Optical module capable of eliminating stray light and near-eye display device

Abstract

An optical module capable of eliminating stray light and a near-eye display device. The optical module comprises: an image display unit (1) used for emitting image light; a first reflection unit (2) comprising a first prism and used for reflecting the image light to the first polarization unit (21); a first polarization unit (21) located between the first prism and a first imaging prism unit (3) and used for reflecting the image light parallel to a first polarization transmission direction and transmitting the image light parallel to a second polarization transmission direction; a second reflection unit (4) comprising at least one lens and provided with a semi-transparent semi-reflective film on the side thereof distant from the first prism; and the first imaging prism unit (3) comprising a second prism and a second polarization unit (31), wherein the second polarization unit (31) is attached to the second prism and arranged close to human eyes, and is used for transmitting light parallel to a third polarization transmission direction and reflecting light perpendicular to the third polarization transmission direction. Halo, glare, eye fatigue, and discomfort caused by interference and light pollution generated by cheek reflection can be avoided, thereby improving user experience and comfort.

Description

Optical module capable of eliminating stray light and near-eye 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 August 30, 2023, with application number 202322356240.2, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application belongs to the field of optical technology, and specifically relates to an optical module capable of eliminating stray light and a near-eye 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. The field of view (FOV), thickness, and display quality of the optical module directly determine the quality of smart wearable devices. Achieving a large FOV, thinness, and excellent image quality while maintaining a large weight has become a key constraint to the development of AR technology.

[0005] Current augmented reality (AR), virtual reality (VR), and mixed reality (MR) solutions, whether Birdbath or Pancake, undergo multiple reflections, posing a significant risk of stray light. During use, the lens near the eye can reflect light onto the user's cheek, impacting the user experience. This is particularly noticeable in AR devices with incomplete displays and bright ambient light. Cheek reflection occurs when light from the AR device's display or ambient light strikes the user's cheek. Due to the reversibility of the optical path, this light reflects back from the cheek, backtracking the path and then back to the display, causing interference and light pollution. This reflection can cause halos and glare in the image viewed by the user, impacting their perception and cognition of the virtual image. Furthermore, when users use AR devices for extended periods, the interference and light pollution caused by cheek reflection can lead to eye fatigue and discomfort, impacting the user's experience and comfort.

[0006] Summary of the Invention

[0007] The purpose of this application is to address the above-mentioned problems and propose an optical module and near-eye display device that can eliminate stray light, which can avoid the interference caused by cheek reflection and the problems of halo, glare, eye fatigue and discomfort caused by light pollution, thereby improving the user experience and comfort.

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

[0009] The present application proposes an optical module capable of eliminating stray light, comprising an image display unit, a first reflection unit, a first polarization unit, a second reflection unit, and a first imaging prism unit, wherein:

[0010] An image display unit, configured to emit image light;

[0011] A first reflecting unit, comprising a first prism, for reflecting the image light to the first polarizing unit;

[0012] a first polarization unit, located between the first prism and the first imaging prism unit, for reflecting image light in a first polarization transmission direction to the second reflection unit and transmitting image light in a second polarization transmission direction, the first polarization transmission direction and the second polarization transmission direction being 90° apart, and the first polarization transmission direction being the same as the polarization transmission direction of the image display unit;

[0013] a second reflecting unit comprising at least one lens and provided with a semi-transparent and semi-reflective film on a side away from the first prism, the semi-transparent and semi-reflective film being configured to reflect image light in the first polarization transmission direction so that the light passes sequentially through the first reflecting unit and the first imaging prism unit to enter the human eye, and to transmit real scene light so that the light passes sequentially through the first reflecting unit and the first imaging prism unit to enter the human eye;

[0014] The first imaging prism unit includes a second prism and a second polarization unit. The second polarization unit is attached to the second prism and is arranged close to the human eye. The second polarization unit is used to transmit light parallel to a third polarization transmission direction and reflect light perpendicular to the third polarization transmission direction. The third polarization transmission direction is the same as the second polarization transmission direction.

[0015] Preferably, the first polarization unit includes a first linear polarizer, a polarization reflector, and a quarter wave plate, which are sequentially arranged along a direction from the second prism to the first prism.

[0016] Preferably, a third polarization unit is further provided on the image display unit, and the third polarization unit is used to convert the image light into 45° linear polarized light.

[0017] Preferably, the second polarizing unit includes a second linear polarizer, and the third polarizing unit includes a third linear polarizer.

