WO2014203677A1 - Lens, lens unit, and lens manufacturing method - Google Patents

Abstract

This invention provides a lens, a lens unit, and a lens manufacturing method that reduce strain in the lens while decreasing the number of components and the amount of labor required for assembly and also effectively reduce unneeded light, which can cause ghosting and the like. Slits are formed in a light-blocking film formed on the lens, so even if said light-blocking film contracts, the slits divide up the resulting compressive stress, reducing strain in the lens as much as possible.

Description

Lens, lens unit and lens manufacturing method

The present invention relates to a lens, a lens unit, and a method for manufacturing a lens.

In recent years, the thinning of imaging lenses mounted on imaging devices called MCUs (micro camera units) incorporated in information terminals such as mobile phones and smartphones has been rapidly progressing. In addition, even in an imaging apparatus mounted on such a portable terminal, an apparatus using an imaging element having a high pixel number has been supplied to the market so that a higher quality image can be obtained. In addition to this, due to intensifying competition with overseas manufacturers, there is also a problem that it is desirable to promote cost reduction of imaging devices.

In order to form a high-quality image, it is important to suppress unnecessary light entering the lens and suppress ghosting. Therefore, a general imaging lens is provided with a light shielding plate that shields unnecessary light adjacent to the lens. As such a light-shielding plate, a metal or a non-transparent resin-processed part arranged to cover the outside of the effective field angle range of the lens is usually used. However, assembling the light shielding plate separate from the lens increases the number of parts and increases the number of assembly steps.

On the other hand, as shown in Patent Document 1, a technique is known in which unnecessary light is shielded by a light shielding film obtained by curing ink applied to a lens instead of a light shielding plate. As a result, in addition to reducing the number of parts and the number of assembly steps, shortening of the optical total length, optimization of the light shielding area, and the like can be expected.

JP 2013-61649 A

However, it has been found that problems may occur after forming a light-shielding film on the lens. More specifically, when ink is applied over a wide area of the lens to form a light-shielding film, compression stress is applied to the lens surface due to shrinkage during curing, resulting in distortion on the optical surface of the lens and aberrations. There is a fear. Furthermore, even when the lens distortion is small at the time of assembly, when the environmental temperature changes, due to the difference between the thermal expansion coefficient of the lens material and the thermal expansion coefficient of the light shielding film, the compressive stress increases and the lens distortion May increase. In particular, such distortion of the lens tends to occur remarkably when the lens is thinned, and can therefore be an obstacle to thinning the lens.

The present invention has been made in view of the problems described above, and manufactures a lens, a lens unit, and a lens capable of suppressing distortion of the lens and effectively suppressing unnecessary light that causes ghosts and the like while reducing the number of parts and the number of assembly steps. It aims to provide a method.

In order to achieve at least one of the objects described above, a lens reflecting one aspect of the present invention is a lens in which a light shielding film is formed by applying ink, and the light shielding film has a slit. It is formed.

According to the present lens, since the slit is formed in the light shielding film, even when the light shielding film contracts, the compressive stress is divided by the slit, so that distortion of the lens can be suppressed as much as possible. The “slit” includes both a case where the light shielding film is not formed and a case where the thickness of the light shielding film is locally thin. Even when the light-shielding film is not formed, if the slit width is small, the amount of unnecessary light that enters can be reduced and ghost can be suppressed. In addition, when the thickness of the light shielding film is locally thin, stress at the time of contraction occurs, but since the light shielding function is reduced by that amount, unnecessary light may pass through the slit, but the unnecessary light is mainly used. Since the amount of light is usually smaller than that of light, even if the light shielding film in the slit is thin, the amount of unnecessary light that has passed through is extremely reduced, so that ghost can be suppressed. When the light shielding film is provided in the slit, it is desirable that the average film thickness of the light shielding film is 50% or less and 20% or more.

