Optical device and image display device

Abstract

To provide an optical device which allows a viewer to visually recognize the periphery while preventing an external light ghost.SOLUTION: An optical device (100) comprises: first linear polarization plates (119, 120) which guide to a viewer from image display elements (111, 112); and a second linear polarization plate (202) which is arranged on the outside of an optical path from the image display elements to the viewer. The transmission axis direction of the first linear polarization plates and the transmission axis direction of the second linear polarization plate are different from each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical device and an image display device suitable for a head-mounted display (HMD) or the like, in which an image on an image display element is magnified and observed through an eyepiece optical system. [Background technology]

[0002] Image display devices that enlarge an image from an image display element (display) and present it to an observer are known. Such image display devices are configured with an eyepiece optical system that enlarges an image displayed on a small image display element that displays a two-dimensional image and presents it to an observer, and are used in head-mounted displays (HMDs) and the like. Patent Document 1 discloses a polarized reflective eyepiece optical system that includes at least one polarizing beam splitter and folds the optical path using polarized light.

[0003] Furthermore, external light that enters through the gap between the image display device and the viewer's eye is refracted or reflected in the eyepiece optical system, and becomes light that returns to the viewer's eye, which may appear as a ghost or flare in the displayed image (external light ghost).Patent Document 2 discloses an image display device that has a light-blocking member for preventing the intrusion of external light that enters through the gap between the image display device and the viewer's eye in order to prevent external light ghost. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-053152 [Patent Document 2] Japanese Patent Application Publication No. 2017-195515 Summary of the Invention [Problem to be solved by the invention]

[0005] From the viewpoint of ensuring safety during the video experience, it is desirable that the viewer be able to directly view the surroundings from the side of the image display device. The image display device disclosed in Patent Document 2 can prevent external light ghost caused by the intrusion of external light, but does not allow the viewer to directly view the surroundings.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image display device that prevents external light ghosts and allows a viewer to view the surroundings. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided an optical device comprising: an eyepiece optical system that includes a first linear polarizer and that guides light from an image display element to an eye of an observer; and a second linear polarizer disposed outside the optical path from the image display element to the eye of the observer. an optical device having a light-shielding portion, the light-shielding portion comprising: a second linear polarizer; and a support member for holding the second linear polarizer. , the support member is a member that is disposed so as to surround the periphery of the second linear polarizer and that blocks visible light, The first linear polarizer is disposed closest to the viewer in the optical path, and the transmission axis direction of the first linear polarizer and the transmission axis direction of the second linear polarizer are different from each other.

[0008] Other objects and features of the present invention will be described in the following embodiments. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an image display device that prevents external light ghosts and allows a viewer to view the surroundings. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a configuration diagram of an image display device in each embodiment. [Figure 2] FIG. 2 is a configuration diagram of an image display device in each embodiment. [Figure 3] FIG. 1 is a diagram illustrating the configuration of an eyepiece optical system according to a first embodiment. [Figure 4] FIG. 2 is a detailed configuration diagram of an eyepiece optical system according to the first embodiment. [Figure 5]FIG. 2 is a schematic diagram showing a state in which the image display device in each embodiment is worn on the head of a viewer. [Figure 6] FIG. 2 is a diagram illustrating a coordinate system in each embodiment. [Figure 7] FIG. 2 is a schematic diagram showing a state in which the image display device in each embodiment is worn on the head of a viewer. [Figure 8] FIG. 2 is a schematic diagram showing a state in which the image display device in each embodiment is worn on the head of a viewer. [Figure 9] FIG. 10 is a diagram illustrating the configuration of an eyepiece optical system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] (First embodiment) First, an image display device according to a first embodiment of the present invention will be described with reference to Figures 1 and 2. Figures 1 and 2 are configuration diagrams of an image display device 100. In Figures 1 and 2, 101 denotes an eyepiece optical system for the left eye, and 102 denotes an eyepiece optical system for the right eye. 103, 104, 105, and 106 denote cameras for capturing images of the external environment and are used for alignment for drawing computer graphics. 107 denotes a cable for video signals, which is connected to a computing device such as a personal computer (not shown).

