Propagation optical system, optical system, virtual image display device and head-mounted display

Abstract

To provide a compact propagation optical system.SOLUTION: A propagation optical system is the optical system which propagates light from an image display element that displays an image to a light guide member of a virtual image display device, and includes a prism and a lens group which has the positive power from the image display element side toward the light guide member side. The first surface being the optical surface of the prism on which the light from the image display element is incident has the negative power.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a propagation optical system, a virtual image display device, and a head-mounted display. [Background technology]

[0002] A virtual image display device is known that enlarges a two-dimensional image and displays the enlarged virtual image so that a viewer can observe it. A light-guiding type virtual image display device is known as an example of this type of virtual image display device.

[0003] A light-guiding type virtual image display device is configured to propagate light emitted from each pixel of an image display element (hereinafter referred to as "image light") to a light-guiding member via a propagation optical system, guide the image light propagated from the propagation optical system using a light-guiding member, and emit the guided image light toward an observer so that the observer can observe the emitted image light as an enlarged virtual image.

[0004] For example, a specific configuration of a propagation optical system provided in a light-guiding type virtual image display device is described in Patent Document 1. The propagation optical system described in Patent Document 1 has a prism that bends the propagation direction of image light from an image display element. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2020-522024 Summary of the Invention [Problem to be solved by the invention]

[0006] To ensure a wide angle of view in a light-guiding type virtual image display device, it is conceivable to configure the propagation optical system with a large diameter, for example. However, increasing the diameter of the propagation optical system is undesirable because it increases the size of the virtual image display device. In particular, in wearable devices such as head-mounted displays, an increase in size can make the device difficult for the wearer to wear and increase the weight, increasing the burden on the wearer.

[0007] The present invention has been made in consideration of the above circumstances, and its object is to provide a propagation optical system that can be configured to be compact, and a virtual image display device and a head-mounted display that include such a propagation optical system. [Means for solving the problem]

[0008] A propagation optical system according to one embodiment of the present invention is an optical system that propagates light from an image display element that displays an image to a light guide member of a virtual image display device, and is configured to include, in order from the image display element side to the light guide member side, a prism and a lens group having positive power. The first surface, which is the optical surface of the prism onto which light from the image display element is incident, has negative power. The lens group includes, in order from the image display element side to the light guide member side, a first positive lens having positive power, a first negative lens having negative power, and a second negative lens having negative power and a second positive lens having a positive power. [Effects of the Invention]

[0009] According to one embodiment of the present invention, there are provided a propagation optical system that can be configured to be compact, and a virtual image display device and a head-mounted display that include such a propagation optical system. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a state in which a head-mounted display, which is an example of a virtual image display device, is worn by a wearer, according to an embodiment of the present invention. [Figure 2A] 1 is a schematic diagram showing a state in which a wearer wears a head-mounted display according to an embodiment of the present invention. [Figure 2B] 1 is a schematic diagram showing a state in which a wearer wears a head-mounted display according to an embodiment of the present invention. [Figure 2C] 1 is a schematic diagram showing a state in which a wearer wears a head-mounted display according to an embodiment of the present invention. [Figure 3] 1 is a diagram showing an example of the optical configuration of a propagation optical system according to one embodiment of the present invention (Numerical Example 1). [Figure 4] 1 is a perspective view showing a schematic configuration of a light guide member according to an embodiment of the present invention. [Figure 5] 3A to 3C are diagrams showing spherical aberration, astigmatism, and distortion of a propagation optical system according to Numerical Example 1 of the present invention. [Figure 6] 4A to 4C are diagrams showing lateral aberration of a propagation optical system according to Numerical Example 1 of the present invention. [Figure 7] FIG. 10 is a diagram illustrating an optical configuration of a propagation optical system according to a second numerical example of the present invention. [Figure 8] 6A to 6C are diagrams showing spherical aberration, astigmatism, and distortion of a propagation optical system according to Numerical Example 2 of the present invention. [Figure 9] 10A and 10B are diagrams showing lateral aberration of a propagation optical system according to Numerical Example 2 of the present invention. [Figure 10] FIG. 10 is a diagram illustrating an optical configuration of a propagation optical system according to a third numerical example of the present invention. [Figure 11] 10A to 10C are diagrams showing spherical aberration, astigmatism, and distortion of a propagation optical system according to Numerical Example 3 of the present invention. [Figure 12] 10A and 10B are diagrams showing lateral aberration of a propagation optical system according to Numerical Example 3 of the present invention. [Figure 13] FIG. 10 is a diagram illustrating an optical configuration of a propagation optical system according to a fourth numerical example of the present invention. [Figure 14] 10A to 10C are diagrams showing spherical aberration, astigmatism, and distortion of a propagation optical system according to Numerical Example 4 of the present invention. [Figure 15] 10A and 10B are diagrams showing lateral aberration of a propagation optical system according to Numerical Example 4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] A propagation optical system, a virtual image display device, and a head-mounted display according to an embodiment of the present invention will be described below with reference to the drawings. In the following description, common or corresponding elements are denoted by the same or similar reference numerals, and duplicate descriptions will be appropriately simplified or omitted.

