Display optical system and display device

Abstract

To provide a display optical system which can be corrected for magnification chromatic aberration and astigmatism.SOLUTION: A display optical system L disclosed herein is configured to display an image displayed on a display surface IP on an observation side, and comprises a diffraction surface MOE with a controlled wavelength dispersion property. The diffraction surface has an Abbe number ν0 that satisfies a condition expressed as: -0.2<1 / ν0<0.2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a display optical system suitable for a display device such as an electronic viewfinder. [Background technology]

[0002] As a display optical system for allowing an observer to observe an image displayed on a display panel, there is one that has a lens with strong positive refractive power for magnifying and observing the image, and a lens with negative refractive power for correcting chromatic aberration and astigmatism caused by the positive refractive power. Patent Document 1 discloses a display optical system that is composed of, in order from the observer side, a first lens with positive refractive power, a second lens with negative refractive power and a meniscus shape with a concave surface facing the display panel side, and a third lens with positive refractive power. Patent Document 2 discloses a display optical system that has two positive lenses, one negative lens, and a diffractive surface.

[0003] Meanwhile, unlike conventional diffractive surfaces, Patent Document 3 discloses a diffractive surface in which the wavelength dispersion characteristics are controlled by using minute shapes of a quarter wavelength size. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-202770 A [Patent Document 2] JP 2020-154190 A [Patent Document 3] U.S. Pat. No. 10,670,782 Summary of the Invention [Problem to be solved by the invention]

[0005] In the display optical system disclosed in Patent Document 1, the correction of lateral chromatic aberration and astigmatism is insufficient. In the display optical system disclosed in Patent Document 2, the correction of lateral chromatic aberration is excellently corrected by using a diffractive surface, but the correction of astigmatism is insufficient.

[0006] The present invention provides a display optical system that is capable of correcting lateral chromatic aberration and astigmatism by using a diffractive surface with controlled wavelength dispersion characteristics. [Means for solving the problem]

[0007] A display optical system according to one aspect of the present invention displays an image displayed on a display surface on a viewing side. The display optical system includes a diffractive surface (or metasurface) with controlled wavelength dispersion characteristics. The Abbe number ν0 of the diffractive surface (or metasurface) is expressed as follows: -0.2<1 / ν0<0.2 The Abbe number v0 will be described later. A display device having the above-described display optical system also constitutes another aspect of the present invention. Effect of the Invention

[0008] According to the present invention, by using a diffractive surface with controlled wavelength dispersion characteristics in the display optical system, lateral chromatic aberration and astigmatism can be corrected satisfactorily. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a cross-sectional view of the display optical system according to the first embodiment. [Diagram 2] 5A to 5C are aberration diagrams of the display optical system according to the first embodiment. [Diagram 3] FIG. 11 is a cross-sectional view of a display optical system according to a second embodiment. [Figure 4] 6A to 6C are aberration diagrams of the display optical system according to the second embodiment. [Diagram 5] FIG. 11 is a cross-sectional view of a display optical system according to a third embodiment. [Figure 6] 11A to 11C are aberration diagrams of the display optical system according to the third embodiment. [Figure 7] FIG. 11 is a cross-sectional view of a display optical system according to a fourth embodiment. [Figure 8]11A to 11C are aberration diagrams of the display optical system according to the fourth embodiment. [Figure 9] FIG. 13 is a cross-sectional view of a display optical system according to a fifth embodiment. [Figure 10] 13A to 13C are aberration diagrams of the display optical system according to the fifth embodiment. [Figure 11] FIG. 13 is a cross-sectional view of a display optical system according to a sixth embodiment. [Figure 12] 13A to 13C are aberration diagrams of the display optical system according to the sixth embodiment. [Figure 13] FIG. 13 is a cross-sectional view of a display optical system according to a seventh embodiment. [Figure 14] 13A to 13C are aberration diagrams of the display optical system according to the seventh embodiment. [Figure 15] FIG. 1 is a diagram showing an image pickup apparatus equipped with an electronic viewfinder including a display optical system according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, prior to describing specific embodiments 1 to 7, matters common to the embodiments will be described.

[0011] 1, 3, 5, 7, 9, 11, and 13 respectively show the configuration of the display optical system L of Examples 1 to 7. The display optical system L of each Example is used in an electronic viewfinder of an imaging device such as a digital camera or a video camera.

[0012] In each figure, the left side is the observation side (exit pupil side or eyepoint side) and the right side is the display surface side (object side or panel side). SP is the observation surface (exit pupil surface or eyepoint) where the observer places his / her eye (pupil). MOE is a diffractive surface with controlled wavelength dispersion characteristics (hereinafter simply referred to as dispersion controlled), and Lm is a meniscus lens. IP is the display surface of the display element. The display element is composed of a liquid crystal panel, an organic EL element, etc. The display optical system L has at least a diffractive surface MOE and a meniscus lens Lm.

[0013] CG1 is a first cover glass that prevents dirt and dust from entering the display optical system from the observation side, and CG2 is a second cover glass that prevents dirt and dust from adhering to the display surface.

[0014] The optical path difference function ψ of a dispersion-controlled diffractive surface can be defined as follows, where the diffraction order is m, the design wavelength of the diffractive 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.

