Large field-of-view lightweight head-mounted display device

Abstract

A large field-of-view lightweight head-mounted display device, comprising: a display image source (1), a light exit side of which being provided with a linear polarizing film; a first imaging prism unit (2), comprising a film system unit and a first prism, wherein the film system unit comprises a polarizing reflective unit and is attached to the side of the first prism away from a first imaging lens unit (4); a second imaging prism unit (3), comprising a second prism and being arranged close to the film system unit; the first imaging lens unit (4), wherein a semi-transparent and semi-reflective film is attached to the side of the first imaging lens unit (4) 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 located between the polarizing reflective unit and the second imaging prism unit (3). The thicknesses of the linear polarizing film, the film system unit, the polarization conversion unit, and the semi-transparent and semi-reflective film are reasonably set. The head-mounted display device is light and thin while increasing the field-of-view angle, ensures the imaging quality, and has a diopter adjustment function.

Description

A large-field-of-view lightweight head-mounted display device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on July 14, 2023, with application number 202310867779.6, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application belongs to the field of near-eye display technology, and specifically relates to a large-field-of-view lightweight head-mounted display device. Background Art

[0004] As AR products become increasingly widely used in augmented reality (AR) applications and corresponding technologies continue to develop, AR products are gaining increasing attention and are expected to replace mobile phones as the next generation of mobile devices. In recent years, augmented reality (AR) technology has been applied and rapidly developed in smart wearable devices. The core component of AR technology is the optical module, whose field of view (FOV), thickness, and display quality directly determine the quality of smart wearable devices. In particular, achieving a large FOV, lightweight, and thin while still maintaining excellent image quality has become a key constraint to the development of AR technology.

[0005] Among current AR solutions, the Birdbath solution, which offers relatively high-quality mass production, is 18mm-20mm thick, which is not thick enough for daily wear. Furthermore, lightweight and thin optical waveguide solutions are not yet mature, and cannot provide good imaging quality and a large field of view (FOV). Achieving a large FOV requires increasing the structural dimensions, which fails to achieve both a large FOV and a small size, and also results in significant color shift and lighting issues. Therefore, a solution to achieve lightweight and thin smart wearable devices while also delivering excellent imaging quality is urgently needed.

[0006] Summary of the Invention

[0007] The purpose of this application is to address the above-mentioned problems and propose a large-field-of-view lightweight head-mounted display device that increases the field of view angle while achieving lightness and thinness, ensures imaging quality, and has a diopter adjustment function.

[0008] To achieve the above objectives, the technical solutions adopted in this application are:

[0009] The present application proposes a large-field-of-view 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, wherein:

[0010] Display image source, with linear polarization film on the light-emitting side;

[0011] A first imaging prism unit includes a film system unit and a first prism, wherein the film system unit includes a polarized reflection unit and is attached to a side of the first prism away from the first imaging lens unit;

[0012] A second imaging prism unit includes a second prism and is disposed close to the film system unit;

[0013] The first imaging lens unit has a semi-transparent and semi-reflective film attached to a side away from the first imaging prism unit;

[0014] a polarization conversion unit, located between the first imaging prism unit and the first imaging lens unit, or between the polarization reflection unit and the first imaging prism unit;

[0015] The thickness of the linear polarizing film is 60nm to 250nm, the thickness of the film unit is 90nm to 280nm, the thickness of the polarization conversion unit is 30nm to 100nm, and the thickness of the semi-transparent and semi-reflective film is 50nm to 300nm;

[0016] The imaging light emitted by the display image source is converted into linearly polarized light by the linear polarization film. The linearly polarized light enters the first imaging prism unit, undergoes total internal reflection, and then reaches the film system unit. It is reflected by the film system unit to the first imaging lens unit, and then reflected back to the first imaging prism unit by the first imaging lens unit. It then passes through the film system unit and the second imaging prism unit in sequence to reach the human eye for imaging.

[0017] 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°.

[0018] Preferably, each prism is a triangular prism, and the polarized reflection unit is a polarized reflection film.

[0019] Preferably, the film system unit further includes a polarization absorption unit, which is a polarization absorption film and is located between the polarization reflection unit and the second imaging prism unit, and the absorption axis of the polarization absorption unit is parallel to the reflection axis of the polarization reflection unit.

[0020] Preferably, the display image source moves relative to the first imaging prism unit, and the moving distance is less than 5 mm.

