Display optical system and display device

Abstract

[Problem] To provide a display optical system capable of correcting lateral chromatic aberration and astigmatism. [Solution] This display optical system L for displaying, on a viewing side, an image shown on a display surface IP, comprises a diffractive surface MOE having controlled wavelength dispersion characteristics. The Abbe number ν0 of the diffractive surface satisfies the condition: -0.2 < 1 / ν0 < 0.2.

Description

Display optics and display devices

[0001] The present invention relates to a display optical system suitable for display devices such as electronic viewfinders.

[0002] As a display optical system for allowing an observer to view an image displayed on a display panel, there is a lens having a strong positive refractive power for magnified observation of the image, and a lens having a negative refractive power for correcting chromatic aberration and astigmatism caused by the positive refractive power. Patent Document 1 discloses a display optical system consisting of, in order from the observer side, a first lens having positive refractive power, a second meniscus-shaped lens having negative refractive power and a concave surface facing the display panel, and a third lens having positive refractive power. Patent Document 2 discloses a display optical system having two positive lenses, one negative lens, and a diffraction surface.

[0003] On the other hand, unlike conventional diffraction surfaces, a diffraction surface in which wavelength dispersion characteristics are controlled using a fine shape with a quarter-wavelength size is disclosed in Patent Document 3.

[0004] Japanese Patent Publication No. 2014-202770, Japanese Patent Publication No. 2020-154190, U.S. Patent No. 10,670,782

[0005] The display optical system disclosed in Patent Document 1 suffers from insufficient correction of chromatic aberration and astigmatism. Furthermore, while the display optical system disclosed in Patent Document 2 effectively corrects chromatic aberration by using a diffractive surface, it suffers from insufficient correction of astigmatism.

[0006] The present invention provides a display optical system that can correct chromatic aberration and astigmatism by using a diffraction surface with controlled wavelength dispersion characteristics.

[0007] One aspect of the present invention is a display optical system that displays an image on a display surface on the observation side. The display optical system includes a diffraction surface (or metasurface) with controlled wavelength dispersion characteristics. The Abbe number ν of the diffraction surface (or metasurface) ０ -0.2 < 1 / ν ０ It is characterized by satisfying the condition < 0.2. Abbe number ν ０This will be discussed later. Furthermore, a display device having the above-mentioned display optical system also constitutes another aspect of the present invention.

[0008] According to the present invention, by using a diffracting surface with controlled wavelength dispersion characteristics in the display optical system, chromatic aberration and astigmatism can be effectively corrected.

[0009] Cross-sectional view of the display optical system of Example 1. Aberration diagram of the display optical system of Example 1. Cross-sectional view of the display optical system of Example 2. Aberration diagram of the display optical system of Example 2. Cross-sectional view of the display optical system of Example 3. Aberration diagram of the display optical system of Example 3. Cross-sectional view of the display optical system of Example 4. Aberration diagram of the display optical system of Example 4. Cross-sectional view of the display optical system of Example 5. Aberration diagram of the display optical system of Example 5. Cross-sectional view of the display optical system of Example 6. Aberration diagram of the display optical system of Example 6. Cross-sectional view of the display optical system of Example 7. Aberration diagram of the display optical system of Example 7. Diagram showing an imaging device equipped with an electronic viewfinder including the display optical system of the example.

[0010] The embodiments of the present invention will be described below with reference to the drawings. First, before describing the specific embodiments 1 to 7, we will explain the matters common to each embodiment.

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

[0012] In each figure, the left side is the observation side (exit pupil side or eye point side), and the right side is the display surface side (object side or panel side). SP is the observation surface (exit pupil surface or eye point) where the observer positions their eye (pupil). MOE is a diffraction 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 diffraction surface MOE and a meniscus lens Lm.

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

[0014] The optical path difference function ψ of the diffraction surface with decentralized control, where m is the diffraction order, λ is the design wavelength of the diffraction surface ０ , λ is the incident wavelength, P(λ) is the optical path difference dispersion of the surface, and ψ is the optical path difference function of the surface at the design wavelength ０ can be defined as follows.

