Optical system and image capturing device having the same

Abstract

To provide an optical lens which offers a wide angle of view and yet can make it less difficult to manufacture an object-side lens.SOLUTION: An optical system is provided, comprising a first lens having negative refractive power, a second lens having positive refractive power, a third lens having positive refractive power, and at least one lens arranged in order from the most object side to the image side, where a first lens surface of the first lens on the object side has an aspherical shape that is more convex toward the object side in the peripheral portion. A focal length of the first lens and a focal length of the second lens are each set appropriately.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical system suitable for digital video cameras, digital still cameras, broadcast cameras, cameras for silver halide film, surveillance cameras, vehicle-mounted cameras, and the like. [Background technology]

[0002] In recent years, there has been a demand for compact wide-angle lenses with short overall length while providing good optical performance at the periphery of the image in optical systems used in imaging devices. Wide-angle lenses generally employ a retrofocus type power arrangement with negative refractive power on the object side of the optical system and positive refractive power on the image side. In retrofocus type optical systems, a configuration is known in which a meniscus lens with negative refractive power or a biconcave lens with negative refractive power, which has a large ratio of peripheral thickness to central thickness (uneven thickness ratio), is arranged closest to the object side (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Publication No. 2020 / 040912 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration of Patent Document 1, when molding a lens with a negative refractive power and a large thickness deviation ratio located closest to the object side, temperature unevenness in the lens is likely to become large, and the deviation from the design value of the surface shape is likely to become large. If the deviation in the surface shape becomes too large, the performance degradation such as curvature of field and distortion from the desired design value will become large.

[0005] An object of the present invention is to provide an optical system that is wide-angle and yet allows for reduced manufacturing difficulty of the lens disposed on the object side. [Means for solving the problem]

[0006] An optical system according to one aspect of the present invention has at least one lens, arranged in this order from the object side to the image side, including a first lens having negative refractive power, a second lens having positive refractive power, and a third lens having positive refractive power, wherein a first lens surface on the object side of the first lens is aspheric and has a shape in which the convex shape toward the object side becomes stronger at a periphery, and when the focal length of the first lens is f1 and the focal length of the second lens is f2, -1.50≦f2 / f1<0 The present invention is characterized in that the following conditional expression is satisfied: Effect of the Invention

[0007] According to the present invention, it is possible to provide an optical system that is wide-angle and yet allows the manufacturing difficulty of the lens disposed on the object side to be reduced. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view of the optical system of the first embodiment when focusing at infinity. [Diagram 2] 4 is a longitudinal aberration diagram of the optical system of Example 1. FIG. [Diagram 3] FIG. 11 is a cross-sectional view of the optical system of the second embodiment when focusing at infinity. [Figure 4] 11A to 11C are longitudinal aberration diagrams of the optical system of Example 2. [Diagram 5] FIG. 11 is a cross-sectional view of the optical system of Example 3 when focusing at infinity. [Figure 6] 11A to 11C are longitudinal aberration diagrams of the optical system of Example 3. [Figure 7] FIG. 11 is a cross-sectional view of the optical system of Example 4 at the time of focusing at infinity. [Figure 8] 13A to 13C are longitudinal aberration diagrams of the optical system of Example 4. [Figure 9] FIG. 13 is a cross-sectional view of the optical system of Example 5 when focusing at infinity. [Figure 10] 13A to 13C are longitudinal aberration diagrams of the optical system of Example 5. [Figure 11] FIG. 13 is a cross-sectional view of the optical system of Example 6 when focusing at infinity. [Figure 12] 13 is a longitudinal aberration diagram of the optical system of Example 6. FIG. [Figure 13] FIG. 13 is a cross-sectional view of the optical system of Example 7 when focusing at infinity. [Figure 14] 13 is a longitudinal aberration diagram of the optical system of Example 7. FIG. [Figure 15] FIG. 4 is an explanatory diagram of a reference spherical surface and a sag amount. [Figure 16] FIG. 1 is a schematic diagram of an imaging device. [Figure 17] FIG. 2 is a schematic diagram of a lens device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same reference numerals are given to the same members, and duplicated explanations will be omitted.

[0010] 1, 3, 5, 7, 9, 11, and 13 are cross-sectional views of the optical system L0 of Examples 1 to 7 when focused at infinity. The optical system L0 of each Example is used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and vehicle-mounted cameras.

[0011] In each cross-sectional view, the left side is the object side and the right side is the image side. When the optical system L0 of each embodiment is used as a projection lens of a projector, the left side is the screen side and the right side is the projected image side.

[0012] The optical system L0 in each embodiment is configured to have a plurality of lens groups. In this specification, a lens group is a group of lenses separated by an aperture stop SP that determines an axial ray. The optical system L0 in each embodiment has a front group LF with positive refractive power, an aperture stop SP, and a rear group LR with negative refractive power, which are arranged in this order from the object side to the image side. The front group LF is a group of all lenses arranged on the object side of the aperture stop SP. The rear group LR is a group of all lenses arranged on the image side of the aperture stop SP. The lens group may be composed of one lens or may be composed of multiple lenses. The lens group may also include optical elements such as an aspherical lens that does not have a paraxial refractive power (having an infinite paraxial radius of curvature), a Fresnel lens, and a diffractive optical element.

[0013] In each cross-sectional view, Gi represents the i-th lens (i is a natural number) counting from the object side. The arrow represents the movement direction of the lens group when focusing from infinity to a close distance. In this embodiment, the entire optical system L0 moves from the image side to the object side when focusing from infinity to a close distance, but the present invention is not limited to this. Focusing may be performed by moving only some lenses of the optical system L0 from the image side to the object side, or from the object side to the image side. IP is an image plane, and when the optical system L0 of each embodiment is used as a photographing optical system of a digital still camera or a digital video camera, the imaging surface of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is disposed thereon. When the optical system L0 of each embodiment is used as a photographing optical system of a silver halide film camera, a photosensitive surface corresponding to the film surface is placed on the image plane IP. FL is an optical block corresponding to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, etc. The optical block is not included in the "lens" in this specification. S represents an aspheric lens surface on the object side of an aspheric lens that satisfies the conditional expression described later.

[0014] 2, 4, 6, 8, 10, 12, and 14 are longitudinal aberration diagrams of the optical system L0 of Examples 1 to 7 when focusing at infinity. In the spherical aberration diagrams, Fno is the F-number, and shows the amount of spherical aberration for the d-line (wavelength 587.6 nm) and the g-line (wavelength 435.8 nm). In the astigmatism diagrams, S shows the amount of astigmatism in the sagittal image plane, and M shows the amount of astigmatism in the meridional image plane. In the distortion diagrams, the amount of distortion for the d-line is shown. In the chromatic aberration diagrams, the amount of chromatic aberration of magnification for the g-line is shown. ω is the half angle of view (°).

[0015] Next, the characteristic configuration of the optical system L0 in each embodiment will be described.

[0016] The optical system L0 in each embodiment has at least one lens, arranged in order from the object side to the image side, including a first lens G1 with negative refractive power, a second lens G2 with positive refractive power, and a third lens G3 with positive refractive power.

[0017] By arranging, in order from the object side to the image side, a first lens G1 with negative refractive power, a second lens G2 with positive refractive power, and a third lens G3 with positive refractive power, a so-called retrofocus power arrangement is achieved, and it becomes easy to ensure the back focus when the optical system L0 has a wide angle.

[0018] In addition, the second lens G2 and the third lens G3 have positive refractive power, so that the strong positive refractive power for making the optical system L0 have a wide angle can be dispersed, thereby suppressing the occurrence of spherical aberration, curvature of field, and coma, and as a result, making it easier to correct aberrations.

[0019] Furthermore, by locating at least one lens closer to the image side than the third lens G3, aberration correction can be performed at a position where the height of off-axis rays is large, which makes it possible to selectively correct the curvature of field and astigmatism generated by the second lens G2 and the third lens G3 while minimizing the effects on spherical aberration and coma aberration.

[0020] In the optical system L0 of each embodiment, the lens surface (first lens surface) on the object side of the first lens G1 is aspheric, and has a shape that becomes increasingly convex toward the object side at the periphery.

[0021] The lens on the object side of a wide-angle lens is likely to have a large ratio of peripheral thickness to central thickness (uneven thickness ratio). When the lens is molded, for example, by glass molding or plastic molding, the temperature unevenness inside the lens is likely to become large, and the error from the design value of the surface shape is likely to become large. Therefore, by making the lens surface on the object side of the first lens G1 aspheric and providing a shape that gradually becomes more convex toward the object side at the periphery, the uneven thickness ratio can be reduced and the difficulty of manufacturing can be reduced. In addition, it is also possible to generate coma aberration of the pupil, increase the aperture efficiency of the peripheral light beam, and improve the peripheral light amount ratio.

[0022] The optical system L0 of each embodiment satisfies the following conditional expression (1).

[0023] -1.50≦f2 / f1<0.00 (1) Here, f1 is the focal length of the first lens G1, and f2 is the focal length of the second lens G2.

