WO2023193784A1

WO2023193784A1 - Projection system

Info

Publication number: WO2023193784A1
Application number: PCT/CN2023/086812
Authority: WO
Inventors: 郝成龙; 谭凤泽; 朱瑞; 朱健
Original assignee: 深圳迈塔兰斯科技有限公司
Priority date: 2022-04-08
Filing date: 2023-04-07
Publication date: 2023-10-12

Abstract

A projection system, comprising a light beam generating apparatus (1), a light beam processing apparatus (2) and an optical system (3). The optical system (3) is used for performing aberration correction on discrete wavelengths, and the optical system (3) comprises at least three lenses, wherein at least one of the at least three lenses is a metalens. The light beam generating apparatus (1) generates an initial light beam suitable for the metalens, wherein the initial light beam comprises at least three beams of narrow-band light having discrete wavelengths. The light beam processing apparatus (2) processes the initial light beam according to information of an image to be projected, and emits the processed initial light beam into the optical system (3), such that the optical system (3) projects the initial light beam. The projection system satisfies WD ≥ 100d, wherein WD is the operating distance of the projection system, and d is the distance from the light beam processing apparatus (2) to an incident plane of the optical system (3).

Description

a projection system

Technical field

The present application relates to the technical field of projection equipment. Specifically, the present application relates to a projection system.

Background technique

Chromatic aberration correction through optical lenses is one of the important means for the projection system to improve imaging quality. With the development of science and technology, the demand for miniaturization of projection systems is increasing day by day, and the loss of image quality during the miniaturization process seems inevitable.

The existing technology usually corrects chromatic aberration by increasing the number of lenses in the projection system in order to pursue higher imaging quality. Generally, the greater the number of lenses, the larger the lens volume and the higher the image quality.

However, the miniaturization of projection systems in the prior art is limited by the number and volume of lenses.

Contents of the invention

In order to solve the problem in the prior art that the miniaturization of projection systems is limited by the number and volume of lenses, embodiments of the present application provide a projection system, which includes: a beam generating device, a beam processing device and an optical system;

Wherein, the optical system is used for aberration correction of discrete wavelengths;

Wherein, the optical system includes at least three lenses, and at least one of the at least three lenses is a super lens;

The beam generating device is configured to generate an initial beam suitable for the metalens, the initial beam including at least three narrowband lights having discrete wavelengths;

The beam processing device processes the initial beam and then injects it into the optical system according to the image information to be projected, so that the initial beam is projected by the optical system;

The projection system must at least satisfy:
WD≥100d;

Wherein, WD is the working distance of the projection system; d is the distance from the beam processing device to the incident surface of the optical system.

Optionally, the projection system also satisfies:
TTL≤10d;

Wherein, TTL is the distance from the beam processing device to the exit surface of the optical system; d is the distance from the beam processing device to the incident surface of the optical system.

Optionally, the at least three lenses are arranged on the same optical axis.

Optionally, the at least three lenses include a super lens and at least two refractive lenses; and,

The metalens is configured to perform aberration correction on the incident light beam.

Optionally, the at least three lenses include two super lenses and at least one refractive lens; and,

The two super lenses are both used to correct the aberration of the incident light beam;

The at least one refractive lens is used to provide optical power.

Optionally, the at least three lenses are all super lenses; and,

Each super lens among the at least three lenses is used to correct the aberration of the incident light beam.

Optionally, the optical system includes four lenses; each of the four lenses is a super lens; and,

Each of the four lenses is used to correct the aberration of the incident light beam.

Optionally, among the at least three lenses, the position of any lens except the first lens and the last lens along the optical axis is adjustable along the projection direction of the optical system.

Optionally, the beam generating device includes at least three narrowband lasers and the same number of beam splitters;

The multiple laser beams generated by the narrowband laser are split by the beam splitter to generate the Initial beam.

Optionally, the light beam generating device includes at least three narrow-band light-emitting diodes and the same number of beam splitters;

The multiple laser beams generated by the narrow-band light-emitting diodes are split by the beam splitter to generate the initial beam.

Optionally, the beam generating device includes at least two blue lasers, a fluorescent material turntable and a spectroscope;

One of the at least two blue lasers is used to generate a blue light beam;

The remaining blue lasers among the at least two blue lasers are used to illuminate the fluorescent material turntable to excite two light beams with wavelengths greater than the blue light beam;

The blue beam and the two beams with wavelengths larger than the blue beam are split by a beam splitter to generate the initial beam.

Optionally, the beam generating device includes a polychromatic laser, a color wheel, a filter and a beam splitter;

The polychromatic laser is used to generate broad spectrum laser;

The color wheel includes sector-shaped color blocks of at least three colors; when the color wheel rotates, the broad-spectrum laser passing through different color blocks on the color wheel sequentially forms light beams of different colors;

After the beam passes through the filter, the initial beam is formed by the beam splitter.

Optionally, the ratio of the bandwidth of the light beam generating device to the central wavelength is less than 0.1.

Optionally, the ratio of the bandwidth of the light beam generating device to the central wavelength is less than 0.03.

Optionally, the initial light beam includes at least narrowband light selected from the three primary colors of red, green and blue.

Optionally, the beam processing device includes at least one digital micromirror device.

Optionally, the beam processing device is at least one liquid crystal display.

Optionally, the focal length of the optical system is less than or equal to 20 mm.

Optionally, the total system length of the optical system is less than or equal to 50 mm.

Optionally, the distance between the beam processing device and the optical system is greater than or equal to 1 mm and less than or equal to 10 mm.

Optionally, the super lens includes a substrate and a nanostructure layer disposed on the substrate;

The nanostructure layer includes nanostructures arranged in an array.

Optionally, the nanostructure layer includes superstructure units arranged in an array;

The superstructural unit is a close-packed pattern; the nanostructure is provided at the center position and/or the vertex position of the close-packed pattern.

