Optical system and imaging device having the same

Abstract

To provide a compact optical system with high optical performance and an imaging device having the same. [Solution] The optical system L0 consists of a front group La, an aperture diaphragm SP, and a rear group Lb with a positive refractive power as a whole, arranged in order from the object side to the image side. The rear group includes a final lens Lp with a positive refractive power that is positioned closest to the image side. The distance TTL on the optical axis from the object-side lens surface to the image plane of the lens positioned closest to the object in the optical system, the diameter Φi of the image circle, the average value PNdave of the refractive index at the d line of all positive lenses included in the optical system, the effective diameter Φp at the image-side lens surface of the final lens, and the air-equivalent length sk of the distance on the optical axis from the image-side lens surface to the image plane of the final lens satisfy a predetermined conditional equation.

Description

Technical Field

[0001] The present invention relates to an optical system and is suitable for digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, etc.

Background Art

[0002] In recent years, with the miniaturization and high pixel count of imaging devices, the optical systems used in imaging devices are required to be small and have high optical performance.

[0003] Patent Document 1 describes an optical system including a first lens with positive refractive power, a second lens with negative refractive power, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in order from the object side to the image side.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] An optical system as one aspect of the present invention is an optical system comprising a front group, an aperture diaphragm, and a rear group having a positive refractive power as a whole, arranged in order from the object side to the image side, wherein the front group consists of one positive lens, and the rear group includes a final lens with positive refractive power that is positioned furthest towards the image side in the rear group, and when TTL is the distance along the optical axis from the lens surface on the object side of the lens furthest towards the object side in the optical system to the image plane, Φi is the diameter of the image circle, PNdave is the average refractive index of the materials of all positive lenses included in the optical system at the d line, Φp is the effective diameter at the lens surface on the image side of the final lens, and sk is the air-equivalent length of the distance along the optical axis from the lens surface on the image side of the final lens to the image plane, 0.5 <TTL / Φi<1.4 1.64 <PNdave<2.00 2.0 < Φp / sk < 4.0 It is characterized by satisfying the following conditional expression. Other objects and features of the present invention are described in the following embodiments. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a compact optical system with high optical performance and an imaging device having the same. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view of the optical system of Example 1. [Figure 2] This is an aberration diagram for Example 1 when the object is in focus at infinity. [Figure 3] This is a cross-sectional view of the optical system of Example 2. [Figure 4] This is an aberration diagram for Example 2 when the object is in focus at infinity. [Figure 5] This is a cross-sectional view of the optical system of Example 3. [Figure 6]It is an aberration diagram at infinity focus in Example 3. [Figure 7] It is a cross-sectional view of the optical system of Example 4. [Figure 8] It is an aberration diagram at infinity focus in Example 4. [Figure 9] It is a cross-sectional view of the optical system of Example 5. [Figure 10] It is an aberration diagram at infinity focus in Example 5. [Figure 11] It is a cross-sectional view of the optical system of Example 6. [Figure 12] It is an aberration diagram at infinity focus in Example 6. [Figure 13] It is a cross-sectional view of the optical system of Example 7. [Figure 14] It is an aberration diagram at infinity focus in Example 7. [Figure 15] It is a schematic diagram of the imaging device.

Modes for Carrying Out the Invention

[0011] Hereinafter, examples of the optical system of the present invention and an imaging device having the same will be described based on the accompanying drawings.

[0012] FIGS. 1, 3, 5, 7, 9, 11, and 13 are cross-sectional views of the optical system L0 at infinity focus in Examples 1 to 7, respectively. The optical system L0 of each example is an optical system used in an imaging device such as a digital video camera, a digital still camera, a broadcast camera, a silver halide film camera, or a surveillance camera.

[0013] In each lens cross-sectional view, the left side is the object side and the right side is the image side. The optical system L0 of each example is configured to have a plurality of lenses.

[0014] In each lens cross-sectional view, La represents the front group, Lb represents the rear group, and Lp represents the lens with positive refractive power (the final lens) arranged on the most image side among the lenses included in the rear group Lb.

[0015] Furthermore, SP is an aperture diaphragm. IP is the image plane (paraxial), and when the optical system L0 of each embodiment is used as the imaging optical system of a digital still camera or digital video camera, the imaging surface of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed thereon. When the optical system L0 of each embodiment is used as the imaging optical system of a silver halide film camera, a photosensitive surface corresponding to the film surface is placed on the image plane IP. In this specification, the "front group La" and the "rear group Lb" may consist of multiple lenses or a single lens.

[0016] Figures 2, 4, 6, 8, 10, 12, and 14 are aberration diagrams of the optical systems L0 of Examples 1 to 7 when focused at infinity.

[0017] In the spherical aberration diagram, Fno is the F-number and indicates the amount of spherical aberration for the d-line (wavelength 587.56 nm) and the g-line (wavelength 435.84 nm). In the astigmatism diagram, dS indicates the amount of astigmatism at the sagittal image plane, and dM indicates the amount of astigmatism at the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of chromatic aberration at the g-line is shown. ω is the half-angle of view (°).

[0018] Next, we will describe the characteristic configuration of the optical system L0 in each embodiment.

[0019] The optical system L0 of each embodiment is an optical system consisting of a front group La, an aperture diaphragm SP, and a rear group Lb with a positive refractive power as a whole, arranged in order from the object side to the image side. The rear group Lb includes a final lens Lp with a positive refractive power, which is located closest to the image side.

[0020] Generally, when a lens is placed close to the image plane IP, the height of the off-axis light beam incident on that lens increases, thus strengthening the refracting force on the off-axis light beam. In the optical system L0 of each embodiment, the rear group Lb is given a positive refractive power, and the final lens Lp, which is a large-aperture lens with a positive refractive power located on the image side of the rear group Lb, is placed to appropriately refract the off-axis light beam, correcting pincushion distortion and suppressing the angle of incidence of the off-axis light beam on the image plane.

[0021] Furthermore, the optical system L0 of each embodiment satisfies the following condition (1).

