Head-mounted display

Abstract

A head-mounted display capable of displaying an image with a wide viewing angle and capable of displaying an image without color unevenness is provided. The head-mounted display displays an image within a user's field of view, and includes an image display unit that generates an image to be displayed, and a first light guide plate and a second light guide plate that reproduce image light from the image display unit, the first light guide plate and the second light guide plate each having parallel one set of main surfaces that enclose the image light by internal reflection, the first light guide plate having an incident surface that internally reflects the image light and two or more emission reflection surfaces that emit the image light toward the second light guide plate, the second light guide plate having an input portion that internally couples the image light from the first light guide plate and an output portion that emits the image light toward the user's pupil, and configured such that, in the emission reflection surface of the first light guide plate that is farthest from the incident surface, the reflectance in a blue wavelength region is higher than the reflectance in a green wavelength region and a red wavelength region.

Description

Technical Field

[0001] This invention relates to a head-mounted display that is worn on a user's head and displays images within their field of vision. Background Technology

[0002] Wearable devices such as head-mounted displays (HMDs) are required not only to provide excellent display performance, ensuring a good field of view and visual recognition of images, but also to be small, lightweight, and comfortable to wear. HMDs achieve transparent image display devices by using light guide plates. Furthermore, because the light guide plate projects image light onto the user, a wide eye box (the area where the user can visually recognize the image) is achieved. Additionally, because the light guide plate uses total internal reflection-based light containment to propagate image light to the user's eyes, it achieves the characteristics of being thin, small, and lightweight.

[0003] As prior art in this technical field, there is Patent Document 1. Patent Document 1 discloses an HMD comprising a first light guide plate and a second light guide plate for replicating image light from a projection unit. The first light guide plate has an input section for reflecting the image light inward and a partially reflective surface for replicating and emitting image light to the second light guide plate. The second light guide plate has a coupling section for coupling the image light from the first light guide plate inward and an output section for replicating and emitting image light to the user's pupil.

[0004] In Patent Document 1, a first light guide plate and a second light guide plate are provided, thereby realizing a wide field of view for the displayed image.

[0005] However, to achieve thinner, smaller, and lighter designs, and to provide wider viewing angles for displayed images, it is necessary to increase the refractive index of the light guide glass material so that the light guide can propagate image light via total internal reflection. Here, the increased refractive index of the light guide glass material leads to greater light absorption, particularly on the blue wavelength side. Furthermore, the longer propagation path within the light guide reduces the emission efficiency of the blue wavelength side of the image light emitted from the reflecting surface furthest from the incident surface. This results in the problem of color unevenness in the displayed image.

[0006] Patent Document 1 does not take into account the color unevenness of the displayed image that is associated with the high refractive index of the light guide plate glass material.

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-116261 Summary of the Invention

[0008] The present invention was made in view of the following circumstances, and its object is to provide an HMD that can achieve thinness, small size, and light weight, and can display images with a wider viewing angle and without color unevenness.

[0009] An example of the present invention is a head-mounted display that displays images within a user's field of vision, comprising: an image display unit that generates an image to be displayed; and a first light guide plate and a second light guide plate that replicate image light from the image display unit. The first light guide plate and the second light guide plate each have a set of parallel main surfaces that block the image light through internal reflection. The first light guide plate has an incident surface that reflects the image light inward and two or more exiting reflective surfaces that emit image light to the second light guide plate. The second light guide plate has an input section that couples the image light from the first light guide plate inward and an output section that emits image light to the user's pupil. The configuration is such that in the exiting reflective surface of the first light guide plate, which is furthest from the incident surface, the reflectivity of the blue wavelength region is higher than that of the green wavelength region and the red wavelength region.

[0010] According to the present invention, an HMD that can achieve thinness, small size, and light weight, and can display images with a wider viewing angle and without color unevenness can be provided. Attached Figure Description

[0011] Figure 1A This is a functional block diagram of the HMD in Example 1.

[0012] Figure 1B It means Figure 1A A block diagram illustrating an example of the hardware structure of an HMD.

[0013] Figure 2 This is a block diagram of the virtual image generation unit in Embodiment 1.

[0014] Figure 3 This illustrates how the HMD is used in Example 1.

[0015] Figure 4 This is a structural diagram of the first light guide plate and the second light guide plate in Embodiment 1.

[0016] Figure 5A The optical path of the virtual image used to illustrate the problem of Example 1 is explained.

[0017] Figure 5B The brightness distribution of the virtual image used to illustrate the problem in Example 1 is explained.

[0018] Figure 6A The wavelength characteristics of the reflectivity of the emission reflective surface of the first light guide plate in Example 1 are explained.

[0019] Figure 6B The brightness distribution of the virtual image in Example 1 is explained.

[0020] Figure 7AThis describes another wavelength characteristic of the reflectivity of the emission reflective surface of the first light guide plate in Example 1.

[0021] Figure 7B This describes another wavelength characteristic of the reflectivity of the emission reflective surface of the first light guide plate in Example 1.

[0022] Figure 7C This illustrates another distribution of the brightness of the virtual image in Example 1.

[0023] Figure 8A This is a top view illustrating the detailed structure of the first light guide plate and the second light guide plate in Embodiment 1.

[0024] Figure 8B This is a side view illustrating the detailed structure of the first light guide plate and the second light guide plate in Embodiment 1.

[0025] Figure 9A The detailed structure and optical path of the first light guide plate and the second light guide plate in Embodiment 1 are described.

[0026] Figure 9B The detailed structure and optical path of the first light guide plate and the second light guide plate in Embodiment 1 are described.

[0027] Figure 10 This is a structural diagram of the first light guide plate and the second light guide plate in Embodiment 2.

[0028] Figure 11 The structure of the second light guide plate in Embodiment 2 is explained.

[0029] Figure 12 This describes a variation of the second light guide plate in Example 2.

[0030] Figure 13 This illustrates an example of HMD usage in Example 3.

[0031] Figure 14 This is a functional block diagram of the HMD in Example 3. Detailed Implementation

[0032] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0033] [Example 1]

[0034] Figure 1A This is a functional block structure diagram of the HMD in this embodiment. Figure 1A In this HMD1, there are virtual image generation unit 101, control unit 102, image signal processing unit 103, power supply unit 104, storage unit 105, sensing unit 106, communication unit 107, voice processing unit 108, camera unit 109, and input / output units 91 to 93.

[0035] The virtual image generation unit 101 magnifies and projects the image generated by the small display unit (described later) into a virtual image to display augmented reality (AR) or mixed reality (MR) images in the wearer's (user's) field of vision.

[0036] The control unit 102 provides comprehensive control of the entire HMD1. The control unit 102 utilizes a computing device such as a CPU to perform its functions. The image signal processing unit 103 supplies image signals for display to the display unit within the virtual image generation unit 101. The power supply unit 104 supplies power to all parts of the HMD1.

[0037] The storage unit 105 stores information required for processing by each part of the HMD1 and information generated by each part of the HMD1. Additionally, when the CPU performs the functions of the control unit 102, it stores the programs and data executed by the CPU. The storage unit 105 may be composed of storage devices such as RAM (Random Access Memory), flash memory, HDD (Hard Disk Drive), or SSD (Solid State Drive).

