Eye contact optical system and display device

Abstract

An eyepiece optical system (12) has an optical axis in which light is guided between a pupil of a user and a display surface, and comprises a first lens element (21) and a second lens element (22). The first lens element has a polarization reflection surface (41) that reflects or transmits incident light in accordance with the polarization of the light on a display side toward the display surface. The second lens element has a partial reflection surface (43) that reflects a portion of incident light and transmits the remainder thereof, the partial reflection surface (43) being disposed between the first lens element and the display surface. The first lens element has, on a pupil side thereof toward the pupil, an aspherical surface that is convex toward the opposite side from the polarization reflection surface and that includes a projecting region in which the optical axis is positioned. The aspherical surface of the first lens element on the pupil side thereof satisfies the condition 0.05 < SagH / BF < 0.25, where SagH is the sag of the display surface at the maximum image height, and BF is the back focus of the eyepiece optical system.

Description

Technical Field

[0001] The present disclosure relates to an eyepiece optical system and a display device including the eyepiece optical system.

Background Art

[0002] Patent Document 1 discloses an eyepiece optical system that forms a virtual image of an image displayed on a two-dimensional display element in the eyes of an observer in a head-mounted display or a viewfinder of various cameras. This eyepiece optical system includes, in order from the observer side, an aspherical resin lens including a first aspherical surface and a second surface that selectively reflects or transmits circularly polarized light, a spherical glass lens having a semi-transmissive mirror surface formed on the first surface, and a polarization conversion element that converts image light from the two-dimensional display element into circularly polarized light. On the first surface of the aspherical resin lens, at least the range through which light rays pass is provided convexly on the observer side. Patent Document 1 enables high-quality virtual image display in an eyepiece optical system having a short overall length and a thin profile.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides an eyepiece optical system and a display device that can easily secure the user's field of view.

Means for Solving the Problems

[0005] The ocular optical system in the present disclosure has an optical axis for guiding light between the pupil of the user and the display surface, and includes a first lens element and a second lens element. The first lens element has a polarization reflecting surface that reflects or transmits the incident light according to the polarization of the incident light on the display side facing the display surface. The second lens element is disposed between the first lens element and the display surface, and has a partial reflecting surface that reflects a part of the incident light and transmits the remaining part. The first lens element has an aspherical surface that is convex toward the pupil side facing the pupil and includes a convex region where the optical axis is located, on the side opposite to the polarization reflecting surface. The aspherical surface on the pupil side of the first lens element satisfies the following condition (1). 0.05 < SagH / BF < 0.25 …(1) Here,[[]]END]] SagH: Sag amount at the maximum image height of the display surface BF: Back focus of the ocular optical system is.[[]]END]]

[0006] The display device in the present disclosure includes a display element having a display surface for displaying an image and the above-described ocular optical system.

Advantages of the Invention

[0007] According to the ocular optical system and the display device in the present disclosure, it is possible to easily secure the visual field of the user.

Brief Description of the Drawings

[0008]

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Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, a more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters or redundant descriptions of substantially the same configurations may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate the understanding of those skilled in the art.

[0010] Note that the applicant provides the accompanying drawings and the following description for those skilled in the art to fully understand the present disclosure, and does not intend to limit the subject matter described in the claims thereby.

[0011] (Embodiment 1) Hereinafter, Embodiment 1 of a visual optical system, which is an example of an eyepiece optical system according to the present disclosure, and a display device using the visual optical system will be described.

[0012] 1. Regarding the display device The display device according to Embodiment 1 will be described with reference to FIGS. 1 and 2.

[0013] FIG. 1 is a diagram showing the configuration of a display device 1 according to Embodiment 1 of the present disclosure. The display device 1 in the present embodiment is a head-mounted display (HMD) that is worn on the head of a user 5 and allows the user 5 to visually recognize a virtual image V. The display device 1 is configured in a glasses type provided with two projection units 10 as parts corresponding to both eyes of the user 5, for example.

[0014] The display device 1 includes, for example, for each projection unit 10 as shown in FIG. 1, a display element 11, a visual optical system 12, and a diopter adjustment mechanism 13. Each projection unit 10 of the display device 1 projects display light, which is light for visually recognizing the virtual image V, from the display element 11 to the eye 50 of the user 5 via the visual optical system 12. Such a display device 1 is useful because it has a wide viewing angle corresponding to the range in which the user 5 visually recognizes the virtual image V and is small and lightweight.

[0015] The visual optical system 12 in this embodiment is composed of a polarization reflection optical system that folds back the optical path by utilizing reflection according to the polarization of light. As a result, the visual optical system 12 can be configured to be thin with a short overall optical length, making it easy to miniaturize the display device 1. The visual optical system 12 of this embodiment has a thin configuration and is provided with a configuration that easily ensures a wide viewing angle in the display device 1. Details of the visual optical system 12 will be described later.

[0016] The diopter adjustment mechanism 13 is an example of a movable mechanism for adjusting the diopter according to the visual acuity of each eye 50 in the display device 1. According to the diopter adjustment mechanism 13, for example, the user 5 can easily adjust the virtual image V to be visually recognized according to his or her own visual acuity in the display device 1. FIG. 2 illustrates the diopter adjustment mechanism 13.

[0017] Hereinafter, as shown in FIG. 2, the direction along the optical axis of the visual optical system 12 is defined as the Z direction, the direction of rotation around the optical axis is defined as the θ direction, and the pupil side where the pupil of the eye 50 is assumed to be located is defined as the -Z side, and the display side where the display element 11 is located is defined as the +Z side, starting from the visual optical system 12.