[0024] Conditional formula (1) defines the relationship between the focal length of the first lens G1 and the focal length of the second lens G2. In order to reduce the thickness deviation ratio of the first lens G1, it is necessary to make the first lens G1 a negative meniscus lens with a convex surface on the object side or a biconcave lens with a weak concave surface on the object side, so it is necessary to reduce the negative focal length of the first lens G1 (to increase the absolute value of the negative focal length). In addition, by reducing the positive focal length of the second lens G2, it is possible to obtain sufficient refractive power to make the optical system L0 wider-angle. Therefore, it is preferable that the value of conditional formula (1) is a negative value and a large value (a negative value close to 0).

[0025] If the negative refractive power of the first lens G1 becomes large below the lower limit of conditional formula (1), it becomes difficult to ensure the necessary back focus, and the thickness deviation ratio of the first lens G1 becomes large, which are undesirable. Also, if the positive refractive power of the second lens G2 becomes small below the lower limit of conditional formula (1), it becomes difficult to make the optical system L0 wider-angle, which is undesirable.

[0026] If the upper limit of conditional expression (1) is exceeded, it becomes difficult to ensure the necessary back focus, which is undesirable. Also, if the upper limit of conditional expression (1) is exceeded and the positive refractive power of the second lens G2 becomes large, the spherical aberration and curvature of field generated by the second lens G2 become large in the under direction, which is undesirable.

[0027] It is preferable that the numerical range of conditional expression (1) be the numerical range of the following conditional expression (1a).

[0028] -1.40≦f2 / f1<-0.10 (1a) It is more preferable that the numerical range of conditional expression (1) be the numerical range of the following conditional expression (1b).

[0029] -1.25≦f2 / ft<-0.20 (1b) It is further preferable that the numerical range of conditional formula (1) be the numerical range of the following conditional formula (1c).

[0030] -1.10≦f2 / f1<-0.35 (1c) Next, a description will be given of configurations that are preferably satisfied in the optical system L0 of each embodiment.

[0031] In the optical system L0 of each embodiment, the aperture stop SP is preferably disposed between the first lens G1 and the second lens G2. Although disposing many lenses on the object side of the aperture stop SP is preferable from the viewpoint of correcting distortion aberration and curvature of field, the diameter and thickness deviation of the lens at a position away from the aperture stop SP in the optical axis direction becomes large. In that case, when the lens is molded, temperature unevenness during molding and errors in the surface shape due to shrinkage tend to become large, making manufacturing difficult. In addition, when the second lens G2 is mated with the first lens G1 at their respective edge portions (end surface portions), if the diameter of the first lens G1 is large, the diameter of the second lens G2 also becomes large, and the diameter of the entire optical system L0 becomes too large. Therefore, by disposing the aperture stop SP between the first lens G1 and the second lens G2 and close to the first lens G1, the diameter of the first lens G1 can be reduced.

[0032] The optical system L0 of each embodiment preferably has a first lens G1 with negative refractive power, a second lens G2 with positive refractive power, a third lens G3 with positive refractive power, and a fourth lens G4 with negative refractive power, arranged in order from the object side to the image side. Also, the optical system L0 of each embodiment preferably has a first lens G1 to a fifth lens group G5 with negative, positive, positive, negative, and positive refractive powers, arranged in order from the object side to the image side. Also, the optical system L0 of each embodiment preferably has a first lens G1 to a fifth lens G5 and a sixth lens G6 with negative, positive, positive, negative, and positive refractive powers, arranged in order from the object side to the image side.

[0033] The fourth lens G4 has a negative refractive power, so that the axial chromatic aberration and spherical aberration generated in the second lens G2 and the third lens G3 can be offset, and aberration correction can be performed satisfactorily.

[0034] In addition, by disposing a fifth lens G5 and a sixth lens G6 with positive refractive power on the image side of the fourth lens G4, aberration correction can be performed at a position away from the aperture stop SP in the optical axis direction. At a position away from the aperture stop SP in the optical axis direction, the height of off-axis rays is large, and the on-axis rays and off-axis rays are sufficiently separated on each surface. Therefore, it is possible to correct field curvature and astigmatism with almost no effect on spherical aberration and coma aberration.

[0035] In addition, since the fifth lens G5 has a positive refractive power, it may be possible to reduce the angle of incidence of off-axis light rays on the image plane. When capturing an image with a solid-state imaging element such as a CMOS sensor, it is possible to reduce vignetting of light rays due to the microlenses of the sensor, etc.

[0036] In the optical system L0 of each embodiment, it is preferable that the object-side lens surface of the fourth lens G4 is a concave surface, which can reduce the angle of incidence of off-axis rays incident on the fourth lens G4 and can reduce fluctuations in field curvature and coma aberration due to manufacturing errors in the surface shape.

[0037] It is preferable that at least one of the lens surfaces on the object side and the image side of the lens included in the optical system L0 in each embodiment has an aspheric shape and is made of plastic resin. By making at least one surface of each lens aspheric, the optical system L0 can be configured with a small number of lenses, and the optical system L0 can be made thin. In addition, by configuring each lens with plastic resin, the optical system L0 can be made lighter. In addition, by molding each lens, the amount of asphericity relative to the spherical surface can be increased so that the refractive power of each surface near the optical axis and around the periphery is greatly changed, and the aberration correction effect can be further improved.

[0038] In the optical system L0 of each embodiment, it is preferable that the lens (final lens) GR arranged on the most image side has a lens surface on the object side with a stationary point, a shape that is convex near the optical axis and concave at the periphery, and a lens surface on the image side with a stationary point, a shape that is concave near the optical axis and convex at the periphery. By having the lens surface on the object side with a shape that is convex near the optical axis and concave at the periphery, it is possible to generate field curvature in the over direction with the concave shape at the periphery while suppressing the generation of aberration in the sagittal direction. This makes it possible to satisfactorily correct the field curvature in the under direction generated by the second lens G2 and the third lens G3. In addition, by having the lens surface on the image side with a shape that is concave near the optical axis and convex at the periphery, it is possible to reduce the angle of incidence of off-axis light rays on the image surface with the convex refractive power at the periphery while correcting the Petzval sum with the negative refractive power near the optical axis.

[0039] The stationary point is a position (position away from the predetermined distance h) where the value of the first derivative dX(h) / dh obtained by differentiating the amount of sag (amount of displacement) X(h) on the optical axis between a position on the aspheric surface a predetermined distance h away from the optical axis in the direction perpendicular to the optical axis and the surface vertex once with respect to the predetermined distance h is 0. The sign of the amount of sag X(h) is positive in the direction from the object side to the image side.

[0040] In the optical system L0 of each embodiment, it is preferable that the lens surface on the object side of the second lens G2 has a concave shape on the object side. Since the second lens G2 is disposed near the aperture stop SP, the on-axis light beam and the off-axis light beam pass through the surface of the second lens G2 so as to overlap each other. At such a position, the manufacturing error of the surface shape is likely to cause fluctuations in the field curvature and coma aberration. However, by making the lens surface on the object side of the second lens G2 concave, the angle of incidence of the off-axis light beam on the lens surface on the object side can be alleviated, and the amount of refraction of the off-axis light beam at the second lens G2 can be reduced. This can reduce the performance effect caused by the manufacturing error of the surface shape.

[0041] In the optical system L0 of each embodiment, the first lens G1 and the lens GR arranged closest to the image side are preferably made of plastic resin, which can reduce the weight of the optical system L0.

[0042] Next, conditions that the optical system L0 of each embodiment should preferably satisfy will be described. The optical system L0 of each embodiment should preferably satisfy one or more of the following conditional expressions (2) to (17).

[0043] 0.05 <x1 / T<0.80 (2) 0.08 <T / TTL<0.25 (3) 0.40 <Dsum / TTL<0.85 (4) -3.50 <f1 / f<-0.80 (5) 0.40 <f3 / f2<1.50 (6) -3.00 <f4 / f<-0.80 (7) 0.001 <f / f5<1.500 (8) -3.00<(G2R2+G2R1) / (G2R2-G2R1)<-0.40 (9) -10.00 <G2R1 / f<-0.80 (10) -1.50 <f / fair<0.00 (11-1) 0.00 <f / fair<0.30 (11-2) -1.00 <f23 / f1<-0.10 (12) 1.5000 <n1<1.6000 (13) 45<νd1<65 (14) 1.580 <nR<1.750 (15) 15<νdR<30 (16) 0.25 <h / TR<0.65 (17) Here, x1 is the sag amount of the lens surface S, which is an aspheric surface on the object side of the first lens G1. T is the distance on the optical axis from the vertex of the lens surface S to the aperture stop SP. TTL is the distance on the optical axis from the lens surface on the object side of the first lens G1 to the image surface (total optical length). Dsum is the sum of the thicknesses of the lenses included in the optical system L0 (the distance on the optical axis from the lens surface on the object side to the lens surface on the image side). f is the focal length of the optical system L0. f1, f2, f3, f4, and f5 are the focal lengths of the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, and the fifth lens G5, respectively. G2Rl is the radius of curvature of the lens surface on the object side of the second lens G2. G2R2 is the radius of curvature of the lens surface on the image side of the second lens G2. fair is the focal length of an air lens consisting of the image-side lens surface (second lens surface) of the first lens G1, the object-side lens surface (third lens surface) of the second lens G2, and the air gap between these two surfaces. f23 is the composite focal length of the second lens G2 and the third lens G3. n1 is the refractive index of the first lens G1. νd1 is the Abbe number of the first lens G1. nR is the refractive index of the lens GR arranged closest to the image side. νdR is the Abbe number of the lens GR arranged closest to the image side. h is the distance from the optical axis to the stationary point of the image-side lens surface of the lens GR arranged closest to the image side in the direction perpendicular to the optical axis. TR is the distance on the optical axis from the aperture stop SP to the image-side lens surface of the lens GR arranged closest to the image side.