Optionally, the super lens also includes filling material;

The filling material is filled between the nanostructures.

Optionally, the absolute value of the difference between the refractive index of the filling material and the refractive index of the nanostructure is greater than or equal to 0.5.

Optionally, the period of the superstructure unit is greater than or equal to _0.3λc and less than or equal to _2λc ;

Wherein, λ _c is the center wavelength of the working band of the projection system.

Optionally, the height of the nanostructure is greater than or equal to _0.3λc and less than or equal to _5λc ;

Optionally, the shape of the nanostructures includes polarization dependent structures.

Optionally, the shape of the nanostructures includes polarization-insensitive structures.

Optionally, the hyperlens further includes an anti-reflection coating;

The antireflection film is disposed on the side of the substrate and the nanostructure layer adjacent to the air.

Optionally, the phase of the super lens satisfies at least:

Where, r is the distance from the center of the hyperlens to the center of any of the nanostructures; λ is the operating wavelength, is any phase related to the operating wavelength, x, y are the mirror coordinates of the hyperlens, and f is the focal length of the hyperlens.

Optionally, the material of the substrate has an extinction coefficient of less than 0.01 for radiation in the working band.

Optionally, the material of the substrate includes fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon and hydrogenated amorphous silicon.

Optionally, the extinction coefficient of the nanostructured material to radiation in the working band is less than 0.01.

Optionally, the material of the nanostructure includes fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon and hydrogenated amorphous silicon.

Optionally, the extinction coefficient of the filling material in the working band is less than 0.01.

Optionally, the filling material includes air, fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, and hydrogenated amorphous silicon.

Optionally, the substrate and the nanostructure are made of the same material.

Optionally, the substrate and the nanostructure are made of different materials.

Optionally, the nanostructure and the filling material are made of the same material.

Optionally, the nanostructure and the filling material are made of different materials.

Optionally, the periods of superstructural units at different positions on the superlens are the same.

Optionally, the periods of superstructural units at different positions on the superlens are at least partially the same.

Optionally, the hyperlens further includes an anti-reflection coating;

The antireflection film is disposed on one side of the substrate and/or on the side of the nanostructure adjacent to the air.

The projection system provided by the embodiments of this application at least achieves the following technical effects:

The projection system provided by the embodiment of the present application uses a beam processing device to process the narrowband light generated by the beam generation device and then injects it into the optical system. The incident light is corrected for aberration including chromatic aberration correction through the optical system including at least one super lens, so that The incident light with the same incident angle but different central wavelength has the same exit angle, thus realizing the application of super lens in the projection system and breaking the technical prejudice in the design of the projection system.

Description of drawings

The accompanying drawings are included to provide a further understanding of the application, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the application and, together with the following description, serve to explain the principles of the application.

Figure 1 shows an optional schematic diagram of the principle of the projection system provided by the embodiment of the present application;

Figure 2 shows another optional schematic diagram of the principle of the projection system provided by the embodiment of the present application;

Figure 3 shows another optional schematic diagram of the principle of the projection system provided by the embodiment of the present application;

Figure 4 shows another optional schematic diagram of the principle of the projection system provided by the embodiment of the present application;

Figure 5 shows an optional structural schematic diagram of the optical system in the projection system provided by the embodiment of the present application;

Figure 6 shows another optional structural schematic diagram of the optical system in the projection system provided by the embodiment of the present application;

Figure 7 shows another optional structural schematic diagram of the optical system in the projection system provided by the embodiment of the present application;

Figure 8 shows an optional perspective schematic diagram of the nanostructure of the hyperlens provided by the embodiment of the present application;

Figure 9 shows another optional perspective schematic diagram of the nanostructure of the super lens provided by the embodiment of the present application;

Figure 10 shows an optional nanostructure of the super lens provided by the embodiment of the present application. arrangement;

Figure 11 shows another optional arrangement of the nanostructures of the hyperlens provided by the embodiment of the present application;

Figure 12 shows another optional arrangement of the nanostructures of the hyperlens provided by the embodiment of the present application;

Figure 13 shows the relationship between an optional nanostructure and transmittance provided by the embodiment of the present application;

Figure 14 shows the relationship between an optional nanostructure and phase modulation provided by the embodiment of the present application;

Figure 15 shows the relationship between an optional nanostructure and transmittance provided by the embodiment of the present application;

Figure 16 shows the relationship between an optional nanostructure and phase modulation provided by the embodiment of the present application;

Figure 17 shows the modulation transfer function in the 480nm band of an optional projection system provided by the embodiment of the present application;

Figure 18 shows the modulation transfer function in the 530nm band of an optional projection system provided by the embodiment of the present application;

Figure 19 shows the modulation transfer function in the 660nm band of an optional projection system provided by the embodiment of the present application;

Figure 20 shows the modulation transfer function in the 480nm band of yet another optional projection system provided by the embodiment of the present application;

Figure 21 shows the modulation transfer function in the 530nm band of yet another optional projection system provided by the embodiment of the present application;

Figure 22 shows the modulation transfer function in the 660nm band of yet another optional projection system provided by the embodiment of the present application;

Figure 23 shows the modulation transfer function in the 480nm band of yet another optional projection system provided by the embodiment of the present application;

Figure 24 shows the modulation transfer function in the 530nm band of yet another optional projection system provided by the embodiment of the present application;

Figure 25 shows the modulation transfer function in the 660nm band of yet another optional projection system provided by the embodiment of the present application;

Figure 26 shows the distortion of an optional projection system provided by the embodiment of the present application;

Figure 27 shows the distortion of yet another optional projection system provided by the embodiment of the present application;

Figure 28 shows the distortion of yet another optional projection system provided by the embodiment of the present application.