[0012] 1 is a schematic diagram showing a state in which a head-mounted display 1, which is an example of a virtual image display device, is worn by a wearer. In FIG. 1, the symbol EY indicates the left eye of the wearer.

[0013] 1, the head-mounted display 1 includes an image display element 10, a propagation optical system 20, and a light-guiding member 30. Image light from the image display element 10 is propagated by the propagation optical system 20, and the propagated image light is guided by the light-guiding member 30 and emitted to display a virtual image. In other words, the image display element 10, the propagation optical system 20, and the light-guiding member 30 constitute a light-guiding type virtual image display device.

[0014] The head mounted display 1 is required to enable the wearer to observe a virtual image with a wide angle of view. In order to ensure a wide angle of view, it is conceivable to configure the propagation optical system 20 with a large diameter. However, due to size restrictions imposed by the fact that it must be worn by a person, there is a limit to how large a diameter the propagation optical system 20 can be configured with. For example, in the case of smart glasses, the propagation optical system 20 is built into the temples (also called "arms") of the frame. If the temples become thicker due to the larger diameter of the propagation optical system 20, it may become difficult for the wearer to wear the smart glasses, or the weight may increase, which may increase the burden on the wearer.

[0015] Therefore, the propagation optical system 20 according to this embodiment is configured to prevent an increase in size of the propagation optical system 20 that would otherwise be required to ensure a wide angle of view. In other words, the propagation optical system 20 can be configured to be compact while ensuring a wide angle of view.

[0016] In the following description, the first horizontal direction in which the image display element 10 and the propagation optical system 20 are aligned is referred to as the z direction, the second horizontal direction perpendicular to the z direction is referred to as the y direction, and the vertical direction perpendicular to both the y direction and the z direction is referred to as the x direction. The mutually perpendicular X direction, Y direction, and Z direction form a right-handed system. Note that the names of directions are used for convenience in describing the relative positional relationships of the components and do not indicate absolute directions. Depending on the posture of the wearer wearing the head-mounted display 1, for example, the z direction is not necessarily horizontal, but may be vertical.

[0017] 2A to 2C are schematic diagrams showing a state in which a wearer wears the head mounted display 1. The head mounted display 1 shown in Figs. 2A to 2C is sometimes called smart glasses.

[0018] The head mounted display 1 shown in FIG. 2A is a binocular type head mounted display, and is configured such that a single light guiding member 30 having a length equivalent to the width of the wearer's face is fixed to a frame 100. The light guiding member 30 forms an eye box in an area including both the left and right eyes. The image display element 10 and the propagation optical system 20 are built into, for example, temples of the frame 100. Furthermore, the frame 100 may be shaped to cover not only both ends of the light guiding member 30, but also the upper and lower edges of the light guiding member 30.

[0019] The head mounted display 1 shown in Fig. 2B is also a binocular type head mounted display, and is configured such that a pair of head mounted displays corresponding to the left and right eyes are fixed to a frame 100. The light guiding member 30 corresponding to the right eye forms an eyebox in an area including the right eye. The light guiding member 30 corresponding to the left eye forms an eyebox in an area including the left eye.

[0020] 2C is a monocular head mounted display, and is configured such that a single head mounted display corresponding to the right eye is fixed to the frame 100. Note that a monocular head mounted display in which a single head mounted display corresponding to the left eye is fixed to the frame 100 also falls within the scope of the present invention.

[0021] The propagation optical system 20 according to this embodiment is not limited to head-mounted displays, but can also be applied to other virtual image display devices, such as head-up displays.

[0022] Each component included in the head mounted display 1 will now be described in detail.

[0023] The image display element 10 is an element that displays an image to be observed as a virtual image, and examples thereof include an OLED (organic light emitting diode) array, an LD (laser diode) array, an LED (light emitting diode) array, a MEMS (micro electro mechanical systems), a DMD (digital micromirror device), etc. When the image display element 10 is configured with an OLED array, for example, the size of the image display area (effective pixel area) is 3 mm × 4 mm, and the number of pixels is about 10,000.

[0024] The image light from the image display element 10 is incident on a propagation optical system 20 .

[0025] Fig. 3 is a diagram showing an example of the optical configuration of the propagation optical system 20. As shown in Fig. 3, the propagation optical system 20 is configured by arranging, in this order, a prism P and a lens group LG from the image display element 10 side toward the light guide member 30 side. The lens group LG is rotationally symmetric with respect to the optical axis AX and has positive power.

[0026] It should be noted that the expression "arranged" in this embodiment does not exclude configuration examples in which another optical element is added within the scope of the technical concept of the present invention. Examples of configuration examples that are not excluded include a configuration example in which a parallel plate that does not substantially contribute to the optical performance of the propagation optical system 20 is added, and a configuration example in which another optical element is added while maintaining the configuration and effects of the propagation optical system 20 according to this embodiment. In other words, a configuration in which an optical element with such a configuration is added to the propagation optical system 20 consisting of the prism P and the lens group LG also falls within the scope of the present invention.

