Optical System and Head-Mounted Display Device

Abstract

Embodiments of the present disclosure disclose an optical system and a head-mounted display device. In a specific implementation solution, the optical system includes: an image source; a first prism having a first surface, a second surface, and a third surface, the first surface of the first prism being close to the image source; a second prism, the second surface of the first prism being on a side of the first prism away from the second prism, the third surface of the first prism being on a side of the first prism close to the second prism, the second prism having a first surface, the first surface of the second prism being close to the third surface of the first prism; a lens located on a side of the second prism away from the first prism, a first angle between the first surface of the second prism and the optical axis of the lens and a second angle between the third surface of the first prism and the optical axis of the lens both being acute angles, the first angle being equal to the second angle; a first film layer located on the second surface of the first prism and capable of reflecting and transmitting light; and a second film layer located on a side of the lens away from the second prism and capable of reflecting light.

Description

Technical Field

[0001] The present disclosure relates to the field of optical imaging technology, and particularly to an optical system and a head-mounted display device. Background Art

[0002] Currently, head-mounted display devices are increasingly widely used. Head-mounted display devices can be used for content display. For example, head-mounted display devices can be used to display movie scenes, game scenes, web pages, etc. The optical system is an important part of the head-mounted display device. Summary of the Invention

[0003] According to one aspect of the embodiments of the present disclosure, an optical system is provided, including: an image source; a first prism having a first surface, a second surface, and a third surface, the first surface of the first prism being close to the image source; a second prism, the second surface of the first prism being on the side away from the second prism, the third surface of the first prism being on the side close to the second prism, the second prism having a first surface, the first surface of the second prism being close to the third surface of the first prism; a lens located on the side of the second prism away from the first prism, a first angle between the first surface of the second prism and the optical axis of the lens and a second angle between the third surface of the first prism and the optical axis of the lens both being acute angles, and the first angle being equal to the second angle; a first film layer located on the second surface of the first prism, capable of reflecting light and transmitting light; a second film layer located on the side of the lens away from the second prism, capable of reflecting light; wherein the light emitted by the image source enters the first prism from the first surface of the first prism, undergoes at least one total reflection in the first prism, is reflected by the first film layer, exits from the third surface of the first prism and enters the second prism from the first surface of the second prism, is reflected by the second film layer after passing through the second prism and the lens, and the light after being reflected by the second film layer sequentially passes through the lens, the first surface of the second prism, the third surface of the first prism, and the second surface of the first prism, and exits through the first film layer.

[0004] According to another aspect of the embodiments of the present disclosure, a head-mounted display device is provided, including: a frame structure; the above optical system, the optical system being installed on the frame structure.

[0005] The technical solutions of the present disclosure will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0006] The above and other objects, features, and advantages of the present disclosure will become more apparent by describing the embodiments of the present disclosure in more detail with reference to the accompanying drawings. The accompanying drawings are used to provide a further understanding of the embodiments of the present disclosure and constitute a part of the specification. Together with the embodiments of the present disclosure, they are used to explain the present disclosure and do not constitute a limitation to the present disclosure. In the accompanying drawings, the same reference numerals generally represent the same components or steps;

[0007] Figure 1 is a schematic structural diagram of an optical system provided by some exemplary embodiments of the present disclosure;

[0008] Figure 2 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0009] Figure 3-1 is a schematic structural diagram of an optical system provided by some further exemplary embodiments of the present disclosure;

[0010] Figure 3-2 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0011] Figure 4 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0012] Figure 5 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0013] Figure 6 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0014] Figure 7 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0015] Figure 8 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0016] Figure 9-1 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0017] Figure 9-2 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0018] Figure 10-1 is a schematic diagram of the effects of an optical system provided by some exemplary embodiments of the present disclosure;

[0019] Figure 10-2 is a schematic diagram of the effects of an optical system provided by some other exemplary embodiments of the present disclosure;

[0020] Figure 10-3 It is a schematic diagram of the effect of the optical system provided in some further exemplary embodiments of the present disclosure;

[0021] Figure 11-1 It is a schematic structural diagram of the optical system provided in some other exemplary embodiments of the present disclosure;

[0022] Figure 11-2 It is a schematic structural diagram of the optical system provided in some other exemplary embodiments of the present disclosure;

[0023] Figure 11-3 It is a schematic structural diagram of the optical system provided in some other exemplary embodiments of the present disclosure;

[0024] Figure 11-4 It is a schematic structural diagram of the optical system provided in some other exemplary embodiments of the present disclosure;

[0025] Figure 12 It is a schematic diagram of the frame structure in some exemplary embodiments of the present disclosure.

[0026] In the figure, 10 is the image source; 20 is the first prism; 30 is the second prism; 40 is the lens; 45 is the first film layer; 50 is the second film layer; 201 is the first surface of the first prism; 203 is the second surface of the first prism; 205 is the third surface of the first prism; 207 is the groove; 100 is the human eye; 301 is the first surface of the second prism; V is the light ray incident on the first prism from the first surface of the first prism; 60 is the third prism; 601 is the first surface of the third prism; 603 is the second surface of the third prism; 70 is the first additional lens; 80 is the second additional lens; Z is the axis; ∠R1 is the angle between the first surface of the second prism and the optical axis of the lens; ∠R2 is the angle between the third surface of the first prism and the optical axis of the lens; U1 is the central thickness of one optical system; U2 is the central thickness of another optical system; P is the position to which the first common side needs to be moved; ∠A is the angle between the second surface of the first prism and the target plane; ∠C is the angle between the first surface of the first prism and the third surface of the first prism; ∠B is the angle between the third surface of the first prism and the target plane; ∠Q is the angle between the first surface of the second prism and the target plane; ∠E is the angle between the light ray incident on the third surface of the first prism from the first surface of the first prism and the third surface of the first prism; ∠R3 is the angle between the normal line of the image source and the optical axis of the lens; ∠R4 is the angle between the second surface of the first prism and the optical axis of the lens; 90 is the frame structure. Detailed implementation manners

[0027] Next, exemplary embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments of the present disclosure. It should be understood that the present disclosure is not limited by the exemplary embodiments described herein.

[0028] In the description of the present disclosure, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present disclosure.

[0029] In the description of the present disclosure, unless otherwise clearly defined and limited, terms such as "mounted", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0030] Exemplary Overview

[0031] A head-mounted display device can also be referred to as a Head-Mounted Display (HMD) or a head-mounted display. The head-mounted display device can be used to achieve Augmented Reality (AR) effects, Virtual Reality (VR) effects, Mixed Reality (MR) effects, etc. The head-mounted display device can be presented in the form of glasses, helmets, etc.

[0032] The optical system is an important part of the head-mounted display device. The optical system can also be referred to as an optical-mechanical device. The optical system can be used to emit light and process the light so that the light enters the eyebox of the optical system. When the user wears the head-mounted display device, the user's eyes can be located in the eyebox, the light can be projected onto the user's eyes, and the user can see the display screen. Therefore, in order to ensure the user experience, it is necessary to reasonably design the optical system.

[0033] Exemplary Structure

[0034] Some exemplary embodiments of the present disclosure provide an optical system. The optical system provided by the embodiments of the present disclosure may include an image source, a prism, and a lens.

[0035] For example, as Figure 1 shown, the optical system provided by the embodiments of the present disclosure may include an image source 10, a first prism 20, and a lens 40.

