WO2022215293A1 - Système de lentilles, dispositif d'imagerie et système d'imagerie - Google Patents

Système de lentilles, dispositif d'imagerie et système d'imagerie Download PDF

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Publication number
WO2022215293A1
WO2022215293A1 PCT/JP2021/042629 JP2021042629W WO2022215293A1 WO 2022215293 A1 WO2022215293 A1 WO 2022215293A1 JP 2021042629 W JP2021042629 W JP 2021042629W WO 2022215293 A1 WO2022215293 A1 WO 2022215293A1
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free
lens
form surface
image
lens system
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PCT/JP2021/042629
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English (en)
Japanese (ja)
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寛幸 庄林
善夫 松村
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パナソニックＩｐマネジメント株式会社
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Publication of WO2022215293A1 publication Critical patent/WO2022215293A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration

Definitions

  • the present disclosure relates to lens systems, imaging devices, and imaging systems.
  • Patent documents 1 and 2 disclose lens systems applicable to imaging systems.
  • the lens system of Patent Literature 1 uses a free-form surface that is asymmetric with respect to the optical axis, so that it is possible to enlarge the vicinity of the center while ensuring a wide angle of view.
  • the lens system of Patent Document 2 produces negative distortion in a specific direction such as the vertical direction in a first direction and a second direction such as the horizontal direction and the vertical direction by controlling light rays using a free-form surface lens. be able to.
  • Patent Document 3 discloses a zoom optical system using a rotationally asymmetric surface. This zoom optical system has a plurality of optical elements that move in directions different from the optical axis to change the power in the optical group, and aims to obtain high optical performance over the entire zoom range.
  • Patent Document 4 discloses a variable focal length lens system using a free-form surface. This variable focal length lens system includes a lens unit that can move in an axial direction perpendicular to the optical axis, and is intended to achieve good imaging performance when enlarging an image from the wide-angle end state to the telephoto end state.
  • the present disclosure provides a lens system, an imaging device, and an imaging system capable of enlarging a central portion in a second direction with a wider angle of view than in the first direction and further enlarging an image in the first direction.
  • a lens system forms an image of light incident from the object side on the image plane side.
  • the lens system includes an aperture through which the optical axis passes, a front group including lens elements arranged closer to the object side than the aperture, and a rear group including lens elements arranged closer to the image plane than the aperture.
  • the front group and the rear group each include a free-form surface lens having a free-form surface rotationally asymmetric with respect to the optical axis.
  • the lens element located closest to the object side in the front group is a free-form surface lens having a negative refractive power and a free-form surface that satisfies the following conditional expression (1).
  • sagV sag amount of the free-form surface in the first direction intersecting the optical axis
  • sagH sag amount of the free-form surface in the second direction intersecting the optical axis
  • Ih image height in the second direction
  • ⁇ h second Half angle of view ⁇ nd in the direction: Difference D obtained by subtracting "1" from the refractive index of the free-form surface lens with respect to the d line: "1" when the free-form surface is on the object side of the free-form surface lens, and the image plane It is "-1" if it is a side.
  • An imaging device includes the above lens system and an imaging device.
  • the imaging device captures an image formed by the lens system.
  • An imaging system includes the imaging device described above and an image processing unit.
  • the image processing unit performs image processing on an image captured by the imaging device of the imaging device.
  • the lens system, the imaging device, and the imaging system according to the present disclosure it is possible to enlarge the central portion in the second direction with a wider angle of view than in the first direction, and further enlarge the image in the first direction.
  • FIG. 1 is a diagram showing the configuration of an imaging system according to Embodiment 1 of the present disclosure
  • FIG. FIG. 1 is a lens arrangement diagram showing the configuration of a lens system according to Example 1
  • Scatter diagram showing the relationship between the angle of view and the image point in the lens system of Numerical Example 1
  • FIG. 4 shows surface data of the lens system in Numerical Example 1
  • FIG. 4 is a diagram showing various data of the lens system in Numerical Example 1
  • FIG. 4 is a diagram showing free-form surface data of the first surface in the lens system of Numerical Example 1
  • FIG. 10 is a diagram showing aspherical surface data of the second surface in the lens system of Numerical Example 1
  • FIG. 10 is a diagram showing free-form surface data of the fifth surface in the lens system of Numerical Example 1;
  • FIG. 10 is a diagram showing free-form surface data of the sixth surface in the lens system of Numerical Example 1;
  • FIG. 10 is a diagram showing free-form surface data of the fifteenth surface in the lens system of Numerical Example 1;
  • FIG. 10 is a diagram showing free-form surface data of the 16th surface in the lens system of Numerical Example 1;
  • Aberration diagram showing various aberrations of the lens system in Numerical Example 1 4 is a chart showing the sufficiency of various conditions in the lens system of Embodiment 1. Graph showing the confirmation result of the effect of condition (1) by the lens system of Embodiment 1 FIG.
  • FIG. 4 is a ray diagram for explaining condition (2) in the lens system of Embodiment 1;
  • FIG. 3 is a ray diagram for explaining condition (3) in the lens system of Embodiment 1;
  • FIG. 4 is a ray diagram for explaining condition (4) in the lens system of Embodiment 1;
  • FIG. 5 is a lens arrangement diagram showing the configuration of a lens system according to Example 2;
  • FIG. 10 is a diagram showing surface data of the lens system in Numerical Example 2;
  • FIG. 10 is a diagram showing various data of the lens system in Numerical Example 2;
  • FIG. 10 is a diagram showing free-form surface data of the first surface in the lens system of Numerical Example 2;
  • FIG. 10 is a diagram showing free-form surface data of the second surface in the lens system of Numerical Example 2;
  • FIG. 10 is a diagram showing free-form surface data of the fifth surface in the lens system of Numerical Example 2;
  • FIG. 10 is a diagram showing free-form surface data of the sixth surface in the lens system of Numerical Example 2;
  • FIG. 10 is a diagram showing free-form surface data of the fifteenth surface in the lens system of Numerical Example 2;
  • FIG. 10 is a diagram showing free-form surface data of the 16th surface in the lens system of Numerical Example 2;
  • Scatter diagram showing the relationship between the angle of view and the image point in the lens system of Numerical Example 2 Aberration diagram showing various aberrations of the lens system in Numerical Example 2 FIG.
