Reflective film, turning element, camera module and electronic device

Abstract

This application provides a reflective film, a folding element, a camera module, and an electronic device, belonging to the field of optical imaging technology. The folding element includes a prism and multiple reflective films. The prism has multiple non-total reflection surfaces, and a reflective film is disposed on each non-total reflection surface. Any two reflective films have the same number of film stacks. Along the path of light passing through multiple non-total reflection surfaces, in two adjacent reflective films, the i-th film stack from the prism to air in one reflector reflects light with a center wavelength of λ1, and the n-th film stack from the prism to air in the other reflector reflects light with the same center wavelength of λ2. λ1 and λ2 are the same, and the optical thickness of the i-th and n-th film stacks is the same. The reflectivity of each film stack for the reflected center wavelength light is greater than or equal to 80%, and the refractive indices of adjacent film layers in each film stack are different. The folding element provided in this application can reduce the size of the camera module.

Description

Technical Field

[0001] This application relates to the field of optical imaging technology, and in particular to a reflective film, a folding element, a camera module, and an electronic device. Background Technology

[0002] Camera modules have become an indispensable functional component in electronic products such as mobile phones, tablets, laptops, and wearable devices. With the increasing thinness and multifunctionality of electronic devices, camera modules are also gradually becoming smaller and thinner, while the image quality and requirements are increasingly approaching those of SLR cameras. The size and functionality of camera modules are gradually becoming one of the important characteristics of electronic devices. A camera module includes a lens assembly and an image sensor. The lens assembly is typically formed by multiple lenses arranged sequentially along the optical axis. Light passes through the lens assembly and is projected onto the image sensor for photoelectric conversion, which is then used for image formation. In related technologies, camera modules use a "periscope" design to achieve long focal lengths to meet the needs of long-distance shooting. However, periscope camera modules are relatively large, increasing the difficulty of miniaturizing electronic devices. Summary of the Invention

[0003] This application provides a reflective film, a folding element, a camera module, and an electronic device, which can reduce the size of the camera module and reduce the difficulty of miniaturizing the electronic device.

[0004] The first aspect of this application provides a reflective film comprising multiple stacked film layers. Adjacent film layers have different optical thicknesses and are used to reflect light of different center wavelengths. Each film layer has a reflectivity greater than or equal to 80% for the reflected center wavelength. Each film layer comprises multiple stacked film layers with different refractive indices for adjacent film layers. Thus, the reflective film can reflect light of different center wavelengths by using different numbers of film layers, thereby improving the reflectivity of the reflective film for different center wavelengths.

[0005] In one possible implementation, the absolute value of the difference in refractive index between two adjacent layers in at least one film stack is greater than or equal to 0.6. Thus, with a fixed number of layers, the reflectivity of the film stack to the reflected light can be further increased, contributing to an improvement in the reflectivity of the reflective film.

[0006] In one possible implementation, each membrane stack has a reflectivity of 98% or greater for the reflected center wavelength light, which can further reduce the reflectivity of the reflective membrane and thus further improve the transmittance.

[0007] In one possible implementation, the refractive index of each layer of at least one film stack is greater than or equal to 1.6. This can improve the reflectivity of the film stack to the reflected light.

[0008] In one possible implementation, the refractive index of each layer of at least one film stack is less than 1.6. This can improve the reflectivity of the film stack to the reflected light.

[0009] In one possible implementation, at least one portion of the film layers in the film stack has a refractive index greater than or equal to 1.6, while the refractive index of another portion of the film layers is less than 0.6. This can improve the reflectivity of the film stack to the reflected light.

[0010] In one possible implementation, at least one layer in the film stack has a thickness greater than or equal to 80 nm and less than or equal to 150 nm with a refractive index greater than or equal to 1.6. This allows for further improvement in the reflectivity of the film stack when the number of layers is constant.

[0011] In one possible implementation, the thickness of at least one film layer with a refractive index less than 1.6 in the film stack is greater than or equal to 100 nm and less than or equal to 180 nm. Thus, with a fixed number of film layers, the reflectivity of the film stack can be further improved.

[0012] In one possible implementation, at least two film stacks comprise two film layers with different refractive indices. This simplifies the structure of the film stacks and helps reduce the difficulty of stacking them.

[0013] In one possible implementation, the optical thicknesses of any two film stacks are different. This reduces the number of film stacks and helps to reduce the thickness of the reflective film.

[0014] In one possible implementation, the reflective film is a dielectric film.

[0015] In one possible implementation, the reflective film is a metal film.

[0016] In one possible implementation, the reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer formed by multiple film stacks.

[0017] In one possible implementation, each membrane stack has a reflectivity of less than 80% for light of other center wavelengths besides the corresponding center wavelength.

[0018] In one possible implementation, each membrane stack has a reflectivity of less than 50% for light of other center wavelengths besides the corresponding center wavelength.

[0019] A second aspect of this application provides a folding element comprising a prism and a plurality of reflective films as described in any of the first aspects. The prism has a plurality of non-total reflection surfaces for reflecting light, and a reflective film is disposed on each non-total reflection surface. Any two reflective films have the same number of film stacks. Along the path of light passing through the plurality of non-total reflection surfaces, in two adjacent reflective films, the i-th film stack from the prism to air in one reflective film is used to reflect light with a center wavelength of λ1, and the n-th film stack from the prism to air in the other reflective film is used to reflect light with the same center wavelength of λ2, where λ1 and λ2 are the same, and the optical thickness of the i-th and n-th film stacks is the same. Where i + n = m + 1, i ≤ m, n ≤ m, i, n, and m are all positive integers, and m is the number of film stacks for each reflective film.

[0020] By placing a reflective film on a non-total internal reflection surface that does not meet the conditions for total internal reflection, total internal reflection can occur at the non-total internal reflection surface, allowing the prism to undergo multiple total internal reflections. This reduces the size of the prism and, consequently, the size of the folding element. Furthermore, achieving total internal reflection through a reflective film decouples the total internal reflection angle of the prism from its constituent angles, allowing prisms at any angle to undergo multiple total internal reflections. This results in high transmittance while simultaneously reducing the prism's size.

[0021] Furthermore, in the path of light passing through multiple non-total reflection surfaces, adjacent reflective films are complementary, ensuring that the optical path difference of light with different center wavelengths passing through all non-total reflection surfaces is zero or reduced. This improves transmittance while also mitigating or resolving dispersion. Complementarity refers to the fact that adjacent reflective films have the same number of film stacks, the same structure of the film stacks, and an opposite arrangement of the film stacks relative to the prism.

[0022] In one possible implementation, the prism has an even number of non-total reflection surfaces, so that the optical path difference after light of different center wavelengths passes through all the non-total reflection surfaces is zero, which can solve the dispersion problem.

[0023] In one possible implementation, each reflective film is a dielectric film. This allows for a further reduction in the size of the folding element while addressing dispersion issues and achieving high transmittance.

[0024] In one possible implementation, each reflective film is a metal film. This allows for a further reduction in the size of the refracting element while addressing dispersion issues and achieving high transmittance.

[0025] In one possible implementation, the reflective film is a metallic dielectric film, comprising a metal layer and a dielectric layer located between the metal layer and the prism. Thus, when the prism at any angle has an even or odd number of non-total reflective surfaces, the absorption characteristics of the metallic material in the metal layer can solve or improve dispersion problems, achieving high transmittance.

