Optical system and display device

Abstract

The present disclosure relates to an optical system and a display device. An optical system guides a light beam from a display element to an exit pupil. The optical system includes: a first optical element, the first optical element including a transmission surface, a reflection-transmission surface, and a reflection surface; and a negative lens, the negative lens including a concave surface on the exit pupil side. The light beam from the display element advances toward the exit pupil via the transmission surface, the reflection-transmission surface, the reflection surface, the reflection-transmission surface, and the negative lens in sequence. A predetermined condition is satisfied.

Description

Technical Field

[0001] Aspects of the embodiments relate to an optical system suitable for a display device such as a head mounted display (HMD) that allows a user to view an image displayed on a display element as an enlarged virtual image. Background Art

[0002] Conventionally, a thin optical system (eyepiece optical system) is known, and the eyepiece optical system is configured by using an optical element having an incident surface, a plurality of reflection surfaces, and an exit surface so that the principal ray of a central viewing angle light beam is reflected multiple times in an eccentric manner. Such an eyepiece optical system needs to have a widened viewing angle. In order to widen the viewing angle, Japanese Patent (JP) Nos. 6392066 and 5791991 disclose optical systems each having a second eccentric optical element disposed between an observer and the eccentric optical element.

[0003] However, it is difficult to achieve both focal length reduction and widening of the viewing angle with the optical systems disclosed in JP 6392066 and 5791991. If the optical system disclosed in JP 6392066 or 5791991 is made to have a short focal length so as to widen the viewing angle, the distance from the principal plane on the display element side of the optical system to the display element is too short to ensure a space for disposing components necessary for housing the display element and the components configuring the optical system interfere with the display element. Summary of the invention

[0004] The present disclosure provides an optical system and a display device, each of which is compact and has a wide viewing angle.

[0005] An optical system according to one aspect of an embodiment guides a light beam from a display element to an exit pupil. The optical system comprises: a first optical element, the first optical element comprising a transmission surface, a reflection-transmission surface, and a reflection surface; and a negative lens, the negative lens comprising a concave surface on the exit pupil side. The light beam from the display element advances toward the exit pupil via the transmission surface, the reflection-transmission surface, the reflection surface, the reflection-transmission surface, and the negative lens in sequence. A predetermined condition is satisfied.

[0006] An optical system according to one aspect of an embodiment guides a light beam from a display element to an exit pupil. The optical system comprises: a first optical element, the first optical element comprising a transmission surface, a reflection-transmission surface, and a reflection surface; and a negative lens, the negative lens comprising a concave surface on the exit pupil side. The reflection-transmission surface and the negative lens are adjacent to each other. The light beam from the display element sequentially advances toward the exit pupil via the transmission surface, the reflection-transmission surface, the reflection surface, the reflection-transmission surface, and the negative lens. A predetermined condition is satisfied.

[0007] An optical system according to one aspect of an embodiment guides a light beam from a display element to an exit pupil. The optical system includes: a first optical element, the first optical element including a transmission surface, a reflection-transmission surface, and a reflection surface; a negative lens, the negative lens including a concave surface on the exit pupil side; and a second optical element, the second optical element being a prism disposed between the first optical element and the negative lens. The light beam from the display element advances toward the exit pupil via the transmission surface, the reflection-transmission surface, the reflection surface, the reflection-transmission surface, and the negative lens in sequence. A predetermined condition is satisfied.

[0008] Further features of the embodiments will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a diagram illustrating a configuration of a display device according to a first embodiment.

[0010] Figure 2A and Figure 2B is an explanatory diagram of the eyepiece optical system according to the first embodiment.

[0011] Figure 3A and Figure 3B is an explanatory diagram of physical interference between the eyepiece optical system and the observer's glasses according to the first embodiment.

[0012] Figure 4 is a diagram illustrating a configuration of a display device according to a second embodiment.

[0013] Figure 5 is an explanatory diagram of an eyepiece optical system according to the second embodiment.

[0014] Figure 6 It is an explanatory diagram of field curvature according to the second embodiment.

[0015] Figure 7 is a diagram illustrating a configuration of a display device according to a third embodiment.

[0016] Figure 8 is a diagram illustrating a configuration of a display device according to a fourth embodiment.

[0017] Fig. 9 It is an explanatory diagram of field curvature according to the fourth embodiment.

[0018] Fig.10 is a diagram illustrating a configuration of a display device according to a fifth embodiment.

[0019] Fig.11 is a diagram illustrating overlapping display of information according to the fifth embodiment.

[0020] Fig.12 This is an explanatory diagram of Numerical Example 1.

[0021] Fig.13 2 is a lateral aberration diagram of the eyepiece optical system according to Numerical Example 1.

[0022] Fig.14 This is an explanatory diagram of Numerical Example 2.

[0023] Fig.15 2 is a lateral aberration diagram of the eyepiece optical system according to Numerical Example 2.

[0024] Fig.16 This is an explanatory diagram of Numerical Example 3.

[0025] Fig.17 2 is a lateral aberration diagram of the eyepiece optical system according to Numerical Example 3.

[0026] Fig.18 This is an explanatory diagram of Numerical Example 4.

[0027] Fig.19 2 is a lateral aberration diagram of the eyepiece optical system according to Numerical Example 4. DETAILED DESCRIPTION

[0028] Referring now to the drawings, a description will be given of embodiments according to the present disclosure.

[0029] In the description of each example, when the origin is the exit pupil (pupil center) and a light beam at the center of the viewing angle (observation angle) observed by the observer is referred to as a central viewing angle light beam, the X-axis, Z-axis, and Y-axis of the absolute coordinate system are defined as follows. The axis matching the principal ray of the central viewing angle light beam is referred to as the Z-axis (a straight line along the principal ray of the central viewing angle light beam, and the direction from the exit pupil to the first plane is regarded as the positive direction), and the absolute coordinate system is defined as follows. Figure 1 The axis formed by rotating the Z axis 90 degrees counterclockwise about the origin in the cross section is called the Y axis, and the axis passing through the origin and orthogonal to the Z axis and the Y axis is called the X axis.

[0030] First embodiment

[0031] First, refer to Figure 1 and Fig.12 A description is given of an eyepiece optical system and a display device according to a first embodiment of the present disclosure. Figure 1 : is a diagram illustrating a configuration of a display device including an eyepiece optical system in this embodiment. Fig.121 is an explanatory diagram corresponding to the numerical example 1 of the embodiment. Reference numeral 101 denotes a display device, which will also be referred to as an observation device or an image display device. The image display device 101 includes an eyepiece optical system as an optical system and an image display element 105 as a display element. The eyepiece optical system is configured to guide a light beam from the image display element 105 to an exit pupil S.

[0032] Reference numeral 102 denotes a first optical element. The first optical element 102 has a transmission surface 102C as an incident surface, a reflection-transmission surface 102A, and a reflection surface 102B, and the interior of the first optical element 102 is filled with a medium with a refractive index of n>1. Reference numeral 103 denotes a second optical element, which is a prism having two transmission surfaces 103B and 103A as refractive surfaces. Reference numeral 104 denotes a concave lens as a negative lens. The concave lens 104 is disposed between the first optical element 102 and the exit pupil S, and has a concave surface on the exit pupil S side. In this embodiment, the eyepiece optical system includes three optical elements: the first optical element 102, the second optical element 103, and the concave lens 104. In this embodiment, the display device 101 includes an eyepiece optical system and an image display element 105. The light beam from the image display element 105 forms the exit pupil S via the first optical element 102 and the concave lens 104. That is, the light beam from the image display element 105 advances to the exit pupil S via the transmission surface 102C as the incident surface of the first optical element 102 , the reflection-transmission surface 102A, the reflection surface 102B and the reflection-transmission surface 102A, and the concave lens 104 in sequence.

