JP2011232614A - Method for manufacturing imaging lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging lens unit which can accurately fix an imaging lens which is capable of easily mass produced to a mirror cell.SOLUTION: A variation of back focus can be suppressed by managing a space between outer flange surfaces as lens total thickness of an imaging lens OU.

Description

  The present invention relates to a method for manufacturing an imaging lens, and more particularly to a method for manufacturing an imaging lens that is small and suitable for mass production.

  Compact and very thin imaging devices (hereinafter also referred to as camera modules) are used in portable terminals such as mobile phones and PDAs which are compact and thin electronic devices such as mobile phones and PDAs (Personal Digital Assistants). Yes. As an image pickup element used in these image pickup apparatuses, a solid-state image pickup element such as a CCD type image sensor or a CMOS type image sensor is known. In recent years, the number of pixels of an image sensor has been increased, and higher resolution and higher performance have been achieved.

  As a manufacturing method of an imaging lens used in an imaging device built in such a portable terminal, a large number of lens elements are simultaneously molded by a replica method on a glass substrate of several inches which is a parallel plate, and there are many of these lens elements. A method of mass-producing lens modules after combining a formed glass substrate (lens wafer) with a sensor wafer and then separating it has been proposed (see Patent Document 1). A lens manufactured by such a manufacturing method is called a wafer scale lens, and a lens module is called a wafer scale lens module.

JP 2010-054810 A

  By the way, in a general imaging lens, when the lens core thickness changes due to a manufacturing error, the back focus fluctuates. However, in the case of a conventional large-sized solid-state imaging device having relatively low pixels, the focus position is relatively insensitive, and this back focus variation problem is particularly apparent even when a single-focus imaging lens is used. There wasn't. However, in recent years, solid-state imaging devices used in imaging devices have been further miniaturized, and in a VGA image format (effective pixel number 640 × 480) sensor, 1/10 inch size (pixel pitch 2.2 μm) or 1 / 12 inch size (pixel pitch 1.75 μm) solid-state image sensor has been commercialized. In such a solid-state imaging device, the tolerance range of the back focus variation of the imaging lens is narrow, and in order to obtain a high-quality image, the distance from the imaging surface is accurately adjusted according to the back focus of the imaging lens. It was necessary to position well. However, since the imaging lens and the solid-state imaging device are extremely small, adjusting the interval between the imaging lens and the imaging surface during assembly causes an increase in the number of manufacturing steps.

  The present invention has been made in view of the problems of the related art, and an object of the present invention is to provide a method for manufacturing an imaging lens capable of providing a back focus with little variation while being capable of mass production. .

According to a first aspect of the present invention, there is provided a method for manufacturing an imaging lens, wherein the optical lens and the outer flange surface are formed from the same mold, and the optical surface and the outer flange surface are formed from the same mold. The second lens is disposed such that one of the outer flange surfaces faces the object side and the other faces the image side,
After adjusting the distance between the outer flange surfaces, the first lens and the second lens are connected to each other.

  There is a lens in which the optical surface and the outer flange surface are formed from the same mold. Here, the “same mold” is defined as the entire mold that is moved or fixed integrally during mold clamping and mold opening at the time of molding, and is formed from a plurality of parts. A mold (for example, a mold in which a core pin is inserted) is also included. In such a lens, the relative position in the optical axis direction between the optical surface and the outer flange surface is accurately formed by the transfer surface of the mold, but the lens core thickness and flange thickness are determined each time molding is performed. It becomes the value of. The back focus of an imaging lens made by laminating such lenses changes as the core thickness of each lens changes, so if the lens core thickness or flange thickness varies, the back focus also varies. Become.

  On the other hand, the present inventors tried to adjust the back focus by adjusting the distance between the optical surfaces facing each other (referred to as the lens interval) between the plurality of lenses. Here, since the lens interval varies depending on the thickness of the adhesive layer between the flanges, there is an idea that the thickness of the adhesive layer may be measured and managed. However, it is difficult to measure the thickness of the adhesive layer, and it is difficult to manage the mass-produced product. Further, it is difficult to strictly manage the back focus only by controlling the thickness of the adhesive layer.

  Therefore, as a result of diligent research, the present inventors manage the total lens thickness (distance in the optical axis direction between the most object-side optical surface and the most image-side optical surface) instead of managing the thickness of the adhesive layer. I came up with it. The error in the lens interval can be expressed by (total lens thickness error-first lens core thickness error-second lens core thickness error). If the total lens thickness is managed to be constant, for example, the lens spacing decreases as the lens core thickness increases, so that the back focus error can be canceled, and the total lens thickness is managed by the thickness of the adhesive layer. Easier than managing. However, for example, if the total lens thickness is to be managed mechanically, the optical surface may be damaged by directly applying a jig or the like to the optical surface. On the other hand, if the total lens thickness is to be managed optically, optical measurement is performed. There is a risk that the apparatus becomes large and costs increase.

