Image forming optical system and image pickup apparatus including the same

Abstract

To provide an imaging optical system capable of achieving both miniaturization and high optical performance.SOLUTION: The imaging optical system is an optical system including a plurality of lens groups, an interval between adjacent lens groups among the plurality of lens groups changing during zooming, the plurality of lens groups including a first lens group having a negative refractive power and a second lens group having a positive refractive power disposed closer to an image side than the first lens group, and the imaging optical system including a first transmissive reflective surface and a second transmissive reflective surface disposed closer to the image side than the first transmissive reflective surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an imaging optical system. [Background technology]

[0002] There is a demand for miniaturization of imaging optical systems (imaging optical systems) used in imaging devices and the like. Summary of the Invention [Problem to be solved by the invention]

[0003] Generally, it is more difficult to design and manufacture a zoom lens than a single focal length lens, making it difficult to achieve both compactness and high optical performance. [Means for solving the problem]

[0004] An image-forming optical system according to one aspect of the present invention is an optical system having a plurality of lens groups, in which the spacing between adjacent lens groups changes during zooming, and in which the plurality of lens groups include a first lens group with negative refractive power and a second lens group with positive refractive power arranged closer to the image than the first lens group, and is characterized by having a first transmissive-reflective surface and a second transmissive-reflective surface arranged closer to the image than the first transmissive-reflective surface. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 2 is a schematic diagram illustrating an optical path of an optical system. [Figure 2] FIG. 2 is a schematic diagram illustrating an optical path of an optical system. [Figure 3] FIG. 2 is a cross-sectional view of the imaging optical system of the first embodiment at the wide-angle end. [Figure 4] 4A to 4C are aberration diagrams of the imaging optical system of Example 1 when focused at infinity. [Figure 5] FIG. 10 is a cross-sectional view of the imaging optical system of Example 2 at the wide-angle end. [Figure 6] 10A and 10B are aberration diagrams of the imaging optical system of Example 2 when focused at infinity. [Figure 7]FIG. 10 is a cross-sectional view of the imaging optical system of Example 3 at the wide-angle end. [Figure 8] 10A and 10B are aberration diagrams of the imaging optical system of Example 3 when focused at infinity. [Figure 9] FIG. 10 is a cross-sectional view of the imaging optical system of Example 4 at the wide-angle end. [Figure 10] 10A and 10B are aberration diagrams of the imaging optical system of Example 4 when focused at infinity. [Figure 11] FIG. 10 is a cross-sectional view of the imaging optical system of Example 5 at the wide-angle end. [Figure 12] 10A to 10C are aberration diagrams of the imaging optical system of Example 5 when focused at infinity. [Figure 13] FIG. 10 is a cross-sectional view of the imaging optical system of Example 6 at the wide-angle end. [Figure 14] 13A to 13C are aberration diagrams of the imaging optical system of Example 6 when focused at infinity. [Figure 15] FIG. 13 is a cross-sectional view of the imaging optical system of Example 7 at the wide-angle end. [Figure 16] 13A to 13C are aberration diagrams of the imaging optical system of Example 7 when focused at infinity. [Figure 17] FIG. 13 is a cross-sectional view of the imaging optical system of Example 8 at the wide-angle end. [Figure 18] 13A to 13C are aberration diagrams of the imaging optical system of Example 8 when focused at infinity. [Figure 19] FIG. 13 is a cross-sectional view of the imaging optical system of Example 9 at the wide-angle end. [Figure 20] 13A to 13C are aberration diagrams of the imaging optical system of Example 9 when focused at infinity. [Figure 21] FIG. 20 is a cross-sectional view of the imaging optical system of Example 10 at the wide-angle end. [Figure 22] 13A to 13C are aberration diagrams of the imaging optical system of Example 10 when focused at infinity. [Figure 23] FIG. 20 is a cross-sectional view of the imaging optical system of Example 11 at the wide-angle end. [Figure 24] 16A to 16C are aberration diagrams of the imaging optical system of Example 11 when focused at infinity. [Figure 25] FIG. 22 is a cross-sectional view of the imaging optical system of Example 12 at the wide-angle end. [Figure 26] 16A to 16C are aberration diagrams of the imaging optical system of Example 12 when focused at infinity. [Figure 27] FIG. 22 is a cross-sectional view of the imaging optical system of Example 13 at the wide-angle end. [Figure 28] 13A to 13C are aberration diagrams of the imaging optical system of Example 13 when focused at infinity. [Figure 29] FIG. 23 is a cross-sectional view of the imaging optical system of Example 14 at the wide-angle end. [Figure 30] 19A to 19C are aberration diagrams of the imaging optical system of Example 14 when focused at infinity. [Figure 31] FIG. 23 is a cross-sectional view of the imaging optical system of Example 15 at the wide-angle end. [Figure 32] 20A to 20C are aberration diagrams of the imaging optical system of Example 15 when focused at infinity. [Figure 33] FIG. 22 is a cross-sectional view of the imaging optical system of Example 16 at the wide-angle end. [Figure 34] 20A to 20C are aberration diagrams of the imaging optical system of Example 16 when focused at infinity. [Figure 35] FIG. 1 is a schematic diagram of an imaging device. DETAILED DESCRIPTION OF THE INVENTION

[0006] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same components, and redundant explanations will be omitted.

[0007] 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, and 33 are cross-sectional views at the wide-angle end of the imaging optical systems of Examples 1 to 16. The imaging optical systems of the respective Examples are used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, cameras for silver halide film, and surveillance cameras.

[0008] In each cross-sectional view, the left side is the object side and the right side is the image side. The imaging optical system of each embodiment may be used as a projection lens for a projector, etc. In this case, the left side is the screen side and the right side is the projected image side.

[0009] The imaging optical system of each embodiment is configured with multiple lens groups. In this specification, a lens group refers to a group of lenses that move or remain stationary as a unit during zooming. That is, in the imaging optical system of each embodiment, the distance between adjacent lens groups changes during zooming. Note that a lens group may be configured with a single lens, or may be configured with multiple lenses. Furthermore, a lens group may include an aperture stop.

[0010] The plurality of lens groups includes, in order from the object side to the image side, a first lens group L1 having a negative refractive power and a second lens group L2 having a positive refractive power.

[0011] Furthermore, SP is an aperture stop. IM is an image plane, and when the imaging optical system of each embodiment is used in a digital still camera or digital video camera, the imaging plane of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is disposed thereon. When the imaging optical system of each embodiment is used as the photographic optical system of a silver halide film camera, a photosensitive surface equivalent to the film surface is disposed on the image plane IM.

[0012] The solid arrows pointing downward in each cross-sectional view indicate the movement locus of each lens group during zooming from the wide-angle end to the telephoto end, and the arrows pointing in the optical axis direction indicate the movement direction of the lens group during focusing.

[0013] The thicknesses of the retarder, polarization-selective transmission / reflection element, and polarizing plate, which will be described later, are omitted. These are sufficiently thin and flat (or have a meniscus shape with almost identical front and back shapes), so their thickness does not affect the essence of the ray-tracing optical design of the present invention. In other words, even if they are inserted in the form of a thin flat plate or the like in consideration of their thickness, it is possible to easily design an imaging optical system with approximately the same aberrations and size by fine-tuning the radius of curvature, thickness, etc. of each lens.

[0014] 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, and 34 are aberration diagrams of the imaging optical systems of Examples 1 to 16 when focused at infinity. (a) and (b) in each diagram show aberration diagrams at the wide-angle end and the telephoto end, respectively.

[0015] In the spherical aberration diagram, Fno is the F-number, and the amount of spherical aberration is shown for the d-line (wavelength 587.6 nm), F-line (wavelength 486.1 nm), C-line (wavelength 656.3 nm), and g-line (wavelength 435.8 nm). In the astigmatism diagram, S indicates the amount of astigmatism on the sagittal image plane, and M indicates the amount of astigmatism on 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 for the g-line is shown. ω is the half angle of view (°).

[0016] Next, the characteristic configuration of the imaging optical system of each embodiment will be described.

[0017] The imaging optical system of each embodiment is a variable magnification optical system that can perform imaging by forming an image of an object on an image plane and obtaining the image by arranging a solid-state image sensor, photosensitive film, or the like on the image plane.

[0018] As described above, the imaging optical system of each embodiment is configured with multiple lens groups, and the multiple lens groups include, in order from the object side to the image side, a first lens group L1 with negative refractive power and a second lens group L2 with positive refractive power. The imaging optical system of each embodiment also includes, in order from the object side to the image side, a first transmission-reflection surface HM1 and a second transmission-reflection surface HM1. Light incident from the object side passes through the first transmission-reflection surface and is reflected by the second transmission-reflection surface. The light then reflects off the first transmission-reflection surface, passes through the second transmission-reflection surface, and enters an imaging unit such as a solid-state image sensor or a photosensitive film.

[0019] The first transmission-reflection surface HM1 and the second transmission-reflection surface HM2 may be provided in the first lens group L1 or in the second lens group L2. Alternatively, the first transmission-reflection surface HM1 may be provided in the first lens group L1, and the second transmission-reflection surface HM2 may be provided in the second lens group L2. Alternatively, the first transmission-reflection surface HM1 and the second transmission-reflection surface HM2 may be provided in lens groups different from the first lens group L1 and the second lens group L2.

[0020] Furthermore, in this specification, the terms "variable magnification optical system" and "zoom lens" have the same meaning. Strictly speaking, a zoom lens refers to an optical system in which the focus does not shift when the magnification is changed, but here the terms "zoom lens" and "variable magnification optical system" will also include optical systems in which the focus shifts.

[0021] Here, the first transmissive-reflective surface HM1 and the second transmissive-reflective surface HM2 do not necessarily have to have a transmittance of 50% and a reflectance of 50%. The ratio of transmittance to reflectance for randomly polarized light is preferably in the range of 1:3 to 3:1. Randomly polarized light is light with Stokes parameters S0 = 1, S1 = S2 = S3 = 0. Furthermore, the first transmissive-reflective surface HM1 and the second transmissive-reflective surface HM2 may absorb light.

[0022] Furthermore, a lens may be formed or bonded to at least one side of the two transmission-reflection surfaces.

[0023] With the above configuration, the imaging optical system of each embodiment can achieve both compactness and high optical performance.

[0024] Next, a description will be given of the configuration that is preferably satisfied in the imaging optical system of each embodiment.

[0025] It is preferable to place an element (a phase shifter) between the first transmission-reflection surface HM1 and the second transmission-reflection surface HM2 to impart a phase difference to the incident light. As the phase shifter, for example, a wave plate (phase plate) such as a quarter-wave plate (QWP) or a 45° polarization rotator (such as a Faraday rotator) can be used.

[0026] For example, a birefringent polymer film or liquid crystal alignment layer can be used as a QWP. A stack of such polymer films or liquid crystal alignment layers can also be used as a QWP. For example, Nippon Kayaku Co., Ltd.'s "WA-140T" or Colorlink Japan Co., Ltd.'s "Polar Correct" can be used. In addition to the above, inorganic wave plates from Dexerials Corporation can also be used as a QWP. Wave plates that exhibit birefringence by orienting atoms or molecules with polarized light irradiation, for example, can also be used. Using such a method, wave plates with higher surface precision can be prepared more easily than with polymer films.

[0027] The QWP can be arranged by bonding it to, for example, the first transmission-reflection surface HM1 or the second transmission-reflection surface HM2. Alternatively, the QWP can be arranged separately from these transmission-reflection surfaces. For example, the film itself can be inserted into the optical path, or a film bonded to a glass plate can be inserted into the optical path. Alternatively, a lens can be formed or bonded to at least one side of the QWP. For example, lenses can be molded on one or both sides of an inorganic waveplate as a substrate using wafer-level optics technology.

