Optical systems and optical devices

Abstract

This provides an optical system that is even smaller than conventional ones. [Solution] The optical system includes an optical element having a diffraction plane MOE with controlled wavelength dispersion characteristics and a lens LN. The Abbe number ν0 of the diffraction plane satisfies the condition -0.2 < 1 / ν0 < 0.2. The diffraction plane has a rotationally asymmetric optical path difference function.

Description

Technical Field

[0001] The present invention relates to an optical system suitable for imaging, display, and the like.

Background Art

[0002] Such an optical system is required to be as small as possible. Further, Patent Document 1 discloses a diffractive surface capable of controlling wavelength dispersion characteristics.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An optical system smaller than the conventional one is desired.

Means for Solving the Problems

[0005] An optical system as one aspect of the present invention includes a diffractive surface (or metasurface) with controlled wavelength dispersion characteristics and a lens. The Abbe number ν0 of the diffractive surface satisfies the condition that -0.2 < 1 / ν0 < 0.2 The Abbe number ν0 will be described later. The diffractive surface is characterized by having a rotationally asymmetric optical path difference function. Note that an optical device having the above optical system also constitutes another aspect of the present invention.

Brief Description of the Drawings

[0006] [Figure 1] Cross-sectional view of the optical system of Example 1 in an infinite focus state [Figure 2] Aberration diagram of the optical system of Example 1 in an infinite focus state [Figure 3] Cross-sectional view of the optical system of Example 2 in an infinite focus state [Figure 4] Aberration diagram of the optical system in Example 2 at infinity focus. [Figure 5] Cross-sectional view of the optical system of Example 3 in the state of infinity focus. [Figure 6] Aberration diagram of the optical system in Example 3 at infinity focus. [Figure 7] Cross-sectional view of the optical system of Example 4 in the state of infinity focus. [Figure 8] Aberration diagram of the optical system in Example 4 at infinity focus. [Figure 9] Cross-sectional view of the optical system of Example 5 in the state of infinity focus. [Figure 10] Aberration diagram of the optical system in Example 5 at infinity focus. [Figure 11] Diagram showing the optical path of the optical system in Example 1 [Figure 12] Figures showing smartphones and head-mounted displays having the optical systems of Examples 1 to 5. [Modes for carrying out the invention]

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0008] Figures 1, 3, 5, 7, and 9 are cross-sectional views showing the configuration of the optical systems of Examples 1 to 5 when they are in focus on an object at infinity (hereinafter referred to as the infinity focus state). In each figure, X, Y, and Z represent the X, Y, and Z axes of the XYZ absolute coordinate system, which is the coordinate axis of the entire optical system. The depth direction perpendicular to the plane of the paper is the Z-axis direction, and the two mutually orthogonal directions perpendicular to the Z-axis direction are the X-axis direction (thickness direction of the optical system) and the Y-axis direction (height direction of the optical system).

[0009] The optical systems of each embodiment are used in various optical devices, including imaging devices such as digital still / video cameras and cameras for broadcasting, surveillance, automotive, and smartphones, display devices such as head-mounted displays and VR goggles, and image projection devices such as projectors. Below, we will describe the case in which the optical system of each embodiment is used as the imaging optical system of an imaging device, that is, the case in which light incident from a subject, which is the object to be imaged, located on the object surface is imaged onto the image surface on which the imaging surface is located. The side with the object surface is also called the object side, and the side with the image surface is also called the image side.

[0010] In each cross-sectional view, IP represents the image plane, where the imaging surface of an image sensor such as a CCD sensor or CMOS sensor in an imaging device is located. In display devices and image projection devices, the display surface of a liquid crystal display element or organic EL display element is located on the object surface corresponding to the image plane IP of the imaging optical system, and light from the display surface is formed on the image plane (pupil plane or projection surface) corresponding to the object surface of the imaging optical system. FL represents an optical block corresponding to various optical filters or dustproof glass.

[0011] REF is a reflective surface, provided on reflective elements such as mirrors and prisms. LN is a lens group. LA is the optical axis of the lens group LN (hereinafter referred to as the lens optical axis). A lens group is a collection of one or more lenses or optical elements. The lens group LN can use refractive lenses, diffractive lenses, metasurface lenses, etc. The lens optical axis LA is the central axis of the lens group LN, positioned between the diffraction surface MOE and the reflective surface REF, and can also be described as the optical path of light rays passing through the center of the diffraction surface MOE and the center of the reflective surface REF (and further, the center of the image plane IP).

[0012] A MOE is a diffraction surface with controlled wavelength dispersion characteristics, and includes a metasurface. A metasurface is constructed by calculating the phase delay amount of metaatoms for each wavelength and arranging the metaatoms to control the wavelength dispersion characteristics. A metasurface may be a so-called single-layer metasurface consisting of one layer, or a so-called stacked metasurface consisting of multiple layers.

[0013] The optical path difference function, focal length, and Abbe number of a diffraction surface with controlled wavelength dispersion characteristics (hereinafter referred to as dispersion-controlled) can be described as follows. When the optical path difference function of the diffraction surface is ψ, the diffraction order is m, the design wavelength of the diffraction surface is λ0, the incident wavelength is λ, the optical path difference dispersion of the surface is P(λ), and the optical path difference function of the surface at the design wavelength is ψ0, it can be defined as follows.

