Fresnel combining optics and stereoscopic display device

Abstract

The application provides a Fresnel combination optical device and a stereoscopic display device. The Fresnel combination optical device is used for modulating a parallel light beam. The Fresnel combination optical device comprises a plurality of Fresnel prism units, and each Fresnel prism unit comprises a Fresnel optical element and a light deflection element. The Fresnel optical element comprises mutually opposite prism surfaces and planes, and the prism surfaces are used for receiving the parallel light beam. The light deflection element comprises a first surface and a second surface, and the planes of each Fresnel prism unit are arranged on the first surface. The prism surfaces of the Fresnel prism units on which the planes are arranged are matched with the surface type of the second surface, so that each Fresnel prism unit and the light deflection element matched with the Fresnel prism unit form an optical flat unit, and the Fresnel combination optical device is equivalent to an optical panel. The shape of an image surface can be controlled after the parallel light beam is modulated through different positions of the Fresnel combination optical device, so that a naked-eye stereoscopic display effect is realized.

Description

Technical Field

[0001] This application relates to the field of stereoscopic display technology, and more specifically, to a Fresnel combined optical device and a stereoscopic display apparatus. Background Technology

[0002] Currently, technologies capable of achieving stereoscopic display effects can be broadly categorized into two types: one requires special glasses, while the other does not require additional equipment and is known as glasses-free stereoscopic display. Existing glasses-free stereoscopic displays can be implemented in the following ways.

[0003] Binocular parallax stereoscopic display, similar in principle to glasses-based stereoscopic displays, achieves a stereoscopic effect by using the slight difference between the images perceived by each eye. Unlike glasses, glasses-free stereoscopic displays require specific optical components to control the different images seen by each eye. Common techniques include using lenticular lenses or grid structures to create separate viewing areas for the left and right eyes, allowing each eye to see images corresponding to different pixels. This is currently the most common glasses-free stereoscopic display solution, but it has drawbacks. First, it spatially divides the spatial light modulator, thus reducing the display's spatial resolution. Second, it requires precise device alignment to separate the left and right eye images, and the observer must be in a specific position to achieve the desired effect. If the observer deviates from the preset position, the images for the left and right eyes can easily be swapped, causing severe dizziness. Furthermore, binocular parallax does not produce a true stereoscopic image, but rather two slightly different planar images, which can easily cause dizziness for some observers.

[0004] Holographic display technology uses coherent light interference to record the optical information of an object, completely preserving the intensity and phase information of the light reflected from the object, thus essentially recording the object's three-dimensional information. After obtaining the holographic plate with the interference record, a specific light beam is then shone onto the holographic plate to recover the light beam reflected from the object, thereby reproducing the object's three-dimensional shape and achieving a naked-eye stereoscopic display effect. This technology requires the use of beam interference to record images, making it difficult to achieve dynamic images and limiting its large-scale commercial application.

[0005] Plasma technology, which uses a laser beam to ionize air in space, is also a naked-eye 3D technology approach. By focusing the laser beam, a highly concentrated energy beam can be obtained at a specific location in space. When the laser energy is strong enough, air plasma can be ionized, generating an electric arc that displays a bright spot at that location. By rapidly scanning the convergence point of the laser beam and controlling whether to activate the plasma, a matrix of arc display dots can be scanned in space, achieving a naked-eye 3D effect. This method can achieve dynamic display effects, but ionizing gas plasma requires very high laser energy, thus posing some challenges in terms of cost and safety.

[0006] Another approach to glasses-free 3D display utilizes acoustic levitation technology. This involves moving and suspending one or more small scattering particles in the air, then tracking them with a laser beam to continuously illuminate these particles. By moving the particles to different positions in the air, an image is displayed, thus achieving glasses-free 3D. Because the beam is displayed through scattering, the energy required is significantly lower than that of plasma displays, and color display is possible. However, moving and suspending particles in the air is quite difficult and currently not suitable for large-scale commercial use. Summary of the Invention

[0007] This application proposes a Fresnel combined optical device and a stereoscopic display device to solve the above-mentioned technical problems.

[0008] The above objectives are achieved through the following technical solutions in the embodiments of this application.

[0009] In a first aspect, embodiments of this application provide a Fresnel combined optical device for modulating a quasi-parallel beam. The Fresnel combined optical device includes a Fresnel optical element and a light deflecting element. The Fresnel optical element includes a plurality of Fresnel prism units, each Fresnel prism unit comprising mutually opposing prism surfaces and a plane, the prism surfaces being used to receive the quasi-parallel beam. The light deflecting element includes a first surface and a second surface. The plane of each Fresnel prism unit is disposed in conjunction with the first surface, and the prism surface of the Fresnel prism unit containing the plane matches the surface shape of the second surface, so that each Fresnel prism unit and its matched light deflecting element form an optical flat panel unit, thereby making the Fresnel combined optical device equivalent to an optical panel, and the refractive index of the light deflecting element is the same as the refractive index of the Fresnel optical element.

