Imaging unit, endoscope, and manufacturing method of imaging unit

Abstract

An imaging unit 10 of the present invention comprises: a laminated lens 22 formed by laminating at least one resin lens; an imager 23 disposed facing an image surface side end surface 22b of the laminated lens; a distal end frame 21 that accommodates at least the laminated lens and the imager therein; and a resin 30 with which a clearance 21b between a side surface 22a in an optical axis O direction of the laminated lens and an inner surface 21a of the distal end frame is filled. The dimensional size of the clearance in a direction orthogonal to the optical axis of the laminated lens is such that the value for an object side end surface 22c is smaller than the value for the image surface side end surface of the laminated lens on at least one surface among side surfaces of the laminated lens.

Description

Imaging Unit, Endoscope, and Method for Manufacturing an Imaging Unit

[0001] The present invention relates to an imaging unit used in an endoscope or the like, and further relates to an endoscope having the imaging unit at the tip of an insertion portion and a method for manufacturing the imaging unit.

[0002] Conventionally, endoscopes configured to have an insertion portion in the shape of an elongated tube are widely used in, for example, the medical field and the industrial field. Among these, medical endoscopes used in the medical field insert the insertion portion, for example, into a body cavity of a living body to observe organs or the like, and perform various treatments using a treatment tool inserted into a treatment tool insertion channel provided in the endoscope as needed for the organs or the like. Further, industrial endoscopes used in the industrial field insert the insertion portion, for example, into the inside of a device such as a jet engine or a factory pipe or mechanical equipment, and are configured to be able to observe and inspect the state of scratches, corrosion, etc. inside the device or mechanical equipment.

[0003] In this type of endoscope, particularly in medical endoscopes used in the medical field, in order to improve the insertability when inserting the insertion portion into the body cavity of a living body, miniaturization and shortening of the diameter of the tip portion of the insertion portion and the hard length of the tip hard member are always required.

[0004] For example, in recent years, as a measure for miniaturizing the imaging optical system and the illumination optical system that constitute a part of the imaging unit used in an endoscope, a manufacturing technique using wafer-level optics (WLO) in which a laminated lens formed by laminating and adhesively fixing a plurality of optical elements (for example, an optical lens made of a resin molded product; a resin lens) in a stacked form in the optical axis direction is cut out by dicing has been put into practical use.

[0005] Further, endoscopes that apply the laminated lens thus manufactured as an objective optical system have been variously proposed, for example, in Reference 1 and the like.

[0006] The imaging unit disclosed in the aforementioned cited document 1, etc., houses a prismatic stacked lens manufactured using wafer-level optics (WLO) inside a tip frame with a clearance (gap space), and then seals the clearance with resin. This fixes the stacked lens in a predetermined position inside the tip frame.

[0007] International Publication Number WO2022 / 254659

[0008] In this case, the resin poured to seal the internal area of ​​the clearance generally has a certain surface tension.

[0009] Therefore, in the configuration described in the aforementioned reference document 1, it may not be possible to completely and thoroughly penetrate the resin into the internal region of the clearance.

[0010] The aforementioned clearance is formed to surround the side surface of the laminated lens, and sealing this clearance with resin serves not only to adhere and fix the laminated lens to the front frame, but also to shield the side surface of the laminated lens from light.

[0011] Furthermore, since laminated lenses are formed using resin materials, reliable resin sealing of the clearance region is necessary to suppress moisture absorption into the laminated lens and to ensure moisture resistance on the base end side around the side of the laminated lens.

[0012] For example, if leakage occurs in the resin seal within the clearance area, it can lead to a decrease in the optical performance of the laminated lens due to light leakage or the effects of humidity.

[0013] The present invention aims to provide an imaging unit having a structure that can reliably seal the area around a stacked lens, which is positioned inside the tip frame of an endoscope, with resin; an endoscope having this imaging unit at the tip of its insertion section; and a method for manufacturing the imaging unit.

[0014] To achieve the above objective, an imaging unit according to one aspect of the present invention comprises a stacked lens formed by stacking at least one resin lens, an imager positioned opposite the image plane side end face of the stacked lens, a front frame housing at least the stacked lens and the imager, and a resin filling the clearance between the side surface of the stacked lens along the optical axis direction and the inner surface of the front frame, wherein the clearance dimension in the direction perpendicular to the optical axis of the stacked lens is such that, at least one of the side surfaces of the stacked lens has a value at the object side end face that is smaller than the value at the image plane side end face of the stacked lens.

[0015] An endoscope according to one aspect of the present invention has the imaging unit at the tip of the insertion section.

[0016] An imaging unit according to another aspect of the present invention comprises a stacked lens formed by stacking at least one resin lens, an imager positioned opposite the image plane-side end face of the stacked lens, a front frame housing at least the stacked lens and the imager, and a clearance between the side surface of the stacked lens along the optical axis direction and the inner surface of the front frame, wherein the numerical value of the gap dimension in the direction perpendicular to the optical axis of the stacked lens decreases as the stacked lens moves from the image plane-side end face toward the object-side end face, and the unit is manufactured by filling the clearance from the image plane-side end face with resin.

