IMAGE PICKUP UNIT, ENDOSCOPE, AND METHOD FOR MANUFACTURING IMAGE PICKUP UNIT

An image pickup unit includes: an optical unit which includes a plurality of stacked optical elements and in which at least corners of four side surfaces have a notch being notched from an exit surface toward an incidence surface; an image sensor including a light-receiving surface; and resin which includes a first region between the light-receiving surface and the exit surface, the first region bonding the optical unit and the image sensor to each other, and a second region filling the notch of the optical unit, and which does not include an interface between the first region and the second region.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image pickup unit in which an image sensor is bonded to an optical unit in which a plurality of optical elements are stacked, an endoscope including an image pickup unit in which an image sensor is bonded to an optical unit in which a plurality of optical elements are stacked, and a method for manufacturing an image pickup unit in which an image sensor is bonded to an optical unit in which a plurality of optical elements are stacked.

2. Description of the Related Art

With an image pickup unit to be arranged in a distal end portion of an insertion portion of an endoscope, downsizing and, in particular, reducing a diameter of the image pickup unit is important in order to realize minimal invasion.

Japanese Patent Application Laid-Open Publication No. 2012-18993 discloses an optical unit made of a wafer-level stacked body as a method of manufacturing an extra-thin optical unit in an efficient manner. The optical unit is fabricated by cutting and dividing a bonded wafer in which are stacked a plurality of lens wafers, each of which includes a plurality of lenses, and a plurality of image pickup device wafers, each of which includes a plurality of image pickup devices.

International Publication No. 2017/203593 discloses an image pickup unit in which a notch is formed on a side surface and the notch is filled with resin in order to increase mechanical strength of a wafer-level optical system.

The image pickup unit described above is fabricated by, for example, arranging an image sensor using resin on an exit surface of the wafer-level optical system a notch of which has been filled with resin and subjected to curing and once again subjecting the wafer-level optical system to curing.

SUMMARY OF THE INVENTION

An image pickup unit according to an embodiment of the present invention includes: an optical unit which includes an incidence surface, an exit surface, and four side surfaces, which includes a plurality of stacked optical elements, and in which at least corners of the four side surfaces have a notch being notched from the exit surface toward the incidence surface; an image sensor including a light-receiving surface configured to receive an object image focused by the optical unit; and resin which includes a first region between the light-receiving surface and the exit surface, the first region bonding the optical unit and the image sensor to each other, and a second region filling the notch of the optical unit, and which does not include an interface between the first region and the second region.

An endoscope according to an embodiment of the present invention includes: an insertion portion configured to be inserted into a subject; and an image pickup unit provided in a distal end portion of the insertion portion, wherein the image pickup unit includes: an optical unit which includes an incidence surface, an exit surface, and four side surfaces, which includes a plurality of stacked optical elements, and in which at least corners of the four side surfaces have a notch being notched from the exit surface toward the incidence surface; an image sensor including a light-receiving surface configured to receive an object image focused by the optical unit; and resin which includes a first region between the light-receiving surface and the exit surface, the first region bonding the optical unit and the image sensor to each other, and a second region filling the notch of the optical unit, and which does not include an interface between the first region and the second region.

A method for manufacturing an image pickup unit according to an embodiment of the present invention includes: fabricating a stacked wafer by stacking a plurality of optical element wafers, each of the optical element wafers including an optical element; forming a plurality of grooves on an exit surface of the stacked wafer to a depth that does not reach an incidence surface of the stacked wafer; arranging uncured resin in the plurality of grooves and on the exit surface of the stacked wafer; mounting at least one image sensor on the exit surface of the stacked wafer on which the resin is arranged; solidifying the resin; and cutting the stacked wafer to which the image sensor is bonded along the plurality of grooves filled with the resin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown inFIG.1, an endoscope9according to an embodiment constitutes an endoscope system6together with a processor5A and a monitor5B.