[0014]

number

[0015]

number

[0016] Furthermore, the optical path difference function ψ0 of the surface at the design wavelength λ0 can be expressed by the following yz polynomial, where y and z are the distances in the y-axis direction and z-axis direction, which are two mutually orthogonal in-plane directions from the optical axis, respectively, in the case of a rotationally asymmetric in-plane optical path difference representation.

[0017]

number

[0018] The deflection angle α of the ray in the y-axis direction due to the dispersed diffraction surface is the linear coefficient U of the y-coordinate of the optical path difference function of the surface at the design wavelength, expressed as a yz polynomial. 1,0 It can be written as follows using this method.

[0019]

number

[0020] On the other hand, the optical path difference function ψ0 of a surface at the design wavelength is usually expressed by the following polynomial, where h is the distance from the optical axis, when it is a frequently used rotationally symmetric surface.

[0021]

number

[0022] The focal length fmoe of the diffraction surface under distributed control can be described as follows using the second-order coefficient U2 of the optical path difference function of the surface at the designed wavelength expressed by a polynomial.

[0023]

Equation

[0024] When the reference wavelength of the diffraction surface under distributed control is the d-line (wavelength 587.6 nm), and the principal dispersions are the F-line (wavelength 486.1 nm) and the C-line (wavelength 656.3 nm), the Abbe number ν0 can be described as follows. ψ d , ψ F , ψ C are the optical path difference functions of the d-line, F-line, and C-line, respectively, and λ d , λ F , λ C represent the incident wavelengths of the d-line, F-line, and C-line, respectively.

[0025]

Equation

[0026] Also, when the reference wavelength of the diffraction surface under distributed control is the d-line, and the principal dispersions are the g-line (wavelength 435.8 nm) and the F-line, the Abbe number ν 0,gF in the short wavelength region below the F-line can be described as follows. ψ d , ψ g , ψ F are the optical path difference functions of the d-line, g-line, and F-line, respectively, and λ d , λ g , λ F represent the incident wavelengths of the d-line, g-line, and F-line, respectively.

[0027]

Equation

[0028] In each embodiment, the diffraction order m is treated as m=1 because the first-order diffracted light is used for design. The d-line is used as the incident wavelength when determining the design wavelength λ0 and focal length.

[0029] Next, the characteristic configuration of the optical system of each embodiment will be described. As mentioned above, the optical system of each embodiment has a dispersion-controlled rotationally asymmetric diffraction plane MOE, a lens group LN, and a reflecting plane REF. The diffraction plane MOE can control the wavelength dispersion characteristics. Therefore, it is possible to suppress the color shift that occurs at the diffraction plane MOE and to correct the magnification chromatic aberration of the entire optical system well. In addition, the diffraction plane MOE has an optical path difference function of a rotationally asymmetric surface and has the function of deflecting the light incident on the optical system in a specific direction.

[0030] The reflective surface REF has the function of bending the optical path by reflecting light, thereby miniaturizing (especially thinning) the optical system. The lens LN is positioned between the diffracting surface MOE and the reflective surface REF.

[0031] Figure 11 shows the optical path of light incident from the diffraction plane MOE into the optical system of Example 1 and imaged at multiple image heights on the image plane IP. In the figure, X, Y, and Z represent the aforementioned XYZ absolute coordinate system (X axis, Y axis, Z axis), while x, y, and z represent the local coordinate system of the diffraction plane MOE (x axis, y axis, z axis). The y-axis and z-axis directions are the in-plane directions of the diffraction plane MOE as described above, and the z-axis direction is perpendicular to the diffraction plane MOE.

[0032] The diffracting surface MOE deflects light incident from the object and transmitted through it in the Y-axis direction through diffraction. In this process, the diffracting surface MOE deflects all light rays of different heights from its center (intersection with the lens optical axis LA) toward the same side (negative side) in the Y-axis direction. This increases the degree of freedom in the layout of the lens group LN, reflective surface REF, and image plane IP, allowing the size of the optical system in the X-direction (thickness direction) to be kept small. To achieve this deflection function, the optical path difference function ψ0 of the diffracting surface MOE has an asymmetrical optical path difference shape centered on zero in the y-axis direction. In particular, to deflect light toward the negative side in the y-axis direction, the coefficient U 1,0 It is preferable that it has a negative value.

[0033] Furthermore, in order to make the optical system thinner, it is preferable to arrange the diffraction plane MOE and the lens group LN adjacent to each other (in close proximity). Moreover, it is preferable that the lens in the lens group LN closest to the diffraction plane MOE has positive power, as this allows for a shorter telephoto ratio and thus a thinner design.

[0034] The optical system of each embodiment is an imaging optical system that images light incident from the object side onto the image plane IP or images light from the image plane IP on the object side, and has, in order from the object side to the image plane side, a diffraction plane MOE, a lens group LN, a reflection plane REF, and an optical block FL. A lens group may be placed between the reflection plane REF and the optical block FL.

[0035] Furthermore, for ease of manufacturing, it is preferable that the diffraction plane MOE be formed on a flat surface of the optical substrate (i.e., the diffraction plane MOE has a planar shape). However, the diffraction plane MOE may be formed in a curved shape. Similarly, the reflective surface REF may have a planar shape or a curved shape to have power.