[0010] In some implementations, the first surface is fitted to a plane, and the surface shape function of the second surface is z2, where z2 has at least two values, and the positions of the at least two values ​​are different from the distance between the prism surfaces.

[0011] In some implementations, the light deflecting element is any one of a transmission prism, a freeform lens, or a reflector.

[0012] In some embodiments, the first surface includes a reflective surface and a bonding surface. The angle between the reflective surface and the optical axis of the quasi-parallel beam is smaller than the angle between the bonding surface and the optical axis of the quasi-parallel beam. The bonding surface is bonded to the plane. The reflective surface is used to directly reflect a portion of the quasi-parallel beam, and the prism surface is used to reflect another portion of the quasi-parallel beam.

[0013] In some implementations, the angle between the reflecting surface and the optical axis of the quasi-parallel beam is 45 degrees.

[0014] In some embodiments, the light deflector receives a quasi-parallel beam modulated by a Fresnel optical element and guides the quasi-parallel beam outward.

[0015] In some embodiments, the light deflecting element is a freeform lens, and the surface shape function of the second surface is z2=(n / (nL))*f(x,y), where f(x,y) is a preset surface shape function, L is the distance between z2 at position (x,y) and the prism surface, and n is the refractive index of the light deflecting element.

[0016] In some implementations, the surface shape function of the first surface is z1=0.

[0017] In some implementations, the surface shape function of the prism is mod((n / (nL))*f(x,y)-H0, T0), where L is the distance between z2 and the prism, H0 is greater than or equal to the maximum value of z2, T0 is a preset value, and mod is a modulo operation with T0 as the base.

[0018] Secondly, embodiments of this application provide a stereoscopic display device. The stereoscopic display device includes a Fresnel combined optical device according to any of the above embodiments and a spatial light modulator, wherein a quasi-parallel light beam emitted by the spatial light modulator is modulated by the Fresnel combined optical device before being emitted.

[0019] In some embodiments, the spatial light modulator is any one of a liquid crystal display device, a silicon-based liquid crystal display device, and a digital micromirror device.

[0020] In some implementations, at least a portion of the quasi-parallel beam is modulated by Fresnel optics.

[0021] In the process of modulating a quasi-parallel beam, the Fresnel combined optical device and stereoscopic display device provided in this application match the surface shape of the prism surface of each Fresnel prism unit in the Fresnel optical element with the surface shape of the second surface of the light deflecting element. This makes each Fresnel prism unit and its matched light deflecting element form an optical flat panel unit, thereby making the Fresnel combined optical device equivalent to an optical panel. This maintains the refraction characteristics of the quasi-parallel beam essentially consistent. Furthermore, the Fresnel combined optical device can change the path length of the quasi-parallel beam through the refraction plane by adjusting the distance between the prism surface and the second surface at different positions. This allows control over the equivalent path length of the quasi-parallel beam through the Fresnel combined optical device. The effective path is reflected as the position of the imaging point corresponding to that position in the image plane. This helps to control the shape of the image plane after the quasi-parallel beam is modulated at different positions by the Fresnel combined optical device. For example, the image plane can be adjusted from a planar shape to a curved shape, so that the image plane seen by the observer is a three-dimensional image plane, thereby achieving the effect of naked-eye stereoscopic display. Moreover, compared with binocular parallax stereoscopic display technology, it does not require the position and viewing angle of the observer, and will not cause the observer to feel dizzy. Compared with holographic display technology, it does not need to use beam interference to record images and can achieve dynamic display. Compared with Plasma technology, it does not need to provide strong laser energy by ionizing gas plasma. Compared with acoustic levitation technology, it does not need to move and suspend one or more small scattering particles in the air. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a comparative diagram of Fresnel lenses and ordinary lenses.

[0024] Figure 2 This is a schematic diagram of the angular magnification effect of an optical device.

[0025] Figure 3 A schematic diagram illustrating the formation of a virtual image using a Fresnel combined optical device provided in an embodiment of this application.

[0026] Figure 4 This is a schematic diagram of the formation of a virtual image by a Fresnel combined optical device provided in another embodiment of this application.

[0027] Figure 5 A schematic diagram illustrating the application scenario of the Fresnel combined optical device provided in the embodiments of this application.

