Display optical system and display device

Abstract

The invention relates to a display optical system and a display device. The display optical system includes a diffractive surface having controlled wavelength dispersion characteristics. A predetermined inequality is satisfied.

Description

Technical Field

[0001] One of the aspects of the embodiments relates to a display optical system suitable for a display device such as an electronic viewfinder (EVF). Background Art

[0002] A display optical system configured to enable an observer to observe an image displayed on a display panel includes a lens with a strong positive refractive power for enabling the observer to observe an enlarged image, and a lens with a negative refractive power for correcting chromatic aberration and astigmatism caused by the positive refractive power. Japanese Patent Laid-Open No. 2014-202770 discloses a display optical system, which includes, from the observer side, a first lens with a positive refractive power, a second lens with a meniscus shape having a negative refractive power and a concave surface facing the display panel side, and a third lens with a positive refractive power. Japanese Patent Laid-Open No. 2020-154190 discloses a display optical system having two positive lenses, one negative lens, and a diffraction surface.

[0003] US Patent No. 10670782 discloses a diffractive surface different from the conventional diffractive surface in which wavelength dispersion characteristics are controlled using a minute shape of a quarter wavelength size.

[0004] The display optical system disclosed in Japanese Patent Laid-Open No. 2014-202770 is insufficient to correct lateral chromatic aberration and astigmatism. The display optical system disclosed in Japanese Patent Laid-Open No. 2020-154190 is sufficient to correct lateral chromatic aberration using a diffractive surface, but is insufficient to correct astigmatism. Summary of the invention

[0005] The display optical system according to one aspect of the present disclosure is configured to display an image displayed on a display surface on the viewing side. The display optical system includes a diffractive surface (or metasurface) having controlled wavelength dispersion characteristics. The following equation is satisfied:

[0006]

[0007] where ν 0 is the Abbe number of the diffractive surface (or metasurface), the reference wavelength is the d-line, the main dispersion is the F-line and the C-line, ψ d , F , and ψ C are the optical path difference functions for the d-line, F-line, and C-line, respectively, d , F , and λ C are the incident wavelengths of the d-line, F-line, and C-line, respectively, P(λ d ), P(λ F), and P(λ C ) are the optical path difference dispersions of the surfaces for the d-line, F-line, and C-line, respectively, and the following inequality is satisfied:

[0008] -0.2<1 / ν 0 <0.2.

[0009] A display device having the above display optical system also constitutes another aspect of the present disclosure.

[0010] Further features of various embodiments of the present disclosure will become apparent from the following description of the embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a cross-sectional view of a display optical system according to Example 1.

[0012] Figure 2 2 is an aberration diagram of the display optical system according to Example 1.

[0013] Figure 3 is a cross-sectional view of a display optical system according to Example 2.

[0014] Figure 4 2 is an aberration diagram of the display optical system according to Example 2.

[0015] Figure 5 is a cross-sectional view of a display optical system according to Example 3.

[0016] Figure 6 : is an aberration diagram of the display optical system according to Example 3.

[0017] Figure 7 is a cross-sectional view of a display optical system according to Example 4.

[0018] Figure 8 : is an aberration diagram of the display optical system according to Example 4.

[0019] Fig. 9 is a cross-sectional view of a display optical system according to Example 5.

[0020] Fig.10 : is an aberration diagram of the display optical system according to Example 5.

[0021] Fig.11 is a cross-sectional view of a display optical system according to Example 6.

[0022] Fig.12 : is an aberration diagram of the display optical system according to Example 6.

[0023] Fig.13 is a cross-sectional view of a display optical system according to Example 7.

[0024] Fig.14 : is an aberration diagram showing the optical system according to Example 7.

[0025] Fig.15 An image pickup apparatus having an electronic viewfinder including the display optical system according to this example is illustrated. DETAILED DESCRIPTION

[0026] Referring now to the drawings, a description will be given of an embodiment according to the present disclosure. Before describing specific examples 1 to 7, a description will now be given of matters common to each example.

[0027] Figure 1 , 3 , 5, 7, 9, 11, and 13 respectively illustrate configurations of display optical systems L according to Examples 1 to 7. The display optical system L according to each example is used for an electronic viewfinder (EVF) of an image pickup device such as a digital camera or a video camera.