[0013] Next, the eyepiece optical systems 101 and 102 in this embodiment will be described with reference to Fig. 3. Fig. 3 is a configuration diagram of the eyepiece optical systems 101 and 102. The eyepiece optical system 101 for the observer's left eye includes an image display element 111 and optical lenses 113 and 114. The eyepiece optical system 102 for the observer's right eye includes an image display element 112 and optical lenses 115 and 116. The image display elements 111 and 112 are, for example, organic EL displays, but are not limited to this.

[0014] The eyepiece optical system 101 enlarges and projects the original image displayed on the image display element 111 as a virtual image and directs it to the observer's left eye 117. The eyepiece optical system 102 enlarges and projects the original image displayed on the image display element 112 as a virtual image and directs it to the observer's right eye 118. The eyepiece optical systems 101 and 102 each have a focal length F1 of 12 mm, a horizontal display angle of view of 45°, a vertical display angle of view of 34°, and a diagonal display angle of view of 54°. The distance (eye relief) E1 between the image display device 100 and the observer's eyeball is 18 mm. The eyepiece optical systems 101 and 102 each include at least one polarizing beam splitter 121 or 122 and are polarizing reflective optical systems that fold the optical path by manipulating the polarization state. The light beams that reach the observer's eyes are linearly polarized. Polarizing beam splitters 121 and 122 are respectively disposed between optical lenses 114 and 116 and first linear polarizers 119 and 120 (described later), and are, for example, but not limited to, wire grid polarizers.

[0015] The eyepiece optical systems 101 and 102 each have a first linear polarizer 119 and 120. When the eyepiece optical systems 101 and 102 use polarized reflection to fold the optical path, the emitted light is linearly polarized. Therefore, by arranging the first linear polarizer so that the direction of the polarized light coincides with the direction of polarization of the emitted light, the placement of the first linear polarizers 119 and 120 does not reduce the intensity of the image light seen by the observer.

[0016] Next, the detailed configuration of the eyepiece optical system 101 will be described with reference to Fig. 4. Fig. 4 is a detailed structural diagram of the eyepiece optical system 101. Note that Fig. 4 shows only the eyepiece optical system for the right eye, but the configuration of the eyepiece optical system for the left eye is the same as that of the eyepiece optical system for the right eye, so its description will be omitted. The eyepiece optical system 101 has a linear polarizer 503, a λ / 4 plate 504, an optical lens 113, a half mirror 506, an optical lens 114, and a λ / 4 plate (second phase plate) 508, which are arranged in this order from the image display element 111 side to the first linear polarizer 119 side. Light from the image display element 111 passes through a linear polarizer (third linear polarizer) 503 and a λ / 4 plate (first phase plate) 504, becoming circularly polarized light. The circularly polarized light passes through an optical lens (first lens) 113, a half mirror (semi-transmissive reflective element) 506, an optical lens (second lens) 114, and a λ / 4 plate (second phase plate) 508, becoming linearly polarized light. Because the direction of this linearly polarized light is perpendicular to the transmission axis direction of the polarized beam splitter (reflective linear polarizer) 121, the linearly polarized light is reflected, passes through the λ / 4 plate 508 again, becomes circularly polarized light, passes through the optical lens 114, and is reflected by the half mirror 506. The reflected circularly polarized light becomes linearly polarized light at the λ / 4 plate 508. Since the direction of this linearly polarized light matches the transmission axis direction of polarizing beam splitter 121, this linearly polarized light is transmitted through first linear polarizer (absorptive linear polarizer) 119, which has the same transmission axis direction, and is guided to viewer's left eye 117. Note that first linear polarizer 119 is positioned so that external light is not reflected by polarizing beam splitter 121, and since the transmission axis direction of first linear polarizer 119 and that of polarizing beam splitter 121 are the same, there is no effect on the image light.

[0017] 5 is a schematic diagram showing a state in which the image display device 100 is worn on the head of a viewer. The image display device 100 is worn on the head of the viewer by a wearing mechanism 200. When worn on the head, the image display device 100 is also called a head-mounted display (HMD).

