Optical system and display device

Abstract

To provide an optical system that has a small size and a wide angle of view.SOLUTION: An optical system (101) guides a light beam from a display device (105) to an exit pupil (S), and the optical system has: a first optical device (102) having a transmission surface (102C), a reflection transmission surface (102A), and a reflection surface (102B); and a negative lens (104) including a surface having a concave shape toward the exit pupil. The light beam from the display device is directed to the exit pupil through the transmission surface, reflection transmission surface, reflection surface, reflection transmission surface, and negative lens in order. When the refractive index on the d-line of the negative lens is nn, and the refractive index on the d-line of the first optical device is nm, the conditional expression nn>nm is satisfied.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to an optical system suitable for a display device such as a head-mounted display (HMD) that presents an image displayed on a display element as a magnified virtual image.

Background Art

[0002] Conventionally, a thin optical system (eyepiece optical system) configured to perform multiple off-axis reflections with respect to the principal ray of the central field angle has been known, which uses an optical element having an incident surface, a plurality of reflection surfaces, and an exit surface. In such an eyepiece optical system, an increase in the observation field angle is required. For an increase in the observation field angle, Patent Document 1 and Patent Document 2 disclose an optical system having a second off-axis optical element disposed between an observer and an off-axis optical element.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the optical systems disclosed in Patent Document 1 and Patent Document 2, it is difficult to achieve short focal length and wide field angle. Further, when the focal length of the optical system is shortened for widening the field angle, the distance from the principal plane on the display element side of the optical system to the display element becomes short, and it is impossible to secure a space for arranging the components necessary for arranging the display element, and the components constituting the optical system and the display element interfere with each other.

[0005] Therefore, an object of the present invention is to provide a small-sized and wide-field-angle optical system and a display device.

Means for Solving the Problems

[0006] An optical system according to one aspect of the present invention is an optical system that guides a light beam from a display element to an exit pupil, and includes a first optical element having a transmission surface, a reflective-transmission surface, and a reflective surface, and A positive lens disposed between the display element and the first optical element and having a convex surface facing the first optical element; a negative lens having a concave surface facing the exit pupil, and the light beam from the display element The positive lens; travels toward the exit pupil through the transmission surface, the reflective-transmission surface, the reflective surface, the reflective-transmission surface, and the negative lens in this order. Let the refractive index of the negative lens at the d-line be n n , the refractive index of the first optical element at the d-line be n m , the optical power of the negative lens be φ n , the optical power of the optical system be φ A , the radius of curvature of the convex surface in a cross section including the chief ray of the central picture angle be R PY , and the radius of curvature of the convex surface in a cross section perpendicular to this cross section be R PX . When n n m > n n and φ A / φ 、R PX <R PY satisfies the conditional expression.

[0007] Other objects and features of the present invention will be described in the following examples.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a small-sized and wide-angle optical system and a display device.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

[0011] In the description of each example, the XYZ axes of the absolute coordinate system are defined with the exit pupil (pupil center) as the origin and the viewing angle (Observation angular field of view)The light beam centered thereon is defined as the central angular beam of view as follows. The axis that coincides with the chief ray of the central angular beam of view is the Z-axis (a straight line along the chief ray of the central angular beam of view, with the direction from the exit pupil to the first surface being positive), the axis obtained by rotating the Z-axis counterclockwise by 90 degrees around the origin (within the cross-section of FIG. 1) is the Y-axis, and the axis passing through the origin and perpendicular to the Z-axis and the Y-axis is the X-axis.

[0012] [Example 1] First, with reference to FIGS. 1 and 12, the eyepiece optical system and the display device in Example 1 of the present invention will be described. FIG. 1 is a configuration diagram of a display device having the eyepiece optical system in this example. FIG. 12 is an explanatory diagram of Numerical Example 1 corresponding to this example. 101 is a display device (observation device An image display device ). The display device 101 has an eyepiece optical system (optical system) and an image display element (display element) 105. The eyepiece optical system is an optical system that guides the light beam from the image display element 105 to the exit pupil S.

[0013] 102 is the first optical element. The first optical element 102 has an incident surface The transmissive surface pass Surface 1 02C, a reflection-transmission surface 102A, and a reflection surface 102B, and its interior is filled with a medium having a refractive index n>1. 103 is a second optical element Transmissive surfaces 1103B and 103A which are composed of two refractive surfaces (Prism) . 104 is a concave lens (negative lens). The concave lens 104 is disposed between the first optical element 102 and the exit pupil S and has a concave surface (concave face) facing the exit pupil S. In this example, the eyepiece optical system is constituted by three optical elements: the first optical element 102, the second optical element 103, and the concave lens 104. Also in this example, the display device 101 is constituted by the eyepiece optical system and the 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 10 4 . That is, the light beam from the image display element 105 travels toward the exit pupil S via the incident surface The transmissive surface as 102C, the reflection-transmission surface 102A, the reflection surface 102B, the reflection-transmission surface 102A, and the concave lens 104 in sequence.

[0014] The movement of light rays inside each optical element is described below. Light emitted from the image displayed on the image display element 105 enters the first optical element 102 from the incident surface The transmissive surface as 102C of the first optical element. 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, resulting in a folded optical path inside the first optical element 102. Then, it exits the optical element 102 through the reflection / transmission surface 102A. The light that has exited the optical element 102 enters the concave lens 104 through the transmission surface 103B、 103 A of the second optical element 103. After exiting the concave lens 104, it is guided to the exit pupil S, and presents the image displayed on the image display element 105 as an enlarged virtual image in the distance from the exit pupil S to an observer who places their pupil near the exit pupil S. Of the system Here, the refractive surface

[0015] of the second optical element 103 functions to cancel the refraction that occurs when passing through the reflection / transmission surface 102A. As a result, it becomes possible to cancel the aberration generated at the reflection / transmission surface 102A. For this reason, it is desirable that the reflection / transmission surface 102A and the refractive surface Transmissive surface 103B which is 103B have the same shape and are made of the same material as the first optical element The transmissive surface which is 102. Also, it is desirable that these first optical element 102 and second optical element 103 are made of an optical resin. The reason for this will be explained later. Note that although it is desirable that the reflection / transmission surface 102A and the refractive surface 102 103B have the same shape, it is not limited to this, and the shape of the transmission surface 103B may be any shape sufficient to cancel the aberration generated when passing through the reflection / transmission surface 102A. The transmissive surface which is 103B have the same shape, it is not limited to this, and the shape of the transmission surface 103B may be any shape sufficient to cancel the aberration generated when passing through the reflection / transmission surface 102A.

[0016] Next, with reference to FIG. 2, the features of the eyepiece optical system of this embodiment will be described. FIG. 2 is an explanatory diagram of the eyepiece optical system of this embodiment. To increase the angle of view of the eyepiece optical system, it is necessary to shorten the focal length of the eyepiece optical system. At this time, the distance from the exit pupil S to the final surface of the eyepiece optical system (eye relief) is set to a value of about 15 to 30 mm in consideration of the ease of observation by the observer. However, when the size of the image display element 105 is small, to obtain a wide angle of view, it is necessary to shorten the focal length of the eyepiece optical system more than the value of the eye relief. The size of the first optical element 102 is almost determined from the eye relief length and the angle of view. That is, the larger the eye relief, the larger the first optical element 102 becomes. As a result of the increase in size of the first optical element 102, the eyepiece optical Of the system When the focal length is short, the eyepiece optical Of the system The focal plane approaches the incident surface The transmissive surface as 102C.

