Projection system

Abstract

The invention discloses a projection system, and relates to the technical field of display. According to the invention, one super-structure lens is used for replacing a plurality of traditional optical lenses to realize a focusing function, and the product size can be reduced. And the first wave band light and the second wave band light in the light beam are focused on different radial positions corresponding to the positions of different pixel subunits of the pixel units of the liquid crystal element through the super-structure lens, so that the use of color filter elements can be reduced to improve the brightness.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and in particular to a projection system. Background Art

[0002] Lens is a basic optical element, which is made according to the law of light refraction and is widely used in the field of optoelectronic technology, such as cameras, projectors, microscopes, etc. In traditional projection equipment, multiple lenses are usually stacked together to achieve functions such as shaping and focusing.

[0003] At present, projectors are widely used in various situations, such as office briefings, film and television playback, installation art, etc. Most projectors are based on spatial light modulators (SLM), which mainly include transmissive LCD (Liquid Crystal Display) projection, reflective LCoS (Liquid Crystal on Silicon) projection and reflective DMD (Digital Micro-Mirror Device) projection. In recent years, LCD projection has been widely used due to its low price. However, the LCD architecture usually uses color filter elements for color adjustment, which will bring about the problem of brightness loss. Summary of the invention

[0004] In view of this, the present invention provides a projection system which can reduce the volume of the product and reduce light loss.

[0005] In a first aspect, the present invention provides a projection system, comprising:

[0006] A light source device, used to generate light source light transmitted along a first light path;

[0007] A beam splitter element is located on the first optical path and is used to split the light from the light source into a first light beam transmitted along the second optical path and a second light beam transmitted along the third optical path, wherein the first light beam includes light of a first wavelength band and light of a second wavelength band, and the second light beam includes light of a third wavelength band;

[0008] A first liquid crystal element, located on the second optical path, and used to modulate the light emitted along the second optical path to form a first modulated light, wherein each pixel unit of the first liquid crystal element includes a first pixel subunit and a second pixel subunit, wherein the first pixel subunit is used to process the first wavelength band light, and the second pixel subunit is used to process the second wavelength band light;

[0009] A second liquid crystal element, located on the third optical path, for modulating the light emitted along the third optical path to form a second modulated light, each pixel unit of the second liquid crystal element includes a third pixel sub-unit, and the third pixel sub-unit is used to process the light in the third wavelength band;

[0010] The meta-lens is located on the second optical path and between the beam splitter and the first liquid crystal element, and is used to guide the first-band light to be incident on the first pixel subunit of the first liquid crystal element, and to guide the second-band light to be incident on the second pixel subunit of the first liquid crystal element.

[0011] A possible implementation also includes:

[0012] An adjusting device is connected to the spectroscopic element and is used to change the filtering characteristics of the spectroscopic element or control the area of ​​the spectroscopic element having the target filtering characteristics to be located on the first optical path, so that the energy of the first band light in the first light beam, the second band light in the first light beam and the third band light in the second light beam meets the target condition.

[0013] In a possible implementation, the wavelengths of the first wavelength band light and the second wavelength band light are different; the lens includes a substrate and a plurality of nanostructures, and the rotation angle of the nanostructure satisfies the following conditions:

[0014]

[0015] in, represents the rotation angle; i=1 or 2; w(x1, λ1)=w(x2, λ2)+k1π, λ1<λ2, λ1 represents the wavelength of the first band light, λ2 represents the wavelength of the second band light, xi represents the coordinate of the focus in the first direction of the incident wavelength λi in the focal coordinate system, k1 is an integer constant, d represents the distance between the metalens and the first liquid crystal element, and (x, y) represents the coordinate of the nanostructure in the nanostructure coordinate system.

[0016] In a possible implementation, the first wavelength band light, the second wavelength band light, and the third wavelength band light have different colors, and are selected from red, green, and blue, respectively.

[0017] In a possible implementation manner, the color of the third wavelength band light is green.

[0018] In one possible implementation, the first liquid crystal element is located at a first position, and the second liquid crystal element is located at a second position, so that pixels in a projection picture formed by the first modulated light and corresponding pixels in a projection picture formed by the second modulated light deviate from a preset distance.

[0019] In a possible implementation manner, the first pixel sub-unit and the second pixel sub-unit have the same size, and the areas of the first pixel sub-unit and the second pixel sub-unit are both half of the area of ​​the third pixel sub-unit.

