Optical system

Abstract

To provide an optical system which satisfies demands for a smaller size and wider view angle, and yet offers good optical characteristics.SOLUTION: An optical system disclosed herein comprises, in order from the pupil plane EP side to the display plane IMG side, a first lens L1 having positive refractive power and a display plane IMG-side surface that is convex near an optical axis, a second lens L2 having negative refractive power and a display plane IMG-side surface that is convex near the optical axis, and a third lens L3 having positive refractive power. The optical system has a semitransparent mirror HM, a reflective polarizing plate 11 provided between the pupil plane and the semitransparent mirror HM, and a first 1 / 4 wavelength plate 21 provided between the pupil plane and the semitransparent mirror HM, and satisfies predefined conditional expressions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system for magnifying an image (for example, an image displayed on an image display device). [Background technology]

[0002] 2. Description of the Related Art Known display devices using image display elements include electronic viewfinders, electronic binoculars, and head-mounted displays.

[0003] In such a display device, the distance between the image display element and the eye must be as short as possible, and the optical system for magnifying the image displayed on the image display element must be housed in a limited space. This often makes it difficult to eliminate various aberrations in the optical system, and the range of correction is also limited.

[0004] As is well known, visual acuity depends on the density of the cones in the photoreceptor cells, and the eye has the characteristic of forming a clear image near the fovea of ​​the macula, i.e., the center of the pupil. Therefore, by utilizing this physiological optical property of the eye to complement the aberration correction of the optical system, it is possible to achieve good optical performance. Specifically, narrowing the pupil increases the depth of focus and reduces the effects of spherical aberration and coma, thereby reducing sensitivity to blur even if the aberration and refractive correction are insufficient or excessive. Furthermore, by utilizing the so-called Stiles-Crawford effect, which is a phenomenon in which the sensitivity of light rays incident from the periphery is lower than that of light rays passing through the center of the pupil, the effects of spherical aberration, coma, and chromatic aberration can be reduced. Furthermore, by maintaining this state, the user gradually becomes accustomed to the condition, which can also reduce the effects of distortion and other aberrations.

[0005] The optical system mounted on such a display device is required to be compact and have a wide angle of view.

[0006] Known conventional optical systems include, for example, the optical system described in Patent Document 1. Patent Document 1 discloses an image display device having a light source, at least one display element, and a magnifying optical means for magnifying a display image on the display element. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-139132 Summary of the Invention [Problem to be solved by the invention]

[0008] If an attempt is made to reduce the size of the optical system described in Patent Document 1, it becomes extremely difficult to correct aberrations in the peripheral area, and good optical performance cannot be obtained.

[0009] The present invention has been made in view of the above-mentioned problems, and aims to provide an optical system that satisfies the demands for compactness and a wide angle of view in a balanced manner, while also having high resolving power with various aberrations well corrected. [Means for solving the problem]

[0010] The optical system according to the present invention comprises, in order from the pupil plane side to the display surface side, a first lens whose surface facing the display surface is convex in the paraxial direction and has positive refractive power, a second lens whose surface facing the display surface is convex in the paraxial direction and has negative refractive power, and a third lens whose surface facing the display surface is positive refractive power, and the optical system further comprises a half mirror, a reflective polarizer disposed between the pupil plane and the half mirror, and a first quarter-wave plate disposed between the pupil plane and the half mirror.In this specification, the terms convex, concave, and flat surfaces of the lenses refer to the shapes in the paraxial direction, and the refractive power refers to the refractive power in the paraxial direction unless otherwise specified.

[0011] A reflective polarizer reflects linearly polarized light having one polarization direction and transmits linearly polarized light having an orthogonal polarization direction.

[0012] A quarter-wave plate converts linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light by delaying the phase of polarized light by 1 / 4λ.

[0013] The first lens has positive refractive power and has a convex surface on the display surface side in the paraxial direction, thereby suppressing spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0014] The second lens has negative refractive power and is convex on the display surface side in the paraxial direction, thereby effectively correcting chromatic aberration, coma, astigmatism, field curvature, and distortion.