[0028] 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 represents the observation surface (exit pupil plane or eye point) where the observer places his eye (pupil). MOE is a diffraction surface with controlled wavelength dispersion characteristics (hereinafter referred to as dispersion controlled), and Lm is a meniscus lens. IP is a display surface of a display element. The display element includes a liquid crystal panel, an organic EL element, etc. The display optical system L includes at least a diffraction surface MOE and a meniscus lens Lm.

[0029] CG1 is the first cover glass that prevents dirt and dust from entering the display optical system from the viewing side. CG2 is the second cover glass that prevents dirt and dust from adhering to the display surface.

[0030] The optical path difference function ψ of a dispersion-controlled diffractive surface can be defined as follows:

[0031]

[0032]

[0033] Where m is the diffraction order, λ 0 is the design wavelength of the diffractive surface, λ is the incident wavelength, P(λ) is the optical path difference dispersion of the surface, and ψ 0 is the optical path difference function of the surface at the design wavelength.

[0034] In the case where the surface is a frequently used rotationally symmetric surface, the optical path difference function ψ0 of the surface at the design wavelength is usually expressed by the following polynomial:

[0035] ψ 0 =U2 h 2 +U 4 h 4 +U 6 h 6 +…

[0036] where h is the distance from the optical axis.

[0037] The focal length f of the dispersion-controlled diffractive surface moe The quadratic coefficient U of the optical path difference function of the surface at the design wavelength expressed by the polynomial 2 The following expression:

[0038]

[0039] Assume that the reference wavelength of the dispersion-controlled diffraction 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). Then, the Abbe number ν 0 can be written as follows:

[0040]

[0041] where ψ d , F and ψ C are the optical path difference functions for the d-line, F-line, and C-line, respectively, and λ d , F and λ C denote the incident wavelengths for the d-line, F-line and C-line, respectively.

[0042] Assume that the reference wavelength of the dispersion-controlled diffraction surface is the d line, and the main dispersion is the g line (wavelength 435.8 nm) and the F line. Then, the Abbe number v in the short wavelength range below the F line is 0，gF can be expressed as follows:

[0043]

[0044] where ψ d , g and ψ F are the optical path difference functions for the d-line, g-line, and F-line, respectively, and λ d , g and λ F denote the incident wavelengths for the d-line, g-line and F-line, respectively.

[0045] Each example uses the first-order diffracted light for design, so the diffraction order m is set to 1. 0 and focal length, the d-line is used as the incident wavelength.

[0046] In the display optical system according to each example, it is assumed that the observer observes a small display panel with a diagonal length of about 10 mm at a field angle of about 35 degrees when observing the magnified image. A strong positive refractive power is used to observe the magnified image. As a result, the optical performance deteriorates in the peripheral area away from the optical axis because large lateral chromatic aberration and astigmatism occur as the height from the optical axis increases. In order to improve such lateral chromatic aberration and astigmatism, a lens with a dispersion-controlled diffraction surface MOE is placed between the observation surface and the display surface according to the display optical system of each example. The diffraction surface MOE can control the wavelength dispersion characteristics to an arbitrary value, so the lateral chromatic aberration can be effectively corrected. The diffraction surface MOE controls the direction of light travel by diffraction, and can effectively correct the lateral chromatic aberration. Since the Petzval term in the diffraction surface MOE is zero, the astigmatism and field curvature of the display optical system can be satisfactorily corrected.

[0047] The display optical system has an overall strong positive refractive power, so for the surface with positive refractive power, a dispersion-controlled diffractive surface MOE with an aberration reduction effect can be used. Thus, aberrations that would otherwise occur due to a refractive lens with positive refractive power (a lens with a refractive effect rather than a diffractive effect) can be suppressed, and a display optical system with satisfactorily reduced aberrations can be obtained.

[0048] For a single dispersion-controlled diffractive surface MOE, spherical aberration and field curvature occur in a deviated manner. Therefore, the field curvature of the periphery is inclined relative to the best image plane on the optical axis, and it becomes difficult to correct both the on-axis aberration and the peripheral aberration at the same time. In order to effectively reduce the aberration, the field curvature is corrected, and for this purpose, at least one refractive lens may be provided.

