Wide-field, lightweight head-mounted display device

Abstract

A wide-field-of-view, lightweight head-mounted display device comprises a display image source (1) having a linear polarizing film on the light-emitting side; a first imaging prism unit (2) including a film system unit and a first prism, the film system unit including a polarizing reflective unit and attached to the side of the first prism away from the first imaging lens unit (4); a second imaging prism unit (3) including a second prism and installed in close proximity to the film system unit; a first imaging lens unit (4) with a semi-transparent, semi-reflective film attached to the side away from the first imaging prism unit (2); and a polarization conversion unit located between the first imaging prism unit (2) and the first imaging lens unit (4), or installed between the polarizing reflective unit and the second imaging prism unit (3). Furthermore, the thicknesses of the linear polarizing film, film system unit, polarization conversion unit, and semi-transparent, semi-reflective film are rationally set. The head-mounted display device increases the field of view, achieves a lightweight and thin design, guarantees image quality, and has a refractive index adjustment function.

Description

Technical Field

[0001] (Cross-Reference to Related Applications) This application claims the priority benefit of Chinese Patent Application No. 2023108677 79.6 filed with the China National Intellectual Property Administration on July 14, 2023, the entire content of which is incorporated into this application by reference.

[0002] The present application belongs to the field of near-eye display technology, and specifically relates to a wide-field light-weight head-mounted display device.

Background Art

[0003] As the application of AR products in the field of augmented reality becomes increasingly widespread, the corresponding technologies have also been continuously developed. AR products are attracting more and more attention from the public and are expected to become the next generation of mobile terminals replacing smartphones. In recent years, augmented reality (Augmented Reality, AR) technology has been applied to smart wearable devices and has developed rapidly. The core component of augmented reality technology is the optical module, and the field of view (FOV), thickness and display effect of the optical module directly determine the quality of smart wearable devices. In particular, achieving a wide field of view (FOV), light weight and thin profile while maintaining excellent image quality has become the main factor restricting the development of AR technology.

[0004] In conventional AR (augmented reality) solutions, the Birdbath method is a mass-producible method that can achieve relatively good image quality, but its thickness of 18mm to 20mm makes it difficult to meet people's everyday wearing needs. Furthermore, the configuration of lightweight and thin optical waveguides is not yet mature and cannot provide excellent imaging effects and a relatively wide field of view. Achieving a wide field of view (FOV) requires increasing the size of the structure, making it impossible to achieve both a wide field of view and a small size, and also resulting in relatively serious color shift and light efficiency problems. Therefore, there is an urgent need to realize a solution that enables lightweight and thin smart wearable devices while achieving relatively good imaging effects. [Disclosure of the Invention]

[0005] In view of the above issues, the object of this application is to provide a wide-field, lightweight head-mounted display device that increases the field of view, achieves a lightweight and thin design, guarantees image quality, and includes a refractive index adjustment function.

[0006] To achieve the above objective, the technical configuration used in this application is as follows.

[0007] This application discloses a wide-field, lightweight head-mounted display device comprising a display image source, a first imaging prism unit, a second imaging prism unit, a first imaging lens unit, and a polarization conversion unit. Of these, The display image source has a linear polarizing film on the light emission side. The first imaging prism unit includes a film system unit and a first prism, the film system unit includes a polarizing reflective unit and is attached to the side of the first prism that is away from the first imaging lens unit. The second imaging prism unit includes a second prism and is installed in close proximity to the membrane unit. The first imaging lens unit has a semi-transparent, semi-reflective coating attached to the side away from the first imaging prism unit. The polarization conversion unit is located between the first imaging prism unit and the first imaging lens unit, or installed between the polarization reflection unit and the first imaging prism unit. The thickness of the linear polarizing film is 60nm to 250nm, the thickness of the film system unit is 90nm to 280nm, the thickness of the polarization conversion unit is 30nm to 100nm, and the thickness of the semi-transparent, semi-reflective film is 50nm to 300nm. The imaging light emitted from the display image source is converted into linearly polarized light by a linearly polarizing film. The linearly polarized light enters the first imaging prism unit, undergoes total internal reflection, reaches the film system unit, is reflected by the film system unit, reaches the first imaging lens unit, is reflected by the first imaging lens unit, reaches the first imaging prism unit, and then passes through the film system unit and the second imaging prism unit in sequence to reach the human eye, where an image is formed.

[0008] Preferably, the polarization conversion unit is a quarter-wave plate, and the angle between the reflection axis of the film system unit and the slow axis of the polarization conversion unit is 45°±1°.

[0009] Preferably, each prism is a triangular prism, and the polarizing reflection unit is a polarizing reflection film.

[0010] Preferably, the film system unit further comprises a polarization absorption unit, the polarization absorption unit being a polarization absorption film, and further located between a polarization reflection unit and a second imaging prism unit, and the absorption axis of the polarization absorption unit is parallel to the reflection axis of the polarization reflection unit.

[0011] Preferably, the display image source moves relative to the first imaging prism unit, and the movement distance is less than 5 mm.

[0012] Preferably, the angle between the direction in which the display image source moves relative to the first imaging prism unit and the optical axis direction of the display image source is 0° to 15°.