[0022] 0.5 <TTL / Φi<1.4 ···(1) Here, TTL is the distance along the optical axis from the object-side lens surface to the image plane IP of the lens positioned closest to the object in the optical system L0 (total lens length). In other words, it is the length obtained by adding the back focus to the distance along the optical axis from the object-side lens surface to the image-side lens surface in the optical system L0. Φi is the diameter of the image circle.

[0023] Condition (1) specifies the ratio of the total lens length to the diameter of the image circle. If the ratio exceeds the upper limit of condition (1), the total lens length becomes too long. If the ratio falls below the lower limit of condition (1) and the diameter of the image circle becomes too large, it becomes difficult to correct both field curvature and distortion simultaneously.

[0024] In this specification, the image circle is defined as a circle whose radius is the height from the optical axis of the light beam that reaches the position furthest from the optical axis among the light beams reaching the image plane IP when the image is focused at infinity. The diameter of the image circle corresponds to twice the image height of the optical system L0. If the ratio of the image plane illumination of the off-axis light beam to the on-axis light beam is less than 20%, the off-axis light beam may be considered not to have reached the image plane IP. Furthermore, when the focal length of the optical system L0 is f and the half-angle of view (°) is ω, the diameter of the image circle Φi may also be expressed as Φi = 2 × f × tanω.

[0025] If the optical system L0 is a zoom lens, TTL is the distance from the object-side lens surface of the lens positioned closest to the object at the wide-angle end to the image plane IP, and Φi is the diameter of the image circle at the wide-angle end.

[0026] Furthermore, the optical system L0 of each embodiment satisfies the following condition (2).

[0027] 1.64 <PNdave<2.00 ···(2) Here, PNdave is the average value (average refractive index) of the refractive indices of all positive lenses included in the optical system L0 at the d line (wavelength 587.56 nm).

[0028] Condition (2) specifies the average refractive index of all positive lenses included in the optical system L0. If the refractive index is higher than the upper limit of condition (2), the dispersion of colors increases, making it difficult to correct axial chromatic aberration. If the refractive index is lower than the lower limit of condition (2), the Petzval sum of the entire optical system L0 increases, making it difficult to correct field curvature.

[0029] Furthermore, the optical system L0 of each embodiment satisfies the following condition (3).

[0030] 2.0 < Φp / sk < 4.0 ···(3) Here, Φp is the effective diameter at the image-side lens surface of the final lens Lp. sk is the air-equivalent length (back focus) of the distance along the optical axis from the image-side lens surface of the final lens Lp to the image plane IP.

[0031] Conditional equation (3) specifies the ratio of the effective diameter at the image-side lens surface of the final lens Lp to the back focus. If the effective diameter of the final lens Lp is large enough to exceed the upper limit of conditional equation (3), the optical system L0 becomes larger in the radial direction. If the effective diameter of the final lens Lp is small enough to fall below the lower limit of conditional equation (3), the incident height of the off-axis light beam incident on the final lens Lp becomes low, and the refractive effect on the off-axis light beam becomes small. This makes it difficult to correct pincushion distortion and suppress the angle of incidence on the image plane.

[0032] In this specification, the effective diameter of a lens is defined as the diameter of a circle whose radius is the height from the optical axis of the ray passing through the lens surface at the point furthest from the optical axis. Alternatively, the effective diameter may be defined as the diameter of a circle inscribed within a mechanical component such as a retaining ring or crimping claw on the lens surface, or, if no mechanical component is present, the diameter of a circle connecting the outermost edges of surfaces generally formed by polishing or molding. When the optical system L0 is a zoom lens, sk is the back focus of the zoom lens at the wide-angle end, and Φp is the effective diameter of the image-side lens surface of the final lens Lp at the wide-angle end.

[0033] Furthermore, it is preferable that the numerical ranges of conditional expressions (1) to (3) be the numerical ranges of the following conditional expressions (1a) to (3a).

[0034] 0.9 <TTL / Φi<1.38 ···(1a) 1.64 <PNdave<1.85 ···(2a) 2.2 < Φp / sk < 3.5 ···(3a) Furthermore, it is even more preferable to set the numerical ranges of conditional expressions (1) to (3) to the numerical ranges of the following conditional expressions (1b) to (3b).

[0035] 0.95 <TTL / Φi<1.37 ···(1b) 1.641 <PNdave<1.792 ···(2b) 2.4 < Φp / sk < 3.2 ···(3b) Next, we will describe the conditions and configurations that are preferable for the optical system L0 of each embodiment to satisfy. It is preferable that the optical system L0 of each embodiment satisfies one or more of the following conditions (4) to (14) and configurations.

[0036] In each embodiment, the optical system L0 preferably satisfies the following condition (4), where fa is the focal length of the front group La and f is the focal length of the optical system L0.

[0037] 0.1 <f / |fa|<1.5 ···(4) Conditional equation (4) specifies the ratio of the focal length of the front lens group La to the focal length of the optical system L0. If the refractive power of the front lens group La becomes too strong, exceeding the upper limit of conditional equation (4), pincushion distortion increases, making it difficult to achieve both field curvature and distortion, which is undesirable. If the refractive power of the front lens group La becomes too weak, falling below the lower limit of conditional equation (4), the optical system approaches a telecentric shape on the image side, the position of the exit pupil becomes farther from the image plane IP, and the overall length of the lens increases, which is also undesirable. Note that if the optical system L0 is a zoom lens, f is the focal length of the zoom lens at the wide-angle end.

[0038] In each embodiment, the optical system L0 preferably satisfies the following condition (5), when the focal length of the final lens Lp is fp.

[0039] 0.6 <fp / f<6.0 ···(5) Conditional equation (5) specifies the ratio of the focal length of the final lens Lp to the focal length of the optical system L0. If the refractive power of the final lens Lp is weaker than the upper limit of conditional equation (5), it becomes difficult to correct pincushion distortion and suppress the angle of incidence on the image plane, which is undesirable. If the refractive power of the final lens Lp is stronger than the lower limit of conditional equation (5), it approaches a telecentric optical system on the image side, and the overall length of the lens increases, which is also undesirable.