[0049] In particular, the refractive lens has a meniscus shape and is disposed adjacent to the lens having the dispersion-controlled diffractive surface MOE. Thus, the field curvature can be appropriately corrected.

[0050] The lens placed closest to the observer may have positive refractive power. By placing the positive lens at a position away from the display surface, it becomes easier to ensure the lens rear (the distance from the positive lens to the display surface) with relatively weak refractive power, and the increase of aberrations can be suppressed. In the case where a long lens rear 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.

[0051] 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 the dispersion controlled diffractive surface and the meniscus lens can perform diopter adjustment with little performance degradation. Moving the display optical system toward the observation side can provide positive diopter correction, and moving it toward the display surface side can provide negative diopter correction.

[0052] The dispersion controlled diffraction surface MOE can have a planar shape. The dispersion controlled diffraction surface with curvature is used as a refractive surface. Thus, a part of the refractive power to be generated by diffraction in the dispersion controlled diffraction surface is shared by the refractive surface, and the wavelength dispersion control and Petzval reduction effects of the dispersion controlled diffraction surface are reduced. In addition, since the fine shape of the dispersion controlled diffraction surface is created using a semiconductor manufacturing process, it is technically difficult to create a fine shape on a curved surface.

[0053] Each example can provide a display optical system L in which lateral chromatic aberration and astigmatism are satisfactorily corrected by appropriately setting the Abbe number and focal length of the dispersion-controlled diffraction surface MOE, the focal length of the meniscus lens Lm, and the total length of the display optical system L. More specifically, it is preferable that at least one of the following inequalities (1) to (5) is satisfied:

[0054] -0.2<1 / ν 0 <0.2 (1)

[0055] 0.7<f moe / f<4.0 (2)

[0056] -4<fmenis / f<4 (3)

[0057] 0.6<OL / f<1.4 (4)

[0058] -0.02<1 / ν 0，gF <0.02 (5)

[0059] In the above inequality, ν 0 is the Abbe number of the MOE of the dispersion-controlled diffraction surface when the reference wavelength is the d-line and the main dispersion is the F-line and C-line. moe 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 surface closest to the display surface and the optical surface farthest from the display surface among the optical surfaces (optical surfaces of the refractive lens and the lens with the dispersion controlled diffractive surface) included in the display optical system. ν 0，gFIt is the Abbe number in the short wavelength range below the F-line of the dispersion-controlled diffraction surface MOE when the reference wavelength is the d-line and the main dispersion is the g-line and the F-line.

[0060] Inequality (1) defines the Abbe number ν as the MOE of a dispersion-controlled diffractive surface: 0 The reciprocal of the appropriate range for correction of lateral chromatic aberration of dispersion. 0 When the value becomes lower than the lower limit of inequality (1), the negative dispersion of the diffraction surface MOE increases, and the amount of chromatic aberration correction of the diffraction surface MOE increases. As a result, chromatic aberration is overcorrected in the entire display optical system. 0 When the upper limit of inequality (1) is exceeded, the positive dispersion of the diffractive surface MOE increases, and the chromatic aberration correction amount of the diffractive surface MOE decreases like a normal refractive lens. As a result, chromatic aberration is undercorrected in the entire display optical system.

[0061] Inequality (2) defines the appropriate range of focal lengths of dispersion-controlled diffractive surfaces MOE for astigmatism correction. moe In the case where / f becomes lower than the lower limit of inequality (2), the refractive power of the diffractive surface MOE becomes weak and the effect of reducing astigmatism caused by diffraction becomes insufficient. moe When / f becomes higher than the upper limit of inequality (2), the refractive power of the diffractive surface MOE becomes strong and the tilt amount of the image plane toward the undercorrection side increases. As a result, large astigmatism occurs according to the tilt amount, and the astigmatism of the entire display optical system increases.

[0062] Inequality (3) defines an appropriate range of the focal length of the meniscus lens Lm for field curvature correction. In the case where fmenis / f becomes lower than the lower limit of inequality (3), the negative refractive power of the meniscus lens Lm becomes stronger, and the meniscus lens Lm causes overcorrection of field curvature and lateral chromatic aberration on the overcorrection side. In the case where fmenis / f becomes higher than the upper limit of the formula, the positive refractive power of the meniscus lens Lm becomes stronger, and causes field curvature and lateral chromatic aberration on the undercorrection side.