[0015]

number

[0016]

number

[0017] In addition, in the case of a rotationally symmetric surface, which is frequently used, the optical path difference function ψ0 of the surface at the design wavelength is usually expressed by the following polynomial, where h is the distance from the optical axis.

[0018]

number

[0019] The focal length fmoe of a dispersion-controlled diffractive surface can be described as follows using the quadratic coefficient U2 of the optical path difference function of the surface at the design wavelength expressed as a polynomial:

[0020]

number

[0021] When the reference wavelength of the dispersion-controlled diffractive surface is the d-line (wavelength 587.6 nm) and the main dispersion is the F-line (wavelength 486.1 nm) and the C-line (wavelength 656.3 nm), the Abbe number ν0 can be written as follows. Also, ψ d , ψ F , ψ Care 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 d-line, F-line, and C-line, respectively.

[0022]

number

[0023] The Abbe number ν in the short wavelength range below the F line when the reference wavelength of the dispersion-controlled diffractive surface is the d line and the main dispersion is the g line (wavelength 435.8 nm) and the F line. 0,gF can be written 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 d-line, g-line, and F-line, respectively.

[0024]

number

[0025] In each embodiment, since the first-order diffracted light is used for design, the diffraction order m is set to 1. Furthermore, the d-line is used as the incident wavelength when determining the design wavelength λ0 and the focal length.

[0026] In the display optical system of each embodiment, it is assumed that the observer will magnify and observe a small display panel with a diagonal length of about 10 mm at a viewing angle of about 35 degrees. For magnified observation, a strong positive refractive power is required. As a result, in the peripheral area away from the optical axis, as the height from the optical axis increases, large lateral chromatic aberration and astigmatism occur, and the optical performance deteriorates. In order to improve such lateral chromatic aberration and astigmatism, a lens having a dispersion-controlled diffractive surface MOE is disposed between the observation surface and the display surface in the display optical system of each embodiment. The diffractive surface MOE can control the wavelength dispersion characteristics to any value, so that the lateral chromatic aberration can be well corrected. In addition, the diffractive surface MOE controls the traveling direction of light by diffraction, and the Petzval term at the diffractive surface MOE becomes zero, so that the astigmatism and field curvature of the display optical system can be well corrected.

[0027] In addition, since a display optical system requires a strong positive refractive power overall, it is desirable to use a dispersion-controlled diffractive surface MOE that has the effect of reducing aberration as a surface with positive refractive power. This suppresses the aberration that conventionally occurred in refractive lenses with positive refractive power (lenses that have a refractive action rather than a diffractive action), making it possible to obtain a display optical system with effectively reduced aberration.

[0028] In addition, with a dispersion-controlled diffractive surface MOE alone, spherical aberration and curvature of field occur in a deviated manner. This causes the peripheral curvature of field to tilt relative to the best on-axis image plane, making it difficult to simultaneously correct both on-axis and peripheral aberrations. Furthermore, to effectively reduce aberrations, it is necessary to correct the curvature of field, and for this purpose it is desirable to have at least one refractive lens. In particular, by forming the refractive lens into a meniscus shape and arranging the refractive lens adjacent to a lens having a dispersion-controlled diffractive surface MOE, it is possible to appropriately correct the curvature of field.

[0029] In addition, it is desirable that the refractive power of the lens placed closest to the observation side is positive. By placing the positive lens at a position away from the display surface, it becomes easy to ensure a lens back (the distance from the positive lens to the display surface) with a relatively weak refractive power, and an increase in aberration is suppressed. If a long lens back can be ensured, there is a high degree of freedom in placing the meniscus lens Lm between the positive lens and the display surface, and the meniscus lens Lm can be placed at a position suitable for aberration correction.

[0030] In addition, by moving the entire display optical system in the optical axis direction (towards the observation side and the display surface side) together with the lens having a dispersion-controlled diffractive surface and the meniscus lens, it is possible to adjust the diopter with little deterioration in performance. By moving the display optical system to the observation side, it is possible to correct the positive diopter, and by moving it to the display surface side, it is possible to correct the negative diopter.

[0031] In addition, it is desirable that the dispersion-controlled diffractive surface MOE has a planar shape. If the dispersion-controlled diffractive surface has a curvature, the diffractive surface functions as a refracting surface. This is undesirable because a part of the refractive power that should be generated by the dispersion-controlled diffractive surface through diffraction is shared by the refracting surface, and the effects of wavelength dispersion control and Petzval reduction of the dispersion-controlled diffractive surface are reduced. Moreover, since the fine shape of the dispersion-controlled diffractive surface is created using a semiconductor manufacturing process, creating a fine shape on a curved surface is technically difficult, which is undesirable.

[0032] In each embodiment, it is possible to provide a display optical system L in which lateral chromatic aberration and astigmatism are well corrected by suitably setting the Abbe number and focal length of the dispersion-controlled diffractive surface MOE, the focal length of the meniscus lens Lm, and the overall length of the display optical system L. Specifically, it is preferable to satisfy at least one of the conditions of the following expressions (1) to (5).