  In contrast, the inventors of the present invention have a first lens in which the optical surface and the outer flange surface are formed from the same mold, and a second lens in which the optical surface and the outer flange surface are formed from the same mold. Focusing on the fact that in an imaging lens combined with a lens, it is almost (error of total lens thickness) = (error of distance between outer flange surfaces), and the distance between outer flange surfaces instead of the total lens thickness. The present invention, which is characterized by managing the above, has been achieved. According to the present invention, the same effect as controlling the total thickness of the lens to satisfactorily suppress the back focus variation is exhibited, and the outer flange surface has little influence on the optical performance even if flaws or the like are attached. The effect that the tool etc. can be contact | abutted directly and it is excellent also in the handleability can also be exhibited. In particular, when the outer flange surfaces are orthogonal to the optical axis, it is easier to manage the spacing between the outer flange surfaces.

  The imaging lens manufacturing method according to claim 2 is the invention according to claim 1, wherein in the first lens and the second lens, the inner flange surfaces, which are the back surfaces of the outer flange surfaces, are brought into close contact with each other. It is characterized by not letting it. Thereby, the space | interval of outer side flange surfaces can be adjusted arbitrarily.

  According to a third aspect of the present invention, there is provided a manufacturing method of an imaging lens according to the first or second aspect, wherein the first flange and the second lens are formed between inner flange surfaces that are back surfaces of the outer flange surfaces. An adhesive layer is formed between them. The gap between the outer flange surfaces can be fixed by adhering the inner flange surfaces after the adjustment.

  The manufacturing method of the imaging lens of Claim 4 WHEREIN: In invention in any one of Claims 1-3, the jig | tool which respectively hold | maintains the said outer side flange surface in a said 1st lens and a said 2nd lens. The distance between the outer flange surfaces is adjusted by bringing them into contact with each other. Thereby, the space | interval of outer side flange surfaces can be adjusted easily.

  According to a fifth aspect of the present invention, there is provided the imaging lens manufacturing method according to any one of the first to fourth aspects, wherein the first lens includes a plurality of the optical surfaces in common with the outer flange surface. And a second lens array having a plurality of optical surfaces in common with the outer flange surface of the second lens, one of the outer flange surfaces being the object side and the other being the image side The first lens array and the second lens array are bonded together after adjusting the distance between the outer flange surfaces, and the first lens and the second lens. The imaging lens is manufactured by cutting every time. Thereby, mass production of an imaging lens is possible.

  According to the present invention, it is possible to provide a method for manufacturing an imaging lens capable of providing a back focus with little variation while being capable of mass production.

It is a figure which shows the shaping | molding process of the imaging lens using a metal mold | die. It is a figure which shows the shaping | molding process of the imaging lens using a metal mold | die. It is a figure which shows the shaping | molding process of the imaging lens using a metal mold | die. It is a perspective view of the front side of 1st glass lens array IM1. It is a perspective view of the back side of 1st glass lens array IM1. It is a perspective view of the front side of 2nd glass lens array IM2. It is a perspective view of the back side of 2nd glass lens array IM2. It is a figure which shows a part of jig | tool JZ holding the back surface of 1st glass lens array IM1 or 2nd glass lens array IM2. It is a figure which shows the process of forming 3rd glass lens array IM3. It is a figure which shows the process of forming 3rd glass lens array IM3. It is a figure which shows the process of forming 3rd glass lens array IM3. It is a perspective view of the imaging lens unit obtained from 3rd glass lens array IM3. It is a figure which shows the shaping | molding process of a lens frame. It is the figure which looked at the lens frame 40 in the arrow XIV direction of FIG. It is the figure which cut | disconnected the lens frame 40 of FIG. 14 by the XV-XV line | wire, and looked at the arrow direction. 4 is an enlarged sectional view of an opening 43. FIG. It is a figure which shows the assembly | attachment process of the lens frame 40. FIG. It is the figure which cut | disconnected by the XVIII-XVIII line | wire and looked in the arrow direction in the state which assembled | attached the imaging lens OU and IR cut filter F to the lens frame of FIG. It is the figure which looked at the lens frame 40 in the axial direction. It is a perspective view of imaging device 50 using an imaging lens and a lens frame concerning this embodiment. It is sectional drawing which cut | disconnected the structure of FIG. 20 by the arrow XXI-XXI line, and looked at the arrow direction. It is a figure which shows the state equipped with the imaging device 50 in the mobile telephone 100 as a portable terminal which is a digital device. 3 is a control block diagram of the mobile phone 100. FIG. It is sectional drawing of the imaging lens of an Example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, manufacture of an imaging lens will be described with reference to FIGS. In the figure, 4 is a bottom plate that covers the ends of the molds 12 and 22, and 5 is a spacer for adjusting the protruding amount of the cores 13 and 23. In FIG. 1, first, a platinum nozzle NZ is connected to a lower mold 22 in which a core support member 21 having a core 23 attached at its upper end is assembled in each of four openings 22a to a storage unit (not shown) in which glass is heated and melted. The droplets of the glass GL melted from the platinum nozzle NZ are collectively dropped onto the upper surface 22b toward the positions equidistant from the plurality of molding surfaces. In such a state, since the viscosity of the glass GL is low, the dropped glass GL spreads on the upper surface 22b and easily enters the transfer surface 23a of the core 23 to transfer the shape, and the shape of the groove 22e is also accurate. Transfer well.