In order to achieve at least one of the objects described above, a lens unit reflecting one aspect of the present invention is a lens unit formed by stacking a plurality of the above-described lenses in the optical axis direction. The light beam that has passed through the slit of the light shielding film of the lens is shielded by the light shielding film of another lens.

According to this lens unit, even if the entrance of unnecessary light is allowed by providing the slit in a certain lens, it is shielded by the light shielding film of another lens, so that the generation of ghost can be effectively suppressed. “The light beam that has passed through the slit of the light-shielding film of a certain lens is shielded by the light-shielding film of another lens” means, for example, the slit formed in the light-shielding film of a certain lens and the light-shielding film of another lens. For example, the phase or position of the formed slit may be shifted.

In order to achieve at least one of the above-described objects, a method for manufacturing a lens reflecting one aspect of the present invention is a method for locally shielding the light having a slit by changing the density of ink applied to the surface of the lens. A film is formed.

According to this lens manufacturing method, since the slit is formed in the light shielding film, even when the light shielding film contracts, compressive stress is divided by the slit, so that distortion of the lens can be suppressed as much as possible.

According to the present invention, since the light shielding plate made of metal or opaque resin can be replaced with a light shielding film without impairing the light shielding function of the lens, the number of parts can be reduced and the number of assembly steps can be reduced by removing the light shielding plate. In addition, it can contribute to driving speed and power saving / thinning due to weight reduction, and also suppresses lens distortion caused by curing shrinkage phenomenon as ink characteristics, which is a problem when replaced with a light shielding film Thus, it is possible to provide a lens, a lens unit, and a lens manufacturing method that do not cause deterioration in optical performance.

It is sectional drawing along the optical axis of the imaging device 10 by this embodiment. It is the figure which looked at the lens which formed the light shielding film of FIG. 1 from the optical axis direction. FIG. 3 is a diagram showing the lens of FIG. 2 cut along line III-III. It is a figure which shows the outline of the inkjet ink coating device which forms a light shielding film. It is the front view (a) and back view (b) of the smart phone which mounts the imaging device 10. It is a control block diagram of the smart phone of FIG. It is a figure which shows the pattern concerning the modification of a light shielding film. It is a figure which shows the pattern concerning the modification of a light shielding film. (A) and (b) are figures which show the pattern concerning the modification of a light shielding film.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view along the optical axis of the imaging apparatus 10 according to the present embodiment. The following configuration is a schematic diagram, and some shapes, dimensions, and the like are different from actual ones.

As shown in FIG. 1, the imaging device 10 causes a CMOS type imaging device 11 as a solid-state imaging device provided with a photoelectric conversion unit (light receiving surface) 11 a and the photoelectric conversion unit 11 a of the imaging device 11 to capture a subject image. The imaging lens 12, a lens frame 13 that holds the imaging lens 12, an IR cut filter 14 that has a parallel plate shape, and a substrate 15 that supports the imaging element 11.

As shown in FIG. 1, the image pickup device 11 is an image pickup device in which pixels (photoelectric conversion elements) are two-dimensionally arranged at the center of the light receiving side (upper surface in FIG. 1) on a parallel plate chip. A photoelectric conversion unit 11a as a surface is formed, and a signal processing circuit (not shown) is formed around the photoelectric conversion unit 11a. 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.

Further, a plurality of pads formed in the vicinity of the outer edge on the light receiving surface side in the chip of the image sensor 11 are connected to the substrate 15 by wires (not shown). The image sensor 11 converts the signal charge from the photoelectric conversion unit 11a into an image signal such as a digital YUV signal, and transmits the image signal to an external circuit (not shown) (for example, a control circuit included in a host device on which the image pickup device is mounted). It is like that. In addition, it is possible to receive power and a clock signal for driving the image sensor 11 from an external circuit. Here, Y is a luminance signal, U (= RY) 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 image sensor is not limited to the CMOS type image sensor, and other types such as a CCD type may be used.