[0063] Inequality (4) defines an appropriate range of the total optical length of the display optical system L for aberration correction. When OL / f becomes lower than the lower limit of inequality (4), the total optical length becomes too short, and the lens spacing, the curvature of the optical surface decreases, and it becomes difficult to properly correct various aberrations, such as spherical aberration and field curvature. When OL / f becomes higher than the upper limit of inequality (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. The strong refractive power of the lens on the display surface side produces various aberrations, such as spherical aberration and field curvature, and it becomes difficult to obtain excellent optical performance.

[0064] Inequality (5) defines the Abbe number v in the short wavelength region as the dispersion-controlled diffraction surface MOE 0，gF The reciprocal of the appropriate range for correction of lateral chromatic aberration of dispersion. 0，gF When the value becomes lower than the lower limit of inequality (5), the negative dispersion in the short wavelength region of the diffractive surface MOE becomes too large, and the chromatic aberration correction amount of the diffractive surface MOE in the short wavelength region becomes large. As a result, the chromatic aberration in the short wavelength region of the entire display optical system becomes overcorrected. 0，gF When the upper limit of inequality (5) becomes higher, the positive dispersion in the short wavelength region of the diffractive surface MOE becomes too large, and the chromatic aberration of the entire display optical system becomes undercorrected.

[0065] Inequalities (1) to (5) can be replaced by the following inequalities (1a) to (5a):

[0066] -0.15<1 / ν 0 <0.10 (1a)

[0067] 0.75<f moe / f<3.90 (2a)

[0068] -3.7<frmenis / f<3.7 (3a)

[0069] 0.65<OL / f<1.30 (4a)

[0070] -0.015<1 / ν 0，gF <0.015 (5a)

[0071] Inequalities (1) to (5) can be replaced by the following inequalities (1b) to (5b):

[0072] -0.10<1 / ν 0 <0.03 (1b)

[0073] 0.8<fmoe / f<3.8 (2b)

[0074] -3.2<fmenis / f<3.2 (3b)

[0075] 0.7<OL / f<1.2 (4b)

[0076] -0.01<1 / ν 0，gF <0.01 (5b)

[0077] A detailed description will now be given of Examples 1 to 7. Following the description according to Example 7, descriptions of Numerical Examples 1 to 7 corresponding to Examples 1 to 7, respectively, will be given.

[0078] In each numerical example, the diagonal length of the display surface is twice as long as the maximum image height. Surface number i represents the order of the optical surface counted from the observation (eye point EP) side, and r represents the paraxial curvature radius of the i-th optical surface. d represents the interval (distance or spacing) on ​​the optical axis between the i-th surface and the (i+1)-th surface. nd and νd represent the refractive index of the glass material between the i-th surface and the (i+1)-th surface for the d-line (wavelength 578.6nm) and the Abbe number based on the d-line, respectively.

[0079] The Abbe number νd based on the d-line is expressed as follows:

[0080] νd=(Nd-1) / (NF-NC)

[0081] Here, Nd, NF, and NC are refractive indices for d-line, F-line (wavelength 486.1 nm), and C-line (wavelength 656.3 nm).

[0082] An asterisk "*" next to a surface number means that the surface has an aspherical shape. The aspherical shape is expressed by the following equation:

[0083] x=(h 2 / R) / [1+{1-(1+K)(h / R) 2} 1 / 2 ]+A4·h 4 +A6·h 6 +A8·h 8

[0084] Where x is the displacement from the surface vertex in the direction of the optical axis, h is the height from the optical axis in the direction orthogonal to the optical axis, the light travel direction is set to be positive, R is the paraxial curvature radius, K is the cone constant, and A4 to A8 are aspheric coefficients. "e±M" in the cone constant and aspheric coefficient means ×10 ±M .

[0085] The optical path difference function of the surface at the design wavelength is expressed by the following expression:

[0086] ψ0=U2·h 2 +U4·h 4 +U6·h 6 +U8·h 8

[0087] Where U2 to U8 are the optical path difference function coefficients of the surface.

[0088] (Diffraction) attached to the surface number indicates that the surface was optically designed using the optical path difference function of the surface. The optical path difference dispersion P(λ) of a surface is expressed by an equation with 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].

