single bonding by contact wear resin that have a light-transmitting An optical system including a focal length f _{F of} the front group lens, a focal length f _{B of} the rear group lens, the front group lens, the rear group lens, the adhesive layer, and the cover glass. The focal length f _el , the total optical length OL corresponding to the distance from the foreground front side of the front group lens to the imaging side rear end surface of the cover glass, and the imaging side final surface of the rear group lens from the imaging side final surface Memories equivalent to the distance to the front edge on the subject side Callback MB _satisfy the relationship of _f el _/ f F <0 and _{f el} / f B> 0 and OL / MB> 7.0, to provide an endoscope.

  ADVANTAGE OF THE INVENTION According to this invention, the structure which fixes an imaging lens and an image pick-up element with an adhesive agent etc. in the imaging unit of an endoscope is realizable.

1 is an overall configuration diagram of an endoscope system using an endoscope according to an embodiment of the present invention. The perspective view which shows the structure of the front-end | tip part of the endoscope which concerns on this embodiment. Sectional drawing of the front-end | tip part of the endoscope which concerns on this embodiment The perspective view which shows the structure of the part except mold resin in the front-end | tip part of the endoscope which concerns on this embodiment. Sectional drawing which shows the structure of the optical lens group of the lens unit which concerns on 1st Embodiment. The figure which shows the lens data of the lens unit of 1st Embodiment. Sectional drawing which shows the structure of the optical lens group of the lens unit which concerns on 2nd Embodiment. The figure which shows the lens data of the lens unit of 2nd Embodiment.

  Hereinafter, embodiments of an endoscope lens unit and an endoscope according to the present invention (hereinafter referred to as “this embodiment”) will be described in detail with reference to the accompanying drawings. In the present embodiment, a configuration example applied to a medical endoscope is shown.

  FIG. 1 is an overall configuration diagram of an endoscope system using an endoscope according to an embodiment of the present invention. FIG. 2 is a perspective view showing the configuration of the distal end portion of the endoscope according to the present embodiment. FIG. 3 is a cross-sectional view of the distal end portion of the endoscope according to the present embodiment. FIG. 4 is a perspective view showing a configuration of a portion excluding the mold resin at the distal end portion of the endoscope according to the present embodiment.

  FIG. 1 is a perspective view showing the entire configuration of the endoscope system 13 including the endoscope 11 and the video processor 19. 2, the configuration of the distal end portion 15 of the endoscope 11 shown in FIG. 1 is shown in a perspective view. 3, the structure of the front-end | tip part 15 shown in FIG. 2 is shown with sectional drawing. FIG. 4 is a perspective view showing a configuration in which the mold resin 17 is removed from the distal end portion 15 shown in FIG.

  In addition, about the direction used for description in this specification, it shall follow the description of the direction in each figure. Here, “upper” and “lower” correspond to the upper and lower sides of the video processor 19 placed on the horizontal plane, respectively, and “front (front)” and “rear” refer to the endoscope main body (hereinafter “endoscope 11”). Corresponds to the distal end side of the insertion portion 21 and the proximal end side of the plug portion 23.

  As shown in FIG. 1, the endoscope system 13 includes an endoscope 11 that is a medical flexible endoscope, and a still image and a moving image obtained by photographing the inside of an observation target (here, a human body). And a video processor 19 that performs known image processing and the like. The endoscope 11 includes an insertion portion 21 that extends substantially in the front-rear direction and is inserted into the observation target, and a plug portion 23 to which the rear portion of the insertion portion 21 is connected.

  The insertion part 21 has a flexible soft part 29 whose rear end is connected to the plug part 23 and a front end part 15 connected to the front end of the soft part 29. The flexible portion 29 has an appropriate length corresponding to various methods such as endoscopic examination and endoscopic surgery.

  The video processor 19 has a socket portion 27 that opens to the front panel 25, and includes an image processing unit and a power supply unit inside the device. The socket portion 27 is inserted into and engaged with the rear end portion of the plug portion 23 of the endoscope 11, whereby the endoscope 11 communicates power and various signals (video signals, control signals) with the video processor 19. Signal).