  • FIG. 10 is a lens arrangement diagram showing the configuration of a lens system according to Example 3;
  • FIG. 10 is a diagram showing surface data of the lens system in Numerical Example 3;
  • FIG. 10 is a diagram showing various data of the lens system in Numerical Example 3;
  • FIG. 10 is a diagram showing free-form surface data of the first surface in the lens system of Numerical Example 3;
  • FIG. 10 is a diagram showing free-form surface data of the second surface in the lens system of Numerical Example 3;
  • FIG. 10 is a diagram showing free-form surface data of the third surface in the lens system of Numerical Example 3;
  • FIG. 10 is a diagram showing free-form surface data of the fourth surface in the lens system of Numerical Example 3;
  • FIG. 10 is a lens arrangement diagram showing the configuration of a lens system according to Example 3;
  • FIG. 10 is a diagram showing surface data of the lens system in Numerical Example 3;
  • FIG. 10 is a diagram showing various data of the lens system in Numer
  • FIG. 10 is a diagram showing free-form surface data of the fifteenth surface in the lens system of Numerical Example 3;
  • FIG. 10 is a diagram showing free-form surface data of the 16th surface in the lens system of Numerical Example 3; Scatter diagram showing the relationship between the angle of view and the image point in the lens system of Numerical Example 3 Aberration diagram showing various aberrations of the lens system in Numerical Example 3
  • FIG. 10 is a lens arrangement diagram showing the configuration of a lens system according to Example 4;
  • FIG. 10 shows surface data of the lens system in Numerical Example 4;
  • FIG. 10 is a diagram showing various data of the lens system in Numerical Example 4;
  • FIG. 10 is a diagram showing free-form surface data of the first surface in the lens system of Numerical Example 4;
  • FIG. 10 is a diagram showing free-form surface data of the second surface in the lens system of Numerical Example 4;
  • FIG. 11 shows aspheric surface data of the third surface in the lens system of Numerical Example 4;
  • FIG. 10 is a diagram showing aspheric surface data of the fourth surface in the lens system of Numerical Example 4;
  • FIG. 10 is a diagram showing aspheric surface data of the fifth surface in the lens system of Numerical Example 4;
  • FIG. 10 is a diagram showing free-form surface data of the seventh surface in the lens system of Numerical Example 4;
  • FIG. 13 is a diagram showing free-form surface data of the 13th surface in the lens system of Numerical Example 4;
  • FIG. 10 is a diagram showing free-form surface data of the 14th surface in the lens system of Numerical Example 4; Scatter diagram showing the relationship between the angle of view and the image point in the lens system of Numerical Example 4 Aberration diagram showing various aberrations of the lens system in Numerical Example 4
  • FIG. 1 is a diagram showing the configuration of an imaging system 10 according to this embodiment.
  • An imaging system 10 includes an imaging device 11 and an image processing unit 13, as shown in FIG. 1, for example.
  • the imaging device 11 includes a lens system IL and an imaging device 12 .
  • the imaging device 11 is a device that captures images of various objects as subjects, and constitutes, for example, various cameras.
  • the image processing unit 13 may be incorporated in a camera or the like.
  • the direction of the optical axis d0 of the lens system IL in the imaging device 11 is defined as the Z direction
  • the horizontal direction orthogonal to the Z direction is defined as the X direction
  • the vertical direction orthogonal to the Z and X directions is defined as the Y direction.
  • the lens system IL takes in incident light from the outside of the imaging device 11 and forms an image such as an image circle by the taken light.
  • the lens system IL is composed of, for example, a refractive optical system. Details of the lens system IL will be described later.
  • the +Z side of the lens system IL is defined as the image plane side
  • the -Z side is defined as the object side.
  • the imaging device 12 is, for example, a CCD or CMOS image sensor.
  • the imaging element 12 has an imaging surface in which a plurality of pixels are two-dimensionally arranged at equal intervals.
  • the imaging device 12 is arranged such that its imaging surface is located on the image plane of the lens system IL in the imaging device 11 .
  • the imaging device 12 captures an image formed on the imaging surface via the lens system IL, and generates an image signal representing the captured image.
  • the imaging surface of the imaging device 12 is rectangular, for example.
  • the image processing unit 13 performs predetermined image processing on the image captured by the imaging device 11 based on the image signal from the imaging device 12 .
  • Image processing includes, for example, gamma correction and distortion correction.
  • the image processing unit 13 includes, for example, a CPU or MPU that implements various functions by executing programs stored in an internal memory.
  • Image processing unit 13 may include dedicated hardware circuitry designed to achieve the desired functionality.
  • the image processing unit 13 may include a CPU, MPU, GPU, DSP, FPGA, ASIC, or the like.
  • the imaging system 10 of the present embodiment as described above can be applied, for example, to in-vehicle applications for imaging the external environment such as the front or rear of the vehicle.
  • the conventional free-form surface optical system by controlling the negative distortion using a free-form surface lens, it is possible to enlarge the vicinity of the center while ensuring a wide angle of view in the horizontal direction, etc., in the above imaging applications.
  • Patent Documents 1 and 2 See Patent Documents 1 and 2.
  • the angle is wide even in the vertical direction, making it difficult to image, for example, a vehicle traveling in the distance or a sign with high resolution.
  • a lens system IL is provided that can further magnify the image in the Y direction, which is the vertical direction, while enlarging the center in the X direction, which is the horizontal direction of the wide angle of view. This makes it possible to take a high-resolution image of a distant sign or the like in the imaging application as described above.
  • the details of the lens system IL of this embodiment will be described below.
  • Lens System Examples 1 to 4 of the lens system IL will be described below as specific examples of the lens system IL according to the present embodiment.
  • Example 1 A lens system IL1 according to Example 1 will be described with reference to FIGS. 2 to 12.
  • FIG. 2 A lens system IL1 according to Example 1 will be described with reference to FIGS. 2 to 12.
  • FIG. 2 A lens system IL1 according to Example 1 will be described with reference to FIGS. 2 to 12.
  • FIG. 2 is a lens arrangement diagram showing the configuration of the lens system IL1 according to Example 1.
  • FIG. The following lens arrangement diagrams show the arrangement of various lenses, for example, when the lens system IL1 is in focus at infinity.
  • FIG. 2(a) shows a lens arrangement diagram in the YZ cross section of the lens system IL1 of this embodiment.
  • FIG. 2(b) shows a lens arrangement diagram in the XZ cross section of the lens system IL1.
  • the YZ section and the XZ section are virtual sections along the optical axis d0 of the lens system IL1.
  • the image plane S on which the lens system IL1 forms an image is illustrated.
  • the curved surface with the symbol " ⁇ " indicates that it is a free curved surface.
  • the free-form surface is a curved surface that is rotationally asymmetric with respect to the optical axis d0.
  • a curved surface with the symbol " ⁇ ” indicates that it is a rotationally symmetrical aspherical surface.
  • various codes are abbreviate
  • the lens system IL of this embodiment has a plurality of free-form surfaces that are asymmetrical between the X direction and the Y direction, as shown in FIGS. 2(a) and 2(b), for example.
  • a lens element having a free-form surface on at least one of the object side and the image plane side will be referred to as a free-form surface lens.
  • the lens system IL1 of Example 1 includes first to eighth lens elements L1 to L8 and an aperture A. As shown in FIG. 2A, in the lens system IL1, the first to eighth lens elements L1 to L8 are arranged along the optical axis d0 in order from the object side to the image plane side. A stop A is an aperture stop. In the lens system IL1 of this embodiment, the first to fourth lens elements L1 to L4 form a lens group arranged closer to the object than the stop A, that is, a front group. The fifth to eighth lens elements L5 to L8 form a lens group arranged closer to the image plane than the stop A, that is, a rear group.
  • the first lens element L1 closest to the object side is, for example, a free-form surface lens having a free-form surface on the object side.
  • the image plane side surface of the first lens element L1 is, for example, an aspherical surface concave toward the image plane side.