The reference symbols in the figure respectively indicate:

1-Beam generating device; 2-Beam processing device; 3-Optical system.

Detailed ways

The present application will now be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. This application may, however, be embodied in many different ways and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. The same reference numbers refer to the same parts throughout. Furthermore, in the drawings, the thicknesses, ratios, and dimensions of components are exaggerated for clarity of illustration.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Unless the context clearly dictates otherwise, "a," "an," "the," and "at least one" as used herein do not imply a limitation on quantity but are intended to include both the singular and the plural. For example, "a component" has the same meaning as "at least one component" unless the context clearly dictates otherwise. "At least one" should not be construed as being limited to the number "one". "Or" means "and/or". The term "and/or" includes any and all combinations of one or more of the associated listed items.

Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by one of ordinary skill in the art. Terms as defined in commonly used dictionaries shall be construed to have the same meaning as in the relevant technical context and shall not be construed in an idealized or overly formal sense unless expressly defined in the specification. has a formal meaning.

The meaning of "including" or "includes" specifies the nature, quantity, steps, operations, parts parts, components or combinations thereof, but other properties, quantities, steps, operations, parts, components or combinations thereof are not excluded.

Embodiments are described herein with reference to cross-sectional illustrations that are idealized embodiments. Thus, variations in shape from those shown in the illustrations are contemplated, for example as a result of manufacturing techniques and/or tolerances. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, regions shown or described as flat may typically have rough and/or non-linear characteristics. Furthermore, the acute angles shown may be rounded. Therefore, the regions shown in the figures are schematic in nature and their shapes are not intended to show the precise shapes of the regions and are not intended to limit the scope of the claims.

Hereinafter, exemplary embodiments according to the present application will be described with reference to the accompanying drawings.

In the prior art, it is generally believed that the projection system magnifies the image to be transmitted and transmits it to the screen or proportionally mixes the three primary colors to obtain the required color. In today's metalens applications, metalens cannot be applied to projection systems because they cannot achieve wide-spectrum chromatic aberration correction. Different from the traditional projector design ideas, the inventor of the present application believes that the projection system utilizes the principle of persistence of vision, that is, only a beam of light in one band enters the optical system of the projection system at a time; or multiple beams of narrow-band light are simultaneously transmitted in different proportions. into the optical system. Therefore, it is feasible to perform targeted chromatic aberration correction on the discrete wavelength beam entering the optical system without performing chromatic aberration correction on the full spectrum.

1 to 4 show schematic principle diagrams of the projection system provided by embodiments of the present application. Referring to FIGS. 1 to 4 , the projection system provided by the embodiment of the present application includes a beam generating device 1 , a beam processing device 2 and an optical system 3 . Moreover, the projection system at least satisfies:
WD≥100d; (1)

In formula (1), WD is the working distance (WD, Working Distance) of the projection system, that is, the distance from the exit surface of the last lens along the transmission direction of the optical system 3 to the projection screen; d is the beam processing device 2 to the optical system 3 distance from the incident surface. The exit surface of the optical system 3 refers to the last lens along the light exit direction in the projection system, that is, the lens closest to the projection screen. The incident surface of the optical system 3 refers to the first lens along the light emission direction in the projection system, that is, the lens closest to the beam processing device 2 .

That is to say, according to the embodiment of the present application, the distance (WD, Working Distance) from the projection system to the projection screen is much greater than the distance from the beam processing device 2 to the incident surface of the optical system 3 .

Specifically, referring to FIGS. 1 to 4 , the beam generating device 1 is configured to generate an initial beam suitable for the metalens, where the initial beam includes at least three laser beams with discrete wavelengths. Optionally, the light beam generating device 1 includes at least two light sources and at least three beam splitters. Further, the light beam generating device further includes one or more of a color wheel, a filter and a fluorescent material turntable. The visible image formed by the visual residue of any two narrow-band lights of different wavelengths at the same location has a third color. In order to optimize the color of the projected image, it is preferable that the central wavelength of the narrow-band light is at least selected from the three primary colors of red (R, Red), green (G, Green) and blue (B, Blue). Furthermore, the light beam generating device 1 can also emit an initial light beam including more discrete wavelengths, so as to further improve the image quality of the projection system.

The beam processing device 2 is configured to process the initial beam generated by the beam generating device 1 according to the image information and then launch it into the optical system 3 . The processing of the initial beam by the beam processing device 2 includes reflection and transmission. For example, the light processing device 2 can reflect the required light beam to the optical system in a time-sharing manner, and can also control the transmittance of light beams of different wavelengths. Optionally, the beam processing device 2 injects the initial beam into the optical system 3 in a time-divided manner. Optionally, the beam processing device 2 projects the initial beams into the optical system 3 simultaneously and in proportion. According to the embodiment of the present application, the aforementioned time-division injection refers to injecting at least three laser beams of discrete wavelengths in the initial light beam into the optical system 3 successively, and the duration of each beam of light does not exceed the duration of visual persistence. For example, for a projection system with a refresh rate of 120Hz, the duration of each light beam is 2.78 milliseconds. For another example, for a projection system with a refresh rate of 60Hz, the duration of each light beam does not exceed 5.56 milliseconds. According to the embodiment of the present application, the aforementioned simultaneous proportional injection, also known as proportional deployment, means that according to the image information to be projected, light of different wavelength bands is simultaneously injected into the optical system 3 in proportion to form the required color.