[0033] A description will be given of the light path inside each optical element. Light emitted from an image displayed on the image display element 105 enters the first optical element 102 from the transmission surface 102C of the first optical element as an incident surface. The light that has entered the first optical element 102 is totally reflected by the reflection-transmission surface 102A and reflected by the reflection surface 102B, so that the light path in the first optical element 102 is folded. Thereafter, the first optical element 102 emits light from the reflection-transmission surface 102A. The light emitted from the first optical element 102 passes through the transmission surfaces 103B and 103A of the second optical element 103, and enters the concave lens 104. After the light is emitted from the concave lens 104, the light is guided to the exit pupil S of the eyepiece optical system, and the image displayed on the image display element 105 is viewed as a distant enlarged virtual image through the exit pupil S by an observer who places a pupil near the exit pupil S.

[0034] Like the surface of the second optical element disclosed in JP 6392066, the transmission surface 103B as a refractive surface of the second optical element 103 has a function of canceling the refraction that occurs when light passes through the reflection-transmission surface 102A. Thus, the aberration that occurs on the reflection-transmission surface 102A can be canceled. The reflection-transmission surface 102A and the transmission surface 103B as a refractive surface can have the same shape, and the second optical element 103 can be made of the same material as the first optical element 102. The first optical element 102 and the second optical element 103 can be made of an optical resin, and the reason will be described later. The reflection-transmission surface 102A and the transmission surface 103B as a refractive surface can have the same shape, but the shape is not limited thereto as long as the transmission surface 103B has a shape that can cancel the aberration that occurs when light is transmitted through the reflection-transmission surface 102A.

[0035] Next, we will refer to Figure 2A and Figure 2B A description is given of the features of the eyepiece optical system according to this embodiment. Figure 2A and Figure 2B 1 is an explanatory diagram of the eyepiece optical system according to this embodiment. When the viewing angle of the eyepiece optical system is to be increased, the focal length of the eyepiece optical system is shortened. The distance from the exit pupil S to the final surface of the eyepiece optical system, i.e., the exit pupil distance (eye relief), is set to a value of about 15 to 30 mm so that the observer can easily perform observation. However, if a wide viewing angle is to be obtained when the image display element 105 is small, the focal length of the eyepiece optical system becomes shorter than the exit pupil distance. The size of the first optical element 102 is roughly determined by the exit pupil distance and the viewing angle. That is, the longer the exit pupil distance, the larger the first optical element 102. If the focal length of the eyepiece optical system is shortened by increasing the size of the first optical element 102, the focal plane of the eyepiece optical system is brought closer to the transmission surface 102C as the incident surface.

[0036] In the case where a mechanical component is provided between the image display element 105 and the first optical element 102, or in the case where the image display element 105 is, for example, electroluminescent and releases heat, a certain distance or more is ensured between the first optical element 102 and the image display element 105. However, if the focal plane of the eyepiece optical system is close to the first optical element 102, for example Figure 2A As shown in FIG. 1 , the distance between the first optical element 102 and the image display element 105, that is, the back focus, is small. Therefore, a sufficient space may not be ensured, and the elements may collide with each other.

[0037] In order to prevent these problems, the position of the image-side principal plane of the eyepiece optical system is shifted to a position closer to the image display element 105, and the focal plane is shifted away from the first optical element 102. As one of the methods for shifting the image-side principal plane, JP 6392066 discloses a technology of inserting a second optical element including a surface having a negative optical focal length (refractive power) between the exit pupil S and the prism corresponding to the first optical element 102. The second optical element 103 is arranged between the exit pupil S and the first optical element 102, so that the focal length of the entire eyepiece optical system is reduced, and the position of the image-side principal plane is shifted to a position closer to the image display element. Thereby, it is possible to ensure that there is sufficient space between the image display element 105 and the first optical element 102 (refer to Figure 2B ).

[0038] In order to make the observation angle wider than that of the configuration of JP 6392066, and in order to further reduce the focal length of the eyepiece optical system, the position of the principal plane is further shifted. For this purpose, the concave lens 104 is made to have an increased negative refractive power and a large curvature. However, if the curvature is too large, the sag amount of the concave lens 104 is so large that the edge of the concave lens 104 protrudes greatly to the exit pupil side. At this time, for example, when an observer wearing glasses views the eyepiece optical system, the glasses hit the edge portion 104a of the concave lens 104, such as Figure 3A As shown in the figure. Figure 3A It is an explanatory diagram of the physical interference between the eyepiece optical system and the observer's glasses when the amount of droop of the concave lens 104 is large.

[0039] In order to prevent the occurrence of physical interference, this embodiment increases the refractive index of the concave lens 104. When the refractive index increases, the negative optical power can be increased while the curvature of the concave lens 104 remains small. Figure 3B As illustrated in FIG. 1 , the droop amount of the concave lens 104 can be reduced, and a sufficient exit pupil distance can be ensured even around the edge of the concave lens 104 . Figure 3B is an explanatory diagram of the physical interference between the eyepiece optical system and the observer's glasses when the droop amount of the concave lens 104 is small. In this embodiment, the following inequality (1) is satisfied, where n n represents the refractive index of the concave lens 104 at the d-line (d-line of the Fraunhofer line, ie, a wavelength of 587.56 nm), and n m represents the refractive index of the first optical element 102 at the d-line.

[0040] n n >n m (1)

[0041] Refractive index n n and nm The following inequality (2) can be satisfied.

[0042] n n / n m >1.05 (2)

[0043] In this embodiment, n n =1.854 and n m =1.531. By increasing the refractive index of the concave lens 104 in this way, this embodiment realizes an eyepiece optical system having a wide viewing angle of 45° while using an image display element of a size (0.7 inches) similar to that of the image display element in JP 6392066. At this time, the focal length of the concave lens 104 is -81.5 mm, which indicates a stronger negative focal power than the negative focal power of the concave lens of JP 6392066 having a focal length of -94.3 mm.

[0044] In order to increase the back focal length by moving the image-side principal plane of the eyepiece optical system, the image plane is shifted by at least a few millimeters. This shift amount requires that the focal power of the concave lens is a certain amount greater than the focal power of the eyepiece optical system. In this embodiment, the following inequality (3) can be satisfied, where, represents the optical power of the concave lens 104 and Indicates the optical power of the eyepiece optical system.

[0045]

[0046] In order to further ensure a sufficient amount of image plane shift, the numerical range of inequality (3) can be set to the numerical range of the following inequality (4).

[0047]

[0048] When inequality (4) is satisfied, the image plane can be sufficiently shifted, and a sufficient distance between the first optical element 102 and the image display element 105 can be ensured. By making the concave lens 104 have a sufficiently strong negative optical power in this way, this embodiment achieves a shift of the image plane of about 5 mm.