[0021] 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°.

[0022] Preferably, the large-field-of-view lightweight head-mounted display device further includes a second imaging lens unit, which is located on the light-emitting side of the display image source, and the linearly polarized light enters the first imaging prism unit through the second imaging lens unit.

[0023] Preferably, the focal length of the second imaging lens unit is 5 mm to 50 mm.

[0024] Preferably, the display image source and the second imaging lens unit move synchronously relative to the first imaging prism unit, and the moving distance is less than 4 mm.

[0025] Preferably, the angle between the direction in which the display image source and the second imaging lens unit move synchronously relative to the first imaging prism unit and the optical axis direction of the display image source is 0° to 10°.

[0026] Preferably, a polarizer is further provided on the side of the second imaging prism unit close to the human eye, and the thickness of the polarizer is 60 nm to 250 nm.

[0027] Preferably, each imaging lens unit includes at least one lens.

[0028] Preferably, the mirror surface of each lens is a free combination of a spherical surface, an aspherical surface, a free-form surface, a Fresnel surface and a plane.

[0029] Preferably, the first imaging lens unit is a curved lens.

[0030] Preferably, the aspheric surface satisfies the following formula:

[0031] Among them, z is the sag height, Y is the center height of the lens, k is the cone coefficient, C is the curvature, a i is the i-th aspheric coefficient, and N is a positive integer.

[0032] Preferably, the display image source is 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.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] This large-field-of-view, lightweight head-mounted display device adopts a folded optical path (Pancake) solution. Through a folded optical element consisting of a first imaging prism unit, a second imaging prism unit, and a first imaging lens unit, the principles of light refraction, reflection, and polarization are utilized to increase the number of inter-mirror reflections to achieve multiple folded optical paths, resulting in a shorter optical path. While increasing the field of view (FOV), it can also be lightweight and thin, ensuring imaging quality, and has a diopter adjustment function. For example, the FOV is increased from 48° in the traditional Birdbath solution to over 60°, and the thickness is reduced by half from the 18mm-20mm of the traditional Birdbath solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a schematic structural diagram of a large-field-of-view lightweight head-mounted display device according to Example 1 of the present application.

[0036] FIG2 is a schematic diagram of diopter adjustment of a large-field-of-view lightweight head-mounted display device according to Example 1 of the present application.

[0037] FIG3 is an MTF curve diagram of Example 1 of the present application at a diopter of 0D.

[0038] FIG4 is an MTF curve diagram of Example 1 of the present application at a diopter of 6D.

[0039] FIG5 is an MTF curve diagram of Example 2 of the present application at a diopter of 0D.

[0040] FIG6 is an MTF curve diagram of Example 2 of the present application at a diopter of 6D.

[0041] FIG7 is an MTF curve diagram of Example 3 of the present application at a diopter of 0D.

[0042] FIG8 is an MTF curve diagram of Example 3 of the present application at a diopter of 6D.

[0043] FIG9 is an MTF curve diagram of Example 4 of the present application at a diopter of 0D.

[0044] FIG10 is an MTF curve diagram of Example 4 of the present application at a diopter of 6D.

[0045] FIG11 is an MTF curve diagram of Example 5 of the present application at a diopter of 0D.

[0046] FIG12 is an MTF curve diagram of Example 5 of the present application at a diopter of 6D.

[0047] Explanation of the accompanying symbols: 1. Display image source; 2. First imaging prism unit; 3. Second imaging prism unit; 4. First imaging lens unit; 5. Second imaging lens unit; 6. Human eye. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0049] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the art of this application. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0050] As shown in FIG1-2 , a large-field-of-view lightweight head-mounted display device includes 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, wherein:

[0051] Display image source 1, with a linear polarization film on the light-emitting side;

[0052] The first imaging prism unit 2 includes a film system unit and a first prism, wherein the film system unit includes a polarized reflection unit and is attached to a side of the first prism away from the first imaging lens unit 4;

[0053] The second imaging prism unit 3 includes a second prism and is disposed close to the film system unit;

[0054] The first imaging lens unit 4 has a semi-transparent and semi-reflective film attached to the side away from the first imaging prism unit 2;

[0055] a polarization conversion unit, located 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;

[0056] The thickness of the linear polarizing film is 60nm to 250nm, the thickness of the film unit is 90nm to 280nm, the thickness of the polarization conversion unit is 30nm to 100nm, and the thickness of the semi-transparent and semi-reflective film is 50nm to 300nm;

[0057] The imaging light emitted by the display image source 1 is converted into linearly polarized light by the linear polarization film. The linearly polarized light enters the first imaging prism unit 2, undergoes total internal reflection, and then reaches the film system unit. It is then reflected by the film system unit to the first imaging lens unit 4. It is then reflected back by the first imaging lens unit 4 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 for imaging.