[0018] Preferably, the 45° linearly polarized light is reflected for the first time on the side of the first prism close to the second reflecting unit to form a first light ray, the first light ray is reflected for the second time on the first polarizing unit to form a second light ray, the second light ray is reflected for the third time on the semi-transparent and semi-reflective film to form a third light ray, the third light ray is converted into a fourth light ray by the first polarizing unit and then enters the human eye through the second polarizing unit. The first light ray is 45° linearly polarized light, the second light ray is left-handed circularly polarized light, the third light ray is right-handed circularly polarized light, and the fourth light ray is -45° linearly polarized light. The second polarizing unit is used to transmit -45° linearly polarized light and reflect 45° linearly polarized light.

[0019] Preferably, the second reflecting unit is a curved lens, and a side close to the first prism is a flat surface, and a side away from the first prism is a convex surface.

[0020] Preferably, the image display unit moves relative to the first reflection unit to perform diopter adjustment.

[0021] Preferably, the optical module capable of eliminating stray light further includes a first imaging lens unit, which is located on the light-emitting side of the image display unit and includes at least one lens.

[0022] Preferably, the first imaging lens unit and the image display unit move synchronously relative to the first reflection unit to perform diopter adjustment.

[0023] A near-eye display device comprises any of the above-mentioned optical modules capable of eliminating stray light.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] Since the lenses close to the human eye side in the prior art inevitably have reflections, cheek reflections are introduced, causing stray light and ghosting. The present application adds a second polarization unit on the eye entrance side. The second polarization unit transmits all light parallel to the third polarization transmission direction and reflects all light perpendicular to the third polarization transmission direction, thereby blocking some external stray light and perfectly covering up the image light emitted by the image display unit through some external stray light, solving problems such as stray light and ghosting in the image, avoiding halo, glare, eye fatigue and discomfort caused by interference and light pollution caused by cheek reflection, without affecting the user's perception and cognition of virtual images, improving the user's usage experience and comfort, and by folding the light path multiple times (three reflections), thereby increasing the field of view angle and helping to achieve lightweightness. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic structural diagram of an optical module capable of eliminating stray light according to the present application.

[0027] FIG2 is a schematic diagram of the cheek reflection principle of the optical module capable of eliminating stray light in the present application.

[0028] FIG3 is a schematic diagram showing the composition of the polarization units of the optical module capable of eliminating stray light according to the present application.

[0029] Explanation of the accompanying drawings: 1. Image display unit; 2. First reflection unit; 3. First imaging prism unit; 4. Second reflection unit; 5. First imaging lens unit; 6. Human eye; 11. Third polarization unit; 21. First polarization unit; 31. Second polarization unit; 211. First linear polarizer; 212. Polarization reflector; 213. Quarter wave plate. DETAILED DESCRIPTION

[0030] 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.

[0031] 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.

[0032] Cheek reflections can affect the image quality and user experience of AR devices. To reduce this impact, it is necessary to optimize the design and user experience of AR devices.

[0033] Example 1:

[0034] As shown in FIG1-3 , an optical module capable of eliminating stray light includes an image display unit 1, a first reflection unit 2, a first polarization unit 21, a second reflection unit 4, and a first imaging prism unit 3, wherein:

[0035] Image display unit 1, used for emitting image light;

[0036] A first reflecting unit 2, comprising a first prism, for reflecting the image light to the first polarizing unit 21;

[0037] A first polarizing unit 21 is located between the first prism and the first imaging prism unit 3, and is used to reflect the image light in the first polarization transmission direction to the second reflecting unit 4 and transmit the image light in the second polarization transmission direction, the first polarization transmission direction and the second polarization transmission direction being 90°, and the first polarization transmission direction is the same as the polarization transmission direction of the image display unit;

[0038] The second reflecting unit 4 includes at least one lens and is provided with a semi-transparent and semi-reflective film on a side away from the first prism. The semi-transparent and semi-reflective film is used to reflect the image light in the first polarization transmission direction and then pass through the first reflecting unit 2 and the first imaging prism unit 3 to enter the human eye 6, and to transmit the real scene light and then pass through the first reflecting unit 2 and the first imaging prism unit 3 to enter the human eye 6;

[0039] The first imaging prism unit 3 includes a second prism and a second polarization unit 31. The second polarization unit 31 is attached to the second prism and is arranged close to the human eye 6. The second polarization unit 31 is used to transmit light parallel to the third polarization transmission direction and reflect light perpendicular to the third polarization transmission direction. The third polarization transmission direction is the same as the second polarization transmission direction.