[0026] A third aspect of this application provides a camera module, including an image sensor, a lens, and a folding element as described in any of the second aspects. The lens and the image sensor are disposed on the same side of the folding element, or the lens and the image sensor are disposed on opposite sides of the folding element.

[0027] Because the folding element is composed of prisms and reflective films at arbitrary angles, it has high transmittance while being small in size, which can reduce the size of the camera module and thus reduce the difficulty of miniaturizing electronic devices.

[0028] A fourth aspect of this application provides an electronic device, including a housing and a camera module as described in the third aspect, wherein the camera module is mounted on the housing. Attached Figure Description

[0029] Figure 1 This is a cross-sectional view of a camera module in related technologies;

[0030] Figure 2A This is a schematic diagram of a prism in related technologies reflecting light through an odd number of reflective surfaces;

[0031] Figure 2B This is a schematic diagram of a prism in related technologies reflecting light through an even number of reflecting surfaces;

[0032] Figure 3 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application;

[0033] Figure 4 This is a schematic diagram of the structure of a camera module provided in an embodiment of this application;

[0034] Figure 5 This is a schematic diagram of another camera module provided in an embodiment of this application;

[0035] Figure 6 A cross-sectional schematic diagram of a reflective film provided in an embodiment of this application;

[0036] Figure 7 This is a schematic diagram of the structure of a folding element provided in an embodiment of this application;

[0037] Figure 8 This is a schematic diagram of another folding element provided in an embodiment of this application;

[0038] Figure 9 for Figure 7 The reflectivity curves of the first reflective film at different centers;

[0039] Figure 10 The reflectivity curves of the second reflective film for different center wavelengths;

[0040] Figure 11 This is a cross-sectional schematic diagram of another reflective film provided in an embodiment of this application.

[0041] Explanation of reference numerals in the attached figures:

[0042] 100. Electronic devices;

[0043] 10. Camera module; 11. Folding element; 12. Lens; 13. Image sensor;

[0044] 20. Shell;

[0045] 30. Trumpet mouth;

[0046] 40. Data interface;

[0047] 50. Prism; 51. First non-total reflection surface; 52. Second non-total reflection surface; 53. Total reflection surface;

[0048] 60. Reflective film; 60A. First reflective film; 60B. Second reflective film;

[0049] 61. First membrane stack; 62. Second membrane stack; 63. Third membrane stack; 64. Fourth membrane stack;

[0050] 65. Dielectric layer; 66. Metal layer;

[0051] c1, blue light; c2, green light; c3, yellow light; c4, red light. Detailed Implementation

[0052] The terminology used in the implementation section of this application is for the purpose of explaining specific embodiments of this application only, and is not intended to limit this application.

[0053] To facilitate understanding, the relevant technical terms involved in the embodiments of this application will first be explained and described.

[0054] Dispersion refers to the phenomenon where polychromatic light is decomposed into monochromatic light to form a spectrum.

[0055] Transmittance: The ratio of the radiant energy projected onto and transmitted through an object to the total radiant energy projected onto the object during the process of incident light flux from the surface of the illuminated surface or the incident surface of the medium to the other side is called the transmittance of the object.

[0056] The center wavelength refers to the wavelength corresponding to the center position of the spectral distribution curve. For example, the wavelength range of red light is 760–622 nm, and the center wavelength is 660 nm; or the wavelength range of green light is 577–492 nm, and the center wavelength is 550 nm, and so on.

[0057] Optical thickness: The geometric thickness of a medium multiplied by its refractive index is called optical thickness. Geometric thickness refers to the physical or actual thickness of the medium.

[0058] Total internal reflection (TIR) ​​is an optical phenomenon. When light travels from a medium with a higher refractive index to a medium with a lower refractive index, if the angle of incidence is greater than a certain critical angle (when the light ray moves away from the normal), the refracted light ray will disappear, and all incident light rays will be reflected and will not enter the medium with the lower refractive index.

[0059] Group delay effect: This is mainly reflected in the fact that the refractive index of light at different frequencies is different, resulting in different reflectivity and reflection depth for different light under the same film system.

[0060] Optical path is a fundamental concept in the field of optics, defined as the product of the geometric path of light propagation and the refractive index of the medium.

[0061] Optical path difference, as the name suggests, is the difference in the optical path length between two beams of light.

[0062] Figure 1 This is a cross-sectional view of a camera module in related technologies. Figure 2A This is a schematic diagram of a prism in related technologies reflecting light through an odd number of reflective surfaces. Figure 2B This is a schematic diagram of a prism in related technologies reflecting light through an even number of reflecting surfaces.

[0063] In related technologies, such as Figure 1 As shown, the periscope camera module 200 includes a prism 210, an image sensor 220, and a lens assembly 230. The lens assembly 230 is positioned between the prism 210 and the image sensor 220, and includes multiple parallel-placed lenses to achieve a long focal length design, meeting the needs of long-distance shooting. However, the periscope camera module 200 is relatively large, which increases the difficulty of miniaturizing electronic devices.

[0064] To reduce the difficulty of miniaturizing electronic devices, in one embodiment, the size of the periscope camera module 200 can be reduced by using multiple reflections of the prism 210. The prism 210 has multiple reflective surfaces for reflecting light, and a total reflection film 240 (e.g., ...) is coated on the reflective surfaces that do not meet the conditions for total internal reflection. Figure 2A As shown, this allows the size of the prism 210 to be made smaller, thereby reducing the volume of the periscope camera module 200 and thus reducing the difficulty of miniaturizing electronic devices.

[0065] like Figure 2AAs shown, prism 210 has three reflecting surfaces: a total reflection surface d1, a first non-total reflection surface d2, and a second non-total reflection surface d3. Light rays satisfy the total reflection condition at the total reflection surface d1, so a total reflection film 240 is not required on d1. Light rays do not satisfy the total reflection condition at the first non-total reflection surface d2 and the second non-total reflection surface d3; therefore, a total reflection film 240 is coated on both the first non-total reflection surface d2 and the second non-total reflection surface d3, causing total reflection to occur at these surfaces. However, the total reflection film 240 is a dielectric film, and dielectric films exhibit group delay effects, causing light of different center wavelengths to be reflected at different depths of the total reflection film 240 (e.g., ...). Figure 2A As shown in M1 and M2, light of different center wavelengths has different optical path lengths after passing through the total reflection film 240, resulting in an optical path difference. Therefore, when light undergoes an odd number of reflections within the prism 210, there is an optical path difference between light of different center wavelengths exiting the prism 210. This causes light of different center wavelengths to not overlap, leading to dispersion and causing one of the first non-total reflection surfaces d2 and the second non-total reflection surface d3 to form a red edge and the other to form a blue edge.

[0066] In another implementation, such as Figure 2B As shown, prism 210 has two reflecting surfaces, namely a first non-total reflection surface d2 and a second non-total reflection surface d3. Light rays do not satisfy the condition for total internal reflection at the first non-total reflection surface d2 and the second non-total reflection surface d3; therefore, both the first non-total reflection surface d2 and the second non-total reflection surface d3 are coated with a total internal reflection film 240 (not shown on...). Figure 2B (As shown in the diagram), this allows light to undergo total internal reflection at the first non-total internal reflection surface d2 and the second non-total internal reflection surface d3. The total internal reflection film 240 is a dielectric film, allowing light of different center wavelengths (such as...) to undergo total internal reflection. Figure 2B As shown in M1 and M2, there is an optical path difference at both reflecting surfaces. Figure 2B It can be seen that when light of different center wavelengths leaving prism 210 coincides, there is no dispersion problem. In this case, β = α, β = 180° - 3α = α, that is, α = 45°. When α ≠ 45°, β ≠ α, and light of different center wavelengths leaving prism 210 does not coincide, resulting in dispersion. Therefore, when light undergoes an even number of reflections within prism 210, if the angle of prism 210 is not equal to 45°, dispersion will occur.

