Projector with flat lens assembly

Abstract

A projector having a flat lens assembly includes a light source for emitting incident light, a flat lens assembly, and an optical element assembly for forming a pattern by the incident light emitted by the flat lens assembly. A flat lens assembly includes a polarizer, a wave plate, and a lens connected to the polarizer or the wave plate. The flat lens assembly is arranged between the light source and the optical element assembly and is used for folding the optical path of the incident light based on the polarization of the incident light so as to reduce the total module height of the projector.

Description

Technical Field

[0001] The present disclosure relates to a projector, and more particularly to a projector having a pancake lens assembly. Background Art

[0002] In 3D sensing, there is often a need for devices to project dot patterns or flood patterns to determine the depth of an object. By projecting a specific dot pattern or flood pattern onto an object, the depth of the object can be decoded via various mechanisms and algorithms. Depending on the application, different projection fields of view are required.

[0003] There is often a need for a light collimation system to project a dot pattern with clear and high-intensity dots. In addition, a lens system is also required to project a flood pattern with a specific intensity distribution.

[0004] However, one of the problems encountered by dot projectors or flood projectors is that the light collimation system or lens system can be of extremely thick total length, and the total module height of the dot projector or flood projector increases respectively depending on the desired field of view.

[0005] In summary, those skilled in the art are eager to provide a novel light collimation system for a dot projector or a lens system for a flood projector to overcome the disadvantages faced by the prior art. Summary of the Invention

[0006] To solve the above problems, the present disclosure provides a projector, comprising: a light source for emitting incident light; a pancake lens assembly for folding the optical path of the incident light, including: a polarizer, a wave plate, and a lens connected to the polarizer or the wave plate; and an optical element assembly for forming a pattern with the incident light emitted by the pancake lens assembly, wherein the pancake lens assembly is disposed between the light source and the optical element assembly.

[0007] In summary, the present disclosure provides a projector using a pancake lens assembly. The pancake lens assembly folds the optical path based on the polarization of the incident light. By the folded optical path, the total module height of the projector used in the present disclosure can be reduced. Brief Description of the Drawings

[0008] Figure 1 Schematic diagram of a projector according to at least one embodiment of the present disclosure.

[0009] Figure 2 Schematic diagram of a projector according to at least one embodiment of the present disclosure.

[0010] Figure 3ASchematic diagram of a flat lens assembly with a substrate for folding an optical path based on linearly polarized light according to at least one embodiment of the present disclosure.

[0011] Figure 3B Schematic diagram of a flat lens assembly with a substrate for folding an optical path based on linearly polarized light according to at least one embodiment of the present disclosure.

[0012] Figure 3C Schematic diagram of a flat lens assembly with a substrate for folding an optical path based on circularly polarized light according to at least one embodiment of the present disclosure.

[0013] Figure 4A Schematic diagram of a flat lens assembly without a substrate for folding an optical path based on linearly polarized light according to at least one embodiment of the present disclosure.

[0014] Figure 4B Schematic diagram of a flat lens assembly without a substrate for folding an optical path based on linearly polarized light according to at least one embodiment of the present disclosure.

[0015] Figure 4C Schematic diagram of a flat lens assembly without a substrate for folding an optical path based on circularly polarized light according to at least one embodiment of the present disclosure.

[0016] Figure 5A Schematic diagram of a projector with a flat lens assembly as the first element of two sets of lens assemblies in the direction from the light source to the optical element assembly according to at least one embodiment of the present disclosure.

[0017] Figure 5B Schematic diagram of a projector with a flat lens assembly as the second element of two sets of lens assemblies in the direction from the light source to the optical element assembly according to at least one embodiment of the present disclosure.

[0018] Figure 6A Schematic diagram of two sets of flat lens assemblies for folding an optical path based on linearly polarized light according to at least one embodiment of the present disclosure.

[0019] Figure 6B Schematic diagram of two sets of flat lens assemblies for folding an optical path based on linearly polarized light according to at least one embodiment of the present disclosure.

[0020] Figure 6C Schematic diagram of two sets of flat lens assemblies for folding an optical path based on circularly polarized light according to at least one embodiment of the present disclosure.

[0021] Reference numerals are as follows:

[0022] 1: Projector

[0023] 2: Light source

[0024] 3: Flat lens assembly

[0025] 4: Optical element assembly

[0026] 30: Non-flat lens assembly

[0027] 32: Wave plate

[0028] 34: Beam splitter

[0029] 35: Substrate

[0030] 301: Reflective linear polarizer

[0031] 302: Reflective circular polarizer

[0032] 304: Circular polarizer

[0033] 331: First lens

[0034] 332: Second lens

[0035] 333: Third lens

[0036] 334: Fourth lens

[0037] 3311: A side

[0038] 3312: B side Detailed implementation manners

[0039] The following embodiments are provided to illustrate the present disclosure in detail. Those skilled in the art in the technical field to which the present disclosure pertains can easily understand the advantages and effects of the present disclosure after reading the disclosure of this specification. However, the embodiments of the present disclosure are not intended to limit the scope of the present disclosure. The present disclosure can be implemented or applied via other alternative embodiments, and each detail included in the present disclosure can be changed or modified without departing from the scope of its different aspects and applications.

[0040] The features such as the ratios, structures, and dimensions shown in the drawings of the present disclosure are only used to cooperate with the content disclosed herein for those skilled in the art in the technical field to which the present disclosure pertains to read and understand the present disclosure, rather than to limit the scope of the present disclosure. Therefore, without affecting the purpose of the present disclosure and the effects brought by the present disclosure, any change in the proportional relationship, modification of the structure, or adjustment of the dimensions should fall within the scope of the technical content disclosed herein.