[0089] Each numerical example makes the surface distance variable for diopter adjustment, and for 0m -1 (standard diopter), -3m -1 、-1m -1 , and +1m -1 Each diopter state of illustrates the corresponding surface distance and the value of the variable surface distance.

[0090] Table 1 summarizes the values ​​associated with inequalities (1) to (5) in Numerical Examples 1 to 7.

[0091] Figure 2 , Figure 4 , Figure 6 , Figure 8 , Fig.10 , Fig.12 and Fig.14 The figure shows the diopter at 0m -1 Longitudinal aberration diagrams (spherical aberration, astigmatism, distortion, and chromatic aberration) of the display optical system according to numerical examples 1 to 7 under the condition of . The vertical axis Fno of the spherical aberration diagram represents the F number, and the vertical axis ω of each of the astigmatism, distortion, and chromatic aberration diagrams represents the half angle of view (half field of view angle: unit: °). The horizontal axis indicates the aberration amount of each aberration. In the spherical aberration diagram, the solid line indicates the spherical aberration amount of the d-line, and the alternating one long and two short dashed lines indicate the spherical aberration amount of the F-line. In the astigmatism diagram, the solid line S indicates the astigmatism amount on the sagittal image plane, and the dashed line M indicates the astigmatism amount on the meridional image plane. The distortion aberration diagram illustrates the distortion amount of the d-line. The chromatic aberration diagram illustrates the lateral chromatic aberration amount of the F-line.

[0092] Example 1

[0093] Figure 1The display optical system L according to Example 1 (Numerical Example 1) shown in includes, in order from the observation side to the display surface side, a lens having a dispersion-controlled diffraction surface MOE, a meniscus lens Lm having a convex surface facing the observation side, and a positive lens Lp.

[0094] Example 2

[0095] Figure 3 The display optical system L according to Example 2 (Numerical Example 2) shown in includes, in order from the observation side to the display surface side, a positive lens Lp, a meniscus lens Lm having a convex surface facing the observation side, and a lens having a dispersion-controlled diffraction surface MOE.

[0096] Example 3

[0097] Figure 5 The display optical system L according to Example 3 (Numerical Example 3) shown in includes, in order from the observation side to the display surface side, a lens having a dispersion-controlled diffraction surface MOE and a meniscus lens Lm having a convex surface facing the display surface side.

[0098] Example 4

[0099] Figure 7 The display optical system L according to Example 7 (Numerical Example 4) shown in includes, in order from the observation side to the display surface side, a lens having a dispersion-controlled diffraction surface MOE, a meniscus lens Lm having a convex surface facing the observation side, and a positive lens Lp.

[0100] Example 5

[0101] Fig. 9 The display optical system L according to Example 5 (Numerical Example 5) shown in includes, in order from the observation side to the display surface side, a lens having a dispersion-controlled diffraction surface MOE, a meniscus lens Lm having a convex surface facing the observation side, and a positive lens Lp.

[0102] Example 6

[0103] Fig.11 The display optical system L according to Example 6 (Numerical Example 6) shown in includes, in order from the observation side to the display surface side, a lens having a dispersion-controlled diffraction surface MOE, a meniscus lens Lm having a convex surface facing the observation side, and a positive lens Lp.

[0104] Example 7

[0105] Fig.13 The display optical system L according to Example 7 (Numerical Example 7) shown in includes, in order from the observation side to the display surface side, a lens having a dispersion-controlled diffraction surface MOE, a meniscus lens Lm having a convex surface facing the observation side, and a positive lens Lp.

[0106] In each example, the optical path difference function of the dispersion-controlled diffraction surface can be realized by a metasurface in which the phase delay amount of the metaatom is calculated for each wavelength and the metaatom is arranged so as to control the wavelength dispersion characteristics of the surface. The metasurface can be a so-called single-layer metasurface composed of one layer, or a so-called stacked metasurface composed of multiple layers.