[0036] In some alternative embodiments of the present disclosure, an image source 10 can be used to emit light for a display screen. The image source 10 can include, but is not limited to, an Organic Light Emitting Diode (OLED) image source, a Liquid Crystal (LC) image source, a Liquid Crystal on Silicon (LCOS) image source, a MicroElectroMechanical System (MEMS) image source, a Digital Micromirror Device (DMD), etc. For example, the image source 10 can be an OLED display screen.

[0037] In some alternative embodiments of the present disclosure, a first prism 20 can be used to extend the optical path of an optical system. The first prism 20 can have a first surface 201, a second surface 203, and a third surface 205. For example, the first surface 201 and the second surface 203 of the first prism 20 can intersect, the first surface 201 and the third surface 205 can intersect, and the second surface 203 and the third surface 205 can intersect. The first surface 201, the second surface 203, and the third surface 205 of the first prism 20 can all be flat surfaces, and the first prism 20 can be a triangular prism. In an alternative example, the first surface 201 of the first prism 20 can be perpendicular to the second surface 203 of the first prism 20, and the first prism 20 can be a right prism.

[0038] It can be understood that the "intersection" or "included angle" described in the present disclosure can be the actual intersection of two elements and the actual included angle between the two elements. If two elements do not actually intersect or do not form an included angle between them, after the two elements are extended along their respective extending directions, the non-actually existing parts after extension can also intersect or form an included angle, meeting the relevant limitations in the embodiments of the present disclosure.

[0039] In some embodiments, the first surface 201 of the first prism 20 can also be a curved surface to facilitate optimizing field curvature and pupil shift distortion.

[0040] In some alternative embodiments of the present disclosure, a lens 40 can be used to bear the optical power and correct aberrations. The first surface 201 of the first prism 20 can be close to the image source 10. The second surface 203 of the first prism 20 can be on the side of the first prism 20 away from the lens 40. The third surface 205 of the first prism 20 can be on the side of the first prism 20 close to the lens 40. For example, the first surface 201 of the first prism 20 can be opposite to the image source 10. The first surface 201 and the second surface 203 of the first prism 20 can both be on the side of the first prism 20 close to the exit pupil of the optical system.

[0041] It can be understood that the eyebox of the optical system can be the area where the human eye (such as the human eye 100 in Figure 1 ) can move. Within this area, the human eye 100 can see the display screen. The eyebox of the optical system can also be referred to as the Eye Box or EB. The size of the eyebox of the optical system is an important design index in the optical system.

[0042] In some alternative embodiments of the present disclosure, as Figure 1 shown, the optical system provided by the embodiments of the present disclosure may further include film layers, such as a first film layer 45 and a second film layer 50. The first film layer 45 may be located on the second surface 203 of the first prism 20 and can reflect and transmit light. The first film layer 45 may be a semi-transmissive semi-reflective film without beam splitting ability or a polarization beam splitting film. The first film layer 45 may be disposed on the second surface 203 of the first prism 20 by means of bonding, coating, etc. The second film layer 50 may be located on the side of the lens 40 away from the first prism 20 and can reflect light. The second film layer 50 may be used for total reflection or partial reflection of light. Thus, the second film layer 50 may be a total reflection film or a semi-transmissive semi-reflective film. The second film layer 50 may be disposed on the side of the lens 40 away from the first prism 20 by means of bonding, coating, etc.

[0043] It should be noted that the light emitted by the image source 10 can enter the first prism 20 from the first surface 201 of the first prism 20. After at least one total reflection within the first prism 20, it is reflected by the first film layer 45 and exits from the third surface 205 of the first prism 20. After passing through the lens 40, it is reflected by the second film layer 50. The light reflected by the second film layer 50 passes through the lens 40, the third surface 205 of the first prism 20, and the second surface 203 of the first prism 20 in sequence and exits through the first film layer 45. The light exiting from the first film layer 45 can enter the eyebox of the optical system.

[0044] In the optical system provided by the embodiments of the present disclosure, through the combined use of the image source 10, the first prism 20, the lens 40, the first film layer 45, and the second film layer 50, the light emitted by the image source 10 can enter the eyebox of the optical system. Thus, the human eye 100 can see the display screen provided by the image source 10. Therefore, the head-mounted display device can normally display content to meet the user's usage requirements, such as meeting the user's movie-watching requirements.

[0045] In some alternative embodiments of the present disclosure, as Figure 2 、 Figure 3-1 、 Figure 3-2As shown, in addition to including an image source 10, a first prism 20, a lens 40, a first film layer 45, and a second film layer 50, the optical system provided by the implementation of the present disclosure may further include a second prism 30. The second surface 203 of the first prism 20 may be located on the side of the first prism 20 away from the second prism 30. The third surface 205 of the first prism 20 may be located on the side of the first prism 20 close to the second prism 30. The second prism 30 may have a first surface 301. The first surface 301 of the second prism 30 may be close to the third surface 205 of the first prism 20. The first surface 301 of the second prism 30 may be a flat surface. The first surface 301 of the second prism 30 and the third surface 205 of the first prism 20 may be opposite and have a gap therebetween.

[0046] In some alternative embodiments of the present disclosure, the lens 40 may be located on the side of the second prism 30 away from the first prism 20. The lens 40 and the second prism 30 may be an integral part, for example, see Figure 2 , Figure 3-2 . Or, the lens 40 and the second prism 30 may be separately arranged, for example, see Figure 3-1 . If the lens 40 and the second prism 30 are an integral part, it can be understood that one surface of the second prism 30 is a curved surface, and the part constituting the lens 40 and the part constituting the second prism 30 may be integrally injection molded. If the lens 40 and the second prism 30 are separately arranged, the lens 40 and the second prism 30 may be injection molded separately and fixedly connected by means such as bonding. In addition, the surface of the lens 40 away from the second prism 30 may be a spherical surface or an aspherical surface. For example, the surface of the lens 40 away from the second prism 30 may be a rotationally symmetric aspherical surface.

[0047] It should be noted that the light emitted by the image source 10 may enter the first prism 20 from the first surface 201 of the first prism 20, and after at least one total reflection in the first prism 20, it is reflected by the first film layer 45, exits from the third surface 205 of the first prism 20 and enters the second prism 30 from the first surface 301 of the second prism 30. After passing through the second prism 30 and the lens 40, it is reflected by the second film layer 50. The light after being reflected by the second film layer 50 sequentially passes through the lens 40, the first surface 301 of the second prism 30, the third surface 205 of the first prism 20, and the second surface 203 of the first prism 20, and exits through the first film layer 45.

[0048] In some alternative embodiments of the present disclosure, the light entering the first prism 20 from the first surface 201 of the first prism 20 (for example Figure 2The light V) in it can first undergo a total internal reflection at the third surface 205 of the first prism 20, and then undergo a reflection at the second surface 203 of the first prism 20 (which can be reflected by the first film layer 45), and then exit from the third surface 205 of the first prism 20 and enter the second prism 30 from the first surface 301 of the second prism 30. Of course, before the light incident on the first surface 201 of the first prism 20 exits from the third surface 205 of the first prism 20, the number of total internal reflections experienced by the light within the first prism 20 may not be limited to one, and the number of reflections within the first prism 20 may also not be limited to one. For example, after undergoing a total internal reflection at the third surface 205 of the first prism 20 and a reflection at the second surface 203 of the first prism 20, it can undergo another total internal reflection at the third surface 205 of the first prism 20 and another reflection at the second surface 203 of the first prism 20, and then exit from the third surface 205 of the first prism 20.