[0058] The display image source 1 is used to provide an image. The first imaging prism unit 2 includes a first prism and a film unit with a light modulation function. The first prism can be made of plastic or glass. The film unit can be attached to the first prism or coated on the first prism, and the film unit performs the function of polarized light reflection. The second imaging prism unit 3 includes a second prism and is positioned near the film unit, such as between the first imaging prism unit 2 and the human eye 6. The polarization conversion unit can be located 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, depending on actual needs.

[0059] The first imaging lens unit 4 is a lens group with aberration correction and light path reflection functions. The material of the lens group can be either glass or plastic, including but not limited to the following types: spherical lens, aspherical lens, free-form lens, Fresnel lens, flat lens, etc., preferably a spherical lens. For example, the first imaging lens unit 4 is a curved lens, and a semi-transparent and semi-reflective film is provided on the inner side of the curved lens (the side away from the first imaging prism unit 2). The semi-transparent and semi-reflective film can be realized by coating or sticking.

[0060] By properly setting the thickness of the linear polarizing film, film system unit, polarization conversion unit, and transflective film, we can ensure both the transflective effect and the feasibility of the film material process, thus achieving a good balance between imaging quality and reliability. Specifically:

[0061] 1) A linear polarizing film that is too thin can lead to unstable optical performance, poor polarization effect, and difficulty in forming. It is also susceptible to external environmental influences such as mechanical damage and chemical corrosion, which reduces its durability. A linear polarizing film that is too thick will increase reflectivity, leading to increased light loss, and also affect its polarization effect, resulting in poor optical performance and the risk of ghost images.

[0062] 2) The polarization reflective element of the film system is a thin film material that uses polarization properties to reflect light. If the polarization reflective element material is too thin, it will result in: 1. It will be difficult to shape, more fragile, and easily deformed, thus affecting the polarization effect; 2. It will have reduced durability: Polarization reflective element material that is too thin will be more easily damaged due to its fragility and easy wear and scratching. If the polarization reflective element material is too thick, it will lead to poor optical performance: the transmittance and polarization rate will be reduced, thus affecting its application effect in optical devices and easily forming ghost images.

[0063] 3) A polarization conversion unit (such as a quarter-wave plate) is an optical device used to adjust the polarization state and phase of light. If it is too thin, it cannot be molded and is prone to brittleness. However, if it is too thick, the optical path difference (OPD) will change. The thickness of the polarization conversion unit is designed based on the wavelength. If it is too thick, the OPD will change beyond the designed value, thus affecting its ability to adjust the polarization state and phase of light.

[0064] 4) When using vapor deposition for transflective films, if they are too thin, they cannot be deposited and thickness uniformity cannot be guaranteed; if they are too thick, there is a risk of the film peeling off. Imaging quality and stability cannot be guaranteed if they are too thin or too thick.

[0065] This head-mounted display performs three reflections, folding the light path multiple times, thereby increasing the field of view (FOV) and achieving lightweight and thinness. Specifically, the first reflection utilizes total internal reflection through air (i.e., there is an air gap between the first imaging prism unit 2 and the first imaging lens unit 4, and the refractive index of air is lower than that of the first imaging prism unit 2 and the first imaging lens unit 4. Therefore, the imaging light can be totally reflected on the wall surface of the first imaging prism unit 2 near the first imaging lens unit 4). The second reflection is the linearly polarized light converted by the linear polarization film hitting the film system unit and reflecting. The third reflection is reflected by the semi-transparent and semi-reflective film. For example, the FOV is increased from 48° in the traditional Birdbath solution to over 60°, and the thickness is reduced by half from the 18mm-20mm of the traditional Birdbath solution.