[0020] In a possible implementation manner, the areas of the first pixel subunit and the second pixel subunit are both half the area of ​​the pixel unit of the first liquid crystal element and / or the second liquid crystal element.

[0021] In a possible implementation manner, the first liquid crystal element is a black and white screen.

[0022] In a possible implementation manner, the second liquid crystal element is a black and white screen.

[0023] The present invention uses a meta-lens to replace multiple traditional optical lenses to achieve the focusing function, which can reduce the volume of the product. The meta-lens can focus the first band light and the second band light in the light beam at different radial positions, corresponding to the positions of different pixel sub-units of the pixel unit of the liquid crystal element, thereby reducing the use of color filter elements to improve brightness. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a functional module schematic diagram of an existing projection device;

[0025] Figure 2 It is a structural schematic diagram of an existing projection device;

[0026] Figure 3 A schematic diagram of the structure of a projection device provided by an embodiment of the present invention;

[0027] Figure 4 A schematic structural diagram of a first liquid crystal element provided by an embodiment of the present invention;

[0028] Figure 5 A schematic structural diagram of a second liquid crystal element provided by an embodiment of the present invention;

[0029] Figure 6 A schematic diagram of a color coordinate provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make those skilled in the art better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Although the disclosure in the present invention is introduced according to one or several exemplary examples, it should be understood that each aspect of these disclosures can also constitute a complete technical solution separately. In the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0031] In the present invention, in order to facilitate the clear description of the technical solutions of the embodiments of the present invention, the words "first", "second" and the like are used to distinguish the same items or similar items with basically the same functions and effects. Those skilled in the art can understand that the words "first", "second" and the like do not limit the quantity and execution order, and are only used to illustrate and distinguish the objects to be described. There is no order distinction, nor does it represent a special limitation on the number of devices or messages in the embodiments of the present invention, and cannot constitute any limitation on the embodiments of the present invention. "Multiple" means two or more, and similar words such as "include" or "comprising" mean that the element or object appearing before the word covers the elements or objects listed after the word and their equivalents, but does not exclude other elements or objects.

[0032] In order to fully understand the present invention, a detailed description will be provided below to illustrate the technical solution of the present invention. Preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other embodiments.

[0033] Figure 1 Schematic diagram of functional modules of a projection device provided by an embodiment of the present invention. Figure 1 As shown, the projection device includes an image processor 101 and a projection optical engine 102. Among them:

[0034] The image processor 101 may be a microcontroller, a dedicated image processing chip, etc. The microcontroller may be an ARM chip, a microcontroller unit (MCU), etc. The dedicated image processing chip may be an image signal processor (ISP), a graphics processing unit (GPU), an embedded neural network processor (NPU), etc. The image processor 101 may be used for video decoding, image quality processing, etc.

[0035] The projection optical machine 102 may include a driver chip, a spatial light modulator, and a light source. The light source may include a laser light source, an LED light source, a fluorescent light source, etc. The spatial light modulator may be a digital micromirror device (DMD), a liquid crystal display (LCD), a liquid crystal on silicon (LCOS), etc., which is used to modulate the light source to generate image light. The driver chip corresponds to the spatial light modulator, for example, the digital micromirror device may be driven by a digital light processing element (DLP). The projection optical machine 102 is used to project the image to be projected into a projection screen.

[0036] In some embodiments, the projection device further includes a central controller 103 with one or more processing cores, which may be a CPU, ARM, MCU or other controller. The central controller 103 is the control center of the projection device, and uses various interfaces and lines to connect various parts of the entire projection device, and can run or execute software programs and / or operating systems stored in the storage module 104, and call data stored in the storage module 104. Optionally, the image processor 101 and the central controller 103 may be integrated into one processor.

[0037] In some embodiments, the projection device further includes a storage module 104 of one or more computer-readable storage media, an input module 105, a communication module 106, a power supply 107 and other components. Those skilled in the art will appreciate that Figure 1 The structure of the projection device shown in the figure does not constitute a limitation on the projection device, and may include more or fewer components than shown in the figure, or combine certain components, or arrange the components differently.

[0038] The storage module 104 can be used to store software programs and operating systems. The central controller 103 executes various functional applications and data processing by running the software programs and operating systems stored in the storage module 104. The storage module 104 can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area can store data created according to the use of the projection device, etc. In addition, the storage module 104 can include a high-speed random access memory, and can also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other volatile solid-state storage devices. Accordingly, the storage module 104 can also include a memory controller to provide the central controller 103 with access to the storage module 104.