[0041] As used herein, "comprising", "including", or "having" (and any of its variants or inflections, such as "containing" or "including") a specific element may additionally include other elements, such as components, structures, regions, parts, devices, systems, or connection relationships, etc., unless otherwise specified, and other limiting elements should not be excluded.

[0042] The terms "upper", "front", "rear", "side", "front face", "between" are only used to describe the embodiments of the present disclosure, and do not limit the scope of implementation of the present disclosure. Without substantially changing the technical content of the present disclosure, the adjustment, replacement, and change of their relative positions and relationships shall be regarded as being within the scope of implementation of the present disclosure.

[0043] The terms "first", "second", "third", "fourth", etc. used herein are only used to describe or distinguish components, structures, regions, parts, devices, or system elements, rather than to limit the scope of implementation of the present disclosure or the spatial order of components. In addition, unless otherwise specified, the singular forms "a" and "the" used herein also include the plural forms, and the terms "or" and "and / or" used herein are interchangeable.

[0044] The numerical ranges used herein are inclusive and combinable, and any number falling within the numerical ranges herein can be regarded as the maximum or minimum value to derive sub-ranges therefrom. For example, it should be understood that the numerical range "0.500 mm to 5.000 mm" includes any sub-ranges between the minimum value of 0.500 mm and the maximum value of 5.000 mm, such as sub-ranges from 0.500 mm to 2.000 mm, from 2.000 mm to 3.500 mm, and from 3.500 mm to 5.000 mm. In addition, any multiple numerical points used herein can be selected as the maximum or minimum value to derive numerical ranges therefrom. For example, 0.771 mm, 2.895 mm, and 4.832 mm can derive numerical ranges of 0.771 mm to 2.895 mm, 2.895 mm to 4.832 mm, or 0.771 mm to 4.832 mm.

[0045] The terms "connected", "connection", "arranged", "arrangement", "coated", "coating", "stacked", "stacking", "formed", "formation", "placed", and "placement" used herein are used to describe multiple elements that are directly or indirectly connected together. "Direct connection" is used to describe multiple elements that are connected together by direct contact; and "indirect connection" is used to describe multiple elements that are connected together by at least one connecting member. For example, the terms "connected", "connection", "arranged", "arrangement", "coated", "coating", "stacked", "stacking", "formed", "formation" used herein can be achieved by means of bonding, joining, adhesion, attachment, insertion, clamping, affixing, embedding, integral molding, gluing, cementing, or any combination thereof. In at least one embodiment of the present disclosure, multiple elements are "detachably" connected, that is, multiple elements can be detached and separated after being connected.

[0046] As used herein, the term "incident light ray" may be, but is not limited to, linear polarization light rays, circular polarization light rays, or non-polarized light rays. If the incident light ray is a non-polarized light ray, a linear or circular polarizer may be arranged, coated, or placed between the non-polarized light ray and the first lens, or between the non-polarized light ray and side A of the first lens.

[0047] As used herein, the term "projector" may be, but is not limited to, a point projector or a floodlight projector.

[0048] In at least one embodiment, the projector used herein may be used in, but is not limited to, televisions, laptops, desktop computers, mobile phones, tablets, digital cameras, car navigation systems, virtual reality (VR) devices, consumer electronic devices, displays, webcams, cars, security systems, medical devices, household appliances, and the Internet of Things (IOT).

[0049] As used herein, the term "lens" may be a convex lens, a concave lens, or a plano lens, but the present disclosure is not limited thereto. In some embodiments, the lens may be, but is not limited to, a collimating lens having an effective focal length (EFL) of 2.5 mm or 5 mm.

[0050] As used herein, the term "reflective linear polarizer" is for transmitting linearly polarized light rays of a certain orientation while reflecting another orthogonal linear orientation. In some embodiments, the reflective linear polarizer may be, but is not limited to, a wire grid polarizer.

[0051] As used herein, the term "reflective circular polarizer" is for transmitting circularly polarized light rays of one handedness while reflecting circularly polarized light rays of the other handedness and changing the handedness of the reflected light rays.

[0052] As used herein, the term "optical element assembly" may be, but is not limited to, a diffractive optical element (DOE), a micro-lens array (MLA), a metasurface element, and a prism array.

[0053] As used herein, the term "pattern" can be, but is not limited to, a projected dot pattern or a projected flood pattern.

[0054] In at least one embodiment of the present disclosure, the flat lens assembly further includes a substrate. In at least one embodiment of the present disclosure, the flat lens assembly does not include a substrate. In some embodiments of the present disclosure, the substrate includes glass.

[0055] In at least one embodiment of the present disclosure, the light source is a laser. In some embodiments of the present disclosure, the laser is a vertical cavity surface emitting laser (VCSEL), a VCSEL array, or an edge emitting laser (EEL).

[0056] In at least one embodiment of the present disclosure, the incident light is linearly polarized light, circularly polarized light, or unpolarized light. In some embodiments of the present disclosure, the projector further includes a linear polarizer or a circular polarizer. When the incident light is unpolarized light, the linear polarizer or the circular polarizer is disposed between the light source and the flat lens assembly. In some embodiments of the present disclosure, the flat lens assembly further includes a beamsplitter (BS). In some embodiments of the present disclosure, when the incident light is linearly polarized light, the beamsplitter is disposed behind the wave plate along the direction from the light source to the optical element assembly. In some embodiments of the present disclosure, when the incident light is circularly polarized light, the beamsplitter is disposed in front of the wave plate along the direction from the light source to the optical element assembly. In some embodiments of the present disclosure, the polarizer is selected from the group consisting of a reflective linear polarizer, a reflective circular polarizer, a circular polarizer, a linear polarizer, and any combination thereof. In some embodiments of the present disclosure, when the incident light is linearly polarized light, the reflective linear polarizer, the wave plate, and the reflective circular polarizer are sequentially disposed along the direction from the light source to the optical element assembly. In some embodiments of the present disclosure, when the incident light is linearly polarized light, the reflective linear polarizer, the wave plate, the beamsplitter, and the circular polarizer are sequentially disposed along the direction from the light source to the optical element assembly. In some embodiments of the present disclosure, when the incident light is circularly polarized light, the beamsplitter, the wave plate, and the reflective linear polarizer are sequentially disposed along the direction from the light source to the optical element assembly.

