WO2023045410A1 - Compensator and preparation method therefor, image display apparatus, and display device - Google Patents

Abstract

The present invention provides a compensator and a preparation method therefor, an image display apparatus, and a display device. The compensator comprises a prism substrate and a compensation element which can be divided into multiple metasurface structural units. The metasurface structural units of the compensation element are configured to compensate a phase of light penetrating through the metasurface structural units. The incident direction of light emitted to the compensator is the same as the exit direction of the light penetrating through the metasurface structural units, the prism substrate, and a free-form-surface prism located on a light exit side of the prism substrate. By means of the technical solution provided by embodiments of the present invention, light can penetrate through the compensator and the free-form-surface prism in an afocal and undistorted manner, and after penetrating through the compensator and the free-form-surface prism, human eyes can normally watch an external object. Moreover, the thickness of the metasurface structural units is relatively small, and the prism substrate can also have relatively small thickness, such that the compensator can be light and thin and is convenient for a user to use.

Description

Compensator and its preparation method, image display device, and display device technical field

The invention relates to the technical field of imaging devices, in particular to a compensator and a preparation method thereof, an image display device, and a display device.

Background technique

Since the concepts of virtual reality (VR, Virtual Reality) and augmented reality (AR, Augmented Reality) were proposed, head-mounted image display devices based on VR or AR modes have made great progress.

Under the premise that the image source does not block the human eye, in order to form an image in front of the human eye, a designed free-form surface optical element is generally required to achieve imaging; and when the ambient light of external things passes through the free-form surface optical element, imaging deformation will occur, resulting in There are aberrations in the external things seen by the human eye. At this time, a lens with a free-form surface is also required to control aberrations so that the human eye can normally view external things. At present, head-mounted image display devices based on free-form surfaces are relatively thick, generally greater than 8mm, or even greater than 10mm, and the products are bulky, inconvenient for users to use, and not conducive to promotion.

Contents of the invention

To solve the above problems, the purpose of the embodiments of the present invention is to provide a compensator and a manufacturing method thereof, an image display device, and a display device.

In the first aspect, an embodiment of the present invention provides a compensator, including: a prism substrate and a compensating element that can be divided into multiple metasurface structural units;

The compensation element is arranged on one side of the prism base;

The metasurface structure unit of the compensation element is used to compensate the phase of the light passing through the metasurface structure unit; The emitting directions behind the surface structure unit, the prism base and the free-form surface prism located on the light emitting side of the prism base are the same.

In a possible implementation, the phase error of the metasurface structure unit at multiple target wavelengths meets the minimum error condition, and the phase error is the actual compensation phase of the metasurface structure unit at the target wavelength The difference between the theoretical phase and the theoretical phase that the metasurface structure unit needs to compensate at the same target wavelength.

In a possible implementation manner, the minimum error condition is the minimum weighted sum of multiple phase errors, and the weighted sum of multiple phase errors is:

为所述超表面结构单元(x,y)在所述目标波长λ _i下的实际补偿相位，

为所述超表面结构单元(x,y)在所述目标波长λ _i下需要补偿的的理论相位，且： Wherein, (x, y) represent the positional coordinates of described metasurface structural unit, m is the numbering of described metasurface structural unit (x, y) in the structural database, λ _i is the i-th described target wavelength, c _i is the weight coefficient of the target wavelength λ _i ;

is the actual compensation phase of the metasurface structure unit (x, y) at the target wavelength _λi ,

is the theoretical phase that needs to be compensated for the metasurface structure unit (x, y) at the target wavelength _λi , and:

Wherein, n ₁ is the refractive index of the prism base, t _{x, y} is the thickness of the prism base in the light propagation direction corresponding to the metasurface structure unit (x, y), and n ₂ is the free-form surface The refractive index of the prism, T _{x, y} is the thickness of the free-form surface prism in the light propagation direction corresponding to the metasurface structure unit (x, y).

In a possible implementation manner, the target wavelength includes wavelengths in the visible light band, and the target wavelength includes at least wavelengths corresponding to yellow light, green light, red light, and purple light;

A smaller value of the weight coefficients of the yellow light and the green light is not smaller than a larger value of the weight coefficients of the red light and the violet light.

In a possible implementation manner, the compensation element includes a transparent base layer and a plurality of nanostructures.

In a possible implementation manner, the nanostructure is an upright structure with a central axis in the height direction, and the nanostructure has a first symmetry plane and a second symmetry plane perpendicular to the first symmetry plane ;

The intersection line between the first symmetry plane and the second symmetry plane is the central axis, the intersection line between the first symmetry plane and the nanostructure, and the intersection line between the second symmetry plane and the The intersection lines between the nanostructures have the same shape.

In a possible implementation, the nanostructure is a cylinder or a regular prism with 4n side edges;

Alternatively, the nanostructure is a cylindrical or regular prism cavity structure with 4n side edges;

Alternatively, the nanostructure is an at least partially hollow cylinder or a regular prism with 4n side edges, and the hollow of the nanostructure is a cylindrical or regular prism-shaped cavity structure with 4n side edges;

Alternatively, the nanostructure is a cylindrical or regular prism cavity structure with 4n side edges, and the cavity structure is provided with a cylinder or a regular prism with 4n side edges.

In a possible implementation manner, the compensation element is arranged on the light incident side of the prism base;

The incident direction of the light directed at the metasurface structure unit is the same as the outgoing direction of the light after passing through the metasurface structure unit, the prism base and the free-form surface prism on the light exit side of the prism base in sequence .