[0044] Hereinafter, the sag amount x1 of the lens surface S, which is an aspheric surface on the object side of the first lens G1, will be described with reference to FIG. 15. When calculating the sag amount x1, first, a reference spherical surface Sref is determined for the lens surface S. When the distance on the optical axis from the surface vertex of the lens surface S to the aperture stop SP is T, the reference spherical surface Sref is a spherical surface that passes through the surface vertex of the lens surface S and a position on the lens surface S that is a distance T / 2 away from the optical axis in the direction perpendicular to the optical axis. Note that although the "position on the lens surface S that is a distance T / 2 away from the optical axis in the direction perpendicular to the optical axis" is expressed as two points on the lens cross section in FIG. 15, it actually includes all positions on a concentric circle on the lens surface S that is a distance T / 2 away from the optical axis in the direction perpendicular to the optical axis. The sag amount x1 is the distance on the optical axis between a position on the reference spherical surface Sref that is a distance 3×T / 2 away from the optical axis in the direction perpendicular to the optical axis and a position on the lens surface S that is a distance 3×T / 2 away from the optical axis in the direction perpendicular to the optical axis. The sign of the sag amount x1 is positive when the lens surface S is located on the image side with respect to the reference spherical surface Sref.

[0045] Conditional formula (2) specifies the amount of sag of the lens surface S. By making the lens surface S have a weak positive or negative refractive power near the optical axis, the first lens G1 as a whole has a negative refractive power, and the optical system L0 can have a power arrangement of a retrofocus type. If the lens surface S has a weak positive or negative refractive power, the thickness of the peripheral part of the first lens G1 tends to be large relative to the thickness at the center, which causes a problem due to the increase in the thickness deviation ratio described above. Therefore, by satisfying conditional formula (2), the amount of sag of the actual lens surface S can be increased with respect to the reference spherical surface defined near the optical axis of the lens surface S, and the lens surface S can have a strong convex shape at the periphery. This can reduce the thickness deviation ratio. In addition, by satisfying conditional formula (2), coma aberration of the pupil can be generated to improve the peripheral light amount. If the amount of sag is reduced below the lower limit of conditional formula (2), the thickness deviation ratio increases, making manufacturing difficult and reducing the peripheral light amount, which is not preferable. If the amount of sag becomes large enough to exceed the upper limit of conditional expression (2), the open angle around the periphery of lens surface S (the angle of the tangent to lens surface S) will become too large, making it difficult to process the mold for molding and to measure it after molding, which is not preferable.

[0046] Conditional formula (3) defines the relationship between the axial distance from the object-side lens surface of the first lens G1 to the aperture stop SP and the axial distance from the object-side lens surface of the first lens G1 to the image plane. If the axial distance from the object-side lens surface of the first lens G1 to the aperture stop SP becomes small below the lower limit of conditional formula (3), off-axis light passing through the first lens G1 passes close to the optical axis, which reduces the effect of correcting off-axis aberrations, which is not preferable. If the axial distance from the object-side lens surface of the first lens G1 to the aperture stop SP becomes large above the upper limit of conditional formula (3), the diameter of the first lens G1 becomes too large, which is not preferable because the optical system L0 becomes large.

[0047] Conditional formula (4) specifies the relationship between the sum of the thicknesses of the lenses included in the optical system L0 and the overall optical length. In order to make the optical system L0 thinner, it is preferable to arrange the lenses with the minimum air gap between them relative to the overall optical length. Therefore, the sum of the lens thicknesses relative to the overall optical length is a large value. If the sum of the thicknesses is small and the overall optical length is long below the lower limit of conditional formula (4), the thickness of the optical system L0 in the optical axis direction is large, which is not preferable. If the sum of the thicknesses is large and the overall optical length is short above the upper limit of conditional formula (4), the back focus of the optical system L0 becomes too small, which is not preferable because it is impossible to arrange a sensor, an optical filter, etc. In addition, the air gap between the lenses becomes too small, which is not preferable because it is difficult to arrange a light-cut mask for reducing ghosts and a mechanical member for holding the lenses.

[0048] Conditional formula (5) defines the focal length f1 of the first lens G1. As described above, the first lens G1 needs to have a negative refractive power that is not too strong in order to reduce the thickness deviation ratio, and conditional formula (5) defines the range. By satisfying conditional formula (5), the optical system L0 can be made wider-angle. If the focal length of the first lens G1 is reduced below the lower limit of conditional formula (5), the negative refractive power of the first lens G1 becomes too small, making it difficult to ensure the required back focus, which is not preferable. If the focal length of the first lens G1 is increased above the upper limit of conditional formula (5), the thickness deviation ratio of the first lens G1 becomes too large, making it difficult to manufacture, which is not preferable. In addition, barrel distortion occurring in the first lens G1 becomes too large, which is not preferable.

[0049] Conditional formula (6) defines the relationship between the focal length of the second lens G2 and the focal length of the third lens G3. In order to make the optical system L0 wider-angle, a strong positive refractive power is required near the aperture stop SP, and conditional formula (6) defines the sharing ratio of the refractive power. If the lower limit of conditional formula (6) is exceeded, the focal length of the second lens G2 is large and the focal length of the third lens G3 is small, the positive refractive power is biased toward the third lens G3, and spherical aberration and curvature of field are generated significantly in the under-angle direction, which is not preferable. If the upper limit of conditional formula (6) is exceeded, the focal length of the second lens f2 is small and the focal length of the third lens G3 is large, the positive refractive power is biased toward the second lens G2, and spherical aberration and curvature of field are generated significantly in the under-angle direction, which is not preferable.

[0050] Conditional formula (7) defines the focal length of the fourth lens G4. Specifically, conditional formula (7) defines the refractive power required for the fourth lens G4 to correct the spherical aberration, field curvature, and axial chromatic aberration in the under direction that occur in the second lens G2 and the third lens G3. If the focal length of the fourth lens G4 is reduced below the lower limit of conditional formula (7), the aberration correction effect becomes insufficient, which is undesirable. If the focal length of the fourth lens G4 is increased above the upper limit of conditional formula (7), the aberration correction effect becomes excessive, which is undesirable.

[0051] Conditional formula (8) defines the focal length of the fifth lens G5. Specifically, conditional formula (8) defines the refractive power required for the fifth lens G5 to refract off-axis rays and reduce the angle of incidence of the off-axis rays on the image plane. If the focal length of the fifth lens G5 is increased below the lower limit of conditional formula (8), the effect of reducing the angle of incidence is insufficient, which is undesirable. If the focal length of the fifth lens G5 is decreased above the upper limit of conditional formula (8), the barrel distortion aberration generated by the fifth lens G5 becomes too large, which is undesirable.

[0052] Conditional formula (9) defines the shape of the second lens G2. Since the second lens G2 is located near the aperture stop SP, off-axis rays and on-axis rays are overlapped on the lens surface and refracted. In such a case, the field curvature and coma aberration are likely to vary due to manufacturing errors in the surface shape. Therefore, it is preferable that the second lens G2 has a meniscus shape concave toward the object side, and conditional formula (9) defines the shape. If the radius of curvature of the lens surface on the object side of the second lens G2 becomes small below the lower limit of conditional formula (9), the angle of incidence of the off-axis rays incident on the second lens G2 becomes too large, which is not preferable. If the radius of curvature G2R2 of the lens surface on the image side of the second lens G2 becomes too large above the upper limit of conditional formula (9), the refractive power of the second lens G2 becomes too large, which is not preferable because spherical aberration and field curvature occur significantly in the under direction.

[0053] Conditional formula (10) specifies the radius of curvature of the lens surface on the object side of the second lens G2. If the radius of curvature of the lens surface on the object side of the second lens G2 is small below the lower limit of conditional formula (10), the angle of incidence of off-axis light rays incident on the second lens G2 becomes too large, which is undesirable because the field curvature and coma aberration tend to vary due to manufacturing errors in the surface shape. If the radius of curvature of the lens surface on the object side of the second lens G2 is large above the upper limit of conditional formula (10), the positive refractive power of the second lens G2 becomes too small, which is undesirable because the refractive power required to make the optical system L0 wider angle cannot be obtained.

[0054] Conditional expressions (11-1) and (11-2) define the focal length of an air lens consisting of the image-side lens surface of the first lens G1, the object-side lens surface of the second lens G2, and the air gap between the two surfaces. By making the air lens have a negative or weak positive refractive power, it is possible to ensure the back focus required for the optical system L0. If the negative focal length of the air lens is increased below the lower limit of conditional expression (11-1), the negative refractive power of the air lens becomes too strong, and barrel distortion becomes too large, which is not preferable. If the positive focal length of the air lens is decreased above the upper limit of conditional expression (11-2), it is not preferable because it becomes difficult to ensure the back focus required for the optical system L0.