In FIG. 1, an imaging lens 12 having a five-lens configuration is provided inside a lens frame 13. The imaging lens 12 and the lens frame 13 constitute a lens unit. The imaging lens 12 as a lens unit includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5 in order from the object side, and each has a flange portion outside the effective diameter. Each lens is made of resin or glass. More specifically, EP5000 resin manufactured by Mitsubishi Gas Chemical can be used as the lens resin material.

The image side surface L1f1 which is a plane orthogonal to the optical axis of the flange portion L1f of the first lens L1 protrudes to the image side, and the light shifted to the image side in the flange portion L2f provided outside the effective diameter of the second lens L2. The surface abuts on the object side surface L2f2, which is a plane perpendicular to the axis.

A light shielding film BKM is formed on a surface L1f6 that is closer to the optical axis than the image side surface L1f1 of the first lens L1 and outside the effective diameter of the image side optical surface L1b. A cationic polymerization type UV curable ink may be used for the light shielding film. The cationic polymerization type causes curing shrinkage of 4 to 5%, but is less effective than the radical type UV ink of several tens%, and is more effective in achieving the object of this embodiment. The film thickness is in the range of 5 μm to 20 μm.

The image side surface L2f1 that is the optical axis orthogonal plane of the flange portion L2f of the second lens L2 protrudes to the image side, and the light shifted to the image side in the flange portion L3f provided outside the effective diameter of the third lens L3. It contacts the object side surface L3f2 that is an axis orthogonal to the surface.

A light shielding film BKM is formed on a surface L2f6 that is closer to the optical axis than the image side surface L2f1 of the second lens L2 and outside the effective diameter of the image side optical surface L2b.

The image side surface L3f1 that is the optical axis orthogonal plane of the flange portion L3f of the third lens L3 protrudes to the image side, and the light shifted to the image side in the flange portion L4f provided outside the effective diameter of the fourth lens L4. It contacts the object side surface L4f2 that is an axis orthogonal to the surface.

A light shielding film BKM is formed on a surface L3f6 of the third lens L3 that is closer to the optical axis than the image side surface L3f1 and outside the effective diameter of the image side optical surface L3b.

FIG. 2 is a view of the lens (here, L) on which the light shielding film BKM of FIG. 1 is formed as seen from the optical axis direction. FIG. 3 is an enlarged view showing the lens of FIG. 2 cut along line III-III. As shown in FIGS. 2 and 3, in the light shielding film BKM formed on the lens L, a slit SL having a width W extends concentrically around the optical axis over the entire circumference. Here, the slit SL is a portion where the light shielding film BKM is not formed. However, as shown in FIG. 3, by applying a textured surface SB as a rough surface on the surface of the lens L forming the slit SL, the applied ink spreads wet (illustrated by a dotted line), whereby a film is formed on the slit SL. A light shielding film having a small thickness may be formed.

FIG. 4 is a diagram showing an outline of an ink jet ink coating apparatus for forming a light shielding film. In FIG. 4, an inkjet head IH that ejects ink droplets from the lower surface is disposed so as to be relatively movable in the vicinity of the surface of the lens L. The drive circuit DR that drives the inkjet head IH stores the pattern PT and position of the light shielding film to be formed.

A method of forming a light shielding film on a lens using the ink jet ink coating apparatus light shielding film will be described. The drive circuit DR changes the density of the applied ink by ejecting ink droplets while moving the inkjet head IH relative to the lens L based on the stored pattern PT and position, thereby changing the pattern. Ink is applied to the region corresponding to PT. Further, the light-shielding film BKM is formed on the lens L by curing the applied ink. Here, the width W of the slit SL is preferably n times the ink drawing resolution. Also, without discharging the ink once, a small amount of ink is first discharged onto the surface of the lens, and after it hardens, the process of discharging the ink again is repeated several times, so that the final A film thickness may be obtained. Since the slit SL that is continuous in the circumferential direction is formed in the light shielding film BKM according to the present embodiment, even if the light shielding film BKM contracts during ink curing, the compression stress is divided by the slit SL. The distortion of the optical surface can be suppressed as much as possible.