[0027] For example, smart glasses with an integrated image display element and light guide member are known. In these types of smart glasses, most of the weight is concentrated on the lens. This places a heavy load on the wearer's nose when wearing the glasses, making it difficult for the wearer to wear them for long periods of time.

[0028] In contrast, light-guiding smart glasses have a configuration in which a propagation optical system is placed between the image display element and the light-guiding member (inside the temples), physically separating the image display element and the light-guiding member. In light-guiding smart glasses, the image display element is built into the temples (more specifically, near the temples). This distributes the load on the wearer to three points: the nose and both ears, making it easier for the wearer to wear the smart glasses for long periods of time.

[0029] The propagation optical system must ensure a wide angle of view, and must be compact because it must be built into the temple. Furthermore, the propagation optical system must be lightweight and have a configuration that reduces the strain on the wearer.

[0030] Furthermore, the closer the image display element, which is a heat source, is located to the wearer's face (for example, the temples), the more likely the wearer will feel uncomfortable due to the heat emitted by the image display element. Therefore, the propagation optical system is also required to be configured so that the image display element is located at a position farther away from the wearer's face.

[0031] Therefore, the propagation optical system 20 according to this embodiment is configured to increase the distance between the wearer's face and the image display element, while providing good optical performance (wide angle of view, good aberration correction, etc.) and being compact.

[0032] Specifically, the prism P provided in the propagation optical system 20 bends the propagation direction of the image light from the image display element 10. By arranging the prism P, the image display element 10 can be arranged at a position farther away from the face of the wearer. By arranging the image display element 10 at a position farther away from the face of the wearer, heat from the image display element 10 is less likely to be transmitted to the wearer. Additionally, by arranging the prism P on the image display element 10 side (i.e., before the lens group LG), the propagation optical system 20 can be made more compact than a configuration in which the prism P is arranged on the light-guiding member 30 side (i.e., after the lens group LG).

[0033] The first surface P1 of the prism P is a surface (more specifically, a concave surface) having negative power. The first surface P1 is an optical surface of the prism P onto which the image light from the image display element 10 is incident.

[0034] By making the first surface P1 a surface having negative power, it is possible to capture light with a wide angle of view while miniaturizing the propagation optical system 20. Furthermore, off-axis light of the image light from the image display element 10 passes through a position on the first surface P1 that is away from the optical axis AX. Therefore, by determining the shape of the surface having negative power (i.e., the first surface P1) in consideration of off-axis aberrations that occur in the lens group LG arranged after the prism P, it is possible to keep off-axis aberrations small for the entire propagation optical system 20.

[0035] The image light incident on the first surface P1 is reflected and deflected by the reflecting surface M1 of the prism P, and emerges from the second surface P2 of the prism P. In other words, the second surface P2 is an optical surface of the prism P from which the image light from the image display element 10, which has been incident on the first surface P1, emerges. The image light emerging from the second surface P2 passes through the lens group LG and enters the light-guiding member 30. The reflecting surface M1 may be a flat surface or a free-form surface.

[0036] 4 is a perspective view showing a schematic configuration of the light guide member 30. As shown in FIG.

[0037] The image light propagated by the propagation optical system 20 is incident on the first light guiding member 31. In Fig. 4, for convenience, the image light incident from the propagation optical system 20 is denoted by the symbol L1.

[0038] A plurality of first mirrors 31a are arranged in the y direction inside the first light guiding member 31. The image light L1 propagated by the propagation optical system 20 is incident on the first mirror 31a that is located furthest to the negative side in the y direction among the plurality of first mirrors 31a. For convenience, only six first mirrors 31a are shown in the schematic diagram of FIG. 4. In reality, the number of first mirrors 31a is greater than this.

[0039] The first mirrors 31a are mirrors that are coated with a specific reflectance and transmittance, and reflect a portion of the incident image light L1 and transmit a portion of the image light L1. The image light L1 that enters the first light guiding member 31 is divided by reflection and transmission at each of the first mirrors 31a. By repeatedly dividing the image light L1 by reflection and transmission, the image light L1 becomes light that spreads in the y direction.

[0040] In the following description, for convenience, the image light that spreads in the y direction is denoted by the symbol L2. Also, in Fig. 4, for convenience, the individual rays of the image light L2 are denoted by the symbol L3.

[0041] The image light L2 is incident on the second light guiding member 32. A second mirror 32a and a plurality of third mirrors 32b are disposed inside the second light guiding member 32. The plurality of third mirrors 32b are arranged side by side in the x direction.

[0042] The second mirror 32a reflects, to the negative side in the x-direction, the image light L2 (in other words, the light rays L3) incident thereon from the first light guiding member 31. As a result, the image light L2 is guided to the negative side in the x-direction within the second light guiding member 32, and is incident on the third mirror 32b.