[0028] The second lens group L2 preferably has a first transmissive-reflective surface (HM1) and a second transmissive-reflective surface (HM2). In the imaging optical system of each embodiment, light diverged by the first lens group L1, which has negative refractive power, enters the second lens group L2. Therefore, the light enters the second lens group L2 at a relatively high ray height. In this way, by arranging a reflective surface that, in principle, does not produce chromatic aberration at a position with a high ray height, chromatic aberration in the imaging optical system can be effectively corrected. Chromatic aberration correction using this reflective surface is particularly effective in optical systems with small F-numbers that require strict correction of axial chromatic aberration. Furthermore, from the perspective of Petzval sum correction, it is preferable to provide a reflective surface in a lens group with positive refractive power, and in this respect, it is also preferable for the second lens group L2 to have a reflective surface. Because imaging optical systems generally have a positive focal length, the positive refractive power of each lens within the imaging optical system inevitably becomes strong, resulting in a tendency for the Petzval sum in refractive systems to become large and positive. To correct this, a powerful negative lens must be used, but this negative lens has a significant adverse effect on other aberrations, such as sagittal coma, which is particularly noticeable in lenses with small F-numbers. On the other hand, the Petzval sum of a reflecting surface is the opposite of that of a refractive lens. A reflecting surface with positive refractive power has a negative Petzval sum, so the positive Petzval sum generated by a refractive lens with positive refractive power can be offset by the reflecting surface with positive refractive power. For this reason, it is preferable that at least one of the two reflecting surfaces has positive refractive power. Furthermore, it is preferable that the sum of the refractive powers of the two reflecting surfaces is positive, or, even if one of them has negative refractive power, that the reflecting surface with positive refractive power has a high ray height. For this reason, it is natural and preferable from the standpoint of optical arrangement to arrange the reflecting surface in the sub-group with positive refractive power, and it is preferable to arrange the reflecting surface in the second lens group L2.

[0029] As mentioned above, reflecting surfaces play a vital role in correcting aberrations, so it is preferable to move the reflecting surfaces during zooming, which is advantageous because it allows for particularly effective correction of aberrations throughout the entire zoom range while keeping the focus group relatively lightweight.

[0030] In the imaging optical systems of each embodiment, it is possible to configure the multiple lens groups to consist of a first lens group L1 and a second lens group L2. However, in this case, determining the refractive power of each lens group and the spacing between them also determines the amount of movement, limiting the degree of freedom in the configuration of each lens group and making it difficult to achieve high magnification, especially when the F-number is fast. Therefore, it is preferable to position the third lens group closer to the image than the second lens group L2. This is preferable because it increases the degree of freedom in the configuration of each lens group, making it possible to achieve high magnification or high image quality while maintaining the same magnification. It is preferable that the third lens group does not move during zooming, or its movement amount is smaller than that of the second lens group L2. Particularly in interchangeable lens applications, a large amount of space is required for mechanical and electronic components near the lens mount, which is the connection point with the camera body. By fixing the lens group located closest to the image or maintaining a small movement amount, the mechanism for moving the lens groups does not occupy the space for mechanical and electronic components near the lens mount, making it possible to position a larger diameter lens near the image plane, which is preferable. This is preferable because it makes it easier to make the incident angle of off-axis light rays to the sensor closer to telecentricity.

[0031] The imaging optical system in each embodiment is preferably a coaxial system. This is preferable because it increases the ease of manufacturing each component and also simplifies the assembly and adjustment processes. However, the lenses and transmitting / reflecting surfaces do not need to have rotationally symmetric effective diameters or outer diameters; for example, rectangular lenses or lenses with notches or orientation flats indicating the orientation of the various polarizing elements may be used.

[0032] The imaging optical system in each embodiment is preferably a first-order imaging system. If the imaging optical system in each embodiment is a second-order or higher-order imaging system that forms an intermediate image, it is necessary to re-image the light rays that have already formed an image, which increases the overall length, and is therefore not preferable.

[0033] During focusing, it is preferable to move at least one of the lenses located closer to the image than the first transmissive-reflective surface HM1, the second transmissive-reflective surface HM2, and the aperture stop SP along the optical axis. A common focusing method for zoom lenses is to move the lens group located closest to the object (or some of the lenses within that group). This method has the advantage that the amount of movement does not change during zooming, making it easy to ensure parfocality without using special mechanical mechanisms or electronic control. However, in large-aperture zoom lenses, the ray height of the lenses located closer to the object is generally higher than that of the lenses located closer to the image. If the lenses located closer to the object are moved significantly during focusing, significant aberration fluctuations will occur because the lenses are moved at positions with high ray heights. This aberration fluctuation will be particularly unacceptable in large-aperture zoom lenses such as the imaging optical systems of each embodiment. Therefore, it is preferable to move the lenses located closer to the image, where the ray height is relatively low. On the other hand, as mentioned above, the behavior of aberrations caused by a reflecting surface is significantly different from that of a refractive lens, and therefore, in order to balance the aberrations caused by the refractive lens and the reflecting surface, it is preferable to move the reflecting surface as well during focusing. Taking all of this into consideration, it is preferable to move the lens element located closer to the image side than the reflecting surface or aperture stop SP during focusing.

[0034] It is preferable that the first transmissive-reflective surface HM1 and the second transmissive-reflective surface HM2 do not rotate more than 0.5° around the optical axis during focusing. As will be described later, in the imaging optical systems of each embodiment, the relative angles of the quarter-wave plates and the transmissive-reflective surfaces with the optical axis as the axis of rotation are important for suppressing ghosting and ensuring the amount of normal light. Therefore, it is desirable that the first transmissive-reflective surface HM1 and the second transmissive-reflective surface HM2 rotate sufficiently little around the optical axis during focusing. If all anisotropic elements, such as quarter-wave plates and transmissive-reflective surfaces, rotate by the same amount, there is no problem in terms of suppressing ghosting and ensuring the amount of normal light. However, if the degree of polarization of the light incident on the imaging optical system is not low, the direction of the transmitted polarization changes as each element rotates by the same amount, which is undesirable because it may cause changes in brightness or color during focusing depending on the subject.

[0035] It is preferable that one of the first transflective surface HM1 or the second transflective surface HM2 be a spherical surface. Using an aspherical surface is advantageous for aberration correction, but it is more difficult to achieve a surface shape that approaches the design value than with a spherical surface, so using a spherical surface makes it easier to manufacture. In addition, minute processing marks tend to remain on aspherical surfaces, and if such processing marks remain on the reflective surface in particular, patterns resulting from the processing marks are likely to appear in the bokeh. In large-aperture lenses for photography and video applications, users also place importance on the quality of the bokeh, so the occurrence of such patterns is undesirable.

[0036] Furthermore, the first transmission-reflection surface HM1 and the second transmission-reflection surface HM2 may be polarization-selective transmission-reflection elements. By inserting a 45° optical rotator such as a Faraday rotator between the transmission-reflection surfaces, loss of light intensity can be significantly reduced. In this case, the first quarter-wave plate, the second quarter-wave plate (QWP2), and the linear polarizer (POL) are not necessarily required in the configuration described below.

[0037] Next, conditions that the imaging optical system of each embodiment should preferably satisfy will be described. The imaging optical system of each embodiment should preferably satisfy one or more of the following conditional expressions (1) to (10).

[0038] 1.0≦fgr / fw≦4.5 (1) 2.0≦(R1×R2) / {(R1+R2)×fgr}≦7.0 (2) 20≦νd mf ≦65 (3) 20≦νd mm ≦96 (4) 50≦νd mr ≦96 (5) 1.40≦nd m ≦1.85 (6) 1.45≦dp / fw≦4.0 (7) 0.0≦|θm|≦8.0 (8) 2.0≦|θl|≦50.0 (9) 0.0≦θin≦40.0 (10) Here, fgr is the focal length of the lens group including the one with the smaller radius of curvature, either the first transmissive-reflective surface HM1 or the second transmissive-reflective surface HM2. fw is the focal length of the imaging optical system at the wide-angle end. R1 is the radius of curvature of the first transmissive-reflective surface HM1. R2 is the radius of curvature of the second transmissive-reflective surface HM2. The radii of curvature R1 and R2 are the absolute values ​​of the radii of curvature of the first transmissive-reflective surface HM1 and the second transmissive-reflective surface HM2, respectively, and are always positive values ​​regardless of their orientation. νd mf is the average value of the Abbe numbers of the positive lenses arranged closer to the object side than the first transmitting-reflecting surface HM1. mm is the average value of the Abbe numbers of the positive lenses arranged between the first transmitting-reflecting surface HM1 and the aperture stop SP when the aperture stop SP is arranged closer to the image side than the second transmitting-reflecting surface HM1. mr is the average value of the Abbe numbers of the positive lenses arranged between the aperture stop SP and the second transmitting-reflecting surface HM2 when the aperture stop SP is arranged closer to the object than the first transmitting-reflecting surface HM1. Note that the Abbe numbers in conditional expressions (3) to (5) are expressed in the same definition as the Abbe number, which will be described later. mis the refractive index at the d-line of the positive lens (first lens) located between the first transmissive-reflective surface HM1 and the second transmissive-reflective surface HM2. dp is the distance on the optical axis between the object-side surface of the lens located closest to the object at the wide-angle end and the entrance pupil. θm [°] is the smaller of the open angle of the first transmissive-reflective surface HM1 and the open angle of the second transmissive-reflective surface HM2. θl [°] is the larger of the open angle of the first transmissive-reflective surface HM1 and the open angle of the second transmissive-reflective surface HM2. The open angle is the angle of the surface normal with respect to the direction perpendicular to the optical axis, and is evaluated as the maximum value within the effective surface. The effective surface is the area through which normal light, i.e., not ghost or stray light, passes. θin [°] is the angle of incidence when the chief ray of the most off-axis light beam first enters the one with the smaller open angle out of the first transmission-reflection surface HM1 and the second transmission-reflection surface HM2.

[0039] If the upper limit of conditional expression (1) is exceeded, the refractive power of the reflecting surface will be too strong for the imaging optical system, causing the light rays to bounce up significantly, resulting in a large lens outer size. Furthermore, since many lenses are required to correct aberrations within a lens group having a large refractive power for the imaging optical system, the weight and overall length of the imaging optical system will increase. If the lower limit of conditional expression (1) is exceeded, the effect of the reflecting surface on the imaging optical system will be weakened, resulting in insufficient aberration correction. Note that, in the present invention, it is not essential that the radii of curvature of the respective transmitting-reflecting surfaces be different from each other. However, it is preferable to have the transmitting-reflecting surfaces be different from each other, as this allows for greater design freedom, for example.

[0040] If the upper limit of conditional expression (2) is exceeded, the refractive power of the reflecting surface becomes too strong, and the lens element positioned closer to the object must be large in order to deflect light rays significantly. Also, the Petzval sum becomes overcorrected. If the lower limit of conditional expression (2) is exceeded, the refractive power of the reflecting surface becomes too weak, resulting in insufficient correction of axial chromatic aberration and Petzval sum.

[0041] The radius of curvature of the flat surface is assumed to be ∞. When only one of the transmissive-reflective surfaces is flat, conditional expression (2) can be transformed into the following conditional expression (2') by setting the radius of curvature of the non-flat transmissive-reflective surface to R.

[0042] 2.0≦R / fgr≦7.0 (2') If the upper limit of conditional expression (3) is exceeded, the balance between the lens element positioned closer to the image than the aperture stop SP and the lateral chromatic aberration cannot be achieved, resulting in large lateral chromatic aberration. If the lower limit of conditional expression (3) is not reached, the dispersion of the positive lens element becomes too large, resulting in large axial chromatic aberration.

[0043] If the upper limit of conditional expression (4) is exceeded, it will be necessary to use a special ultra-low dispersion glass material that is difficult to process, which is undesirable as it makes manufacturing difficult.If the lower limit of conditional expression (4) is exceeded, the wavelength dispersion of the positive lens will become too large, and axial chromatic aberration and lateral chromatic aberration will become large.

[0044] If the upper limit of conditional expression (5) is exceeded, it will be necessary to use a special ultra-low dispersion glass material that is difficult to process, which is undesirable as it makes manufacturing difficult.If the lower limit of conditional expression (5) is exceeded, the wavelength dispersion of the positive lens will become too large, and the axial chromatic aberration and chromatic aberration of magnification will become large.

[0045] If the upper limit of conditional expression (6) is exceeded, and if the reflecting surface is given sufficient power, the refractive power of the lens acting on the light rays three times between the transmitting and reflecting surfaces will be too strong, disrupting the power balance of the entire imaging optical system. If the curvature of the reflecting surface is reduced, the power of the reflecting surface will be too weak, making it difficult to make full use of the aberration correction ability of the reflecting surface. If the lower limit of conditional expression (6) is exceeded, a special material that is difficult to process will have to be used, making manufacturing difficult and undesirable.

