Optical systems and display devices

Abstract

This invention provides a compact optical system with high magnification and sufficient eye relief. [Solution] The optical system L0 guides light from the display element to the observation side. The optical system is composed of a first lens L1 with positive refractive power, a second lens L2 with negative refractive power, a third lens L3 with refractive power, and a fourth lens L4 with refractive power. The focal length of the third lens is f3, the focal length of the fourth lens is f4, the radius of curvature of the display element side surface of the fourth lens is R41, the radius of curvature of the observation side surface of the fourth lens is R42, the air-equivalent distance from the display surface of the display element to the display element side surface of the first lens when the diopter is -1 diopter is L1, and the distance along the optical axis from the display element side surface of the first lens to the observation side surface of the fourth lens is LD. -10.00

Description

[Technical Field]

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

[0002] Electronic viewfinders used in imaging devices such as video cameras and broadcast cameras employ an optical system that magnifies and displays the image on a display element. Such optical systems are required to have a sufficiently large field of view (i.e., high magnification), a long eye relief, and good correction of various aberrations.

[0003] Patent Document 1 discloses an optical system composed of four lenses: positive, negative, positive, positive. Patent Document 2 discloses an optical system composed of four lenses: positive, positive, negative, positive. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-002814 [Patent Document 2] Japanese Patent Publication No. 2023-131451 [Overview of the project] [Problems that the invention aims to solve]

[0005] There is a need for an optical system that is smaller than conventional systems, has high magnification, and also has sufficient eye relief. [Means for solving the problem]

[0006] An optical system, as one aspect of the present invention, guides light from a display element that displays an image to the observation side. This optical system is composed of a first lens with positive refractive power, a second lens with negative refractive power, a third lens with refractive power, and a fourth lens with refractive power, arranged in order from the display element side to the observation side. When the focal length of the third lens is f3, the focal length of the fourth lens is f4, the radius of curvature of the display element side surface of the fourth lens is R41, the radius of curvature of the observation side surface of the fourth lens is R42, the air-equivalent distance from the display surface of the display element to the display element side surface of the first lens when the diopter is -1 diopter is L1, and the distance along the optical axis from the display element side surface of the first lens to the observation side surface of the fourth lens is LD, -10.00 <f4 / f3<0.15 -5.00<(R41+R42) / (R41-R42)<-0.19 0.5 <LD / L1<40.0 It is characterized by satisfying the following conditions.

[0007] Another aspect of the present invention is the optical system, 0.5 <LD / L1<40.0 It is characterized by satisfying the following conditions. Furthermore, a display device equipped with the above optical system also constitutes another aspect of the present invention. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a compact optical system with high magnification. Furthermore, it is possible to provide an optical system with sufficient eye relief. [Brief explanation of the drawing]

[0009] [Figure 1] Cross-sectional view of the display optical system of Example 1. [Figure 2] Aberration diagram of the display optical system in Example 1. [Figure 3] Cross-sectional view of the display optical system in Example 2. [Figure 4] Aberration diagram of the display optical system in Example 2. [Figure 5] Cross-sectional view of the display optical system of Example 3. [Figure 6] Aberration diagram of the display optical system of Example 3. [Figure 7] Cross-sectional view of the display optical system of Example 4. [Figure 8] Aberration diagram of the display optical system of Example 4. [Figure 9] Cross-sectional view of the display optical system of Example 5. [Figure 10] Aberration diagram of the display optical system of Example 5. [Figure 11] Cross-sectional view of the display optical system of Example 6. [Figure 12] Aberration diagram of the display optical system of Example 6. [Figure 13] Cross-sectional view of the display optical system of Example 7. [Figure 14] Aberration diagram of the display optical system of Example 7. [Figure 15] Cross-sectional view of the display optical system of Example 8. [Figure 16] Aberration diagram of the display optical system of Example 8. [Figure 17] Cross-sectional view of the display optical system of Example 9. [Figure 18] Aberration diagram of the display optical system of Example 9. [Figure 19] Cross-sectional view of the display optical system of Example 10. [Figure 20] Aberration diagram of the display optical system of Example 10. [Figure 21] Diagram showing an imaging device equipped with the display optical systems of Examples 1 to 10. [[ID=4​​​​​​​​​​​​ In each figure, the left side is the display element side, and the right side is the observation side (exit pupil side). The display optical system L0 in each embodiment guides light from the display element to the observation side. The display element is composed of liquid crystal elements, organic EL elements, etc., and displays an image (original image) on its display surface IP. This allows an observer, who positions their eye on the observation surface (eye point) EP set at the position of the exit pupil, to observe a magnified image of the original image.

[0012] In order to enable magnified observation at a sufficiently large field of view (e.g., 30° or more) using a small display element (e.g., with a diagonal length of the display surface of 20 mm or less), it is necessary that each lens constituting the display optical system has a strong positive or negative refractive power, and that the entire display optical system has a strong positive refractive power. However, in such a display optical system, spherical aberration, field curvature, astigmatism, and chromatic aberration occur frequently, making it difficult to correct these aberrations well and obtain high optical performance.

[0013] Therefore, the display optical system L0 in each embodiment is composed of a first lens L1 with positive refractive power, a second lens L2 with negative refractive power, a third lens L3 with positive or negative refractive power, and a fourth lens L4 with positive or negative refractive power, arranged in order from the display element side to the observation side. Specifically, the display optical system L0 in embodiments 1 to 5 and embodiments 8 to 10 is composed of a first lens L1 with positive refractive power, a second lens L2 with negative refractive power, a third lens L3 with negative refractive power, and a fourth lens L4 with positive refractive power. By making the third lens L3 a negative lens, the Petzval sum of the display optical system L0 is corrected, and field curvature is well corrected. Furthermore, the display optical system L0 in embodiments 6 and 7 is composed of a first lens L1 with positive refractive power, a second lens L2 with negative refractive power, a third lens L3 with positive refractive power, and a fourth lens L4 with positive refractive power. By making the third lens L3 a positive lens, the positive refractive power on the observation side is increased, resulting in higher magnification. Alternatively, if the third lens L3 is a positive lens, the fourth lens L4 may be a negative lens.

[0014] Furthermore, Examples 1, 2 and Examples 4-10 are provided with a first cover glass CG1 that covers the display surface IP of the display element and a second cover glass CG2 that covers the image-side surface of the fourth lens L4. Both the first and second cover glasses CG1 and CG2 are parallel plates, have no refractive power, and are not included as components of the display optical system L0.