[0057] In at least one embodiment of the present disclosure, the wave plate is a quarter-wave plate.

[0058] In at least one embodiment of the present disclosure, the lens is a convex lens, a concave lens, a plano lens, or any combination thereof.

[0059] In at least one embodiment of the present disclosure, the flat lens assembly includes a first lens. In some embodiments of the present disclosure, the wave plate is arranged closer to the first lens along the direction from the light source to the optical element assembly. In some embodiments of the present disclosure, the flat lens assembly further includes a second lens. In some embodiments of the present disclosure, the wave plate is arranged before the first lens, between the first lens and the second lens, or after the second lens along the direction from the light source to the optical element assembly. In some embodiments of the present disclosure, the flat lens assembly further includes a third lens and a fourth lens. In some embodiments of the present disclosure, the wave plate is arranged before the third lens, between the third lens and the fourth lens, or after the fourth lens along the direction from the light source to the optical element assembly. In some embodiments of the present disclosure, a substrate is further included, which is arranged between the first lens and the second lens and / or between the third lens and the fourth lens.

[0060] In at least one embodiment of the present disclosure, the optical element assembly is selected from the group consisting of a diffractive optical element, a microlens array, a metasurface element, and a prism array.

[0061] In at least one embodiment of the present disclosure, the pattern is a dot pattern or a flood pattern.

[0062] In some embodiments of the present disclosure, the thickness of the substrate (e.g., a glass substrate) can be in the range of 0.10 mm to 1.10 mm, 0.10 mm to 0.90 mm, 0.10 mm to 0.70 mm, 0.10 mm to 0.50 mm, 0.10 mm to 0.30 mm, 0.30 mm to 1.10 mm, 0.30 mm to 0.90 mm, 0.30 mm to 0.70 mm, 0.30 mm to 0.50 mm, 0.50 mm to 1.10 mm, 0.50 mm to 0.90 mm, 0.50 mm to 0.70 mm, 0.70 mm to 1.10 mm, 0.70 mm to 0.90 mm, and / or 0.90 mm to 1.10 mm, but the present disclosure is not limited thereto.

[0063] In some embodiments of the present disclosure, the object height of the light source (e.g., a laser) can be in the range of 0.10 mm to 0.75 mm, 0.10 mm to 0.60 mm, 0.10 mm to 0.20 mm, 0.20 mm to 0.75 mm, 0.20 mm to 0.60 mm, and / or 0.60 mm to 0.75 mm.

[0064] In some embodiments of the present disclosure, the total track length (TTL) of the projector of the present disclosure having two lens surfaces (i.e., the distance between the light source and the vertex of the second lens / vertex B of the first lens) can be in the range of 0.5 mm to 2.0 mm, 0.5 mm to 3.5 mm, 0.5 mm to 5.0 mm, 2.0 mm to 5.0 mm, 2.0 mm to 3.5 mm, 3.5 mm to 5.0 mm, but the present disclosure is not limited thereto.

[0065] In some embodiments of the present disclosure, the total track length (TTL) of the projector of the present disclosure having four lens surfaces (i.e., the distance between the light source and the vertex of the fourth lens) can be in the range of 2.0 mm to 5.0 mm, 2.0 mm to 4.0 mm, 2.0 mm to 3.0 mm, 3.0 mm to 5.0 mm, 3.0 mm to 4.0 mm, and 4.0 mm to 5.0 mm, but the present disclosure is not limited thereto.

[0066] Figure 1 Shown is a projector 1 according to at least one embodiment of the present disclosure, including a light source 2; a flat lens assembly 3, including a first lens 331, a substrate 35, and a second lens 332; and an optical element assembly 4. It should be noted that the number and connection manner of each component are exemplary, and can be increased, decreased, or changed according to actual requirements. As Figure 1 shown, the light source 2 is used to emit linearly polarized light, circularly polarized light, or unpolarized light; the flat lens assembly 3 is used to fold the optical path based on the polarization of the light; and the optical element assembly 4 is used to split the light or shape the light into a desired intensity distribution to form a pattern.

[0067] Figure 2 Shown is a projector 1 according to at least one embodiment of the present disclosure, including a light source 2; a flat lens assembly 3, which includes a first lens having side A 3311 and side B 3312; It should be noted that the number and connection manner of each component are exemplary, and can be increased, decreased, or changed according to actual requirements. As Figure 2 shown, the light source 2 is used to emit linearly polarized light, circularly polarized light, or unpolarized light; the flat lens assembly 3 is used to fold the optical path based on the polarization of the light; and the optical element assembly 4 is used to split the light or shape the light into a desired intensity distribution to form a pattern.