[0018] Reference numeral 201 denotes a light-shielding section for the left eye, which prevents light from a light source other than the image display element from entering the optical system. A second linear polarizer 202 is provided in a part of the light-shielding section 201 and is arranged outside the optical path from the image display element to the viewer. The part of the light-shielding section 201 other than the second linear polarizer 202 is a support member for holding the second linear polarizer 202, and is made of a member (light-shielding member) that blocks visible light. Reference numeral 203 denotes a light-shielding section for the right eye, which prevents light from a light source other than the image display element from entering the optical system. A second linear polarizer (not shown), similar to the light-shielding section 201, is provided in a part of the light-shielding section 203. The part of the light-shielding section 203 other than the second linear polarizer is a support member for holding the second linear polarizer, and is made of a member (light-shielding member) that blocks visible light.

[0019] FIG. 6 is a schematic diagram showing a coordinate system for representing the direction of linearly polarized light. The axis connecting the viewer's left eye 117 and right eye 118 is defined as the x-axis, the direction in which the viewer views the image is defined as the z-axis, and the direction perpendicular to the x-axis and z-axis is defined as the y-axis. In this embodiment, the first linear polarizer 119 has the property of transmitting light polarized in the x-axis direction but not transmitting light polarized in the y-axis direction. On the other hand, the second linear polarizer 202 formed in the light-shielding portion 201 has the property of transmitting light polarized in the y-axis direction but not transmitting light polarized in the x-axis direction. That is, the angle (transmission axis angle α) between the polarization transmission direction (transmission axis direction) of the first linear polarizer 119 and the polarization transmission direction of the second linear polarizer 202 is 90 degrees (the polarization transmission directions of the two linear polarizers are approximately perpendicular). However, the transmission axis angle α in this embodiment is not limited to 90 degrees, as long as the polarization transmission direction of the first linear polarizer 119 and the polarization transmission direction of the second linear polarizer 202 are different from each other. That is, in this embodiment, when two linear polarizers are arranged on the same axis (when the transmission axis directions are projected onto the same plane), the angles they form are compared in local coordinates (when compared two-dimensionally), and the transmission axis directions are different from each other. If the angles are different when compared three-dimensionally but the same when compared two-dimensionally, this embodiment is outside the scope of application.

[0020] The first linear polarizer 119 and the second linear polarizer 202 are disposed at positions spaced apart from each other. Therefore, the angle between the transmission axis direction of the first linear polarizer 119 and the transmission axis direction of the second linear polarizer 202 can be determined by projecting the transmission axis direction of the second linear polarizer 202 onto a plane including the first linear polarizer 119 (for example, the xy plane in FIG. 6). In FIG. 6, the direction of the transmission axis direction of the second linear polarizer 202 projected onto the xy plane is indicated by a dashed line. Using the angle θ between the direction of the dashed line and the y-axis, the angle between the transmission axis direction of the first linear polarizer 119 and the transmission axis direction of the second linear polarizer 202 (transmission axis angle α) can be expressed as α = 90 ± θ (degrees). For example, when the angle θ is 10 degrees, the transmission axis angle α is 100 degrees or 80 degrees.

[0021] 7, part of the light 401 traveling from outside the observer toward the eyepiece optical system 101 through the vicinity of the light-shielding portion 201 is blocked by the light-shielding portion 201. Meanwhile, another part of the light 401 passes through the second linear polarizer 202, becomes light polarized in the y-axis direction, and travels toward the eyepiece optical system 101 or the eyepiece optical system 102. Light polarized in the y-axis direction, which forms an angle of 90 degrees with the transmission direction of the first linear polarizer 119, cannot enter the eyepiece optical systems 101 and 102, and does not become an external light ghost.

[0022] 8, light 402 traveling from outside the observer toward the observer's eye through the vicinity of the light-shielding portion 201 is reduced to approximately half by the second linear polarizing plate 202, but still reaches the observer's eye, allowing the observer to directly view the outside. The light-shielding portion 203 on the right eye side functions in the same way, allowing the observer to directly view the outside on the right and left sides of the image display device 100.