[0049] The concave lens 104 is arranged so that its strong concave surface faces the pupil side. Thus, by making the arrangement closer to a concentric arrangement with the pupil centered, the occurrence of aberrations caused by the concave lens 104 is reduced. Compared with the case where the concave lens 104 is arranged in an opposing manner, the arrangement of this embodiment has the effect of reducing the distance between the first optical element 102 and the concave lens 104 by the droop amount of the concave lens 104 and making the optical system small.

[0050] Each optical surface of the first optical element 102 often uses a non-rotationally symmetrical surface (i.e., a free-form surface) to reduce the influence of oblique incident light. When the optical system uses such a free-form surface, the first optical element 102 is often manufactured by molding using an optical resin, because the manufacturing is easy and the cost can be reduced. The optical resin to be used is, for example, an acrylic resin, a polycarbonate resin, a cycloolefin polymer resin, etc. In this embodiment, for the second optical element 103, the same optical material is used. Thus, the aberration generated on the reflection-transmission surface 102A of the first optical element 102 can be offset by the transmission surface 103B as the incident surface of the second optical element, and the two surfaces have the same shape and are made of the same material. The molding using resin can make it possible to manufacture an optical element with a complex shape, but the material may cause corrosion and expansion due to being susceptible to oil and moisture, and may be easily scratched due to its softness. In order to solve these problems, there are measures such as arranging a protective glass window and applying a protective coating to the resin surface, but these measures lead to an increase in the number of components and processes.

[0051] In this embodiment, the concave lens 104 is made of optical glass (glass material). Compared with resin materials, optical glass is very hard and stable, has high environmental resistance, and is scratch-resistant, so the optical glass can be used to protect the resin material. That is, when the concave lens 104 is made of optical glass, the concave lens can also be used as a protective window for the first optical element. In addition, when optical glass is used, it is easy to select the refractive index and dispersion, and give the concave lens 104 an appropriate optical focal length.

[0052] In this embodiment, when ν n represents the Abbe number of the concave lens 104 and ν m When expressing the Abbe number of the first optical element 102, the following inequality (5) can be satisfied.

[0053] 15<ν n < m (5)

[0054] The Abbe number is calculated by the following equation, where nd, nF, and nC represent refractive indices at d-line (wavelength 587.6 nm), F-line (wavelength 486.1 nm), and C-line (wavelength 656.3 nm) of Fraunhofer lines, respectively.

[0055] ν=(nd-1) / (nF-nC)

[0056] In this embodiment, the following inequality (6) can be satisfied, where n O represents the refractive index of the second optical element 103 at the d-line.

[0057] nn >n O (6)

[0058] In this embodiment, the optical system is an eyepiece optical system, but the optical system may be, for example, an image pickup optical system in which an image sensor is provided at the position of the image display element 105 and an aperture is provided at a position corresponding to the position of the exit pupil S. In this case, the optical system is a front aperture type image pickup optical system and can be applied to, for example, a fundus camera.

[0059] Second embodiment

[0060] Next, we will refer to Figure 4 and Fig.14 A description is given of an eyepiece optical system and a display device according to a second embodiment of the present disclosure. Figure 4 1 is a configuration diagram of a display device having an eyepiece optical system in this embodiment. Fig.14 4 is an explanatory diagram corresponding to Numerical Example 2 of this embodiment. An image display device 401 as a display device includes an eyepiece optical system as an optical system and an image display element 405 as a display element. The eyepiece optical system is configured to guide a light beam from the image display element 405 to an exit pupil S.

[0061] The eyepiece optical system according to this embodiment includes a convex lens 406 as a positive lens disposed between the first optical element 402 and the image display element 405. The convex lens 406 has a strong convex surface 406A, which has a shape protruding toward the first optical element 402. When the direction orthogonal to the plane on which the exit pupil S is formed is referred to as the first direction, inside the convex lens 406, the length of the optical path of the light beam passing through the position closest to the reflection surface 402B in the first direction is longer than the length of the optical path of the light beam passing through the position closest to the reflection-transmission surface 402A in the first direction. That is, the length of the optical path of the outermost off-axis light beam (the light beam from the edge of the display surface) closest to the reflection surface in the Z-axis direction is longer than the length of the optical path of the outermost off-axis light beam closest to the reflection-transmission surface in the Z-axis direction. This embodiment can achieve a wider viewing angle (50°) while using an image display element (0.5 inches) smaller than the image display element in the first embodiment. In addition, the observer can superimpose the transmission image and the display image for observation.

[0062] Light emitted from the image displayed on the image display element 405 passes through the convex lens 406, enters the first optical element 402, exits from the first optical element 402 after being reflected multiple times by the inner surface, and enters the second optical element 403. After exiting from the second optical element 403, the light beam enters the concave lens 404. After the light beam is emitted from the concave lens 404, the light beam is guided to the exit pupil S of the eyepiece optical system, and the image displayed on the image display element 405 is viewed as a distant enlarged virtual image through the exit pupil S by an observer who places a pupil near the exit pupil S.

[0063] The third optical element 407 is disposed on a side of the first optical element 402, which side is opposite to the exit pupil S. When the reflectivity of the reflection surface 402B of the first optical element 402 is set to be lower than 100%, an observer who places a pupil near the exit pupil S can also observe an external image, which will also be referred to as an external image, via the concave lens 404, the second optical element 403, the first optical element 402, and the third optical element 407. That is, the observer can observe the external image and the image displayed on the image display element 405 at the same time.

[0064] Figure 5 4 is an explanatory diagram of the eyepiece optical system, and illustrates the arrangement of the third optical element 407. Figure 5 As illustrated in FIG. 4 , the reflectivity of the reflective surface 402B of the first optical element is reduced (e.g., to a reflectivity of 50%), and a third optical element 407 is added. This allows an observer who places a pupil near the exit pupil S of the eyepiece optical system to observe an external image via the concave lens 404, the second optical element 403, the first optical element 402, and the third optical element 407. The outer surface 407B of the third optical element 407 has a positive power, which almost cancels out the negative power of the concave lens 404, and makes the total power of the third optical element 407 and the concave lens 404 afocal or very weak, thereby allowing observation of an external image.

[0065] In the case where the power of the concave lens 404 is very strong, the power of the surface 407B of the third optical element 407 is also strong, so that an external image is observed. If the first optical element 402 and the third optical element 407 are made of different materials, aberrations such as chromatic aberration and astigmatism occur at the interface 501A of the two optical elements, making it difficult to observe an external image. Therefore, the third optical element 407 may be made of the same material as the first optical element 402. As described in the first embodiment, the first optical element 402 is made of the same material as the second optical element 403, so the refractive index of the third optical element 407 is lower than that of the concave lens 404. Therefore, if the power of the concave lens 404 is too strong, the power to be given to the surface 407B of the third optical element is even stronger, and therefore, a surface 407B having a very large curvature is required. If the curvature is too large, the surface 407B has a hemispherical shape, and not only the third optical element 407 cannot be configured as an optical element, but also a great aberration is caused when observing an external image, making it difficult to observe an external image.

[0066] Therefore, as expressed by the following inequality (7), a limit is imposed on the optical power of the concave lens 404.

[0067]

[0068] In inequality (7), represents the optical power of the concave lens 404, and Represents the optical power of the entire eyepiece optical system of the display device 401. If the value is lower than the lower limit of inequality (7), the optical power of surface 407B is too strong, making it difficult to observe the external image. On the other hand, if the value of inequality (7) is too large, the optical power of concave lens 404 is insufficient, and the distance between image display element 405 and convex lens 406 is too small, so that it is difficult to set image display element 405. Based on inequality (7) and inequality (3) in the first embodiment, the following inequality (8) can be satisfied.