[0068] Embodiment 1: A flat lens assembly with two lens surfaces and a substrate

[0069] Figure 3AShown is a flat lens assembly 3 according to at least one embodiment of the present disclosure, including a reflective linear polarizer 301, a first lens 331, a wave plate 32, a substrate 35, a second lens 332, and a reflective circular polarizer 302. As Figure 3A shown, the flat lens assembly 3 is used to fold an optical path based on the linear polarization of light. Specifically, the reflective linear polarizer 301 and the reflective circular polarizer 302 are respectively formed, coated, or disposed on the first lens 331 and the second lens 332; the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the first lens 331. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example, (1) the wave plate 32 can be formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332; (2) the reflective linear polarizer 301 and the wave plate 32 can be formed, coated, or disposed on the surface of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331; or (3) the reflective circular polarizer 302 and the wave plate 32 can be formed, coated, or disposed on the surface of the second lens 332, stacked in two layers, and conform to the contour of the second lens 332. According to Figure 3A , the reflective linear polarizer 301, the wave plate 32, and the reflective circular polarizer 302 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0070] In at least one embodiment of the present disclosure, the flat lens assembly 3 includes a reflective linear polarizer 301, a first lens 331, a wave plate 32, a substrate 35, a reflective circular polarizer 302, and a second lens 332 (not shown in the figure). The flat lens assembly 3 is used to fold an optical path based on the linear polarization of light. Specifically, the reflective linear polarizer 301 is formed, coated, or disposed on the surface of the first lens 331 and conforms to the contour of the first lens 331; the wave plate 32 is formed, coated, or disposed on the substrate 35 on the side of the first lens 331. The reflective circular polarizer 302 is formed, coated, or disposed on the substrate 35 on the side of the second lens 332. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example, (1) the reflective linear polarizer 301 and the wave plate 32 can be formed, coated, or disposed on the surface of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331; or (2) the wave plate 32 and the reflective circular polarizer 302 can be formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332. According to at least one embodiment of the present disclosure, the reflective linear polarizer 301, the wave plate 32, and the reflective circular polarizer 302 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0071] Figure 3B Shown is a flat lens assembly 3 according to at least one embodiment of the present disclosure, including a reflective linear polarizer 301, a first lens 331, a wave plate 32, a substrate 35, a second lens 332, a beam splitter 34, and a circular polarizer 304. As Figure 3B shown, the flat lens assembly 3 is configured to fold an optical path based on the linear polarization of light. Specifically, the reflective linear polarizer 301 is formed, coated, or disposed on the surface of the first lens 331 and conforms to the contour of the first lens 331. The wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the first lens 331. The beam splitter 34 and the circular polarizer 304 are formed, coated, or disposed on the surface of the second lens 332, stacked in two layers, and conform to the contour of the second lens 332. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example, (1) the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331; (2) the wave plate 32, the beam splitter 34, and the circular polarizer 304 are formed, coated, or disposed on the surface of the second lens 332, stacked in three layers, and conform to the contour of the second lens 332; or (3) the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332. According to Figure 3B , the reflective linear polarizer 301, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0072] In at least one embodiment of the present disclosure, the flat lens assembly 3 includes a reflective linear polarizer 301, a first lens 331, a wave plate 32, a substrate 35, a beam splitter 34, a second lens 332, and a circular polarizer 304 (not shown in the figure). The flat lens assembly 3 is configured to fold an optical path based on the linear polarization of light. Specifically, the reflective linear polarizer 301 is formed, coated, or disposed on the surface of the first lens 331 and conforms to the contour of the first lens 331; the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the first lens 331; the beam splitter 34 is formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332; and the circular polarizer 304 is formed, coated, or disposed on the surface of the second lens 332 and conforms to the contour of the second lens 332. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example, (1) the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331; or (2) the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332. According to at least one embodiment of the present disclosure, the reflective linear polarizer 301, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are sequentially arranged in the direction from the light source 2 to the optical element assembly 4.

[0073] In at least one embodiment of the present disclosure, the flat lens assembly 3 includes a reflective linear polarizer 301, a first lens 331, a wave plate 32, a substrate 35, a beam splitter 34, a circular polarizer 304, and a second lens (not shown in the figure). The flat lens assembly 3 is configured to fold an optical path based on the linear polarization of light. Specifically, the reflective linear polarizer 301 is formed, coated, or disposed on the surface of the first lens 331 and conforms to the contour of the first lens 331; the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the first lens 331; and the beam splitter 34 and the circular polarizer 304 are formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332 and stacked in two layers. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example, (1) the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331; or (2) the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the contour of the second lens 332. According to at least one embodiment of the present disclosure, the reflective linear polarizer 301, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are sequentially arranged in the direction from the light source 2 to the optical element assembly 4.

[0074] Figure 3C Shown is a flat lens assembly 3 according to at least one embodiment of the present disclosure, including a beam splitter 34, a first lens 331, a substrate 35, a wave plate 32, a second lens 332, and a reflective linear polarizer 301. As Figure 3C shown, the flat lens assembly 3 is used to fold an optical path based on the circular polarization of light. Specifically, the beam splitter 34 is formed, coated, or disposed on the surface of the first lens 331 and conforms to the contour of the first lens 331; the reflective linear polarizer 301 is formed, coated, or disposed on the surface of the second lens 332 and conforms to the contour of the second lens 332; the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example, (1) the wave plate 32 and the reflective linear polarizer 301 are formed, coated, or disposed on the surface of the second lens 332, stacked in two layers, and conform to the contour of the second lens 332; (2) the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the first lens 331; or (3) the beam splitter 34 and the wave plate 32 are formed, coated, or disposed on the surface of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331. According to Figure 3C , the beam splitter 34, the wave plate 32, and the reflective linear polarizer 301 are sequentially disposed along the direction from the light source 2 to the optical element assembly 4.

[0075] In at least one embodiment of the present disclosure, the flat lens assembly 3 includes a beam splitter 34, a first lens 331, a substrate 35, a wave plate 32, a reflective linear polarizer 301, and a second lens 332 (not shown in the figure). The flat lens assembly 3 is used to fold an optical path based on the circular polarization of light. Specifically, the beam splitter 34 is formed, coated, or disposed on the surface of the first lens 331 and conforms to the contour of the first lens 331; and the wave plate 32 and the reflective linear polarizer 301 are formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332, stacked in two layers. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example: (1) the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the first lens 331; (2) the beam splitter 34 and the wave plate 32 are formed, coated, or disposed on the surface of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331. According to at least one embodiment of the present disclosure, the beam splitter 34, the wave plate 32, and the reflective linear polarizer 301 are sequentially disposed along the direction from the light source 2 to the optical element assembly 4.