[0038] The sensing unit 106 is connected to various sensors via a connector, i.e., the input / output unit 91, and detects the posture (i.e., the user's posture, the orientation of the user's head), motion, ambient temperature, etc., of the HMD1 based on the signals detected by the various sensors. These various sensors include, for example, tilt sensors, accelerometers, temperature sensors, and GPS (Global Positioning System) sensors that detect the user's location information.

[0039] The communication unit 107 communicates with external information processing devices via a connector, i.e., the input / output unit 92, through short-range wireless communication, long-range wireless communication, or wired communication. Specifically, communication is conducted via Bluetooth, Wi-Fi, mobile communication networks, Universal Serial Bus (USB), High Definition Multimedia Interface (HDMI), etc.

[0040] The voice processing unit 108 is connected to voice input / output devices such as microphones, headphones, and speakers via a connector, i.e., the input / output unit 93, to input or output voice signals. The camera unit 109 is, for example, a small camera or a small TOF (Time of Flight) sensor, to capture the user's field of vision on the HMD1.

[0041] Figure 1B This is a block diagram illustrating an example of the hardware structure of HMD1. For example... Figure 1BAs shown, HMD1 includes CPU 201, system bus 202, ROM (Read-Only Memory) 203, RAM 204, storage device 210, communication processor 220, power supply 230, video processor 240, audio processor 250 and sensor 260.

[0042] CPU201 is the microprocessor unit that controls the entire HMD1. CPU201 and... Figure 1A The control unit 102 corresponds to this. The system bus 202 is a data communication line used for sending and receiving data between the CPU 201 and the various action blocks within the HMD1.

[0043] ROM203 is a memory that stores basic operating programs and other operating programs, such as EEPROM (Electrically Erasable Programmable Read-Only Memory) or flash ROM, which are rewritable ROMs.

[0044] RAM 204 serves as the working area for executing basic or other programs. ROM 203 and RAM 204 can be integrated with the CPU 201. Alternatively, ROM 203 may not be... Figure 1B The independent structure shown uses a portion of the storage area within storage device 210.

[0045] Storage device 210 stores the operating program and operating settings of HMD1, personal information 210a of the user using HMD1, etc. Although not specifically illustrated below, it may also store operating programs downloaded from the network and various data generated by those operating programs. Furthermore, a portion of the storage area of ​​storage device 210 may replace some or all of the functions of ROM 203. Storage device 210 may be, for example, a flash ROM, SSD, HDD, or other similar device. ROM 203, RAM 204, and storage device 210 correspond to storage unit 105. By performing download processing from various devices on the network, the aforementioned operating programs stored in ROM 203 or storage device 210 can be updated and their functions expanded.

[0046] The communication processor 220 is configured to include a LAN (Local Area Network) communicator 221, a telephone network communicator 222, an NFC (Near Field Communication) communicator 223, and a Bluetooth communicator 224. The communication processor 220 and... Figure 1A The communication unit 107 corresponds to this. Figure 1BThe example shown illustrates a scenario where the communication processor 220 includes a LAN communicator 221, an NFC communicator 223, and a Bluetooth communicator 224, but it can also be implemented as shown in the example. Figure 1A As described, these are connected as external devices to the HMD1 via the input / output unit 92. The LAN communicator 221 connects to the network via an access point and sends and receives data with devices on the network. The NFC communicator 223 wirelessly sends and receives data when a corresponding reader / writer is nearby. The Bluetooth communicator 224 wirelessly sends and receives data with a nearby information processing device. The HMD1 may also include a telephone network communicator 222 for making calls and sending and receiving data with a base station of a mobile phone communication network.

[0047] Virtual image generation mechanism 225 and Figure 1A This corresponds to the virtual image generation unit 101 in the middle. Using... Figure 2 The specific structure of the virtual image generation mechanism 225 will be described later.

[0048] Power supply unit 230 is a power supply device that supplies power to HMD1 according to predetermined specifications. Power supply unit 230 corresponds to Figure 1A The power supply department 104. Figure 1B The example shown is that the HMD1 includes a power supply 230, but they can be connected as external devices of the HMD1 via any one of the input / output sections 91 to 93, from which the HMD1 receives power.

[0049] The video processor 240 is configured to include a display 241, an image signal processing processor 242, and a camera 243. The image signal processing processor 242 corresponds to... Figure 1A The image signal processing unit 103 is located therein. Additionally, the camera 243 corresponds to... Figure 1A The camera unit 109 and the display unit 241 correspond to the small display unit described later. Figure 1B The example shown illustrates a scenario where the video processor 240 includes a display 241 and a camera 243, but it can also be implemented as shown in... Figure 1A As explained, they are connected as external devices of HMD1 via input / output unit 93.

[0050] Display 241 displays image data processed by image signal processing processor 242. Image signal processing processor 242 causes display 241 to display the input image data. Camera 243 is a camera unit that functions as an imaging device that uses electronic devices such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensors to convert light input from the lens into electrical signals, thereby inputting image data of the surroundings or objects.

[0051] The audio processor 250 includes a speaker 251, a voice signal processor 252, and a microphone 253. The audio processor 250 corresponds to... Figure 1A The speech processing unit 108 is located within the [location / component]. Figure 1B The example shown illustrates a configuration where the audio processor 250 includes a speaker 251 and a microphone 253, but it can also be implemented as described in... Figure 1A As explained, they are connected as external devices of HMD1 via input / output unit 93.

[0052] Speaker 251 outputs the processed speech signal from speech signal processor 252. Speech signal processor 252 outputs the input speech data to speaker 251. Microphone 253 converts speech into speech data and outputs it to speech signal processor 252.

[0053] Sensor 260 is a sensor group used to detect the state of HMD1, configured to include a GPS receiver 261, a gyroscope sensor 262, a geomagnetic sensor 263, an accelerometer sensor 264, an illuminance sensor 265, and a proximity sensor 266. Sensor 260 corresponds to sensing unit 106. Figure 1B The example shown illustrates a sensor 260 that includes a GPS receiver 261, a gyroscope sensor 262, a geomagnetic sensor 263, an accelerometer 264, an illuminance sensor 265, and a proximity sensor 266. However, it can also be implemented as shown in the example. Figure 1A As explained, they are connected to the HMD1 as external devices via the input / output unit 91. These individual sensors are typical sensor groups known to exist, therefore their description is omitted here. Furthermore, Figure 1B The structure of HMD1 shown is just one example and may not have all of these components.

[0054] Figure 2This is a block diagram of the virtual image generation unit 101 in this embodiment. The virtual image generation unit 101 is composed of an image display unit 120, a projection unit 121, a first light guide plate 122, and a second light guide plate 123. The image display unit 120 is a device for generating the image to be displayed, irradiating light from a light source such as an LED or laser onto a built-in miniature display unit. The miniature display unit is an element for displaying images, using liquid crystal displays, digital micromirror devices, organic EL displays, miniature LED displays, MEMS (Micro Electro Mechanical Systems), fiber optic scanning devices, etc. The projection unit 121 is a device with a projection lens that magnifies the image light from the image display unit 120 and projects it as a virtual image. The first light guide plate 122 replicates the image light to enlarge the eyebox. The second light guide plate 123 replicates the image light to enlarge the eyebox in a different direction than the first light guide plate 122, and transmits the image light from the projection unit 121 and the first light guide plate 122 to the user's pupil 20. Users can visually recognize images by imaging light onto the retina within the pupil 20.