[0049] The light exiting from the third surface 205 of the first prism 20 can enter the second prism 30 from the first surface 301 of the second prism 30. The light incident on the second prism 30 can propagate to the second film layer 50 after passing through the second prism 30 and the lens 40 in sequence. The second film layer 50 can reflect the light to adjust the light propagation direction. For example, referring to Figure 2 , the second film layer 50 can adjust the propagation direction of the light from the horizontal rightward direction to the horizontal leftward direction. In this way, the light with the adjusted propagation direction can pass through the lens 40, the first surface 301 of the second prism 30, the third surface 205 of the first prism 20, the second surface 203 of the first prism 20, and the first film layer 45 in sequence until it reaches the eyebox of the optical system.

[0050] In the optical system provided by the embodiments of the present disclosure, through the combined use of the image source 10, the first prism 20, the second prism 30, the lens 40, the first film layer 45, and the second film layer 50, the light emitted by the image source 10 can enter the eyebox of the optical system. In this way, the human eye 100 can see the display screen provided by the image source 10. Therefore, the head-mounted display device can normally display content to meet the user's usage requirements, such as meeting the user's movie-watching requirements.

[0051] In some alternative embodiments of the present disclosure, the optical system may further include a compensating member. The compensating member can compensate for the deflection of light in the first prism 20 and can also perform an optical path compensation function to make up for the optical path difference generated after the light emitted from different light-emitting positions on the image source 10 propagates in the first prism 20, so that the optical paths of the light emitted from different light-emitting positions are substantially the same. The compensating member can be close to the second surface 203 of the first prism 20. After the light reflected by the second film layer 50 passes through the first prism 20 again, it exits through the compensating member. For example, the light emitted from the image source 10 can propagate along the following target path: the first prism 20 → the first film layer 45 → the first prism 20 → the second prism 30 → the lens 40 → the second film layer 50 → the lens 40 → the second prism 30 → the first prism 20 → the first film layer 45 → the compensating member → the eyebox of the optical system.

[0052] In this way, in the case where the compensating member is introduced, the light emitted from the image source 10 can enter the eyebox of the optical system. Thus, the human eye 100 can see the display screen provided by the image source 10. In addition, in the case where the compensating member is introduced, it is beneficial to ensure that the optical paths of the light emitted from different light-emitting positions are substantially the same, and it is beneficial to compensate for the deflection of the light in the first prism 20, thereby improving the imaging quality of the optical system.

[0053] In some alternative embodiments of the present disclosure, as Figures 2 to 5 shown, the compensating member can be a third prism 60. The third prism 60 can have a first surface 601 and a second surface 603. The first surface 601 of the third prism 60 can be located on the side of the third prism 60 away from the first prism 20. The second surface 603 of the third prism 60 can be located on the side of the third prism 60 close to the first prism 20. After the light reflected by the second film layer 50 passes through the first prism 20 again, it exits through the second surface 603 and the first surface 601 of the third prism 60.

[0054] Optionally, both the first surface 601 and the second surface 603 of the third prism 60 can be flat surfaces. For example, reference can be made to Figure 2 、 Figure 3-1 、 Figure 3-2 . Or, the first surface 601 of the third prism 60 can be a curved surface, and the second surface 603 of the third prism 60 can be a flat surface. For example, reference can be made to Figure 4 、 Figure 5The first surface 601 and the second surface 603 of the third prism 60 may intersect. The first film layer 45 may be a polarization beam splitting film located between the second surface 603 of the third prism 60 and the second surface 203 of the first prism 20. A quarter-wave plate may be provided between the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30. The polarization beam splitting film and the quarter-wave plate may be used in combination to enable the light emitted by the image source 10 to propagate along the target path described above.

[0055] After the light reflected by the second film layer 50 passes through the first prism 20 again, it may exit from the second surface 203 of the first prism 20 and enter the third prism 60 from the second surface 603 of the third prism 60, and then exit from the first surface 601 of the third prism 60 until it reaches the exit pupil of the optical system.

[0056] In this way, when the compensating member is the third prism 60, the light emitted by the image source 10 can enter the exit pupil of the optical system. Thus, the human eye 100 can see the display screen provided by the image source 10. In addition, the third prism 60 is beneficial to ensuring that the optical paths of the light emitted from different light-emitting positions are basically the same, and is beneficial to compensating for the deflection of the light in the first prism 20, improving the imaging quality of the optical system. Moreover, the surface shape of the third prism 60 is simple and convenient for processing.

[0057] In some alternative embodiments of the present disclosure, as Figures 4 to 8 shown, the optical system may further include a first additional lens 70. The first additional lens 70 may be located between the image source 10 and the first surface 201 of the first prism 20. The light emitted by the image source 10 may enter the first prism 20 after passing through the first additional lens 70.

[0058] Optionally, the first additional lens 70 may be a positive lens. For example, the first additional lens 70 may be a plano-convex lens. For another example, the first additional lens 70 may be a biconvex lens.

[0059] Due to the arrangement of the first additional lens 70, the light emitted by the image source 10 may first pass through the first additional lens 70 and then enter the first prism 20 from the first surface 201 of the first prism 20. The first additional lens 70 may be an aspherical lens, which is beneficial to correcting aberration to ensure the imaging quality of the optical system.

[0060] In some embodiments of the present disclosure, at least one of the image source 10 and the first additional lens 70 may move relative to the first prism 20 for diopter adjustment.

[0061] In some alternative embodiments of the present disclosure, the second film layer 50 may be a semi-transmissive and semi-reflective film. As Figure 5 、 Figure 7 、 Figure 8As shown, the optical system may further include a second additional lens 80. The second additional lens 80 may be located on a side of the second film layer 50 away from the lens 40.

[0062] Optionally, the second additional lens 80 and the second film layer 50 may be in contact. Alternatively, there may be a gap between the second additional lens 80 and the second film layer 50.

[0063] Here, the second additional lens 80 may be used as a compensating lens for the lens 40. Since the second additional lens 80 is located on a side of the second film layer 50 away from the lens 40, light in the external environment (which may also be referred to as ambient light) may sequentially pass through the second additional lens 80, the second film layer 50, the lens 40, the second prism 30, the first prism 20, the third prism 60, and reach the eyebox of the optical system. In this way, the ambient light can enter the human eye 100 without deflection, and when the user wears the head-mounted display device to observe the external environment, the user can see an undistorted environmental image.

[0064] In some embodiments, the first surface 601 of the third prism 60 may be a curved surface, for example, a concave surface, and the concave surface can effectively compensate the optical power of the lens 40. In this case, it may not be necessary to additionally provide the second additional lens 80 used as a compensating lens for the lens 40.

[0065] In some alternative embodiments of the present disclosure, as Figure 8 , Figure 9-1 , Figure 9-2 shown, a partial region of the second surface 203 of the first prism 20 close to the image source 10 may have a groove 207. The groove 207 may be recessed inward from this partial region (subsequently, this partial region may be referred to as the target region) into the first prism 20.

[0066] Optionally, the common edge of the first surface 601 and the second surface 603 of the third prism 60 may be denoted as the first common edge. The target region may be located in the second surface 203 of the first prism 20, in the region between the first surface 201 of the first prism 20 and the first common edge. The groove 207 may be a V-shaped groove.