[0015] In the above configuration, the focal length of the third lens L3 is set to f3. The focal length of the fourth lens L4 is set to f4, the radius of curvature of the display element side surface of the fourth lens L4 is set to R41, and the radius of curvature of the observation side surface of the fourth lens L is set to R42. Furthermore, when the diopter is -1 diopter (D), the air-equivalent distance from the display surface IP of the display element to the display element side surface of the first lens L1 is set to L1, and the distance along the optical axis from the display element side surface of the first lens L1 to the observation side surface of the fourth lens L4 is set to LD. At this time, the display optical system L0 of each embodiment is: -10.00 <f4 / f3<0.15 (1) -5.00<(R41+R42) / (R41-R42)<-0.19 (2) 0.5 <LD / L1<40.0 (3) It satisfies at least one of the following conditions.

[0016] The conditions in equation (1) indicate an appropriate relationship between the focal length f3 of the third lens L3 and the focal length f4 of the fourth lens L4. If f4 / f3 exceeds the upper limit of equation (1), the focal length of the third lens L3 becomes too short, meaning the positive refractive power of the third lens L3 becomes too strong, causing the rear principal point of the display optical system L0 to move too far from the observation side. This is undesirable because it makes it difficult to increase the eye relief. If f4 / f3 falls below the lower limit of equation (1), the negative refractive power of the third lens L3 becomes too strong, causing the front principal point of the display optical system L0 to move too far from the display surface IP. This is undesirable because it makes it difficult to increase the focal length of the display optical system L0 and thus makes it difficult to achieve high magnification.

[0017] Furthermore, it is more preferable to set the lower limit of equation (1) to -5.00, -3.00, or -1.00. Also, it is more preferable to set the upper limit of equation (1) to 0.145, 0.143, or 0.141.

[0018] The conditions in equation (2) indicate the appropriate shape of the fourth lens L4 (the shape factor, expressed by the radius of curvature R41 on the display element side and the radius of curvature R42 on the observation side). If the shape factor of the fourth lens L4 exceeds the upper limit of equation (2), the positive refractive power of the observation side of the fourth lens L4 becomes too strong, and the positive refractive power of the display element side of the fourth lens L4 becomes too weak. As a result, the height of the outermost rays at the second lens L2 and third lens L3 becomes low, making it difficult to correct field curvature and astigmatism, which is undesirable. If the shape factor of the fourth lens L4 falls below the lower limit of equation (2), the positive refractive power of the observation side of the fourth lens L4 becomes too weak, causing the rear principal point to move away from the observation side, making it difficult to increase the eye relief, which is also undesirable.

[0019] Furthermore, it is more preferable to set the lower limit of equation (2) to -3.00, -2.00, -1.50, or -1.30. Also, it is more preferable to set the upper limit of equation (2) to -0.195, or -0.20.

[0020] The conditions in equation (3) indicate an appropriate relationship between the air-equivalent distance L1 from the display surface IP to the first lens L1 and the distance LD from the first lens L1 to the fourth lens L4. If the air-equivalent distance L1 from the display surface IP to the first lens L1 becomes too long so that LD / L1 falls below the lower limit of equation (3), the focal length of the entire display optical system L0 becomes long, making it difficult to achieve a high magnification rate, which is undesirable. If the distance LD from the first lens L1 to the fourth lens L4 becomes long so that LD / L1 exceeds the upper limit of equation (3), the display optical system L0 becomes larger, which is undesirable.

[0021] Furthermore, it is more preferable to set the lower limit of equation (3) to 1.0, 1.5, or 2.0. Also, it is more preferable to set the upper limit of equation (3) to 30.0, 20.0, 10.0, 5.0, or 4.0.

[0022] The display optical system L0 in each embodiment satisfies the above-described configuration and the conditions of equations (1) to (3), resulting in a compact design while still providing high magnification and sufficient eye relief.

[0023] The display optical system L0 in each embodiment preferably satisfies at least one of the following conditions (4) to (10).

[0024] 0.10 ≤ f₄ / f ≤ 5.00 (4) -5.00 ≤ f / f3 ≤ 0.50 (5) -2.00 ≤ f2 / f3 ≤ 5.00 (6) -50.0≦(R32+R31) / (R32-R31)≦-0.1 (7) 0.8 ≤ LD / f ≤ 3.0 (8) 0.30 ≤ H / f ≤ 0.50 (9) 0.3 ≤ 2 × He / φ ≤ 0.8 (10) In equations (4) to (10), the focal length of the entire display optical system L0 is f, the focal length of the fourth lens L4 is f4, the focal length of the third lens L3 is f3, and the focal length of the second lens L2 is f2. Also, the radius of curvature of the display element side surface of the third lens L3 is R31, and the radius of curvature of the observation side surface of the third lens L3 is R32. Furthermore, H is half the diagonal length of the display surface IP of the display element. In addition, the first to fourth lenses include an aspherical lens in which one of the surfaces, the display element side or the observation side, has an inflection point, and the height from the optical axis of the inflection point in the aspherical lens is He, and the effective diameter of the surface having the inflection point in the aspherical lens is φ. The inflection point of a surface is the point where the sign of the curvature of the surface changes and the curvature becomes 0 (the point where the inclination of the surface becomes 0, and the sign of the inclination of the surface changes between the optical axis side and the peripheral side of that point). The effective diameter of a surface is the radius of the region within that surface through which the light rays contributing to image formation pass.

[0025] The conditions in equation (4) indicate an appropriate relationship between the focal length f4 of the fourth lens L4 and the focal length f of the entire display optical system L0. These conditions are necessary to balance the sensitivity of the display optical system L0 to uneven focus (the amount of uneven focus that occurs when the display optical system L0 is tilted) with the correction of various aberrations such as field curvature and astigmatism. If f4 / f exceeds the upper limit of equation (4), the refractive power of the entire display optical system L0 becomes too strong, increasing the sensitivity of the display optical system L0 to uneven focus and making manufacturing more difficult, which is undesirable. If f4 / f falls below the lower limit of equation (4), the refractive power of the fourth lens L4 becomes too strong, increasing various aberrations such as field curvature and astigmatism, which is also undesirable.

[0026] Furthermore, it is more preferable to set the lower limit of equation (4) to 0.20, 0.30, or 0.40. Also, it is more preferable to set the upper limit of equation (4) to 4.0, 3.0, 2.0, or 1.8.

[0027] The conditions in equation (5) indicate an appropriate relationship between the focal length f3 of the third lens L3 and the focal length f of the entire display optical system L0. These conditions are necessary to ensure high magnification and sufficient eye relief while effectively correcting various aberrations such as field curvature and astigmatism. If f / f3 exceeds the upper limit of equation (5), the positive refractive power of the third lens L3 becomes stronger, increasing the Petzval sum of the display optical system L0, which makes it difficult to correct various aberrations such as field curvature and astigmatism, and is therefore undesirable. If f3 / f falls below the lower limit of equation (5), the negative refractive power of the third lens L3 becomes too strong, resulting in insufficient positive refractive power for the entire display optical system L0, which makes it difficult to achieve high magnification, and is therefore undesirable.