[0046] If the upper limit of conditional expression (7) is exceeded, the entrance pupil will be located in a recessed position, and the position where off-axial light beams pass through the lens located on the object side will be farther from the optical axis. This will result in the lens diameter of the lens located on the object side becoming larger, making handling inconvenient. If the lower limit of conditional expression (7) is exceeded, it will be impossible to ensure sufficient space for arranging a sufficient number of lenses located on the object side of the aperture stop SP or sufficient spacing for movement of the lens groups during zooming, which is undesirable.

[0047] As will be described later, in the imaging optical system of each embodiment, at least one of the first transmissive-reflective surface HM1 and the second transmissive-reflective surface HM2 uses a polarization-selective transmissive-reflective element such as a polarizing beam splitter. It is difficult to form a polarization-selective transmissive-reflective element on a curved surface. If the shape is close to a flat surface, it can be manufactured using a process similar to that of a flat surface. However, the more the shape deviates from a flat surface, the more specialized the process becomes. Therefore, exceeding the upper limit of conditional expression (8) increases the difficulty of forming the polarization-selective transmissive-reflective element. By definition, the lower limit of conditional expression (8) cannot be exceeded.

[0048] Furthermore, when a flexible material such as a resin film or a wire grid using a resin film as a base material is used as the polarization-selective transmission / reflection element, it is necessary to maintain the surface precision of the transmission / reflection surface appropriately. Therefore, when either the first transmission / reflection surface HM1 or the second transmission / reflection surface HM2 is made of such a material, it is preferably bonded to glass or a hard resin with a glass transition temperature of 40°C or higher. It is more preferable that both surfaces are bonded to glass or a hard resin with a glass transition temperature of 40°C or higher. While the adhesive (including elastic adhesive) used for bonding is not particularly specified, the adhesive layer is preferably 25 μm or less, and more preferably 15 μm or less. Furthermore, when only one surface is bonded, it is preferable that the holding member does not come into direct contact with the transmission / reflection surface when holding the lens. For example, it is preferable to hold it at the bonded glass or hard resin member. This reduces surface distortion of the transmission / reflection surface. Regarding surface precision, it is preferable to make the roughness of the reflected wavefront sufficiently smooth, and it is preferable that the rms of the component of 1 / mm or more on the reflected wavefront is 10 nm or less, and the rms of the component of 0.05 / mm or more and 1 / mm or less is 10 nm or less. This is preferable because it makes it possible to sufficiently suppress degradation of image quality due to poor surface precision of the reflecting surface.

[0049] If the upper limit of conditional expression (9) is exceeded, the open angle of the transmission-reflection surface becomes too large, making it difficult to fabricate a homogeneous transmission-reflection element, and if the lower limit of conditional expression (9) is not met, the power of the reflection surface becomes too weak, making it impossible to satisfactorily correct aberrations by the reflection surface.

[0050] Since the characteristics of a polarization element such as a polarization-selective transmission / reflection element are angle-dependent, it becomes difficult to obtain the desired characteristics when the upper limit of conditional expression (10) is exceeded. By definition, the lower limit of conditional expression (10) cannot be exceeded.

[0051] It is more preferable that the lower limit of conditional expression (1) be set to 1.1, 1.2, 1.3, 1.4, or 1.5, and the upper limit of conditional expression (1) be set to 4.3, 4.1, 3.9, 3.7, or 3.5.

[0052] It is more preferable that the lower limit of conditional expression (2) be set to 2.1, 2.2, 2.3, 2.4, or 2.5, and it is more preferable that the upper limit of conditional expression (2) be set to 6.8, 6.6, 6.4, 6.2, or 6.0.

[0053] It is more preferable that the lower limit of conditional expression (3) be set to 21, 22, 23, 24, or 25. It is more preferable that the upper limit of conditional expression (3) be set to 63, 61, 59, 57, or 55.

[0054] It is more preferable that the lower limit of conditional expression (4) be set to 21, 22, 23, 24, or 25. It is more preferable that the upper limit of conditional expression (4) be set to 91, 87, 83, 79, or 75.

[0055] It is more preferable that the lower limit of conditional expression (5) be set to 51, 52, 53, 54, or 55. It is more preferable that the upper limit of conditional expression (5) be set to 95, 92, 89, 86, or 83.

[0056] It is more preferable that the lower limit of conditional expression (6) be set to 1.41, 1.42, 1.43, 1.44, or 1.45, and it is more preferable that the upper limit of conditional expression (6) be set to 1.84, 1.83, 1.82, 1.81, or 1.80.

[0057] It is more preferable that the lower limit of conditional expression (7) be set to 1.50, 1.55, 1.60, 1.65, or 1.70, and it is more preferable that the upper limit of conditional expression (7) be set to 3.9, 3.8, 3.7, 3.6, or 3.5.

[0058] Furthermore, it is more preferable that the upper limit of conditional expression (8) be set to 7.0, 6.0, 5.0, 4.5, or 4.0.

[0059] It is more preferable that the lower limit of conditional expression (9) be set to 2.5, 3.0, 3.5, 4.0, or 5.0, and it is more preferable that the upper limit of conditional expression (9) be set to 45, 42, 40, 38, or 35.

[0060] It is more preferable that the upper limit of conditional expression (10) be set to 37, 34, 31, 28, or 25.

[0061] One of the first transflective surface HM1 and the second transflective surface HM2 is preferably a surface that separates incident light into reflected light and transmitted light according to its polarization state. For example, it is preferably a polarization-selective transflective element. Examples of polarization-selective transflective elements include those manufactured by Asahi Kasei Corporation under the trade name "WGF," 3M Company under the trade name "IQP-E," and Moxtek, Inc. under the trade name "ProFlux." The polarization-selective reflective element may be an optical element created by forming a grid on the lens reflective surface during lens molding and then depositing, printing, or lithographically depositing a metal or dielectric material thereon. The other may be a half mirror, cholesteric liquid crystal, or the like. When a half mirror is used, the amount of randomly polarized light incident from the object side is reduced to 12.5% ​​or less by the time it reaches the image plane. Furthermore, when a cholesteric liquid crystal is used, the amount of light on the image plane can be approximately doubled compared to when a half mirror is used.

[0062] Furthermore, in the imaging optical system of each embodiment, for example, by adopting the following configuration, it is possible to suppress a decrease in the amount of light in the normal imaging optical path while reducing ghost light (unwanted light leakage) from the optical path that passes through the transmissive-reflective surface without ever reflecting. [Polarized light configuration 1] A configuration using polarized light will be described with reference to FIG. 1. The imaging optical system of this configuration has two transmissive-reflective surfaces. Here, the transmissive-reflective surface located on the object side of the imaging optical system of this configuration is configured by placing a polarization-selective transmissive-reflective element (PBS):A. The transmissive-reflective surface located on the image plane side of the imaging optical system of this configuration is configured by placing a half mirror (HM):C. In addition, a first quarter-wave plate (QWP1):B is placed between the polarization-selective transmissive-reflective element PBS and the half mirror HM. In addition, a second quarter-wave plate (QWP2):D and a linear polarizer (POL):E are placed, in that order from the object side to the image side, between the half mirror HM and the imaging plane IM.

[0063] Here, the polarization-selective transmission-reflection element A is an element configured to reflect linearly polarized light polarized in the same direction as when it passed through the linear polarizer E, and to transmit linearly polarized light perpendicular to that. The polarization-selective transmission-reflection element A is, for example, a wire grid polarizer or a reflective polarizer having a laminated retardation film configuration. In this case, the wire grid-formed surface or retardation film surface of the polarization-selective transmission-reflection element A functions as the transmission-reflection surface. Note that the wire grid polarizer does not necessarily have to be one in which metal wires are aligned, but may be one that has thin metal or dielectric layers at predetermined intervals and functions as a polarization-selective transmission-reflection element. For example, an element in which metal or dielectric layers are aligned by vapor deposition can be used.

[0064] The first quarter-wave plate B and the second quarter-wave plate D are arranged with their slow axes tilted at 45° with respect to the polarization transmission axis of the linear polarizer E. Preferably, the first quarter-wave plate B and the second quarter-wave plate D are arranged with their slow axes tilted at 90°. With this arrangement, when light passes through the first quarter-wave plate B and the second quarter-wave plate D, the wavelength dispersion characteristics of the wave plates cancel each other out.

[0065] The half mirror C is formed of, for example, a dielectric multilayer film or metal vapor deposition, and the mirror surface of the half mirror C functions as a transmission / reflection surface. The linear polarizer E is, for example, an absorptive linear polarizer.

[0066] Next, the optical path selection and operation in the polarization utilization configuration will be described.

[0067] Light entering the imaging optical system from the object side becomes linearly polarized light by polarization-selective transmission / reflection element A, then becomes circularly polarized light by first quarter-wave plate B, and enters half mirror C. Part of the light that reaches half mirror C is reflected, becomes reverse-circularly polarized light, and returns to first quarter-wave plate B.

[0068] The counter-circularly polarized light that returned to the first quarter-wave plate B is converted by the first quarter-wave plate B into linearly polarized light polarized in a direction perpendicular to the direction when the light first passed through the polarization-selective transmission-reflection element A and returns to the polarization-selective transmission-reflection element A. The light that returned to the polarization-selective transmission-reflection element A is reflected by the polarization-selective transmission-reflection element A. Due to the polarization selectivity of the polarization-selective transmission-reflection element A, linearly polarized light polarized in a direction perpendicular to the direction when the light first passed through the polarization-selective transmission-reflection element A is reflected.

[0069] On the other hand, part of the light that reaches the half mirror C is transmitted and becomes linearly polarized light polarized in the same direction as when it passed through the polarization-selective transmission-reflection element A by the second quarter-wave plate D, and is incident on the linear polarizer E and absorbed by the linear polarizer E.

[0070] The light reflected by the polarization-selective transmission / reflection element A is converted into circularly polarized light by the first quarter-wave plate B and enters the half mirror C. A portion of the light that reaches the half mirror C is transmitted and enters the second quarter-wave plate D. The second quarter-wave plate D converts the incident light into linearly polarized light that is oriented parallel to the linearly polarized light reflected by the polarization-selective transmission / reflection element A. The light that passes through the second quarter-wave plate D enters the linear polarizer E. Here, the polarization of the light and the transmission axis of the linear polarizer E are aligned, so most of the light is transmitted and directed to the imaging plane IM.

[0071] Due to the above-mentioned action, only the light that has been transmitted through the polarization-selective transmission / reflection element PBS, reflected by the half mirror C, reflected by the polarization-selective transmission / reflection element PBS, and transmitted through the half mirror C is guided to the imaging plane IM.

[0072] If a cholesteric liquid crystal is used instead of the half mirror C, it is preferable to set it up so that it reflects a large amount of circularly polarized light in the direction of the incident light during the first reflection of the cholesteric liquid crystal. This makes it possible to reduce ghost light while increasing the amount of light in the normal optical path.

[0073] Furthermore, solid-state imaging elements and CCDs (charge-coupled devices) that can be used as the imaging surface IM generally have high surface reflectivity. In this configuration, light reflected by the imaging surface IM passes through the linear polarizer E again and is converted into circularly polarized light by the second quarter-wave plate D. The light exiting the second quarter-wave plate D is then reflected by the half mirror C, becoming circularly polarized light in the opposite direction, and passes through the second quarter-wave plate D again. At this time, the circularly polarized light is converted by the second quarter-wave plate D into linearly polarized light in a direction perpendicular to the direction of the light immediately after passing through the linear polarizer E. Because the direction of this linearly polarized light is perpendicular to the transmission axis of the linear polarizer E, most of the light is absorbed by the linear polarizer E. In this configuration, most of the light reflected by the imaging surface IM and the half mirror C in this order is blocked, making ghosts and flare associated with the imaging surface IM less noticeable. To achieve this reflection reduction effect, it is preferable that an optical low-pass filter utilizing birefringence not be present between the imaging surface IM and the linear polarizer E. This is because the optical low-pass filter causes the polarization state to deviate from the desired polarization state.