[0033] -0.2<1 / ν0<0.2 (1) 0.7 <fmoe / f<4.0 (2) -4 <fmenis / f<4 (3) 0.6 <OL / f<1.4 (4) -0.02<1 / ν 0,gF <0.02 (5) In the above formula, ν0 is the Abbe number of the dispersion-controlled diffractive surface MOE when the reference wavelength is the d-line and the primary dispersion is the F-line and C-line. fmoe is the focal length of the dispersion-controlled diffractive surface MOE. fmenis is the focal length of the meniscus lens Lm. f is the focal length of the entire display optical system L. OL is the total optical length of the display optical system L, and is the distance on the optical axis (the distance between the vertices of the surfaces) between the optical surfaces closest to the display surface and the optical surfaces furthest from the display surface among the optical surfaces included in the display optical system (optical surfaces of lenses or refractive lenses having a dispersion-controlled diffractive surface). ν 0,gF is the Abbe number in the short wavelength region below the F-line of a dispersion-controlled diffractive surface MOE when the reference wavelength is the d-line and the main dispersion is the g-line and F-line.

[0034] The condition of formula (1) indicates an appropriate range for performing favorable correction of lateral chromatic aberration of dispersion, which is the reciprocal of the Abbe number ν0 of the dispersion-controlled diffractive surface MOE. When 1 / ν0 is below the lower limit of formula (1), the negative dispersion of the diffractive surface MOE becomes large, and the amount of chromatic aberration correction at the diffractive surface MOE becomes large. As a result, chromatic aberration is overcorrected in the entire display optical system, which is not preferable. When 1 / ν0 is above the upper limit of formula (1), the positive dispersion of the diffractive surface MOE becomes large, and the amount of chromatic aberration correction at the diffractive surface MOE becomes small, like that of a normal refractive lens. As a result, chromatic aberration is undercorrected in the entire display optical system, which is not preferable.

[0035] The condition of formula (2) shows an appropriate range for performing good astigmatism correction of the focal length of the dispersion-controlled diffractive surface MOE. When fmoe / f is below the lower limit of formula (2), the refractive power of the diffractive surface MOE is weak, and the effect of reducing astigmatism by diffraction is not sufficiently obtained, which is not preferable. On the other hand, when fmoe / f is above the upper limit of formula (2), the refractive power of the diffractive surface MOE becomes strong, and the amount of inclination of the image plane in the under direction increases. As a result, large astigmatism occurs according to the amount of inclination, which increases the astigmatism of the entire display optical system, which is not preferable.

[0036] The condition of formula (3) shows an appropriate range for performing good correction of the field curvature of the focal length of the meniscus lens Lm. If fmenis / f is below the lower limit of formula (3), the negative refractive power of the meniscus lens Lm becomes strong, which is undesirable because the meniscus lens Lm causes overcorrection of the chromatic aberration of magnification and overcorrection of the field curvature. If fmenis / f is above the upper limit of formula (3), the positive refractive power of the meniscus lens Lm becomes strong, which is undesirable because it causes chromatic aberration of magnification and undercorrection of the field.

[0037] The condition of formula (4) indicates an appropriate range for performing good aberration correction of the total optical length of the display optical system L. When OL / f is below the lower limit of formula (4), the total optical length becomes too short, the lens spacing and the curvature of the optical surface become small, and it becomes difficult to properly correct various aberrations such as spherical aberration and curvature of field, which is not preferable. When OL / f is above the upper limit of formula (4), the total optical length becomes too long, resulting in an unbalanced power arrangement in which the positive refractive power of the observation side is weak and the positive refractive power of the lens on the display surface side is strong. When the refractive power of the lens on the display surface side becomes strong, various aberrations such as spherical aberration and curvature of field occur, which is not preferable because good optical performance cannot be obtained.

[0038] The condition of formula (5) is the Abbe number ν 0,gF This shows the appropriate range for achieving good correction of lateral chromatic aberration of dispersion, which is the reciprocal of 1 / ν 0,gF If 1 / ν falls below the lower limit of formula (5), the negative dispersion of the diffractive surface MOE in the short wavelength range becomes too large, and the amount of chromatic aberration correction in the short wavelength range by the diffractive surface MOE becomes large. As a result, the chromatic aberration in the short wavelength range of the entire display optical system becomes overcorrected, which is not preferable. 0,gF If exceeds the upper limit of the formula (5), the positive dispersion of the diffractive surface MOE in the short wavelength region becomes too large, and the chromatic aberration of the entire display optical system becomes insufficiently corrected, which is undesirable.

[0039] It is more preferable that the numerical ranges of the formulas (1) to (5) are as follows:

[0040] -0.15<1 / ν0<0.10 (1a) 0.75 <fmoe / f<3.90 (2a) -3.7 <fmenis / f<3.7 (3a) 0.65 <OL / f<1.30 (4a) -0.015<1 / ν 0,gF <0.015 (5a) Moreover, it is more preferable that the numerical ranges of the formulas (1) to (5) are as follows:

[0041] -0.10<1 / ν0<0.03 (1b) 0.8 <fmoe / f<3.8 (2b) -3.2 <fmenis / f<3.2 (3b) 0.7 <OL / f<1.2 (4b) -0.01<1 / ν 0,gF <0.01 (5b) Below, a specific description will be given of Examples 1 to 7. After the description of Example 7, Numerical Examples 1 to 7 corresponding to Examples 1 to 7, respectively, will be shown.

[0042] In the numerical example, the diagonal length of the display surface is twice the maximum image height. Surface number i indicates the order of the optical surface when counting from the observation (eye point EP) side, and r indicates the paraxial radius of curvature of the i-th optical surface. d indicates the spacing (distance) on the optical axis between the i-th surface and the (i+1)-th surface. nd and νd respectively indicate the refractive index at the d-line (wavelength 578.6 nm) of the glass material between the i-th surface and the (i+1)-th surface, and the Abbe number based on the d-line.

