JP2016033542A - Image pickup lens and image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce aberration of an optical system.SOLUTION: This image pickup lens is provided with an object-side lens group, a transparent body, and an image-side lens group. In the image pickup lens, the object-side lens group, the transparent body, and the image-side lens group are sequentially disposed from the object side to the image side without the inclusion of air. Furthermore, in the image pickup lens, the image-side lens group among the object-side lens group, the transparent body, and the image-side lens group is formed from an image-side tablet lens, the object-side lens group, transparent body, and image-side lens group being sequentially disposed without the inclusion of air.SELECTED DRAWING: Figure 2

Description

  The present technology relates to an imaging lens and an imaging apparatus. Specifically, the present invention relates to an imaging lens and an imaging apparatus used in a small device.

  In recent years, camera modules are often mounted on small electronic devices such as smartphones and tablet terminals. Such a camera module for a small electronic device is generally required to be low-cost and space-saving. In order to reduce the cost of this camera module, a method of simultaneously manufacturing a plurality of imaging lenses from a single glass substrate has been proposed (for example, see Patent Document 1). In this prior art, a plurality of concave lenses are formed on one surface of a disk-shaped glass substrate, and a plurality of convex lenses are formed on the other surface. And each of the part in which the lens was formed is isolate | separated as an imaging lens from a glass substrate. According to this method, since it is not necessary to adjust the positional relationship of each lens on the optical axis, an imaging lens in which lenses are formed on both surfaces of a glass substrate can be mass-produced at low cost.

JP 2012-81102 A

  However, the above-described conventional technique has a problem in that an image point shift (that is, aberration) from an ideal image cannot be sufficiently reduced. In order to reduce the aberration of the imaging lens (in other words, the optical system), in addition to the concave lens and convex lens on both sides of the glass substrate, an adjustment lens may be further provided. Cost may increase. Further, the addition of the lens may increase the thickness of the optical system. Therefore, it is difficult to reduce the aberration of the optical system.

  The present technology has been developed in view of such a situation, and an object thereof is to reduce the aberration of an optical system.

  The present technology has been made to solve the above-described problems. The first side surface of the present technology includes an object-side lens group, a transparent body, and an object-side lens group that are arranged in order without sandwiching air from the object side to the image side. The image side lens group is an image pickup lens including an image side doublet lens. This brings about an effect that the aberration is reduced by the image side lens group constituted by the image side doublet lens.

In the first aspect, the radius of curvature R _top1 of the object side surface of the object side lens group and the focal length f of the imaging lens may satisfy the following conditional expression (a). . This brings about the effect that the aberration is reduced by the imaging lens satisfying the conditional expression (a).
Conditional expression (a): ₋₅ ≦ R _top1 /f≦−0.1

In the first aspect, the following conditional expression (a1) may be further satisfied. This brings about the effect that the aberration is reduced by the imaging lens satisfying the conditional expression (a1).
Conditional expression (a1): _−0.50 ≦ R _top1 /f≦−0.14

In the first aspect, the image-side doublet lens includes a lens having a positive refractive power and a lens having a negative refractive power.
The curvature radius R _reverse2 of the object side surface of the lens having the positive refractive index and the focal length f of the imaging lens may satisfy the following conditional expression (b). Thereby, an effect that the aberration is reduced by the imaging lens satisfying the conditional expression (b) is brought about.
Conditional expression (b): 0.09 ≦ R _reverse2 /f≦0.50

In the first aspect, the following conditional expression (b1) may be further satisfied. This brings about the effect that the aberration is reduced by the imaging lens satisfying the conditional expression (b1).
Conditional expression (b1): 0.12 ≦ R _reverse2 /f≦0.22

In the first aspect, the image-side doublet lens includes a lens having a positive refractive power and a lens having a negative refractive power.
The curvature radius R _reverse1 of the image side surface of the lens having positive refractive power and the focal length f of the imaging lens may satisfy the following conditional expression (c). This brings about the effect that the aberration is reduced by the imaging lens satisfying the conditional expression (c).
Conditional expression (c): −5.0 ≦ R _reverse1 /f≦−0.2

In the first aspect, the following conditional expression (c1) may be further satisfied. This brings about the effect that the aberration is reduced by the imaging lens satisfying the conditional expression (c1).
Conditional expression (c1): _−1.0 ≦ R _reverse1 /f≦−0.5

  In the first aspect, the object side lens group may be composed of a single lens having negative refractive power. This brings about an effect that the aberration is reduced by the imaging lens in which the object side lens group composed of one lens having negative refractive power is arranged.

  In the first aspect, the object side lens group may be composed of an object side doublet lens. Thereby, an effect that the aberration is reduced by the imaging lens in which the object-side lens group including the object-side doublet lens is arranged is brought about.

In the first aspect, the image-side doublet lens includes a lens having a positive refractive power and a lens having a negative refractive power.
The curvature radius R _top2 of the image side surface of the lens having negative refractive power and the focal length f of the imaging lens may satisfy the following conditional expression (d). This brings about the effect that the aberration is reduced by the imaging lens satisfying the conditional expression (d).
Conditional expression (d): 0.08 ≦ R _top2 /f≦2.00

In the first aspect, the following conditional expression (d1) may be further satisfied. This brings about the effect that the aberration is reduced by the imaging lens satisfying the conditional expression (d1).
Conditional expression (d1): 0.21 ≦ R _top2 /f≦0.40

  The first side surface may further include a light blocking portion that blocks light at a specific location between the object side lens group and the transparent body. This brings about the effect | action that light is condensed with the imaging lens which further comprises the light-shielding part.