[0040] The optical system L0 of each embodiment preferably satisfies the following condition (6).

[0041] 0.1 <sk / f<0.7 ···(6) Conditional equation (6) specifies the ratio of the back focus to the focal length of the optical system L0. If the back focus is longer than the upper limit of conditional equation (6), the overall length of the lens will increase, which is undesirable. If the back focus is shorter than the lower limit of conditional equation (6), the effective diameter of the final lens Lp located on the image side will increase, and the optical system L0 will become larger in the radial direction, which is also undesirable.

[0042] In each embodiment, the optical system L0 preferably satisfies the following condition (7), where SPIP is the distance along the optical axis from the aperture diaphragm SP to the image plane IP.

[0043] 0.6 <SPIP / TTL<1.0 ···(7) Conditional equation (7) specifies the ratio of the position of the aperture diaphragm SP to the total length of the lens of the optical system L0. If the position of the aperture diaphragm SP is on the object side, exceeding the upper limit of conditional equation (7), vignetting bias is likely to occur, resulting in an abnormal shape of bokeh, which is undesirable. If the position of the aperture diaphragm SP is on the image side, below the lower limit of conditional equation (7), the exit pupil approaches the image plane IP, making it difficult to suppress the angle of incidence of off-axis light beams on the image plane, which is also undesirable. Note that if the optical system L0 is a zoom lens, SPIP is the distance from the aperture diaphragm SP of the zoom lens to the image plane IP at the wide-angle end.

[0044] In the optical system L0 of each embodiment, the rear group Lb preferably includes at least four lenses. This corrects both axial chromatic aberration and lateral chromatic aberration.

[0045] In the optical system L0 of each embodiment, it is preferable that the rear group Lb includes a negative lens Ln (first negative lens) positioned on the object side of the final lens Lp in order to correct chromatic aberration and field curvature.

[0046] In each embodiment, the optical system L0 preferably satisfies the following condition (8), where R1 is the paraxial radius of curvature of the object-side lens surface of the negative lens Ln, and R2 is the paraxial radius of curvature of the image-side lens surface of the negative lens Ln.

[0047] 0.0<(R1+R2) / (R2-R1)<50.0 (8) Conditional equation (8) defines the shape of the negative lens Ln. If the values ​​of R1 and R2 approach each other beyond the upper limit of conditional equation (8), the refractive power of the negative lens Ln weakens, resulting in insufficient correction of chromatic aberration, which is undesirable. If the values ​​fall below the lower limit of conditional equation (8), the radius of curvature of the image-side lens surface of the negative lens Ln becomes small, making it difficult to correct both field curvature and distortion, which is also undesirable.

[0048] In each embodiment, the optical system L0 preferably satisfies the following condition (9), where Ndn is the refractive index of the negative lens Ln at the d line and νdn is the Abbe number at the d line of the negative lens Ln.

[0049] 1.500 <Ndn<4.1945 / νdn+1.520 ···(9) Conditional equation (9) specifies the refractive index of the negative lens Ln. If the refractive index of the negative lens Ln is high, exceeding the upper limit of conditional equation (9), the Petzval sum of the entire optical system L0 becomes large, making it difficult to correct field curvature, which is undesirable. If the refractive index of the negative lens Ln is low, falling below the lower limit of conditional equation (9), it becomes impossible to select a material with high dispersion, resulting in insufficient correction of chromatic aberration, which is also undesirable.

[0050] In each embodiment, the optical system L0 preferably satisfies the following condition (10) when the focal length of the rear group Lb is fb.

[0051] 0.10 <fb / |fa|<10.00 ···(10) Conditional equation (10) specifies the ratio of the focal length of the front group La to the focal length of the rear group Lb. If the positive refractive power of the rear group Lb weakens beyond the upper limit of conditional equation (10), it becomes difficult to correct pincushion distortion and suppress the angle of incidence on the image plane, which is undesirable. If the refractive power of the rear group Lb strengthens below the lower limit of conditional equation (10), the optical system approaches a telecentric shape on the image side, and the overall length of the lens increases, which is also undesirable.

[0052] In the optical system L0 of each embodiment, the front group La includes a positive lens Lap (first positive lens), and when the refractive index of the positive lens Lap at the d line is Ndap, it is preferable that the following condition (11) is satisfied.

[0053] 1.60 <Ndap<2.00 ···(11) Conditional equation (11) specifies the refractive index of the positive lens Lap. If the refractive index of the positive lens Lap is higher than the upper limit of conditional equation (11), the dispersion of colors will increase, making it difficult to correct axial chromatic aberration, which is undesirable. If the refractive index of the positive lens Lap is lower than the lower limit of conditional equation (11), the Petzval sum of the entire optical system L0 will increase, making it difficult to correct field curvature, which is also undesirable.

[0054] In the optical system L0 of each embodiment, the rear group Lb includes a positive lens Lbp (second positive lens), and when the refractive index of the positive lens Lbp at the d line is Ndbp, it is preferable that the following condition (12) is satisfied.

[0055] 1.60 <Ndbp<2.00 ···(12) Conditional equation (12) specifies the refractive index of the positive lens Lbp. If the refractive index of the positive lens Lbp is higher than the upper limit of conditional equation (12), the dispersion of colors will increase, making it difficult to correct axial chromatic aberration, which is undesirable. If the refractive index of the positive lens Lbp is lower than the lower limit of conditional equation (12), the Petzval sum of the entire optical system L0 will increase, making it difficult to correct field curvature, which is also undesirable.

[0056] In the optical system L0 of each embodiment, the rear group Lb includes a negative lens Lbn (second negative lens), and when the refractive index of the negative lens Lbn at the d line is Ndbn, it is preferable that the following condition (13) is satisfied.