[0017] Here, when mechanical parts are arranged between the image display element 105 and the first optical element 102, or for example, when the image display element 105 is a self-luminous element and heat dissipation is required, it is necessary to ensure a distance of a certain length or more between the first optical element 102 and the image display element 105. However, the eyepiece optical Of the system When the focal plane is near the first optical element 102, for example, as shown in FIG. 2(A), the interval (back focus) between the first optical element 102 and the image display element 105 becomes narrow. As a result, it may not be possible to secure sufficient space or the elements may collide with each other.

[0018] To avoid this, the eyepiece optical Of the system needs to move the image-side principal plane position closer to the image display element 105 side and move the focal plane away from the first optical element 102. As one means of moving the image-side principal plane, a technique is disclosed in Patent Document 1 in which a second optical element having a surface with a negative optical power (refractive power) is inserted between the exit pupil S and a prism corresponding to the first optical element 102. The second optical element 103By arranging it between the exit pupil S and the first optical element 102, while shortening the focal length of the entire eyepiece optical system, the image-side principal plane position is moved toward the image display element side, and sufficient space can be secured between the image display element 105 and the first optical element 102 (see Fig. 2(B)).

[0019] To widen the observation angle of view compared to the configuration of Patent Document 1 and achieve short focalization of the eyepiece optical system, it is necessary to move the position of the principal plane even further. For this purpose, it is necessary to increase the negative power of the concave lens 104, but a large curvature is required for the concave lens 104. However, if the curvature becomes too large, the sag amount of the concave lens 104 increases, and the periphery of the concave lens 104 protrudes significantly toward the exit pupil side. At this time, for example, when an observer wearing glasses looks into the eyepiece optical system, as shown in Fig. 3(A), the glasses hit the peripheral portion 104a of the concave lens 104. Fig. 3(A) is an explanatory diagram of the physical interference between the eyepiece optical system and the observer's glasses when the sag amount of the concave lens 104 is large.

[0020] To avoid this, in this embodiment, the refractive index of the concave lens 104 is increased. By increasing the refractive index, the negative optical power can be increased while keeping the curvature of the concave lens 104 small. As a result, as shown in Fig. 3(B), the sag amount of the concave lens 104 is reduced, and sufficient eye relief can be ensured even around the concave lens 104. Fig. 3(B) is an explanatory diagram of the physical interference between the eyepiece optical system and the observer's glasses when the sag amount of the concave lens 104 is small. From the above, in this embodiment, when the refractive index of the concave lens 104 at the d-line (d-line in the Fraunhofer lines, that is, wavelength 587.56 nm) is n n and the refractive index of the first optical element 102 at the d-line is n m the following conditional expression (1) is satisfied.

[0021] n n >n m …(1) Preferably, the refractive indices n n and n m satisfy the following conditional expression (2).

[0022] n n / n m >1.05 …(2) In this embodiment, n n = 1.854, n m = 1.531. By increasing the refractive index of the concave lens 104 in this way, in this embodiment, while using an image display element of the same size (0.7 type) as that of Patent Document 1, an eyepiece optical system with a wide angle of 45° is realized. At this time, the focal length of the concave lens 104 is -81.5 mm, which has a stronger negative power than the focal length of the concave lens in Patent Document 1, -94.3 mm.

[0023] Eyepiece optics Of the system To move the image plane side principal plane and increase the back focus, an image plane movement amount of at least several millimeters is required. To realize this movement amount, the optical power of the concave lens needs to be a certain size or more compared to the eyepiece optics Of the system optical power. Therefore, in this embodiment, when the optical power of the concave lens 104 is φ n and the optical power of the eyepiece optical system is φ A it is preferable to satisfy the following conditional expression (3).

[0024] φ n / φ A < -0.05 …(3) Furthermore, to ensure a sufficient image plane movement amount, it is preferable to set the numerical range of the conditional expression (3) as in the following conditional expression (4).

[0025] φ n / φ A < -0.08 ■(4) By satisfying the conditional expression (4), the image plane can be sufficiently moved and the distance between the first optical element 102 and the image display element 105 can be sufficiently ensured. In this embodiment, φ n / φ A = -0.26. By giving a negative optical power of sufficient strength to the concave lens 10 4 in this way, a movement of the image plane of about 5 mm is realized in this embodiment.

[0026] Also, the concave lens 104 is arranged such that its strong concave surface faces the pupil side. This is to reduce the occurrence of aberrations caused by the concave lens 104 and to approach a concentric arrangement centered on the pupil. Also, by arranging it in this way, compared to the case where the concave lens 104 is arranged in the opposite direction, the distance between the first optical element 102 and the concave lens 104 is reduced by the amount of sag of the concave lens 104, which also has the effect of miniaturizing the optical system.

[0027] Each optical surface of the first optical element 102 often uses a non-rotationally symmetric surface (freeform surface) in order to reduce the influence of obliquely incident light rays. In the case of an optical system using such a freeform surface, the first optical element 102 is often manufactured by molding using an optical resin due to the cost reduction effect by ease of manufacturing. Examples of the optical resin to be used include acrylic resin, polycarbonate resin, cycloolefin polymer resin, etc. Also, in this embodiment, the second optical element 103 also uses the same optical material. This is to cancel the aberration generated at the reflection / transmission surface 102A of the first optical element 102 at the incident surface The transmissive surface which is 103B of the second optical element, and the two surfaces are constructed with the same shape and the same material. By using molding with these resins as materials, it becomes possible to manufacture optical elements with complex shapes, but there are also material-derived problems such as being vulnerable to grease, moisture, etc., being prone to corrosion and expansion, and being easily scratched because the material itself is soft. Against these problems, there are measures such as arranging a protective glass window and applying a protective coating to the resin surface, but this will cause an increase in the number of parts and processes.

[0028] Therefore, in this embodiment, the concave lens 104 is made of optical glass (glass material). Optical glass is a very hard and stable material compared to resin materials, has high environmental resistance and is not easily scratched, so it can be used for protecting resin materials. That is, by making the concave lens 104 of optical glass, it becomes possible to also serve as the protective window of the first optical element. Also, by using optical glass, it becomes easier to select the refractive index and dispersion, and it becomes easier to give the necessary optical power to the concave lens 104.

[0029] Also, in this embodiment, let the Abbe number of the concave lens 104 be ν n , and when the Abbe number of the first optical element 102 is ν m , it is preferable to satisfy the following conditional expression (5).

[0030] 15 < ν n < ν m …(5) Note that the Abbe number is expressed by the following formula when the refractive indices at the d-line (wavelength 587.6 nm), F-line (wavelength 486.1 nm), and C-line (wavelength 656.3 nm) of the Fraunhofer lines are nd, nF, and nC, respectively.

[0031] ν = (nd - 1) / (nF - nC) Also, in this embodiment, when the refractive index at the d-line of the second optical element 103 is n O , it is preferable to satisfy the following conditional expression (6).