[0017] A method for manufacturing an imaging unit according to one aspect of the present invention includes the steps of cutting out a stacked lens, which is made by stacking at least one resin lens, with a dicing blade, forming a slope on the side surface of the stacked lens such that the width in the direction perpendicular to the optical axis of the stacked lens decreases from the object-side end face toward the image plane-side end face, and housing the stacked lens and imager inside a tip frame, and filling the clearance between the tip frame and the stacked lens with resin while the unit is upright.

[0018] According to the present invention, it is possible to provide an imaging unit having a structure that can reliably seal the area around a stacked lens, which is arranged inside the tip frame of an endoscope, with resin; an endoscope having this imaging unit at the tip of the insertion section; and a method for manufacturing the imaging unit.

[0019] The diagram shows an external view of an endoscope to which the imaging unit of the first embodiment of the present invention is applied, an enlarged cross-sectional perspective view of a key part showing a portion of the tip of the endoscope in Figure 1, a cross-sectional view of the imaging unit of Figure 1 removed from the diagram, a diagram showing the process of filling the gap space with filling resin, an enlarged view of a key part showing an enlarged area of ​​the region indicated by reference numeral [5] in Figure 4, a schematic diagram showing the process of cutting out a laminated lens by dicing, an enlarged cross-sectional view of a key part of the imaging unit of the second embodiment of the present invention, a conceptual diagram showing the process of forming an inclined surface with coating resin on the side surface of a laminated lens used in the imaging unit of the second embodiment of the present invention, a schematic diagram showing a first configuration example in which the minimum width position of the gap space on the side surface of the laminated lens is set to the middle of the side surface of the laminated lens, a schematic diagram showing a second configuration example in which the minimum width position of the gap space on the side surface of the laminated lens is set to the middle of the side surface of the laminated lens, and a diagram showing another configuration example of the imaging unit of the present invention, the main part being an enlarged cross-sectional perspective view shown by cutting a portion of the tip of the endoscope.

[0020] The present invention will be described below with reference to the illustrated embodiments. The drawings used in the following description are schematic. Therefore, in these drawings, each component is shown at a size that is recognizable on the drawing. For this reason, the dimensional relationships and scales of each component may differ on the drawing. The present invention is not limited to the illustrated forms with respect to the quantity, shape, size ratio, relative positional relationships, etc., of each component shown in each drawing.

[0021] The embodiments described below are examples of applying stacked lenses manufactured using wafer-level optics (WLO) as the imaging optical system for an imaging unit used in an endoscope. Furthermore, each embodiment is an example intended for a medical endoscope.

[0022] [First Embodiment] First, before describing the detailed configuration of the imaging unit of the first embodiment of the present invention, the general configuration of the endoscope to which the imaging unit is applied will be described below with reference to Figures 1 and 2.

[0023] Figures 1 and 2 show a schematic configuration of an endoscope to which the imaging unit of the first embodiment of the present invention is applied. Of these, Figure 1 is an external view of the endoscope. Figure 2 is an enlarged cross-sectional perspective view of a key part, showing a portion of the tip of the endoscope in Figure 1.

[0024] As shown in Figure 1, the endoscope 1 to which the imaging unit of the first embodiment of the present invention is applied mainly comprises an insertion section 2, an operating section 3, a universal cord 4, an endoscope connector 5, and the like.

[0025] The insertion portion 2 is formed in an overall elongated tube shape and is a tubular member that is inserted into the body cavity of a living organism. This insertion portion 2 is formed by connecting a tip portion 6, a curved portion 7, and a flexible tube portion 8 in order from the tip side, and is flexible as a whole.

[0026] Of these, the tip portion 6 is provided with a hard tip portion 6b (see Figure 2) which forms the main body of the tip portion. This hard tip portion 6b is composed of various constituent units, such as an imaging unit (details to be described later; see reference numeral 10 in Figures 2 and 3) which is an imaging device consisting of an imaging optical system, an image sensor and its imaging substrate, etc., as well as a treatment instrument insertion channel and an illumination unit (none of which are shown in Figure 1).

[0027] The curved section 7 is a mechanism unit configured to be actively curved in the up, down, left, and right directions in response to the rotational operation of the curved knob, which is one of the operating members provided on the operating section 3 for performing the bending operation.

[0028] The flexible tube section 8 is a tubular member formed to be flexible so as to be able to be passively bent. Inside this flexible tube section 8, in addition to a channel for inserting treatment tools, various electrical signal lines and light guide fiber bundles (not shown) are inserted.

[0029] Here, the various electrical signal lines refer to multiple signal lines that extend from the tip 6 to the processor (not shown), which is an external control device, in order to connect the imaging unit 10 etc. built into the tip 6 with the processor (not shown), which is an external control device. These signals are routed through the insertion section 2, the operation section 3, and the universal cord 4 to the processor (not shown), which is an external control device.