In the first aspect, the maximum image height Ym of the imaging lens and the optical total length TT of the imaging lens may satisfy the following conditional expression (e). This brings about the effect that the aberration is reduced by the imaging lens satisfying the conditional expression (e).
Conditional expression (e): 2 ≦ TT / Ym ≦ 8

In the first aspect, the following conditional expression (e1) may be further satisfied. This brings about the effect that the aberration is reduced by the imaging lens satisfying the conditional expression (e1).
Conditional expression (e1): 2 ≦ TT / Ym ≦ 4

  The second aspect of the present technology includes an object-side lens group, a transparent body, and an image-side lens group that are sequentially arranged without air from the object side to the image side. An imaging apparatus comprising: an imaging lens including an image-side doublet lens; and an imaging unit that captures an image by converting light collected by the imaging lens into an electrical signal. This brings about an effect that the aberration is reduced by the image side lens group constituted by the image side doublet lens.

  In the first aspect, the image processing apparatus may further include a distortion correction unit that corrects optical distortion generated in the imaging lens by image processing on the image. As a result, the optical distortion is corrected.

  According to the present technology, an excellent effect that the aberration of the optical system can be reduced can be obtained. Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.

1 is a block diagram illustrating a configuration example of an imaging apparatus according to a first embodiment. It is a figure which shows the lens structure of the imaging lens in 1st Embodiment. FIG. 6 is an aberration diagram illustrating an example of spherical aberration, astigmatism, and distortion of the imaging lens according to the first embodiment. 3 is a graph illustrating an example of an MTF (Modulation Transfer Function) curve of the imaging lens according to the first embodiment. It is a figure which shows the lens structure of the imaging lens in the modification of 1st Embodiment. It is a figure which shows the lens structure of the imaging lens in 2nd Embodiment. FIG. 10 is an aberration diagram illustrating an example of spherical aberration, astigmatism, and distortion of the imaging lens according to the second embodiment. It is a graph which shows an example of the MTF curve of the imaging lens in 2nd Embodiment. FIG. 10 is an aberration diagram illustrating an example of spherical aberration, astigmatism, and distortion of the imaging lens according to the third embodiment. It is a graph which shows an example of the MTF curve of the imaging lens in 3rd Embodiment. It is a figure for demonstrating the manufacturing method of the imaging lens in 4th Embodiment. It is a block diagram which shows one structural example of the image process part in 5th Embodiment. It is a figure which shows an example of the flame | frame before and behind distortion correction in 5th Embodiment.

Hereinafter, modes for carrying out the present technology (hereinafter referred to as embodiments) will be described. The description will be made in the following order.
1. 1st Embodiment (example which has arrange | positioned in order of an object side lens, a transparent substrate, and a doublet lens)
2. Second Embodiment (Example in which an object side lens composed of a doublet lens, a transparent substrate, and a doublet lens are arranged in this order)
3. Third embodiment (example in which optical parameters are changed and an object side lens composed of a doublet lens, a transparent substrate, and a doublet lens are arranged in this order)
4). Fourth embodiment (an example in which an imaging lens is manufactured in the order of an object side lens, a transparent substrate, and a doublet lens)
5). Fifth Embodiment (Example in which distortion is corrected by arranging an object side lens, a transparent substrate, and a doublet lens in this order)

<1. First Embodiment>
[Configuration example of imaging device]
FIG. 1 is a block diagram illustrating a configuration example of the imaging apparatus 100 according to the first embodiment. The imaging device 100 is a device for capturing an image, and includes an imaging lens 200, an imaging element 110, an image processing unit 120, a control unit 130, and a recording unit 140. As the imaging device 100, a small electronic device such as a mobile phone device such as a smartphone, a mobile device, or a wearable terminal is assumed.

  The imaging lens 200 collects light and guides it to the imaging device 110. The imaging element 110 captures an image (frame) by converting light from the imaging lens 200 into an electrical signal under the control of the control unit 130. The image sensor 110 supplies the captured frame to the image processing unit 120 via the signal line 119. For example, a CMOS (Complementary MOS) sensor, a CCD (Charge Coupled Device) image sensor, or the like is used as the image sensor 110. The image sensor 110 is an example of an imaging unit described in the claims.

  The image processing unit 120 performs predetermined image processing on the frame. For example, demosaic processing, white balance processing, gamma correction processing, and the like are performed as image processing. The frame after image processing is supplied to the recording unit 140 via the signal line 129. The recording unit 140 records a frame after image processing.

  The control unit 130 controls the entire imaging apparatus 100. For example, when a predetermined operation for starting imaging is performed, the control unit 130 causes the imaging device 110 to start imaging a frame.

  Note that the imaging apparatus 100 records the frame in the recording unit 140, but the frame may be displayed on the display unit or output to the outside via an interface. In addition, although the imaging lens 200, the imaging element 110, the image processing unit 120, the control unit 130, and the recording unit 140 are provided in one imaging device 100, they may be distributed and provided in separate devices. For example, the imaging lens 200, the imaging element 110, the control unit 130, and the recording unit 140 may be provided in the imaging device 100, and the image processing unit 120 may be provided in the image processing device.