[0032] n n > n O …(6) Note that in this embodiment, the optical system is an eyepiece optical system. However, for example, if an imaging element is arranged at the position of the image display element 105 and a diaphragm is arranged at the position corresponding to the exit pupil S, it can also be an imaging optical system. In this case, it becomes an imaging optical system with a front diaphragm and can be applied to, for example, a fundus camera. 〔Embodiment 2〕 Next, with reference to FIGS. 4 and 14, the eyepiece optical system and the display device in Embodiment 2 of the present invention will be described. FIG. 4 is a configuration diagram of a display device having the eyepiece optical system in this embodiment. FIG. 14 is an explanatory diagram of Numerical Example 2 corresponding to this embodiment. The image display device (display device) 401 has an eyepiece optical system (optical system) and an image display element (display element) 405. The eyepiece optical system is an optical system that guides the light beam from the image display element 405 to the exit pupil S.

[0033] The eyepiece optical system of this embodiment has a convex lens (positive lens) 406 disposed between the first optical element 402 and the image display element 405. The convex lens 406 has a surface convex toward the first optical element 402 (a strongly convex surface)406A It has. Also, when the direction perpendicular to the surface on which the exit pupil S is formed is defined as the first direction, inside the convex lens 406, the optical path length of the light beam passing through the side of the most reflective surface in the first direction 402B is longer than the optical path length of the light beam passing through the side of the most reflective and transmissive surface in the first direction. That is, the optical path length of the most off-axis light beam (the light beam from the outermost end of the display surface) on the most reflective surface side in the Z-axis direction is longer than the optical path length of the most off-axis light beam on the most reflective and transmissive surface side. According to this embodiment, compared with Embodiment 1, it is possible to realize further wide-angle conversion (50°) while reducing the size of the image display element (0.5 type). Also, it is possible for the observer to observe the transmitted image and the displayed image superimposed. 402A The light emitted from the image displayed on the image display element 405 passes through the convex lens 406 and enters the first optical element 402, then is emitted from the first optical element 402 after multiple internal surface reflections, and enters the second optical element 403. After the light beam exits the second optical element 403, it enters the concave lens 404, exits the concave lens 404, and then is guided to the exit pupil S of the eyepiece optical

[0034] system, and presents the image displayed on the image display element 405 as an enlarged virtual image far away from the exit pupil S to an observer with a pupil placed near the exit pupil S. Of the system Also, on the side opposite to the exit pupil S of the first optical element 402, there is a third optical element 407. Here, when the reflectivity of the reflecting surface 402B of the first optical element 402 is set lower than 100%, the observer can observe the image of the outside world through the concave lens 404, the second optical element 403, the first optical element 402, and the third optical element 407 by placing the pupil near the exit pupil S. That is, the observer can observe the image of the outside world and the image displayed on the image display element 405 simultaneously.

[0035] FIG. 5 is an explanatory diagram of the eyepiece optical system and shows the arrangement of the third optical element 407. As shown in FIG. 5, the reflectivity of the reflecting surface 402B of the first optical element is lowered (for example, the reflectivity is 50%), and the third optical element 407 is added. Thereby, the eyepiece optical

[0036] system Of the systemAn observer placing their eye near the exit pupil S can observe the external image through the concave lens 404, the second optical element 403, the first optical element 402, and the third optical element 407. At this time, the outer surface 407B of the third optical element 407 has positive optical power, which approximately cancels out the negative optical power of the concave lens 404, so that as a whole, it has non-power or very weak optical power, enabling the observation of the external image.

[0037] Here, when the optical power of the concave lens 404 becomes very strong, in order to observe the external image, the optical power of the surface 407B of the third optical element 407 also needs to become strong. Here, when the first optical element 402 and the third optical element 407 are made of different materials, aberrations such as chromatic aberration and spherical aberration occur at the interface 501A between the two optical elements, making it difficult to observe the external image. Therefore, it is desirable that the third optical element 407 be made of the same material as the first optical element 402. However, as described in Example 1, the first optical element 402 is made of the same material as the second optical element 403, and inevitably the refractive index of the third optical element 407 is lower than that of the concave lens 404. For this reason, when the optical power of the concave lens 404 becomes too strong, the optical power to be given to the surface 407B of the third optical element becomes even stronger, and as a result, a surface with a very strong curvature is required. If the curvature becomes too strong, the surface 407B approaches a hemispherical shape, not only making it impossible to be configured as an optical element, but also increasing the aberration in the observation of the external image and making it difficult to observe the external image.

[0038] Therefore, the optical power of the concave lens 404 is restricted by the following conditional expression (7).

[0039] -0.4 < φ n / φ A ■(7) In the conditional expression (7), φ n is the optical power of the concave lens 404, and φ A is the total optical power of the entire ocular optical system of the display device 401. If it is below the lower limit of the conditional expression (7), the optical power of the surface 407B becomes too strong, making it difficult to observe the external image. On the other hand, for the conditional expression (7)The value is too large would result in insufficient optical power of the concave lens 404, and the distance between the image display element 405 and the convex lens 406 would become small, making it difficult to arrange the image display element 405. That is, from the viewpoint of conditional expression (7) and conditional expression (3) in the first embodiment, it is preferable to satisfy the following conditional expression (8).

[0040] -0.40<φ n / φ A <-0.05 …(8) By satisfying these conditions, it is possible to move the position of the image plane sufficiently and also to make it easy to observe the outside world. In addition, by setting the numerical range of conditional expression (8) to the following conditional expression (9), it becomes even easier to achieve both movement of the image plane and observation of the outside world.

[0041] -0.35<φ n / φ A <-0.08 ■(9) In this embodiment, φ n / φ A =-0.17. Here, attention is focused on 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, by increasing the refractive index of the concave lens 404, a larger negative optical power is imparted than by providing a negative optical power on the second optical element 403, and the position of the image-side principal plane is significantly shifted. This negative optical power is Emission Since this occurs at the interface between surface 404A and the air, (n n -1) is (n O -1), it is possible to increase the distance between the convex lens 406 and the image display element 405. For this reason, it is preferable to satisfy the following conditional expression (10).

[0042] (n n -1) / (n O -1)>1.3 …(10) When the value is below the lower limit of conditional expression (10), the optical power of the concave lens 404 is insufficient, and the image display element 405 interferes with the convex lens 406. By setting the numerical range of conditional expression (10) as in the following conditional expression (11), it becomes easier to avoid the interference between the image display element 405 and the convex lens 406.

[0043] (n n -1) / (n O -1)>1.4 …(11) In the eyepiece optical system of this embodiment, by inserting the concave lens 404, the position of the image plane of about 5 mm moves. In this embodiment, (n n -1) / (n O -1)=1.59.

[0044] FIG. 6 is an explanatory diagram of the field curvature generated by the first optical element 402 and the concave lens 404 in the eyepiece optical system of this embodiment. An image plane 601 is taken 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 points where the marginal rays passing through the edges of the exit pupil S intersect at the central field angle and the marginal field angle are obtained. At this time, the coordinate value of the intersection point on the axis 602 when the axis 602 is taken in the normal direction of the image plane 601 has the marginal field angle > the central field angle. That is, the image plane 603 formed by the first optical element 402 and the concave lens 404 is in an over state.