  Next, before the glass GL cools, the lower mold 22 is brought close to a position facing the lower side of the upper mold 12 in which the core support member 11 having the core 13 attached to the lower end is assembled in each of the four openings 12a. The upper mold 12 is aligned using a positioning guide (not shown). Further, as shown in FIG. 2, the upper mold 12 and the lower mold 22 are brought close to each other for molding. Thereby, the shape of the transfer surface 13a (here, convex shape) of the core 13 is transferred. Since a shallow circular step is formed around the transfer surface 13a, it is also transferred at the same time. At this time, the lower surface 12b of the upper mold 12 and the upper surface 22b of the lower mold 22 are held so as to be separated from each other by a predetermined distance to cool the glass GL. The glass GL solidifies in a state where it goes around and covers the tapered portion 22g.

  Thereafter, as shown in FIG. 3, the upper mold 12 and the lower mold 22 are separated from each other, and the glass GL is taken out to form the first glass lens array IM1. Similarly, the second glass lens array IM2 can be formed by another mold. 4 is a perspective view of the front side of the first glass lens array IM1, and FIG. 5 is a perspective view of the back side.

  As shown in FIGS. 4 and 5, the first glass lens array IM1 has a disk shape as a whole, and is a surface (inner flange surface) IM1a that is a high-accuracy plane transferred and molded by the lower surface 12b of the upper mold 12. And four concave optical surfaces IM1b formed on the surface IM1a by the transfer surface 13a of the same mold, and a shallow circular groove IM1c transferred by a circular step portion around the concave optical surface IM1b. The circular groove IM1c is for accommodating a light shielding member SH described later.

  Further, the first glass lens array IM1 includes a back surface (outer flange surface) IM1d which is a high-precision plane transferred and molded by the upper surface 22b of the lower mold 22, and four transferred and formed on the back surface IM1d by the transfer surface 23a. It has a convex optical surface IM1e and a convex portion IM1f transferred and formed by the groove 22e. In addition, you may form the convex-shaped mark IM1g which shows a direction simultaneously. The optical surface IM1b and the optical surface IM1e constitute the first lens unit L1. The convex portion IM1f is parallel to the optical axis of the first lens portion L1, and includes a first reference surface portion IM1x facing the x direction and a second reference surface portion IM1y facing the y direction. . The back surface IM1d forms a first tilt reference surface, and the first reference surface portion IM1x and the second reference surface portion IM1y form a first shift reference surface.

  6 is a perspective view of the front side of the second glass lens array IM2 formed by transfer using another mold, and FIG. 7 is a perspective view of the back side. As shown in FIGS. 6 and 7, the second glass lens array IM2 formed in the same manner as the first glass lens array has a disk shape as a whole, and is a high-accuracy flat surface formed by transfer molding using a mold (not shown). A surface (inner flange surface) IM2a, and four concave optical surfaces IM2b formed on the surface IM2a by the transfer surface of the same mold. In the second glass lens array IM2, a shallow groove around the optical surface IM2b used for accommodating a light shielding member SH described later is omitted, but it may be provided.

  The second glass lens array IM2 includes a back surface (outer flange surface) IM2d, which is a high-precision plane transferred by a mold (not shown), and four convex optical surfaces IM2e formed on the back surface IM2d. , And has a convex portion IM2f. In addition, you may form the convex-shaped mark IM2g which shows a direction simultaneously. The optical surface IM2b and the optical surface IM2e constitute the second lens unit L2. The convex part IM2f is parallel to the optical axis of the second lens part L2, and has a third reference surface part IM2x facing the x direction and a fourth reference surface part IM2y facing the y direction. The back surface IM2d forms the second tilt reference surface, and the third reference surface portion IM2x and the fourth reference surface portion IM2y form the second shift reference surface.

  Next, a process of forming the third glass lens array IM3 by bonding the first glass lens array IM1 and the second glass lens array IM2 will be described. FIG. 8 is a diagram illustrating a part of the jig JZ that holds the back surface of the first glass lens array IM1 or the second glass lens array IM2. In FIG. 8, the end surface of the jig JZ having a circular diameter is cut into a cross shape. That is, four land portions JZa having a uniform height are formed on the end face of the jig JZ, the end face JZb is a flat surface, and the end face JZb is a negative pressure source (not shown). A communicating suction hole JZc is formed. The land portion JZa has a reference holding surface JZx facing in the x direction and a reference holding surface JZy facing in the y direction at the cut portion. Furthermore, the jig JZ includes a spring SPx (simplified illustration) that urges the glass lens array to be held in the x direction and a spring SPy (simplified illustration) that urges the glass lens array in the y direction. Although not shown in FIG. 8, an outer cylindrical portion JZo formed so as to surround the first glass lens array IM1 or the second glass lens array IM2 outside the land portion JZa in the radial direction (see FIG. 9). The jig JZ is integrally formed.

  Here, the second glass lens array IM2 is held against the vertical. The jig JZ is turned upside down, and the end surface JZb of the land portion JZa is abutted against the back surface IM2d of the second glass lens array IM2 while sucking air from the suction hole JZc. At this time, the end surface JZb of the land portion JZa of the jig JZ is in close contact with the back surface IM2d, whereby the inclination of the second glass lens array IM2 with respect to the jig JZ can be set with high accuracy. In addition, the reference holding surface JZx of the land portion JZa abuts on the third reference surface portion IM2x by being biased by the spring SPx, and the reference holding surface JZy is biased to the fourth reference surface portion by being biased by the spring SPy. Abuts on IM2y. At this time, the mark IM2g serves as an index indicating which of the positions of the third reference surface portion IM2x and the fourth reference surface portion IM2y. As a result, the second glass lens array IM2 can be accurately positioned with respect to the jig JZ in the xy direction. Since the third reference surface portion IM2x and the fourth reference surface portion IM2y are respectively formed on both sides of the lens portion, high-precision positioning can be performed by effectively using a long span.