[0074] In this configuration, a quarter-wave plate may be placed between the polarization-selective transflector A and the object. The quarter-wave plate is positioned so that its fast or slow axis forms a 45° angle with the transmission axis of the polarization-selective transflector A. This allows imaging regardless of the polarization direction, even if the light incident from the object side is linearly polarized. Alternatively, a depolarizing element may be placed instead of the quarter-wave plate. For example, Toyobo Co., Ltd.'s "Cosmoshine SRF" can be used as a depolarizing element. Cosmoshine SRF is a film with a large birefringence around 10,000 nm. Using such a film can potentially reduce color unevenness caused by the wavelength and angle characteristics of the wave plate compared to using a quarter-wave plate. [Polarized Configuration 2] A configuration using polarized light will be described with reference to FIG. The imaging optical system of this configuration has two transmissive-reflective surfaces. Here, the transmissive-reflective surface located on the object side of the imaging optical system of this configuration is configured by placing a half mirror (HM):C. In addition, the transmissive-reflective surface located on the imaging surface side of the imaging optical system of this configuration is configured by placing a polarization-selective transmissive-reflective element (PBS):A. In addition, a first quarter-wave plate (QWP1):B is placed between the polarization-selective transmissive-reflective element PBS and the half mirror HM. Between the half mirror HM and the object surface, a linear polarizer (POL):E and a second quarter-wave plate (QWP2):D are placed, in that order from the object side to the image side.

[0075] Here, the configuration of each polarizing element and the preferred arrangement of the optical axis orientation are the same as in the polarized light-utilizing configuration 1.

[0076] Next, the optical path selection and operation in the polarization utilization configuration will be described.

[0077] Light entering the imaging optical system from the object side becomes linearly polarized light by linear polarizer E, then becomes circularly polarized light by second quarter-wave plate D, and enters half mirror C. Part of the light that reaches half mirror C is reflected and becomes circularly polarized in the reverse direction, returning to the second quarter-wave plate D.

[0078] The light that reaches and is reflected by half mirror C is circularly polarized in the opposite direction to when it was incident. This light is then transformed by second quarter-wave plate D into linearly polarized light polarized in the direction perpendicular to when it passed through linear polarizer E, and is then incident on and absorbed by linear polarizer E.

[0079] Meanwhile, the light that passes through half mirror C is converted by first quarter-wave plate B into linearly polarized light polarized in the same direction as the light immediately after passing through linear polarizer E. This linearly polarized light is reflected by polarization-selective transmission / reflection element A and returns to first quarter-wave plate B. The light is then converted into circularly polarized light by first quarter-wave plate B, and a portion of this circularly polarized light is reflected by half mirror C. The light reflected by half mirror C enters first quarter-wave plate B again and is converted into linearly polarized light whose polarization direction is orthogonal to that when it was reflected by polarization-selective transmission / reflection element A. This linearly polarized light passes through polarization-selective transmission / reflection element A and is directed to the imaging plane IM.

[0080] Due to the above-mentioned action, only the light that passes through the half mirror C, is reflected by the polarization-selective transmission / reflection element PBS, is reflected by the half mirror C, and is transmitted through the polarization-selective transmission / reflection element PBS is guided to the imaging plane IM.

[0081] In this arrangement, a linear polarizer A' may be placed between the polarization-selective transmission / reflection element A and the imaging plane IM. In this case, the transmission axes of the linear polarizer A' and the polarization-selective transmission / reflection element A are aligned. In this way, it is possible to absorb light that is reflected by the imaging plane IM, further reflected by the polarization-selective transmission / reflection element A, and then re-enters the imaging plane IM, causing ghosts and flares.

[0082] In this configuration, a quarter-wave plate may be placed between the linear polarizer E and the object. In this case, the quarter-wave plate is placed so that the fast axis or slow axis of the quarter-wave plate forms a 45° angle with the transmission axis of the linear polarizer E. By doing so, even if the light incident from the object side is linearly polarized, it is possible to capture an image regardless of its polarization direction. Furthermore, a depolarizing element may be placed instead of the quarter-wave plate. For example, Toyobo Co., Ltd.'s "Cosmoshine SRF" can be used as the depolarizing element.

[0083] In the above description of the configuration, terms such as orthogonal, parallel, and 45° are used, but these do not necessarily have to be strictly 90°, 0°, or 45°. However, these should be within ±5° of the desired angle, preferably within ±2°, and even more preferably within ±1°.

[0084] However, this depends heavily on the characteristics of the first and second quarter-wave plates. If the quarter-wave plate characteristics are ideal and the change in characteristics with respect to wavelength and angle of incidence is sufficiently small, then, for example, in the configuration shown in Figure 1, the relative angle between "A and B" and "D and E" can be any number of degrees. In reality, it is difficult to make the characteristics of the quarter-wave plate that ideal, so an angle that makes the intensity and color of ghost light less noticeable can be used.

[0085] In both of these configurations, it is desirable to use the same two QWPs. This would not be a problem if the QWP were ideal (one that provides a phase of exactly 1 / 4 wavelength for all wavelengths and all incident angles within the range of use). However, in reality, such a QWP does not exist, and the phase imparted to light varies depending on the wavelength of the transmitted light, etc. In these two configurations, the phases imparted by QWP1 and QWP2 are precisely offset when light passes through the two QWPs, allowing only the desired light to exit toward the image plane. In other words, light that has been reflected once by the first and second transflective surfaces is emitted toward the image plane, while light that has not been reflected once or has been reflected twice is absorbed by the polarizer. If the characteristics of the QWPs differ, unintended light will be emitted toward the image plane, resulting in increased ghosting and flare, degrading image quality.

[0086] Consider the case where the above two configurations are used in combination with an image sensor including an optical low-pass filter. In this case, it is preferable to set the relative angle between the transmission axis of the polarizing plate closest to the image and the fast axis of the birefringent plate closest to the object among the birefringent plates constituting the optical low-pass filter to 45° or 135°. This allows for a low-pass effect similar to that of a conventional optical system (one that is almost polarization-independent, unlike a typical refractive optical system). Alternatively, a quarter-wave plate may be further disposed on the image side of the polarizing plate closest to the image. In this case, it is preferable to set the angle between the transmission axis of the polarizing plate closest to the image and the fast axis of the quarter-wave plate to 45° or 135°. By doing so, circularly polarized light can be emitted toward the image sensor, thereby achieving a low-pass effect similar to that of a conventional optical system. Alternatively, a plastic molded lens with high birefringence may be disposed on the image side of the polarizing plate closest to the image to convert the emitted light into pseudo-random polarized light, thereby achieving a low-pass effect similar to that of a conventional optical system. In addition, in the above two types of configurations, the polarization-selective transmission / reflection element, quarter-wave plate, and linear polarizer may be circular or rectangular. These optical elements are primarily made of polymer materials and are available at low cost. When using such elements, it is preferable to bond them to a glass or resin plate, for example, as described above, to ensure sufficient surface accuracy. In this configuration, material waste can be eliminated by bonding a large-sized element and then cutting out the required rectangular portion. Furthermore, as described above, the azimuth between each element is important in the above two types of configurations. Using rectangular elements makes it easier to guarantee the outer shape of the component and the orientation of the element (fast axis / slow axis, transmission axis / absorption axis, transmission axis / reflection axis) on a component-by-component basis, simplifying or eliminating the need for azimuth adjustment.

[0087] In the imaging optical system of each embodiment, the lenses may be made of either a resin material or a glass material, but it is preferable that the lens disposed between the first transmission-reflection surface HM1 and the second transmission-reflection surface HM2 has low birefringence.

[0088] Next, the imaging optical system of each embodiment will be described in detail.

[0089] The lens groups in Example 1 are composed of first to third lens groups arranged in order from the object side to the image side. The first and second lens groups have negative and positive refractive powers, respectively. The third lens group is composed of a sensor protection glass. The first and second lens groups correspond to the first lens group L1 and the second lens group L2, respectively.

[0090] The lens groups in Examples 2, 3, and 9 and 10 are composed of first to fourth lens groups arranged in order from the object side to the image side. The first to third lens groups have negative, positive, and positive refractive powers, respectively. The fourth lens group is composed of a sensor protection glass. The first and second lens groups correspond to the first and second lens groups L1 and L2, respectively.

[0091] The lens groups in Examples 4 to 5 and 13 to 15 are composed of first to fifth lens groups arranged in order from the object side to the image side. The first to fourth lens groups have positive, negative, positive, and positive refractive powers, respectively. The fifth lens group is composed of a sensor protection glass. The second and third lens groups correspond to the first and second lens groups L1 and L2, respectively.

[0092] The lens groups in Examples 6 to 8 are composed of first to fifth lens groups arranged in order from the object side to the image side. The first to fourth lens groups have negative, positive, positive, and positive refractive powers, respectively. The fifth lens group is composed of a sensor protection glass. The first and second lens groups correspond to the first and second lens groups L1 and L2, respectively.

[0093] The lens groups of Example 11 are composed of first to fifth lens groups having negative, positive, positive, negative, and positive refractive powers, arranged in this order from the object side to the image side. The first lens group and the third lens group correspond to the first lens group L1 and the second lens group L2, respectively.

[0094] The lens groups of Example 12 are composed of first to fourth lens groups having negative, positive, negative, and positive refractive powers, arranged in this order from the object side to the image side. The first and second lens groups correspond to the first and second lens groups L1 and L2, respectively.

[0095] The lens groups of Example 16 are composed of first to fourth lens groups arranged in order from the object side to the image side. The first to third lens groups have negative, positive, and negative refractive powers, respectively. The first and second lens groups correspond to the first and second lens groups L1 and L2, respectively. The fourth lens group is composed of a sensor protection glass.

[0096] In the imaging optical system of Example 7, for example, the amount of light reaching the imaging plane can be significantly increased by adopting the following configuration. The first transmissive-reflective surface HM1 is a half mirror, the second transmissive-reflective surface HM2 is a polarization-selective transmissive-reflective element, and a polarization-selective transmissive-reflective element is also disposed on the object-side surface of the fifth lens, counting from the object side. Furthermore, a quarter-wave plate is disposed between the polarization-selective transmissive-reflective element and the first transmissive-reflective surface HM1. Both the light reflected by and transmitted through the first transmissive-reflective surface HM1 are reflected by different polarization-selective transmissive-reflective elements. Of these, the light reflected by the second transmissive-reflective surface HM2 is reflected again by the first transmissive-reflective surface HM1 and proceeds toward the image side. The light reflected by the other polarization-selective transmissive-reflective element passes through the first transmissive-reflective surface HM1 and proceeds toward the image side. Here, the fifth and sixth lenses, counting from the object side, are symmetrical with respect to the first transmissive-reflective surface HM1. For this reason, the two beams of light that first enter the first transmitting-reflecting surface HM1 and branch off will overlap when they next emerge from the first transmitting-reflecting surface HM1 toward the image side (in an ideal state with no manufacturing errors, etc.) In this way, by forming both beams of light branched by the half mirror at the same position on the image plane, the illuminance on the image plane can be roughly doubled.

[0097] In the imaging optical system of Example 8, the lens on the image side of the fourth lens group is molded from resin. In this way, by using resin to provide only the aspherical component, an aspherical surface can be easily realized.

[0098] In the imaging optical system of the twelfth embodiment, three lenses arranged immediately after the aperture stop SP (on the image side) may be used as a vibration reduction group.

[0099] Numerical Examples 1 to 16 corresponding to Examples 1 to 16, respectively, are shown below.

[0100] 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. Also, nd represents the refractive index of each optical element with respect to the d-line, and vd represents the Abbe number of the optical element. Note that the Abbe number vd of a certain material is given by the following when the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines are Nd, NF, and NC, respectively: νd=(Nd-1) / (NF-NC) For regions where the medium is air, the refractive index and Abbe number are omitted.

[0101] 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 on the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length. "Total lens length" is the distance on the optical axis from the forefront lens surface (the lens surface closest to the object) of the imaging optical system to the final surface plus the back focus. Note that the "total lens length" is calculated by taking into account overlapping portions of the optical paths. In other words, it is the physical distance (not the optical path length) traveled by an axial ray between the first surface and the image plane.

[0102] If the optical surface is aspherical, an asterisk (*) is added to the right of the surface number. The aspherical shape is expressed as follows: X is the displacement from the vertex 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, and A12 are the aspherical 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 In addition, "e±XX" in each aspherical coefficient is "×10± XX " means.