[0040] The image display unit 1 is configured to emit image light and may be, for example, 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, or a laser beam scanning (LBS) display, preferably an OLED display. The image display unit 1 includes, but is not limited to, the aforementioned devices. The first prism and the second prism can be of any shape, preferably a triangular prism, such as a right-angle triangular prism having a first right-angle optical surface, a second right-angle optical surface and an inclined optical surface, and the first right-angle optical surface of the second prism is vertically arranged close to the human eye 6, the second right-angle optical surface is horizontally arranged, and the inclined optical surface is arranged toward the first reflection unit 2; the first prism is a triangular prism having a first optical surface, a second optical surface and a third optical surface, the first optical surface is inclined toward the image display unit 1, the second optical surface is vertically arranged close to the second reflection unit 4, and the third optical surface is parallel to the inclined optical surface of the second prism.

[0041] The second reflection 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 surface lens, Fresnel lens, flat lens, etc., preferably a spherical lens, and the semi-transparent and semi-reflective film can be achieved by coating or pasting.

[0042] The first reflector 2 is used to reflect image light toward the first polarizer 21, utilizing the principle of total internal reflection through air. The first polarizer 21 is configured to reflect image light with a first polarization transmission direction and transmit image light with a second polarization transmission direction, for example, a first polarization transmission direction of 45° and a second polarization transmission direction of -45°. The image light reflected by the first polarizer 21 is then reflected by the second reflector 4, passed through the first reflector 2, and reached the first polarizer 21. After being converted by the first polarizer 21, the image light enters the human eye 6.

[0043] Since the lens close to the human eye side in the prior art inevitably has reflections, cheek reflection is introduced (as shown in Figure 2, the horizontal right-pointing thick arrow indicates external stray light entering the second prism, and the thin arrow indicates the filtered external stray light), causing stray light and ghosting. The optical module adds a second polarization unit 31 on the eye entrance side. The second polarization unit 31 transmits all light parallel to the third polarization transmission direction and reflects all light perpendicular to the third polarization transmission direction. In this way, 50% of the external stray light is first blocked, that is, all light perpendicular to the third polarization transmission direction is reflected. In addition, although 50% of the external stray light is fully transmitted parallel to the third polarization transmission direction, its energy is much lower than the image light emitted by the image display unit 1, so that it is perfectly covered. In this way, there will be no problems such as stray light and ghosting in the image, and the problems of halo, glare, eye fatigue and discomfort caused by interference from cheek reflection and light pollution are avoided. It does not affect the user's perception and cognition of the virtual image, and improves the user's usage experience and comfort. In addition, the optical module also increases the field of view and helps achieve lightweight and thinness by folding the light path multiple times (three reflections).

[0044] In one embodiment, the first polarizing unit 21 includes a first linear polarizer 211 , a polarizing reflector 212 , and a quarter-wave plate 213 , which are sequentially arranged along a direction from the second prism to the first prism.

[0045] The first linear polarizer 211 filters the vibration direction of light, primarily by allowing light in a specific direction to pass through based on its polarization state, while blocking light in other directions. For example, in this embodiment, linear polarization of -45° is allowed to pass through, while linear polarization of 45° is not.

[0046] Polarizing reflector 212 selectively reflects or transmits light of a specific polarization direction. It is constructed by alternating multiple layers of material to achieve this polarized reflective property. In practical applications, the reflectivity of the film for different polarization states can be controlled by adjusting the thickness and composition of the film layers, thereby achieving precise control of light.

[0047] Quarter-wave plates 213 are used to change the polarization state of polarized light. They primarily convert linearly polarized light into circularly polarized light, or vice versa. Quarter-wave plates are often used in conjunction with other polarization elements (such as linear polarizers and polarizing reflectors) to achieve complex optical control and adjustment.

[0048] In one embodiment, the image display unit 1 is further provided with a third polarizing unit 11 for converting image light into 45° linearly polarized light. The third polarizing unit 11 is located on the light-emitting side of the image display unit 1 and can be attached to the image display unit 1. It is configured to convert image light into 45° linearly polarized light, allowing the first polarizing unit 21 to reflect the image light.

[0049] In one embodiment, the second polarizing unit 31 includes a second linear polarizer, and the third polarizing unit 11 includes a third linear polarizer. The second polarizing unit 31 uses the second linear polarizer to transmit light parallel to the third polarization transmission direction and to reflect light perpendicular to the third polarization transmission direction. The third polarizing unit 11 uses a third linear polarizer to convert image light. For example, the third linear polarizer is a 45° linear polarizer, emitting 45° linearly polarized light.

