Optical system and imaging device

Abstract

To provide an optical system which has high optical performance despite its small size.SOLUTION: An optical system (1a) comprises a first unit (L1), a second unit (L2) and a third unit (L3) which are arranged in order from an object side to an image side, the first unit having a first substrate (11), a negative power first lens (12) which is arranged on the image side of the first substrate, and a flare cut diaphragm (S1), the second unit having a second substrate (21), a positive power second lens (22) which is arranged on the object side or image side of the second substrate, and an aperture diaphragm (SP), the third unit having a third substrate (31) and a positive power third lens (32) which is arranged on the object side or image side of the third substrate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical system and an imaging device.

Background Art

[0002] In recent years, as an optical system used in an imaging device such as a medical endoscope, there is a demand for a small-sized one having high optical performance. Patent Documents 1 and 2 disclose a wafer-level lens (wafer-level optics) which is a small-sized optical system manufactured by a wafer-level process.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the lens system disclosed in Patent Document 1, the number of substrates and the bonding process in the wafer-level process are numerous, increasing the cost. Also, since Patent Document 1 does not disclose a plurality of diaphragms, it is difficult to achieve miniaturization of the optical system. Patent Document 2 discloses a wafer-level optics having a plurality of diaphragms, but since various aberrations cannot be sufficiently reduced, it is difficult to realize an optical system having high optical performance.

[0005] Therefore, an object of the present invention is to provide an optical system that is small-sized and has high optical performance.

Means for Solving the Problems

[0006] One aspect of the present invention is an optical system consisting of a first unit, a second unit, and a third unit arranged in order from the object side to the image side. an optical system The first unit comprises a first substrate, a negative-power first lens positioned on the image side of the first substrate, and a flare-cutting aperture; the second unit comprises a second substrate, a positive-power second lens positioned on the object side of the second substrate, and an aperture diaphragm; the third unit comprises a third substrate, a positive-power third lens positioned on either the object side or the image side of the third substrate, wherein the circularity of the aperture of the flare-cutting aperture and the aperture diaphragm are different from each other. When the focal length of the third lens is f3 and the focal length of the optical system is f, the conditional expression 1.4 < f3 / f < 3.0 is satisfied ru.

[0007] Other objects and features of the present invention are described in the following examples. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an optical system that is compact yet possesses high optical performance. [Brief explanation of the drawing]

[0009]

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[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] The optical systems in each embodiment are compact optical systems obtained using a technique called wafer-level processing. Such optical systems are called wafer-level lenses (wafer-level optics), and imaging devices that use wafer-level lenses as imaging optical systems are called wafer-level cameras. Due to their compact size and low cost, the optical systems in each embodiment are suitable for use as optical systems in cameras embedded in electronic devices such as mobile phones, smartphones, and wearable devices, as well as as objective optical systems in endoscopes.

[0012] Figures 1, 6, 9, 12, 16, 19, 22, and 25 are cross-sectional views of the optical systems (wafer-level lenses) 1a, 1b, 1c, 1d, 1e, 1f, 1g, and 1h of Examples 1 to 8, respectively. In each cross-sectional view, the left side is the object side (front) and the right side is the image side (rear). S1 is a flare-cutting aperture (light beam aperture), SP is an aperture aperture, and IP is the image plane. The flare-cutting aperture S1 is provided separately from the aperture aperture and is a component for blocking unwanted light (flare light) from the off-axis light beam that causes flare. The image plane IP is a photosensitive surface corresponding to the imaging surface of a solid-state image sensor such as a CCD sensor or CMOS sensor in an imaging device, or the film surface of a silver halide film camera.

[0013] Figures 2, 7, 10, 13, 17, 20, 23, and 26 are aberration diagrams for the optical systems 1a, 1b, 1c, 1d, 1e, 1f, 1g, and 1h of Examples 1 to 8, respectively. Each aberration diagram includes (A) a spherical aberration diagram, (B) an astigmatism diagram, (C) a distortion diagram, and (D) a chromatic aberration diagram. The spherical aberration diagram shows the amount of spherical aberration for the d line (wavelength 587.6 nm), g line (wavelength 435.8 nm), C line (wavelength 656.3 nm), and F line (wavelength 486.1 nm), respectively. In the astigmatism diagram, ΔSd shows the amount of astigmatism at the sagittal image plane for the d line, and ΔMd shows the amount of astigmatism at the meridional image plane for the d line. The distortion diagram shows the amount of distortion for the d line. In the chromatic aberration diagram, the amount of chromatic aberration for the g-line, C-line, and F-line is shown. Fno is the F-number, and Y is the image height (mm).

[0014] The optical system of each embodiment consists of a first unit L1, a second unit L2, and a third unit L3 arranged in order from the object side to the image side. The first unit L1 has a flare cut aperture S1, a first substrate 11, and a negative power first lens 12 located on the image side of the first substrate 11. The second unit L2 has a second substrate 21, a second lens 22 located on either the object side or the image side of the second substrate 21, and an aperture aperture SP. The third unit L3 has a third substrate 32 and a third lens 31 located on either the object side or the image side of the third substrate 32.

[0015] The first substrate 11 is a planar substrate, and the first lens 12 is a plano-concave lens. The first lens 12 is formed on the image-side surface of the first substrate 11 using a wafer-level process and is positioned in close contact with the first substrate 11. The image-side surface of the first lens 12 is aspherical. The second substrate 21 is a planar substrate, and the second lens 22 is a plano-convex lens. The second lens 22 is formed on the surface of the second substrate 21 using a wafer-level process and is positioned in close contact with the second substrate 21. The surface of the second lens 22 opposite to the second substrate 21 is aspherical. The third substrate 32 is a planar substrate, and the third lens 31 is a plano-convex lens. The third lens 31 is formed on the surface of the third substrate 31 using a wafer-level process and is positioned in close contact with the third substrate 32. The surface of the third lens 31 opposite to the third substrate 31 is aspherical.

[0016] In the optical systems of each embodiment, in order to realize a compact and low-cost optical system, the first unit L1, the second unit L2, and the third unit L3 are each manufactured using a wafer-level process. That is, the first unit L1, the second unit L2, and the third unit L3 are manufactured by forming a lens layer made of a curable resin material on a wafer (planar substrate) made of glass material. Thus, in each embodiment, the materials of the first substrate 11 and the first lens 12 are different from each other. Similarly, the materials of the second substrate 12 and the second lens 22, and the materials of the third substrate 31 and the third lens 32 are different from each other.

[0017] In the first unit L1 and the second unit L2, apertures (flare-cut aperture S1, aperture aperture SP) are formed on the substrate using a similar wafer process. By arranging the manufactured first unit L1, second unit L2, third unit L3, and image sensor at desired intervals, bonding them at the light-effective outer edge, and then cutting them, a large number of wafer-level lenses can be manufactured. The material forming the lens layer can be any curable resin material, such as a thermoplastic resin or an ultraviolet-curable resin. Examples include acrylic resin, silicone resin, and cycloolefin polymer.

[0018] In each embodiment, the first substrate 11, the second substrate 21, and the third substrate 31 are made of glass, and the first lens 12, the second lens 22, and the third lens 32 are made of resin, but the invention is not limited to these. If the refractive indices of the first substrate 11 and the first lens 12 are different, for example, both the first substrate 11 and the first lens 12 may be made of resin. The same applies to the second unit L2 and the third unit L3. The flare cut aperture S1 and the aperture aperture SP can be formed by, for example, depositing a light-shielding film such as chromium using a mask, or by etching after deposition to form the aperture. In this case, forming the aperture aperture SP on a flat surface such as a substrate is preferable from a manufacturing standpoint because it facilitates control of the mask arrangement in the thickness direction.

[0019] The optical system in each embodiment is an integrated optical system comprising a first unit L1, a second unit L2, and a third unit L3. In the optical system of each embodiment, the third substrate 31 functions as both a back cover glass for the optical system and a sensor cover glass. By forming the lens surface of the third lens 32 on the object side of the third substrate (back cover glass) 31 in this way, it becomes possible to provide a compact optical system with high optical performance while suppressing material and manufacturing costs (i.e., at low cost).

[0020] In each embodiment, the cover glass (third substrate 31) is made as a single glass substrate, but this is not the only way. For example, the third substrate 31 may be divided into two flat substrates. First, the lens surface of the third lens 32 is formed on the object side of the divided object-side glass substrate, and the wafer lens is formed by bonding it to the first unit L1 and the second unit L2. Then, the divided image-side glass substrate is made as a cover glass for the sensor, and the wafer-level optics can be formed by bonding the divided glass substrates together. This makes it possible to create a wafer lens using a process that is easy to manufacture and highly stable.