[0028] Furthermore, it is more preferable to set the lower limit of equation (5) to -4.00, -3.00, or -2.00. Also, it is more preferable to set the upper limit of equation (5) to 0.30, 0.20, or 0.10.

[0029] The conditions in equation (6) indicate an appropriate relationship between the focal length f2 of the second lens L2 and the focal length f3 of the third lens L3. These conditions are necessary to ensure high magnification and sufficient eye relief while effectively correcting various aberrations such as field curvature, astigmatism, and lateral aberration. If f2 / f3 exceeds the upper limit of equation (6), the negative refractive power of the third lens L3 weakens, increasing the Petzval sum of the display optical system L0, which makes it difficult to correct various aberrations such as field curvature and astigmatism, and is therefore undesirable. If f2 / f3 falls below the lower limit of equation (6), the refractive power of the second lens L2 becomes insufficient, making it difficult to correct lateral aberration, and is therefore undesirable.

[0030] Furthermore, it is more preferable to set the lower limit of equation (6) to -1.00, -0.50, -0.20, or -0.15. Also, it is more preferable to set the upper limit of equation (6) to 4.50, 4.00, 3.50, or 3.10.

[0031] The conditions in equation (7) indicate an appropriate shape factor for the third lens L3, and represent the conditions necessary to achieve both high magnification of the display optical system L0 and correction of various aberrations such as field curvature, astigmatism, and distortion. If the shape factor of the third lens L3 exceeds the upper limit of equation (7), it becomes difficult to correct various aberrations such as field curvature and astigmatism, which is undesirable. If the shape factor of the third lens L3 falls below the lower limit of equation (7), it becomes difficult to correct distortion, which is also undesirable.

[0032] Furthermore, it is more preferable to set the lower limit of equation (7) to -40.0, -37.0, or -35.0. Also, it is more preferable to set the upper limit of equation (7) to -0.2, -0.4, or -0.6.

[0033] The conditions in equation (8) represent an appropriate relationship between the total thickness LD of the display optical system L0 and the total focal length f of the display optical system L0. These conditions are necessary to achieve both high magnification of the display optical system L0 and correction of various aberrations such as spherical aberration and lateral aberration. If LD / f exceeds the upper limit of equation (8), the thickness of the display optical system L0 becomes too large, making high magnification difficult, which is undesirable. If LD / f falls below the lower limit of equation (8), it becomes impossible to set an appropriate curvature for each lens, making correction of various aberrations such as spherical aberration and lateral aberration difficult, which is also undesirable.

[0034] Furthermore, it is more preferable to set the lower limit of equation (8) to 0.9, 1.0, or 1.1. Also, it is more preferable to set the upper limit of equation (8) to 2.0, 1.5, or 1.3.

[0035] The conditions in equation (9) represent an appropriate relationship between half the diagonal length H of the display surface IP and the focal length f of the entire display optical system L0. These conditions are necessary to achieve both a wide field of view and correction of various aberrations such as spherical aberration, field curvature, and astigmatism. If H / f exceeds the upper limit of equation (9), the magnification of the display optical system L0 becomes too large, making it difficult to correct various aberrations such as spherical aberration, field curvature, and astigmatism, which is undesirable. If H / f falls below the lower limit of equation (9), it becomes difficult to achieve a wide field of view, which is also undesirable.

[0036] Furthermore, it is more preferable to set the lower limit of equation (9) to 0.32, 0.35, or 0.38. Also, it is more preferable to set the upper limit of equation (9) to 0.48, 0.45, or 0.42.

[0037] The conditions in equation (10) indicate an appropriate relationship between the height He of the inflection point in an aspherical lens and the effective diameter φ of the surface having the inflection point. If 2 × He / φ exceeds the upper limit of equation (9), it is undesirable because the inflection point of the aspherical lens cannot be located inside the lens surface, making it difficult to correct field curvature and astigmatism in the intermediate region of the field of view. If 2 × He / φ falls below the lower limit of equation (9), it is undesirable because the inflection point of the aspherical lens becomes too close to the optical axis, making it difficult to correct field curvature and astigmatism in the intermediate region of the field of view.

[0038] Furthermore, it is more preferable to set the lower limit of equation (10) to 0.4, 0.45, or 0.5. Also, it is more preferable to set the upper limit of equation (10) to 0.79, 0.78, or 0.77.

[0039] Numerical examples 1 to 10 are shown below. In each numerical example, the surface number i indicates the order of the surfaces when counted from the object side. The first surface is the display surface IP of the display element, and the second surface in numerical examples 1, 2, 4 to 10 is the observation side surface of the first cover glass CG1. r is the radius of curvature of the i-th surface (mm), and d is the lens thickness or distance (air gap) on the optical axis between the i-th surface and the (i+1)-th surface (mm). nd is the refractive index of the optical material between the i-th surface and the (i+1)-th surface at the d-line. νd is the Abbe number of the optical material between the i-th surface and the (i+1)-th surface with respect to the d-line. The Abbe number νd with respect to the d-line is given by Nd, NF, and NC, respectively, when the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) are Nd, NF, and NC, respectively. νd = (Nd-1) / (NF-NC) It is represented as follows: φ is the effective diameter of the i-th surface.

[0040] The focal length f (mm) is the focal length of the entire display optical system L0, and the display diagonal length (mm) is the diagonal length (2 × H) of the display surface IP. The apparent field of view (°) is the half-angle of view ω (°) of the display optical system L0, and 2ω is the field of view (°) as the full angle of view.

[0041] 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 direction of the optical axis, h is the height from the optical axis in the direction perpendicular to the optical axis, with the direction of light propagation being positive, r is the radius of paraxial curvature, K is the cone constant, and A4, A6, A8, A10, A12 are aspherical coefficients. The cone constant and aspherical coefficients "e±M" are multiplied by 10⁻¹⁴. ±M It means...

[0042] x=( h 2 / r) / [1+√{1-(1+k)(h / R) 2}] +A2×h2 +A4×h 4 +A6×h 6 +A8×h 8 +A8×h 8 +A10×h 10 +A12×h 12 In addition, in each numerical example, the diopter and the focal length of each lens, which are adjusted by changing the distance between the second surface and the third surface (the object-side lens surface of the first lens 1) by moving the display element ID itself that moves the entire display optical system with respect to the display element ID, are shown.

[0043] The values corresponding to the aforementioned formulas (1) to (10) in Numerical Examples 1 to 10 are summarized in Table 1. Each numerical example satisfies all the conditions of formulas (1) to (10).