[0015] The third lens has a positive refractive power, and thereby effectively corrects spherical aberration, astigmatism, curvature of field, and distortion.

[0016] A half mirror transmits 50% of the light and reflects the remaining 50%.

[0017] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (1): (1) 1.5 <r5 / f<6.0 Here, r5 is the paraxial radius of curvature of the surface of the third lens on the pupil plane side, and f is the focal length of the entire optical system.

[0018] By satisfying the range of conditional expression (1), it becomes possible to make good corrections for astigmatism, curvature of field, and distortion.

[0019] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (2): (2)0.15<(D1+T1) / (D2+T2) / D3<0.75 where D1 is the thickness of the first lens on the optical axis, T1 is the distance on the optical axis from the surface of the first lens on the display surface side to the surface of the second lens on the pupil surface side, D2 is the thickness of the second lens on the optical axis, T2 is the distance on the optical axis from the surface of the second lens on the display surface side to the surface of the third lens on the pupil surface side, and D3 is the thickness of the third lens on the optical axis.

[0020] By satisfying the range of conditional expression (2), it becomes possible to achieve a low profile and to make good correction for astigmatism and distortion.

[0021] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (3): (3)-5.25 <r2 / f<-1.50 Here, r2 is the paraxial radius of curvature of the surface of the first lens on the display surface side, and f is the focal length of the entire optical system.

[0022] By satisfying the range of conditional expression (3), it becomes possible to make good corrections for coma, astigmatism, curvature of field, and distortion.

[0023] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (4): (4)-5.25 <r3 / f<-1.50 Here, r3 is the paraxial radius of curvature of the surface of the second lens on the pupil plane side, and f is the focal length of the entire optical system.

[0024] By satisfying the range of conditional expression (4), it becomes possible to make good corrections for coma, astigmatism, curvature of field, and distortion.

[0025] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (5): (5) 2.5<|r6| / f<325.0 Here, r6 is the paraxial radius of curvature of the surface of the third lens on the display surface side, and f is the focal length of the entire optical system.

[0026] By satisfying the range of conditional expression (5), it becomes possible to make good correction for curvature of field and distortion.

[0027] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (6): (6)3 <f1 / f<10 Here, f1 is the focal length of the first lens, and f is the focal length of the entire optical system.

[0028] By satisfying the range of conditional expression (6), it becomes possible to make good corrections for spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0029] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (7): (7)-37.0 <f2 / f<-3.5 Here, f2 is the focal length of the second lens, and f is the focal length of the entire optical system.

[0030] By satisfying the range of conditional expression (7), chromatic aberration, coma, astigmatism, curvature of field, and distortion can be corrected satisfactorily.

[0031] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (8): (8)2.6 <f3 / f<10.0 Here, f3 is the focal length of the third lens, and f is the focal length of the entire optical system.

[0032] By satisfying the range of conditional expression (8), it becomes possible to make good corrections for spherical aberration, astigmatism, curvature of field, and distortion.

[0033] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (9): (9) -5<(n1 / r2)×100<-1 Here, n1 is the refractive index of the first lens with respect to the d-line, and r2 is the paraxial radius of curvature of the surface of the first lens on the display surface side.

[0034] By satisfying the range of conditional expression (9), it becomes possible to make good corrections for coma, astigmatism, curvature of field, and distortion.

[0035] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (10): (10)0.5 <r2 / r3<1.5 Here, r2 is the paraxial radius of curvature of the surface of the first lens on the display surface side, and r3 is the paraxial radius of curvature of the surface of the second lens on the pupil plane side.

[0036] By satisfying the range of conditional expression (10), it becomes possible to make good corrections for coma, astigmatism, curvature of field, and distortion.

[0037] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (11): (11)-0.85 <r2 / f1<-0.25 Here, r2 is the paraxial radius of curvature of the surface of the first lens on the display surface side, and f1 is the focal length of the first lens.