[0015]

[0016]

[0017] Note that the expression of the optical path difference function ψ of the surface at the design wavelength ０ For a rotationally symmetric surface with a high usage frequency, it is usually expressed as the following polynomial, where h is the distance from the optical axis.

[0018]

[0019] The focal length f_moe of the diffraction surface with decentralized control can be described as follows using the quadratic coefficient U of the optical path difference function of the surface at the design wavelength expressed as a polynomial ２

[0020]

[0021] When the reference wavelength of the diffraction surface with decentralized control is the d line (wavelength 587.6 nm), and the main dispersions are the F line (wavelength 486.1 nm) and the C line (wavelength 656.3 nm), the Abbe number ν ０ can be described as follows. Also, 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.

[0022]

[0023] When the reference wavelength of the diffraction surface with decentralized control is the d line, and the main 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 ＦThese are the optical path difference functions for the d-line, g-line, and F-line, respectively, and λ ｄ , λ ｇ , λ Ｆ These represent the incident wavelengths of the d-line, g-line, and F-line, respectively.

[0024]

[0025] In each embodiment, the diffraction order m is set to 1 because the first diffracted light is used for design. ０ The d-line is used as the incident wavelength when determining the focal length.

[0026] In each embodiment of the display optical system, it is assumed that a small display panel with a diagonal length of about 10 mm will be magnified for observation by the observer at a field of view of about 35 degrees. Magnified observation requires a strong positive refractive power. As a result, in the peripheral region away from the optical axis, large chromatic aberration and astigmatism occur as the height from the optical axis increases, degrading the optical performance. To improve such chromatic aberration and astigmatism, each embodiment of the display optical system places a lens with a dispersed and controlled diffraction plane (MOE) between the observation surface and the display surface. Since the wavelength dispersion characteristics of the diffraction plane (MOE) can be controlled to an arbitrary value, chromatic aberration can be effectively corrected. Furthermore, the diffraction plane (MOE) controls the direction of light propagation by diffraction, and since the Petzval term at the diffraction plane (MOE) is zero, astigmatism and field curvature of the display optical system can be effectively corrected.

[0027] Furthermore, since the display optical system as a whole requires a strong positive refractive power, it is desirable to use a dispersion-controlled diffraction surface (MOE) that has an aberration reduction effect as the positive refractive power surface. This suppresses the aberrations that occurred in conventional positive refractive power lenses (lenses that have refractive action rather than diffraction action), thus enabling the creation of a display optical system with well reduced aberrations.

[0028] Furthermore, with a dispersed-controllable diffraction plane (MOE) alone, spherical aberration and field curvature occur separately. As a result, peripheral field curvature is tilted relative to the best on-axis image plane, making it difficult to correct both on-axis and peripheral aberrations simultaneously. To further reduce aberrations effectively, it is necessary to correct field curvature, and for this purpose, it is desirable to have at least one refractive lens. In particular, by making the refractive lens a meniscus shape and arranging it adjacent to a lens having a dispersed-controllable diffraction plane (MOE), field curvature can be appropriately corrected.

[0029] Furthermore, it is desirable that the refractive power of the lens positioned closest to the observer be positive. By positioning the positive lens at a distance from the display surface, it becomes easier to secure a lens back (distance from the positive lens to the display surface) with a relatively weak refractive power, thereby suppressing the increase in aberrations. When a long lens back can be secured, the degree of freedom in positioning the meniscus lens Lm between the positive lens and the display surface increases, allowing the meniscus lens Lm to be positioned in a location suitable for aberration correction.

[0030] Furthermore, by moving the entire display optical system in the optical axis direction (observation side and display surface side) along with a lens having a dispersed diffraction surface and a meniscus lens, diopter adjustment with minimal performance degradation can be performed. Positive diopter correction can be performed by moving the display optical system towards the observation side, and negative diopter correction can be performed by moving it towards the display surface side.