[0067] It should be noted that from the edge region of the image source 10 (for example Figures 2 to 9-2After the light rays emitted from the lower left edge area of the middle image source 10 enter the first prism 20 from the first surface 201 of the first prism 20, they may directly project onto the target area of the second surface 203 of the first prism 20 (that is, they do not project onto the third surface 205 of the first prism 20 first according to the designed optical path). If the light rays directly projecting onto the target area of the second surface 203 of the first prism 20 subsequently reach the exit pupil of the optical system together with the normal optical path, it may cause ghost images and cannot guarantee the imaging quality of the optical system. Through research, it is found that by setting a groove 207 in a partial area of the second surface 203 of the first prism 20 close to the image source 10, the propagation path of the light rays directly projecting onto the target area of the second surface 203 of the first prism 20 can be changed, so that the light rays cannot reach the exit pupil of the optical system. For example, making the light rays not satisfy the total reflection condition (such as not satisfying the condition that the incident angle is greater than or equal to the critical angle), which is beneficial to eliminating ghost images and guaranteeing the imaging quality of the optical system.

[0068] In some alternative embodiments of the present disclosure, a partial area of the second surface 203 of the first prism 20 close to the image source 10 may be coated black. For example, the groove walls of the groove 207 may be coated black.

[0069] Optionally, the groove walls of the groove 207 may be coated black through a coating process. In this way, the light rays directly projecting onto the target area of the second surface 203 of the first prism 20 will be absorbed and total reflection will not occur, which is beneficial to eliminating ghost images and guaranteeing the imaging quality of the optical system.

[0070] In some alternative embodiments of the present disclosure, a partial area of the second surface 203 of the first prism 20 close to the image source 10 may be a rough surface. For example, the groove walls of the groove 207 may be rough surfaces.

[0071] Optionally, the groove walls of the groove 207 may have a large surface roughness. In this way, the light rays directly projecting onto the target area of the second surface 203 of the first prism 20 will undergo diffuse reflection and total reflection will not occur, which is beneficial to eliminating ghost images and guaranteeing the imaging quality of the optical system.

[0072] In some alternative embodiments of the present disclosure, the first included angle between the first surface 301 of the second prism 30 and the optical axis of the lens 40 and the second included angle between the third surface 205 of the first prism 20 and the optical axis of the lens 40 may both be acute angles, and the first included angle may be equal to the second included angle. Herein, the first included angle may be equal to the second included angle can be understood that the two included angles may be equal or substantially the same.

[0073] Optionally, the optical axis of the lens 40 may be represented as Figure 2the axis Z therein. The first surface 301 of the second prism 30 can be inclined relative to the optical axis of the lens 40 such that the first included angle between the first surface 301 of the second prism 30 and the optical axis of the lens 40 is an acute angle. The third surface 205 of the first prism 20 can be inclined relative to the optical axis of the lens 40 such that the second included angle between the third surface 205 of the first prism 20 and the optical axis of the lens 40 is an acute angle. The inclination of the third surface 205 of the first prism 20 relative to the optical axis of the lens 40 can be consistent with the inclination of the first surface 301 of the second prism 30 relative to the optical axis of the lens 40. The inclination of the third surface 205 of the first prism 20 relative to the optical axis of the lens 40 can be characterized by the first included angle between the first surface 301 of the second prism 30 and the optical axis of the lens 40. The first included angle can be referred to Figure 2 ∠R1 in. The inclination of the first surface 301 of the second prism 30 relative to the optical axis of the lens 40 can be characterized by the second included angle between the third surface 205 of the first prism 20 and the optical axis of the lens 40, and the second included angle can be referred to Figure 2 ∠R2 in. Here, both ∠R1 and ∠R2 can be between 0 degrees and 90 degrees, and ∠R1 and ∠R2 can be equal.

[0074] Figure 10-1 、 Figure 10-2 、 Figure 10-3 both show two optical systems. In Figure 10-1 、 Figure 10-2 、 Figure 10-3 in any one of the three, for the optical system on the right, the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 are both inclined relative to the optical axis of the lens 40, and the inclination of the third surface 205 of the first prism 20 relative to the optical axis of the lens 40 is consistent with the inclination of the first surface 301 of the second prism 30 relative to the optical axis of the lens 40. For the optical system on the left, the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 are both not inclined relative to the optical axis of the lens 40 (i.e., the case where ∠R1 and ∠R2 are substantially right angles). In addition, the thickness (central thickness) along the optical axis of the lens 40 of the optical system on the left can be expressed as U1, and the thickness (central thickness) along the optical axis of the lens 40 of the optical system on the right can be expressed as U2, and U1 and U2 are the same. It should be noted that Figure 10-1 schematically shows Figures 2 to 9-2 the direction of light rays emitted from a certain point in the right half region of the image source 10 in Figure 10-2 schematically shows Figures 2 to 9-2 the direction of light rays emitted from a certain point in the left half region of the image source 10 in Figure 10-3 simultaneously schematically shows Figures 2 to 9-2The directions of light rays emitted from a certain point in the left half region and a certain point in the right half region of the image source 10. The dashed line in the figure represents the optical axis of the optical system.

[0075] The eye box of the optical system needs to cover the light rays in each region of the image source 10 to ensure the user experience. In Figure 10-3 the thick vertical line schematically shows the size of the eye box of the optical system in this cross-section. By comparing the two optical systems, it can be seen that when the central thickness is the same and the same field of view angle is achieved, the size of the eye box of the optical system on the left is smaller than the size of the eye box of the optical system on the right. Therefore, in the embodiments of the present disclosure, by making both the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 inclined with respect to the optical axis of the lens 40, and making the inclination of the third surface 205 of the first prism 20 with respect to the optical axis of the lens 40 consistent with the inclination of the first surface 301 of the second prism 30 with respect to the optical axis of the lens 40, it is beneficial to achieve a larger eye box under the same central thickness and the same field of view angle. In addition, by observation, it can be seen that if the size of the eye box of the optical system on the right is to be reduced to the size of the eye box of the optical system on the left, the first common side (i.e., the common side of the first surface 601 and the second surface 603 of the third prism 60) in the above can be moved to Figure 10-1 the position P in. Obviously, if the first common side is moved to the position P, U2, which is the central thickness of the optical system on the right, will also be reduced accordingly. Therefore, in the embodiments of the present disclosure, by making both the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 inclined with respect to the optical axis of the lens 40, and making the inclination of the third surface 205 of the first prism 20 with respect to the optical axis of the lens 40 consistent with the inclination of the first surface 301 of the second prism 30 with respect to the optical axis of the lens 40, it is also beneficial to achieve a smaller central thickness under the same field of view angle and the same size of the eye box, thereby facilitating the miniaturization and light weight of the optical system.

[0076] In some alternative embodiments of the present disclosure, the angle between the second surface 203 of the first prism 20 and the plane perpendicular to the optical axis of the lens 40 is the third angle, and the angle between the first surface 201 and the third surface 205 of the first prism 20 is the fourth angle, then the fourth angle can be greater than twice the third angle.

[0077] For the sake of convenience of description, the plane perpendicular to the optical axis of the lens 40 can be referred to as the target plane. The angle between the second surface 203 of the first prism 20 and the target plane (i.e., the third angle) can be expressed as Figure 2 the ∠A shown in. The angle between the third surface 205 of the first prism 20 and the target plane (i.e., the fifth angle hereinafter) can be expressed as Figure 2The included angle ∠B shown. The included angle (i.e., the third included angle) between the first surface 201 and the third surface 205 of the first prism 20 can be expressed as Figure 2 The included angle ∠C shown.