[0018] The display element 11 includes a display surface S for displaying various images. The display surface S includes, for example, a plurality of pixels and emits display light indicating an image for visually recognizing the virtual image V. The display element 11 is configured, for example, by providing a circular polarizing plate 14 on an organic EL display. The display light from the display element 11 is emitted to the -Z side in circular polarization set to rotate clockwise or counterclockwise, for example, in the circular polarizing plate 14.

[0019] The display element 11 is not limited to the above configuration, and may be, for example, a liquid crystal display device, a reflective liquid crystal device (LCOS), a digital micromirror device (DMD), a micro LED display, or various micro displays. Also, the display element 11 does not particularly need to include the circular polarizing plate 14. The circular polarizing plate 14 may be included in the visual optical system 12.

[0020] As shown in FIG. 2, the visual optical system 12 has a distance to the eye 50, i.e., the eye relief ER, along the optical axis on the -Z side and a distance to the display surface S of the display element 11, i.e., the back focus BF, on the +Z side.

[0021] In the present embodiment, the diopter adjustment mechanism 13 realizes the diopter adjustment with a simple configuration in which the visual optical system 12 is moved in the Z direction as a single lens group. For example, the diopter adjustment mechanism 13 adjusts the diopter so as to correct a strong myopic vision as the visual optical system 12 is moved to the +Z side. The movable range in such diopter adjustment depends on the length of the back focus BF of the visual optical system 12. Therefore, in the present embodiment, a thin and wide-angle visual optical system 12 is provided while securing the back focus BF so that the diopter adjustment can be performed.

[0022] The diopter adjustment mechanism 13 may be configured not to rotate in the θ direction when the visual optical system 12 moves in the Z direction, and is, for example, configured by a cam mechanism. For example, as shown in FIG. 2, the diopter adjustment mechanism 13 includes a cam cylinder 31, a lens holding portion 32, and a rotation restricting portion 33.

[0023] The cam cylinder 31 is, for example, a cylindrical member having a spiral cam groove and is configured to be rotatable in the θ direction. The diopter adjustment mechanism 13 may include a member operable by the user 5, and may include, for example, a dial or a ring for rotating the cam cylinder 31.

[0024] The lens holding portion 32 is a member that holds the visual optical system 12 therein. In the lens holding portion 32, the relative positions between various lenses in the visual optical system 12 are fixed. The lens holding portion 32 is provided with a pin or the like that engages with the cam groove of the cam cylinder 31.

[0025] The rotation restricting portion 33 fixes the angular position of the lens holding portion 32 in the θ direction while allowing the movement of the lens holding portion 32 in the Z direction. The rotation restricting portion 33 is configured by providing, for example, a cylindrical member having a hole through which the pin of the lens holding portion 32 penetrates and extending in the Z direction between the cam cylinder 31 and the lens holding portion 32.

[0026] According to the visibility adjustment mechanism 13 as described above, the lens holding part 32 moves in the Z direction in response to the rotation of the cam cylinder 31, and at this time, the rotation of the lens holding part 32 is restricted. Thereby, for example, when the display light from the display element 11 has a deviation from circular polarization, it is possible to suppress a deterioration in image quality caused by a deviation in the angular position of the visual optical system 12, which is a concern.

[0027] Particularly when suppression of the above-described deterioration in image quality is not necessary, the visibility adjustment mechanism 13 does not have to restrict the rotation of the visual optical system 12, and may be configured by, for example, a screwing method. The visual optical system 12 and the visibility adjustment mechanism 13 may be a module provided integrally. The eyepiece optical system of the present embodiment may include the visibility adjustment mechanism 13 in addition to the visual optical system 12.

[0028] 2. Regarding the visual optical system Details of the visual optical system 12 in the present embodiment will be described below.

[0029] 2-1. Configuration The configuration of the visual optical system 12 in the present embodiment will be described with reference to FIG. 3. In the following description, an example of the visual optical system 12 will be used.

[0030] FIG. 3 is a lens layout diagram showing the configuration of the visual optical system 12 according to Example 1 of the present embodiment. In FIG. 3, on the -Z side of the visual optical system 12, a virtual aperture A corresponding to the pupil of the user 5 of the display device 1 is shown (hereinafter also referred to as "pupil A"). Further, in FIG. 3, light rays from each part of the display surface S of the display element 11 to the pupil A through the parallel plate-shaped circular polarizing plate 14 and the visual optical system 12 are illustrated.

[0031] The visual optical system 12 in the present embodiment includes a first lens element 21 and a second lens element 22 arranged in order from the pupil side (-Z side) to the display side (+Z side) along the Z direction of the optical axis. The first lens element 21 and the second lens element 22 constitute, for example, a single lens group that is movable in the Z direction with their relative positions fixed to each other.

[0032] For example, the visual optical system 12 is composed of such a single lens group and is movable using the diopter adjustment mechanism 13 (FIG. 2) described above. FIG. 3 illustrates the arrangement of the visual optical system 12 in the state of zero diopter without diopter adjustment. The position of the visual optical system 12 in the state of zero diopter is the most -Z side within the movable range of the diopter adjustment mechanism 13.

[0033] In the visual optical system 12, the first lens element 21 is a reflective polarizing lens provided with a polarizing reflector 41. The first lens element 21 is composed of a lens material such as resin or glass, for example. According to the resin lens material, it is easy to reduce the weight of the visual optical system 12, for example. The -Z side surface of the first lens element 21 is the most pupil side in the visual optical system 12 and faces the eye 50 of the user 5, for example (see FIG. 2).