Referring to Figures 5 to 8, the optical system 3 is used to correct discrete wavelength aberrations, and the optical system 3 includes at least three lenses. Wherein, at least one of the at least three lenses in the optical system 3 is a metalens (ML, Metalens). This super lens can perform aberration correction on incident light of different wavelengths, so that incident light with the same incident angle but different central wavelengths can pass through The exit angle after passing through the optical system 3 is the same. Optionally, at least three lenses in the optical system 3 are arranged on the same optical axis. Since the light beam generated by the light beam generating device 1 in the projection system provided by the embodiment of the present application is narrow-band light with discrete wavelengths, the transmittance of the super lens meets the imaging requirements of the projection system. Aberration correction includes monochromatic on-axis and off-axis aberration (spherical aberration, coma, astigmatism, field curvature and distortion) correction, as well as chromatic aberration correction at multiple discrete wavelengths.

Illustratively, as shown in Figure 1, the beam generating device 1 includes at least three narrowband lasers and the same number of beam splitters. The multiple laser beams generated by the at least three narrowband lasers are split by a Dichroic Mirror (DM). The initial beam is emitted from the beam generating device 1 . In an optional implementation, the laser can be replaced by a narrowband light emitting diode (LED, Light Emitting Diode). As another example shown in Figure 2, the light beam generating device 1 includes at least two blue lasers, a fluorescent material turntable and a beam splitter. Among them, a blue laser is used to generate blue laser, which is emitted from the beam generating device 1 in the form of narrow-band light after being split by a beam splitter. The remaining blue lasers illuminate the disk of fluorescent material to excite lasers of other colors, such as red and green. Lasers of other colors are respectively split by a beam splitter and then emitted from the beam generating device 1.

According to an embodiment of the present application, the beam generating device 1 includes a polychromatic laser, a color wheel, a filter and a beam splitter. Polychromatic lasers produce broad spectrum laser light, such as white light (W, White). The color wheel includes sector-shaped color blocks of at least three colors. When the color wheel rotates, the broad-spectrum laser light of different color blocks on the color wheel sequentially forms light of different colors (such as red, green, blue and/or white). After the light beam passing through the color wheel passes through filters of different colors, it passes through a spectroscope to form an initial light beam and is emitted from the light beam generating device 1 .

The light beam generating device 1 in any of the above embodiments is used to generate an initial light beam suitable for the optical system 3 to perform chromatic aberration correction. The initial light beam emitted from the light beam generating device 1 enters the beam processing device 2, and the beam processing device 2 injects light beams of different center wavelengths into the optical system 3 in time sequence or proportion according to the image information. In order to further improve the imaging quality of the projection system, the ratio between the bandwidth and the central wavelength of the light beam generating device 1 needs to meet a preset value, so that the optical system 3 can achieve better chromatic aberration correction effect. According to the embodiment of the present application, optionally, the ratio of the bandwidth of the light beam generating device 1 to the central wavelength is less than 0.1. Optionally, the ratio of the bandwidth of the beam generating device 1 to the central wavelength is less than 0.03. Book The bandwidth of the light beam generating device 1 in the application embodiment refers to the bandwidth of each beam of light in the initial light beam generated by the light beam generating device 1 . The smaller the ratio between the bandwidth and the central wavelength of the light beam generating device 1 is, the stronger its monochromaticity is and the more suitable it is for the metalens in the optical system 3 of the embodiment of the present application.

For example, three narrow-band light-emitting diodes are selected in the light beam generating device 1 to emit blue light, green light and red light respectively. Among them, the central wavelength of blue light is 450nm, the bandwidth is 16nm, and the ratio of bandwidth to central wavelength is 3.56%; the central wavelength of green light is 525nm, the bandwidth is 25nm, and the ratio of bandwidth to central wavelength is 4.76%; the central wavelength of red light is 635nm, the bandwidth is 1nm, and the ratio of bandwidth to central wavelength is 0.16%.

For another example, the light beam generating device 1 includes a white LED light source and three narrowband filters, and the three narrowband filters are used to generate blue light, green light and red light respectively. Among them, the central wavelength of blue light is 450nm, the bandwidth is 10nm, and the ratio of bandwidth to central wavelength is 2.22%; the central wavelength of green light is 525nm, the bandwidth is 10nm, and the ratio of bandwidth to central wavelength is 1.92%; the central wavelength of red light is 635nm, the bandwidth is 10nm, and the ratio of bandwidth to central wavelength is 1.57%.

For another example, three narrow-band lasers are selected in the beam generating device 1 to emit blue light, green light and red light respectively. Among them, the central wavelength of blue light is 450nm, the bandwidth is 2nm, and the ratio of bandwidth to central wavelength is 0.44%; the central wavelength of green light is 525nm, the bandwidth is 2nm, and the ratio of bandwidth to central wavelength is 0.38%; the central wavelength of red light is 635nm, the bandwidth is 1nm, and the ratio of bandwidth to central wavelength is 0.16%.

In an optional implementation, the beam processing device 2 includes at least one Digital Micromirror Device (DMD). The beam processing device 2 controls the deflection of the lens at the corresponding position in the DMD based on the image information, and reflects the narrowband light corresponding to the central wavelength to the optical system 3 in a time sequence or in proportion. Preferably, the beam processing device 2 controls the DMD to reflect the beam that does not require projection to the black body. Preferably, the beam processing device 2 includes at least three DMDs, each DMD corresponding to a narrowband light of a central wavelength.

According to the embodiment of the present application, the digital micromirror device can also be replaced by a liquid crystal display (LCD). LCD controls the transmittance at different locations based on image information. Narrow-band light of different colors can pass through the LCD in chronological order and then enter the light Learning system 3. Or the LCD controls the transmittance at different locations based on the image information, and proportionally allocates the simultaneously incident narrow-band light beams of different wavelengths. It should be understood that it is a common technical means in the art that the aforementioned beam processing device 2 is equipped with a corresponding image information processing chip.

By way of example, a speckle reducing device is also provided on the optical path between the beam generating device 1 and the beam processing device 2 . For example, the speckle reduction device may be a rotating random phase version. In an optional embodiment, the projection system also includes a prism. The prism is used to adjust the light path in the projection system. The initial light beam emitted by the light beam generating device 1 is injected into the beam processing device 2 and processed by the beam processing device 2. The light beam used for projection imaging is injected into the optical system 3. The prism helps further compress the volume of the projection system provided by the embodiments of the present application.