[0021] Wafer lenses, such as the optical systems in each embodiment, are desirable to be as small as possible. When miniaturizing very wide-angle optical systems with a half-angle of view of 50 degrees or more, as in each embodiment, it is necessary to reduce the effective ray diameter on the object-side surface, shorten the overall length, and control various aberrations. If the effective ray diameter on the object-side surface becomes large, the size of a single optical system increases, which reduces the number of optical systems that can be made from a single wafer, resulting in a high-cost manufacturing method. In wide-angle lenses, to reduce the effective ray diameter on the object-side surface, it is effective to provide a flare-cut diaphragm on the object-side surface rather than an aperture diaphragm to reduce the diameter of the off-axis light beam.

[0022] Furthermore, forming apertures on each lens of a wafer lens makes it difficult to control the placement accuracy of the apertures due to thickness errors during lens molding, etc., so it is desirable to form the apertures on the substrate on which the lenses are formed. Also, in the case of a wide-angle wafer lens optical system, the first lens 12 on the object side has a large aberration correction effect, so forming the apertures near the first lens 12, i.e., on the first substrate 11, allows for a more effective configuration that balances aberration correction and miniaturization. Forming apertures in the wafer process requires additional processes such as mask deposition, resulting in a high-cost manufacturing process, so it is desirable to keep the apertures to a minimum.

[0023] In the case of wide-angle wafer lenses as in each embodiment, the plane on which the off-axis light beam has the maximum effective diameter may differ from the plane on which the light beam at the intermediate image height has the maximum effective diameter. In the case of photographic lenses manufactured without using a wafer process, apertures are often provided on each plane to control the light beam at each image height, but as mentioned above, in the wafer process, it is desirable to use the minimum necessary aperture. For this reason, in each embodiment, the shape of the flare cut aperture is made appropriate so as to achieve the maximum effective diameter at each image height, and the arrangement of the flare cut aperture is optimized so that aberration correction and light intensity control at each image height of the image are appropriately performed with a single flare cut aperture. It is important that the aperture is formed on a flat surface, and similar effects can be obtained by, for example, forming a thin flat layer of resin or the like on a planar substrate and placing the aperture on top of it.

[0024] Preferably, the optical system of each embodiment satisfies the following condition (1).

[0025] 30(degree)<(ds×W1) / ((Fs1-Fsp)×N1A)<70(degree)...(1) In conditional equation (1), Fsp is the maximum effective diameter of the aperture diaphragm SP provided in the second unit L2, and Fs1 is the maximum effective diameter of the flare cut diaphragm S1 provided in the first unit L1. W1 (degrees) is the maximum half-angle of view of the optical system, N1A is the average refractive index of the first substrate 11 and the first lens 12 in the first unit L1, and ds is the distance on the optical axis between the aperture diaphragm SP and the flare cut diaphragm S1. The average refractive index N1A is the refractive index at the design wavelength of the optical system, and in the case of an optical system used in the visible range, it is the refractive index of the d line.

[0026] Conditional equation (1) is a conditional equation for determining the appropriate incident angle when the off-axis light beam passes through the flare cut aperture S1 and the aperture diaphragm SP. The aperture diaphragm SP is mainly determined by the specifications of the optical system, such as FNo, but as mentioned above, by appropriately setting the effective diameter of the flare cut aperture S1, the aberration of the off-axis light beam can be efficiently corrected. However, the smaller the effective diameter of the flare cut aperture S1 and the less off-axis light beam there is, the less light is emitted at the edges of the image. Therefore, in order to balance aberration correction and peripheral light intensity, it is necessary to appropriately set the position and effective diameter of the flare cut aperture, and by satisfying conditional equation (1), a configuration that balances aberration correction and peripheral light intensity can be achieved. Exceeding the upper limit of conditional equation (1) is undesirable because it reduces peripheral light intensity. On the other hand, falling below the lower limit of conditional equation (1) is undesirable because it makes it difficult to correct aberrations (especially field curvature) at the edges of the off-axis light beam, and the performance of the optical system deteriorates.

[0027] More preferably, the numerical range of condition (1) is set as shown in condition (1a) below.

[0028] 32(degree)<(ds×W1) / ((Fs1-Fsp)×N1A)<60(degree) ···(1a) More preferably, the numerical range of condition (1) is set as shown in condition (1c) below.

[0029] 35(degree)<(ds×W1) / ((Fs1-Fsp)×N1A)<50(degree)...(1b) Preferably, the optical system of each embodiment satisfies the following condition (2).

[0030] 2 5< ((ds×W1) / N1A+16×f / f1×d12) / (Fs1-Fsp)<6 0 ...(2) In condition (2), f is the focal length of the optical system (entire system), f1 is the focal length of the first lens 12, and d12 is the distance between the first unit and the second unit on the optical axis. When the second lens 22 is located on the object side of the substrate 21, the distance d12 is the air gap between the first lens 12 and the second lens 22. On the other hand, when the second lens 22 is located on the image side of the substrate 21, the distance d12 is the air gap between the first lens 12 and the second substrate 21.

[0031] Conditional equation (2), like conditional equation (1), is a conditional equation that indicates the appropriate placement of the flare-cut aperture S1. In the optical system of each embodiment, the first lens 12 is positioned between the flare-cut aperture S1 and the aperture aperture SP, and the off-axis light beam is subjected to a large refractive effect by the first lens 12. Therefore, by appropriately setting the power of the first lens 12 and the length of the air gap on the image side of the first lens, a configuration can be achieved that balances the correction of off-axis light beam aberrations and peripheral light intensity. Exceeding the upper limit of conditional equation (2) is undesirable because it reduces peripheral light intensity. On the other hand, falling below the lower limit of conditional equation (2) is undesirable because it makes it difficult to correct aberrations (especially field curvature) in the peripheral part of the off-axis light beam, and the performance of the optical system deteriorates.

[0032] More preferably, the numerical range of condition (2) is set as shown in condition (2a) below.

[0033] 2 8<((ds×W1) / N1A+16×f / f1×d12) / (Fs1-Fsp)<5 5 ...(2a) More preferably, the numerical range of condition (2) is set as shown in condition (2b) below.

[0034] 3 0< ((ds×W1) / N1A+16×f / f1×d12) / (Fs1-Fsp)<4 5 ...(2c) In each embodiment, the shape of the aperture diaphragm SP is preferably approximately circular. In each embodiment, the shape of the flare cut diaphragm S1 is preferably set to an appropriate shape based on the shape of the image sensor (image plane) and the way the off-axis light beam of the optical system passes. In the case of a small optical system such as wafer-level optics, it is preferable to make the shape of the image sensor rectangular because it simplifies the process of cutting the lenses into individual lenses after they have been fabricated by stacking the lenses. In particular, it is preferable to make the shape of the image sensor close to a square because it allows the size of the optical system to be reduced relative to the area of ​​the image sensor, and at the same time makes it easier to cut the wafer lenses after they have been stacked.

[0035] The shape of the flare-cut aperture S1 should preferably be based on the rectangular (or approximately square) shape of the image sensor, taking into account aberrations such as distortion in each lens. By doing so, aberration correction can be efficiently performed by blocking the appropriate amount of light without unnecessarily increasing the area of ​​the flare-cut aperture. In other words, it is preferable that the circularity of the aperture of the flare-cut aperture S1 and the aperture of the aperture SP are different from each other. Here, different circularity means that the maximum effective diameter and the minimum effective diameter of the aperture are different from each other. Specifically, when R1 is the ratio of the maximum effective diameter to the minimum effective diameter of the aperture of the flare-cut aperture S1, and Rs is the ratio of the maximum effective diameter to the minimum effective diameter in the imaging region of the image plane, it is preferable that the following condition (3) is satisfied.

[0036] 0.72 <R1 / Rs<1.20 ···(3) If the upper or lower limit of condition (3) is exceeded, the shape of the flare-cut aperture S1 becomes unnecessarily large, preventing it from becoming a small wafer lens, or the amount of off-axis light beam decreases, resulting in an undesirable image.

[0037] More preferably, the numerical range of condition (3) is set as shown in condition (3a) below.

[0038] 0.74 <R1 / Rs<1.10 ···(3a) Furthermore, in the optical systems of each embodiment, off-axis light beam aberrations are controlled by positioning a first lens 12 with a larger negative power on the image side than the flare cut aperture S1. In addition, by reducing the effective diameter of the first lens 12, the width outside the effective diameter of the first lens 12 is secured, improving the ease of manufacturing when bonding the first lens 12 and the second lens 22. For this reason, when the difference between the effective diameter of the object-side surface of the optical system and the effective diameter of the first lens L12 is E1, and the maximum image height is Y, it is preferable that the following conditional equation is satisfied.

[0039] 0.8 <E1 / Y<1.5 ···(4) More preferably, the numerical range of condition (4) is set as shown in condition (4a) below.