[0028] Figure 6 This is a schematic diagram illustrating another application scenario of the Fresnel combined optical device provided in the embodiments of this application.

[0029] Figure 7 This is a schematic diagram of a Fresnel combined optical device forming a virtual image, provided as another embodiment of this application.

[0030] Figure 8 for Figure 7 A schematic diagram of the virtual image formed by Fresnel combination optical devices.

[0031] Figure 9 This is a schematic diagram of the formation of a virtual image by a Fresnel combined optical device provided in another embodiment of this application.

[0032] Figure 10 A schematic diagram illustrating a scenario application of a Fresnel combined optical device provided in another embodiment of this application.

[0033] Figure 11 A schematic diagram of the surface design of a Fresnel combined optical device provided for an embodiment of this application.

[0034] Figure 12 A schematic diagram of the surface design of a Fresnel combined optical device provided for another embodiment of this application.

[0035] Figure 13 A schematic diagram of the surface design of a Fresnel combined optical device provided for another embodiment of this application. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without inventive effort are within the scope of protection of the present application.

[0037] This application provides a Fresnel-based optical combination device for realizing naked-eye stereoscopic display. The Fresnel-based optical combination device of this application utilizes Fresnelized optical components. Figure 1 The image shows a standard lens 10 and a Fresnel lens 11. Traditional geometric optics elements control beam propagation through reflection or refraction at interfaces, thereby enabling image rotation, magnification, and reduction. If the shape of the interface is preserved but discretized, a roughly similar effect can be achieved. Figure 1In the example, discretizing the interface of the ordinary lens 10 yields a Fresnel lens 11. The Fresnel lens 11 achieves roughly the same effect as the ordinary lens 10, and its overall thickness can be made very thin, ensuring that the path difference of the light beam passing through the edge and center of the Fresnel lens 11 is approximately the same. Therefore, Fresnelized optical devices, when achieving similar beam refraction effects, can also design and control the beam path to a certain extent.

[0038] Furthermore, the Fresnel combined optics of this application considers the angular magnification effect of optical devices. When using lens imaging, the magnification of the projection along the axis is not the same as the magnification along the plane perpendicular to the axis. If the object itself is a tilted plane, then the imaging plane is also tilted, but the tilt angle differs from that of the object. For example... Figure 2 As shown, object 20 is imaged by lens 21 to form image plane 22. The magnification of lens 21 for object 20 in the direction perpendicular to the optical axis 23 is a. Then the magnification of lens 21 in the axial direction is a. 2 The tilt angle of object 20 changes from the original θ to θ', and the two satisfy the relationship: tan(θ) = a*tan(θ'). Therefore, when lens 21 forms a magnified virtual image, the angle between the normal of image plane 22 and optical axis 23 will be magnified.

[0039] Based on the Fresnel principle and angular magnification effect of the aforementioned optical devices, please refer to... Figure 3 The Fresnel combined optical device 1000 provided in this application embodiment is used to modulate the quasi-parallel beam 31, so that the Fresnel combined optical device 1000 can realize naked-eye stereoscopic display.

[0040] The Fresnel combined optical device 1000 includes a Fresnel optical element 100 and a light deflecting element 200. The Fresnel optical element 100 includes a plurality of Fresnel prism units, i.e., the number of Fresnel prism units is greater than or equal to two. Each Fresnel prism unit includes a prism surface 110 and a plane 120 that are opposite to each other. The prism surface 110 is used to receive a quasi-parallel beam 31. The light deflecting element 200 includes a first surface 210 and a second surface 220. The plane 120 of each Fresnel prism unit is attached to the first surface 210. The prism surface 110 of the Fresnel prism unit containing the plane 120 matches the surface shape of the second surface 220, so that each Fresnel prism unit and its matched light deflecting element 200 form an optical flat panel unit, thereby making the Fresnel combined optical device equivalent to an optical panel. The refractive index of the light deflecting element 200 is the same as that of the Fresnel optical element 100.

[0041] In the process of modulating the quasi-parallel beam 31 emitted from the light-emitting plane 30, the Fresnel combined optical device 1000 provided in this application has a matching surface shape between the prism surface 110 of each Fresnel prism unit in the Fresnel optical element 100 and the second surface 220 of the light deflecting element 200. This makes each Fresnel prism unit and its matched light deflecting element 200 form an optical plate unit, thereby making the Fresnel combined optical device 1000 equivalent to an optical panel. This allows the deflection characteristics of the quasi-parallel beam 31 to remain basically consistent. The prism surface 110 of this optical panel can be a sawtooth surface, and the second surface 220 can be a plane (e.g., ...). Figure 3 (as shown), or the prism surface 110 of the optical panel can be a sawtooth surface and the second surface 220 is an irregularly shaped structure surface, such as a corrugated surface (e.g. Figure 8 or Figure 12 (As shown).