[0103] When considering the radius of curvature of conditional expression (2) for an aspherical surface, the value of R in the above expression is used for calculation.

[0104] (Numerical Example 1) Unit: mm Surface Data Surface number rd nd νd 1* 126.887 1.20 1.88202 37.2 2* 12.293 4.94 3 29.319 2.23 2.10420 17.0 4 56.426 (variable) 5 (Aperture) ∞ 0.10 6 31.847 6.52 1.92119 24.0 7 ∞ 2.49 1.48749 70.2 8 -27.763 -2.49 9∞2.49 10 -27.763 1.00 2.00100 29.1 11 8.415 0.36 12* 15.156 3.47 1.49710 81.6 13* -10.100 0.63 14 8.532 3.77 1.65160 58.5 15 -16.421 (variable) 16 ∞ 0.80 1.51633 64.1 17 ∞ (variable) Image plane ∞ Aspheric data Front page K = 0.00000e+00 A 4= 1.95177e-05 A 6=-1.02993e-07 2nd side K = 0.00000e+00 A 4=-5.80928e-06 A 6=-6.10324e-07 A 8= 4.29523e-09 A10=-4.70092e-11 Side 12 K = 0.00000e+00 A 4=-6.73561e-04 A 6=-4.54930e-05 A 8= 4.22526e-06 A10=-2.56569e-07 Page 13 K = 0.00000e+00 A 4=-1.60439e-04 A 6=-1.85977e-05 Various data Zoom ratio 1.55 Wide-angle Mid-range Telephoto Focal length 4.20 5.35 6.50 F-number 1.20 1.20 1.20 Half angle of view [°] 40.21 33.57 28.64 Image height 3.55 3.55 3.55 Lens length 56.47 43.66 35.57 BF 0.30 0.30 0.30 d 4 23.56 10.25 1.66 d15 0.10 0.60 1.11 d17 0.30 0.30 0.30 Zoom lens group data Group starting plane focal length 1 1 -24.38 2 5 10.66 3 16 ∞ (Numerical Example 2) Unit: mm Surface Data Surface number rd nd νd 1 179.690 2.25 1.88300 40.8 2 68.423 12.72 3 -325.384 2.00 1.83481 42.7 4 134.138 8.73 5 127.906 6.64 1.80809 22.8 6 4979.634 (variable) 7* 189.612 0.05 1.52000 50.0 8 185.018 14.25 2.00100 29.1 9 -277.632 10.15 10 -128.362 2.00 1.86966 20.0 11 173.498 8.91 1.65412 39.7 12∞ -8.91 13 173.498 8.91 14 ∞ 1.20 1.51633 64.1 15 ∞ (variable) 16 (Aperture) ∞ 9.16 17 46.992 8.54 1.80809 22.8 18 -39.174 1.50 1.91082 35.2 19 41.527 3.62 20* -74.151 1.00 2.00100 29.1 21 63.678 6.73 1.43875 94.7 22 -42.731 0.26 23 87.411 10.62 1.43875 94.7 24 -32.587 0.70 25 57.255 9.91 1.43875 94.7 26 -52.383 0.10 27 -93.749 3.00 1.95150 29.8 28* 2595.989 (variable) 29 ∞ 3.00 1.51633 64.1 30 ∞ (variable) Image plane ∞ Aspheric data Side 7 K = 0.00000e+00 A 4=-2.82292e-07 A 6= 8.05501e-11 A 8=-2.96788e-13 A10= 3.79341e-16 A12=-1.71510e-19 Page 20 K = 0.00000e+00 A 4=-3.03173e-06 A 6= 6.42594e-10 A 8=-4.28805e-12 Page 28 K = 0.00000e+00 A 4= 2.96862e-06 A 6=-6.45369e-09 A 8= 3.90106e-11 A10=-8.22782e-14 A12= 7.45235e-17 Various data Zoom ratio 1.61 Wide-angle Mid-range Telephoto Focal length 28.00 35.00 45.00 F-number 1.20 1.20 1.20 Half angle of view [°] 37.26 31.32 25.33 Image height 21.30 21.30 21.30 Lens length 222.37 194.22 171.73 BF 0.40 0.40 0.40 d 6 62.52 29.69 0.50 d15 1.00 5.69 12.39 d28 13.60 13.60 13.60 d30 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 -101.44 2 7 55.49 3 16 83.42 4 29 ∞ (Numerical Example 3) Unit: mm Surface Data Surface number rd nd νd 1 253.089 2.25 1.88300 40.8 2 70.885 12.70 3 -250.087 2.00 1.72916 54.7 4 127.485 5.38 5 105.692 12.83 1.63987 34.6 6 -224.790 (variable) 7 152.928 3.28 2.00073 25.9 8 1006.842 0.50 9 360.164 2.00 1.95906 17.5 10 152.231 2.51 11∞-2.51 12 152.231 2.51 13 ∞ 1.20 1.51633 64.1 14 ∞ (variable) 15 (Aperture) ∞ 10.33 16 26.347 8.52 1.69895 30.1 17 -61.500 1.50 1.83023 44.7 18 29.992 2.86 19 70.013 1.50 2.00074 26.0 20 22.553 4.71 1.43875 94.9 21 501.767 3.13 22 41.326 12.38 1.43875 94.9 23 -40.904 0.70 24 -93.842 6.26 1.43875 94.9 25 -27.458 0.10 26* 177.076 3.00 1.95150 29.8 27* 76.741 (variable) 28 ∞ 3.00 1.51633 64.1 29 ∞ (variable) Image plane ∞ Aspheric data Page 26 K = 0.00000e+00 A 4=-5.45733e-05 Page 27 K = 0.00000e+00 A 4=-5.27699e-05 A 6= 3.19864e-08 A 8=-6.16153e-12 Various data Zoom ratio 1.58 Wide-angle Mid-range Telephoto Focal length 28.50 35.00 45.00 F-number 1.40 1.40 1.40 Half angle of view [°] 35.22 31.72 25.68 Image height 20.12 21.64 21.64 Lens length 189.76 161.78 137.77 BF 0.40 0.40 0.40 d 6 67.14 33.39 0.50 d14 1.00 6.77 15.66 d27 13.56 13.56 13.56 d29 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 -134.43 2 7 67.83 3 15 69.17 4 28 ∞ (Numerical Example 4) Unit: mm Surface Data Surface number rd nd νd 1 133.313 3.79 1.84666 23.8 2 141.297 (variable) 3 164.046 1.39 1.60471 66.6 4 41.403 17.99 5* -65.618 1.50 1.49700 81.5 6 123.599 0.10 7 81.194 5.18 1.69895 30.1 8 369.534 (variable) 9 -465.041 1.40 1.77260 25.2 10 135.519 3.21 1.79611 45.2 11∞ -3.21 12 135.519 3.21 13 ∞ 1.70 2.00330 28.3 14 345.434 (variable) 15 (Aperture) ∞ 3.66 16 19.679 7.46 1.69894 30.1 17 -35.718 1.00 1.79147 48.0 18 23.464 1.66 19 162.486 1.00 2.00330 28.3 20 15.825 5.01 1.43875 94.9 21 -61.605 4.39 22 48.305 6.61 1.49697 81.4 23 -25.091 0.70 24 -39.230 4.06 1.55800 72.9 25 -20.385 0.10 26* 281.010 2.00 1.95150 29.8 27* 102.305 (variable) 28 ∞ 2.00 1.51633 64.1 29 ∞ (variable) Image plane ∞ Aspheric data 5th page K = 0.00000e+00 A 4= 3.56820e-07 A 6=-2.67043e-10 A 8= 6.04949e-13 A10=-4.23551e-16 Page 26 K = 0.00000e+00 A 4=-1.43829e-04 A 6= 4.88031e-08 A 8= 5.51813e-10 Page 27 K = 0.00000e+00 A 4=-1.40599e-04 A 6= 2.36851e-07 A 8= 8.21599e-11 Various data Zoom ratio 2.76 Focal length 15.40 29.00 42.50 36.01 F-number 1.42 1.42 1.42 1.42 Half angle of view [°] 36.86 24.94 17.61 20.54 Image height 11.54 13.49 13.49 13.49 Lens total length 165.18 165.18 165.18 165.18 BF 0.40 0.40 0.40 0.40 d 2 0.70 33.25 35.08 35.88 d 8 68.66 20.03 2.02 9.03 d14 1.54 17.61 33.79 25.98 d27 11.55 11.55 11.55 11.55 d29 0.40 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 2288.08 2 3 -59.87 3 9 44.51 4 15 43.71 5 28 ∞ (Numerical Example 5) Unit: mm Surface Data Surface number rd nd νd 1 148.065 10.80 1.49700 81.5 2 600.901 (variable) 3 468.543 2.48 1.49700 81.5 4 61.662 12.59 5 -107.650 2.20 1.72964 54.6 6 194.384 10.10 7 189.512 5.07 1.76785 30.0 8 -467.589 (variable) 9 662.352 5.10 1.78125 49.0 10 -151.191 3.77 11 -103.757 2.20 1.81946 29.2 12 199.808 2.71 1.75772 51.4 13∞ -2.71 14 199.808 2.71 15 ∞ 3.00 1.51633 64.1 16 ∞ (variable) 17 (Aperture) ∞ 14.57 18 34.101 8.36 1.71379 29.3 19 -67.924 1.65 1.84593 43.4 20 38.768 7.12 21 182.416 1.65 1.95715 32.0 22 31.407 17.14 1.43875 94.9 23 -115.314 0.10 24 49.852 8.52 1.43875 94.9 25 -57.684 0.70 26 -145.292 5.35 1.43875 94.9 27 -39.718 3.68 28* -272.421 3.30 1.95150 29.8 29* 295.219 (variable) 30 ∞ 3.00 1.51633 64.1 31 ∞ (variable) Image plane ∞ Aspheric data Page 28 K = 0.00000e+00 A 4=-3.37812e-05 A 6= 6.67955e-09 A 8= 1.89280e-11 Page 29 K = 0.00000e+00 A 4=-3.13542e-05 A 6= 1.28966e-08 A 8= 3.35922e-11 A10=-6.33814e-14 A12= 4.80398e-17 Various data Zoom ratio 1.90 Wide-angle Mid-range Telephoto Focal length 35.70 49.38 68.00 F-number 1.40 1.40 1.40 Half angle of view [°] 28.55 23.66 17.65 Image height 19.42 21.63 21.64 Lens total length 227.59 227.59 227.59 BF 0.40 0.40 0.40 d 2 10.43 38.62 59.68 d 8 64.53 30.01 0.50 d16 1.04 7.37 15.82 d29 10.60 10.60 10.60 d31 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 392.22 2 3 -90.26 3 9 64.19 4 17 84.84 5 30 ∞ (Numerical Example 6) Unit: mm Surface Data Surface number rd nd νd 1 168.064 2.25 1.74255 53.1 2 63.385 17.01 3 -595.089 2.00 1.72916 54.7 4 120.383 11.39 5 117.604 6.86 1.84472 31.2 6 420.629 (variable) 7 156.180 8.90 1.94991 32.7 8 -71.649 1.70 1.95985 23.5 9 -246.247 6.77 10 (Aperture) ∞ 0.10 11 ∞ 1.50 1.51633 64.1 12 ∞ 2.85 2.00330 28.3 13 876.831 3.19 14 -181.118 -3.19 15 876.831 -2.85 2.00330 28.3 16∞2.85 17 876.831 3.19 18 -181.118 1.20 1.49700 81.5 19 ∞ 3.75 1.59522 67.7 20 -155.002 (variable) 21 371.091 3.88 1.82121 22.1 22 -114.613 1.50 1.88288 40.8 23 96.404 0.52 24 50.068 5.75 1.48749 70.2 25 -480.756 9.85 26 -98.466 1.00 1.91831 36.1 27 32.355 4.40 1.43875 94.9 28 164.422 0.79 29 76.891 7.57 1.43875 94.9 30 -30.293 1.00 1.88284 40.8 31 -50.837 0.10 32 76.720 5.51 1.73172 28.4 33 -137.824 0.10 34 -263.659 3.00 1.49700 81.5 35 -73.106 (variable) 36 -159.545 4.73 1.43881 94.9 37 -43.694 0.90 38 -71.609 4.44 1.43875 94.9 39 -44.866 0.72 40 -40.150 0.90 1.88828 33.5 41* -80.858 (variable) 42 ∞ 3.00 1.51633 64.1 43 ∞ (variable) Image plane ∞ Aspheric data Page 41 K = 0.00000e+00 A 4= 3.65499e-06 Various data Zoom ratio 1.89 Wide-angle Mid-range Telephoto Focal