[0078] In some alternative embodiments of the present disclosure, ∠C≠2∠A. For example, ∠C>2∠A.

[0079] Optionally, the common edge of the second surface 203 and the third surface 205 of the first prism 20 can be referred to as the second common edge. The target plane can be a plane passing through the second common edge and perpendicular to Figure 2 the axis Z therein.

[0080] It can be understood that when the prism has a tip, two adjacent surfaces extend until they contact each other to form an actual common edge. When the prism does not have a tip, that is, two adjacent surfaces cannot extend until they contact each other, but stop at different positions, the common edge can be the edge formed by the theoretical extension of two adjacent surfaces until they contact each other.

[0081] For the case where the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 introduced above are not inclined relative to the optical axis of the lens 40, ∠C = 2∠A can be satisfied. By making ∠C≠2∠A, the optical system provided by the embodiments of the present disclosure can be significantly different from the optical system in this case. For example, in the optical system provided by the embodiments of the present disclosure, the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 are both inclined relative to the optical axis of the lens 40, and the inclination of the third surface 205 of the first prism 20 relative to the optical axis of the lens 40 can be the same as the inclination of the first surface 301 of the second prism 30 relative to the optical axis of the lens 40. In this way, it is beneficial to achieve a larger eyebox under the same center thickness and the same field of view angle, and it is beneficial to achieve a smaller center thickness under the same field of view angle and the same size of the eyebox, so as to be beneficial to the miniaturization and lightweight of the optical system.

[0082] In some alternative embodiments of the present disclosure, the fourth included angle can be equal to the sum of the fifth included angle and twice the third included angle. That is, ∠C = 2∠A + ∠B.

[0083] In some alternative embodiments of the present disclosure, the absolute value of the difference between the sum of the fifth included angle and twice the third included angle and the fourth included angle is less than or equal to 0.8 degrees. That is, |∠C-(2∠A + ∠B)|≤0.8°.

[0084] Optionally, |∠C - (2∠A + ∠B)| can be equal to 0, that is, ∠C and (2∠A + ∠B) can be the same. Of course, ∠C and (2∠A + ∠B) can also be different but close enough, that is, ∠C and (2∠A + ∠B) can be substantially the same. For example, |∠C - (2∠A + ∠B)| can be equal to 0.1°, 0.2°, 0.7°, etc., which will not be listed one by one here.

[0085] By the limiting condition of |∠C - (2∠A + ∠B)| ≤ 0.8°, ∠C and (2∠A + ∠B) can be made the same or substantially the same. Through research, it is found that ∠C and (2∠A + ∠B) being the same or substantially the same is beneficial to ensuring that for the optical system provided by the embodiments of the present disclosure, the light rays emitted by the image source 10 propagate along the target path introduced above.

[0086] In some alternative embodiments of the present disclosure, the ratio of twice the sum of the third angle and the fifth angle to the complementary angle of the third angle is greater than 0.9. That is, 2(∠A + ∠B) / (90° - ∠A) > 0.9.

[0087] In some alternative embodiments of the present disclosure, the difference between twice the sum of the third angle and the fifth angle and the complementary angle of the third angle is greater than -6 degrees. That is, 2(∠A + ∠B) - (90° - ∠A) > -6°. 2(∠A + ∠B) - (90° - ∠A) > -6° can also be transformed into 3∠A + ∠2B - 90° > -6°.

[0088] Through geometric derivation, it can be known that 2(∠A + ∠B) can be equal to the angle between the normal of the image source 10 and the optical axis of the lens 40, and the angle between the normal of the image source 10 and the optical axis of the lens 40 can be represented as Figure 2 ∠R3 in. In addition, 90° - ∠A can be equal to the angle between the second surface 203 of the first prism 20 and the optical axis of the lens 40, and the angle between the second surface 203 of the first prism 20 and the optical axis of the lens 40 can be represented as Figure 2 ∠R4 in. Through research, it is found that limiting ∠A and ∠B to 2(∠A + ∠B) / (90° - ∠A) > 0.9, 3∠A + ∠2B - 90° > -6° is beneficial to making the light rays that may form ghost images as far away from the effective display screen as possible to ensure the imaging quality of the optical system.

[0089] In some alternative embodiments of the present disclosure, the fifth angle can be greater than 5 degrees and less than 15 degrees. That is, ∠B can be greater than 5° and less than 15°. In other words, ∠B can be restricted within the range of (5°, 15°). For example, ∠B can be 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14°, etc., which will not be listed one by one here.

[0090] Through research, it is found that restricting ∠B within the range of (5°, 15°) is beneficial to ensuring the rationality of the parameters of the first prism 20, and thus beneficial to ensuring the imaging quality of the optical system.

[0091] In some alternative embodiments of the present disclosure, the fifth included angle can be greater than 5 degrees and less than 8 degrees, or the fifth included angle can be greater than 8 degrees and less than 15 degrees. That is to say, ∠B can be greater than 5° and less than 8°, or ∠B can be greater than 8° and less than 15°. In other words, ∠B can be restricted within the range of (5°, 8°) ∪ (8°, 15°). For example, ∠B can be 6°, 7°, 9°, 10°, 11°, 12°, 13°, 14°, etc., which will not be listed one by one here.

[0092] In some alternative embodiments of the present disclosure, the fifth included angle can be greater than or equal to 7.5 degrees and less than or equal to 8 degrees. That is to say, ∠B can be greater than or equal to 7.5° and less than or equal to 8°. In other words, ∠B can be restricted within the range of [7.5°, 8°]. For example, ∠B can be 7.5°, 7.7°, 7.8°, 7.9°, 8°, etc., which will not be listed one by one here.

[0093] In some alternative embodiments of the present disclosure, the fifth included angle can be greater than 8.1 degrees and less than 8.7 degrees. That is to say, ∠B can be greater than 8.1° and less than 8.7°. In other words, ∠B can be restricted within the range of (8.1°, 8.7°). For example, ∠B can be 8.2°, 8.3°, 8.4°, 8.5°, 8.6°, etc., which will not be listed one by one here.

[0094] In some alternative embodiments of the present disclosure, the fifth included angle can be greater than or equal to 8.7 degrees and less than or equal to 9.3 degrees. That is to say, ∠B can be greater than or equal to 8.7° and less than or equal to 9.3°. In other words, ∠B can be restricted within the range of [8.7°, 9.3°]. For example, ∠B can be 8.7°, 8.8°, 8.9°, 9.1°, 9.2°, 9.3°, etc., which will not be listed one by one here.

[0095] In some alternative embodiments of the present disclosure, the fifth included angle can be greater than or equal to 9.4 degrees and less than or equal to 9.8 degrees. That is to say, ∠B can be greater than or equal to 9.4° and less than or equal to 9.8°. In other words, ∠B can be restricted within the range of [9.4°, 9.8°]. For example, ∠B can be 9.4°, 9.5°, 9.6°, 9.7°, 9.8°, etc., which will not be listed one by one here.

[0096] In some alternative embodiments of the present disclosure, the third included angle may be greater than 20 degrees and less than 30 degrees. That is, ∠A may be greater than 20° and less than 30°. In other words, ∠A may be restricted within the range of (20°, 30°). For example, ∠A may be 21°, 23°, 24°, 25°, 27°, 28°, 29°, etc., and will not be listed one by one here.