[0040] 0.9 <E1 / Y<1.4 ···(4a) The optical systems of each embodiment generate significant negative distortion in order to obtain a wide-angle, compact optical system. By generating distortion, the maximum effective diameter of the flare-cut aperture S1 can be reduced. Specifically, when the distortion at the maximum image height of the optical system is DST (%), it is preferable to satisfy the following condition (5).

[0041] -40 <DST<-10 ···(5) If the upper or lower limit of condition (5) is exceeded, the effective diameter of the flare-cutting aperture S1 will increase, resulting in a larger optical system, or distortion will increase, degrading the resolution at the edges of the image, which is undesirable.

[0042] Preferably, the optical system of each embodiment satisfies the following condition (6).

[0043] 0.60 <f2 / f<1.60 ···(6) In condition (6), f2 is the focal length of the second lens 22. By satisfying condition (6), it becomes possible to correct spherical aberration to an appropriate value.

[0044] More preferably, the numerical range of condition (6) is set as shown in condition (6a) below.

[0045] 0.75 <f2 / f<1.52 ···(6a) More preferably, the numerical range of condition (6) is set as shown in condition (6b) below.

[0046] 0.85 <f2 / f<1.40 ···(6b) Preferably, the optical system of each embodiment satisfies the following condition (7).

[0047] -3.5 <f3 / f1<-1.5 ···(7) In condition (7), f3 is the focal length of the third lens 32. By satisfying condition (7), it becomes possible to correct astigmatism and distortion to appropriate values.

[0048] Preferably, the numerical range of condition (7) is set as shown in condition (7a) below.

[0049] -3.2 <f3 / f1<-1.6 ···(7a) Furthermore, in the optical system of each embodiment, the structure is such that aberrations are canceled between the first lens 12 and the second lens 22, which are positioned closer to the object than the aperture diaphragm SP, while balancing this with the aberrations generated by the third lens 32, which is positioned closer to the image than the aperture diaphragm SP. For this reason, it is preferable that the following condition (8) is satisfied.

[0050] 0.30<(f2-f1) / f3<1.60 (8) If the value falls below the lower limit of condition equation (8), the power of the third lens 32 decreases, disrupting the balance of aberration correction before and after the aperture diaphragm SP, which is undesirable. On the other hand, if the value exceeds the upper limit of condition equation (8), the power of the third lens 32 increases, making it difficult to correct various aberrations. Furthermore, the diameter of the third lens 32 increases, making it difficult to secure the effective width, resulting in a configuration that is difficult to manufacture, which is also undesirable.

[0051] More preferably, the numerical range of condition (8) is set as shown in condition (8a) below.

[0052] 0.50<(f2-f1) / f3<1.60 (8a) More preferably, the numerical range of condition (8) is set as shown in condition (8b) below.

[0053] 0.60<(f2-f1) / f3<1.55 (8b) As described above, by arranging the first lens 12 and the second lens 22 in close proximity and facing each other, aberration correction on the object side can be performed better than that on the aperture diaphragm SP. For this reason, it is preferable to place the second lens 22 on the object side of the second substrate 21 in the second unit. Preferably, various aberrations can be corrected even better by satisfying the following conditional equation (9).

[0054] 1.4 <f3 / f<3.0 ···(9) More preferably, the numerical range of condition (9) is set as shown in condition (9a) below.

[0055] 1.5 <f3 / f<2.5 ···(9a) Preferably, the optical system of each embodiment satisfies the following condition (10).

[0056] 0.07 <d / f<0.65 ···(10) In condition (10), d is the distance along the optical axis from the aperture diaphragm SP to the object-side surface of the third lens 32. By satisfying condition (10), it becomes possible to correct astigmatism and distortion to appropriate values.

[0057] More preferably, the numerical range of condition expression (10) is set as shown in condition expression (10a) below.

[0058] 0.10 <d / f<0.62 ···(10a) Furthermore, in the optical system of each embodiment, aberration correction is performed solely by the third lens 32 on the image side of the aperture diaphragm SP. In addition, higher-order aberrations are corrected by significantly bending the light rays at the outer edge of the third lens 32. For this reason, it is preferable to appropriately set the distance d on the optical axis from the aperture diaphragm SP to the third lens 32 and the power of the third lens 32. Specifically, it is preferable to satisfy the numerical range of the following conditional equation (11).

[0059] 0.03 <d / f3<0.40 ···(11) If the value falls below the lower limit of condition (11), the power of the third lens 32 decreases, making it difficult to correct aberrations that occur on the image side rather than the aperture diaphragm SP. On the other hand, if the value exceeds the upper limit of condition (11), the angle of light rays incident on the outer edge of the third lens 32 becomes gentler, making it difficult to correct higher-order aberrations.

[0060] More preferably, the numerical range of condition expression (11) is set as shown in condition expression (11a) below.

[0061] 0.04 <d / f3<0.35 ···(11a) More preferably, the numerical range of conditional expression (11) is set as shown in conditional expression (11b) below.

[0062] 0.05 <d / f3<0.34 ···(11b) Preferably, the optical system of each embodiment satisfies the following condition (12).

[0063] 1.0 <L / f<2.4 ···(12) In condition (12), L is the distance along the optical axis from the third lens 32 to the image plane IP. By satisfying condition (12), it becomes possible to correct spherical aberration and astigmatism to appropriate values.

[0064] More preferably, the numerical range of condition expression (12) is set as shown in condition expression (12a) below.

[0065] 1.2 <L / f<2.2 ···(12a) In each embodiment, the wafer-level lens can achieve good aberration correction by positioning the first lens 12 and the second lens 22 in close proximity with an air layer in between. In this case, during the wafer lens manufacturing process, when joining the first unit L1 including the first lens 12 and the second unit L2 including the second lens 22, it is necessary to bond the outer peripheries of the first lens 12 and the second lens 22 together. Since the first lens 12 and the second lens 22 are usually made of resin, a manufacturing challenge is to bond the outer periphery of the resin material with high precision to suppress deformation, etc. Furthermore, in the optical system of each embodiment, the configuration corrects higher-order aberrations by making the power of the first lens 12 and the second lens 22 relatively strong, so each lens tends to become larger, and the difference in thickness between the optical axis and the outer periphery tends to increase. Therefore, the optical system of each embodiment preferably satisfies the following conditional equation (13).

[0066] 0.60 <Lar / (d1+d2)<2.00 ···(13) In condition (13), Lar is the distance between the first lens 12 and the second substrate 21 on the optical axis, d1 is the thickness of the first substrate 11, and d2 is the thickness of the second substrate 21. If the value falls below the lower limit of condition (13), the thicknesses of the first substrate 11 and the second substrate 21 become too thick, making it impossible to obtain a compact optical system. On the other hand, if the value exceeds the upper limit of condition (13), the thicknesses of the first substrate 11 and the second substrate 21 become too thin, leading to excessive deformation and making manufacturing difficult, or the distance between the first lens 12 and the second lens 22 on the optical axis and the thickness of the second lens 22 become too large, making it difficult to reduce spherical aberration, astigmatism, etc.

[0067] More preferably, the numerical range of conditional expression (13) is set as shown in conditional expression (13a) below.

[0068] 0.75 <Lar / (d1+d2)<1.80 ···(13a) Furthermore, when wafer-level optics are used as small imaging devices such as endoscopes and smartphones, it is desirable that the surface closest to the object be made of a hard, environmentally resistant material such as glass. Since it is difficult to create a curved surface for glass materials in wafer processing, it is preferable that the surface closest to the object be a flat glass surface.

[0069] The optical systems of each embodiment will be described in detail below. [Examples]

[0070] First, the optical system 1a in Example 1 (Numerical Example 1) will be described with reference to Figures 1 to 4.

[0071] As shown in Figure 1, the optical system 1a consists of a first unit L1, a second unit L2, and a third unit L3. The first unit L1 consists of a first substrate (front cover glass) 11, a flare-cut aperture S1 positioned on the object side of the first substrate 11, and a first lens 12 positioned on the image side of the first substrate. The first lens 12 is a negative lens with its concave surface facing the image side, and is formed on the image-side surface of the first substrate 11 using a wafer-level process.

[0072] The second unit L2 consists of a second substrate 21, a second lens 22 positioned on the object side of the second substrate 21, and an aperture diaphragm SP positioned on the image side of the second substrate. The second lens 22 is a positive lens with its convex surface facing the object side, and is formed on the object-side surface of the second substrate 21 using a wafer-level process.

[0073] The third unit L3 consists of a third substrate 31 and a third lens 32 positioned on the object side of the third substrate 31. The third substrate 31 serves as both a sensor cover glass and a back cover glass. The third lens 32 is a positive lens with its convex surface facing the object side, and is formed on the object-side surface of the third substrate 31 using a wafer-level process.

[0074] The optical system 1a in this embodiment is designed to focus on an object located 5 mm from the object-side surface of the first unit L1. The optical system 1a has a half-angle of view of 59° and an FNo of 2.8, providing a bright, wide-angle optical system despite its very compact size.