[0044] Figures 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 respectively show the longitudinal aberration (spherical aberration, astigmatism, distortion, and chromatic aberration) in the state where the diopter of the display optical system in Numerical Examples 1 to 10 is set to -1.0 diopter (standard diopter). In the spherical aberration figure, the pupil diameter is 10 mm or 7.59 mm. The solid line indicates the spherical aberration at the d-line (wavelength 587.6 nm), and the two-dot chain line indicates the spherical aberration at the F-line (wavelength 486.1 nm). In the astigmatism figure, the solid line S indicates the astigmatism at the sagittal image plane, and the broken line M indicates the astigmatism at the meridional image plane. The distortion aberration figure shows the distortion aberration at the d-line. The chromatic aberration figure shows the lateral chromatic aberration at the F-line. H is half of the diagonal length of the display surface (maximum image height). [Numerical Example 1] Unit: mm Surface data Surface number r d nd νd φ 1 ∞ 0.50 1.52100 65.1 2 ∞ (variable) 3* 376.116 10.00 1.76802 49.2 23.7 4* -8.765 3.36 25.8 5* -14.720 1.00 1.635_{40} 23.9 20.8 6* -68.410 2.00 24.4 7* -11.368 5.51 1.53500 56.0 25.4 8* -14.724 0.30 25.8 9* 17.798 3.88 1.53500 56.0 22.9 10* -61.298 (variable) 22.7 11 ∞ 0.80 1.49171 57.4 12 ∞ 23.00 13 (Eye Point) Aspherical data 3rd page K =-1.89164e+05 A 4=-5.02068e-05 A 6= 5.62461e-07 A 8=-3.83199e-09 A10 = 8.20913e-12 Side 4 K =-3.27897e+00 A 4=-6.79417e-05 A 6= 7.94990e-08 A 8= 1.08833e-11 A10 = -2.87555e-12 5th page K =-1.64110e+01 A 4=-2.55131e-04 A 6=-1.27690e-06 A 8= 9.09432e-09 A10 = -3.01778e-12 Page 6 K =-9.50543e+00 A 2= 3.36298e-02 A 4=-4.33191e-04 A 6= 2.31754e-06 A8=-5.71593e-09 A10= 5.28515e-12 Side 7 K =-8.70412e+00 A 4= 1.42829e-04 A 6=-2.77784e-07 A 8=-8.50853e-10 A10=2.58965e-12 A12=-1.61740e-15 Side 8 K =-3.47459e+00 A 4=-4.58612e-05 A 6=-4.67695e-07 A 8= 5.98832e-09 A10=-2.70281e-11 A12= 4.19776e-14 9th page K =-8.60151e+00 A 4=-1.26506e-04 A 6= 1.92372e-06 A 8=-2.00432e-08 A10 = 6.77368e-11 Side 10 K =-8.66410e+01 A 4=-1.29062e-04 A 6= 1.89353e-06 A 8=-1.70580e-08 A10 = 5.44821e-11 Various data Diopter (D) -1.00 -4.00 +2.00 Focal length 20.28 20.28 20.28 Apparent field of view (°): 21.33, 20.20, 22.46 d 2 6.57 5.21 7.78 d10 2.11 3.38 0.70 [Numerical Example 2] Unit: mm Surface data Surface number rd nd νd φ 1 ∞ 0.50 1.52100 65.1 24.0 2 ∞ (variable) 3* 513.859 9.31 1.76802 49.2 24.0 4* -8.365 3.24 25.7 5* -14.757 1.00 1.63540 23.9 20.7 6* -182.926 1.90 24.5 7* -14.553 6.00 1.53500 56.0 26.0 8* -18.071 0.35 26.1 9* 16.857 3.91 1.53500 56.0 22.2 10* -59.514 (variable) 21.6 11 ∞ 0.80 1.49171 57.4 12 ∞ 23.00 13 (Eye Point) Aspherical data 3rd page K =-5.54471e+05 A 4=-9.25184e-05 A 6= 1.09708e-06 A 8=-6.38694e-09 A10 = 1.26580e-11 Side 4 K =-3.41127e+00 A 4=-8.97690e-05 A 6= 2.88068e-07 A 8=-8.42500e-10 A10 = -1.75989e-12 5th page K =-2.02579e+01 A 4=-2.04836e-04 A 6=-1.92237e-06 A 8= 1.03788e-08 A10 = 3.07955e-12 Page 6 K = 1.87220e+02 A 2= 3.66874e-02 A 4=-4.92639e-04 A 6= 2.14900e-06 A8=5.67822e-10 A10=-1.67267e-11 Side 7 K =-1.37291e+01 A 4= 1.13408e-04 A 6= 5.56589e-08 A 8=-7.42850e-10 A10=-6.13332e-12 A12= 3.08258e-14 Side 8 K =-4.78849e+00 A 4=-2.96841e-05 A 6=-5.38377e-07 A 8= 4.51576e-09 A10=-2.21221e-11 A12= 6.33920e-14 9th page K =-7.00279e+00 A 4=-3.57300e-05 A 6= 2.08429e-06 A 8=-2.41742e-08 A10 = 8.35094e-11 Side 10 K =-9.04274e+01 A 4=-7.36519e-05 A 6= 2.75506e-06 A 8=-2.57115e-08 A10 = 8.37098e-11 Various data Diopter (D) -1.00 -4.00 +2.00 Focal length 20.28 20.28 20.28 Display diagonal length (mm) 16.20 16.20 16.20 Apparent field of view (°): 21.28, 20.14, 22.41 d 2 6.92 5.56 8.13 d10 2.08 3.38 0.70 [Numerical Example 3] Unit: mm Surface data Surface number rd nd νd φ 1 ∞ (variable) 2* 18.739 10.66 1.76802 49.2 27.2 3* -11.259 2.78 27.1 4* -5.388 1.00 1.63540 23.9 23.3 5* -50.632 1.00 23.3 6* -7.892 1.61 1.53500 56.0 23.3 7* 66.883 1.00 22.7 8* 5.828 5.66 1.53500 56.0 20.8 9* -35.025 (variable) 20.0 10 (Eye Point) Aspherical data 2nd side K = 2.26455e-01 A 4=-5.68837e-05 A 6=-1.19209e-07 A 8= 1.11644e-09 A10 = -4.02931e-12 3rd page K =-6.67505e+00 A 4=-5.99596e-05 A 6= 3.81109e-07 A 8=-1.37120e-09 A10 = 1.63789e-12 Side 4 K =-4.28005e+00 A 4=-5.05845e-05 A 6= 1.77765e-07 A 8=-1.08490e-09 A10 = 2.90458e-12 5th page K = 0.00000e+00 A 4= 1.38981e-04 A 6=-9.94031e-07 A 8= 3.30110e-09 A10 = -3.87427e-12 Page 6 K =-1.23392e+01 A 4= 2.39087e-04 A 6=-1.26320e-06 A 8= 3.45854e-09 A10 = -2.49234e-12 Side 7 K = 0.00000e+00 A 4= 4.86520e-05 A 6=-9.80939e-07 A 8= 3.36450e-09 A10 = -2.72016e-12 Side 8 K =-5.26844e+00 A 4= 4.13928e-05 A 6=-3.15514e-07 A 8= 1.50115e-09 A10 = -9.54206e-12 9th page K =-3.54234e+01 A 4= 4.45326e-05 A 6= 6.44307e-09 A 8= 1.75263e-09 A10 = -7.41726e-12 Various data Diopter (D) -1.00 -4.00 +2.00 Focal length 20.37 20.37 20.37 Display diagonal length (mm) 16.20 16.20 16.20 Apparent field of view (°): 21.44, 20.35, 22.26 d 1 11.41 10.03 12.45 d 9 25:00 26:38 23:96 [Numerical Example 4] Unit: mm Surface data Surface number rd nd νd φ 1 ∞ 0.50 1.52100 65.1 2 ∞ (variable) 3* 24.387 9.56 1.76802 49.2 28.2 4* -13.114 3.94 28.4 5* -6.015 1.00 1.63540 23.9 23.0 6* -26.987 1.33 24.3 7* -9.756 3.64 1.53500 56.0 24.7 8* -16.671 0.50 24.5 9* 10.122 4.33 1.53500 56.0 22.0 10* -106.049 (variable) 21.7 11 ∞ 0.80 1.49171 57.4 12 ∞ 23.00 13 (Eye Point) Aspherical data 3rd page K = 6.70822e-01 A 4=-5.00618e-05 A 6=-1.18474e-07 A 8= 1.13930e-09 A10=-4.53268e-12 A12= 5.04919e-15 Side 4 K =-4.54994e+00 A 4=-6.06901e-05 A 6= 2.57069e-07 A 8=-1.15658e-09 A10=3.08087e-12 A12=-4.68990e-15 5th page K =-2.71187e+00 A 4=-6.42669e-05 A 6= 3.16971e-07 A 8=-2.28961e-09 A10= 6.08757e-12 A12= 9.41133e-15 Page 6 K = 9.01337e-01 A 4= 1.63743e-04 A 6=-9.99798e-07 A 8= 3.69695e-09 A10=-5.04138e-12 A12= 2.72274e-15 Side 7 K =-7.76278e+00 A 4= 2.21440e-04 A 6=-1.18424e-06 A 8= 3.71999e-09 A10=-1.05764e-12 A12=-7.47856e-15 Side 8 K =-6.41891e+00 A 4= 7.36232e-05 A 6=-8.33475e-07 A 8= 4.09237e-09 A10=-6.74545e-12 A12= 6.89504e-15 9th page K =-5.62166e+00 A 4=-2.54994e-05 A 6= 2.09700e-07 A 8=-3.08453e-09 A10=-3.76948e-11 A12= 2.70052e-13 Side 10 K = 4.16435e+01 A 4= 1.50868e-05 A 6= 1.97823e-07 A 8=-3.97950e-09 A10=-1.31872e-11 A12= 1.64345e-13 Various data Diopter (D) -1.00 -4.00 +2.00 Focal length 20.37 20.37 20.37 Display diagonal length (mm): 16.40 16.40 16.40 Apparent field of view (°): 21.25, 20.08, 22.38 d 2 9.18 7.79 10.40 d10 1.67 3.07 0.70 [Numerical Example 5] Unit: mm Surface data Surface number rd nd νd φ 1 ∞ 0.50 1.52100 65.1 2 ∞ (variable) 3* 20.197 9.85 1.76802 49.2 27.7 4* -13.690 3.67 27.8 5* -5.580 1.00 1.63540 23.9 23.2 6* -88.973 1.34 23.3 7* -10.081 2.59 1.63540 23.9 23.3 8* -12.105 0.30 23.4 9* 11.208 5.50 1.53500 56.0 23.4 10* -36.282 (variable) 23.4 11 ∞ 0.80 1.49171 57.4 12 ∞ 23.00 13 (Eye Point) Aspherical data 3rd page K = 3.87413e-01 A 4=-3.89860e-05 A 6=-8.67976e-08 A 8= 8.28362e-10 A10=-5.30948e-12 A12= 4.80023e-15 Side 4 K =-4.89947e+00 A 4=-3.68131e-05 A 6= 2.03082e-07 A 8=-1.11227e-09 A10=3.58940e-12 A12=-7.29729e-15 5th page K =-2.37322e+00 A 4=-7.28159e-06 A 6= 3.55254e-07 A 8=-3.51693e-09 A10= 1.76606e-11 A12=-4.11756e-14 Page 6 K =-1.49948e+01 A 4= 1.85571e-04 A 6=-1.26406e-06 A 8= 5.01073e-09 A10=-8.97244e-12 A12=-9.97681e-16 Side 7 K =-1.10608e+01 A 4= 2.49744e-04 A 6=-1.10783e-06 A 8= 2.41642e-09 A10= 7.66818e-12 A12=-7.77741e-14 Side 8 K =-2.09391e+00 A 4= 1.89660e-04 A 6=-3.28364e-07 A 8= 3.68979e-09 A10=-3.01581e-11 A12= 3.23950e-14 9th page K =-1.00450e+01 A 4=-1.07204e-04 A 6= 6.80934e-07 A 8=-2.98798e-09 A10=-3.73369e-12 A12= 4.16627e-14 Side 10 K = 2.35431e+00 A 4=-5.53434e-05 A 6= 8.92519e-08 A 8= 6.92353e-10 A10=-1.11632e-11 A12= 3.76060e-14 Various data Diopter (D) -1.00 -4.00 +2.00 Focal length 20.37 20.37 20.37 Display diagonal length (mm) 16.20 16.20 16.20 Apparent field of view (°): 21.10, 20.02, 22.05 d 2 9.21 7.81 10.43 d10 1.78 3.08 0.70 [Numerical Example 6] Unit: mm Surface data Surface number rd nd νd φ 1 ∞ 0.50 1.52100 65.1 2 ∞ (variable) 3* 397.212 10.00 1.76802 49.2 23.5 4* -8.822 3.32 25.7 5* -15.026 1.00 1.63540 23.9 20.8 6* -51.662 1.97 24.5 7* -12.387 5.95 1.53500 56.0 25.5 8* -13.147 0.30 25.9 9* 20.995 3.53 1.53500 56.0 22.9 10* -93.552 (variable) 22.7 11 ∞ 0.80 1.49171 57.4 12 ∞ 23.00 13 (Eye Point) Aspherical data 3rd page K =-2.23533e+05 A 4=-4.68928e-05 A 6= 4.85224e-07 A 8=-3.74330e-09 A10 = 8.78146e-12 Side 4 K =-3.30000e+00 A 4=-6.70728e-05 A 6= 6.09390e-08 A 8= 3.44398e-11 A10 = -3.09088e-12 5th page K =-1.71486e+01 A 4=-2.69762e-04 A 6=-1.01007e-06 A 8= 6.53288e-09 A10 = 5.80030e-12 Page 6 K =-5.48685e+00 A 2= 3.61488e-02 A 4=-4.35401e-04 A 6= 2.34055e-06 A8=-6.10400e-09 A10=6.82350e-12 Side 7 K =-9.05184e+00 A 4= 1.24223e-04 A 6=-1.68995e-07 A 8=-9.08025e-10 A10= 1.59955e-12 A12= 3.95063e-16 Side 8 K =-2.54933e+00 A 4=-2.73555e-05 A 6=-5.18865e-07 A 8= 6.01841e-09 A10=-2.58214e-11 A12= 3.70967e-14 9th page K =-8.08215e+00 A 4=-1.50436e-04 A 6= 2.03581e-06 A 8=-1.98158e-08 A10 = 6.54008e-11 Side 10 K = 2.12130e+01 A 4=-1.24533e-04 A 6= 1.80098e-06 A 8=-1.59562e-08 A10 = 5.08091e-11 Various data Diopter (D) -1.00 -4.00 +2.00 Focal length 20.28 20.28 20.28 Display diagonal length (mm) 16.20 16.20 16.20 Apparent field of view (°): 21.36, 20.24, 22.47 d 2 6.55 5.20 7.77 d10 2.11 3.38 0.70 [Numerical Example 7] Unit: mm Surface data Surface number rd nd νd φ 1 ∞ 0.50 1.52100 65.1 2 ∞ (variable) 3* 425.161 9.79 1.76802 49.2 23.4 4* -8.696 3.06 25.4 5* -15.539 1.38 1.63540 23.9 20.8 6* -50.461 2.06 24.5 7* -10.428 6.00 1.53500 56.0 25.5 8* -11.804 0.30 25.8 9* 16.937 3.22 1.53500 56.0 22.6 10* 170.326 (variable) 22.2 11 ∞ 0.80 1.49171 57.4 12 ∞ 23.00 13 (Eye Point) Aspherical data 3rd page K =-2.95506e+05 A 4=-3.47748e-05 A 6= 4.31092e-07 A 8=-3.59952e-09 A10 = 8.15728e-12 Side 4 K =-3.32024e+00 A 4=-5.92942e-05 A 6= 2.60604e-08 A 8= 2.25111e-10 A10 = -3.75703e-12 