In a possible implementation manner, the surface shape of the light-emitting side of the prism base matches the surface shape of a side of the free-form surface prism close to the prism base.

In a possible implementation manner, the surface shape of the light-emitting side of the prism base is a concave free-form surface.

In a possible implementation manner, the refractive index of the prism base is the same as that of the free-form surface prism.

In a possible implementation manner, a tempered film and/or an anti-reflection film is provided on a side of the compensation element away from the prism base.

In the second aspect, the embodiment of the present invention also provides an image display device, which is characterized in that it includes: a free-form surface prism and any one of the above-mentioned compensators.

In a possible implementation manner, the free-form surface prism includes a transmissive surface, a transflective surface, and a light-splitting surface; the light-splitting surface is a side close to the light-emitting side of the prism base of the compensator;

The transmission surface is used to transmit external imaging light, and the imaging light transmitted by the transmission surface is directed to the transflective surface;

The transflective surface is used to totally reflect the imaging light transmitted by the transmissive surface to the spectroscopic surface;

The light splitting surface is used to reflect the imaging light totally reflected by the transflective surface to the transflective surface;

The transflective surface is also used for transmitting the imaging light reflected by the light splitting surface.

In a possible implementation manner, the transflective surface is a concave spherical surface.

In a possible implementation manner, the transmittance ratio of the dichroic surface is not less than (I _max -I ₀ )/I ₀ ; wherein, I _max is the maximum brightness of the external imaging light, and I ₀ is the maximum brightness required for imaging. maximum brightness.

In a possible implementation manner, the image display device further includes an image source; the image source is configured to emit imaging light directed to the free-form surface prism.

In a third aspect, an embodiment of the present invention further provides a near-eye projection display device, including any image display device as described above.

In the fourth aspect, the embodiment of the present invention also provides a method for preparing a compensator, including:

setting an isolation layer on the temporary substrate;

setting a transparent base layer on the side of the isolation layer away from the temporary base;

A structural layer is arranged on the side of the transparent base layer away from the isolation layer;

Structuring a plurality of nanostructures on the structural layer;

removing the isolation layer, transferring the separated transparent base layer and multiple nanostructures to one side of the prism base to make the compensator;

Wherein, the metasurface structure unit comprising the nanostructure is used for compensating the phase of the light passing through the metasurface structure unit; The exit directions behind the metasurface structure unit, the prism base and the free-form surface prism located on the light exit side of the prism base are the same.

In a possible implementation manner, before removing the isolation layer, the method further includes: setting a transfer layer on the surface of the nanostructure;

The transfer of the separated transparent base layer and a plurality of nanostructures to the light incident side of the prism base comprises:

transferring the separated transparent base layer, the nanostructure and the transfer layer to the light incident side of the prism base, and the transparent base layer is attached to one side of the prism base; and

The transfer layer is removed.

In a possible implementation manner, the arranging the transparent base layer on the side of the isolation layer away from the temporary base includes:

setting a transfer layer on the side of the isolation layer away from the temporary base, and then setting the transparent base layer on the side of the transfer layer away from the isolation layer;

The transfer of the separated transparent base layer and a plurality of nanostructures to the light incident side of the prism base comprises:

transferring the separated transparent substrate layer, the nanostructure and the transfer layer to the light incident side of the prism substrate, and the nanostructure is attached to one side of the prism substrate; and

The transfer layer is removed.

In the solution provided by the first aspect of the embodiment of the present invention, the metasurface structure unit of the compensation element can perform phase compensation on the light, so that the incident direction of the light that hits the compensator is the same as that of the light that passes through the compensator and the free-form surface prism. The outgoing direction of the two is the same, so the light can pass through the compensator and the free-form prism without focus and distortion. After the human eye passes through the compensator and the free-form prism, it can view external things normally. Moreover, the thickness of the metasurface structure unit is small, and the prism substrate can also be made to have a small thickness, so the compensator and the free-form surface prism can form an afocal and thin image display device, which can realize light and thin, and is convenient for users use.

In order to make the above-mentioned objects, features and advantages of the present invention more comprehensible, preferred embodiments will be described in detail below together with the accompanying drawings.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

FIG. 1 shows a schematic structural diagram of a compensator provided by an embodiment of the present invention;

Fig. 2 shows another schematic structural diagram of the compensator provided by the embodiment of the present invention;

Fig. 3 shows another schematic structural diagram of the compensator provided by the embodiment of the present invention;

Fig. 4 shows a schematic diagram of the thickness of the prism in the compensator provided by the embodiment of the present invention;

Fig. 5 shows a schematic structural view of a nanostructure provided by an embodiment of the present invention;

Fig. 6 shows another schematic structural view of the nanostructure provided by the embodiment of the present invention;

Figure 7 shows a schematic structural view of various nanostructures provided by the embodiments of the present invention;

FIG. 8 shows a schematic structural diagram of an image display device provided by an embodiment of the present invention;

Fig. 9 shows a schematic flow chart of the preparation method of the compensator provided by the embodiment of the present invention;

Fig. 10 shows another schematic flow chart of the preparation method of the compensator provided by the embodiment of the present invention;

Fig. 11 shows another schematic flow chart of the preparation method of the compensator provided by the embodiment of the present invention;

FIG. 12 shows a schematic structural diagram of an image display device provided by an embodiment of the present invention;

Fig. 13 shows the spot diagram of 0 ° and 20 ° field of view provided by the embodiment of the present invention;

Fig. 14 shows an imaging simulation diagram provided by an embodiment of the present invention.

icon:

100-prism substrate, 200-compensation element, 210-transparent base layer, 220-nanometer structure, 10-compensator, 20-freeform surface prism, 21-transmission surface, 22-transflective surface, 23-splitting surface, 30-image Source, 1-Temporary substrate, 2-Isolation layer, 3-Structural layer, 4-Transfer layer.