[0050] In one embodiment, 45° linearly polarized light undergoes a first reflection on the side of the first prism near the second reflective unit 4 to form a first light ray. The first light ray undergoes a second reflection on the first polarizing unit 21 to form a second light ray. The second light ray undergoes a third reflection on the semi-transparent and semi-reflective film to form a third light ray. The third light ray is converted into a fourth light ray by the first polarizing unit 21 and then enters the human eye 6 through the second polarizing unit 31. The first light ray is 45° linearly polarized light, the second light ray is left-handed circularly polarized light, the third light ray is right-handed circularly polarized light, and the fourth light ray is -45° linearly polarized light. The second polarizing unit 31 is used to transmit -45° linearly polarized light and reflect 45° linearly polarized light. It is easy to understand that the specific type and direction of light can also be adjusted according to actual needs to meet actual use.

[0051] In one embodiment, the second reflective unit 4 is a curved lens, with a flat surface on the side closest to the first prism and a convex surface on the side away from the first prism. A curved lens has aberration correction and light path reflection functions, and the lens material can be either glass or plastic. It will be readily understood that the number and shape of the lenses in the second reflective unit 4 can be adjusted based on actual needs.

[0052] In one embodiment, the image display unit 1 moves relative to the first reflection unit 2 to adjust the diopter, and the diopter adjustment from 0D to 6D can be achieved.

[0053] In one embodiment, the optical module capable of eliminating stray light further includes a first imaging lens unit 5, located on the light-emitting side of the image display unit 1 and comprising at least one lens. The focal length of the first imaging lens unit 5 is preferably 5 mm to 50 mm, which improves imaging quality. Due to the addition of the positive focal length of the first imaging lens unit 5, the image light rays are constrained to converge before entering the first reflective unit 2. Therefore, the angle and movement required for diopter adjustment are both smaller than those required by moving only the image display unit 1.

[0054] In one embodiment, the first imaging lens unit 5 and the image display unit 1 are synchronously moved relative to the first reflective unit 2 to perform diopter adjustment. Specifically, to ensure the integrity of the final image and excellent imaging quality, the direction in which the first imaging lens unit 5 and the image display unit 1 are synchronously moved can be made to present a certain angle with the optical axis direction of the image display unit 1, that is, there is a movement component parallel to the light-emitting surface of the image display unit 1 during movement, which can ensure that the image light emitted by the image display unit 1 within the entire movement range can normally enter the first reflective unit 2 for light conduction, ensuring that within the diopter adjustment range, the final imaging picture is complete, the entire light-emitting surface of the image display unit 1 can be fully utilized, and diopter adjustment from 0D to 6D can be achieved.

[0055] Moreover, the image display unit 1 and the first imaging lens unit 5 move synchronously. This movement method can ensure that during the movement, the angles of the light emitted from the same position of the image display unit 1 after passing through the first imaging lens unit 5 are consistent, that is, at different refractive powers, the divergence degree of the light emitted by the first imaging lens unit 5 is consistent, which can ensure that the final imaging FOV is consistent and will not be significantly reduced.

[0056] Working principle:

[0057] The image display unit 1 emits image light, which is converted into 45° linearly polarized light (the polarization transmission direction is perpendicular to the paper surface and inward) by the third polarizing unit 11. The 45° linearly polarized light passes through the first imaging lens unit 5 and is reflected for the first time on the side of the first prism near the second reflecting unit 4. After the first reflection, the 45° linearly polarized light is reflected for the second time on the first polarizing unit 21 to form left-handed circularly polarized light. The left-handed circularly polarized light is reflected for the third time on the semi-transparent and semi-reflective film to form right-handed circularly polarized light. The right-handed circularly polarized light is again converted into -45° linearly polarized light by the first polarizing unit 21 due to the action of the 1 / 4 wave plate 213, and then passes through the second polarizing unit 31 to enter the human eye 6. The first polarizing unit 21 is used to transmit -45° linearly polarized light and reflect 45° linearly polarized light, and realizes direct conversion between linearly polarized light and circularly polarized light. It can also be combined with a vapor-deposited semi-transparent and semi-reflective film to convert the polarization state of circularly polarized light.