[0031] Furthermore, it is desirable that the dispersed diffraction surface MOE has a planar shape. If the dispersed diffraction surface has curvature, it will function as a refractive surface. This is undesirable because a portion of the refractive force that should be generated by diffraction is shared with the refractive surface, reducing the effectiveness of wavelength dispersion control and Petzval reduction of the dispersed diffraction surface. Moreover, since the fine shape of the dispersed diffraction surface is created using semiconductor manufacturing processes, creating a curved surface for the fine shape becomes technically difficult and is therefore undesirable.

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

[0033] -0.2 < 1 / ν ０ <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, ν ０ fmoe is the Abbe number of the dispersion-controlled diffraction plane MOE when the reference wavelength is the d line and the principal dispersions are the F line and the C line. fmoe is the focal length of the dispersion-controlled diffraction plane 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 along the optical axis (distance between surface vertices) between the optical surface closest to the display surface and the optical surface furthest from the display surface among the optical surfaces included in the display optical system (optical surfaces of lenses and refractive lenses with dispersion-controlled diffraction planes). ０，ｇＦ This is the Abbe number in the short wavelength range below the F-line of the dispersion-controlled diffraction plane MOE, where the reference wavelength is the d-line and the main dispersions are the g-line and F-line.

[0034] The condition in equation (1) is the Abbe number ν of the dispersion-controlled diffraction plane MOE. ０ This indicates an appropriate range for achieving good chromatic aberration correction of the variance, which is the reciprocal of ν. 1 / ν ０ When the value falls below the lower limit of equation (1), the negative dispersion of the diffraction plane MOE increases, and the amount of chromatic aberration correction at the diffraction plane MOE increases. As a result, chromatic aberration becomes overcorrected throughout the entire display optical system, which is undesirable. 1 / ν ０ When this value exceeds the upper limit of equation (1), the positive dispersion of the diffraction plane MOE increases, and the amount of chromatic aberration correction at the diffraction plane MOE becomes small, similar to that of a normal refractive lens. As a result, chromatic aberration is undercorrected throughout the entire display optical system, which is undesirable.

[0035] The conditions in equation (2) indicate an appropriate range for good astigmatism correction of the focal length of the dispersed-controlled diffraction plane MOE. If fmoe / f falls below the lower limit of equation (2), the refractive power of the diffraction plane MOE is weak, and the effect of reducing astigmatism by diffraction is not sufficiently obtained, which is undesirable. Also, if fmoe / f exceeds the upper limit of equation (2), the refractive power of the diffraction plane MOE becomes strong, and the amount of tilt in the under-image direction increases. As a result, astigmatism occurs in proportion to this amount of tilt, increasing the astigmatism of the entire display optical system, which is undesirable.

[0036] The conditions in equation (3) indicate an appropriate range for good field curvature correction of the focal length of the meniscus lens Lm. If fmenis / f falls below the lower limit of equation (3), the negative refractive power of the meniscus lens Lm becomes strong, which is undesirable because it causes overcorrection of chromatic aberration and overcorrection of field curvature by the meniscus lens Lm. If it exceeds the upper limit of the fmenis / f equation, the positive refractive power of the meniscus lens Lm becomes strong, which is undesirable because it causes chromatic aberration and under-image field curvature.

[0037] The conditions in equation (4) indicate an appropriate range for good aberration correction of the total optical length of the display optical system L. If OL / f falls below the lower limit of equation (4), the total optical length becomes too short, reducing the lens spacing and the curvature of the optical surfaces, making it difficult to properly correct aberrations such as spherical aberration and field curvature, which is undesirable. If OL / f exceeds the upper limit of equation (4), the total optical length becomes too long, resulting in an unbalanced power distribution where the positive refractive power on the observation side is weak and the positive refractive power of the lens on the display side is strong. The increased refractive power of the lens on the display side causes various aberrations such as spherical aberration and field curvature, preventing good optical performance from being obtained, which is undesirable.