[0075] Next, with reference to Figure 5, an optical system (wafer-level lens) 20 as a comparative example will be described. Figure 5 is a cross-sectional view of the optical system 20 as a comparative example. The optical system 20 consists of a first unit L10, a second unit L20, and a third unit L30. The first unit L10 has a first substrate 211 and a first lens 212 positioned on the image side of the first substrate 211. The first lens 212 is a negative lens with its concave surface facing the image side. The second unit L20 has a second substrate 221 and a second lens 222 positioned on the object side of the second substrate 221. The second lens 222 is a positive lens with its convex surface facing the object side. The second unit L20 also has a third substrate 231 and a third lens 232 positioned on the image side of the third substrate 231. The third lens 232 is a positive lens with its convex surface facing the image side. The second unit L20 also has an aperture diaphragm SP between the second substrate 221 and the third substrate 231. The third unit L30 has a fourth substrate (back cover glass) 261 and a fifth substrate (sensor cover glass) 241.

[0076] On the other hand, in this embodiment, the optical system 1a reduces the number of substrates by using the third substrate 31, which is necessary for forming the third lens 32, as a back cover glass. Thus, according to this embodiment, by forming the final lens of the optical system 1a on the object side, it is possible to provide a compact optical system with high optical performance while suppressing material and manufacturing costs. For this reason, it is preferable to place the third lens 32 on the image side of the third substrate 31, thereby suppressing manufacturing costs.

[0077] Furthermore, the comparative optical system 20 does not have a flare-cutting aperture in the first unit L10, so it is necessary to restrict the beam width of the off-axis light beam with an aperture aperture SP or the effective diameter of the first lens 212 or the second lens 222. When the beam width of the off-axis light beam is restricted with an aperture aperture SP, it becomes difficult to reduce aberrations in the peripheral part of the off-axis light beam, and the optical system becomes larger, which is undesirable. When the off-axis light beam is restricted with the effective diameter of the first lens 212 or the second lens 222, it is necessary to significantly deform the shape of the lens in the effective diameter portion, which makes it difficult to accurately form the lens shape during manufacturing, and thus makes it difficult to obtain the desired surface shape.

[0078] In the wafer lens of this embodiment, the sensor (image plane) has a square shape, with a side width of 0.396 mm for the effective area contributing to imaging and a maximum effective diameter of 0.560 mm in the diagonal direction. In this embodiment, the aperture diaphragm SP has a circular shape with an effective diameter of 0.117 mm, and the flare cut diaphragm S1 has the shape shown in Figure 3.

[0079] Figure 3 shows the shape of the flare-cut aperture S1 in a plane perpendicular to the optical axis OA, with the horizontal axis representing the X direction and the vertical axis representing the Y direction. The solid line in Figure 2 corresponds to the edge of the flare-cut aperture S1, with the area outside the solid line being the light-shielding portion and the area inside the solid line being the aperture. As shown in Figure 3, the shape of the flare-cut aperture S1 is not circular, but rather a distorted shape based on the square shape of the sensor (image plane). The shape of the flare-cut aperture S1 is designed based on the aberration correction of the off-axis light beam and peripheral light intensity of the optical system 1a in this embodiment.

[0080] Figure 4 shows the effective diameter of the flare-cut aperture S1. It plots the effective diameter R of the flare-cut aperture S1 at a point rotated by an angle θ (deg) relative to the optical axis OA, with the horizontal X direction in Figure 3 as the reference point. Note that in Figure 4, the angle θ is in the range of 0 to 90 degrees, but as shown in Figure 3, the shape in the range of 90 to 360 degrees is inverted from the shape in the 0 to 90 degree range.

[0081] Figures 2(A) to 2(D) show the aberration diagrams of the optical system 1a in this embodiment. As shown in Figure 2(A), the spherical aberration of this embodiment is less than 0.04 mm. As shown in Figure 2(B), the astigmatism of this embodiment is less than 0.04 mm. As shown in Figure 2(C), the distortion of this embodiment is less than 40%. As shown in Figure 2(D), the chromatic aberration of this embodiment is less than 0.01 mm.

[0082] Thus, the optical system 1a of this embodiment, by appropriately setting the flare-cutting aperture S1, is a compact, bright, and wide-angle optical system in which aberrations from the axial to the off-axial beam are well corrected. [Examples]

[0083] Next, with reference to Figures 6 to 8, the optical system 1b in Example 2 (Numerical Example 2) will be described.

[0084] As shown in Figure 6, the basic configuration of the optical system 1b of this embodiment is the same as that of the optical system 1a of Embodiment 1. The optical system 1b of this embodiment is designed to focus on an object located 5 mm from the object-side surface of the first unit L1. The optical system 1b of this embodiment has a half-angle of view of 57° and an FNo of 2.8, providing a bright, wide-angle optical system despite its very compact size. In addition, in the optical system 1b of this embodiment, the flare-cut aperture S1 is located on the image side of the first substrate 11 in the first unit L1.

[0085] In the wafer lens of this embodiment, the sensor (image plane) has a square shape, with a side width of 0.396 mm for the effective area contributing to imaging and a maximum effective diameter of 0.560 mm in the diagonal direction. In this embodiment, the aperture diaphragm SP has a circular shape with an effective diameter of 0.126 mm, and the flare cut diaphragm S1 has a distorted shape based on the shape of the sensor (image plane).

[0086] Figure 8 shows the effective diameter R of the flare-cut aperture S1 at an angle θ with respect to the optical axis OA. In Figure 8, the angle θ is shown in the range of 0 to 90 degrees, but as in Example 1, the shape in the range of 90 to 360 degrees is inverted from the shape in the range of 0 to 90 degrees.

[0087] Figures 7(A) to 7(D) show the aberration diagrams of the optical system 1b in this embodiment. As shown in Figure 7(A), the spherical aberration of this embodiment is less than 0.04 mm. As shown in Figure 7(B), the astigmatism of this embodiment is less than 0.04 mm. As shown in Figure 7(C), the distortion of this embodiment is less than 40%. As shown in Figure 7(D), the chromatic aberration of this embodiment is less than 0.01 mm.

[0088] Thus, the optical system 1b of this embodiment, by appropriately setting the flare-cutting aperture S1, is a compact, bright, and wide-angle optical system in which aberrations from the on-axis to the off-axis beam are well corrected. [Examples]

[0089] Next, with reference to Figures 9 to 11, the optical system 1c in Example 3 (Numerical Example 3) will be described.

[0090] As shown in Figure 9, the basic configuration of the optical system 1c of this embodiment is the same as that of the optical system 1a of Embodiment 1. The optical system 1c of this embodiment is designed to focus on an object located 5 mm from the object-side surface of the first unit L1. The optical system 1b of this embodiment has a half-angle of view of 59° and an FNo of 2.8, providing a bright, wide-angle optical system despite its very compact size. In addition, in the optical system 1c of this embodiment, the flare-cut aperture S1 is located on the object side of the first substrate 11 in the first unit L1.

[0091] In the wafer lens of this embodiment, the sensor (image plane) has a square shape, with a side width of 0.396 mm and a maximum effective diameter in the diagonal direction of 0.560 mm. In this embodiment, the aperture diaphragm SP has a circular shape with an effective diameter of 0.105 mm, and the flare cut diaphragm S1 has a distorted shape based on the shape of the sensor (image plane).

[0092] Figure 11 shows the effective diameter R of the flare-cut aperture S1 in this embodiment at an angle θ with respect to the optical axis OA. In Figure 11, the angle θ is shown in the range of 0 to 90 degrees, but as in Embodiment 1, the shape in the range of 90 to 360 degrees is inverted from the shape in the range of 0 to 90 degrees.

[0093] Figures 10(A) to (D) show the aberration diagrams of the optical system 1c in this embodiment. As shown in Figure 10(A), the spherical aberration of this embodiment is less than 0.04 mm. As shown in Figure 10(B), the astigmatism of this embodiment is less than 0.04 mm. As shown in Figure 10(C), the distortion of this embodiment is less than 40%. As shown in Figure 10(D), the chromatic aberration of this embodiment is less than 0.01 mm.

[0094] Thus, by appropriately setting the flare-cutting aperture S1, the optical system of this embodiment is a compact, bright, and wide-angle optical system in which aberrations from the axial to the off-axial beam are well corrected. [Examples]

[0095] Next, with reference to Figures 12 to 15, the optical system 1d in Example 4 (Numerical Example 4) will be described.

[0096] As shown in Figure 12, the basic configuration of the optical system 1d in this embodiment is the same as that of the optical system 1a in Embodiment 1. The optical system 1d in this embodiment is designed to focus on an object located 5 mm from the object-side surface of the first unit L1. The optical system 1d in this embodiment has a half-angle of view of 59° and an FNo of 2.8, providing a bright, wide-angle optical system despite its very compact size. In addition, in the optical system 1d in this embodiment, the flare-cut aperture S1 is located on the object side of the first substrate 11 in the first unit L1.