[0036] Furthermore, it is preferable that the optical system of each embodiment satisfies at least one of the following conditions (1) to (5).

[0037] -0.2 < 1 / ν0 < 0.2 (1) -30° < α / 2 - θdiff < 30° (2) -30°<θrefl / 2-θdiff<30° (3) 0°<α<50° (4) 0° < θdiff < 50° (5) -0.02 < 1 / ν 0,gF <0.02 (6) In equations (1) to (6) above, ν0 is the Abbe number of a dispersion-controlled rotationally asymmetric diffraction plane MOE, where the reference wavelength is the d-line and the principal dispersions are the F-line and C-line. α is the deflection angle of the incident light deflected by the diffraction plane MOE, and is the deflection angle with respect to the d-line when the reference wavelength, the d-line, is incident perpendicularly to the center of the diffraction plane MOE. As mentioned above, the center of the diffraction plane MOE is the intersection of the diffraction plane MOE and the lens optical axis LA.

[0038] θdiff is the angle of inclination of the surface normal of the diffraction surface MOE with respect to the lens optical axis LA (the angle between the lens optical axis LA and the surface normal of the diffraction surface MOE), as shown in Figure 1. θrefl is the angle of inclination of the surface normal of the reflection surface REF with respect to the lens optical axis LA (the angle between the lens optical axis LA and the surface normal of the reflection surface REF). Note that if the diffraction surface MOE or the reflection surface REF has a curved shape, the surface normal referred to here is the surface normal at their center (the point of intersection with the lens optical axis LA).

[0039] ν 0,gF As mentioned above, this is the Abbe number in the short wavelength range below the F line of the dispersion-controlled diffraction plane MOE, when the reference wavelength is the d line and the main dispersions are the g line and the F line.

[0040] The condition in equation (1) represents the range of dispersion, which is the reciprocal of the Abbe number ν0 of the dispersion-controlled rotationally asymmetric diffracted surface MOE, and indicates an appropriate range for good control of chromatic aberration. If 1 / ν0 falls below the lower limit of equation (1), the negative dispersion of the diffracted surface MOE increases, and the color shift of the light deflected by the diffracted surface MOE increases. As a result, chromatic aberration increases throughout the entire display optical system, which is undesirable. If 1 / ν0 exceeds the upper limit of equation (1), the positive dispersion of the diffracted surface MOE increases, and the color shift of the light deflected by the diffracted surface MOE increases. As a result, chromatic aberration increases throughout the entire display optical system, which is undesirable.

[0041] Furthermore, it is more preferable to set the lower limit of equation (1) to -0.15, -0.10, -0.05, or -0.01. Also, it is more preferable to set the upper limit of equation (1) to 0.15, 0.10, 0.05, or 0.01.

[0042] The conditions in equation (2) show an appropriate relationship between the deflection angle α and the inclination θdiff of the diffraction plane MOE, and are conditions for obtaining good field curvature performance. If α / 2-θdiff falls below the lower limit of equation (2), the meridional image plane deviates significantly from the sagittal image plane at the diffraction plane MOE, resulting in large astigmatism, which is undesirable. If α / 2-θdiff exceeds the upper limit of equation (2), the meridional image plane deviates from the sagittal image plane towards the meridional side, resulting in large astigmatism, which is also undesirable.

[0043] Furthermore, it is more preferable to set the lower limit of equation (2) to -25°, -20°, or -16°. Also, it is more preferable to set the upper limit of equation (2) to 25°, 20°, 15°, or 10°.

[0044] The conditions in equation (3) represent an appropriate relationship between the inclination θdiff of the diffraction plane MOE and the inclination of the reflection plane REF, and are conditions for thinning the optical system and obtaining good field curvature performance. If θrefl / 2-θdiff falls below the lower limit of equation (3), the reflection plane REF and the diffraction plane MOE are tilted too much, increasing the thickness of the optical system, which is undesirable for thinning the optical system. If θrefl / 2-θdiff exceeds the upper limit of equation (3), the angle of the light rays emitting from the diffraction plane MOE becomes too large compared to the angle of the light rays incident on the diffraction plane MOE, resulting in an imbalance between the two angles and causing astigmatism, which is undesirable.

[0045] Furthermore, it is more preferable to set the lower limit of equation (3) to -25°, -20°, or -16°. Also, it is more preferable to set the upper limit of equation (3) to 25° or 20°.

[0046] The conditions in equation (4) indicate an appropriate range for the deflection angle α of the diffractive surface MOE, and are conditions for obtaining good image performance while making the optical system thinner. If α falls below the lower limit of equation (4), the deflection angle becomes too small, which is undesirable because it reduces the effect of thinning the optical system. If α exceeds the upper limit of equation (4), the deflection power at the diffractive surface MOE becomes too large, which is undesirable because it increases the deterioration of aberration performance due to positional displacement of the diffractive surface MOE caused by assembly errors in the optical system, etc.

[0047] Furthermore, it is preferable to set the upper limit of equation (4) to 48°, 45°, or 40°.