Detailed ways

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Orientation or position indicated by "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. The relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, therefore It should not be construed as a limitation of the present invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrally connected; it may be mechanically connected or electrically connected; it may be directly connected or indirectly connected through an intermediary, and it may be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

An embodiment of the present invention provides a compensator for compensating and correcting incident ambient light. Referring to FIG. 1 , the compensator includes: a prism substrate 100 and a compensating element 200 that can be divided into multiple metasurface structural units. Wherein, the compensating element 200 is disposed on one side of the prism substrate 100 ; as shown in FIG. 1 , the compensating element 200 is disposed on the right side of the prism substrate 100 . The metasurface structure unit of compensation element 200 is used for compensating the phase of the light passing through the metasurface structure unit; The emitting directions behind the free-form surface prisms 20 on the light emitting side of 100 are the same.

In the embodiment of the present invention, the prism base 100 can transmit light incident on the prism base 100 , and the prism base 100 can be made of glass or other transparent materials. When the ambient light needs to be compensated, the prism substrate 100 has a light incident side where the ambient light is incident and a light output side where the ambient light exits. As shown in FIG. 1 , ambient light A can be incident from right to left, then the right side of the prism substrate 100 is the light incident side, and the left side is the light output side. The compensation element 200 that can realize the compensation function is arranged on one side of the prism base 100; The element 200 may also be disposed on the light exit side of the prism substrate 100 .

The compensation element 200 can be divided into a plurality of metasurface structural units. Since the thickness of the metasurface structural units is small, generally micron or nanoscale, the compensation element 200 is arranged on one side of the prism substrate 100, so that the prism substrate 100 can It plays the role of supporting the compensating element 200 . As shown in FIGS. 1-3 , the side of the prism substrate 100 on which the compensation element 200 is set is a plane, so as to facilitate the processing of the compensation element 200 on the prism substrate 100 . The side of the prism substrate 100 not provided with the compensating element 200 can be flat (as shown in FIG. 2 or FIG. 3 ) or non-flat. In order to ensure that the image display device has a smaller thickness when the compensator is applied to the image display device, the compensation element 200 is disposed on the light incident side of the prism substrate 100 . At this time, as shown in FIG. 1, the light-emitting side of the prism base 100 can be non-planar, for example, the surface shape of this side matches the surface shape of the side of the free-form surface prism 20 close to the prism base 100, for example, it is concave. freeform surface. Wherein, the free-form surface prism 20 is a prism used for imaging. In order to form a magnified image, at least one surface of the free-form surface prism 20 is a free-form surface. Changes will occur, resulting in imaging distortion (optical aberration), and the embodiment of the present invention is mainly based on the compensating element 100 for compensating and correcting the imaging distortion.

In the embodiment of the present invention, the compensation element 100 implements phase compensation for the light incident on the compensation element 100 through the metasurface structure unit, so that the incident direction of the light before entering the compensator is the same as that of the light passing through the metasurface structure. The emitting directions behind the unit (that is, the compensating element 100 ), the prism substrate 100 and the free-form surface prism 20 are the same. As shown in Figure 1, light A is incident on the compensation element 100 in the compensator, and the corresponding metasurface structure unit in the compensation element 100 compensates the phase of the light A, and converts light A into light B; generally, Light A and B travel in different directions. After that, the light B passes through the prism base 100 and the free-form surface prism 20 in sequence and then is converted into light E. The light E is the light after the light A passes through the compensator and the free-form surface prism 20. The propagation direction of the light E is the same as that of the light A .

Optionally, the compensating element 200 is arranged on the light-incident side of the prism substrate 100; The outgoing directions behind the free-form surface prism 20 are the same.

It should be noted that, in order to facilitate the display of the propagation direction of light, a certain interval is provided between the various components in FIG. The incident side of 100. Moreover, those skilled in the art can understand that the light incident side and the light exit side of the prism substrate 100 in the embodiment of the present invention are only relative terms, and are not used to limit the transmission of light from the "light incident side" to the "light exit side"; as shown in Figure 1 As shown, the light can also pass through the prism substrate 100 from left to right, that is, the light can also be emitted from the “light exit side” to the “light entry side” of the prism substrate 100 . In FIG. 1 , when light sequentially transmits through the free-form surface prism 20 , the prism substrate 100 , and the compensation element 200 from left to right, the compensation element 200 can still implement phase compensation for the light.

In the compensator provided by the embodiment of the present invention, the metasurface structure unit of the compensating element 200 can perform phase compensation on the light, so that the incident direction of the light that hits the compensator is the same as that of the light that passes through the compensator and the free-form surface prism 20 The outgoing direction of the light is the same, so the light can pass through the compensator and the free-form prism 20 without focus and without distortion. After passing through the compensator and the free-form prism 20, the human eye can normally view external things. Moreover, the thickness of the metasurface structure unit is small, and the prism substrate 100 can also be made to have a small thickness, so the compensator and the free-form surface prism 20 can form an afocal and thin image display device, thereby realizing thinning and thinning. User-friendly.