Figures 5 to 7 show optional structural schematic diagrams of the optical system 3 provided by the embodiment of the present application. The optical system 3 includes at least three super lenses, and the aforementioned super lenses are discrete wavelength chromatic aberration correction super lenses. Optionally, the optical system 3 also includes an aperture. The diaphragm is arranged between any two adjacent lenses in the optical system 3 to improve the imaging contrast of the projection system.

In an exemplary embodiment, in the optical system 3, along the exit direction of the light beam, the position of any lens along the optical axis except the first lens and the last lens is adjustable. That is to say, among the at least three lenses of the optical system 3, one lens whose position is adjustable along the optical axis is used to assist the focusing of the optical system 3.

In an optional implementation, the phase of the super lens in the optical system 3 at least satisfies the following formula:

Among them, r is the distance from the center of the hyperlens to the center of any nanostructure; λ is the operating wavelength, is any phase related to the working wavelength, x, y are the mirror coordinates of the hyperlens, and f is the focal length of the hyperlens. The phase of the metalens can be expressed by high-order polynomials, including even-order polynomials and odd-order polynomials. In the embodiment of the present application, formulas (2), (3), (4), (8), and (9) can optimize the phase that satisfies an even-order polynomial without destroying the rotational symmetry of the metasurface phase. . Compared with formulas (2), (3), (4), (8), and (9), formulas (5), (6), and (7) can not only optimize the phase that satisfies even-order polynomials, but also optimize The phase that satisfies the odd-order polynomial is optimized without destroying the rotational symmetry of the hyperlens phase, which significantly improves the optimization freedom of the hyperlens. It should be noted that the positive and negative coefficients in the above formula are related to the optical power of the hyperlens. For example, when the hyperlens has positive power, in formulas (2), (3), and (4), a ₁ is less than zero; and in formulas (5) and (6), a ₂ is less than zero.

It should be understood that the projection system provided by the embodiment of the present application is preferably used in conjunction with a projection screen. Optionally, the projection screen is a diffuse reflective plane, such as a hard diffuse reflective screen, a soft diffuse reflective screen, a wall or other opaque plane.

In traditional projection systems, the total system length (TTL, Total Track Length) of the optical system is determined by factors such as the number of lenses and the distance between lens groups. It is also limited by the thickness and processing technology of the refractive lens itself. In order to ensure the projection quality, due to the traditional projection system design It is believed that metalens cannot perform wide-spectrum chromatic aberration correction and therefore cannot be used in optical systems to promote the miniaturization and lightweight of projection systems. Therefore, the miniaturization design of traditional projectors focuses more on designing the optical path to compress the distance between the light source, image generator and optical system. The hyperlens used in this application reduces the weight, total system length and cost of the entire optical system 3.

According to the implementation of the present application, optionally, the projection system also satisfies:
TTL≤10d; (10)

Among them, TTL is the total system length of the optical system 3, specifically the distance from the beam processing device 2 to the exit surface of the optical system 3; d is the distance from the beam processing device 2 to the incident surface of the optical system 3. Without reducing the quality of projection imaging, using a hyperlens is beneficial to reducing the number of lenses in the optical system 3, and is also beneficial to reducing the focal length and lens group spacing of the optical system 3. Therefore, the embodiments of the present application not only realize the application of hyperlens in the projection system, but also reduce the total system length of the optical system 3 in the projection system through the hyperlens.

According to embodiments of the present application, in some cases, the optical system 3 includes one super lens and at least two refractive lenses. In this case, a metalens is configured to provide aberration correction for all discrete wavelengths of narrowband light in the initial beam. According to the embodiments of the present application, in some cases, the optical system 3 includes at least two super lenses. In this case, at least two metalens each participate in aberration correction. The above-mentioned aberration correction includes monochromatic on-axis and off-axis aberration (spherical aberration, coma, astigmatism, field curvature and distortion) correction, as well as chromatic aberration correction of multiple discrete wavelengths. That is, the metalens also provides optical power.

According to the embodiment of the present application, the focal length f of the optical system 3 is less than or equal to 20 mm. For example, the focal length f of the optical system 3 satisfies: 0≤f≤5mm. For example, the focal length of the optical system 3 satisfies 0≤f≤5mm.

According to the embodiment of the present application, the total system length (TTL) of the optical system 3 is less than or equal to 50 mm. For example, the total system length of the optical system 3 satisfies: f≤45mm, f≤40mm, f≤35mm, f≤30mm, f≤25mm or f≤20mm.

According to the embodiment of the present application, optionally, the distance d between the exit surface of the beam processing device 2 and the entrance surface of the optical system 3 satisfies 1 mm ≤ d ≤ 10 mm. Optionally, the distance d from the exit surface of the beam processing device 2 to the entrance surface of the optical system 3 satisfies: 1mm≤d≤2mm, 1mm≤d≤3mm, 1mm≤d≤4mm, 1mm≤d≤5mm, 1mm≤d ≤6mm, 1mm≤d≤7mm, 1mm≤d≤8mm, 1mm≤d≤9mm or 1mm≤d≤10mm. Optionally, the distance d from the exit surface of the beam processing device 2 to the incident surface of the optical system 3 satisfies: 1mm≤d≤10mm, 2mm≤d≤10mm, 3mm≤d≤10mm, 4mm≤d ≤10mm, 5mm≤d≤10mm, 6mm≤d≤10mm, 7mm≤d≤10mm, 8mm≤d≤10mm or 9mm≤d≤10mm.