[0045] This field curvature occurs for the following reasons. In the optical system of this embodiment, the eye relief is about 21 mm. This value is longer than the focal length (13.5 mm) of the eyepiece optical system, so the size of the reflecting surface 402B of the first optical element 402 becomes larger. When the reflecting surface 402B becomes larger, the sag of the reflecting surface 402B becomes larger, and the amount of sag remains as field curvature. Therefore, although it is an optical system with positive power, negative field curvature occurs.

[0046] To correct this field curvature, there is a method of arranging an element with strong positive optical power and performing correction using the amount of sag. As the surface that gives positive optical power, the incident surface of the first optical element 402 The transmissive surface asA method using 402C can be considered. However, when the observation angle of view becomes wide-angle, when tracing the light rays from the exit pupil S side, the light beam of the peripheral angle of view is incident on the incident surface The transmissive surface as total reflection occurs at 402C, and the image cannot be observed. Therefore, it is not desirable to give a strong positive power to the incident surface of the first optical element 402 The transmissive surface as 402C.

[0047] Therefore, a convex lens 406 is arranged as a positive power between the first optical element 402 and the image display element 405. Also, at that time, the Convex surface 406A having a strong positive power is arranged facing the first optical element 402 side. Thereby, even when wide-angle conversion is performed At the transmissive surface 402C total reflection does not occur, and the image can be observed.

[0048] Also, at this time, in order to correct the optical path difference due to the sag amount of the transmission surface of the convex lens 406 with respect to the sag amount generated at the reflection surface 402B, the positive power of the convex lens 406 The convex of a strong curvature is required for the surface 406A. Therefore, the central angle of view Of the light beam the radius of curvature of the reflection surface 402B at the intersection with the chief ray (the line connecting the center of the image along the Z-axis and the center of the exit pupil S) is R B , the Convex surface 406A radius of curvature of the convex lens 406 facing the first optical element 402 is R P when taking this, the following conditional expression (12) is satisfied.

[0049] -8.0 < R B / R P < -2.0 …(12) Preferably, the numerical range of the conditional expression (12) is set as the following conditional expression (13).

[0050] -5.0 < R B / R P < -1.5 …(13) By setting the radius of curvature in this way, the field curvature generated by the concave lens 40 4 and the first optical element 402 can be corrected. In this embodiment, R B / R P=-3.68.

[0051] By arranging the convex lens 406, curvature of field can be corrected, but chromatic aberration will occur due to the arrangement of a strong positive power. To correct this chromatic aberration, the convex lens 40 6 is divided to form an achromatic lens, or the refractive index and dispersion of the concave lens 40 4 are adjusted appropriately for correction.

[0052] Generally, the chromatic aberration correction condition is expressed as the following conditional expression (14).

[0053]

Equation

[0054] Here, φ n is the optical power of the concave lens 404 φ p is the optical power of the convex lens 406 v n is the Abbe number of the concave lens 404, v p is the Abbe number of the convex lens 406. h n and h p are the beam radii on the concave lens Central angular field of view and convex lens Central angular field of view respectively, when the light beams passing through the center of the angular field of view vertically and horizontally are defined as 404 light beams when observed by the observer. Also, here, the chromatic aberration caused by the first optical element 402 is ignored as being small. 406

[0055] When the concave lens 404 and the convex lens 406 are adjacent, h n and h p in the conditional expression (14) become approximately the same value. Therefore, since the values of φ n / v n and φ p / v p also become approximately the same, inevitably φ Absolute n ​​A large value is also required. However, while a large positive power is required for field curvature correction, if the power of the concave lens also increases, the effect of correcting field curvature will be reduced.

[0056] In contrast, in this embodiment, the concave lens 404 and the convex lens 406 are arranged separately, and the beam diameters on each lens are several times different. Specifically, since the beam is close to the pupil on the concave lens 404, the beam has a large beam diameter, and since it is close to the imaging surface on the convex lens 406, the beam is thin.

[0057] The beam diameter h on the concave lens 404 n is larger than the beam diameter h on the convex lens 406 p Therefore, according to the conditional expression (14), it becomes possible to reduce the optical power required for the concave lens 404. As described in the first embodiment, the concave lens 404 cannot reduce the radius of curvature and it is difficult to increase the optical power. However, since the beam diameter on the concave lens 404 is sufficiently large as described here, even with a large radius of curvature, it becomes possible to provide an optical power for obtaining a sufficient chromatic aberration correction effect. Since the difference in beam diameter between the concave lens 404 and the convex lens 406 is about 1.5 to 3 times, the following conditional expression (15) is satisfied.

[0058] φ p ν n / φ n ν p < -2 …(15) By setting the optical power and the optical material of each lens so that such a relationship holds, chromatic aberration can be reduced. In this embodiment, φ p = 0.0631, φ n = -0.0102, ν p = 35.25, ν n = 23.78, (φ p ν n ) / (φ n ν p ) = -4.17.

[0059] Furthermore, here, the refracting surface of the second optical element 403 Transmissive surface 403B which isfunctions to cancel the refraction that occurs when passing through the reflective transmission surface 402A 。 Refractive surface The transmissive surface which is 403B has the same shape as the reflective transmission surface 402A and The second optical element 403 the first optical element 402 is desirably made of the same material. However, the refractive surface Transmissive surface 403B which is and the reflective transmission surface 402A do not necessarily have to be of the same shape, and any shape that can sufficiently cancel the aberration generated when passing through the reflective transmission surface 402A is acceptable. As a condition for canceling the aberration, at the intersection of the emission surface The reflective transmissive surface which is 402A of the first optical element and The principal ray of the central angular field of view light beam let the angle formed by the surface normal and the Z-axis be α1, and at the intersection of the refractive surface The transmissive surface which is 403B and The principal ray of the central angular field of view light beam let the angle formed by the surface normal and the Z-axis be α2. Then, the following conditional expression (16) is satisfied.

[0060] |α1 - α2| < 5 …(16) In this embodiment, since the two surfaces have the same shape, |α1 - α2| = 0.

[0061] Also in this embodiment, regarding the upper limit of the conditional expression (2), if the negative power of the third optical element 407 is too strong, the influence of aberration may not be negligible. Therefore, it is preferable to satisfy the following conditional expression (17).

[0062] 1.50 > n n / n m > 1.05 …(17) More preferably, the numerical range of the conditional expression (17) is set as the following conditional expression (18).

[0063] 1.40 > n n / n m > 1.10 …(18) 〔Example 3〕 Next, with reference to FIGS. 7 and 16, the eyepiece optical system and the display device in Example 3 of the present invention will be described. FIG. 7 is a configuration diagram of a display device having the eyepiece optical system in this embodiment. FIG. 16 is an explanatory diagram of Numerical Example 3 corresponding to this embodiment. The image display device (display device) 701 has an eyepiece optical system (optical system) and an image display element (display element) 70 5 and. The eyepiece optical system is an optical system that guides the light beam from the image display element 70 5 to the exit pupil S.

[0064] In this embodiment, with respect to the eyepiece optical system of Example 1, by removing the second optical element, the position of the reflecting surface of the first optical element 702 is brought closer to the exit pupil S, and the size of the first optical element 702 is reduced. By adopting such a configuration, even if the image display element 70 5 is miniaturized, a wide-angle effect can be realized without substantially changing the optical power of the concave lens 703.