5th page K =-1.61589e+01 A 4=-2.51907e-04 A 6=-1.56356e-06 A 8= 1.21736e-08 A10 = -1.05361e-11 Page 6 K =-3.04191e+00 A 2= 3.52360e-02 A 4=-4.26318e-04 A 6= 2.40118e-06 A8=-6.83282e-09 A10=8.59899e-12 Side 7 K =-8.88090e+00 A 4= 1.31777e-04 A 6=-2.09126e-07 A 8=-7.94830e-10 A10= 2.34009e-12 A12= 9.58615e-16 Side 8 K =-1.95219e+00 A 4=-1.07224e-05 A 6=-4.41017e-07 A 8= 5.82392e-09 A10=-2.74169e-11 A12= 4.79560e-14 9th page K =-1.16423e+01 A 4=-1.71690e-04 A 6= 1.98413e-06 A 8=-1.70396e-08 A10 = 6.04553e-11 Side 10 K =-3.71617e+03 A 4=-2.17353e-04 A 6= 2.39597e-06 A 8=-1.78623e-08 A10 = 5.93749e-11 Various data Diopter (D) -1.00 -4.00 +2.00 Focal length 20.28 20.28 20.28 Display diagonal length (mm) 16.20 16.20 16.20 Apparent field of view (°): 21.33, 20.25, 22.40 d 2 6.81 5.46 8.03 d10 2.03 3.38 0.70 [Numerical Example 8] Unit: mm Surface data Surface number rd nd νd φ 1 ∞ 0.50 1.52100 65.1 2 ∞ (variable) 3* 384.091 10.00 1.76802 49.2 23.4 4* -8.547 3.00 25.5 5* -14.856 1.00 1.63540 23.9 20.5 6* -83.067 1.94 24.0 7* -12.617 5.65 1.53500 56.0 24.9 8* -14.789 0.30 25.4 9* 24.857 4.06 1.53500 56.0 23.3 10* -37.365 (variable) 23.2 11 ∞ 0.80 1.49171 57.4 12 ∞ 23.00 13 (Eye Point) Aspherical data 3rd page K =-2.17733e+05 A 4=-5.11908e-05 A 6= 5.60697e-07 A 8=-3.78838e-09 A10 = 8.04770e-12 Side 4 K =-3.36508e+00 A 4=-6.93029e-05 A 6= 7.67309e-08 A 8= 1.32288e-11 A10 = -2.96058e-12 5th page K =-1.73943e+01 A 4=-2.61688e-04 A 6=-1.27273e-06 A 8= 8.76287e-09 A10 = 2.95618e-12 Page 6 K = 1.33446e+01 A 2= 3.42425e-02 A 4=-4.42056e-04 A 6= 2.36438e-06 A8=-5.70590e-09 A10=5.94429e-12 Side 7 K =-9.58046e+00 A 4= 1.42666e-04 A 6=-2.63028e-07 A 8=-8.54596e-10 A10=2.74952e-12 A12=-4.31377e-15 Side 8 K =-4.68902e+00 A 4=-4.32305e-05 A 6=-4.87542e-07 A 8= 6.12324e-09 A10=-2.73575e-11 A12= 4.00571e-14 9th page K =-7.67937e+00 A 4=-1.23119e-04 A 6= 1.86970e-06 A 8=-1.96532e-08 A10 = 6.46920e-11 Side 10 K =-2.70481e+01 A 4=-1.30006e-04 A 6= 1.91854e-06 A 8=-1.68608e-08 A10 = 5.12757e-11 Various data Diopter (D) -1.00 -4.00 +2.00 Focal length 20.28 20.28 20.28 Apparent field of view (°): 21.36, 20.27, 22.43 Display diagonal length (mm) 16.20 16.20 16.20 d 2 6.51 5.16 7.73 d10 2.09 3.38 0.70 [Numerical Example 9] Unit: mm Surface data Surface number rd nd νd φ 1 ∞ 0.50 1.52100 65.1 2 ∞ (variable) 3* 381.662 9.96 1.76802 49.2 23.6 4* -8.609 3.11 25.6 5* -15.078 1.01 1.63540 23.9 20.8 6* -64.767 2.26 24.4 7* -10.579 6.00 1.53500 56.0 25.5 8* -12.817 0.30 25.9 9* 15.940 3.29 1.53500 56.0 22.5 10 * 253.550 (variable) 22.1 11 ∞ 0.80 1.49171 57.4 12 ∞ 23.00 13 (Eye Point) Aspherical data 3rd page K =-1.87125e+05 A 4=-4.91444e-05 A 6= 5.57210e-07 A 8=-3.81933e-09 A10 = 7.99736e-12 Side 4 K =-3.30596e+00 A 4=-6.66232e-05 A 6= 8.51735e-08 A 8=-6.13695e-12 A10 = -3.08901e-12 5th page K =-1.59486e+01 A 4=-2.50965e-04 A 6=-1.37055e-06 A 8= 9.52523e-09 A10 = -1.95386e-12 Page 6 K =-8.65996e+00 A 2= 3.29093e-02 A 4=-4.25197e-04 A 6= 2.34596e-06 A8=-6.28200e-09 A10=7.02474e-12 Side 7 K =-9.02297e+00 A 4= 1.41144e-04 A 6=-2.61141e-07 A 8=-8.54577e-10 A10=3.00635e-12 A12=-1.59596e-15 Side 8 K =-2.27918e+00 A 4=-2.93589e-05 A 6=-4.19851e-07 A 8= 5.86368e-09 A10=-2.76518e-11 A12= 4.60724e-14 9th page K =-8.82778e+00 A 4=-1.63479e-04 A 6= 2.03969e-06 A 8=-1.89952e-08 A10 = 6.81850e-11 Side 10 K =-6.23994e+03 A 4=-1.75794e-04 A 6= 2.08448e-06 A 8=-1.73037e-08 A10 = 6.03257e-11 Various data Diopter (D) -1.00 -4.00 +2.00 Focal length 20.28 20.28 20.28 Apparent field of view (°): 21.31, 20.22, 22.41 Display diagonal length (mm) 16.20 16.20 16.20 d 2 6.70 5.34 7.91 d10 2.11 3.38 0.70 [Numerical Example 10] Unit: mm Surface data Surface number rd nd νd φ 1 ∞ 0.50 1.52100 65.1 2 ∞ (variable) 3* 222.663 10.00 1.76802 49.2 23.2 4* -7.543 1.89 25.2 5* -22.034 1.00 1.63540 23.9 20.6 6* -95.300 2.57 23.7 7* -6.296 2.78 1.53500 56.0 24.8 8* -35.492 0.65 25.0 9* 9.742 7.00 1.53500 56.0 24.2 10* -21.380 (variable) 24.0 11 ∞ 0.80 1.49171 57.4 12 ∞ 23.00 13 (Eye Point) Aspherical data 3rd page K =-5.36684e+04 A 4=-4.89392e-05 A 6= 5.73285e-07 A 8=-3.81851e-09 A10 = 7.79489e-12 Side 4 K =-3.51747e+00 A 4=-6.94365e-05 A 6= 8.24824e-08 A 8= 2.82925e-11 A10 = -3.05228e-12 5th page K =-3.59603e+01 A 4=-2.01346e-04 A 6=-2.91271e-06 A 8= 2.17096e-08 A10 = -2.68354e-11 Page 6 K = 4.05609e+01 A 2= 4.15693e-02 A 4=-5.03937e-04 A 6= 2.70995e-06 A8=-7.12854e-09 A10=9.84489e-12 Side 7 K =-7.65111e+00 A 4= 2.74715e-04 A 6=-1.13764e-06 A 8= 1.18191e-09 A10= 1.23324e-11 A12=-5.87537e-14 Side 8 K =-8.80935e+00 A 4=-2.23285e-05 A 6=-3.64339e-07 A 8= 6.32929e-09 A10=-3.26822e-11 A12= 4.46417e-14 9th page K =-1.30307e+01 A 4=-8.98635e-05 A 6= 1.60254e-06 A 8=-1.71821e-08 A10 = 5.58828e-11 Side 10 K =-1.21206e+01 A 4=-1.48902e-04 A 6= 1.85068e-06 A 8=-1.39353e-08 A10 = 4.03491e-11 Various data Diopter (D) -1.00 -4.00 +2.00 Focal length 20.28 20.28 20.28 Display diagonal length (mm) 16.20 16.20 16.20 Apparent field of view (°): 21.33, 20.30, 22.33 d 2 6.73 5.38 7.95 d10 2.09 3.38 0.70