[0030] Furthermore, the light guide fiber bundle (not shown) is a light guide member that guides the illumination light emitted from the external light source device (not shown) to the illumination window 12 (see Figure 2) provided on the tip surface 6a of the tip portion 6.

[0031] The operating section 3 is connected to the base end of the insertion section 2 and is a component unit that has multiple operating members, etc. The multiple operating members include, for example, a curved knob.

[0032] The universal cord 4 is a flexible, hollow, tubular member extending from the operating section 3. This universal cord 4 is a composite cable through which various electrical signal lines and light guide fiber bundles described above, as well as, for example, air and water supply tubes from an external device such as an air and water supply device (not shown), are inserted.

[0033] The endoscope connector 5 is located at the tip of the universal cord 4 and is a connecting member for ensuring connection to various external devices. The endoscope connector 5 is composed of an electrical connector section (not shown) to which an electrical cable (not shown) containing various electrical signal lines connecting to a processor (not shown) is connected, a light source connector section (not shown) that connects to an external light source device through a light guide fiber bundle, and an air and water supply plug (not shown) for connecting an air and water supply tube (not shown) from an air and water supply device.

[0034] As shown in Figure 2, the tip surface 6a of the hard tip portion 6b of the tip portion 6 of the insertion portion 2 of the endoscope 1 is provided with an observation window 11, illumination windows 12 (multiple), a treatment instrument insertion channel opening 13, and the like.

[0035] Of these, the observation window 11 is located on the frontmost side of the imaging optical system (described later) included in the imaging unit 10, and is an aperture window that takes in light from the object to be observed. A transparent flat plate made of glass or resin material is fitted into this observation window 11.

[0036] The illumination window 12 is provided on the front side of the illumination unit (illumination section) and is an opening window that emits illumination light from the light source device, guided by a light guide fiber bundle (not shown), toward the front of the endoscope 1.

[0037] The instrument insertion channel opening 13 is the tip opening of the instrument insertion channel that is inserted into the insertion section 2, and is an opening for allowing the tip of the instrument inserted into the instrument insertion channel to protrude.

[0038] The endoscope 1 illustrated in Figure 1 is a so-called flexible endoscope, equipped with, for example, a flexible insertion section 2. The basic configuration of this endoscope 1 is substantially the same as that of conventionally used endoscopes. Therefore, no further explanation of the configuration of the endoscope 1 will be provided.

[0039] The direction indicated by the arrow symbol Ax in Figures 1, 2, and 3 is referred to as the insertion axis direction of the endoscope 1. This insertion axis direction Ax is also the direction that approximately coincides with the optical axis O (see Figure 3) of the imaging optical system of the imaging unit 10.

[0040] Next, the basic configuration of the imaging unit according to the first embodiment of the present invention will be described below with reference to Figure 3. Figure 3 is a diagram showing the imaging unit of the first embodiment taken out of the diagram, and is a cross-sectional view along the optical axis.

[0041] The imaging unit 10 of the first embodiment mainly consists of an observation window 11, a holding lens barrel 21, a stacked lens 22, an imager 23, an imaging circuit board 24, a plurality of imaging signal lines 25, an imaging cable 26, a heat shrink tubing 27 which is a protective tube, and a filling resin 30, etc.

[0042] The lens holder 21 is a hollow cylindrical tip frame and holding member. The lens holder 21 houses and securely holds components such as the stacked lens 22, imager 23, imaging circuit board 24, and part of the imaging signal line 25. An observation window 11 made of parallel flat plates is fitted into one end (tip side) of the lens holder 21. This observation window 11 watertightly seals the tip opening of the lens holder 21. The lens holder 21 is formed from a metal material such as SUS or a molded resin material.

[0043] The stacked lens 22 is an imaging optical system that forms an optical image of an imaging object. The stacked lens 22 has a form in which at least one resin lens is stacked. The stacked lens 22 is, for example, one manufactured using wafer level optics (WLO). Thereby, the cross section of the stacked lens 22 orthogonal to the optical axis O is formed in a substantially rectangular shape. In this case, the length of the short side of the stacked lens 22 (one side of the surface orthogonal to the optical axis O; the width described later) is 0.8 - 1.2 mm. Also, the height of the stacked lens 22 along the optical axis O direction is 1.8 - 2.2 mm.

[0044] The imager 23 is an imaging element that receives the optical image formed by the stacked lens 22 and converts it into an image signal. The imager 23 is disposed to face the image-side end face 22b of the stacked lens 22. The imager 23 is, for example, a photoelectric conversion element using a solid-state imaging element such as a CCD or a CMOS (Complementary Metal Oxide Semiconductor).