[Configuration example of imaging lens]
FIG. 2A is a diagram illustrating a lens configuration of the imaging lens 200 according to the first embodiment. The imaging lens 200 includes an object-side lens group 210, a transparent substrate 220, and an image-side lens group 230 that are arranged in order from the object side to the image side without interposing air. The imaging lens 200 includes a cover glass 240 disposed between the image side lens group 230 and the image plane. Here, the image plane corresponds to the light receiving surface of the image sensor 110. The object side is the left side of the figure, and the image side is the right side of the figure. Note that the imaging lens 200 may further include a lens that has substantially no lens power.

  The object side lens group 210 includes, for example, an object side concave lens 211. The object side lens group 210 is formed on the object side surface of the transparent substrate 220 by, for example, a replica process (resin molding). In this replica process, the object-side lens group 210 is formed by molding a thin film made of a resin material on the transparent substrate 220. Instead of using the replica process, the object side lens group 210 may be manufactured and bonded to the transparent substrate 220 by processing or polishing the glass material.

  The transparent substrate 220 is a transparent substrate formed of glass, resin, or the like, and is disposed at a position where both surfaces thereof are perpendicular to the optical axis. The transparent substrate 220 is an example of a transparent body described in the claims.

  The image side lens group 230 is a lens formed on the image side surface of the transparent substrate 220 by a replica process (resin molding) or the like. The image side lens group 230 includes an image side doublet lens 231. The image side doublet lens 231 includes an image side concave lens 232 and an image side convex lens 233. The image side concave lens 232 is provided on the image side surface of the transparent substrate 220, and the image side convex lens 233 is provided on the image side surface of the image side concave lens 232.

  The cover glass 240 is a component for protecting the image sensor 110. The cover glass 240 is disposed between the image side lens group 230 and the image plane at a position where the plane is perpendicular to the optical axis. In addition, air exists between the image side lens group 230 and the cover glass 240, and a medium having a higher refractive index (for example, about 1.5) than air is formed between the cover glass 240 and the image plane.

  Note that only the cover glass 240 is disposed between the image-side lens group 230 and the image plane, but an optical member such as an infrared cut filter or a low-pass filter may be further disposed therebetween. .

  In this way, by forming the image-side doublet lens 231 on the image side of the transparent substrate 220, compared to the imaging lens of Patent Document 1 described above in which one convex lens is provided on the image side of the transparent substrate 220, Aberration can be reduced.

  In FIG. 2, b is a diagram for explaining the surface number of the imaging lens 200. In the imaging lens 200, surface number 1 is assigned to the object-side surface of the object-side concave lens 211, and surface number 2 is assigned to the image-side surface. The surface number 3 is assigned to the object side surface of the image side concave lens 232, and the surface number 4 is assigned to the image side surface. Further, the surface number 5 is assigned to the image side surface of the image side convex lens 233, and the surface number 6 is assigned to the object side surface of the cover glass 240.

Of these surfaces, the shape of the aspheric surface is such that the direction from the object side to the image side is positive, k is a conical coefficient, A, B, C, and D are aspheric coefficients, and r is a central radius of curvature. It is expressed by the following formula.
X = cy ² / {1+ (1− (1 + k) c ² y ² )} ^1/2
+ Ay ⁴ + By ⁶ + Cy ⁸ + Dy ¹⁰ ... Formula 1
In the above equation, y represents the height of the light beam from the optical axis, and c represents the reciprocal (1 / r) of the central radius of curvature r. X is the distance from the tangent plane to the aspheric vertex.

Further, the radius of curvature of the object side surface (surface number 1) of the object side concave lens 211 is hereinafter referred to as “R _top1 ”. The radius of curvature of the object side surface (surface number 4) of the image side convex lens 233 is hereinafter referred to as “R _reverse1 ”, and the radius of curvature of the image side surface (surface number 5) is hereinafter referred to as “R _reverse2 ”. .

The imaging lens 200 is designed so that each optical parameter satisfies the following equations, where f is the focal length of the imaging lens, Ym is the maximum image height, and TT is the total optical length.
−5.0 ≦ R _top1 /f≦−0.1 Formula 2
0.09 ≦ R _reverse2 /f≦0.50 Expression 3
−5.0 ≦ R _reverse1 /f≦−0.2 Formula 4
2 ≦ TT / Ym ≦ 8 Equation 5

  In Equations 2 to 4, the unit of each radius of curvature and focal length f is, for example, millimeters (mm). In Equation 5, the units of the maximum image height Ym and the optical total length TT are, for example, millimeters (mm).

Expression 2 is a conditional expression regarding the radius of curvature of the object-side surface of the object-side lens group 210, and represents that this surface is concave on the object side. In order to obtain better camera characteristics with the one-group configuration, it is necessary to efficiently correct curvature of field by making the optical path passing through the lens longer in the periphery than in the center. When R _top1 / f is smaller than the lower limit of Equation 2, correction is insufficient, and when it exceeds the upper limit, _{overcorrection} is required. Therefore, it is necessary to satisfy this equation. R _top1 / f is more preferably −0.50 to −0.14.

  As a whole power configuration, the object side lens group 210 is configured with a negative refractive power and the image side lens group 230 is configured with a positive refractive power for the above-described reason, and a desired positive refractive power is established. Thus, in order for the image side lens group 230 to have a positive refractive power, it is necessary to satisfy Expression 4.