[0048] The conditions in equation (5) indicate an appropriate range for the tilt angle θdiff of the diffraction plane MOE, and are conditions for obtaining good image performance while making the optical system thinner. If θdiff falls below the lower limit of equation (5), the diffraction plane MOE tilts too much in the direction that increases the thickness of the optical system, which is undesirable for thinning the optical system. If θdiff exceeds the upper limit of equation (5), the angle of the light rays emitting from the diffraction plane MOE becomes too large compared to the angle of the light rays incident on the diffraction plane MOE, resulting in an imbalance between the two angles and causing astigmatism, which is undesirable.

[0049] Furthermore, it is more preferable to set the upper limit of equation (5) to 45°, 40°, or 35°.

[0050] The condition in equation (6) is the Abbe number ν in the short wavelength range of the dispersion-controlled diffraction plane MOE. 0,gF This is the range of variance, which is the reciprocal of ν, and indicates an appropriate range for achieving good chromatic aberration correction. 1 / ν 0,gF If the value falls below the lower limit of equation (6), the negative dispersion of the diffraction plane MOE in the short-wavelength region becomes too large, resulting in a large chromatic shift in the short-wavelength region of the diffraction plane MOE. This is undesirable because it increases the magnification chromatic aberration of the entire display optical system in the short-wavelength region. 1 / ν 0,gF If the value exceeds the upper limit of equation (6), the positive dispersion of the diffraction plane MOE in the short wavelength range becomes too large, which is undesirable because it increases the magnification chromatic aberration of the entire display optical system.

[0051] Furthermore, it is more preferable to set the lower limit of equation (6) to -0.015, -0.010, or -0.005. Also, it is more preferable to set the upper limit of equation (6) to 0.02, 0.01, 0.005, or 0.001.

[0052] The optical systems of Examples 1 to 5 will be described in detail below. Numerical examples 1 to 5 corresponding to each of Examples 1 to 5 are shown after Example 5. [Examples]

[0053] The optical system of Embodiment 1 (Numerical Example 1) shown in Figure 1 comprises optical elements such as lenses with dispersed, rotationally asymmetric diffraction planes MOE arranged sequentially from the object side (object plane side) to the image side (image plane side), a lens group LN, a reflective surface REF, and an image plane side lens group (unsigned). The surface normals of the diffraction plane MOE and the reflective surface REF are each inclined with respect to the lens optical axis LA.

[0054] Figure 2 shows the longitudinal aberrations (spherical aberration, astigmatism, and chromatic aberration) of the optical system in numerical example 1 at infinity focus. In the spherical aberration diagram, Fno is the F number, the solid line shows the spherical aberration with respect to the d line (wavelength 587.6 nm), and the dashed line shows the spherical aberration with respect to the g line (wavelength 435.8 nm). The horizontal axis shows the amount of defocus in the range of -0.003 to +0.003 [mm]. In the astigmatism diagram, the solid line S shows the astigmatism of the sagittal image plane, and the dashed line M shows the astigmatism of the meridional image plane. The horizontal axis is the same as for spherical aberration. The chromatic aberration diagram shows the chromatic aberration at the g line. The horizontal axis shows the range of -0.003 to +0.003 [mm]. ω is the half-angle of view [°]. The explanation of these longitudinal aberration diagrams is the same for the other numerical examples. [Examples]

[0055] The optical system of Embodiment 2 (Numerical Example 2) shown in Figure 3 comprises optical elements with a dispersed, rotationally asymmetric diffraction plane MOE arranged sequentially from the object side to the image side, a lens group LN, a reflective surface REF formed on one surface of an optical prism, an image-side lens group (unsigned), and an image-side reflective surface (unsigned). The surface normals of the diffraction plane MOE and the reflective surface REF are each inclined with respect to the lens optical axis LA.

[0056] Figure 4 shows the longitudinal aberration of the optical system in numerical example 2 when it is focused at infinity. [Examples]

[0057] The optical system of Embodiment 3 (Numerical Example 3) shown in Figure 5 comprises optical elements with dispersed, rotationally asymmetric diffraction planes MOE arranged sequentially from the object side to the image side, a lens group LN, and a reflective surface REF. The surface normals of the diffraction plane MOE and the reflective surface REF are each inclined with respect to the lens optical axis LA.

[0058] Figure 6 shows the longitudinal aberration of the optical system in numerical example 3 when it is focused at infinity. [Examples]

[0059] The optical system of Embodiment 4 (Numerical Example 4) shown in Figure 7 comprises optical elements with dispersed, rotationally asymmetric diffraction planes MOE arranged sequentially from the object side to the image side, a lens group LN including a diffraction plane with a light-gathering effect, and a reflection plane REF. The surface normals of the diffraction plane MOE and the reflection plane REF are each inclined with respect to the lens optical axis LA.

[0060] Figure 8 shows the longitudinal aberration of the optical system in numerical example 4 when it is focused at infinity. [Examples]

[0061] The optical system of Example 5 (Numerical Example 5) shown in Figure 9 comprises optical elements having a dispersed, rotationally asymmetric diffraction plane MOE arranged sequentially from the object side to the image side, a lens group LN including a diffraction plane with a light-gathering effect, a half mirror (unsigned: transmission), a reflective surface REF, a half mirror (unsigned: reflection), a first image-side reflective surface (unsigned), a second image-side reflective surface (unsigned), and a lens (unsigned). The surface normals of the diffraction plane MOE and the reflective surface REF are each inclined with respect to the lens optical axis LA.