[0013] Preferably, the wide-field, lightweight head-mounted display device further includes a second imaging lens unit, the second imaging lens unit being located on the light-emitting side of the display image source, and linearly polarized light passing through the second imaging lens unit into the first imaging prism unit.

[0014] Preferably, the focal length of the second imaging lens unit is 5mm to 50mm.

[0015] Preferably, the display image source and the second imaging lens unit move in synchronization with the first imaging prism unit, and the movement distance is less than 4 mm.

[0016] Preferably, the angle between the direction in which the display image source and the second imaging lens unit move synchronously with respect to the first imaging prism unit and the optical axis direction of the display image source is 0° to 10°.

[0017] Preferably, a polarizing plate is provided on the side of the second imaging prism unit closest to the human eye, and the thickness of the polarizing plate is 60 nm to 250 nm.

[0018] Preferably, each imaging lens unit comprises at least one lens.

[0019] Preferably, the surface shape of each lens is any combination of a spherical surface, an aspherical surface, a free-form surface, a Fresnel surface, and a plane.

[0020] Preferably, the first imaging lens unit is a curved lens.

[0021] Preferably, the aspherical surface satisfies the following equation.

[0022]

number

[0023] In the formula, z is the vector height, Y is the lens center height, k is the conicity coefficient, C is the curvature, and a irepresents the i-th aspheric coefficient, and N is a positive integer.

[0024] Preferably, the display image source is any one of an organic light emitting diode display, a liquid crystal on silicon display, a micro light emitting diode display, a digital light processing display, and a laser beam scanning display.

[0025] Compared with the prior art, the beneficial effects of the present application are as follows.

[0026] The wide-field lightweight head-mounted display device adopts an optical path folding (pancake) scheme. A foldable optical element composed of a first imaging prism unit, a second imaging prism unit, and a first imaging lens unit realizes a multiple-folding optical path by utilizing the principles of light refraction, reflection and polarization and increasing the number of reflections between optical elements (prisms and lenses). This shortens the optical path length, increases the field of view (FOV), ensures imaging quality while maintaining light weight and thinness, and also has a diopter adjustment function. For example, the FOV is increased from 48° of the conventional Birdbath scheme to 60° or more, and the thickness is reduced to half of that of the conventional Birdbath scheme which is 18mm to 20mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] [Figure 1] It is a structural schematic diagram of the wide-field lightweight head-mounted display device according to Embodiment 1 of the present application. [Figure 2] It is a schematic diagram of diopter adjustment of the wide-field lightweight head-mounted display device according to Embodiment 1 of the present application. [Figure 3] It is an MTF curve diagram at a diopter of 0D in Embodiment 1 of the present application. [Figure 4] It is an MTF curve diagram at a diopter of 6D in Embodiment 1 of the present application. [Figure 5] It is an MTF curve diagram at a diopter of 0D in Embodiment 2 of the present application. [Figure 6] This is an MTF curve diagram for a refractive error of 6D in Embodiment 2 of this application. [Figure 7] This is an MTF curve diagram at refractive error 0D in Embodiment 3 of this application. [Figure 8] This is an MTF curve diagram for a refractive error of 6D in Embodiment 3 of this application. [Figure 9] This is an MTF curve diagram at refractive error 0D in Embodiment 4 of this application. [Figure 10] This is an MTF curve diagram for a refractive error of 6D in Embodiment 4 of this application. [Figure 11] This is an MTF curve diagram at refractive error 0D in Example 5 of this application. [Figure 12] This is an MTF curve diagram for a refractive error of 6D in Embodiment 5 of this application.

[0028] (Explanation of symbols) 1. Image source for display; 2. First imaging prism unit; 3. Second imaging prism unit; 4. First imaging lens unit; 5. Second imaging lens unit; 6. Human eye. [Modes for carrying out the invention]

[0029] The technical configurations in the embodiments of this application will be described clearly and completely below with reference to the drawings of the embodiments. It will be clear that the embodiments described are only a part of the embodiments of this application, not all of them. All other embodiments that a person skilled in the art could obtain without creative work based on the embodiments of this application are within the scope of protection of this application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art. The terms used herein are for illustrative purposes only and do not limit this application.

[0031] As shown in Figures 1 and 2, the wide-field lightweight head-mounted display device comprises a display image source 1, a first imaging prism unit 2, a second imaging prism unit 3, a first imaging lens unit 4, and a polarization conversion unit, among which,

[0032] The display image source 1 has a linear polarizing film on its light-emitting side.

[0033] The first imaging prism unit 2 includes a film system unit and a first prism. The film system unit has a polarizing reflective unit and is attached to the side of the first prism that is away from the first imaging lens unit 4.

[0034] The second imaging prism unit 3 is equipped with a second prism and is installed in close proximity to the membrane unit.

[0035] The first imaging lens unit 4 has a semi-transparent, semi-reflective film attached to the side that is away from the first imaging prism unit 2.

[0036] The polarization conversion unit is installed between the first imaging prism unit 2 and the first imaging lens unit 4, or between the polarization reflection unit and the first imaging prism unit 2.