[0065] The light emitted from the image displayed on the image display element 70 5 enters the first optical element 702, is emitted from the first optical element 702 after multiple internal surface reflections, and enters the concave lens 703. After exiting the concave lens 703, it is guided to the exit pupil S, and for an observer with a pupil placed near the exit pupil S, the image displayed on the image display element 70 Of the system is presented as an enlarged virtual image far away from the pupil S. 5 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 eye relief. Therefore, the size of the first optical element 702 becomes smaller, and as a result, the distance from the image-side principal plane of the eyepiece optical system to the incident surface

[0066] of the first optical element Of the system 702C also becomes smaller, making it easier to ensure the back focus. 702 of the first optical element The transmissive surface which is 702C is also reduced, making it easier to secure the back focus.

[0067] Conversely, the concave lens 703 and the first optical element 702When the distance to the reflecting surface 702B increases, the size of the first optical element 702 becomes large, and the effect of removing the second optical element cannot be obtained. Therefore, the concave lens 703 The exit surface 703 of A and the first optical element 702 satisfies the following conditional expression (19) with respect to the distance between the reflecting surface 702B of

[0068] L PB / fL < 0.75 …(19) Here, L PB is the distance on the Z-axis between the exit surface 703A of the concave lens 703 and the reflecting surface 702B of the first optical element 702 when the direction of the chief ray of the central picture angle light beam in the exit pupil S is taken as the Z-axis, and fL is the focal length of the eyepiece optical system. By arranging the concave lens 703 and the first optical element 702 adjacent to each other and bringing the reflecting surface 702B closer to the exit pupil S, a wide-angle effect is realized while slightly reducing the optical power of the concave lens 703. In this embodiment, L PB = 8.0 mm, f L=16.2 mm, L PB / fL = 0.4 9 is satisfied.

[0069] The focal length of the concave lens 703 is is substantially equivalent to the focal length of the negative surface of Example 1 of Patent Document 1, which is -94.3 mm. By adopting such a configuration, a 45° wide-angle effect is realized while using an image display element smaller than that of the 0.6 type compared to Patent Document 1. The amount of movement of the image plane is about 4 mm.

[0070] When the concave lens 703 is made of optical glass, giving it a special shape such as a free-form surface as the optical surface would lead to increased costs, etc., so it is desirable to use a coaxial optical element. Therefore, it is difficult for the concave lens 703 to make the exit surface of the first optical element shown in Patent Document 1 and the first surface of the second optical element have the same shape to cancel aberrations. Therefore, the concave lens 703 is tilted according to the exit surface 702 of the first optical element Reflective transmissive surface 702A which is to reduce the influence of the difference in surface shape. Specifically, the first optical element702 of Reflective transmission plane 7 02A, the angle α1 formed by the principal ray (line A in FIG. 1) of the center ray of the picture angle and Reflective transmission plane 7 the normal of the plane at the intersection with 02A and the Z-axis, and when the angle formed by the optical axis of the concave lens 7 03 and the Z-axis is α3, the following conditional expression (20) is satisfied.

[0071] |α1 - α3| < 5 …(20) By satisfying the conditional expression (20), it is possible to cancel the aberration with respect to the light beam emitted from the first optical element 7 02. In the case of the optical system in this embodiment, |α1 - α3| = 1.6.

[0072] Also, in the X-axis direction of FIG. 7, in order to cancel the aberration between the exit surface 7 of the first optical element Reflective transmissive surface 702A which is 02 and the concave lens 703 the following conditional expression (21) is satisfied.

[0073] 0.3 < R AX / R MX < 2.0 …(21) Here, R AX is the radius of curvature in the direction perpendicular to the paper surface at the intersection of the reflection / transmission surface 702 of the first optical element 7 02A and Central angular field of view light beam the principal ray, and R MX is the radius of curvature of the surface 7 03 of the concave lens Incidence plane 7 03B. In other words, R MX is the radius of curvature of the convex surface of the concave lens Light beam 03 in a cross-section perpendicular to the cross-section including the principal ray of the center picture angle from the image display element to the exit pupil S, and R 7 is also the exit surface of the first optical element Incident surface 703B which is in the cross-section at the intersection of the first optical element AX 02 and the principal ray of the center picture angle beam 7 02 at the intersection 7It is the radius of curvature of the emitting surface of 02. By approaching the curvatures of the two surfaces in this way, the aberrations at the two surfaces are canceled. In this embodiment, R AX = -48.8, R MX = -67.7, R AX / R MX = 0.72. Note that in this embodiment, the concave lens 7 03 is a meniscus lens, but it is not limited thereto.

[0074] [Embodiment 4] Next, with reference to FIGS. 8 and 1 8 , the eyepiece optical system and the display device in Embodiment 4 of the present invention will be described. FIG. 8 is a configuration diagram of a display device having the eyepiece optical system in this embodiment. FIG. 1 8 is an explanatory diagram of Numerical Example 4 corresponding to this embodiment. The image display device (display device) 801 has an eyepiece optical system (optical system) and an image display element (display element) 804. The eyepiece optical system is an optical system that guides the light beam from the image display element 804 to the exit pupil S. In this embodiment, the image display element of Embodiment 3 is made smaller, and the observer is configured to be able to observe the transmitted image and the display image superimposed.

[0075] The light beam emitted from the image display element 804 forms the exit pupil S through the convex lens (positive lens) 805, the first optical element 802 Concave lens 80 3 . Also in this embodiment, as in Embodiment 2, the third optical element 80 6 is arranged on the side opposite to the exit pupil S of the first optical element 802. Here, when the reflectance of the reflecting surface 802B of the first optical element is set lower than 100%, the observer can also observe the image of the outside world through the concave lens 80 3, the the first optical element 802 and the third optical element 806 by placing the pupil near the exit pupil S. That is, the observer can observe the image of the outside world and the image displayed on the image display element 804 simultaneously.

[0076] The optical system of this embodiment uses the image display element 804 as a 0.5 type and has an angular field of view of 50°. The eyepiece optical Of the systemThe focal length is approximately 13.5 mm. Also, since the eye point is as large as 25 mm, as shown in FIG. 9, the field curvature generated by the concave lens 803 and the first optical element 802 becomes extremely large. For this reason, similarly to Example 2, the convex lens 805 is disposed between the first optical element 802 and the image display element 804.

[0077] Here, referring to FIG. 9, the field curvature generated by the concave lens 803 and the first optical element 802 will be described. FIG. 9 is an explanatory diagram of the field curvature in the present embodiment. 901 is 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. 902 is the Normal axis in the direction of the imaging plane 901. 903 is the image plane formed by the first optical element 802 and the concave lens 803. As described in Example 2, the main factor of this field curvature is due to the sag of the reflecting surface 802B. However, actually, two more factors are added to form the image plane.