[0043] The Abbe number νd based on the d-line is given by, where Nd, NF, and NC are the refractive indices at the d-line, F-line (wavelength 486.1 nm), and C-line (wavelength 656.3 nm), respectively. νd=(Nd-1) / (NF-NC) It is expressed as:

[0044] An "*" next to a surface number means that the surface has an aspheric shape. An aspheric shape is expressed by the following formula, where x is the displacement from the apex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, K is the conic constant, and A4 to A8 are aspheric coefficients. Note that the conic constant and the aspheric coefficients "e±M" are expressed as x10 ±M means.

[0045] x=(h 2 / R) / [1+{1-(1+K)(h / R) 2} 1 / 2 ] +A4·h 4 +A6·h 6 +A8·h 80 Moreover, the optical path difference function of the surface at the design wavelength is expressed by the following formula, where U2 to U10 are the optical path difference function coefficients of the surface.

[0046] ψ0=U2 h 2 +U4·h 4 +U6·h 6 +U8·h 8 The (diffraction) attached to the surface number means that the surface is optically designed according to the optical path difference function of the surface. The optical path difference dispersion P(λ) of a surface is expressed by a formula that uses the incident wavelength λ as a variable. When calculating the optical path difference dispersion of a surface, the incident wavelength λ is calculated using the unit [μm].

[0047] In each numerical example, the surface spacing can be changed to adjust the diopter. -1 (Standard diopter), -3m -1 , -1m -1 , +1m -1 The figures show the corresponding surface spacing and variable surface spacing values ​​for each diopter state.

[0048] The values ​​of Numerical Examples 1 to 7 relating to the above-mentioned formulas (1) to (5) are shown in Table 1.

[0049] 2, 4, 6, 8, 10, 12, and 14 are diagrams showing the case where the diopter of the display optical system of Numerical Examples 1 to 7 is 0 m.-1 The diagrams show longitudinal aberration diagrams (spherical aberration, astigmatism, distortion, and chromatic aberration) for a given focal length of 100mm x 100mm. The vertical axis Fno of the spherical aberration diagram indicates the F-number, and the vertical axis ω of the astigmatism, distortion, and chromatic aberration diagrams indicates the half angle of view (half field of view: unit: °). The horizontal axis indicates the amount of each aberration. In the spherical aberration diagrams, the solid line indicates the spherical aberration at the d-line, and the two-dot chain line indicates the spherical aberration at the F-line. In the astigmatism diagrams, the solid line S indicates the astigmatism at the sagittal image plane, and the dashed line M indicates the astigmatism at the meridional image plane. The distortion diagrams show distortion at the d-line. The chromatic aberration diagrams show chromatic aberration of magnification at the F-line. EXAMPLES

[0050] The display optical system L of Example 1 (Numerical Example 1) shown in Figure 1 has a lens having a dispersion-controlled diffractive surface MOE, a meniscus lens Lm with its convex surface facing the observation side, and a positive lens Lp, arranged in order from the observation side to the display surface side. EXAMPLES

[0051] The display optical system L of Example 2 (Numerical Example 2) shown in Figure 3 has, arranged in order from the observation side to the display surface side, a positive lens Lp, a meniscus lens Lm with its convex surface facing the observation side, and a lens having a dispersion-controlled diffractive surface MOE. EXAMPLES

[0052] The display optical system L of Example 3 (Numerical Example 3) shown in Figure 5 has a lens having a dispersion-controlled diffractive surface MOE and a meniscus lens Lm with its convex surface facing the display surface side, arranged in order from the observation side to the display surface side. EXAMPLES

[0053] The display optical system L of Example 4 (Numerical Example 4) shown in Figure 7 has a lens having a dispersion-controlled diffractive surface MOE, a meniscus lens Lm with its convex surface facing the observation side, and a positive lens Lp, arranged in order from the observation side to the display surface side. EXAMPLES

[0054] The display optical system L of Example 5 (Numerical Example 5) shown in Figure 9 has a lens having a dispersion-controlled diffractive surface MOE, a meniscus lens Lm with its convex surface facing the observation side, and a positive lens Lp, arranged in order from the observation side to the display surface side. EXAMPLES

[0055] The display optical system L of Example 6 (Numerical Example 6) shown in Figure 11 has a lens having a dispersion-controlled diffractive surface MOE, a meniscus lens Lm with its convex surface facing the observation side, and a positive lens Lp, arranged in order from the observation side to the display surface side. EXAMPLES

[0056] The display optical system L of Example 7 (Numerical Example 7) shown in Figure 13 has a lens having a dispersion-controlled diffractive surface MOE, a meniscus lens Lm with its convex surface facing the observation side, and a positive lens Lp, arranged in order from the observation side to the display surface side.