[0034] In the present embodiment, the polarizing reflector 41 is provided on the +Z side surface of the first lens element 21. For example, the polarizing reflector 41 is configured by attaching a reflective polarizing film. At this time, by attaching to the +Z side surface of the first lens element 21, a situation where the attached film is exposed to the pupil side and the film is likely to peel off can be avoided. The polarizing reflector 41 reflects light of one of the polarization components (for example, p-polarized light) orthogonal to each other with respect to linearly polarized light and transmits light of the other polarization component (for example, s-polarized light). The +Z side surface of the first lens element 21 is an example of the polarization reflecting surface in the present embodiment.

[0035] In the first lens element 21 of Example 1, a quarter-wave plate 42 is provided further on the +Z side of the polarizing reflector 41. The quarter-wave plate 42 is an example of a quarter-wave phase element that imparts a phase delay of a quarter wavelength in a preset polarization direction with respect to incident light. For example, the quarter-wave plate 42 is configured by attaching a quarter-wave film on the +Z side of the reflective polarizing film on the +Z side surface of the first lens element 21. The quarter-wave plate 42 and the polarizing reflector 41 are arranged with their directions regarding the polarization direction aligned with each other.

[0036] In this embodiment, the surface on the -Z side of the first lens element 21 is formed of an aspherical surface that is rotationally symmetric about the optical axis. The surface on the -Z side of the first lens element 21 is formed convex in the vicinity of the center where the optical axis is located, and has a curved shape that bends back in the peripheral portion (see FIG. 5). In Example 1, the surface on the +Z side of the first lens element 21 is planar. The first lens element 21 has a positive power (i.e., refractive power) at least in the vicinity of the center, and basically functions as a positive lens.

[0037] The second lens element 22 is a beam splitter lens provided with a half mirror 43. The second lens element 22 is made of a lens material such as resin or glass, for example. According to the glass lens material, for example, it is possible to avoid a situation where the image quality deteriorates due to birefringence in the resin, and the image quality of the visual optical system 12 can be improved.

[0038] In this embodiment, the half mirror 43 is provided on the surface on the +Z side of the second lens element 22. For example, the half mirror 43 is configured by applying a visible light reflection coating or vapor deposition or the like with a reflectance set to a predetermined value to the surface on the +Z side of the second lens element 22. The predetermined value of the reflectance is, for example, 50%. The surface on the +Z side of the second lens element 22 is an example of a partial reflection surface that reflects a part of the incident light and transmits the remainder.

[0039] The second lens element 22 has a positive power and constitutes a positive lens. The power of the second lens element 22 is, for example, larger than the power of the first lens element 21. The surfaces on the ±Z sides of the second lens element 22 are, for example, rotationally symmetric aspherical surfaces, respectively.

[0040] In this example, the surface on the -Z side of the second lens element 22 is convex on the -Z side at least in the vicinity of the center. The surface on the +Z side of the second lens element 22 is, for example, convex on the +Z side as a whole, and the curvature increases from the center portion toward the peripheral portion.

[0041] 2-2. Operation The operation in which the visual optical system 12 configured as described above functions as a polarization reflection optical system in the display device 1 will be described with reference to FIG. 4.

[0042] In the display device 1, first, the display light B1 from the display element 11 is incident on the visual optical system 12 from the +Z side in circular polarization preset by the circular polarizing plate 14, as shown in FIG. 4 for example.

[0043] In the visual optical system 12, the half mirror 43 on the +Z side of the second lens element 22 transmits a portion of the incident display light B1, for example, the display light B2 with a predetermined transmittance such as 50%, and emits it to the -Z side.

[0044] The display light B2 transmitted through the half mirror 43 is converted from circular polarization to p-polarization when passing through the quarter-wave plate 42 in the first lens element 21. For example, the p-polarized display light B3 is incident on the polarization reflection plate 41 from the quarter-wave plate 42.

[0045] The polarization reflection plate 41 reflects the display light B3 incident from the quarter-wave plate 42 as described above to the +Z side based on its polarization state. The display light B4 reflected by the polarization reflection plate 41 passes through the quarter-wave plate 42 again and is converted from p-polarization to circular polarization. The converted display light B5 travels to the +Z side and is incident on the half mirror 43 again.

[0046] The half mirror 43 reflects a portion of the incident display light B5, for example, the display light B6 in a ratio corresponding to a predetermined reflectance such as 50%. The display light B6 after reflection by the half mirror 43 travels to the -Z side in circular polarization opposite to that of the display light B2 that previously passed through the half mirror 43, and is incident on the quarter-wave plate 42, similar to the display light B2 during transmission.

[0047] This counterclockwise circularly polarized display light B6 is converted into display light B7 with s polarization different from the p polarization during the previous passage when passing through the quarter-wave plate 42 and is incident on the polarization reflection plate 41. The polarization reflection plate 41 transmits the converted display light B7 based on its polarization state. As a result, the transmitted display light B7 exits from the visual optical system 12 to the -Z side. The display light B10 that has thus exited from the visual optical system 12 can reach the eyes 50 of the user 5 (Fig. 1).

[0048] As described above, by using the optical path in which the display lights B1 to B10 travel back and forth between the polarization reflection plate 41 and the half mirror 43 in the visual optical system 12, a lens element with a long optical path length and a thin lens thickness can be adopted, and it is easy to make the visual optical system 12 thinner.

[0049] In this embodiment, by providing the polarization reflection plate 41 on the +Z side of the first lens element 21, the range in which the optical paths of the display lights B2 to B7 in the visual optical system 12 are folded back is limited from the +Z side surface of the first lens element 21 to the +Z side surface of the second lens element 22 (see Fig. 3). That is, the number of times the optical path of the display light B10 passes through the -Z side surface of the first lens element 21 is set to one time.