[0037] The thickness of the linear polarizing film is 60 nm to 250 nm, the thickness of the film system unit is 90 nm to 280 nm, the thickness of the polarization conversion unit is 30 nm to 100 nm, and the thickness of the semi-transparent, semi-reflective film is 50 nm to 300 nm.

[0038] The imaging light emitted from the display image source 1 is converted into linearly polarized light by a linearly polarizing film. The linearly polarized light enters the first imaging prism unit 2, undergoes total internal reflection and reaches the film system unit, is reflected again by the film system unit and reaches the first imaging lens unit 4. Furthermore, it is reflected again by the first imaging lens unit 4 and returns to the first imaging prism unit 2, and then passes through the film system unit and the second imaging prism unit 3 in sequence to reach the human eye 6 and form an image.

[0039] Of these, the display image source 1 is used to provide an image screen. The first imaging prism unit 2 comprises a first prism and a film system unit having a light modulation function. The first prism can be made of plastic or glass. The film system unit can be attached to the first prism or coated on the first prism. The film system unit performs a light polarization reflection function. The second imaging prism unit 3 includes a second prism and is installed in close proximity to the film system unit; for example, the second imaging prism unit 3 is installed between the first imaging prism unit 2 and the human eye 6. The polarization conversion unit can be installed between the first imaging prism unit 2 and the first imaging lens unit 4, or between the polarization reflection unit and the first imaging prism unit 2, and can be installed according to the actual needs.

[0040] The first imaging lens unit 4 is a group of lenses equipped with aberration correction and optical path reflection functions. The material of the lens group can be glass or plastic, and examples of types include, but are not limited to, spherical lenses, aspherical lenses, free-form lenses, Fresnel lenses, and flat lenses. Spherical lenses are preferred. For example, the first imaging lens unit 4 is a curved lens, and a semi-transparent, semi-reflective coating is provided on the inside of the curved lens (the side away from the first imaging prism unit 2). This semi-transparent, semi-reflective coating can be realized by a coating method or a film bonding method.

[0041] Furthermore, by rationally setting the thickness of the linear polarizing film, film system unit, polarization conversion unit, and semi-transparent / semi-reflective film, the transmission and reflection effects are guaranteed, as is the feasibility of the film material process, resulting in a good balance between image quality and reliability. Specifically,

[0042] 1) If the linear polarizing film is too thin, problems such as unstable optical performance, reduced polarization effect, and inability to mold can occur. Furthermore, it becomes more susceptible to external environmental influences such as mechanical damage and chemical corrosion, leading to reduced durability. If the linear polarizing film is too thick, the reflectivity increases, leading to increased light loss and affecting the polarization effect, resulting in reduced optical performance and an increased risk of ghosting.

[0043] 2) The polarizing reflective unit of a film system is a film material that reflects light by utilizing its polarization properties. If the polarizing reflective unit material is too thin, the following problems occur: 1. It becomes difficult to mold and is more brittle and easily deformed, affecting the polarization effect. 2. Reduced durability: If the polarizing reflective unit material is too thin, it becomes relatively brittle and easily damaged by abrasion and scratches. If the polarizing reflective unit material is too thick, it leads to a decrease in optical performance, with reduced transmittance and polarization rate, which affects the application effect in the optical device and makes ghost images more likely to occur.

[0044] 3) Polarization conversion units (e.g., quarter-wave plates) are optical elements used to adjust the polarization state of light and change its phase. If they are too thin, they become difficult to mold and prone to brittle fracture. If they are too thick, they cause changes in the optical path difference. Therefore, the thickness of the polarization conversion unit is designed according to the wavelength. If it is too thick, the change in optical path difference exceeds the design value, which affects its ability to adjust the polarization state and phase of light.

[0045] 4) When using vapor deposition to create a semi-transparent, semi-reflective film, if the film is too thin, deposition is not possible, and thickness uniformity cannot be guaranteed. If it is too thick, there is a risk of the film layer peeling off. Whether it is too thin or too thick, it becomes difficult to guarantee imaging effect and stability.

[0046] This head-mounted display device achieves an expanded field of view (FOV) and a lightweight, thin design through three reflections and multiple optical path folding. Specifically, the first reflection utilizes total internal reflection in air (i.e., an air gap exists between the first imaging prism unit 2 and the first imaging lens unit 4, and since the refractive index of air is lower than that of the first imaging prism unit 2 and the first imaging lens unit 4, the imaging light is totally reflected at the surface of the first imaging prism unit 2 closest to the first imaging lens unit 4). The second reflection occurs when linearly polarized light converted by a linearly polarizing film is incident on a film system unit and reflected. The third reflection occurs when light is reflected by a semi-transparent, semi-reflective film. For example, the field of view (FOV) has increased from 48° in the conventional Birdbath system to over 60°, and the thickness has been reduced to half of the 18mm-20mm of the conventional Birdbath system.

[0047] In one embodiment, the polarization conversion unit is a quarter-wave plate, and the angle between the reflection axis of the film system unit and the retard axis of the polarization conversion unit is 45° ± 1°. To ensure image quality, the film system unit and the polarization conversion unit have a certain angular relationship. The retard axis of the polarization conversion unit must be attached at an angle of 45° with respect to the reflection axis of the film system unit, with a tolerance of ±1°. This ensures that linearly polarized light is converted to standard circularly polarized light.