[0097] In the wafer lens of this embodiment, the sensor (image plane) has a rectangular shape, with the width of the short side of the effective area contributing to imaging being 0.311 mm, the width of the long side being 0.466 mm, and the maximum effective diameter in the diagonal direction being 0.560 mm. In this embodiment, the aperture diaphragm SP has a circular shape with an effective diameter of 0.121 mm, and the flare cut diaphragm S1 has a distorted shape based on the shape of the sensor (image plane).

[0098] Figure 14 shows the shape of the flare-cut aperture S1 in a plane perpendicular to the optical axis OA. The solid lines in Figure 14 represent the edges of the flare-cut aperture S1, with the area outside the solid lines being the light-shielding portion and the area inside the solid lines being the opening. As shown in Figure 14, the shape of the flare-cut aperture S1 is not circular, but rather a distorted shape based on the rectangular shape of the sensor (image plane).

[0099] Figure 15 shows the effective diameter R of the flare-cut aperture S1 at an angle θ with respect to the optical axis OA. Note that in Figure 15, the angle θ is shown in the range of 0 to 90 degrees, but as shown in Figure 14, the shape in the range of 90 to 360 degrees is inverted from the shape in the 0 to 90 degree range.

[0100] Figures 13(A) to (D) show the aberration diagrams of the optical system 1d in this embodiment. As shown in Figure 13(A), the spherical aberration of this embodiment is less than 0.04 mm. As shown in Figure 13(B), the astigmatism of this embodiment is less than 0.04 mm. As shown in Figure 13(C), the distortion of this embodiment is less than 40%. As shown in Figure 13(D), the chromatic aberration of this embodiment is less than 0.01 mm.

[0101] Thus, the optical system 1d of this embodiment, by appropriately setting the flare-cutting aperture S1, is a compact, bright, and wide-angle optical system in which aberrations from the on-axis to the off-axis beam are well corrected. [Examples]

[0102] Next, with reference to Figures 16 to 18, the optical system 1e in Example 5 (Numerical Example 5) will be described.

[0103] As shown in Figure 16, the basic configuration of the optical system 1e in this embodiment is the same as that of the optical system 1a in Embodiment 1. The optical system 1e in Embodiment 5 is designed to focus on an object located 5 mm from the object-side surface of the first unit L1. The optical system 1e in this embodiment has a half-angle of view of 59° and an FNo of 2.9, providing a bright, wide-angle optical system despite its very compact size. In addition, in the optical system 1e of this embodiment, the flare-cut aperture S1 is located on the image side of the first substrate 11 in the first unit L1.

[0104] In the wafer lens of this embodiment, the sensor (image plane) has a square shape, with a side width of 1.16 mm for the effective area contributing to imaging and a maximum effective diameter of 1.64 mm in the diagonal direction. In this embodiment, the aperture diaphragm SP has a circular shape with an effective diameter of 0.285 mm, and the flare cut diaphragm S1 has a distorted shape based on the shape of the sensor (image plane).

[0105] Figure 18 shows the effective diameter R of the flare-cut aperture S1 at an angle θ with respect to the optical axis OA. In Figure 18, the angle θ is shown in the range of 0 to 90 degrees, but as in Example 1, the shape in the range of 90 degrees to 360 degrees is inverted from the shape in the range of 0 to 90 degrees.

[0106] Figures 17(A) to (D) show the aberration diagrams of the optical system 1e in this embodiment. As shown in Figure 17(A), the spherical aberration of this embodiment is less than 0.1 mm. As shown in Figure 17(B), the astigmatism of this embodiment is less than 0.1 mm. As shown in Figure 17(C), the distortion of this embodiment is less than 40%. As shown in Figure 17(D), the chromatic aberration of this embodiment is less than 0.03 mm.

[0107] Thus, the optical system 1e of this embodiment, by appropriately setting the flare-cutting aperture S1, is a compact, bright, and wide-angle optical system in which aberrations from the axial to the off-axial beam are well corrected. [Examples]

[0108] Next, with reference to Figures 19 to 21, the optical system 1f in Example 6 (Numerical Example 6) will be described.

[0109] As shown in Figure 19, the basic configuration of the optical system 1f in this embodiment is the same as that of the optical system 1a in Embodiment 1. The optical system 1f in Embodiment 6 is designed to focus on an object located 5 mm from the object-side surface of the first unit L1. The optical system 1f in this embodiment has a half-angle of view of 59° and an FNo of 2.8, providing a bright, wide-angle optical system despite its very compact size. In this embodiment, the flare-cut aperture S1 is located on the image side of the first substrate 11 in the first unit L1.

[0110] In the wafer lens of this embodiment, the sensor (image plane) has a square shape, with a side width of 0.396 mm for the effective area contributing to imaging and a maximum effective diameter of 0.560 mm in the diagonal direction. In this embodiment, the aperture diaphragm SP has a circular shape with an effective diameter of 0.119 mm, and the flare cut diaphragm S1 has a distorted shape based on the shape of the sensor (image plane).

[0111] Figure 21 shows the effective diameter R of the flare-cut aperture S1 at an angle θ with respect to the optical axis OA. In Figure 21, the angle θ is shown in the range of 0 to 90 degrees, but as in Example 1, the shape in the range of 90 to 360 degrees is inverted from the shape in the range of 0 to 90 degrees.

[0112] Figures 20(A) to (D) show the aberration diagrams of the 1f optical system in this embodiment. As shown in Figure 20(A), the spherical aberration in this embodiment is less than 0.04 mm. As shown in Figure 20(B), the astigmatism in this embodiment is less than 0.04 mm. As shown in Figure 20(C), the distortion in this embodiment is less than 40%. As shown in Figure 20(D), the chromatic aberration in this embodiment is less than 0.01 mm.

[0113] Thus, the optical system 1f of this embodiment, by appropriately setting the flare-cutting aperture S1, is a compact, bright, and wide-angle optical system in which aberrations from the on-axis to the off-axis beam are well corrected. [Examples]

[0114] Next, with reference to Figures 22 to 24, the optical system 1g in Example 7 (Numerical Example 7) will be described.

[0115] As shown in Figure 22, the basic configuration of the optical system 1g in this embodiment is the same as that of the optical system 1a in Embodiment 1. In addition, in optical system 1g, unlike Embodiments 1 to 6, the aperture diaphragm SP is located on the object-side surface of the second substrate 21. The optical system 1g in this embodiment is designed to focus on an object located 5 mm from the object-side surface of the first unit L1. The optical system 1g in this embodiment has a half-angle of view of 59° and an FNo of 2.8, providing a bright, wide-angle optical system despite its very compact size. In addition, in the optical system 1g in this embodiment, the flare-cut diaphragm S1 is located on the image side of the first substrate 11 in the first unit L1.

[0116] In the wafer lens of this embodiment, the sensor (image plane) has a square shape, with a side width of 0.396 mm for the effective area contributing to imaging and a maximum effective diameter of 0.560 mm in the diagonal direction. In this embodiment, the aperture diaphragm SP has a circular shape with an effective diameter of 0.119 mm, and the flare cut diaphragm S1 has a distorted shape based on the shape of the sensor (image plane).

[0117] Figure 24 shows the effective diameter R of the flare-cut aperture S1 at an angle θ with respect to the optical axis OA. In Figure 24, the angle θ is shown in the range of 0 to 90 degrees, but as in Example 1, the shape in the range of 90 to 360 degrees is inverted from the shape in the range of 0 to 90 degrees.

[0118] Figures 23(A) to (D) show the aberration diagrams for the 1g optical system in this embodiment. As shown in Figure 23(A), the spherical aberration in this embodiment is less than 0.04 mm. As shown in Figure 23(B), the astigmatism in this embodiment is less than 0.04 mm. As shown in Figure 23(C), the distortion in this embodiment is less than 40%. As shown in Figure 23(D), the chromatic aberration in this embodiment is less than 0.01 mm.

[0119] Thus, the optical system 1g of this embodiment, by appropriately setting the flare-cut aperture S1, is a compact, bright, and wide-angle optical system in which aberrations from the axial to the off-axial beam are well corrected. [Examples]

[0120] Next, with reference to Figures 25 to 27, the optical system 1h in Example 8 (Numerical Example 8) will be described.