[0057] 0.00 <Ndbp-Ndbn<0.40 ···(13) Conditional equation (13) specifies the refractive index difference between the positive lens Lbp and the negative lens Lbn. Selecting a material with a refractive index difference that exceeds the upper limit of conditional equation (13) is undesirable because it makes achromatic aberration difficult and the correction of axial chromatic aberration is insufficient. Selecting a material with a refractive index difference that falls below the lower limit of conditional equation (13) is undesirable because it increases the Petzval sum of the entire optical system L0, making it difficult to correct field curvature.

[0058] In each embodiment, the optical system L0 preferably satisfies the following condition (14), where Φa is the largest effective diameter of the lens having the largest effective diameter in the front group La.

[0059] 1.0 < Φp / Φa < 4.0 ···(14) Conditional equation (14) specifies the ratio of the effective diameter of the front group La to the effective diameter of the final lens Lp, which is positioned closest to the image. If the effective diameter of the final lens Lp is larger than the upper limit of conditional equation (14), it is undesirable because the optical system L0 becomes larger in the radial direction. If the effective diameter of the final lens Lp is smaller than the lower limit of conditional equation (14), it is undesirable because it becomes difficult to correct pincushion distortion and suppress the angle of incidence on the image plane.

[0060] In order to achieve both high optical performance and miniaturization, the optical system L0 of each embodiment is preferably composed of 5 to 8 lenses.

[0061] Furthermore, it is more preferable that the numerical ranges of conditional expressions (4) to (14) be within the ranges of conditional expressions (4a) to (14a) below.

[0062] 0.15 <f / |fa|<1.40 ···(4a) 0.7 <fp / f<5.0 ···(5a) 0.2 <sk / f<0.6 ···(6a) 0.70 <SPIP / TTL<0.95 ···(7a) 0.5<(R1+R2) / (R2-R1)<25.0 (8a) 1.510 <Ndn<4.1945 / νdn+1.500 ···(9a) 0.15 <fb / |fa|<8.50 ···(10a) 1.61 <Ndap<1.95 ···(11a) 1.70 <Ndbp<1.95 ···(12a) 0.00 <Ndbp-Ndbn<0.30 ···(13a) 1.2 < Φp / Φa < 3.0 ···(14a) Furthermore, it is even more preferable that the numerical ranges of conditional expressions (4) to (14) be within the ranges of the following conditional expressions (4b) to (9b).

[0063] 0.19 <f / |fa|<1.30 ···(4b) 0.9 <fp / f<4.2 ···(5b) 0.3 <sk / f<0.5 ···(6b) 0.76 <SPIP / TTL<0.91 ···(7b) 1.0<(R1+R2) / (R2-R1)<13.0 (8b) 1.520 <Ndn<4.1945 / νdn+1.470 ···(9b) 0.19 <fb / |fa|<7.50 ···(10b) 1.615 <Ndap<1.920 ···(11b) 1.75 <Ndbp<1.91 ···(12b) 0.015 <Ndbp-Ndbn<0.262 ···(13b) 1.5 < Φp / Φa < 2.7 ···(14b) In addition, in the optical system L0 of each embodiment, optical elements such as cover glass or IR cut filter may be placed between the final lens Lp and the image plane IP. Furthermore, the refractive power of the lens represents the refractive power near the optical axis (paraxial).

[0064] Next, the optical system L0 of each embodiment will be described in detail.

[0065] The optical system L0 of Example 1 consists of a front group La, an aperture diaphragm SP, and a rear group Lb with an overall positive refractive power, arranged in order from the object side to the image side. The front group La consists of a single positive lens. The rear group Lb consists of a cemented lens of a positive and negative lens, a negative lens, a positive lens, and a positive lens, arranged in order from the object side to the image side.

[0066] The optical system L0 of Example 2 consists of a front group La, an aperture diaphragm SP, and a rear group Lb with an overall positive refractive power, arranged in order from the object side to the image side. The front group La consists of a positive lens and a negative lens, arranged in order from the object side to the image side. The rear group Lb consists of a cemented lens of a negative lens and a positive lens, a negative lens, a negative lens, and a positive lens, arranged in order from the object side to the image side.

[0067] The optical system L0 of Example 3 consists of a front group La, an aperture diaphragm SP, and a rear group Lb with an overall positive refractive power, arranged in order from the object side to the image side. The front group La consists of a single positive lens. The rear group Lb consists of a cemented lens of a negative lens and a positive lens, a negative lens, a negative lens, and a positive lens, arranged in order from the object side to the image side.

[0068] The optical system L0 of Example 4 consists of a front group La, an aperture diaphragm SP, and a rear group Lb with an overall positive refractive power, arranged in order from the object side to the image side. The front group La consists of a single positive lens. The rear group Lb consists of a cemented lens of a negative lens and a positive lens, a negative lens, a negative lens, a negative lens, and a positive lens, arranged in order from the object side to the image side.

[0069] The optical system L0 of Example 5 consists of a front group La, an aperture diaphragm SP, and a rear group Lb with an overall positive refractive power, arranged in order from the object side to the image side. The front group La consists of a negative lens and a positive lens, arranged in order from the object side to the image side. The rear group Lb consists of a cemented lens of a positive and a negative lens, a negative lens, a positive lens, and a positive lens, arranged in order from the object side to the image side.

[0070] The optical system L0 of Example 6 consists of a front group La, an aperture diaphragm SP, and a rear group Lb with an overall positive refractive power, arranged in order from the object side to the image side. The front group La is composed of a cemented lens of a negative lens and a positive lens, arranged in order from the object side to the image side. The rear group Lb is composed of a cemented lens of a positive lens and a negative lens, a negative lens, a positive lens, and a positive lens, arranged in order from the object side to the image side.

[0071] The optical system L0 of Example 7 consists of a front group La, an aperture diaphragm SP, and a rear group Lb with an overall positive refractive power, arranged in order from the object side to the image side. The front group La consists of a negative lens and a positive lens, arranged in order from the object side to the image side. The rear group Lb consists of a positive lens, a cemented lens of a positive and a negative lens, a negative lens, a positive lens, and a positive lens, arranged in order from the object side to the image side.