[0038] By satisfying the range of conditional expression (11), it becomes possible to make good corrections for spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0039] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (12): (12)-30 <r4 / f<-2 Here, r4 is the paraxial radius of curvature of the surface of the second lens on the display surface side, and f is the focal length of the entire optical system.

[0040] By satisfying the range of conditional expression (12), it becomes possible to make good corrections for astigmatism, curvature of field, and distortion.

[0041] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (13): (13)-9.00 <r4 / r5<-0.85 Here, r4 is the paraxial radius of curvature of the surface of the second lens on the display surface side, and r5 is the paraxial radius of curvature of the surface of the third lens on the pupil plane side.

[0042] By satisfying the range of conditional expression (13), it becomes possible to make good corrections for astigmatism, curvature of field, and distortion.

[0043] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (14): (14)0.25 <r5 / f3<1.35 Here, r5 is the paraxial radius of curvature of the pupil plane side surface of the third lens, and f3 is the focal length of the third lens.

[0044] By satisfying the range of conditional expression (14), it becomes possible to make good corrections for spherical aberration, astigmatism, curvature of field, and distortion.

[0045] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (15): (15)4.5 <r5 / D3<15.5 Here, r5 is the paraxial radius of curvature of the pupil plane side surface of the third lens, and D3 is the thickness of the third lens on the optical axis.

[0046] By satisfying the range of conditional expression (15), it becomes possible to achieve a low profile and to make good corrections for astigmatism, curvature of field, and distortion.

[0047] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (16): (16)0.01 <r5 / |r6|<1.00 Here, r5 is the paraxial radius of curvature of the surface of the third lens on the pupil plane side, and r6 is the paraxial radius of curvature of the surface of the third lens on the display plane side.

[0048] By satisfying the range of conditional expression (16), it becomes possible to make good corrections for astigmatism, curvature of field, and distortion.

[0049] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (17): (17) 0.5<|r6| / f3<54.0 Here, r6 is the paraxial radius of curvature of the surface of the third lens on the display surface side, and f3 is the focal length of the third lens.

[0050] By satisfying the range of conditional expression (17), it becomes possible to make good corrections for spherical aberration, astigmatism, curvature of field, and distortion.

[0051] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (18): (18) 2.5<(D1 / f1)×100<10.0 Here, D1 is the thickness of the first lens on the optical axis, and f1 is the focal length of the first lens.

[0052] By satisfying the range of conditional expression (18), it becomes possible to achieve a low profile and to make good corrections for spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0053] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (19): (19)-2.70<(D2 / f2)×100<-0.25 Here, D2 is the thickness of the second lens on the optical axis, and f2 is the focal length of the second lens.

[0054] By satisfying the range of conditional expression (19), it becomes possible to achieve a low profile and to make good corrections for chromatic aberration, coma, astigmatism, curvature of field, and distortion.

[0055] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (20): (20) 2.0<(D3 / f3)×100<14.5 Here, D3 is the thickness of the third lens on the optical axis, and f3 is the focal length of the third lens.

[0056] By satisfying the range of conditional expression (20), it becomes possible to achieve a low profile and to make good corrections for spherical aberration, astigmatism, curvature of field, and distortion.

[0057] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (21): (21)-690 <f2 / T2<-115 Here, f2 is the focal length of the second lens, and T2 is the distance on the optical axis from the surface of the second lens on the display surface side to the surface of the third lens on the pupil plane side.

[0058] By satisfying the range of conditional expression (21), it becomes possible to achieve a low height and to make good corrections for chromatic aberration, coma, astigmatism, curvature of field, and distortion.

[0059] It is also desirable that the optical system having the above configuration satisfy the following conditional expression (22): (22)-1.25 <f1 / f2<-0.10 Here, f1 is the focal length of the first lens, and f2 is the focal length of the second lens.

[0060] By satisfying the range of conditional expression (22), it becomes possible to make good corrections for spherical aberration, chromatic aberration, coma, astigmatism, curvature of field, and distortion.

[0061] In the optical system having the above configuration, it is desirable that the surface of the second lens on the paraxial side of the pupil plane be a concave surface.