[0045] The imaging circuit board 24 is a circuit board unit that receives the output signal from the imager 23 and performs various signal processes. The imaging circuit board 24 is a circuit board connected to the imager 23 on the surface opposite to the surface of the imager 23 facing the stacked lens 22. In the imaging unit 10 of the present embodiment, the imaging circuit board 24 shows a configuration example in which, for example, a molded interconnect device (MID) is applied.

[0046] Note that in the imaging unit 10, the configuration is not limited to the example in which the MID is applied as the imaging circuit board 24, and other forms of circuit boards, for example, a printed circuit board (PCB), a flexible printed circuit (FPC), a wire harness, etc., forms that employ conventionally common forms of circuit boards may also be used.

[0047] The imaging cable 26 is a cable unit that bundles a plurality of imaging signal lines 25 that transmit the output signal from the imaging circuit board 24 to a processor (not shown).

[0048] The heat-shrinkable tube 27 is a protective tube that covers a part of the outer surfaces of the imaging signal line 25, the imaging cable 26, and the holding lens barrel 21.

[0049] The filling resin 30 is a resin for fixedly holding a part of the laminated lens 22, the imager 23, the imaging circuit board 24, and the imaging signal line 25 inside the holding lens barrel 21. When the imaging unit 10 including the laminated lens 22, the imager 23, the imaging circuit board 24, the imaging signal line 25, and the imaging cable 26 is accommodated and arranged inside the holding lens barrel 21, the filling resin 30 is filled in the clearance (gap space 21b) between the side surface 22a along the optical axis O direction of the outer surface of the imaging unit 10 and the inner surface 21a of the holding lens barrel 21 (see FIG. 3).

[0050] Thus, by filling the gap space 21b, the filling resin 30 at least watertightly and optically seals the side surface 22a of the laminated lens 22. Thereby, light leakage and hygroscopicity to the laminated lens 22 can be suppressed. As the filling resin 30, for example, an epoxy resin or a UV curable resin is applied.

[0051] Here, in order to fill the filling resin 30 into the gap space 21b, for example, it is performed as follows. FIG. 4 is a diagram showing the operation when the filling resin 30 is filled into the gap space 21b.

[0052] The imaging unit 10 shown in FIG. 4 shows a state in which an integrated unit in an assembled state of the laminated lens 22, the imager 23, the imaging circuit board 24, and the imaging signal line 25 is arranged inside the holding lens barrel 21 in which the observation window 11 is fitted. That is, this state shows the state before the imaging cable 26 and the heat-shrinkable tube 27 are incorporated.

[0053] Also, at this time, the imaging unit 10 is in a state where the direction along the optical axis O substantially coincides with the vertical direction (that is, the upright state). In this state, the base end side opening of the holding lens barrel 21 faces upward, and thus the gap space 21b opens upward.

[0054] In this state, as shown in Figure 4, the filling resin 30 is dripped from the upper opening of the gap space 21b into the gap space 21b inside the holding barrel 21 using a dispenser 40 or the like. Then, the filling resin 30 flows downward from the upper opening towards the gap space 21b inside the holding barrel 21.

[0055] In this embodiment, the laminated lens 22 of the first embodiment is further formed by an inclined surface 22aa on at least one surface of the side surface 22a along the optical axis O direction, as shown in Figure 5. This inclined surface 22aa is formed such that the width of the laminated lens 22 decreases from the object-side end surface 22c toward the image plane-side end surface 22b.

[0056] In this case, the width of the stacked lens 22 refers to the dimension of the stacked lens 22 in the direction perpendicular to the optical axis O. In the following explanation, the direction perpendicular to the optical axis O may also be referred to as the width direction or the transverse direction.

[0057] Here, Figure 5 is an enlarged view of the main part, showing an enlarged version of the region indicated by the reference numeral [5] in Figure 4. As shown in Figure 5, the inclined surface 22aa of the side surface 22a of the laminated lens 22 is formed such that the width 22Wb of the image plane side end surface 22b is smaller than the width 22Wa of the object side end surface 22c of the laminated lens 22 (22Wa > 22Wb).

[0058] Furthermore, as a means for forming an inclined surface 22aa on the side surface 22a of the stacked lens 22, for example, a desired inclined surface can be arbitrarily formed by appropriately selecting a dicing blade used when cutting out the stacked lens 22 by dicing.

[0059] Here, Figure 6 schematically shows the process of cutting a stacked lens by dicing. In Figure 6, the side surface 22a of the stacked lens 22 is cut in the area indicated by the symbol [C] (the area indicated by cross-hatching) according to the cutting edge shape of the dicing blade 41. As a result, an inclined surface 22aa is formed on the side surface 22a of the stacked lens 22.

[0060] When the laminated lens 22 formed in this manner is housed in a predetermined position inside the lens barrel 21, a gap space 21b is formed between the inner surface 21a of the lens barrel 21 and the inclined surface 22aa of the side surface 22a of the laminated lens 22, as described above.