[0078] (Factor 1) Reflective transmission On the surface 802A, the light beam incident from the incident surface 802C is totally reflected. Also, in the cross section (YZ cross section) of the reflection-transmission surface 802A in FIG. 9, since the light beam is incident at a very large angle (an angle equal to or greater than the total reflection angle), it does not have a strong optical power from the aberration correction surface, and it is desirable that the YZ cross section does not have a strong optical power. However, in order to maintain the total reflection angle, Reflective transmission the upper part of the surface 802A deviates from a straight line and becomes a surface having a negative power (a warped surface). For this reason, as shown in FIG. 9, Reflective transmission the light beam passing through the upper part of the surface 802A is affected by the negative optical power and is imaged farther than the light beam passing through the lower side.

[0079] (Factor 2) Reflective transmission Since the X cross section direction of the surface 802A has a configuration close to concentric as described in Example 3, it is a surface having a curvature. For this reason, the reflection-transmission surface 802A has a negative power when totally reflecting, and as a result, a stronger negative field curvature occurs in the X cross section direction than in the Y cross section direction.

[0080] Due to the above two factors, the concave lens 803 and the first optical element 802 have an asymmetric field curvature in the YZ cross-section and a strong negative field curvature in the X-axis direction. To correct these, the convex lens 80 5 has the following characteristics. (1) The convex lens 805 is arranged such that the light beam passing through the reflecting surface 802B side of the first optical element is shifted to pass through the thicker part of the positive lens than the light beam passing through the reflecting and transmitting surface 802A side. Convex lens 805 which is (2) The convex lens 805 has an anamorphic surface on the exit surface 805A (the convex surface 805A on the side of the first optical element 802 and satisfies the following conditional expression (22).

[0081] R PX <R PY …(22) Here, R PX is the curvature radius in the X-axis direction of the convex surface 805A of the convex lens 805, and R PY is Of the convex surface 805A of the convex lens 805 the curvature radius in the Y-axis direction. In other words, the Convex surface 805A of the convex lens 805 faces the first optical element 802, R PY is the curvature radius in the cross-section including the chief ray of the central angle of view from the image display element 804 to the exit pupil S Of the light beam in the cross-section including the chief ray, Of the convex surface 805A of the convex lens 805 R PX is the curvature radius of the Convex surface 805A of the convex lens 805 in the cross-section perpendicular to this cross-section.

[0082] For the asymmetrically occurring field curvature, by shifting and arranging the convex lens 805 within the YZ cross-section, the sag amount is made asymmetric to efficiently correct the field curvature. Also, for the strongly occurring field curvature in the X-axis direction, by reducing the curvature radius in the X-axis direction, the field curvature can be effectively corrected in all cross-section directions.

[0083] In this embodiment, within the cross-section of FIG. 8, the most Reflective transmissionThe thickness of the convex lens 805 near the light beam passing through the surface 802A side is approximately 2.7 mm, and the thickness of the convex lens 805 near the light beam passing through the most reflective surface 802B side is approximately 5 mm. Also, the convex lens 805 exit surface The convex surface which is 805A of the curvature radii are each R PX = 15.51 mm, R PY = 22.51 mm.

[0084] 〔Example 5〕 Next, referring to FIG. 10, the observation device (display device) 1001 in Example 5 of the present invention will be described. FIG. 10 is a configuration diagram of the observation device 1001 having the eyepiece optical system of Example 4. The observation device 1001 is configured as a smart glass having an optical see-through display.

[0085] The observation device 1001 includes the eyepiece optical systems 801a, 801b of Example 4, image display elements 80 4 a, 80 4 b, and an image display circuit 1002 connected thereto. The observation device 1001 also includes a camera 1003, an imaging circuit 1004 that processes the image acquired by the camera 1003, and an image recognition unit 1005 that recognizes the object being photographed from the image processed by the imaging circuit 1004. The eyepiece optical systems 801a, 801b, and the camera 1003 are disposed inside the headset unit 1006.

[0086] The observer wears the headset unit 1006 of the observation device 1001 like glasses. By wearing the headset unit 1006, the observer's eye pupils (both eyes) are disposed near the respective exit pupils S and S' (not shown) of the eyepiece optical systems 801a, 801b mounted on the headset unit 1006. Thereby, Image the images displayed on the display elements 80 4 a, 80 4 b are enlarged as virtual images and presented to the observer.

[0087] Here, the camera 1003 attached to the headset unit 1006 acquires an image in the observer's viewing direction. The image captured by the camera 1003 is sent to the image recognition unit 1005 via the imaging circuit 1004. The image recognition unit 1005 recognizes what is shown in the captured image and sends character information or the like that describes the object shown to the image display circuit 1002. Based on the information received from the image recognition unit 1005, the image display circuit 1002 displays the necessary character information for the vicinity or overlapping part of the object on the image display elements 80 4 a, 80 4 b. As an example of the information, it includes the name of a restaurant or menu information shown in the field of view, detailed information of exhibits in a museum, price and production place information of products in a store, or map information, navigation information, etc. By superimposing and displaying this information on the image of the external world visible through the eyepiece optical systems 801a and 801b, as shown in FIG. 11, the observer can observe the surroundings with these information added to the real space. FIG. 11 is a diagram showing the superimposed display of information. Also, the information is not limited to character information only, and may also be video / still image information, etc. Furthermore, not only simple information provision, but it is also possible to present to the observer an extended reality space in which another image such as a game image or an image of a virtual building is superimposed on the real space.

[0088] When the performance of the image recognition unit 1005 and the camera 1003 in detecting external information is insufficient, information obtained by another method such as a method of acquiring three-dimensional direction information using an acceleration sensor or a method of adding information on the observer's position and viewing direction using GPS and map information may be used. By acquiring external information by such multiple means, the position accuracy of the superimposed information can be improved, and the information can be superimposed on the real space without deviation. Thereby, for example, navigation information can be displayed in front of the eyes during driving of a bicycle or the like, and direction indication information based on the accurate position by GPS can be obtained without significantly moving the line of sight, realizing safe driving.

[0089] In addition, when the display angle of view is narrow, the information to be displayed concentrates near the center of the field of view, making the display feel cumbersome. In the case of the eyepiece optical systems 801a and 801b of the present embodiment, since the display angle of view is wide, information can be displayed within a range where the observer does not feel cumbersome.

[0090] In this way, by configuring an optical see-through display having a wide-angle eyepiece optical system, it is possible to construct smart glasses that superimpose a new information image within a range where the observer does not feel cumbersome on a relatively wide-field-of-view real space. Such smart glasses can, for example, present information without the observer feeling cumbersome with the display within the field of view and without significantly moving the line of sight during driving, during sports, during work using both hands, etc. Note that in the present embodiment, an observation device that displays information to both eyes of the observer has been described, but an observation device that displays to only one eye of the observer may also be used. In that case, an eyepiece optical system for one eye is sufficient.

[0091] Hereinafter, Examples 1 to 4 Numerical Examples 1 to 4 corresponding thereto will be described respectively. In the description of each example, the explanation was made in order from the optical path on the light source side, but in the numerical examples, the description will be in the form of tracing the light rays in reverse from the pupil position side of the projection optical system. Tables 1 to 12 describe each numerical example. When describing, the reference of the absolute coordinate system is expressed with the Global origin as the reference. Note that Tables 1 to 3 correspond to Example 1, Table 4 A ~6 correspond to Example 2, Tables 7 to 9 correspond to Example 3, and Table 10 A ~12 correspond to Example 4 respectively.

[0092] In the absolute coordinate system, the three-dimensional coordinate axes are defined as the Z-axis, Y-axis, and X-axis as follows.