[0038] The condition in equation (5) is the Abbe number ν in the short wavelength range of the dispersion-controlled diffraction plane MOE. ０，ｇＦ This indicates an appropriate range for achieving good chromatic aberration correction of the variance, which is the reciprocal of 1 / ν. ０，ｇＦIf the value falls below the lower limit of equation (5), the negative dispersion of the diffraction plane MOE in the short-wavelength region becomes too large, resulting in a large chromatic aberration correction amount in the short-wavelength region at the diffraction plane MOE. As a result, the chromatic aberration of the entire display optical system in the short-wavelength region becomes overcorrected, which is undesirable. 1 / ν ０，ｇＦ If the value exceeds the upper limit of equation (5), the positive dispersion of the diffraction plane MOE in the short wavelength range becomes too large, resulting in insufficient correction of chromatic aberration in the entire display optical system, which is undesirable.

[0039] Furthermore, it is preferable to set the numerical ranges for equations (1) to (5) as follows.

[0040] -0.15 < 1 / ν ０ <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) Furthermore, it is even more preferable to set the numerical ranges of equations (1) to (5) as follows.

[0041] -0.10 < 1 / ν ０ <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) Examples 1 to 7 will be described in detail below. After the description of Example 7, numerical examples 1 to 7 corresponding to each of Examples 1 to 7 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 surfaces when counted from the observation (eyepoint EP) side, and r indicates the paraaxial radius of curvature of the i-th optical surface. d indicates the distance between the i-th surface and the (i+1)-th surface along the optical axis. nd and νd indicate the refractive index of the glass material between the i-th surface and the (i+1)-th surface at the d-line (wavelength 578.6 nm) and the Abbe number based on the d-line, respectively.

[0043] The Abbe number νd, with respect to the d-line, is given by νd = (Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices of the d-line, F-line (wavelength 486.1 nm), and C-line (wavelength 656.3 nm), respectively.

[0044] 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, K is the cone constant, and A4 to A8 are the aspherical coefficients. Note that the cone constant and the aspherical coefficients "e±M" are multiplied by 10⁻¹⁴. ±Ｍ It means...

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

[0046] ψ0 = U²h ２ +U4・h ４ +U6・h ６ +U8・h ８ The (diffraction) designation next to the surface number indicates a surface whose optical design has been performed using the surface's optical path difference function. The optical path difference dispersion P(λ) of the surface is expressed by an equation in which the incident wavelength λ is a variable. When calculating the optical path difference dispersion of the surface, the incident wavelength λ is calculated using the unit [μm].

[0047] In each numerical example, the plane spacing can be varied to adjust the diopter, and 0m －１ (Standard diopter), -3m －１ -1m －１ , +1m －１ For each diopter, the corresponding surface spacing and the variable surface spacing values ​​are shown.

[0048] Table 1 summarizes the values ​​related to equations (1) to (5) mentioned above for numerical examples 1 to 7.

[0049] Furthermore, Figures 2, 4, 6, 8, 10, 12, and 14 show the diopter of the display optical systems for numerical examples 1 to 7 as 0 m. －１ The diagrams show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) at the specified values. In the spherical aberration diagram, the vertical axis Fno represents the F number, and the vertical axis ω for astigmatism, distortion, and chromatic aberration represents the half-angle of view (half-field of view: in degrees). The horizontal axis represents the amount of each aberration. In the spherical aberration diagram, the solid line represents spherical aberration at line d, and the dashed line represents spherical aberration at line F. In the astigmatism diagram, the solid line S represents astigmatism at the sagittal image plane, and the dashed line M represents astigmatism at the meridional image plane. The distortion diagram shows distortion at line d. The chromatic aberration diagram shows lateral chromatic aberration at line F.

[0050] The display optical system L of Embodiment 1 (Numerical Example 1) shown in Figure 1 includes lenses with dispersed and controlled diffraction planes MOE arranged in order from the observation side to the display surface side, a meniscus lens Lm with a convex surface facing the observation side, and a positive lens Lp.

