Imaging optical system and image pickup apparatus having the same

Abstract

The invention provides an imaging optical system and an imaging apparatus having the same. The imaging optical system includes a plurality of lens units. Each distance between adjacent lens units of the plurality of lens units varies during zooming. The plurality of lens units includes: a first lens unit having a negative refractive power and a second lens unit having a positive refractive power, the second lens unit being disposed closer to the image plane than the first lens unit; and a first transmissive reflective surface and a second transmissive reflective surface disposed closer to the image surface than the first transmissive reflective surface.

Description

Technical Field

[0001] This disclosure relates to one or more embodiments of an imaging optical system and a camera device having an imaging optical system. Background Technology

[0002] Imaging optical systems used in camera equipment, etc., are required to have reduced size. Summary of the Invention

[0003] One or more embodiments of an imaging optical system according to one or more aspects of this disclosure may include a plurality of lens units. The distances between adjacent lens units in the plurality of lens units change during zooming. The plurality of lens units include: a first lens unit having negative refractive power and a second lens unit having positive refractive power, the second lens unit being configured closer to the image plane than the first lens unit; and a first transmission reflective surface and a second transmission reflective surface, the second transmission reflective surface being configured closer to the image plane than the first transmission reflective surface. One or more imaging devices may include one or more imaging optical systems according to one or more other aspects of this disclosure.

[0004] Other features of various embodiments of this disclosure will become apparent from the following description of embodiments with reference to the accompanying drawings. The following description of embodiments will be provided by way of example. Attached Figure Description

[0005] Figure 1 This is a schematic diagram showing the optical path in an optical system.

[0006] Figure 2 This is a schematic diagram showing the optical path in an optical system.

[0007] Figure 3 It is a cross-sectional view of the imaging optical system at the wide-angle end based on Example 1.

[0008] Figure 4A and Figure 4B It is an aberration diagram of the imaging optical system of Example 1 when it is in a focused state at infinity.

[0009] Figure 5 It is a cross-sectional view of the imaging optical system at the wide-angle end based on Example 2.

[0010] Figure 6A and Figure 6B It is an aberration diagram of the imaging optical system in Example 2 when it is in a focused state at infinity.

[0011] Figure 7 It is a cross-sectional view of the imaging optical system at the wide-angle end based on Example 3.

[0012] Figure 8A and Figure 8B It is an aberration diagram of the imaging optical system in Example 3 when it is in a focused state at infinity.

[0013] Figure 9 It is a cross-sectional view of the imaging optical system at the wide-angle end based on Example 4.

[0014] Figure 10A and Figure 10B It is an aberration diagram of the imaging optical system in Example 4 when it is in a focused state at infinity.

[0015] Figure 11 It is a cross-sectional view of the imaging optical system at the wide-angle end based on Example 5.

[0016] Figure 12A and Figure 12B It is an aberration diagram of the imaging optical system in Example 5 when it is in a focused state at infinity.

[0017] Figure 13 It is a cross-sectional view of the imaging optical system at the wide-angle end based on Example 6.

[0018] Figure 14A and Figure 14B It is an aberration diagram of the imaging optical system in Example 6 when it is in a focused state at infinity.

[0019] Figure 15 It is a cross-sectional view of the imaging optical system at the wide-angle end based on Example 7.

[0020] Figure 16A and Figure 16B It is an aberration diagram of the imaging optical system in Example 7 when it is in a focused state at infinity.

[0021] Figure 17 It is a cross-sectional view of the imaging optical system at the wide-angle end based on Example 8.

[0022] Figure 18A and Figure 18B It is an aberration diagram of the imaging optical system in Example 8 when it is in a focused state at infinity.

[0023] Figure 19 It is a cross-sectional view of the imaging optical system at the wide-angle end based on Example 9.

[0024] Figure 20A and Figure 20B It is an aberration diagram of the imaging optical system of Example 9 when it is in a focused state at infinity.

[0025] Figure 21 It is a cross-sectional view of the imaging optical system at the wide-angle end according to Example 10.

[0026] Figure 22A and Figure 22B It is an aberration diagram of the imaging optical system of Example 10 in a focused state at infinity.

[0027] Figure 23 It is a cross-sectional view of the imaging optical system at the wide-angle end according to Example 11.

[0028] Figure 24A and Figure 24B It is an aberration diagram of the imaging optical system of Example 11 when it is in a focused state at infinity.

[0029] Figure 25 It is a cross-sectional view of the imaging optical system at the wide-angle end according to Example 12.

[0030] Figure 26A and Figure 26B It is an aberration diagram of the imaging optical system of Example 12 in a focused state at infinity.

[0031] Figure 27 It is a cross-sectional view of the imaging optical system at the wide-angle end according to Example 13.

[0032] Figure 28A and Figure 28B It is an aberration diagram of the imaging optical system of Example 13 in a focused state at infinity.

[0033] Figure 29 It is a cross-sectional view of the imaging optical system at the wide-angle end according to Example 14.

[0034] Figure 30A and Figure 30B It is an aberration diagram of the imaging optical system of Example 14 in a focused state at infinity.

[0035] Figure 31 It is a cross-sectional view of the imaging optical system at the wide-angle end according to Example 15.

[0036] Figure 32A and Figure 32B It is an aberration diagram of the imaging optical system of Example 15 in a focused state at infinity.

[0037] Figure 33 It is a cross-sectional view of the imaging optical system at the wide-angle end according to Example 16.

[0038] Figure 34A and Figure 34B It is an aberration diagram of the imaging optical system of Example 16 in a focused state at infinity.

[0039] Figure 35 This is a schematic diagram of the camera equipment. Detailed Implementation

[0040] A detailed description will now be given based on examples according to this disclosure, with reference to the accompanying drawings. Corresponding elements in the figures will be indicated by the same reference numerals, and repeated descriptions thereof will be omitted.

[0041] Figure 3 , Figure 5 , Figure 7 , Figure 9 , Figure 11 , Figure 13 , Figure 15 , Figure 17 , Figure 19 , Figure 21 , Figure 23 , Figure 25 , Figure 27 , Figure 29 , Figure 31 and Figure 33 These are cross-sectional views at the wide-angle end of the imaging optical systems according to Examples 1 to 16. The imaging optical systems according to the various examples are used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, film-based cameras, and surveillance cameras.

[0042] In the cross-sectional views, the left side is the object side, and the right side is the image side. The imaging optical systems described in the various examples can be used as projection lenses for projectors (projection devices), etc. In this case, the left side is the screen side, and the right side is the projected image side.

[0043] The imaging optical systems according to the various examples have multiple lens units. In this specification, a lens unit is a group of lenses that moves as units or remains stationary during zooming. That is, in the imaging optical systems according to the various examples, the distances between adjacent lens units change during zooming. A lens unit may include one or more lenses. A lens unit may include an aperture stop.

[0044] Multiple lens units include a first lens unit L1 with negative refractive power and a second lens unit L2 with positive refractive power, which are arranged sequentially from the object side to the image side.

[0045] SP represents the aperture stop. IM represents the image plane. In cases where the imaging optical system according to the examples is used in a digital still camera or digital video camera, the imaging plane of a solid-state image sensor (photoelectric conversion element), such as a CCD sensor or a CMOS sensor, is disposed on the image plane IM. In cases where the imaging optical system according to the examples is used as an imaging optical system for a film-based camera, a photosensitive surface equivalent to the film plane is disposed on the image plane IM.

[0046] The solid arrows shown in the following cross-sectional diagrams indicate the movement trajectory of each lens element during zooming from the wide-angle end to the telephoto end. The arrows along the optical axis indicate the direction of movement of the lens element during focusing.

[0047] The thicknesses of the waveplates (phase shifters), polarization-selective transmission-reflection elements, and polarizers described below are omitted. This is because they are thin and flat enough (or have a meniscus shape that is nearly identical on both the front and back sides) that their thickness does not affect the nature of the ray-tracing optical design of this disclosure. In other words, even if they are inserted in the form of thin plates, etc., taking into account their thickness, imaging optical systems with approximately equal aberrations and dimensions can be easily designed by finely adjusting the radius of curvature and thickness of each lens.