[0039] The projection device may further include an input module 105, which may be used to receive input digital or character information and generate remote control, keyboard, mouse, joystick, optical or trackball signal input related to user settings and function control.

[0040] The projection device may further include a communication module 106. In some embodiments, the communication module 106 may include a wireless module. The projection device may perform short-distance wireless transmission through the wireless module of the communication module 106, thereby providing the user with wireless broadband Internet access. For example, the communication module 106 may be used to help the user access streaming media, etc.

[0041] The projection device further includes a power supply 107 for supplying power to various components. In some embodiments, the power supply 107 can be logically connected to the central controller 103 through a power management system, so as to manage charging, discharging, and power consumption through the power management system. The power supply 107 can also include any components such as one or more DC or AC power supplies, recharging systems, power failure detection circuits, power converters or inverters, and power status indicators.

[0042] Figure 2 A schematic diagram of the structure of a projection device provided by an embodiment of the present invention. Figure 2 As shown, the projection device includes a light source device 201, a light homogenizing element 202, an illumination system 203, a display chip 204, and an imaging system 205. The light source light generated by the light source device 201 is homogenized by the light homogenizing element 202, and the illumination system 203 images the light spot of the exit surface of the light homogenizing element 202 on the display chip 204. The display chip 204 modulates the incident light source light into image light and irradiates it into the imaging system 205, and finally images the image light onto a projection object such as a screen to form a projection picture. Among them, the display chip 204 can be any one of DMD, LCOS, and LCD; the imaging system 205 is generally a lens system, such as a projection lens.

[0043] In addition, the projection device may also include a light source control module (not shown in the figure), which can control the operation of one or more light sources in the light source device 201, so that the light source device 201 emits light of a specified wavelength band required for generating an image. Further, the light source device 201, the light homogenizing element 202, the illumination system 203, the display chip 204 and the imaging system 205 may all be included in the projection optical machine 102 (refer to Figure 1 )middle.

[0044] The light source device 201 may include one or more light sources. The light source may be a laser light source, an LED light source, or a fluorescent light source, etc. Further, the light source may be a single light emitting element or a light emitting element array, and the light emitting element array may include light emitting elements of different colors. For example, the light source may be an LD light source or an LED light source that generates blue light, green light, or red light, etc., or the light source may be a multicolor laser, i.e., a light emitting element array that includes multiple lasers, such as a light source that includes a blue laser and a red laser, or includes a blue laser and a green laser, or includes a blue laser, a red laser, and a green laser at the same time.

[0045] The light homogenizing element 202 is used to homogenize the light source light generated by the light source device 201. Specifically, the light homogenizing element 202 includes an incident surface and an exit surface, and the light homogenizing element 202 is used to homogenize the light source light incident from its incident surface, so as to form a light spot having the same shape as the display chip on its exit surface, such as a light spot in a rectangular, circular, etc. shape. For example, the light homogenizing element 202 can be a light rod, a compound eye, etc.

[0046] The illumination system 203 is a part from the light homogenizing element to the display chip, and is used to image the light spot on the exit surface of the light homogenizing element 202 onto the display chip 204. By way of example, the illumination system 203 may include one or more lenses.

[0047] Figure 3 A schematic diagram of the structure of a projection device provided by an embodiment of the present invention. Figure 3 As shown, the projection device includes a light source device 1, a beam splitter element 9, a first shaping lens 2, a meta-lens 3, a first liquid crystal element 4, a second shaping lens 7, a second liquid crystal element 8, a light combining element 5 and a projection lens 6. The light source light generated by the light source device 1 and transmitted along the first optical path is divided into a first light beam transmitted along the second optical path and a second light beam transmitted along the third optical path by the beam splitter element 9. The first light beam is incident on the first liquid crystal element 4 after passing through the first shaping lens 2 and is modulated by the first liquid crystal element 4 to form a first modulated light. The second light beam is incident on the second liquid crystal element 8 after passing through the second shaping lens 8 and is modulated by the second liquid crystal element 8 to form a second modulated light. The first modulated light and the second modulated light are combined by the light combining element 5 and incident on the projection lens 6, and finally the image light is imaged onto the projection screen.