[0055] Figure 3 This indicates how HMD1 is used in this embodiment. Figure 3 This represents the view from above user 2's head, with the X-axis being the horizontal direction, the Y-axis the vertical direction, and the Z-axis the direction of user 2's line of sight. The directions of the X, Y, and Z axes will also be defined similarly in the subsequent figures.

[0056] like Figure 3 As shown, the HMD1 is worn on the head of user 2, allowing the image generated by the virtual image generation unit 101 to be transmitted to the user's pupil 20 via the second light guide plate 123. At this time, user 2 can visually recognize the image (virtual image) in a perspective-based manner within a portion of the image display area 111 within their field of vision. Figure 3 The diagram shows the structure for a monocular display image, but it can also be configured as a binocular structure. The HMD1 can also... Figure 1A The camera unit 109 captures the field of view of user 2.

[0057] Figure 4 This is a structural diagram of the first light guide plate and the second light guide plate in this embodiment. From the viewpoint of visual recognizability of the image, it is preferable to enlarge the eyebox formed by the virtual image generation unit 101 in the 2D direction. In order to enlarge the eyebox in 2D, in Figure 4The first light guide plate 122 amplifies the horizontal direction of the eyebox. The first light guide plate 122 includes: an incident surface 130 that reflects image light into its interior; main surfaces 131 and 132 that close the two main parallel planes of the image light through total internal reflection; and two or more exiting reflector groups 133 that emit the internal image light outwards from the first light guide plate. The second light guide plate 123 includes: an incident surface 140 (input section) that reflects image light into its interior; main surfaces 141 and 142 that close the two main parallel planes of the image light through total internal reflection; and an exiting reflector group 143 (output section) that emits the internal image light outwards from the second light guide plate. The second light guide plate 123 emits an image towards the user's pupil 20. Thus, in the virtual image generation unit 101 of this embodiment, the first light guide plate 122 and the second light guide plate 123 respectively have a set of parallel main surfaces 131, 132 and 141, 142 that block the image light through internal reflection. The first light guide plate 122 has an incident surface 130 that reflects the image light inward and two or more emission reflective surface groups 133 that emit the image light to the second light guide plate 123. The incident surface 130 and the emission reflective surface groups 133 are parallel to each other and at an angle different from the main surfaces. The second light guide plate 123 has an incident surface 140 (input section) that couples the image light from the first light guide plate 122 inward and an emission reflective surface group 143 (output section) that emits the image light to the user's pupil 20.

[0058] The emission reflective surface group 133 of the first light guide plate 122 and the emission reflective surface group 143 of the second light guide plate 123 are partially reflective surfaces that reflect a portion of the light and transmit or absorb a portion of the light, and these partially reflective surfaces are arranged in an array. The arrangement direction of the emission reflective surface group 133 of the first light guide plate 122 is different from that of the emission reflective surface group 143 of the second light guide plate 123, thereby enabling a two-dimensional expansion of the eyebox. Therefore, the light diameter P of the image display unit 120 and the projection unit 121 can be reduced (by increasing the F-value), and the virtual image generation unit 101 can be significantly miniaturized.

[0059] From an image quality perspective, it is preferable that the emitting reflective surface group 133 of the first light guide plate 122 is parallel to each other, so that the reflected image light does not have an angular offset. Similarly, it is preferable that the emitting reflective surface group 143 of the second light guide plate 123 is also parallel to each other. If the parallelism is reduced, the angle of the light reflected by the emitting reflective surface group 133 or 143 will be different on each reflective surface, generating stray light and thus degrading the image quality.

[0060] Furthermore, when the incident surface 130 of the first light guide plate 122 is also parallel to the emission reflective surface group 133, the processing steps can be simplified, thereby reducing manufacturing costs. This can be achieved by stacking and bonding the plates on which the reflective films are formed into one piece and then cutting them, thereby processing the incident surface to the emission reflective surface in a consolidated manner, and multiple first light guide plates can be cut from this basis. When the angle of the incident surface 130 is different, a film needs to be formed on the incident surface after the process of cutting out the light guide plate and cutting the incident surface to a predetermined angle. The incident surface 140 of the second light guide plate 123 is also parallel to the emission reflective surface group 143, thereby simplifying the processing and reducing costs.

[0061] In addition, Figure 4 In the diagram, thick arrows indicate the approximate light paths at the four corners of the displayed image (virtual image). Light from the left side of the viewing angle (positions 1 and 3) propagates to the pupil 20 from the reflecting surface of the first light guide plate 122 near the incident surface 130, while light from the right side of the viewing angle (positions 2 and 4) propagates to the pupil 20 from the reflecting surface of the first light guide plate 122 away from the incident surface 130. Additionally, light from the upper side of the viewing angle (positions 1 and 2) propagates to the pupil 20 from the reflecting surface of the second light guide plate 123 near the incident surface 140, while light from the lower side of the viewing angle (positions 3 and 4) propagates to the pupil 20 from the reflecting surface of the second light guide plate 123 away from the incident surface 140.

[0062] As described above, in the first light guide plate 122 and the second light guide plate 123, such as Figure 4 As shown, in order for the second light guide plate 123 to receive the image light emitted from the first light guide plate 122, the main surfaces 131 and 132 of the first light guide plate and the main surfaces 141 and 142 of the second light guide plate are located in different planes. The main surfaces 131 and 132 of the first light guide plate are arranged on the side of the second light guide plate closer to the projection portion 121, and the two main surfaces 131 and 132 of each plate are arranged parallel to each other. In addition, in order for the incident surface 140 of the second light guide plate to efficiently receive the image light emitted from the main surface 131 of the first light guide plate, the first light guide plate 122 and the second light guide plate 123 need to be close together.

[0063] Next, the refractive index of the light guide plate glass material will be described. The light guide plate propagates image light through total internal reflection. Therefore, the viewing angle of the image light that the light guide plate can propagate is limited by a critical angle determined by the refractive index of the light guide plate glass material. If the refractive index of the light guide plate glass material is increased, the critical angle becomes smaller, thus enabling the propagation of image light with a wider viewing angle. In addition, by increasing the refractive index of the light guide plate glass material, light diffusion is suppressed, thus providing the advantage of making the light guide plate smaller and lighter.

[0064] However, compared to commonly used glass materials like BK7, light absorption is greater with high-refractive-index glass. Furthermore, light absorption in high-refractive-index glass increases with decreasing wavelength, particularly at the blue wavelength. Therefore, in light guide plates made of high-refractive-index glass, especially within the light guide plate itself, the propagation path is long, resulting in reduced emission efficiency of the blue wavelength side of the image light from the reflecting surface furthest from the incident surface. This leads to the problem of color unevenness in the displayed image.