  The power and various signals described above are guided from the plug portion 23 to the flexible portion 29 and the distal end portion 15 via the transmission cable 31 (see FIGS. 2 and 3) inserted through the flexible portion 29. An image signal output from the image sensor 33 provided at the distal end portion 15 of the endoscope 11 is transmitted from the plug portion 23 to the video processor 19 via the transmission cable 31. The video processor 19 performs image processing such as color correction and gradation correction on the image signal received by the image processing unit, and outputs the image signal after image processing to a display device (not shown). The display device is a monitor device having a display device such as a liquid crystal display panel, for example, and displays a subject image captured by the endoscope 11.

  As shown in FIGS. 2 and 3, the endoscope 11 according to the present embodiment has an imaging unit mounted on the distal end portion 15, and includes a lens unit 35 constituting an imaging lens and an imaging element 33. The lens unit 35 is configured by accommodating a plurality of lenses (for example, a first lens L <b> 1 to a third lens L <b> 3 to be described later) inside a lens barrel 39. The end of the lens unit 35 on the image sensor 33 side (rear side), the outer periphery of the image sensor 33, and the end of the transmission cable 31 on the image sensor 33 side (front side) are mold resins that are sealing resin members. 17 is covered. That is, the distal end portion 15 of the insertion portion 21 of the endoscope 11 is covered with the mold resin 17 on the entire imaging device 33 and at least a part of the lens unit 35 on the imaging device 33 side.

  As shown in FIG. 3, the image pickup surface 33 of the image pickup device 33 is covered with a cover glass 43. The end of the lens unit 35 on the imaging side is bonded and fixed to the cover glass 43 of the imaging element 33 by an adhesive resin 37 that forms an adhesive layer. The adhesive resin 37 is made of, for example, a transparent UV / thermosetting resin, and fixes the lens unit 35 and the cover glass 43 of the image sensor 33 with a separation portion 47. At this time, the lens unit 35 and the image sensor 33 are aligned with the optical axis of the lens aligned with the center of the imaging surface 41, and then the focus position adjustment (focusing) of the lens unit 35 in the optical axis direction is performed. Adhesion and fixing are performed with an adhesive resin 37. Thereby, the lens unit 35 and the image sensor 33 are directly bonded and fixed by the bonding resin 37. For example, the adhesive resin 37 is a type of adhesive that requires heat treatment to obtain final hardness, but cures to a certain degree of hardness even when irradiated with ultraviolet rays.

  The mold resin 17 is made of a resin material having a light shielding property such as black. As described above, the connection fixing portion between the lens unit 35 and the image pickup device 33 has a light shielding property such as black on the outer peripheral portion of the translucent adhesive resin 37 such as a transparent material that transmits the light beam of the subject image. A double structure is provided in which the mold resin 17 is provided and covered.

  A circuit board 49 is mounted on the surface opposite to the cover glass 43 of the image sensor 33 (rear side), and a capacitor 45 for preventing static electricity is attached. The transmission cable 31 is electrically connected at the rear part of the circuit board 49, and the connection part of the circuit board 49 is covered with a molding resin 17 for sealing. In the following description, the term “adhesive” does not have a strict meaning of a substance used for bonding the surfaces of solid objects, but is a substance that can be used to bond two objects or has been cured. When the adhesive has a high barrier property against gas and liquid, it is used in a broad sense as a substance having a function as a sealing material.