[0076] Embodiment 2: Flat lens assembly with two lens surfaces and without a substrate

[0077] Figure 4A Shown is a flat lens assembly 3 according to at least one embodiment of the present disclosure, including a reflective linear polarizer 301, a wave plate 32, a first lens 331 having an A side 3311 and a B side 3312, and a reflective circular polarizer 302. As Figure 4A shown, the flat lens assembly 3 is configured to fold an optical path based on the linear polarization of light. Specifically, the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the A side 3311 of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331; and the reflective circular polarizer 302 is formed, coated, or disposed on the surface of the B side 3312 of the first lens 331 and conforms to the contour of the first lens 331. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example, the wave plate 32 and the reflective circular polarizer 302 are formed, coated, or disposed on the surface of the B side of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331. According Figure 4A to, the reflective linear polarizer 301, the wave plate 32, and the reflective circular polarizer 302 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0078] Figure 4B Shown is a flat lens assembly 3 according to at least one embodiment of the present disclosure, including a reflective linear polarizer 301, a wave plate 32, a first lens 331 having an A side 3311 and a B side 3312, a beam splitter 34, and a circular polarizer 304. As Figure 4B shown, the flat lens assembly 3 is configured to fold an optical path based on the linear polarization of light. Specifically, the reflective linear polarizer 301 and the wave plate 32 are molded, coated, or disposed on the surface of the A side 3311 of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331; and the beam splitter 34 and the circular polarizer 304 are formed, coated, or disposed on the surface of the B side 3312 of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are formed, coated, or disposed on the surface of the B side 3312 of the first lens 331, stacked in three layers, and conform to the contour of the first lens 331. According Figure 4B to, the reflective linear polarizer 301, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0079] Figure 4C Shown is a flat lens assembly 3 according to at least one embodiment of the present disclosure, including a beam splitter 34, a first lens 331 having a side A 3311 and a side B 3312, a wave plate 32, and a reflective linear polarizer 301. As Figure 4C shown, the flat lens assembly 3 is used to fold an optical path based on the circular polarization of light. Specifically, the beam splitter 34 is formed, coated, or disposed on the surface of the side A 3311 of the first lens 331 and conforms to the contour of the first lens 331; and the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the side B 3312 of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual needs. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example, the beam splitter 34 and the wave plate 32 are formed, coated, or disposed on the surface of the side A 3311 of the first lens 331, stacked in two layers, and conform to the contour of the first lens 331. According to Figure 4C , the beam splitter 34, the wave plate 32, and the reflective linear polarizer 301 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0080] Embodiment 3: Two lens assemblies with four lens surfaces and including a flat lens assembly and a non-flat lens assembly

[0081] Figure 5A Shown is a projector 1 according to at least one embodiment of the present disclosure, including a light source 2; a flat lens assembly 3 having a first lens 331, a substrate 35, and a second lens 332; and a non-flat lens assembly 30 having a third lens 333, a substrate 35, and a fourth lens 334. Among them, along the direction from the light source 2 to the optical element assembly 4, the flat lens assembly 3 is the first element of the two lens assemblies, and the non-flat lens assembly 30 is the second element of the two lens assemblies. As Figure 5A shown, the flat lens assembly 3 is used to fold an optical path based on the linear polarization or circular polarization of light. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual needs. Therefore, the flat lens assembly 3 and the non-flat lens assembly 30 may not have a substrate 35 (not shown in the figure); and the flat lens assembly 3 may further include a reflective linear polarizer 301, a wave plate 32, a reflective circular polarizer 302, a beam splitter 34, and / or a circular polarizer 304 (not shown in the figure). The configurations of the reflective linear polarizer 301, the wave plate 32, the reflective circular polarizer 302, the beam splitter 34, and / or the circular polarizer 304 may be positioned as described in Embodiment 1 and Embodiment 2 (not shown in the figure).

[0082] Figure 5B A projector 1 according to at least one embodiment of the present disclosure is shown, including a light source 2; a non-flat lens assembly 30 having a first lens 331, a substrate 35, and a second lens 332; and a flat lens assembly 3 having a third lens 333, a substrate 35, and a fourth lens 334. Among them, along the direction from the light source 2 to the optical element assembly 4, the flat lens assembly 3 is the second element of the two lens assemblies, and the non-flat lens assembly 30 is the first element of the two lens assemblies. As Figure 5B shown, the flat lens assembly 3 is used to fold the optical path based on the linear polarization or circular polarization of light. It should be noted that the number and connection method of each component are exemplary and can be increased, decreased, or changed according to actual needs. Therefore, the flat lens assembly 3 and the non-flat lens assembly 30 may not have the substrate 35 (not shown in the figure); and the flat lens assembly 3 may further include a reflective linear polarizer 301, a wave plate 32, a reflective circular polarizer 302, a beam splitter 34, and / or a circular polarizer 304 (not shown in the figure). The configurations of the reflective linear polarizer 301, the wave plate 32, the reflective circular polarizer 302, the beam splitter 34, and / or the circular polarizer 304 may be positioned as described in Embodiment 1 and Embodiment 2 (not shown in the figure).