[0065] use Figure 5A , Figure 5B Provide a detailed explanation of the topic. Figure 5A This indicates the virtual image generation unit 101 as viewed from above, the virtual image displayed by the virtual image generation unit 101, and the optical paths corresponding to each viewing angle P1, P2, and P3. Here, P1, P2, and P3 are the viewing angles at the left, center, and right ends of the image display area 111, respectively. Figure 5B express Figure 5A The brightness of the virtual image at the dashed line Q.

[0066] Figure 5A The image light corresponding to the viewing angles P1, P2, and P3 of the virtual image is reflected by the emission reflective surfaces R1, R(N / 2), and RN of the first light guide plate 122 and propagates to the pupil 20. Here, the emission reflective surface group of the first light guide plate 122 consists of N emission reflective surfaces, which are designated as R1 to RN (N is an integer) starting from the side closest to the incident surface 130.

[0067] Figure 5A The virtual image at the left end of the viewing angle P1 is light reflected by the emission reflecting surface R1 and propagated to the pupil 20. Compared with light reflected from other emission reflecting surfaces, the light reflected by the emission reflecting surface R1 travels a shorter distance inside the first light guide plate 122, and the effect caused by absorption by the glass material of the first light guide plate 122 is small. Therefore, regarding the brightness of the virtual image, such as... Figure 5B The difference between red, green and blue is small, like in P1.

[0068] Figure 5A The virtual image of P2 at the center of the viewing angle is light that propagates to the pupil 20 by being reflected from the centrally located emission reflector R(N / 2) in the emission reflector assembly of the first light guide plate 122. The light reflected by this emission reflector R(N / 2) travels a greater distance within the first light guide plate 122 compared to the light at the left end of the viewing angle, P1. Therefore, it is affected by the light absorption of the glass material. The light absorption of high-refractive-index glass materials increases with decreasing wavelength, especially in the blue wavelength region, thus reducing the emission efficiency in the blue wavelength region. As a result, as... Figure 5BAs shown in P2, the brightness of the blue wavelength region is reduced compared to the brightness of the red and green wavelength regions.

[0069] Figure 5A The virtual image at the right end of the viewing angle P3 is light reflected by the emission reflecting surface RN and propagated to the pupil 20. This light is reflected and emitted from the emission reflecting surface RN, which is the farthest from the incident surface in the light guide plate and is located at the innermost side. This light travels the longest distance within the first light guide plate 122 in the viewing angle. Therefore, the light absorption effect of the glass material is most significant. As a result, as... Figure 5B As shown in P3, the brightness of the blue wavelength region is reduced compared to the brightness of the red and green wavelength regions, resulting in the most significant color unevenness.

[0070] As mentioned above, the longer the propagation path inside the light guide plate from the incident surface, that is, the further inward it travels from the incident surface, the greater the influence of light absorption by the glass material of the light guide plate. The result is that, Figure 5B As shown, as the viewpoint moves to the right, the brightness of blue decreases relative to red, resulting in color unevenness in the displayed image. The solutions to these problems are explained below.

[0071] use Figure 6A , Figure 6B This embodiment will describe a solution to the problem of uneven color caused by the first light guide plate 122. Figure 6A This represents the wavelength characteristics of the reflectivity of the emission reflecting surfaces R1, R(N / 2), and RN. Figure 6B This indicates when using this solution. Figure 5A The brightness of the virtual image at the dashed line Q.

[0072] As described above, light reflected and emitted from the emission reflector located further away from the incident surface 130 travels a longer distance within the light guide plate, and is therefore more significantly affected by the absorption of the light guide plate glass material. Therefore, by considering the magnitude of light absorption by the light guide plate glass material to determine the wavelength characteristics of the reflectivity of the emission reflector, color uniformity can be improved.

[0073] Figure 6A This example illustrates the wavelength characteristics of the reflectivity of the emission reflector surfaces R1, R(N / 2), and RN based on this solution. In the emission reflector surface R1 of the image light at the left end of the emission viewing angle P1, since the influence of absorption by the glass material is small, the image light in the blue, green, and red wavelength regions can be emitted approximately uniformly by roughly eliminating wavelength dependence.

[0074] In the image light emitted from the center of the emission angle P2, considering the light absorption of the glass material, by making the reflectivity of the blue wavelength region higher than that of the green and red wavelength regions, the reduction in emission efficiency caused by the light absorption of the light guide plate glass material can be eliminated, thereby improving color uniformity.

[0075] Furthermore, by making the reflectivity of the image light emitted from the right end of the emission angle P3 on the emission reflector surface RN higher in the blue wavelength region than in the green and red wavelength regions, the reduction in emission efficiency caused by light absorption by the light guide plate glass material can be eliminated, thereby improving color uniformity. Additionally, compared to the emission reflector surface R(N / 2), the emission reflector surface RN is positioned further away from the incident surface 130, and thus travels a greater distance in the first light guide plate 122, making it more susceptible to light absorption by the light guide plate glass material. Therefore, by making the ratio of the reflectivity of the blue wavelength region to the reflectivity of the red wavelength region, (reflectivity of the blue wavelength region) / (reflectivity of the red wavelength region), greater than that of the emission reflector surface R(N / 2), color uniformity can be further improved. Figure 6A The reason why RN has a larger absolute value of reflectivity among the outgoing reflective surfaces R1, R(N / 2), and RN is that the light that passes through the outgoing reflective surfaces R1 and R(N / 2) is incident on the outgoing reflective surface RN. Therefore, the amount of light is reduced compared to the outgoing reflective surfaces R1 and R(N / 2), and thus the light needs to be covered to cover the reduction in the amount of light.

[0076] Furthermore, the blue, green, and red wavelength regions mentioned here are preferably wavelength regions corresponding to the three primary color wavelength regions of the projector's light source, such as the blue wavelength region being 380nm to 480nm, the green wavelength region being 480nm to 580nm, and the red wavelength region being 580nm to 680nm.

[0077] In addition, Figure 6A , Figure 6B The paper describes the reflection characteristics of three emission reflector surfaces: R1, R(N / 2), and RN. However, by using the same approach to determine the reflection characteristics of other emission reflector surfaces, it is possible to improve the color uniformity across the entire viewing angle.

[0078] In summary, at least in the emitting reflective surface of the first light guide plate that is furthest from the incident surface, color unevenness can be improved by making the reflectivity of the blue wavelength region higher than that of the green and red wavelength regions.

[0079] More preferably, in the emission reflective surface of the first light guide plate that is furthest from the incident surface, the reflectivity of the blue wavelength region is higher than that of the green and red wavelength regions compared to the previous emission reflective surface, which can improve color uniformity over a wider viewing angle.

[0080] Furthermore, when the reflectivity of the blue wavelength region is higher than that of the green and red wavelength regions among two or more outgoing reflective surfaces, the ratio of the reflectivity of the blue wavelength region to that of the red wavelength region, i.e., (reflectivity of the blue wavelength region) / (reflectivity of the red wavelength region), is greater for the outgoing reflective surface that is 130° away from the incident surface. This can improve the color unevenness that increases as light propagates.