In an optional implementation, as shown in FIG. 5 , in the projection system provided by the embodiment of the present application, the optical system 3 includes four super lenses. Each of the four metalens is a discrete wavelength chromatic aberration correction metalens, and each of the four metalens provides projection power and aberration correction. In this exemplary embodiment, the key parameters of the optical system 3 are shown in Table 1. The modulation transfer functions of this optical system 3 for narrow-band light with central wavelengths of 480nm, 530nm and 660nm are shown in Figures 17, 18 and 19 respectively. It can be seen from Figures 17 to 19 that the optical system 3 provided by the embodiment of the present application has good projection clarity for incident light of discrete wavelengths. In addition, as shown in Figure 26, the distortion of the optical system 3 in all fields of view is less than 1%, and the total system length is 40 mm, which is conducive to miniaturization of the projection system.

Table 1

In the DMD dimensions shown in Table 1, H represents the horizontal dimension, V represents the vertical dimension, and D represents the depth dimension (usually the dimension along the optical axis).

In yet another optional implementation, as shown in FIG. 6 , in the projection system provided by the embodiment of the present application, the optical system 3 includes three coaxially arranged lenses. a lens and a refractive lens, wherein two super lenses are configured to perform aberration correction on at least three beams of narrowband light, and the refractive lens is configured to provide primary optical power. According to the embodiment of the present application, the hyperlens and the refractive lens in the optical system 3 correct all aberrations together, and the hyperlens has a chromatic aberration correction function for incident light of a single or more than two discrete wavelengths. In this exemplary embodiment, the key parameters of the optical system 3 are shown in Table 2. The modulation transfer functions of this optical system 3 for narrow-band light with central wavelengths of 480 nm, 530 nm and 660 nm are shown in Figure 20, Figure 21 and Figure 22 respectively. It can be seen from Figures 20 to 22 that the optical system 3 provided in the embodiment of the present application has good projection clarity for incident light of discrete wavelengths. In addition, as shown in Figure 27, the distortion of the optical system 3 in all fields of view is less than 1%, and the total system length is 45 mm, which is conducive to miniaturization of the projection system.

Table 2

In the DMD dimensions shown in Table 2, H represents the horizontal dimension, V represents the vertical dimension, and D represents the depth dimension (usually the dimension along the optical axis).

In yet another optional implementation, as shown in FIG. 7 , in the projection system provided by the embodiment of the present application, the optical system 3 includes four super lenses, and the optical system 3 is configured as an optical system for discrete wavelength chromatic aberration correction. system. Each of the four metalens provides optical power and aberration correction for incident light. In this exemplary embodiment, the key parameters of the optical system 3 are shown in Table 3. The modulation transfer functions of this optical system 3 for narrow-band light with central wavelengths of 480 nm, 530 nm and 660 nm are shown in Figure 23, Figure 24 and Figure 25 respectively. It can be seen from Figures 23 to 25 that the optical system 3 provided by the embodiment of the present application has good projection clarity for incident light of discrete wavelengths. In addition, as shown in Figure 28, the distortion of the optical system 3 in all fields of view is less than 1%, and the total system length is 30 mm, which is conducive to miniaturization of the projection system.

table 3

In the DMD dimensions shown in Table 3, H represents the horizontal dimension, V represents the vertical dimension, and D represents the depth dimension (usually the dimension along the optical axis).

It can be seen from the above embodiments that the optical system 3 in the projection system provided by the embodiment of the present application has a short focal length and a small total system length, which is beneficial to promoting the miniaturization of the projection system.

Next, the metalens in the embodiment of the present application will be described in detail with reference to FIGS. 8 to 16 .

Metalenses are a specific application of metasurfaces, which modulate the phase, amplitude, and polarization of incident light through periodically arranged subwavelength-sized nanostructures. As shown in Figures 8 to 12, the super lens includes a base and a nanostructure layer provided on one side of the base layer; the nanostructure layer includes periodically arranged superstructure units, and nanostructures are provided at the vertices and/or centers of the superstructure units. . In some cases, a nanostructure layer is provided on one side of the substrate. In some cases, the substrate is provided with nanostructured layers on both sides.

Figures 8 and 9 show perspective views of a nanostructure of a super lens used in the variable focus optical system provided by embodiments of the present application. Optionally, air or other materials that are transparent or translucent in the working band can be filled between the nanostructures on the metalens. According to an embodiment of the present application, the absolute value of the difference between the refractive index of the filled material and the refractive index of the nanostructure should be greater than or equal to 0.5. As shown in Figure 8, nanostructures can be polarization-sensitive structures that impose a geometric phase on incident light. For example, structures such as elliptical cylinder, hollow elliptical cylinder, elliptical hole, hollow elliptical hole, rectangular cylinder, rectangular hole, hollow rectangular cylinder and hollow rectangular hole. As shown in Figure 9, nanostructures can be polarization-insensitive structures that impose a propagation phase on incident light. For example, structures such as cylindrical shape, hollow cylindrical shape, round hole shape, hollow round hole shape, square cylindrical shape, square hole shape, hollow square cylindrical shape and hollow square hole shape.

As shown in Figure 12, according to embodiments of the present application, the superstructure units may be arranged in a fan shape. As shown in FIG. 13 , according to the embodiment of the present application, the superstructure units may be arranged in a regular hexagonal array. In addition, as shown in FIG. 14 , according to embodiments of the present application, the superstructure units may be arranged in a square array. Those skilled in the art will recognize that nanojunctions The superstructural units included in the structural layer may also include other forms of array arrangements, and all these variations are covered by the scope of this application.