[0058] The second polarization unit 31 is used to transmit -45° linearly polarized light and reflect 45° linearly polarized light, effectively directing the imaging light into the human eye 6. At the same time, due to the light selectivity of the second polarization unit 31, 50% of the external stray light can be directly filtered out, and the remaining 50% of the external stray light is coupled into the imaging system's most energetic point, namely, the image light emitted by the image display unit 1, thereby being perfectly masked and having almost no impact on the user experience. As shown in FIG3 , the composition of each polarization unit is illustrated. The figure is for ease of understanding only, and the relative positions of the polarization units are not strictly set according to the actual corresponding settings.

[0059] Example 2:

[0060] A near-eye display device includes the optical module capable of eliminating stray light described in any of the embodiments of Example 1, as shown in Figures 1-3. The near-eye display device can be any AR device that uses the aforementioned optical module capable of eliminating stray light. This avoids halo, glare, eye fatigue, and discomfort caused by stray light and ghosting due to cheek reflection, does not affect the user's perception and cognition of virtual images, and improves the user's user experience and comfort. The optical module formed by multiple folded light paths (three reflections) helps to increase the field of view and achieve lightweight and thinness.

[0061] 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.

[0062] 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 present invention. 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 invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. An optical module capable of eliminating stray light, wherein: The optical module capable of eliminating stray light comprises an image display unit, a first reflection unit, a first polarization unit, a second reflection unit and a first imaging prism unit, wherein: The image display unit is used to emit image light; The first reflecting unit includes a first prism, which is used to reflect the image light to the first polarizing unit; The first polarization unit is located between the first prism and the first imaging prism unit, and is used to reflect the image light in a first polarization transmission direction to the second reflection unit and transmit the image light in a second polarization transmission direction, the first polarization transmission direction is 90° to the second polarization transmission direction, and the first polarization transmission direction is the same as the polarization transmission direction of the image display unit; The second reflection unit includes at least one lens, and a semi-transparent and semi-reflective film is provided on a side away from the first prism, the semi-transparent and semi-reflective film is used to reflect the image light in the first polarization transmission direction and then pass through the first reflection unit and the first imaging prism unit in sequence to enter the human eye, and to transmit the real scene light and then pass through the first reflection unit and the first imaging prism unit in sequence to enter the human eye; The first imaging prism unit includes a second prism and a second polarization unit, the second polarization unit is attached to the second prism and arranged close to the human eye, and the second polarization unit is used to transmit light parallel to a third polarization transmission direction and reflect light perpendicular to the third polarization transmission direction, and the third polarization transmission direction is the same as the second polarization transmission direction.

2. The optical module capable of eliminating stray light according to claim 1, wherein: The first polarization unit includes a first linear polarizer, a polarization reflector, and a quarter wave plate which are sequentially arranged along a direction from the second prism to the first prism.

3. The optical module capable of eliminating stray light as claimed in claim 2, wherein: The image display unit is also provided with a third polarization unit, and the third polarization unit is used to convert the image light into 45° linear polarized light.

4. The optical module capable of eliminating stray light according to claim 3, wherein: The second polarization unit includes a second linear polarizer, and the third polarization unit includes a third linear polarizer.

5. The optical module capable of eliminating stray light as claimed in claim 3, wherein: The 45° linearly polarized light is reflected for the first time on the side of the first prism close to the second reflecting unit to form a first light ray, the first light ray is reflected for the second time on the first polarizing unit to form a second light ray, the second light ray is reflected for the third time on the semi-transparent and semi-reflective film to form a third light ray, the third light ray is converted into a fourth light ray by the first polarizing unit and then enters the human eye through the second polarizing unit, the first light ray is 45° linearly polarized light, the second light ray is left-handed circularly polarized light, the third light ray is right-handed circularly polarized light, the fourth light ray is -45° linearly polarized light, and the second polarizing unit is used to transmit -45° linearly polarized light and reflect 45° linearly polarized light.

6. The optical module capable of eliminating stray light according to claim 1, wherein: The second reflection unit is a curved lens, and a side close to the first prism is a flat surface, and a side away from the first prism is a convex surface.

7. The optical module capable of eliminating stray light according to claim 1, wherein: The image display unit moves relative to the first reflection unit to adjust the diopter.

8. The optical module capable of eliminating stray light according to claim 1, wherein: The optical module capable of eliminating stray light further includes a first imaging lens unit, which is located at the light-emitting side of the image display unit and includes at least one lens.

9. The optical module capable of eliminating stray light according to claim 8, wherein: The first imaging lens unit and the image display unit move synchronously relative to the first reflection unit to perform diopter adjustment.

10. A near-eye display device, wherein: The near-eye display device comprises an optical module capable of eliminating stray light as described in any one of claims 1-9.

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