length 28.50 34.99 54.00 F-number 1.40 1.40 1.40 Half angle of view [°] 34.84 31.33 21.83 Image height 19.84 21.30 21.64 Lens total length 272.08 228.42 170.16 BF 0.40 0.40 0.40 d 6 117.15 69.84 0.50 d20 1.42 1.60 5.67 d35 0.70 4.18 11.19 d41 11.20 11.20 11.20 d43 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 -114.55 2 7 59.12 3 21 106.68 4 36 34093.90 5 42 ∞ (Numerical Example 7) Unit: mm Surface Data Surface number rd nd νd 1 98.502 2.50 1.88300 40.8 2 38.198 22.65 3 -111.773 2.50 1.49700 81.5 4* 46.515 1.87 5 71.420 6.81 1.84942 25.7 6 375.265 (variable) 7 114.319 3.45 1.81939 45.6 8 -556.232 24.38 9 142.406 2.56 1.51441 53.8 10 ∞ 2.56 1.51441 53.8 11 -142.406 -2.56 12∞2.56 13 -142.406 1.20 1.86966 20.0 14 571.251 (variable) 15 (Aperture) ∞ 1.31 16 -297.015 1.80 1.75904 51.3 17 69.186 4.00 18 -226.974 6.00 1.86966 20.0 19 -24.092 1.00 1.92075 28.9 20 -68.689 4.57 21 -33.984 1.00 1.99716 29.4 22 101.672 0.44 23 60.162 5.52 1.43875 94.9 24 -32.334 0.10 25* 37.858 8.52 1.49700 81.5 26* -45.070 (variable) 27 55.676 7.41 1.43875 94.9 28 -40.600 0.90 29 -91.333 2.00 1.72916 54.7 30* -263.383 (variable) 31 ∞ 2.00 1.51633 64.1 32 ∞ (variable) Image plane ∞ Aspheric data Side 4 K = 0.00000e+00 A 4=-2.87835e-06 A 6=-4.95339e-11 A 8=-7.62383e-13 A10= 7.94564e-16 A12=-3.64687e-19 Page 25 K = 0.00000e+00 A 4=-5.87027e-06 A 6= 1.00665e-08 A 8=-2.44702e-11 A10= 1.20858e-14 Page 26 K = 0.00000e+00 A 4= 6.80783e-06 A 6= 3.21604e-09 Page 30 K = 0.00000e+00 A 4= 5.54573e-06 A 6= 8.12503e-09 A 8= 1.93185e-11 Various data Zoom ratio 2.11 Wide-angle Mid-range Telephoto Focal length 14.00 21.50 29.50 F-number 1.20 1.20 1.20 Half angle of view [°] 45.41 33.45 25.70 Image height 14.20 14.20 14.20 Lens length 195.37 165.53 154.57 BF 0.40 0.40 0.40 d 6 57.71 19.80 0.53 d14 1.34 9.25 17.40 d26 0.70 1.59 2.47 d30 13.04 12.32 11.59 d32 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 -48.52 2 7 40.74 3 15 101.41 4 27 75.21 5 31 ∞ (Numerical Example 8) Unit: mm Surface Data Surface number rd nd νd 1 109.300 2.38 1.88300 40.8 2 43.625 16.38 3 753.174 2.50 1.59522 67.7 4 120.673 6.76 5 -260.400 1.90 1.43875 94.7 6 102.631 7.67 1.92286 20.9 7 372.961 0.10 1.53172 48.8 8* 217.855 (variable) 9* 87.617 13.07 1.59270 35.3 10 -43.753 1.80 1.95375 32.3 11 -69.143 8.83 12 -113.086 1.90 1.86966 20.0 13 184.499 8.16 1.83481 42.7 14∞-8.16 15 184.499 8.16 16 ∞ 1.20 1.51633 64.1 17 ∞ (variable) 18 (Aperture) ∞ 6.55 19 46.847 5.49 1.92286 20.9 20 -39.949 0.95 1.85025 30.1 21 37.776 2.81 22* -66.069 0.95 2.00100 29.1 23 41.340 6.24 1.43875 94.7 24 -45.887 0.62 25 59.331 11.13 1.43875 94.7 26 -31.010 (variable) 27 -130.580 7.06 1.43875 94.7 28 -30.949 1.29 29* 299.776 2.38 1.95150 29.8 30* 118.562 (variable) 31 ∞ 1.80 1.51633 64.1 32 ∞ (variable) Image plane ∞ Aspheric data Side 8 K = 0.00000e+00 A 4=-1.00738e-06 A 6= 1.94315e-10 A 8=-8.92776e-14 A10= 8.76201e-18 9th page K = 0.00000e+00 A 4=-9.45836e-07 A 6= 3.59897e-10 Page 22 K = 0.00000e+00 A 4=-6.30082e-06 A 6=-5.37086e-09 A 8= 2.51835e-11 A10=-1.26875e-13 Page 29 K = 0.00000e+00 A 4=-3.72607e-05 A 6=-4.65488e-08 A 8= 8.30739e-11 Page 30 K = 0.00000e+00 A 4=-3.29966e-05 A 6=-4.56380e-08 A 8= 1.72438e-10 A10=-1.92890e-13 A12= 1.05183e-16 Various data Zoom ratio 1.93 Wide-angle Mid-range Telephoto Focal length 20.50 32.00 39.50 F-number 1.40 1.40 1.40 Half angle of view [°] 46.10 33.65 28.34 Image height 21.30 21.30 21.30 Lens total length 205.25 181.08 176.45 BF 0.40 0.40 0.40 d 8 51.06 14.77 2.57 d17 1.00 13.12 20.68 d26 0.70 3.06 4.78 d30 15.87 13.52 11.79 d32 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 -56.48 2 9 47.56 3 18 134.26 4 27 158.05 5 31 ∞ (Numerical Example 9) Unit: mm Surface Data Surface number rd nd νd 1 185.415 2.48 1.49700 81.5 2 76.223 11.88 3 -117.407 2.20 1.72916 54.7 4 248.528 7.45 5 198.975 4.77 1.79870 29.7 6 -1291.653 (variable) 7 475.311 5.67 1.79097 48.1 8 -189.829 4.64 9 -111.921 2.20 1.86209 27.7 10 198.001 3.39 1.67278 31.9 11∞ -3.39 12 198.001 3.39 13 ∞ 3.00 1.51633 64.1 14 ∞ (variable) 15 (Aperture) ∞ 18.16 16 30.770 8.89 1.65142 33.6 17 -73.437 1.65 1.74831 52.1 18 38.589 2.96 19 122.223 1.65 1.96994 30.9 20 26.566 18.62 1.43875 94.9 21 -501.664 2.08 22 53.604 8.70 1.43875 94.9 23 -53.575 0.70 24 -209.852 6.10 1.43875 94.9 25 -38.068 3.09 26* -478.193 3.30 1.95150 29.8 27* 163.967 (variable) 28 ∞ 3.00 1.51633 64.1 29 ∞ (variable) Image plane ∞ Aspheric data Page 26 K = 0.00000e+00 A 4=-3.65701e-05 A 6= 1.05258e-08 A 8= 1.99619e-11 Page 27 K = 0.00000e+00 A 4=-3.37165e-05 A 6= 2.03152e-08 A 8= 2.49601e-11 A10=-5.45362e-14 A12= 4.45900e-17 Various data Zoom ratio 1.90 Wide-angle Mid-range Telephoto Focal length 35.70 50.00 68.00 F-number 1.40 1.40 1.40 Half angle of view [°] 28.55 23.40 17.65 Image height 19.42 21.63 21.64 Lens length 229.05 193.32 177.02 BF 0.40 0.40 0.40 d 6 80.12 32.18 0.50 d14 4.17 16.38 31.75 d27 11.01 11.01 11.01 d29 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 -124.85 2 7 71.49 3 15 88.04 4 28 ∞ (Numerical Example 10) Unit: mm Surface Data Surface number rd nd νd 1 106.283 2.48 1.49700 81.5 2 52.944 11.46 3 -123.905 2.20 1.88216 40.8 4 169.626 5.80 5 147.623 5.02 1.94981 29.4 6 -720.003 (variable) 7 243.884 4.59 1.94021 33.7 8 -269.028 7.30 9 -100.663 2.20 1.75108 29.6 10 159.866 3.16 1.54133 47.4 11∞-3.16 12 159.866 3.16 13 ∞ 3.00 1.51633 64.1 14 ∞ (variable) 15 (Aperture) ∞ 12.71 16 31.387 8.96 1.61234 37.1 17 -60.684 1.65 1.76467 50.7 18 35.909 4.62 19 121.939 1.65 1.90464 37.8 20 27.711 11.71 1.43875 94.9 21 -413.721 0.10 22 50.526 8.74 1.44746 92.9 23 -47.229 0.70 24 -1390.325 7.48 1.43875 94.9 25 -33.284 0.23 26* 336.957 3.30 1.95150 29.8 27* 85.370 (variable) 28 ∞ 3.00 1.51633 64.1 29 ∞ (variable) Image plane ∞ Aspheric data Page 26 K = 0.00000e+00 A 4=-4.48721e-05 A 6= 7.83232e-09 A 8= 3.34031e-11 Page 27 K = 0.00000e+00 A 4=-4.35798e-05 A 6= 2.45916e-08 A 8= 3.54921e-11 A10=-6.55859e-14 A12= 4.70594e-17 Various data Zoom ratio 1.41 Wide-angle Mid-range Telephoto Focal length 35.00 42.00 49.50 F-number 1.22 1.22 1.22 Half angle of view [°] 30.08 27.25 23.61 Image height 20.27 21.63 21.64 Lens length 169.81 152.71 141.35 BF 0.40 0.40 0.40 d 6 39.46 17.29 0.50 d14 1.00 6.06 11.49 d27 10.59 10.59 10.59 d29 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 -116.94 2 7 58.02 3 15 73.84 4 28 ∞ (Numerical Example 11) Unit: mm Surface Data Surface number rd nd νd 1 84.878 3.50 1.72916 54.7 2 48.738 15.05 3* 264.074 4.00 1.51899 78.0 4 48.655 30.38 5 -73.816 2.47 1.80809 22.8 6 -61.123 4.10 7 -60.837 1.50 1.72922 54.7 8 -860.139 3.12 9 -139.443 0.90 2.00330 28.3 10 -225.301 4.37 1.72389 55.1 11 -84.336 (variable) 12* 154.255 7.91 1.93438 34.3 13 -163.365 1.50 1.83458 21.5 14 134.710 10.73 1.77647 49.5 15 -109.996 (variable) 16 -95.662 7.14 1.74577 52.7 17 -52.418 0.90 1.70160 30.4 18 -301.118 0.10 19 305.709 2.89 1.51633 64.1 20∞2.13 21 -509.189 -2.13 22∞2.13 23 -509.189 1.80 1.91942 36.0 24 553.217 6.39 1.86966 20.0 25 -153.153 (variable) 26 (Aperture) ∞ 2.40 27 -101.928 1.50 1.83448 29.4 28 35.723 12.26 1.89055 22.8 29 -71.423 1.96 30 -57.562 1.30 1.90118 38.2 31 276.629 (variable) 32 52.718 1.40 1.90639 37.5 33 33.181 16.56 1.50204 81.8 34 -86.818 0.10 35 74.378 9.08 1.49903 82.3 36 -173.952 0.26 37 47.949 14.73 1.43875 94.7 38 -64.093 0.10 39 -185.314 5.35 1.43875 94.7 40 -60.052 1.80 2.00330 28.3 41 33.305 0.10 42 32.283 7.71 1.70730 56.5 43* 330.952 (variable) Image plane ∞ Aspheric data 3rd page K = 0.00000e+00 A 4= 1.05449e-06 A 6= 2.81263e-11 Side 12 K = 0.00000e+00 A 4=-2.97880e-07 A 6= 6.17907e-12 Page 43 K = 0.00000e+00 A 4= 6.73095e-06 A 6= 4.22312e-09 Various data Zoom ratio 2.00 Focal length 20.00 25.50 32.57 40.00 F-number 1.34 1.36 1.38 1.40 Half angle of view [°] 47.25 40.31 33.60 28.41 Image height 21.64 21.64 21.64 21.64 Lens total length 269.21 269.21 269.21 269.21 BF 20.28 20.28 20.28 20.28 d11 41.23 26.87 14.55 5.83 d15 1.01 7.73 7.97 1.76 d25 0.10 11.64 29.55 49.50 d31 14.85 10.94 5.12 0.10 d43 20.28 20.28 20.28 20.28 Zoom lens group data Group starting plane focal length 1 1 -41.53 2 12 78.04 3 16 188.57 4 26 -76.03 