[0067] In view of this, embodiments of this application provide a reflective film 60, a folding element 11, a camera module 10, and an electronic device 100. The folding element 11 includes a prism 50 and a reflective film 60. The prism 50 has multiple reflective surfaces, and the reflective film 60 is coated on the non-total reflection surface among the multiple reflective surfaces, allowing light to undergo total internal reflection at the non-total reflection surface, eliminating the need to coat the total reflection surface with the reflective film 60. Along the path of light passing through all reflective surfaces, adjacent reflective films 60 are complementary, enabling the prism 50 at any angle to have high transmittance while also improving or solving dispersion problems. This reduces the size of the camera module 10, thereby reducing the difficulty of miniaturizing the electronic device 100.

[0068] Among them, the electronic device 100 may include, but is not limited to, mobile phones, tablets, laptops, ultra-mobile personal computers (UMPCs), handheld computers, walkie-talkies, netbooks, POS machines, personal digital assistants (PDAs), wearable devices, virtual reality devices, vehicle-mounted devices, and other devices with camera modules 10.

[0069] In this embodiment, the electronic device 100 is taken as a mobile phone, which can be a candybar phone or a foldable phone. The following description uses a candybar phone as an example.

[0070] Figure 3 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application.

[0071] See Figure 3 As shown, the electronic device 100 includes a display screen, a housing 20, and a camera module 10. The camera module 10 is mounted on the housing 20 and is used to perform shooting functions. The display screen, mounted on the housing 20, is used to display text, images, and other information.

[0072] The camera module 10 can be located on the front of the electronic device 100 (the side with the display screen) for taking selfies or photographing other objects. Alternatively, see... Figure 3 As shown, the camera module 10 can also be located on the back of the electronic device 100 (the side facing away from the display screen) for taking pictures of other objects, and of course, for taking selfies.

[0073] The number of camera modules 10 can be one, or the number of camera modules 10 can be multiple, to meet different shooting needs.

[0074] Electronic device 100 may also include other structural components, for example, see continue. Figure 3As shown, the housing 20 of the electronic device 100 may also have a speaker opening 30, which can be used to play audio, etc., from the electronic device 100. (Continue to see...) Figure 3 As shown, the housing 20 of the electronic device 100 may also be provided with a data interface 40. The data interface 40 can be used to power the electronic device 100, or the data interface 40 can also be used to connect the electronic device 100 to headphones, external multimedia devices, etc. (such as external cameras, external projectors, etc.).

[0075] Of course, in some other examples, the electronic device 100 may also include other structural components to complete the functionality of the electronic device 100, such as sensors, processors, circuit boards, drive structures, etc., which are not limited in the embodiments of this application.

[0076] Figure 4 This is a schematic diagram of the structure of a camera module provided in an embodiment of this application.

[0077] like Figure 4 As shown, the camera module 10 includes an image sensor 13, a lens 12, and a folding element 11. The folding element 11 folds the optical axis, giving the camera module 10 a periscope-like structure. The folding element 11 receives incident light. The incident light undergoes multiple total internal reflections within the folding element 11 before exiting and being received by the photosensitive surface (also called the imaging surface) of the image sensor 13, thus achieving image formation. By performing multiple total internal reflections of the incident light through the folding element 11, the volume of the folding element 11 can be further reduced, achieving a smaller camera module 10. Simultaneously, the folding element 11, while having high transmittance for incident light, can improve or solve chromatic aberration problems.

[0078] The image sensor 13 can be a charge-coupled device (CCD), or a complementary metal oxide semiconductor (CMOS). Alternatively, it can be any other device capable of photoelectric conversion.

[0079] Lens 12 may include one or more lens elements, without specific limitations.

[0080] It should be noted that the camera module 10 may also include other components, such as a lens barrel, a filter, etc. The lens barrel is used to house the image sensor 13, the filter, or the lens 12, etc.

[0081] like Figure 4As shown, the lens 12 and the image sensor 13 are disposed on the same side of the folding element 11. At this time, the folding element 11 is used to receive the incident light emitted from the lens 12 and project the incident light onto the photosensitive surface of the image sensor 13.

[0082] However, in some implementations, the image sensor 13 and the lens 12 can also be respectively disposed on opposite sides of the folding element 11, such as... Figure 5 As shown. Among them, Figure 5 This is a schematic diagram of another camera module provided in an embodiment of this application.

[0083] In this embodiment, the folding element 11 includes a prism 50 and a plurality of reflective films 60. The prism 50 has multiple non-total reflection surfaces for reflecting light, and each non-total reflection surface is provided with a reflective film 60. Therefore, the reflective films 60 and the non-total reflection surfaces correspond one-to-one. For example, as... Figure 4 As shown, there are two reflective films 60, and correspondingly, there are two non-total reflective surfaces. Each reflective film 60 is a dielectric film.

[0084] The specific structure of prism 50 is not limited here. In some implementations, such as... Figure 4 As shown, prism 50 can be an isosceles trapezoid. In other implementations, such as Figure 5 As shown, prism 50 can also be a parallelogram.

[0085] In some implementations, prism 50 can have an even number of non-total reflection surfaces. For example... Figure 4 As shown, prism 50 has two non-total reflection surfaces, and correspondingly, there are two reflective films 60. Of course, the number of non-total reflection surfaces can also be more than two, such as 4, 6, 8, etc.

[0086] In some implementations, prism 50 may also have an odd number of non-total reflection surfaces. For example, prism 50 may have three non-total reflection surfaces. Of course, the number of non-total reflection surfaces may also be more than three, such as 5, 7, 9, etc.

[0087] The prism 50 also has a total reflection surface 53, and the number of total reflection surfaces 53 can be one or more. For example Figure 4 As shown, the number of total reflection surfaces 53 is one. Or, as... Figure 5 As shown, there are two total reflection surfaces 53.

[0088] Figure 6 This is a cross-sectional schematic diagram of a reflective film provided in an embodiment of this application.

[0089] See Figure 6As shown, each reflective film 60 comprises multiple stacked film layers. Adjacent film layers have different optical thicknesses and are used to reflect light of different center wavelengths. Each film layer has a reflectivity greater than or equal to 80% for the reflected center wavelength. Each film layer comprises multiple stacked film layers with different refractive indices for adjacent film layers. Thus, the reflective film 60 can reflect light of different center wavelengths using different numbers of film layers, improving its reflectivity and achieving high optical efficiency. It also solves or improves the dispersion problem of the prism 50.

[0090] For example, such as Figure 6 As shown, the reflective film 60 includes four film stacks, namely a first film stack 61, a second film stack 62, a third film stack 63, and a fourth film stack 64 stacked together. Of course, the number of film stacks may be more or less than four.

[0091] For example, such as Figure 6 As shown, a membrane stack can include six membrane layers stacked together. Of course, the number of membrane layers in a membrane stack can be more or less than six.