[0057] In each embodiment, the optical path difference function of the dispersion-controlled diffractive surface may be realized by a metasurface in which the meta-atoms are arranged so as to calculate the phase delay amount of the meta-atoms for each wavelength and control the wavelength dispersion characteristics of the surface. The metasurface may be a so-called single-layer metasurface made of one layer, or a so-called stacked metasurface made of multiple layers. [Numerical example 1] Unit: mm At 0m-1 diopter focal length f=16.72 pupil diameter 10 Diagonal length of display surface: 9.98 Maximum image height: 4.99 Surface Data Surface number rd nd νd 1(EP)∞ 19.00 2∞0.80 1.49171 57.4 3 ∞ (variable) 4 ∞ 1.00 1.45867 67.9 5(diffraction) ∞ 0.50 6* 9.021 3.41 1.63400 23.9 7* 5.492 6.40 8* 21.184 2.76 1.53504 55.7 9 -18.659 (can be changed) 10 ∞ 0.50 1.52310 65.0 11 ∞ 4.00 12 ∞ 0.70 1.51680 64.2 13 ∞ (optional) Indicates surface∞ Aspheric surface Surface 5 (return surface) Design wavelength 0.58756 [μm] U 2=-2.53150e-02 U 4= 4.38151e-05 U 6=-4.61170e-08 Surface optical path difference dispersion λ unit [μm] P(λ)=0.58756 / λ P(λ d ) = 1.000000e+00 P(λ C ) = 8.952981e-01 P(λ F ) = 1.208640e+00 Page 6 K =-1.59289e+00 A 4= 5.17471e-05 A 6=-1.38686e-07 A 8= 7.83985e-10 Page 7 K =-9.99779e-01 A 4=-1.11333e-04 Page 8 K = 0.00000e+00 A 4=-4.72586e-05 A 6=-4.71393e-07 Variable interval 0m-1 -3 +1 -1 d 3 1.86 2.73 1.58 2.14 d 9 2.12 1.24 2.39 1.83 [Value example 2] Unit mm At 0m-1 diopter focal length f=16.0 pupil diameter 10 Diagonal length of image plane: 9.98 Maximum image height: 4.99 Surface Data Surface number rd nd νd 1(EP)∞ 19.00 2∞0.80 1.49171 57.4 3 ∞ (variable) 4* 21.783 3.83 1.51630 64.2 5 -36.536 3.72 6* 13.943 2.23 1.63400 23.9 7* 8.970 7.75 8 ∞ 1.00 1.45867 67.9 9 (diffraction) ∞ (variable) 10 ∞ 0.50 1.52310 65.0 11∞4.00 12 ∞ 0.70 1.51680 64.2 13 ∞ (variable) Display surface ∞ Aspheric Data Side 4 K =-8.93047e+00 A 4= 2.30097e-05 A 6=-5.57757e-07 A 8= 2.13321e-09 Side 6 K = 0.00000e+00 A 4= 2.02707e-05 Side 7 K =-5.74146e-01 A 4= 4.48809e-05 9th surface (diffraction surface) Design wavelength 0.58756 [μm] U 2=-3.85783e-02 U 4= 6.42238e-06 U 6=-1.21295e-07 Optical path difference dispersion of the surface λ unit [μm] P(λ)=0.58756 / λ P(λ d ) = 1.000000e+00 P(λ C ) = 8.952981e-01 P(λ F ) = 1.208640e+00 Variable interval 0m-1 -3 +1 -1 d 3 0.75 1.58 0.50 1.01 d 9 3.23 2.40 3.48 2.96 [Numerical example 3] Unit: mm At 0m-1 diopter focal length f=16.14 Pupil diameter 10 Diagonal length of display surface: 9.98 Maximum image height: 4.99 Surface Data Surface number rd nd νd 1(EP)∞ 19.00 2∞0.80 1.49171 57.4 3 ∞ (variable) 4 ∞ 1.00 1.50000 50.0 5(diffraction) ∞ 6.13 6* -16.036 5.65 1.53504 55.7 7* -11.106 (variable) 8 ∞ 0.50 1.52310 65.0 9∞4.00 10 ∞ 0.70 1.51680 64.2 11 ∞ (variable) Display surface ∞ Aspheric Data 5th surface (diffraction surface) Design wavelength 0.58756 [μm] U 2=-2.96405e-02 U 4= 4.04969e-05 U 6= 3.44237e-08 U 8= 2.14619e-09 Optical path difference dispersion of the surface λ unit [μm] P(λ)=0.58756 / λ P(λ d ) = 1.000000e+00 P(λ C ) = 8.952981e-01 P(λ F ) = 1.208640e+00 Side 6 K = 0.00000e+00 A 4= 4.18678e-04 A 6=-1.10551e-08 A 8=-1.19198e-10 Side 7 K = 0.00000e+00 A 4= 5.00954e-04 A 6= 9.64656e-09 A 8= 1.07173e-10 Variable interval 0m-1 -3 +1 -1 d 3 0.75 1.56 0.50 1.02 d 7 3.22 2.42 3.48 2.96 [Numerical example 4] Unit: mm At 0m-1 diopter focal length f=16.0 pupil diameter 10 Diagonal length of display surface: 9.98 Maximum image height: 4.99 Surface Data Surface number rd nd νd 1(EP)∞ 19.00 2∞0.80 1.49171 57.4 3 ∞ (variable) 4 ∞ 1.00 1.45867 67.9 5(diffraction) ∞ 0.50 6* 12.239 6.69 1.69053 23.7 7* 5.578 2.32 8* 10.203 6.52 1.61999 60.3 9 -13.936 (variable) 10 ∞ 0.50 1.52310 65.0 11∞4.00 12 ∞ 0.70 1.51680 64.2 13 ∞ (variable) Display surface ∞ Aspheric surface Surface 5 (return surface) Design wavelength 0.58756 [μm] U 2=-1.31462e-02 U 4= 