[0069]

[0070] When this condition of inequality (8) is satisfied, the position of the image plane can be sufficiently shifted and the outside can be easily observed. When the numerical range of inequality (8) is set to the numerical range of the following inequality (9), it is easier to ensure both the shift of the image plane and the observation of the outside.

[0071]

[0072] This embodiment makes Here, a description will be given of the relationship between the refractive index of the concave lens 404 and the refractive index of the second optical element 403. As described in the first embodiment, the refractive index of the concave lens 404 is increased so that a negative power larger than that obtained by imparting a negative power to the second optical element 403 is obtained, and the position of the image side principal plane is largely shifted. This negative power is generated at the interface between the exit surface 404A of the concave lens 404 and the air, and therefore, when (n n -1) is sufficiently greater than (n O -1), the convex lens 406 and the image display element 405 can be separated from each other. Therefore, the following inequality (10) can be satisfied.

[0073] (n n -1) / (n O -1)>1.3 (10)

[0074] If the value is lower than the lower limit of inequality (10), the optical power of concave lens 404 is insufficient, and image display element 405 interferes with convex lens 406. By setting the numerical range of inequality (10) to the numerical range of the following inequality (11), interference between image display element 405 and convex lens 406 can be more easily prevented.

[0075] (n n -1) / (n O -1)>1.4 (11)

[0076] In the eyepiece optical system of this embodiment, the position of the image plane is shifted by about 5 mm by inserting the concave lens 404. n -1) / (n O -1)=1.59.

[0077] Figure 6 601 is an explanatory diagram of the field curvature that occurs in the first optical element 402 and the concave lens 404 in the eyepiece optical system of this embodiment. The imaging plane 601 is set near the position where the light beam passing through the exit pupil S is imaged by the concave lens 404 and the first optical element 402, and the marginal rays (marginal rays) passing through the edge of the exit pupil S are calculated at the corresponding points where the central angle of view and the marginal angle of view intersect. When the axis 602 is set in the normal direction of the imaging plane 601, the coordinate value of the axis 602 at the intersection is in the following relationship: marginal angle of view> central angle of view. That is, the image plane 603 imaged by the first optical element 402 and the concave lens 404 is in an overcorrected state.

[0078] This field curvature is caused as will be described. In the optical system of this embodiment, the exit pupil distance is about 21 mm. This value is longer than the focal length (13.5 mm) of the eyepiece optical system, so the reflecting surface 402B of the first optical element 402 is large. When the reflecting surface 402B is large, the droop of the reflecting surface 402B is large, and the droop amount causes field curvature. Therefore, although the optical system has positive power, negative field curvature occurs.

[0079] In order to correct this field curvature, there is a method of using an element with strong positive power and performing correction using the droop amount of the element. As a surface to which positive power is imparted, it can be considered to use the transmission surface 402C of the first optical element 402 as an incident surface. However, when the viewing angle is widened, in the path of the light traced from the exit pupil S side, the light beam at the edge viewing angle is totally reflected on the transmission surface 402C as the incident surface, making it impossible to observe the image. Therefore, it may not be possible to impart strong positive power to the transmission surface 402C of the first optical element 402 as the incident surface.

[0080] Therefore, as a positive power, the convex lens 406 is provided between the first optical element 402 and the image display element 405. The convex lens is provided so that the convex surface 406A having a strong positive power faces the first optical element 402. This makes it possible to observe an image without total reflection occurring on the transmission surface 402C even when the viewing angle is widened.

[0081] Correction is performed with respect to the droop amount of the reflective surface 402B by using the optical path difference obtained by the droop amount of the transmission surface of the convex lens 406, and thus a strong curvature is imparted on the convex surface 406A having positive power of the convex lens 406. The following inequality (12) is satisfied, where R B represents the radius of curvature of the reflective surface 402B at the intersection with the principal ray of the central viewing angle beam, which is a line along the Z axis connecting the center of the image with the center of the exit pupil S, and R P denoted by the radius of curvature of the convex surface 406A of the convex lens 406 that faces the first optical element 402 .

[0082] -8.0 <R B / R P <-2.0 (12)

[0083] The numerical range of inequality (12) can be set to the numerical range of the following inequality (13).

[0084] -5.0 <R B / R P <-1.5 (13)

[0085] By setting the radius of curvature in this manner, the field curvature generated by the concave lens 404 and the first optical element 402 can be corrected. B / R P =-3.68.

[0086] The field curvature can be corrected by providing the convex lens 406, but chromatic aberration occurs because a strong positive power is given. To correct this chromatic aberration, it is conceivable to divide the convex lens 406 to form an achromatic lens, or to perform correction by appropriately setting the refractive index and dispersion of the concave lens 404.

[0087] Generally, the correction condition of chromatic aberration is expressed as the following equation (14).

[0088]

[0089] here, represents the optical power of the concave lens 404, represents the focal power of the convex lens 406, ν n represents the Abbe number of the concave lens 404, and ν p represents the Abbe number of the convex lens 406. When a light beam passing through the center of the top, bottom, left, and right of the viewing angle when the observer performs observation is referred to as a central viewing angle light beam, h n and h p represents the beam radius of the central viewing angle light beam on the concave lens 404 and the convex lens 406. Here, since the chromatic aberration is small, the chromatic aberration caused by the first optical element 402 can be ignored.

[0090] When the concave lens 404 and the convex lens 406 are adjacent to each other, h in equation (14) n and h p The values ​​of are basically the same. Therefore, and The absolute values ​​of are essentially the same, and However, a large amount of positive power is used in field curvature correction, and if the power of the concave lens is also increased, the field curvature correction effect is weakened.

[0091] On the other hand, in this embodiment, the concave lens 404 and the convex lens 406 are arranged separately from each other, and the beam diameters on the lenses differ by several times. Specifically, on the concave lens 404, the beam has a large beam diameter because the concave lens 404 is close to the pupil, and on the convex lens 406, the beam is thin because the convex lens 406 is close to the imaging plane.

[0092] Since the beam radius h on the concave lens 404 n Greater than the beam radius h on the convex lens 406 p, so when equation (14) is satisfied, the optical power of the concave lens 404 can be reduced. As described in the first embodiment, it is difficult to reduce the radius of curvature of the concave lens 404 and increase the optical power of the concave lens 404. However, since the beam diameter on the concave lens 404 is sufficiently large as described herein, the concave lens 404 can have an optical power for obtaining a sufficient chromatic aberration correction effect while having a large radius of curvature. The beam diameters on the concave lens 404 and the convex lens 406 differ by about 1.5 to 3 times, and thus the following inequality (15) is satisfied.

[0093]

[0094] By setting the focal length and glass material of each lens so as to satisfy the relationship of inequality (15), chromatic aberration can be reduced. ν p =35.25, ν n =23.78 and

[0095] The transmission surface 403B as a refractive surface of the second optical element 403 has a function of canceling the refraction that occurs when light passes through the reflection-transmission surface 402A. The transmission surface 403B as a refractive surface may have the same shape as the reflection-transmission surface 402A, and the second optical element 403 may be made of the same material as the first optical element 402. However, the transmission surface 403B as a refractive surface and the reflection-transmission surface 402A may not have the same shape as long as the transmission surface 403B has a shape that can sufficiently cancel the aberration that occurs when light passes through the reflection-transmission surface 402A. As a condition for canceling the aberration, the following inequality (16) is satisfied, wherein α1 represents the angle formed by the Z axis and the surface normal of the reflection-transmission surface 402A as the exit surface of the first optical element at the intersection with the main ray of the central viewing angle light beam, and α2 represents the angle formed by the Z axis and the surface normal of the transmission surface 403B as a refractive surface at the intersection with the main ray of the central viewing angle light beam.