[0092] In this embodiment, each membrane stack reflects not only light of its corresponding center wavelength but also light of other center wavelengths, with a reflectivity of less than 80% for these other center wavelengths. For example, as shown... Figure 6 As shown, the first film stack 61 reflects blue light c1 with a center wavelength of 440nm, while also reflecting light with center wavelengths such as red light c4, green light c2, and yellow light c3. The reflectivity of the first film stack 61 for light with center wavelengths such as red light c4, green light c2, and yellow light c3 can be less than 50%.

[0093] The reflectivity of each membrane stack to light of other center wavelengths besides the corresponding center wavelength may include, but is not limited to, 20%, 30%, 40%, 50%, 55%, 60%, or 70%.

[0094] In some implementations, the reflectivity of each membrane stack to light of other center wavelengths besides the corresponding center wavelength can be less than 50%. This increases the transmittance of each membrane stack to light of other center wavelengths besides the corresponding center wavelength, ensuring that the reflective membrane 60 completely reflects light of each center wavelength through different numbers of membrane stacks.

[0095] Figure 7 This is a schematic diagram of the structure of a folding element provided in an embodiment of this application. Figure 8 This is a schematic diagram of another folding element provided in an embodiment of this application.

[0096] See Figure 7As shown, along the path of light passing through multiple non-total reflection surfaces (such as...) Figure 7 or Figure 8 (Solid line with arrow in the middle) Two adjacent reflective films 60 are complementary, which allows the prism 50 at any angle to have high transmittance while improving or solving dispersion problems. Complementarity means that the two adjacent reflective films 60 have the same number of film stacks, the same film stack composition, and the opposite arrangement order of the film stacks relative to the prism 50. The same film stack composition can be understood as two film stacks of the same optical thickness having the same type of film layers, arrangement, thickness, and number of film layers.

[0097] Specifically, any two reflective films 60 have the same number of film stacks, along the path of light passing through multiple non-total reflection surfaces (such as...). Figure 7 or Figure 8 (Solid line with arrows) In two adjacent reflective films 60, the i-th film stack from prism 50 to air in one reflective film 60 is used to reflect light with a center wavelength of λ1, and the n-th film stack from prism 50 to air in the other reflective film 60 is used to reflect light with the same center wavelength of λ2. λ1 and λ2 are the same. In other words, the i-th film stack from prism 50 to air in one reflective film 60 and the n-th film stack from prism 50 to air in the other reflective film 60 are used to reflect light with the same center wavelength. The i-th and n-th film stacks have the same optical thickness and the same structure. Where i+n=m+1, i≤m, n≤m, i, n, and m are all positive integers, and m is the number of film stacks in each reflective film 60. This arrangement makes the two adjacent reflective films 60 complementary, allowing prism 50 at any angle to have high transmittance while improving or solving dispersion problems.

[0098] The complementary characteristics of two adjacent reflective films 60 are illustrated below:

[0099] For example, such as Figure 7 As shown, the prism 50 has two non-total reflection surfaces and one total reflection surface 53. Light enters the interior of the prism 50 through the total reflection surface 53, and then is reflected in sequence by the first non-total reflection surface 51, the total reflection surface 53 and the second non-total reflection surface 52 before leaving the prism 50 through the total reflection surface 53.

[0100] See also Figure 7As shown, along the path of light passing through all the non-total reflection surfaces of prism 50, the first reflective film 60A and the second reflective film 60B are adjacent. The first reflective film 60A is disposed on the first non-total reflection surface 51 and includes four stacked film stacks. The first film stack a1 is closest to the first non-total reflection surface 51, and the fourth film stack a4 is farthest from the first non-total reflection surface 51. The second reflective film 60B is disposed on the second non-total reflection surface 52 and includes four stacked film stacks. The first film stack b1 is closest to the second non-total reflection surface 52, and the fourth film stack b4 is farthest from the second non-total reflection surface 52.

[0101] In this design, the first film stack a1 in the first reflective film 60A and the fourth film stack b4 in the second reflective film 60B reflect light of the same center wavelength. The second film stack a2 in the first reflective film 60A and the third film stack b3 in the second reflective film 60B reflect light of the same center wavelength. The third film stack a3 in the first reflective film 60A and the second film stack b2 in the second reflective film 60B reflect light of the same center wavelength. The fourth film stack a4 in the first reflective film 60A and the first film stack b1 in the second reflective film 60B reflect light of the same center wavelength. Therefore, the arrangement order of the film stacks in the first reflective film 60A and the second reflective film 60B is reversed.

[0102] In this design, the first film stack a1 in the first reflective film 60A has the same optical thickness and structure as the fourth film stack b4 in the second reflective film 60B. Similarly, the second film stack a2 in the first reflective film 60A has the same optical thickness and structure as the third film stack b3 in the second reflective film 60B. The third film stack a3 in the first reflective film 60A has the same optical thickness and structure as the second film stack b2 in the second reflective film 60B. Finally, the fourth film stack a4 in the first reflective film 60A has the same optical thickness and structure as the first film stack b1 in the second reflective film 60B.

[0103] The following example uses four different center wavelengths of light—blue c1, green c2, yellow c3, and red c4—to illustrate how two adjacent reflective films 60 reflect light of different center wavelengths to achieve complementarity.

[0104] See also Figure 7 As shown, in the first reflective film 60A, the first film stack a1 is used to reflect blue light c1 with a center wavelength of 440nm, the second film stack a2 is used to reflect green light c2 with a center wavelength of 550nm, the third film stack a3 is used to reflect yellow light c3 with a center wavelength of 570nm, and the fourth film stack a4 is used to reflect red light c4 with a center wavelength of 660nm.

[0105] See also Figure 7 As shown, in the second reflective film 60B, the first film stack b1 is used to reflect red light c4 with a center wavelength of 660nm, the second film stack b2 is used to reflect yellow light c3 with a center wavelength of 570nm, the third film stack b3 is used to reflect green light c2 with a center wavelength of 550nm, and the fourth film stack b4 is used to reflect blue light c1 with a center wavelength of 440nm.

[0106] Therefore, it can be seen that the i-th film stack in the first reflective film 60A and the n-th film stack in the second reflective film 60B reflect light with the same center wavelength, and the i-th and n-th film stacks have the same optical thickness. In this case, m = 4, i + n = 5, i ≤ 4, n ≤ 4, and i and n are positive integers. For example, when i = 1 and n = 4, the first film stack a1 in the first reflective film 60A and the fourth film stack b4 in the second reflective film 60B reflect blue light c1 with the same center wavelength, and the first film stack a1 and the fourth film stack b4 have the same optical thickness.

[0107] Figure 9 for Figure 7 The first reflective film in the diagram shows the reflectivity curves for different centers. Among them, in... Figure 9 In the diagram, R represents reflectivity, g1 represents the reflectivity curve of the first reflective film 60A for blue light c1, g2 represents the reflectivity curve of the first reflective film 60A for green light c2, g3 represents the reflectivity curve of the first reflective film 60A for yellow light c3, and g4 represents the reflectivity curve of the first reflective film 60A for red light c4.

[0108] exist Figure 7 During the process of the first reflective film 60A reflecting light of different center wavelengths, see [reference needed]. Figure 9 As shown, blue light c1 is reflected by the first film stack a1 in the first reflective film 60A; green light c2 is reflected by the first film stack a1 and the second film stack a2 in the first reflective film 60A; yellow light c3 is reflected by the first film stack a1, the second film stack a2, and the third film stack a3 in the first reflective film 60A; and red light c4 is reflected by the first film stack a1, the second film stack a2, the third film stack a3, and the fourth film stack a4 in the first reflective film 60A. Therefore, it can be seen that light of different center wavelengths has an optical path difference after passing through the first reflective film 60A. For example, the optical path difference between red light c4 and green light c2 on the first reflective film 60A is equal to that between the second film stack a2 and the third film stack a3.