[0048] In one embodiment, each prism is a triangular prism, and the polarizing reflection unit is a polarizing reflection film.

[0049] In one embodiment, the film system unit further comprises a polarization absorption unit, which is a polarization absorption film, located between the polarization reflection unit and the second imaging prism unit 3, and the absorption axis of the polarization absorption unit is parallel to the reflection axis of the polarization reflection unit. The reflection axis of the polarization reflection unit (e.g., a polarization reflection film) and the absorption axis of the polarization absorption unit (e.g., a polarization absorption film) must be parallel, which is advantageous for eliminating ghost images (double images). That is, the polarization conversion unit, the polarization reflection unit, and the polarization absorption unit are arranged in order along the direction closest to the human eye 6.

[0050] In one embodiment, the display image source 1 moves relative to the first imaging prism unit 2, and the distance of this movement is less than 5 mm. This makes it possible to adjust the refractive index from 0 D to 6 D.

[0051] In one embodiment, the angle between the direction in which the display image source 1 moves relative to the first imaging prism unit 2 and the optical axis direction of the display image source 1 is 0° to 15°. The optical axis direction of the display image source 1 is perpendicular to the screen light-emitting surface of the display image source 1.

[0052] In actual use, it is preferable to set this angle to 0° for ease of processing, shaping, and assembly. However, in this case, if the display image source 1 is too large, when the display image source 1 moves to the edge of its range of motion, the display content at the edge of the light-emitting surface of the display image source 1 may not be properly incident on and guided to the first imaging prism unit 2 due to constraints such as the optical lens. As a result, the image that ultimately reaches the eye may be missing, misaligned, or significantly distorted.

[0053] Therefore, for the integrity of the final image and excellent image quality, it is preferable that the movement direction of the display image source 1 has a constant angle with respect to the optical axis. That is, during movement, there is a movement component parallel to the light-emitting surface of the display image source 1. As a result, the image light emitted from the display image source 1 can be normally incident on and guided to the first imaging prism unit 2 throughout the entire movement range, ensuring the integrity of the final image within the adjustment range of the refractive power, and making full use of the entire light-emitting surface of the display image source 1.

[0054] However, this angle must not be too large. When the display image source 1 moves, the movement component parallel to the light-emitting surface of the display image source 1 should be relatively small, and the main movement component of the display image source 1 should be in the direction of the optical axis. If this angle is too large, that is, when the display image source 1 moves, the movement component parallel to the light-emitting surface of the display image source 1 will be too large, and in order for all the imaging light emitted from the display image source 1 to enter the incident surface of the first imaging prism unit 2 over the entire refractive power adjustment range, the incident surface of the first imaging prism unit 2 would need to be very large, the overall volume of the device would also become very large, and the volume of the augmented reality device would also become relatively large, making it difficult to meet the requirements for lightweight and thin design. In addition, if the angle is too large, screen loss, positional shift, and significant distortion will also occur. Specifically, considering lightweight and thin design, image quality, and image integrity as a whole, this included angle is preferably 7°, which ensures lightweight and thin design while guaranteeing the integrity of the display screen and the display effect.

[0055] In one embodiment, the wide-field lightweight head-mounted display device further comprises a second imaging lens unit 5, which is installed on the light-emitting side of the display image source 1, and linearly polarized light is incident on the first imaging prism unit 2 via the second imaging lens unit 5.

[0056] In one embodiment, the focal length of the second imaging lens unit 5 is 5mm to 50mm. This is advantageous for improving image quality.

[0057] In one embodiment, the display image source 1 and the second imaging lens unit 5 move synchronously with respect to the first imaging prism unit 2, and the distance of this movement is less than 4 mm. This makes it possible to adjust the refractive power from 0D to 6D.

[0058] In one embodiment, the angle between the direction in which the display image source 1 and the second imaging lens unit 5 move synchronously with respect to the first imaging prism unit 2 and the optical axis direction of the display image source 1 is 0° to 10°. The optical axis direction of the display image source 1 is perpendicular to the direction of the light-emitting surface of the screen of the display image source 1.

[0059] In actual use, it is preferable to set this angle to 0° for ease of processing, molding, and assembly. However, in this case, if the display image source is too large, when the display image source 1 and the second imaging lens unit 5 move synchronously to the edge of the range, the display content at the edge of the light-emitting surface of the display image source 1 cannot be properly incident on and guided to the first imaging prism unit 2 due to constraints such as the optical lens. As a result, the image that ultimately reaches the eye may be missing, misaligned, or significantly distorted.

[0060] Therefore, in order to ensure the integrity of the final image and excellent image quality, the direction in which the display image source 1 and the second imaging lens unit 5 move synchronously can be set to exhibit a constant angle with respect to the optical axis of the display image source 1. That is, during movement, there is a movement component parallel to the light-emitting surface of the display image source 1. As a result, the image light emitted from the display image source 1 can be properly incident on and guided to the first imaging prism unit 2 throughout the entire range of movement, ensuring the integrity of the final image within the adjustment range of the refractive power, and making full use of the entire light-emitting surface of the display image source 1.