  • the first lens element L1 is composed of, for example, a negative lens having negative refractive power in the X and Y directions.
  • the free-form surface of the first lens element L1 is concave toward the object side in the X direction as shown in FIG. Stronger in the periphery. As a result, negative distortion is strongly generated, and the image can be enlarged in the central portion rather than in the peripheral portion.
  • the first lens element L1 is made of a lens material having a relatively high refractive index, such as a glass material.
  • the free-form surface of the first lens element L1 is concave toward the object side with a weaker curvature in the Y direction than in the X direction, as shown in FIG. 2(a).
  • the refractive power in the Y direction of the first lens element L1 becomes positive relative to the refractive power in the X direction, and the negative distortion can be weakened (or the positive distortion can be strengthened) in the Y direction.
  • the second lens element L2 is, for example, a biconcave spherical lens.
  • the second lens element L2 in this embodiment is an example of a rotationally symmetrical lens arranged between the first and third lens elements L1 and L3.
  • the third lens element L3 is, for example, a free-form surface lens having free-form surfaces on both the object side and the image plane side.
  • the third lens element L3 is composed of, for example, a positive lens having positive refractive power.
  • the difference in shape (for example, sag difference) between the X direction and the Y direction in each free-form surface of the third lens element L3 is smaller than that of the first lens element L1 (for example, 1/10 to 1/1/10). 20).
  • the free-form surface on the object side has a curvature that strengthens the positive refractive power in the Y direction more than in the X direction, and the free-form surface on the image side has a positive refractive power in the Y direction. has a weakening curvature than
  • the fourth lens element L4 is, for example, a positive meniscus-shaped spherical lens convex to the object side.
  • a diaphragm A is arranged between the fourth lens element L4 and the fifth lens element L5.
  • the fifth lens element L5 is, for example, a biconvex spherical lens and cemented with the sixth lens element L6.
  • the sixth lens element L6 is, for example, a negative meniscus spherical lens convex toward the image plane side.
  • the seventh lens element L7 is, for example, a biconvex spherical lens.
  • the eighth lens element L8 is, for example, a free-form surface lens having free-form surfaces on both sides.
  • the object-side free-form surface of the eighth lens element L8 is, for example, concave toward the object side in the X and Y directions, and has a curvature such that the refracting power in the Y direction is relatively positive with respect to the refracting power in the X direction.
  • the free-form surface on the image plane side of the eighth lens element L8 is, for example, concave toward the image plane side in the Y direction and convex toward the image plane side in the X direction. It is relatively negative with respect to the directional power.
  • the shape difference between the X and Y directions in the eighth lens element L8 is, for example, about the same as that in the first lens element L1.
  • the lens system IL1 configured as described above includes first and third lens elements L1 and L3 as free-form surface lenses of the front group in the front group and the rear group formed through the diaphragm A.
  • An eighth lens element L8 is provided as a free-form surface lens.
  • the free-form surface of the free-form surface lens in the lens system IL1 has symmetry that allows mirror inversion with respect to the optical axis d0 in the YZ plane, that is, inversion symmetry in the Y direction, as shown in FIG. be. This provides, for example, a symmetric refractive power in the Y direction with respect to axial rays. Also, the free-form surface of the lens system IL1 is inversion symmetrical in the X direction as well, as shown in FIG. 2(b), for example. By using a rotationally asymmetric free-form surface within the range of inversion symmetry in the X and Y directions in this way, it is possible to easily realize desired asymmetric image magnification while avoiding the occurrence of aberration due to unnecessary asymmetry.
  • the light beams taken in by the lens system IL1 from the outside are controlled to be asymmetrically refracted four or more times in stages. Therefore, it is possible to easily secure imaging performance while enlarging the image asymmetrically.
  • by providing two or more free-form surface lenses such as the first and third lens elements L1 and L3 in the front group it is easy to achieve both asymmetric image enlargement and aberration correction.
  • the free-form surface lens such as the first lens element L1 provides a wide angle of view based on negative distortion in the X direction and magnifies the image in the central portion, while the distortion is relatively positive in the Y direction.
  • the image can be further magnified based on the distortion of . Functions and effects of such a lens system IL1 will be described with reference to FIG.
  • FIG. 3 is a scatter diagram showing the relationship between the angle of view and the image point P1 in the lens system IL1 of this embodiment.
  • image points P1 at which incident light forms an image on the image plane are plotted for each predetermined angular width over the entire field angle of the lens system IL1.
  • the angle width was set to 5°.
  • the rotation phase on the XY plane was set every 10°.
  • the lens system IL1 was set to an infinity focused state.
  • FIG. 3 illustrates the image point P1 in the first quadrant on the XY plane of the image plane with the position of the optical axis d0 as the origin. Since the lens system IL1 of this embodiment is linearly symmetrical with respect to the X-axis and the Y-axis, the second to fourth quadrants are the same as those in FIG.
  • the distance between the image points P1 increases as it approaches the origin, for example, in the X direction, and negative distortion occurs.
  • the imaging device 11 of the present embodiment can, for example, capture an image with a higher resolution in the vicinity of the center in the X direction.
  • the change in the distance between the image points P1 in the Y direction is smaller than in the X direction. That is, positive distortion is obtained in the Y direction relative to the X direction.
  • the interval between the image points P1 along the Y axis for example, is wider than the interval between the image points P1 along the X axis. Therefore, the lens system IL1 of this embodiment can form an enlarged image in the Y direction. According to such image enlargement, more pixels on the imaging surface of the imaging element 12 are allocated along the Y direction than along the X direction. Therefore, the imaging device 11 of this embodiment can capture a high-resolution captured image in the Y direction.
  • FIG. 4 is a diagram showing surface data of the lens system IL1 in Numerical Example 1.
  • the surface data of FIG. 4 are for each surface s1 to s16 arranged in order from the object side in the lens system IL1, the type of each surface, the radius of curvature r in units of mm, the distance between surfaces d, and the size of each lens element with respect to the d line.
  • Refractive index nd and Abbe number vd are shown.
  • Surface types include a spherical surface, an aspherical surface, and an XY polynomial surface as an example of a free-form surface.
  • Surface types may include anamorphic aspheric surfaces as another example of free-form surfaces.
  • FIG. 5 is a diagram showing various data of the lens system IL1 in Numerical Example 1.
  • the various data in FIG. 5 are the F-number of this numerical embodiment, the vertical half angle of view at the vertical image height, the horizontal half angle of view at the horizontal image height, the horizontal half angle of view at the vertical image height, and the vertical half angle of view. , the horizontal image height at the horizontal half angle of view, and the total optical length.
  • the units of various image heights and optical total lengths are "mm", and the units of each half angle of view are "°".
  • FIG. 6 is a diagram showing free-form surface data of the first surface s1 in the lens system IL1 of Numerical Example 1.
  • FIG. The free-form surface data in FIG. 6 indicate various coefficients of an XY polynomial that defines an XY polynomial surface as a free-form surface for the object-side surface of the first lens element L1.
  • the XY polynomial is represented by the following equation (E1).
  • c is the vertex curvature
  • k is the conic constant
  • j is an integer of 2 or more and 66 or less, and the sum of each j is taken.