[0066] In one embodiment, the polarization conversion unit is a quarter-wave plate, and the angle between the reflection axis of the film assembly and the slow axis of the polarization conversion unit is 45°±1°. To ensure the best imaging effect, the film assembly and the polarization conversion unit have a certain angle relationship. The slow axis of the polarization conversion unit needs to be attached at a 45° angle to the reflection axis of the film assembly, with a tolerance of plus or minus one degree. This ensures that linearly polarized light is converted to standard circularly polarized light.

[0067] In one embodiment, each prism is a triangular prism, and the polarized reflection unit is a polarized reflection film.

[0068] In one embodiment, the film system unit further includes a polarization absorbing unit, which is a polarization absorbing film and is positioned between the polarization reflecting unit and the second imaging prism unit 3 , with the absorption axis of the polarization absorbing unit and the reflection axis of the polarization reflecting unit being parallel. The reflection axis of the polarization reflecting unit (e.g., a polarization reflecting film) and the absorption axis of the polarization absorbing unit (e.g., a polarization absorbing film) should be parallel to each other to facilitate ghosting elimination. Specifically, the polarization conversion unit, polarization reflecting unit, and polarization absorbing unit are sequentially positioned in a direction close to the human eye 6 .

[0069] In one embodiment, the display image source 1 is further movable relative to the first imaging prism unit 2, and the moving distance is less than 5 mm, so that diopter adjustment from 0D to 6D can be achieved.

[0070] In one embodiment, the angle between the direction in which the image source 1 moves relative to the first imaging prism unit 2 and the optical axis of the image source 1 is 0° to 15°. The optical axis of the image source 1 is perpendicular to the light-emitting surface of the screen.

[0071] In actual use, for the convenience of processing, molding, assembly, etc., the angle may preferably be 0°. However, at this time, if the display image source 1 is too large, when the display image source 1 moves to the end point of the range, due to limitations such as optical lenses, the display content at the edge of the light-emitting surface of the display image source 1 may not be able to normally enter the first imaging prism unit 2 to transmit light, resulting in the final image being missing or displaced or severely distorted.

[0072] Therefore, in order to ensure the integrity of the final image and excellent imaging quality, the moving direction of the display image source 1 can be made to present a certain angle with the optical axis direction, that is, there is a moving component parallel to the light-emitting surface of the display image source 1 during movement, which can ensure that the imaging light emitted by the display image source 1 within the entire moving range can normally enter the first imaging prism unit 2 for light conduction, ensuring that within the diopter adjustment range, the final imaging picture is complete and the entire light-emitting surface of the display image source 1 can be fully utilized.

[0073] However, the angle should not be too large to ensure that when the display image source 1 moves, the movement component parallel to the light-emitting surface of the display image source 1 is small, and the main movement component of the display image source 1 is in the direction of the optical axis; if the 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 is too large, and in order to ensure that the imaging light emitted by the display image source 1 can enter the incident surface of the first imaging prism unit 2 within the entire diopter adjustment range, the incident surface of the first imaging prism unit 2 needs to be made very large, and the volume of the entire device will also be very large, making the volume of the augmented reality device used larger, making it difficult to meet the requirements of lightness and thinness. At the same time, too large an angle will also lead to image loss, displacement, and serious distortion. Specifically, considering lightness and thinness, imaging quality, and image integrity, the angle is preferably 7°, which can ensure lightness and thinness while ensuring the integrity of the display image and guaranteeing the display effect.

[0074] In one embodiment, the large-field-of-view lightweight head-mounted display device further includes a second imaging lens unit 5 , which is located on the light-emitting side of the display image source 1 , and the linearly polarized light enters the first imaging prism unit 2 through the second imaging lens unit 5 .

[0075] In one embodiment, the focal length of the second imaging lens unit 5 is 5 mm to 50 mm, which is beneficial to improving imaging quality.

[0076] In one embodiment, the display image source 1 and the second imaging lens unit 5 also move synchronously relative to the first imaging prism unit 2, and the moving distance is less than 4 mm, so as to achieve diopter adjustment from 0D to 6D.

[0077] In one embodiment, the angle between the direction in which the display image source 1 and the second imaging lens unit 5 move synchronously relative to the first imaging prism unit 2 and the optical axis of the display image source 1 is 0° to 10°. The optical axis of the display image source 1 is perpendicular to the light-emitting surface of the screen of the display image source 1.