[0042] Furthermore, the Fresnel combined optical device 1000 can also change the path length of the quasi-parallel beam 31 through the refraction plane by adjusting the distance between the prism surface 110 and the second surface 220 at different positions, thereby controlling the equivalent path length of the quasi-parallel beam 31 at position z through the Fresnel combined optical device 1000. Where n is the refractive index of the Fresnel optical element 100; L is the path length of the quasi-parallel beam 31 from position z on the prism surface to the second surface 220. Since in typical applications, the optical axis 33 of the Fresnel combined optical device 1000 is perpendicular to the emitting plane 30, as... Figure 3 As shown, even if the optical axis 33 of the Fresnel combined optical device 1000 deviates from the light-emitting plane 30 by 90° due to factors such as assembly error or manufacturing error, for example, if the deviation angle is in the range of 0 to 10°, the quasi-parallel beam 31 will not be greatly deflected. Therefore, the actual propagation path of the collimated beam 31 in the Fresnel combined optical device 1000 can be understood as the thickness of the Fresnel combined optical device 1000.

[0043] Due to the equivalent path length at different positions of the Fresnel combined optical device 1000 This will be reflected as the position of the imaging point corresponding to that location in the image plane, such as the equivalent path at position z. This will be reflected as the position of the imaging point 320 at the corresponding position z in the image plane 32, and the surface shape function of the second surface 220 is z2. z2 has at least two values, and these at least two values ​​are different from the distance between the prism surface 110. For example, the surface shape function of the second surface 220 is z2, and z2 includes several values, among which z2 has at least two values, and these at least two values ​​are different from the distance between the prism surface 110. The function z2 can include a first value and a second value. The distance between the position of the first value and the prism surface 110 can be L1, and the distance between the position of the second value and the prism surface 110 can be L2, where L2 ≠ L1. This changes the shape of the image surface 32 relative to the light-emitting plane 30, thereby allowing the quasi-parallel beam 31 to control the shape of the image surface 32 after being modulated by the Fresnel combined optical device 1000. For example, the image surface 32 can be adjusted from a planar shape to a curved shape, so that the image surface seen by the observer is a three-dimensional image surface 32, thus achieving the effect of naked-eye stereoscopic display. It does not require the observer to be in a specific position or viewing angle, nor does it cause dizziness. Compared to holographic display technology, it does not require the use of beam interference to record images and can achieve dynamic display. Compared to Plasma technology, it does not require the ionization of gas to provide strong laser energy. Compared to acoustic levitation technology, it does not require moving and suspending one or more small scattering particles in the air.

[0044] The first value mentioned above can be the maximum value of the function z2, the minimum value of the function z2, or any value between the maximum and minimum values ​​of the function z2; correspondingly, the second value can be the maximum value of the function z2, the minimum value of the function z2, or any value between the maximum and minimum values ​​of the function z2, and the second value is not equal to the first value, therefore... Figure 3 L1 and L2 in this example are for illustrative purposes only and do not represent L1 and L2 as absolute values. Figure 3 The size of a fixed position in the middle. Similarly, Figure 3 The position z in the middle is only used as an example position.

[0045] Fresnel optical element 100 refers to an optical element obtained by Fresnelizing the interface of a common optical element. This application uses a Fresnel prism as an example to illustrate the Fresnel optical element 100. The prism surface 110 of the Fresnel optical element 100 is the interface after discretizing the surface of a common optical element.

[0046] The light deflecting element 200 can be a common optical device, such as a mirror or a lens, which helps the Fresnel optical combination device 1000 to adapt the type of the light deflecting element 200 according to different applications. For example, when the light deflecting element 200 is a lens, specifically a transmission prism, it receives the quasi-parallel beam 31 modulated by the Fresnel optical element 100 and guides it outward. As another example, when the light deflecting element 200 is a mirror, it can directly receive a portion of the quasi-parallel beam 31, allowing the image plane formed by the light deflecting element 200 to cooperate with the image plane formed by the other portion of the quasi-parallel beam 31 received by the Fresnel optical element 100 to display a stereoscopic display effect.

[0047] In some embodiments, the light deflecting element 200 is a prism, for example, a triangular prism. Figure 3 As shown, the luminescent plane 30 emits a quasi-parallel beam 31, which enters the Fresnel combined optical device 1000 through the prism surface 110 and exits through the second surface 220. This causes the quasi-parallel beam 31 to be modulated by the Fresnel combined optical device 1000 to form an image plane 32, which causes the image plane 32 to be tilted relative to the luminescent plane 30.