  Similarly, the back surface IM1d of the first glass lens array IM1 can be accurately held in the tilt direction and the xy direction by another jig JZ. That is, the end surface JZb of the land portion JZa of the jig JZ is in close contact with the back surface IM1d, whereby the inclination of the first glass lens array IM1 with respect to the jig JZ can be set with high accuracy. Further, the reference holding surface JZx of the land portion JZa abuts on the first reference surface portion IM1x by being biased by the spring SPx, and the reference holding surface JZy is biased to the second reference surface portion by being biased by the spring SPy. Abuts on IM1y. At this time, the mark (first mark) IM1g serves as an index indicating the position of the first reference surface portion IM1x or the second reference surface portion IM1y. By determining the relative positions of the two jigs JZ with high accuracy as described above, the first glass lens array IM1 and the second glass lens array IM2 can be positioned with high accuracy.

  As shown in FIG. 9, the end surface of the outer cylindrical portion JZo of each jig JZ has an optical axis by a length Δ (which may be different for each jig) than the end surface JZb of the land portion JZa that is an adsorption surface. Protruding in the direction. As described above, the surface IM1a of the first glass lens array IM1 accurately held by the land portion JZa of the jig JZ and the surface of the second glass lens array IM2 accurately held by the land portion JZa of another jig JZ. The IM2a is opposed to each other, and four donut plate-shaped light-shielding members SH are arranged between the two to make them approach each other. Then, as shown in FIG. 10, the end surfaces of the outer cylindrical portions JZo of the two jigs JZ first come into contact with each other. In such a state, the back surface IM1d of the first glass lens array IM1 and the front surface IM2d of the second glass lens array IM2 are not in contact with each other at a predetermined interval (a value determined by the length Δ and the thickness of the glass lens array). Will be held. Thereafter, the nozzle NZL is inserted from a hole (not shown) formed in the jig JZ, and the adhesive BD is discharged from the tip of the nozzle NZL between the first glass lens array IM1 and the second glass lens array IM2, Wait for solidification. The adhesive BD is solidified to form an adhesive layer having a predetermined thickness, and the light shielding member SH is fitted and fixed in the circular groove IM1c. Thereby, the third glass lens array IM3 is formed by bonding the first glass lens array IM1 and the second glass lens array IM2.

  Thereafter, the suction of the upper jig JZ is stopped and separated, so that the third glass lens array IM3 held by the lower jig JZ can be taken out. The third glass lens array IM3 can be cut by DB to obtain an imaging lens OU as shown in FIG. The imaging lens OU includes a first lens L1 having optical surfaces S1 and S2, a second lens L2 having optical surfaces S3 and S4, and a rectangular plate flange portion F1 (first glass lens IM1) around the first lens L1. Of the first lens L1), a rectangular plate flange F2 around the second lens L2 (configured by a part of the surfaces IM2a and IM2d of the second glass lens IM2), and the first lens L1. A light shielding member SH disposed between the second lenses L2. According to the present embodiment, the optical axis orthogonality and the optical axis direction position of the flange portions F1 and F2 are formed with high accuracy with respect to the optical surfaces S1 to S4 of the lenses L1 and L2. Further, by managing the distance between the outer flange surfaces facing the object side and the image side in the flange portions F1 and F2, variations in the total thickness of the imaging lens OU are suppressed.

  FIG. 13 is a diagram illustrating a lens frame forming process. The outer peripheral surface of the lens frame 40 is formed from a hollow square cylindrical upper mold M1, and the inner peripheral surface of the lens frame 40 is formed from a prismatic lower mold M2. Here, a tapered surface TP is formed in the lower part of the outer peripheral surface of the lower mold M2, as shown in FIG. 13, and the surface roughness of the tapered surface is deteriorated by shot blasting.

  After the upper mold M1 and the lower mold M2 are clamped, a lens frame 40 is formed by injection molding a resin in the internal space. Since the tapered surface TP has a draft, it is relatively easy to mold. The lens frame 40 includes a peripheral wall 41, a top wall 42 that closes one end of the peripheral wall 41, and a circular opening 43 formed in the center of the top wall 42. The top wall 42 side of the inner peripheral surface of the peripheral wall 41 is a surface 41a substantially parallel to the axis, and the open end side of the inner peripheral surface of the peripheral wall 41 is a tapered surface 41b as a roughened surface. The surface shape of the tapered surface TP of the lower mold M2 is transferred to the tapered surface 41b, and the surface roughness is deteriorated. A step portion 41 c for fixing the IR cut filter F is formed at the lower end of the peripheral wall 41 on the entire inner periphery. As described above, the lens frame 40 is formed by a single molding using a mold, so that the distance between a contact portion 42a and an end surface of the peripheral wall 41, which will be described later, and the position of the opening 43 with respect to the peripheral wall 41 are formed with high accuracy. ing.