Note that in the following description, the drawings based on each of the embodiments are schematic in nature. A relationship between a thickness and a width in each portion, a ratio of thicknesses among respective portions, relative angles of respective portions, and the like differ from reality. Even among the drawings, the drawings include portions having a relationship or a ratio among dimensions that differ from each other. Furthermore, illustration of some of the components may be omitted.

The endoscope9includes an insertion portion3, a grasping portion4arranged in a proximal end portion of the insertion portion3, a universal cord4B extended from the grasping portion4, and a connector4C arranged in a proximal end portion of the universal cord4B. The insertion portion3includes a distal end portion3A, a bending portion3B which is extended from the distal end portion3A, which is bendable, and which is used for changing a direction of the distal end portion3A, and a flexible portion3C which is extended from the bending portion3B. A rotatable angle knob4A which is an operation portion that enables an operator to operate the bending portion3B is arranged in the grasping portion4.

The universal cord4B is connected to the processor5A by the connector4C. The processor5A controls the entire endoscope system6, performs signal processing on an image pickup signal, and outputs an image signal. The monitor5B displays the image signal outputted by the processor5A as an endoscopic image. Although the endoscope9is a flexible scope, the endoscope9may be a rigid scope instead. In addition, the endoscope9may be used in either medical application or industrial application.

The endoscope9includes the insertion portion3configured to be inserted into a subject and an image pickup unit1(1A to1D) which is provided in the distal end portion3A of the insertion portion3.

First Embodiment

FIGS.2to4show the image pickup unit1according to the present embodiment. The image pickup unit1includes an optical unit10, an image sensor30, and resin40. The image sensor30that is bonded to the optical unit10by the resin40receives an object image focused by the optical unit10. Reference sign “O” denotes an optical axis of the optical unit10.

As will be described later, the resin40that is transparent curable resin not only includes a first region40A which bonds the image sensor30but also includes a second region40B which is arranged in a notch C10of a side surface10SS of the optical unit10. The first region40A and the second region40B are a continuous integrated object. In other words, the first region40A and the second region40B do not have an interface between the regions.

The image sensor30includes a light-receiving surface30SA and a rear surface30SB on an opposite side to the light-receiving surface30SA. The image sensor30includes an image pickup device31, a cover glass33, and an adhesion layer32. The image pickup device31includes a light-receiving unit31A made of a CCD or a CMOS, and a plurality of electrodes34connected to the light-receiving unit31A via through wirings (not illustrated) are arranged on the rear surface30SB. The image pickup device31receives a drive signal and transmits an image pickup signal using the wiring (not illustrated) connected to each of the plurality of electrodes34. The image pickup device31may be either a front-illuminated image sensor or a back-illuminated image sensor.

The optical unit10includes an incidence surface10SA, an exit surface10SB on an opposite side to the incidence surface10SA, and four side surfaces10SS. In the optical unit10, a plurality of optical elements11to15are bonded by resin20arranged between the optical elements.

For example, a first optical element11is a plano-concave lens including the incidence surface10SA. A second optical element12is a convex-convex lens. A third optical element13is a plano-convex lens. A fourth optical element14is a spacer element with a through-hole to be an optical path at center of the element. A fifth optical element15is a concave-plano lens including the exit surface10SB.

Although not illustrated, the optical unit10also includes other optical elements such as an infrared cut filter, a flare diaphragm, and an aperture stop. In addition, the optical element constituting the lenses may be a hybrid lens element in which a resin lens is arranged on a transparent substrate. A configuration of the optical unit10is appropriately selected according to specifications.

The optical unit10includes the notch C10which is notched from the exit surface10SB toward the incidence surface10SA on the four side surfaces10SS. The notch C10reaches the side surface of the first optical element11which includes the incidence surface10SA but does not reach the incidence surface10SA. The notch C10of the optical unit10is formed up to midway toward the side surface10SS of the first optical element11which includes the incidence surface10SA.