[0078] In actual use, for the convenience of processing, molding, assembly, etc., the angle may preferably be 0°. However, at this time, 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 end point of the range, due to limitations such as optical lenses, the display content at the edge of the light-emitting surface of the display image source 1 may not be able to normally enter the first imaging prism unit 2 to transmit light, resulting in the final image being missing or displaced or severely distorted.

[0079] Therefore, in order to ensure the integrity and excellent imaging quality of the final image, the direction in which the display image source 1 and the second imaging lens unit 5 move synchronously can be made to present a certain angle with the optical axis direction of the display image source 1, that is, there is a movement component parallel to the light-emitting surface of the display image source 1 during movement, which can ensure that the imaging light emitted by the display image source 1 within the entire movement range can normally enter the first imaging prism unit 2 for light conduction, and ensure that within the diopter adjustment range, the final imaging picture is complete and the entire light-emitting surface of the display image source 1 can be fully utilized.

[0080] However, the angle should not be too large to ensure that when the display image source 1 moves, the movement component parallel to the light-emitting surface of the display image source 1 is small, and the main movement component of the display image source 1 is in the direction of the optical axis; if the 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 is too large, and in order to ensure that the imaging light emitted by the display image source 1 can enter the incident surface of the first imaging prism unit 2 within the entire diopter adjustment range, the incident surface of the first imaging prism unit 2 needs to be made very large, and the volume of the entire device will also be very large, which will make the volume of the augmented reality device used larger, making it difficult to meet the requirements of lightness and thinness. At the same time, too large an angle will also lead to severe image loss, displacement, and distortion.

[0081] Compared to the aforementioned solution in which only the display image source 1 is moved, the addition of the second imaging lens unit 5 with a positive focal length constrains the convergence of the imaging light rays before entering the first imaging prism unit 2. Therefore, the required angle and amount of movement are both smaller than the solution 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. This movement ensures that during the movement process, the angles of light rays emitted from the same position on the display image source 1 after passing through the second imaging lens unit 5 remain consistent. That is, the divergence of the light rays emitted by the second imaging lens unit 5 remains consistent for different diopters, ensuring a consistent final imaging FOV without significant reduction.

[0082] In one embodiment, a polarizer is further provided on the side of the second imaging prism unit 3 close to the human eye, and the thickness of the polarizer is 60 nm to 250 nm.

[0083] When there is no second imaging lens unit 5, it has a high design compatibility, which is conducive to mass production; if the second imaging lens unit 5 is set, the imaging quality can be further improved. The second imaging lens unit can be in the form of a lens group, and in order to reduce the rainbow pattern generated by the second imaging lens unit 5, a polarization absorption film can be attached to the near-eye surface of the second imaging prism unit 3, which can also reduce the rainbow pattern. The principle is to use linear polarized light in the imaging direction without affecting the imaging while reducing half of the stray light, because the stray light has directions parallel to the imaging linear polarized light and perpendicular to the linear polarized light.

[0084] For example, a polarizer can be attached to the near-eye surface of the second imaging prism unit 3. The thickness of the polarizer should be between 60nm and 250nm. If the thickness is too thin, the film cannot be stacked to ensure the desired effect. If the thickness is too thick, light will be reflected within the film, causing ghost images. Therefore, a thickness of 60nm to 250nm is sufficient to ensure the desired effect without causing any other negative effects, thus eliminating external stray light.

[0085] In one embodiment, each imaging lens unit includes at least one lens.

[0086] In one embodiment, the mirror surface of each lens is a free combination of a spherical surface, an aspherical surface, a free-form surface, a Fresnel surface, and a flat surface.

[0087] Among them, each imaging lens unit is a series of lens groups with aberration correction function. Each lens can be made of plastic or glass. The number of lenses in the lens group is not limited, including but not limited to the following types: spherical lens, aspherical lens, free-form surface lens, Fresnel lens, flat lens, etc., preferably a spherical lens.

[0088] In one embodiment, the first imaging lens unit 4 is a curved lens.

[0089] In one embodiment, the aspheric surface satisfies the following formula:

[0090] Among them, z is the sag height, Y is the center height of the lens, k is the cone coefficient, C is the curvature, a i is the i-th aspheric coefficient, and N is a positive integer.

[0091] In one embodiment, the display image source 1 is one of an organic light-emitting diode (OLED) display, a liquid crystal on silicon (LCOS) display, a micro light-emitting diode (MicroLED) display, a digital light processing (DLP) display, and a laser beam scanning (LBS) display. The display image source 1 includes, but is not limited to, the above devices, and is preferably an OLED display.