[0048] Since the Fresnel optical element 100 and the light deflecting element 200 in the Fresnel combined optical device 1000 have the same refractive index, and both have the same angle with the optical axis 33 (i.e., the angle between the prism surface 110 and the optical axis 33 is equal to the angle between the second surface 220 and the optical axis 33), the Fresnel optical element 100 and the light deflecting element 200 compensate for each other, making the quasi-parallel beam 31 equivalent to passing through an optical plate when passing through the Fresnel combined optical device 1000. Therefore, the propagation direction of the quasi-parallel beam 31 does not change. Furthermore, since the equivalent path length of the quasi-parallel beam 31 when passing through the Fresnel combined optical device 1000 is... The equivalent path is related to the thickness of the Fresnel combined optical device 1000; the thicker the Fresnel combined optical device 1000, the longer the equivalent path. The longer the image plane 32 formed by the emitting plane 30 is, the farther away it is from the emitting plane 30. Therefore, the Fresnel combined optical device 1000 formed by the Fresnel optical element 100 and the light deflecting element 200 can form different thicknesses at different positions, so that it can be equivalent to an optical plate of different thicknesses at different positions. At thicker positions, the emitting point 301 of the emitting plane 30 is far away from the equivalent emitting point 320 of the image plane 32; at thinner positions, the emitting point 301 of the emitting plane 30 is close to the equivalent emitting point 320 of the image plane 32. Thus, by adjusting the thickness of the Fresnel combined optical device 1000 at different positions, the image plane 32 can be tilted compared to the original emitting plane 30.

[0049] Since the tilt of the image plane 32 is related to the refractive index of the Fresnel optical combination device 1000 and the angle between the Fresnel optical combination device 1000 and the optical axis 33, the larger the angle between the Fresnel optical combination device 1000 and the optical axis 33 and the higher the refractive index, the greater the tilt of the image plane 32. Therefore, the Fresnel optical combination device 1000 can form multiple regions of different thicknesses through the cooperation of the Fresnel optical element 100 and the light deflection element 200 to modulate the emission plane 30 to emit a quasi-parallel beam 31, so that the quasi-parallel beam 31 has different path lengths in regions of different thicknesses. This allows the image plane 32 to be tilted or twisted in different regions, thereby controlling the shape of the image plane 32 and achieving a naked-eye stereoscopic display effect.

[0050] Based on the above principle, the Fresnel combined optical device 1000, which produces an inclined image plane, can be used in automotive head-up displays (HUDs). For example... Figure 4 As shown, taking the light deflecting element 200 in the Fresnel combined optical device 1000 as a prism as an example, the Fresnel combined optical device 1000 is disposed between the emitting plane 40 and the lens system 41. The emitting plane 40 is used to emit a quasi-parallel light beam that produces a planar image. The Fresnel combined optical device 1000 covers a portion of the emitting plane 40, that is, the Fresnel combined optical device 1000 modulates a portion of the light beam emitted by the emitting plane 40. The lens system 41 is used to magnify the image produced by the emitting plane 40 into a magnified virtual image 42. Because the Fresnel combined optical device 1000 covers a portion of the emitting plane 40, the virtual surface 42 of the virtual image 42 corresponding to the covered portion of the emitting plane 40 is tilted, and after being magnified by the lens system 41, it forms the tilted image surface 420 of the virtual image 42; conversely, the image surface of the virtual image 42 corresponding to the uncovered portion of the emitting plane 40 is consistent with conventional imaging, and after being magnified by the lens system 41, it forms the vertical image surface 421 of the virtual image 42. The tilted image plane 420 and the vertical image plane 421 can work together to display driving conditions, such as... Figure 5and Figure 6 As shown, for example, the vertical image plane 421 can display vehicle status information, while the tilted image plane 420 can display road navigation icons and road condition information. Since the tilted image plane 420 is tilted, it can fit well with the road surface 43. When displaying road navigation icons and road condition information, the displayed image and the road can be integrated without parallax, thus better displaying the content.

[0051] In some embodiments, the light deflecting element 200 can also be a reflector, enabling the Fresnel combined optics device 1000 to achieve glasses-free stereoscopic display. For example, Figure 7 As shown, the first surface 210 includes a reflective surface 2010 and a bonding surface 2020. The angle between the reflective surface 2010 and the optical axis 73 of the quasi-parallel beam 70 is smaller than the angle between the bonding surface 2020 and the optical axis 73 of the quasi-parallel beam 70. The bonding surface 2020 is bonded to the plane 120 of the Fresnel optical element 100. The reflective surface 2010 is used to directly reflect a portion of the quasi-parallel beam 70, and the prism surface 110 is used to reflect another portion of the quasi-parallel beam 70.