[0050] As a result, in the visual optical system 12 of this embodiment, for each light ray direction in the various light rays of the incident display light B10 over the range of the viewing angle (see Fig. 3), it is easy to control by the surface shape of the -Z side surface of the first lens element 21, and it is easy to secure a wide viewing angle. For example, it is assumed that when the back focus BF is long, the difficulty of widening the viewing angle of the optical system increases. In contrast, the visual optical system 12 of this embodiment can achieve widening while taking the length of the back focus BF for diopter adjustment due to the configuration of the -Z side surface of the first lens element 21 described below, and the user 5 can obtain a viewing field in which it is easy to see the virtual image V at a wide viewing angle.

[0051] 2-3. Regarding various conditions The conditions satisfied by the visual optical system 12 of this embodiment due to the -Z side surface of the first lens element 21 and the like will be described with reference to Fig. 5. Fig. 5 is a diagram for explaining the aspherical shape in the visual optical system 12.

[0052] The visual optical system 12 of this embodiment satisfies condition (1) defined by the following equation. 0.05 < SagH / BF < 0.25 …(1)

[0053] Here, SagH is the sag amount of the -Z side surface of the first lens element 21 at the reference height H. The sag amount is positive on the +Z side and negative on the -Z side. For the back focus BF, for example, the value in the state of zero diopter is used. The reference height H is the maximum image height of the display surface S. The maximum image height H is the maximum image height within the range where the display light B1 emitted from the display surface S of the display element 11 can enter the pupil A through the visual optical system 12. With reference to FIG. 5, the above various parameters and the shape of the +Z side surface of the first lens element 21 will be described.

[0054] In FIG. 5, the optical path of the display light B1a emitted from the maximum image height H on the display surface S until it reaches the pupil A through the visual optical system 12 is illustrated. In the optical path of this example, the display light B10a that reaches the first lens element 21 has a ray height greater than the maximum image height H. Such display light B10a enters the pupil A from the -Z side surface of the first lens element 21 at the incident angle α corresponding to the end portion in the field angle range.

[0055] The -Z side surface of the first lens element 21 includes a convex region Ra provided convexly with the central position through which the optical axis passes as the vertex p1, and a curved region Rb provided around the convex region Ra. The curved region Rb has a shape that curves, i.e., bends, more towards the -Z side as it moves away from the center of the first lens element 21.

[0056] The ray (for example, the chief ray) of the display light B10a corresponding to the end portion of the above-described field angle passes through the curved region Rb on the -Z side surface of the first lens element 21 and reaches the pupil A. In this embodiment, due to the bending of the curved region Rb, the portion corresponding to the end portion of the field angle (through which the display light B10a passes) on the -Z side surface of the first lens element 21 is brought closer to the pupil A, making it easier to obtain a wide field angle while maintaining the imaging performance of the visual optical system 12.

[0057] The above conditional expression (1) defines the ratio of the sag amount of the -Z side surface of the first lens element 21 to the back focus BF. By satisfying the conditional expression (1), the visual optical system 12 according to the present embodiment can realize a polarization reflection optical system that is small and lightweight and has an adjustable diopter with a wide viewing angle of, for example, 90° or more. On the other hand, for example, the eyepiece optical system of Patent Document 1 does not satisfy the conditional expression (1), and the viewing angle is narrow, less than 25°.

[0058] When exceeding the upper limit of the conditional expression (1), in a state where the length of the back focus BF is ensured, the sag amount of the -Z side surface of the first lens element 21 becomes excessive in the peripheral portion. That is, the distance between the peripheral portion of the first lens element 21 and the pupil A becomes too long, making it difficult to secure a wide viewing angle. Or, since the back focus BF becomes short, the movable range of the lens group for diopter adjustment becomes narrow, and it becomes difficult for the user 5 to easily see the virtual image V when having myopia.

[0059] On the other hand, when falling below the lower limit of the conditional expression (1), the sag amount of the -Z side surface of the first lens element 21 becomes too small, making it difficult to appropriately correct the astigmatism of the off-axis light beam. That is, good imaging performance cannot be obtained in the visual optical system 12. Or, since the back focus BF becomes too long, the overall optical length becomes long, making miniaturization difficult.

[0060] The above-described effects of the conditional expression (1) can be obtained more remarkably when the visual optical system 12 satisfies the following conditional expression (1a). 0.05 < SagH / BF < 0.18 …(1a)

[0061] In the example of FIG. 5, the position of the maximum image height H that serves as the reference for the sag amount SagH in the conditional expressions (1) and (1a) is near the boundary between the convex region Ra and the curved region Rb on the -Z side surface of the first lens element 21. For example, as shown in FIG. 5, in the cross-section passing through the optical axis of the first lens element 21, on the -Z side surface, in order from the center to the periphery, there are arranged the vertex p1 in the convex region Ra, the inflection point p2 and the end point p3 in the curved region Rb. The position of the maximum image height H is near the inflection point p2 in this example, but is not particularly limited thereto.

[0062] In the convex region Ra, for example, as going from the vertex p1 toward the periphery, the sag amount increases. At this time, the rate at which the sag amount increases (i.e., the gradient of the sag amount) gradually increases from the vertex p1 to an intermediate position, and gradually decreases after exceeding that position.

[0063] In the curved region Rb, the inflection point p2 indicates the position where the sag amount is maximum (i.e., the maximum point). The end point p3 indicates the outer end of the curved region Rb. In the convex region Ra, as going from the inflection point p2 toward the end point p3, the sag amount decreases. At this time, the rate at which the sag amount decreases (the absolute value of the gradient) gradually increases, for example.