[0055] Conditional formula (12) specifies the relationship between the composite focal length of the second lens G2 and the third lens G3 and the focal length of the first lens G1. If the composite focal length is large and the focal length of the first lens G1 is small below the lower limit of conditional formula (12), the positive composite refractive power becomes too small, which is undesirable since it is difficult to make the optical system L0 wider-angle. In addition, the thickness deviation ratio of the first lens G1 becomes large, which is undesirable. If the composite focal length is small and the focal length of the first lens G1 is small above the upper limit of conditional formula (12), the positive composite refractive power becomes too large, which is undesirable since spherical aberration and curvature of field occur significantly in the under direction. In addition, the negative refractive power of the first lens G1 becomes too small, which is undesirable since it is difficult to ensure the back focus.

[0056] Conditional expressions (13) and (14) respectively prescribe the refractive index and Abbe number of the first lens G1. By satisfying both conditional expressions (13) and (14), it is possible to correct lateral chromatic aberration while making the first lens G1 out of plastic resin. If the values ​​of conditional expressions (13) and (14) are not satisfied, it becomes difficult to make the first lens G1 out of plastic resin, and if glass is used instead, the weight increases, which is not preferable.

[0057] Conditional expressions (15) and (16) respectively stipulate the refractive index and Abbe number of the lens GR arranged closest to the image side. By satisfying both conditional expressions (15) and (16), the curvature of the lens GR can be made small, and the occurrence of aberration can be suppressed. In addition, the negative refractive power of the periphery of the lens GR makes it possible to correct lateral chromatic aberration. Deviating from the values ​​of conditional expressions (15) and (16) is undesirable because it becomes difficult to construct the lens GR from plastic resin while obtaining the aberration correction effect.

[0058] Conditional expression (17) specifies the ratio of the distance h in the direction perpendicular to the optical axis from the optical axis to the stationary point of the lens surface on the image side, which has a shape concave toward the image side near the optical axis of the lens GR and convex toward the image side at the periphery, to the distance TR on the optical axis from the aperture stop SP to the lens surface. By satisfying conditional expression (17), the axial curvature and peripheral curvature of the lens GR can be changed significantly, and the correction effect of the field curvature and astigmatism of the lens GR can be improved. In addition, since the lens surface on the image side of the lens GR has a shape concave toward the image side near the optical axis and convex toward the image side at the periphery, it is possible to correct astigmatism at the periphery while correcting the Petzval sum paraxially. If the lower limit of conditional expression (17) is not satisfied, the paraxial curvature becomes small and the concave shape near the optical axis becomes shallow, so that the paraxial negative refractive power becomes small. As a result, it becomes difficult to correct the Petzval sum, which is not preferable. Exceeding the upper limit of condition (17) is undesirable because the peripheral convex area becomes smaller in the radial direction, reducing the effect of correcting astigmatism for off-axis rays and the effect of mitigating the angle of incidence of off-axis rays on the image plane.

[0059] It is preferable that the numerical ranges of the conditional expressions (2) to (17) be the numerical ranges of the following conditional expressions (2a) to (17a).

[0060] 0.06 <x1 / T<0.70 (2a) 0.09 <T / TTL<0.23 (3a) 0.42 <Dsum / TTL<0.80 (4a) -3.40 <f1 / f<-0.90 (5a) 0.45 <f3 / f2<1.35 (6a) -2.80 <f4 / f<-0.90 (7a) 0.01 <f / f5<1.30 (8a) -2.85<(G2R2+G2R1) / (G2R2-G2R1)<-0.45 (9a) -9.00 <G2R1 / f<-0.90 (10a) -1.40 <f / fair<0.00 (11a-1) 0.00 <f / fair<0.25 (11a-2) -0.90 <f23 / f1<-0.13 (12a) 1.5100 <n1<1.5900 (13a) 47<νd1<63 (14a) 1.590 <nR<1.730 (15a) 16<νdR<29 (16a) 0.27 <h / TR<0.62 (17a) It is more preferable that the numerical ranges of the conditional expressions (2) to (17) be the numerical ranges of the following conditional expressions (2b) to (17b).

[0061] 0.07 <x1 / T<0.60 (2b) 0.10 <T / TTL<0.21 (3b) 0.44 <Dsum / TTL<0.75 (4b) -3.30 <f1 / f<-1.00 (5b) 0.50 <f3 / f2<1.20 (6b) -2.60 <f4 / f<-1.00 (7b) 0.03 <f / f5<1.00 (8b) -2.70<(G2R2+G2R1) / (G2R2-G2R1)<-0.50 (9b) -8.00 <G2R1 / f<-1.00 (10b) -1.30 <f / fair<0.00 (11b-1) 0.00 <f / fair<0.20 (11b-2) -0.80 <f23 / f1<-0.15 (12b) 1.5200 <n1<1.5750 (13b) 49<νd1<61 (14b) 1.600 <nR<1.720 (15b) 17<νdR<28 (16b) 0.30 <h / TR<0.60 (17b) It is further preferable that the numerical ranges of the conditional expressions (2) to (17) be the numerical ranges of the following conditional expressions (2c) to (17c).

[0062] 0.09 <x1 / T<0.55 (2c) 0.12 <T / TTL<0.18 (3c) 0.50 <Dsum / TTL<0.70 (4c) -3.20 <f1 / f<-1.20 (5c) 0.55 <f3 / f2<1.10 (6c) -2.40 <f4 / f<-1.10 (7c) 0.05 <f / f5<0.70 (8c) -2.60<(G2R2+G2R1) / (G2R2-G2R1)<-0.55 (9c) -7.00 <G2R1 / f<-1.20 (10c) -1.20 <f / fair<0.00 (11c-1) 0.00 <f / fair<0.15 (11c-2) -0.60 <f23 / f1<-0.20 (12c) 1.5250 <n1<1.5600 (13c) 53<νd1<59 (14c) 1.610 <nR<1.700 (15c) 18<νdR<27 (16c) 0.32 <h / TR<0.55 (17c) Next, the optical system L0 of each embodiment will be described in detail.

[0063] The optical system L0 of the first, second, fourth, sixth and seventh embodiments is composed of the first lens G1 to the sixth lens G6, which are arranged in order from the object side to the image side, and have negative, positive, positive, negative, positive and negative refractive powers. The optical system L0 of the third embodiment is composed of the first lens G1 to the sixth lens G6, which are arranged in order from the object side to the image side, and have negative, positive, positive, negative, positive and positive refractive powers. In the optical systems L0 of the first to fourth, sixth and seventh embodiments, the lens GR arranged closest to the image side corresponds to the sixth lens G6. In the optical systems L0 of the first to fourth, sixth and seventh embodiments, the front group LF is composed of the first lens G1, and the rear group LR is composed of the second lens G2 to the sixth lens G6.

[0064] The optical system L0 of the fifth embodiment is composed of a first lens G1 to a seventh lens G7, which are arranged in order from the object side to the image side, and have negative, positive, positive, negative, positive, positive, negative refractive powers. In the optical system L0 of the fifth embodiment, the lens GR arranged closest to the image side corresponds to the seventh lens G7. In the optical system L0 of the fifth embodiment, the front group LF is composed of the first lens G1, and the rear group LR is composed of the second lens G2 to the seventh lens G7.

[0065] Each single lens included in the optical system L0 in Examples 1 to 7 has aspheric surfaces on both sides, which allows for good correction of aberrations such as spherical aberration and curvature of field when the optical system L0 is made compact.

[0066] Image blur correction can be performed by moving a part or the whole of the optical system L0 in any one of the first to seventh embodiments in a direction perpendicular to the optical axis.

[0067] Each single lens included in the optical system L0 in Examples 1 to 7 is made of plastic resin. This allows the optical system L0 to be made lighter. In addition, by using plastic resin, it becomes possible to use a mold to mold an aspheric surface with a large sag amount.

[0068] Numerical examples 1 to 7 corresponding to the first to seventh embodiments, respectively, are shown below.

[0069] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial spacing (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incident side. In addition, nd represents the refractive index of each optical member with respect to the d-line, and νd represents the Abbe number of the optical member. The Abbe number νd of a certain material is given by Nd, NF, NC, and Ng, respectively, when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (wavelength 435.8 nm) are νd=(Nd-1) / (NF-NC) It is expressed as:

[0070] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values ​​when the optical system L0 of each example is focused on an object at infinity. "Back focus" is the distance on the optical axis from the final surface (the lens surface closest to the image) to the paraxial image surface expressed as an air-equivalent length. "Total lens length" is the distance on the optical axis from the foreground (the lens surface closest to the object) of the optical system L0 to the final surface (not including the optical block FL) plus the back focus.

[0071] If the optical surface is aspheric, a * symbol is added to the right of the surface number. The aspheric shape is expressed as follows, where X is the displacement from the apex of the surface in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, A10, A12, A14, and A16 are the aspheric coefficients of each order: x=(h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ]+A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12 +A14×h 14 +A16×h 16 In addition, "e±XX" in each aspheric coefficient is "×10± XX " It means.