[0109] It is understandable that the first layer a1 of the first reflective film 60A can reflect light of all center wavelengths, and reflects all blue light c1 with a corresponding center wavelength of 440nm, allowing light of all center wavelengths except blue light c1 to reach the second layer a2. Similarly, the second layer a2 of the first reflective film 60A can reflect light of all center wavelengths except blue light c1, and under the combined action of the first layer a1 and the second layer a2, reflects all green light c2 with a corresponding center wavelength of 550nm. The third layer a3 of the first reflective film 60A can reflect light of all center wavelengths except blue light c1 and green light c2, and under the combined action of the first layer a1, the second layer a2, and the third layer a3, reflects all yellow light c3 with a center wavelength of 570nm. The fourth layer a4 of the first reflective film 60A can reflect light of all center wavelengths except blue c1, green c2, and yellow c3. Through the combined action of the first layer a1, the second layer a2, the third layer a3, and the fourth layer a4, it completely reflects the red light c4 with a center wavelength of 660nm. Therefore, light of different center wavelengths has an optical path difference after passing through the first reflective film 60A.

[0110] Figure 10 The second reflective film in the diagram shows the reflectivity curves for different center wavelengths. Figure 10 In the diagram, R represents reflectivity, g1 represents the reflectivity curve of the second reflective film 60B for blue light c1, g2 represents the reflectivity curve of the second reflective film 60B for green light c2, g3 represents the reflectivity curve of the second reflective film 60B for yellow light c3, and g4 represents the reflectivity curve of the second reflective film 60B for red light c4.

[0111] exist Figure 7 During the process of the second reflective film 60B reflecting light of different center wavelengths, see [reference needed]. Figure 10 As shown, blue light c1 is reflected by the first film stack b1, the second film stack b2, the third film stack b3, and the fourth film stack b4 in the second reflective film 60B; green light c2 is reflected by the first film stack b1, the second film stack b2, and the third film stack b3 in the second reflective film 60B; yellow light c3 is reflected by the first film stack b1 and the second film stack b2 in the second reflective film 60B; and red light c4 is reflected by the first film stack b1 in the second reflective film 60B. Therefore, it can be seen that light of different center wavelengths has an optical path difference after passing through the second reflective film 60B. For example, the optical path difference between red light c4 and green light c2 is equal to that between the second film stack b2 and the third film stack b3.

[0112] Understandably, the first layer of the second reflective film 60B can reflect light of all center wavelengths, including all red light c4 with a center wavelength of 660nm, allowing light of all other center wavelengths except red c4 to reach the second layer b2. Similarly, the second layer b2 of the second reflective film 60B can reflect light of all other center wavelengths except red c4, and under the combined action of the first layer b1 and the second layer b2, it can reflect all yellow light c3 with a center wavelength of 570nm. The third layer b3 of the second reflective film 60B can reflect light of all other center wavelengths except red c4 and yellow c3, and under the combined action of the first layer b1, the second layer b2, and the third layer b3, it can reflect all green light c2 with a center wavelength of 550nm. The fourth layer b4 of the second reflective film 60B can reflect light of all center wavelengths except red c4, green c2, and yellow c3. Under the combined action of the first layer b1, the second layer b2, the third layer b3, and the fourth layer b4, it reflects all blue light c1 with a center wavelength of 440nm. Therefore, it can be seen that light of different center wavelengths has an optical path difference after passing through the second reflective film 60B.

[0113] Combination Figure 9 and Figure 10 It can be seen that the optical path difference between red light c4 and green light c2 on the first reflective film 60A is equal to the optical path difference between the second film stack a2 and the third film stack a3, and the optical path difference between red light c4 and green light c2 is equal to the optical path difference between the second film stack b2 and the third film stack b3. The optical thickness of the second film stack a2 of the first reflective film 60A is the same as the optical thickness of the third film stack b3 of the second reflective film 60B, and the optical thickness of the third film stack a3 of the first reflective film 60A is the same as the optical thickness of the third film stack b2 of the second reflective film 60B. Therefore, the absolute value of the optical path difference between red light c4 and green light c2 on the first reflective film 60A is the same as the absolute value of the optical path difference between red light c4 and green light c2 on the second reflective film 60B.

[0114] Combination Figure 7 It is known that the reversed stacking order of the first reflective film 60A and the second reflective film 60B results in a negative optical path difference between red light c4 and green light c2 on the second reflective film 60B. Consequently, the sum of the optical path differences between red light c4 and green light c2 at the first reflective film 60A and the second reflective film 60B is zero. Therefore, light of any center wavelength has the same optical path through two adjacent reflective films 60, and thus the optical path difference between any two center wavelengths is the same. Consequently, the optical path difference between any two center wavelengths at two adjacent reflective films 60 is zero, ensuring that light of different center wavelengths will not be deflected when passing through two adjacent reflective films 60, and that no dispersion occurs.

[0115] It is understandable that the sum of the optical path difference between red light c4 and green light c2 on the first reflective film 60A and the optical path difference between red light c4 and green light c2 on the second reflective film 60B = A + (-B). Where A = B, A is the optical path difference between red light c4 and green light c2 on the first reflective film 60A, and B is the optical path difference between red light c4 and green light c2 on the second reflective film 60B. Since the film stacking order in the first and second reflective films 60B is reversed, the optical path difference between red light c4 and green light c2 after passing through one of the two adjacent reflective films 60 is positive, and the optical path difference after passing through the other reflective film 60 is negative. Therefore, A is positive and B is negative, or vice versa.

[0116] When the number of non-total reflective surfaces is even, the sum of the optical path differences between any two center wavelengths of light after passing through the reflective films 60 on all the non-total reflective surfaces is zero, thus solving the dispersion problem. Simultaneously, each film stack has a reflectivity greater than 80% for the corresponding center wavelength, resulting in high reflectivity of the reflective film 60 and improved transmittance of the prism 50. Furthermore, the angle of the prism 50 can be decoupled from the dispersion problem, allowing the prism 50 to have any angle.

[0117] When the number of non-total reflective surfaces is odd, the sum of the optical path differences between any two center wavelengths of light after passing through the reflective films 60 on all the non-total reflective surfaces decreases, effectively improving the dispersion problem. Simultaneously, each film stack has a reflectivity greater than 80% for the corresponding center wavelength, resulting in high reflectivity of the reflective film 60, which increases the transmittance of the prism 50. Furthermore, the angle of the prism 50 can be decoupled from the dispersion problem, allowing the prism 50 to have any angle.

[0118] It should be noted that, Figure 7 The positions of the first reflective film 60A and the second reflective film 60B can be interchanged to solve or improve the dispersion problem and achieve the same effect. Specifically, the first reflective film 60A can also be placed on the second non-total reflection surface 52, and the second reflective film 60B can be placed on the first non-total reflection surface 51. In the first reflective film 60A, the first film stack a1 is closest to the second non-total reflection surface 52, and the fourth film stack a4 is farthest from the second non-total reflection surface 52. In the second reflective film 60B, the first film stack b1 is closest to the first non-total reflection surface 51, and the fourth film stack b4 is farthest from the first non-total reflection surface 51.