Expression 3 is a conditional expression regarding the radius of curvature of the object-side surface of the image-side lens group 230, and is necessary to efficiently perform chromatic aberration reduction and astigmatism correction. In order to maximize the effect of the image-side doublet lens 231, it is desirable to combine a concave lens (232) with a small Abbe number and a convex lens (233) with a large Abbe number. Since the image side surface (surface number 5) has a convex shape on the image side, the front surface (surface number 4) has a concave shape on the image side, and Equation 2 is a convex lens (233) that is strong on the image side. This indicates that aberration can be corrected most efficiently by forming. If R _reverse2 / f is smaller than the lower limit of Equation 3, the correction is insufficient, and if the upper limit is exceeded, the curvature becomes too tight to be suitable for production, and this Equation 3 must be satisfied. R _reverse2 / f is more preferably 0.12 to 0.22.

Expression 4 is a conditional expression regarding the radius of curvature of the object-side surface of the image-side lens convex lens 233. If R _reverse1 / f is smaller than the lower limit of Expression 4, the refractive power on the image side and the object side becomes loose, and the correction of field curvature is insufficient, so this lower limit must be satisfied. On the other hand, if R _reverse1 / f exceeds the upper limit of Equation 4, it will be _{overcorrected} , and this upper limit must be satisfied. Note that R _reverse1 / f is more preferably −1.0 to −0.5.

  Expression 5 represents the relationship between the maximum image height Ym and the optical total length TT. The lower limit of Equation 5 is set because there is a limit that can shorten the optical total length TT because aberration correction is performed by the negative action of the object side lens group 210. The upper limit of Equation 5 is provided because the purpose of using the imaging lens 200 is a small module and the purpose is not to have a long optical length. Note that TT / Ym is more preferably 2 to 4.

  As a specific example of the imaging lens 200, a design example when a CMOS imager having a 1/20 size, a 1.12 micrometer (μm) pitch, and a VGA resolution is used as the imaging element 110 is shown. In this design example, the optical total length is 1.70 millimeters (mm), and the half angle of view is 37 degrees. The focal length is 1.1023 millimeters (mm), and the F value is 2.8.

For example, R _top1 / f is −0.934, R _reverse2 / f is 0.172, R _reverse1 / f is −0.537, and TT / Ym is 3.86 according to the conditions of Expressions 2 to 5. Designed to be

The lens configuration data of the above design example is shown in the following table.

An example of each coefficient of Equation 1 is shown in the following table as aspheric data.

  By employing the imaging lens 200, it is possible to provide the imaging device 100 having high resolution and sensitivity and a thickness of about 1 to 2 millimeters (mm). Therefore, the imaging lens 200 is suitable for an ultra-small camera module that is mounted on a mobile device, a wearable terminal, or the like. In the imaging lens 200, since the object side lens group 210, the transparent substrate 220, and the image side lens group 230 are integrated, it is not necessary to assemble these lenses individually, and the productivity is high. In the method of manufacturing and assembling the lenses individually, the focus adjustment mechanism is too small to be adjusted, and problems such as the inability to control mechanical factors such as tilt arise, making it difficult to reduce the size. In addition, a configuration in which a lens is assembled into a barrel using a plastic lens is conceivable. However, in this configuration, when the optical length is about 1 millimeter (mm), the assembly is difficult because the size is too small. On the other hand, in the imaging lens 200, since each lens is integrated, an optical system having a small optical length can be easily realized.

  In addition, since the structure is simple, it is easy to provide a plurality of imaging lenses 200 to form a compound eye lens.

  Further, the curvature of the image plane can be efficiently corrected by the negative action of the object side lens group 210. This is because the optical path passing through the center of the lens is longer in the periphery than in the center.

  Moreover, since the decrease in the amount of peripheral light becomes gentle by the cosine fourth law at the beginning of the negative group, it is advantageous for maintaining the peripheral light amount.

  In addition, since the image side lens group 230 has a doublet structure, it is possible to enhance the respective effects of correction of chromatic aberration and correction of curvature of the image surface.

  Further, since no diaphragm is provided, it is not necessary to assemble the diaphragm, and the error factor can be reduced.

  Further, there are only two interfaces (surface numbers 1 and 5) between the lens having refractive power and air, and there are few factors that cause reflection. Further, only two surfaces (surface numbers 1 and 5) are required for coating the antireflection film.

  Further, the imaging lens 200 can be used for a general-purpose sensor of a CSP (Chip Size Package) often used for a second camera mounted on a smartphone.

  FIG. 3 is an aberration diagram illustrating an example of spherical aberration, astigmatism, and distortion of the imaging lens 200 according to the first embodiment. A in the figure is an aberration diagram of spherical aberration of the imaging lens 200, and b in the figure is an aberration diagram of astigmatism. In a and b of the figure, the dotted line shows the characteristic for light with a wavelength of 587.56 nanometers (nm), and the solid line shows the characteristic for light with a wavelength of 546.07 nanometers (nm). The alternate long and short dash line indicates characteristics with respect to light having a wavelength of 486.13 nanometers (nm).

  3c is an aberration diagram of distortion aberration of the imaging lens 200. FIG. As illustrated in the figure, spherical aberration and astigmatism are particularly small as compared with each aberration of Patent Document 1 (FIG. 3 of the same document) in which only the convex lens is provided in the image side lens group.