[0048] The light source device 301 is used to emit illumination light, and the illumination light may include a single wavelength band or multiple different wavelength bands. The light source device 301 may be a single light source or may include multiple light sources, and the light source may be a laser light source, an LED light source, or a fluorescent light source, etc. Further, the light source may be a single light-emitting element or a light-emitting element array, and the light-emitting element array may include light-emitting elements of different colors. For example, the light source is a multicolor laser, and the light source is a light-emitting element array including multiple lasers, such as the light source may include a blue laser and a red laser, or include a blue laser and a green laser, or include a blue laser, a red laser, and a green laser at the same time.

[0049] Optionally, the light source includes a light source unit, which includes a substrate and a plurality of light-emitting elements. The substrate has a quadrilateral shape, such as a roughly square or roughly rectangular shape, when viewed from above. The substrate has a mounting surface for mounting the light-emitting elements, and the mounting surface is, for example, a flat surface. In addition, a heat dissipation component such as a heat sink may be provided on the surface opposite to the mounting surface of the substrate. The substrate is formed of a material with high heat dissipation properties, such as a metal material. The plurality of light-emitting elements are arranged in an array relative to the mounting surface of the substrate. The light-emitting element is a laser light source having an emitting surface for emitting laser light; it may also be an LED light source. The light source may be a single red, green, and blue LED light source, an LED light source array, or a COB light source; it may also be a blue LED light source and a yellow light source.

[0050] The light splitting element 9 is used to split the light source light emitted by the light source device 1 into a first light beam transmitted along the second light path and a second light beam transmitted along the third light path, wherein the first light beam includes the first band light and the second band light, and the second light beam includes the third band light. For example, the first band light, the second band light and the third band light can be synthesized into white light, such as the colors of the first band light, the second band light and the third band light are different and are selected from the three colors of red, green and blue respectively. Furthermore, the third band light is green light, such as Figure 3 shown.

[0051] The metalens 3 may also be called a metalenses, which is made of an optical element that focuses light on a metasurface. The metasurface mainly refers to a two-dimensional metamaterial composed of nanostructures with an ultra-thin thickness. The nanostructures that make up the metasurface may be structures such as holes, slits, or protrusions. The following further describes the metalens 3 by taking the nanostructure of the metasurface as a nanocolumn as an example. It should be understood that the metalens may be a transmission type metalens or a reflection type metalens.

[0052] Continue reading Figure 3The meta-lens 3 includes a substrate 31 and a plurality of nano-pillars 32, and the substrate 31 and the plurality of nano-pillars 32 are formed of a material having a high transmittance for the wavelength band of the light beam. If the wavelength of the light beam is in the visible wavelength region, for example, 445 nm, the materials of the substrate 31 and the plurality of nano-pillars 32 may include, for example, optical glass, silicon oxide (SiO2), titanium oxide (TiO2), etc. The substrate 31 and the nano-pillars 32 may be formed integrally with each other, or may be formed independently of each other, and joined when arranged in the X direction and the Y direction. The plurality of nano-pillars 32 are arranged on the surface of the substrate 31 at intervals d. That is, the widths t and w of the nano-pillars adjacent to each other on the XY plane may be the same size or different sizes. The nano-pillars are adjusted to realize the change of the light transmission phase from 0-2, and these nano-pillars are arranged in a corresponding manner to form a meta-lens to realize the focusing function, and the light focusing is realized by the phase obtained by the different rotation angles of the nano-pillars.

[0053] The first liquid crystal element 4 is located upstream of the second optical path and is used to modulate the light emitted along the second optical path. Each pixel unit of the first liquid crystal element 4 includes two pixel subunits, such as a first pixel subunit 401 and a second pixel subunit 402. Figure 3-4 As shown, the first pixel subunit 401 is used to process the light of the first wavelength band, and the second pixel subunit 402 is used to process the light of the second wavelength band.

[0054] The meta-lens 3 guides the first-band light in the first light beam to the first pixel sub-unit 401, and guides the second-band light in the first light beam to the second pixel sub-unit 402. For example, the first pixel sub-unit 401 is a red pixel sub-unit, and the second pixel sub-unit 402 is a blue pixel sub-unit. The red pixel sub-unit is used to process red light, and the blue pixel sub-unit is used to process blue light. The meta-lens 3 guides the red light in the first light beam to the red pixel sub-unit, and guides the blue light in the first light beam to the blue pixel sub-unit. In some other embodiments, the two pixel sub-units in each pixel unit of the first liquid crystal element 4 may also be a red pixel sub-unit and a green pixel sub-unit, or a blue pixel sub-unit and a green pixel sub-unit. Since the meta-lens 3 guides light of different colors to the corresponding pixel sub-units on the first liquid crystal element 4, the first liquid crystal element 4 can be a black and white screen to avoid light loss caused by the color filter element.