  The lens barrel 39 is constituted by a cylindrical material having high rigidity, for example, a metal cylindrical member. By using a hard material for the lens barrel 39, the tip 15 constitutes a hard part. For example, nickel is used as the metal material constituting the lens barrel 39. Nickel has a relatively high rigidity and high corrosion resistance, and is suitable as a material constituting the tip portion 15. Instead of nickel, for example, a copper nickel alloy may be used. The copper nickel alloy also has high corrosion resistance and is suitable as a material constituting the tip portion 15. Moreover, as a metal material which comprises the lens-barrel 39, Preferably, the material which can be manufactured by electroforming (electroplating) is selected. Here, the reason why electroforming is used is that the dimensional accuracy of a member manufactured by electroforming is extremely high, less than 1 μm (so-called sub-micron accuracy), and the variation when a large number of members are manufactured is small. As will be described later, the lens barrel 39 is an extremely small member, and the error in the inner and outer diameter dimensions affects the optical performance (image quality) of the endoscope 11. By configuring the lens barrel 39 with, for example, a nickel electroformed tube, it is possible to obtain the endoscope 11 capable of capturing a high-quality image while ensuring high dimensional accuracy despite a small diameter.

  The lens barrel 39 includes a plurality (three in the illustrated example) of lenses (first lens L1 to third lens L3) formed of an optical material (glass, resin, etc.), and the first lens L1 and the second lens. A diaphragm 51 sandwiched between L2 is incorporated in a state of being in close contact with each other in the direction of the optical axis LC. The first lens L1 and the third lens L3 are fixed to the inner peripheral surface of the lens barrel 39 with an adhesive over the entire circumference. The front end of the lens barrel 39 is sealed (sealed) by the first lens L1, and the rear end is sealed (sealed) by the third lens L3 so that air, moisture, or the like does not enter the inside of the lens barrel 39. Therefore, air or the like cannot escape from one end of the lens barrel 39 to the other end. In the following description, the first lens L1 to the third lens L3 are collectively referred to as an optical lens group LNZ. The optical lens group LNZ with a plurality of lenses is not limited to a three-lens configuration, and the number of lenses is arbitrary as long as the configuration includes a front group lens and a rear group lens, such as two lenses or four or more lenses. .

  As shown in FIGS. 3 and 4, the imaging device 33 is configured by an imaging device such as a small CCD (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor) having a square shape when viewed from the front-rear direction. . In this case, an imaging surface 41 having a square shape in front view is provided at the center of the imaging element 33. Light incident on the imaging unit from the outside forms an image on the imaging surface 41 of the imaging element 33 by the optical lens group LNZ in the lens barrel. The circuit board 49 mounted on the rear portion (rear side) of the image sensor 33 has an outer shape slightly smaller than that of the image sensor 33 when viewed from the rear. The image sensor 33 has, for example, an LGA (Land Grid Array) on the back surface, and is electrically connected to an electrode pattern formed on the circuit board 49.

  Here, the circle forming the outer periphery of the lens barrel 39 is inscribed in a square that is substantially inscribed in the square formed by the imaging element 33 and circumscribed in the square that is formed by the imaging surface 41. The center of the imaging surface 41 (intersection of diagonal lines of the imaging surface 41), the center of the lens unit 35 (center of the circle formed by the inner periphery of the lens unit 35), and the center of the lens barrel 39 (the circle formed by the outer periphery of the lens barrel 39) The center of the optical axis LC passes through the optical axis LC. More precisely, the lens unit 35 is positioned with respect to the image sensor 33 so that the normal passing through the center of the imaging surface 41 is the optical axis LC and the optical axis LC penetrates the center of the lens unit 35. It is matched.

  Next, a configuration example of the optical lens group LNZ (first lens L1 to third lens L3) in the lens unit 35 of the endoscope 11 will be described.

  FIG. 5 is a cross-sectional view showing the configuration of the optical lens group of the lens unit according to the first embodiment.