5 32 47.82 (Numerical Example 12) Unit: mm Surface Data Surface number rd nd νd 1 55.562 2.50 1.72877 54.7 2 33.518 12.43 3* 102.019 2.50 1.49700 81.5 4* 40.391 11.63 5 -177.869 2.00 1.57670 70.0 6 58.752 15.39 1.69770 30.2 7 -728.089 17.60 8 -53.324 2.00 1.57786 69.8 9 416.717 4.19 1.89406 39.2 10 -241.432 (variable) 11 ∞ 3.75 1.45394 91.4 12 -264.140 -3.75 13∞3.75 14 -264.140 0.10 15* 87.201 6.51 1.88351 40.7 16 244.144 0.52 17 312.991 2.00 1.90197 21.1 18 78.265 10.58 1.61296 65.7 19 -187.827 (variable) 20 (Aperture) ∞ 17.55 21 -70.654 0.90 1.88300 40.8 22 119.146 1.23 23 -4893.502 0.90 1.88300 40.8 24 63.713 3.39 1.86966 20.0 25 -550.920 (variable) 26 115.188 9.81 1.43875 94.9 27 -75.289 0.10 28 74.502 12.79 1.43875 94.9 29 -88.297 0.10 30 71.959 14.26 1.43875 94.9 31 -63.393 2.00 1.93001 34.8 32 148.911 0.10 33 46.778 13.42 1.43875 94.9 34 -195.930 2.21 35* 102.726 7.32 1.70255 56.9 36* 1583.881 (variable) Image plane ∞ Aspheric data 3rd page K = 0.00000e+00 A 4= 3.48654e-06 A 6=-3.01850e-09 A 8= 1.55267e-12 A10=-6.73634e-17 Side 4 K = 0.00000e+00 A 4= 1.24068e-06 A 6=-4.06820e-09 Page 15 K = 0.00000e+00 A 4=-1.53474e-07 A 6=-2.04153e-11 Page 35 K = 0.00000e+00 A 4=-7.54691e-06 A 6=-4.81392e-09 Page 36 K = 0.00000e+00 A 4=-7.31080e-06 A 6=-2.12153e-09 Various data Zoom ratio 1.74 Wide-angle Mid-range Telephoto Focal length 24.00 32.00 41.80 F-number 1.41 1.41 1.41 Half angle of view [°] 42.03 34.06 27.37 Image height 21.64 21.64 21.64 Lens total length 237.50 237.50 237.50 BF 15.00 15.00 15.00 d10 18.23 7.72 0.80 d19 0.80 16.53 33.61 d25 16.19 10.96 0.80 d36 15.00 15.00 15.00 Zoom lens group data Group starting plane focal length 1 1 -36.93 2 11 48.18 3 20 -53.60 4 26 40.70 (Numerical Example 13) Unit: mm Surface Data Surface number rd nd νd 1 150.771 4.73 1.79044 25.9 2 171.746 (variable) 3 201.485 2.23 1.55353 73.0 4 63.525 32.67 5* -101.841 1.98 1.59039 68.3 6 158.146 0.10 7 123.939 5.46 1.75872 27.2 8 507.262 (variable) 9 472.499 1.98 1.94854 23.0 10 192.178 3.95 1.60406 55.9 11∞ -3.95 12 192.178 3.95 13 ∞ 2.70 1.84666 23.8 14 676.684 (variable) 15 (Aperture) ∞ 4.86 16 28.481 8.28 1.59844 38.6 17 -97.117 1.49 1.79780 47.4 18 39.866 6.85 19 63.761 0.90 1.88300 40.8 20 22.021 6.14 1.43875 94.9 21 412.942 6.97 22 89.335 7.13 1.53634 48.4 23 -52.699 1.92 24 -402.983 8.52 1.43875 94.9 25 -29.864 0.10 26* 74.719 2.97 1.95150 29.8 27* 39.525 (variable) 28 ∞ 2.70 1.51633 64.1 29 ∞ (variable) Image plane ∞ Aspheric data 5th page K = 0.00000e+00 A 4= 9.68786e-08 A 6=-3.83814e-11 A 8= 2.62582e-14 A10=-5.42579e-18 Page 26 K = 0.00000e+00 A 4=-6.23466e-05 A 6= 2.57040e-08 A 8= 2.74399e-11 Page 27 K = 0.00000e+00 A 4=-6.49110e-05 A 6= 6.04427e-08 A 8=-1.75742e-11 Various data Zoom ratio 2.71 Focal length 24.70 45.28 67.00 57.05 F-number 1.42 1.42 1.42 1.42 Half angle of view [°] 36.85 25.54 17.90 20.77 Image height 18.51 21.63 21.64 21.64 Lens total length 226.54 226.54 226.54 226.54 BF 0.40 0.40 0.40 0.40 d 2 1.28 40.55 41.61 43.55 d 8 88.35 26.63 1.03 10.45 d14 1.59 24.04 48.58 37.22 d27 12.41 12.41 12.41 12.41 d29 0.40 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 1420.47 2 3 -84.81 3 9 63.71 4 15 76.84 5 28 ∞ (Numerical Example 14) Unit: mm Surface Data Surface number rd nd νd 1 175.734 18.05 1.51742 52.4 2 -218.204 3.00 1.93665 22.5 3 -400.892 (variable) 4* -861.610 2.48 1.57255 70.5 5 68.941 12.82 6 -90.058 2.20 1.59521 67.7 7 196.878 3.36 1.90077 21.1 8 930.565 0.10 9 130.845 4.55 1.54145 48.2 10 370.473 (variable) 11 550.543 2.20 1.99266 25.0 12 221.551 4.21 1.57492 70.6 13∞ -4.21 14 221.551 4.21 15 ∞ 3.00 1.59522 67.7 16 1112.066 (variable) 17 (Aperture) ∞ 13.53 18 32.379 9.00 1.61460 36.9 19 -130.324 1.65 1.72916 54.7 20 54.189 5.97 21 96.940 1.00 1.94500 33.2 22 24.721 5.43 1.43876 94.9 23 270.914 14.63 24 69.150 7.60 1.49975 60.2 25 -68.560 0.70 26 -240.443 6.02 1.52042 51.7 27 -41.016 1.95 28* 143.334 3.30 1.95150 29.8 29* 60.642 (variable) 30 ∞ 3.00 1.51633 64.1 31 ∞ (variable) Image plane ∞ Aspheric data Side 4 K = 0.00000e+00 A 4=-3.79059e-08 A 6=-2.18257e-11 A 8= 5.24129e-15 Page 28 K = 0.00000e+00 A 4=-3.73914e-05 A 6= 1.95830e-08 A 8= 7.11096e-12 Page 29 K = 0.00000e+00 A 4=-3.64531e-05 A 6= 3.14709e-08 A 8=-6.70468e-12 Various data Zoom ratio 2.72 Focal length 35.70 50.00 97.00 70.46 F-number 1.42 1.42 1.42 1.42 Half angle of view [°] 28.55 23.40 12.57 17.07 Image height 19.42 21.63 21.64 21.64 Lens total length 239.94 239.94 239.94 239.94 BF 0.40 0.40 0.40 0.40 d 3 0.70 23.86 43.74 39.95 d10 86.81 54.67 1.24 25.48 d16 1.46 10.45 44.00 23.54 d29 12.42 12.42 12.42 12.42 d31 0.40 0.40 0.40 0.40 Zoom lens group data Group starting plane focal length 1 1 299.32 2 4 -79.11 3 11 73.44 4 17 89.11 5 30 ∞ (Numerical Example 15) Unit: mm Surface Data Surface number rd nd νd 1 104.697 22.08 1.49931 61.7 2 -331.488 3.00 1.86966 20.0 3 -1180.926 (variable) 4* 300.444 2.48 1.50654 80.0 5 44.979 15.19 6 -68.740 2.20 1.63722 63.0 7 222.013 3.55 1.86964 20.0 8 -1256.527 0.10 9 92.678 3.67 1.56206 57.9 10 151.515 (variable) 11 219.114 2.20 2.00071 25.7 12 159.842 4.30 1.47045 73.0 13∞ -4.30 14 159.842 4.30 15 ∞ 3.00 1.88277 40.8 16 683.601 (variable) 17 (Aperture) ∞ 12.22 18 37.361 9.00 1.66244 32.7 19 -63.832 1.65 1.88300 40.8 20 47.612 6.50 21 77.156 1.00 2.00183 28.4 22 33.878 12.23 1.43875 94.9 23 437.419 0.90 24 86.248 7.27 1.63653 63.1 25 -64.284 0.70 26 -257.189 6.10 1.50405 81.4 27 -37.980 0.10 28* 207.305 3.30 1.95150 29.8 29* 91.103 (variable) 30 ∞ 3.00 1.51633 64.1 31 ∞ (variable) Image plane ∞ Aspheric data Side 4 K = 0.00000e+00 A 4= 8.97542e-08 A 6=-1.44928e-10 A 8= 9.46460e-14 A10=-2.94001e-17 Page 28 K = 0.00000e+00 A 4=-3.78907e-05 A 6= 1.15529e-08 A 8= 1.03307e-11 Page 29 K = 0.00000e+00 A 4=-3.75283e-05 A 6= 2.71695e-08 A 8=-6.10519e-12 Various data Zoom ratio 1.90 Focal length 35.70 49.70 67.99 60.16 F-number 1.10 1.10 1.10 1.10 Half angle of view [°] 28.55 23.52 17.65 19.78 Image height 19.42 21.63 21.64 21.64 Lens total length 193.27 193.27 193.27 193.27 BF 0.39 0.39 0.39 0.39 d 3 0.70 18.42 31.54 26.89 d10 45.54 21.96 1.56 9.33 d16 1.55 7.40 14.68 11.56 d29 10.79 10.79 10.79 10.79 d31 0.39 0.39 0.39 0.39 Zoom lens group data Group starting plane focal length 1 1 226.73 2 4 -65.25 3 11 54.72 4 17 64.22 5 30 ∞ (Numerical Example 16) Unit: mm Surface Data Surface number rd nd νd 1 77.198 2.50 1.88300 40.8 2 35.841 8.17 3* 74.129 2.00 1.58164 69.4 4 34.322 17.04 5 -72.734 2.00 1.43875 94.9 6 55.580 1.87 7 54.932 8.88 1.60342 38.0 8 -343.771 (variable) 9 90.635 5.91 1.96293 29.9 10 -50.892 1.20 1.85262 22.3 11 -6400.947 10.20 12 (Aperture) ∞ 2.39 13 33.447 5.36 1.43875 94.9 14 191.204 0.10 15 60.520 7.00 1.43875 94.9 16 -39.753 1.20 1.93287 34.5 17 81.476 5.85 18 -69.450 7.10 1.86966 20.0 19 -36.388 2.42 20 34.688 7.24 1.43875 94.9 21 -45.661 0.90 1.97382 30.6 22 1502.650 0.17 23 ∞ 1.00 1.51633 64.1 24 ∞ 1.42 25* -209.082 -1.42 26∞1.42 27* -209.082 1.50 1.84666 23.8 28 -135.080 0.10 29 -340.846 3.55 1.52307 78.2 30 -68.170 (variable) 31 -243.204 4.77 1.72937 54.7 32 -43.779 0.10 33 -137.030 1.20 2.00362 28.2 34 120.403 2.91 35* 130.672 2.00 1.86997 42.7 36* 165.390 (variable) 37 ∞ 2.30 1.51633 64.1 38 ∞ (variable) Image plane ∞ Aspheric data 3rd page K = 0.00000e+00 A 4= 1.79104e-06 A 6=-1.52439e-10 A 8= 4.83040e-13 Page 25 K = 0.00000e+00 A 4= 2.78921e-06 A 6=-6.78247e-10 A 8= 1.41782e-12 Page 27 K = 0.00000e+00 A 4= 2.78921e-06 A 6=-6.78247e-10 A 8= 1.41782e-12 Page 35 K = 0.00000e+00 A 4=-1.05608e-05 A 6=-2.27656e-07 A 8= 4.42322e-10 Page 36 K = 0.00000e+00 A 4= 4.86933e-06 A 6=-2.48532e-07 A 8= 6.93077e-10 A10=-4.71647e-13 Various data Zoom ratio 1.48 Wide-angle Mid-range Telephoto Focal length 16.50 20.00 24.50 F-number 1.38 1.39 1.41 Half angle of view [°] 49.72 47.25 41.45 Image height 19.47 21.64 21.64 Lens length 174.61 157.88 144.85 BF 0.10 0.10 0.10 d 8 38.73 18.51 1.00 d30 1.00 4.48 8.96 d36 11.60 11.60 11.60 d38 0.10 0.10 0.10 Zoom lens group data Group starting plane focal length 1 1 -43.33 2 9 43.56 3 31 -1999.90 4 37 ∞ The various values ​​in each numerical example are summarized in Table 1 below.