[0092] The operating principle of this device is that the imaging light emitted by the display image source 1 is converted by a linear polarizing film into 45° linearly polarized light, which then passes through the second imaging lens unit 5 and is then transmitted to the first imaging prism unit 2. A film system unit with optical path modulation is attached to the side of the first imaging prism unit 2 near the second imaging prism unit 3. The 45° linearly polarized light is first totally internally reflected by the first imaging prism unit 2 and reaches the film system unit. The film system then reflects the 45° linearly polarized light, which is then transmitted through the -45° linearly polarized light and reflected onto the outer surface of the first imaging lens unit 4. A semi-transparent and semi-reflective film is applied to the first imaging lens unit 4, reflecting the light back to the first imaging prism unit 2. The linearly polarized light now has a -45° angle and can then pass through the film system unit and the second imaging prism unit 3, ultimately reaching the human eye 6 for imaging, as shown in Figure 1. Figure 2 shows the optical path and diopter adjustment (showing the synchronous movement of the image source 1 and the second imaging lens unit 5).

[0093] The following is a detailed description of the specific embodiments. In each table, OBJ represents the object plane, IMG represents the image plane, Stop represents the aperture, Eye represents the Relief represents the exit pupil distance. In the surface serial number, S2 and S3 both represent the mirror surface on the second imaging prism unit 3 close to the human eye 6, S4, S5, S12, and S13 both represent the mirror surface on the first imaging prism unit 2 close to the second imaging prism unit 3, S6, S7, S11, S14, and S15 both represent the mirror surface on the first imaging prism unit 2 close to the first imaging lens unit 4, S8 and S10 both represent the mirror surface on the first imaging lens unit 4 close to the first imaging prism unit 2, S9 represents the mirror surface on the first imaging lens unit 4 away from the first imaging prism unit 2, S16 and S17 both represent the mirror surface on the first imaging prism unit 2 close to the second imaging lens unit 5, S18 and S19 both represent the light exit surface of the second imaging lens unit 5, and S20 represents the light incident surface of the second imaging lens unit 5. The light exit side of the display image source 1 is provided with flat glass (surface serial number S21), and the standard surface is a spherical surface.

[0094] Example 1:

[0095] In this embodiment, the device includes 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 disposed 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 move synchronously along the optical axis to achieve diopter adjustment. The thicknesses of the linear polarization film, the film system unit, and the polarization conversion unit are 120nm, 200nm, and 60nm, respectively. The thickness of the semi-transparent and semi-reflective film is 100nm. A polarizer is provided on the side of the second imaging prism unit 3 closest to the human eye. The polarizer is 120nm thick. In this embodiment, the film thickness is preferably intermediate, achieving a good balance between imaging quality and reliability.

[0096] Table 1 Optical parameters of diopter 0D position of Example 1

[0097] Table 2 Optical parameters of 6D diopter position of Example 1

[0098] According to the optical parameters in Tables 1 and 2, the field of view (FOV) of the large-field-of-view lightweight head-mounted display device of this embodiment can reach 60° and the thickness can reach 9.4mm. As shown in Figures 3 and 4, the corresponding modulation transfer function (MTF) curves are respectively adjusted under the diopter of 0D and the diopter of 6D. In the figure, the MTF is greater than 0.1 at 10lp / mm. Because the device belongs to the visual optical system, combined with the human eye angle resolution, the MTF index can ensure that the human eye receives a very clear and sharp image, which can effectively ensure the wearing experience.

[0099] Example 2:

[0100] In this embodiment, the device includes 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 disposed 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 to achieve diopter adjustment. The thicknesses of the linear polarizing film, the film system unit, and the polarization conversion unit are 60nm, 90nm, and 30nm, respectively. The thickness of the transflective film is 50nm. A polarizer with a thickness of 60nm is provided on the side of the second imaging prism unit 3 closest to the eye. The film thickness in this embodiment is the thinnest possible, suitable for optical systems with extreme thinning requirements. This poses significant challenges in terms of process complexity, and the raw materials required to thin the linear polarizing film, the film system unit, and the polarization conversion unit are relatively expensive. However, the imaging effect is similar to that of Example 1. The minimum thickness of the evaporated transflective film is 50nm; otherwise, there is a risk of uneven coating, which would affect the imaging effect.