[0096] |α1-α2|<5 (16)

[0097] In this embodiment, since the two surfaces have the same shape, the value is |α1-α2|=0.

[0098] In this embodiment, regarding the upper limit of inequality (2), if the negative power of the third optical element 407 is too strong, the influence of aberration may not be negligible. Therefore, the following inequality (17) may be satisfied.

[0099] 1.50>n n / n m >1.05 (17)

[0100] The numerical range of inequality (17) can be set to the numerical range of the following inequality (18).

[0101] 1.40>n n / n m >1.10 (18)

[0102] Third embodiment

[0103] Next, we will refer to Figure 7 and Fig.16 A description is given of an eyepiece optical system and a display device according to a third embodiment of the present disclosure. Figure 7 : is a diagram illustrating the configuration of a display device having an eyepiece optical system in this embodiment. Fig.16 3 is an explanatory diagram corresponding to Numerical Example 3 of this embodiment. An image display device 701 as a display device includes an eyepiece optical system as an optical system and an image display element 705 as a display element. The eyepiece optical system is configured to guide a light beam from the image display element 705 to an exit pupil S.

[0104] This embodiment removes the second optical element from the eyepiece optical system of the first embodiment to position the reflection surface of the first optical element 702 closer to the position of the exit pupil S and reduce the size of the first optical element 702. With such a configuration, even when the size of the image display element 705 is reduced, a wide viewing angle can be achieved while the power of the concave lens 703 is substantially unchanged.

[0105] Light emitted from the image displayed on the image display element 705 enters the first optical element 702, exits from the first optical element 702 after being reflected multiple times inside, and enters the concave lens 703. After the light is emitted from the concave lens 703, the light is guided to the exit pupil S of the eyepiece optical system, and the image displayed on the image display element 705 is viewed as a distant enlarged virtual image through the exit pupil S by an observer who places a pupil near the exit pupil S.

[0106] In this embodiment, the concave lens 703 and the first optical element 702 are adjacent to each other. That is, it can be said that the first optical element 702 is brought closer to the pupil while maintaining the length of the exit pupil distance. Thereby, the size of the first optical element 702 is reduced, and therefore, the distance from the image-side principal plane of the eyepiece optical system to the transmission surface 702C as the incident surface of the first optical element is also reduced, making it possible to easily ensure the back focus.

[0107] On the other hand, if the distance between the concave lens 703 and the reflective surface 702B of the first optical element is large, the size of the first optical element 702 is large, and the effect of removing the second optical element cannot be obtained. Therefore, the distance between the exit surface 703A of the concave lens 703 and the reflective surface 702B of the first optical element 702 satisfies the following inequality (19).

[0108] L PB / fL<0.75 (19)

[0109] Here, when the direction of the principal ray of the central viewing light beam in the exit pupil S is referred to as the Z axis, L PB represents the distance on the Z axis between the exit surface 703A of the concave lens 703 and the reflection surface 702B of the first optical element 702, and fL represents the focal length of the eyepiece optical system. As described above, the concave lens 703 and the first optical element 702 are adjacent to each other, and the reflection surface 702B is made closer to the exit pupil S, so that a wide viewing angle is achieved while the optical power of the concave lens 703 is slightly weakened. This embodiment makes L PB =8.0mm, fL=18.4mm and L PB / fL=0.43.

[0110] The focal length of the concave lens 703 is substantially the same as the focal length of the negative surface of the first embodiment of JP 6392066, which is -94.3 mm. By using such a configuration, a wide viewing angle of 45° is achieved while the image display element has a size of 0.6 inches smaller than that of JP 6392066. The shift amount of the image plane is about 4 mm.

[0111] When the concave lens 703 is made of optical glass, if the concave lens 703 has a special shape such as a free-form shape, the cost may increase, and therefore the concave lens 703 may be a coaxial optical element. Therefore, it is difficult to configure the concave lens 703 so that the aberration is offset by making the exit surface of the first optical element and the first surface of the second optical element have the same shape as described in JP 6392066. The concave lens 703 is tilted to match the reflection-transmission surface 702A which is the exit surface of the first optical element 702, so that the influence of the surface shape difference is reduced. Specifically, the following inequality (20) is satisfied, where α1 represents the difference between the Z axis and the reflection-transmission surface 702A of the first optical element 702 in relation to the central viewing angle light beam. Figure 1 α represents the angle formed by the surface normal at the intersection of the main light ray indicated by line A, and α3 represents the angle formed by the Z axis and the optical axis of the concave lens 703.

[0112] |α1-α3|<5 (20)

[0113] When the inequality (20) is satisfied, it is possible to cancel out the aberration of the light beam emitted from the first optical element 702. The optical system in this embodiment is such that |α1-α3|=1.6.

[0114] In addition, Figure 7 In the X-axis direction indicated in , the aberration is canceled by the reflection-transmission surface 702A which is the exit surface of the first optical element 702 and the concave lens 703, and the following inequality (21) is satisfied.

[0115] 0.3 <R AX / R MX <2.0 (21)

[0116] Here, R AX represents the radius of curvature of the first optical element 702 in a direction orthogonal to the plane of the drawing at the intersection of the reflection-transmission surface 702A and the principal ray of the central viewing angle light beam, and R MX represents the radius of curvature of the incident surface 703B of the concave lens 703. In other words, R MX is the radius of curvature of the incident surface 703 which is the convex surface of the concave lens 703 in the cross section orthogonal to the cross section including the principal ray of the central viewing angle light beam passing through the image display element to the exit pupil S, and R AX is the radius of curvature of the exit surface of the first optical element 702 at the intersection of the exit surface of the first optical element 702 and the principal ray of the central viewing angle light beam in a cross section orthogonal to the cross section including the principal ray. By making the curvatures of the two surfaces closer in this way, the aberrations on the two surfaces are offset. In this embodiment, R AX =-48.8, R MX = -67.7 and R AX / R MX =0.72. In this embodiment, the concave lens 703 is a meniscus lens, but the present disclosure is not limited thereto.

[0117] Fourth embodiment

[0118] Next, we will refer to Figure 8 and Fig.18 A description is given of an eyepiece optical system and a display device according to a fourth embodiment of the present disclosure. Figure 8 : is a diagram illustrating the configuration of a display device having an eyepiece optical system in this embodiment. Fig.18: is an explanatory diagram corresponding to Numerical Example 4 of this embodiment. An image display device 801 as a display device includes an eyepiece optical system as an optical system and an image display element 804 as a display element. The eyepiece optical system is configured to guide a light beam from the image display element 804 to an exit pupil S. In this embodiment, the image display element is configured so that the image display element of the third embodiment is smaller, and an observer can superimpose a transmission image and a display image for observation.