[0097] Through research, it is found that restricting ∠A within the range of (20°, 30°) is beneficial to ensuring the rationality of the parameters of the first prism 20, and thus beneficial to ensuring the imaging quality of the optical system.

[0098] In some alternative embodiments of the present disclosure, the included angle between the third surface 205 of the first prism 20 and the target plane may be equal to the included angle between the first surface 301 of the second prism 30 and the target plane.

[0099] Optionally, the included angle between the third surface 205 of the first prism 20 and the target plane may be equal to Figure 2 the shown ∠B, and the included angle between the first surface 301 of the second prism 30 and the target plane may be equal to Figure 2 the ∠Q in, then, there may be ∠Q = ∠B. In this case, the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 may be parallel to each other.

[0100] Through research, it is found that if ∠Q = ∠B, then ∠R2 = ∠R1, ∠C = 2∠A + ∠B. In this way, it can be ensured that for the optical system provided by the embodiments of the present disclosure, the light rays emitted by the image source 10 propagate along the target path described above.

[0101] By observing Figure 2 it can be known that ∠R1 = 90° - ∠Q = 90° - ∠B. Assuming that the included angle between the light ray incident on the first surface 201 of the first prism 20 and the third surface 205 of the first prism 20 when projected onto the third surface 205 of the first prism 20 is represented as Figure 2 the ∠E in, then through geometric derivation, it can be known that ∠R1 = 2∠A + ∠E, ∠C + ∠E = 90°. Then there may be 90° - ∠B = 2∠A + ∠E. Since ∠C + ∠E = 90°, then there may be ∠C + ∠E - ∠B = 2∠A + ∠E, and thus ∠C = 2∠A + ∠B can be obtained.

[0102] Of course, the structure of the optical system provided by the embodiments of the present disclosure is not limited to Figures 1 to 9-2 the structure shown.

[0103] For example, for the structure of the optical system provided by the embodiments of the present disclosure, reference may also be made to Figure 11-1 or Figure 11-2 . Such as Figure 11-1 ,Figure 11-2 As shown, the first surface 601 of the third prism 60 may be a flat surface, and the surface of the second additional lens 80 close to the external environment may be a curved surface. By setting the surface of the second additional lens 80 close to the external environment as a curved surface, such as a convex surface or a concave surface, it is beneficial to compensate for external light, so that the user can see an undistorted environmental image.

[0104] For another example, the structure of the optical system provided by the embodiments of the present disclosure can be referred to Figure 11-3 or Figure 11-4 . As Figure 11-3 . Figure 11-4 As shown, the first surface 601 of the third prism 60 may be a curved surface, and the surface of the second additional lens 80 close to the external environment may also be a curved surface. For example, the two can be a free combination of a convex surface and a concave surface. By setting the first surface 601 of the third prism 60 as a curved surface, it is beneficial to achieve a larger eyebox at the same field of view angle and is also beneficial to improving aberration. By setting the surface of the second additional lens 80 close to the external environment as a curved surface, it is beneficial to compensate for external light, so that the user can see an undistorted environmental image.

[0105] In some alternative embodiments of the present disclosure, the refractive indices of the first prism 20, the second prism 30, and the third prism 60 may be the same.

[0106] Here, the same refractive indices of the first prism 20, the second prism 30, and the third prism 60 can be understood as the same or substantially the same refractive indices of the three.

[0107] Through research, it is found that by setting the refractive indices of the first prism 20, the second prism 30, and the third prism 60 to be the same, it can be ensured that when the first surface 301 of the second prism 30 is inclined with respect to the optical axis of the lens 40, the third surface 205 of the first prism 20 is inclined with respect to the optical axis of the lens 40, and the inclination of the third surface 205 of the first prism 20 with respect to the optical axis of the lens 40 is the same as the inclination of the first surface 301 of the second prism 30 with respect to the optical axis of the lens 40, the light rays emitted by the image source 10 propagate along the target path in the above text through the same optical path.

[0108] In some alternative embodiments of the present disclosure, the refractive index of the third prism 60 may be greater than or equal to 1.45 and less than or equal to 1.85. That is, the refractive index of the third prism 60 can be limited within the range of [1.45, 1.85]. For example, the refractive index of the third prism 60 can be 1.45, 1.55, 1.65, 1.75, 1.85, etc., and will not be listed one by one here.

[0109] Through research, it is found that restricting the refractive index of the third prism 60 within the range of [1.45, 1.85] is beneficial to effectively compensate for the optical path difference generated after the light rays emitted from different light-emitting positions on the image source 10 propagate in the first prism 20, thereby facilitating the guarantee of the imaging quality of the optical system.

[0110] In some alternative embodiments of the present disclosure, the refractive index of the third prism 60 may be greater than or equal to 1.45 and less than 1.547, or the refractive index of the third prism 60 may be greater than 1.547 and less than or equal to 1.85. That is to say, the refractive index of the third prism 60 can be restricted within the range of [1.45, 1.547) ∪ (1.547, 1.85]. For example, the refractive index of the third prism 60 can be 1.45, 1.52, 1.54, 1.546, 1.55, 1.65, 1.75, 1.85, etc., which will not be listed one by one here.

[0111] In some alternative embodiments of the present disclosure, the Abbe number of the third prism 60 may be greater than or equal to 40 and less than or equal to 80. That is to say, the Abbe number of the third prism 60 can be restricted within the range of [40, 80]. For example, the Abbe number of the third prism 60 can be 40, 50, 60, 70, 80, etc., which will not be listed one by one here.

[0112] Through research, it is found that restricting the Abbe number of the third prism 60 within the range of [40, 80] is beneficial to effectively compensate for the optical path difference generated after the light rays emitted from different light-emitting positions on the image source 10 propagate in the first prism 20, thereby facilitating the guarantee of the imaging quality of the optical system.

[0113] In some alternative embodiments of the present disclosure, the refractive index of the lens 40 and the second prism 30 may be the same. Here, the same refractive index of the lens 40 and the second prism 30 can be understood as the same or substantially the same refractive index of the two.

[0114] In some alternative embodiments of the present disclosure, if the refractive index of the lens 40 and the second prism 30 is the same, the lens 40 and the second prism 30 can be an integral part. In this way, the lens 40 and the second prism 30 can be integrally formed. Due to the integral formation of the lens 40 and the second prism 30, compared with a separate lens 40, its edge thickness (such as Figure 2 , Figures 3-2 to 9-2 the left edge thickness in) increases, and the large edge thickness is beneficial to reducing the processing difficulty and facilitating mass production.

[0115] In some alternative embodiments of the present disclosure, for the light rays emitted from the source 10 and propagating along the optical axis of the lens 40, the optical path length from the incidence of the light rays on the first surface 201 of the first prism 20 to the first arrival at the second film layer 50 is denoted as d, and the focal length of the lens 40 is denoted as f. Then, f / d can be greater than or equal to 0.4 and less than or equal to 0.6. That is to say, f / d can be limited within the range of [0.4, 0.6]. For example, f / d can be 0.4, 0.45, 0.5, 0.51, 0.52, 0.54, 0.57, 0.6, etc., and will not be listed one by one here.

[0116] Through research, it is found that limiting f / d within the range of [0.4, 0.6] is beneficial to achieving a larger eye relief (ER) and a larger eye box (EB) through an optical system with a smaller volume. Limiting f / d within the range of [0.4, 0.6] is also beneficial to the correction of field curvature and pupil shift distortion.