[0062] By making the surface of the second lens on the pupil plane side a concave surface in the paraxial direction, it becomes possible to make good corrections for astigmatism, field curvature, and distortion. [Effects of the Invention]

[0063] The present invention makes it possible to obtain an optical system with high resolution and excellent correction of aberrations while satisfying the demands for miniaturization and wide angle of view in a well-balanced manner. Furthermore, since the imaging lens according to the present invention effectively corrects aberrations, the number of lenses can be reduced, and environmental protection can be achieved by reducing the amount of lens material used. [Brief explanation of the drawings]

[0064] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of an optical system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a partially enlarged view of the optical system shown in FIG. [Figure 3] 2A to 2C are aberration diagrams showing spherical aberration, astigmatism, and distortion of the optical system shown in FIG. [Figure 4] FIG. 10 is a cross-sectional view showing a schematic configuration of an optical system according to Example 2 of the present invention. [Figure 5] FIG. 5 is a partially enlarged view of the optical system shown in FIG. [Figure 6] 5A to 5C are aberration diagrams showing spherical aberration, astigmatism, and distortion of the optical system shown in FIG. [Figure 7] FIG. 10 is a cross-sectional view showing a schematic configuration of an optical system according to Example 3 of the present invention. [Figure 8] FIG. 8 is a partial enlarged view of the optical system shown in FIG. [Figure 9] 8A to 8C are aberration diagrams showing spherical aberration, astigmatism, and distortion of the optical system shown in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0065] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0066] 1, 4, and 7 are cross-sectional views showing the schematic configurations of the optical systems of Examples 1 to 3 according to the present embodiment, respectively. Also, Fig. 2, 5, and 8 show enlarged partial views of the optical systems of Examples 1 to 3, respectively. The optical system according to the present embodiment will be described in detail below with reference to the optical system of Example 1.

[0067] As shown in FIG. 1, the optical system according to this embodiment includes, in order from a pupil plane EP toward a display surface IMG of an image display element, a first lens L1 whose paraxial surface facing the display surface IMG is convex and has positive refractive power, a second lens L2 whose paraxial surface facing the display surface IMG is convex and has negative refractive power, and a third lens L3 whose paraxial surface facing the display surface IMG is convex and has negative refractive power, and a third lens L3 whose paraxial surface is positive refractive power. The optical system includes a half mirror HM, a reflective polarizer 11 disposed between the pupil plane and the half mirror HM, and a first quarter-wave plate 21 disposed between the pupil plane and the half mirror HM. A filter IR, such as a glass block, is disposed between the optical system and the display surface IMG. Note that this filter IR can be omitted.

[0068] The optical system according to this embodiment may be mounted on any object, but may be mounted on a head-mounted display, for example, as an optical system for enlarging an image displayed on a display surface IMG. In this case, the pupil of the observer is located on the pupil plane EP. An aperture stop may be disposed on the pupil plane EP.

[0069] In the optical system according to this embodiment, anti-reflection films may be attached to both sides of the half mirror HM. Since anti-reflection films have the function of preventing light reflection, this configuration can prevent a decrease in image contrast due to reflection of external light.

[0070] 1, the first lens L1 has a flat surface on the pupil plane side in the paraxial direction and a convex surface on the display surface IMG side in the paraxial direction. This shape of the first lens L1 can suppress spherical aberration, coma, astigmatism, field curvature, and distortion. The shape of the surface of the first lens L1 on the pupil plane side is not limited to the shape according to the first embodiment, and may be a shape that is convex or concave in the paraxial direction.

[0071] 1, the second lens L2 has a paraxial concave surface facing the pupil plane and a paraxial convex surface facing the display surface IMG, which allows for excellent correction of chromatic aberration, coma, astigmatism, field curvature, and distortion.

[0072] As shown in FIG. 1, the third lens L3 of this embodiment has a paraxial convex surface on the pupil plane side and a paraxial concave surface on the display surface IMG side. This shape of the third lens L3 allows for excellent correction of spherical aberration, astigmatism, field curvature, and distortion. The shape of the third lens L3 may also be a biconvex shape on the paraxial surface, as in the optical system described in Example 2. In this case, the positive refractive power on both sides is advantageous for miniaturization.