[0072] The numerical values ​​corresponding to Examples 1 to 7 are shown below.

[0073] In the surface data for each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axial spacing (distance along the optical axis) between the m-th surface and the (m+1)-th surface. Here, m is the surface number counted from the light incident side. Also, nd represents the refractive index of each optical element with respect to the d line, and νd represents the Abbe number of the optical element. Note that the Abbe number νd of a certain material is expressed as νd = (Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices at the Fraunhofer lines d-line (587.56 nm), F-line (486.13 nm), and C-line (656.27 nm).

[0074] In each numerical example, d, focal length (mm), F-number, and half-angle of view (°) are all values ​​when the optical system of each example is focused on an object at infinity. "Back focus" is the distance along the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed in terms of air equivalent length. "Total lens length" is the length obtained by adding the back focus to the distance along the optical axis from the frontmost lens surface (the lens surface closest to the object) to the final surface of the optical system.

[0075] Furthermore, if the optical surface is aspherical, the symbol * is added to the right of the surface number. The aspherical shape is defined as follows, where X is the displacement from the surface vertex in the optical axis direction, H is the height from the optical axis perpendicular to the optical axis, R is the paraaxial radius of curvature, K is the cone constant, and A3 to A15 are the aspherical coefficients of each order.

[0076]

number

[0077] It is expressed by the following formula. Note that "e±XX" in each aspherical coefficient is "×10± XX It means "...".