On the basis of the above-mentioned embodiments, the phase error of the metasurface structure unit in the compensation element 200 at multiple target wavelengths meets the minimum error condition; wherein, the phase error is the difference between the actual compensation phase of the metasurface structure unit at the target wavelength and The difference between the theoretical phases that metasurface structural units need to compensate for at the same target wavelength.

In the embodiment of the present invention, a structural database containing multiple metasurface structural units can be preset. The structural database can use an existing database, or can adaptively add new metasurface structural units based on the existing database. For a certain metasurface structure unit, its compensation effect on light of different wavelengths is generally different; for different metasurface structure units in the structure database, its compensation effect on light of the same wavelength is also different. In the embodiment of the present invention, the target wavelength is the wavelength that needs to be compensated, and the target wavelength can include wavelengths in the visible light band; based on the shape and structure of the compensator and the free-form surface prism 20, the phase that needs to be compensated for the light of each target wavelength can be determined , which is the theoretical phase. Moreover, based on the structure database, the compensation phase of each metasurface structure unit to light of different target wavelengths, that is, the actual compensation phase can be determined. In the embodiment of the present invention, the difference between the theoretical phase and the actual compensation phase at the same target wavelength is used as the phase difference value at the target wavelength; if the phase error of a metasurface structural unit at multiple target wavelengths meets the minimum error condition , indicating that the phase compensation effect of the metasurface structure unit is not much different from the theoretically required compensation effect. At this time, the metasurface structure unit can be selected as the corresponding metasurface structure unit in the compensation element 200 .

最小，即补偿元件100中所选用的超表面结构单元，与结构数据库中其他超表面结构单元相比，加权和

最小。本发明实施例中，多个相位误差的加权和为： Optionally, the error minimum condition is the weighted sum of multiple phase errors

Minimum, that is, the metasurface structure unit selected in the compensation element 100, compared with other metasurface structure units in the structure database, the weighted sum

minimum. In the embodiment of the present invention, the weighted sum of multiple phase errors is:

为超表面结构单元(x,y)在目标波长λ _i下的实际补偿相位，

为超表面结构单元(x,y)在目标波长λ _i下需要补偿的的理论相位，且： Among them, (x, y) represents the position coordinates of the metasurface structural unit, m is the number of the metasurface structural unit (x, y) in the structure database, λ _i is the i-th target wavelength, and c _i is the target wavelength λ _i The weight factor of;

is the actual compensation phase of the metasurface structure unit (x, y) at the target wavelength _λi ,

is the theoretical phase that needs to be compensated for the metasurface structure unit (x,y) at the target wavelength _λi , and:

Wherein, n ₁ is the refractive index of the prism base 100, t _{x, y} is the thickness of the prism base 100 on the light propagation direction corresponding to the metasurface structure unit (x, y), n ₂ is the refractive index of the free-form surface prism 20, T _x,y is the thickness of the free-form surface prism 20 in the light propagation direction corresponding to the metasurface structure unit (x,y).

In the embodiment of the present invention, the compensation element 200 can be divided into a plurality of metasurface structural units, and the metasurface structural units at different positions of the compensation element 200 are not completely the same. In this embodiment, the metasurface structural units are used on the compensation element 200 The position (x, y) of the corresponding metasurface structure unit. For example, the side of the prism substrate 100 close to the compensating element 200 is a plane, and the metasurface structural units of the compensating element 200 can be distributed on the plane. At this time, the position coordinates (x, y) as the identification ID of the metasurface structural unit.

补偿器在环境光光路的相位为

则需要满足

并且，补偿器的棱镜基底100和超表面结构单元在环境光光路上也分别具有相应的相位

且

故该超表面结构单元应当具有的相位

该相位

即为在目标波长λ _i下需要补偿的的理论相位。 In order to make the compensator and the free-form prism 20 form an afocal optical system, for any target wavelength λ _i , if the power of the free-form prism 20 is Φ ₁ (λ _i ), the power of the compensator is Φ ₂ (λ _i ), it needs to satisfy Φ ₁ (λ _i )+Φ ₂ (λ _i )=0. Therefore, when the optical system incident ambient light, if the phase of the free-form surface prism 20 in the ambient light path is

The phase of the compensator in the ambient light path is

then need to meet

Moreover, the prism substrate 100 and the metasurface structure unit of the compensator also have corresponding phases on the ambient light path

and

Therefore, the phase of the metasurface structure unit should have

the phase

That is, the theoretical phase that needs to be compensated at the target wavelength λ _i .

相应地，超表面结构单元(x,y)对应的光线传播方向上自由曲面棱镜20的厚度为T _x,y，则该位置处的自由曲面棱镜20的相位

为

因此，对于(x,y)处的超表面结构单元，其在目标波长λ _i下需要补偿的的理论相位为： As shown in Figure 4, for a metasurface structure unit (x, y), the thickness of the prism substrate 100 in the corresponding light propagation direction is t _{x, y} , then the phase of the prism substrate 100 at this position

Correspondingly, the thickness of the free-form surface prism 20 in the light propagation direction corresponding to the metasurface structure unit (x, y) is T _{x, y} , then the phase of the free-form surface prism 20 at this position

for

Therefore, for the metasurface structure unit at (x, y), the theoretical phase that needs to be compensated at the target wavelength _λi is:

为超表面结构单元(x,y)所对应的自由曲面棱镜20的相位，

为超表面结构单元(x,y)所对应的棱镜基底100的相位。n ₁为棱镜基底100的折射率，n ₂为自由曲面棱镜20的折射率；一般情况下，n ₁与n ₂可以相同，例如，棱镜基底100与自由曲面棱镜20采用相同的材质，如均采用相同的玻璃材质等。 in,

is the phase of the free-form surface prism 20 corresponding to the metasurface structure unit (x, y),

is the phase of the prism substrate 100 corresponding to the metasurface structure unit (x, y). _n1 is the refractive index of the prism base 100, and _n2 is the refractive index of the free-form surface prism 20; in general, _n1 and _n2 can be the same, for example, the prism base 100 and the free-form surface prism 20 adopt the same material, such as uniform Use the same glass material, etc.