[0045] [Table 1]

[0046] [Display device 1] Figure 21 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 (EVF) as a display device, including the display optical system L of Examples 1 to 10.

[0047] 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.

[0048] The 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.

[0049] The electronic viewfinder (EVF) is provided with an eyepiece optical system 111, which is composed of one of the display optical systems L from Examples 1 to 10. 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.

[0050] 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.

[0051] [Display device 2] Figure 22 shows a head-mounted display (HMD) as a display device using the display optical systems of Examples 1 to 10. The HMD is mounted on the observer's head (in front of the eyes) by mounting gear (not shown).

[0052] The HMD includes image display elements RID and LID for the right and left eyes, a right-eye display optical system ROS that directs the display light from the right-eye image display element RID to the observer's right eye, and a left-eye display optical system LOS that directs the display light from the left-eye image display element LID to the observer's left eye.

[0053] By using the display optical systems shown in Examples 1 to 10 as the right-eye and left-eye display optical systems ROS and LOS, a wide-field-of-view and thin HMD can be realized.

[0054] Furthermore, by similarly using image display elements for the right and left eyes and the display optical system shown in Example 3, a wide-viewing-angle optical see-through type HMD can also be realized.

[0055] Furthermore, the display optical systems of Examples 1 to 10 can also be used in various display devices other than electronic viewfinders and head-mounted displays.

[0056] The above embodiments include the following configuration.