[0083] Embodiment 4: Two sets of flat lens assemblies with four lens surfaces

[0084] Figure 6A Two sets of flat lens assemblies 3 according to at least one embodiment of the present disclosure are shown, including a first lens 331 (not shown in the figure), a substrate 35, a second lens 332, a reflective linear polarizer 301, a wave plate 32, and a reflective circular polarizer 302. As Figure 6A shown, based on the linear polarization of light, the folded optical path may be, but is not limited to, between the second lens 332 and the third lens 333 through the two sets of flat lens assemblies 3. Specifically, the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the second lens 332, stacked in two layers, and conform to the contour of the second lens 332. The reflective circular polarizer 302 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333. It should be noted that the number and connection method of each component are exemplary and can be increased, decreased, or changed according to actual needs. Therefore, the two sets of flat lens assemblies 3 may not have the substrate 35 (not shown in the figure); and the position of the wave plate 32 may be changed (not shown in the figure). For example, the wave plate 32 and the reflective circular polarizer 302 are formed, coated, or disposed on the surface of the third lens 333, stacked in two layers, and conform to the contour of the third lens 333. According to Figure 6A , the reflective linear polarizer 301, the wave plate 32, and the reflective circular polarizer 302 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0085] In at least one embodiment of the present disclosure (not shown in the figures), two sets of flat lens assemblies 3 include a first lens 331, two substrates 35, a second lens 332, a reflective linear polarizer 301, a wave plate 32, a third lens 333, a reflective circular polarizer 302, and a fourth lens 334. Specifically, the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the second lens 332, stacked in two layers, and conform to the contour of the second lens 332; and the reflective circular polarizer 302 is formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual needs. Therefore, the two sets of flat lens assemblies 3 may not have the substrate 35 (not shown in the figures); and the position of the wave plate 32 may be changed (not shown in the figures). For example, the wave plate 32 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333; or the wave plate 32 and the reflective circular polarizer 302 are formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333 and stacked in two layers. According to at least one embodiment of the present disclosure, the reflective linear polarizer 301, the wave plate 32, and the reflective circular polarizer 302 are sequentially disposed along the direction from the light source 2 to the optical element assembly 4.

[0086] Figure 6B Two sets of flat lens assemblies 3 according to at least one embodiment of the present disclosure are shown, including a first lens 331 (not shown in the figures), two substrates 35 (not shown in the figures), a second lens 332, a reflective linear polarizer 301, a wave plate 32, a beam splitter 34, a circular polarizer 304, a third lens 333, and a fourth lens 334. As Figure 6B shown, based on the linear polarization of light, the folded optical path may be, but is not limited to, between the second lens 332 and the third lens 333 through the two sets of flat lens assemblies 3. Specifically, the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the second lens 332, stacked in two layers, and conform to the contour of the second lens 332; and the beam splitter 34 and the circular polarizer 304 are formed, coated, or disposed on the surface of the third lens 333, stacked in two layers, and conform to the contour of the third lens 333. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual needs. Therefore, the two sets of flat lens assemblies 3 may not have the substrate 35 (not shown in the figures); and the position of the wave plate 32 may be changed (not shown in the figures). For example, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are formed, coated, or disposed on the surface of the third lens 333, stacked in three layers, and conform to the contour of the third lens 333. According to Figure 6B, a reflective linear polarizer 301, a wave plate 32, a beam splitter 34, and a circular polarizer 304 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0087] In at least one embodiment of the present disclosure, the two sets of flat lens assemblies 3 (not shown in the figure) include a first lens 331, two substrates 35, a second lens 332, a reflective linear polarizer 301, a wave plate 32, a beam splitter 34, a third lens 333, a circular polarizer 304, and a fourth lens 334. Based on the linear polarization of light, the folded optical path can be, but is not limited to, between the second lens 332 and the third lens 333 through the two sets of flat lens assemblies 3. Specifically, the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the second lens 332, stacked in two layers, and conform to the contour of the second lens 332; the beam splitter 34 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333; and the circular polarizer 304 is formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333. It should be noted that the number and connection method of each component are exemplary and can be increased, decreased, or changed according to actual needs. Therefore, the two sets of flat lens assemblies 3 may not have the substrate 35; and the position of the wave plate 32 can be changed (not shown in the figure), for example, the wave plate 32 and the beam splitter 34 are formed, coated, or disposed on the surface of the third lens 333, stacked in two layers, and conform to the contour of the third lens 333. According to at least one embodiment of the present disclosure, the reflective linear polarizer 301, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0088] In at least one embodiment of the present disclosure, two sets of flat lens assemblies 3 (not shown in the figure) include a first lens 331, two substrates 35, a second lens 332, a reflective linear polarizer 301, a wave plate 32, a lens 333, a beam splitter 34, a circular polarizer 304, and a fourth lens 334. Based on the linear polarization of light, the folded optical path may be, but is not limited to, passing through the two sets of flat lens assemblies 3 between the second lens 332 and the third lens 333. Specifically, the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the second lens 332, stacked in two layers, and conform to the contour of the second lens 332; and the beam splitter 34 and the circular polarizer 304 are formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual needs. Therefore, the two sets of flat lens assemblies 3 may not have the substrate 35; and the position of the wave plate 32 may be changed (not shown in the figure). For example, the wave plate 32 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333; or, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333 and stacked in three layers. According to at least one embodiment of the present disclosure, the reflective linear polarizer 301, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0089] In at least one embodiment of the present disclosure, two sets of flat lens assemblies 3 (not shown in the figure) include a first lens 331, two substrates 35, a reflective linear polarizer 301, a second lens 332, a wave plate 32, a reflective circular polarizer 302, a third lens 333, and a fourth lens 334. Based on the linear polarization of light, the folded optical path may be, but is not limited to, passing through the two sets of flat lens assemblies 3 between the second lens 332 and the third lens 333. Specifically, the reflective linear polarizer 301 is formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332; the wave plate 32 is formed, coated, or disposed on the surface of the second lens 332 and conforms to the contour of the second lens 332; and the reflective circular polarizer 302 is formed, coated, or disposed on the surface of the substrate 35 on the third lens 333. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual needs. Therefore, the position of the wave plate 32 may be changed (not shown in the figure). For example, the wave plate 32 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333; or the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333. According to at least one embodiment of the present disclosure, the reflective linear polarizer 301, the wave plate 32, and the reflective circular polarizer 302 are sequentially disposed along the direction from the light source 2 to the optical element assembly 4.