[0062] Figure 10 shows the longitudinal aberration of the optical system in numerical example 5 when it is focused at infinity.

[0063] Numerical examples 1 to 5 are shown below. In each numerical example, the maximum image height is half the diagonal length of the imaging plane (or display plane) on the image plane. In the surface data, r represents the paraaxial radius of curvature of the i-th plane (i=0,1,2,3,...) counted from the object plane. Nd represents the refractive index of the optical material at the d-line between the i-th plane and the (i+1)-th plane. νd represents the Abbe number of the optical material at the d-line between the i-th plane and the (i+1)-th plane. The Abbe number νd at the d-line is given by Nd, NF, and NC, respectively, where the refractive indices at the d-line, F-line, and C-line are Nd, NF, and NC. νd = (Nd-1) / (NF-NC) It is represented as follows: X and Y represent the X and Y coordinates in the absolute XYZ coordinate system of the vertices of each face. The angle represents the angle that the face normal of each face makes with the X axis. The unit of length in each numerical example is [mm]. However, since the optical system can be magnified or reduced proportionally to obtain equivalent optical performance, the unit is not limited to [mm] and other units can be used. The unit of angle is [°].

[0064] The asterisk (*) next to the surface number indicates that the surface has an aspherical shape. The aspherical shape is expressed by the following formula, where x is the displacement from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, the direction of light propagation is positive, R is the radius of paraxial curvature at the surface vertex, k is the cone constant, and A2, A4, A6, A8, and A10 are aspherical coefficients. The cone constant and aspherical coefficients "e±x" are multiplied by 10. ±x It means...

[0065]

number

[0066] Furthermore, the optical path difference function of a rotationally asymmetric surface at the design wavelength is given by U1,0, U0,1, U2,0, U1,1, U0,2,..., where U1,1, U0,2,... are the coefficients of the optical path difference function of the surface, and the in-plane coordinates are y,z. ψ0=U1,0·y 1 z 0 +U0,1·y 0 z 1 +U2,0·y 2 z0 +U1,1·y 1 z 1 +U0,2·y 0 z 2 It is represented as follows.

[0067] On the other hand, the optical path difference function of a rotationally symmetric surface at the design wavelength is obtained when U2, U4, U6, U8, and U10 are coefficients of the optical path difference function of the surface. ψ0 = U²·h 2 +U4·h 4 +U6·h 6 +U8·h 8 +U10·h 10 It is represented as follows.

[0068] The (diffraction) of the second surface indicates a surface whose optical design has been performed using the optical path difference function of the surface. The optical path difference dispersion P(λ) of the surface is expressed by an equation in which the incident wavelength λ is a variable. The incident wavelength λ used when calculating the optical path difference dispersion of the surface is in units of [μm]. The (reflection) appended to the surface number indicates a reflective surface, which is a reflective surface due to total internal reflection at the glass-air interface or mirror reflection by a metal film.

[0069] Table 1 summarizes the values ​​of equations (1) to (6) described above for numerical examples 1 to 5. Each numerical example satisfies all the conditions of equations (1) to (6). [Numerical Example 1] Unit: mm Object distance -1e30 Focal length f=1.00 Maximum image height 0.1709 Surface data JPEG2026073912000011.jpg112119

[0070] Aspherical data Second surface (rotationally asymmetric diffraction surface): Design wavelength 0.58756 [μm] U1,0=-2.079117e-01 U0,2= 9.83896e-05 Surface optical path difference dispersion in units of λ [μm] P(λ)= 527.57657λ10 - 3174.19670λ9 + 8657.87534λ8 - 14126.68701λ7 + 15317.54115λ6 - 11587.24417λ5 + 6239.36490λ4 - 2391.27108λ3 + 639.21962λ2 - 113.49263λ + 12.05454 P(λd) = 1.0000e+00 P(λC) = 8.9933e - 01 P(λF) = 1.2032e+00 The 3rd surface k = 0.00000e+00 A4 = 1.20586e+00 A6 = 8.98576e+00 A8 = - 1.82227e+02 The 4th surface k = 0.00000e+00 A4 = 4.47986e+00 A6 = - 5.12325e+01 A8 = 3.01105e+02 The 5th surface k = 0.00000e+00 A4 = - 1.04478e+01 A6 = 1.35878e+02 A8 = - 3.16868e+02 The 6th surface k = 0.00000e+00 A4 = - 1.29157e+01 A6 = 2.21840e+02 A8 = - 1.13266e+03 The 8th surface k = 2.63122e+00 A4 = 4.79468e+00 A6 = - 1.72269e+02 A8 = 1.33012e+04 A10 = - 2.11595e+05 The 9th surface k = - 1.03415e+01 A4 = - 3.58510e+00 A6 = - 2.94229e+02 A8 = 3.77558e+04 A10 = - 9.98007e+05 The 10th surface k = 2.61649e+00 A4 = - 2.59002e+01 A6 = 1.62112e+03 A8 = - 2.77462e+04 A10 = -9.69094e+05 Page 11 k = 3.93507e+00 A 4= 6.53905e+00 A 6= 2.15643e+03 A 8=-7.25790e+04 A10 = 1.00999e+06 [Numerical Example 2] Unit: mm Object distance -1e30 Focal length f=1.00 Maximum image height 0.1636 Surface data JPEG2026073912000012.jpg121116