[0043] Like the first mirror 31a, the third mirror 32b is a mirror coated with a specific reflectance and transmittance, and reflects a portion of the incident image light L2 while transmitting a portion of the image light L2. The image light L2 reflected by the second mirror 32a is divided by reflection and transmission at each of the third mirrors 32b. By repeatedly dividing the image light L2 by reflection and transmission, the image light L2 becomes light that spreads in the x direction as well as the y direction, and is emitted from the second light guiding member 32 to the outside (specifically, toward the wearer's eye EY). Note that, for convenience, only five third mirrors 32b are shown in the schematic diagram of FIG. 4. In reality, the number of third mirrors 32b is greater than this.

[0044] In the following description, for convenience, the image light that spreads in two dimensions, the x and y directions, is designated by the symbol L4. Also, in Fig. 4, for convenience, each ray of the image light L4 is designated by the symbol L5. Note that, for clarity of the drawing, only some of the rays L5 are designated by the symbol L5.

[0045] When the image light L4 enters the eye EY, it is formed on the retina as a conjugate image of a virtual image, so that the wearer sees an enlarged virtual image of the image displayed on the image display device 10.

[0046] In this way, the light guide member 30 is configured to expand the eyebox (the range in which a virtual image is visible) in two dimensions, that is, the x direction and the y direction.

[0047] The specific configuration of the propagation optical system 20 according to this embodiment will be further described.

[0048] The first surface P1 of the prism P may be aspherical. By making the first surface P1 aspherical, it is possible to correct off-axis aberrations while ensuring a wider angle of view.

[0049] When the effective ray height (in other words, the effective ray radius) at the first surface P1 is H and the sag amount at the effective ray height H at the first surface P1 is SAG, the propagation optical system 20 may be configured to satisfy the following equation (1).

[0050] Formula (1) -0.4 <SAG / H<-0.05 However, the sag amount SAG takes a negative value when it is closer to the image display element 10 than the surface vertex of the first surface P1.

[0051] By satisfying the formula (1), it is possible to secure a wider angle of view and reduce the size of the propagation optical system 20, and also to correct off-axis aberrations.

[0052] In the image display element 10, the intensity of light emitted from each pixel arranged in the effective pixel area in the forward direction (vertical direction of the screen) is the highest, and the intensity of light emitted at an angle inclined relative to the vertical direction of the screen decreases. When "SAG / H" in formula (1) is below the lower limit (i.e., -0.4), it becomes difficult for the prism P to capture high-intensity light emitted in the vertical direction of the screen, particularly among light emitted from pixels in the peripheral part of the effective pixel area. This makes it difficult to ensure the amount of peripheral light. Furthermore, when "SAG / H" in formula (1) is above the upper limit (i.e., -0.05), the first surface P1 assumes a surface shape that approximates a flat surface, making it difficult to achieve both a wide angle of view and a compact propagation optical system 20, as well as to correct off-axis aberrations.

[0053] Furthermore, in order to achieve both a wider angle of view and a smaller size of the propagation optical system 20, and to correct off-axis aberrations, the propagation optical system 20 may be configured to satisfy the following formula (2).

[0054] Formula (2) -0.3 <SAG / H<-0.1

[0055] When the distance on the optical axis AX from the first surface P1 to the second surface P2 of the prism P is DP and the length of the longest side of the effective pixel area of ​​the image display element 10 is LY, the propagation optical system 20 may be configured to satisfy the following formula (3). The effective pixel area of ​​the image display element 10 is rectangular, with a short side in the vertical direction (X direction) and a long side in the horizontal direction (Z direction). Therefore, the length LY represents the length of the effective pixel area in the Z direction.

[0056] Formula (3) 1.0 <DP / LY<2.0

[0057] By satisfying the formula (3), it is possible to secure a wider angle of view and also to make the propagation optical system 20 more compact.

[0058] If "DP / LY" in formula (3) is equal to or smaller than the lower limit (i.e., 1.0), the prism P becomes too small, making it difficult for the prism P to capture light emitted from peripheral pixels within the effective pixel area of ​​the image display element 10. This makes it difficult for the light emitted from peripheral pixels within the effective pixel area to propagate to the light-guiding member 30. If "DP / LY" in formula (3) is equal to or larger than the upper limit (i.e., 2.0), the prism P becomes too large, making it difficult to miniaturize the propagation optical system 20.

[0059] When the distance on the optical axis AX from the lens surface LP1 closest to the image display element 10 on the optical path to the lens surface LP2 closest to the light-guiding member 30 among the lens surfaces included in the lens group LG is DL, the propagation optical system 20 may be configured to satisfy the following equation (4).

[0060] Formula (4) 0.5 <DP / DL<2.0

[0061] By satisfying the formula (4), the configuration becomes advantageous for correcting various aberrations.