[0117] It should be noted that the eye relief (ER) is an important design index in the optical system. The eye relief can refer to: the distance from a preset eye position to the plane of the first optical element placed in the optical system (which can be considered as the optical element closest to the preset eye position). Taking Figure 2 、 Figure 3-1 、 Figure 3-2 as an example, the distance between the human eye 100 and the first surface 601 of the third prism 60 can be used as the eye relief.

[0118] In some alternative embodiments of the present disclosure, the refractive index of the first prism 20 can be greater than or equal to 1.45 and less than or equal to 1.85. That is to say, the refractive index of the first prism 20 can be limited within the range of [1.45, 1.85]. For example, the refractive index of the first prism 20 can be 1.45, 1.5, 1.6, 1.7, 1.8, 1.85, etc., and will not be listed one by one here.

[0119] Through research, it is found that limiting the refractive index of the first prism 20 within the range of [1.45, 1.85] is beneficial to ensuring the rationality of the parameters of the first prism 20, and thus beneficial to ensuring the imaging quality of the optical system.

[0120] In some alternative embodiments of the present disclosure, the refractive index of the first prism 20 is greater than or equal to 1.45 and less than 1.547, or the refractive index of the first prism 20 is greater than 1.547 and less than or equal to 1.85.

[0121] That is, the refractive index of the first prism 20 can be limited within the range of [1.45, 1.547) ∪ (1.547, 1.85]. For example, the refractive index of the first prism 20 can be 1.45, 1.457, 1.542, 1.546, 1.549, 1.6, 1.7, 1.8, 1.85, etc., which will not be enumerated one by one here.

[0122] In some alternative embodiments of the present disclosure, the Abbe number of the first prism 20 can be greater than or equal to 40 and less than or equal to 80. That is, the Abbe number of the first prism 20 can be limited within the range of [40, 80]. For example, the Abbe number of the first prism 20 can be 40, 50, 60, 70, 80, etc., which will not be enumerated one by one here.

[0123] Through research, it is found that limiting the Abbe number of the first prism 20 within the range of [40, 80] is beneficial to ensuring the rationality of the parameters of the first prism 20, and thus beneficial to ensuring the imaging quality of the optical system.

[0124] In some alternative embodiments of the present disclosure, the refractive index of the second prism 30 can be greater than or equal to 1.45 and less than or equal to 1.85. That is, the refractive index of the second prism 30 can be limited within the range of [1.45, 1.85]. For example, the refractive index of the second prism 30 can be 1.45, 1.5, 1.6, 1.7, 1.8, 1.85, etc., which will not be enumerated one by one here.

[0125] Through research, it is found that limiting the refractive index of the second prism 30 within the range of [1.45, 1.85] is beneficial to ensuring the rationality of the parameters of the second prism 30, and thus beneficial to ensuring the imaging quality of the optical system.

[0126] In some alternative embodiments of the present disclosure, the refractive index of the second prism 30 can be greater than or equal to 1.45 and less than 1.547, or the refractive index of the second prism 30 can be greater than 1.547 and less than or equal to 1.85.

[0127] That is, the refractive index of the second prism 30 can be limited within the range of [1.45, 1.547) ∪ (1.547, 1.85]. For example, the refractive index of the second prism 30 can be 1.45, 1.5, 1.52, 1.54, 1.545, 1.6, 1.7, 1.8, 1.85, etc., which will not be enumerated one by one here.

[0128] In some alternative embodiments of the present disclosure, the Abbe number of the second prism 30 can be greater than or equal to 40 and less than or equal to 80. That is, the Abbe number of the second prism 30 can be limited within the range of [40, 80]. For example, the Abbe number of the second prism 30 can be 40, 50, 60, 70, 80, etc., which will not be enumerated one by one here.

[0129] Through research, it is found that restricting the Abbe number of the second prism 30 within the range of [40, 80] is beneficial to ensuring the rationality of the parameters of the second prism 30, and thus beneficial to ensuring the imaging quality of the optical system.

[0130] In some alternative embodiments of the present disclosure, the lens 40 and the second prism 30 can be separately provided, and the refractive index of the lens 40 can be greater than or equal to 1.4 and less than or equal to 1.95. That is, if the lens 40 and the second prism 30 are separately provided, the refractive index of the lens 40 can be different from that of the second prism 30, and can be restricted within the range of [1.4, 1.95]. For example, the refractive index of the lens 40 can be 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.95, etc., and will not be listed one by one here.

[0131] Through research, it is found that for the case where the lens 40 and the second prism 30 are separately provided, restricting the refractive index of the lens 40 within the range of [1.4, 1.95] is beneficial to ensuring the rationality of the parameters of the lens 40, and thus beneficial to ensuring the imaging quality of the optical system.

[0132] In some alternative embodiments of the present disclosure, the Abbe number of the lens 40 can be greater than or equal to 40 and less than or equal to 100. That is, the Abbe number of the lens 40 can be restricted within the range of [40, 100]. For example, the Abbe number of the lens 40 can be 40, 50, 60, 70, 80, 90, 100, etc., and will not be listed one by one here.

[0133] Through research, it is found that restricting the Abbe number of the lens 40 within the range of [40, 100] is beneficial to ensuring the rationality of the parameters of the lens 40, and thus beneficial to ensuring the imaging quality of the optical system.

[0134] In some alternative embodiments of the present disclosure, the refractive index of the first additional lens 70 can be greater than or equal to 1.45 and less than or equal to 2.0. That is, the refractive index of the first additional lens 70 can be restricted within the range of [1.45, 2.0]. For example, the refractive index of the first additional lens 70 can be 1.45, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, etc., and will not be listed one by one here.

[0135] Through research, it is found that restricting the refractive index of the first additional lens 70 within the range of [1.45, 2.0] is beneficial to ensuring the rationality of the parameters of the first additional lens 70, and thus beneficial to ensuring the imaging quality of the optical system.

[0136] In some alternative embodiments of the present disclosure, the Abbe number of the first additional lens 70 may be greater than or equal to 15 and less than or equal to 100. That is to say, the Abbe number of the first additional lens 70 can be limited within the range of [15, 100]. For example, the Abbe number of the first additional lens 70 can be 15, 20, 30, 40, 50, 60, 80, 90, 100, etc., which will not be enumerated one by one here.

[0137] Through research, it is found that limiting the Abbe number of the first additional lens 70 within the range of [15, 100] is beneficial to ensuring the rationality of the parameters of the first additional lens 70, and thus beneficial to ensuring the imaging quality of the optical system.

[0138] Some exemplary embodiments of the present disclosure also provide a head-mounted display device. The head-mounted display device may include Figure 12 the frame structure 90 shown in the figure and the optical system in any of the above embodiments. The optical system may be installed on the frame structure 90.

[0139] In some alternative embodiments of the present disclosure, the frame structure 90 may be a structure capable of supporting and accommodating the optical system. For example, the frame structure 90 may include, but is not limited to, a spectacle frame, a headband, etc.

[0140] In the embodiments of the present disclosure, through the setting of the frame structure 90, the installation of the optical system can be reliably achieved. Through the cooperation of the various optical elements in the optical system, the human eye 100 can see the display screen provided by the image source 10 to meet the user's usage requirements. In some embodiments, the human eye 100 can also see the external environment.