[0061] In this case, as shown in Figure 5, the gap space 21b is formed such that it narrows from the image plane side end face 22b of the stacked lens 22 toward the object side end face 22c (i.e., the numerical value of the gap dimension in the lateral direction decreases).

[0062] In other words, the gap space 21b is formed such that the lateral gap dimension decreases as you move from the image plane side end face 22b of the stacked lens 22 toward the object side end face 22c. In this case, the lateral gap dimension 21bb of the image plane side end face 22b is larger than the lateral gap dimension 21ba of the object side end face 22c (21bb > 21ba).

[0063] Here, for example, the lateral gap dimension 21ba of the gap space 21b at the object-side end face 22c of the laminated lens 22 is 0.01–0.3 mm, and a more preferable value is 0.07–0.12 mm. Also, the minimum value of the lateral gap dimension of the gap space 21b at the image plane-side end face 22b of the laminated lens 22 is 0.02–0.5 mm, and a more preferable value is 0.12–0.15 mm.

[0064] The imaging unit 10 of the first embodiment of the present invention, configured in this manner, is manufactured as follows.

[0065] First, the laminated lens 22, which consists of at least one resin lens stacked on top of each other, is cut out by a dicing blade (laminated lens cutting process).

[0066] In this cutting process using a dicing blade, an inclined surface 22aa is formed on the side surface 22a of the stacked lens 22, where the width dimension in the direction perpendicular to the optical axis O of the stacked lens 22 decreases as it moves from the object-side end surface 22c toward the image plane-side end surface 22b (inclination formation process).

[0067] Next, the unit, with at least the stacked lens 22 and imager 23 assembled, is housed inside the retaining barrel 21 (tip frame). At this time, the stacked lens 22 and imager 23 are positioned upright inside the retaining barrel 21 (stacked lens and imager arrangement step).

[0068] Next, using a dispenser 40 or the like, the filling resin 30 is dropped from the image plane side end face 22b into the clearance (gap space 21b) between the holding lens barrel 21 and the stacked lens 22, thereby filling the gap space 21b with the filling resin 30 (resin filling step). The imaging unit 10 is manufactured by this manufacturing method.

[0069] As described above, according to the configuration of the first embodiment, the filling resin 30 dropped toward the gap space 21b of the holding lens barrel 21 flows downward from the relatively wide space of the upper opening in the gap space 21b. Here, since the gap space 21b has an inclined surface 22aa formed on at least one surface of the side surface 22a of the laminated lens 22, it narrows as it goes downward. As a result, the filling resin 30 dropped into the gap space 21b can fill the entire area of ​​the gap space 21b without leakage by so-called capillary action. In other words, an improvement in the filling performance of the filling resin 30 into the gap space 21b can be expected.

[0070] Furthermore, in addition to the configuration of the imaging unit 10 as shown in Figure 4, it is more preferable to have the dimensional relationship between the width 22Wb of the image plane side end face 22b of the stacked lens 22, the width 23W of the imager 23, and the width 24W of the imaging circuit board 24 as follows: 22Wb > 23W > 24W. With this configuration, the gap space 21b can be more clearly formed as it narrows from the image plane side towards the object plane side.

[0071] [Second Embodiment] In the imaging unit 10 of the first embodiment described above, an inclined surface 22aa is formed on at least one surface of the side surface 22a of the stacked lens 22. In this case, the inclined surface 22aa is formed when the stacked lens 22 is cut out by dicing.

[0072] In contrast to the first embodiment with the above configuration, the second embodiment shown below differs in that a coating resin 42 is provided on the side surface 22a of the laminated lens 22 to form an inclined surface 42aa.

[0073] In other words, the imaging unit 10 of this second embodiment has essentially the same configuration as the first embodiment described above, except for the configuration in which the inclined surface 42aa is provided by the coating resin 42. Therefore, in describing the second embodiment below, components that are the same as those of the first embodiment described above will be denoted by the same reference numerals and their descriptions will be omitted, and only the different components will be described. Figure 7 is an enlarged cross-sectional view of the main part of the imaging unit of the second embodiment of the present invention.

[0074] As shown in Figure 7, the imaging unit 10 of the second embodiment has an inclined surface 42aa formed by a coating resin 42 on the side surface 22a of the stacked lens 22. Here, the coating resin 42 can be, for example, epoxy resin or UV curing resin.

[0075] This inclined surface 42aa has a slope such that the width dimension in the direction perpendicular to the optical axis O of the laminated lens 22 decreases as it moves from the object-side end face 22c toward the image-plane-side end face 22b. Therefore, because an inclined surface 42aa made of the coating resin 42 is formed on the side surface 22a of the laminated lens 22, the gap space 21b is formed such that the numerical value of the lateral gap dimension decreases as it moves from the image-plane-side end face 22b toward the object-side end face 22c of the laminated lens 22.

[0076] Such an inclined surface 42aa made of coating resin 42 can be formed as follows. Figure 8 is a conceptual diagram showing the process of forming an inclined surface made of coating resin on the side surface of a stacked lens used in the imaging unit of the second embodiment.