[0064] Due to such a curvature of the curved region Rb, the -Z side surface of the first lens element 21 has a sag amount smaller than the sag amount SagH of the maximum image height H at a position on the curved region Rb farther from the optical axis than the position of the maximum image height H and the inflection point p2. For example, in the example of FIG. 5, the sag amount of the end point p3 of the curved region Rb is smaller than the sag amounts of the respective parts of the convex region Ra. Note that the curved region Rb may be regarded as an effective region within the range through which the display light B10a that can enter the pupil A passes.

[0065] Further, the visual optical system 12 of the present embodiment may satisfy the condition (2) represented by the following formula. 0.01 < fl / r1 < 0.20 …(2)

[0066] Here, fl is the focal length of the visual optical system 12, and r1 is the radius of curvature of the -Z side surface of the first lens element 21. The radius of curvature r1 is measured, for example, at the vertex p1.

[0067] The above conditional expression (2) defines the ratio of the focal length fl of the visual optical system 12 to the radius of curvature r1 of the -Z side surface of the first lens element 21. By satisfying the conditional expression (2), the visual optical system 12 according to the present embodiment can easily realize a polarization reflection optical system that is small and lightweight while having a wide viewing angle and adjustable diopter.

[0068] When exceeding the upper limit of the conditional expression (2), the radius of curvature r1 of the -Z side surface of the first lens element 21 becomes too small compared to the focal length fl of the visual optical system 12. For this reason, the positive power of the first lens element 21 becomes excessively strong, and it may be difficult to widen the viewing angle of the visual optical system 12. On the other hand, when falling below the lower limit of the conditional expression (2), the power of the first lens element 21 becomes too weak, and it may be difficult to appropriately correct various aberrations. For this reason, it may be difficult to obtain good imaging performance in the visual optical system 12.

[0069] The effects described above for the conditional expression (2) can be obtained more significantly when the visual optical system 12 satisfies the following conditional expression (2a). 0.01 < fl / r1 < 0.16 …(2a)

[0070] 2-3-1. Example 1 Regarding the numerical example of the visual optical system 12 of Example 1 that satisfies the above conditional expressions (1) and (2), it will be described with reference to FIGS. 6 to 10.

[0071] FIG. 6 shows the surface data of the visual optical system 12 in Numerical Example 1. The surface data in FIG. 6 shows the information of each surface through which the display lights B1 to B10 pass for the visual optical system 12, in the order from the exit destination to the display surface S of the exit source on the -Z side of the pupil A. For example, the second and third surfaces are the -Z side surface and the +Z side surface of the first lens element 21, respectively, and the fourth and fifth surfaces are the -Z side surface and the +Z side surface of the second lens element 22, respectively. Further, the sixth surface indicates the same surface as the fourth surface based on the reflection of the display light (the same applies to the seventh to ninth surfaces).

[0072] In the surface data of FIG. 6, the information of each surface includes, for example, the radius of curvature r of the vertex and the surface interval d (e.g., in mm units), the refractive index nd and the Abbe number vd of each element with respect to the d line. The surface interval d has a sign corresponding to the ±Z sides. Also, in FIG. 6, an asterisk is attached to the surface numbers of the aspherical surfaces.

[0073] FIG. 7 shows the aspherical surface data of the visual optical system 12 in Numerical Example 1. The aspherical surface data in FIG. 7 shows the various coefficients of the following equation (10) that define the shape of the rotationally symmetric aspherical surface for each aspherical surface in FIG. 6.

Equation

[0074] In the above equation (10), h is the height from the optical axis, z is the sag amount at the height h, K is the conic constant, r is the radius of curvature of the vertex, and An is the aspherical coefficient of the nth order. In the second term on the right side of the above equation (10), for example, n is an even number from 4 to 10, and the sum for each n is taken. According to the above equation (10), the sag amount z corresponding to the distance between the point at the height h and the tangent plane of the vertex on the target surface is defined to have a deviation from the spherical shape according to the aspherical coefficient An.

[0075] FIG. 8 shows various data of the visual optical system 12 in Numerical Example 1. The various data in FIG. 8 show the focal length fl, the pupil diameter, the half field angle, the image height, the overall optical length, and the back focus BF of the visual optical system 12 of this numerical example. The pupil diameter is the diameter of pupil A. The half field angle corresponds to 1 / 2 of the field angle (see α in FIG. 5). The back focus BF is, for example, the length in air. The unit of each length is "mm", and the unit of the half field angle is "°".

[0076] FIG. 9 is an aberration diagram showing various aberrations of the visual optical system 12 in this numerical example. Each of the following aberration diagrams illustrates various longitudinal aberrations in the state of zero diopter. FIGS. 9(a), (b), and (c) show the spherical aberration diagram, the astigmatism diagram, and the distortion aberration diagram of the visual optical system 12 in this numerical example, respectively.

[0077] The horizontal axis of FIG. 9(a) shows the spherical aberration "SA" in mm units, and the vertical axis normalizes the pupil height. In the spherical aberration diagram, the solid line of "d-line" shows the characteristics of the d-line, the dashed line of "F-line" shows the characteristics of the F-line, and the dashed line of "C-line" shows the characteristics of the C-line. The horizontal axis of FIG. 9(b) shows the astigmatism "AST" in mm units, and the vertical axis is the image height. In the astigmatism diagram, the solid line of "s" shows the characteristics of the sagittal plane, and the dashed line of "m" shows the characteristics of the meridional plane. The horizontal axis of FIG. 9(c) shows the distortion aberration "DIS" in % units, and the vertical axis is the image height.