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

[0052] The display optical system L of Embodiment 3 (Numerical Example 3) shown in Figure 5 has lenses with dispersed and controlled diffraction planes MOE arranged sequentially from the observation side to the display surface side, and a meniscus lens Lm with a convex surface facing the display surface side.

[0053] The display optical system L of Embodiment 4 (Numerical Example 4) shown in Figure 7 includes lenses with dispersed and controlled diffraction planes MOE arranged in order from the observation side to the display surface side, a meniscus lens Lm with a convex surface facing the observation side, and a positive lens Lp.

[0054] The display optical system L of Embodiment 5 (Numerical Example 5) shown in Figure 9 includes lenses with dispersed and controlled diffraction planes MOE arranged in order from the observation side to the display surface side, a meniscus lens Lm with a convex surface facing the observation side, and a positive lens Lp.

[0055] The display optical system L of Embodiment 6 (Numerical Example 6) shown in Figure 11 includes lenses with dispersed and controlled diffraction planes MOE arranged in order from the observation side to the display surface side, a meniscus lens Lm with a convex surface facing the observation side, and a positive lens Lp.

[0056] The display optical system L of Embodiment 7 (Numerical Example 7) shown in Figure 13 includes lenses with dispersed and controlled diffraction planes MOE arranged in order from the observation side to the display surface side, a meniscus lens Lm with a convex surface facing the observation side, and a positive lens Lp.