[0093] Z-axis: A straight line passing through the center of the 0th surface and the center of the first surface (absolute coordinate origin), and this direction is taken as positive.

[0094] Y-axis: A straight line passing through the center of the first surface (absolute coordinate origin) and making a 90-degree counterclockwise angle with respect to the Z-axis.

[0095] X-axis: A straight line passing through the origin and perpendicular to the Z-axis and the Y-axis.

[0096] Also, the surface shape of the i-th surface constituting the optical system shall be expressed by a function based on the local coordinate system set. The tilt angle in the YZ plane of the i-th surface is represented by an angle θgi (unit: degree) with the positive direction being counterclockwise with respect to the Z-axis of the absolute coordinate system. In each numerical example, the tilt angle is set only in the YZ plane. The y and z axes 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 by an angle θgi in the YZ plane.

[0097] z-axis: A straight line passing through the origin of the local coordinates and making an angle θi in the counterclockwise direction in the YZ plane with respect to the Z-axis of the absolute coordinate system.

[0098] y-axis: A straight line passing through the origin of the local coordinates and making a 90-degree angle in the counterclockwise direction in the YZ plane with respect to the z direction.

[0099] x-axis: A straight line passing through the origin of the local coordinates and perpendicular to the YZ plane.

[0100] Ndi and νdi represent the refractive index and Abbe number of the d-line between the i-th surface and the i + 1-th surface.

[0101] Hereinafter, the surface shape without a rotational symmetry axis used in each numerical example is expressed by the following mathematical formula. In the table, the non-rotationally symmetric surface is denoted as XYP.

[0102]

Number

[0103] This function is a function that defines the surface shape by the local coordinates (x, y, z) of the i-th surface. Also, by setting the terms related to the odd powers of x to 0 in the local coordinate system in the same function, a surface symmetric with respect to the yz plane can be obtained. Also, the following shows the mathematical formula of the toroidal surface used in each numerical example. In each numerical example, it is denoted as XTO.

[0104] [Number]

[0105] In each numerical example, since only the surface vertices of each surface are shifted and eccentric in the y and z-axis directions and tilted and eccentric around the x-axis, the conventional bus cross-section and the local bus cross-section are the same cross-section, but the conventional sub-line cross-section and the local sub-line cross-section of each surface are different.

[0106] In addition, in each numerical example, in the table showing the position of the local origin, if numerical values are entered in Yg, Zg, and θg, it indicates that the origin of the surface is at the position rotated around the Y-axis, Z-axis, and X-axis center from the surface described as the Global origin. For the surfaces without the description of each item, it indicates that the surface is at the position shifted in the Z-axis direction by the distance D from the previous surface. Also, the coordinate system of each numerical example is based on the position of the Global origin.

[0107] The surface with a free-form surface is shown as XYP, the surface with a spherical surface is shown as SPH, and the surface with a toroidal surface is shown as XTO, and each coefficient is shown in a separate table. The notation M indicates that the surface is a reflecting surface.

[0108] (Numerical Example 1) The horizontal field angle (perpendicular to the paper plane) is ±20.5 deg, the vertical field angle (in the paper plane) is ±11.25 deg, and the pupil diameter is 4 mm. To show the correspondence with each surface number, the correspondence is shown using Fig. 12. Fig. 12 shows the same optical system as Fig. 1. Table 1 shows the position of the local origin of each surface. Table 2 shows the coefficients of the non-rotationally symmetric surfaces. Table 3 shows the values of various conditions. Fig. 13 is the lateral aberration diagram of the eye optical system in this numerical example.

[0109] [Table 1]

[0110] [Table 2]

[0111]

Table 3

[0112] (Numerical Example 2) The horizontal viewing angle (in the direction perpendicular to the paper surface) is ±20.5 deg, the vertical viewing angle (in the direction within the paper surface) is ±15.56 deg, and the pupil diameter is 4 mm. To show the correspondence with each surface number, the correspondence is shown using FIG. 14. FIG. 14 shows the same optical system as FIG. 4. Table 4A shows the positions of the local origins of each surface in the optical path for observing the image from the display element. Table 4B shows the positions of the local origins of each surface when observing the outside world. Table 5 shows the coefficients of the non-rotationally symmetric surfaces. Table 6 shows the values of various conditions. FIG. 15 is a lateral aberration diagram of the eyepiece optical system in this numerical example.

[0113]

Table 4A

[0114]

Table 4B

[0115]

Table 5

[0116]

Table 6

[0117] (Numerical Example 3) The horizontal viewing angle (perpendicular to the paper plane) is ±20.5 deg, the vertical viewing angle (within the paper plane) is ±11.25 deg, and the pupil diameter is 4 mm. To show the correspondence with each surface number, the correspondence is shown using FIG. 16. FIG. 16 shows the same optical system as FIG. 7. Table 7 shows the positions of the local origins of each surface in the optical path for observing the image from the display element. Table 8 shows the coefficients of the non-rotationally symmetric surfaces. Table 9 shows the values of various conditions. FIG. 17 is a lateral aberration diagram of the eye optical system in this numerical example.

[0118]

Table 7

[0119]

Table 8

[0120]

Table 9

[0121] (Numerical Example 4) The horizontal viewing angle (perpendicular to the paper plane) is ±20.5 deg, the vertical viewing angle (within the paper plane) is ±15.56 deg, and the pupil diameter is 4 mm. To show the correspondence with each surface number, the correspondence is shown using FIG. 18. FIG. 18 shows the same optical system as FIG. 8. Table 10A shows the positions of the local origins of each surface in the optical path for observing the image from the display element, and Table 10B shows the positions of the local origins of each surface when observing the outside world. Table 11 shows the coefficients of the non-rotationally symmetric surfaces and the coefficients of the toroidal surfaces. Table 12 shows the values of various conditions. FIG. 19 is a lateral aberration diagram of the eye optical system in this numerical example.

[0122]

Table 10A

[0123]

Table 10B

[0124]

Table 11

[0125]

Table 12

[0126] According to each embodiment, it is possible to provide a small-sized and wide-angle optical system and a display device.

[0127] As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.

Description of Reference Numerals

[0128] 101, 401, 701, 801 Eyepiece optical system (optical system) 102, 402, 702, 802 First optical element 104, 404, 703, 803 Concave lens (negative lens) 105, 405, 704, 804 Image display element (display element)

Claims

1. An optical system that guides a light beam from a display element to an exit pupil, comprising a first optical element having a transmission surface, a reflective transmission surface, and a reflective surface, a positive lens disposed between the display element and the first optical element and having a convex surface facing the first optical element, and a negative lens having a concave surface facing the exit pupil, wherein the light beam from the display element travels toward the exit pupil through the positive lens, the transmission surface, the reflective transmission surface, the reflective surface, the reflective transmission surface, and the negative lens in sequence, when the refractive index of the negative lens at the d-line is n ｎ , the refractive index of the first optical element at the d-line is n ｍ , the optical power of the negative lens is φ ｎ , the optical power of the optical system is φ Ａ , the radius of curvature of the convex surface in a cross-section including the chief ray of the central picture angle is R ＰＹ , and the radius of curvature of the convex surface in a cross-section perpendicular to the said cross-section is R ＰＸ , then n ｎ > n ｍ φ ｎ / φ Ａ < -0.05 R ＰＸ < R ＰＹ An optical system characterized by satisfying the conditional expression.