[0057] (Composition 1) An optical system that guides light from a display element to the observation side, It consists of a first lens with positive refractive power, a second lens with negative refractive power, a third lens with refractive power, and a fourth lens with refractive power, arranged in order from the display element side to the observation side. When the focal length of the third lens is f3, the focal length of the fourth lens is f4, the radius of curvature of the display element side surface of the fourth lens is R41, the radius of curvature of the observation side surface of the fourth lens is R42, the air-equivalent distance from the display surface of the display element to the display element side surface of the first lens when the diopter is -1 diopter is L1, and the distance along the optical axis from the display element side surface of the first lens to the observation side surface of the fourth lens is LD, -10.00 <f4 / f3<0.15 -5.00<(R41+R42) / (R41-R42)<-0.19 0.5 <LD / L1<40.0 An optical system characterized by satisfying the following conditions. (Configuration 2) When the focal length of the optical system is f and the focal length of the fourth lens is f4, 0.10 ≤ f4 / f ≤ 5.00 The optical system according to configuration 1, characterized by satisfying the following conditions. (Composition 3) When the focal length of the optical system is f and the focal length of the third lens is f3, -5.00 ≤ f / f3 ≤ 0.50 The optical system according to configuration 1 or 2, characterized by satisfying the following conditions. (Composition 4) When the focal length of the second lens is f2 and the focal length of the third lens is f3, -2.00 ≤ f2 / f3 ≤ 5.00 An optical system according to any one of configurations 1 to 3, characterized by satisfying the following conditions. (Composition 5) When the radius of curvature of the display element side surface of the third lens is R31 and the radius of curvature of the observation side surface of the third lens is R32, -50.0≦(R32+R31) / (R32-R31)≦-0.1 An optical system according to any one of configurations 1 to 4, characterized by satisfying the following conditions. (Composition 6) 0.8 ≤ LD / f ≤ 3.0 An optical system according to any one of configurations 1 to 5, characterized by satisfying the following conditions. (Composition 7) When H is half the diagonal length of the display surface of the display element, and f is the focal length of the optical system, 0.30 ≤ H / f ≤ 0.50 An optical system according to any one of configurations 1 to 6, characterized by satisfying the following conditions. (Composition 8) The optical system according to any one of configurations 1 to 7, characterized in that at least one of the first to fourth lenses is an aspherical lens having an inflection point on at least one of the display element side and the observation side. (Composition 9) In the aspherical lens, when the height of the inflection point from the optical axis is He and the effective diameter of the surface having the inflection point in the aspherical lens is φ, 0.3 ≤ 2 × He / φ ≤ 0.8 An optical system according to any one of configurations 1 to 8, characterized by satisfying the following conditions. (Composition 10) The optical system according to any one of configurations 1 to 9, characterized in that the third lens has a negative refractive power and the fourth lens has a positive refractive power. (Composition 11) The optical system according to any one of configurations 1 to 9, characterized in that the third lens has a positive refractive power and the fourth lens has a positive refractive power. (Composition 12) An optical system that guides light from a display element to the observation side, It consists of a first lens with positive refractive power, a second lens with negative refractive power, a third lens with refractive power, and a fourth lens with refractive power, arranged in order from the display element side to the observation side. When the diopter is -1 diopter, let L1 be the air-equivalent distance from the display surface of the display element to the display element side surface of the first lens, and let LD be the distance along the optical axis from the display element side surface of the first lens to the observation side surface of the fourth lens. 0.5 <LD / L1<40.0 An optical system characterized by satisfying the following conditions. (Composition 13) The optical system described in any one of configurations 1 to 12, A display device characterized by having the aforementioned display element.

[0058] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention. [Explanation of Symbols]

[0059] L1 First Lens L2 Second Lens L3 3rd lens L4 4th lens IP display surface EP Eye Point

Claims

1. An optical system that guides light from a display element to the observation side, It consists of a first lens with positive refractive power, a second lens with negative refractive power, a third lens with refractive power, and a fourth lens with refractive power, arranged in order from the display element side to the observation side. When the focal length of the third lens is f3, the focal length of the fourth lens is f4, the radius of curvature of the display element side surface of the fourth lens is R41, the radius of curvature of the observation side surface of the fourth lens is R42, the air-equivalent distance from the display surface of the display element to the display element side surface of the first lens when the diopter is -1 diopter is L1, and the distance along the optical axis from the display element side surface of the first lens to the observation side surface of the fourth lens is LD, -10.00<f4 / f3<0.15 -5.00<(R41+R42) / (R41-R42)<-0.19 0.5<LD / L1<40.0 An optical system characterized by satisfying the following conditions.

2. When the focal length of the optical system is f and the focal length of the fourth lens is f4, 0.10 ≤ f₄ / f ≤ 5.00 The optical system according to claim 1, characterized in that it satisfies the following conditions.

3. When the focal length of the optical system is f and the focal length of the third lens is f3, -5.00 ≤ f / f3 ≤ 0.50 The optical system according to claim 1, characterized in that it satisfies the following conditions.

4. When the focal length of the second lens is f2 and the focal length of the third lens is f3, -2.00 ≤ f² / f³ ≤ 5.00 The optical system according to claim 1, characterized in that it satisfies the following conditions.

5. When the radius of curvature of the display element side surface of the third lens is R31 and the radius of curvature of the observation side surface of the third lens is R32, -50.0≦(R32+R31) / (R32-R31)≦-0.1 The optical system according to claim 1, characterized in that it satisfies the following conditions.

6. 0.8 ≤ LD / f ≤ 3.0 The optical system according to claim 1, characterized in that it satisfies the following conditions.

7. When H is half the diagonal length of the display surface of the display element, and f is the focal length of the optical system, 0.30 ≤ H / f ≤ 0.50 The optical system according to claim 1, characterized in that it satisfies the following conditions.

8. The optical system according to claim 1, characterized in that at least one of the first to fourth lenses is an aspherical lens having an inflection point on at least one of the display element side and the observation side.

9. In the aspherical lens, when He is the height of the inflection point from the optical axis and φ is the effective diameter of the surface having the inflection point in the aspherical lens, 0.3 ≤ 2 × He / φ ≤ 0.8 The optical system according to claim 1, characterized in that it satisfies the following conditions.

10. The optical system according to claim 1, characterized in that the third lens has a negative refractive power and the fourth lens has a positive refractive power.

11. The optical system according to claim 1, characterized in that the third lens has a positive refractive power and the fourth lens has a positive refractive power.

12. An optical system that guides light from a display element to the observation side, It consists of a first lens with positive refractive power, a second lens with negative refractive power, a third lens with refractive power, and a fourth lens with refractive power, arranged in order from the display element side to the observation side. When the diopter is -1 diopter, let L1 be the air-equivalent distance from the display surface of the display element to the display element side surface of the first lens, and let LD be the distance along the optical axis from the display element side surface of the first lens to the observation side surface of the fourth lens. 0.5<LD / L1<40.0 An optical system characterized by satisfying the following conditions.

13. An optical system according to any one of claims 1 to 12, A display device characterized by having the aforementioned display element.

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