[0061] However, this angle should not be too large. When the display image source 1 moves, the movement component parallel to the light-emitting surface of the display image source 1 should be relatively small, and the main movement component of the display image source 1 should be along the optical axis. If this angle is too large, that is, when the display image source 1 moves, the movement component parallel to the light-emitting surface of the display image source 1 will be too large. In order to direct all the imaging light emitted from the display image source 1 onto the incident surface of the first imaging prism unit 2 across the entire refractive adjustment range, the incident surface of the first imaging prism unit 2 would need to be very large, the entire device would become very large, and the augmented reality device that uses this would also become large, making it difficult to meet the need for lightweight and thin designs. In addition, if the included angle is too large, screen loss, positional shifts, and significant distortion will occur.

[0062] Compared to the above configuration in which only the display image source 1 is moved, the addition of a second imaging lens unit 5 with a positive focal length restricts and converges the imaging light before it enters the first imaging prism unit 2. Therefore, both the required angle of entry and the amount of movement are smaller than in the method in which only the display image source 1 is moved. Furthermore, the display image source 1 and the second imaging lens unit 5 move synchronously. With this movement method, during the movement process, the angle at which light emitted from the same position of the display image source 1 passes through the second imaging lens unit 5 remains constant. In other words, the divergence of light emitted from the second imaging lens unit 5 remains constant at different refractive indices, resulting in a consistent final field of view (FOV) without significant reduction.

[0063] In one embodiment, the second imaging prism unit 3 is further provided with a polarizing plate on the side closer to the human eye, and the thickness of the polarizing plate is 60 nm to 250 nm.

[0064] If the second imaging lens unit 5 is not provided, the design offers high compatibility and excellent mass-producibility. By installing the second imaging lens unit 5, the imaging quality can be further improved. The second imaging lens unit can be in the form of a lens group, and a polarizing absorption film can be attached to the surface of the second imaging prism unit 3 closest to the eye in order to reduce the rainbow fringes generated by the second imaging lens unit 5. This suppresses the rainbow fringes. The principle is that by using linearly polarized light in the imaging direction, half of the stray light is reduced without affecting the image, and stray light contains components parallel and perpendicular to the linearly polarized light used for imaging.

[0065] For example, a polarizing plate may be attached to the surface of the second imaging prism unit 3 closest to the eye. The thickness of the polarizing plate is 60 nm to 250 nm. If the thickness is too thin, it is difficult to guarantee the desired effect even if the thin film is laminated. If the film thickness is too thick, light may be reflected inside the film, causing ghost images. Therefore, a thickness of 60 nm to 250 nm can guarantee the effect without causing other adverse effects and can eliminate stray light from the outside.

[0066] In one embodiment, each imaging lens unit includes at least one lens.

[0067] In one embodiment, the surface shape of each lens is any combination of a spherical, aspherical, free-form surface, Fresnel lens, and plane.

[0068] Each imaging lens unit is a series of lens groups having aberration correction functions. Each lens can be made of plastic or glass. The number of lenses in the lens group is not limited and includes, but is not limited to, spherical lenses, aspherical lenses, free-form lenses, Fresnel lenses, and flat lenses. Spherical lenses are preferred.

[0069] In one embodiment, the first imaging lens unit 4 is a curved lens.

[0070] In one embodiment, the aspherical surface satisfies the following equation.

[0071]

number

[0072] Here, z is the vector height, Y is the lens center height, k is the conicity coefficient, C is the curvature, and a i is the i-th order aspherical coefficient, and N is a positive integer.

[0073] In one embodiment, the display image source 1 is one of the following: an organic light-emitting diode (OLED) display, a liquid crystal on silicon (LCOS) display, a micro light-emitting diode (Micro LED) display, a digital light processing (DLP) display, or a laser beam scanning (LBS) display. The display image source 1 includes, but is not limited to, the above devices. Preferably, it is an OLED display.

[0074] The operating principle of this device is as follows: Imaging light emitted from the display image source 1 is converted to 45° linear polarization by a linear polarization film, then passes through the second imaging lens unit 5 and reaches the first imaging prism unit 2. A film system unit with optical path modulation functionality is attached to the side of the first imaging prism unit 2 closest to the second imaging prism unit 3. The 45° linear polarization is first totally reflected within the first imaging prism unit 2 and reaches the film system unit. There, the 45° linear polarization is reflected by the film system unit, and the -45° linear polarization is transmitted and reflected to the outer surface of the first imaging lens unit 4. A semi-transparent, semi-reflective film is provided on the first imaging lens unit 4, and the light is reflected back to the first imaging prism unit 2. At this time, the angle of linear polarization becomes -45°, and as shown in Figure 1, it is transmitted sequentially through the film system unit and the second imaging prism unit 3, and finally reaches the human eye 6 to form an image. Figure 2 shows a schematic diagram of the optical path and refractive adjustment (showing the synchronized movement of the display image source 1 and the second imaging lens unit 5).