[0062] When "DP / DL" in formula (4) is below its lower limit (i.e., 0.5), the distance DP on the optical axis AX from the first surface P1 to the second surface P2 of the prism P becomes too short, making it difficult for light emitted from peripheral pixels within the effective pixel area of ​​the image display element 10 to propagate to the light-guiding member 30. When "DP / DL" in formula (4) is above its upper limit (i.e., 2.0), the overall length of the lens group LG becomes too short, making it difficult to correct various aberrations. For example, shortening the overall length of the lens group LG requires shortening the spacing between the lenses constituting the lens group LG. As a result, the power that must be imparted to each lens surface increases. As the power of each lens surface increases, the various aberrations that occur at each lens surface also increase. This makes it difficult to correct aberrations that occur throughout the lens group LG.

[0063] In order to provide a configuration that is more advantageous for correcting various aberrations, the propagation optical system 20 may be configured to satisfy the following formula (5).

[0064] Formula (5) 0.5 <DP / DL<1.5

[0065] The lens group LG includes, in order from the image display element 10 side to the light guide member 30 side, a first positive lens L1 having a positive power. P , a negative lens group LG having negative power and including at least one lens; N , a second positive lens L2 having a positive power P The negative lens group LG may be arranged as follows: N is made up of, for example, one lens or two lenses.

[0066] By arranging lenses (or lens groups) having positive, negative, and positive powers in this order from the image display element 10 side toward the light guide member 30 side, various aberrations can be corrected well. P or second positive lens L2 P The negative lens group LG NBy forming the negative lens from a material having a larger Abbe number than the negative lens of the first embodiment, chromatic aberration can be corrected more effectively.

[0067] First positive lens L1 P The focal length of the negative lens group LG is f1. N When the focal length of the light beam is fn, the propagation optical system 20 may be configured to satisfy the following formula (6).

[0068] Formula (6) -2.0 <fn / f1<-0.3

[0069] By satisfying the formula (6), various aberrations can be corrected more effectively.

[0070] When "fn / f1" in equation (6) is equal to or less than the lower limit (i.e., -2.0), the negative lens group LG N The focal length fn of the first positive lens L1 is too long. P The negative lens group LG for the aberrations generated by N When "fn / f1" in formula (6) is equal to or greater than the upper limit (i.e., -0.3), the focal length fn is too short, and the first positive lens L1 P The negative lens group LG for the aberrations generated by N As a result, the correction is overdone and various aberrations cannot be corrected sufficiently.

[0071] In order to correct various aberrations more effectively, the propagation optical system 20 may be configured to satisfy the following formula (7).

[0072] Formula (7) -1.8 <fn / f1<-0.5

[0073] Second positive lens L2 P When the focal length of the optical system 20 is f2, the optical system 20 may be configured to satisfy the following formula (8):

[0074] Formula (8) -2.0 <fn / f2<-0.3

[0075] By satisfying the formula (8), various aberrations can be corrected more effectively.

[0076] When "fn / f2" in equation (8) is equal to or less than the lower limit (i.e., -2.0), the negative lens group LG N The focal length fn of the second positive lens L2 is too long. P The negative lens group LG for the aberrations generated by N When "fn / f2" in formula (6) is equal to or greater than the upper limit (i.e., -0.3), the focal length fn is too short, and the second positive lens L2 P The negative lens group LG for the aberrations generated by N As a result, the correction is overdone and various aberrations cannot be corrected sufficiently.

[0077] In order to correct various aberrations more effectively, the propagation optical system 20 may be configured to satisfy the following formula (9).

[0078] Formula (9) -1.8 <fn / f2<-0.4

[0079] When the angle between the first surface P1 and the second surface P2 of the prism P is θ, the propagation optical system 20 may be configured to satisfy the following formula (10): More specifically, the angle θ is the angle between the tangent plane at the vertex of the first surface P1 located on the optical axis AX and the second surface P2. If the second surface P2 is not a flat surface but a spherical or aspherical surface, the angle θ is the angle between the tangent plane at the vertex of the first surface P1 located on the optical axis AX and the tangent plane at the vertex of the second surface P2 located on the optical axis AX (see FIG. 13 illustrating Numerical Example 4 described later).

[0080] Formula (10) 70°<θ<110°

[0081] By satisfying the formula (10), the propagation optical system 20 can be made even more compact.

[0082] When the angle θ is equal to or smaller than the lower limit (70°) of Equation (10), the reflecting surface M1 and the second surface P2 must be extended farther from the image display element 10 in order to allow the light deflected at the portion of the reflecting surface M1 of the prism P that is farthest from the image display element 10 to exit from the second surface P2. This results in a larger prism P. This makes it difficult to reduce the size of the propagation optical system 20. When the angle θ is equal to or larger than the upper limit (110°) of Equation (10), the reflecting surface M1 must be positioned farther from the image display element 10 and the second surface P2 must be extended toward the image display element 10 in order to allow the light deflected at the portion of the reflecting surface M1 of the prism P that is closest to the image display element 10 to exit from the second surface P2 without interfering with the first surface P1. This results in a larger prism P. This makes it difficult to reduce the size of the propagation optical system 20.

[0083] Next, specific numerical examples 1 to 4 of the propagation optical system 20 will be shown. Numerical examples 1 to 4 have the following in common.