  1st Embodiment shows the 1st structural example of the optical lens group LNZ of the lens unit 35 in the front-end | tip part 15 of an endoscope. In the lens unit 35 of the present embodiment, the first lens L1 functions as a front group lens, and the second lens L2 and the third lens L3 function as a rear group lens. Here, the first lens L1 is the leading lens of the optical lens group LNZ, and the third lens L3 is the final lens of the optical lens group LNZ. In the lens unit 35, in order from the subject side to the imaging side, the first surface L1R1 of the first lens L1, which is the foremost surface, is a concave surface, the second surface L1R2 is a concave surface, and the first surface L2R1 of the second lens L2 is a convex surface, The second surface L2R2 has a convex surface, the first surface L3R1 of the third lens L3 has a concave surface, and the second surface L3R2, which is the final surface, has a concave surface.

  A diaphragm 51 is provided between the first lens L1 and the second lens L2, that is, between the front group lens and the rear group lens. Between the second surface L3R2 (final surface) of the third lens L3 that is a concave surface and the cover glass 43 of the image sensor 33, an adhesive resin 37 is filled to form an adhesive layer.

  FIG. 6 is a diagram illustrating lens data of the lens unit according to the first embodiment. In FIG. 6, the surfaces correspond to the surfaces L1R1 to L3R2 of the first lens L1 to the third lens L3, the diaphragm 51, and the adhesive layer (adhesive resin 37), respectively, and the curvature radius (mm) of each surface, conic The coefficient and effective diameter (mm) are shown. The thickness (mm) indicates the distance (thickness) in the optical axis direction at the optical center from the corresponding surface to the next surface, and the refractive index and the Abbe number are the refractive index of the optical member forming the corresponding surface. Indicates the Abbe number. Here, the outer diameter φ of the optical lens group LNZ (the outer diameters of the first lens L1 and the third lens L3) is about φ = 0.9 to 1.0 mm. The thickness of the cover glass 43 of the image sensor 33 is 0.4 mm.

In the first embodiment, the overall focal length f _el of the optical lens group LNZ is f _el = 0.58 mm, and the focal length f _F of the front group lens (first lens L1) is f _F = −0.714. The focal length f _B of the rear lens group (the second lens L2 and the third lens L3) is set to f _B = 0.481. Further, the total optical length OL of the optical lens group LNZ is the length from the forefront surface of the first lens (the first surface L1R1 of the first lens L1) to the imaging surface (the rear end surface on the imaging side of the cover glass 43 of the imaging device 33). Then, the total optical length OL = 2.287 mm.

  Further, when the length from the peripheral end surface of the final surface of the final lens (the second surface L3R2 of the third lens L3) to the front end surface on the subject side of the cover glass 43 of the image sensor 33 is a metal back MB, Metal back MB = 0.04 mm. Note that the metal back MB may be referred to as a back focus (BackFocus) due to unevenness of the final surface of the final lens. Here, the metal back MB is used as a conceptual parameter including the back focus BF, and the description is made unified with the metal back MB. As shown in FIG. 6, the thickness of the adhesive layer at the optical center is 0.05 mm, but the second surface L3R2 of the third lens L3 is a concave surface, so that the cover glass 43 extends from the peripheral end surface of the second surface L3R2. The metal back MB corresponding to the distance to the front end surface is shorter than the optical center.

At this time, f _el / f _F = −0.812, f _el / f _B = 1.206, OL / MB = 38.12,
f _el / f _F <0 and f _el / f _B > 0 and OL / MB> 7.0
Meet the relationship.

In addition, the radius of curvature rLbR2 (rL3R2) of the imaging side final surface of the rear lens group (the second surface L3R2 of the third lens L3) is rLbR2 = −214.043 ≠ ∞. Further, the refractive index n _be (n3) of the final lens (third lens L3) of the rear group lens is n _be = 1.68, and the refractive index n _ad of the adhesive layer is n _ad = 1.52. , N _be ≠ _nad .

The Abbe number ν _be (ν3) of the final lens (third lens L3) of the rear group lens is ν _be = 31> 25, and the refractive index n _be = 1.68 of the final lens. The relationship of 1.40 <n _be <1.90 is satisfied.