[0072] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd 1* 44.854 0.40 1.53504 55.7 2* 2.438 0.64 3(Aperture) ∞ 0.11 4* -5.918 0.62 1.53504 55.7 5* -1.544 0.12 6* 6.355 1.05 1.53504 55.7 7* -2.291 0.11 8* -1.528 0.34 1.67070 19.3 9* -5.647 0.26 10* 2.622 0.52 1.53504 55.7 11* -15.980 0.10 12* 1.290 0.50 1.67070 19.3 13* 1.007 0.62 14 ∞ 0.50 1.51633 64.1 15∞0.40 Image plane ∞ Aspheric Data Front page K =-5.10974e+00 A 4= 2.58374e-01 A 6=-2.32403e-01 A 8= 2.59763e-01 A10=-2.15870e-01 A12= 1.20915e-01 A14=-3.82090e-02 A16= 4.86914e-03 2nd side K = 4.54238e+00 A 4= 3.73616e-01 A 6=-2.82707e-01 A 8= 7.57143e-01 A10=-1.49881e+00 A12= 2.05411e+00 A14=-8.61383e-01 A16=-2.85612e-01 Page 4 K = 0.00000e+00 A 4=-1.12583e-01 A 6=-2.23016e-01 A 8= 5.21309e-01 A10=-1.41813e+00 Page 5 K = 0.00000e+00 A 4=-1.06122e-01 A 6= 3.64098e-02 A 8=-3.61070e-01 A10= 6.65467e-01 A12=-6.66978e-01 Page 6 K = 0.00000e+00 A 4=-2.08793e-02 A 6= 4.48319e-03 A 8= 1.49744e-02 A10=-1.64420e-02 A12= 2.27920e-04 Page 7 K = 0.00000e+00 A 4=-1.16027e-01 A 6= 8.40470e-02 A 8=-2.23349e-02 A10=-1.86714e-03 Page 8 K = 0.00000e+00 A 4=-9.53043e-04 A 6= 2.46981e-01 A 8=-1.81603e-01 A10= 4.88421e-02 A12=-1.55463e-03 Page 9 K = 0.00000e+00 A 4=-1.01472e-01 A 6= 2.32428e-01 A 8=-1.39297e-01 A10= 3.71883e-02 A12=-3.75772e-03 Page 10 K = 0.00000e+00 A 4=-2.08842e-02 A 6= 9.53825e-03 A 8=-8.81207e-03 A10 = 1.07801e-03 Page 11 K = 0.00000e+00 A 4= 1.49550e-01 A 6=-5.86093e-02 A 8= 8.61236e-03 A10=-4.80035e-04 Side 12 K =-8.00242e-01 A 4=-1.85283e-01 A 6= 3.30634e-02 A 8=-2.87588e-03 A10= 5.57656e-05 Page 13 K =-2.22227e+00 A 4=-1.21405e-01 A 6= 4.22141e-02 A 8=-9.76127e-03 A10= 1.40866e-03 A12=-1.10634e-04 A14= 3.51288e-06 Focal length 2.30 F-number 2.50 Half angle of view (°) 55.12 Image height 3.30 Lens length 6.13 BF 1.35 Single lens data Lens starting surface focal length 1 1 -4.83 2 4 3.72 3 6 3.29 4 8 -3.23 5 10 4.25 6 12 -23.53 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd 1* -4.868 0.50 1.53504 55.7 2* 5.832 0.57 3(Aperture) ∞ 0.09 4* -10.877 1.08 1.53504 55.7 5* -2.008 0.11 6* 4.905 1.13 1.53504 55.7 7* -2.856 0.08 8* -2.542 0.40 1.67070 19.3 9* -7.209 0.24 10* 2.889 0.62 1.53504 55.7 11* 4.511 0.67 12* 2.632 0.60 1.67070 19.3 13* 1.615 0.50 14 ∞ 0.50 1.51633 64.1 15∞0.40 Image plane ∞ Aspheric Data Front page K = 1.55071e-01 A 4= 1.15187e-01 A 6=-5.49141e-02 A 8= 2.36799e-02 A10=-7.44272e-03 A12= 1.54259e-03 A14=-1.85168e-04 A16= 9.59947e-06 2nd side K = 7.37724e+00 A 4= 1.65535e-01 A 6= 6.79976e-02 A 8=-3.87778e-01 A10= 9.33812e-01 A12=-1.16883e+00 A14= 7.82685e-01 A16=-2.13246e-01 A18=-6.13183e-05 Side 4 K = 0.00000e+00 A 4=-4.48745e-02 A 6=-5.31522e-02 A 8= 5.53273e-02 A10=-8.80872e-02 5th page K = 0.00000e+00 A 4=-5.56343e-02 A 6= 2.19971e-03 A 8=-1.29578e-02 A10= 9.56925e-03 A12=-7.92801e-03 Page 6 K = 0.00000e+00 A 4=-1.56737e-02 A 6= 7.04130e-03 A 8=-7.61633e-03 A10= 2.61939e-03 A12=-1.15650e-03 Page 7 K = 0.00000e+00 A 4=-3.30001e-02 A 6= 8.51259e-03 A 8=-4.03181e-04 A10=-1.37088e-03 Page 8 K = 0.00000e+00 A 4=-1.14635e-02 A 6= 4.18063e-02 A 8=-1.66850e-02 A10= 2.34474e-03 A12= 1.08198e-04 Page 9 K = 0.00000e+00 A 4=-4.95884e-03 A 6= 3.09452e-02 A 8=-1.29088e-02 A10= 2.99390e-03 A12=-2.97265e-04 Page 10 K = 0.00000e+00 A 4=-1.15464e-02 A 6=-1.21732e-02 A 8= 2.84234e-03 A10=-5.64496e-04 A12= 4.17671e-05 Page 11 K = 0.00000e+00 A 4= 2.86345e-02 A 6=-2.31415e-02 A 8= 5.25689e-03 A10=-7.44364e-04 A12= 4.32956e-05 Page 12 K = 3.27936e-02 A 4=-1.05352e-01 A 6= 1.37559e-02 A 8= 1.46391e-03 A10=-1.39417e-03 A12= 2.42353e-04 A14=-1.40640e-05 Page 13 K =-3.13639e+00 A 4=-6.85409e-02 A 6= 1.97372e-02 A 8=-3.80389e-03 A10= 4.25439e-04 A12=-2.48455e-05 A14= 5.76159e-07 Focal length 2.96 F-number: 2.57 Half angle of view(°) 52.64 Image height 3.88 Lens length 7.33 BF 1.23 Single lens data Lens starting surface focal length 1 1 -4.88 2 4 4.41 3 6 3.55 4 8 -6.06 5 10 13.24 6 12 -8.16 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd 1* -2.428 0.50 1.53504 55.7 2* -6.165 0.63 3(Aperture) ∞ 0.15 4* -7.628 1.07 1.53504 55.7 5* -1.815 -0.08 6 ∞ 0.18 7* 7.545 1.25 1.53504 55.7 8* -2.571 0.27 9* -1.727 0.40 1.67070 19.3 10* -5.353 0.17 11* 2.612 0.65 1.53496 55.8 12* 2.704 0.28 13* 1.750 0.60 1.62520 25.4 14* 1.626 0.52 15 ∞ 0.50 1.51633 64.1 16∞0.40 Image plane ∞ Aspheric Data Front page K =-1.00000e+01 A 4= 6.03286e-02 A 6=-1.75332e-02 A 8= 3.69655e-03 A10=-4.24181e-04 A12= 2.00824e-05 2nd side K = 0.00000e+00 A 4= 1.54097e-01 A 6=-3.00773e-02 A 8=-3.29964e-03 A10=9.99220e-03 A12=-1.95079e-03 Side 4 K = 0.00000e+00 A 4=-5.73510e-02 A 6=-1.43112e-02 A 8=-3.70522e-02 5th page K = 0.00000e+00 A 4=-6.58922e-03 A 6=-2.69578e-02 A 8= 1.03067e-02 Side 7 K = 0.00000e+00 A 4= 1.85376e-02 A 6=-2.89351e-02 A 8= 1.98658e-02 A10=-3.56162e-03 Side 8 K = 0.00000e+00 A 4=-5.62447e-02 A 6= 3.67543e-02 A 8=-1.44583e-02 A10= 3.60593e-03 9th page K = 0.00000e+00 A 4=-4.12051e-02 A 6= 1.08458e-01 A 8=-3.95017e-02 A10= 5.66188e-03 Side 10 K = 0.00000e+00 A 4=-6.15660e-02 A 6= 6.82598e-02 A 8=-1.82649e-02 A10 = 1.61523e-03 Page 11 K = 0.00000e+00 A 4=-6.15071e-02 A 6= 5.55664e-03 A 8=-7.48021e-04 Side 12 K = 0.00000e+00 A 4=-4.30437e-02 A 6=-1.47047e-03 A 8=-1.26674e-08 Page 13 K =-2.66556e+00 A 4=-8.92747e-02 A 6= 9.67091e-03 A 8=-1.97026e-04 A10=4.59495e-06 A12=-1.29352e-06 Page 14 K =-1.21200e+00 A 4=-9.83604e-02 A 6= 1.78466e-02 A 8=-1.72373e-03 A10=8.43631e-05 A12=-1.71442e-06 Focal length 2.94 F-number: 2.57 Half angle of view(°) 52.81 Image height 3.88 Lens length 7.33 BF 1.25 Single lens data Lens starting surface focal length 1 1 -7.85 2 4 4.18 3 7 3.75 4 9 -3.98 5 11 41.32 6 13 42.52 [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd 1* -3.658 0.50 1.53504 55.7 2* -30.836 0.70 3(Aperture) ∞ 0.13 4* -9.207 0.69 1.53504 55.7 5* -1.993 0.36 6* 7.400 1.25 1.53504 55.7 7* -2.336 0.29 8* -0.914 0.40 1.67070 19.3 9* -1.482 0.10 10* 5.701 0.78 1.53504 55.7 11* -5.993 0.08 12* 2.111 0.60 1.67070 19.3 13* 1.244 0.72 14 ∞ 0.50 1.51633 64.1 15∞0.40 Image plane ∞ Aspheric Data Front page K =-1.00000e+01 A 4= 5.61175e-02 A 6=-1.50380e-02 A 8= 2.88552e-03 A10=-3.03416e-04 A12= 1.31367e-05 2nd side K = 7.71923e+00 A 4= 1.05704e-01 A 6=-3.69317e-03 A 8= 6.49340e-04 A10=-2.28333e-03 A12= 3.05181e-03 Side 4 K = 0.00000e+00 A 4=-7.33122e-02 A 6=-3.56565e-02 A 8=-1.21429e-02 A10=-5.18042e-02 Page 5 K = 0.00000e+00 A 4=-6.55551e-02 A 6=-2.51965e-02 A 8= 1.67314e-02 A10=-2.80733e-02 Page 6 K = 0.00000e+00 A 4=-2.13289e-02 A 6= 6.16056e-03 A 8=-1.71390e-03 A10=-9.21731e-04 Page 7 K = 0.00000e+00 A 4=-2.23579e-02 A 6=-4.14788e-03 