[0078] FIG. 10 shows the adequacy of various conditions in the visual optical system 12 according to this embodiment. In FIG. 10, for each example of the visual optical system 12, together with the field angle and the eye relief ER, the calculated values of each intermediate side in the conditional expressions (1) and (2) are shown. As shown in FIG. 10, the visual optical system 12 of Example 1 satisfies the above-described conditions (1) and (2).

[0079] The visual optical system 12 according to this embodiment can be implemented in various forms, not limited to the above-described Example 1. Hereinafter, Examples 2 to 4 of the visual optical system 12 will be described.

[0080] 2-3-2. Example 2 In Example 2, an example in which the arrangement of the quarter-wave plate 42 is different from that of the visual optical system 12 in Example 1 will be described with reference to FIGS. 11 to 15.

[0081] FIG. 11 shows the configuration of the visual optical system 12A according to Example 2 in the same manner as FIG. 3 of Example 1. In the visual optical system 12A of this example, the quarter-wave plate 42 is provided on the -Z side surface of the second lens element 22 as shown in FIG. 11, instead of being provided on the +Z side surface of the first lens element 21 in Example 1 (FIG. 3). Also in this case, the range in which the optical path of the display light is folded back is limited between the +Z side surface of the first lens element 21 and the +Z side surface of the second lens element 22, as in Example 1.

[0082] Further, in Example 1, the +Z side surface of the first lens element 21 was a flat surface (see FIG. 3), but in this example, the -Z side surface of the second lens element 22 is a flat surface. In this example, the +Z side surface of the first lens element 21 is, for example, a rotationally symmetric aspherical surface. The +Z side surface of the first lens element 21 is convex on the +Z side as shown in FIG. 11, for example. This makes it easier for the first lens element 21 to function as a positive lens. In this example, the polarization reflection surface 41 is provided on the +Z side surface of the first lens element 21 by, for example, film attachment.

[0083] Numerical examples corresponding to the visual optical system 12A of Example 2 are shown in FIGS. 12 to 14. FIG. 12 shows the surface data of the visual optical system 12A in Numerical Example 2 in the same manner as FIG. 6. FIG. 13 shows the aspherical data in this example in the same manner as FIG. 7. FIG. 14 shows various data in this example in the same manner as FIG. 8.

[0084] FIG. 15 shows various aberrations of the visual optical system 12A in Numerical Example 2. FIGS. 15(a), (b), and (c) show aberration diagrams of the visual optical system 12A in this example, similar to FIGS. 9(a), (b), and (c) respectively. Also, as shown in FIG. 10, the visual optical system 12A of this example satisfies conditions (1) and (2). The visual optical system 12A of this example can also obtain the same effects as in Example 1. For example, for the user 5 of the display device 1, it is easy to secure a field of view in which the virtual image V can be viewed well with a wide viewing angle and the like.

[0085] 2-3-3. Example 3 The visual optical system 12B of Example 3 will be described with reference to FIGS. 16 to 20.

[0086] FIG. 16 shows the configuration of the visual optical system 12B according to Example 3, similar to FIG. 3 of Example 1. The visual optical system 12B of this example has the same configuration as the visual optical system 12 of Example 1, but changes the parameters such as the shape of various aspherical surfaces. For example, in this example, the -Z side surface of the first lens element 21 has a sag amount SagH that is larger than that in Example 1 at the maximum image height of the display surface S (see Equation (1)).

[0087] Numerical examples corresponding to the visual optical system 12B of Example 3 are shown in FIGS. 17 to 19. FIG. 17 shows the surface data of the visual optical system 12B in Numerical Example 3, similar to FIG. 6. FIG. 18 shows the aspherical data in this example, similar to FIG. 7. FIG. 19 shows various data in this example, similar to FIG. 8.

[0088] FIG. 20 shows various aberrations of the visual optical system 12B in Numerical Example 3. FIGS. 20(a), (b), and (c) show aberration diagrams of the visual optical system 12B in this example, similar to FIGS. 9(a), (b), and (c) respectively. Also, as shown in FIG. 10, the visual optical system 12B of this example satisfies conditions (1) and (2), and thus the same effects as in Example 1 can also be obtained.

[0089] 2-3-4. Example 4 The visual optical system 12C of Example 4 will be described with reference to FIGS. 21 to 25.

[0090] FIG. 21 shows the configuration of the visual optical system 12C according to Example 4, similar to FIG. 3 of Example 1. The visual optical system 12C of this example is configured such that the eye relief ER is relatively short in the same configuration as in Examples 1 and 3 (see FIG. 10).

[0091] Numerical examples corresponding to the visual optical system 12C of Example 4 are shown in FIGS. 22 to 24. FIG. 22 shows the surface data of the visual optical system 12C in Numerical Example 4, similar to FIG. 6. FIG. 23 shows the aspherical data in this example, similar to FIG. 7. FIG. 24 shows various data in this example, similar to FIG. 8.

[0092] FIG. 25 shows the various aberrations of the visual optical system 12C in Numerical Example 4. FIGS. 25(a), (b), and (c) show the aberration diagrams of the visual optical system 12C in this example, similar to FIGS. 9(a), (b), and (c), respectively. Also, as shown in FIG. 10, the visual optical system 12C of this example satisfies conditions (1) and (2), and thus, the same effect as in Example 1 can be obtained.