[0119] The light beam emitted from the image display element 804 passes through the convex lens 805 as a positive lens, the first optical element 802, and the concave lens 803, and forms an exit pupil S. In this embodiment, as in the second embodiment, the third optical element 806 is provided on the side of the first optical element 802, which is opposite to the exit pupil S. Here, when the reflectivity of the reflection surface 802B of the first optical element is set to be lower than 100%, an observer who places the pupil near the exit pupil S can also observe an external image via the concave lens 803, the first optical element 802, and the third optical element 806. That is, the observer can observe the external image and the image displayed on the image display element 804 at the same time.

[0120] In the optical system of this embodiment, the image display element 804 is configured so that the size is 0.5 inches and the viewing angle is 50°. The focal length of the eyepiece optical system is about 13.5 mm. The viewpoint is as large as 25 mm, and thus Fig. 9 As shown in FIG. 8 , the field curvature occurring in the concave lens 803 and the first optical element 802 is very large. Therefore, as in the second embodiment, the convex lens 805 is provided between the first optical element 802 and the image display element 804.

[0121] Here, we will refer to Fig. 9 A description is given of field curvature occurring in the concave lens 803 and the first optical element 802. Fig. 9 901 is an illustration of the image field curvature in this embodiment. Reference numeral 901 represents an imaging plane near the position where the light beam passing through the exit pupil S is imaged by the concave lens 803 and the first optical element 802. Reference numeral 902 is an axis in the normal direction of the imaging plane 901. Reference numeral 903 represents the image plane of the first optical element 802 and the concave lens 803. As described in the second embodiment, the main factor of the image field curvature is the droop of the reflection surface 802B. However, in reality, two factors (factor 1 and factor 2) are also involved in forming the image plane.

[0122] Factor 1

[0123] The reflection-transmission surface 802A totally reflects the light beam entering the incident surface 802C. The light beam is reflected at a very large angle equal to or greater than the total reflection angle. Fig. 9The reflection-transmission surface 802A is entered into the cross section (i.e., the YZ cross section), and therefore, when aberration correction is considered, the reflection-transmission surface 802A may not have a strong optical power, and the YZ cross section may not have a strong optical power. However, in order to have a total reflection angle, the upper part of the reflection-transmission surface 802A deviates from the straight line, and the reflection-transmission surface 802A has a negative power, that is, has a backward curved shape. Therefore, as Fig. 9 As illustrated in FIG. 8 , the light beam passing through the upper portion of the reflection-transmission surface 802A is affected by the negative optical power and is imaged at a position farther than the position where the light beam passing through the lower portion of the reflection-transmission surface 802A is imaged.

[0124] Factor 2

[0125] The reflection-transmission surface 802A has a configuration close to the concentric configuration described in the third embodiment, and has a curvature in the cross section in the X-axis direction. Therefore, the reflection-transmission surface 802A has negative power at the time of total reflection, and therefore, a stronger negative field curvature occurs in the cross section in the X-axis direction than in the cross section in the Y direction.

[0126] The above two factors cause the concave lens 803 and the first optical element 802 to produce asymmetric field curvature in the YZ cross section and strong negative field curvature in the X-axis direction. In order to correct these aberrations, the convex lens 805 has the following characteristics.

[0127] Feature 1

[0128] The convex lens 805 is shifted and arranged so that the light beam passing through the reflection surface 802B side of the first optical element passes through a portion of the convex lens 805 as a positive lens which is thicker than a portion through which the light beam passes on the reflection-transmission surface 802A side.

[0129] Feature 2

[0130] In the convex lens 805, the convex surface 805A which is the emission surface on the first optical element 802 side is a deformed surface and satisfies the following inequality (22).

[0131] R PX <R PY (twenty two)

[0132] Here, R PX represents the curvature radius of the convex surface 805A of the convex lens 805 in the X-axis direction, and R PY represents the curvature radius of the convex surface 805A of the convex lens 805 in the Y-axis direction. In other words, the convex surface 805A of the convex lens 805 faces the first optical element 802, R PYis the radius of curvature of the convex surface 805A of the convex lens 805 in the cross section including the principal ray of the central viewing angle light beam passing through the image display element 804 to the exit pupil S, and R PX is the radius of curvature of the convex surface 805A of the convex lens 805 in a cross section orthogonal to the cross section including the principal ray of the central view light beam.

[0133] Regarding the asymmetrically occurring field curvature, the convex lens 805 is shifted in the YZ cross section and is arranged so as to make the droop amount asymmetrical, thereby effectively correcting the field curvature. Regarding the field curvature that strongly occurs in the X-axis direction, the convex lens 805 is configured so that the radius of curvature in the X-axis direction is reduced, thereby effectively correcting the field curvature in all cross-sectional directions.

[0134] In this embodiment, Figure 8 In the cross section of , the thickness of the convex lens 805 near the light beam passing through the position closest to the reflection-transmission surface 802A is about 2.7 mm, and the thickness of the convex lens 805 near the light beam passing through the position closest to the reflection surface 802B is about 5 mm. The curvature radius of the convex surface 805A as the exit surface of the convex lens 805 is set to R PX =15.51mm and R PY =22.51mm.

[0135] Fifth embodiment

[0136] Next, we will refer to Fig.10 A description is given of an observation device 1001 as a display device according to a fifth embodiment of the present disclosure. Fig.10 : is a diagram illustrating a configuration of an observation device 1001 including an eyepiece optical system of the fourth embodiment. The observation device 1001 is configured as smart glasses including an optical see-through display.

[0137] The observation device 1001 includes the eyepiece optical systems 801a and 801b and the image display elements 804a and 804b according to the fourth embodiment, and an image display circuit 1002 connected thereto. The observation device 1001 also includes a camera 1003, an image pickup circuit 1004 configured to process an image acquired by the camera 1003, and an image recognition unit 1005 configured to recognize an object being captured from the image processed by the image pickup circuit 1004. The eyepiece optical systems 801a and 801b and the camera 1003 are provided inside a headset unit 1006.

[0138] The observer wears the earphone unit 1006 of the observation device 1001 in the same manner as glasses. When the earphone unit 1006 is worn, the pupils of the observer's eyes (both eyes) are respectively located near the exit pupil S and exit pupil S' (not shown) of the eyepiece optical systems 801a and 801b mounted on the earphone unit 1006. Therefore, the images displayed on the image display elements 804a and 804b are viewed as enlarged virtual images by the observer.

[0139] The camera 1003 attached to the earphone unit 1006 acquires an image in the viewing direction of the observer. The image imaged by the camera 1003 is transmitted to the image recognition unit 1005 via the image pickup circuit 1004. The image recognition unit 1005 recognizes the content captured in the captured image, and transmits text information describing the imaged object, etc. to the image display circuit 1002. The image display circuit 1002 displays useful character information on the image display elements 804a and 804b near the object or overlapping with the object based on the information received from the image recognition unit 1005. For example, the information is the name and menu information of a restaurant captured in the field of view, detailed information about an exhibition at a museum, etc., information about the price and origin of products in a store, map information, navigation information, etc. By superimposing such information on an external image that can be seen through the eyepiece optical systems 801a and 801b, as Fig.11 As shown in the figure, the observer can observe the surrounding real space with the information added. Fig.11 is a diagram illustrating an overlapping display of information. The information is not limited to text information, but may be image information of a moving image or a still image. In addition to simply providing information, an observer may also view an augmented reality space in which another image such as a game image, an imaginary building image, etc. is superimposed on the real space.