[0078] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd Effective diameter 1 6.260 0.86 1.72916 54.7 4.80 2 10.445 0.67 4.58 3 (aperture) ∞ 0.90 4.47 4 6.769 1.21 1.90043 37.4 4.14 5 -17.277 0.50 1.74077 27.8 3.80 6 5.222 1.38 3.35 7* -17.501 0.71 1.63560 23.9 4.36 8* -102.984 1.65 5.27 9* -6.645 1.30 1.63560 23.9 7.43 10* -6.698 0.36 8.53 11* 5.559 1.95 1.53500 56.0 12.13 12* 7.159 (variable) 12.62 Image plane ∞ Aspherical data Side 7 K = 0.00000e+00 A 4=-1.07563e-02 A 6=-1.05029e-02 A 8=-6.35129e-04 A 3= 4.83637e-03 A 5= 1.12736e-02 A 7= 4.29894e-03 Side 8 K = 0.00000e+00 A 4= 7.30840e-03 A 6=-4.56636e-04 A 8=-9.60399e-05 A 3=-2.56213e-03 A 5=-4.86845e-03 A 7= 7.05515e-04 9th page K = 1.46022e+00 A 4= 3.50415e-02 A 6= 2.52119e-04 A 8=-1.67257e-04 A10 = 2.35759e-06 A 3=-1.55185e-02 A 5=-1.27191e-02 A 7= 8.24290e-04 Side 10 K =-1.25577e+00 A 4= 1.62098e-02 A 6= 1.87296e-03 A 8= 5.42303e-06 A10 = -2.12988e-08 A 3=-3.98973e-03 A 5=-8.68766e-03 A 7=-1.76229e-04 Page 11 K =-1.44696e+01 A 4= 7.50341e-03 A 6= 1.22100e-03 A 8=-8.39694e-05 A10 = -4.58570e-07 A 3= 3.44333e-03 A 5=-6.75667e-03 A 7= 1.70998e-04 A 9= 1.04779e-05 Side 12 K =-1.20114e+01 A 4=-8.25372e-03 A 6=-4.77190e-03 A 8=-2.89053e-04 A10 = -1.08364e-06 A 3= 2.30350e-03 A 5= 7.76429e-03 A 7= 1.58451e-03 A 9= 2.76387e-05 Various data Focal length 13.82 F-number 2.88 Half-angle (°): 29.72 Image height 7.89 Lens length: 16.32 BF 4.83 d12 4.83 Single lens data Lens starting plane, focal length 1 1 19.72 2 4 5.53 3 5 -5.36 4 7 -33.28 5 9 154.89 6 11 32.60 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd Effective diameter 1 8.535 1.78 1.72916 54.7 8.35 2 54.576 1.59 7.97 3 1116.973 0.50 1.76182 26.5 6.96 4 15.804 1.18 6.63 5 (aperture) ∞ 1.00 6.34 6 -16.891 0.50 1.63980 34.5 6.09 7 5.764 2.04 1.90043 37.4 5.98 8 -19.006 0.33 6.27 9* 9.018 0.55 1.61550 25.8 6.74 10* 6.674 2.94 7.04 11* -4.712 1.80 1.67070 19.3 7.95 12* -6.144 0.16 9.79 13* 8.031 1.93 1.53110 56.0 12.23 14* 10.796 (variable) 13.08 Image plane ∞ Aspherical data 9th page K = 0.00000e+00 A 4=-1.84389e-03 A 6=-1.16302e-04 A 8= 4.41572e-06 A10= 1.25231e-07 A12=-7.95831e-09 Side 10 K = 0.00000e+00 A 4=-1.02522e-03 A 6=-1.31968e-04 A 8= 8.52375e-06 A10=-9.50218e-08 A12=-2.02084e-09 Page 11 K = 0.00000e+00 A 4= 5.16315e-03 A 6=-3.54315e-04 A 8= 2.68121e-05 A10=-1.19044e-06 A12= 2.36728e-08 Side 12 K = 0.00000e+00 A 4= 1.70854e-03 A 6=-8.20838e-05 A 8= 4.87853e-06 A10=-1.77527e-07 A12= 2.49283e-09 Page 13 K =-9.97557e+00 A 4=-1.35719e-03 A 6= 1.42774e-05 A 8= 8.19110e-07 A10=-4.84714e-08 A12= 9.59127e-10 A14=-6.48919e-12 Page 14 K =-2.08501e+01 A 4=-9.41503e-04 A 6=-1.72682e-05 A 8= 1.41035e-06 A10=-4.48295e-08 A12= 6.50318e-10 A14=-3.78611e-12 Various data Focal length 17.20 F-number 2.06 Half-angle (°): 24.65 Image height 7.89 Lens length: 21.52 BF 5.22 d14 5.22 Single lens data Lens starting plane, focal length 1 1 13.65 2 3 -21.05 3 6 -6.66 4 7 5.11 5 9 -45.81 6 11 -60.86 7 13 47.55 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd Effective diameter 1 4.707 1.13 1.61800 63.4 5.68 2 9.145 1.07 4.97 3 (aperture) ∞ 0.88 3.73 4 -13.939 0.40 1.60342 38.0 3.47 5 4.094 1.49 1.85150 40.8 3.37 6 -10.702 0.16 3.89 7* -20.317 0.92 1.63560 23.9 4.05 8* 16.176 2.24 4.80 9* -2.684 1.11 1.67070 19.3 5.38 10* -4.213 0.07 7.49 11 144.002 2.21 1.90366 31.3 11.56 12 -15.708 (variable) 12.19 Image plane ∞ Aspherical data Side 7 K = 0.00000e+00 A 4=-4.18307e-03 A 6= 1.49689e-03 A 8=-8.47348e-04 A10= 2.67501e-04 A12=-3.97751e-05 A14= 2.16051e-06 Side 8 K = 0.00000e+00 A 4=-2.16772e-03 A 6= 5.73321e-04 A 8=-1.35772e-04 A10=2.41817e-05 A12=-1.37987e-06 A14=-9.50059e-09 9th page K =-4.70448e+00 A 4=-2.76003e-02 A 6= 5.61591e-03 A 8=-1.38408e-03 A10= 2.30576e-04 A12=-2.32076e-05 A14= 9.79590e-07 Side 10 K = 0.00000e+00 A 4= 1.27980e-03 A 6= 5.55638e-05 A 8=-5.37022e-06 A10= 9.26509e-07 A12=-6.95746e-08 A14= 2.53834e-09 Various data Focal length 12.64 F-number 2.91 Half-angle (°): 31.97 Image height 7.89 Lens length: 15.87 BF 4.19 d12 4.19 Single lens data Lens starting plane, focal length 1 1 14.30 2 4 -5.20 3 5 3.65 4 7 -14.03 5 9 -15.58 6 11 15.78 [Numerical Example 4] Unit: mm Surface data Face number rd nd νd Effective diameter 1 4.508 1.10 1.69680 55.5 5.41 2 10.717 1.00 4.80 3 (aperture) ∞ 1.02 3.90 4 -13.463 0.40 1.69895 30.1 3.43 5 4.776 1.39 1.83481 42.7 3.91 6 -9.237 0.16 4.36 7* -16.299 0.43 1.53110 55.9 4.46 8* -187.887 1.34 4.77 9 -2.854 0.86 1.92286 20.9 4.91 10 -4.834 0.42 6.52 11* -4.029 0.55 1.53110 55.9 6.64 12* -5.433 0.15 8.35 13 132.002 2.50 2.00100 29.1 12.25 14 -13.257 (variable) 12.81 Image plane ∞ Aspherical data Side 7 K = 0.00000e+00 A 4=-8.03294e-03 A 6= 6.42603e-04 A 8=-1.71864e-05 A10=-2.18210e-05 A12= 5.95829e-06 A14=-3.26994e-07 Side 8 K = 0.00000e+00 A 4=-9.37478e-03 A 6= 5.54245e-04 A 8=-6.69460e-05 A10=-6.99311e-06 A12= 1.91513e-06 A14=-4.31530e-08 Page 11 K = 0.00000e+00 A 4= 2.04929e-03 A 6= 2.43258e-04 A 8=-7.52984e-05 A10= 7.10962e-06 A12=-4.53349e-07 A14= 1.70146e-08 Side 12 K = 0.00000e+00 A 4= 2.56257e-03 A 6= 2.07946e-04 A 8=-4.35551e-05 A10= 3.28693e-06 A12=-1.10371e-07 A14= 1.45867e-09 Various data Focal length 12.94 F-number 2.80 Half-angle (°): 31.36 Image height 7.89 Lens length: 15.50 BF 4.19 d14 4.19 