[0121] Figure 25 is a cross-sectional view of the optical system 1h of Embodiment 8. The optical system 1h consists of a first unit L1, a second unit L2, and a third unit L3. The first unit L1 has a first substrate 11 and a first lens 12 positioned on the image side of the first substrate 11. The first lens 12 is a negative lens with its concave surface facing the image side. The second unit L2 has a second substrate 21 and a second lens 22 positioned on the object side of the second substrate 21. The second lens 22 is a positive lens with its convex surface facing the object side. The third unit L3 has a third substrate 31, a third lens 32 positioned on the image side of the third substrate 31, and a fourth substrate 41. The third lens 32 is a positive lens with its convex surface facing the image side. In this embodiment, unlike Embodiments 1 to 7, the third lens 32 is positioned on the image side of the third substrate 31.

[0122] In this embodiment, the first unit L1 has a flare-cut aperture S1 on the image-side surface of the first substrate 11, and the second unit L2 has an aperture aperture SP on the image-side surface of the second substrate 21. In this embodiment, the second substrate 21 and the third substrate 31 are joined with the aperture aperture SP in between, but this embodiment is not limited to this configuration, and the second substrate 21 and the third substrate 31 may be arranged with an air gap between them.

[0123] The fourth substrate 41 in the third unit L3 functions as both a back cover glass for the wafer lens and a sensor cover glass. The optical system 1h in this embodiment is designed to focus on an object located 5 mm from the object-side surface of the first unit L1. The optical system 1h in this embodiment has a half-angle of view of 59° and an FNo of 2.8, providing a bright, wide-angle optical system despite its very compact size. In addition, in the optical system 1h in this embodiment, the flare-cut aperture S1 is located on the image side of the first substrate 11 in the first unit L1.

[0124] In the wafer lens of this embodiment, the sensor (image plane) has a square shape, with a side width of 0.396 mm for the effective area contributing to imaging and a maximum effective diameter of 0.560 mm in the diagonal direction. In this embodiment, the aperture diaphragm SP has a circular shape with an effective diameter of 0.111 mm, and the flare cut diaphragm S1 has a distorted shape based on the shape of the sensor (image plane).

[0125] Figure 27 shows the effective diameter R of the flare-cut aperture S1 at an angle θ with respect to the optical axis OA. In Figure 27, the angle θ is shown in the range of 0 to 90 degrees, but as in Example 1, the shape in the range of 90 to 360 degrees is inverted from the shape in the range of 0 to 90 degrees.

[0126] Figures 26(A) to (D) show the aberration diagrams of optical system 1h in this embodiment. As shown in Figure 26(A), the spherical aberration of this embodiment is less than 0.04 mm. As shown in Figure 26(B), the astigmatism of this embodiment is less than 0.04 mm. As shown in Figure 26(C), the distortion of this embodiment is less than 40%. As shown in Figure 26(D), the chromatic aberration of this embodiment is less than 0.01 mm.

[0127] As described above, the optical system 1h of this embodiment appropriately sets the arrangement and shape of the flare-cut aperture S1, as well as the power of the first lens 12 and the second lens 22 near the flare-cut aperture S1. Therefore, despite being a small, bright, and wide-angle optical system, it is an optical system in which aberrations from the on-axis to the off-axis beam are well corrected.

[0128] The following shows numerical examples 1 to 8, corresponding to each of the examples 1 to 8. In each numerical example, r is the radius of curvature of the i-th surface from the object side (mm), d is the interplanar spacing between the i-th and (i+1)-th axes from the object side (mm), and nd and νd are the refractive index and Abbe number of the i-th optical element with respect to the d line, respectively. The Abbe number νd of a certain material is given by Nd, NF, and NC, respectively, when the refractive indices at the Fraunhofer lines d line (587.6 nm), F line (486.1 nm), and C line (656.3 nm) are Nd, NF, and NC. νd = (Nd-1) / (NF-NC) It is represented as follows.

[0129] The focal length f (mm) is the value when the lens is focused on an object at infinity. BF is the back focus, which is the distance from the final surface of the optical system to the image plane. The total length of the lens is the distance from the first surface to the image plane. Aspherical surfaces are indicated by adding the sign * after the surface number. The aspherical shape is expressed as follows: x is the amount of variation from the vertex of the surface in the direction of the optical axis, h is the height from the optical axis in the direction perpendicular to the optical axis, r is the radius of paraxial curvature, k is the cone constant, A i When (i=4, 6, 8, ...) are the aspherical coefficients of each order, the following equations apply.

[0130]

number

[0131] The display "e±Z" is "10 ±Z It means "...".

[0132] In each numerical example, S1 is the flare-cut diaphragm and SP is the aperture diaphragm. The effective diameter indicates the maximum luminous flux diameter when the light beam contributing to image formation passes through each surface.