[0048] Figure 4A , Figure 4B , Figure 6A , Figure 6B , Figure 8A , Figure 8B , Figure 10A , Figure 10B , Figure 12A , Figure 12B , Figure 14A , Figure 14B , Figure 16A , Figure 16B , Figure 18A , Figure 18B , Figure 20A , Figure 20B , Figure 22A , Figure 22B , Figure 24A , Figure 24B , Figure 26A , Figure 26B , Figure 28A , Figure 28B , Figure 30A , Figure 30B , Figure 32A , Figure 32B , Figure 34A , Figure 34B These are aberration diagrams of the imaging optical systems according to Examples 1 to 16 in a focused state at infinity (on the object). Figure 4A , Figure 6A , Figure 8A , Figure 10A , Figure 12A , Figure 14A , Figure 16A , Figure 18A , Figure 20A , Figure 22A , Figure 24A , Figure 26A , Figure 28A , Figure 30A , Figure 32A and Figure 34AThe aberration diagram at the wide-angle end is shown. Figure 4B , Figure 6B , Figure 8B , Figure 10B , Figure 12B , Figure 14B , Figure 16B , Figure 18B , Figure 20B , Figure 22B , Figure 24B , Figure 26B , Figure 28B , Figure 30B , Figure 32B and Figure 34B Aberration diagrams at the telephoto end are shown separately.

[0049] In the spherical aberration map, Fno represents the F-number. The spherical aberration map shows the amount of spherical aberration 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 map, S shows the amount of astigmatism in the sagittal plane, and M shows the amount of astigmatism in the meridional plane. The distortion map shows the distortion for the d-line. The chromatic aberration map shows the chromatic aberration for the g-line. ω is the half-angle of view (°).

[0050] The following is a description of the characteristic structure of the imaging optical system according to each example.

[0051] The imaging optical system described in each example is a zoom optical system that can capture images by forming an image of an object on an image plane and acquiring the image by placing a solid image sensor, a photosensitive film, etc., on the image plane.

[0052] As described above, the imaging optical system according to the various examples includes multiple lens units, which include a first lens unit L1 with negative refractive power and a second lens unit L2 with positive refractive power arranged sequentially from the object side to the image side. The imaging optical system according to the various examples has a first transmission-reflection surface HM1 and a second transmission-reflection surface HM2 arranged sequentially from the object side to the image side. Light incident from the object side passes through the first transmission-reflection surface HM1 and is reflected by the second transmission-reflection surface HM2. Then, the light is reflected by the first transmission-reflection surface HM1, passes through the second transmission-reflection surface HM2, and enters an imaging unit such as a solid-state image sensor or a photosensitive film.

[0053] The first transmission-reflecting surface HM1 and the second transmission-reflecting surface HM2 can be disposed in either the first lens unit L1 or the second lens unit L2. The first transmission-reflecting surface HM1 can be disposed in the first lens unit L1, and the second transmission-reflecting surface HM2 can be disposed in the second lens unit L2. The first transmission-reflecting surface HM1 and the second transmission-reflecting surface HM2 can be disposed in one or more lens units different from the first lens unit L1 and the second lens unit L2.

[0054] In this specification, the terms "zoom optical system" and "zoom lens" have the same meaning. Strictly speaking, a zoom lens refers to an optical system that does not shift the focus during magnification changes, but here, the terms "zoom lens" or "magnification-changing optical system" also include optical systems that do shift the focus.

[0055] The first and second transmission-reflection surfaces HM1 and HM2 may not each have 50% transmittance and 50% reflectance. The transmittance to reflectance ratio of randomly polarized light can be in the range of 1:3 to 3:1. Randomly polarized light is light with Stokes parameters S0=1 and S1=S2=S3=0. The first and second transmission-reflection surfaces HM1 and HM2 can absorb light.

[0056] The lens can be formed on at least one side of the two transmission and reflection surfaces, or joined to at least one side of the two transmission and reflection surfaces.

[0057] Due to the above structure, the imaging optical systems according to the examples can reduce size and achieve high optical performance.

[0058] The following is a description of the structures that can be satisfied in the imaging optical systems according to the various examples. An element (wavelength plate or phase shifter) for imparting a phase difference (delay) to the incident light can be configured between the first transmission reflector HM1 and the second transmission reflector HM2. For example, a wavelength plate (phase plate) such as a quarter-wave plate (QWP) or a 45° rotator (Faraday rotator, etc.) can be used as the phase shifter.

[0059] For example, a birefringent polymer film or liquid crystal alignment layer can be used as a QWP. A laminate formed by stacking such a polymer film and liquid crystal alignment layer can also be used as a QWP. For example, Nippon Kayaku Co., Ltd.'s "WA-140T" and Colorlink Japan Co., Ltd.'s "Polar Correct" can be used. In addition to the above, inorganic wavelength plates from Dexerials Co., Ltd. can also be used as QWPs. Wavelength plates that exhibit birefringence by aligning atoms or molecules through polarized light irradiation can also be used. By using such methods, wavelength plates with higher surface accuracy can be fabricated more easily than polymer films.

[0060] A QWP can be configured by bonding it to, for example, a first transmission / reflection surface HM1 or a second transmission / reflection surface HM2. The QWP can also be configured as a component separate from these transmission / reflection surfaces. For example, the film can be directly inserted into the optical path, or a film bonded to a glass plate can be inserted into the optical path. Lenses can also be formed or bonded to at least one side of the QWP. For example, an inorganic wavelength plate can be used as a substrate, and lenses can be formed on one or both sides of the inorganic wavelength plate using wafer-level optics technology.

[0061] The second lens unit L2 may have a first transmission-reflecting surface (HM1) and a second transmission-reflecting surface (HM2). In the imaging optical system according to the various examples, light diverging from the first lens unit L1, which has negative refractive power, is incident on the second lens unit L2. Thus, the light is incident on the second lens unit L2 at a relatively high ray height. Therefore, by placing a reflective surface at a position that, in principle, does not cause chromatic aberration, at a high ray height, chromatic aberration of the imaging optical system can be effectively corrected. In particular, chromatic aberration correction via this reflective surface is especially effective in optical systems with small F-numbers where strict correction of longitudinal chromatic aberration is required. Furthermore, from the viewpoint of Petzval sum correction, a lens unit with positive refractive power may have a reflective surface, and in this respect, the second lens unit L2 may have a reflective surface. Since imaging optical systems typically have a positive focal length, the positive refractive power of each lens in the imaging optical system inevitably becomes stronger, and the Petzval sum tends to become positive in the refractive system. To correct this, a strong negative lens is needed; however, this negative lens has a significant adverse effect on other aberrations, such as sagittal coma, which is particularly pronounced in lenses with small F-numbers. On the other hand, the Petzval sum of the reflecting surface is opposite to that of the refracting lens, and the reflecting surface with positive refractive power has a negative Petzval sum, such that the positive Petzval sum generated in the refracting lens with positive refractive power can be canceled out by the reflecting surface with positive refractive power. Therefore, at least one of the two reflecting surfaces can have positive refractive power. In the case where the sum of the refractive powers of the two reflecting surfaces is positive or one of the two reflecting surfaces has negative refractive power, the reflecting surface with positive refractive power can have a high ray height. Therefore, in terms of optical arrangement, it may be natural to place the reflecting surface in the subgroup with positive refractive power, and the reflecting surface can be set in the second lens unit L2.

[0062] As mentioned above, the reflective surface is crucial for aberration correction, and therefore it can be moved during zooming. This allows for particularly effective aberration correction across the entire zoom range, while keeping the weight of the focusing unit low.

[0063] In the imaging optical systems according to various examples, multiple multi-lens units can be composed of a first lens unit L1 and a second lens unit L2. However, given that the refractive power and distance between each lens unit are determined, as well as the amount of movement, and there are almost no degrees of freedom in the arrangement of each lens unit, it becomes difficult to achieve high magnification, especially at F-number brightness. Therefore, the third lens unit can be closer to the image plane than the second lens unit L2. This improves the degrees of freedom in the structure of each lens unit and allows for high magnification or high image quality while maintaining magnification. The third lens unit can remain stationary during zooming, or the amount of movement of the third lens can be smaller than that of the second lens unit L2. Especially in interchangeable lens applications, a large space is needed near the lens mount for mechanical and electronic components, where the lens mount is the junction with the camera body. By fixing the lens unit closest to the image plane or maintaining a small amount of movement, the space near the lens mount for mechanical and electronic components is not compressed by the mechanism for moving the lens unit, and lenses with larger diameters can be positioned near the image plane. Therefore, the angle of incidence of off-axis rays onto the sensor can be close to telecentricity.

[0064] The imaging optical systems in the examples can be coaxial systems. This improves the ease of manufacturing the components and makes assembly and adjustment easier. However, the effective and outer diameters of the lenses and transmission / reflection surfaces do not need to be rotationally symmetric, and rectangular shapes with notches or flat orientations can be used, for example, to indicate the orientation of various polarizing elements.