[0101] Table 3 Optical parameters of diopter 0D position of Example 2

[0102] Table 4 Optical parameters of 6D diopter position of Example 2

[0103] According to the optical parameters in Tables 3 and 4, the field of view (FOV) of the lightweight, large-field-of-view head-mounted display device of this embodiment can reach 60° and a thickness of 9.4mm. Figures 5 and 6 show the corresponding MTF curves for 0D and 6D diopters, respectively. The MTF in the figure is greater than 0.1 at 10lp / mm. Because the device is a visual optical system, combined with the human eye's angle of view, this MTF indicator ensures that the human eye receives a very clear and sharp image, effectively ensuring a comfortable wearing experience.

[0104] Example 3:

[0105] In this embodiment, the device includes 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 disposed 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 move synchronously along the optical axis to achieve diopter adjustment. The thicknesses of the linear polarizing film, the film assembly unit, and the polarization conversion unit are 250nm, 280nm, and 100nm, respectively. The thickness of the transflective film is 300nm. A polarizer is provided on the side of the second imaging prism unit 3 closest to the eye, and the thickness of the polarizer is 250nm. In this embodiment, the film thicknesses are all set to the maximum value, and a wide range of raw material types are available for the linear polarizing film, the film assembly unit, and the polarization conversion unit. However, thicker films are generally available earlier and have average performance, especially slightly lower conversion efficiency for polarized light. The upper limit of the transflective film thickness is 300nm, as exceeding this value may increase the risk of film delamination, which may affect imaging quality.

[0106] Table 5 Optical parameters of diopter 0D position of Example 3

[0107] Table 6 Optical parameters of 6D diopter position of Example 3

[0108] According to the optical parameters in Tables 5 and 6, the field of view (FOV) of the lightweight, large-field-of-view head-mounted display device of this embodiment can reach 60° and a thickness of 9.4mm. Figures 7 and 8 show the corresponding MTF curves for 0D and 6D diopters, respectively. The MTF in the figure is greater than 0.1 at 10lp / mm. Because the device is a visual optical system, combined with the human eye's angle of view, this MTF indicator ensures that the human eye receives a very clear and sharp image, effectively ensuring a comfortable wearing experience.

[0109] Example 4:

[0110] In this embodiment, the device includes 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 disposed 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 move synchronously along the optical axis to achieve diopter adjustment. The thicknesses of the linear polarizing film, the film system unit, and the polarization conversion unit are 100 nm, 180 nm, and 80 nm, respectively. The thickness of the semi-transparent and semi-reflective film is 100 nm. A polarizer is provided on the side of the second imaging prism unit 3 closest to the human eye. The polarizer is 100 nm thick. In this embodiment, the film thickness preferably has the aforementioned values ​​so that the primary surface is compatible with a small FOV (i.e., less than 60°).

[0111] Table 7 Optical parameters of diopter 0D position of Example 4

[0112] Table 8 Optical parameters of 6D diopter position of Example 4

[0113] According to the optical parameters in Tables 7 and 8, the field of view (FOV) of the lightweight, large-field-of-view head-mounted display device of this embodiment can reach 57°, and the thickness can reach 9.4mm. Figures 9 and 10 show the corresponding MTF curves under 0D and 6D diopter adjustment, respectively. In the figure, the MTF is greater than 0.1 at 10lp / mm. Because the device belongs to a visual optical system, combined with the human eye's angle of view resolution, this MTF indicator ensures that the human eye receives a very clear and sharp image, effectively ensuring a good wearing experience.

[0114] Example 5:

[0115] In this embodiment, the device includes 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 disposed 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 move synchronously along the optical axis to achieve diopter adjustment. The thicknesses of the linear polarizing film, the film system unit, and the polarization conversion unit are 115nm, 195nm, and 60nm, respectively. The thickness of the semi-transparent and semi-reflective film is 100nm. A polarizer with a thickness of 115nm is provided on the side of the second imaging prism unit 3 closest to the human eye. The film thickness in this embodiment preferably has the aforementioned values, so that the primary surface is compatible with a large field of view (FOV) (i.e., greater than 60°).