[0052] The emitting plane 70 is used to emit a quasi-parallel beam 71 that produces a planar image. The quasi-parallel beam 71 is modulated by the Fresnel combined optical device 1000 to form a virtual image 72. The quasi-parallel beam 71 is modulated by the reflecting surface 2010 to form a first virtual image surface 720 of the virtual image 72. The quasi-parallel beam 71 is modulated by the prism surface 110 of the Fresnel optical element 100 to form a second virtual image surface 721 of the virtual image 72. The distance from the first virtual image surface 720 formed by the reflecting surface 2010 to the emitting plane 40 and the reflecting surface 2010 is equal. Similarly, the distance from the second virtual image surface 721 formed by the prism surface 110 to the emitting plane 40 and the prism surface 110 is also equal. Therefore, the second virtual image surface 721 formed after the quasi-parallel beam 71 is modulated by the prism surface 110 should be symmetrical about the prism surface 110 to the emitting plane 70. Since the angle between the reflecting surface 2010 and the optical axis 73 of the quasi-parallel beam 70 is smaller than the angle between the bonding surface 2020 and the optical axis 73 of the quasi-parallel beam 70 (i.e., the reflecting surface 2010 and the prism surface 110 are tilted), the second virtual image surface 721 produced by the prism surface 110 and the first virtual image surface 720 produced by the reflecting surface 2010 are deflected, altering the shape of the original planar image. This results in an image that appears as if the image is not fully formed by the prism surface 110. Figure 7 When the virtual image 72 is formed by the method, the virtual image 72 makes the human eye perceive as... Figure 8 The illusion of spatial proximity shown can achieve a naked-eye stereoscopic display effect, allowing the light deflecting element 200 in the Fresnel combined optical device 1000 to be used as a reflector and also applied to vehicle HUDs.

[0053] In some embodiments, the angle between the reflecting surface 2010 and the optical axis 73 of the quasi-parallel beam 71 is 45 degrees, which helps to avoid ghosting at the junction of the first virtual image surface 720 and the second virtual image surface 721, thereby improving the imaging effect of the Fresnel combined optical device 1000.

[0054] In some embodiments, the light deflecting element 200 can be a freeform lens, which can also enable the Fresnel combined optics device 1000 to achieve naked-eye stereoscopic display. For example, Figure 9 As shown, the multiple regions of different thicknesses of the Fresnel combined optical device 1000 can be regarded as the sub-regions formed by the Fresnel optical element 100 and the light deflection element 200 in the above embodiment are arranged densely enough so that the prism surface 110 and the second surface 2020 are approximately free-form surfaces. Ultimately, the direction of light propagation remains unchanged after the light beam passes through the Fresnel optical element 100 and the light deflection element 200. Moreover, the images in different regions have experienced different path differences, so that the shape of the virtual image 81 formed by the Fresnel combined optical device 1000 on the light-emitting plane 80 changes from the original light-emitting plane 80, transforming the planar image of the light-emitting plane 80 into a curved image, thus achieving a naked-eye stereoscopic display effect.

[0055] In some embodiments, besides achieving a naked-eye stereoscopic display effect by forming a virtual image as described above, the Fresnel optical combination device 1000 can also achieve a naked-eye stereoscopic display effect by forming a real image. For example... Figure 10 As shown, when an image needs to be projected onto a specific curved surface 91 (such as a building or mountain), since the curved surface 91 is not a plane, the image projected directly from the emitting plane 90 may be out of focus at different locations on the curved surface 91, resulting in poor display quality. The Fresnel combined optical device 1000 can distort the planar image of the emitting plane 90 into a curved real image 92. The real image 92 is then imaged onto the curved surface 91 through the lens system 93, making the shape of the real image 92 consistent with the shape of the curved surface 91, thereby obtaining a curved projection image that is well-focused everywhere, achieving a naked-eye stereoscopic display effect.

[0056] In some embodiments, the Fresnel combined optics 1000 can be designed with the surface profiles of the Fresnel optical element 100 and the light deflecting element 200 based on a preset display surface. Please refer to... Figure 11 , Figure 11 Let xyz be the coordinate system, where the y-axis is perpendicular to the paper and points inwards. For example, if the original image displayed on the luminous plane is a plane, and the surface shape function of the original image is assumed to be z0=0, then the original image lies in the plane where z0=0; the preset surface shape function of the displayed curved surface is z... f=f(x,y) represents the position of the preset displayed surface at coordinates (x,y), or the height of the preset displayed surface at coordinates (x,y) relative to the plane containing the original image. In this coordinate system, any two constant values ​​determine the value of another; for example, the values ​​of x and y determine the value of z. Once the positions of x and y in the coordinate system are determined, the value of z can be determined. The preset displayed surface shape function z... f It can be designed according to the desired bending effect.