[0093] 3. Summary As described above, the visual optical system 12 in the present embodiment is an example of an eyepiece optical system having an optical axis along the Z direction that guides light between the pupil A of the user 5 and the display surface S. The visual optical system 12 includes a first lens element 21 and a second lens element 22. The first lens element 21 has a polarization reflecting surface that reflects or transmits light according to the polarization of the incident light by the polarization reflector 41 on the display side (+Z side) facing the display surface S. The second lens element 22 is disposed between the first lens element 21 and the display surface S and has a partial reflecting surface that reflects a part of the incident light by the half mirror 43 and transmits the remaining part. The first lens element 21 has an aspherical surface that is convex toward the side opposite to the polarization reflecting surface on the pupil side (-Z side) facing the pupil and includes a convex region Ra where the optical axis is located. The aspherical surface on the pupil side of the first lens element 21 satisfies the following condition (1). 0.05 < SagH / BF < 0.25 …(1) Here, SagH: Sag amount at the maximum image height H of the surface S BF: Back focus of the eyepiece optical system is as follows.

[0094] According to the above visual optical system 12, the -Z side surface of the first lens element 21 that satisfies the condition (1) can form a polarization reflection optical system with a thin thickness and a wide viewing angle while ensuring, for example, the back focus BF, and it is easy to ensure the viewing field of the user 5. For example, it is possible to ensure the viewing field of the user 5 where the virtual image V or the like in the display device 1 is easy to see at a wide viewing angle.

[0095] In the present embodiment, the visual optical system 12 satisfies the following condition (2). 0.01 < fl / r1 < 0.20 …(2) Here, fl: Focal length of the visual optical system 12 r1: Curvature radius of the pupil-side surface of the first lens element 21 is as follows. According to the condition (2), the power of the first lens element 21 in the visual optical system 12 can be appropriately controlled, and it is easy to ensure the viewing field of the user 5 well.

[0096] In the present embodiment, the first lens element 21 and the second lens element 22 constitute one lens group. The eyepiece optical system of the present embodiment may include a diopter adjustment mechanism 13 which is an example of a movable mechanism in addition to the visual optical system 12. The movable mechanism moves the lens group along the optical axis within the range of the back focus BF. The movable mechanism is configured to move the lens group, for example, as the diopter adjustment mechanism 13 to adjust the diopter of the user 5. According to the visual optical system 12 of the present embodiment, the diopter can be adjusted with a simple movable mechanism.

[0097] In the present embodiment, the aspherical surface on the pupil side of the first lens element 21 may include a position having a sag amount smaller than the sag amount SagH in a range farther from the optical axis than the maximum image height H. Thereby, the peripheral portion far from the optical axis on the -Z side surface of the first lens element 21 can be brought closer to the eye 50 of the user 5, and it is easy to ensure a wide viewing angle.

[0098] In this embodiment, the aspherical surface on the pupil side of the first lens element 21 may include a curved region Rb that curves toward the pupil side as it moves away from the optical axis around the convex region Ra. The curved region Rb may be provided at a position where the light beam B10a of the display light that reaches the pupil A from the maximum image height H of the display surface S via the visual optical system 12 passes through the aspherical surface on the pupil side of the first lens element 21. Also, such a curved region Rb can bring the peripheral portion on the -Z side surface of the first lens element 21 closer to the eye 50 of the user 5, making it easier to secure a wide viewing angle.

[0099] In this embodiment, the surface on the pupil side of the first lens element 21 has at least one inflection point p2, for example, at a position away from the optical axis. Due to the inflection point p2, the tendency of the sag amount to change (for example, the sign of the gradient of the sag amount) changes on the -Z side surface of the first lens element 21 as it moves from the convex region Ra near the optical axis toward the peripheral portion, enabling appropriate control of the light beam direction of the display light B10 and making it easier to ensure a good viewing field for the user 5.

[0100] In this embodiment, the first lens element 21 and the second lens element 22 each have a positive power, for example. The positive power of each lens element 21, 22 can make it easier to secure a wide viewing angle.

[0101] In this embodiment, the partial reflection surface by the half mirror 43 is provided, for example, on the display side surface of the second lens element 22. As a result, the range where the optical path bends in the polarization reflection optical system reaches the +Z side surface of the second lens element 22, making it easier to ensure a long optical path length for the display lights B2 to B6.

[0102] In this embodiment, the visual optical system 12 further includes a quarter-wave plate 42, which is an example of a quarter-wave phase element. The quarter-wave plate 42 is provided on the display side surface of the first lens element 21 or the pupil side surface of the second lens element 22. The surface on which the quarter-wave plate 42 is provided is a flat surface. This makes it easier to provide the quarter-wave plate 42 in the visual optical system 12.

[0103] The display device 1 in the present embodiment includes a display element 11 having a display surface S for displaying an image and a visual optical system 12. According to the display device 1 of the present embodiment, the visual optical system 12 can make it easier to secure the visual field of the user 5.

[0104] (Other embodiments) As described above, as an example of the technology disclosed in the present application, Embodiment 1 has been described. However, the technology in the present disclosure is not limited to this, and is also applicable to embodiments in which appropriate changes, substitutions, additions, omissions, etc. are made. Further, it is also possible to combine the components described in each of the above embodiments to form a new embodiment. Therefore, other embodiments will be exemplified below.

[0105] In the above-described Embodiment 1, the diopter adjustment mechanism 13 has been described as an example of the movable mechanism in the eyepiece optical system. In the present embodiment, the movable mechanism of the eyepiece optical system may move the lens groups of the first and second lens elements 11 and 12 in the Z direction for uses other than diopter adjustment, and may be used for, for example, zooming or focusing.

[0106] Further, in each of the above embodiments, an example of securing the back focus BF of the visual optical system 12 for the movable range of the movable mechanism such as the visual field adjustment mechanism 13 has been described. In the present embodiment, the back focus BF of the visual optical system 12 is not particularly limited to the movable range of various movable mechanisms, and may be secured for various optical design purposes.