[0055] In some embodiments, the wavelengths of the first band light and the second band light in the first light beam are different, and the meta-lens 3 focuses the light of different wavelengths at different positions, which correspond to the positions of the first pixel subunit 401 and the second pixel subunit 402 on the first liquid crystal element 4, respectively. The meta-lens 3 satisfies:

[0056] If the incident light includes two wavelengths of light, λ1<λ2, then,

[0057] w(x1, λ1)=w(x2, λ2)+k1π

[0058] The rotation angle of the nanocolumns of the metalens 3 satisfies:

[0059]

[0060] in, represents the rotation angle, xi represents the coordinate of the first direction of the focus of the incident wavelength λi in the focus coordinate system, k1 is an integer constant, d represents the distance between the meta-lens and the first liquid crystal element, and (x, y) represents the coordinate of the nanostructure in the nanostructure coordinate system. (xi, yi) represents the coordinate of the focus coordinate system, xi represents the first direction, yi represents the second direction, and the above two wavelengths of light satisfy that the focus position falls on a position that is different in the first direction and the same in the second direction, that is, it falls on a position with the same longitudinal position and different lateral position in the focus coordinate system.

[0061] In some other embodiments, the polarization directions of the first band light and the second band light incident on the metalens 3 are different. The metalens 3 focuses the light with different polarization directions at different positions, which correspond to the positions of the first pixel subunit 401 and the second pixel subunit 402 on the first liquid crystal element 4, respectively. The polarization angle of the light incident on the metalens 3 satisfies:

[0062]

[0063] in, represents the polarization angle, λi represents the wavelength of the incident light, d represents the distance between the meta-lens and the liquid crystal panel, and Δr represents the center distance between adjacent pixel sub-units of each pixel unit in the liquid crystal element.

[0064] The second liquid crystal element 8 is located on the third optical path and is used to modulate the light emitted along the third optical path. Figure 3 , the light splitting element guides the red light R and the blue light B to the second light path, and guides the green light G to the third light path, that is, the second liquid crystal element 8 is used to modulate the green light. Since there is only one color of light on the third light path, each pixel unit of the first liquid crystal element 8 may include a pixel subunit, such as the third pixel subunit, and further, the second liquid crystal element 8 may be a black and white screen.

[0065] Optionally, see Figure 4-Figure 5, the pixel unit of the first liquid crystal element 4 and the pixel unit of the second liquid crystal element 8 have the same size. For example, the width and / or height of two pixel subunits in the pixel unit of the first liquid crystal element 4 are equal to the width and / or height of one pixel subunit in the pixel unit of the second liquid crystal element 8. Further, the first pixel subunit 401 and the second pixel subunit 402 in the pixel unit of the first liquid crystal element 4 have the same size, and the areas of the first pixel subunit and the second pixel subunit are both half of the area of ​​the third pixel subunit, such as Figure 4 shown.

[0066] Furthermore, the first liquid crystal element 4 and the second liquid crystal element 8 can realize the difference of the first displacement value in the physical space. Specifically, the first liquid crystal element 4 is located at the first position, and the second liquid crystal element 8 is located at the second position, so that the pixels in the projection picture formed by the first modulated light emitted by the first liquid crystal element 4 and the corresponding pixels in the projection picture formed by the second modulated light emitted by the second liquid crystal element 8 deviate from the preset distance, such as the pixels in the projection picture formed by the first modulated light and the pixels in the projection picture formed by the second modulated light can deviate from the spacing of half a pixel in the row direction and the column direction, thereby realizing pixel expansion.

[0067] In some embodiments, the spectroscopic element 9 is a variable spectroscopic device, and the projection device further includes an adjustment device (not shown in the figure) connected to the spectroscopic element 9, through which different voltages can be applied to the spectroscopic element 9 to change its filtering characteristics, or the spectroscopic element 9 includes a plurality of regions with different filtering characteristics, and the region with the target filtering characteristics is placed on the optical path by controlling the spectroscopic element to rotate or move up, down, left, and right by the adjustment device to achieve different spectroscopic effects. For example, the filtering characteristics of the spectroscopic element 9 are determined according to the set mode, such as mode 1: transmission R, G, reflection B; mode 2: transmission R, B, reflection G, mode 3: transmission G, B, reflection R, and the ratio of the three primary colors is adjusted by the variable spectroscopic device to adjust the color accuracy of the output light, such as Figure 6 The isochromatic temperature lines in the color coordinate diagram shown can be used to adjust the positions of the points corresponding to the proportions of the three primary colors on the isochromatic temperature lines according to needs, thereby adjusting the color accuracy.