[0119] When the first reflective film 60A is disposed on the second non-total reflection surface 52, in the first reflective film 60A, the first film stack a1 is used to reflect red light c4 with a center wavelength of 660nm, the second film stack a2 is used to reflect yellow light c3 with a center wavelength of 570nm, the third film stack a3 is used to reflect green light c2 with a center wavelength of 550nm, and the fourth film stack a4 is used to reflect blue light c1 with a center wavelength of 440nm. At this time, the reflectivity curves of the first reflective film 60A for light of each center wavelength are shown in the figure. Figure 10 same.

[0120] When the second reflective film 60B is disposed on the first non-total reflection surface 51, in the second reflective film 60B, the first film stack b1 is used to reflect blue light c1 with a center wavelength of 440nm, the second film stack b2 is used to reflect green light c2 with a center wavelength of 550nm, the third film stack b3 is used to reflect yellow light c3 with a center wavelength of 570nm, and the fourth film stack b4 is used to reflect red light c4 with a center wavelength of 660nm. At this time, the reflectivity curves of the second reflective film 60B reflecting light of various center wavelengths are shown in the figure. Figure 9 same.

[0121] In some possible implementations, the optical thicknesses of any two film stacks are different, for example, as Figure 6 As shown, the optical thicknesses of the four film stacks in the reflective film 60 are all different. This reduces the number of film stacks and helps to reduce the thickness of the reflective film 60.

[0122] It should be noted that, apart from being different, the optical thicknesses of any two film stacks in the reflective film 60 can be varied. In some implementations, the optical thicknesses of some film stacks in the reflective film 60 can be the same, while the optical thicknesses of other film stacks can be different.

[0123] In some possible implementations, each membrane stack has a reflectivity of 98% or greater for the reflected center wavelength light, which can further reflect the reflectivity of the reflective membrane 60, thereby further improving the transmittance of the folding element 11.

[0124] For example, such as Figure 6 As shown, each of the four film stacks of the reflective film 60 has a reflectivity of 98% or greater for the reflected center wavelength light.

[0125] It should be noted that, in addition to setting the reflectivity of each film stack in the reflective film 60 to be greater than or equal to 98% for the reflected center wavelength light, it is also possible to set the reflectivity of a portion of the film stacks in the reflective film 60 to be greater than or equal to 98% for the reflected center wavelength light, and to set the reflectivity of another portion of the film stacks to be greater than 80% and less than 98%. For example, the reflective film 60 includes four film stacks, of which three film stacks have a reflectivity of greater than or equal to 98% for the reflected center wavelength light, and the remaining film stack has a reflectivity of greater than 80% and less than 98% for the reflected center wavelength light.

[0126] In some possible implementations, the number of film layers in at least two film stacks of the reflective film 60 is the same. For example Figure 6 As shown, there are four membrane stacks, each consisting of six membrane layers. However, the number of membrane stacks with the same number of membrane layers can be less than four. For example, three of the four membrane stacks may consist of six membrane layers, and the remaining membrane stack may consist of five membrane layers.

[0127] In some other possible implementations, the number of film layers in any two film stacks in the reflective film 60 may also be different. For example, the reflective film 60 includes four film stacks: the first film stack can be composed of two film layers, the second film stack can be composed of three film layers, the third film stack can be composed of four film layers, and the fourth film stack can be composed of five film layers.

[0128] In some possible implementations, the number of membrane layers in at least one membrane stack can be greater than or equal to 2 and less than or equal to 50, for example... Figure 6 As shown, the number of film layers in each film stack is greater than 2 and less than 20. In this way, when the refractive index difference between two adjacent film layers is large, high reflectivity can be achieved while helping to reduce the physical thickness of the film stack.

[0129] In some possible implementations, the absolute value of the difference in refractive index between two adjacent layers of at least one layer in the reflective film 60 is greater than or equal to 0.6. Thus, with a fixed number of layers, the reflectivity of the film stack for the reflected center wavelength can be further increased, contributing to an improvement in the reflectivity of the reflective film 60.

[0130] For example, such as Figure 6 As shown, the absolute value of the difference in refractive index between any two adjacent layers in the four layers of the reflective film 60 is greater than or equal to 0.6. However, in some implementations, the absolute value of the difference in refractive index between any two adjacent layers in a subset of the four layers of the reflective film 60 may be set to be greater than or equal to 0.6, while the absolute value of the difference in refractive index between any two adjacent layers in another subset may be set to be less than 0.6.

[0131] It should be noted that the absolute value of the difference in refractive index between two adjacent layers in at least one of the film stacks in the reflective film 60 may also be less than 0.6.

[0132] In this embodiment, each film stack in the reflective film 60 is composed of at least two film layers with different refractive indices. In some implementations, at least two film stacks in the reflective film 60 include two film layers with different refractive indices, which simplifies the structure of the film stacks and helps reduce the stacking difficulty. In other implementations, at least one film stack in the reflective film 60 may also include at least three film layers with different refractive indices.

[0133] For example, such as Figure 6 As shown, the reflective film 60 includes a first film stack 61, a second film stack 62, a third film stack 63, and a fourth film stack 64. The first film stack 61 includes a first film layer 611 and a second film layer 612 with different refractive indices. The second film stack 62 includes a third film layer 621 and a fourth film layer 622 with different refractive indices. The third film stack 63 includes a fifth film layer 631 and a sixth film layer 632 with different refractive indices. The fourth film stack 64 includes a seventh film layer 641 and an eighth film layer 642 with different refractive indices.

[0134] In this application, materials with a refractive index greater than or equal to 1.6 are defined as high refractive index materials, such as metal oxides or metal nitrides with a refractive index greater than or equal to 1.6, like metal oxides containing Ti / Ta. Materials with a refractive index less than 1.6 are defined as low refractive index materials, such as metal oxides or metal fluorides with a refractive index less than 1.6, like SiO2, Al2O3, MgF2, etc.

[0135] The materials used for the individual layers in the membrane stack are not limited here. In some implementations, the refractive index of each layer in the membrane stack is greater than or equal to 1.6; in other words, the membrane stack can be constructed from at least two high-refractive-index materials. In other implementations, the refractive index of each layer in the membrane stack is less than 0.6; in other words, the membrane stack can be constructed from at least two low-refractive-index materials. In still other implementations, some layers in the membrane stack have a refractive index greater than or equal to 1.6, while others have a refractive index less than 1.6; in other words, the membrane stack can be constructed from at least one high-refractive-index material and at least one low-refractive-index material.

[0136] In some possible implementations, the refractive index of each layer in each stack of reflective film 60 is greater than or equal to 1.6, such that each stack of reflective film 60 is made of a high refractive index material.

[0137] In some other possible implementations, the refractive index of each layer of a portion of the film stack in the reflective film 60 is greater than or equal to 1.6, the refractive index of a portion of the film stack is greater than or equal to 1.6, and the refractive index of a portion of the film stack is less than 1.6, such that a portion of the film stack in the reflective film 60 is composed of high refractive index materials, and the other portion of the film stack is composed of both high refractive index materials and low refractive index materials.

[0138] In some other possible implementations, the refractive index of each layer of each film stack in the reflective film 60 is less than 1.6, such that each film stack in the reflective film 60 is made of a low refractive index material.

[0139] In some other possible implementations, a portion of the film layers in each stack of the reflective film 60 has a refractive index greater than or equal to 1.6, while another portion has a refractive index less than 1.6, such that each stack of the reflective film 60 is composed of high-refractive-index materials and low-refractive-index materials.