[0075] The following will provide a detailed explanation using specific examples. In each table, OBJ represents the object plane, IMG represents the image plane, Stop represents the aperture, and Eye relief represents the eye relief (exit pupil distance). In the plane numbers, S2 and S3 both indicate prism planes on the second imaging prism unit 3 that are close to the human eye 6. S4, S5, S12, and S13 all indicate prism planes on the first imaging prism unit 2 that are close to the second imaging prism unit 3. S6, S7, S11, S14, and S15 all indicate prism planes on the first imaging prism unit 2 that are close to the first imaging lens unit 4. S8 and S10 both indicate lens planes on the first imaging lens unit 4 that are close to the first imaging prism unit 2. S9 indicates a lens plane on the first imaging lens unit 4 that is far from the first imaging prism unit 2. S16 and S17 both indicate prism planes on the first imaging prism unit 2 that are close to the second imaging lens unit 5. S18 and S19 both indicate the light-emitting surface of the second imaging lens unit 5. S20 indicates the light-ingress surface of the second imaging lens unit 5. The light-emitting side of the display image source 1 is a glass plate (surface number S21), and the reference plane is a sphere. [Examples]

[0076] In this embodiment, the device comprises a display image source 1, a first imaging prism unit 2, a second imaging prism unit 3, a first imaging lens unit 4, and a second imaging lens unit 5. A polarization conversion unit is installed between the first imaging prism unit 2 and the first imaging lens unit 4. The display image source 1 and the second imaging lens unit 5 can also be moved synchronously along the optical axis for refractive adjustment. The thicknesses of the linear polarizing film, film system unit, and polarization conversion unit are 120 nm, 200 nm, and 60 nm, respectively. The thickness of the semi-transparent, semi-reflective film is 100 nm. A polarizing plate is provided on the side of the second imaging prism unit 3 closest to the human eye, and the thickness of the polarizing plate is 120 nm. In this embodiment, the film thickness is preferably a value close to the center to achieve a good balance between image quality and reliability.

[0077] Table 1 Optical parameters at refractive index 0D in Example 1

[0078] [Table 1]

[0079] Table 2 Optical parameters at refractive index 6D in Example 1

[0080] [Table 2]

[0081] According to the optical parameters in Tables 1 and 2, the field of view (FOV) of the wide-field, lightweight head-mounted display device of this embodiment reaches 60°, and the thickness reaches 9.4 mm. Figures 3 and 4 show the corresponding modulation transfer function (MTF) curves when adjusted for refractive indices of 0D and 6D, respectively. In the figures, the MTF is greater than 0.1 at 10 lp / mm. This device belongs to the visual optical system, and when combined with the angular resolution of the human eye, this MTF index ensures that the human eye receives a very clear and sharp image, effectively guaranteeing a comfortable wearing experience. [Examples]

[0082] In this embodiment, the device comprises a display image source 1, a first imaging prism unit 2, a second imaging prism unit 3, a first imaging lens unit 4, and a second imaging lens unit 5. A polarization conversion unit is installed between the first imaging prism unit 2 and the first imaging lens unit 4, and the display image source 1 and the second imaging lens unit 5 can also be moved synchronously along the optical axis to adjust the refractive index. The thicknesses of the linear polarizing film, film system unit, and polarization conversion unit are 60 nm, 90 nm, and 30 nm, respectively. The thickness of the semi-transparent, semi-reflective film is 50 nm. A polarizing plate with a thickness of 60 nm is provided on the side of the second imaging prism unit 3 closest to the human eye. In this embodiment, the film thicknesses are combined to be as thin as possible, making it suitable for optical systems that require ultra-thinness. This is a difficult challenge in the manufacturing process, and the raw material costs for thinning the linear polarizing film, film system unit, and polarization conversion unit are relatively high, but the imaging effect is similar to that of Embodiment 1. The thinnest possible thickness for a deposited semi-transparent, semi-reflective film is 50 nm; thinner films risk becoming non-uniform, which can affect the imaging effect.

[0083] Table 3 Optical parameters at refractive index 0D in Example 2

[0084] [Table 3]

[0085] Table 4 Optical parameters at refractive index 6D in Example 2

[0086] [Table 4]

[0087] According to the optical parameters in Tables 3 and 4, the field of view (FOV) of the wide-field, lightweight head-mounted display device of this embodiment reaches 60°, and the thickness reaches 9.4 mm. Figures 5 and 6 show the corresponding modulation transfer function (MTF) curves when adjusting for refractive indices of 0D and 6D, respectively. In the figures, the MTF is greater than 0.1 at 10 lp / mm. This device belongs to the visual optical system, and when combined with the angular resolution of the human eye, this MTF index ensures that the human eye receives a very clear and sharp image, effectively guaranteeing a comfortable wearing experience. [Examples]