[0065] The imaging optical system according to each example can be a single-image system. In the case where the imaging optical system according to each example 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 been imaged once, and the total length increases.

[0066] During focusing, at least one of the lenses positioned closer to the image plane than the first transmission reflective surface HM1, the second transmission reflective surface HM2, and the aperture stop SP can be moved along the optical axis. A common focusing method for zoom lenses is to move the lens unit (or part of the lens) positioned closest to the object. In this method, the extension does not change during zooming, thus parfocality can be easily ensured without the use of special mechanical mechanisms or electronic controls. However, typically in zoom lenses with large aperture diameters, the ray height of the lens positioned on the object side is higher than that of the lens positioned on the image side. When the lens positioned on the object side moves significantly during focusing, large aberration changes occur because the lens moves at a position with a high ray height. In particular, in zoom lenses with large aperture diameters, such as those in imaging optical systems according to the examples, aberration fluctuations are at unacceptable levels. Therefore, it is possible to move the lens positioned on the image side, where the ray height is relatively low. On the other hand, as mentioned above, the aberration behavior of the reflecting surface is significantly different from that of the refractive lens. Therefore, in order to balance the aberrations of the refractive lens and the reflecting surface, the reflecting surface can be moved during focusing. Taking these factors into account, a lens configured to be closer to the image plane than the reflecting surface or the aperture stop SP can be moved during focusing.

[0067] The first transmission reflector HM1 and the second transmission reflector HM2 can each be rotated about the optical axis by 0.5° or more during focusing. As will be described later, in the imaging optical systems according to the various examples, the relative angles of the quarter-wave plate and the transmission reflector are important for suppressing ghosting and ensuring normal light intensity when the optical axes are set as the rotation axes. Therefore, the rotational movement of the first transmission reflector HM1 and the second transmission reflector HM2 about the optical axis during focusing can be sufficiently small. If all anisotropic elements such as the quarter-wave plate and the transmission reflector are rotated by the same amount, there is no problem in suppressing ghosting and ensuring normal light intensity. However, when the polarization of the light incident on the imaging optical system is not low, the direction of the transmitted polarized light changes due to the same amount of rotation of the elements, and depending on the subject, this may lead to changes in brightness and color with focusing.

[0068] One of the first and second transmission-reflecting surfaces, HM1 and HM2, can be spherical. Using aspherical surfaces is advantageous for aberration correction, but it is more difficult to make the surface shape closer to the design values ​​compared to using spherical surfaces; therefore, spherical surfaces are easier to manufacture. Fine machining marks tend to remain on aspherical surfaces, and especially when these marks remain on the reflecting surface, the resulting pattern may be reflected in the blur. In lenses with large aperture diameters used for still and moving image applications, users also value blur quality and therefore can avoid such patterns.

[0069] The first transmission and reflection surface HM1 and the second transmission and reflection surface HM2 can be polarization-selective transmission and reflection elements. By inserting a 45° rotator, such as a Faraday rotator, between the transmission and reflection surfaces, light loss 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 structure described below.

[0070] The following is a description of the conditions that the imaging optical systems according to the examples can satisfy. The imaging optical systems according to the examples can satisfy one or more of the following inequalities (1) to (10).

[0071]

[0072] Here, fgr is the focal length of the lens unit comprising the first and second transmission reflective surfaces HM1 and HM2, which have the smaller radius of curvature. fw is the focal length of the imaging optics system at the wide-angle end. R1 is the radius of curvature of the first transmission reflective surface HM1. R2 is the radius of curvature of the second transmission reflective surface HM2. The radii of curvature R1 and R2 are the absolute values ​​of the radii of curvature of the first and second transmission reflective surfaces HM1 and HM2, respectively, and are always positive regardless of their orientation. νd mf It is the average Abbe number of one or more positive lenses configured to be closer to the object than the first transmissive reflective surface HM1. νd mm It is the average Abbe number of one or more positive lenses positioned between the first transmission surface HM1 and the aperture stop SP, when the aperture stop SP is positioned closer to the image plane than the second transmission surface HM2. mr This is the average Abbe number of the positive lens positioned between the aperture stop SP and the second transmission surface HM2, when the aperture stop SP is positioned closer to the object than the first transmission surface HM1. The Abbe number in inequalities (3) to (5) is expressed by the same definition as the Abbe number described later. md is the refractive index of the positive lens (first lens) positioned between the first and second transmission reflective surfaces HM1 and HM2, relative to the d-line. dp is 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. θm [°] is the smaller of the opening angles of the first and second transmission reflective surfaces HM1 and HM2. θl [°] is the larger of the opening angles of the first and second transmission reflective surfaces HM1 and HM2. The opening angle is the angle of the surface normal relative to the direction perpendicular to the optical axis and is evaluated at its maximum value within the effective surface. The effective surface is the area through which normal rays pass, excluding ghosting or stray light. θin [°] is the angle of incidence when the principal ray of the most off-axis beam first enters the transmission reflective surface with the smaller opening angle between the first and second transmission reflective surfaces HM1 and HM2.

[0073] When the value becomes higher than the upper limit of inequality (1), the refractive power of the reflecting surface becomes too strong for the imaging optics system, and the external dimensions of the lens increase to cause light to bounce significantly upwards. Furthermore, to correct aberrations in lens units with high refractive power relative to the imaging optics system, many lenses are required, and the weight and overall length of the imaging optics system increase. When the value becomes lower than the lower limit of inequality (1), the effect of the reflecting surface on the imaging optics system decreases, and aberration correction becomes insufficient. In this disclosure, it is not necessary for the radii of curvature of the transmission and reflection surfaces to be different from each other. However, the transmission and reflection surfaces can be different from each other, for example, this allows for improved design freedom.

[0074] When the value becomes higher than the upper limit of inequality (2), the refractive power of the reflecting surface increases, and the external dimensions of the lens disposed on the object side increase, causing light to bounce significantly upwards. Additionally, Petzval and become overcorrected. When the value becomes lower than the lower limit of inequality (2), the refractive power of the reflecting surface decreases, and the corrections for longitudinal chromatic aberration and Petzval and become insufficient.

[0075] The radius of curvature of the flat surface is ∞. In the case where only one transmission and reflection surface is flat, and in the case where the radius of curvature of the non-flat transmission and reflection surface is R, inequality (2) can be transformed into the following inequality (2').

[0076]

[0077] When the value becomes higher than the upper limit of inequality (3), the lens configured closer to the image plane than the aperture stop SP cannot balance the lateral chromatic aberration, and the lateral chromatic aberration increases. When the value becomes lower than the lower limit of inequality (3), the dispersion of the positive lens increases, and the longitudinal chromatic aberration increases.

[0078] When the value becomes higher than the upper limit of inequality (4), special ultra-low dispersion glass materials that are difficult to process must be used, and manufacturing becomes difficult. When the value becomes lower than the lower limit of inequality (4), the wavelength dispersion of the positive lens increases, and the longitudinal and lateral chromatic aberrations increase.

[0079] When the value becomes higher than the upper limit of inequality (5), special ultra-low dispersion glass materials that are difficult to process must be used, and manufacturing becomes difficult. When the value becomes lower than the lower limit of inequality (5), the wavelength dispersion of the positive lens increases, and the longitudinal and lateral chromatic aberrations increase.

[0080] When the value becomes higher than the upper limit of inequality (6) and the reflecting surface has sufficient refractive power, the refractive power of the lens that acts on the beam three times between the transmitting and reflecting surfaces increases, and the refractive power balance of the entire imaging optical system is disrupted. When the curvature of the reflecting surface is reduced, the refractive power of the reflecting surface decreases, and it becomes difficult to utilize the aberration correction capability of the reflecting surface. When the value becomes lower than the lower limit of inequality (6), special materials that are difficult to process must be used, and manufacturing becomes difficult.

[0081] When the value becomes higher than the upper limit of inequality (7), the incident pupil becomes concave, and the off-axis beam is separated from the optical axis by the position of the lens placed on the object side. Therefore, the lens diameter of the lens placed on the object side increases, and handling becomes inconvenient. When the value becomes lower than the lower limit of inequality (7), it is not sufficiently guaranteed that there is enough space for placing a sufficient number of lenses configured to be closer to the object than the aperture stop SP, as well as the distance the lens unit moves during zooming.