2. n ｎ / n ｍ > 1.05 The optical system according to claim 1, characterized by satisfying the conditional expression.

3. When the Abbe number of the negative lens is ν ｎ , and the Abbe number of the first optical element is ν ｍ , then 15 < ν ｎ < ν ｍ The optical system according to claim 1 or 2, characterized by satisfying the conditional expression.

4. Let the radius of curvature of the reflecting surface at the intersection with the chief ray be R Ｂ and the radius of curvature of the convex surface be R Ｐ When this is the case, -8.0 < R Ｂ / R Ｐ < -2.0 The optical system according to any one of claims 1 to 3, characterized in that it satisfies the conditional expression.

5. When the direction perpendicular to the surface on which the exit pupil is formed is taken as the first direction, inside the positive lens, the optical path length of the light beam passing through the side of the reflecting surface closest to the first direction is longer than the optical path length of the light beam passing through the side of the reflection-transmission surface closest to the first direction. The optical system according to any one of claims 1 to 4, characterized by this.

6. Let the optical power of the positive lens be φ ｐ and the optical power of the negative lens be φ ｎ Let the Abbe number of the positive lens be ν ｐ and the Abbe number of the negative lens be ν ｎ When this is the case, φ ｐ ν ｎ / φ ｎ ν ｐ < -2 The ocular optical system according to any one of claims 1 to 5, characterized in that it satisfies the conditional expression.

7. An optical system that guides a light beam from a display element to an exit pupil, a first optical element having a transmission surface, a reflection-transmission surface, and a reflection surface, a positive lens disposed between the display element and the first optical element, and a negative lens having a concave surface facing the exit pupil, and the light beam from the display element travels toward the exit pupil through the positive lens, the transmission surface, the reflection-transmission surface, the reflection surface, the reflection-transmission surface, and the negative lens in this order, Let the refractive index of the first optical element at the d line be n ｍ and the refractive index of the negative lens at the d line be n ｎ, the optical power of the positive lens is φ ｐ , the optical power of the negative lens is φ ｎ , the optical power of the optical system is φ Ａ , the Abbe number of the positive lens is ν ｐ , the Abbe number of the negative lens is ν ｎ When it is set as follows, n ｎ >n ｍ φ ｎ / φ Ａ <-0.05 φ ｐ ν ｎ / φ ｎ ν ｐ <-2 An optical system characterized by satisfying the conditional expression.

8. An optical system that guides the light beam from the display element to the exit pupil, A first optical element having a first transmission surface, a reflective transmission surface, and a reflective surface, A negative lens including a surface that is concave toward the exit pupil, And a second optical element that is a prism disposed between the first optical element and the negative lens, The surface of the second optical element on the side of the display element has the same shape as the reflective transmission surface, The light beam from the display element travels toward the exit pupil through the first transmission surface, the reflective transmission surface, the reflective surface, the reflective transmission surface, the second optical element, and the negative lens in this order, The refractive index of the negative lens at the d line is n ｎ , the refractive index of the first optical element at the d line is n ｍ When it is set as follows, n ｎ >n ｍ An optical system characterized by satisfying the conditional expression.

9. The second optical element has a second transmission surface facing the reflective transmission surface, When the angle formed by the principal ray of the central drawing angle passing through the position and the normal line of the reflection-transmission surface is α1, and the angle formed by the principal ray and the normal line of the second transmission surface at the position where the principal ray passes through is α2, |α1 - α2| < 5 The optical system according to claim 8, characterized by satisfying the conditional expression.

10. When the refractive index of the second optical element at the d-line is n Ｏ Then, n ｎ > n Ｏ The optical system according to claim 8 or 9, characterized by satisfying the conditional expression.

11. (n ｎ - 1) / (n Ｏ - 1) > 1.3 The optical system according to claim 10, characterized by satisfying the conditional expression.

12. The optical system according to any one of claims 1 to 11, further comprising a third optical element disposed on the side opposite to the negative lens with respect to the first optical element.

13. An optical system that guides a light beam from a display element to an exit pupil, A first optical element having a transmission surface, a reflection-transmission surface, and a reflection surface, A negative lens including a concave surface facing the exit pupil, And a third optical element disposed on the side opposite to the negative lens with respect to the first optical element, The light beam from the display element travels toward the exit pupil through the transmission surface, the reflection-transmission surface, the reflection surface, the reflection-transmission surface, and the negative lens in sequence, When the refractive index of the negative lens at the d-line is n ｎ , the refractive index of the first optical element at the d-line is n ｍ , the optical power of the negative lens is φ ｎ , and the optical power of the optical system is φ Ａ Then, n ｎ > n ｍ φ ｎ / φ Ａ < -0.05 An optical system characterized by satisfying the conditional expression.

14. Let the distance between the exit surface of the negative lens and the reflecting surface on the chief ray of the central picture angle be L ＰＢ When the focal length of the optical system is fL, L ＰＢ / fL < 0.75 The optical system according to any one of claims 1 to 13, characterized by satisfying the conditional expression.

15. When the angle formed by the normal of the reflection / transmission surface and the chief ray at the position where the chief ray of the central picture angle passes through is α1, and the angle formed by the optical axis of the negative lens and the chief ray is α3, |α1 - α3| < 5 The ocular optical system according to any one of claims 1 to 14, characterized by satisfying the conditional expression.

16. The negative lens is a meniscus lens including a convex surface, Let the radius of curvature of the convex surface of the negative lens in a cross-section perpendicular to the cross-section including the chief ray of the central picture angle be R ＭＸ and the radius of curvature of the reflection / transmission surface at the position where the chief ray passes through in this cross-section be R ＡＸ When, 0.3 < R ＡＸ / R ＭＸ < 2.0 The optical system according to any one of claims 1 to 15, characterized by satisfying the conditional expression.

17. An optical system that guides a light beam from a display element to an exit pupil, having a first optical element having a transmission surface, a reflection / transmission surface, and a reflecting surface, and a negative lens including a surface concave toward the exit pupil, The negative lens is a meniscus lens including a convex surface, The light beam from the display element travels toward the exit pupil through the transmission surface, the reflective transmission surface, the reflection surface, the reflective transmission surface, and the negative lens in this order. Let n be the refractive index of the negative lens for the d-line, ｎ n be the refractive index of the first optical element for the d-line, ｍ φ be the optical power of the negative lens, ｎ φ be the optical power of the optical system, Ａ R be the radius of curvature of the convex surface of the negative lens in a cross-section perpendicular to the cross-section including the chief ray of the central picture angle, ＭＸ R be the radius of curvature of the reflective transmission surface at the position where the chief ray passes through in this cross-section, ＡＸ When this is the case, n ｎ > n ｍ φ ｎ / φ Ａ < -0.05 0.3 < R ＡＸ / R ＭＸ < 2.0 An optical system characterized by satisfying the conditional expression.

18. The optical system according to any one of claims 1 to 17, wherein the negative lens is made of a glass material.

19. A display device characterized by having the optical system according to any one of claims 1 to 18 and a display element.

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