[0071] Aspherical data Second surface (rotationally asymmetric diffraction surface): Design wavelength 0.58756 [μm] U1,0 = -6.840978e-01 Surface optical path difference dispersion in units of λ [μm] P(λ) = 0.58756 / λ P(λd) = 1.0000e+00 P(λC) = 8.9530e-01 P(λF) = 1.2086e+00 3rd page k = 0.00000e+00 A 4= 6.58447e-01 A 6= 9.48907e+00 A 8=-3.30503e+02 Side 4 k = 0.00000e+00 A 4= 8.90350e+00 A 6=-1.17770e+02 A 8= 7.99854e+02 5th page k = 0.00000e+00 A 4= 3.54355e+00 A 6= 3.95168e+01 A 8=-5.66294e+01 Side 6 k = 0.00000e+00 A 4=-5.52202e+00 A 6= 2.90222e+02 A 8=-1.31225e+03 Side 10 k =-8.95602e-04 A 4= 1.02326e+01 A 6= 4.36553e+01 A 8= 1.68329e+03 A10 = 2.38035e+02 [Numerical Example 3] Unit: mm Object distance -1e30 Focal length f=1.00 Maximum image height 0.1687 Surface data JPEG2026073912000013.jpg105116

[0072] Aspherical data Second surface (rotationally asymmetric diffraction surface): Design wavelength 0.58756 [μm] U1,0 = -5.000000e-01 Surface optical path difference dispersion in units of λ [μm] P(λ) = 0.58756 / λ P(λd) = 1.0000e+00 P(λC) = 8.9530e-01 P(λF) = 1.2086e+00 3rd page k = 0.00000e+00 A 4= 9.05073e-01 A 6= 6.19227e+01 A 8=-6.60058e+02 Side 4 k = 0.00000e+00 A 4= 2.72106e+01 A 6=-2.82674e+02 A 8= 2.70664e+02 5th page k = 0.00000e+00 A 4= 1.22278e+01 A 6=-7.26521e+01 Side 6 k =-9.96929e-02 A 4=-3.73118e+01 A 6= 4.93371e+01 Side 7 k = 1.95291e-04 A 4= 7.47533e+00 A 6=-7.30413e+02 Page 8 k = 0.00000e+00 A 4= 1.06083e+01 A 6=-4.42946e+02 A 8=-3.55538e+03 [Value example 4] Unit mm Object distance -1e30, focal distance f=1.00, maximum image height 0.1648 Noodles JPEG2026073912000014.jpg107114

[0073] Aspheric surface The second surface (asymmetric fold surface) has a designed wavelength of 0.58756 μm. U1,0=-3.459701e-01 Surface optical path difference dispersion λ unit [μm] P(λ)= 514.85586λ10-3120.72379λ9+8564.02289λ8-14045.78557λ7+15297.54185λ6 -11617.00000λ5+6276.73734λ4-2412.89836λ3+646.74064λ2-115.11227λ+12.24250 P(λd) = 1.0000e+00 P(λC) = 8.9429e-01 P(λF) = 1.2100e+00 The third surface (also known as the folding surface) has a designed wavelength of 0.58756 μm. U 2=-4.47549e-01 U 4= 3.31953e-01 U 6=-1.08658e+01 Surface optical path difference dispersion λ unit [μm] P(λ) = 0.58756 / λ P(λd) = 1.0000e+00 P(λC) = 8.9530e-01 P(λF) = 1.2086e+00 Page 5 k = 0.00000e+00 A 4=-8.28235e+00 A 6=-7.24949e+01 Page 6 k =-2.93125e-05 A 4=-1.68056e+01 A 6= 2.70867e+01 Page 7 k =-3.32584e-05 A 4= 2.47878e+01 A 6= 8.89100e+01 Page 8 k = 0.00000e+00 A 4= 3.25749e+01 A 6= 1.38217e+02 A 8= 5.50824e+03 [Value example 5] Unit mm Object distance -1e30, focal distance f=1.00, maximum image height 0.1709 Noodles JPEG2026073912000015.jpg132118

[0074] Aspheric surface Surface 2 (non-symmetrical return surface) Design wavelength 0.58756 [μm] U1,0=-6.008954e-01 Surface optical path difference dispersion λ unit [μm] P(λ) = 0.58756 / λ P(λd) = 1.0000e+00 P(λC) = 8.9530e-01 P(λF) = 1.2086e+00 The third surface (asymmetrical folded surface) has a design wavelength of 0.58756 μm. U 2=-3.56954e-01 U 4=-3.03515e-02 U 6= 5.01286e-01 Surface optical path difference dispersion λ unit [μm] P(λ) = 0.58756 / λ P(λd) = 1.0000e+00 P(λC) = 8.9530e-01 P(λF) = 1.2086e+00 5th page k = 9.14991e-01 A 4=-1.63991e+00 A 6=-8.34075e+00 Side 6 k = 2.25391e+00 A 4=-1.39947e+00 A 6= 5.51291e+00 Page 13 k = 5.96308e+00 A 4=-1.96327e+01 A 6= 1.68880e+02 A 8=-8.46664e-02 Page 14 k =-3.88389e+00 A 4=-1.80744e+01 A 6= 2.58679e+02 A 8=-2.24108e+03

[0075] [Table 1]

[0076] [Imaging device] Figure 12(a) shows a smartphone 10 as an imaging device including the optical system OS of Examples 1 to 5. A display 11, a microphone 12, and a speaker 13 are arranged on the front of the smartphone 10. The optical system OS takes in light from an object from the back of the smartphone 10, bends the optical path to form an image on an image sensor (imaging surface) not shown. This allows the object to be imaged. By using the optical system OS of Examples 1 to 5, it is possible to provide a smartphone that is thin and can produce high-quality images.