[0073] The optical systems of Examples 1, 2, and 3 are examples in which a first quarter-wave plate 21 is disposed between a reflective polarizer 11 and a first lens L1, as shown in FIGS. 2, 5, and 8. A composite film formed by bonding a polarizer 01, a reflective polarizer 11, and a first quarter-wave plate 21 together is attached to the first lens L1, facilitating industrial manufacturing. This reduces costs and improves the axial accuracy of the reflective polarizer 11 and the first quarter-wave plate 21. The composite film is also coated with an anti-reflection coating (AR coating) to reduce reflections on the lens. The adhesive sheet OCA shown in FIG. 5 is used for adhesion.

[0074] The polarizer 01 allows only light polarized or polarized in a specific direction to pass through.

[0075] Furthermore, the optical system according to the example is an example in which half-mirror characteristics are imparted between the first lens L1 and the second lens L2 by vapor deposition, as shown in FIGS.

[0076] As a device having a display surface IMG, for example, a liquid crystal display or a micro OLED (Organic Light Emitting Diode) display can be adopted.

[0077] As shown in FIG. 1, light emitted from the display surface IMG passes through the third lens L3, passes through the second lens L2, and enters the half mirror HM. A portion of the light that enters the half mirror HM is transmitted through the half mirror HM and converted into linearly polarized light by the first quarter-wave plate 21, and then enters the reflective polarizer 11. This linearly polarized light is reflected by the polarization selectivity of the reflective polarizer 11. The light reflected by the reflective polarizer 11 is converted into circularly polarized light by the first quarter-wave plate 21, and then enters the half mirror HM, where it is reflected. The light reflected by the half mirror HM becomes circularly polarized light with the opposite rotation to the light before reflection. This circularly polarized light is converted into linearly polarized light by the first quarter-wave plate 21, and then enters the reflective polarizer 11. This linearly polarized light is transmitted through the reflective polarizer 11 due to its polarization selectivity, and is guided to the pupil plane EP.

[0078] The optical system of this embodiment provides desirable effects by satisfying the following conditional expressions (1) to (22). (1) 1.5 <r5 / f<6.0 (2)0.15<(D1+T1) / (D2+T2) / D3<0.75 (3)-5.25 <r2 / f<-1.50 (4)-5.25 <r3 / f<-1.50 (5) 2.5<|r6| / f<325.0 (6)3 <f1 / f<10 (7)-37.0 <f2 / f<-3.5 (8)2.6 <f3 / f<10.0 (9) -5<(n1 / r2)×100<-1 (10)0.5 <r2 / r3<1.5 (11)-0.85 <r2 / f1<-0.25 (12)-30 <r4 / f<-2 (13)-9.00 <r4 / r5<-0.85 (14)0.25 <r5 / f3<1.35 (15)4.5 <r5 / D3<15.5 (16)0.01 <r5 / |r6|<1.00 (17) 0.5<|r6| / f3<54.0 (18) 2.5<(D1 / f1)×100<10.0 (19)-2.70<(D2 / f2)×100<-0.25 (20) 2.0<(D3 / f3)×100<14.5 (21)-690 <f2 / T2<-115 (22)-1.25 <f1 / f2<-0.10 however, n1: refractive index of the first lens L1 for the d line D1: Thickness of the first lens L1 on the optical axis X D2: Thickness of the second lens L2 on the optical axis X D3: Thickness of the third lens L3 on the optical axis X T1: the distance on the optical axis X from the surface of the first lens L1 on the display surface side to the surface of the second lens L2 on the pupil plane side T2: the distance on the optical axis X from the surface of the second lens L2 on the display surface side to the surface of the third lens L3 on the pupil plane side f: focal length of the entire optical system f1: focal length of the first lens L1 f2: Focal length of the second lens L2 f3: focal length of the third lens element L3 r2: paraxial curvature radius of the display surface side surface of the first lens L1 r3: paraxial curvature radius of the pupil-side surface of the second lens L2 r4: paraxial curvature radius of the surface of the second lens L2 facing the display surface r5: paraxial curvature radius of the pupil-side surface of the third lens L3 r6: paraxial curvature radius of the display surface side surface of the third lens L3

[0079] It is not necessary to satisfy all of the above conditional expressions, and by satisfying each conditional expression individually, it is possible to obtain the effects corresponding to each conditional expression.