  • the sag amount z at the (x, y) coordinate position on the target surface is defined more freely than the regularity of the anamorphic aspherical surface. With such an XY polynomial surface, the degree of freedom in the shape of the free-form surface can be increased, and for example, the effect of enlarging the subject image on the imaging surface 22 and the effect of correcting various aberrations can be improved.
  • FIG. 7 is a diagram showing aspheric surface data of the second surface s2 in the lens system IL1 of Numerical Example 1.
  • FIG. The aspheric surface data in FIG. 7 indicates various coefficients of the following equation (E2) that defines the shape of the aspheric surface for the image plane side surface of the first lens element L1.
  • h is the height in the radial direction
  • K is the conic constant
  • An is the n-th order aspheric coefficient.
  • n is an even number of 4 or more and 20 or less, and the sum of each n is taken.
  • the sag amount z at the height h in the radial direction on the target surface is defined rotationally symmetrically.
  • FIG. 8 is a diagram showing free-form surface data of the fifth surface s5 in the lens system IL1 of Numerical Example 1.
  • FIG. 9 is a diagram showing free-form surface data of the sixth surface s6 in the lens system IL1 of Numerical Example 1.
  • Each of the free-form surface data in FIGS. 8 and 9 indicates various coefficients of formula (E1) for each of the object side and image plane side surfaces of the third lens element L3, as in FIG.
  • FIGS. 10 and 11 are diagrams showing the free-form surface data of the 15th surface s15 and the 16th surface s16 in the lens system IL1 of Numerical Example 1, respectively.
  • Each of the free-form surface data in FIGS. 10 and 11 indicates various coefficients of formula (E1) for each of the object-side and image-plane-side surfaces of the eighth lens element L8, similarly to FIG.
  • FIG. 12 is an aberration diagram showing various aberrations of the lens system IL1 in this embodiment.
  • the aberration diagrams below illustrate various longitudinal aberrations in the infinity focused state.
  • FIG. 12(a) shows the spherical aberration "SA” in the lens system IL1.
  • 12(b), (c), and (d) show astigmatism "AST-V” in the Y direction, astigmatism "AST-D” in the diagonal direction, and astigmatism "AST-D” in the X direction, respectively. -H”.
  • FIGS. 12(a) to (d) are each expressed in units of mm.
  • the vertical axis of FIG. 12(a) is based on the pupil height.
  • FIG. 12A shows characteristic curves of spherical aberration for the d-line, F-line and C-line.
  • the vertical axes in FIGS. 12(b) to 12(d) are based on the half angle of view.
  • FIGS. 12B to 12D show characteristic curves of astigmatism on the XZ cross section or YZ cross section along the X direction or Y direction and the optical axis d0, respectively.
  • FIG. 13 is a chart showing the sufficiency of various conditions in the lens system IL of this embodiment.
  • the chart shown in FIG. 13 shows the calculation results of evaluation targets under various conditions (1) to (4) below for each of the lens elements L1 to L8 in each of Numerical Examples 1 to 4.
  • the underlined calculated values indicate that conditions (1) to (4) are satisfied.
  • L1R1 denotes the object-side surface of the first lens element L1
  • L1R2 denotes the image-plane-side surface.
  • Condition (1) is that the first lens element L1 composed of a negative lens in the lens system IL has a free-form surface that satisfies the following conditional expression (1).
  • sagV is the sag amount of the free-form surface in the Y direction
  • sagH is the sag amount of the free-form surface in the X direction
  • Ih is the image height in the X direction.
  • the respective sag amounts sagV and sagH are measured on the same height reference.
  • the reference height is the image height Ih in the X direction.
  • D is a sign constant, which is "1" when the free-form surface is the object-side surface of the first lens element L1, and "-1" when it is the image-plane-side surface.
  • ⁇ h is a half angle of view in the X direction, for example, 0° ⁇ h ⁇ 90°.
  • Various heights are represented by distances from the optical axis d0.
  • the difference ⁇ n of the refractive index nd is incorporated from the viewpoint of obtaining strong negative distortion in the first lens element L1, which is a negative lens.
  • the sag amounts sagV and sagH are negative values on the object side surface and positive values on the image side surface.
  • the product is negative.
  • the product of the difference between the sag amounts sagV and sagH in the Y and X directions and the code constant D is referred to as "sag difference".
  • the sag difference (sagV-sagH)*D is a larger positive value
  • the free-form surface can positively strengthen or negatively weaken the distortion in the Y direction relative to the negative distortion in the X direction. It is considered that such an effect due to the difference in the free-form surface shape can be easily obtained because the first lens element L1 with a wide angle of view causes variations in the positions through which light rays pass. Reflecting this point, tan( ⁇ h) is included in the evaluation target of condition (1). In other words, it reflects that the wider the angle of view, the more likely it is to be affected by distortion.
  • condition (1) the negative distortion caused by the negative refractive power of the first lens element L1 is weakened in the Y direction relative to the X direction, that is, the distortion is relatively positive in the X direction. Distortion is obtained in the Y direction. As a result, it is possible to obtain the effect of enlarging the image in the Y direction (overall) more than in the X direction, while widening the angle of view by negative distortion in the X direction and enlarging the image in the central portion.
  • Experimental results confirming the effect of condition (1) will be described with reference to FIG.
  • FIG. 14 shows the relationship between condition (1) and the horizontal central enlargement factor Ehc and the vertical/horizontal enlargement factor Evh.
  • the horizontal central enlargement factor Ehc indicates the ratio of enlarging the central portion of the image to the peripheral portion in the X direction.
  • the vertical/horizontal enlargement factor Evh indicates the ratio by which the image is enlarged in the Y direction compared to the X direction.
  • the horizontal central enlargement factor Ehc is expressed by the following equation (11) using, for example, the image height Ih in the X direction and the half angle of view ⁇ h.
  • Ehc (I ⁇ h/ ⁇ )/(Ih/ ⁇ h) (11)
  • I ⁇ h is an image height corresponding to a minute angle ⁇ in the X direction.
  • ⁇ h is the half angle of view in the X direction.
  • the horizontal central enlargement factor Ehc is based on the projection relationship of the equidistant projection method.
  • the vertical/horizontal enlargement factor Evh is expressed by the following equation (13) based on the horizontal central enlargement factor Eh, the image height Iv in the Y direction, the half angle of view ⁇ v, and the image height I ⁇ v corresponding to the minute angle ⁇ . .
  • the vertical and horizontal magnification Evh is also expressed as a ratio between the paraxial focal length ratio fhc/fvc in the X and Y directions and the focal length ratio fha/fva of the entire system.
  • Evh the central portion of the image is enlarged and the peripheral portion is reduced in the Y direction to the same extent as in the X direction.
  • the vertical/horizontal enlargement factor Evh is larger than, for example, “1”, the effect of enlarging the image in the Y direction as a whole within the angle of view in comparison with the X direction can be obtained.
  • magnification factors Ehc and Evh can be significantly increased by satisfying condition (1).