Optionally, the period of the superstructure unit is greater than or equal to _0.3λc and less than or equal to _2λc ; where, _λc is the central wavelength of the working band; when the working band is multi-band, _λc is the shortest wavelength of the working band. central wavelength. Optionally, the height of the nanostructure is greater than or equal to _0.3λc and less than or equal to _5λc ; where _λc is the center wavelength of the working band; when the working band is multi-band, _λc is the center of the shortest wavelength working band wavelength. Optionally, the periods of superstructural units at different positions on the superlens are the same. Optionally, the periods of the superstructure units at different positions on the metalens are at least partially the same.

According to embodiments of the present application, the nanostructure is an all-dielectric structural unit. The material of the nanostructure is a material with high transmittance in the working band of the variable focus optical system. Optionally, the extinction coefficient of the material of the nanostructure to radiation in the working band is less than 0.01. For example, the material of the nanostructure includes one or more of fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, hydrogenated amorphous silicon and other materials.

In an optional implementation, the material of the substrate and the nanostructure are the same. In yet another optional implementation, the material of the substrate is different from the material of the nanostructure. The material of the substrate is a material with high transmittance in the working band of the projection system provided by the embodiment of the present application. Optionally, the extinction coefficient of the substrate to radiation in the working band is less than 0.01. For example, the base material may be one or more of fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, hydrogenated amorphous silicon and other materials.

Illustratively, the metalens includes a silicon nitride nanostructure layer and a quartz glass base layer. Among them, the period of the superstructural unit is 400nm, the height of the nanostructure is 1150nm, the shape is a nanocylinder, and the diameter of the nanostructure is smaller than the period of the superstructural unit. Figure 13 shows the relationship between the nanostructure size of an optional super lens and the transmittance of the super lens to incident light in different wavelength bands provided by the embodiment of the present application. Figure 14 shows the relationship between the size of the nanostructure of an optional super lens and the phase modulation of the super lens on incident light in different wavelength bands provided by the embodiment of the present application.

Exemplarily, the metalens includes a silicon nitride structural layer and a quartz glass base layer. Among them, the period of the superstructural unit is 400nm, the height of the nanostructure is 1150nm, and the shape is nanometer Toroidal pillars, the diameter of the nanostructure is smaller than the period of the superstructural unit. FIG. 15 shows the relationship between the nanostructure size of an optional super lens and the transmittance of the super lens to incident light in different wavelength bands provided by the embodiment of the present application. Figure 16 shows the relationship between the size of the nanostructure of an optional super lens and the phase modulation of the super lens on incident light in different wavelength bands provided by the embodiment of the present application.

According to the embodiment of the present application, the filling material is a material with high transmittance in the working band. Optionally, the extinction coefficient of the filling material in the working band is less than 0.01. Illustratively, the filling material may be air. For example, the filling material may be one or more of fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon, amorphous silicon, hydrogenated amorphous silicon and other materials. Preferably, the material of the filler structure is different from the base material and nanostructure material.

According to an embodiment of the present application, the hyperlens further includes an antireflection coating layer for increasing the transmittance of narrowband light. The antireflection coating layer is disposed on one side of the substrate and/or on the side of the nanostructure adjacent to the air.

It should be noted that the hyperlens provided by the embodiments of the present application can be processed through semiconductor technology, and has the advantages of light weight, thin thickness, simple structure and process, low cost, and high consistency in mass production.

To sum up, the projection system provided by the embodiment of the present application uses a beam processing device to inject the initial light beams generated by the beam generating device into the optical system respectively or in proportion in time sequence, through the optical system including at least one super lens. Aberration correction is performed on narrow-band incident light with discrete wavelengths, so that the incident light with the same incident angle but different central wavelengths has the same exit angle, thus realizing the application of super lenses in projection systems. Compared with traditional projection systems, the embodiments of the present application reduce the minimum number of lenses in the optical system from four to three by using discrete wavelength hyperlenses, breaking through the limit of the number of lenses on the total length of the optical system, thereby compressing the optical system The volume promotes the miniaturization of the projection system. In addition, the thickness and weight of a single lens are reduced by introducing a metalens, further promoting the miniaturization of the projection system.

The above are only specific implementation modes of the embodiments of the present application, but the protection scope of the embodiments of the present application is not limited thereto. Any person familiar with the technical field can easily implement the implementation within the technical scope disclosed in the embodiments of the present application. Any changes or substitutions contemplated shall be covered by this application Please be within the protection scope of the embodiment. Therefore, the protection scope of the embodiments of the present application should be subject to the protection scope of the claims.

Claims

A projection system, characterized in that the projection system includes: a beam generating device, a beam processing device and an optical system;

Wherein, the optical system is used for discrete wavelength aberration correction;

Wherein, the optical system includes at least three lenses, and at least one of the at least three lenses is a super lens;

The beam generating device is configured to generate an initial beam suitable for the metalens, the initial beam including at least three narrowband lights having discrete wavelengths;

The beam processing device processes the initial beam and then injects it into the optical system according to the image information to be projected, so that the initial beam is projected by the optical system;

The projection system must at least satisfy:
WD≥100d;

Wherein, WD is the working distance of the projection system; d is the distance from the beam processing device to the incident surface of the optical system.
The projection system according to claim 1, characterized in that the projection system also satisfies:
TTL≤10d;

Wherein, TTL is the distance from the beam processing device to the exit surface of the optical system; d is the distance from the beam processing device to the incident surface of the optical system.
The projection system of claim 1, wherein the at least three lenses in the optical system are arranged on the same optical axis.
The projection system of claim 1, wherein the at least three lenses in the optical system include a super lens and at least two refractive lenses; and,

The metalens is configured to perform aberration correction on the incident light beam.
The projection system of claim 1, wherein the at least three lenses in the optical system include two super lenses and at least one refractive lens; and,

The two super lenses are both used to correct the aberration of the incident light beam;

The at least one refractive lens is used to provide optical power.
The projection system of claim 1, wherein the at least three lenses in the optical system are super lenses; and,