[0088] In this embodiment, the device comprises a display image source 1, a first imaging prism unit 2, a second imaging prism unit 3, a first imaging lens unit 4, and a second imaging lens unit 5. A polarization conversion unit is installed between the first imaging prism unit 2 and the first imaging lens unit 4, and the display image source 1 and the second imaging lens unit 5 can also be moved synchronously along the optical axis to adjust the refractive index. The thicknesses of the linear polarizing film, film system unit, and polarization conversion unit are 250 nm, 280 nm, and 100 nm, respectively. The thickness of the semi-transparent, semi-reflective film is 300 nm. A polarizing plate with a thickness of 250 nm is provided on the side of the second imaging prism unit 3 closest to the human eye. In this embodiment, the maximum values ​​are used for all film thicknesses, and there are a relatively large number of raw material types available for selection for the linear polarizing film, film system unit, and polarization conversion unit. Relatively thick films are generally available on the market earlier, their performance is average, and their polarization conversion efficiency is slightly less than average. The upper limit for the thickness of the semi-transparent, semi-reflective film is 300 nm, because exceeding this value carries the risk of delamination and affects the imaging effect.

[0089] Table 5 Optical parameters at refractive index 0D in Example 3

[0090] [Table 5]

[0091] Table 6 Optical parameters at refractive index 6D in Example 3

[0092] [Table 6]

[0093] According to the optical parameters in Tables 5 and 6, the field of view (FOV) of the wide-field, lightweight head-mounted display device of this embodiment reaches 60°, and the thickness reaches 9.4 mm. Figures 7 and 8 show the corresponding modulation transfer function (MTF) curves when adjusted for refractive indices of 0D and 6D, respectively. In the figures, the MTF is greater than 0.1 at 10 lp / mm. This device belongs to the visual optical system, and when combined with the angular resolution of the human eye, this MTF index ensures that the human eye receives a very clear and sharp image, effectively guaranteeing a comfortable wearing experience. [Examples]

[0094] In this embodiment, the device comprises a display image source 1, a first imaging prism unit 2, a second imaging prism unit 3, a first imaging lens unit 4, and a second imaging lens unit 5. A polarization conversion unit is installed between the first imaging prism unit 2 and the first imaging lens unit 4, and the display image source 1 and the second imaging lens unit 5 can also be moved synchronously along the optical axis for refractive adjustment. The thicknesses of the linear polarizing film, film system unit, and polarization conversion unit are 100 nm, 180 nm, and 80 nm, respectively. The thickness of the semi-transparent semi-reflective film is 100 nm. A polarizing plate with a thickness of 100 nm is provided on the side of the second imaging prism unit 3 closest to the human eye. In this embodiment, the film thickness is preferably the above value to ensure compatibility with a narrow field of view (FOV) (i.e., less than 60°).

[0095] Table 7 Optical parameters at refractive index 0D in Example 4

[0096] [Table 7]

[0097] Table 8 Optical parameters at refractive index 6D in Example 4

[0098] [Table 8]

[0099] According to the optical parameters in Tables 7 and 8, the field of view (FOV) of the wide-field, lightweight head-mounted display device of this embodiment reaches 57°, and the thickness reaches 9.4 mm. Figures 9 and 10 show the corresponding modulation transfer function (MTF) curves when adjusted for refractive indices of 0D and 6D, respectively. In the figures, the MTF is greater than 0.1 at 10 lp / mm. This device belongs to the visual optical system, and when combined with the angular resolution of the human eye, this MTF index ensures that the human eye receives a very clear and sharp image, effectively guaranteeing a comfortable wearing experience. [Examples]

[0100] In this embodiment, the device comprises a display image source 1, a first imaging prism unit 2, a second imaging prism unit 3, a first imaging lens unit 4, and a second imaging lens unit 5. A polarization conversion unit is installed between the first imaging prism unit 2 and the first imaging lens unit 4, and the display image source 1 and the second imaging lens unit 5 can also be moved synchronously along the optical axis for refractive adjustment. The thicknesses of the linear polarizing film, film system unit, and polarization conversion unit are 115 nm, 195 nm, and 60 nm, respectively. The thickness of the semi-transparent semi-reflective film is 100 nm. A polarizing plate with a thickness of 115 nm is provided on the side of the second imaging prism unit 3 closest to the human eye. In this embodiment, the film thickness is preferably the above value to ensure compatibility with a wide field of view (FOV) (i.e., 60° or more).

[0101] Table 9 Optical parameters at refractive index 0D in Example 5

[0102] [Table 9]

[0103] Table 10 Optical parameters at refractive index 6D in Example 5

[0104] [Table 10]

[0105] According to the optical parameters in Tables 9 and 10, the field of view (FOV) of the wide-field, lightweight head-mounted display device of this embodiment reaches 65°, and the thickness reaches 9.4 mm. Figures 11 and 12 show the corresponding modulation transfer function (MTF) curves when adjusted for refractive indices of 0D and 6D, respectively. In the figures, the MTF is greater than 0.1 at 10 lp / mm. This device belongs to the visual optical system, and when combined with the angular resolution of the human eye, this MTF index ensures that the human eye receives a very clear and sharp image, effectively guaranteeing a comfortable wearing experience.

[0106] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as these combinations of technical features do not contradict each other, they should be considered to be within the scope described herein.

[0107] The embodiments described above are merely specific and detailed examples of the embodiments described in this application and should not be interpreted as limiting the scope of the patent application. Those skilled in the art should note that various modifications and improvements can be made without departing from the spirit of this application, and all such modifications and improvements are included within the scope of protection of this application. Therefore, the scope of protection of this patent application should be defined by the attached claims.