[0133] (Numerical Example 1) Unit: mm Surface data Face number rd nd νd Effective diameter 1(S1) ∞ 0.100 1.51680 64.2 0.62 2 ∞ 0.045 1.52290 50.3 0.48 3* 0.0846 0.120 0.28 4* 0.1231 0.141 1.52290 50.3 0.25 5 ∞ 0.100 1.51680 64.2 0.19 6(SP) ∞ 0.054 0.12 7* 0.2286 0.072 1.52290 50.3 0.27 8 ∞ 0.400 1.51680 64.2 0.30 9 ∞ 0.020 0.55 Image plane ∞ Aspherical data 3rd page K =-6.21168e+00 ,A4= 6.25636e+02 ,A6=-8.47952e+04 ,A8= 7.80586e+06 ,A10=-4.40616e+08 ,A12= 1.38205e+10 ,A14=-1.84957e+11 Side 4 K =-4.15041e+00 ,A4= 2.01549e+02 ,A6=-1.89467e+04 ,A8= 1.87535e+06 ,A10=-1.38040e+08 ,A12= 5.97522e+09 ,A14=-1.13123e+11 Side 7 K =-5.85227e+01 ,A4= 2.60048e+02 ,A6=-5.58127e+04 ,A8= 7.10305e+06 ,A10=-5.13511e+08 ,A12= 1.94389e+10 ,A14=-2.98356e+11 Focal length 0.217 F-number 2.83 Half-angle 59.00 Image height 0.28 Lens length 1.052 BF 0.020 (Numerical Example 2) Unit: mm Surface data Face number rd nd νd Effective diameter 1 ∞ 0.100 1.51680 64.2 0.62 2(S1) ∞ 0.045 1.52290 50.3 0.49 3* 0.1087 0.081 0.29 4* 0.1272 0.130 1.52290 50.3 0.27 5 ∞ 0.100 1.51680 64.2 0.23 6(SP) ∞ 0.037 0.13 7* 0.2355 0.070 1.52290 50.3 0.25 8 ∞ 0.436 1.51680 64.2 0.28 9 ∞ 0.020 0.54 Image plane ∞ Aspherical data 3rd page K =-7.43588e+00 ,A4= 4.87017e+02 ,A6=-6.30018e+04 ,A8= 5.88716e+06 ,A10=-3.17706e+08 ,A12= 8.90173e+09 ,A14=-9.27729e+10 Side 4 K =-1.29842e+00 ,A4= 3.07945e+01 ,A6=-2.42278e+03 ,A8= 4.47425e+05 ,A10=-3.15142e+07 ,A12= 1.04795e+09 ,A14=-1.02518e+10 Side 7 K =-4.78137e+01 ,A4= 2.30855e+02 ,A6=-4.83783e+04 ,A8= 6.29551e+06 ,A10=-4.66358e+08 ,A12= 1.79953e+10 ,A14=-2.79997e+11 Focal length 0.277 F-number 2.79 Half-angle 56.96 Image height 0.28 Lens length 1.019 BF 0.020 (Numerical Example 3) Unit: mm Surface data Face number rd nd νd Effective diameter 1(S1) ∞ 0.100 1.51680 64.2 0.63 2 ∞ 0.045 1.52290 50.0 0.51 3* 0.0848 0.106 0.32 4* 0.1083 0.144 1.52290 50.0 0.26 5 ∞ 0.100 1.51680 64.2 0.19 6(SP) ∞ 0.053 0.10 7* 0.2293 0.082 1.52290 50.0 0.32 8 ∞ 0.309 1.51680 64.2 0.35 9 ∞ 0.020 0.53 Image plane ∞ Aspherical data 3rd page K =-2.22646e+00 ,A4= 1.43149e+02 ,A6=-1.16286e+04 ,A8= 8.05061e+05 ,A10=-4.13691e+07 ,A12= 1.22414e+09 ,A14=-1.53923e+10 Side 4 K =-5.84575e-01 ,A4=-5.09576e+01 ,A6=-3.17416e+03 ,A8= 6.34170e+05 ,A10=-7.71692e+07 ,A12= 4.11231e+09 ,A14=-8.73425e+10 Side 7 K =-2.35858e+01 ,A4= 4.86585e+01 ,A6=-1.61169e+03 ,A8=-1.37022e+05 ,A10= 1.62943e+07 ,A12=-5.94181e+08 ,A14= 7.49715e+09 Focal length 0.212 F-number 2.82 Half-angle 59.00 Image height 0.280 Lens length 0.959 BF 0.020 (Numerical Example 4) Unit: mm Surface data Face number rd nd νd Effective diameter 1(S1) ∞ 0.100 1.51680 64.2 0.70 2 ∞ 0.045 1.52290 50.3 0.58 3* 0.0973 0.150 0.35 4* 0.1380 0.157 1.52290 50.3 0.29 5 ∞ 0.100 1.51680 64.2 0.22 6(SP) ∞ 0.060 0.12 7* 0.2483 0.073 1.52290 50.3 0.28 8 ∞ 0.400 1.51680 64.2 0.31 9 ∞ 0.020 0.54 Image plane ∞ Aspherical data 3rd page K =-4.31087e+00 ,A4= 3.12202e+02 ,A6=-2.60622e+04 ,A8= 1.53039e+06 ,A10=-5.47887e+07 ,A12= 1.05391e+09 ,A14=-8.39699e+09 Side 4 K =-3.99923e+00 ,A4= 1.44168e+02 ,A6=-1.01800e+04 ,A8= 6.98040e+05 ,A10=-3.27411e+07 ,A12= 8.17274e+08 ,A14=-8.95918e+09 Side 7 K =-4.61520e+01 ,A4= 1.79406e+02 ,A6=-3.32097e+04 ,A8= 3.71515e+06 ,A10=-2.35268e+08 ,A12= 7.74406e+09 ,A14=-1.02722e+11 Focal length 0.219 F-number 2.83 Half-angle 59.22 Image height 0.280 Lens length 1.105 BF 0.020 (Numerical Example 5) Unit: mm Surface data Face number rd nd νd Effective diameter 1 ∞ 0.240 1.51680 64.2 1.80 2(S1) ∞ 0.060 1.52290 50.3 1.49 3* 0.2544 0.281 0.99 4* 0.2977 0.450 1.52290 50.3 0.81 5 ∞ 0.300 1.51680 64.2 0.59 6(SP) ∞ 0.133 0.29 7* 0.7301 0.183 1.52290 50.3 1.04 8 ∞ 0.924 1.51680 64.2 1.07 9 ∞ 0.020 1.62 Image plane ∞ Aspherical data 3rd page K =-2.90252e+00 ,A4= 7.67701e+00 ,A6=-7.89117e+01 ,A8= 5.30402e+02 ,A10=-2.28315e+03 ,A12= 5.43220e+03 ,A14=-5.40674e+03 Side 4 K =-3.20861e+00 ,A4= 8.02516e+00 ,A6=-6.13489e+01 ,A8= 2.79381e+02 ,A10=-2.00807e+02 ,A12=-4.57858e+03 ,A14= 1.37008e+04 Side 7 K =-2.89556e+01 ,A4= 1.88999e+00 ,A6=-6.36789e+00 ,A8=-4.17162e+01 ,A10= 4.63584e+02 ,A12=-1.51718e+03 ,A14= 1.71499e+03 Focal length 0.656 F-number 2.87 Half-angle 58.98 Image height 0.820 Lens length 2.591 BF 0.020 (Numerical Example 6) Unit: mm Surface data Face number rd nd νd Effective diameter 1 ∞ 0.100 1.51680 64.2 0.63 2 (S1) ∞ 0.045 1.52290 50.3 0.50 3* 0.0937 0.143 0.31 4* 0.1370 0.176 1.52290 50.3 0.26 5 ∞ 0.100 1.51680 64.2 0.18 6(SP) ∞ 0.058 0.12 7* 0.2361 0.077 1.52290 50.3 0.29 8 ∞ 0.400 1.51680 64.2 0.31 9 ∞ 0.020 0.53 Image plane ∞ Aspherical data 3rd page K =-4.35383e+00 ,A4= 3.03083e+02 ,A6=-2.33866e+04 ,A8= 1.21821e+06 ,A10=-3.88120e+07 ,A12= 7.40225e+08 ,A14=-7.20437e+09 Side 4 K =-4.38610e+00 ,A4= 1.61005e+02 ,A6=-1.37464e+04 ,A8= 1.17778e+06 ,A10=-7.39169e+07 ,A12= 2.77408e+09 ,A14=-4.59940e+10 Side 7 K =-3.54983e+01 ,A4= 1.46617e+02 ,A6=-2.13243e+04 ,A8= 1.98907e+06 ,A10=-1.07830e+08 ,A12= 3.09135e+09 ,A14=-3.62056e+10 Focal length 0.218 F-number 2.83 Half-angle 59.00 Image height 0.28 Lens length 1.119 BF 0.020 (Numerical Example 7) Unit: mm Surface data Face number rd nd νd Effective diameter 1 ∞ 0.100 1.51680 64.2 0.57 2(S1) ∞ 0.045 1.52290 50.3 0.43 3* 0.1124 0.130 0.27 4* 0.1500 0.138 1.52290 50.3 0.20 5(SP) ∞ 0.100 1.51680 64.2 0.12 6 ∞ 0.030 0.20 7* 0.2121 0.070 1.52290 50.3 0.28 8 ∞ 0.400 1.51680 64.2 0.30 9 ∞ 0.020 0.56 Image plane ∞ Aspherical data 3rd page K =-1.63505e+01 ,A4= 6.36339e+02 ,A6=-1.01041e+05 ,A8= 1.09655e+07 ,A10=-7.15386e+08 ,A12= 2.49124e+10 ,A14=-3.56161e+11 Side 4 K =-1.07892e+00 ,A4= 6.31243e+01 ,A6=-2.10484e+04 ,A8= 6.27839e+06 ,A10=-1.09374e+09 ,A12= 9.27067e+10 ,A14=-3.06602e+12 Side 7 K =-5.92530e+01 ,A4= 2.36212e+02 ,A6=-4.29304e+04 ,A8= 4.45845e+06 ,A10=-2.69945e+08 ,A12= 8.80798e+09 ,A14=-1.20003e+11 Focal length 0.224 F-number 2.75 Field of view 59.00 Image height 0.280 Lens length 1.034 BF 0.020 (Numerical Example 8) Unit: mm Surface data Face number rd nd νd Effective diameter 1 ∞ 0.100 1.51680 64.2 0.58 2(S1) ∞ 0.050 1.52290 50.3 0.44 3* 0.0974 0.090 0.27 4* 0.1555 0.064 1.59000 31.0 0.21 5 ∞ 0.102 1.51680 64.2 0.17 6(SP) ∞ 0.102 1.51680 64.2 0.11 7 ∞ 0.070 1.52290 50.3 0.21 8* -0.1633 0.020 0.24 9 ∞ 0.400 1.51680 64.2 0.30 10 ∞ 0.020 0.57 Image plane ∞ Aspherical data 3rd page K =-3.01024e+00 ,A4= 2.24250e+02 ,A6=-1.97947e+04 ,A8= 1.18249e+06 ,A10=-4.88341e+07 ,A12= 8.60187e+08 Side 4 K =-1.35803e+01 ,A4= 3.37966e+02 ,A6=-5.66619e+04 ,A8= 6.67495e+06 ,A10=-4.71784e+08 ,A12= 1.36394e+10 Side 8 K = 4.17062e-01 ,A4= 8.23255e+01 ,A6=-4.82286e+03 ,A8= 9.99409e+05 ,A10=-6.40171e+07 ,A12= 1.86036e+09 Focal length 0.207 F-number 2.80 Half-angle 59.00 Image height 0.280 Lens length 1.018 BF 0.020 Table 1 shows the numerical values ​​related to the aforementioned conditional equations (1) to (13) in each numerical example.

[0134] [Table 1]

[0135] The optical systems of each embodiment are suitable for use in imaging optical systems used in cameras embedded in electronic devices such as mobile phones, smartphones, and wearable devices, as well as in objective optical systems for endoscopes. [Examples]

[0136] Next, with reference to Figure 28, the electronic device in Embodiment 9 of the present invention will be described. Figure 28 is a schematic diagram of the main parts of the electronic device (smartphone 70) of this embodiment. The smartphone 70 has an imaging device 71 as a front camera module. The imaging device 71 has an optical system 72 corresponding to any of the optical systems of Embodiments 1 to 8 described above, and an image sensor 73 that receives the image formed by the optical system 72. In this way, by applying the optical systems of each of the embodiments described above to an imaging device such as a smartphone, it is possible to realize an imaging device that is small yet has high optical performance. [Examples]

[0137] Next, with reference to Figure 29, the imaging device in Embodiment 10 of the present invention will be described. Figure 29 is a schematic diagram of the main parts of the imaging device 100 of this embodiment. The imaging device 100 is used in a small endoscope and has a camera head 120 and an electrical cable 150. The camera head 120 has a lens housing 121 equipped with an optical system of any of Embodiments 1 to 8, an image sensor (image element) 122, and a ceramic substrate 123. The wiring of the electrical cable 150 is connected to the image sensor 122 via the ceramic substrate 123. In this way, by applying the optical systems of each of the above embodiments to the imaging device of an endoscope, it is possible to realize an imaging device that is small yet has high optical performance.