[0084] <<Common features of Numerical Examples 1 to 4>> Effective pixel area of ​​the image display element 10 Rectangular shape with a short side (X direction) of 3 mm and a long side (Z direction) of 5 mm Eye relief 15mm Aberration diagram Calculation based on imaging with an ideal lens with a focal length of 17 mm Diagonal angle of the virtual image 40.4 degrees

[0085] [Numerical Example 1] The optical configuration of the propagation optical system 20 according to Numerical Example 1 of the present invention is shown in Fig. 3. As shown in Fig. 3, the propagation optical system 20 according to Numerical Example 1 is configured by arranging, in order from the image display element 10 side, a prism P and a lens group LG. The lens group LG includes, in order from the image display element 10 side, a first positive lens L1 P , a negative lens group LG having negative power N , a second positive lens L2 having a positive power P In Numerical Example 1, the negative lens group LG NIt consists of two lenses.

[0086] Specific numerical configurations of the propagation optical system 20 according to Numerical Example 1 are shown in Table 1. Numbers in Table 1 are assigned to the surfaces of the image display element 10, the propagation optical system 20, and the light-guiding member 30, in order from the image display element 10 side. Supplementally, number 0 in the table indicates the image display surface (pixel array surface) of the image display element 10. Numbers 1 and 2 in the table indicate cover glasses provided on the image display element 10. The cover glass is a glass member that covers the image display surface of the image display element 10. In the optical configuration diagrams of each Numerical Example, the element indicated by reference numeral 10 indicates the cover glass. Numbers 3 to 6 in the table indicate a prism P. Numbers 7 to 14 in the table indicate a lens group LG. Numbers 15 to 17 in the table indicate the light-guiding member 30. In Table 1, R (unit: mm) indicates the radius of curvature of each surface of the optical element, D (unit: mm) indicates the thickness of the optical element on the optical axis AX or the spacing between the optical elements, Nd indicates the refractive index of the d-line (wavelength 587.56 nm), and νd indicates the Abbe number for the d-line. The column to the right of the Abbe number lists the trade name and manufacturer of the material of the optical element.

[0087] [Table 1] JPEG0007786092000001.jpg77155

[0088] In Table 1, surfaces marked with an "*" are aspherical. Table 2 shows the data for each aspherical surface. In Table 2, the notation E indicates a power with 10 as the base and the number to the right of E as the exponent. The radius of curvature R of an aspherical element indicates the radius of curvature on the optical axis AX (paraxial radius of curvature). The aspherical shape is expressed by the following equation, where Z is the sag, C is the paraxial curvature (1 / R), h (unit: mm) is the height from the optical axis, K is the conic coefficient, and A4, A6, ... are aspherical coefficients of even orders of 4 or higher.

[0089] Z=Ch 2 / {1+√(1-(1+K)C 2 h 2 )}+A 4 h 4 +A 6 h 6 +A 8 h8 +A 10 h 10

[0090] The table format is the same in the following numerical examples 2 to 4.

[0091] [Table 2] JPEG0007786092000002.jpg52150

[0092] FIG. 5 shows various aberration diagrams (spherical aberration, astigmatism, and distortion) of the propagation optical system 20 according to Numerical Example 1. The spherical aberration diagram in FIG. 5 shows spherical aberration at the d-line and g-line (435.84 nm). The solid line shows spherical aberration at the d-line, and the dotted line shows spherical aberration at the g-line. The astigmatism diagram in FIG. 5 shows astigmatism at the d-line (i.e., the difference between the sagittal image plane and the meridional image plane). The solid line shows aberration in the sagittal direction, and the dashed line shows aberration in the meridional direction. The vertical axis of the spherical aberration diagram and the astigmatism diagram indicates image height, and the horizontal axis indicates the amount of aberration. The vertical axis of the distortion diagram in FIG. 5 indicates image height, and the horizontal axis indicates the distortion rate at the d-line.

[0093] FIG. 6 is a diagram of lateral aberration of the propagation optical system 20 according to Numerical Example 1. The lateral aberration diagram shows the lateral aberration at the d-line and the g-line at each image height. The solid line shows the lateral aberration at the d-line, and the dotted line shows the lateral aberration at the g-line. The lateral aberration is measured in the X and Y directions. The left diagram of FIG. 6 (the diagram with "Y-FAN" added to the upper column) shows the lateral aberration in the Y direction, and the right diagram of FIG. 6 (the diagram with "X-FAN" added to the upper column) shows the lateral aberration in the X direction.

[0094] As described below, in Numerical Example 1, all of the above formulas (1) to (10) are satisfied. SAG / H: -0.21 (see equations (1) and (2)) DP / LY: 1.35 (see formula (3)) DP / DL: 1.13 (see equations (4) and (5)) fn / f1: -1.35 (see equations (6) and (7)) fn / f2: -1.25 (see equations (8) and (9)) θ: 90° (see formula (10))

[0095] The propagation optical system 20 according to Numerical Example 1 satisfactorily corrects various aberrations (see FIGS. 5 and 6), and also ensures a wide angle of view (a diagonal angle of view exceeding 40 degrees), thereby achieving good imaging performance. Furthermore, the propagation optical system 20 according to Numerical Example 1 achieves various effects by satisfying the above expressions (1) to (10).