[0068] In some embodiments, each pixel unit of the second liquid crystal element 8 may also include two pixel sub-units. For example, the pixel unit of the second liquid crystal element 8 includes a blue pixel sub-unit and a green pixel sub-unit, and the pixel unit of the first liquid crystal element 4 includes a red pixel sub-unit and a green pixel sub-unit. The light splitting element 9 transmits red light and reflects blue light, and semi-transmits and semi-reflects green light to achieve light splitting. In this embodiment, a meta-lens may also be provided on the incident side of the second liquid crystal element 8. The principle is the same as that of FIG. Figure 3 The embodiments shown are the same and will not be described again here.

[0069] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A projection system, characterized in that: include: A light source device, used to generate light source light transmitted along a first light path; A beam splitter element is located on the first optical path and is used to split the light from the light source into a first light beam transmitted along the second optical path and a second light beam transmitted along the third optical path, wherein the first light beam includes light of a first wavelength band and light of a second wavelength band, and the second light beam includes light of a third wavelength band; A first liquid crystal element, located on the second optical path, and used to modulate the light emitted along the second optical path to form a first modulated light, wherein each pixel unit of the first liquid crystal element includes a first pixel subunit and a second pixel subunit, wherein the first pixel subunit is used to process the first wavelength band light, and the second pixel subunit is used to process the second wavelength band light; A second liquid crystal element, located on the third optical path, for modulating the light emitted along the third optical path to form a second modulated light, each pixel unit of the second liquid crystal element includes a third pixel sub-unit, and the third pixel sub-unit is used to process the light in the third wavelength band; The meta-lens is located on the second optical path and between the beam splitter and the first liquid crystal element, and is used to guide the first-band light to be incident on the first pixel subunit of the first liquid crystal element, and to guide the second-band light to be incident on the second pixel subunit of the first liquid crystal element.

2. A projection system according to claim 1, characterized in that: Also includes: An adjusting device is connected to the spectroscopic element and is used to change the filtering characteristics of the spectroscopic element or control the area of ​​the spectroscopic element having the target filtering characteristics to be located on the first optical path, so that the energy of the first band light in the first light beam, the second band light in the first light beam and the third band light in the second light beam meets the target condition.

3. A projection system according to claim 1, characterized in that: The wavelengths of the first wavelength band light and the second wavelength band light are different; the lens includes a substrate and a plurality of nanostructures, and the rotation angle of the nanostructures satisfies the following conditions: in, represents the rotation angle; i=1 or 2; w(x1, λ1)=w(x2, λ2)+k1π, λ1<λ2, λ1 represents the wavelength of the first band light, λ2 represents the wavelength of the second band light, xi represents the coordinate of the focus in the first direction of the incident wavelength λi in the focal coordinate system, k1 is an integer constant, d represents the distance between the metalens and the first liquid crystal element, and (x, y) represents the coordinate of the nanostructure in the nanostructure coordinate system.

4. A projection system according to claim 1, characterized in that: The colors of the first wavelength band light, the second wavelength band light and the third wavelength band light are different and are selected from three colors: red, green and blue.

5. A projection system according to claim 1, characterized in that: The color of the third wavelength band light is green.

6. A projection system according to claim 1, characterized in that: The first liquid crystal element is located at a first position, and the second liquid crystal element is located at a second position, so that pixels in a projection picture formed by the first modulated light and corresponding pixels in a projection picture formed by the second modulated light deviate from a preset distance.

7. A projection system according to claim 1, characterized in that: The first pixel sub-unit and the second pixel sub-unit have the same size, and the areas of the first pixel sub-unit and the second pixel sub-unit are both half of the area of ​​the third pixel sub-unit.

8. The projection system according to claim 1, characterized in that: The areas of the first pixel subunit and the second pixel subunit are both half of the area of ​​the pixel unit of the first liquid crystal element and / or the second liquid crystal element.

9. The projection system according to claim 1, characterized in that: The first liquid crystal element is a black and white screen.

10. The projection system according to claim 1, characterized in that: The second liquid crystal element is a black and white screen.

Images