[0140] In summary, the multiple film stacks of the reflective film 60 can all be made of high refractive index materials, or the multiple film stacks of the reflective film 60 can all be made of low refractive index materials and high refractive index materials, or the multiple film stacks of the reflective film 60 can all be made of low refractive index materials.

[0141] It should be noted that the refractive index of each film layer and the changes in the thickness of multiple film layers can be used to determine which film stack each layer belongs to. Of course, other methods can also be used to determine which film stack each film layer belongs to.

[0142] For example, such as Figure 6 As shown, the reflective coating 60 includes a first film stack 61, a second film stack 62, a third film stack 63, and a fourth film stack 64. The first film stack 61 is composed of first film layers 611 and second film layers 612 with different refractive indices; the first film layers 611 and second film layers 612 have the same thickness. The second film stack 62 is composed of third film layers 621 and fourth film layers 622 with different refractive indices; the third film layers 621 and fourth film layers 622 have the same thickness. The third film stack 63 is composed of fifth film layers 631 and sixth film layers 632 with different refractive indices; the fifth film layers 631 and sixth film layers 632 have the same thickness. The fourth film stack 64 is composed of seventh film layers 641 and eighth film layers 642; the seventh film layers 641 and eighth film layers 642 have the same thickness. Therefore, within the same film stack, film layers with the same refractive index have the same thickness. Therefore, the thickness variation of the membrane layer can be used to determine which membrane stack the membrane layer belongs to.

[0143] Due to manufacturing errors, the thicknesses of films with the same refractive index within the same film stack will not be exactly the same, and a certain degree of error is permissible. For example, films with the same refractive index whose thicknesses fluctuate by ≤±5% are considered to be part of the same film stack, while those exceeding this range are considered to be different film stacks.

[0144] In this embodiment, the thickness of the film layer is not limited. The thickness of the film layer may include, but is limited to, 1nm, 2nm, 5nm, 10nm, 50nm, 100nm, 180nm, 200nm, etc.

[0145] In some possible implementations, at least one layer in the film stack has a thickness greater than or equal to 80 nm and less than or equal to 150 nm with a refractive index greater than or equal to 1.6. It is understood that setting the thickness of the layer with a refractive index greater than or equal to 1.6 between 80 nm and 150 nm means limiting the thickness of the high-refractive-index material to between 80 nm and 150 nm. In this way, with a fixed number of layers, the reflectivity of the film stack can be further improved.

[0146] In some possible implementations, the thickness of at least one layer in the film stack with a refractive index less than 1.6 is greater than or equal to 100 nm and less than or equal to 180 nm. It is understood that setting the thickness of the layer with a refractive index less than 1.6 to 100 nm to 180 nm means limiting the thickness of the low-refractive-index material to 100 nm to 180 nm. In this way, with a fixed number of layers, the reflectivity of the film stack can be further improved.

[0147] In the above description, the reflective film 60 is a dielectric film. In this case, the dielectric film is composed of multiple stacked film layers, such as... Figure 6 As shown. However, in some implementations, the reflective film 60 can also be a metal film, in which case the metal film is also constructed by multiple stacked film layers. In still other implementations, the reflective film 60 can also be a metallic dielectric film, in which case, as shown... Figure 11 As shown, the metal dielectric film includes a metal layer 66 and a dielectric layer 65. The dielectric layer 65 is formed by multiple stacked films and is disposed between the metal layer 66 and the prism 50. Figure 11 This is a cross-sectional schematic diagram of another reflective film provided in an embodiment of this application.

[0148] It should be noted that when the reflective film 60 is a metallic film, since the metallic film is made of metallic materials, and metallic materials have absorption properties, it can improve the dispersion problem. Therefore, the complementary reflective film 60 is mainly used to improve the transmittance of the prism 50. When the reflective film 60 is a metallic dielectric film, the complementary reflective film 60 can effectively balance transmittance and dispersion problems, achieving high transmittance while improving or solving the dispersion problem.

[0149] The multiple reflective films 60 in the deflecting element 11 are of the same type, for example... Figure 4 As shown, both reflective films 60 are dielectric films. However, the folding element 11 can also have various types of reflective films 60.

[0150] In some implementations, at least one of the multiple reflective films 60 of the folding element 11 may be a dielectric film, and the remaining reflective films 60 may be a dielectric film or a metal dielectric film. For example, there may be two reflective films 60, one of which may be a dielectric film and the other may be a metal film or a metal dielectric film.

[0151] In other implementations, the first portion of the reflective film 60 of the multiple reflective films 60 of the folding element 11 can be a dielectric film, the second portion of the reflective film 60 can be a metal film, and the third portion of the reflective film 60 can be a metal-dielectric film. For example, if there are three reflective films 60, the first reflective film 60 can be a dielectric film, the second reflective film 60 can be a metal film, and the third reflective film 60 can be a metal-dielectric film.

[0152] In some other implementations, a portion of the reflective films 60 of the multiple reflective films 60 of the folding element 11 may be set as dielectric films and another portion of the reflective films 60 may be set as metallic dielectric films.

[0153] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0154] The devices or elements referred to in the embodiments of this application or implied herein must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the embodiments of this application. In the description of the embodiments of this application, "a plurality of" means two or more, unless otherwise precisely specified.

[0155] The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the present application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0156] The term "multiple" in this article refers to two or more. The term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Furthermore, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects; in formulas, the character " / " indicates a "division" relationship between the preceding and following related objects.

[0157] It is understood that the various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application.

Claims

1. A folding element, characterized in that, Includes prisms and multiple reflective films; The reflective film comprises multiple stacked film layers; The optical thickness of two adjacent film stacks is different, and the two adjacent film stacks are used to reflect light of different center wavelengths. The reflectivity of each film stack for the reflected center wavelength light is greater than or equal to 80%. Each film stack includes multiple film layers stacked together, and the refractive index of two adjacent film layers is different. The prism has multiple non-total reflection surfaces for reflecting light, and each of the non-total reflection surfaces is provided with a reflective film; Any two reflective films have the same number of film stacks. Along the path of light passing through the plurality of non-total reflection surfaces, in two adjacent reflective films, the i-th film stack from the prism to the air in one reflective film is used to reflect light with a center wavelength of λ1, and the n-th film stack from the prism to the air in the other reflective film is used to reflect light with the same center wavelength of λ2, where λ1 and λ2 are the same, and the optical thickness of the i-th film stack and the n-th film stack is the same; where i+n=m+1, i≤m, n≤m, i, n and m are all positive integers, and m is the number of film stacks in each reflective film.

2. The folding element according to claim 1, characterized in that, The absolute value of the difference in refractive index between two adjacent layers in at least one of the film stacks is greater than or equal to 0.

6.

3. The folding element according to claim 1 or 2, characterized in that, Each of the membrane stacks has a reflectivity of 98% or greater for the reflected center wavelength light.

4. The folding element according to claim 1 or 2, characterized in that, The refractive index of each layer of at least one of the film stacks is greater than or equal to 1.

6.

5. The folding element according to claim 3, characterized in that, The refractive index of each layer of at least one of the film stacks is greater than or equal to 1.

6.

6. The folding element according to any one of claims 1, 2, and 5, characterized in that, At least one of the film stacks has a refractive index of less than 1.6 for each of the film layers.