2.61297e-05 U 6= 2.78964e-07 Surface optical path difference dispersion λ unit [μm] P(λ)=11.98025λ 10 -112.89592λ 9 +636.82770λ 8 -2386.30684λ 7 +6238.00928λ 6 -11608.78282λ 5 +15381.84501λ 4 -14223.52046λ 3 +8743.65017λ 2 -3216.93538λ+536.92283 P(λ d ) = 1.000000e+00 P(λ C ) = 9.012396e-01 P(λ F ) = 1.200604e+00 Page 6 K =-3.46571e+00 A 4= 6.60309e-05 A 6=-2.11974e-08 A 8=-2.01337e-09 Page 7 K =-1.83926e+00 A 4= 4.84614e-05 Page 8 K = 0.00000e+00 A 4=-3.80728e-04 A 6= 2.61749e-07 Variable interval 0m-1 -3 +1 -1 d 3 0.75 1.55 0.50 1.01 d 9 3.22 2.42 3.48 2.96 [Value example 5] Unit mm At 0m-1 diopter focal length f=16.75 pupil diameter 10 Diagonal length of display surface: 9.98 Maximum image height: 4.99 Surface Data Surface number rd nd νd 1(EP) ) ∞ 19.00 2∞0.80 1.49171 57.4 3 ∞ (variable) 4 ∞ 1.00 1.45867 67.9 5(diffraction) ∞ 0.50 6* 11.734 3.00 1.63400 23.9 7* 4.745 2.44 8 19.285 7.61 1.53504 55.7 9 -14.416 (variable) 10 ∞ 0.50 1.52310 65.0 11∞4.00 12 ∞ 0.70 1.51680 64.2 13 ∞ (variable) Display surface ∞ Aspheric Data 5th surface (diffraction surface) Design wavelength 0.58756 [μm] A 2=-3.49300e-02 A 4= 1.49066e-04 A 6=-2.69699e-07 Optical path difference dispersion of the surface λ unit [μm] P(λ)=24.42245λ 10 -295.85949λ 9 +1906.46259λ 8 -7762.66850λ 7 +21467.37098λ 6 -41580.67832λ 5 +56722.34999λ 4 -53578.32705λ 3 +33441.10472λ 2 -12429.40936λ+2086.06535 P(λ d ) = 1.000000e+00 P(λ C ) = 8.910070e-01 P(λ F ) = 1.221691e+00 Side 6 K =-5.53093e+00 A 4=-1.31491e-05 A 6= 1.60024e-06 A 8=-9.51399e-09 Side 7 K =-1.72196e+00 A 4= 6.65881e-05 Variable interval 0m-1 -3 +1 -1 d 3 0.78 1.65 0.50 1.06 d 9 3.20 2.33 3.48 2.91 [Numerical example 6] Unit: mm At 0m-1 diopter focal length f=16.0 pupil diameter 10 Diagonal length of display surface: 9.98 Maximum image height: 4.99 Surface Data Surface number rd nd νd 1(EP)∞ 19.00 2∞0.80 1.49171 57.4 3 ∞ (variable) 4 ∞ 1.00 1.45867 67.9 5(diffraction) ∞ 0.50 6* 14.639 8.39 1.84666 23.8 7* 6.623 1.74 8* 9.698 5.40 1.60375 60.9 9 -12.489 (variable) 10 ∞ 0.50 1.52310 65.0 11∞4.00 12 ∞ 0.70 1.51680 64.2 13 ∞ (variable) Indicates surface∞ Aspheric surface Surface 5 (return surface) Design wavelength 0.58756 [μm] U 2=-1.10948e-02 U 4= 6.84484e-06 U 6= 5.37528e-07 Surface optical path difference dispersion λ unit [μm] P(λ)=12.24651λ 10 -119.47397λ 9 +698.93882λ 8 -2720.50250λ 7 +7400.15195λ 6 -14357.23666λ 5 +19873.42249λ 4 -19240.92948λ 3 +12415.09163λ 2 -4807.95901λ+847.46800 P(λ d ) = 1.000000e+00 P(λ C ) = 9.061300e-01 P(λ F ) = 1.194903e+00 Page 6 K =-3.82019e+00 A 4= 4.72584e-05 A 6= 3.68312e-07 A 8=-4.49077e-09 Page 7 K =-1.74933e+00 A 4=-1.45945e-05 Page 8 K = 0.00000e+00 A 4=-4.52111e-04 A 6=-1.95257e-07 Variable interval 0m-1 -3 +1 -1 d 3 0.75 1.55 0.50 1.01 d 9 3.22 2.42 3.48 2.96 [Value example 7] Unit: mm At 0m-1 diopter focal length f=16.0 pupil diameter 10 Diagonal length of display surface: 9.98 Maximum image height: 4.99 Surface Data Surface number rd nd νd 1(EP)∞ 19.00 2∞0.80 1.49171 57.4 3 ∞ (variable) 4 ∞ 1.00 1.45867 67.9 5(diffraction) ∞ 0.50 6* 11.791 7.96 1.64001 23.8 7* 5.830 2.13 8* 9.726 5.94 1.61883 60.4 9 -14.252 (variable) 10 ∞ 0.50 1.52310 65.0 11∞4.00 12 ∞ 0.70 1.51680 64.2 13 ∞ (variable) Display surface ∞ Aspheric Data 5th surface (diffraction surface) Design wavelength 0.58756 [μm] U 2=-8.39149e-03 U 4= 1.05774e-05 U 6= 3.06101e-07 Optical path difference dispersion of the surface λ unit [μm] P(λ)=-434.73044λ 10 +8122.08910λ 9 -67394.74965λ 8 +329209.06586λ 7 -1049750.44998λ 6 +2284260.64803λ 5 -3435917.19850λ 4 +3528102.09277λ 3 -2367044.44179λ 2+937029.43952λ-166209.30017 P(λ d ) = 1.000000e+00 P(λ C ) = 9.218490e-01 P(λ F ) = 1.177334e+00 Side 6 K =-1.29514e+00 A 4=-4.01519e-05 A 6= 7.95368e-07 A 8=-8.07760e-09 Side 7 K =-1.36365e+00 A 4=-1.13348e-04 Side 8 K = 0.00000e+00 A 4=-3.52583e-04 A 6=-1.37849e-06 Variable interval 0m-1 -3 +1 -1 d 3 0.75 1.55 0.50 1.01 d 9 3.23 2.42 3.48 2.97