[0077] First, multiple stacked lenses 22 cut by the dicing blade are arranged in a matrix at predetermined intervals. Next, a coating resin is filled in to cover the spaces between adjacent sides and the periphery of the arranged stacked lenses 22 (see reference numeral [8A] in Figure 8).

[0078] Next, cutting is performed along each side of the multiple stacked lenses 22 using a dicing blade (see reference numeral [8B] in Figure 8). Here, in the diagram indicated by reference numeral [8B] in Figure 8, reference numerals 42x1 and 42y1 indicate the cutting lines made by the dicing blade. Of these, cutting line 42x1 conceptually shows the cutting line when the dicing blade is advanced along arrow 42x in Figure 8. Similarly, cutting line 42y1 conceptually shows the cutting line when the dicing blade is advanced along arrow 42y in Figure 8.

[0079] Through this cutting process using a dicing blade, an inclined surface 42aa made of coating resin 42 is formed on the side surface 22a of the laminated lens 22, where the width dimension in the direction perpendicular to the optical axis O of the laminated lens 22 decreases as it moves from the object-side end face 22c toward the image plane-side end face 22b. Here, the shape of the inclined surface 42aa (such as the inclination angle) can be arbitrarily formed by appropriately selecting the dicing blade. Through this process, an inclined surface 42aa made of coating resin 42 can be formed.

[0080] Furthermore, in addition to forming the inclined surface of the coating resin 42 on the side surface 22a of the stacked lens 22, it may also be formed on the side region of the imager 23, as shown in Figure 7 (see inclined surface 42ab in Figure 7).

[0081] With this configuration, the inclined surface 42ab on the side of the imager 23 is formed such that the width dimension in the direction perpendicular to the optical axis O of the laminated lens 22 decreases as it moves from the image plane side end face 22b of the laminated lens 22 toward the object plane side end face 23c of the imager 23. As shown in Figure 7, this inclined surface 42ab can eliminate the step difference that occurs between the image plane side end face 22b (width 22Wb) of the laminated lens 22 and the object plane side end face 23c (width 23Wc) of the imager 23. As a result, the inclined surfaces 42ab and 42aa formed from the side of the imager 23 toward the side of the laminated lens 22 can be made into a smoothly continuous inclined surface. Therefore, the filling resin 30 can be filled into the gap space 21b more smoothly and without leakage.

[0082] In the second embodiment described above, the inclined surfaces 42aa and 42ab made of the coating resin 42 are formed separately on the stacked lens 22 and the imager 23, respectively. However, the configuration is not limited to this example. For example, the inclined surfaces made of the coating resin 42 may be formed after the stacked lens 22, the imager 23, and the imaging circuit board 24 have been assembled. In this way, a smoother and more continuous inclined surface can be formed on the side surfaces from the stacked lens 22 to the imager 23 and the imaging circuit board 24.

[0083] [Third Embodiment] In the first and second embodiments described above, an example is provided in which an inclined surface is formed on at least one side surface 22a of the laminated lens 22, such that the width dimension in the direction perpendicular to the optical axis O of the laminated lens 22 decreases as it moves from the object-side end surface 22c toward the image plane-side end surface 22b. In such a configuration, the position where the lateral width of the gap space formed on the side surface of the laminated lens is minimized (hereinafter abbreviated as the minimum lateral width position of the gap space) is at the same position as the object-side end surface 22c of the laminated lens 22, or at a position close to the object-side end surface 22c. However, the present invention is not limited to these embodiments.

[0084] Next, an example of the configuration of a third embodiment of the present invention will be illustrated. In the imaging unit of the third embodiment of the present invention, the position of the minimum width of the gap space formed on the side surface of the stacked lens is located in the middle of the side surface of the stacked lens in a direction along the optical axis of the stacked lens.

[0085] Figure 9 is a schematic diagram showing a first configuration example in which the minimum width of the gap space on the side surface of the stacked lens is set to the middle of the side surface of the stacked lens.

[0086] In the first configuration example shown in Figure 9, the inclined surface 22aa of the side surface 22a of the stacked lens 22 is formed having a first inclined surface 22ac and a second inclined surface 22ad.

[0087] The width dimension of the first inclined surface 22ac increases in the direction perpendicular to the optical axis O of the stacked lens 22 as it moves from the image plane side end face 22b toward the object side end face 22c (the width of the gap dimension decreases), and the minimum width of the gap space 21b is set at position 22d in the middle of the side surface 22a of the stacked lens 22. Here, the gap dimension at the minimum width position (21d) is indicated by reference numeral 21bc, as shown in Figure 9. Also, the lateral width dimension of the gap space 21b at the position corresponding to the image plane side end face 22b of the stacked lens 22 is indicated by reference numeral 21bb.