[0107] Numerical Example 1

[0108] Unit: mm

[0109] Diopter: 0m -1 Focal length f: 16.72 Pupil diameter: 10

[0110] Diagonal length of display surface: 9.98 Maximum image height: 4.99

[0111] Surface data

[0112]

[0113] Aspheric surface data

[0114] 5th surface (diffraction surface) design wavelength: 0.58756 [μm]

[0115] U2=-2.53150e-02U4=4.38151e-05U6=-4.611 70e-08

[0116] Surface optical path difference dispersion λUnit: [μm]

[0117] P(λ)=0.58756 / λ

[0118] P(λ d )=1.000000e+00

[0119] P(λ C ) = 8.952981e-01

[0120] P(λ F )=1.208640e+00

[0121] Surface 6

[0122] K=-1.59289e+00 A4=5.17471e-05 A6=-1.38686e-07 A8=7.83985e-10

[0123] No. 7 Wheat Noodles

[0124] K=-9.99779e-01 A4=-1.11333e-04

[0125] Surface 8

[0126] K=0.00000e+00 A4=-4.72586e-05 A6=-4.71393e-07

[0127]

[0128] Numerical Example 2

[0129] Unit: mm

[0130] Diopter: 0m -1 Focal length f: 16.0 Pupil diameter: 10

[0131] Diagonal length of display surface: 9.98 Maximum image height: 4.99

[0132] Surface data

[0133]

[0134]

[0135] Aspheric surface data

[0136] Surface 4

[0137] K=-8.93047e+00 A4=2.30097e-05 A6=-5.57757e-07 A8=2.13321e-09

[0138] Surface 6

[0139] K=0.00000e+00 A4=2.02707e-05

[0140] Surface 7

[0141] K=-5.74146e-01 A4=4.48809e-05

[0142] 9th surface (diffraction surface) design wavelength: 0.58756 [μm]

[0143] U2=-3.85783e-02 U4=6.42238e-06 U6=-1.21295e-07

[0144] Surface optical path difference dispersion λUnit: [μm]

[0145] P(λ)=0.58756 / λ

[0146] P(λ d )=1.000000e+00

[0147] P(λ C ) = 8.952981e-01

[0148] P(λ F )=1.208640e+00

[0149]

[0150] Numerical Example 3

[0151] Unit: mm

[0152] Diopter: 0m -1 Focal length f: 16.14 Pupil diameter: 10

[0153] Diagonal length of display surface: 9.98 Maximum image height: 4.99

[0154] Surface data

[0155]

[0156] Aspheric surface data

[0157] 5th surface (diffraction surface) design wavelength: 0.58756 [μm]

[0158] U2=-2.96405e-02 U4=4.04969e-05 U6=3.44237e-08 U8=2.14619e-09

[0159] Surface optical path difference dispersion λUnit: [μm]

[0160] P(λ)=0.58756 / λ

[0161] P(λ d )=1.000000e+00

[0162] P(λ C ) = 8.952981e-01

[0163] P(λ F )=1.208640e+00

[0164] Surface 6

[0165] K=0.00000e+00 A4=4.18678e-04 A6=-1.10551e-08 A8=-1.19198e-10

[0166] Surface 7

[0167] K=0.00000e+00 A4=5.00954e-04 A6=9.64656e-09 A8=1.07173e-10

[0168]

[0169] Numerical Example 4

[0170] Unit: mm

[0171] Diopter: 0m -1 Focal length f: 16.0 Pupil diameter: 10

[0172] Diagonal length of display surface: 9.98 Maximum image height: 4.99

[0173] Surface data

[0174]

[0175] Aspheric surface data

[0176] 5th surface (diffraction surface) design wavelength: 0.58756 [μm]

[0177] U2=-1.31462e-02 U4=2.61297e-05 U6=2.78964e-07

[0178] Surface optical path difference dispersion λUnit: [μm]

[0179] 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

[0180] P(λ d )=1.000000e+00

[0181] P(λ C ) = 9.012396e-01

[0182] P(λ F )=1.200604e+00

[0183] Surface 6

[0184] K=-3.46571e+00 A4=6.60309e-05 A6=-2.11974e-08 A8=-2.01337e-09

[0185] Surface 7

[0186] K=-1.83926e+00 A4=4.84614e-05

[0187] Surface 8

[0188] K=0.00000e+00 A4=-3.80728e-04 A6=2.6174%-07

[0189]

[0190] Numerical Example 5

[0191] Unit: mm

[0192] Diopter: 0m -1 Focal length f: 16.75 Pupil diameter: 10

[0193] Diagonal length of display surface: 9.98 Maximum image height: 4.99

[0194] Surface data

[0195]