  The forefront lens (the first surface L1R1 of the first lens L1) is a concave surface, and the sag (SAG) amount d of the concave surface is d = 0.021 mm. Here, the concave sag amount d and the lens outer diameter φ of the optical lens group LNZ are d / φ = 0.021 when φ = 1.0 mm, and −0.1 <d / φ <0. The relationship of 1 is satisfied.

  FIG. 7 is a cross-sectional view showing the configuration of the optical lens group of the lens unit according to the second embodiment.

  2nd Embodiment shows the 2nd structural example of the optical lens group LNZ of the lens unit 35 in the front-end | tip part 15 of an endoscope. In the lens unit 35 of this embodiment, as in the first embodiment, the first lens L1 functions as a front group lens, and the second lens L2 and the third lens L3 function as a rear group lens. Here, the first lens L1 is the leading lens of the optical lens group LNZ, and the third lens L3 is the final lens of the optical lens group LNZ. In the lens unit 35, in order from the subject side to the imaging side, the first surface L1R1 of the first lens L1, which is the foremost surface, is a concave surface, the second surface L1R2 is a concave surface, and the first surface L2R1 of the second lens L2 is a convex surface, The second surface L2R2 has a convex surface, the first surface L3R1 of the third lens L3 has a concave surface, and the second surface L3R2, which is the final surface, has a convex surface.

  FIG. 8 is a diagram illustrating lens data of the lens unit according to the second embodiment. In FIG. 8, as in FIG. 6, each surface L <b> 1 </ b> R <b> 1 to L <b> 3 </ b> R <b> 2, diaphragm, radius of curvature (mm), conic coefficient, thickness (mm), effective diameter (mm) in the adhesive layer, The refractive index and Abbe number are shown. Here, the outer diameter φ of the optical lens group LNZ (the outer diameters of the first lens L1 and the third lens L3) is about φ = 0.9 to 1.0 mm. The thickness of the cover glass 43 of the image sensor 33 is 0.4 mm.

In the second embodiment, the overall focal length f _el of the optical lens group LNZ is f _el = 0.61 mm, and the focal length f _F of the front group lens (first lens L1) is f _F = −0.79. The focal length f _B of the rear lens group (second lens L2 and third lens L3) is set to f _B = 0.501. Further, the total optical length OL of the optical lens group LNZ is OL = 2.300 mm. The metal back MB is MB = 0.08 mm. As shown in FIG. 8, the thickness of the adhesive layer at the optical center is 0.05 mm. However, since the second surface L3R2 of the third lens L3 is a convex surface, the cover glass 43 extends from the peripheral end surface of the second surface L3R2. The metal back MB corresponding to the distance to the front end surface is longer than the optical center.

At this time, f _el / f _F = −0.772, f _el / f _B = 1.217, OL / MB = 37.1,
f _el / f _F <0 and f _el / f _B > 0 and OL / MB> 7.0
Meet the relationship.

In addition, the radius of curvature rLbR2 (rL3R2) of the imaging-side final surface of the rear lens group (the second surface L3R2 of the third lens L3) is rLbR2 = −1.345 ≠ ∞. Further, the refractive index n _be (n3) of the final lens (third lens L3) of the rear group lens is n _be = 1.55, and the refractive index n _ad of the adhesive layer is n _ad = 1.52. , N _be ≠ _nad .

The Abbe number ν _be (ν3) of the final lens (third lens L3) of the rear group lens is ν _be = 71.7> 25, and the refractive index n _be = 1.55 of the final lens. Therefore, the relationship of 1.40 <n _be <1.90 is satisfied.

  Further, the forefront lens (the first surface L1R1 of the first lens L1) is a concave surface, and the sag amount d of the concave surface is d = 0.030 mm. Here, when the sag amount d of the concave surface and the lens outer diameter φ of the optical lens unit LNZ are φ = 1.0 mm, d / φ = 0.030, and −0.1 <d / φ <0. The relationship of 1 is satisfied.