Single lens data Lens starting plane, focal length 1 1 10.41 2 4 -5.00 3 5 3.95 4 7 -33.63 5 9 -9.55 6 11 -33.93 7 13 12.14 [Numerical Example 5] Unit: mm Surface data Face number rd nd νd Effective diameter 1 -11.704 0.29 1.59270 35.3 5.34 2 4.905 0.08 4.65 3 5.130 1.22 1.91082 35.2 4.63 4 -29.778 0.32 4.26 5 (aperture) ∞ 0.92 4.17 6 5.703 1.26 1.87070 40.7 3.92 7 -8.099 0.18 1.76182 26.5 3.61 8 5.381 0.68 3.38 9* -21.874 0.63 1.53500 56.0 3.81 10* -135.199 1.97 4.63 11* -5.817 1.59 1.53500 56.0 8.06 12* -5.050 0.18 8.94 13* 6.415 1.77 1.53500 56.0 11.65 14* 8.812 (variable) 12.22 Image plane ∞ Aspherical data 9th page K = 0.00000e+00 A 4=-2.23331e-02 A 6=-1.37107e-02 A 8=-4.99539e-04 A 3= 1.02926e-02 A 5= 2.10970e-02 A 7= 4.33469e-03 Side 10 K = 0.00000e+00 A 4=-1.34981e-02 A 6=-8.17785e-03 A 8=-2.49052e-04 A 3= 1.01369e-02 A 5= 1.34718e-02 A 7= 2.44157e-03 Page 11 K =-3.44235e+01 A 4=-1.31612e-02 A 6=-6.61143e-03 A 8=-1.37858e-04 A10 = 6.72689e-07 A 3= 3.65090e-04 A 5= 1.47395e-02 A 7= 1.44729e-03 Side 12 K =-3.08794e+00 A 4=-4.69366e-02 A 6=-9.52789e-03 A 8=-1.71551e-04 A10 = 7.65261e-07 A 3= 4.54234e-02 A 5= 2.71741e-02 A 7= 1.88545e-03 Page 13 K =-4.72297e+01 A 4=-3.62984e-02 A 6=-3.40402e-03 A 8=-8.43606e-05 A10 = -2.63594e-07 A 3= 5.57242e-02 A 5= 1.28857e-02 A 7= 6.48527e-04 A 9= 6.89276e-06 Page 14 K =-1.98741e+01 A 4=-2.10859e-02 A 6=-5.43361e-03 A 8=-2.11629e-04 A10 = -6.17168e-07 A 3= 1.69037e-02 A 5= 1.31038e-02 A 7= 1.38770e-03 A 9= 1.76760e-05 Various data Focal length 10.39 F-number 2.55 Half-angle (°): 37.20 Image height 7.89 Lens length: 15.65 BF 4.54 d14 4.54 Single lens data Lens starting plane, focal length 1 1 -5.79 2 3 4.89 3 6 4.01 4 7 -4.22 5 9 -48.87 6 11 41.54 7 13 35.08 [Numerical Example 6] Unit: mm Surface data Face number rd nd νd Effective diameter 1 -9.182 0.26 1.59270 35.3 5.05 2 7.573 1.16 1.91082 35.2 4.55 3 -15.973 0.36 4.19 4 (aperture) ∞ 0.95 3.70 5 5.201 1.28 1.87070 40.7 3.52 6 -11.975 0.18 1.76182 26.5 3.23 7 4.561 0.76 3.42 8* -85.757 0.61 1.53500 56.0 3.99 9* -3646.869 1.98 4.79 10* -4.133 1.32 1.53500 56.0 8.03 11* -3.726 0.08 8.68 12* 6.434 1.79 1.53500 56.0 11.47 13* 8.046 (variable) 11.95 Image plane ∞ Aspherical data Side 8 K = 0.00000e+00 A 4=-2.15591e-02 A 6=-1.45344e-02 A 8=-6.45412e-04 A 3= 7.31285e-03 A 5= 2.05408e-02 A 7= 4.98873e-03 Page 9 K = 0.00000e+00 A 4=-1.38627e-02 A 6=-7.94143e-03 A 8=-2.15749e-04 A 3= 6.84598e-03 A 5= 1.26489e-02 A 7= 2.30518e-03 Page 10 K =-1.83110e+01 A 4=-1.28739e-02 A 6=-6.60464e-03 A 8=-1.38472e-04 A10 = 5.89377e-07 A 3=-4.50600e-03 A 5= 1.51074e-02 A 7= 1.45049e-03 Page 11 K =-4.49148e+00 A 4=-4.78510e-02 A 6=-9.42635e-03 A 8=-1.74438e-04 A10 = 6.95369e-07 A 3= 3.87383e-02 A 5= 2.75181e-02 A 7= 1.89210e-03 Page 12 K =-5.38183e+01 A 4=-3.59530e-02 A 6=-3.36121e-03 A 8=-8.55245e-05 A10 = -2.45687e-07 A 3= 5.16366e-02 A 5= 1.29027e-02 A 7= 6.49569e-04 A 9= 6.80215e-06 Page 13 K =-2.25124e+01 A 4=-2.20658e-02 A 6=-5.43967e-03 A 8=-2.11458e-04 A10 = -6.20841e-07 A 3= 1.55469e-02 A 5= 1.34176e-02 A 7= 1.38383e-03 A 9= 1.77223e-05 Various data Focal length 10.39 F-number 2.86 Half-angle (°): 37.20 Image height 7.89 Lens length: 15.55 BF 4.83 d13 4.83 Single lens data Lens starting plane, focal length 1 1 -6.96 2 2 5.78 3 5 4.31 4 6 -4.31 5 8 -164.16 6 10 33.15 7 12 43.30 [Numerical Example 7] Unit: mm Surface data Face number rd nd νd Effective diameter 1* -3586.364 0.50 1.58313 59.4 4.98 2* 3.305 0.40 4.07 3 6.805 1.15 1.72916 54.7 3.97 4 -20.438 0.41 3.51 5 (aperture) ∞ 0.92 3.45 6 6.513 1.36 1.75500 52.3 4.01 7 -6.331 0.11 4.25 8 -8.195 1.51 1.65844 50.9 4.27 9 -3.404 0.50 1.73800 32.3 4.52 10 13.112 1.15 5.05 11* -10.477 0.56 1.53500 56.0 5.24 12* -12.314 0.82 6.05 13* -4.165 1.53 1.53500 56.0 7.58 14* -4.049 0.18 8.44 15* 4.151 1.87 1.53500 56.0 12.30 16* 4.590 (variable) 12.86 Image plane ∞ Aspherical data Front page K = 0.00000e+00 A 4=-1.58804e-02 A 6= 2.24199e-03 A 8= 1.83096e-04 A 3=-3.16093e-03 A 5= 4.71244e-03 A 7=-1.32163e-03 2nd side K = 4.72161e-01 A 4=-1.76482e-02 A 6= 1.39866e-03 A 8=-9.37739e-05 A 3=-5.29217e-03 A 5= 3.59190e-03 A 7=-4.59994e-04 Page 11 K = 0.00000e+00 A 4=-1.05979e-02 A 6=-2.78920e-04 A 8= 1.32419e-04 A10 = -5.02271e-06 Side 12 K = 0.00000e+00 A 4=-5.08433e-03 A 6=-3.11798e-04 A 8= 1.12668e-04 A10 = -4.13907e-06 Page 13 K =-1.22936e+01 A 4= 9.88450e-03 A 6= 2.44515e-03 A 8= 8.11852e-05 A10 = -7.20367e-07 A 3=-8.89814e-03 A 5=-5.23719e-03 A 7=-6.59829e-04 Page 14 K =-1.34110e+00 A 4=-1.16917e-04 A 6=-1.54999e-03 A 8=-3.18547e-05 A10 = -6.97583e-08 A 3=-3.16936e-03 A 5= 3.22415e-03 A 7= 3.73888e-04 Page 15 K =-1.12242e+00 A 4=-2.35753e-02 A 6=-4.14295e-03 A 8=-1.53627e-04 A10 = -4.33086e-07 A 3= 4.45348e-03 A 5= 1.17935e-02 A 7= 1.01655e-03 A 9= 1.26550e-05 Page 16 K =-6.08828e-01 A 4=-1.82200e-02 A 6=-1.43596e-03 A 8=-3.10115e-05 A10 = -5.37345e-08 A 3= 5.03772e-03 A 5= 6.01578e-03 A 7= 2.59656e-04 A 9= 2.01631e-06 Various data Focal length 8.79 F-number 2.88 Half-angle (°): 41.92 Image height 7.89 Lens length: 17.05 BF 4.07 d16 4.07 Single lens data Lens starting plane, focal length 1 1 -5.66 2 3 7.13 3 6 4.46 4 8 7.86 5 9 -3.62 6 11 -147.00 7 13 48.53 8 15 32.60 The various values ​​in each numerical example are summarized in Table 1 below.