[0057] In each embodiment, the optical path difference function of the dispersion-controlled diffraction surface may be realized by calculating the phase delay amount of the metaatoms for each wavelength and arranging the metaatoms to control the wavelength dispersion characteristics of the surface using a metasurface. Furthermore, the metasurface may be a so-called single-layer metasurface consisting of one layer, or a so-called stacked metasurface consisting of multiple layers.[Numerical Example 1] Unit: mm Focal length f=16.72 at 0m-1 diopter 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 (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=-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 ) = 1.0000e+00 P(λC ) = 8.9530e-01 P(λ F) = 1.2086e+00 Face 6 K = -1.59289e+00 A 4 = 5.17471e-05 A 6 = -1.38686e-07 A 8 = 7.83985e-10 Face 7 K = -9.99779e-01 A 4 = -1.11333e-04 Face 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 [Numerical example 2] Unit: mm At diopter 0m-1, focal length f=16.0, pupil diameter 10, diagonal length of image plane 9.98, maximum image height 4.99. Plane data: Plane 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) Represents surface ∞ Aspherical data 4th surface K = -8.93047e+00 A4 = 2.30097e-05 A6 = -5.57757e-07 A8 = 2.13321e-09 6th surface K = 0.00000e+00 A4 = 2.02707e-05 7th surface K = -5.74146e-01 A4 = 4.48809e-05 9th surface (reflection surface) Design wavelength 0.58756 [μm] U2 = -3.85783e-02 U4 = 6.42238e-06 U 6 = -1.21295e-07 Surface optical path difference dispersion λ unit [μm] P(λ) = 0.58756 / λ P(λ). d ) = 1.0000e+00 P(λ C ) = 8.9530e-01 P(λ F) = 1.2086e+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 Focal length f=16.14 at 0m-1 diopter 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 ∞ Aspherical 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.The optical path difference dispersion of the 14619e-09 surface is λ unit [μm] P(λ)=0.58756 / λ P(λ). d ) = 1.0000e+00 P(λ C ) = 8.9530e-01 P(λ F) = 1.2086e+00 6th face K = 0.00000e+00 A 4 = 4.18678e-04 A 6 = -1.10551e-08 A 8 = -1.19198e-10 7th face 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 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 ∞ (changeable) Represents surface ∞ Aspherical data 5th surface (reflection surface) Design wavelength 0.58756 [μm] U 2=-1.31462e-02 U 4= 2.61297e-05 U 6= 2.78964e-07 Optical path difference dispersion λ unit [μm] P(λ)= 536.92283λ. 10 -3216.93538λ 9 +8743.65017λ 8 -14223.52046λ 7 +15381.84501λ 6 -11608.78282λ 5 +6238.00928λ 4 -2386.30684λ 3 +636.82770λ 2 -112.89592λ+11.98025 P(λ d ) = 1.0000e+00 P(λ C ) = 9.0124e-01 P(λ F) = 1.2006e+00 Face 6 K = -3.46571e+00 A 4 = 6.60309e-05 A 6 = -2.11974e-08 A 8 = -2.01337e-09 Face 7 K = -1.83926e+00 A 4 = 4.84614e-05 Face 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 [Numerical example 5] Unit: mm At diopter 0m-1, 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 ∞ (changeable) Represents surface ∞ Aspherical data 5th surface (reflection surface) Design wavelength 0.58756 [μm] A 2=-3.49300e-02 A 4= 1.49066e-04 A 6=-2.69699e-07 Surface optical path difference dispersion λ unit [μm] P(λ)= 2086.06535λ. 10 -12429.40936λ 9 +33441.10472λ 8 -53578.32705λ 7 +56722.34999λ 6 -41580.67832λ 5 +21467.37098λ 4 -7762.66850λ 3 +1906.46259λ 2 -295.85949λ+24.42245 P(λ d ) = 1.0000e+00 P(λ C ) = 8.9101e-01 P(λ F) = 1.2217e+00 6th face K = -5.53093e+00 A 4 = -1.31491e-05 A 6 = 1.60024e-06 A 8 = -9.51399e-09 7th face 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 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 ∞ (changeable) Represents surface ∞ Aspherical data 5th surface (reflection surface) Design wavelength 0.58756 [μm] U 2=-1.10948e-02 U 4= 6.84484e-06 U 6= 5.37528e-07 Optical path difference dispersion λ unit [μm] P(λ)= 847.46800λ. 10 -4807.95901λ 9 +12415.09163λ 8 -19240.92948λ 7 +19873.42249λ 6 -14357.23666λ 5 +7400.15195λ 4 -2720.50250λ 3 +698.93882λ 2 -119.47397λ+12.24651 P(λ d ) = 1.0000e+00 P(λ C ) = 9.0613e-01 P(λ F) = 1.1949e+00 6th face K = -3.82019e+00 A 4 = 4.72584e-05 A 6 = 3.68312e-07 A 8 = -4.49077e-09 7th face K = -1.74933e+00 A 4 = -1.45945e-05 8th face 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 [Numerical example 7] Unit: mm At diopter 0m-1, 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 ∞ (changeable) Represents surface ∞ Aspherical data 5th surface (reflection surface) Design wavelength 0.58756 [μm] U 2=-8.39149e-03 U 4= 1.05774e-05 U 6= 3.06101e-07 Surface optical path difference dispersion λ unit [μm] P(λ)=-166209.30017λ. 10 +937029.43952λ 9 -2367044.44179λ 8 +3528102.09277λ 7 -3435917.19850λ 6 +2284260.64803λ 5 -1049750.44998λ 4 +329209.06586λ 3 -67394.74965λ 2 +8122.08910λ-434.73044 P(λ d ) = 1.0000e+00 P(λ C ) = 9.2185e-01 P(λ F = 1.1773e+00 6th face K = -1.29514e+00 A 4 = -4.01519e-05 A 6 = 7.95368e-07 A 8 = -8.07760e-09 7th face K = -1.36365e+00 A 4 = -1.13348e-04 8th face K = 0.00000e+00 A 4 = -3.52583e-04 A 6 = -1.37849e-06 Changeable 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]

[0059] [Display Device] Figure 15 shows the configuration of an imaging device (hereinafter simply referred to as "camera") 100, such as a digital camera or video camera, which is equipped with an electronic viewfinder as a display device, including the display optical system L of Examples 1 to 7.