[0090] In at least one embodiment of the present disclosure, two sets of flat lens assemblies 3 (not shown in the figure) include a first lens 331, two substrates 35, a reflective linear polarizer 301, a second lens 332, a wave plate 32, a beam splitter 34, a circular polarizer 304, a third lens 333, and a fourth lens 334. Based on the linear polarization of light, the folded optical path can be, but is not limited to, passing through the two sets of flat lens assemblies 3 between the second lens 332 and the third lens 333. Specifically, the reflective linear polarizer 301 is formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332; the wave plate 32 is formed, coated, or disposed on the surface of the second lens 332 and conforms to the contour of the second lens 332; and the beam splitter 34 and the circular polarizer 304 are configured as described below: (1) The beam splitter 34 and the circular polarizer 304 are formed, coated, or disposed on the surface of the third lens 333 and stacked in two layers, (2) The beam splitter 34 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333, and the circular polarizer 304 is formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333, or (3) The beam splitter 34 and the circular polarizer 304 are formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. Therefore, the position of the wave plate 32 can be changed (not shown in the figure). For example, the wave plate 32 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333; or the wave plate 32 is formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333. According to at least one embodiment of the present disclosure, the reflective linear polarizer 301, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0091] In at least one embodiment of the present disclosure, two sets of flat lens assemblies 3 (not shown in the figure) include a first lens 331, two substrates 35, a reflective linear polarizer 301, a wave plate 32, a second lens 332, a reflective circular polarizer 302, a third lens 333, and a fourth lens 334. Based on the linear polarization of light, the folded optical path can be, but is not limited to, passing through the two sets of flat lens assemblies 3 between the second lens 332 and the third lens 333. Specifically, the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332, and are stacked in two layers; and the reflective circular polarizer 302 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. According to at least one embodiment of the present disclosure, the reflective linear polarizer 301, the wave plate 32, and the reflective circular polarizer 302 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0092] In at least one embodiment of the present disclosure, two sets of flat lens assemblies 3 (not shown in the figure) include a first lens 331, two substrates 35, a reflective linear polarizer 301, a wave plate 32, a second lens 332, a beam splitter 34, a circular polarizer 304, a third lens 333, and a fourth lens 334. Based on the linear polarization of light, the folded optical path can be, but is not limited to, passing through the two sets of flat lens assemblies 3 between the second lens 332 and the third lens 333. Specifically, the reflective linear polarizer 301 and the wave plate 32 are formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332; and the configurations of the beam splitter 34 and the circular polarizer 304 are as described below: (1) The beam splitter 34 and the circular polarizer 304 are formed, coated, or disposed on the surface of the third lens 333, stacked in two layers, and conform to the contour of the third lens 333, (2) The beam splitter 34 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333, and the circular polarizer 304 is formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333, or (3) The beam splitter 34 and the circular polarizer 304 are formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. The configurations of each part are, but are not limited to, that the reflective linear polarizer 301, the wave plate 32, the beam splitter 34, and the circular polarizer 304 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0093] In at least one embodiment of the present disclosure, two sets of flat lens assemblies 3 (not shown in the figure) include a first lens 331, two substrates 35, a second lens 332, a beam splitter 34, a wave plate 32, a reflective linear polarizer 301, a third lens 333, and a fourth lens 334. Based on the circular polarization of light, the folded optical path may be, but is not limited to, between the second lens 332 and the third lens 333 through the two sets of flat lens assemblies 3. Specifically, the reflective linear polarizer 301 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333; the beam splitter 34 is formed, coated, or disposed on the surface on the side of the second lens 332; and the wave plate 32 is formed, coated, or disposed on the surface of the third lens 333 (i.e., the reflective linear polarizer 301 and the wave plate 32 may be stacked in two layers on the surface of the third lens 333) or on the surface of the second lens 332 (i.e., the beam splitter 34 and the wave plate 32 may be stacked in two layers on the surface of the second lens 332). It should be noted that the number and connection manner of each component are only exemplary and can be increased, decreased, or changed according to actual needs. For example, the two sets of flat lens assemblies 3 may not be provided with the substrates 35. The beam splitter 34, the wave plate 32, and the reflective linear polarizer 301 are sequentially arranged in the direction from the light source 2 to the optical element assembly 4.

[0094] In at least one embodiment of the present disclosure, two sets of flat lens assemblies 3 (not shown in the figure) include a first lens 331, two substrates 35, a beam splitter 34, a second lens 332, a wave plate 32, a reflective linear polarizer 301, a third lens 333, and a fourth lens 334. Based on the circular polarization of light, the folded optical path may be, but is not limited to, between the second lens 332 and the third lens 333 through the two sets of flat lens assemblies 3. Specifically, the reflective linear polarizer 301 is formed, coated, or disposed on the surface of the third lens 333 and conforms to the contour of the third lens 333; the beam splitter 34 is formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332; and the wave plate 32 may be formed, coated, or disposed on (1) the surface of the substrate 35 on the side of the second lens 332 (i.e., the beam splitter 34 and the wave plate 32 may be stacked in two layers on the surface of the substrate 35), (2) the surface of the second lens 332, or (3) the surface of the third lens 333 (i.e., the wave plate 32 and the reflective linear polarizer 301 may be stacked in two layers on the surface of the third lens 333). It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual requirements. According to at least one embodiment of the present disclosure, the beam splitter 34, the wave plate 32, and the reflective linear polarizer 301 are sequentially arranged in the direction from the light source 2 to the optical element assembly 4.