[0082] As will be described later, in the imaging optical systems according to the various examples, at least one of the first transmission reflective surface HM1 and the second transmission reflective surface HM2 uses a polarization-selective transmission reflective element, such as a polarization beam splitter. It is difficult to form a polarization-selective transmission reflective element in a curved shape. When the shape is close to a flat surface, it can be manufactured using a process similar to that used for flat surfaces, but the further the shape deviates from a flat surface, the more specialized the process becomes. Therefore, the difficulty of forming a polarization-selective transmission reflective element increases when the value becomes higher than the upper limit of inequality (8). By definition, the value cannot become lower than the lower limit of inequality (8).

[0083] When using flexible materials such as resin films or wire grids using resin films as substrates as polarization-selective transmission and reflection elements, the surface accuracy of the transmission and reflection surfaces can be appropriately maintained. Therefore, when one of the first transmission and reflection surfaces HM1 and the second transmission and reflection surface HM2 is made of such a material, it can be bonded to glass or a rigid resin with a glass transition temperature of 40°C or higher. Both surfaces can be bonded to glass or a rigid resin with a glass transition temperature of 40°C or higher. The adhesive used for bonding (including elastic adhesives) is not particularly specified, but the adhesive layer can be 25 μm or less, or 15 μm or less. In the case of bonding only one side, the retaining member does not need to directly contact the transmission and reflection surface when holding the lens. For example, the lens can be held at a portion of the bonded glass or rigid resin member. This reduces surface distortion of the transmission and reflection surfaces. Regarding surface accuracy, the roughness of the reflecting wavefront can be sufficiently smooth, and the rms of components with 1 / mm or more on the reflecting wavefront can be 10 nm or less, and the rms of components with 0.05 / mm or more and 1 / mm or less can be 10 nm or less. Therefore, image quality degradation caused by poor surface accuracy of the reflective surface can be effectively suppressed.

[0084] When the value becomes higher than the upper limit of inequality (9), the opening angle of the transmission and reflection surface increases, and it becomes difficult to manufacture uniform transmission and reflection elements. When the value becomes lower than the lower limit of inequality (9), the refractive power of the reflection surface decreases, and the aberration correction using the reflection surface becomes insufficient.

[0085] Since the characteristics of polarization elements, such as polarization-selective transmission and reflection elements, are angle-dependent, it becomes difficult to obtain the desired characteristics when the value becomes higher than the upper limit of inequality (10). By definition, the value cannot become lower than the lower limit of inequality (10).

[0086] The lower limit of inequality (1) can be set to 1.1, 1.2, 1.3, 1.4 or 1.5. The upper limit of inequality (1) can be set to 4.3, 4.1, 3.9, 3.7 or 3.5.

[0087] The lower limit of inequality (2) can be set to 2.1, 2.2, 2.3, 2.4 or 2.5. The upper limit of inequality (2) can be set to 6.8, 6.6, 6.4, 6.2 or 6.0.

[0088] The lower limit of inequality (3) can be set to 21, 22, 23, 24 or 25. The upper limit of inequality (3) can be set to 63, 61, 59, 57 or 55.

[0089] The lower limit of inequality (4) can be set to 21, 22, 23, 24 or 25. The upper limit of inequality (4) can be set to 91, 87, 83, 79 or 75.

[0090] The lower limit of inequality (5) can be set to 51, 52, 53, 54 or 55. The upper limit of inequality (5) can be set to 95, 92, 89, 86 or 83.

[0091] The lower limit of inequality (6) can be set to 1.41, 1.42, 1.43, 1.44 or 1.45. The upper limit of inequality (6) can be set to 1.84, 1.83, 1.82, 1.81 or 1.80.

[0092] The lower limit of inequality (7) can be set to 1.50, 1.55, 1.60, 1.65 or 1.70. The upper limit of inequality (7) can be set to 3.9, 3.8, 3.7, 3.6 or 3.5.

[0093] The upper limit of inequality (8) can be set to 7.0, 6.0, 5.0, 4.5 or 4.0.

[0094] The lower limit of inequality (9) can be set to 2.5, 3.0, 3.5, 4.0 or 4.5.

[0095] The upper limit of inequality (9) can be set to 45, 42, 40, 38 or 35.

[0096] The upper limit of inequality (10) can be set to 37, 34, 31, 28 or 25.

[0097] One of the first transmission-reflecting surface HM1 and the second transmission-reflecting surface HM2 can be a surface that separates incident light into reflected light and transmitted light according to the polarization state. For example, a polarization-selective transmission-reflection element can be used. Examples of polarization-selective transmission-reflection elements include "WGF" manufactured by Asahi Kasei Corporation, "IQP-E" manufactured by 3M Corporation, and "ProFlux" manufactured by Moxtek, Inc. As a polarization-selective transmission-reflection element, an optical element created by forming a grid on the lens reflecting surface during lens forming and then depositing, printing, or photolithographically depositing metal or dielectric on the grid can be used. On the other hand, a semi-reflective mirror or cholesteric liquid crystal can be used. When using a semi-reflective mirror, the amount of randomly polarized light incident from the object side reaches the image plane at 12.5% ​​or less. When using a cholesteric liquid crystal, the amount of light on the image plane can be approximately doubled compared to the case of using a semi-reflective mirror.

[0098] In the imaging optical systems according to the various examples, for example, the following structure can suppress the reduction of light in the normal imaging optical path while reducing ghost light (unnecessary light leakage) from the light path that passes through the transmissive reflective surface without being reflected even once.

[0099] Utilizing polarization structure 1

[0100] Now for reference Figure 1 A description of the structure utilizing polarization will be given. The imaging optical system using this structure has two transmission and reflection surfaces. Here, the transmission and reflection surface on the object side of the imaging optical system using this structure is a polarization-selective transmission and reflection element (PBS): A. The transmission and reflection surface on the image plane side of the imaging optical system using this structure is a half-reflector (HM): C. A first quarter-wave plate (QWP1): B is disposed between the polarization-selective transmission and reflection element PBS and the half-reflector HM. A second quarter-wave plate (QWP2): D and a linear polarizer (POL): E are disposed sequentially from the object side to the image side between the half-reflector HM and the imaging plane IM.

[0101] 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 passes through the linear polarizer E, and to transmit linearly polarized light perpendicular to the linear polarizer. The polarization-selective transmission-reflection element A is, for example, a wire-grid polarizer or a reflective polarizer with a stacked retardation film structure. In this case, the wire-grid forming surface or the retardation film surface of the polarization-selective transmission-reflection element A serves as the transmission-reflection surface. The wire-grid polarizer does not necessarily have to be a metal-line aligned polarizer, as long as it has a thin metal or dielectric layer at a specified distance and is used as a polarization-selective transmission-reflection element. For example, an element with metal or dielectric layers aligned by vapor deposition can be used.

[0102] The first quarter-wave plate B and the second quarter-wave plate D are arranged such that their slow axes are tilted at 45° relative to the polarization transmission axis of the linear polarizer E. Alternatively, the first quarter-wave plate B and the second quarter-wave plate D can be arranged such that their slow axes are tilted at 90°. This arrangement cancels out the wavelength dispersion characteristics of the wavelength plates when light passes through them.

[0103] The semi-reflective mirror C is, for example, formed by dielectric multilayer film or metal deposition, and the mirror surface of the semi-reflective mirror C serves as a transmission and reflection surface. The linear polarizer E is, for example, an absorption-type linear polarizer.

[0104] The following is a description of the optical path selection and operation in the polarization utilization structure.

[0105] Light incident on the imaging optics from the object side is converted into linearly polarized light by polarization-selective transmission and reflection element A, then into circularly polarized light by the first quarter-wave plate B, and then incident on the semi-reflective mirror C. A portion of the light reaching the semi-reflective mirror C is reflected and becomes circularly polarized in the opposite direction, returning to the first quarter-wave plate B.

[0106] The circularly polarized light that has returned to the first quarter-wave plate B, now linearly polarized in a direction perpendicular to the direction in which the light first passes through the polarization-selective transmission and reflection element A, returns to the polarization-selective transmission and reflection element A. The light that has returned to the polarization-selective transmission and reflection element A is then reflected by the element. Here, due to the polarization selectivity of the element, linearly polarized light in a direction perpendicular to the direction in which the light first passes through the element, is reflected.

[0107] On the other hand, a portion of the light that has reached the semi-reflecting mirror C passes through the semi-reflecting mirror C and is linearly polarized by the second quarter-wave plate D in the same direction as when the light passes through the polarization-selective transmission and reflection element A, and is incident on the linear polarizer E and absorbed by the linear polarizer E.