Each super lens among the at least three lenses is used to correct the aberration of the incident light beam.
The projection system of claim 1, wherein the optical system includes four lenses; each of the four lenses is a super lens; and,

Each of the four lenses is used to correct the aberration of the incident light beam.
The projection system according to claim 1, wherein among the at least three lenses, along the projection direction of the optical system, any lens except the first lens and the last lens has an angle along the optical axis. Position adjustable.
The projection system of claim 1, wherein the beam generating device includes at least three narrowband lasers and an equal number of beam splitters;

The multiple laser beams generated by the narrowband laser are split by the beam splitter to generate the initial beam.
The projection system of claim 1, wherein the light beam generating device includes at least three narrow-band light-emitting diodes and an equal number of beam splitters;

The multiple laser beams generated by the narrow-band light-emitting diodes are split by the beam splitter to generate the initial beam.
The projection system of claim 1, wherein the light beam generates The apparatus includes at least two blue lasers, a fluorescent material turntable, and a spectroscope;

One of the at least two blue lasers is used to generate a blue light beam;

The remaining blue lasers among the at least two blue lasers are used to illuminate the fluorescent material turntable to excite two light beams with wavelengths greater than the blue light beam;

The blue beam and the two beams with wavelengths larger than the blue beam are split by a beam splitter to generate the initial beam.
The projection system of claim 1, wherein the light beam generating device includes a polychromatic laser, a color wheel, a filter and a beam splitter;

The polychromatic laser is used to generate broad spectrum laser;

The color wheel includes sector-shaped color blocks of at least three colors; when the color wheel rotates, the broad-spectrum laser passing through different color blocks on the color wheel sequentially forms light beams of different colors;

After the beam passes through the filter, the initial beam is formed by the beam splitter.
The projection system according to any one of claims 1 to 12, characterized in that the ratio of the bandwidth of the light beam generating device to the central wavelength is less than 0.1.
The projection system according to any one of claims 1 to 12, characterized in that the ratio of the bandwidth of the light beam generating device to the central wavelength is less than 0.03.
The projection system of claim 1, wherein the initial light beam includes at least narrow-band light selected from three primary colors: red, green, and blue.
The projection system of claim 1, wherein the beam processing device includes at least one digital micromirror device.
The projection system of claim 1, wherein the light beam processing device is at least one liquid crystal display.
The projection system according to any one of claims 1 to 8, wherein the focal length of the optical system is less than or equal to 20 mm.
The projection system according to any one of claims 1 to 8, wherein the total system length of the optical system is less than or equal to 50 mm.
The projection system according to any one of claims 1 to 8, wherein the distance between the beam processing device and the optical system is greater than or equal to 1 mm and less than or equal to 10 mm.
The projection system of claim 1, wherein the metalens includes a substrate and a nanostructure layer disposed on the substrate;

The nanostructure layer includes nanostructures arranged in an array.
The projection system of claim 21, wherein the nanostructure layer includes superstructure units arranged in an array;

The superstructural unit is a close-packed pattern; the nanostructure is provided at the center position and/or the vertex position of the close-packed pattern.
The projection system of claim 21, wherein the metalens further includes a filling material;

The filling material is filled between the nanostructures.
The projection system of claim 23, wherein the absolute value of the difference between the refractive index of the filling material and the refractive index of the nanostructure is greater than or equal to 0.5.
The projection system of claim 22, wherein the period of the superstructure unit is greater than or equal to 0.3λc and less than or equal to 2λc ;

Wherein, λ c is the center wavelength of the working band of the projection system.
The projection system of claim 21, wherein the height of the nanostructure is greater than or equal to 0.3λc and less than or equal to 5λc ;

Wherein, λ c is the center wavelength of the working band of the projection system.
21. The projection system of claim 21, wherein the shape of the nanostructures includes polarization dependent structures.
The projection system of claim 21, wherein the shape of the nanostructures includes polarization-insensitive structures.
The projection system of claim 21, wherein the hyperlens further includes an anti-reflection coating;

The antireflection film is disposed on the side of the substrate and the nanostructure layer adjacent to the air.
The projection system of claim 21, wherein the phase of the super lens satisfies at least:

Where, r is the distance from the center of the hyperlens to the center of any of the nanostructures; λ is the operating wavelength, is any phase related to the operating wavelength, x, y are the mirror coordinates of the hyperlens, and f is the focal length of the hyperlens.
The projection system according to any one of claims 21 to 30, wherein the material of the substrate has an extinction coefficient of less than 0.01 for radiation in the working band.
The projection system according to any one of claims 21 to 30, wherein the material of the substrate includes one of fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon and amorphous silicon. or more.
The projection system according to any one of claims 21 to 30, wherein the extinction coefficient of the nanostructured material to radiation in the working band is less than 0.01.
The projection system of claim 33, wherein the material of the nanostructure includes one or more of fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon and amorphous silicon.
The projection system according to claim 23 or 24, wherein the extinction coefficient of the filling material in the working band is less than 0.01.
The projection system of claim 35, wherein the filling material includes one or more of air, fused quartz, quartz glass, crown glass, flint glass, sapphire, crystalline silicon and amorphous silicon.
The projection system of claim 21, wherein the substrate and the nanostructure are made of the same material.
The projection system of claim 21, wherein the substrate and the nanostructure are made of different materials.
The projection system of claim 23, wherein the nanostructure and the filling material are made of the same material.
The projection system of claim 23, wherein the nanostructures and the filling material are made of different materials.
The projection system of claim 23, wherein the periods of the superstructure units at different positions on the superlens are the same.
The projection system of claim 23, wherein the periods of the superstructure units at different positions on the superlens are at least partially the same.
The projection system of claim 21, wherein the hyperlens further includes an anti-reflection coating;

The antireflection film is disposed on one side of the substrate and/or on the side of the nanostructure adjacent to the air.