[0081] Next, the wavelength characteristics of specific reflectivity will be described. In high-refractive-index glass materials commonly used as optical components, the transmittance per 10 mm thickness is approximately 100% in the red wavelength region, compared to 99%–95% in the blue wavelength region.

[0082] When image light is incident on a light guide plate and reflected by the innermost reflecting surface of the light guide plate, the length of the optical path of the image light propagating in the light guide plate is roughly calculated using... Figure 5A The incident surface 130 of the light guide plate shown, the distance Lw from the incident surface 130 to the farthest exiting reflective surface, and the total reflection angle φ propagating through total internal reflection are written as Lw / sinφ (1).

[0083] The distance Lw from the incident surface 130 to the farthest exiting reflective surface of the light guide plate is typically 20mm to 60mm. When the image light is reflected by the exiting reflective surface located at the innermost part of the light guide plate, it propagates at a total internal reflection angle close to the critical angle, so the total internal reflection angle φ is in the range of approximately 30 degrees to 40 degrees. As described above, when the image light is incident on the light guide plate and reflected by the exiting reflective surface located at the innermost part of the light guide plate, the optical path length of the image light propagating in the light guide plate, according to the above formula (1), is in the widest range of 30mm to 120mm.

[0084] In high-refractive-index glass materials commonly used as optical components, the transmittance t per 10 mm thickness is 95%–99% in the blue wavelength region. When image light is incident on a light guide plate and reflected by the innermost outgoing reflective surface of the light guide plate, the transmittance T of the image light in the blue wavelength region can be calculated using T = t^(S ÷ 10 mm), and the transmittance T is 50%–96%. Therefore, if the reflectance in the blue wavelength region is increased by approximately 1.0 to 2.0 times relative to the approximately 100% reflectance in the red wavelength region, color unevenness is improved.

[0085] exist Figure 6AThe reflection characteristics described herein are assumed to be wavelength-independent, meaning the reflectivity of the reflecting surface R1 is approximately independent of wavelength. However, from the perspective of manufacturing reflective films, it is difficult to achieve a reflection characteristic that is approximately wavelength-independent. Furthermore, in order to average out the wavelength dependence of dielectrics with different wavelength dependencies through multilayering, if the dielectrics forming the reflective surface are to be multilayered until the wavelength dependence is approximately eliminated, the manufacturing difficulty of the reflective film increases, and the time required for the evaporation of the reflective film also increases, thus increasing the manufacturing cost of the light guide plate.

[0086] Furthermore, the incident angle of image light onto an ejector reflecting surface, such as the ejector reflecting surface R1, which is positioned near the incident surface 130, is larger than that of other ejector reflecting surfaces. Therefore, it is difficult to achieve a reflection characteristic that is largely independent of wavelength, necessitating the use of more multilayered dielectrics. The challenge lies in the fact that if the display image is widened, the incident angle onto the ejector reflecting surface also increases, making the widening of the display image even more significant.

[0087] Therefore, even if the reflection characteristics of the reflecting surface R1 are not set to be approximately wavelength-independent, the problem can be solved in the following ways. For example, as... Figure 7A As shown, the reflectivity of the emitted reflective surface R1 is set to exhibit a reflectivity characteristic that decreases as the wavelength increases, such as (reflectivity in the blue wavelength region) > (reflectivity in the green wavelength region) > (reflectivity in the red wavelength region). Furthermore, the ratios of (reflectivity in the blue wavelength region), (reflectivity in the green wavelength region), and (reflectivity in the red wavelength region) are made approximately equal in the emitted reflective surface group 133. The difference in the absolute values ​​of the reflectivity in the emitted reflective surfaces R1, R(N / 2), and RN is intended to homogenize the emitted light quantity relative to the decrease in incident light quantity.

[0088] Furthermore, as in Figure 6A , Figure 6B As explained, to reduce color unevenness caused by absorption in the blue wavelength region of the light guide plate, the ratio of reflectivity in the blue wavelength region to reflectivity in the red wavelength region, i.e., (reflectivity in the blue wavelength region) / (reflectivity in the red wavelength region), is set to be larger the further away from the incident surface (130°). Therefore, the reduction in emission efficiency in the blue wavelength region caused by absorption in the blue wavelength region of the light guide plate can also be considered to reduce color unevenness. As an example, in... Figure 7B The reflection characteristics at this time are shown in the figure.

[0089] Thus, as Figure 7CAs shown, regardless of the viewing angle of the image, the brightness ratio of the blue, green, and red wavelength regions of the image light can be kept constant, reducing color unevenness. Furthermore, with such reflective characteristics, the chromaticity of the image displayed by the image display unit 120 differs from the chromaticity of the image emitted from the second light guide plate 123 and reaching the pupil 20. For example, in Figure 7C In the image, the blue light becomes strong. Therefore, the chromaticity of the image display unit 120 needs to be adjusted in advance so that the chromaticity of the image reaching the pupil 20 is the desired value.

[0090] By setting the reflective film characteristics as described above, the manufacturing difficulty of the reflective film can be greatly reduced. Even a low-cost thin reflective film can be used to display a light guide plate that does not produce images with uneven color for the user.

[0091] Next, use Figure 8A , Figure 8B The structures of the first light guide plate and the second light guide plate in this embodiment will be described in detail. Figure 8A This is a top view of the first light guide plate 122 and the second light guide plate 123 in this embodiment, viewed from the top vertical direction along the Y-axis. Figure 8B This is a side view of the first light guide plate 122 and the second light guide plate 123 in this embodiment, viewed from the horizontal direction of the X-axis.

[0092] In this embodiment, as Figure 8A As shown, the first light guide plate 122 has an emission reflective surface group 133 composed of N emission reflective surfaces, with the N emission reflective surfaces designated as R1 to RN (N being an integer) starting from the side closest to the incident surface 130. Furthermore, the interval between the emission reflective surfaces is designated as L1 to LN-1, starting from the side closest to the incident surface 130. Additionally, as... Figure 8B As shown, the emission reflective surface group 143 of the second light guide plate 123 is composed of M emission reflective surfaces, and the M emission reflective surfaces are set as V1 to VM (M is an integer) starting from the side close to the incident surface 140. In addition, the interval between the emission reflective surfaces is set as H1 to HM-1 starting from the side close to the incident surface 140.

[0093] The image light within the first light guide plate 122 is gradually reflected by a portion of the reflective surfaces of the emission reflective surface group 133. The light intensity decreases as it propels internally, and finally, the entire image light is output to the second light guide plate 123 via the final surface RN of the emission reflective surface group 133, thereby improving efficiency. Therefore, the reflectivity of the emission reflective surfaces of the emission reflective surface group 133 gradually increases from the side closest to the incident surface towards the final surface RN, thereby improving the uniformity of the image light intensity within the eye chamber.