[0095] Figure 6CShown are two sets of flat lens assemblies 3 according to at least one embodiment of the present disclosure, including a first lens 331 (not shown in the figure), two substrates 35, a beam splitter 34, a second lens 332, a wave plate 32, a third lens 333, a reflective linear polarizer 301, and a fourth lens 334 (not shown in the figure). As Figure 6C shown, based on the circular polarization of light, the folded optical path can be, but is not limited to, between the second lens 332 and the third lens 333 through the two sets of flat lens assemblies 3. Specifically, the reflective linear polarizer 301 is formed, coated, or disposed on the surface of the substrate 35 on the side of the third lens 333; and the beam splitter 34 and the wave plate 32 are configured as described below: (A) the beam splitter 34 is formed, coated, or disposed on the surface of the second lens 332, and the wave plate 32 is formed, coated, or disposed on the surface of the third lens 333 or the surface of the second lens 332 (i.e., the beam splitter 34 and the wave plate 32 can be stacked as two layers on the surface of the second lens 332), or (B) the beam splitter 34 is formed, coated, or disposed on the surface of the substrate 35 on the side of the second lens 332, and the wave plate 32 can be formed, coated, or disposed on (1) the surface of the substrate 35 on the side of the second lens 332 (i.e., the beam splitter 34 and the wave plate 32 can be stacked as two layers on the surface of the substrate 35), (2) the surface of the second lens 332, or (3) the third lens 333. It should be noted that the number and connection manner of each component are exemplary and can be increased, decreased, or changed according to actual needs. According to Figure 6C , the beam splitter 34, the wave plate 32, and the reflective linear polarizer 301 are sequentially arranged along the direction from the light source 2 to the optical element assembly 4.

[0096] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims

1. A projector with a flat lens assembly, comprising: A light source for emitting incident light; A flat lens assembly for folding the optical path of the incident light, the flat lens assembly comprising: A polarizer; A wave plate; A lens connected to the polarizer or the wave plate; and An optical element assembly for forming a pattern with incident light emitted by the flat lens assembly, wherein, The flat lens assembly is disposed between the light source and the optical element assembly.

2. The projector with a flat lens assembly according to claim 1, wherein, The flat lens assembly further comprises a substrate.

3. The projector with a flat lens assembly as claimed in claim 2, wherein, The substrate comprises glass.

4. The projector with a flat lens assembly according to claim 1, wherein, The light source is a laser.

5. The projector with a flat lens assembly according to claim 4, wherein, The laser is a vertical cavity surface emitting laser (VCSEL), a vertical cavity surface emitting laser array, or an edge emitting laser.

6. The projector with a flat lens assembly as claimed in claim 1, wherein, The incident light is linearly polarized light, circularly polarized light, or unpolarized light.

7. The projector with a flat lens assembly according to claim 6 further includes a linear polarizer or a circular polarizer, wherein, When the incident light is the unpolarized light, the linear polarizer or the circular polarizer is disposed between the light source and the flat lens assembly.

8. The projector with a flat lens assembly as claimed in claim 6, wherein, The flat lens assembly further comprises a beam splitter.

9. The projector having a flat lens assembly as claimed in claim 8, wherein, When the incident light is the linearly polarized light, the beam splitter is disposed behind the wave plate along the direction from the light source to the optical element assembly.

10. The projector with a flat lens assembly according to claim 8, wherein, When the incident light is the circularly polarized light, the beam splitter is disposed in front of the wave plate along the direction from the light source to the optical element assembly.

11. The projector with a flat lens assembly according to claim 8, wherein, The polarizer is selected from the group consisting of a reflective linear polarizer, a reflective circular polarizer, a circular polarizer, a linear polarizer, and any combination thereof.

12. The projector with a flat lens assembly as claimed in claim 11, wherein, When the incident light is the linearly polarized light, the reflective linear polarizer, the wave plate, and the reflective circular polarizer are sequentially disposed along the direction from the light source to the optical element assembly.

13. The projector with a flat lens assembly as claimed in claim 11, wherein, When the incident light is the linearly polarized light, the reflective linear polarizer, the wave plate, the beam splitter, and the circular polarizer are sequentially disposed along the direction from the light source to the optical element assembly.

14. The projector with a flat lens assembly as claimed in claim 11, wherein, When the incident light is the circularly polarized light, the beam splitter, the wave plate, and the reflective linear polarizer are sequentially disposed along the direction from the light source to the optical element assembly.

15. The projector with a flat lens assembly as claimed in claim 1, wherein, The wave plate is a quarter-wave plate.

16. The projector with a flat lens assembly as claimed in claim 1, wherein, The lens is a convex lens, a concave lens, a plano lens, or any combination thereof.

17. The projector with a flat lens assembly as claimed in claim 1, wherein, The flat lens assembly comprises a first lens.

18. The projector with a flat lens assembly as claimed in claim 17, wherein, The wave plate is disposed close to the first lens along the direction from the light source to the optical element assembly.

19. The projector with a flat lens assembly as claimed in claim 17, wherein, The flat lens assembly further comprises a second lens.

20. The projector with a flat lens assembly as claimed in claim 19, wherein, The wave plate is disposed in front of the first lens, between the first lens and the second lens, or behind the second lens along the direction from the light source to the optical element assembly.

21. The projector having a flat lens assembly as claimed in claim 19, wherein, The flat lens assembly further comprises a third lens and a fourth lens.

22. The projector with a flat lens assembly as claimed in claim 21, wherein, The wave plate is disposed in front of the third lens, between the third lens and the fourth lens, or behind the fourth lens along the direction from the light source to the optical element assembly.

23. The projector with a flat lens assembly according to claim 21, further comprising a substrate disposed between the first lens and the second lens and / or between the third lens and the fourth lens.

24. The projector with a flat lens assembly as claimed in claim 1, wherein, The optical element assembly is selected from the group consisting of a diffractive optical element, a microlens array, a metasurface element, and a prism array.

25. The projector with a flat lens assembly as claimed in claim 1, wherein, The pattern is a dot pattern or a flood pattern.

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