[0108] Light reflected by polarization-selective transmission-reflection element A is circularly polarized by first quarter-wave plate B and incident on semi-reflective mirror C. A portion of the light reaching semi-reflective mirror C passes through it and incident on second quarter-wave plate D. Second quarter-wave plate D converts the incident light into linearly polarized light parallel to the linearly polarized light reflected by polarization-selective transmission-reflection element A. The light that has passed through second quarter-wave plate D then enters linear polarizer E. Here, the polarization of the light coincides with the transmission axis of linear polarizer E; therefore, most of the light passes through linear polarizer E and is guided to the imaging plane IM.

[0109] Due to the above operations, only the light that has passed through the polarization-selective transmission and reflection element PBS, been reflected by the semi-reflecting mirror C, and passed through the semi-reflecting mirror C is guided to the imaging surface IM.

[0110] When cholesteric liquid crystal is used instead of the semi-reflective mirror C, the cholesteric liquid crystal can reflect a large amount of circularly polarized light in the direction of the incident light during the first reflection. This reduces ghosting while increasing the amount of light in the normal optical path.

[0111] Solid-state image sensors and charge-coupled devices (CCDs) that can be used as the imaging surface IM typically have high surface reflectivity. In this structure, light reflected from 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. Then, light emitted from the second quarter-wave plate D is reflected by the semi-reflective mirror C, becoming circularly polarized light in the opposite direction, and passes through the second quarter-wave plate D again. 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 preceding its passage through the linear polarizer E. Since 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 way, in this structure, most of the light reflected by the imaging surface IM and the semi-reflective mirror C in this sequence is cut off, and ghosting and glare associated with the imaging surface IM are less noticeable. To achieve such a reflection reduction effect, a birefringent optical low-pass filter can be omitted between the imaging surface IM and the linear polarizer E. This is because an optical low-pass filter causes the polarization state to deviate from the desired polarization state.

[0112] In this structure, a quarter-wave plate can be placed between the polarization-selective transmission-reflection element A and the object. In this case, the quarter-wave plate is configured such that its fast or slow axis forms a 45° angle with respect to the transmission axis of the polarization-selective transmission-reflection element A. Therefore, even if the light incident from the object side is linearly polarized, imaging can be performed regardless of its polarization direction. Alternatively, a depolarization element can be placed instead of the quarter-wave plate. For example, Toyobo Cosmoshine SRF can be used as the depolarization element. Cosmoshine SRF is a film with a high birefringence of approximately 10,000 nm, and compared to using a quarter-wave plate, using such a film can suppress color unevenness caused by the wavelength and angular characteristics of the waveplate.

[0113] Utilizing polarization structure 2

[0114] Now for reference Figure 2 A description of the structure utilizing polarization will be given. The imaging optical system using this structure includes two transmission and reflection surfaces. Here, the transmission and reflection surface disposed on the object side of the imaging optical system using this structure is a half-reflector (HM): C. The transmission and reflection surface disposed on the imaging surface of the imaging optical system using this structure is a polarization-selective transmission and reflection element (PBS): A. A first quarter-wave plate (QWP1): B is disposed between the polarization-selective transmission and reflection element PBS and the half-reflector HM. A linear polarizer (POL): E and a second quarter-wave plate (QWP2): D are arranged sequentially from the object side to the image side between the half-reflector HM and the object surface.

[0115] Here, the structure and optical axis orientation of each polarization element are the same as those of the polarization elements in structure 1 using polarization.

[0116] The following is a description of the optical path selection and operation in the structure utilizing polarization.

[0117] Light incident on the imaging optical system from the object side is linearly polarized by linear polarizer E, circularly polarized by the second quarter-wave plate D, and then incident on the semi-reflecting mirror C. A portion of the light reaching the semi-reflecting mirror C is reflected and becomes circularly polarized in the opposite direction, returning to the second quarter-wave plate D.

[0118] The light that has reached the semi-reflecting mirror C and been reflected becomes circularly polarized light in the opposite direction to its incident direction. This light is then transformed by the second quarter-wave plate D into linearly polarized light in a direction perpendicular to the direction in which it passes through the linear polarizer E, and is incident on the linear polarizer E and absorbed by it.

[0119] On the other hand, the light that has passed through the semi-reflecting mirror C is converted by the first quarter-wave plate B into linearly polarized light in the same direction as the light that was polarized immediately after passing through the linear polarizer E. This linearly polarized light is reflected by the polarization-selective transmission and reflection element A and returns to the first quarter-wave plate B. Thereafter, the light is converted into circularly polarized light by the first quarter-wave plate B, and a portion of the light is reflected by the semi-reflecting mirror C. The light reflected by the semi-reflecting mirror C re-enters the first quarter-wave plate B and is converted into linearly polarized light with a polarization direction perpendicular to the direction it was reflected by the polarization-selective transmission and reflection element A. This linearly polarized light passes through the polarization-selective transmission and reflection element A and is guided to the imaging plane IM.

[0120] Due to the above operations, only the light that has passed through the semi-reflecting mirror C, been reflected by the polarization-selective transmission and reflection element PBS, and passed through the polarization-selective transmission and reflection element PBS is guided to the imaging surface IM.

[0121] In this arrangement, a linear polarizer A' can be positioned between the polarization-selective transmission-reflection element A and the imaging surface IM. In this case, the transmission axes of the linear polarizer A' and the polarization-selective transmission-reflection element A are aligned. Therefore, light that is reflected by the imaging surface IM, further reflected by the polarization-selective transmission-reflection element A, and then incident again on the imaging surface IM, causing ghosting and glare, can be absorbed.

[0122] In this configuration, a quarter-wave plate can be positioned between the linear polarizer E and the object. In this case, the quarter-wave plate is positioned such that its fast or slow axis forms a 45° angle with respect to the transmission axis of the linear polarizer E. Therefore, even if the light incident from the object side is linearly polarized, imaging can be performed regardless of its polarization direction. A depolarizing element can be used instead of the quarter-wave plate. For example, Toyobo Cosmoshine SRF can be used as the depolarizing element.

[0123] In the above description of the structure, terms such as perpendicular, parallel, and 45° are used, but they do not necessarily have to be strictly 90°, 0°, and 45°. However, they can be set within ±5°, ±2°, or ±1° of the angle.

[0124] This depends significantly on the characteristics of the first and second quarter-wave plates. When the characteristics of the quarter-wave plates are ideal and the changes in characteristics relative to wavelength and angle of incidence are sufficiently small (e.g., in...), Figure 1 In the structure of a quarter-wave plate, the relative angles between "A and B" and "D and E" are unrestricted. In practice, it is difficult to make the characteristics of a quarter-wave plate so ideal, so angles that make the intensity and hue of ghosting less noticeable can be used.

[0125] In both of the above-described structures, the same two QWPs can be used. If the QWPs are ideal (giving a phase of exactly one-quarter of the wavelength for all wavelengths and all incident angles within the usable range), there is no problem. However, in reality, such QWPs do not exist, and the phase imparted to the light varies depending on the wavelength of the transmitted light, etc. In both of these structures, when light passes through the two QWPs, the phases given by QWP1 and QWP2 are exactly canceled out, and it is only desirable for the light to be emitted towards the image plane. That is, light reflected once by both the first and second transmission reflectors is emitted to the image side, and light not reflected once or reflected twice is absorbed by the polarizer. In this case, if the characteristics of the QWPs differ, unintended light may be emitted towards the image plane, ghosting and glare may increase, and image quality may deteriorate.

[0126] Now consider the combination of the two types of structures described above with an image sensor that includes an optical low-pass filter. Furthermore, the relative angle between the transmission axis of the polarizer closest to the image plane and the fast axis of the birefringent plate closest to the object in the birefringent plate constituting the optical low-pass filter can be 45° or 135°. Therefore, a low-pass effect similar to that of a typical optical system (such as a general refractive optical system, which has almost no polarization dependence) can be obtained. Alternatively, a quarter-wave plate can be configured closer to the image plane than the polarizer closest to the image plane. In this case, the transmission axis of the polarizer closest to the image plane and the fast axis of the quarter-wave plate can be 45° or 135°. Therefore, emitting circularly polarized light toward the image sensor can provide a low-pass effect similar to that of a typical optical system. Alternatively, placing a plastic-molded lens with high birefringence closer to the image plane than the polarizer closest to the image plane can make the emitted light pseudo-randomly polarized and provide a low-pass effect similar to that of a typical optical system.