  Here, an example of the dimensions of the endoscope lens unit and the endoscope according to the present embodiment will be shown. In addition, the numerical value shown below shows one specific example, and various examples can be considered according to a use, a use environment, etc. As an example, the lens unit 35 has a total optical length OL of 2.2 to 2.3 mm and a lens outer diameter φ of 1.0 mm as in the above example, and the length of the imaging unit including the lens barrel 39 and the imaging element 33. The directional dimension is about 2.5 mm and the outer diameter is about 1.1 mm. Further, the length of the distal end portion 15 on which the imaging unit is mounted is about 3.5 mm, and the maximum outer diameter is about 1.5 mm.

  In the present embodiment described above, in the endoscope lens unit 35, the front lens group (first lens L1) having negative power and the rear lens group (second lens L2, third lens L3) having positive power are provided. And the total optical length OL is larger than that of the metal back MB. Accordingly, the metal back MB is small with respect to the total optical length OL, and the distance from the final surface of the optical lens group LNZ to the front end surface of the cover glass 43 of the image sensor 33 is shortened. It is possible to adopt a structure in which LNZ and the cover glass 43 of the image sensor 33 are directly bonded and fixed. Therefore, the imaging unit can have a structure with high strength and a small number of parts, an imaging lens with a short focal length can be realized, and the length and size of the imaging lens can be reduced.

  As described above, in this embodiment, the imaging lens is reduced in diameter, and the optical design is made by shortening the length of the imaging unit including the imaging lens and the imaging device, and the imaging lens and the imaging device are directly fixed by the adhesive layer. As a structure to achieve this, an even smaller imaging unit is realized.

  Further, in the structure in which the optical lens group LNZ and the cover glass 43 are directly fixed by the adhesive layer of the adhesive resin 37, the final surface (L3R2) of the optical lens group LNZ is a curved surface and bonded to the final lens (third lens L3). The refractive indexes of the layers are different. Thereby, since the refracting power can be given to the final surface of the optical lens group LNZ, it is possible to further improve the convergence of the light beam from the subject passing through the lens unit 35 and contribute to the reduction of aberration. . Further, regarding the optical performance (resolution, chromatic aberration, distortion, etc.) of the optical lens group LNZ, the number of lenses for obtaining necessary optical performance can be reduced. Therefore, it is possible to obtain desired optical performance while reducing the size and cost of the imaging lens.

Further, the chromatic aberration of magnification is reduced by setting the Abbe number ν _be (ν3) of the final lens (third lens L3) to _be greater than 25 and the refractive index n _be (n3) in the range of 1.40 to 1.90. In addition, since it can be smaller than the pixel pitch of the image sensor 33, color blurring in the periphery of the captured image can be reduced.

  Further, the forefront surface (L1R1) of the optical lens group LNZ is a concave surface, and the sag amount d of the concave surface is set so that the absolute value of the relative ratio d / φ to the lens outer diameter φ is smaller than 0.1. The forefront can be brought close to a flat surface, and the adhesion of dirt when using an endoscope can be reduced. The forefront surface (L1R1) of the optical lens group LNZ may be a convex surface. In this case, the sag amount d of the convex surface is set so that the absolute value of d / φ is smaller than 0.1.

  Various aspects of the embodiment according to the present invention include the following.

An endoscope lens unit according to an aspect of the present invention is disposed between a lens barrel, a front group lens and a rear group lens housed in the lens barrel, and the front group lens and the rear group lens. A final surface on the imaging side of the rear lens group is fixed to the cover glass of the image sensor by an adhesive layer, and the focal length f _F of the front lens group, the rear lens group The focal length f _{B of} the group lens, the focal length f _{el of the} entire optical lens group including the front group lens and the rear group lens, the total optical length OL of the optical lens group, and the metal back MB of the optical lens group are: ,
f _el / f _F <0 and f _el / f _B > 0 and OL / MB> 7.0
It satisfies the relationship.