  FIG. 4 is a graph illustrating an example of the MTF curve of the imaging lens 200 according to the first embodiment. In the figure, the vertical axis represents MTF, and the horizontal axis represents the real image height. The solid line indicates a curve in the normal direction, and the alternate long and short dash line indicates a curve in the tangential direction. Here, the MTF is one of the indexes representing the high image quality, and the higher the MTF, the less the image is blurred and the higher the image quality. As illustrated in the figure, the MTF of the imaging lens 200 is a sufficiently high value.

  Thus, according to the first embodiment of the present technology, since the doublet lens is provided on the image side of the transparent substrate 220, the aberration can be reduced.

[Modification]
In the first embodiment, the imaging lens 200 is not provided with a diaphragm, but a diaphragm can be further provided. The imaging lens 200 according to the modification is different from the first embodiment in that a diaphragm is provided.

  FIG. 5 is a diagram illustrating a lens configuration of the imaging lens 200 according to a modification of the first embodiment. The imaging lens 200 according to the modified example is different from the first embodiment in that it further includes a light shielding unit 250.

  The light shielding unit 250 blocks a part of light and is used as a diaphragm. The light shielding part 250 is formed, for example, by applying a light shielding paint to a specific portion of the transparent substrate 220.

  Thus, according to the modification, since the stop (light-shielding part 250) is further provided, the amount of light can be adjusted.

<2. Second Embodiment>
In the first embodiment, the object-side lens group 210 includes the object-side concave lens 211. However, a doublet lens may be provided instead of the object-side concave lens 211. The imaging lens 200 of the second embodiment is different from the first embodiment in that the object side lens group 210 is composed of a doublet lens.

  FIG. 6A is a diagram illustrating a lens configuration of the imaging lens 200 according to the second embodiment. The object side lens group 210 according to the second embodiment includes an object side doublet lens 212. The object side doublet lens 212 includes an object side concave lens 213 and an object side convex lens 214. The object side convex lens 214 is provided on the object side surface of the transparent substrate 220, and the object side concave lens 213 is provided on the object side surface of the object side convex lens 214. If the object side lens group 210 is also of a doublet configuration, the difference in the outer periphery of the shaft can be corrected efficiently.

  In FIG. 6, b is a diagram for explaining the surface number of the imaging lens 200. In the imaging lens 200, surface number 1 is assigned to the object-side surface of the object-side concave lens 213, and surface number 2 is assigned to the image-side surface. The surface number 3 is assigned to the image side surface of the object side convex lens 214. The surface number 4 is assigned to the object side surface of the image side concave lens 232, and the surface number 5 is assigned to the image side surface. Further, the surface number 6 is assigned to the image side surface of the image side convex lens 233, and the surface number 7 is assigned to the object side surface of the cover glass 240.

In the second embodiment, the image-side surface (surface number 2) of the object-side concave lens 213 is referred to as “R _top2 ”, and the design is performed so as to satisfy Expressions 2 to 5 and the following expression. .
0.08 ≦ R _top2 /f≦2.00 Equation 6

  Expression 5 is a conditional expression regarding the radius of curvature of the object-side surface of the object-side lens group 210, and is necessary to efficiently correct off-axis aberrations. In order to maximize the effect of the image-side doublet lens 231, the configuration of the first embodiment is optimal. However, with that alone, only the on-axis aberration correction becomes strong, and the image height increases. Conversely, the characteristics deteriorate. Here, if a glass material having a large wavelength dispersion and a small Abbe number is provided on the incident surface (surface number 1) on the object side, the effect of the wavelength dispersion becomes too large to be corrected, so that the glass material having a large Abbe number on the incident surface. Is preferably provided. In addition, this incident surface corrects off-axis aberrations by increasing its negative refractive power.

  The difference between the first embodiment and the second embodiment is that the object side lens group 210 is a single lens or a doublet, but the curvature of the object side lens group 210 is stronger when the object side lens group 210 is a doublet. As a result, off-axis aberrations can be corrected well.

In order to increase this negative effect, it is desirable that the object side lens (232) in the image side doublet lens 231 be a negative lens, that is, the surface of surface number 2 is convex toward the object side. . Equation 6 shows this. The lower limit of Equation 6 is necessary because of the manufacturing condition that if R _top2 / f is smaller than the lower limit, the curvature becomes too tight and is not suitable for manufacturing. Further, the upper limit of Equation 6 is necessary because the effect of aberration correction is lost when R _top2 / f exceeds the upper limit. R _top2 / f is more preferably 0.21 to 0.40.

  In the first embodiment, the imaging lens 200 includes an image-side lens group 230 that includes a combination of a concave lens (232) having a small Abbe number and a convex lens (233) having a large Abbe number that strongly corrects various on-axis aberrations. It was. On the other hand, in 2nd Embodiment, it is comprised by the reverse pattern on the object side.

  As a specific example of the second embodiment, a design example when a CMOS imager having a 1/20 size, a 1.12 micrometer (μm) pitch, and a VGA resolution is used as the image sensor 110 is shown. In this design example, the optical total length is 1.45 millimeters (mm), and the half angle of view is 36 degrees. The focal length is 1.1035 millimeters (mm), and the F value is 2.62.

For example, R _top1 / f is −0.491, R _reverse2 / f is 0.120, R _reverse1 / f is −0.522, and R _top2 / f is −0 according to the conditions of Expressions 2 to 6. .268, TT / Ym is designed to be 3.30.

The lens configuration data of the above design example is shown in the following table.

The aspheric data of the above design example is shown in the following table.