[0096] [Numerical Example 2] 7 is a diagram showing the optical configuration of the propagation optical system 20 according to Numerical Example 2 of the present invention. As shown in FIG. 7, the optical configuration of the propagation optical system 20 according to Numerical Example 2 is the same as the optical configuration of the propagation optical system 20 according to Numerical Example 1.

[0097] Specific numerical configurations of the propagation optical system 20 according to Numerical Example 2 are shown in Table 3. Supplementally, number 0 in the table indicates the image display surface (pixel array surface) of the image display element 10. Numbers 1 and 2 in the table indicate cover glasses provided on the image display element 10. Numbers 3 to 6 in the table indicate prisms P. Numbers 7 to 14 in the table indicate lens groups LG. Numbers 15 to 17 in the table indicate the light-guiding member 30. Data on each aspheric surface in Numerical Example 2 is shown in Table 4.

[0098] [Table 3] JPEG0007786092000003.jpg77154

[0099] [Table 4] JPEG0007786092000004.jpg51150

[0100] 8A and 8B are diagrams showing various aberrations (spherical aberration, astigmatism, and distortion) of the propagation optical system 20 according to Numerical Example 2. FIG. 9 is a diagram showing lateral aberrations of the propagation optical system 20 according to Numerical Example 2.

[0101] As will be described below, in Numerical Example 2, all of the above formulas (1) to (10) are satisfied. SAG / H: -0.18 (see equations (1) and (2)) DP / LY: 1.36 (see formula (3)) DP / DL: 1.02 (see equations (4) and (5)) fn / f1: -1.22 (see equations (6) and (7)) fn / f2: -1.45 (see equations (8) and (9)) θ: 100° (see formula (10))

[0102] In the propagation optical system 20 according to Numerical Example 2, various aberrations are also corrected well (see FIGS. 8 and 9), a wide angle of view (a diagonal angle of view exceeding 40 degrees) is secured, and good imaging performance is achieved. Furthermore, in the propagation optical system 20 according to Numerical Example 2, various effects are achieved by satisfying the above expressions (1) to (10).

[0103] [Numerical Example 3] 10 is a diagram showing the optical configuration of a propagation optical system 20 according to Numerical Example 3 of the present invention. As shown in FIG. 10, the optical configuration of the propagation optical system 20 according to Numerical Example 3 includes a negative lens group LG N The optical configuration is the same as that of the propagation optical system 20 according to Numerical Example 1, except that it is made up of one lens.

[0104] Specific numerical configurations of the propagation optical system 20 according to Numerical Example 3 are shown in Table 5. Supplementally, number 0 in the table indicates the image display surface (pixel array surface) of the image display element 10. Numbers 1 and 2 in the table indicate cover glasses provided on the image display element 10. Numbers 3 to 6 in the table indicate prisms P. Numbers 7 to 12 in the table indicate lens groups LG. Numbers 13 to 15 in the table indicate light-guiding members 30. Data on each aspheric surface in Numerical Example 3 is shown in Table 6.

[0105] [Table 5] JPEG0007786092000005.jpg68153

[0106] [Table 6] JPEG0007786092000006.jpg41148

[0107] 11A and 11B are diagrams showing various aberrations (spherical aberration, astigmatism, and distortion) of the propagation optical system 20 according to Numerical Example 3. FIG. 12A and 12B are diagrams showing lateral aberrations of the propagation optical system 20 according to Numerical Example 3.

[0108] As shown below, in Numerical Example 3, all of the above formulas (1) to (10) are satisfied. SAG / H: -0.17 (see equations (1) and (2)) DP / LY: 1.58 (see formula (3)) DP / DL: 1.40 (see equations (4) and (5)) fn / f1: -1.04 (see equations (6) and (7)) fn / f2: -0.62 (see equations (8) and (9)) θ: 80° (see formula (10))

[0109] In the propagation optical system 20 according to Numerical Example 3, various aberrations are also corrected well (see FIGS. 11 and 12), a wide angle of view (a diagonal angle of view exceeding 40 degrees) is secured, and good imaging performance is achieved. Furthermore, in the propagation optical system 20 according to Numerical Example 3, various effects are achieved by satisfying the above expressions (1) to (10).

[0110] [Numerical Example 4] 13 is a diagram showing the optical configuration of a propagation optical system 20 according to Numerical Example 4 of the present invention. As shown in FIG. 13, the optical configuration of the propagation optical system 20 according to Numerical Example 4 includes a negative lens group LG N The optical configuration is the same as that of the propagation optical system 20 according to Numerical Example 1, except that it is made up of one lens.

[0111] Specific numerical configurations of the propagation optical system 20 according to Numerical Example 4 are shown in Table 7. Supplementally, number 0 in the table indicates the image display surface (pixel array surface) of the image display element 10. Numbers 1 and 2 in the table indicate the cover glass provided on the image display element 10. Numbers 3 to 7 in the table indicate the prism P. Numbers 8 to 13 in the table indicate the lens group LG. Numbers 14 to 16 in the table indicate the light-guiding member 30. Data for each aspheric surface in Numerical Example 4 is shown in Table 8.