  14 is a view of the lens frame 40 as viewed in the direction of the arrow XIV in FIG. FIG. 15 is a view of the lens frame 40 of FIG. 14 taken along line XV-XV and viewed in the direction of the arrow. As shown in FIGS. 14 and 15, the inner surface of the top wall 42 of the lens frame 40 is formed with a ring-shaped contact portion (first contact portion) 42 a that rises one step so as to surround the opening 43. . Therefore, the space between the abutting portion 42a and the peripheral wall 41 is a flat surface that is the inner surface of the top wall 42 that is lowered one step (closer to the object side), the outer side is rectangular, and the inner side is circular. Part 42b. Furthermore, a recess (also referred to as a communication portion) 41 d as a notch is formed on the diagonal line at the corner of the step portion 41 c of the peripheral wall 41.

  FIG. 16 is an enlarged cross-sectional view of the cross section of the opening 43 of the top wall 42 together with the lens L1. In FIG. 16, the opening 43 that is the second contact portion has a tapered surface 43 a that is adjacent to the inner surface of the top wall 42 and that decreases in diameter toward the outside. Here, the tapered surface 43a is more inclined than the S1 surface which is the convex lens surface of the lens L1, and on the cross section in the optical axis direction, the tapered surface 43a is in contact with the S1 surface of the lens L1 when in contact with the S1 surface of the lens L1. It touches at one point P. The dimensions are controlled so that the inner diameter of the tapered surface 43a passing through the point P is slightly larger (for example, 1 μm to 10 μm larger) than the outer diameter of the S1 surface passing through the point P. It is desirable that the taper surface 43a be inclined more tightly than the S1 surface of the lens L1 on the cross section in the optical axis direction. However, if the taper surface 43a is in contact with the S1 surface of the lens L1 at a single point P, the inclination is inclined. May be loose.

  Next, a process of assembling the imaging lens OU and the IR cut filter F constituting a part of the imaging lens unit to the lens frame 40 will be described. FIG. 17 is a diagram illustrating an assembly process of the lens frame 40. First, as shown in FIG. 17A, the lens frame 40 is fixed so that the open end of the peripheral wall 41 faces upward, and tube-shaped adhesive application members TB are provided at the four corners (or the entire periphery) of the inner peripheral surface. The adhesive BD is applied via Subsequently, as shown in FIG. 17B, the imaging lens OU is inserted from above the lens frame 40, and the S4 surface of the imaging lens OU is directed toward the top wall 42 of the lens frame 40 using the pushing jig PZ. And press. Since the pressing jig PZ is in contact with only the periphery of the S4 surface and not in contact with the vicinity of the optical axis, the imaging lens OU can be stably pressed while suppressing the inclination of the optical axis.

  At this time, first, the S1 surface of the lens L1 of the imaging lens OU contacts the tapered surface 43a of the opening 43. Referring to FIG. 16, when the S1 surface, which is an optical surface curved surface of the lens L1, is pressed by the tapered surface 43a, a reaction force f (only a radial component is shown here) is received in the direction orthogonal to the optical axis. Using the reaction force f (that is, by the guide function of the tapered surface 43a), the imaging lens OU is moved in the optical axis orthogonal direction, and the positioning of the imaging lens OU and the lens frame 40 in the optical axis orthogonal direction is managed. This can be performed with high accuracy within a slight backlash range (that is, within the backlash range generated by the difference between the inner diameter of the tapered surface 43a passing through the point P and the outer diameter of the S1 surface passing through the point P). . Eventually, the flange portion F1 of the first lens L1 of the imaging lens OU comes into contact with the abutting portion 42a formed on the top wall 42 of the lens frame 40, so that the optical axis is thereby adjusted. The imaging lens OU and the lens frame 40 can be accurately positioned in the direction. Note that when the imaging lens OU is inserted from above the lens frame 40, if the deviation between the optical axis of the imaging lens OU and the optical axis of the opening 43 is smaller than the slightly controlled play, the lens L1 of the imaging lens OU. The S1 surface and the tapered surface 43a of the opening 43 do not contact each other.

  The imaging lens OU enters the inside of the lens frame 40 while scraping off the adhesive BD from the outer peripheral surface of the flange portion. According to the present embodiment, since there is a relatively large gap between the flange portions F1 and F2 of the imaging lens OU and the peripheral wall 41 of the lens frame 40, the adhesive BD is filled between the flanges F1 and F2 and the imaging lens OU. The lens frame 40 can be firmly fixed. Further, even if the application amount of the adhesive BD is slightly larger than a predetermined amount, the capture portion 42b formed between the contact portion 42a and the peripheral wall 41 becomes an adhesive reservoir, and the adhesive BD becomes the contact portion 42a. It can be captured so that it does not contaminate the optical surface. Since the flange portion of the imaging lens OU and the lens frame 40 are both rectangular tube shapes, referring to FIG. 18, the diagonal gap Δ in the lens frame 40 is relatively large, so that the coating is applied to the four corners. This is advantageous for capturing the adhesive BD. The imaging lens OU is continuously pressed using the pressing jig PZ until the adhesive BD is solidified.