Owing to the notch C10, the incidence surface10SA of the first optical element11is larger than a main surface of any of the other optical elements12to15such as the exit surface10SB of the fifth optical element.

In addition, the notch C10is filled with the resin40. The resin40is not only arranged in the notch C10and on the exit surface10SB which bonds the image sensor30and the optical unit10to each other but also arranged on the side surface10SS (notch C10).

Since the resin40made of, for example, epoxy resin is arranged in the notch C10of the side surface10SS, mechanical strength of the optical unit10is improved. The optical unit10is extra thin, with the incidence surface10SA being, for example, a 5-mm square. However, the optical unit10reinforced by the resin40has no risk of damage to a bonding surface by becoming detached or broken even when subjected to stress. In addition, since the resin40is accommodated in the notch C10, an external dimension of the optical unit10is not increased by arranging the resin40on the side surface10SS and the optical unit10can be made extra thin.

In order to secure mechanical strength, for example, the resin40is preferably hard resin with a Vickers hardness (ISO 6507-1) Hv of 5 GPa or higher. In addition, a thickness T40of the resin40of the side surface10SS is preferably 5 μm or more and more preferably 20 μm or more.

In order to secure mechanical strength, the notch C10preferably reaches the side surface of the first optical element11which includes the incidence surface10SA among the plurality of optical elements.

With a conventional image pickup unit with a notch filled with resin, the notch is first filled with the resin and subjected to curing, the resin is then arranged on an exit surface of an optical system, an image sensor is mounted, and the image pickup unit is subjected to curing once again. In other words, the conventional image pickup unit requires that two resin arranging steps and two curing steps be performed.

In the optical unit10, the resin40not only secures mechanical strength but also bonds the image sensor30. As will be described later, the resin40is configured to a state of including two functions due to one resin arranging step and one curing step with respect to a stacked wafer to become the optical unit10.

In other words, resin that bonds the image sensor30and the optical unit10to each other and resin that seals side surfaces of the optical unit10are made of a same integrally-arranged material.

Therefore, the image pickup unit1can be readily manufactured. In addition, it goes without saying that productivity of the endoscope9equipped with the image pickup unit1in the distal end portion3A is high.

<Method for Manufacturing Optical Unit>

Next, a method for manufacturing the image pickup unit according to the embodiment will be described along a flowchart shown inFIG.5.

A plurality of optical element wafers11W to15W (refer toFIG.6), each of which includes a plurality of optical elements11to15, are fabricated.

A stacked wafer10W (refer toFIG.6) is fabricated by stacking and bonding the plurality of optical element wafers11W to15W. The plurality of optical element wafers11W to15W are bonded by the resin20which is energy-curable.

As shown inFIGS.6and7, the incidence surface10SA of the stacked wafer10W is fixed to, for example, a dicing tape95. In addition, a plurality of grooves T90with a depth that does not reach the incidence surface10SA is formed on the exit surface10SB of the stacked wafer10W along a cut line CL for dividing the stacked wafer10W. In other words, the plurality of grooves T90which open on the exit surface10SB of the stacked wafer10W are formed.

Note that the cut line CL is a cut line for dividing the stacked wafer10W into image pickup units1and is made up of a plurality of mutually orthogonal lines. The optical elements11to15are positioned in each of regions enclosed by four cut lines CL.

The grooves T90are formed so as to have an opening width of W90and to have a bottom surface in the first element wafer11W that is stacked at a bottommost position of the stacked wafer10W by a first dicing blade90a width of which (cutting margin) is W90. For example, when a thickness of the first element wafer11W is 200 μm, the grooves T90are formed to a depth that is half (100 μm) of the thickness of the first element wafer11W. Note that groove forming may be performed by etching or the like instead of machining.

When the stacked wafer10W is cut, the grooves T90become the notch C10of the side surface10SS of the image pickup unit1. When the grooves T90reach the incidence surface10SA, the image pickup unit1can no longer be readily detached from the dicing tape95after being cut. Therefore, preferably, the depth of the grooves T90(notch C10) does not reach the incidence surface10SA.