[0058] [Table 1]

[0059] [Display device] FIG. 15 shows the configuration of an imaging device (hereinafter simply referred to as a camera) 100 such as a digital camera or video camera equipped with an electronic viewfinder as a display device including the display optical system L of the first to seventh embodiments.

[0060] The camera 100 has an imaging optical system 101, an imaging element 102 such as a CCD sensor or a CMOS sensor that captures (photoelectrically converts) an image of a subject (not shown) through the imaging optical system 101, and an image processing unit 103 that generates image data using a signal output from the imaging element 102.

[0061] The image data generated by the image processing unit 103 is output to a display element 110 of the electronic viewfinder EVF. The display element 110 displays a subject image corresponding to the image data on a display surface IP.

[0062] The electronic viewfinder EVF is provided with an eyepiece optical system 111 configured with the display optical system L of any one of Examples 1 to 7. A user (observer) of the camera 100 can observe an enlarged subject image displayed on a display element 110 through the eyepiece optical system 111.

[0063] By using the display optical system L of Examples 1 to 7 as the eyepiece optical system 111, it is possible to observe a good subject image with little degradation in image quality due to various aberrations such as lateral chromatic aberration and astigmatism.

[0064] The display optical system L of the first to seventh embodiments can also be used in display devices other than electronic viewfinders, such as a head mounted display.

[0065] The above embodiment includes the following configurations.

[0066] (Configuration 1) A display optical system for displaying an image displayed on a display surface on a viewing side, a diffractive surface having controlled wavelength dispersion characteristics; The Abbe number of the diffractive surface is ν0, the reference wavelength is d-line, the primary dispersion is F-line and C-line, and the optical path difference function at each wavelength is ψ d , ψ F , ψ C , the optical path difference dispersion of the surface at each wavelength is P(λ d ), P(λ F ), P(λ C ) as

[0067]

number

[0068] When -0.2<1 / ν0<0.2 A display optical system characterized in that the following conditions are satisfied. (Configuration 2) 2. The display optical system according to configuration 1, comprising a refractive lens that does not have the diffractive surface. (Configuration 3) 3. The display optical system according to configuration 2, wherein the refractive lens is a meniscus lens. (Configuration 4) 4. The display optical system according to any one of configurations 1 to 3, comprising a positive lens having the diffractive surface. (Configuration 5) The focal length of the diffractive surface is fmoe, the focal length of the display optical system is f, the diffraction order of the diffractive surface is m, the design wavelength is λ0, the incident wavelength is λ, the optical path difference dispersion of the surface at the incident wavelength is P(λ), the optical path difference function of the surface at the reference wavelength is ψ0, and the second-order coefficient of the optical path difference function of the surface at the design wavelength is U2,

[0069]

number

[0070] When 0.7 <fmoe / f<4.0 5. The display optical system according to any one of configurations 1 to 4, which satisfies the following condition: (Configuration 6) When the focal length of the meniscus lens is fmenis and the focal length of the display optical system is f, -4 <fmenis / f<4 4. The display optical system according to configuration 3, which satisfies the following condition: (Configuration 7) The display optical system according to any one of configurations 1 to 6, comprising a positive lens arranged in order from the observation side to the display surface side, and a meniscus lens as a refractive lens not having the diffractive surface. (Configuration 8) The display optical system according to any one of configurations 1 to 7, wherein the diffractive surface has a planar shape. (Configuration 9) a lens having the diffractive surface; and a refractive lens that does not have the diffractive surface, Let OL be the distance on the optical axis between the lens having the diffractive surface and the refractive lens that is closest to the display surface and the farthest from the lens, and f be the focal length of the display optical system. 0.6 <OL / f<1.4 9. The display optical system according to any one of configurations 1 to 8, which satisfies the following condition: (Configuration 10) When the main dispersion of the diffractive surface is g-line and F-line, the Abbe number in the wavelength range below the F-line is ν 0,gF , d-line, g-line, and F-line optical path difference functions are ψ d , ψ g , ψ F , d-line, g-line, and F-line incident wavelengths are λ d , λ g , λ F As,