[0127] In both of the above-described structures, the polarization-selective transmission and reflection elements, quarter-wave plates, and linear polarizers can be circular or rectangular. These optical elements are primarily made of polymer materials and are readily available at low cost. For such elements, as described above, they can be bonded to, for example, glass or resin plates to ensure sufficient surface accuracy. This embodiment can eliminate material loss by fitting them in large sizes and cutting out the required rectangular shape from them. As mentioned above, the azimuth angles between the elements are important in both of the above-described structures. By using rectangular elements, it becomes easier to ensure the shape of the components and the orientation of the elements (fast axis / slow axis, transmission axis / absorption axis, transmission axis / reflection axis) for each part, and azimuth angle adjustments can be simplified or omitted.

[0128] In the imaging optical systems according to the various examples, the lens can be made of resin or glass. However, the lens disposed between the first transmission reflective surface HM1 and the second transmission reflective surface HM2 can have low birefringence.

[0129] The imaging optical systems according to the examples will be described in detail below.

[0130] The plurality of lens units according to Example 1 include a first lens unit to a third lens unit, which are arranged sequentially from the object side to the image side. The first lens unit and the second lens unit have negative refractive power and positive refractive power, respectively. The third lens unit includes a sensor protective glass. The first lens unit and the second lens unit correspond to the first lens unit L1 and the second lens unit L2, respectively.

[0131] The multiple lens units according to Examples 2 to 3 and 9 to 10 include a first lens unit to a fourth lens unit, which are arranged sequentially from the object side to the image side. The first lens unit to the third lens unit have negative refractive power, positive refractive power, and positive refractive power, respectively. The fourth lens unit includes a sensor protective glass. The first lens unit and the second lens unit correspond to the first lens unit L1 and the second lens unit L2, respectively.

[0132] The multiple lens units according to Examples 4 to 5 and 13 to 15 include a first lens unit to a fifth lens unit, which are arranged sequentially from the object side to the image side. The first lens unit to the fourth lens unit have positive refractive power, negative refractive power, positive refractive power, and positive refractive power, respectively. The fifth lens unit includes a sensor protective glass. The second lens unit and the third lens unit correspond to the first lens unit L1 and the second lens unit L2, respectively.

[0133] The plurality of lens units according to Examples 6 to 8 include a first lens unit to a fifth lens unit, which are arranged sequentially from the object side to the image side. The first lens unit to the fourth lens unit have negative refractive power, positive refractive power, positive refractive power, and positive refractive power, respectively. The fifth lens unit includes a sensor protective glass. The first lens unit and the second lens unit correspond to the first lens unit L1 and the second lens unit L2, respectively.

[0134] According to Example 11, the plurality of lens units include a first lens unit to a fifth lens unit arranged sequentially from the object side to the image side, and the first lens unit to the fifth lens unit respectively have negative refractive power, positive refractive power, positive refractive power, negative refractive power, and positive refractive power. The first lens unit and the third lens unit correspond to the first lens unit L1 and the second lens unit L2, respectively.

[0135] According to Example 12, the plurality of lens units include a first lens unit to a fourth lens unit arranged sequentially from the object side to the image side, and the first lens unit to the fourth lens unit respectively have negative refractive power, positive refractive power, negative refractive power, and positive refractive power. The first lens unit and the second lens unit correspond to the first lens unit L1 and the second lens unit L2, respectively.

[0136] According to Example 16, the multiple lens units consist of a first lens unit to a fourth lens unit arranged sequentially from the object side to the image side. The first to third lens units have negative refractive power, positive refractive power, and negative refractive power, respectively. The first lens unit and the second lens unit correspond to the first lens unit L1 and the second lens unit L2, respectively. The fourth lens unit includes a sensor protective glass.

[0137] In the imaging optical system according to Example 7, for example, the amount of light reaching the imaging surface can be significantly increased by employing the following structure. The first transmission reflective surface HM1 is a semi-reflective mirror, the second transmission reflective surface HM2 is a polarization-selective transmission reflective element, and the polarization-selective transmission reflective element is also disposed on the object-side surface of the fifth lens, counted from the object side. Furthermore, a quarter-wave plate is disposed between the polarization-selective transmission reflective element and the first transmission reflective surface HM1. The light reflected by the first transmission reflective surface HM1 and the transmitted light are both reflected by different polarization-selective transmission reflective elements. The light reflected by the second transmission reflective surface HM2 is again reflected by the first transmission reflective surface HM1 and travels towards the image side. The light reflected by the other polarization-selective transmission reflective element passes through the first transmission reflective surface HM1 and travels towards the image side. Here, the fifth and sixth lenses, counted from the object side, are symmetrical with respect to the first transmission reflective surface HM1. Therefore, the two beams that are initially incident on the first transmission reflective surface HM1 and branch out overlap each other when subsequently emitted from the first transmission reflective surface HM1 to the image side (in an ideal state without manufacturing errors, etc.). Therefore, by imaging the two beams branched by the semi-reflecting mirror at the same location on the image plane, the illuminance on the image plane can be roughly doubled.

[0138] In the imaging optical system according to Example 8, the lens on the image side of the fourth lens unit is molded from resin. Therefore, aspherical surfaces can be easily achieved by using only resin for the aspherical component.

[0139] In the imaging optical system according to Example 12, three lenses arranged immediately after the aperture stop SP (on the image side) can be used as image stabilization units.

[0140] The following are the values ​​corresponding to Examples 1 through 16 respectively.

[0141] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axis distance between the m-th and (m+1)-th surfaces, where m is the surface number counted from the light incident side. nd represents the refractive index of each optical element for line d, and vd represents the Abbe number of the optical element. The Abbe number νd of a certain material is expressed as follows:

[0142]

[0143] Wherein, Nd, NF, and NC are 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.

[0144] For regions where the medium is air, the refractive index and Abbe number are omitted.

[0145] In the numerical examples, d, focal length (mm), F-number, and half angle of view (°) are all values ​​for the optical system of each example when focused on an object at infinity. "Back focal length" is the distance on the optical axis from the final lens surface (the lens surface closest to the image plane) to the paraxial image plane, expressed as the air equivalent length. "Total lens length" is the distance on the optical axis from the foremost lens surface (the lens surface closest to the object) of the imaging optics to the final surface plus the back focal length. For overlapping portions of the optical path, the "total lens length" is calculated repeatedly. In other words, the "total lens length" is the physical distance (not the optical path length) that an on-axis ray travels between the first surface and the image plane.

[0146] When the optical surface is aspherical, an asterisk * is added to the right of the surface number. The shape of an aspherical surface is represented as follows:

[0147]

[0148] Where x is the displacement from the vertex of the surface along the optical axis, 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 aspheric coefficients of various orders. The "e±XX" in each aspheric coefficient refers to "×10"... ±XX ".

[0149] When considering the radius of curvature in inequality (2) for aspherical surfaces, the value of R in the above equation is used for calculation. WIDE (wide-angle) represents the wide-angle end, MIDDLE (middle) represents the middle zoom position, and TELE (telephoto) represents the telephoto end.

[0150] Numerical Example 1

[0151] Unit: mm

[0152] Surface data

[0153]

[0154] Aspherical data

[0155] First page

[0156] K = 0.00000e+00 A 4= 1.95177e-05 A 6=-1.02993e-07

[0157] Second side

[0158] K = 0.00000e+00 A 4=-5.80928e-06 A 6=-6.10324e-07 A 8= 4.29523e-09A10=-4.70092e-11

[0159] Page Twelve

[0160] K = 0.00000e+00 A 4=-6.73561e-04 A 6=-4.54930e-05 A 8= 4.22526e-06A10=-2.56569e-07

[0161] Page Thirteen

[0162] K = 0.00000e+00 A 4=-1.60439e-04 A 6=-1.85977e-05

[0163] Various data

[0164]

[0165] Zoom lens unit data

[0166]

[0167] Numerical Example 2

[0168] Unit: mm

[0169] Surface data

[0170]

[0171] Aspherical data

[0172] Seventh page

[0173] K = 0.00000e+00 A 4=-2.82292e-07 A 6= 8.05501e-11 A 8=-2.96788e-13A10= 3.79341e-16 A12=-1.71510e-19

[0174] Page 20

[0175] K = 0.00000e+00 A 4=-3.03173e-06 A 6= 6.42594e-10 A 8=-4.28805e-12

[0176] Page 28

[0177] K = 0.00000e+00 A 4= 2.96862e-06 A 6=-6.45369e-09 A 8= 3.90106e-11A10=-8.22782e-14 A12= 7.45235e-17

[0178] Various data

[0179] Zoom ratio 1.61

[0180]

[0181] Zoom lens unit data

[0182]