[0057] For the light deflecting element 200, since the refractive index of the light deflecting element 200 and the Fresnel optical element 100 are the same and both are n, if the Fresnel combined optical device 1000 is approximated as a flat plate, as follows: Figure 12 As shown, under paraxial approximation and a small optical cone angle, the optical path of the light beam emitted from the emitting plane 111 changes from L to L / n after passing through the Fresnel combined optical device 1000 with a refractive index of n. The position of the virtual image 112 formed by the Fresnel combined optical device 1000 is equivalent to shifting forward by a distance of L / n. Therefore, if the original image z0=0 is adjusted to the preset display surface z... f =f(x,y), which requires shifting the virtual image of each point on the (x,y) plane in the original image forward by a distance of f(x,y). Therefore, the thickness z2 of the light deflection element 200 at (x,y) needs to satisfy z2-z2 / n=z f Therefore, the surface shape function of the second surface 220 of the light deflecting element 200 is z2=(n / (nL))*f(x,y), as shown below. Figure 11 As shown, the surface function z is displayed according to the above preset. f =f(x,y), after determining the x and y values ​​of the preset display image, z f If the value is constant, then we can use the formula z² - z² / n = z f The surface height (thickness) z2 of the second surface 220 is determined, and L can then be determined based on z2, where L is the distance between z2 at position (x,y) and the prism surface 110. In addition, in order to ensure that the thickness of the light deflecting element 200 is z2, the surface shape function of the first surface 210 is z1=z0=0.

[0058] For the Fresnel optical element 100, it is necessary to ensure that the propagation direction of the light beam does not change after passing through the light deflector 200. Under paraxial approximation and small light cone angle conditions, another freeform lens 100' complementary to the light deflector 200 can be attached to the first surface 210 of the light deflector 200, such as... Figure 11As shown, the thickness of the combined two complementary freeform lenses is constant at any position. The two complementary freeform lenses approximate a distorted flat plate, and the beam propagation direction will not change after the beam passes through any position z of the Fresnel combined optical device 1000. Therefore, the surface shape function of the freeform lens 100' is z3=(n / (nL))*f(x,y)-H0. Since z0 is set to 0 in this embodiment, to ensure that z3 does not affect the maximum value of z2, z3 is offset relative to z2 along the z-axis from the position of z2, so that the minimum offset of z3 is greater than or equal to the maximum value of z2. Therefore, H0 can be regarded as the offset of z3 relative to z2, where H0 is greater than or equal to the maximum value of z2. In addition, since z3 is offset relative to z2 in the negative direction of the z-axis in this embodiment, to ensure that |z2|+|z3|=H0, z3=z2-H0. In other embodiments, if z3 is offset relative to z2 along the positive direction of the z-axis, then z3 = z2 + H0.

[0059] After determining the surface shape function of the freeform lens 100', the freeform lens 100' is then Fresnelized, as follows: Figure 13 As shown, the freeform lens 100' is approximated as a thin film and serves as a Fresnel optical element 100. Therefore, the surface shape function of the prism surface 110 of the Fresnel optical element 100 is mod((n / (nL))*f(x,y)- H0,T0), where mod is a modulo operation with T0 as the base. The value of T0 can be set according to the actual required thickness. At this time, compared with the freeform lens before Fresnelization, the Fresnel optical element 100's function of changing the beam propagation direction remains unchanged, and the beam path is not changed, so the virtual image will not move back and forth. Finally, the Fresnel combined optical device 1000 formed by the Fresnel optical element 100 and the light deflection element 200 can distort the original image displayed on the light-emitting plane into a curved surface, thereby achieving a stereoscopic naked-eye effect.

[0060] This application provides a stereoscopic display device (not shown). The stereoscopic display device includes a Fresnel combined optical device 1000 according to any of the above embodiments and a spatial light modulator (not shown). The quasi-parallel light beam emitted by the spatial light modulator is modulated by the Fresnel combined optical device 1000 and then emitted.