[0079] [Table 1]

[0080] [Imaging device] Next, an embodiment of a digital still camera 10 (imaging device) using the optical system L0 of the present invention as an imaging optical system will be described with reference to Figure 15. In Figure 15, 13 is the camera body, and 11 is the imaging optical system composed of any of the optical systems L0 described in Embodiments 1 to 7. 12 is a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor, which is built into the camera body 13 and receives the optical image formed by the imaging optical system 11 and converts it into photoelectric light. The camera body 13 may be a so-called single-lens reflex camera with a quick-turn mirror, or a so-called mirrorless camera without a quick-turn mirror.

[0081] By applying the optical system L0 of the present invention to an imaging device such as a digital still camera, an imaging device with a compact lens can be obtained.

[0082] Although preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of its gist. [Explanation of symbols]

[0083] L0 optical system La front group SP aperture diaphragm Lb rear group Lp final lens

Claims

1. An optical system consisting of a front group, an aperture diaphragm, and a rear group with a positive refractive power as a whole, arranged in order from the object side to the image side, The aforementioned front group consists of one positive lens, The rear group includes the final lens with positive refractive power that is positioned closest to the image in the rear group, In the optical system, let TTL be the distance along the optical axis from the lens surface on the object side of the lens positioned closest to the object to the image plane, Φi be the diameter of the image circle, PNdave be the average refractive index of the materials of all positive lenses included in the optical system at the d line, Φp be the effective diameter at the lens surface on the image side of the final lens, and sk be the air-equivalent length of the distance along the optical axis from the lens surface on the image side of the final lens to the image plane. 0.5<TTL / Φi<1.4 1.64<PNdave<2.00 2.0<Φp / sk<4.0 An optical system characterized by satisfying the following conditional equation.

2. When the focal length of the front group is fa and the focal length of the optical system is f, 0.1<f / |fa|<1.5 The optical system according to claim 1, characterized in that it satisfies the following condition.

3. When the focal length of the final lens is fp and the focal length of the optical system is f, 0.6<fp / f<6.0 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

4. When the focal length of the optical system is f, 0.1<sk / f<0.7 An optical system according to any one of claims 1 to 3, characterized in that it satisfies the following conditional expression.

5. When SPIP is the distance along the optical axis from the aperture diaphragm to the image plane, 0.6<SPIP / TTL<1.0 An optical system according to any one of claims 1 to 4, characterized in that it satisfies the following conditional expression.

6. The optical system according to any one of claims 1 to 5, characterized in that the rear group includes at least four lenses.

7. The optical system according to any one of claims 1 to 6, characterized in that the rear group includes a first negative lens positioned on the object side of the final lens.

8. When R1 is the paraxial radius of curvature of the object-side lens surface of the first negative lens, and R2 is the paraxial radius of curvature of the image-side lens surface of the first negative lens, 0.0<(R1+R2) / (R2-R1)<50.0 The optical system according to claim 7, characterized in that it satisfies the following conditional equation.

9. When the refractive index of the material of the first negative lens in the d-line is Ndn, and the Abbe number of the first negative lens in the d-line is νdn, 1.500 < Ndn < 4.1945 / νdn + 1.520 The optical system according to claim 7 or 8, characterized in that it satisfies the following conditional expression.

10. When the focal length of the front group is fa and the focal length of the rear group is fb, 0.10<fb / |fa|<10.00 An optical system according to any one of claims 1 to 9, characterized in that it satisfies the following conditional expression.

11. When the refractive index of the material of the positive lens constituting the front group is Ndap at the d line, 1.60<Ndap<2.00 An optical system according to any one of claims 1 to 10, characterized in that it satisfies the following conditional expression.

12. The aforementioned rear group includes a second positive lens, When the refractive index of the material of the second positive lens in the d-line is Ndbp, 1.60<Ndbp<2.00 An optical system according to any one of claims 1 to 11, characterized in that it satisfies the following conditional expression.

13. The aforementioned rear group includes a second negative lens, When the refractive index of the material of the second negative lens in the d-line is Ndbn, 0.0<Ndbp−Ndbn<0.4 The optical system according to claim 12, characterized in that it satisfies the following conditional expression.

14. When the largest effective diameter of the lens having the largest effective diameter in the aforementioned front group is denoted as Φa, 1.0<Φp / Φa<4.0 An optical system according to any one of claims 1 to 13, characterized in that it satisfies the following conditional expression.

15. The optical system according to any one of claims 1 to 14, characterized in that the optical system is composed of five or more lenses and eight or fewer lenses.

16. An imaging device characterized by having an optical system according to any one of claims 1 to 15 and an image sensor that receives an image formed by the optical system.

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