并可以确定多个相位误差的加权和

进而可以确定最小的加权和所对应的超表面结构单元m，即对于任意的k，

故可以将结构数据库中的超表面结构单元m设置在(x,y)处，作为超表面结构单元(x,y)。对补偿元件200其他位置处的超表面结构单元，可以采用相同的方式确定，此处不做赘述。 For any metasurface structural unit k(k∈A) in the structural database A, the actual compensation phase of the metasurface structural unit k at the corresponding target wavelength _λi can be determined, that is, it can be determined that the metasurface structural unit k is set to Actual compensation phase at (x,y)

and can determine the weighted sum of multiple phase errors

Furthermore, the metasurface structure unit m corresponding to the minimum weighted sum can be determined, that is, for any k,

Therefore, the metasurface structure unit m in the structure database can be set at (x, y) as the metasurface structure unit (x, y). The metasurface structure units at other positions of the compensating element 200 can be determined in the same way, which will not be repeated here.

Wherein, different target wavelengths λ _i may set corresponding weight coefficients c _i . Optionally, the target wavelengths at least include wavelengths corresponding to yellow light, green light, red light, and purple light; and, the smaller value among the weight coefficients of yellow light and green light is not less than larger value. That is, yellow light and green light have larger weight coefficients, and red light and purple light have smaller weight coefficients. Based on this weighted sum, the metasurface structural units determined can better compensate for the more sensitive yellow light and Green light can improve the viewing effect of human eyes.

Based on any of the above embodiments, as shown in FIG. 1 , the compensation element 200 of the compensator includes a transparent base layer 210 and a plurality of nanostructures 220 . Wherein, the nanostructure 220 and a part of the transparent base layer 210 can be divided into a metasurface structure unit. Each metasurface structure unit can modulate the incident light, and the nanostructure 220 can directly adjust the phase and other characteristics of light; Selected materials include: titanium oxide, silicon nitride, fused silica, aluminum oxide, gallium nitride, gallium phosphide, and hydrogenated amorphous silicon. Among them, a plurality of nanostructures 220 are arranged in an array, so that metasurface structural units can be divided; the metasurface structural units can be regular hexagons, squares, fan shapes, etc., and the central position of each metasurface structural unit, or each A nanostructure is respectively provided at the center position and the apex position of the metasurface structure unit. Wherein, all the nanostructures 220 can be located on the same side of the transparent base layer 210, or some nanostructures 220 are located on one side of the transparent base layer 210, and another part of the nanostructures are located on the other side of the transparent base layer 210. This is not limited.

It should be noted that the transparent base layer 210 is an integral layer structure, and the multiple metasurface structural units in the compensation element 200 can be artificially divided, that is, a plurality of nanostructures 220 are arranged on the transparent base layer 210, so that they can be divided A metasurface structure unit including one or more nanostructures 220 is shown, or in other words, a plurality of metasurface structure units can form a compensating element 200 with an integrated structure.

Optionally, the compensator provided in the embodiment of the present invention is mainly used to compensate the external ambient light. Since the ambient light is polarization-independent, in order to make the nanostructure 220 insensitive to the polarization of the incident light, the nanostructure 220 in the embodiment of the present invention The structure adopts a specific symmetrical structure. As shown in Figure 5, the nanostructure 220 provided by the embodiment of the present invention is an upright structure with a central axis 221 in the height direction, such as a columnar structure, etc., and the nanostructure 220 has a first symmetry plane 222 and the first symmetry plane Vertical second plane of symmetry 223 . As shown in FIG. 5 , the intersection line between the first symmetry plane 222 and the second symmetry plane 223 is the central axis 221, and the intersection line between the first symmetry plane 222 and the nanostructure 220 is the same as the second symmetry plane 223 and the nanostructure 220. The intersection lines between the structures 220 have the same shape. As shown in FIG. 5 , the nanostructure 220 is a solid cylinder, and the intersection lines between the two symmetry planes and the nanostructure 220 are all rectangles with the same shape.

For example, the nanostructure 220 can be a cylinder as shown in Figure 5, or the nanostructure 220 can also be a regular prism with 4n side edges, where n is a positive integer; for example, the nanostructure 220 can be a regular square prism, a regular octagon Prisms, etc., FIG. 6 shows a nanostructure 220 of regular quadrangular prisms.

Alternatively, the nanostructure 220 is an at least partially hollow cylinder or a regular prism with 4n side edges, and the hollow of the nanostructure 220 is a cylindrical or regular prism-shaped cavity structure with 4n side edges. As shown in diagram (a) of FIG. 7 , the cylindrical nanostructure 220 is partially hollow, and the hollow structure is a regular quadrangular prism. Alternatively, further, smaller cylinders or regular prisms with 4n side edges are arranged in the hollow cavity structure of the nanostructure 220 . As shown in (b) of FIG. 7 , the nanostructure 220 is cylindrical as a whole, and also has a cylindrical hollow cavity structure, and there are regular quadrangular prisms in the cavity structure.