[0138] According to each embodiment, it is possible to provide an optical system and imaging device that are compact yet have high optical performance with reduced aberrations.

[0139] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its essence. [Explanation of symbols]

[0140] 1a~1h Optical system 11. First circuit board 12. First lens 21 Second board 22. Second lens 31 Third board 32 Third Lens L1 Unit 1 L2 Unit 2 L3 Unit 3 S1 Flare Cut Aperture SP aperture diaphragm

Claims

1. An optical system consisting of a first unit, a second unit, and a third unit arranged in order from the object side to the image side, The first unit comprises a first substrate, a negative-power first lens positioned on the image side of the first substrate, and a flare-cutting aperture. The second unit comprises a second substrate, a positive-power second lens positioned on the object side of the second substrate, and an aperture diaphragm. The third unit comprises a third substrate and a positive-power third lens positioned on the object side or image side of the third substrate. The circularity of the opening of the flare-cut aperture and the circularity of the opening of the aperture aperture are different from each other. When the focal length of the third lens is f3 and the focal length of the optical system is f, 1.4<f3 / f<3.0 An optical system characterized by satisfying the following condition.

2. The optical system according to claim 1, characterized in that the aperture diaphragm is arranged on the second substrate.

3. The optical system according to claim 1 or 2, characterized in that the flare-cutting aperture is arranged on the first substrate.

4. When the focal length of the second lens is f2, 0.60<f2 / f<1.60 The optical system according to any one of claims 1 to 3, characterized in that it satisfies the following conditional expression.

5. An optical system comprising a first unit, a second unit, and a third unit arranged in order from the object side to the image side, The first unit comprises a first substrate, a negative-power first lens positioned on the image side of the first substrate, and a flare-cutting aperture. The second unit comprises a second substrate, a positive-power second lens positioned on the object side of the second substrate, and an aperture diaphragm. The third unit comprises a third substrate and a positive-power third lens positioned on the object side or image side of the third substrate. The circularity of the opening of the flare-cut aperture and the circularity of the opening of the aperture aperture are different from each other. When the focal length of the second lens is f2 and the focal length of the optical system is f, 0.60<f2 / f<1.60 An optical system characterized by satisfying the following conditional equation.

6. When the focal length of the first lens is f1, -3.5<f3 / f1<-1.5 The optical system according to any one of claims 1 to 5, characterized in that it satisfies the following conditional expression.

7. An optical system comprising a first unit, a second unit, and a third unit arranged in order from the object side to the image side, The first unit comprises a first substrate, a negative-power first lens positioned on the image side of the first substrate, and a flare-cutting aperture. The second unit comprises a second substrate, a positive-power second lens positioned on the object side of the second substrate, and an aperture diaphragm. The third unit comprises a third substrate and a positive-power third lens positioned on the object side or image side of the third substrate. The circularity of the opening of the flare-cut aperture and the circularity of the opening of the aperture aperture are different from each other. When the focal length of the first lens is f1 and the focal length of the third lens is f3, -3.5<f3 / f1<-1.5 An optical system characterized by satisfying the following conditional equation.

8. When the focal length of the first lens is f1 and the focal length of the second lens is f2, 0.30<(f2-f1) / f3<1.60 The optical system according to any one of claims 1 to 7, characterized in that it satisfies the following conditional expression.

9. An optical system comprising a first unit, a second unit, and a third unit arranged in order from the object side to the image side, The first unit comprises a first substrate, a negative-power first lens positioned on the image side of the first substrate, and a flare-cutting aperture. The second unit comprises a second substrate, a positive-power second lens positioned on the object side of the second substrate, and an aperture diaphragm. The third unit comprises a third substrate and a positive-power third lens positioned on the object side or image side of the third substrate. The circularity of the opening of the flare-cut aperture and the circularity of the opening of the aperture aperture are different from each other. When the focal length of the first lens is f1 and the focal length of the second lens is f2, 0.30<(f2-f1) / f3<1.60 An optical system characterized by satisfying the following conditional equation.

10. When the distance along the optical axis from the aperture diaphragm to the object-side surface of the third lens is d, 0.03<d / f3<0.40 The optical system according to any one of claims 1 to 9, characterized in that it satisfies the following conditional expression.

11. An optical system comprising a first unit, a second unit, and a third unit arranged in order from the object side to the image side, The first unit comprises a first substrate, a negative-power first lens positioned on the image side of the first substrate, and a flare-cutting aperture. The second unit comprises a second substrate, a positive-power second lens positioned on the object side of the second substrate, and an aperture diaphragm. The third unit comprises a third substrate and a positive-power third lens positioned on the object side or image side of the third substrate. The circularity of the opening of the flare-cut aperture and the circularity of the opening of the aperture aperture are different from each other. When the distance along the optical axis from the aperture diaphragm to the object-side surface of the third lens is d, and the focal length of the third lens is f3, 0.03<d / f3<0.40 An optical system characterized by satisfying the following conditional equation.

12. When L is the distance along the optical axis from the image-side surface of the third lens to the image plane, 1.0<L / f<2.4 The optical system according to any one of claims 1 to 11, characterized in that it satisfies the following conditional expression.

13. When the thickness of the first substrate is d1, the thickness of the second substrate is d2, and the distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second substrate is Lar, 0.60<Lar / (d1+d2)<2.00 The optical system according to any one of claims 1 to 12, characterized in that it satisfies the following conditional expression.

14. An optical system comprising a first unit, a second unit, and a third unit arranged in order from the object side to the image side, The first unit comprises a first substrate, a negative-power first lens positioned on the image side of the first substrate, and a flare-cutting aperture. The second unit comprises a second substrate, a positive-power second lens positioned on the object side of the second substrate, and an aperture diaphragm. The third unit comprises a third substrate and a positive-power third lens positioned on the object side or image side of the third substrate. The circularity of the opening of the flare-cut aperture and the circularity of the opening of the aperture aperture are different from each other. When the thickness of the first substrate is d1, the thickness of the second substrate is d2, and the distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second substrate is Lar, 0.60<Lar / (d1+d2)<2.00 An optical system characterized by satisfying the following conditional equation.

15. When R1 is the ratio of the maximum effective diameter to the minimum effective diameter of the aperture of the flare-cut diaphragm, and Rs is the ratio of the maximum effective diameter to the minimum effective diameter in the imaging region of the image plane, 0.72<R1 / Rs<1.20 The optical system according to any one of claims 1 to 14, characterized in that it satisfies the following conditional expression.

16. When E1 is the difference between the effective diameter of the object-side surface of the optical system and the effective diameter of the first lens, and Y is the maximum image height, 0.8<E1 / Y<1.5 The optical system according to any one of claims 1 to 15, characterized in that it satisfies the following conditional expression.

17. When the distortion at the maximum image height of the optical system is denoted as DST (%), -40<DST<-10 The optical system according to any one of claims 1 to 16, characterized in that it satisfies the following conditional expression.

18. The optical system according to any one of claims 1 to 17, characterized in that the materials of the first substrate and the first lens are different from each other.

19. The optical system according to any one of claims 1 to 18, characterized in that the materials of the second substrate and the second lens are different from each other.

20. The optical system according to any one of claims 1 to 19, characterized in that the materials of the third substrate and the third lens are different from each other.

21. When the maximum effective diameter of the aperture diaphragm is Fsp, the maximum effective diameter of the flare-cut diaphragm is Fs1, the maximum half-angle of view is W1 (degrees), the average refractive index of the first substrate and the first lens of the first unit is N1A, and the distance between the aperture diaphragm and the flare-cut diaphragm on the optical axis is ds, 30 (degrees)<(ds×W1) / ((Fs1-Fsp)×N1A)<70(degrees) The optical system according to any one of claims 1 to 20, characterized in that it satisfies the following conditional expression.

22. When the focal length of the optical system is f (mm), the focal length of the first lens is f1 (mm), the distance between the first unit and the second unit on the optical axis is d12 (mm), the maximum effective diameter of the aperture diaphragm is Fsp (mm), the maximum effective diameter of the flare cut diaphragm is Fs1 (mm), the maximum half-angle of view is W1 (degrees), the average refractive index of the first substrate and the first lens of the first unit is N1A, and the distance between the aperture diaphragm and the flare cut diaphragm on the optical axis is ds (mm), 25<((ds×W1) / N1A+16×f / f1×d12) / (Fs1-Fsp)<60 The optical system according to any one of claims 1 to 21, characterized in that it satisfies the following conditional expression.

23. An imaging device characterized by having an optical system according to any one of claims 1 to 22 and an image sensor that receives an image formed by the optical system.

Images