  Thereafter, as shown in FIG. 17 (c), an IR cut filter F, which is a rectangular parallel plate as an optical element, is adhered to the step portion 41c of the peripheral wall 41 of the lens frame 40. As shown in FIG. The adhesive BD is applied to the step portion 41c so as to avoid the depression 41d on the diagonal line. In a subsequent process, the imaging device is mounted on the lens frame 40 by passing through a reflow furnace together with a substrate (not shown). At this time, even if the air inside the heated lens frame 40 expands, the arrow in FIG. As shown by, since it passes through the recess 41d and escapes to the outside, the breakage of the lens frame 40 and the like can be suppressed. In addition, since the depressions 41d are provided on two diagonal lines, air can escape through the remaining depressions 41d even if the IR cut filter F is shifted to one side during assembly. According to the present embodiment, air escape can be ensured even in the case of a structure in which the entire circumference of the flange portion is bonded and sealed, particularly for securing the adhesive strength of the imaging lens. The depression 41d is not limited to the diagonal line, and may be provided on a part of the opposite side of the step portion 41c.

  FIG. 20 is a perspective view of an imaging device 50 using an imaging lens unit including an imaging lens and a lens frame according to the present embodiment, and FIG. 21 is a cross-sectional view of the configuration of FIG. 20 taken along the arrow XXI-XXI line. It is sectional drawing seen in the arrow direction. As illustrated in FIG. 20, the imaging device 50 includes a CMOS image sensor 51 as a solid-state imaging device having a photoelectric conversion unit 51a, an imaging lens OU that causes the photoelectric conversion unit 51a of the image sensor 51 to capture a subject image, A substrate 52 having an external connection terminal (not shown) for holding the image sensor 51 and transmitting / receiving the electric signal is provided, and these are integrally formed.

  In the image sensor 51, a photoelectric conversion unit 51a as a light receiving unit in which pixels (photoelectric conversion elements) are two-dimensionally arranged is formed in the center of a plane on the light receiving side, and signal processing (not shown) is performed. Connected to the circuit. Such a signal processing circuit includes a drive circuit unit that sequentially drives each pixel to obtain a signal charge, an A / D conversion unit that converts each signal charge into a digital signal, and a signal that forms an image signal output using the digital signal. It consists of a processing unit and the like. A number of pads (not shown) are arranged near the outer edge of the plane on the light receiving side of the image sensor 51, and are connected to the substrate 52 via wires (not shown). The image sensor 51 converts the signal charge from the photoelectric conversion unit 51a into an image signal such as a digital YUV signal, and outputs the image signal to a predetermined circuit on the substrate 52 via a wire (not shown). Here, Y is a luminance signal, U (= R−Y) is a color difference signal between red and the luminance signal, and V (= BY) is a color difference signal between blue and the luminance signal. Note that the solid-state imaging device is not limited to the CMOS image sensor, and other devices such as a CCD may be used.

  The substrate 52 that supports the image sensor 51 is communicably connected to the image sensor 51 through a wiring (not shown).

  The substrate 52 is connected to an external circuit (for example, a control circuit included in a host device of a portable terminal mounted with an imaging device) via an external connection terminal (not shown), and a voltage for driving the image sensor 51 from the external circuit. And a clock signal can be received, and a digital YUV signal can be output to an external circuit.

  The upper part of the image sensor 51 is sealed with a cover glass (not shown), and an IR cut filter F is disposed between the upper part of the image sensor 51 and the second lens L2. The hollow rectangular tube-shaped lens frame 40 is open at the bottom, but is covered with a top wall 42 at the top. An opening 43 is formed in the center of the top wall 42. An imaging lens OU is disposed in the lens frame 40.

  The imaging lens OU includes, in order from the object side (upper side in FIG. 21), an aperture stop in which the opening edge of the lens frame functions, a first lens portion L1, a light blocking member SH that blocks unnecessary light, and a second lens portion L2. As described above, since the first lens portion L1 and the second lens portion L2 are made of glass, they have excellent optical characteristics. In the present embodiment, the imaging lens OU can be positioned in the optical axis direction by bringing the flange portion of the imaging lens OU into contact with the contact portion 42a of the lens frame 40, and the optical surface S1 of the imaging lens OU. Since the positioning of the imaging lens OU in the direction crossing the optical axis can be realized by bringing a part of the entire circumference of the lens frame 40 into contact with the tapered surface 43a of the opening 43 of the lens frame 40, the lens frame 40 is placed on the substrate 52. It is possible to accurately position the light receiving surface of the image sensor 51 at the focal position of the imaging lens OU. Further, since the tapered surface 41b of the lens frame 40 is a rough surface and is formed in a range that covers at least the S4 surface of the image side lens L2, there is a large gap between the lens frame 40 and the imaging lens OU. Even if it occurs, the ghost can be effectively suppressed. The roughened surface may be provided on the entire inner peripheral surface of the peripheral wall 41.

  Next, a usage mode of the above-described imaging device 50 will be described. FIG. 22 is a diagram illustrating a state in which the imaging device 50 is mounted on a mobile phone 100 as a mobile terminal that is a digital device. FIG. 23 is a control block diagram of the mobile phone 100.

  The imaging device 50 is disposed, for example, such that the object-side end surface of the imaging lens OU is provided on the back surface of the mobile phone 100 (the liquid crystal display unit side is the front surface) and corresponds to a position below the liquid crystal display unit. .