[0112] [Table 7] JPEG0007786092000007.jpg72152

[0113] [Table 8] JPEG0007786092000008.jpg41149

[0114] 14A and 14B are diagrams showing various aberrations (spherical aberration, astigmatism, and distortion) of the propagation optical system 20 according to Numerical Example 4. FIG. 15A and 15B are diagrams showing lateral aberrations of the propagation optical system 20 according to Numerical Example 4.

[0115] As will be described below, in Numerical Example 4, all of the above formulas (1) to (10) are satisfied. SAG / H: -0.16 (see equations (1) and (2)) DP / LY: 1.60 (see formula (3)) DP / DL: 1.26 (see equations (4) and (5)) fn / f1: -0.79 (see equations (6) and (7)) fn / f2: -0.52 (see equations (8) and (9)) θ: 90° (see formula (10))

[0116] In the propagation optical system 20 according to Numerical Example 4, various aberrations are also corrected well (see FIGS. 14 and 15), a wide angle of view (a diagonal angle of view exceeding 40 degrees) is secured, and good imaging performance is achieved. Furthermore, in the propagation optical system 20 according to Numerical Example 4, various effects are achieved by satisfying the above expressions (1) to (10).

[0117] The above is a description of exemplary embodiments of the present invention. The embodiments of the present invention are not limited to those described above, and various modifications are possible within the scope of the technical concept of the present invention. For example, the embodiments of the present application also include appropriate combinations of embodiments explicitly shown in the specification or obvious embodiments. [Explanation of symbols]

[0118] 1: Head-mounted display 10: Image display element 20: Propagation optical system 30: Light guide member 31: First light guide member 31a: 1st mirror 32: Second light guide member 32a: 2nd mirror 32b: 3rd mirror 100: Frame LG: Lens group P: Prism

Claims

1. In a propagation optical system that propagates light from an image display element that displays an image to a light guiding member of a virtual image display device, a prism and a lens group having positive power are arranged in this order from the image display element side to the light guide member side, an optical surface of the prism onto which light from the image display element is incident is designated as a first surface; the first surface has negative power; the lens group includes, in order from the image display element side to the light guiding member side, a first positive lens having positive power, a first negative lens having negative power, a second negative lens having negative power, and a second positive lens having positive power; Propagation optics.

2. the first surface of the prism is aspherical; The propagation optical system according to claim 1 .

3. When the effective ray height on the first surface is H and the sag amount at the effective ray height H on the first surface is SAG, the following equation is satisfied: -0.4<SAG / H<-0.05 However, the sag amount SAG takes a negative value when it is closer to the image display element than the surface vertex of the first surface. fulfill, 3. The propagation optical system according to claim 1 or 2.

4. When an optical surface of the prism, from which light from the image display element incident on the first surface is emitted, is defined as a second surface, a distance on the optical axis from the first surface to the second surface is defined as DP, and a distance from a lens surface included in the lens group that is closest to the image display element on the optical path to a lens surface that is closest to the light guiding member on the optical path is defined as DL, the following formula can be used: 0.5<DP / DL<2.0 fulfill, The propagation optical system according to any one of claims 1 to 3.

5. When the focal length of the first positive lens is f1 and the focal length of the negative lens group consisting of the first negative lens and the second negative lens is fn, the following equation is satisfied: -2.0<fn / f1<-0.3 fulfill, The propagation optical system according to claim 1 .

6. When the focal length of the second positive lens is f2 and the focal length of the negative lens group consisting of the first negative lens and the second negative lens is fn, the following equation is satisfied: -2.0<fn / f2<-0.3 fulfill, The propagation optical system according to any one of claims 1 to 5.

7. When the optical surface of the prism, from which the light incident on the first surface and from the image display element is emitted, is defined as a second surface, and the angle between the first surface and the second surface is defined as θ, the following formula is satisfied: 70°<θ<110° fulfill, The propagation optical system according to any one of claims 1 to 6.

8. an image display element for displaying an image; a propagation optical system according to claim 1 that propagates light from the image display element; In the propagation optical system, when an optical surface of the prism from which light incident on the first surface from the image display element is emitted is defined as a second surface, a distance on the optical axis from the first surface to the second surface is defined as DP, and a length of the longest side of an effective pixel area of ​​the image display element is defined as LY, the following equation is satisfied: 1.0<DP / LY<2.0 fulfill, optical system.

9. an optical system according to claim 8; a light guiding member that guides the light propagated by the optical system and outputs the light for displaying a virtual image. Virtual image display device.

10. an image display element for displaying an image; a propagation optical system according to claim 1 , which propagates light from the image display element; and a light guide member that guides the light propagated by the propagation optical system and outputs the light for displaying a virtual image; Equipped with Virtual image display device.

11. A virtual image display device according to claim 10, Head-mounted display.

Images