[0088] The second inclined surface 22ad is set such that the width dimension in the direction perpendicular to the optical axis O of the laminated lens 22 decreases (the width of the gap dimension increases) as it moves from the position of minimum width of the gap space 21b (22d) toward the object-side end face 22c. In this case, the lateral width dimension 21bc of the gap space 21b at the object-side end face 22c of the laminated lens 22 is approximately equal to the lateral width dimension 21bb of the gap space 21b at the image plane-side end face 22b of the laminated lens 22 (21bc ≈ 21bb).

[0089] In this way, by setting the position of the minimum width of the gap space 21b to the middle position 22d of the side surface 22a of the laminated lens 22, the filling resin 30 can be prevented from flowing into the region 22e closer to the object-side end face 22c than the position 22d.

[0090] Here, as described above, an observation window 11 is provided on the front side of the object-side end face 22c of the laminated lens 22. This observation window 11 is fitted in a watertight manner to the tip side of the retaining barrel 21. Therefore, even if the area 22e near the tip of the gap space 21b (the area closer to the object-side end face 22c than the middle position 22d) is not filled with the filling resin 30, it does not affect the moisture resistance of the laminated lens 22.

[0091] Furthermore, since the dimension of the region 22e in the direction along the optical axis O is extremely short, even if the filling resin 30 is not filled into the region 22e, it will not affect the light-shielding properties of the laminated lens 22.

[0092] Furthermore, if the filling resin 30 is filled to the area 22e near the tip of the gap space 21b, there is a possibility that the filling resin 30 may seep out between the object-side end face 22c of the stacked lens 22 and the observation window 11 (the front surface of the imaging unit 10).

[0093] However, by providing a region 22e near the tip of the gap space 21b where the filling resin 30 is not filled, the possibility of the filling resin 30 seeping between the object-side end face 22c of the laminated lens 22 and the observation window 11 can be suppressed.

[0094] Figure 10 is a schematic diagram showing a second configuration example in which the minimum width of the gap space on the side surface of the stacked lens is set to the middle of the side surface of the stacked lens.

[0095] In the second configuration example shown in Figure 10, the inclined surface 22aa of the side surface 22a of the stacked lens 22 is formed having a first inclined surface 22ac and a parallel surface 22ae. Of these, the first inclined surface 22ac has the same shape as in the second configuration example described above.

[0096] The parallel surface 22ae is formed parallel to the side surface 22a of the laminated lens 22, extending from the minimum width position (22d) of the gap space 21b toward the object-side end surface 22c. In this case, the lateral width dimension 21ba of the gap space 21b at the object-side end surface 22c of the laminated lens 22 is approximately equal to the lateral width dimension 21bc at the minimum width position (21d) of the gap space 21b (21ba ≈ 21bc).

[0097] The second configuration, having the same features as the first configuration described above, can also achieve substantially the same effects. Furthermore, according to the second configuration example, the region 22e near the tip of the gap space 21b can be made smaller in volume compared to the first configuration example described above, thus further reducing concerns about moisture absorption and light leakage.

[0098] By the way, in each of the embodiments and configuration examples described above, the imaging unit 10 was configured to include a retaining lens barrel 21 as the tip frame, but other configuration examples are also possible, as shown below.

[0099] Figure 11 is a diagram showing another configuration example of the imaging unit of the present invention, and is an enlarged cross-sectional perspective view of the main part, showing a portion of the tip of the endoscope.

[0100] As shown in Figure 11, the imaging unit 10 in this alternative configuration is constructed without the holding barrel 21 which serves as the tip frame in each of the embodiments described above. In this alternative configuration, instead of the holding barrel 21, the imaging housing section 6x formed on the hard tip section 6b that constitutes the tip 6 of the endoscope 1 is used as the tip frame. That is, at least the stacked lens 22 and imager 23 of the assembled imaging unit 10 are housed in the imaging housing section 6x.

[0101] Even with this alternative configuration, substantially the same effects as those of the embodiments described above can be obtained. Furthermore, in this alternative configuration, the retaining lens barrel 21, which serves as the tip frame, can be omitted from the components of the imaging unit 10, and a part of the tip rigid portion 6b (imaging housing portion 6x) can be used as the tip frame. Therefore, the number of parts can be reduced, contributing to a reduction in product cost.

[0102] Furthermore, the technology of the present invention can also be similarly applied to the illumination optical system (light guide section) of an illumination unit used in an endoscope.

[0103] The present invention is not limited to the embodiments described above, and various modifications and applications can be implemented without departing from the spirit of the invention. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriate combinations of the multiple components disclosed. For example, if the problem that the invention aims to solve can be solved and the effects of the invention can be obtained even if some components are deleted from all the components shown in one embodiment, then the configuration with these components deleted can be extracted as an invention. Furthermore, components from different embodiments may be combined as appropriate. This invention is not limited by any particular embodiment other than being limited by the appended claims.