Claims

1. A wide-field, lightweight head-mounted display device comprising a display image source (1), a first imaging prism unit (2), a second imaging prism unit (3), a first imaging lens unit (4), and a polarization conversion unit, among which, The aforementioned display image source (1) is provided with a linear polarizing film on the light emission side. The first imaging prism unit (2) includes a film system unit and a first prism, the film system unit includes a polarizing reflective unit and is attached to the side of the first prism away from the first imaging lens unit (4), The second imaging prism unit (3) includes a second prism and is installed in close proximity to the film system unit. The first imaging lens unit (4) has a semi-transparent, semi-reflective film attached to the side away from the first imaging prism unit (2). The polarization conversion unit is located between the first imaging prism unit (2) and the first imaging lens unit (4), or installed between the polarization reflection unit and the first imaging prism unit (2). The thickness of the linear polarizing film is 60 nm to 250 nm, the thickness of the film system unit is 90 nm to 280 nm, the thickness of the polarization conversion unit is 30 nm to 100 nm, and the thickness of the semitransmissive semi-reflective film is 50 nm to 300 nm. The wide-field, lightweight head-mounted display device is characterized in that the imaging light emitted from the display image source (1) is converted into linearly polarized light by the linearly polarizing film, the linearly polarized light is incident on the first imaging prism unit (2), undergoes total internal reflection and reaches the film system unit, is further reflected by the film system unit and reaches the first imaging lens unit (4), is then reflected by the first imaging lens unit (4) and reaches the first imaging prism unit (2), and further passes through the film system unit and the second imaging prism unit (3) to reach the human eye (6) and form an image.

2. The wide-field lightweight head-mounted display device according to claim 1, characterized in that the polarization conversion unit is a quarter-wave plate, and the angle between the reflection axis of the film system unit and the slow axis of the polarization conversion unit is 45° ± 1°.

3. The wide-field, lightweight head-mounted display device according to claim 1, characterized in that each of the prisms is a triangular prism and the polarization reflection unit is a polarization reflection film.

4. The wide-field lightweight head-mounted display device according to claim 1, characterized in that the film system unit further comprises a polarization absorption unit, the polarization absorption unit is a polarization absorption film, is located between the polarization reflection unit and the second imaging prism unit (3), and the absorption axis of the polarization absorption unit is parallel to the reflection axis of the polarization reflection unit.

5. The wide-field lightweight head-mounted display device according to claim 1, characterized in that the display image source (1) moves relative to the first imaging prism unit (2), and the distance of movement is less than 5 mm.

6. The wide-field lightweight head-mounted display device according to claim 5, characterized in that the angle between the direction in which the display image source (1) moves relative to the first imaging prism unit (2) and the optical axis direction of the display image source (1) is between 0° and 15°.

7. The wide-field lightweight head-mounted display device according to claim 1, further comprising a second imaging lens unit (5), wherein the second imaging lens unit (5) is located on the light-emitting side of the display image source (1), and the linearly polarized light is incident on the first imaging prism unit (2) via the second imaging lens unit (5).

8. The wide-field, lightweight head-mounted display device according to claim 7, characterized in that the focal length of the second imaging lens unit (5) is 5 mm to 50 mm.

9. The wide-field, lightweight head-mounted display device according to claim 7, characterized in that the display image source (1) and the second imaging lens unit (5) move synchronously with respect to the first imaging prism unit (2), and the movement distance is less than 4 mm.

10. The wide-field lightweight head-mounted display device according to claim 9, characterized in that the angle between the direction in which the display image source (1) and the second imaging lens unit (5) move synchronously with respect to the first imaging prism unit (2) and the optical axis direction of the display image source (1) is 0° to 10°.

11. The wide-field lightweight head-mounted display device according to claim 7, characterized in that a polarizing plate is further provided on the side of the second imaging prism unit (3) closest to the human eye, and the thickness of the polarizing plate is 60 nm to 250 nm.

12. The wide-field, lightweight head-mounted display device according to claim 7, characterized in that each imaging lens unit comprises at least one lens.

13. The wide-field lightweight head-mounted display device according to claim 12, characterized in that the surface shape of each lens is any combination of a spherical surface, an aspherical surface, a free-form surface, a Fresnel surface, and a plane.

14. The wide-field, lightweight head-mounted display device according to claim 12, characterized in that the first imaging lens unit (4) is a curved lens.

15. The aforementioned aspherical surface is given by the following equation: [Math 1] (In the formula, z is the vector height, Y is the lens center height, k is the conicity coefficient, C is the curvature, a) ｉ (where is the i-th order aspherical coefficient and N is a positive integer) A wide-field, lightweight head-mounted display device according to claim 13, characterized in that it satisfies the requirements.

16. The wide-field, lightweight head-mounted display device according to claim 1, characterized in that the display image source (1) is one of an organic light-emitting diode display, a silicon liquid crystal display, a micro light-emitting diode display, a digital light processing display, and a laser beam scanning display.

Images