  • condition (1) As shown in FIG. 14, in the prior example, the calculated value of condition (1) was below the lower limit of "0.3" and did not satisfy condition (1). Further, each of the enlargement factors Ehc and Evh of the prior example was less than "1.2".
  • the rate Evh was significantly larger than that of the preceding example.
  • FIG. 15 is a ray diagram for explaining condition (2) in the lens system IL of this embodiment.
  • FIG. 15 illustrates an axial ray B1 along the optical axis d0 and a ray B2 forming an image at the end of the image plane S in the X direction in the lens system IL1 similar to FIG. 2(b). .
  • Condition (2) is that the front group closer to the object side than the diaphragm A in the lens system IL includes a lens element that satisfies the following conditional expression (2).
  • X1 is, for example, as shown in FIG. height to pass.
  • X2 is the height at which the light ray B2 passes through the image plane side surface of the lens element.
  • X SS is the height of the diaphragm A.
  • AX RL is the optical path length of the axial ray B1 through the lens element.
  • HRL is the optical path length of the light ray B2 when it passes through the lens element.
  • the sign constant Da is "1" if the lens element is a positive lens and "-1" if it is a negative lens.
  • a chief ray may be used for the measurement of the optical path length and height of various light beams B1 and B2, or other light beams may be used.
  • Condition (2) is set from the viewpoint of increasing the horizontal central magnification Ehc by increasing the negative distortion in the X direction in the lens system IL.
  • the negative distortion can be strengthened as the optical path length HRL of the light ray B1 near the edge is longer than that of the axial light ray B1 in the negative lens.
  • the first term is considered to have a large effect on distortion when, for example, the light ray B2 passes through a high position in the target lens element. , including the average height (X 1 +X 2 )/2 of ray B2 at that lens element.
  • the second term reflects that the optical path length H RL of ray B2 is longer than the optical path length AX RL of on-axis ray B1 to accommodate the desired distortion.
  • image enlargement that is, positive distortion
  • the necessity of arranging positive and negative lenses in a well-balanced manner in the front group and the rear group is not satisfied, making aberration correction difficult.
  • condition (2) when the lower limit value of condition (2) is not reached, for example, the height XSS of the diaphragm A becomes small, so that the F-number becomes large and the optical system becomes dark. For this reason, when assuming an optical system of a sensing camera, for example, the detection rate may be lowered. Alternatively, if the height of light rays passing through the target lens element (for example, the first lens element L1) becomes too large, the diameter of the lens also becomes large, which may lead to the enlargement of the optical system.
  • the target lens element for example, the first lens element L1
  • the negative lens in the front group of the lens system IL can cause the light rays to be affected by the negative refractive power and generate negative distortion. can.
  • the condition (2) in the lens system IL that enlarges the central portion of the screen, it is possible to widen the image of the central portion in the X direction while enlarging the image. Such an effect is obtained more significantly when the following formula (2a) is satisfied.
  • condition (2) the optical path length of the positive lens in the front group is lengthened or the optical path length of the negative lens in the rear group is shortened to weaken the positive distortion. It is also conceivable to weaken the negative distortion by lengthening the optical path length. From this point of view as well, a conditional expression similar to the above expression (2) may be used.
  • the sign constant Da may be, for example, "1" for the negative lens and "-1" for the positive lens in the rear group.
  • FIG. 16 is a ray diagram for explaining condition (3) in the lens system IL of this embodiment.
  • FIGS. 16A and 16B in the lens system IL1 similar to FIGS. Light rays B3 and B4 that form images at the same angle are respectively illustrated.
  • Condition (3) is that in the lens system IL, the front group includes a free-form surface lens that satisfies conditional expression (3a) below, and the rear group includes a free-form surface lens that satisfies conditional expression (3b) below. .
  • X 1F is the height at which the light ray B2 forming an image on the edge of the image plane S, such as the edge of the image sensor 12 in the X direction, passes through the object-side surface of the free-form surface lens in the front group.
  • X2F is the height at which the light ray B2 passes through the surface of the free-form surface lens on the image plane side (see FIG. 16(b)).
  • VRLF is the optical path length of a light ray B3 forming an image at the end of the imaging device 12 in the Y direction, as shown in FIG. 16A, when passing through the free-form surface lens.
  • HRLF is the optical path length of the light ray B4 forming an image at the same height (for example, image height Iv) as the light ray B3 in the X direction when passing through the free-form surface lens.
  • X 1B and X 2B in the above equation (3b) are such that the ray B4 forming an image at the end in the X direction passes through the object-side and image-plane-side surfaces of the free-form surface lens in the rear group. It is the height to pass through each.
  • V RLB and H RLB are the optical path lengths of the light beams B3 and B4 forming images at the height of the end in the Y direction in the Y and X directions, respectively, when they pass through the free-form surface lens.
  • the optical path length V RLF in the Y direction is shorter than the optical path length H RLF in the X direction in the free-form surface lens of the front group, and the refracting power in the Y direction is strengthened more positively than in the X direction.
  • the free-form surface lens in the front group in the Y direction relative to the X direction, along with positive distortion, field curvature toward the -Z side of the image sensor 12 (that is, under) occurs.
  • the optical path length V RLB in the Y direction in the free-form surface lens of the rear group is longer than the optical path length H RLB in the X direction, and the refracting power in the Y direction is more negative than in the X direction. strengthened.
  • field curvature toward the +Z side of the image pickup device 12 that is, over
  • the curvature of field can be corrected by canceling each other between the front group and the rear group.
  • positive distortion in the Y direction relative to the X direction is ensured across the front group and the rear group, and the image enlarging effect in the Y direction can be enhanced.
  • the imaging performance can be improved while performing desired asymmetrical image magnification in the lens system IL.
  • Such an effect is obtained more remarkably when the following expressions (3aa) and (3ba) are satisfied.
  • FIG. 17 is a ray diagram for explaining condition (4) in the lens system IL of this embodiment.
  • FIGS. 17(a) and 17(b) illustrate various light beams B1 to B4, respectively, similarly to FIGS. 16(a) and 16(b).
  • Condition (4) is that the free-form surface lens of the front group and the free-form surface lens of the rear group in the lens system IL satisfy the following conditional expression (4).
  • sagV F is the sag amount of the free-form surface of the front group in the Y direction
  • sagH F is the sag amount of the free-form surface in the X direction
  • sagVB is the sag amount of the free-form surface of the rear group in the Y direction
  • sagH B is the sag amount of the free-form surface in the X direction.
  • Each of the sag amounts sagV F , sagH F , sagV B , and sagH B is measured based on the image height Ih in the X direction of the image sensor 12 as shown in FIGS. 17A and 17B, for example.
  • the sign constant D F is “1" when the free-form surface of the front group is on the object side of the free-form surface lens, and is “-1" when it is on the image plane side.
  • the sign constant D B is "1" when the free-form surface of the rear group described above is on the object side of the free-form surface lens, and is "-1" when it is on the image plane side.
  • condition (4) the curvature of field generated on the free-form surface of the front group can be corrected by the free-form surface of the rear group, and high imaging performance can be obtained. Also, while field curvature is corrected as described above, negative distortion in the X direction and relatively positive distortion in the Y direction can be maintained without canceling out between the front and rear groups. .