[0196]

[0197] Aspheric surface data

[0198] 5th surface (diffraction surface) design wavelength: 0.58756 [μm]

[0199] A2=-3.49300e-02 A4=1.49066e-04 A6=-2.69699e-07

[0200] Surface optical path difference dispersion λUnit: [μm]

[0201] P(λ)=24.42245λ1 0 -295.85949λ 9 +1906.46259λ 8 -7762.66850λ 7 +21467.37098λ 6 -41580.67832λ 5 +56722.34999λ4 -53578.32705λ 3 +33441.10472λ 2 -12429.40936λ+2086.06535

[0202] P(λ d )=1.000000e+00

[0203] P(λ C )=8.910070e-01

[0204] P(λ F )=1.221691e+00

[0205] Surface 6

[0206] K=-5.53093e+00 A4=-1.31491e-05 A6=1.60024e-06 A8=-9.51399e-09

[0207] Surface 7

[0208] K=-1.72196e+00 A4=6.65881e-05

[0209]

[0210]

[0211] Numerical Example 6

[0212] Unit: mm

[0213] Diopter: 0m -1 Focal length f: 16.0 Pupil diameter: 10

[0214] Diagonal length of display surface: 9.98 Maximum image height: 4.99

[0215] Surface data

[0216]

[0217] Aspheric surface data

[0218] 5th surface (diffraction surface) design wavelength: 0.58756 [μm]

[0219] U2=-1.10948e-02 U4=6.84484e-06 U6=5.37528e-07

[0220] Surface optical path difference dispersion λUnit: [μm]

[0221] 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

[0222] P(λ d )=1.000000e+00

[0223] P(λ C ) = 9.061300e-01

[0224] P(λ F )=1.194903e+00

[0225] Surface 6

[0226] K=-3.82019e+00 A4=4.72584e-05 A6=3.68312e-07 A8=-4.49077e-09

[0227] Surface 7

[0228] K=-1.74933e+00 A4=-1.45945e-05

[0229] Surface 8

[0230] K=0.00000e+00 A4=-4.52111e-04 A6=-1.95257e-07

[0231]

[0232] Numerical Example 7

[0233] Unit: mm

[0234] Diopter: 0m -1 Focal length f: 16.0 Pupil diameter: 10

[0235] Diagonal length of display surface: 9.98 Maximum image height: 4.99

[0236] Surface data

[0237]

[0238] Aspheric surface data

[0239] 5th surface (diffraction surface) design wavelength: 0.58756 [μm]

[0240] U2=-8.39149e-03 U4=1.05774e-05 U6=3.06101e-07

[0241] Surface optical path difference dispersion λUnit: [μm]

[0242] 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

[0243] P(λ d )=1.000000e+00

[0244] P(λ C ) = 9.218490e-01

[0245] P(λ F )=1.177334e+00

[0246] Surface 6

[0247] K=-1.29514e+00 A4=-4.01519e-05 A6=7.95368e-07 A8=-8.07760e-09

[0248] Surface 7

[0249] K=-1.36365e+00 A4=-1.13348e-04

[0250] Surface 8

[0251] K=0.00000e+00 A4=-3.52583e-04 A6=-1.37849e-06

[0252]

[0253] Table 1

[0254]

[0255] Display device

[0256] Fig.15 The configuration of an image pickup device such as a digital camera or a video camera (hereinafter simply referred to as a camera) 100 having an EVF as a display device including the display optical system L according to any one of Examples 1 to 7 is illustrated.

[0257] The camera 100 includes an imaging optical system 101, an image sensor 102 such as a CCD sensor or a CMOS sensor configured to capture (photoelectrically convert) an image of an object (not shown) through the imaging optical system 101, and an image processing unit 103 configured to generate image data using a signal output from the image sensor 102.

[0258] The image data generated by the image processing unit 103 is output to the display element 110 of the EVF. The display element 110 displays an object image corresponding to the image data on its display surface IP.

[0259] The EVF has the display element 110 according to any one of Examples 1 to 7. An eyepiece optical system 111 is provided, which includes the display optical system L according to any one of Examples 1 to 7. A user (observer) of the camera 100 can observe a magnified image of an object displayed on the display element 110 through the eyepiece optical system 111.