[0080] Furthermore, the optical system of this embodiment will achieve more desirable effects if it satisfies the following conditional expressions (1a) to (22a). (1a)2.5 <r5 / f<4.5 (2a)0.22<(D1+T1) / (D2+T2) / D3<0.62 (3a)-4.25 <r2 / f<-2.50 (4a)-4.25 <r3 / f<-2.50 (5a) 4<|r6| / f<270 (6a)4.5 <f1 / f<8.0 (7a)-30.0 <f2 / f<-5.5 (8a)3.4 <f3 / f<8.5 (9a) -4<(n1 / r2)×100<-2 (10a)0.75 <r2 / r3<1.25 (11a)-0.70 <r2 / f1<-0.40 (12a)-24.0 <r4 / f<-3.5 (13a)-7.5 <r4 / r5<-1.0 (14a)0.35 <r5 / f3<1.10 (15a)7 <r5 / D3<13 (16a)0.016 <r5 / |r6|<0.850 (17a) 1.0<|r6| / f3<44.5 (18a) 4.5<(D1 / f1)×100<8.5 (19a)-2.25<(D2 / f2)×100<-0.40 (20a)3.5<(D3 / f3)×100<12.0 (21a)-570 <f2 / T2<-175 (22a)-1.00 <f1 / f2<-0.20 However, the symbols in each conditional expression are the same as those explained in the previous paragraph. Note that for conditional expressions (1a) to (22a), the lower limit or upper limit of the corresponding conditional expression (1) to (22) may be applied.

[0081] In this embodiment, the aspherical shape adopted for the aspherical lens surface is expressed by Equation 1, where Z is the axis in the optical axis direction, H is the height in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic coefficient, and An is the n-th order aspherical coefficient.

[0082]

number

[0083] Next, examples of the optical system according to this embodiment will be shown. In each example, f represents the focal length of the entire optical system, Fno represents the F-number, ω represents the half angle of view, ih represents the maximum image height, and TTL represents the total optical length. Here, the total optical length is the distance on the optical axis from the pupil plane to the display surface. The values ​​of the total optical length and back focus are the distances obtained by converting the thickness of a filter IR placed between the optical system and the display surface IMG into air.

[0084] Additionally, i denotes the surface number counted from the pupil surface side, r denotes the paraxial radius of curvature, d denotes the distance between lens surfaces on the optical axis (surface spacing), Nd denotes the refractive index of the d-line (reference wavelength), and νd denotes the Abbe number for the d-line. Aspherical surfaces are indicated by adding an asterisk (*) after the surface number i.

[0085] In the optical systems of each embodiment, the distance on the optical axis between the pupil plane EP, which is the eyepoint, and the lens surface closest to the pupil plane is called the pupil distance. In evaluating aberrations, there is a one-to-one correspondence between the aberration of a light ray that reaches the pupil plane EP when a light emitting point is provided on the display surface side and the aberration of a light ray that reaches the display surface IMG when a light emitting point is provided on the pupil plane EP side. For this reason, in each embodiment, the aberration of the light ray that reaches the display surface IMG is evaluated.

[0086] Example 1

[0087] The basic lens data is shown in Table 1 below.

[0088] [Table 1]

[0089] The optical system of Example 1 satisfies conditional expressions (1) to (22) as shown in Table 4.

[0090] FIG. 3 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the optical system of Example 1. The spherical aberration diagram shows the amount of aberration for each wavelength: F-line (486 nm), d-line (588 nm), and C-line (656 nm). The astigmatism diagram also shows the amount of aberration for the d-line at the sagittal image plane S (solid line) and the amount of aberration for the d-line at the tangential image plane T (dashed line) (the same applies to FIGS. 6 and 9). As shown in FIG. 3, each aberration is well corrected.