Alternatively, the nanostructure 220 is a cylindrical or regular prism cavity structure with 4n side edges. As shown in diagram (c) of FIG. 7 , the nanostructure 220 is a cavity structure in the shape of a regular quadrangular prism. Or, further, a cylinder or a regular prism with 4n side edges is arranged in the cavity structure. As shown in (d) of FIG. 7 , the nanostructure 220 is a cylindrical cavity structure, and a regular quadrangular prism is also arranged in the cavity structure.

It should be noted that the nanostructure 220 is a cavity structure, which means that the surroundings of the nanostructure 220 are filled with structural materials, such as filled with transparent materials such as silicon nitride. Since the metasurface structure units are divided, corresponding nanostructures 220 can be formed by carving cavity structures in the complete structure layer. In addition, FIG. 5 to FIG. 7 only show schematic diagrams of metasurface structural units, and the dimensions, size ratios, etc. in the figures are not used to limit the metasurface structural units. According to actual needs, metasurface structural units of required size can be designed or selected.

In addition, optionally, for the compensator shown in FIG. 1 and FIG. 2 , the compensating element 200 is located on the outer surface. At this time, a tempered film can be provided on the side of the compensating element 200 away from the prism substrate 100 to play a protective role. In addition, an anti-reflection coating may also be provided on the side of the compensating element 200 away from the prism substrate 100 to increase the transmittance when ambient light is incident on the compensator.

In the compensator provided by the embodiment of the present invention, the metasurface structure unit of the compensating element 200 can perform phase compensation on the light, so that the incident direction of the light that hits the compensator is the same as that of the light that passes through the compensator and the free-form surface prism 20 The outgoing direction of the light is the same, so the light can pass through the compensator and the free-form prism 20 without focus and without distortion. After passing through the compensator and the free-form prism 20, the human eye can normally view external things. Moreover, the thickness of the metasurface structure unit is small, and the prism substrate 100 can also be made to have a small thickness, so the compensator and the free-form surface prism 20 can form an afocal and thin image display device, thereby realizing thinning and thinning. User-friendly. Selecting an appropriate metasurface structure unit based on the minimum error condition can ensure that the compensation element 200 has a high compensation effect; selecting a nanostructure 220 with a specific symmetrical structure can better modulate non-polarized ambient light.

Based on the same inventive concept, an embodiment of the present invention also provides an image display device, as shown in FIG. 8 , the image display device includes: a free-form surface prism 20 and a compensator 10 as provided in any one of the above embodiments. The free-form surface prism 20 can form a magnified image. After the external ambient light passes through the compensator 10 and the free-form surface prism 20, the propagation direction of the light does not change, that is, the image display device comprising the compensator 10 and the free-form surface prism 20 is afocal system without causing distortion of ambient light. Based on the image display device, the user can normally view the image formed by the free-form surface prism 20, and can normally view the external environment, which can realize the effect of augmented reality.

For example, as shown in FIG. 8 , the free-form surface prism 20 includes a transmissive surface 21 , a transflective surface 22 and a light-splitting surface 23 ; Wherein, the transmissive surface 21 is used to transmit external imaging light, and the imaging light transmitted by the transmissive surface 21 is directed to the transflective surface 22; The surface 23 is used to reflect the imaging light totally reflected by the transflective surface 22 to the transflective surface 22 ; the transflective surface 22 is also used to transmit the imaging light reflected by the dichroic surface 23 . Wherein, the transflective surface 22 is a concave spherical surface, which is convenient for processing.

In the embodiment of the present invention, the image display device may also include an image source 30, which emits imaging rays directed to the free-form surface prism 20; as shown in FIG. The transmission surface 21 of the curved prism 20 . The imaging ray M passes through the transmissive surface 21 , and then enters the transflective surface 22 at a larger incident angle, and is totally reflected on the transflective surface 22 , so that the imaging ray M is totally reflected to the spectroscopic surface. The beam splitting surface 23 has non-reflective and transmissive functions. For example, the beam splitting surface 23 is provided with a semi-transparent and semi-reflective film, which can reflect at least part of the light in the imaging light M; The angle is incident on the transflective surface 22 again, and then passes through the transflective surface 22 to the human eye. The external ambient light A can also be emitted to human eyes after passing through the compensator 10 , the dichroic surface 23 , and the transflective surface 22 .

Wherein, the dichroic surface 23 of the free-form surface prism 20 matches the surface shape of the light-emitting side of the prism base 100 of the compensator 10, and is generally a free-form surface, so that the free-form surface prism 20 and the prism base 100 can be bonded together. For example, the two can be glued together; if the refractive index of the free-form surface prism 20 and the prism base 100 are the same, then the glue used is close to the refractive index of the two; for example, the refractive index of the glue is the same as the refractive index of the two The error between the ratios does not exceed 0.1.

In addition, since the dichroic surface 23 can reflect and transmit light, the external ambient light A will also be partially reflected when it passes through the dichroic surface 23, that is, the dichroic surface 23 reflects part of the ambient light; in order to ensure that the human eye can see the external environment with normal brightness , the splitting surface 23 needs to have sufficient transmittance. In the embodiment of the present invention, the transmittance ratio (that is, the ratio of transmittance to reflectance) of the splitting surface 23 is not less than (I _max -I ₀ )/I ₀ ; wherein, I _max is the maximum brightness of the external imaging light, and I ₀ The maximum brightness required for imaging. Generally, the transmittance-reflectance ratio is greater than 1, that is, the light transmitted by the dichroic surface 23 is more than the reflected light.