[0071]

number

[0072] When -0.02<1 / ν 0,gF <0.02 10. The display optical system according to any one of configurations 1 to 9, which satisfies the following condition: (Configuration 11) 11. The display optical system according to any one of configurations 1 to 10, wherein the lens having the diffractive surface and the refractive lens not having the diffractive surface are disposed adjacent to each other. (Configuration 12) a lens having the diffractive surface and a refractive lens not having the diffractive surface, 12. The display optical system according to any one of configurations 1 to 11, wherein diopter adjustment is performed by moving the lens having the diffractive surface and the refractive lens. (Configuration 13) A display optical system for displaying an image displayed on a display surface on a viewing side, A metasurface having controlled wavelength dispersion characteristics; The Abbe number of the metasurface is ν0, the reference wavelength is the d-line, the main dispersion is the F-line and the C-line, and the optical path difference function at each wavelength is ψ d , ψ F , ψ C , the optical path difference dispersion of the surface at each wavelength is P(λ d ), P(λ F ), P(λ C ) as

[0073]

number

[0074] When -0.2<1 / ν0<0.2 A display optical system characterized in that the following conditions are satisfied. (Configuration 14) A display optical system according to any one of configurations 1 to 13; and a display element having the display surface.

[0075] The embodiments described above are merely representative examples, and various modifications and alterations are possible for each embodiment when implementing the present invention. [Explanation of symbols]

[0076] SP Observation surface L Display optical system IP display surface MOE Diffractive Surface Lm Meniscus Lens

Claims

1. A display optical system for displaying an image displayed on a display surface on a viewing side, a diffractive surface having controlled wavelength dispersion characteristics; The Abbe number of the diffractive surface is ν ０ The reference wavelength is the d-line, the primary dispersion is the F-line and the C-line, and the optical path difference function at each wavelength is ψ ｄ , ψ Ｆ , ψ Ｃ , the optical path difference dispersion of the surface at each wavelength is P (λ ｄ ), P(λ Ｆ ), P(λ Ｃ ) as [0010] When -0.2<1 / n ０ <0.2 A display optical system characterized in that the following conditions are satisfied.

2. 2. The display optical system according to claim 1, further comprising a refractive lens that does not have the diffractive surface.

3. 3. The display optical system according to claim 2, wherein the refractive lens is a meniscus lens.

4. 2. The display optical system according to claim 1, further comprising a positive lens having the diffractive surface.

5. The focal length of the diffractive surface is fmoe, the focal length of the display optical system is f, the diffraction order of the diffractive surface is m, and the design wavelength is λ ０ , the incident wavelength is λ, the optical path difference dispersion of the surface at the incident wavelength is P(λ), and the optical path difference function of the surface at the reference wavelength is ψ ０ , the quadratic coefficient of the optical path difference function of the surface at the design wavelength is U ２ As, [0025] When 0.7<fmoe / f<4.0 2. The display optical system according to claim 1, wherein the following condition is satisfied:

6. When the focal length of the meniscus lens is f and the focal length of the display optical system is f, -4<fmenis / f<4 4. The display optical system according to claim 3, wherein the following condition is satisfied:

7. 2. The display optical system according to claim 1, comprising: a positive lens arranged in order from the observation side to the display surface side; and a meniscus lens serving as a refractive lens not having the diffractive surface.

8. 2. The display optical system according to claim 1, wherein the diffractive surface has a planar shape.

9. a lens having the diffractive surface; and a refractive lens that does not have the diffractive surface, Let OL be the distance on the optical axis between the surface closest to the display surface and the surface farthest from the surface of the lens having the diffractive surface and the surface of the refractive lens, and f be the focal length of the display optical system. 0.6<OL / f<1.4 2. The display optical system according to claim 1, wherein the following condition is satisfied:

10. When the main dispersion of the diffractive surface is g-line and F-line, the Abbe number in the wavelength range below the F-line is ν ０，ｇＦ , d-line, g-line, and F-line optical path difference functions are ψ ｄ , ψ ｇ , ψ Ｆ , d-line, g-line, and F-line incident wavelengths are λ ｄ , λ ｇ , λ Ｆ As, [0030] When -0.02<1 / n ０，ｇＦ <0.02 2. The display optical system according to claim 1, wherein the following condition is satisfied:

11. 2. The display optical system according to claim 1, wherein the lens having the diffractive surface and the refractive lens not having the diffractive surface are disposed adjacent to each other.

12. a lens having the diffractive surface and a refractive lens not having the diffractive surface, 2. The display optical system according to claim 1, wherein diopter adjustment is performed by moving said lens having said diffractive surface and said refractive lens.

13. A display optical system for displaying an image displayed on a display surface on a viewing side, A metasurface having controlled wavelength dispersion characteristics; The Abbe number of the metasurface is v ０ The reference wavelength is the d-line, the primary dispersion is the F-line and the C-line, and the optical path difference function at each wavelength is ψ ｄ , ψ Ｆ , ψ Ｃ , the optical path difference dispersion of the surface at each wavelength is P (λ ｄ ), P(λ Ｆ ), P(λ Ｃ ) as [0045] When -0.2<1 / n ０ <0.2 A display optical system characterized in that the following conditions are satisfied.

14. A display optical system according to any one of claims 1 to 13; and a display element having the display surface.

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