[0091] Example 2

[0092] The basic lens data is shown in Table 2 below.

[0093] [Table 2]

[0094] The optical system of Example 2 satisfies conditional expressions (1) to (22) as shown in Table 4.

[0095] Fig. 6 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the optical system of Example 2. As shown in Fig. 6, each aberration is well corrected.

[0096] Example 3

[0097] The basic lens data is shown in Table 3 below.

[0098] [Table 3]

[0099] The optical system of Example 3 satisfies conditional expressions (1) to (22) as shown in Table 4.

[0100] Fig. 9 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the optical system of Example 3. As shown in Fig. 9, each aberration is well corrected.

[0101] Table 4 shows the values ​​of conditional expressions (1) to (22) in the optical systems of Examples 1 to 3.

[0102] [Table 4] [Industrial Applicability]

[0103] When the optical system according to the present invention is applied to an image display device, it contributes to the miniaturization and widening of the angle of view of the image display device, and also makes it possible to improve the performance of the image display device. [Explanation of symbols]

[0104] EP pupil plane L1 First lens L2 Second lens L3 Third lens AR AR Coat OCA adhesive sheet 01 Polarizing plate 11 Reflective polarizer 21 First quarter-wave plate 22 Second quarter-wave plate HM Half Mirror IR filter IMG display surface

Claims

1. From the pupil plane to the display plane, a first lens having a positive refractive power; a second lens having negative refractive power; and a third lens having a positive refractive power, The optical system comprises: Equipped with a half mirror, a reflective polarizer disposed between the pupil plane and the half mirror; a first quarter-wave plate disposed between the pupil plane and the half mirror; the first lens has a convex surface on the display surface side in a paraxial direction, the second lens has a convex surface on the display surface side in a paraxial direction, An optical system characterized by satisfying the following conditional expressions (1) and (2): (1) 1.5<r5 / f<6.0 (2) 0.15<(D1+T1) / (D2+T2) / D3<0.75 however, r5: paraxial radius of curvature of the pupil plane side surface of the third lens, f: focal length of the entire optical system, D1: thickness of the first lens on the optical axis, T1: the distance on the optical axis from the surface of the first lens on the display surface side to the surface of the second lens on the pupil plane side, D2: thickness of the second lens on the optical axis, T2: the distance on the optical axis from the surface of the second lens on the display surface side to the surface of the third lens on the pupil plane side, D3: thickness of the third lens on the optical axis, Let's say.

2. 2. The optical system according to claim 1, wherein the following conditional expression (3) is satisfied: (3) -5.25<r2 / f<-1.50 r2: paraxial radius of curvature of the display surface side surface of the first lens, f: focal length of the entire optical system, Let's say.

3. 2. The optical system according to claim 1, wherein the following conditional expression (4) is satisfied: (4) -5.25<r3 / f<-1.50 however, r3: paraxial radius of curvature of the pupil plane side surface of the second lens, f: focal length of the entire optical system, Let's say.

4. 2. The optical system according to claim 1, wherein the following conditional expression (5) is satisfied: (5) 2.5<|r6| / f<325.0 r6: paraxial radius of curvature of the display surface side surface of the third lens, f: focal length of the entire optical system, Let's say.

5. 2. The optical system according to claim 1, wherein the following conditional expression (6) is satisfied: (6) 3<f1 / f<10 f1: focal length of the first lens, f: focal length of the entire optical system, Let's say.

6. 2. The optical system according to claim 1, wherein the following conditional expression (7) is satisfied: (7) -37.0<f2 / f<-3.5 f2: focal length of the second lens, f: focal length of the entire optical system, Let's say.

7. 2. The optical system according to claim 1, wherein the following conditional expression (8) is satisfied: (8) 2.6<f3 / f<10.0 f3: focal length of the third lens, f: focal length of the entire optical system, Let's say.

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