[0077] [Display device] Figure 12(b) shows a head-mounted display 20 as a display device including an optical system OS according to Examples 1 to 5. The optical system OS guides light from an unshown display element (display surface) to the observer's eye E by bending the optical path. This allows the observer to view the image. By using the optical system OS of Examples 1 to 5, a head-mounted display that allows viewing of thin, high-resolution display images can be provided.

[0078] The above embodiments include the following configuration.

[0079] (Composition 1) An optical element having a diffraction surface with controlled wavelength dispersion characteristics, Including the lens, Let ν0 be the Abbe number of the diffraction plane, and let the reference wavelength of the diffraction plane be the d-line and the principal dispersions be the F-line and C-line. The optical path difference function at each wavelength is ψ d ψ F ψ C P(λ) is the optical path difference dispersion of the surface at each wavelength. d ), P(λ F ), P(λ C ) as,

[0080]

number

[0081] When that is the case, -0.2 < 1 / ν0 < 0.2 The following conditions are met: The optical system is characterized in that the diffracted surface has a rotationally asymmetric optical path difference function. (Configuration 2) The diffraction surface deflects the incident light, When α is the deflection angle due to the diffraction surface with respect to a d-line incident perpendicularly at the intersection of the optical axis of the lens with the diffraction surface, and θdiff is the angle between the optical axis of the lens and the surface normal of the diffraction surface, -30°<α / 2-θdiff<30° The optical system according to configuration 1, characterized by satisfying the following conditions. (Composition 3) The optical system according to configuration 1 or 2, characterized in that it includes a reflective surface. (Composition 4) When the inclination of the surface normal of the reflective surface with respect to the optical axis of the lens is θrefl, and the inclination of the surface normal of the diffracting surface with respect to the optical axis is θdiff, -30° < θrefl / 2 - θdiff < 30° An optical system according to any one of configurations 1 to 3, characterized by satisfying the following conditions. (Composition 5) When the deflection angle of the light ray due to the diffraction surface is α, 0°<α<60° An optical system according to any one of configurations 1 to 4, characterized by satisfying the following conditions. (Composition 6) When the angle between the optical axis of the lens and the surface normal of the diffraction surface is denoted as θdiff, 0° < θdiff < 30° An optical system according to any one of configurations 1 to 5, characterized by satisfying the following conditions. (Composition 7) The optical system according to any one of configurations 1 to 6, characterized in that the diffraction surface deflects all light rays of different heights from the point of intersection with the optical axis of the lens toward the same side. (Composition 8) The optical system according to any one of configurations 1 to 7, characterized in that the lens is a refractive lens, a diffractive lens, or a metasurface lens. (Composition 9) The optical system according to any one of configurations 1 to 8, characterized in that the diffraction surface and the lens are arranged adjacent to each other. (Composition 10) The optical system is characterized by forming an image of light incident from the object surface onto the image plane, as described in any one of configurations 1 to 9. (Composition 11) The optical system according to configuration 10, characterized in that it is an imaging optical system that guides light from a subject located on the object surface to an imaging surface arranged on the image surface. (Composition 12) The optical system according to configuration 11, characterized in that the diffraction plane is arranged between the object plane and the lens. (Composition 13) The optical system according to configuration 12, characterized in that it has the diffraction surface, the lens, and the reflection surface in order from the object surface side to the image surface side. (Composition 14) The optical system according to configuration 10, characterized in that it is a display optical system that guides light from a display surface located on the object surface to the observer's eye positioned on the image surface. (Composition 15) The optical system according to configuration 14, characterized in that the diffraction plane is arranged between the lens and the image plane. (Composition 16) The optical system according to configuration 15, characterized in that it has the reflective surface, the lens, and the diffracting surface in order from the object surface side to the image surface side. (Composition 17) The optical system according to any one of configurations 1 to 16, characterized in that the diffraction surface has a planar shape. (Composition 18) The optical system according to any one of configurations 1 to 17, characterized in that the lens closest to the diffraction surface is a positive lens. (Composition 19) When the main dispersions of the diffraction plane are the g-line and the F-line, the Abbe number in the wavelength range below the F-line is ν 0,gF The optical path difference functions for the d-line, g-line, and F-line are respectively ψ d ψ g ψ F The incident wavelengths of the d-line, g-line, and F-line are λ, respectively. d , λ g , λ F as,

[0082]

number

[0083] When -0.02 < 1 / ν 0,gF<0.02 An optical system according to any one of configurations 1 to 18, characterized by satisfying the following conditions. (Composition 20) Metasurfaces with controlled wavelength dispersion characteristics, Including the lens, Let ν0 be the Abbe number of the metasurface, and let the reference wavelength of the metasurface be the d-line and the principal dispersions be the F-line and C-line. The optical path difference function at each wavelength is ψ d ψ F ψ C P(λ) is the optical path difference dispersion of the surface at each wavelength. d ), P(λ F ), P(λ C ) as,

[0084]

number

[0085] When that is the case, -0.2 < 1 / ν0 < 0.2 The following conditions are met: The aforementioned metasurface is characterized by having a rotationally asymmetric optical path difference function. (Composition 21) The optical system described in any one of configurations 1 to 20, An optical device characterized by having an image sensor or a display element.