As shown inFIG.8, the uncured resin40is arranged in the plurality of grooves T90and on the exit surface10SB of the stacked wafer10W. For example, using an ink-jet method, the grooves T90are also filled with the resin40. In other words, since the resin40of the first region40A on the exit surface10SB to which the image sensor30is mounted and the resin40of the second region40B which fills the grooves T90(the notch C10of the optical unit10) are simultaneously arranged, the resin40does not include an interface between the first region40A and the second region40B.

Note that even when the first region40A and the second region40B are made of the same resin, an interface exists between the two regions if resins of the two regions are arranged in different steps. For example, a boundary surface can be observed when observing a cross section. Due to the absence of an interface between the first region40A and the second region40B, the first region40A and the second region40B can be determined to have been applied simultaneously.

The resin40is transparent energy-curable resin. In an energy-curable resin, a cross-linking reaction or a polymerization reaction is promoted when receiving energy such as heat, ultraviolet light, or an electron beam from outside. For example, the resin40is ultraviolet-curable silicone resin, epoxy resin, or acrylic resin.

Note that “transparent” means that levels of light absorption and scattering of the material are low enough to withstand use in a wavelength range of the image pickup unit1.

<Step S50> Image Sensor Mounting Step

As shown inFIG.9, the image sensor30is mounted to the exit surface10SB of the stacked wafer10W on which the resin40is arranged. The resin40fills the first region40A between the light-receiving surface30SA of the image sensor30and the exit surface10SB.

The resin40of the stacked wafer10W to which the image sensor30is mounted is cured and solidified. In other words, the resin40of the first region40A between the light-receiving surface30SA of the image sensor30and the exit surface10SB and the resin40of the second region40B which fills the grooves T90(the notch C10of the optical unit10) are simultaneously cured.

For example, in a case of ultraviolet-curable/thermosetting combined resin, after the exit surface10SB of the stacked wafer10W is irradiated with ultraviolet rays, heat treatment is performed using a heating furnace or a hot plate.

As shown inFIG.10, the stacked wafer10W to which the image sensor30is bonded is cut along the plurality of grooves T90(cut lines CL) filled with the resin40.

When the stacked wafer10W is cut by a second dicing blade91with a width (cutting margin) of W91, the stacked wafer10W is divided into a plurality of the image pickup units1. The width W91of the cutting margin is smaller than the width W90of the grooves. Therefore, a cutting surface of the stacked wafer10W or, in other words, the side surface10SS of the image pickup unit1is made up of a cutting surface of a part of the first element wafer11W and a cutting surface of the resin40. Laser dicing or plasma dicing may be used for the cutting.

With the manufacturing method according to the present embodiment, the image pickup unit1mechanical strength of which is improved by the resin40can be efficiently manufactured.

Modifications of First Embodiment

Next, image pickup units1A and1B according to modifications of the first embodiment will be described. Since the image pickup units1A and1B are similar to the image pickup unit1and produce same effects, components with same functions will be assigned same reference signs and descriptions of such components will be omitted.

First Modification of First Embodiment

As shown inFIG.11, in the image pickup unit1A according to the present modification, a thickness T40of the resin40in the second region40B is configured so as to continuously decrease from the exit surface10SB toward the incidence surface10SA.

In a method for manufacturing the image pickup unit1A, in the groove forming step S30, since a groove a wall surface of which is inclined with respect to the exit surface10SB is formed, an opening width of the groove T90is wider than an internal width of the groove T90. The groove T90described above can be readily formed by, for example, selecting a shape of the first dicing blade90.

With the image pickup unit1A, the groove T90can be more readily filled with the resin40in the resin arranging step (S40) than the image pickup unit1.