In FIG. 1, an image side surface L4f1 projecting to the image side, which is a plane orthogonal to the optical axis, of the flange portion L4f provided around the effective diameter of the fourth lens L4, and a periphery outside the effective diameter of the fifth lens L5. Between the object side surface L5f2 protruding to the object side which is the optical axis orthogonal plane of the flange portion L5f, a donut-shaped light shielding plate AP is abutted and sandwiched. The outer periphery of the light shielding plate AP is in contact with the inner periphery of the lens frame 13 and extends in a cantilever manner to the vicinity of the effective diameter of the fourth lens L4.

The object side surface L1f2 of the flange portion L1f of the first lens L1 is in contact with the image side surface of the wall portion 13a having the opening of the lens frame 13, and the outer peripheral surface L1f4 of the flange portion L1f is the small diameter portion 13b adjacent to the wall portion 13a. It is in contact with the inner peripheral surface. On the other hand, the outer peripheral surface of the flange portion L5f of the fifth lens L5 is in contact with the inner peripheral surface of the lens frame 13 adjacent to the light shielding plate AP.

The IR cut filter 14 is disposed on the imaging element 11 side of the flange portion L5f of the fifth lens L5 via an annular spacer SP. The lower end of the lens frame 13 is in contact with the substrate 15 via an annular holder 16 that holds the IR cut filter 14.

¡The flange of each lens is accurately formed by injection molding. Therefore, at the time of assembly, when the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are assembled to the lens frame 13, the abutting contact surfaces of the flange portion come into contact with each other. By matching, the relative position in the optical axis direction from the first lens L1 to the fourth lens L4 is adjusted with high accuracy. In addition, since the thickness of the light shielding plate AP4 is managed with high accuracy, when the fifth lens L5 is assembled with the light shielding plate AP4 interposed, the relative position in the optical axis direction between the fourth lens L4 and the fifth lens L5 is determined. It is adjusted with high accuracy.

According to the present embodiment, when the transition surface extends in the direction orthogonal to the optical axis, the effect of suppressing unnecessary light can be enhanced while suppressing the cost by forming the light shielding film (black film) BKM. Instead of the light shielding plate AP, a similar light shielding film may be formed on one of the fourth lens L4 and the fifth lens L5.

The operation of the imaging device 10 described above will be described. FIG. 5A is a front view of a smartphone 100 as a mobile terminal equipped with the imaging device 10, and FIG. 5B is a rear view thereof. FIG. 6 is a control block diagram of the smartphone 100.

In the imaging device 10, for example, the object side end surface of the lens frame 13 is provided on the back surface of the smartphone 100 in FIG. 5B, and is disposed at a position corresponding to the lower side of the liquid crystal display unit.

The imaging device 10 is connected to the control unit 101 of the smartphone 100 via an external connection terminal (indicated by an arrow in FIG. 6), 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. 6, the smartphone 100 in FIGS. 5A and 5B controls each unit in an integrated manner and executes a program corresponding to each process, a power source, etc. An input unit 60 for instructing and inputting switches, numbers, and the like on the touch pad, and a display unit 65 for displaying captured images in addition to predetermined data on the liquid crystal panel (however, the liquid crystal panel of the display unit and the input unit) The touchpad is also used by the touch panel 70) and a wireless communication unit 80 for realizing various information communication between the external server, and the system program and various processing programs of the smartphone 100 and necessary data such as a terminal are stored. Storage unit (ROM) 91 and various processing programs and data executed by the control unit 101, or processing data, or the imaging device 10 And a, and a temporary memory (RAM) 92 used as a work area for temporarily storing more resulting imaging data and the like.