  • the free-form surface of the front group positively strengthens the refractive power in the Y direction rather than in the X direction. This results in positive distortion and under field curvature in the Y direction relative to the X direction.
  • the denominator of the evaluation target since the denominator of the evaluation target is negative, the free-form surface of the rear group strengthens the refractive power in the Y direction more negatively than in the X direction, so that In the Y direction, it produces over field curvature with positive distortion. As a result, field curvature can be selectively canceled and corrected between the front group and the rear group.
  • both the front group and the rear group produce under or over curvature of field in the Y direction relative to the X direction, resulting in aberrations. Correction becomes difficult. Also, relatively positive distortion can be reduced.
  • the lower limit of condition (4) is exceeded, the absolute value of the sag difference
  • the image plane can Curvature can be corrected, and the imaging performance of the lens system IL can be improved. Such an effect can be obtained even more significantly when the following formula (4a) is satisfied.
  • the lens system IL1 has two lens systems on the object side and the image plane side, which have a relatively high light ray height and a large effect on distortion.
  • a free-form surface is arranged on the lens elements L1 and L8.
  • the height (L1: about 2.6 mm, L8 : about 2 mm), and the lens shape was changed between the X and Y directions from that height toward the periphery.
  • the angle of view in the Y direction is narrowed, that is, the image is enlarged in the X direction, while a wide angle of view is obtained in the X direction.
  • the height of light rays is low, and the vertical and horizontal magnification Evh of the central portion of the image is A free-form surface is placed on the third lens element L3, which may affect the .
  • the refracting power in the Y direction relative to the X direction is positively enhanced on the object side surface and negatively enhanced on the image plane side surface.
  • the luminous flux becomes thicker at an intermediate position such as the third lens element L3 with respect to the lens elements L1 and L8.
  • an intermediate position such as the third lens element L3 with respect to the lens elements L1 and L8.
  • the lens system IL according to this embodiment can be implemented in various forms other than the lens system IL1 of Example 1 described above. Examples 2 to 4 of the lens system IL will be described below.
  • Example 2 The lens system IL2 of Example 2 will be described with reference to FIGS. 18 to 28.
  • FIG. 1 one surface of the first lens element L1 is provided with a free-form surface.
  • Example 2 a lens system IL2 in which free curved surfaces are provided on both surfaces of the first lens element L1 will be described.
  • FIG. 18 shows the configuration of the lens system IL2 according to Example 2.
  • FIGS. 18(a) and 18(b) show lens layout diagrams of the lens system IL2 in the same manner as FIGS. 2(a) and 2(b), respectively.
  • the lens system IL2 of Example 2 has the same configuration as that of Example 1, but the shapes of various lens elements L1 to L8 are changed.
  • the surface of the first lens element L1 on the image plane side was an aspherical surface in Example 1, but is a free-form surface in this example.
  • the free-form surface lens in the lens system IL2 of this embodiment includes two lenses on the object side of the diaphragm A and one lens on the image plane side of the diaphragm A, as in the first embodiment.
  • the image-plane-side free-form surface of the first lens element L1 has such a curvature that the negative refractive power in the Y direction is weaker than in the X direction.
  • the positive distortion is strengthened in the Y direction relative to the X direction, and the curvature of field is on the under side.
  • the effect of the first lens element L1 similar to that of the first embodiment can be reinforced in addition to the object-side free-form surface.
  • the free-form surface on the object side of the eighth lens element L8 has such a curvature that the negative refractive power is stronger in the Y direction than in the X direction.
  • the positive distortion is strengthened in the Y direction relative to the X direction, and the curvature of field is on the over side.
  • the sag difference on each free-form surface is smaller than that in the first embodiment by reinforcing the effects of the free-form surfaces on both sides of the first and eighth lens elements L1 and L8. can be done.
  • Numerical examples corresponding to the lens system IL2 of Example 2 are shown in FIGS.
  • FIG. 19 is a diagram showing surface data of the lens system IL2 in Numerical Example 2.
  • FIG. FIG. 20 is a diagram showing various data of the lens system IL2 in this embodiment. 19 and 20 show respective data in the same manner as in FIGS. 4 and 5 of Numerical Example 1, respectively.
  • FIG. 21 and 22 show free-form surface data of the first and second surfaces s1 and s2 in the lens system IL2 of this embodiment, respectively.
  • Each piece of free-form surface data indicates various coefficients of formula (E1) for both the object-side and image-plane-side surfaces of the first lens element L1, as in Numerical Example 1.
  • FIG. 21 and 22 show free-form surface data of the first and second surfaces s1 and s2 in the lens system IL2 of this embodiment, respectively.
  • Each piece of free-form surface data indicates various coefficients of formula (E1) for both the object-side and image-plane-side surfaces of the first lens element L1, as in Numerical Example 1.
  • Each piece of free-form surface data indicates various coefficients of formula (E1) for the surfaces on both sides of the third lens element L3 and the surfaces on both sides of the eighth lens element L8, similarly to Numerical Example 1.
  • FIG. 27 shows the relationship between the angle of view and the image point P2 in the lens system IL2 of this example.
  • FIG. 28 shows various aberrations of the lens system IL2 in this embodiment.
  • FIGS. 28(a), (b), (c), and (d) show respective aberration diagrams of the lens system IL2 in this embodiment, similarly to FIGS. 12(a) to (d).
  • the lens system IL2 of the present embodiment satisfies the conditions (1) to (4) (see FIG. 13), similarly to the first embodiment, magnifies the image in the central portion more than the peripheral portion in the X direction, and The image can be further magnified in the Y direction.
  • Example 3 The lens system IL3 of Example 3 will be described with reference to FIGS. 29 to 39. FIG. In Example 3, a modification of the arrangement of the free-form surface lens will be described.
  • FIG. 29 shows the configuration of the lens system IL3 according to Example 3.
  • FIGS. 29(a) and 29(b) show lens layout diagrams of the lens system IL3 in the same manner as FIGS. 2(a) and 2(b), respectively.
  • the third lens element L3 is a free-form surface lens, but the lens system IL of this embodiment is not particularly limited to this.
  • the second lens element L2 is composed of a free-form surface lens instead of the third lens element L3.
  • the second lens element L2 of this embodiment has free-form surfaces on both sides.
  • the object-side surface is a free-form surface having a stronger negative refractive power in the Y direction than in the X direction, and the image-side surface has a relatively small shape difference between the X and Y directions. It is a concave free-form surface.
  • the first lens element L1 of this embodiment has, for example, a negative meniscus shape convex toward the object side.
  • the refractive power in the Y direction relative to the X direction is negative on the object side and positive on the image plane side.
  • FIG. 30 shows the surface data of the lens system IL3 in Numerical Example 3, similarly to FIG. 4 of Numerical Example 1.
  • FIG. FIG. 31 shows various data of the lens system IL3 in this embodiment in the same manner as FIG.
  • FIGS. 32 and 33 respectively show the free-form surface data of the first and second surfaces s1 and s2 in the lens system IL3 of this embodiment, that is, the surfaces on both sides of the first lens element L1.