7. The folding element according to claim 3, characterized in that, At least one of the film stacks has a refractive index of less than 1.6 for each of the film layers.

8. The folding element according to claim 4, characterized in that, At least one of the film stacks has a refractive index of less than 1.6 for each of the film layers.

9. The folding element according to any one of claims 1, 2, 5, 7, and 8, characterized in that, At least one portion of the film layer in the film stack has a refractive index greater than or equal to 1.6, and the refractive index of another portion of the film layer is less than 0.

6.

10. The folding element according to claim 3, characterized in that, At least one portion of the film layer in the film stack has a refractive index greater than or equal to 1.6, and the refractive index of another portion of the film layer is less than 0.

6.

11. The folding element according to claim 4, characterized in that, At least one portion of the film layer in the film stack has a refractive index greater than or equal to 1.6, and the refractive index of another portion of the film layer is less than 0.

6.

12. The folding element according to claim 6, characterized in that, At least one portion of the film layer in the film stack has a refractive index greater than or equal to 1.6, and the refractive index of another portion of the film layer is less than 0.

6.

13. The folding element according to any one of claims 1, 2, 5, 7, 8, 10 to 12, characterized in that, The thickness of at least one of the film layers in the film stack having a refractive index greater than or equal to 1.6 is greater than or equal to 80 nm and less than or equal to 150 nm.

14. The folding element according to claim 3, characterized in that, The thickness of at least one of the film layers in the film stack having a refractive index greater than or equal to 1.6 is greater than or equal to 80 nm and less than or equal to 150 nm.

15. The folding element according to claim 4, characterized in that, The thickness of at least one of the film layers in the film stack having a refractive index greater than or equal to 1.6 is greater than or equal to 80 nm and less than or equal to 150 nm.

16. The folding element according to claim 6, characterized in that, The thickness of at least one of the film layers in the film stack having a refractive index greater than or equal to 1.6 is greater than or equal to 80 nm and less than or equal to 150 nm.

17. The folding element according to claim 9, characterized in that, The thickness of at least one of the film layers in the film stack having a refractive index greater than or equal to 1.6 is greater than or equal to 80 nm and less than or equal to 150 nm.

18. The folding element according to any one of claims 1, 2, 5, 7, 8, 10 to 12, 14 to 17, characterized in that, The thickness of at least one of the film layers in the film stack with a refractive index less than 1.6 is greater than or equal to 100 nm and less than or equal to 180 nm.

19. The folding element according to claim 3, characterized in that, The thickness of at least one of the film layers in the film stack with a refractive index less than 1.6 is greater than or equal to 100 nm and less than or equal to 180 nm.

20. The folding element according to claim 4, characterized in that, The thickness of at least one of the film layers in the film stack with a refractive index less than 1.6 is greater than or equal to 100 nm and less than or equal to 180 nm.

21. The folding element according to claim 6, characterized in that, The thickness of at least one of the film layers in the film stack with a refractive index less than 1.6 is greater than or equal to 100 nm and less than or equal to 180 nm.

22. The folding element according to claim 9, characterized in that, The thickness of at least one of the film layers in the film stack with a refractive index less than 1.6 is greater than or equal to 100 nm and less than or equal to 180 nm.

23. The folding element according to claim 13, characterized in that, The thickness of at least one of the film layers in the film stack with a refractive index less than 1.6 is greater than or equal to 100 nm and less than or equal to 180 nm.

24. The folding element according to any one of claims 1, 2, 5, 7, 8, 10 to 12, 14 to 17, 19 to 23, characterized in that, At least two of the film stacks comprise two film layers with different refractive indices.

25. The folding element according to claim 3, characterized in that, At least two of the film stacks comprise two film layers with different refractive indices.

26. The folding element according to claim 4, characterized in that, At least two of the film stacks comprise two film layers with different refractive indices.

27. The folding element according to claim 6, characterized in that, At least two of the film stacks comprise two film layers with different refractive indices.

28. The folding element according to claim 9, characterized in that, At least two of the film stacks comprise two film layers with different refractive indices.

29. The folding element according to claim 13, characterized in that, At least two of the film stacks comprise two film layers with different refractive indices.

30. The folding element according to claim 18, characterized in that, At least two of the film stacks comprise two film layers with different refractive indices.

31. The folding element according to any one of claims 1, 2, 5, 7, 8, 10 to 12, 14 to 17, 19 to 23, 25 to 30, characterized in that, The optical thicknesses of any two of the film stacks are different.

32. The folding element according to claim 3, characterized in that, The optical thicknesses of any two of the film stacks are different.

33. The folding element according to claim 4, characterized in that, The optical thicknesses of any two of the film stacks are different.

34. The folding element according to claim 6, characterized in that, The optical thicknesses of any two of the film stacks are different.

35. The folding element according to claim 9, characterized in that, The optical thicknesses of any two of the film stacks are different.

36. The folding element according to claim 13, characterized in that, The optical thicknesses of any two of the film stacks are different.

37. The folding element according to claim 18, characterized in that, The optical thicknesses of any two of the film stacks are different.

38. The folding element according to claim 24, characterized in that, The optical thicknesses of any two of the film stacks are different.

39. The folding element according to any one of claims 1, 2, 5, 7, 8, 10 to 12, 14 to 17, 19 to 23, 25 to 30, 32 to 38, characterized in that, The reflective film is a dielectric film; or, The reflective film is a metal film; or, The reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer formed by the plurality of film stacks.

40. The folding element according to claim 3, characterized in that, The reflective film is a dielectric film; or, The reflective film is a metal film; or, The reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer formed by the plurality of film stacks.

41. The folding element according to claim 4, characterized in that, The reflective film is a dielectric film; or, The reflective film is a metal film; or, The reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer formed by the plurality of film stacks.

42. The folding element according to claim 6, characterized in that, The reflective film is a dielectric film; or, The reflective film is a metal film; or, The reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer formed by the plurality of film stacks.

43. The folding element according to claim 9, characterized in that, The reflective film is a dielectric film; or, The reflective film is a metal film; or, The reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer formed by the plurality of film stacks.

44. The folding element according to claim 13, characterized in that, The reflective film is a dielectric film; or, The reflective film is a metal film; or, The reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer formed by the plurality of film stacks.

45. The folding element according to claim 18, characterized in that, The reflective film is a dielectric film; or, The reflective film is a metal film; or, The reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer formed by the plurality of film stacks.

46. ​​The folding element according to claim 24, characterized in that, The reflective film is a dielectric film; or, The reflective film is a metal film; or, The reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer formed by the plurality of film stacks.

47. The folding element according to claim 31, characterized in that, The reflective film is a dielectric film; or, The reflective film is a metal film; or, The reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer formed by the plurality of film stacks.

48. The folding element according to claim 1, characterized in that, The prism has an even number of the non-total reflective surfaces.

49. The folding element according to claim 1 or 48, characterized in that, Each of the aforementioned reflective films is a dielectric film or a metal film.

50. The folding element according to claim 1 or 48, characterized in that, The reflective film is a metallic dielectric film, which includes a metal layer and a dielectric layer located between the metal layer and the prism.

51. A camera module, characterized in that, Includes an image sensor, a lens, and a folding element as described in any one of claims 1 to 50; The lens and the image sensor are disposed on the same side of the folding element, or the lens and the image sensor are disposed on opposite sides of the folding element.

52. An electronic device, characterized in that, It includes a housing and a camera module as described in claim 51, wherein the camera module is mounted on the housing.

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