[0141] It should be noted that the various alternative embodiments and alternative implementation manners disclosed above can be flexibly selected and combined according to needs to achieve the corresponding functions and effects, and the present disclosure will not enumerate them one by one.

[0142] The basic principles of the present disclosure have been described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, benefits, effects, etc. mentioned in the present disclosure are only examples and not limitations, and it cannot be considered that these advantages, benefits, effects, etc. are essential for each embodiment of the present disclosure. In addition, the above-disclosed specific details are only for the purposes of illustration and easy understanding, rather than limitations, and the above details do not limit the present disclosure to necessarily adopt the above specific details to implement.

[0143] Each embodiment in this specification is described in a progressive manner, and the key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0144] Those skilled in the art can make various changes and modifications to the present disclosure without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present disclosure and their equivalent technologies, the present disclosure also intends to include these changes and modifications.

Claims

1. An optical system, comprising: An image source; A first prism having a first surface, a second surface, and a third surface, with the first surface of the first prism being close to the image source; A second prism, where the second surface of the first prism is on the side of the first prism away from the second prism, the third surface of the first prism is on the side of the first prism close to the second prism, the second prism has a first surface, and the first surface of the second prism is close to the third surface of the first prism; A lens located on the side of the second prism away from the first prism, with the first angle between the first surface of the second prism and the optical axis of the lens and the second angle between the third surface of the first prism and the optical axis of the lens both being acute angles, and the first angle being equal to the second angle; A first film layer located on the second surface of the first prism, capable of reflecting light and transmitting light; A second film layer located on the side of the lens away from the second prism, capable of reflecting light; Wherein, the light emitted by the image source enters the first prism from the first surface of the first prism, undergoes at least one total internal reflection in the first prism, is reflected by the first film layer, exits from the third surface of the first prism and enters the second prism from the first surface of the second prism, is reflected by the second film layer after passing through the second prism and the lens, and the light after being reflected by the second film layer sequentially passes through the lens, the first surface of the second prism, the third surface of the first prism, and the second surface of the first prism, and exits through the first film layer.

2. The optical system according to claim 1, wherein, The angle between the second surface of the first prism and the plane perpendicular to the optical axis of the lens is the third angle, and the angle between the first surface and the third surface of the first prism is the fourth angle, then the fourth angle is greater than twice the third angle.

3. The optical system according to claim 2, wherein, The angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, then the fourth angle is equal to the sum of the fifth angle and twice the third angle.

4. The optical system according to claim 2, wherein, The angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, then the absolute value of the difference between the sum of the fifth angle and twice the third angle and the fourth angle is less than or equal to 0.8 degrees.

5. The optical system according to claim 2, wherein, The angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, then the ratio of twice the sum of the third angle and the fifth angle to the complementary angle of the third angle is greater than 0.

9.

6. The optical system according to claim 2, wherein, The angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, then the difference between twice the sum of the third angle and the fifth angle and the complementary angle of the third angle is greater than -6 degrees.

7. The optical system according to claim 2, wherein, The angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, then the fifth angle is greater than 5 degrees and less than 15 degrees.

8. The optical system according to claim 7, wherein, The fifth included angle is greater than 5 degrees and less than 8 degrees, or the fifth included angle is greater than 8 degrees and less than 15 degrees.

9. The optical system according to claim 7, wherein, The fifth included angle is greater than or equal to 7.5 degrees and less than or equal to 8 degrees.

10. The optical system according to claim 7, wherein, The fifth included angle is greater than 8.1 degrees and less than 8.7 degrees.

11. The optical system according to claim 7, wherein, The fifth included angle is greater than or equal to 8.7 degrees and less than or equal to 9.3 degrees.

12. The optical system according to claim 7, wherein, The fifth included angle is greater than or equal to 9.4 degrees and less than or equal to 9.8 degrees.

13. The optical system according to claim 2, wherein, The third included angle is greater than 20 degrees and less than 30 degrees.

14. The optical system according to claim 1, further comprising: A compensating member, the compensating member is close to the second surface of the first prism, and after the light reflected by the second film layer passes through the first prism again, it exits after passing through the compensating member.

15. The optical system according to claim 14, wherein, The compensating member is a third prism, the third prism has a first surface and a second surface, the first surface of the third prism is on the side of the third prism away from the first prism, and the second surface of the third prism is on the side of the third prism close to the first prism. After the light reflected by the second film layer passes through the first prism again, it exits after passing through the second surface of the third prism and the first surface of the third prism.

16. The optical system according to claim 15, wherein, The refractive indices of the first prism, the second prism, and the third prism are the same.

17. The optical system according to claim 15, wherein, The first surface of the third prism is a curved surface.

18. The optical system according to claim 15, wherein, The refractive index of the third prism is greater than or equal to 1.45 and less than or equal to 1.

85.

19. The optical system according to claim 15, wherein, The Abbe number of the third prism is greater than or equal to 40 and less than or equal to 80.

20. The optical system according to claim 1, wherein, A part of the second surface of the first prism close to the image source has a groove, and the groove is recessed from this part of the area into the interior of the first prism.

21. The optical system according to claim 1 or 20, wherein, A part of the second surface of the first prism close to the image source is coated black.

22. The optical system according to claim 1 or 20, wherein, A part of the second surface of the first prism close to the image source is a rough surface.

23. The optical system according to claim 1, wherein, The refractive index of the lens is the same as that of the second prism.

24. The optical system according to claim 23, wherein, The lens and the second prism are an integral part.

25. The optical system according to claim 1, wherein, For the light rays in the light rays emitted by the image source that propagate along the optical axis of the lens, the optical path length from the time when the light rays enter the first prism from the first surface of the first prism until they first reach the second film layer is represented by d, and the focal length of the lens is represented by f, then f / d is greater than or equal to 0.4 and less than or equal to 0.

6.

26. The optical system according to claim 1, wherein, The refractive index of the first prism is greater than or equal to 1.45 and less than or equal to 1.

85.

27. The optical system according to claim 1, wherein, The Abbe number of the first prism is greater than or equal to 40 and less than or equal to 80.

28. The optical system according to claim 1, wherein, The first surface of the first prism is a curved surface.

29. The optical system according to claim 1, wherein, The refractive index of the second prism is greater than or equal to 1.45 and less than or equal to 1.

85.

30. The optical system according to claim 1, wherein, The Abbe number of the second prism is greater than or equal to 40 and less than or equal to 80.

31. The optical system according to claim 1, wherein, The lens and the second prism are separately arranged, and the refractive index of the lens is greater than or equal to 1.4 and less than or equal to 1.

95.

32. The optical system according to claim 1, wherein, The Abbe number of the lens is greater than or equal to 40 and less than or equal to 100.

33. The optical system according to claim 1, further comprising: A first additional lens, the first additional lens is located between the image source and the first surface of the first prism; Wherein, the light rays emitted by the image source enter the first prism after passing through the first additional lens.

34. The optical system according to claim 33, wherein, The refractive index of the first additional lens is greater than or equal to 1.45 and less than or equal to 2.

0.

35. The optical system according to claim 33, wherein, The Abbe number of the first additional lens is greater than or equal to 15 and less than or equal to 100.

36. The optical system according to claim 1, wherein, The second film layer is a semi-transmissive and semi-reflective film, and the optical system further includes: A second additional lens, which is located on the side of the second film layer away from the lens.

37. A head-mounted display device, comprising: A frame structure; An optical system according to any one of claims 1-36, the optical system being mounted on the frame structure.

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