  FIG. 7 is an aberration diagram illustrating an example of spherical aberration, astigmatism, and distortion of the imaging lens 200 according to the second embodiment. A in the figure is an aberration diagram of spherical aberration of the imaging lens 200, and b in the figure is an aberration diagram of astigmatism. In a and b of the figure, the dotted line shows the characteristic for light with a wavelength of 587.56 nanometers (nm), and the solid line shows the characteristic for light with a wavelength of 546.07 nanometers (nm). The alternate long and short dash line indicates characteristics with respect to light having a wavelength of 486.13 nanometers (nm).

  In FIG. 7, c is an aberration diagram of the distortion aberration of the imaging lens 200. As illustrated in the figure, in the second embodiment, spherical aberration and astigmatism are further reduced as compared with the first embodiment.

  FIG. 8 is a graph illustrating an example of the MTF curve of the imaging lens 200 according to the first embodiment. In the figure, the vertical axis represents MTF, and the horizontal axis represents the real image height. The solid line indicates a curve in the normal direction, and the alternate long and short dash line indicates a curve in the tangential direction. As illustrated in the figure, the MTF of the second embodiment is higher than that of the first embodiment.

  As described above, according to the second embodiment of the present technology, since the doublet lens is provided also on the object side of the transparent substrate 220, the aberration can be further reduced.

<3. Third Embodiment>
In the third embodiment, the optical total length is designed to be larger than 1 millimeter (mm). However, the optical total length can be set to 1 millimeter (mm) or less. The imaging lens 200 of the third embodiment is different from the second embodiment in that the optical system is further thinned.

  The configuration of the imaging lens 200 of the third embodiment is the same as that of the second embodiment except that the optical parameters are different.

  As a specific example of the third embodiment, a design example when a CMOS imager of 1/24 size, 0.9 micrometer (μm) pitch, and VGA resolution is used as the image sensor 110 is shown. In this design example, the optical length is 1.00 millimeter (mm) and the half angle of view is 39 degrees. The focal length is 0.821 millimeters (mm), and the F value is 2.44.

Further, according to the conditions of Expressions 2 to 6, for example, R _top1 / f is −0.727, R _reverse2 / f is 0.143, R _reverse1 / f is −0.693, and R _top2 / f is The TT / Ym is designed to be 2.78 at 0.212.

The lens configuration data of the above design example is shown in the following table.

The aspheric data of the above design example is shown in the following table.

  FIG. 9 is an aberration diagram illustrating an example of spherical aberration, astigmatism, and distortion of the imaging lens 200 according to the third embodiment. A in the figure is an aberration diagram of spherical aberration of the imaging lens 200, and b in the figure is an aberration diagram of astigmatism. In a and b of the figure, the dotted line shows the characteristic for light with a wavelength of 587.56 nanometers (nm), and the solid line shows the characteristic for light with a wavelength of 546.07 nanometers (nm). The alternate long and short dash line indicates characteristics with respect to light having a wavelength of 486.13 nanometers (nm).

  9c is an aberration diagram of distortion aberration of the imaging lens 200. FIG. As illustrated in the figure, in the third embodiment, spherical aberration and astigmatism are reduced to the same extent as in the second embodiment.

  FIG. 10 is a graph illustrating an example of the MTF curve of the imaging lens 200 according to the first embodiment. In the figure, the vertical axis represents MTF, and the horizontal axis represents the real image height. The solid line indicates a curve in the normal direction, and the alternate long and short dash line indicates a curve in the tangential direction. As illustrated in the figure, the MTF of the third embodiment has a sufficiently high value.

Each optical parameter in Table 7 is a value when a medium having a refractive index of about 1.5 is filled between the cover glass 240 and the image plane, but the cover glass is not filled with such a medium. It is also possible to adopt a configuration in which air exists between 240 and the image plane. Examples of optical parameters at that time are shown in the following table.

  As described above, according to the third embodiment of the present technology, since the optical total length of the optical system is reduced to 1.00 millimeter (mm), the imaging device 100 can be reduced in thickness.

<4. Fourth Embodiment>
In the first embodiment, the manufacturing method of the imaging lens is not mentioned, but a large number of imaging lenses 200 can be manufactured simultaneously by a simple method.

  FIG. 11 is a diagram for explaining a method of manufacturing the imaging lens 200 according to the fourth embodiment. First, a disk-shaped glass substrate 300 is prepared. By the manufacturing system, a plurality of object side lens groups 210 are formed on one surface of both surfaces of the glass substrate 300, and a plurality of image side lens groups 230 are formed on the other surface. These lens groups are formed at positions facing each other.

  A plurality of cover glasses 240 are formed on the wafer 400 by the manufacturing system. Then, the surface of the wafer 400 provided with the cover glass 240 and the surface of the glass substrate 300 provided with the image side lens group 230 are bonded together by the manufacturing system. At the time of bonding, a spacer may be sandwiched, or a protector or a spacer may be attached to the glass substrate 300 or the wafer 400. In many cases, an IR cut filter is further provided on the glass substrate 300.

  After the glass substrate 300 and the wafer 400 are bonded together, each of the places where the object side lens group 210 is provided is separated from the glass substrate 300 and the wafer 400 as an imaging lens by the manufacturing system. With such a manufacturing method, a large number of imaging lenses 200 can be manufactured simultaneously.