[0140] When the performance of the image recognition unit 1005 and the camera 1003 in detecting information about the outside (external information) is insufficient, the information to be used can be obtained by another method such as a method of obtaining information in a three-dimensional direction using an acceleration sensor and a method of adding information about the position and observation direction of the observer using GPS and map information. By obtaining external information by multiple methods, the position accuracy of the superimposed information can be improved, and the information can be superimposed on the real space without deviation. Therefore, for example, while driving a bicycle, etc., the observer can have navigation information displayed in front of his eyes, can obtain direction indication information of an accurate position based on GPS without significantly moving the line of sight, and can achieve safe driving.

[0141] If the display viewing angle is narrow, the displayed information is concentrated near the center of the field of view, and the display may bother the observer. When the eyepiece optical systems 801a and 801b of this embodiment are used, since the display viewing angle is wide, information can be displayed within a range that does not bother the observer.

[0142] By configuring an optical see-through display with a wide viewing angle eyepiece optical system as described above, it is possible to obtain smart glasses that can superimpose new information images on a real space with a relatively wide field of view within a range that does not bother the observer. Such smart glasses make it possible to display information while preventing the display in the field of view from bothering the observer and preventing the line of sight from moving significantly during, for example, driving, sports, or working with both hands. This embodiment describes an observation device that displays information to both eyes of the observer, but the observation device may display information to one eye of the observer. In this case, it is sufficient to have an eyepiece optical system for one eye.

[0143] Hereinafter, descriptions of numerical examples 1 to 4 corresponding to the first to fourth embodiments will be given respectively. In the description of each embodiment, descriptions of the optical path are given sequentially from the light source, but in each numerical example, light rays are tracked from the pupil position of the projection optical system.

[0144] Tables 1 to 12 describe corresponding numerical examples. In the description, the reference of the absolute coordinate system is described as the global origin. Tables 1 to 3 correspond to the first embodiment, Tables 4A to 6 correspond to the second embodiment, Tables 7 to 9 correspond to the third embodiment, and Tables 10A to 12 correspond to the fourth embodiment.

[0145] The three-dimensional coordinate axes in the absolute coordinate system are defined as a Z axis, a Y axis, and an X axis as follows.

[0146] The Z axis is a straight line passing through the center of the 0th surface to the center of the first surface (ie, the origin of the absolute coordinates), and this direction is a positive direction.

[0147] The Y axis is a straight line passing through the center of the first surface (ie, the origin of the absolute coordinates) and forms 90 degrees counterclockwise with the Z axis.

[0148] The X-axis is a straight line passing through the origin and perpendicular to the Z-axis and the Y-axis.

[0149] A local coordinate system is set, and the surface shape of the i-th surface included in the optical system is expressed by a function based on the local coordinate system. The inclination angle of the i-th surface in the YZ plane is expressed by an angle θgi (unit: degree) formed with the Z axis of the absolute coordinate system, where the counterclockwise direction is the positive direction. In each numerical example, the inclination angle is set only in the YZ plane. The y-axis and z-axis of the local coordinate system (x, y, z) of the i-th surface are in the YZ plane of the absolute coordinate system, and are inclined at an angle θgi in the YZ plane.

[0150] The z-axis is a straight line that passes through the origin of the local coordinate system and forms an angle θi with the Z-axis of the absolute coordinate system counterclockwise in the YZ plane.

[0151] The y-axis is a straight line passing through the origin of the local coordinate system and forming a 90 degree angle with the z-direction counterclockwise in the YZ plane.

[0152] The x-axis is the line that passes through the origin of the local coordinate system and is perpendicular to the YZ plane.

[0153] Ndi and νdi represent the refractive index and Abbe number at the d-line between the i-th plane and the (i+1)-th plane.

[0154] The surface shape without a rotational symmetry axis used in each numerical example is expressed by the following function. In each table, the non-rotational symmetry plane is described as XYP.

[0155]

[0156] This function defines the surface shape by the local coordinates (x, y, z) of the i-th surface. In this same function, when the term of x with an odd order is 0, a plane symmetric with respect to the yz plane can be obtained in the local coordinate system. Below, the function of the torus used in each numerical example is given. In each numerical example, the torus is described as XTO.

[0157]

[0158] In each numerical example, the eccentricity of the face vertex of each face is only the shift eccentricity in the y-axis and z-axis directions and the tilt eccentricity around the x-axis, and therefore, in each face, the section on the standard generatrix and the section on the local generatrix are the same section, while the section on the standard sagittal line and the section on the local sagittal line are different.

[0159] In each numerical example, if a numerical value is written in the column Yg, Zg or θg indicating the position of the local origin in the table, the origin of the face is at a position rotated about the Y axis, Z axis or X axis from the face described as the global origin. If these columns are empty, the face is located at a position shifted by a distance D in the Z axis direction from the face in front of the face. The coordinate system of each numerical example is based on the position of the global origin.

[0160] The XYP indicating surface is a free-form surface, the SPH indicating surface has a spherical shape, and the XTO indicating surface is a torus, and the corresponding coefficients are described in the attached table. The M indicating surface is a reflective surface.

[0161] Numerical Example 1

[0162] The horizontal viewing angle in the direction perpendicular to the plane of the drawing is ±20.5 degrees, the vertical viewing angle in the direction parallel to the plane of the drawing is ±11.25 degrees, and the pupil diameter is 4 mm. Each face number corresponds to Fig.12 Those shown in the figure. Fig.12 The diagram shows Figure 1 The same optical system in Table 1. Table 1 indicates the position of the local origin on each surface. Table 2 indicates the coefficients of the non-rotationally symmetric surface. Table 3 indicates the values ​​of various conditions. Fig.13 is a lateral aberration diagram of the eyepiece optical system according to this numerical example.

[0163] Table 1

[0164]

[0165] Table 2

[0166]

[0167] Table 3

[0168]

[0169] Numerical Example 2

[0170] The horizontal viewing angle in the direction perpendicular to the plane of the drawing is ±20.5 degrees, the vertical viewing angle in the direction parallel to the plane of the drawing is ±15.56 degrees, and the pupil diameter is 4 mm. Each face number corresponds to Fig.14 Those shown in the figure. Fig.14 The diagram shows Figure 4 The same optical system is used in FIG. 4A. Table 4A indicates the position of the local origin on each surface in the optical path through which the image from the display element is observed. Table 4B indicates the position of the local origin on each surface in the optical path through which the outside is observed. Table 5 indicates the coefficients of the non-rotationally symmetric surface. Table 6 indicates the values ​​of various conditions. Fig.15 is a lateral aberration diagram of the eyepiece optical system according to this numerical example.

[0171] Table 4A

[0172]

[0173] Table 4B

[0174] type Face number Y ZGar θg Rx R D Nd Vd SPH 0.000 0.000 0.000 -1400.000 -1400.000 -1400.000 SPH S 0.000 0.000 0.000 SPH 404A 21.100 -69.858 -69.858 0.500 1.8467 23.78 SPH 403A 21.600 0.000 0.000 0.000 1.5311 55.75 XY 403B 2.509 23.932 -6.163 0.000 0.000 0.000 XY 402B 2.509 24.032 -6.163 0.000 0.000 0.000 1.5311 55.75 ASP 407B 0.000 16.000 0.000 -49.077 -49.077 0.000

[0175] Table 5

[0176]

[0177] Table 6

[0178]

[0179] Numerical Example 3

[0180] The horizontal viewing angle in the direction perpendicular to the plane of the drawing is ±20.5 degrees, the vertical viewing angle in the direction parallel to the plane of the drawing is ±11.25 degrees, and the pupil diameter is 4 mm. Each face number corresponds to Fig.16 Those shown in the figure. Fig.16 The diagram shows Figure 7 The same optical system is used in Table 7. Table 7 indicates the position of the local origin on each surface in the optical path through which the image from the display element is observed. Table 8 indicates the coefficients of the non-rotationally symmetric surface. Table 9 indicates the values ​​of various conditions. Fig.17 is a lateral aberration diagram of the eyepiece optical system according to this numerical example.