[0183] Numerical Example 3

[0184] Unit: mm

[0185] Surface data

[0186]

[0187] Aspherical data

[0188] Page 26

[0189] K = 0.00000e+00 A 4=-5.45733e-05

[0190] Page 27

[0191] K = 0.00000e+00 A 4=-5.27699e-05 A 6= 3.19864e-08 A 8=-6.16153e-12

[0192] Various data

[0193] Zoom ratio 1.58

[0194]

[0195] Zoom lens unit data

[0196]

[0197] Numerical Example 4

[0198] Unit: mm

[0199] Surface data

[0200]

[0201] Aspherical data

[0202] Fifth page

[0203] K = 0.00000e+00 A 4= 3.56820e-07 A 6=-2.67043e-10 A 8= 6.04949e-13A10=-4.23551e-16

[0204] Page 26

[0205] K = 0.00000e+00 A 4=-1.43829e-04 A 6= 4.88031e-08 A 8= 5.51813e-10

[0206] Page 27

[0207] K = 0.00000e+00 A 4=-1.40599e-04 A 6= 2.36851e-07 A 8= 8.21599e-11

[0208] Various data

[0209] Zoom ratio 2.76

[0210]

[0211] Zoom lens unit data

[0212]

[0213] Numerical Example 5

[0214] Unit: mm

[0215] Surface data

[0216]

[0217] Aspherical data

[0218] Page 28

[0219] K = 0.00000e+00 A 4=-3.37812e-05 A 6= 6.67955e-09 A 8= 1.89280e-11

[0220] Page 29

[0221] K = 0.00000e+00 A 4=-3.13542e-05 A 6= 1.28966e-08 A 8= 3.35922e-11A10=-6.33814e-14 A12= 4.80398e-17

[0222] Various data

[0223] Zoom ratio 1.90

[0224]

[0225] Zoom lens unit data

[0226]

[0227] Numerical Example 6

[0228] Unit: mm

[0229] Surface data

[0230]

[0231]

[0232] Aspherical data

[0233] Forty-first page

[0234] K = 0.00000e+00 A 4= 3.65499e-06

[0235] Various data

[0236] Zoom ratio 1.89

[0237]

[0238] Zoom lens unit data

[0239]

[0240] Numerical Example 7

[0241] Unit: mm

[0242] Surface data

[0243]

[0244]

[0245] Aspherical data

[0246] Fourth page

[0247] K = 0.00000e+00 A 4=-2.87835e-06 A 6=-4.95339e-11 A 8=-7.62383e-13A10= 7.94564e-16 A12=-3.64687e-19

[0248] Page 25

[0249] K = 0.00000e+00 A 4=-5.87027e-06 A 6= 1.00665e-08 A 8=-2.44702e-11A10= 1.20858e-14

[0250] Page 26

[0251] K = 0.00000e+00 A 4= 6.80783e-06 A 6= 3.21604e-09

[0252] Page 30

[0253] K = 0.00000e+00 A 4= 5.54573e-06 A 6= 8.12503e-09 A 8= 1.93185e-11

[0254] Various data

[0255] Zoom ratio 2.11

[0256]

[0257] Zoom lens unit data

[0258]

[0259] Numerical Example 8

[0260] Unit: mm

[0261] Surface data

[0262]

[0263]

[0264] Aspherical data

[0265] Eighth page

[0266] K = 0.00000e+00 A 4=-1.00738e-06 A 6= 1.94315e-10 A 8=-8.92776e-14A10= 8.76201e-18

[0267] Ninth page

[0268] K = 0.00000e+00 A 4=-9.45836e-07 A 6= 3.59897e-10

[0269] Page 22

[0270] K = 0.00000e+00 A 4=-6.30082e-06 A 6=-5.37086e-09 A 8= 2.51835e-11A10=-1.26875e-13

[0271] Page 29

[0272] K = 0.00000e+00 A 4=-3.72607e-05 A 6=-4.65488e-08 A 8= 8.30739e-11

[0273] Page 30

[0274] K = 0.00000e+00 A 4=-3.29966e-05 A 6=-4.56380e-08 A 8= 1.72438e-10A10=-1.92890e-13 A12= 1.05183e-16

[0275] Various data

[0276] Zoom ratio 1.93

[0277]

[0278] Zoom lens unit data

[0279]

[0280] Numerical Example 9

[0281] Unit: mm

[0282] Surface data

[0283]

[0284] Aspherical data

[0285] Page 26

[0286] K = 0.00000e+00 A 4=-3.65701e-05 A 6= 1.05258e-08 A 8= 1.99619e-11

[0287] Page 27

[0288] K = 0.00000e+00 A 4=-3.37165e-05 A 6= 2.03152e-08 A 8= 2.49601e-11A10=-5.45362e-14 A12= 4.45900e-17

[0289] Various data

[0290] Zoom ratio 1.90

[0291]

[0292] Zoom lens unit data

[0293]

[0294] Numerical Example 10

[0295] Unit: mm

[0296] Surface data

[0297]

[0298] Aspherical data

[0299] Page 26

[0300] K = 0.00000e+00 A 4=-4.48721e-05 A 6= 7.83232e-09 A 8= 3.34031e-11

[0301] Page 27

[0302] K = 0.00000e+00 A 4=-4.35798e-05 A 6= 2.45916e-08 A 8= 3.54921e-11A10=-6.55859e-14 A12= 4.70594e-17

[0303] Various data

[0304] Zoom ratio 1.41

[0305]

[0306] Zoom lens unit data

[0307]

[0308] Numerical Example 11

[0309] Unit: mm

[0310] Surface data

[0311]

[0312]

[0313] Aspherical data

[0314] Third side

[0315] K = 0.00000e+00 A 4= 1.05449e-06 A 6= 2.81263e-11

[0316] Page Twelve

[0317] K = 0.00000e+00 A 4=-2.97880e-07 A 6= 6.17907e-12

[0318] Page 43

[0319] K = 0.00000e+00 A 4= 6.73095e-06 A 6= 4.22312e-09

[0320] Various data

[0321] Zoom ratio 2.00

[0322]

[0323] Zoom lens unit data

[0324]

[0325] Numerical Example 12

[0326] Unit: mm

[0327] Surface data

[0328]

[0329]

[0330] Aspherical data

[0331] Third side

[0332] K = 0.00000e+00 A 4= 3.48654e-06 A 6=-3.01850e-09 A 8= 1.55267e-12A10=-6.73634e-17

[0333] Fourth page

[0334] K = 0.00000e+00 A 4= 1.24068e-06 A 6=-4.06820e-09

[0335] Page 15

[0336] K = 0.00000e+00 A 4=-1.53474e-07 A 6=-2.04153e-11

[0337] Page 35

[0338] K = 0.00000e+00 A 4=-7.54691e-06 A 6=-4.81392e-09

[0339] Page 36

[0340] K = 0.00000e+00 A 4=-7.31080e-06 A 6=-2.12153e-09

[0341] Various data

[0342] Zoom ratio 1.74

[0343]

[0344] Zoom lens unit data

[0345]

[0346] Numerical Example 13

[0347] Unit: mm

[0348] Surface data

[0349]

[0350] Aspherical data

[0351] Fifth page

[0352] K = 0.00000e+00 A 4= 9.68786e-08 A 6=-3.83814e-11 A 8= 2.62582e-14A10=-5.42579e-18

[0353] Page 26

[0354] K = 0.00000e+00 A 4=-6.23466e-05 A 6= 2.57040e-08 A 8= 2.74399e-11

[0355] Page 27

[0356] K = 0.00000e+00 A 4=-6.49110e-05 A 6= 6.04427e-08 A 8=-1.75742e-11

[0357] Various data

[0358] Zoom ratio 2.71

[0359]

[0360] Zoom lens unit data

[0361]

[0362] Numerical Example 14

[0363] Unit: mm

[0364] Surface data

[0365]

[0366] Aspherical data

[0367] Fourth page

[0368] K = 0.00000e+00 A 4=-3.79059e-08 A 6=-2.18257e-11 A 8= 5.24129e-15

[0369] Page 28

[0370] K = 0.00000e+00 A 4=-3.73914e-05 A 6= 1.95830e-08 A 8= 7.11096e-12

[0371] Page 29

[0372] K = 0.00000e+00 A 4=-3.64531e-05 A 6= 3.14709e-08 A 8=-6.70468e-12

[0373] Various data

[0374] Zoom ratio 2.72

[0375]

[0376] Zoom lens unit data

[0377]