Second Modification of First Embodiment

As shown inFIG.12, in a method for manufacturing the image pickup unit1B, in the image sensor mounting step (S50), a sensor block30W including a plurality of image sensors30B is mounted to the exit surface10SB of the stacked wafer10W. The sensor block30W may be a circular wafer or a rectangular block cut from a circular wafer.

As shown inFIG.13, in the image pickup unit1B, an outer dimension of the image sensors30B is the same as an outer dimension of the optical unit10including the resin40.

Second Embodiment

Since an image pickup unit1C according to a second embodiment is similar to the image pickup units1to1B and produces same effects, same components will be assigned same reference signs and descriptions of such components will be omitted.

As shown inFIGS.14to16, in the image pickup unit1C according to the present embodiment, only each corners of the four side surfaces10SS or, in other words, each ridges where two side surfaces intersect each other of an optical unit10C includes a notch C10C which is notched from the exit surface10SB toward the incidence surface10SA. The resin40that fills the notch C10C is resin in the second region40B.

Mechanical strength of the image pickup unit1C is improved by the resin40in the second region40B. In addition, as will be described later, the image pickup unit1C can be readily manufactured.

In a method for manufacturing the image pickup unit1C, a hole forming step is performed in place of the groove forming step (S30) of the image pickup unit1. As shown inFIG.17, a plurality of bottomed holes H40are formed on the exit surface10SB of a stacked wafer10WC. The holes H40are respectively formed at intersections of the cut line CL or, in other words, four corners of the optical element after being cut. A depth of the holes H40preferably reaches the side surface of the first optical element11which includes the incidence surface10SA but does not reach the incidence surface10SA.

In the resin arranging step (S40), the uncured resin40is arranged in the plurality of holes H40and on the exit surface10SB of the stacked wafer10WC. Note that an area parallel to the exit surface10SB of the holes H40preferably continuously decreases from the exit surface10SB toward the incidence surface10SA to enable the holes H40to be more readily filled with resin.

Since the resin40of the first region40A on the incidence surface10SA to which the image sensor30is mounted and the resin40of the second region40B which fills the grooves T90(the notch C10C of the optical unit10) are simultaneously arranged, the resin40does not include an interface between the first region40A and the second region40B.

In addition, in the curing step (S60), the resin40of the first region40A on the incidence surface10SA to which the image sensor30is mounted and the resin40of the second region40B which fills the holes H40(the notch C10C of the optical unit10) are simultaneously cured.

As shown inFIG.18, in the cutting step (S70), the stacked wafer10WC to which the image sensor30is bonded is cut along the cut line CL which straddles the plurality of holes H40filled with the resin40.

With the manufacturing method according to the present embodiment, the image pickup unit1C mechanical strength of which is improved by the resin40can be efficiently manufactured.

Modification of Second Embodiment

Since an image pickup unit1D according to the present modification is similar to the image pickup unit1C and produces same effects, same components will be assigned same reference signs and descriptions of such components will be omitted.

As shown inFIG.19, the image pickup unit1D includes a notch C10D at not only corners of the side surfaces10SS but also at approximately center of the side surfaces10SS of an optical unit10D. The notch C10D is filled with resin40C of a third region. In other words, the resin40includes resin40[[A]] in a first region40A, resin40[[B]] in a second region40B, and the resin40[[C]] in the third region40C.

The notch C10D is formed by a hole formed in a stacked wafer in a same manner as the notch C10C at the corners of the side surfaces10SS. The resin40is simultaneously arranged on the exit surface10SB, in the notch C10C, and in the notch C10D and is simultaneously cured. The resin40does not include interfaces among the first region40A, the second region40B, and the third region40C.

Mechanical strength of the image pickup unit1D is more improved than the image pickup unit1C.

It goes without saying that an endoscope including the image pickup units1A to1D in a distal end portion of the endoscope shares the effects of the endoscope9including the image pickup unit1and also shares the respective effects of the image pickup units1A to1D.

The present invention is not limited to the embodiments and the like described above and various modifications, alterations, and the like can be made within the scope of the gist of the present invention.