[0060] The camera 100 includes an imaging optical system 101, an image sensor 102 such as a CCD sensor or CMOS sensor that captures (photoelectrically converts) an unshown subject through the imaging optical system 101, and an image processing unit 103 that generates image data using the signal output from the image sensor 102.

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

[0062] The electronic viewfinder (EVF) is provided with an eyepiece optical system 111, which is composed of a display optical system L from any of the embodiments 1 to 7. The user (observer) of the camera 100 can magnify and observe the subject image displayed on the display element 110 through the eyepiece optical system 111.

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

[0064] Furthermore, the display optical system L in Examples 1 to 7 can also be used in display devices other than electronic viewfinders, such as head-mounted displays.

[0065] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention.

Claims

1. A display optical system for displaying an image on a display surface on an observation side, comprising a diffraction surface with controlled wavelength dispersion characteristics, wherein the Abbe number of the diffraction surface is ν ０ Let the reference wavelength be the d-line, the principal dispersion be the F-line and the 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, When this is the case, -0.2 < 1 / ν ０ A display optical system characterized by satisfying the condition < 0.

2.

2. The display optical system according to claim 1, characterized in that it includes a refractive lens that does not have the diffraction surface.

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

4. The display optical system according to any one of claims 1 to 3, characterized in that it includes a positive lens having the diffraction surface.

5. Let the focal length of the diffractive surface be \(f_{moe}\), the focal length of the display optical system be \(f\), the diffraction order on the diffractive surface be \(m\), and the design wavelength be \(\lambda\). ０ Let the incident wavelength be \(\lambda\), the wavefront optical path difference dispersion at this incident wavelength be \(P(\lambda)\), and the wavefront optical path difference function at the reference wavelength be \(\psi\). ０ Let the second-order coefficient of the wavefront optical path difference function at the design wavelength be \(U\). ２ Then, When it is as such, the display optical system according to any one of claims 1 to 4, characterized in that it satisfies the condition \(0.7 < f_{moe} / f < 4.0\).

6. The display optical system according to claim 3, characterized in that, when the focal length of the meniscus lens is fmenis and the focal length of the display optical system is f, the condition -4 < fmenis / f < 4 is satisfied.

7. The display optical system according to any one of claims 1 to 6, characterized in that it includes positive lenses arranged sequentially from the observation side to the display surface side, and a meniscus lens as a refractive lens that does not have a diffraction surface.

8. The display optical system according to any one of claims 1 to 7, characterized in that the diffraction surface has a planar shape.

9. A display optical system according to any one of claims 1 to 8, comprising a lens having a diffraction surface and a refractive lens not having a diffraction surface, wherein when OL is the distance on the optical axis between the surface of the lens having a diffraction surface and the surface of the refractive lens closest to the display surface and the surface furthest from the display surface, and the focal length of the display optical system is f, the condition 0.6 < OL / f < 1.4 is satisfied.

10. 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 of 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 respectively λ ｄ , λ ｇ , λ Ｆ as, When this is the case, -0.02 < 1 / ν ０，ｇＦ The display optical system according to any one of claims 1 to 9, characterized in that it satisfies the condition of <0.

02.

11. The display optical system according to any one of claims 1 to 10, characterized in that the lens having the diffraction surface and the refractive lens not having the diffraction surface are arranged adjacent to each other.

12. The display optical system according to any one of claims 1 to 11, comprising a lens having a diffraction surface and a refractive lens not having a diffraction surface, characterized in that diopter adjustment is performed by moving the lens having a diffraction surface and the refractive lens.

13. A display optical system for displaying an image on a display surface on the observation side, comprising a metasurface with controlled wavelength dispersion characteristics, wherein the Abbe number of the metasurface is ν ０ Let the reference wavelength be the d-line, the principal dispersion be the F-line and the 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, When this is the case, -0.2 < 1 / ν ０ A display optical system characterized by satisfying the condition < 0.

2.

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

Images