The smartphone 100 operates by operating the input unit 60, drives the imaging lens 12 by an actuator (not shown) to perform an autofocus operation, and presses the release button 71 or the like to operate the imaging device 10 to perform imaging. It can be performed. The image signal input from the imaging device 10 is stored in the storage unit 92 or displayed on the touch panel 70 by the control system of the smartphone 100, and further transmitted to the outside as video information via the wireless communication unit 80. Is done.

FIG. 7 is a diagram showing a pattern according to a modification of the light shielding film. In the example of FIG. 7, the light shielding film BKM has slits SL extending radially over the entire width of the light shielding film BKM. By providing such a slit SL, even when the light shielding film BKM contracts, the compressive stress in the circumferential direction is divided, so that distortion of the optical surface of the lens L can be suppressed as much as possible.

FIG. 8 is a diagram showing a pattern according to another modification of the light shielding film. In the example of FIG. 8, the light shielding film BKM has a slit SL extending in a spiral shape over the entire width of the light shielding film BKM. By providing such a slit SL, even when the light shielding film BKM contracts, the compressive stress in the circumferential direction is divided, so that distortion of the optical surface of the lens L can be suppressed as much as possible.

FIG. 9 is a diagram showing a pattern according to another modification of the light shielding film. 9A shows a pattern of the light shielding film BKM formed on one surface of the lens L in the optical axis direction, and FIG. 9B shows a pattern of the light shielding film BKM formed on the other surface of the lens L. However, for the sake of easy understanding, both are shown as viewed from the object side.

9A and 9B, it is clear that the slits SL of the light shielding film BKM are out of phase with each other, so that unnecessary light passes through the slit SL of the light shielding film BKM on one surface. However, since the light is shielded by the light shielding film BKM on the other surface, unnecessary light can be shielded in total.

9B, the light shielding film BKM having the pattern shown in FIG. 9A is formed on one lens, and the phase of the slit SL is shifted on another lens, as shown in FIG. 9B. A light-shielding film BKM having a pattern (however, the inner and outer diameters change according to the refraction of light passing therethrough) may be formed. In addition, when the light shielding film BKM having the concentric pattern shown in FIG. 2 is formed, the slit SL of the light shielding film BKM of a certain lens is positioned at the slit of the light shielding film BKM of another lens (or another surface of the same lens). It may be shifted from the position of SL. Accordingly, unnecessary light can be effectively shielded by allowing the light flux that has passed through the slit SL of one of the light shielding films BKM to be shielded by the other light shielding film.

Hereinafter, preferred embodiments will be described together.

In the lens L, it is preferable that the slits are concentric circles continuous in the circumferential direction around the optical axis of the lens. If the slits are concentric, the compressive stress acting in the direction perpendicular to the optical axis of the lens when the light shielding film contracts can be divided.

Further, it is preferable that the slit is a radial shape extending over the entire width of the light shielding film in the direction perpendicular to the optical axis. If the slits are radial, compressive stress acting in the circumferential direction of the lens when the light shielding film contracts can be divided.

Further, it is preferable that the slit has a spiral shape extending over the entire width of the light shielding film in the direction perpendicular to the optical axis. If the slit is spiral, the compressive stress acting in the circumferential direction of the lens when the light shielding film contracts can be divided.

The light shielding film is preferably formed by ejecting ink droplets toward the lens by an ink jet method and then curing, and the width of the slit is preferably n times the drawing resolution of the ink. Accordingly, there is an advantage that the slit can be easily formed by the landing control of the ink. The “ink drawing resolution” can be expressed, for example, by the number of ink dots per inch (dpi).

Further, it is preferable that a texture is formed on the surface of the lens where the slit is to be formed. Accordingly, the applied ink is easily spread on the lens surface where the texture is formed, which is convenient for forming the slit. The “texture” refers to a roughened surface. Specifically, it is effective to have a ten-point average roughness Rz 4 μm (Ayamadai AHO-1003 equivalent).