[0086] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention. [Explanation of symbols]

[0087] LN lens group LA lens optical axis MOE dispersion-controlled diffraction plane REF reflective surface IP image plane

Claims

1. An optical element having a diffraction surface with controlled wavelength dispersion characteristics, The lens includes the Abbe number of the diffraction surface ν ０ Let the reference wavelength of the diffraction plane be the d-line, and the principal dispersions be the F-line and C-line, and the optical path difference function at each wavelength be ψ ｄ ψ Ｆ ψ Ｃ P(λ) is the optical path difference dispersion of the surface at each wavelength. ｄ ), P(λ Ｆ ), P(λ Ｃ ) as, [Math 1] When that is the case, -0.2<1 / n ０ <0.2 The following conditions are met: The optical system is characterized in that the diffracted surface has a rotationally asymmetric optical path difference function.

2. The diffraction surface deflects the incident light, When α is the deflection angle due to the diffraction surface with respect to a d-line incident perpendicularly at the intersection of the optical axis of the lens and the diffraction surface, and θdiff is the angle between the optical axis of the lens and the surface normal of the diffraction surface, -30°<α / 2-θdiff<30° The optical system according to claim 1, characterized in that it satisfies the following conditions.

3. The optical system according to claim 1, characterized in that it includes a reflective element having a reflective surface.

4. When the angle between the optical axis of the lens and the surface normal of the reflective surface is θrefl, and the angle between the optical axis and the surface normal of the diffracting surface is θdiff, -30°<θrefl / 2-θdiff<30° The optical system according to claim 1, characterized in that it satisfies the following conditions.

5. When the deflection angle of the light ray due to the diffraction surface is α, ０°＜α＜６０° The optical system according to claim 1, characterized in that it satisfies the following conditions.

6. When the angle between the optical axis of the lens and the surface normal of the diffraction plane is θdiff, 0°<θdiff<30° The optical system according to claim 1, characterized in that it satisfies the following conditions.

7. The optical system according to claim 1, characterized in that the diffraction plane deflects all light rays of different heights from the point of intersection with the optical axis of the lens toward the same side.

8. The optical system according to claim 1, characterized in that the lens is one of a refractive lens, a diffractive lens, and a metasurface lens.

9. The optical system according to claim 1, characterized in that the diffraction surface and the lens are arranged adjacent to each other.

10. The optical system according to claim 1, characterized in that it forms an image of light incident from the surface of an object onto the image plane.

11. The optical system according to claim 10, characterized in that it is an imaging optical system characterized in that it guides light from a subject located on the object surface to an imaging surface arranged on the image surface.

12. The optical system according to claim 11, characterized in that the diffraction plane is arranged between the object plane and the lens.

13. The optical system according to claim 12, characterized in that it has the diffraction surface, the lens, and the reflection surface in order from the side of the object surface to the side of the image surface.

14. The optical system according to claim 10, characterized in that it is a display optical system that guides light from a display surface located on the object surface to the observer's eye positioned on the image surface.

15. The optical system according to claim 14, characterized in that the diffraction plane is arranged between the lens and the image plane.

16. The optical system according to claim 15, characterized in that it has the reflective surface, the lens, and the diffracting surface in order from the side of the object surface to the side of the image surface.

17. The optical system according to claim 1, characterized in that the diffraction surface has a planar shape.

18. The optical system according to claim 1, characterized in that the lens closest to the diffraction plane is a positive lens.

19. The Abbe number in the wavelength range below the F line when the main dispersion of the diffractive surface is the g line and the F line is ν ０，ｇＦ , the optical path difference functions of the d line, the g line, and the F line are ψ ｄ , ψ ｇ , ψ Ｆ , the incident wavelengths of the d line, the g line, and the F line are λ ｄ , λ ｇ , λ Ｆ respectively, [Math 2] When -0.02<1 / n ０，ｇＦ <0.02 The optical system according to claim 1, characterized in that it satisfies the following conditions.

20. An optical element having a metasurface with controlled wavelength dispersion characteristics, Including the lens, The Abbe number of the aforementioned metasurface is ν ０ Let the reference wavelength of the metasurface be the d-line and the principal dispersions be the F-line and C-line, and the optical path difference function at each wavelength be ψ ｄ ψ Ｆ ψ Ｃ P(λ) is the optical path difference dispersion of the surface at each wavelength. ｄ ), P(λ Ｆ ), P(λ Ｃ ) as, [Math 3] When that is the case, -0.2<1 / n ０ <0.2 The following conditions are met: The aforementioned metasurface is characterized by having a rotationally asymmetric optical path difference function.

21. The optical system according to claim 1 or 20, An optical device characterized by having an image sensor or a display element.

Images