  If each of the object side lens group 210 and the image side lens group is manufactured individually and manufactured by a method of assembling them, the smaller the size of the imaging lens, the more difficult it is to assemble. In particular, it is difficult to adjust the position of each lens on the optical axis and to adjust the deviation of each optical axis of a plurality of lenses. Even if adjustments are possible, these adjustments increase costs. In contrast, according to the manufacturing method of the fourth embodiment, each of the object side lens group 210 and the image side lens group 230 is integrated with the transparent substrate 220, and the imaging lens is aligned with the optical axes aligned. Manufactured. For this reason, it is not necessary to adjust the position of each lens on the optical axis, and the imaging lens 200 can be manufactured with low cost and space. In addition, there is a reality of preventing warping in the thickness of the CSP glass, the lens and the foot between the CSP (not shown), and the lens substrate (300).

  Thus, according to the fourth embodiment, since a plurality of lenses are formed on both surfaces of the glass substrate, a plurality of imaging lenses 200 can be manufactured simultaneously by a simple procedure.

<5. Fifth embodiment>
In the first embodiment, the imaging apparatus 100 does not correct the optical distortion generated in the imaging lens 200, but may correct the optical distortion. The imaging apparatus 100 according to the fifth embodiment is different from the first embodiment in that optical distortion is corrected.

  FIG. 12 is a block diagram illustrating a configuration example of the image processing unit 120 according to the fifth embodiment. The image processing unit 120 according to the fifth embodiment includes a frame memory 121 and a distortion correction unit 122. In the figure, the configuration for performing image processing other than distortion correction, such as demosaic processing and gamma correction, is omitted.

  The frame memory 121 holds a frame from the image sensor 110. The frame to be held may be before demosaicing or after demosaicing. This frame includes a plurality of pixel data arranged in a two-dimensional grid.

  The distortion correction unit 122 corrects optical distortion in the frame held in the frame memory 121. For example, optical distortion is measured in advance, and a table in which the coordinates of each pixel before correction and the coordinates of each pixel after correction are associated is stored in the distortion correction unit 122. Then, the distortion correction unit 122 refers to the table and converts each of the coordinates of the pixel data read from the frame memory 121 into corrected coordinates. Then, the distortion correction unit 122 outputs the pixel data of the coordinates before correction as pixel data of the coordinates after correction. Thereby, a frame in which the optical distortion is corrected is generated.

  Note that the distortion correction unit 122 may calculate the corrected coordinates from the uncorrected coordinates using a predetermined function indicating the correspondence between the uncorrected coordinates and the corrected coordinates without using a table.

  FIG. 13 is a diagram illustrating an example of a frame before and after distortion correction in the fifth embodiment. In the figure, a is an example of a frame 501 before distortion correction when a subject on which a two-dimensional grid pattern is drawn is imaged, and b in the figure is an example of a frame 502 after distortion correction. As illustrated in FIG. 5A, optical distortion is generated near the outer periphery of the frame 501. This optical distortion is corrected by the coordinate transformation of the distortion correction unit 122 as illustrated in FIG.

  As described above, according to the fifth embodiment, the imaging apparatus 100 can improve the image quality of the frame because the optical distortion is corrected.

  The above-described embodiment shows an example for embodying the present technology, and the matters in the embodiment and the invention-specific matters in the claims have a corresponding relationship. Similarly, the invention specific matter in the claims and the matter in the embodiment of the present technology having the same name as this have a corresponding relationship. However, the present technology is not limited to the embodiment, and can be embodied by making various modifications to the embodiment without departing from the gist thereof.

  Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.

In addition, this technique can also take the following structures.
(1) An object-side lens group, a transparent body, and an image-side lens group, which are arranged in order without interposing air from the object side to the image side,
The image-side lens group is an imaging lens including an image-side doublet lens.
(2) The imaging lens according to (1), wherein a radius of curvature R _top1 of the object side surface of the object side lens group and a focal length f of the imaging lens satisfy the following conditional expression (a).
Conditional expression (a): −5.0 ≦ R _top1 /f≦−0.1
(3) The imaging lens according to (2), further satisfying the following conditional expression (a1):
Conditional expression (a1): _−0.50 ≦ R _top1 /f≦−0.14
(4) The image-side doublet lens is composed of a lens having a positive refractive power and a lens having a negative refractive power,
The curvature radius R _reverse2 of the object side surface of the lens having the positive refractive index and the focal length f of the imaging lens satisfy any of the following conditional expressions (b): An imaging lens according to claim 1.
Conditional expression (b): 0.09 ≦ R _reverse2 /f≦0.50
(5) The imaging lens according to any one of (4), further satisfying the following conditional expression (b1):
Conditional expression (b1): 0.12 ≦ R _reverse2 /f≦0.22
(6) The image-side doublet lens includes a lens having a positive refractive power and a lens having a negative refractive power,
The curvature radius R _reverse1 of the image side surface of the lens having a positive refractive power and the focal length f of the imaging lens satisfy any of the following conditional expressions (c): The imaging lens described in 1.
Conditional expression (c): −5.0 ≦ R _reverse1 /f≦−0.2
(7) The imaging lens according to any one of (6), further satisfying the following conditional expression (c1):
Conditional expression (c1): _−1.0 ≦ R _reverse1 /f≦−0.5
(8) The imaging lens according to any one of (1) to (7), wherein the object side lens group includes one lens having negative refractive power.
(9) The imaging lens according to any one of (1) to (8), wherein the object side lens group includes an object side doublet lens.
(10) The image-side doublet lens includes a lens having a positive refractive power and a lens having a negative refractive power,
The imaging lens according to (9), wherein a radius of curvature R _top2 of the image side surface of the lens having negative refractive power and a focal length f of the imaging lens satisfy the following conditional expression (d).
Conditional expression (d): 0.08 ≦ R _top2 /f≦2.00
(11) The imaging lens according to (10), further satisfying the following conditional expression (d1):
Conditional expression (d1): 0.21 ≦ R _top2 /f≦0.40
(12) The imaging lens according to any one of (1) to (11), further including a light blocking unit that blocks light at a specific location between the object side lens group and the transparent body.
(13) The imaging lens according to any one of (1) to (12), wherein a maximum image height Ym of the imaging lens and an optical total length TT of the imaging lens satisfy the following conditional expression (e):
Conditional expression (e): 2 ≦ TT / Ym ≦ 8
(14) The imaging lens according to any one of (13), which satisfies the following conditional expression (e1):
Conditional expression (e1): 2 ≦ TT / Ym ≦ 4
(15) The imaging lens according to any one of (1) to (14), further including a lens having substantially no lens power.
(16) An object-side lens group, a transparent body, and an image-side lens group that are sequentially arranged without air from the object side to the image side, and the image-side lens group includes an image-side doublet lens. An imaging lens;
An image pickup apparatus comprising: an image pickup unit that picks up an image by converting light collected by the image pickup lens into an electric signal.
(17) The imaging apparatus according to (16), further including a distortion correction unit that corrects optical distortion generated in the imaging lens by image processing on the image.