Further, when the light shielding film is formed on one surface and the other surface in the optical axis direction of the lens, the light flux that has passed through the slit of the light shielding film on the one surface is reflected on the light shielding on the other surface. It is preferable that the film is shielded from light. As a result, even if unnecessary light is allowed to enter through the slit of the light shielding film provided on the object side surface of the lens, it is shielded by the light shielding film on the image side surface, so that the occurrence of ghost can be effectively suppressed. “The light beam that has passed through the slit of the light shielding film on one surface of the lens is shielded by the light shielding film on the other surface” means, for example, the slit of the light shielding film formed on one surface of the lens and the other The phase or position of the slit of the light shielding film formed on the surface may be shifted.

The present invention is not limited to the embodiments and modifications described in this specification, and includes other embodiments and modifications based on the embodiments and technical ideas described in this specification. It will be apparent to those skilled in the art. For example, the ink application method is not limited to the ink jet method.

DESCRIPTION OF SYMBOLS 10 Image pick-up device 11 Image pick-up element 11a Photoelectric conversion part 12 Imaging lens 13 Mirror frame 14 IR cut filter 15 Board | substrate 16 Holder 60 Input key part 65 Display part 70 Touch panel 71 Release button 80 Wireless communication part 92 Memory | storage part 100 Smartphone 101 Control part L1- L5 Lens AP Light shielding member BKM Light shielding film SL Slit

Claims (15)

1. A lens having a light shielding film formed by applying ink, wherein the light shielding film has a slit.
2. 2. The lens according to claim 1, wherein the slit has a concentric shape continuous in a circumferential direction around the optical axis of the lens.
3. 2. The lens according to claim 1, wherein the slits are radially extending over the entire width of the light shielding film in the direction perpendicular to the optical axis.
4. The lens according to claim 1, wherein the slit has a spiral shape extending over the entire width of the light shielding film in the direction perpendicular to the optical axis.
5. The light-shielding film is formed by ejecting ink droplets toward the lens by an ink jet method and then curing, and the width of the slit is n times the drawing resolution of the ink. Item 5. The lens according to any one of Items 1 to 4.
6. The lens according to any one of claims 1 to 5, wherein a texture is formed on a surface of the lens where the slit is to be formed.
7. When the light shielding film is formed on one surface and the other surface in the optical axis direction of the lens, the light flux that has passed through the slit of the light shielding film on the one surface is reflected by the light shielding film on the other surface. The lens according to any one of claims 1 to 6, wherein the lens is shielded from light.
8. A lens unit formed by stacking a plurality of lenses according to any one of claims 1 to 7 in the direction of the optical axis, and the light flux that has passed through the slit of the light shielding film of a lens is different from that of another lens. The lens unit is shielded by the light shielding film.
9. A lens manufacturing method, wherein a light shielding film having a slit is formed by locally changing the density of ink applied to the surface of the lens.
10. 10. The method for manufacturing a lens according to claim 9, wherein the slit has a concentric shape that is continuous in a circumferential direction around the optical axis of the lens.
11. 10. The method for manufacturing a lens according to claim 9, wherein the slits are radially extending over the entire width of the light shielding film in the direction perpendicular to the optical axis.
12. 10. The lens manufacturing method according to claim 9, wherein the slit has a spiral shape extending over the entire width of the light shielding film in the direction perpendicular to the optical axis.
13. 10. The light shielding film is formed by ejecting ink droplets toward the lens by an ink jet method and then curing, and the width of the slit is n times the drawing resolution of the ink. The method for producing a lens according to any one of items 12 to 12.
14. 14. The method for manufacturing a lens according to claim 9, wherein a texture is formed on a surface of the lens where the slit is to be formed.
15. 15. The method for manufacturing a lens according to claim 9, wherein after the ink is applied to the surface of the lens and cured, the ink is applied again from above.

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