  • 34 and 35 respectively show the free-form surface data of the third and fourth surfaces s3 and s4 in the lens system IL3 of this embodiment, that is, the surfaces on both sides of the second lens element L2.
  • 36 and 37 show the free-form surface data of the 15th and 16th surfaces s15 and s16 in the lens system IL3 of this embodiment, respectively, that is, the surfaces on both sides of the eighth lens element L8.
  • Each piece of free-form surface data indicates various coefficients of the formula (E1) as in Numerical Example 1.
  • FIG. 38 shows the relationship between the angle of view and the image point P3 in the lens system IL3 of this example.
  • FIG. 39 shows various aberrations of the lens system IL3 in this embodiment.
  • FIGS. 39(a), (b), (c), and (d) show respective aberration diagrams of the lens system IL3 in this embodiment, similarly to FIGS. 12(a) to (d).
  • the lens system IL3 of this embodiment satisfies the conditions (1), (2) and (4) (see FIG. 13). Also with the lens system IL3 of this embodiment, as in the first embodiment, it is possible to magnify the image in the central portion more than the peripheral portion in the X direction, and further magnify the image in the Y direction.
  • Example 4 The lens system IL4 of Example 4 will be described with reference to FIGS. 40 to 53.
  • FIG. 40 The lens system IL4 of Example 4 will be described with reference to FIGS. 40 to 53.
  • FIG. 40 shows the configuration of the lens system IL4 according to Example 4.
  • FIGS. 40(a) and 40(b) show lens layout diagrams of the lens system IL4 in the same manner as FIGS. 2(a) and 2(b), respectively.
  • the number of lenses is eight, but the lens system IL of this embodiment is not particularly limited to this.
  • the lens system IL4 of Example 4 is composed of seven lens elements L1 to L7.
  • the free-form surface lens in the lens system IL4 of this embodiment consists of the first lens element L1 closest to the object side, the seventh lens element L7 closest to the image plane side, and the fourth lens element L4 in the front group between them. There are 3 sheets.
  • the number of free-form surfaces in this embodiment is 5 surfaces on both sides of the first and seventh lens elements L1 and L7 and on the object side of the fourth lens element L4, and is 4 or more.
  • the fourth lens element L4 of this embodiment has, for example, a free curved surface with a relatively small shape difference between the X and Y directions on the object side.
  • the second and third lens elements L2, L3 each have an aspherical surface on both sides.
  • the object-side surface is a free-form surface with a relatively small shape difference between the X and Y directions, and the image-side surface has negative refraction in the Y direction rather than in the X direction. It is a strong free-form surface.
  • a shape difference between the X and Y directions is provided in the peripheral portion at a position (for example, 3 mm) higher than the image height Iv in the Y direction. As a result, aberration correction at the ends in the X direction was reinforced.
  • FIG. 41 shows surface data of the lens system IL4 in Numerical Example 4 in the same manner as in Numerical Example 1 shown in FIG.
  • FIG. 42 shows various data of the lens system IL4 in this embodiment, similarly to FIG.
  • FIG. 43 and 44 show free-form surface data of the first and second surfaces s1 and s2 in the lens system IL4 of this embodiment, respectively.
  • Each piece of free-form surface data indicates various coefficients of formula (E1) for both the object-side and image-plane-side surfaces of the first lens element L1, as in Numerical Example 1.
  • FIG. 43 and 44 show free-form surface data of the first and second surfaces s1 and s2 in the lens system IL4 of this embodiment, respectively.
  • Each piece of free-form surface data indicates various coefficients of formula (E1) for both the object-side and image-plane-side surfaces of the first lens element L1, as in Numerical Example 1.
  • Each aspheric surface data indicates various coefficients of the formula (E2) for the surfaces on both sides of the second lens element L2 and the surfaces on both sides of the third lens element L3, similarly to Numerical Example 1.
  • each piece of free-form surface data indicates various coefficients of formula (E1) for the object-side surface of the fourth lens element L4 and both side surfaces of the seventh lens element L7, as in Numerical Example 1.
  • FIG. 52 shows the relationship between the angle of view and the image point P4 in the lens system IL4 of this example.
  • FIG. 53 shows various aberrations of the lens system IL4 in this embodiment.
  • FIGS. 53(a), (b), (c), and (d) show respective aberration diagrams of the lens system IL4 in this embodiment, similarly to FIGS. 12(a) to (d).
  • the lens system IL4 of this embodiment satisfies the conditions (1) to (4) as in the first embodiment (see FIG. 13).
  • the condition (1) is satisfied not only on the object side of the first lens element L1, but also on the image plane side. Effects similar to those of the first embodiment can also be obtained with the lens system IL4 of the present embodiment.
  • Embodiment 1 has been described as an example of the technology disclosed in the present application.
  • the technology in the present disclosure is not limited to this, and can also be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate.
  • the XY polynomial surface was exemplified as an example of the free-form surface.
  • the free-form surface is not limited to the above, and may include, for example, an anamorphic aspherical surface or a toric surface.
  • the free-form surface lens that satisfies the condition (1) and the like may have a free-form surface that is not anamorphic.
  • a free-form surface that is not anamorphic includes an XY polynomial surface but does not include an anamorphic aspheric surface.
  • a free-form surface that is not anamorphic may not have a plane of symmetry, for example.
  • the imaging system 10 of the present embodiment can be applied to various uses, and is not particularly limited to in-vehicle use.
  • the imaging system 10 of this embodiment can also be applied to surveillance cameras that monitor various situations.
  • a first aspect of the present disclosure is a lens system that forms an image of light incident from the object side on the image plane side.
  • the lens system includes a diaphragm through which the optical axis passes, a front group including lens elements arranged closer to the object side than the diaphragm, and a rear group including lens elements disposed closer to the image plane than the diaphragm.
  • the front group and the rear group each include a free-form surface lens having a free-form surface rotationally asymmetric with respect to the optical axis.
  • the lens element located closest to the object side in the front group is a free-form surface lens having a negative refractive power and a free-form surface that satisfies the following conditional expression (1): here, sagV: sag amount of the free-form surface in the first direction intersecting the optical axis sagH: sag amount of the free-form surface in the second direction intersecting the optical axis and the first direction Ih: image height in the second direction ⁇ h: Half angle of view in the second direction ⁇ nd: Difference obtained by subtracting “1” from the refractive index of the free-form surface lens with respect to line d D: “1” if the free-form surface is on the object side of the free-form surface lens and "-1" when on the image plane side.
  • sagV sag amount of the free-form surface in the first direction intersecting the optical axis
  • sagH sag amount of the free-form surface in the second direction intersecting the optical
  • the negative distortion in the second direction is relative to the second direction in the first direction. positively strengthened by As a result, it is possible to form an image in which the central portion is enlarged in the second direction with a wider angle of view than in the first direction, and the image is further enlarged in the first direction.
  • the front group includes a lens element that satisfies the following conditional expression (2): here, X 1 : Height at which a light ray forming an image on the edge of the image plane in the second direction passes through the object-side surface of the lens element X 2 : Image is formed on the edge of the image plane in the second direction Height X SS at which a light ray passes through the image plane side surface of the lens element: height of the diaphragm AX RL : optical path length H RL when the axial light ray passes through the lens element: the second direction Optical path length Da when a light ray forming an image at the edge of the image plane passes through the lens element: "1" when the lens element is a positive lens, and "-1" when the lens element is a negative lens ”.