DESCRIPTION OF SYMBOLS 100 Image pick-up device 110 Image pick-up element 120 Image processing part 121 Frame memory 122 Distortion correction part 130 Control part 140 Recording part 200 Imaging lens 210 Object side lens group 211,213 Object side concave lens 212 Object side doublet lens 214 Object side convex lens 220 Transparent substrate 230 Image side lens group 231 Image side doublet lens 232 Image side concave lens 233 Image side convex lens 240 Cover glass 250 Light-shielding part 300 Glass substrate 400 Wafer

Claims (16)

An object-side lens group, a transparent body, and an image-side lens group that are arranged in order without interposing air from the object side to the image side;
The image-side lens group is an imaging lens including an image-side doublet lens. The imaging lens according to claim 1, wherein a radius of curvature R _top1 of the object side surface of the object side lens group and a focal length f of the imaging lens satisfy the following conditional expression (a).
Conditional expression (a): −5.0 ≦ R _top1 /f≦−0.1 The imaging lens according to claim 2, further satisfying the following conditional expression (a1):
Conditional expression (a1): _−0.50 ≦ R _top1 /f≦−0.14 The image-side doublet lens is composed of a lens having a positive refractive power and a lens having a negative refractive power,
The imaging lens according to claim 1, wherein a radius of curvature R _reverse2 of the object side surface of the lens having the positive refractive index and a focal length f of the imaging lens satisfy the following conditional expression (b).
Conditional expression (b): 0.09 ≦ R _reverse2 /f≦0.50 The imaging lens according to claim 4, further satisfying the following conditional expression (b1):
Conditional expression (b1): 0.12 ≦ R _reverse2 /f≦0.22 The image-side doublet lens is composed of a lens having a positive refractive power and a lens having a negative refractive power,
The imaging lens according to claim 1, wherein a radius of curvature R _reverse1 of the image side surface of the lens having positive refractive power and a focal length f of the imaging lens satisfy the following conditional expression (c).
Conditional expression (c): −5.0 ≦ R _reverse1 /f≦−0.2 The imaging lens according to claim 6, further satisfying the following conditional expression (c1):
Conditional expression (c1): _−1.0 ≦ R _reverse1 /f≦−0.5 The imaging lens according to claim 1, wherein the object side lens group includes a single lens having a negative refractive power. The imaging lens according to claim 1, wherein the object side lens group includes an object side doublet lens. The image-side doublet lens is composed of a lens having a positive refractive power and a lens having a negative refractive power,
The imaging lens according to claim 9, wherein a radius of curvature R _top2 of the image side surface of the lens having the negative refractive power and a focal length f of the imaging lens satisfy the following conditional expression (d).
Conditional expression (d): 0.08 ≦ R _top2 /f≦2.00 The imaging lens according to claim 10, further satisfying the following conditional expression (d1):
Conditional expression (d1): 0.21 ≦ R _top2 /f≦0.40 The imaging lens according to claim 1, further comprising a light shielding portion that shields light at a specific location between the object side lens group and the transparent body. The imaging lens according to claim 1, wherein a maximum image height Ym of the imaging lens and an optical total length TT of the imaging lens satisfy the following conditional expression (e).
Conditional expression (e): 2 ≦ TT / Ym ≦ 8 The imaging lens of Claim 13 which further satisfies the following conditional expressions (e1).
Conditional expression (e1): 2 ≦ TT / Ym ≦ 4 An object side lens group, a transparent body, and an image side lens group, which are arranged in order without air from the object side to the image side, and the image side lens group includes an imaging lens composed of an image side doublet lens; ,
An image pickup apparatus comprising: an image pickup unit that picks up an image by converting light collected by the image pickup lens into an electric signal. The imaging apparatus according to claim 15, further comprising a distortion correction unit that corrects optical distortion generated in the imaging lens by image processing on the image.

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