  According to this configuration, since the distance from the final surface of the rear lens group to the front end surface of the cover glass of the image sensor is shortened, the optical lens group and the cover glass of the image sensor are directly bonded and fixed by the adhesive layer. Is possible. For this reason, the imaging unit of the endoscope can have a structure with high strength and a small number of parts, an imaging lens with a short focal length can be realized, and the length and size of the imaging lens can be reduced.

In the endoscope lens unit of one aspect of the present invention, the curvature radius rLbR2 of the imaging-side final surface of the rear group lens is rLbR2 ≠ ∞, and the refractive index of the final lens on the imaging side of the rear group lens n _be and the refractive index n _{ad of the} adhesive layer when the rear lens group is fixed by the adhesive layer may _be n _be ≠ n _ad .

  According to this configuration, the surface closest to the imaging surface of the image sensor is a curved surface, and refractive power can be obtained on this curved surface, which can contribute to the convergence of light rays from the subject and the reduction of aberrations in the optical system. .

In the endoscope lens unit of one aspect of the present invention, the Abbe number ν _be of the final lens on the imaging side of the rear group lens is ν _be > 25, and the final lens on the imaging side of the rear group lens The refractive index n _be may _be 1.40 <n _be <1.90.

  According to this configuration, it is possible to reduce the lateral chromatic aberration of the lens unit, and it is possible to reduce color bleeding in the peripheral portion of the captured image.

  In the endoscope lens unit of one aspect of the present invention, the forefront side of the front group lens is a concave surface or a convex surface, the sag amount d of the concave surface or the convex surface, and the optical lens group. The lens outer diameter φ may satisfy a relationship of −0.1 <d / φ <0.1.

  According to this configuration, the forefront surface of the lens unit can be flattened close to a flat surface, and adhesion of dirt when using an endoscope can be reduced.

  An endoscope according to one aspect of the present invention includes an endoscope lens unit according to any one of the above, an imaging element whose imaging surface is covered with a cover glass, and the rear group lens in the endoscope lens unit. An imaging-side final surface and an adhesive layer made of an adhesive resin that fixes the cover glass of the imaging element.

  According to this configuration, it is possible to provide an endoscope that can realize a structure in which the imaging lens and the imaging element are fixed with an adhesive or the like in the imaging unit, and can obtain necessary optical performance while further downsizing.

  While various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood. In addition, the constituent elements in the above-described embodiment may be arbitrarily combined without departing from the spirit of the invention.

The present invention has an effect of the imaging unit of the endoscope can be realized a structure for fixing the imaging lens and the imaging device with an adhesive or the like, comprising an endoscope lens units of small diameter to be used, for example, in the medical field It is useful as an endoscope.

DESCRIPTION OF SYMBOLS 11 ... Endoscope 15 ... Tip part 21 ... Insertion part 31 ... Transmission cable 33 ... Imaging element 35 ... Lens unit 37 ... Resin for adhesion | attachment (adhesion layer)
DESCRIPTION OF SYMBOLS 39 ... Lens tube 41 ... Imaging surface 43 ... Cover glass 51 ... Diaphragm L1, L2, L3 ... Lens LNZ ... Optical lens group

Claims (1)

A lens barrel,
A front group lens and a rear group lens housed in the lens barrel;
An imaging device whose imaging surface is covered by a cover glass;
Interposed between the imaging side end surface of the rear lens group and the surface constituted by the image pickup side end surface of the lens barrel, and the objective side surface of the cover glass of the image pickup device, to fix them, translucent a single adhesive layer by contact wear resin that have a have,
The focal length f _{F of} the front group lens, the focal length f _{B of} the rear group lens, the focal length f _{el of the} entire optical system including the front group lens, the rear group lens, the adhesive layer, and the cover glass, and Total optical length OL corresponding to the distance from the foreground front side of the front group lens to the imaging side rear end surface of the cover glass, and the distance from the imaging side final surface of the rear group lens to the subject side front end surface of the cover glass The metal back MB corresponding to
f _el / f _F <0 and f _el / f _B > 0 and OL / MB> 7.0
An endoscope that satisfies the relationship.

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