[0094] To maintain transparency as an HMD, the reflectivity of the emission reflective surface group 143 of the second light guide plate is lower than that of the emission reflective surface group 133. Because of the low reflectivity, even if all the emission reflective surface groups 143 have the same reflectivity (the same reflective film), it will not be a major cause of large brightness unevenness. Instead, it can be processed in the same film deposition process, reducing manufacturing costs. In particular, from the viewpoint of ensuring brightness uniformity and transparency, it is preferable that the reflectivity of the emission reflective surface group 143 of the second light guide plate is 10% or less.

[0095] On the other hand, if the reflectivity is increased in order to prioritize light utilization efficiency over transparency, the reflective film of the emitted reflective surface group 143 can be a film whose reflectivity gradually increases from the side close to the incident surface, thereby improving the uniformity of the amount of image light in the eye chamber and thus improving the image quality.

[0096] When the surface spacing L1 to LN-1 of the emission reflective surface group 133 of the first light guide plate 122 and the surface spacing H1 to HM-1 of the emission reflective surface group 143 of the second light guide plate 123 are wider than the light diameter P of the projection section 121, the overlap between adjacent replicated image lights becomes insufficient, resulting in an eyebox with low image light intensity. Therefore, by making the surface spacing L1 to LN-1 of the emission reflective surface group 133 and the surface spacing H1 to HM-1 of the emission reflective surface group 143 of the second light guide plate 123 smaller than the light diameter P of the projection section 121, the brightness uniformity within the eyebox and the visual recognition image is improved.

[0097] Next, use Figure 9A , Figure 9B The detailed geometric conditions for the tilt angle θ of the ejector reflecting surface and the critical angle of total internal reflection are explained. Relative to the principal surfaces 131 and 132, which are parallel planes, the ejector reflecting surface assembly 133 has a predetermined tilt angle θ to change its direction in order to guide the image light out of the light guide plate. Figure 9A In the diagram, solid line A represents the ray at the center of the viewing angle, while single-dotted and double-dotted lines B and C represent rays at the ends of the viewing angle. Ray A at the center of the viewing angle, after reflection from incident surface 130, travels at an incident angle of 2θ relative to the parallel principal surfaces 131 and 132. Furthermore, considering refraction at incident surface 130, the incident angles of rays B and C within the light guide plate relative to principal surfaces 131 and 132 are in the range of 2θ ± arcsin[sin(Φ / 2) / n]. From the perspective of avoiding stray light, ray B needs to satisfy...

[0098] 2θ+arcsin[sin(Φ / 2) / n]<90°Equation (2).

[0099] In addition, in order to satisfy the condition of total internal reflection, the ray C needs to satisfy...

[0100] 2θ-arcsin[sin(Φ / 2) / n]<arcsin[1 / n], Equation (3).

[0101] n is the refractive index of the substrate. Usually, the refractive index n is about 1.5 - 2.0. When displaying an image with a viewing angle Φ of about 20 - 50°, the tilt angle θ of the incident surface 130 and the outgoing reflection surface group 133 is in the range of 20° - 40°.

[0102] The same conditions need to be satisfied in the second light guide plate. The tilt angle θ of the incident surface 140 and the outgoing reflection surface group 143 is in the range of 20° - 40°.

[0103] Figure 9B It is a schematic diagram showing the incidence and reflection of light on the reflection surfaces in the first light guide plate 122 and the second light guide plate 123. In Figure 9B In it, the image light with a predetermined viewing angle in the first light guide plate 122 and the second light guide plate 123 is incident on the outgoing surface group at a predetermined angle range and output outside the light guide plate (normal reflection). On the other hand, since the light is enclosed in the light guide plate, a state of reflected light generated by the incidence from the back of the outgoing reflection surface groups 133 and 143 (back reflection) occurs. This back reflection is an unnecessary reflection and is the main cause of stray light generation and efficiency reduction.

[0104] From a geometric configuration perspective, regarding the range of the incident angle with respect to the reflection surfaces of the outgoing reflection surface groups 133 and 143, the normal reflection is θ±arcsin[sin(Φ / 2) / n], and the back reflection is 3θ±arcsin[sin(Φ / 2) / n]. Usually, there is a refractive index difference between the reflection film forming the partial reflection surface and the light guide plate glass material. Therefore, the back reflection increases rapidly as the incident angle θb approaches 90 degrees. Therefore, it is necessary to make θb less than 90 degrees, preferably less than 86 degrees, and more preferably less than 83 degrees for all image lights. Therefore, at least the following Equation (4) needs to be satisfied:

[0105] 3θ+arcsin[sin(Φ / 2) / n]<90°, Equation (4).

[0106] Next, the transparency of the second light guide plate 123 will be described. In Figure 8B In it, the light ray 400 represents the light from the outside that enters the pupil 20 through the outgoing reflection surface group 143 of the second light guide plate 123. As an example, an example of the light ray 400 from the outside entering the outgoing reflection surface V1 of the outgoing reflection surface group 143 is shown.

[0107] The light 400 from the outside is divided into two paths: one that passes through the outgoing reflecting surface V1 to the pupil 20, and the other that is reflected by the outgoing reflecting surface V1 and then by the adjacent outgoing reflecting surface V2 to reach the pupil 20. The amount of light passing through the outgoing reflecting surface V1 to reach the pupil is set as I1, and the amount of light reflected by the adjacent outgoing reflecting surface V2 to reach the pupil 20 is set as I2.

[0108] When the light amounts I1 and I2 are equal, the external light is split by the reflective surface group 143, thus creating a problem for the user of seeing the outside world twice. Therefore, the light amount of I2 needs to be significantly less than the light amount of I1. Let the light amount of the external ray 400 be I0, the reflectivity of the reflecting surface V1 be r1, and the reflectivity of the reflecting surface V2 be r2, then I1 = (1 - r1) × I0, and I2 = r1 × r2 × I0. If the contrast C of the split light is defined as C = I1 / I2, then C = (1 - r1) / r1 × r2.

[0109] To prevent users from seeing a double image, it is preferable that the light intensity of I2 is less than 1 / 100 of I1, and more preferably less than 1 / 150. That is, it is preferable that the contrast ratio C is 100 or higher, and more preferably 150 or higher.

[0110] Consider a scenario where all the ejector reflective surface groups 143 are made of the same film, allowing for processing in the same film-forming step and thus reducing manufacturing costs. In this case, the reflectivity of all the ejector reflective surface groups 143 is equal, and its reflectivity is set as r. The contrast ratio is C = (1 - r) / r^2. From the viewpoint of visual recognizability of the double image described above, it is preferable that the contrast ratio C is 100 or more, more preferably 150 or more, and therefore it is preferable that the reflectivity r is 10% or less, more preferably 8% or less.

[0111] As described above, according to this embodiment, an HMD using a light guide plate can be provided, which can achieve thinness, small size and light weight, and can display images with a wider viewing angle and can display images without color unevenness.

[0112] [Example 2]

[0113] Figure 10 This is a structural diagram of the light guide plate in this embodiment. Figure 10 In the middle, to and Figure 4 The same structures are labeled with the same reference numerals, and their descriptions are omitted. Figure 10 In, with Figure 4 The difference is that the incident surface 140 of the second light guide plate 123 is composed of multiple input reflective surfaces.