An embodiment of the present invention also provides a near-eye projection display device, which includes any image display device as described above. Based on the near-eye projection display device, human eyes can see the image formed by the image source 30 and can normally watch the external environment. Wherein, "near-eye" means that the display device is close to the human eye, and the distance between the display device and the human eye is generally less than 10 cm, generally 1-3 cm.

The embodiment of the present invention also provides a preparation method of the compensator provided in any one of the above embodiments, the compensator includes a prism substrate 100 and a compensation element 200 , and the compensation element 200 includes a transparent base layer 210 and a nanostructure 220 . The metasurface structure unit comprising the nanostructure 220 is used for compensating the phase of the light passing through the metasurface structure unit; the incident direction of the light directed to the compensator is related to the light passing through the metasurface structure unit, the prism substrate 100, and the The emitting directions behind the free-form surface prisms 20 on the light emitting side of the substrate 100 are the same.

Wherein, because the prism substrate 100 may be irregular, the prism substrate 100 as shown in Figure 1 is similar to the triangular prism structure, and when making the nanostructure 220, there are requirements for the substrate; Thickness and other requirements make it difficult to directly grow the nanostructure 220 on the prism substrate 100 . In the embodiment of the present invention, the temporary substrate 1 that meets the requirements of the processing technology is used for processing, and then the compensator is manufactured by transfer. Referring to shown in Figure 9, the preparation method comprises:

Step S91 : setting an isolation layer 2 on the temporary substrate 1 .

In the embodiment of the present invention, the temporary base 1 is a one-layer structure temporarily used as a base, and the material of the temporary base 1 may be silicon or quartz glass. The isolation layer 2 is a removable material, and is different from the materials of the substrate (including the temporary base 1, the transparent base layer 210) and the nanostructure 220; the material of the isolation layer 2 can be a soluble metal material, such as germanium, aluminum, Copper, gold and other metal materials. Wherein, the isolation layer 2 can be formed by a deposition growth method, such as CVD (vapor phase deposition) method, etc., and the thickness of the isolation layer 2 can be 1-300 μm.

Step S92 : setting a transparent base layer 210 on the side of the isolation layer 2 away from the temporary base 1 .

In the embodiment of the present invention, a transparent base layer is grown on the isolation layer 2 , and this layer can be used as the transparent base layer 210 . The material of the transparent base layer 210 is a transparent material, which has a relatively high transmittance to light of a target wavelength band (such as a visible light band), and specifically silicon oxide can be selected. The transparent base layer 210 can be deposited by CVD or ALD (atomic layer deposition), and its thickness can be 0.5-5 μm.

Step S93 : setting the structural layer 3 on the side of the transparent base layer 210 away from the isolation layer 2 .

In the embodiment of the present invention, a layer of structural layer 3 is grown on the transparent base layer 210. The material of the structural layer 3 is different from that of the transparent base layer 210, and the material of the structural layer 3 is also selected to be transparent in the target band, such as titanium oxide, nitride Silicon, fused silica, alumina, gallium nitride, gallium phosphide and hydrogenated amorphous silicon, etc. The structural layer 3 can be deposited by CVD or ALD, and its thickness can be 300-3000 nm.

Step S94 : Structuring a plurality of nanostructures 220 on the structural layer 3 .

Wherein, a plurality of nanostructures 220 may be structured on the structural layer 3 by means of photolithography or the like. For example, a masking layer can be coated on the structure layer 3, and the masking layer can include photoresist and/or a hard mask, wherein the hard mask can be various oxides or metals such as aluminum and chromium. After that, the nano pattern is exposed on the shielding layer, and the optional exposure methods include electron beam exposure, deep ultraviolet lithography exposure, nanoimprinting and laser direct writing; and then adopt methods such as dry etching to obtain the nanostructure 220, And remove photoresist and/or hardmask.

Step S95: removing the isolation layer 2, transferring the separated transparent base layer 210 and the plurality of nanostructures 220 to one side of the prism base 100 to make a compensator.

In the embodiment of the present invention, the isolation layer 2 is removed by dissolving the isolation layer 2, thereby separating the temporary substrate 1, and then the structure including the transparent base layer 210 and the nanostructure 220 can be transferred to the pre-set prism substrate 100 , thus forming the required compensator.

Optionally, since the thickness of the transparent base layer 210 and the nanostructure 220 is small, the embodiment of the present invention implements transfer by adding a transfer layer 4 . Referring to Fig. 10, before the step S95 "removing the isolation layer 2", the method also includes:

Step S950 : setting the transfer layer 4 on the surface of the nanostructure 220 .

Moreover, the above step S95 of "removing the isolation layer 2, and transferring the separated transparent base layer 210 and the plurality of nanostructures 220 to the light-incident side of the prism base 100" includes:

Step S951 : removing the isolation layer 2 .

Step S952 : Transfer the separated transparent base layer 210 , nanostructures 220 and transfer layer 4 to the light incident side of the prism base 100 , and attach the transparent base layer 210 to one side of the prism base 100 .

Step S953: removing the transfer layer 4 to obtain the required compensator.