A 8= 5.77057e-03 A10=-1.59222e-03 Page 8 K =-1.82227e+00 A 4=-2.59014e-02 A 6= 3.24122e-02 A 8=-7.67586e-03 A10 = 8.03138e-04 Page 9 K =-5.48902e-01 A 4= 7.92887e-02 A 6=-7.05805e-03 A 8= 3.42842e-03 A10=-2.61252e-04 Page 10 K = 3.72147e+00 A 4= 2.82999e-02 A 6=-1.44233e-02 A 8= 1.08416e-03 A10=-7.23917e-06 Page 11 K =-7.25742e+00 A 4= 1.19414e-01 A 6=-4.25677e-02 A 8= 6.86460e-03 A10=-6.17852e-04 A12= 2.34147e-05 Page 12 K =-8.37208e-01 A 4=-6.68710e-02 A 6= 2.03052e-03 A 8= 8.55185e-04 A10=-1.24435e-04 A12= 4.78200e-06 Page 13 K =-3.30201e+00 A 4=-3.43016e-02 A 6= 4.28150e-03 A 8=-2.61852e-04 A10= 7.98050e-06 A12=-1.68955e-07 Focal length 2.95 F-number: 2.57 Half angle of view (°) 52.75 Image height 3.88 Lens length 7.33 BF 1.45 Single lens data Lens starting surface focal length 1 1 -7.81 2 4 4.60 3 6 3.47 4 8 -4.96 5 10 5.59 6 12 -6.25 [Numerical Example 5] Unit: mm Surface Data Surface number rd nd νd 1* 6.458 0.40 1.53504 55.7 2* 2.118 0.58 3(Aperture) ∞ 0.15 4* -3.465 0.49 1.53504 55.7 5* -1.376 0.05 6* 8.119 0.89 1.53504 55.7 7* -2.162 0.08 8* -1.407 0.34 1.67070 19.3 9* -2.759 0.10 10* 19.587 0.78 1.53504 55.7 11* -7.259 0.10 12* -10.932 0.40 1.53504 55.7 13* -2.257 0.10 14* 1.510 0.50 1.67070 19.3 15* 0.936 0.63 16 ∞ 0.50 1.51633 64.1 17 ∞ 0.13 Image plane ∞ Aspheric Data Front page K =-1.00000e+01 A 4= 2.47895e-01 A 6=-2.07611e-01 A 8= 1.92539e-01 A10=-1.07413e-01 A12= 2.80386e-02 A14= 3.03216e-03 A16=-2.57441e-03 2nd side K = 3.77580e+00 A 4= 3.44844e-01 A 6=-4.37041e-03 A 8=-1.26955e+00 A10= 6.22456e+00 A12=-1.38639e+01 A14= 1.65132e+01 A16=-8.02800e+00 Side 4 K = 0.00000e+00 A 4=-1.23183e-01 A 6=-3.84616e-01 A 8= 1.29881e+00 A10=-2.78564e+00 5th page K = 0.00000e+00 A 4=-1.05101e-01 A 6= 1.27912e-01 A 8=-8.19392e-01 A10= 1.79775e+00 A12=-1.83464e+00 Page 6 K = 0.00000e+00 A 4=-4.58550e-02 A 6= 3.17041e-02 A 8= 9.22088e-03 A10=-3.28449e-02 A12=-3.76701e-03 Page 7 K = 0.00000e+00 A 4=-1.35054e-01 A 6= 1.59987e-01 A 8=-9.10422e-02 A10 = 1.05087e-02 Page 8 K = 0.00000e+00 A 4= 1.63585e-01 A 6= 9.60355e-02 A 8=-8.29861e-02 A10= 2.45568e-04 A12= 1.31236e-02 Page 9 K = 0.00000e+00 A 4= 1.00876e-01 A 6= 3.60420e-02 A 8=-3.91878e-02 A10= 9.91130e-03 A12=-5.81637e-04 Page 10 K = 0.00000e+00 A 4=-9.01749e-02 A 6= 6.85541e-02 A 8=-1.39937e-02 A10 = 4.66725e-04 Page 11 K = 0.00000e+00 A 4=-1.92859e-01 A 6= 1.08180e-01 A 8=-1.78849e-02 A10 = 1.04349e-03 Page 12 K = 0.00000e+00 A 4=-5.90942e-02 A 6= 3.09392e-02 A 8=-8.94600e-03 A10 = 1.30745e-03 Page 13 K = 0.00000e+00 A 4= 1.61211e-01 A 6=-5.92086e-02 A 8= 1.20593e-02 A10=-9.47694e-04 Page 14 K =-5.12936e-01 A 4=-2.13959e-01 A 6= 5.36712e-02 A 8=-1.02618e-02 A10= 3.48894e-04 Page 15 K =-2.98502e+00 A 4=-9.15929e-02 A 6= 3.21065e-02 A 8=-7.48850e-03 A10= 1.05863e-03 A12=-8.69042e-05 A14= 3.07161e-06 Focal length 2.24 F-number 2.50 Half angle of view(°) 55.78 Image height 3.30 Lens length 6.06 BF 1.09 Single lens data Lens starting surface focal length 1 1 -6.08 2 4 3.94 3 6 3.29 4 8 -4.76 5 10 10.00 6 12 5.23 7 14 -5.64 [Numerical Example 6] Unit: mm Surface Data Surface number rd nd νd 1* -2.624 0.40 1.53504 55.7 2* -6.036 0.72 3(Aperture) ∞ 0.13 4* -8.191 0.66 1.53504 55.7 5* -2.039 0.32 6* 7.725 1.21 1.53504 55.7 7* -2.594 0.28 8* -0.843 0.35 1.67070 19.3 9* -1.269 0.10 10* 3.121 0.85 1.54390 56.0 11* 64.912 0.23 12* 2.437 0.55 1.67070 19.3 13* 1.439 0.60 14 ∞ 0.50 1.51633 64.1 15∞0.40 Image plane ∞ Aspheric Data Front page K =-1.00000e+01 A 4= 6.03554e-02 A 6=-1.59995e-02 A 8= 2.99761e-03 A10=-2.94646e-04 A12= 1.17489e-05 2nd side K =-9.96687e+00 A 4= 1.33583e-01 A 6=-3.64447e-02 A 8= 2.32001e-02 A10=-1.21158e-02 A12= 3.96097e-03 Side 4 K = 0.00000e+00 A 4=-7.63143e-02 A 6=-3.08724e-02 A 8=-2.90072e-02 A10=-2.44607e-02 5th page K = 0.00000e+00 A 4=-7.28440e-02 A 6=-1.77884e-02 A 8= 1.38527e-02 A10=-2.51818e-02 Page 6 K = 0.00000e+00 A 4=-3.11454e-02 A 6= 1.41508e-02 A 8=-6.95509e-03 A10=-3.06658e-05 Side 7 K = 0.00000e+00 A 4=-4.49178e-02 A 6= 1.48582e-02 A 8=-5.71955e-03 A10= 2.46606e-04 Side 8 K =-1.87509e+00 A 4= 5.63301e-03 A 6= 2.49331e-02 A 8=-8.76314e-03 A10= 1.18459e-03 9th page K =-1.54008e+00 A 4= 7.36240e-02 A 6=-2.05254e-02 A 8= 8.26123e-03 A10=-1.14720e-03 Side 10 K =-8.66931e+00 A 4= 1.10526e-02 A 6=-6.33933e-03 A 8=-1.89969e-04 A10= 8.46076e-05 Page 11 K = 6.26560e+02 A 4= 5.48271e-02 A 6=-2.10990e-02 A 8= 2.72630e-03 A10=-1.55540e-04 Side 12 K =-3.76670e-01 A 4=-8.12549e-02 A 6= 3.99403e-03 A 8= 9.77794e-04 A10=-1.72885e-04 A12= 6.42501e-06 Page 13 K =-3.16175e+00 A 4=-4.63295e-02 A 6= 7.65771e-03 A 8=-6.88444e-04 A10=3.39710e-05 A12=-7.98143e-07 Focal length 2.95 F-number: 2.57 Half angle of view(°) 52.76 Image height 3.88 Lens length 7.13 BF 1.33 Single lens data Lens starting surface focal length 1 1 -9.05 2 4 4.89 3 6 3.78 4 8 -5.58 5 10 6.00 6 12 -6.73 [Numerical Example 7] Unit: mm Surface Data Surface number rd nd νd 1* 21.538 0.40 1.54390 56.0 2* 2.004 0.75 3(Aperture) ∞ 0.09 4* -18.220 0.85 1.54390 56.0 5* -2.042 0.07 6* 5.785 1.22 1.54390 56.0 7* -2.686 0.05 8* -7.121 0.30 1.67070 19.3 9* 8.800 0.33 10* 2.576 0.55 1.54390 56.0 11* 3.399 0.65 12* 2.148 0.60 1.63910 23.5 13* 1.542 0.58 14 ∞ 0.50 1.51633 64.1 15∞0.40 Image plane ∞ Aspheric Data Front page K =-6.28931e+00 A 4= 4.16536e-02 A 6=-1.27342e-02 A 8= 2.04754e-03 A10=-1.38619e-04 2nd side K =-7.13889e+00 A 4= 1.99690e-01 A 6=-1.08505e-02 A 8=-2.14950e-04 A10 = 2.35800e-02 Page 4 K = 0.00000e+00 A 4=-6.01295e-02 A 6=-5.30816e-02 A 8= 4.26704e-02 A10=-7.62943e-02 Page 5 K = 0.00000e+00 A 4=-5.08759e-02 A 6=-2.02665e-02 A 8= 6.23772e-03 A10=-1.15120e-02 Page 6 K = 0.00000e+00 A 4=-6.43750e-03 A 6=-4.76298e-03 A 8= 2.66962e-04 Page 7 K = 0.00000e+00 A 4=-6.02636e-02 A 6= 2.87875e-02 A 8=-6.34031e-03 Page 8 K = 0.00000e+00 A 4=-5.17712e-02 A 6= 3.57924e-02 A 8=-7.01990e-03 Page 9 K = 0.00000e+00 A 4=-9.45214e-03 A 6= 1.96647e-02 A 8=-3.46866e-03 Page 10 K = 0.00000e+00 A 4=-2.47074e-02 A 6=-2.47926e-03 A 8= 2.66088e-04 A10=-3.24499e-05 Page 11 K = 0.00000e+00 A 4= 2.58321e-03 A 6=-7.89756e-03 A 8= 1.20035e-03 A10=-9.34877e-05 Page 12 K =-3.63370e-01 A 4=-1.02392e-01 A 6= 1.79814e-02 A 8=-2.19312e-03 A10=4.62600e-05 A12=-2.34196e-07 Page 13 K =-3.17912e+00 A 4=-5.13866e-02 A 6= 1.16378e-02 A 8=-1.61568e-03 A10= 1.09141e-04 A12=-2.91799e-06 Focal length 2.96 F-number: 2.57 Half angle of view(°) 52.60 Image height 3.88 Lens length 7.18 BF 1.31 Single lens data Lens starting surface focal length 1 1 -4.09 2 4 4.15 3 6 3.55 4 8 -5.82 5 10 15.81 6 12 -13.93 Various values ​​in each numerical example are summarized in Tables 1 and 2 below.