[0061] In the process of modulating a quasi-parallel beam, the prism surface 110 of each Fresnel prism unit in the Fresnel optical element 100 and the surface shape of the second surface 220 of the light deflection element 200 are matched, so that each Fresnel prism unit and its matched light deflection element 200 form an optical plate unit, thereby making the Fresnel combined optical device 1000 equivalent to an optical panel. This maintains the refraction characteristics of the quasi-parallel beam essentially consistent. Furthermore, the Fresnel combined optical device 1000 can change the path length of the quasi-parallel beam through the refraction plane by adjusting the distance between the prism surface 110 and the second surface 220 at different positions, thereby controlling the equivalent path length of the quasi-parallel beam through the Fresnel combined optical device 1000. The equivalent path length at different positions of the Fresnel combined optical device 1000 is reflected as the position of the imaging point at the corresponding position in the image plane. This helps to control the shape of the image plane after the quasi-parallel beam is modulated at different positions by the Fresnel combined optical device 1000. For example, the image plane can be adjusted from a planar shape to a curved shape, so that the image plane seen by the observer is a three-dimensional image plane, thereby achieving the effect of naked-eye stereoscopic display. Moreover, there are no requirements for the position and viewing angle of the observer, and it will not cause dizziness to the observer. Compared with holographic display technology, it does not need to use beam interference to record images and can achieve dynamic display. Compared with Plasma technology, it does not need to provide strong laser energy by ionizing gas plasma. Compared with acoustic levitation technology, it does not need to move and suspend one or more small scattering particles in the air.

[0062] In some embodiments, the spatial light modulator is any one of a liquid crystal display (LCD) device, a liquid crystal on silicon (LCOS) device, or a digital micromirror device (DMD). For example, in an embodiment where the stereoscopic display device is used in an automotive HUD, the spatial light modulator can be an LCD device or a DMD device; in an embodiment where the stereoscopic display device is used in a projector, the spatial light modulator can be an LCD device, an LCOS device, or a DMD device.

[0063] In some embodiments, at least a portion of the quasi-parallel beam is modulated by the Fresnel optical element 100. For example, when the entire quasi-parallel beam is modulated by the Fresnel optical element 100, the stereoscopic display device can be used as a stereoscopic video conferencing device; when a portion of the quasi-parallel beam is modulated by the Fresnel optical element 100, the stereoscopic display device can be used as a HUD display device.

[0064] In this application, unless otherwise expressly specified or limited, the terms "installation," "connection," "fixation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components; they can refer to mere surface contact; or they can refer to surface contact connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0065] Furthermore, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as referring to specific or particular structures. The terms "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this application, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this application, as well as the features of different embodiments or examples.

[0066] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A stereoscopic display device, characterized in that, The stereoscopic display device includes a Fresnel combined optical element and a spatial light modulator. The quasi-parallel light beam emitted by the spatial light modulator is modulated by the Fresnel combined optical element and then emitted. The Fresnel combined optical device includes: A Fresnel optical element comprising a plurality of Fresnel prism units, each Fresnel prism unit including mutually opposing prism surfaces and a plane, the prism surfaces being used to receive the quasi-parallel beam; and The light deflecting element includes a first surface and a second surface. The plane of each Fresnel prism unit is attached to the first surface. The prism surface of the Fresnel prism unit containing the plane matches the surface shape of the second surface, so that each Fresnel prism unit and the light deflecting element it matches form an optical plate unit. This makes the Fresnel combined optical device equivalent to an optical plate, so that the quasi-parallel light beam does not change its propagation direction after passing through the Fresnel optical element and the light deflecting element. The refractive index of the light deflecting element is the same as that of the Fresnel optical element. The surface shape function of the second surface is z2, and z2 has at least two values. The positions of these at least two values ​​are located at different distances from the prism surface, so that the equivalent path length of the quasi-parallel beam passing through at least two positions of the Fresnel optical combination device is different. The equivalent path length is L / n, where L is the path length of the quasi-parallel beam from the position located on the prism surface to the second surface, and n is the refractive index of the Fresnel optical element. The different positions of the Fresnel optical combination device can control the shape of the image plane after modulating the quasi-parallel beam, so as to realize naked-eye stereoscopic display.

2. The stereoscopic display device according to claim 1, characterized in that, The light deflection element is a transmission prism or a freeform lens.

3. The stereoscopic display device according to claim 1, characterized in that, The light deflecting element receives the quasi-parallel beam modulated by the Fresnel optical element and guides the quasi-parallel beam outward.

4. The stereoscopic display device according to claim 1, characterized in that, The spatial light modulator is a liquid crystal display device.

5. The stereoscopic display device according to claim 1, characterized in that, The spatial light modulator is a silicon-based liquid crystal display device.

6. The stereoscopic display device according to claim 1, characterized in that, The spatial light modulator is a digital micromirror device.

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