[0107] Further, in each of the above embodiments, an example in which the display device 1 includes a visual field adjustment mechanism 13 movable in the Z direction has been described. In the present embodiment, the display device 1 may include a diopter adjustment means different from the diopter adjustment mechanism 13 movable in the Z direction. For example, a correction lens for diopter adjustment may be configured to be separately attachable.

[0108] In each of the above embodiments, an example in which the polarization reflection surface of the visual optical system 12 reflects p-polarized light and transmits s-polarized light has been described. However, the polarization reflection surface is not limited to this. In the visual optical system 12 of the present embodiment, the polarization reflection surface may reflect s-polarized light and transmit p-polarized light, or may selectively reflect or transmit circularly polarized light as in Patent Document 1, for example. Also, in each of the above embodiments, an example in which the polarization reflection plates 41 and the quarter-wave plates 42 are used in the visual optical system 12 has been described. However, the quarter-wave plates 42 may be omitted.

[0109] Also, in each of the above embodiments, an example in which rotationally symmetric aspherical surfaces are used in the lens elements 11 and 12 of the visual optical system 12 has been described. In the present embodiment, rotationally asymmetric aspherical surfaces may be used in the lens elements 11 and 12, and for example, free-form surfaces such as anamorphic aspherical surfaces or XY polynomial surfaces may be used.

[0110] Also, in each of the above embodiments, a glasses-type HMD has been exemplified as an example of the display device 1. However, the display device 1 is not limited to this. In the present embodiment, the display device 1 may be a goggle-type HMD, not limited to the glasses type, or may be a monocular HMD. Also, in the present embodiment, the display device 1 is not limited to an HMD, and may be various viewfinders such as an electronic viewfinder, for example. Also in such various display devices 1, the visual optical system 12 can make it easier to secure the user's field of view.

[0111] As described above, embodiments have been described as examples of the technology in the present disclosure. For this purpose, the accompanying drawings and detailed description have been provided.

[0112] Therefore, among the components described in the accompanying drawings and the detailed description, there may be included not only the components essential for solving the problems, but also the components not essential for solving the problems for exemplifying the above technology. Therefore, just because those non-essential components are described in the accompanying drawings and the detailed description, it should not be immediately determined that those non-essential components are essential.

[0113] In addition, since the above-described embodiments are for exemplifying the technology in the present disclosure, various changes, substitutions, additions, omissions, etc. can be made within the scope of the claims or the equivalent scope thereof.

Industrial Applicability

[0114] The present disclosure is applicable to various display devices such as, for example, an HMD or a viewfinder.

Claims

1. An eyepiece optical system having an optical axis for guiding light between a user's pupil and a display surface, on the display side facing the display surface, a first lens element having a polarization reflecting surface that reflects or transmits the incident light according to the polarization of the incident light, and a second lens element disposed between the first lens element and the display surface and having a partial reflecting surface on the display side that reflects a part of the incident light and transmits the remainder, the first lens element has an aspherical surface that is convex toward the pupil side facing the pupil and includes a convex region where the optical axis is located on the side opposite to the polarization reflecting surface, the aspherical surface on the pupil side of the first lens element satisfies the following condition (1): 0.05 < SagH / BF < 0.25... (1) Here, SagH: Sag amount at the maximum image height of the display surface BF: Back focus of the eyepiece optical system is an eyepiece optical system.

2. satisfies the following condition (2): 0.01 < fl / r1 < 0.20... (2) Here, fl: Focal length of the eyepiece optical system r1: Curvature radius of the surface on the pupil side of the first lens element The eyepiece optical system according to claim 1.

3. The first lens element and the second lens element constitute one lens group, and further includes a movable mechanism that moves the lens group along the optical axis within the range of the back focus The eyepiece optical system according to claim 1 or 2.

4. The movable mechanism is configured to move the lens group to adjust the diopter of the user. The eyepiece optical system according to claim 3.

5. The aspherical surface on the pupil side of the first lens element includes a position having a sag amount smaller than the sag amount SagH in a range farther from the optical axis than the maximum image height. The ocular optical system according to any one of claims 1 to 4.

6. The aspherical surface on the pupil side of the first lens element includes a curved region that curves toward the pupil side as it moves farther from the optical axis around the convex region. The ocular optical system according to any one of claims 1 to 5.

7. The curved region is provided at a position where a light ray that reaches the pupil from the maximum image height of the display surface through the ocular optical system passes through the aspherical surface on the pupil side of the first lens element. The ocular optical system according to claim 6.

8. The surface on the pupil side of the first lens element has at least one inflection point at a position away from the optical axis. The ocular optical system according to any one of claims 1 to 7.

9. The first lens element and the second lens element each have a positive power. The ocular optical system according to any one of claims 1 to 8.

10. The partial reflection surface is provided on the surface on the display side of the second lens element. The ocular optical system according to any one of claims 1 to 9.

11. The first lens element further includes a quarter-wavelength phase element provided on the surface on the display side thereof, or the second lens element further includes a quarter-wavelength phase element provided on the surface on the pupil side thereof. The surface on which the quarter-wavelength phase element is provided is a flat surface. The ocular optical system according to any one of claims 1 to 10.

12. A display element having a display surface for displaying an image, The ocular optical system according to any one of claims 1 to 11, and A display device comprising **Claim 13**: Further comprising a polarization conversion element provided between the polarization reflection surface and the partial reflection surface for converting the polarization of incident light The ophthalmic optical system according to claim 1. **Claim 14**: The first lens element and the second lens element are arranged so as to have a viewing angle of 90° or more The ophthalmic optical system according to claim 1.

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