[0073] [Table 1]

[0074] [Table 2]

[0075] [Imaging device] Next, an embodiment of the imaging device of the present invention will be described. Fig. 16 is a schematic diagram of an imaging device (digital still camera) 10 of this embodiment. The imaging device 10 includes a camera body 13, an optical system 11 similar to any of the optical systems L0 of the first to seventh embodiments, and a light receiving element (image sensor) 12 that photoelectrically converts an image formed by the optical system 11.

[0076] The imaging device 10 of this embodiment can obtain a high-quality image formed by the optical system 11 which has a wide angle, corrects distortion aberration, and improves the peripheral illumination ratio.

[0077] An imaging element such as a CCD or CMOS sensor can be used as the light receiving element 12. In this case, various aberrations such as distortion aberration and chromatic aberration of the image acquired by the light receiving element 12 can be electrically corrected to improve the image quality of the output image.

[0078] The optical system L0 of each of the above-mentioned embodiments can be applied not only to the digital still camera shown in Fig. 16 but also to various optical devices such as a silver halide film camera, a video camera, a telescope, etc. Furthermore, the camera may be of an integrated lens type or of an interchangeable lens type. [Lens device] 17 is a schematic diagram of a lens device 20 of the present invention. The lens device 20 is a so-called interchangeable lens that is detachably attached to a camera body (not shown).

[0079] The lens device 20 has a photographing optical system 21 that is similar to any of the optical systems L0 of Examples 1 to 7. The lens device 20 also has a focus operating means 22 and an operating means 23 for changing the photographing mode.

[0080] When the user operates the focus operation means 22, the arrangement of the photographing optical system 21 is changed mechanically or electrically, thereby changing the focal position.

[0081] Furthermore, the user may operate the operation means 23 to change the arrangement of the lens groups in the photographing optical system 21 for a purpose other than focusing. For example, the arrangement of the lens groups in the photographing optical system 21 may be mechanically or electrically changed in response to the operation of the operation means 23 to change the aberration of the photographing optical system 21. In this case, it is preferable that the focal position does not substantially change.