  • X 1 Height at which a light ray forming an image on the edge of the image plane in the second direction passes through the object-side surface of the lens element
  • X 2 Image is formed on the edge of the image plane in the
  • the front group includes a free-form surface lens that satisfies conditional expression (3a) below, and the rear group satisfies conditional expression (3b) below.
  • X 1F Height X 2F at which a light ray forming an image on the edge of the image plane in the second direction passes through the object-side surface of the free-form surface lens in the front group
  • X 2F Edge of the image plane in the second direction
  • X SS height of the stop
  • V RLF image is formed at the edge of the image plane in the first direction
  • Optical path length H RLF when a light ray passes through the free-form surface lens of the front group In the second direction, the light ray forming an image at the height of the edge of the image plane in the
  • the field distortion caused along with this can be corrected by the free-form surface lens of the rear group, thereby improving the image quality. It is possible to easily achieve both the enlargement effect and the imaging performance.
  • the free-form surface of the free-form surface lens arranged in the front group and the free-form surface of the free-form surface lens arranged in the rear group satisfies the following conditional expression (4), here, sagV F : sag amount of the image height in the second direction of the free-form surface of the front group in the first direction sagH F : image height in the second direction of the free-form surface of the front group in the second direction Sag amount sagV B : Sag amount sagH B of the image height of the free-form surface of the rear group in the first direction in the second direction sagH B : Image in the second direction of the free-form surface of the rear group in the second direction High sag amount D F : "1" when the free-form surface of the front group is on the object side of the free-form surface lens arranged in the front group, and "-1" when it is on the
  • the lens element closest to the object has a , has a free-form surface that makes the negative refractive power stronger in the peripheral portion than in the central portion.
  • the lens element closest to the object can increase the negative distortion in the second direction, making it easy to enlarge the central portion while maintaining a wide angle of view.
  • the lens element closest to the object side has a concave surface shape toward the object side. This makes it easier for the lens element closest to the object side to generate negative distortion, making it easier to magnify the central portion in the first direction.
  • the lens element arranged closest to the image plane side in the rear group has a refractive power in the first direction that is the second direction. has a free-form surface that is relatively negative with respect to the refractive power at As a result, the lens element closest to the image plane in the rear group can correct field curvature while maintaining the desired distortion caused by the free-form surface of the front group, thereby improving the image magnification effect and imaging performance. It can be easily compatible.
  • the lens element closest to the object side has the free-form surface on the image plane side, and the free-form surface extends toward the object side from the first concave in the direction and convex in the second direction.
  • the free-form surface lens in the front group has refractive power in the first direction relative to refractive power in the second direction. has a free-form surface positive to The free-form surface lens in the rear group has a free-form surface whose refractive power in the first direction is relatively negative with respect to refractive power in the second direction.
  • a lens element rotationally symmetrical with respect to the optical axis is arranged between the two free-form surface lenses. This facilitates the control of rotationally asymmetric light rays over various heights by means of two free-form lenses in which the light rays can have different heights via rotationally symmetrical lens elements.
  • the free-form surface has inversion symmetry in the first direction.
  • the free-form surface has inversion symmetry in the second direction.
  • the free-form surface that is rotationally asymmetric in the range of inversion symmetry in the first and second directions, unnecessary asymmetry can be avoided and the performance of the lens system can be easily obtained.
  • the total number of the free-form surfaces of the free-form surface lens included in the front group and the free-form surface of the free-form surface lens included in the rear group is , four faces or more.
  • stepwise control is performed to refract the incident light beam four or more times in a rotationally asymmetric manner, thereby making it easier to achieve both aberration correction and image enlarging effect.
  • the front group includes two or more free-form surface lenses.
  • stepwise control of rotationally asymmetrical refraction in the front group can be performed, making it easier to achieve both aberration correction and image enlarging effect.
  • a fifteenth aspect provides an imaging device comprising the lens system according to any one of the first to fourteenth aspects and an imaging device for imaging an image formed by the lens system.
  • the lens system can enlarge the central portion in the second direction with a wider angle of view than the first direction, and further enlarge the image in the first direction.
  • a sixteenth aspect provides an imaging system comprising the imaging device of the fifteenth aspect and an image processing unit that performs image processing on an image captured by an imaging element of the imaging device.
  • the lens system of the imaging device can enlarge the central portion in the second direction with a wider angle of view than the first direction, and further enlarge the image in the first direction.
  • the imaging system according to the present disclosure can be applied to various imaging applications, such as in-vehicle cameras, surveillance cameras, web cameras, and digital cameras. Also, the lens system according to the present disclosure may be provided in an interchangeable lens device.

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Abstract

L'invention concerne un système de lentille pour former, sur le côté de la surface d'image, une image de lumière incidente à partir du côté objet comprenant : une butée à travers laquelle passe un axe optique ; un groupe avant comprenant des éléments de lentille disposés plus près du côté objet que la butée ; et un groupe arrière comprenant des éléments de lentille disposés plus près du côté de la surface d'image que la butée. Le groupe avant et le groupe arrière comprennent chacun une lentille de surface de forme libre ayant une surface de forme libre asymétrique en rotation autour de l'axe optique. Un élément de lentille disposé le plus près du côté objet dans le groupe avant est une lentille de surface de forme libre ayant une surface de forme libre, qui a une réfringence négative et satisfait l'expression conditionnelle : {(sagV-sagH)/Ih}*Δnd*D*tan(θh) > 0,03.
PCT/JP2021/042629 2021-04-06 2021-11-19 Système de lentilles, dispositif d'imagerie et système d'imagerie WO2022215293A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004077921A (ja) * 2002-08-20 2004-03-11 Olympus Corp ズーム光学系及びそれを用いた撮像装置
WO2019187221A1 (fr) * 2018-03-28 2019-10-03 パナソニックＩｐマネジメント株式会社 Système de lentilles, dispositif d'imagerie et système d'imagerie
WO2020017201A1 (fr) * 2018-07-18 2020-01-23 パナソニックＩｐマネジメント株式会社 Système optique d'imagerie, dispositif d'imagerie et système d'imagerie
CN111367048A (zh) * 2020-03-31 2020-07-03 玉晶光电(厦门)有限公司 光学成像镜头

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004077921A (ja) * 2002-08-20 2004-03-11 Olympus Corp ズーム光学系及びそれを用いた撮像装置
WO2019187221A1 (fr) * 2018-03-28 2019-10-03 パナソニックＩｐマネジメント株式会社 Système de lentilles, dispositif d'imagerie et système d'imagerie
WO2020017201A1 (fr) * 2018-07-18 2020-01-23 パナソニックＩｐマネジメント株式会社 Système optique d'imagerie, dispositif d'imagerie et système d'imagerie
CN111367048A (zh) * 2020-03-31 2020-07-03 玉晶光电(厦门)有限公司 光学成像镜头

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