[0114] exist Figure 10The illustration shows, as an example, the light path from the emission reflective surface of the first light guide plate 122 (away from the incident surface 130) to the second light guide plate 123 and propagating to the right side of the viewing angle of the pupil 20 at viewing positions 2 and 4. If the incident surface 140 of the second light guide plate 123, which couples the image light from the first light guide plate 122, does not have a predetermined width, it cannot receive the image light. Without a predetermined width, it is particularly difficult to receive the image light at viewing positions 2 and 4, resulting in problems such as the inability to display the image at viewing positions 2 and 4, or reduced brightness at those locations. This problem becomes particularly significant when a wide viewing angle is desired.

[0115] However, when the light guide plate is thickened to increase the area of ​​the incident surface 140 of the second light guide plate, the interval of total internal reflection of the image light inside becomes wider, and the emission interval of the replicated image light also becomes wider, resulting in uneven brightness. In addition, the increased thickness also leads to an increase in weight and manufacturing cost.

[0116] Therefore, as a method to improve the coupling efficiency of image light from the first light guide plate 122 without increasing the thickness of the second light guide plate 123, a method is provided in which the incident surface 140 is composed of multiple reflective surfaces. By providing multiple incident surfaces, the area of ​​the effective incident surface can be increased without increasing the thickness.

[0117] Figure 11 The light guide plate of this embodiment is illustrated from the horizontal direction along the X-axis. Figure 11 In this light guide plate 123, the incident surface 140 is composed of four input reflective surfaces, which are set as C0 to C3 starting from the side away from the output reflective surface group 143 (output section). In addition, the interval between the input reflective surfaces is set as W1 to W3 starting from the side away from the output reflective surface group 143 (output section).

[0118] To maintain the image quality, it is preferable that multiple input reflective surfaces C0 to C3 are parallel.

[0119] Furthermore, the image light reflected from the input reflective surface C0 needs to pass through the input reflective surfaces C1, C2, and C3. Therefore, in order to improve the coupling efficiency of the image light from the first light guide plate 122, the input reflective surface C0 can be made to have a high reflectivity close to 100%.

[0120] Furthermore, the closer the multiple input reflective surfaces C0 to C3 are to the output reflective surface group 143 (output section) of the second light guide plate 123, the lower the reflectivity. As a result, the unevenness of image brightness generated when the image light from the first light guide plate 122 is coupled to the second light guide plate can be reduced.

[0121] Furthermore, the color unevenness caused by absorption by the second light guide plate 123 can be reduced by utilizing the wavelength dependence of the reflectivity of multiple input reflective surfaces. Figure 11 In the diagram, arrow 500 represents the light path from the lower side of the viewing angle to the pupil 20, and dashed arrow 501 represents the light path from the upper side of the viewing angle to the pupil 20. Additionally, arrow 502 represents the light path from the lower side of the viewing angle when the light couples from the first light guide plate 122 to the second light guide plate 123, and dashed arrow 503 represents the light path from the lower side of the viewing angle when the light couples from the first light guide plate 122 to the second light guide plate 123.

[0122] like Figure 11 As shown, the light path propagating in the second light guide plate is longer on the lower side of the viewing angle compared to the upper side. Therefore, the image light on the lower side of the viewing angle is greatly affected by the absorption of the blue wavelength region by the glass material of the light guide plate, resulting in reduced emission efficiency on the blue wavelength side and causing color unevenness.

[0123] When the image light from the lower side of the viewing angle couples from the first light guide plate and the second light guide plate, it couples with the input reflection surface furthest from the output reflection surface group 143 (output section) among the multiple input reflection surfaces. Therefore, if at least the input reflection surface furthest from the output reflection surface group 143 (output section) among the multiple input reflection surfaces (in...) Figure 11 If the reflectivity of the blue wavelength region (C0) is higher than that of the green and red wavelength regions, then the emission efficiency of the blue wavelength side of the image light from the lower viewpoint is improved, which can reduce color unevenness.

[0124] More preferably, in the input reflective surface of the second light guide plate that is furthest from the output section, the reflectivity of the blue wavelength region is higher than that of the green and red wavelength regions compared to the previous input reflective surface, thereby improving color uniformity over a wider viewing angle.

[0125] Furthermore, when the reflectivity of the blue wavelength region is higher than that of the green and red wavelength regions among two or more input reflective surfaces, the color unevenness that increases with light propagation can be improved by setting the ratio of the reflectivity of the blue wavelength region to that of the red wavelength region, i.e., (reflectivity of the blue wavelength region) / (reflectivity of the red wavelength region), to be larger the further away the input reflective surface is from the output.

[0126] Furthermore, when the intervals W1 to W3 between adjacent reflective surfaces of the multiple input reflective surfaces are wider than the light diameter P of the projection section 121, the overlap between adjacent replicated image lights becomes insufficient, resulting in eyebox areas with low image light intensity. Therefore, by making the intervals W1 to W3 between adjacent reflective surfaces smaller than the light diameter P of the projection section 121, the brightness uniformity within the eyebox and the visual recognition image is improved.

[0127] As described above, according to the structure shown in this embodiment, even when wide-viewing-angle image light is incident, it is possible to suppress the increase in the size of the light guide plate and expand the eyebox to display high-quality images.

[0128] This explains the structure using an ejector reflective surface assembly for the first light guide plate 122 and the second light guide plate 123. However, the eyebox can also be enlarged by using light guide plates of different types. For example, Figure 12 This illustrates an example of a light guide plate that uses a diffraction grating or a volume hologram in the second light guide plate. Figure 12 In this design, an input section 146 is provided in the second light guide plate 123 to replace the incident surface 140. The input section 146 is a surface relief diffraction grating or a volume hologram, which deflects the direction of travel of the input image light and guides it into the interior of the light guide plate. Similarly, a surface relief diffraction grating or a volume hologram is formed in the output section 147, which deflects a portion of the image light propagating within the light guide plate toward the pupil 20, thereby achieving image display while magnifying the eye chamber. The surface relief diffraction grating or volume hologram of the output section 147 is designed to reduce diffraction efficiency to external light, thus giving the second light guide plate transparency.

[0129] [Example 3]

[0130] In this embodiment, an application example of HMD described in Embodiments 1 and 2 above will be explained. Figure 13 This illustrates an example of HMD usage in this embodiment.

[0131] exist Figure 13 In the image (virtual image) display area 111 from HMD1, content is displayed within the user 2's field of view. For example, it displays work procedure sheets 301 and attached drawings 302 for tasks such as inspecting and assembling industrial equipment. Since the image display area 111 is limited, displaying both work procedure sheets 301 and attached drawings 302 simultaneously results in small content and poor visual recognition. Therefore, head tracking is performed using an accelerometer to detect the user 2's head orientation, and the displayed content is adjusted according to the head orientation, thereby improving visual recognition. That is, in Figure 13 In the image display area 111, the work procedure book 301 is displayed when the user 2 is facing left. If the user is facing right, the attached drawing 302 is displayed in the image display area 111, as if there were an imaginary image display area 112 that could visually recognize the work procedure book 301 and the attached drawing 302 with a wide field of view.