[0082] The disclosure of this embodiment includes the following configuration. (Configuration 1) The optical system has at least one lens, which are arranged in order from the object side to the image side, including a first lens having a negative refractive power, a second lens having a positive refractive power, and a third lens having a positive refractive power, a first lens surface on the object side of the first lens is aspheric and has a shape in which the convex shape toward the object side is strengthened at a peripheral portion, When the focal length of the first lens is f1 and the focal length of the second lens is f2, -1.50≦f2 / f1<0 An optical system characterized in that the following condition is satisfied: (Configuration 2) Let T be the distance on the optical axis from the first lens surface to the aperture stop, and x1 be the distance along the optical axis between a position on a reference spherical surface that passes through a surface vertex of the first lens surface, the vertex being a distance 3×T / 2 away from the optical axis in a direction perpendicular to the optical axis, and a position on the first lens surface that is a distance T / 2 away from the optical axis in a direction perpendicular to the optical axis, and a position on the first lens surface that is a distance 3×T / 2 away from the optical axis in a direction perpendicular to the optical axis, 0.05 <x1 / T<0.80 2. The optical system according to claim 1, wherein the following condition is satisfied: (Configuration 3) 3. The optical system according to configuration 1 or 2, further comprising an aperture stop between the first lens and the second lens for determining an axial ray. (Configuration 4) When the distance on the optical axis from the object side lens surface of the first lens to the image plane is TTL, and the distance on the optical axis from the object side lens surface of the first lens to the aperture stop is T, 0.08 <T / TTL<0.25 4. The optical system according to configuration 3, wherein the following condition is satisfied: (Configuration 5) When the distance on the optical axis from the object side lens surface of the first lens to the image plane is TTL and the sum of the thicknesses of the lenses included in the optical system is Dsum, 0.40 <Dsum / TTL<0.85 5. The optical system according to any one of configurations 1 to 4, wherein the following condition is satisfied: (Configuration 6) When the focal length of the optical system is f, -3.50 <f1 / f<-0.80 6. The optical system according to any one of configurations 1 to 5, wherein the following condition is satisfied: (Configuration 7) When the focal length of the third lens is f3, 0.40 <f3 / f2<1.50 7. The optical system according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 8) The optical system described in any one of configurations 1 to 7, characterized in having, in order from the object side to the image side, the first lens, the second lens, the third lens, and a fourth lens having negative refractive power. (Configuration 9) The optical system described in configuration 8, comprising, in order from the object side to the image side, the first lens, the second lens, the third lens, the fourth lens, and a fifth lens having positive refractive power. (Configuration 10) The optical system described in configuration 9, comprising the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and a sixth lens arranged in this order from the object side to the image side. (Configuration 11) The optical system described in configuration 10, characterized in that it comprises, arranged in order from the object side to the image side, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and a sixth lens having negative refractive power. (Configuration 12) The optical system described in configuration 10, characterized in that it comprises, arranged in order from the object side to the image side, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and a sixth lens having positive refractive power. (Configuration 13) The optical system described in configuration 10, comprising, in order from the object side to the image side, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, a sixth lens having positive refractive power, and a seventh lens having negative refractive power. (Configuration 14) When the focal length of the optical system is f and the focal length of the fourth lens is f4, -3.00 <f4 / f<-0.80 14. The optical system according to any one of configurations 8 to 13, wherein the following condition is satisfied: (Configuration 15) 14. The optical system according to any one of configurations 8 to 13, wherein the object-side lens surface of the fourth lens is a concave surface. (Configuration 16) When the focal length of the optical system is f and the focal length of the fifth lens is f5, 0.001 <f / f5<1.500 16. The optical system according to any one of configurations 9 to 15, wherein the following condition is satisfied: (Configuration 17) 17. The optical system according to any one of configurations 1 to 16, wherein the object-side lens surface of the second lens has a concave shape facing the object side. (Configuration 18) When the radius of curvature of the lens surface on the object side of the second lens is G2R1 and the radius of curvature of the lens surface on the image side of the second lens is G2R2, -3.00<(G2R2+G2R1) / (G2R2-G2R1)<-0.40 18. The optical system according to claim 17, wherein the following condition is satisfied: (Configuration 19) Let f be the focal length of the optical system, and G2R1 be the radius of curvature of the lens surface of the second lens on the object side. -10.00 <G2R1 / f<-0.80 19. The optical system according to any one of configurations 1 to 18, wherein the following condition is satisfied: (Configuration 20) Let f be the focal length of the optical system, and fair be the focal length of an air lens formed by a second lens surface on the image side of the first lens, a third lens surface on the object side of the second lens, and an air gap between the second lens surface and the third lens surface. -1.50 <f / fair<0.00 0.00 <f / fair<0.30 20. An optical system according to any one of configurations 1 to 19, characterized in that the following condition is satisfied: (Configuration 21) When the composite focal length of the second lens and the third lens is f23, -1.00 <f23 / f1<-0.10 21. The optical system according to any one of configurations 1 to 20, wherein the following condition is satisfied: (Configuration 22) The first lens is made of a plastic resin, When the refractive index of the first lens is n1 and the Abbe number of the first lens is νd1, 1.5 <n1<1.6 45<νd1<65 22. The optical system according to any one of configurations 1 to 21, characterized in that the following condition is satisfied: (Configuration 23) Among the lenses included in the optical system, a final lens arranged closest to the image side is made of plastic resin, When the refractive index of the final lens is nR and the Abbe number of the final lens is νdR, 1.58 <nR<1.75 15<νdR<30 23. The optical system according to any one of configurations 1 to 22, characterized in that the following condition is satisfied: (Configuration 24) An optical system described in any one of configurations 1 to 23, characterized in that at least one of the object-side lens surface and the image-side lens surface of a lens included in the optical system has an aspheric shape and is made of plastic resin. (Configuration 25) a lens surface on the object side of a final lens arranged closest to the image side among the lenses included in the optical system has a stationary point and has a shape that is convex near the optical axis and concave on the periphery, An optical system described in any one of configurations 1 to 24, characterized in that the image-side lens surface of the final lens has a stationary point and has a concave shape near the optical axis and a convex shape on the periphery. (Configuration 26) Let h be the distance from the optical axis to the stationary point on the image-side lens surface of the final lens in the direction perpendicular to the optical axis, and TR be the distance on the optical axis from the aperture stop to the image-side lens surface of the final lens. 0.25 <h / TR<0.65 26. The optical system according to claim 25, wherein the following condition is satisfied: (Configuration 27) An optical system according to any one of configurations 1 to 26; and an image sensor that receives an image formed by the optical system. (Configuration 28) A lens device comprising the optical system according to any one of configurations 1 to 26.

[0083] Although the 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 the gist of the present invention. [Explanation of symbols]

[0084] G1 First Lens G2 Second Lens G3 third lens IP image plane L0 optical system SP aperture stop

Claims

1. An optical system having, arranged in order from the object side to the image side, a first lens with negative refractive power, a second lens with positive refractive power, a third lens with positive refractive power, a fourth lens with negative refractive power, and at least one lens positioned closer to the image side than the fourth lens, The first lens surface, which is the object-side lens surface of the first lens, is aspherical and has a shape in which the convex shape toward the object side becomes stronger at the periphery. When the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the entire optical system is f, and the focal length of the fourth lens is f4, -1.50≦f2 / f1<0 -2.40<f4 / f<-0.80 An optical system characterized by satisfying the following conditional equation.

2. When T is the distance along the optical axis from the first lens surface to the aperture diaphragm, and x1 is the distance in the optical axis direction between a position on the reference sphere that passes through the vertex of the first lens surface, which is 3 × T / 2 away from the optical axis in the direction perpendicular to the optical axis, and a position on the first lens surface that is 3 × T / 2 away from the optical axis in the direction perpendicular to the optical axis, and a position on the first lens surface that is 3 × T / 2 away from the optical axis in the direction perpendicular to the optical axis, 0.05<x1 / T<0.80 The optical system according to claim 1, characterized in that it satisfies the following condition.

3. The optical system according to claim 1 or 2, further comprising an aperture diaphragm that determines an on-axial ray between the first lens and the second lens.

4. When TTL is the distance along the optical axis from the first lens surface to the image plane, and T is the distance along the optical axis from the first lens surface to the aperture diaphragm, 0.08<T / TTL<0.25 The optical system according to claim 3, characterized in that it satisfies the following conditional expression.

5. When TTL is the distance along the optical axis from the first lens surface to the image plane, and Dsum is the sum of the thicknesses of the lenses included in the optical system, 0.40<Dsum / TTL<0.85 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

6. When the focal length of the entire optical system is f, -3.50<f1 / f<-0.80 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

7. When the focal length of the third lens is f3, 0.40<f3 / f2<1.50 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

8. The optical system according to claim 1, characterized in that it comprises a first lens, a second lens, a third lens, a fourth lens, and a fifth lens with positive refractive power, arranged in order from the object side to the image side.

9. The optical system according to claim 8, characterized in that it has a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in order from the object side to the image side.

10. The optical system according to claim 9, characterized in that it comprises the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens having negative refractive power, arranged in order from the object side to the image side.

11. The optical system according to claim 9, characterized in that it comprises the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens having a positive refractive power, arranged in order from the object side to the image side.

12. The optical system according to claim 9, characterized in that it comprises the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens having positive refractive power, and the seventh lens having negative refractive power, arranged in order from the object side to the image side.

13. The optical system according to any one of the configurations 8 to 12, characterized in that the lens surface of the fourth lens on the object side has a shape in which a concave surface faces the object side.

14. When the focal length of the entire optical system is f and the focal length of the fifth lens is f5, 0.001<f / f5<1.500 The optical system according to claim 8 or 9, characterized in that it satisfies the following conditional expression.

15. The optical system according to claim 1 or 2, characterized in that the lens surface of the second lens on the object side has a shape in which a concave surface faces the object side.

16. When the radius of curvature of the object-side lens surface of the second lens is G2R1, and the radius of curvature of the image-side lens surface of the second lens is G2R2, -3.00<(G2R2+G2R1) / (G2R2-G2R1)<-0.80 The optical system according to claim 15, characterized in that it satisfies the following conditional expression.

17. When the focal length of the optical system is f and the radius of curvature of the object-side lens surface of the second lens is G2R1, -10.00<G2R1 / f<-0.40 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

18. When the image-side lens surface of the first lens is the second lens surface, and the object-side lens surface of the second lens is the third lens surface, the focal length of the air lens formed by the air gap between the second lens surface and the third lens surface is fair, and the focal length of the entire optical system is f, -1.50<f / fair<0.00 0.00<f / fair<0.30 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

19. When the combined focal length of the second lens and the third lens is f23, -1.00<f23 / f1<-0.10 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

20. The first lens is made of plastic resin, When the refractive index of the material of the first lens with respect to the d line is n1 and the Abbe number of the material of the first lens is νd1, 1.5<n1<1.6 45 < νd1 < 65 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

21. The final lens, which is positioned closest to the image sensor among the lenses included in the optical system, is made of plastic resin. When the refractive index of the material of the final lens with respect to the d line is nR and the Abbe number of the material of the final lens is νdR, 1.58<nR<1.75 15 < νdR < 30 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

22. The optical system according to claim 1 or 2, characterized in that the lens included in the optical system has at least one surface, the object-side lens surface and the image-side lens surface, having an aspherical shape and being made of plastic resin.

23. The object-side lens surface of the final lens, which is positioned closest to the image among the lenses included in the optical system, has a stationary point and is convex near the optical axis and concave at the periphery. The optical system according to claim 1 or 2, characterized in that the image-side lens surface of the final lens has a stationary point and is concave near the optical axis and convex at the periphery.

24. When h is the distance in the direction perpendicular to the optical axis from the optical axis to the stationary point of the image-side lens surface of the final lens, and TR is the distance along the optical axis from the aperture diaphragm to the image-side lens surface of the final lens, 0.25<h / TR<0.65 The optical system according to claim 23, characterized in that it satisfies the following condition.

25. The optical system according to claim 1 or 2, An imaging device characterized by having an image sensor that receives an image formed by the optical system.

26. A lens device characterized by having the optical system described in claim 1 or 2.

Images