  An external connection terminal (not shown) of the imaging device 50 is connected to the control unit 101 of the mobile phone 100 and outputs an image signal such as a luminance signal or a color difference signal to the control unit 101 side.

  On the other hand, as shown in FIG. 23, the cellular phone 100 controls each part in an integrated manner, and controls and inputs a control part (CPU) 101 that executes a program corresponding to each process, and a number and the like with keys. An input unit 60, a display unit 70 for displaying captured images and videos, a wireless communication unit 80 for realizing various information communications with an external server, a system program and various processing programs for the mobile phone 100, A storage unit (ROM) 91 that stores necessary data such as a terminal ID, and various processing programs and data executed by the control unit 101, processing data, imaging data by the imaging device 50, and the like are temporarily stored. And a temporary storage unit (RAM) 92 used as a work area for storage.

  When the photographer holding the mobile phone 100 points the imaging lens OU of the imaging device 50 toward the subject, an image signal of a still image or a moving image is captured by the image sensor 51. When the photographer presses the button BT shown in FIG. 22 at a desired photo opportunity, the release is performed, and the image signal is taken into the imaging device 50. The image signal input from the imaging device 50 is transmitted to the control system of the mobile phone 100 and stored in the storage unit 92 or displayed on the display unit 70, and further, video information is transmitted via the wireless communication unit 80. Will be transmitted to the outside.

The present inventors actually designed an imaging lens and examined the influence on the back focus. FIG. 24 is a cross-sectional view of the designed lens, which includes an aperture stop S, a lens l1, and a lens L2 from the object side. IM is an imaging surface of the solid-state imaging device. Table 1 shows lens data of the designed imaging lens. The symbols used here are as follows.
FL: Focal length of the entire imaging lens system
Fno: F number r: Radius of curvature d: Distance between shaft upper surfaces
nd: Refractive index for d-line of lens material
vd: Abbe number with respect to the d-line of the lens material The surface indicated by “*” after the effective radius is a surface having an aspherical shape, and the aspherical shape has the vertex of the surface as the origin and the optical axis. The X axis is taken in the direction, and the height in the direction perpendicular to the optical axis is h, and is expressed by the following formula (1).

However,
Ai: i-order aspherical coefficient (i = 3,4,5,6,... 20)
R (r in the lens data table): radius of curvature K: conic constant In addition, in the aspherical coefficient, a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02). ing.

(Table 1)
SURF DATA
NUM. Rd nd vd
OBJ INFINITY 1000.0000
STO INFINITY 0.0500
2 INFINITY -0.1700
3 * 0.9400 0.7200 1.58313 59.44
4 * 1.6900 0.6400
5 * -7.7600 1.2200 1.58313 59.44
6 * -1e + 018 0.6623
IMG INFINITY 0.0038

ASPHERICAL SURFACE
3, K = -7.90500e + 000, A4 = 1.08300e + 000, A6 = -1.43200e + 000, A8 = -2.91200e + 000, A10 = 2.88600e + 000, A12 = 1.63100e + 002, A14 =- 6.75800e + 002, A16 = 7.92700e + 002, A18 = 0.00000e + 000, A20 = 0.00000e + 000
Four
K = -5.36900e + 000, A4 = 3.09300e-001, A6 = 4.33000e-001, A8 = 3.78100e + 000, A10 = -2.31500e + 001, A12 = 1.10900e + 001, A14 = 2.78400e + 002 , A16 = -5.20000e + 002, A18 = 0.00000e + 000, A20 = 0.00000e + 000
Five
K = 3.93500e + 001, A4 = -1.73600e-001, A6 = -1.13000e + 000, A8 = 4.67400e + 000, A10 = -8.60900e + 000, A12 = -9.99000e + 000, A14 = 8.08800e + 001, A16 = -2.09700e + 002, A18 = 2.98300e + 002, A20 = -1.93000e + 002
6
K = -3.82900e + 001, A4 = -4.83200e-002, A6 = -1.01500e-001, A8 = 8.81300e-002, A10 = -3.52400e-002, A12 = -3.73000e-004, A14 =- 3.55700e-003, A16 = 5.39700e-003, A18 = -1.17700e-003, A20 = -1.73600e-004

FL 2.9706
Fno 2.8400

Elem Surfs Focal Length Diameter
1 3- 7 2.970617 3.5093

Elem Surfs Focal Length Diameter
1 3- 4 2.683463 1.1410
2 5--6 -13.307496 2.7648

  Table 2 shows the back focus in the imaging lens of the example, with the core thickness of the lens L1 and the lens L2 varied, and the total lens thickness set to the design value of 2.580 mm. The result is shown. In the implementation error example 1, when the core thickness error of the lens L1 with respect to the design value is −0.002 mm and the core thickness error of the lens L2 is −0.012 mm, the back focus value is −0. The error was 005 mm. Further, in the working error example 2, when the core thickness error of the lens L1 with respect to the design value is +0.006 mm and the core thickness error of the lens L2 is +0.009 mm, the back focus value is −0. The error was 001 mm. Further, in Example 3, when the core thickness error of the lens L1 with respect to the design value is −0.008 mm and the core thickness error of the lens L2 is −0.009 mm, the back focus value is −with respect to the design value. The error was 0.005 mm.