[0378] Numerical Example 15

[0379] Unit: mm

[0380] Surface data

[0381]

[0382] Aspherical data

[0383] Fourth page

[0384] K = 0.00000e+00 A 4= 8.97542e-08 A 6=-1.44928e-10 A 8= 9.46460e-14A10=-2.94001e-17

[0385] Page 28

[0386] K = 0.00000e+00 A 4=-3.78907e-05 A 6= 1.15529e-08 A 8= 1.03307e-11

[0387] Page 29

[0388] K = 0.00000e+00 A 4=-3.75283e-05 A 6= 2.71695e-08 A 8=-6.10519e-12

[0389] Various data

[0390] Zoom ratio 1.90

[0391]

[0392] Zoom lens unit data

[0393]

[0394] Numerical Example 16

[0395] Unit: mm

[0396] Surface data

[0397]

[0398]

[0399] Aspherical data

[0400] Third side

[0401] K = 0.00000e+00 A 4= 1.79104e-06 A 6=-1.52439e-10 A 8= 4.83040e-13

[0402] Page 25

[0403] K = 0.00000e+00 A 4= 2.78921e-06 A 6=-6.78247e-10 A 8= 1.41782e-12

[0404] Page 27

[0405] K = 0.00000e+00 A 4= 2.78921e-06 A 6=-6.78247e-10 A 8= 1.41782e-12

[0406] Page 35

[0407] K = 0.00000e+00 A 4=-1.05608e-05 A 6=-2.27656e-07 A 8= 4.42322e-10

[0408] Page 36

[0409] K = 0.00000e+00 A 4= 4.86933e-06 A 6=-2.48532e-07 A 8= 6.93077e-10A10=-4.71647e-13

[0410] Various data

[0411] Zoom ratio 1.48

[0412]

[0413] Zoom lens unit data

[0414]

[0415] Table 1 below summarizes the various values ​​in each numerical example.

[0416] Table 1

[0417]

[0418] camera equipment

[0419] Now for reference Figure 35 This section will provide descriptions of examples of digital still cameras (video recording devices) using imaging optical systems according to various examples. Figure 35 In the figures, reference numeral 10 denotes the camera body, and reference numeral 11 denotes an imaging optical system including any of the imaging optical systems according to Examples 1 to 16. Reference numeral 12 denotes a solid-state image sensor (photoelectric conversion element), such as a CCD sensor or a CMOS sensor, which is built into the camera body and receives and photoelectrically converts the optical image formed by the imaging optical system 11. The camera body 10 can be a so-called single-lens reflex camera with a fast-shifting mirror, or a so-called mirrorless camera without a fast-shifting mirror.

[0420] Therefore, applying the imaging optical system according to each example to a camera device such as a digital still camera can provide a camera device with a small lens.

[0421] The imaging optical systems described in the examples can be used in cameras in smartphones, distance detection cameras, interchangeable lenses for interchangeable lens cameras, fixed lens cameras, film cameras with lenses (disposable cameras), binoculars, etc. This disclosure can be used in camera viewfinders or XR devices for applications such as gaze detection, biometric recognition, facial expression recognition, etc. This disclosure can be used in external environment recognition applications, such as XR devices and autonomous robots.

[0422] While exemplary embodiments have been described in this disclosure, it should be understood that this disclosure is not limited to the exemplary embodiments. The scope of the appended claims shall be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. An imaging optical system, comprising: Multiple lens units, The characteristic feature is that the distances between adjacent lens units in the plurality of lens units change during zooming. The plurality of lens units include: A first lens unit with negative refractive power and a second lens unit with positive refractive power, the second lens unit being configured to be closer to the image plane than the first lens unit, and A first transmission reflective surface and a second transmission reflective surface, wherein the second transmission reflective surface is configured to be closer to the image plane than the first transmission reflective surface.

2. The imaging optical system according to claim 1, characterized in that, The second lens unit includes the first transmission and reflection surface and the second transmission and reflection surface.

3. The imaging optical system according to claim 1, characterized in that, The first and second transmission reflective surfaces move during zooming.

4. The imaging optical system according to claim 1, characterized in that, The second lens unit moves during zooming, and The plurality of lens units includes a third lens unit, which is configured to be closer to the image plane than the second lens unit, and the third lens unit moves less during zoom than the second lens unit moves during zoom.

5. The imaging optical system according to claim 1, characterized in that, The following inequalities must be satisfied: 1.0 ≤ fgr / fw ≤ 4.5, Wherein, fgr is the focal length of the lens unit including the first and second transmission and reflection surfaces with a smaller radius of curvature, and fw is the focal length of the imaging optical system at the wide-angle end.

6. The imaging optical system according to claim 1, characterized in that, The following inequalities must be satisfied: 2.0 ≤ (R1×R2) / {(R1+R2)×fgr} ≤ 7.0, Wherein, fgr is the focal length of the lens unit including the first and second transmission and reflection surfaces, the transmission and reflection surface having the smaller radius of curvature, R1 is the radius of curvature of the first transmission and reflection surface, and R2 is the radius of curvature of the second transmission and reflection surface.

7. The imaging optical system according to claim 1, characterized in that, The following inequalities must be satisfied: 20 ≤ νd mf ≤ 65, Among them, νd mf It is the average Abbe number of one or more positive lenses configured to be closer to the object than the first transmissive reflective surface.

8. The imaging optical system of claim 1, further comprising an aperture stop configured to be closer to the image plane than the second transmission reflective surface, and Its features are, The following inequalities must be satisfied: 20 ≤ νd mm ≤ 96, Among them, νd mm It is the average Abbe number of one or more positive lenses disposed between the first transmission and reflection surface and the aperture stop.

9. The imaging optical system of claim 1, further comprising an aperture stop configured to be closer to the object than the first transmission reflective surface. Its features are, The following inequalities must be satisfied: 50 ≤ νd mr ≤ 96, Among them, νd mr It is the average Abbe number of one or more positive lenses disposed between the aperture stop and the second transmission and reflection surface.

10. The imaging optical system according to claim 1, characterized in that, The following inequalities must be satisfied: 1.40 ≤ n dm ≤ 1.85， Where, n dm It is the refractive index of the first lens positioned between the first and second transmission and reflection surfaces with respect to the d-line.

11. The imaging optical system according to claim 1, further comprising an aperture stop, Its features are, At least one of the lens, the first transmissive reflective surface, and the second transmissive reflective surface, which is configured to be closer to the image plane than the aperture stop, moves during focusing.

12. The imaging optical system according to claim 11, characterized in that, The first and second transmission reflective surfaces move during focusing.

13. The imaging optical system according to claim 1, characterized in that, The following inequalities must be satisfied: 1.5 ≤ dp / fw ≤ 4.0 Wherein, dp is the distance on the optical axis between the object-side surface of the lens configured to be closest to the object at the wide-angle end and the entrance pupil, and fw is the focal length of the imaging optical system at the wide-angle end.

14. The imaging optical system according to claim 1, characterized in that, The following inequalities must be satisfied: 0.0 ≤ |θm| ≤ 8.0, Wherein, θm is the smaller of the opening angle of the first transmission and reflection surface and the opening angle of the second transmission and reflection surface, and the unit of θm is degrees.

15. The imaging optical system according to claim 1, characterized in that, The following inequalities must be satisfied: 2.0 ≤ |θl| ≤ 50.0, Wherein, θl is the larger of the opening angle of the first transmission and reflection surface and the opening angle of the second transmission and reflection surface, and the unit of θl is degrees.

16. The imaging optical system of claim 1, further comprising a waveplate disposed between the first transmission-reflecting surface and the second transmission-reflecting surface. Its features are, Light from the object side passes sequentially through the first transmission and reflection surface and the waveplate, is reflected towards the object side by the second transmission and reflection surface, passes through the waveplate, is reflected towards the image side by the first transmission and reflection surface, and then passes sequentially through the waveplate and the second transmission and reflection surface towards the image side.

17. The imaging optical system according to claim 16, characterized in that, The following inequalities must be satisfied: 0.0 ≤ θin ≤ 40.0, Wherein, θin is the incident angle of the principal ray of the most off-axis beam when it first enters the first or second transmission and reflection surface with a smaller opening angle. The unit of θin is degrees.

18. The imaging optical system according to any one of claims 1 to 17, characterized in that, The plurality of lens units also includes a lens unit with positive refractive power that is configured to be closer to the object than the first lens unit.

19. A camera device, comprising: The imaging optical system according to any one of claims 1 to 18; as well as An image sensor is configured to receive an image formed by the imaging optical system.

Images