[0132] This improves visual recognition, and allows user 2 to perform the task while simultaneously visually recognizing the work object (equipment, tools, etc.) and the work instructions, thus enabling more reliable work and reducing errors.

[0133] Figure 14 This is a functional block diagram of the HMD in this embodiment. Figure 14 In this document, structures identical to those in Figure 1 are labeled with the same reference numerals, and their descriptions are omitted. Figure 14 The difference from Figure 1 is that a head tracking function has been added. That is, a head tracking unit 103H is provided in the image signal processing unit 103A of HMD1. The head tracking unit 103H detects the orientation of the user 2's head based on the information from the accelerometer 106H of the sensing unit 106A, and changes the displayed content according to the orientation of the head.

[0134] Furthermore, HMDs are used both indoors and outdoors. Therefore, the brightness of the displayed image needs to be adjusted according to the brightness of the surrounding environment. As an example, an illuminance sensor 106M is installed in the sensing unit 106A, and the brightness of the image displayed by the image signal processing unit 103A can be adjusted according to the output of the illuminance sensor.

[0135] The embodiments described above illustrate that the present invention provides an HMD that achieves thinness, miniaturization, and lightweight design, and can display images with a wider viewing angle and without color unevenness, while suppressing the amount of processing materials. Therefore, it can reduce carbon emissions, prevent global warming, and contribute to achieving the SDGs (Sustainable Development Goals), particularly Project 7, in terms of energy.

[0136] Furthermore, the present invention is not limited to the above embodiments, but includes various modifications. For example, for ease of understanding, the functional structures of the HMD and the virtual image generation unit described above are categorized according to the main processing content. The present invention is not limited to the classification method and names of the constituent elements. The structures of the HMD and the virtual image generation unit can be categorized into more constituent elements according to the processing content. Alternatively, they can be categorized into one constituent element to perform more processing.

[0137] Furthermore, the present invention can be applied not only to HMDs, but also to other image (virtual image) display devices with structures having virtual image generation units as described in the various embodiments.

[0138] Furthermore, a portion of the structure in one embodiment can be replaced with a structure from another embodiment. Additionally, structures from other embodiments can be added to the structure of one embodiment. Furthermore, for a portion of the structure in each embodiment, other structures can be added, deleted, or replaced.

[0139] Explanation of reference numerals in the attached figures

[0140] 1: Head-mounted display (HMD), 101: Virtual image generation unit, 102: Control unit, 103: Image signal processing unit, 104: Power supply unit, 105: Storage unit, 106: Sensing unit, 107: Communication unit, 108: Voice processing unit, 109: Camera unit, 91-93: Input / output unit, 111: Image display area, 112: Virtual image display area, 120: Image display unit, 121: Projection unit, 122: First light guide plate, 123: Second light guide plate, 131, 132, 141, 142: Main surface, 130, 140: Incident surface, 133, 143: Emitting reflective surface group, 146: Input unit, 147: Output unit, 103H: Head tracking unit, 106H: Accelerometer sensor.

Claims

1. A head-mounted display that displays images within a user's field of vision, characterized in that, have: An image display unit that generates the image to be displayed; and The first light guide plate and the second light guide plate replicate the image light from the image display unit. The first light guide plate and the second light guide plate each have a set of parallel main surfaces that block the image light through internal total internal reflection. The first light guide plate has an incident surface that reflects image light inward and two or more exiting reflective surfaces that emit image light into the second light guide plate. The second light guide plate has an input section that couples image light from the first light guide plate inward and an output section that emits image light into the user's pupil. In the emission reflective surface of the first light guide plate that is farthest from the incident surface, the reflectivity of the blue wavelength region is higher than that of the green wavelength region and the red wavelength region.

2. The head-mounted display according to claim 1, characterized in that, In the emitted reflective surface where the reflectivity in the blue wavelength region is higher than that in the green and red wavelength regions, the reflectivity in the blue wavelength region is in the range of 1.0 to 2.0 times that in the red wavelength region.

3. The head-mounted display according to claim 1, characterized in that, In the two or more emission reflective surfaces of the first light guide plate, the reflectivity of the blue wavelength region is higher than that of the green wavelength region and the red wavelength region.

4. The head-mounted display according to claim 1, characterized in that, Among the two or more emission reflective surfaces of the first light guide plate, the farther away from the incident surface, the greater the ratio of reflectivity of the blue wavelength region to reflectivity of the red wavelength region becomes.

5. The head-mounted display according to claim 1, characterized in that, In the emitted reflective surface where the reflectivity in the blue wavelength region is higher than that in the green and red wavelength regions, the reflectivity of the emitted reflective surface exhibits a wavelength dependence of reflectivity in the blue wavelength region > reflectivity in the green wavelength region > reflectivity in the red wavelength region.

6. The head-mounted display according to claim 1, characterized in that, The head-mounted display has a projection section that amplifies the image light from the image display section and projects it onto the first light guide plate. The surface spacing between two or more emission reflective surfaces of the first light guide plate is smaller than the light diameter of the projection part.

7. The head-mounted display according to claim 1, characterized in that, The incident surface and the emitted reflective surface of the first light guide plate are parallel to each other and at an angle different from the main surface.

8. The head-mounted display according to claim 1, characterized in that, The angle of inclination of the emission reflective surface of the first light guide plate relative to the main surface is a predetermined angle θ. The angle θ is in the range of 20° to 40°.

9. The head-mounted display according to claim 1, characterized in that, The farther away from the incident surface, the higher the reflectivity of the two or more outgoing reflective surfaces of the first light guide plate.

10. The head-mounted display according to claim 1, characterized in that, The output section of the second light guide plate has two or more partially reflective surfaces.

11. The head-mounted display according to claim 10, characterized in that, The reflectivity of the partially reflective surface is less than 10%.

12. The head-mounted display according to claim 1, characterized in that, The input section of the second light guide plate has two or more input reflective surfaces.

13. The head-mounted display according to claim 12, characterized in that, The closer to the output section of the second light guide plate, the lower the reflectivity of the two or more input reflective surfaces becomes.

14. The head-mounted display according to claim 12, characterized in that, Among the two or more input reflective surfaces that are furthest from the output section, the reflectivity of the blue wavelength region is higher than that of the green wavelength region and the red wavelength region.

15. The head-mounted display according to claim 1, characterized in that, The second light guide plate is a light guide plate equipped with a diffraction grating or a volume hologram.

16. The head-mounted display according to claim 1, characterized in that, The head-mounted display includes: The power supply department supplies electricity; The sensing unit detects the user's position and posture; The speech processing unit is responsible for inputting or outputting speech signals. as well as The control unit controls the power supply unit, the sensing unit, and the voice processing unit.

17. The head-mounted display according to claim 1, characterized in that, The head-mounted display includes: An accelerometer sensor detects the movement of the user's head; A head tracking unit that changes the displayed content based on the movement of the user's head detected by the accelerometer; The power supply department supplies electricity; The speech processing unit is responsible for inputting or outputting speech signals. as well as The control unit controls the acceleration sensor, the head tracking unit, the power supply unit, and the voice processing unit.

Images