[0105] [Table 1]

[0106] [Imaging device] Next, an embodiment of a digital still camera (image capture device) using the imaging optical system of each embodiment as an imaging optical system will be described with reference to Fig. 35. In Fig. 35, 10 denotes a camera body, and 11 denotes an imaging optical system configured with any of the imaging optical systems described in Embodiments 1 to 16. 12 denotes a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into the camera body and receives and photoelectrically converts an optical image formed by the imaging optical system 11. The camera body 10 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera having no quick-turn mirror.

[0107] In this way, by applying the imaging optical system of each embodiment to an imaging device such as a digital still camera, an imaging device with a small lens can be obtained.

[0108] The imaging optical system of each embodiment can be used in imaging cameras and distance detection cameras for smartphones, interchangeable lenses for interchangeable lens cameras, fixed lens cameras, film cameras with lenses (disposable cameras), binoculars, etc. It may also be used in camera viewfinders and XR devices for, for example, line-of-sight detection, biometric recognition, and facial expression recognition. It may also be used for external environment recognition applications such as XR devices and automatic robots.

[0109] The disclosure of each embodiment includes the following configuration. (Configuration 1) An optical system having a plurality of lens groups, the spacing between adjacent lens groups among the plurality of lens groups changes during zooming; the plurality of lens groups include a first lens group having negative refractive power and a second lens group having positive refractive power that is disposed closer to the image side than the first lens group, An imaging optical system comprising: a first transmission-reflection surface; and a second transmission-reflection surface disposed closer to an image than the first transmission-reflection surface. (Configuration 2) 2. The imaging optical system according to configuration 1, wherein the second lens group includes the first and second transmissive-reflective surfaces. (Configuration 3) 3. The imaging optical system according to configuration 1 or 2, wherein the first and second transmissive-reflective surfaces move during zooming. (Configuration 4) the second lens group moves during zooming, 4. The imaging optical system according to any one of configurations 1 to 3, wherein the plurality of lens groups includes a third lens group that is disposed closer to the image side than the second lens group and that moves less during zooming than the second lens group. (Configuration 5) When the focal length of the lens group including the first or second transmissive-reflective surface having the smaller radius of curvature is defined as fgr, and the focal length of the optical system at the wide-angle end is defined as fw, 1.0≦fgr / fw≦4.5 5. The imaging 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 lens group including the one of the first and second transmissive-reflective surfaces having the smaller radius of curvature is denoted by fgr, the radius of curvature of the first transmissive-reflective surface is denoted by R1, and the radius of curvature of the second transmissive-reflective surface is denoted by R2, 2.0≦(R1×R2) / {(R1+R2)×fgr}≦7.0 6. The imaging optical system according to any one of configurations 1 to 5, wherein the following condition is satisfied: (Configuration 7) The average Abbe number of the positive lens arranged on the object side of the first transmission-reflection surface is defined as νd mf When 20≦νd mf ≦65 7. The imaging optical system according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 8) an aperture stop disposed on the image side of the second transmitting-reflecting surface, The average Abbe number of the positive lens arranged between the first transmission-reflection surface and the aperture stop is defined as νd mm When 20≦νd mm ≦96 8. The imaging optical system according to any one of configurations 1 to 7, wherein the following condition is satisfied: (Configuration 9) an aperture stop disposed on the object side of the first transmitting-reflecting surface, The average Abbe number of the positive lens disposed between the aperture stop and the second transmission-reflection surface is defined as νd mr When 50≦νd mr ≦96 9. The imaging optical system according to any one of configurations 1 to 8, wherein the following condition is satisfied: (Configuration 10) The refractive index at the d-line of the first lens disposed between the first and second transmissive-reflective surfaces is defined as nd m When 1.40≦nd m ≦1.85 10. The imaging optical system according to any one of configurations 1 to 9, wherein the following condition is satisfied: (Configuration 11) further comprising an aperture stop; 11. The imaging optical system according to any one of configurations 1 to 10, wherein at least one of the lens arranged closer to the image side than the aperture stop, the first transmissive-reflective surface, and the second transmissive-reflective surface moves during focusing. (Configuration 12) 12. The imaging optical system according to configuration 11, wherein the first and second transmissive-reflective surfaces move during focusing. (Configuration 13) When the distance on the optical axis between the object-side surface of the lens positioned closest to the object at the wide-angle end and the entrance pupil is dp, and the focal length of the optical system at the wide-angle end is fw, 1.5≦dp / fw≦4.0 13. The imaging optical system according to any one of configurations 1 to 12, wherein the following condition is satisfied: (Configuration 14) When the smaller of the open angle of the first transmitting-reflecting surface and the open angle of the second transmitting-reflecting surface is θm [°], 0.0≦|θm|≦8.0 14. The imaging optical system according to any one of configurations 1 to 13, wherein the following condition is satisfied: (Configuration 15) When the larger of the open angle of the first transmitting-reflecting surface and the open angle of the second transmitting-reflecting surface is θl [°], 2.0≦|θl|≦50.0 15. The imaging optical system according to any one of configurations 1 to 14, wherein the following condition is satisfied: (Configuration 16) a retarder disposed between the first and second transmission-reflection surfaces, 16. The imaging optical system according to any one of configurations 1 to 15, wherein light from the object side passes through the first transmissive-reflective surface and the phase shifter in this order, is reflected by the second transmissive-reflective surface toward the object side, passes through the phase shifter, is reflected by the first transmissive-reflective surface toward the image side, and passes through the phase shifter and the second transmissive-reflective surface in this order, and proceeds toward the image side. (Configuration 17) When the chief ray of the most off-axis light beam first enters the one of the first and second transmitting-reflecting surfaces with the smaller open angle, the angle of incidence of the chief ray is defined as θin [°], 0.0≦θin≦40.0 17. The imaging optical system according to configuration 16, wherein the following condition is satisfied: (Configuration 18) 18. The imaging optical system according to any one of configurations 1 to 17, wherein the plurality of lens groups includes a lens group having a positive refractive power that is arranged on the object side of the first lens group. (Configuration 19) 19. An imaging apparatus comprising: an imaging optical system according to any one of structures 1 to 18; and an imaging element that receives an image formed by the imaging optical system.

[0110] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0111] HM1 First transflective surface HM2 Second transflective surface L1 First lens group L2 Second lens group

Claims

1. An optical system having a plurality of lens groups, the spacing between adjacent lens groups among the plurality of lens groups changes during zooming; the plurality of lens groups include a first lens group having negative refractive power and a second lens group having positive refractive power that is disposed closer to the image side than the first lens group, An imaging optical system comprising: a first transmissive-reflective surface; and a second transmissive-reflective surface disposed closer to an image than the first transmissive-reflective surface.

2. 2. The imaging optical system according to claim 1, wherein the second lens group comprises the first and second transmissive-reflective surfaces.

3. 3. The imaging optical system according to claim 1, wherein the first and second transmissive-reflective surfaces move during zooming.

4. the second lens group moves during zooming, 3. The imaging optical system according to claim 1, wherein the plurality of lens groups includes a third lens group that is disposed closer to the image side than the second lens group and that moves less during zooming than the second lens group.

5. When the focal length of the lens group including the first or second transmissive-reflective surface having the smaller radius of curvature is defined as fgr and the focal length of the optical system at the wide-angle end is defined as fw, 1.0≦fgr / fw≦4.5 3. The imaging optical system according to claim 1, wherein the following condition is satisfied:

6. When the focal length of the lens group including the one of the first and second transmissive-reflective surfaces having the smaller radius of curvature is denoted by fgr, the radius of curvature of the first transmissive-reflective surface is denoted by R1, and the radius of curvature of the second transmissive-reflective surface is denoted by R2, 2.0≦(R1×R2) / {(R1+R2)×fgr}≦7.0 3. The imaging optical system according to claim 1, wherein the following condition is satisfied:

7. The average value of the Abbe numbers of the positive lenses arranged on the object side of the first transmitting-reflecting surface is defined as νd ｍｆ When 20≦νd ｍｆ ≦65 3. The imaging optical system according to claim 1, wherein the following condition is satisfied:

8. an aperture stop disposed on the image side of the second transmitting-reflecting surface, The average Abbe number of the positive lens arranged between the first transmission-reflection surface and the aperture stop is defined as νd ｍｍ When 20≦νd ｍｍ ≦96 3. The imaging optical system according to claim 1, wherein the following condition is satisfied:

9. an aperture stop disposed on the object side of the first transmitting-reflecting surface, The average value of the Abbe numbers of the positive lenses disposed between the aperture stop and the second transmission-reflection surface is defined as νd ｍｒ When 50≦νd ｍｒ ≦96 3. The imaging optical system according to claim 1, wherein the following condition is satisfied:

10. The refractive index at the d-line of the first lens disposed between the first and second transmission-reflection surfaces is defined as nd ｍ When 1.40≦nd ｍ ≦1.85 3. The imaging optical system according to claim 1, wherein the following condition is satisfied:

11. further comprising an aperture stop; 3. The imaging optical system according to claim 1, wherein at least one of the lens disposed closer to the image side than the aperture stop, the first transmissive-reflective surface, and the second transmissive-reflective surface moves during focusing.

12. 12. The imaging optical system according to claim 11, wherein the first and second transmissive-reflective surfaces move during focusing.

13. When the distance on the optical axis between the object-side surface of the lens located closest to the object at the wide-angle end and the entrance pupil is dp and the focal length of the optical system at the wide-angle end is fw, 1.5≦dp / fw≦4.0 3. The imaging optical system according to claim 1, wherein the following condition is satisfied:

14. When the smaller of the open angle of the first transmitting-reflecting surface and the open angle of the second transmitting-reflecting surface is θm [°], 0.0≦|θm|≦8.0 3. The imaging optical system according to claim 1, wherein the following condition is satisfied:

15. When the larger of the open angle of the first transmitting-reflecting surface and the open angle of the second transmitting-reflecting surface is θl [°], 2.0≦|θl|≦50.0 3. The imaging optical system according to claim 1, wherein the following condition is satisfied:

16. a retarder disposed between the first and second transmissive-reflective surfaces; 3. The imaging optical system according to claim 1, wherein light from the object side passes through the first transmission-reflection surface and the phase shifter in that order, is reflected by the second transmission-reflection surface toward the object side, passes through the phase shifter, is reflected by the first transmission-reflection surface toward the image side, and passes through the phase shifter and the second transmission-reflection surface in that order toward the image side.

17. When the chief ray of the most off-axis light beam first enters one of the first and second transmitting-reflecting surfaces with the smaller open angle, the incident angle of the chief ray is defined as θin [°], 0.0≦θin≦40.0 17. The imaging optical system according to claim 16, wherein the following condition is satisfied:

18. 3. The imaging optical system according to claim 1, wherein the plurality of lens groups includes a lens group having a positive refractive power, the lens group being arranged on the object side of the first lens group.

19. 3. An imaging apparatus comprising: the imaging optical system according to claim 1; and an imaging element that receives an image formed by the imaging optical system.

Images