[0104] 1…Endoscope 2…Insertion section 3…Operation section 4…Universal cord 5…Endoscope connector 6…Tip section 6a…Tip surface 6b…Rigid tip section 6x…Imaging housing section 7…Bending section 8…Flexible tube section 10…Imaging unit 11…Observation window 12…Illumination window 13…Instrument insertion channel opening 21…Retaining tube (tip frame) 21a…Inner surface of retaining tube 21b…Gap space (clearance) 21ba…Gap dimension, width dimension (object side end face) 21bb…Gap dimension, width dimension (image plane side end face) 21bc…Gap dimension, width dimension (minimum width position) 22…Stacked lens 22Wa…Width of object side end face 22Wb…Width of image plane side end face 22a…Side view 22aa…Inclined surface 22ae…Parallel surface 22b…Image plane side end face 22c…Object side end face 22d... Minimum width position 22e... Area near the tip 23... Imager 23W, 23Wc... Imager width 24... Imaging circuit board 24W... Width of imaging circuit board 25... Imaging signal line 26... Imaging cable 27... Heat shrink tubing 30... Filling resin 40... Dispenser 41... Dicing blade 42... Coating resin 42aa, 42ab... Inclined surface 42x1, 42y1... Cutting line

Claims

1. An imaging unit comprising: a stacked lens formed by stacking at least one resin lens; an imager disposed opposite the image plane side end face of the stacked lens; a front frame housing at least the stacked lens and the imager; and a resin filling the clearance between the side surface of the stacked lens along the optical axis direction and the inner surface of the front frame, wherein the clearance dimension in the direction perpendicular to the optical axis of the stacked lens is smaller at the object side end face than at the image plane side end face of the stacked lens for at least one of the side surfaces of the stacked lens.

2. The imaging unit according to claim 1, wherein the side surface of the stacked lens is formed such that the width in the direction perpendicular to the optical axis decreases as it moves from the object-side end surface toward the image plane-side end surface, and the clearance decreases as it moves from the image plane-side end surface toward the object-side end surface of the stacked lens due to the inclined surface.

3. The imaging unit according to claim 1, wherein the side surface of the stacked lens has an inclined surface formed up to the middle of the side surface of the stacked lens, the width of which decreases in the direction perpendicular to the optical axis as it moves from the object-side end surface toward the image plane side, and the clearance of the stacked lens in the direction perpendicular to the optical axis is smaller at the object-side end surface than at the image plane-side end surface of the stacked lens.

4. The imaging unit according to claim 1, wherein an inclined surface is formed on the side surface of the stacked lens with a coating resin, the width of which decreases as it moves from the object-side end face toward the image-plane-side end face, and the clearance decreases as it moves from the image-plane-side end face toward the object-side end face of the stacked lens due to the inclined surface.

5. The imaging unit according to claim 1, characterized in that it has a circuit board connected to the imager on the surface of the imager opposite to the surface of the imager facing the stacked lens.

6. The imaging unit according to claim 1, characterized in that the numerical value of the clearance at the object-side end face of the stacked lens is 0.01-0.3 mm.

7. The imaging unit according to claim 1, characterized in that the numerical value of the clearance at the object-side end face of the stacked lens is 0.07-0.12 mm.

8. The imaging unit according to claim 1, characterized in that the minimum value of the numerical value of the clearance at the image plane side end face of the stacked lens is 0.02-0.5 mm.

9. The imaging unit according to claim 1, characterized in that the minimum value of the numerical value of the clearance at the image plane side end face of the stacked lens is 0.12-0.15 mm.

10. The imaging unit according to claim 1, characterized in that the height of the stacked lens along the optical axis direction is 1.8-2.2 mm.

11. The imaging unit according to claim 1, characterized in that the length of the short side of the stacked lens is 0.8-1.2 mm.

12. The imaging unit according to claim 3, characterized in that the coating resin is made of epoxy resin or UV-curing resin.

13. The imaging unit according to claim 1, characterized in that the resin is made of epoxy resin or UV-curing resin.

14. An endoscope characterized by having the imaging unit described in claim 1 at the tip of the insertion section.

15. An imaging unit comprising: a stacked lens comprising at least one resin lens; an imager disposed opposite the image plane end face of the stacked lens; a front frame housing at least the stacked lens and the imager; and a clearance between the side surface of the stacked lens along the optical axis direction and the inner surface of the front frame, wherein the numerical value of the gap dimension in the direction perpendicular to the optical axis of the stacked lens decreases as the stacked lens moves from the image plane end face toward the object side face, and the unit is manufactured by filling the clearance from the image plane end face with resin.

16. A method for manufacturing an imaging unit, comprising the steps of: cutting out a stacked lens, which is made by stacking at least one resin lens, with a dicing blade; forming a slope on the side surface of the stacked lens such that the width in the direction perpendicular to the optical axis of the stacked lens decreases from the object-side end face toward the image plane-side end face; and housing the stacked lens and the imager inside a tip frame, and filling the clearance between the tip frame and the stacked lens with resin by dripping resin into the clearance while the frame is upright.

Images