[0260] By using the display optical system L according to Examples 1 to 7 as the eyepiece optical system 111 , an excellent object image can be observed with little degradation in image quality caused by various aberrations such as lateral chromatic aberration and astigmatism.

[0261] The display optical system L according to any of Examples 1 to 7 can also be used in a display device other than an EVF, such as a head-mounted display (HMD).

[0262] Although the present disclosure has described example embodiments, it is to be understood that some embodiments are not limited to the disclosed embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0263] Each example can effectively correct lateral chromatic aberration and astigmatism using a diffractive surface with controlled wavelength dispersion characteristics in a display optical system.

Claims

1. A display optical system, comprising: Diffractive surfaces with controlled wavelength dispersion properties, It is characterized by the following equation being satisfied: where ν0 is the Abbe number of the diffractive surface, the reference wavelength is the d-line, the main dispersions are the F-line and the C-line, ψ d , F , and ψ C are the optical path difference functions for the d-line, F-line, and C-line, respectively, d , F , and λ C are the incident wavelengths of the d-line, F-line, and C-line, respectively, P(λ d ), P(λ F ), and P(λ C ) are the optical path difference dispersions of the surface for the d-line, F-line, and C-line, respectively, and The following inequalities are satisfied: 0.2＜1 / v0＜0.2。 2 . The display optical system according to claim 1 , further comprising a refractive lens not having the diffractive 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 claim 1 , further comprising a lens having the diffractive surface and a positive refractive power.

5. The display optical system according to claim 1, characterized in that The following equation is satisfied: where f moe is the focal length of the diffractive surface, m is the diffraction order of the diffractive surface, λ0 is the design wavelength, λ is the incident wavelength, P(λ) is the optical path difference dispersion of the surface at the incident wavelength, U2 is the second order coefficient of the optical path difference function of the surface at the design wavelength, and The following inequalities are satisfied: 0.7<f moe / f<4.0 Wherein f is the focal length of the display optical system.

6. The display optical system according to claim 3, characterized in that The following inequalities are satisfied: -4<fmenis / f<4 Where fmenis is the focal length of the meniscus lens and f is the focal length of the display optical system. 7 . The display optical system according to claim 1 , further comprising, in order from the observation side to the display surface side, a lens having a positive refractive power and a meniscus lens as a refractive lens without the diffraction surface.

8. The display optical system according to claim 1, characterized in that The diffractive surface has a planar shape.

9. The display optical system according to claim 1, further comprising: A lens having the diffractive surface; as well as a refractive lens without said diffractive surface, The following inequalities are satisfied: 0.6<OL / f<1.4 Wherein OL is the distance on the optical axis between the surface closest to the display surface and the surface farthest from the display surface among the surfaces of the lens having the diffractive surface and the refractive lens, and f is the focal length of the display optical system.

10. The display optical system according to claim 1, characterized in that The following equation is satisfied: where ν 0,gF is the Abbe number in the wavelength region below the F line when the main dispersion of the diffraction surface is the g line and the F line, ψ g is the optical path difference function for the g-line, and λ g is the incident wavelength of the g-line, and P(λ g ) is the optical path difference dispersion of the surface for the g-line, and The following inequalities are satisfied: -0.02<1 / v 0，g F<0.02。 11. The display optical system according to claim 1, further comprising a lens having the diffractive surface, and a refractive lens not having the diffractive surface, and the lens having the diffractive surface and the refractive lens are arranged next to each other.

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

13. A display optical system, comprising: Metasurfaces with controlled wavelength dispersion properties, It is characterized by the following equation being satisfied: where ν0 is the Abbe number of the metasurface, the reference wavelength is the d-line, the main dispersions are the F-line and the C-line, ψ d , F , and ψ C are the optical path difference functions for the d-line, F-line, and C-line, respectively, d , F , and λ C are the incident wavelengths of the d-line, F-line, and C-line, respectively, P(λ d ), P(λ F ), and P(λ C ) are the optical path difference dispersions of the surface for the d-line, F-line, and C-line, respectively, and The following inequalities are satisfied: -0.2＜1 / v0＜0.2。 14. A display device, comprising: The display optical system according to any one of claims 1 to 13; as well as A display element having a display surface.

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