[0181] Table 7

[0182]

[0183] Table 8

[0184]

[0185] Table 9

[0186]

[0187] Numerical Example 4

[0188] The horizontal viewing angle in the direction perpendicular to the plane of the drawing is ±20.5 degrees, the vertical viewing angle in the direction parallel to the plane of the drawing is ±15.56 degrees, and the pupil diameter is 4 mm. Each face number corresponds to Fig.18 Those shown in the figure. Fig.18 The diagram shows Figure 8 The same optical system is used in FIG. 10A. Table 10A indicates the position of the local origin on each surface in the optical path through which the image from the display element is observed, and Table 10B indicates the position of the local origin on each surface in the optical path through which the outside is observed. Table 11 indicates the coefficients of the non-rotationally symmetric surface and the coefficients of the torus surface. Table 12 indicates the values ​​of various conditions. Fig.19 is a lateral aberration diagram of the eyepiece optical system according to this numerical example.

[0189] Table 10A

[0190]

[0191] Table 10B

[0192] type Face number Y ZGar θg Rx R D Nd Vd SPH 0.000 0.000 0.000 -1400.000 -1400.000 -1400.000 SPH S 0.000 0.000 0.000 SPH 803A 25.000 8.000 -69.858 -69.858 0.500 1.8467 23.78 SPH 803B 0.000 0.000 0.000 1.5311 55.75 XY 802A 2.174 25.193 -19.872 0.000 0.000 0.000 XY 802B -2.010 32.668 3.138 0.000 0.000 0.000 1.5311 55.75 ASP 806B -1.406 40.857 8.000 -49.077 -49.077 0.000

[0193] Table 11

[0194]

[0195] Table 12

[0196]

[0197] According to each embodiment, an optical system and a display device, each of which is compact and has a wide viewing angle, can be provided.

[0198] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An optical system for directing a light beam from a display element to an exit pupil, the optical system comprising: a first optical element, the first optical element comprising a transmission surface, a reflection-transmission surface, and a reflection surface; as well as a negative lens including a concave surface on the exit pupil side, The invention is characterized in that the light beam from the display element advances toward the exit pupil via the transmission surface, the reflection-transmission surface, the reflection surface, the reflection-transmission surface and the negative lens in sequence, Among them, the following inequality is satisfied: n n >n m Among them, n n represents the refractive index of the negative lens at the d line, n m represents the refractive index of the first optical element at the d-line, represents the optical power of the negative lens, and Represents the optical power of the optical system.

2. The optical system according to claim 1, wherein: The following inequality is satisfied: n n / n m >1.05。 3. The optical system according to claim 1, wherein: The following inequality is satisfied: 15<ν n <ν m Among them, ν n denotes the Abbe number of the negative lens, and ν m represents the Abbe number of the first optical element. 4 . The optical system according to claim 1 , further comprising a positive lens disposed between the first optical element and the display element.

5. The optical system according to claim 4, wherein: The positive lens has a convex surface facing the first optical element, and Among them, the following inequality is satisfied: -8.0<R B / R P <-2.0 Among them, R B represents the radius of curvature of the reflecting surface at the intersection with the principal ray of the central viewing angle beam, and R P represents the radius of curvature of the convex surface.

6. The optical system according to claim 4, wherein: The positive lens has a convex surface facing the first optical element, and Among them, the following inequality is satisfied: R PX <R PY Among them, R PY represents the radius of curvature of the convex surface in a cross section including the principal ray of the central viewing angle light beam from the display element to the exit pupil, and R PX represents the radius of curvature of the convex surface in a cross section orthogonal to the cross section including the principal ray.

7. The optical system according to claim 6, wherein: When a direction orthogonal to a plane on which the exit pupil is formed is a first direction, inside the positive lens, a length of an optical path of a light beam passing through a position closest to the reflection surface in the first direction is longer than a length of an optical path of a light beam passing through a position closest to the reflection-transmission surface in the first direction.

8. The optical system according to claim 4, wherein: The following inequality is satisfied: in, represents the optical power of the positive lens, represents the focal power of the negative lens, ν p represents the Abbe number of the positive lens, and ν n represents the Abbe number of the negative lens.

9. An optical system for directing a light beam from a display element to an exit pupil, the optical system comprising: a first optical element, the first optical element comprising a first transmission surface, a reflection-transmission surface, and a reflection surface; a negative lens including a concave surface on an exit pupil side; and a second optical element, the second optical element being a prism disposed between the first optical element and the negative lens, The invention is characterized in that the second optical element has a second transmission surface facing the reflection-transmission surface, The surface of the second optical element on the display element side has the same shape as the reflection-transmission surface, The light beam from the display element advances toward the exit pupil via the first transmission surface, the reflection-transmission surface, the reflection surface, the reflection-transmission surface, the second transmission surface and the negative lens in sequence. Among them, the following inequality is satisfied: n n >n m |α1-α2|<5 Among them, n n represents the refractive index of the negative lens at the d line, n m represents the refractive index of the first optical element at the d-line, α1 represents the angle formed by the main light of the central viewing angle and the normal of the reflection-transmission surface at the position where the main light is transmitted, and α2 represents the angle formed by the main light and the normal of the second transmission surface at the position where the main light is transmitted.

10. The optical system according to claim 9, wherein: The following inequality is satisfied: n n >n O Among them, n O represents the refractive index of the second optical element at the d-line.

11. The optical system according to claim 10, wherein: The following inequality is satisfied: (n n -1) / (n O -1)>1.3。 12 . The optical system according to claim 1 , further comprising a third optical element disposed on a side of the first optical element opposite to the negative lens.

13. The optical system according to claim 1, wherein: The following inequality is satisfied: L PB / fL<0.75 Among them, L PB represents the distance between the exit surface of the negative lens on the principal ray of the central viewing angle and the reflection surface, and fL represents the focal length of the optical system.

14. The optical system according to claim 1, wherein: The following inequality is satisfied: |α1-α3|<5 Here, α1 represents the angle formed by the principal ray of the central viewing angle and the normal of the reflection-transmission surface at the position where the principal ray is transmitted, and α3 represents the angle formed by the principal ray and the optical axis of the negative lens.

15. The optical system of claim 1, wherein: The negative lens is a meniscus lens including a convex surface, and Among them, the following inequality is satisfied: 0.3<R AX / R MX <2.0 Among them, R MX represents the radius of curvature of the convex surface of the negative lens in a cross section orthogonal to the cross section including the principal ray of the central viewing angle, and R AX The curvature radius of the reflection-transmission surface at a position where the principal ray is transmitted in a cross section orthogonal to the cross section including the principal ray.

16. An optical system according to any one of claims 1 to 15, wherein: The negative lens is made of glass material.

17. A display device, characterized in that: The display device comprises: An optical system according to any one of claims 1 to 16; and Display components.

Images