  Here, the allowable range of the core thickness error is assumed. If the F number is F and the allowable circle of confusion is δ, the depth of focus can be expressed by 2Fδ, and the allowable circle of confusion is assumed to be 2 pixels. If the pixel pitch is 1.75 μm, the depth of focus is about 10 μm. According to the results of Table 2, when the total lens thickness is set to the design value of 2.580 mm, the back focus error falls within ± 0.010 mm, which is an allowable range.

  On the other hand, in Table 3, the same imaging lens is used as a comparative example, the core thicknesses of the lens L1 and the lens L2 are similarly varied, and the lens interval (the thickness of the adhesive layer) is a design value of 0. This shows the result of obtaining the back focus with the total lens thickness set to .650 mm. In the comparative error example 1, when the core thickness error of the lens L1 with respect to the design value is −0.002 mm and the core thickness error of the lens L2 is −0.012 mm, the back focus value is +0.013 mm with respect to the design value. It was an error. In Comparative Error Example 2, when the core thickness error of the lens L1 with respect to the design value is +0.006 mm and the core thickness error of the lens L2 is +0.009 mm, the back focus value is −0. The error was 022 mm. Further, in Comparative Error Example 3, when the core thickness error of the lens L1 with respect to the design value is −0.008 mm and the core thickness error of the lens L2 is −0.009 mm, the back focus value is +0 with respect to the design value. The error was 0.028 mm. Thus, even if the lens interval (adhesion layer thickness) is managed, the back focus error exceeds ± 0.010 mm, which is not preferable.

  Further, Table 4 shows that the same imaging lens is used and the lens thicknesses of the lens L1 and the lens L2 are varied in the same manner, and the total lens thickness is further varied in consideration of manufacturing errors. This shows the result of obtaining each focus. In the implementation error example 4, when the core thickness error of the lens L1 with respect to the design value is −0.002 mm, the core thickness error of the lens L2 is −0.012 mm, and the total lens thickness error is −0.008 mm, the back focus is increased. The value was an error of +0.005 mm with respect to the design value. In Example 5 of the error, when the core thickness error of the lens L1 with respect to the design value is +0.006 mm, the core thickness error of the lens L2 is +0.009 mm, and the total lens thickness error is +0.005 mm, The value was an error of -0.008 mm with respect to the design value. Further, in Example 6, when the core thickness error of the lens L1 with respect to the design value is -0.008 mm, the core thickness error of the lens L2 is -0.009 mm, and the total lens thickness error is +0.009 mm, The focus value was an error of -0.007 mm with respect to the design value. That is, even if a total lens thickness error taking into account a manufacturing error occurs, it can be seen that the back focus error is within ± 0.010 mm, so there is no practical problem.

  Table 5 summarizes the lens intervals of Examples 1 to 6 and Comparative Errors 1 to 3.

  The present invention is not limited to the embodiments described in the specification, and other embodiments and modifications are apparent to those skilled in the art from the embodiments and ideas described in the present specification. It is.

40 lens frame 41 peripheral wall 41a substantially parallel surface 41b tapered surface 41c stepped portion 41d recess 42 top wall 42a abutting portion 42b capturing portion 43 opening 43a tapered surface 50 imaging device 51 image sensor 51a photoelectric conversion portion 52 substrate 60 input portion 70 display Part 80 Wireless communication part 92 Storage part 100 Cellular phone 101 Control part BD Adhesive BT Button F IR cut filter F1, F2 Flange part L1 Lens part L2 Lens part M1 Upper mold M2 Lower mold OU Imaging lens PZ Pressing jig S1 S4 Optical surface SH Shading member TB Tube TP Tapered surface

Claims (5)

One of the outer flange surfaces includes a first lens having an optical surface and an outer flange surface formed from the same mold, and a second lens having an optical surface and an outer flange surface formed from the same mold. Is arranged so that the object side faces the image side,
After adjusting the space | interval of the said outer side flange surfaces, the said 1st lens and the said 2nd lens are connected mutually, The manufacturing method of the imaging lens characterized by the above-mentioned.   2. The method for manufacturing an imaging lens according to claim 1, wherein in the first lens and the second lens, inner flange surfaces that are back surfaces of the outer flange surfaces are not brought into close contact with each other.   3. The imaging lens according to claim 1, wherein in the first lens and the second lens, an adhesive layer is formed between inner flange surfaces that are back surfaces of the outer flange surface. Production method.   The space | interval of the said outer side flange surfaces is adjusted by making the jig | tool which each hold | maintains the said outer side flange surface in a said 1st lens and a said 2nd lens contact | abut mutually. 4. A method for manufacturing an imaging lens according to any one of 3 above. A first lens array having a plurality of optical surfaces with the outer flange surface common to the first lens, and a first lens array having a plurality of optical surfaces with the outer flange surface common to the second lens. 2 lens array,
The first lens array and the second lens array are bonded after the outer flange surfaces are arranged so that one of the outer flange surfaces faces the object side and the other faces the image side and the distance between the outer flange surfaces is adjusted. ,
Furthermore, the said imaging lens is manufactured by cut | disconnecting for every said 1st lens and said 2nd lens, The manufacturing method of the imaging lens in any one of Claims 1-4 characterized by the above-mentioned.