[0023] In this embodiment, the second linear polarizer 202 is formed as a part of the light-shielding section 201, but the entire light-shielding section 201 may be formed of a linear polarizer. Furthermore, in this embodiment, the effect of this embodiment can be achieved as long as the polarization transmission direction of the first linear polarizers 119 and 129 and the polarization transmission direction of the second linear polarizer 202 are different from each other. Note that the relationship between the angle (transmission axis angle α) formed between the first linear polarizers 119 and 129 and the second linear polarizer 202 and the intensity of transmitted light is expressed as cos 2 The angle is expressed as α. Therefore, when the transmission axis angle α is set in the range of 70 degrees or more and 110 degrees or less, the amount of external light entering the film is reduced to just over 10%, which is particularly effective. More preferably, when the transmission axis angle α is set in the range of 80 degrees or more and 100 degrees or less, the intensity of the transmitted light is reduced to about 3%, which is highly effective in preventing ghosts. Even more preferably, the transmission axis angle α is set to 90 degrees (the transmission axis directions of the two linear polarizers are approximately perpendicular).

[0024] In this embodiment, the eye relief of each of the eyepiece optical systems 101 and 102 is 18 mm. However, if the eye relief is longer than a certain amount, external light is more likely to enter, so this embodiment is particularly effective in image display devices having eyepiece optical systems with an eye relief of 10 mm or more.

[0025] In this embodiment, the first linear polarizers 119 and 120 are disposed at positions closest to the eye in the eyepiece optical systems 101 and 102, respectively, but this is not limitative. The first linear polarizers 119 and 120 can prevent external light ghosts as long as they are disposed closer to the eye than the reflective or refracting surfaces that are the main cause of external light returning to the viewer's eye as external light ghosts within the eyepiece optical systems 101 and 102.

[0026] (Second embodiment) Next, an image display device according to a second embodiment of the present invention will be described with reference to Fig. 9. In this embodiment, the configuration of the eyepiece optical system is different from that of the first embodiment. However, since the other basic configurations of the image display device in this embodiment are the same as those in the first embodiment, a description thereof will be omitted.

[0027] FIG. 9 is a structural diagram of the eyepiece optical system 101a for the left eye in this embodiment, showing an eyepiece optical system using a decentered prism. The coordinate system is the same as that shown in FIG. 6. The prism is molded from optical plastic and has optical surfaces 301, 302, and 303. Light from the image display element 111 enters the prism through optical surface 303, undergoes total internal reflection at optical surface 301, travels toward optical surface 302, reflects off metal-deposited optical surface 302, and is refracted from optical surface 301 before traveling toward the viewer's left eye 117.

[0028] Reference numeral 108 denotes a first linear polarizer. In the eyepiece optical system 101a of this embodiment, there is also an optical path that generates an external light ghost when external light enters. However, like the first embodiment, the eyepiece optical system 101a has a first linear polarizer 108. Therefore, by combining this with a second linear polarizer 202 provided in the light-shielding portion 201, the external light ghost can be suppressed while the viewer can view the outside from the side of the image display device 100.

[0029] According to each embodiment, it is possible to provide an image display device that prevents external light ghosting and allows the viewer to view the surroundings.

[0030] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0031] 100 Image display device 101, 102 Eyepiece optical system 111, 112 Image display element 119, 120 First linear polarizer 202 Second linear polarizer

Claims

1. an eyepiece optical system having a first linear polarizer and directing light from the image display element to an observer's eye; a light blocking unit disposed outside an optical path from the image display element to the viewer's eye, the light-shielding portion includes a second linear polarizing plate and a support member for holding the second linear polarizing plate, the support member is a member that is disposed so as to surround the periphery of the second linear polarizer and that blocks visible light, the first linear polarizer is disposed closest to the viewer in the optical path, an optical device, wherein the transmission axis direction of the first linear polarizer and the transmission axis direction of the second linear polarizer are different from each other;

2. 2. The optical device according to claim 1, wherein an angle formed between the transmission axis direction of the first linear polarizer and the transmission axis direction of the second linear polarizer is equal to or greater than 70 degrees and equal to or less than 110 degrees.

3. 3. The optical device according to claim 1, wherein the eyepiece optical system has, arranged in order from the image display element side to the first linear polarizer side, a third linear polarizer, a first phase plate, a first lens, a semi-transmissive reflective element, a second lens, and a second phase plate.

4. 4. The optical device according to claim 1, wherein the eyepiece optical system includes a polarizing beam splitter disposed between the image display element and the first linear polarizer.

5. 5. The optical device according to claim 1, wherein the eyepiece optical system has an eye relief of 10 mm or more.

6. An image display device comprising: the optical device according to claim 1; and the image display element.

Images