[0116] Table 9 Optical parameters of diopter 0D position of Example 5

[0117] Table 10 Optical parameters of the diopter 6D position of Example 5

[0118] According to the optical parameters in Tables 9 and 10, the large-field-of-view, lightweight head-mounted display device of this embodiment can achieve a field of view of 65° and a thickness of 9.4mm. Figures 11 and 12 show the corresponding MTF curves at 0D and 6D diopters, respectively. The MTF in these figures is greater than 0.1 at 10 lp / mm. Because this device is a visual optical system, combined with the human eye's angular resolution, this MTF ensures that the human eye receives a very clear and sharp image, effectively ensuring a pleasant wearing experience.

[0119] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0120] The above-described embodiments merely represent specific and detailed examples of the present application and should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A lightweight head-mounted display device with a large field of view, wherein: The large-field-of-view 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, wherein: The display image source (1) has a linear polarization film on the light-emitting side; The first imaging prism unit (2) comprises a film system unit and a first prism, wherein the film system unit comprises a polarized reflection unit and is attached to a side of the first prism away from the first imaging lens unit (4); The second imaging prism unit (3) comprises a second prism and is arranged close to the film system unit; The first imaging lens unit (4) has a semi-transparent and semi-reflective film attached to a 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 between the polarization reflection unit and the first imaging prism unit (2); 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 and semi-reflective film is 50nm to 300nm; The imaging light emitted by the display image source (1) is converted into linearly polarized light by the linear polarization film. The linearly polarized light enters the first imaging prism unit (2) and undergoes total reflection before reaching the film system unit. The linearly polarized light is then reflected by the film system unit to the first imaging lens unit (4). The linearly polarized light is then reflected back to the first imaging prism unit (2) by the first imaging lens unit (4) and sequentially passes through the film system unit and the second imaging prism unit (3) to reach the human eye (6) for imaging.

2. The large-field-of-view lightweight head-mounted display device according to claim 1, wherein: 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 large-field-of-view lightweight head-mounted display device according to claim 1, wherein: Each of the prisms is a triangular prism, and the polarized reflection unit is a polarized reflection film.

4. The large-field-of-view lightweight head-mounted display device according to claim 1, wherein: The film system unit also includes a polarization absorption unit, which is a polarization absorption film and 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 large-field-of-view lightweight head-mounted display device according to claim 1, wherein: The display image source (1) moves relative to the first imaging prism unit (2), and the moving distance is less than 5 mm.

6. The large-field-of-view lightweight head-mounted display device according to claim 5, wherein: 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°.

7. The large-field-of-view lightweight head-mounted display device according to claim 1, wherein: The large-field-of-view lightweight head-mounted display device further comprises a second imaging lens unit (5), wherein the second imaging lens unit (5) is located at the light-emitting side of the display image source (1), and the linearly polarized light enters the first imaging prism unit (2) through the second imaging lens unit (5).

8. The large-field-of-view lightweight head-mounted display device according to claim 7, wherein: The focal length of the second imaging lens unit (5) is 5 mm to 50 mm.

9. The large-field-of-view lightweight head-mounted display device according to claim 7, wherein: The display image source (1) and the second imaging lens unit (5) move synchronously relative to the first imaging prism unit (2), and the moving distance is less than 4 mm.

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

11. The large-field-of-view lightweight head-mounted display device according to claim 7, wherein: A polarizing film is also provided on the side of the second imaging prism unit (3) close to the human eye, and the thickness of the polarizing film is 60 nm to 250 nm.

12. The large-field-of-view lightweight head-mounted display device according to claim 7, wherein: Each of the imaging lens units includes at least one lens.

13. The large-field-of-view lightweight head-mounted display device according to claim 12, wherein: The mirror surface type of each lens is a free combination of a spherical surface, an aspherical surface, a free-form surface, a Fresnel surface and a plane.

14. The large-field-of-view lightweight head-mounted display device according to claim 12, wherein: The first imaging lens unit (4) is a curved lens.

15. The large-field-of-view lightweight head-mounted display device according to claim 13, wherein: The aspheric surface satisfies the following formula: Among them, z is the sag, Y is the center height of the lens, k is the cone coefficient, C is the curvature, a i is the i-th aspheric coefficient, and N is a positive integer.

16. The large-field-of-view lightweight head-mounted display device according to claim 1, wherein: The display image source (1) is one of an organic light emitting diode display, a silicon-based liquid crystal display, a micro light emitting diode display, a digital light processing display, and a laser beam scanning display.

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