In the embodiment of the present invention, the transfer layer 4 is made of a material with a certain hardness, which can be plastic, such as PMMA (polymethyl methacrylate), PDMS (polydimethylsiloxane), PE (polyethylene ), PC (polycarbonate) and other materials. Generally, the thickness of the transfer layer 4 needs to be ten times greater than the thickness of the structural layer 2 , for example, the thickness of the transfer layer 4 may be 10 μm˜1 mm. In the embodiment of the present invention, by adding the transfer layer 4 before removing the isolation layer 2 , the transparent base layer 210 and the nanostructures 220 can be transferred to the prism substrate 100 by using the transfer layer 4 with a certain thickness.

The method shown in FIG. 10 can arrange the prism substrate 100 and the nanostructure 220 on both sides of the transparent base layer 210 respectively, so that a compensator similar to that in FIG. 1 can be obtained. In addition, the prism substrate 100 may also be disposed on one side of the nanostructure 220, so that a compensator such as that shown in FIG. 3 can be obtained. Referring to Fig. 11, the step S92 of the preparation method "setting the transparent base layer 210 on the side of the isolation layer 2 away from the temporary base 1" includes:

Step S921 : setting the transfer layer 4 on the side of the isolation layer 2 away from the temporary substrate 1 .

Step S922: Afterwards, a transparent base layer 210 is provided on the side of the transfer layer 4 away from the isolation layer 2 .

Subsequent steps S93 and S94 are all performed on the basis of including the transfer layer 4 . And, the above step S95 "removing the isolation layer 2, and transferring the separated transparent base layer 210 and the plurality of nanostructures 220 to the light incident side of the prism base 100" includes:

Step S951 : removing the isolation layer 2 .

Step S954 : Transfer the separated transparent base layer 210 , nanostructure 220 and transfer layer 4 to the light incident side of the prism substrate 100 , and attach the nanostructure 220 to one side of the prism substrate 100 .

Step S955 : removing the transfer layer 4 to obtain the required compensator, the nanostructure 220 of the compensator is between the prism substrate 100 and the transparent base layer 210 .

In the method for preparing a compensator provided by the embodiment of the present invention, processing is performed on the basis of the temporary substrate 1 to obtain a compensation element 200 including a transparent base layer 210 and a nanostructure 220, and the compensation element 200 is transferred to the Prism substrate 100, so that it can adapt to various shapes of prism substrate 100, and generate corresponding compensators. Utilizing the transfer layer 4 can increase the thickness of the compensating element 200 to facilitate transfer.

The function of the compensator provided by the embodiment of the present invention will be described in detail below through an embodiment. As shown in FIG. 12 , the compensator 10 includes a prism substrate 100 and a compensating element 200 , and the compensator 100 and the free-form surface prism 20 can form an image display device. Wherein, the outer surface of the free-form surface prism 20 (ie, the transflective surface 22 ) is a concave spherical refracting surface with a radius of -130 mm. The distance from the center point of the outer surface of the free-form surface prism 20 to the eye pupil plane (EPD) is 15mm. The thickness from the center of the compensation element 200 to the center point of the outer surface of the free-form surface prism 20 is 6 mm; the thickness of the transparent base layer 210 of the compensation element 200 is 0.1 mm; the viewing angle is ±20°. The materials of the free-form surface prism 20 and the prism substrate 100 are both PMMA, the material of the metasurface transparent base layer 210 is fused silica, and the material of the metasurface nanostructure 220 is silicon nitride, with a period of 600nm, a height of 1350nm, and a characteristic size of 100nm.

Since the compensator mainly acts on the ambient light path, the afocal system of the ambient light path is mainly analyzed here. Taking the phase modulation of three wavelengths of 486nm, 587nm, and 656nm as an example, the spot diagrams of 0° and 20° field of view are shown in Figure 13, and the imaging simulation diagram of the external environment is shown in Figure 14, and the left side of Figure 14 The side is the actual object, and the right side is the image formed by the image display device. It can be seen from the figure that the metasurface-based compensator 10 well compensates the optical aberration caused by the free-form surface prism 20, and achieves diffraction-limited imaging quality.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field can easily think of changing or replacing technologies within the technical scope disclosed in the present invention. Schemes should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (21)

A compensator, characterized in that it comprises: a prism substrate (100) and a compensating element (200) capable of being divided into a plurality of metasurface structural units; The compensation element (200) is arranged on one side of the prism base (100); The metasurface structure unit of the compensation element (200) is used to compensate the phase of the light passing through the metasurface structure unit; The outgoing directions behind the metasurface structure unit, the prism substrate (100) and the free-form surface prism (20) located on the light exit side of the prism substrate (100) are the same. The compensator according to claim 1, wherein the phase error of the metasurface structure unit at a plurality of target wavelengths meets the minimum error condition, and the phase error is that the metasurface structure unit is at the target wavelength The difference between the actual compensation phase at the same target wavelength and the theoretical phase that the metasurface structure unit needs to compensate for at the same target wavelength. The compensator according to claim 2, wherein the minimum error condition is the minimum weighted sum of multiple phase errors, and the weighted sum of multiple phase errors is:

Wherein, (x, y) represent the positional coordinates of described metasurface structural unit, m is the numbering of described metasurface structural unit (x, y) in the structural database, λ _i is the i-th described target wavelength, c _i is the weight coefficient of the target wavelength λ _i ;

is the actual compensation phase of the metasurface structure unit (x, y) at the target wavelength _λi ,

is the theoretical phase that needs to be compensated for the metasurface structure unit (x, y) at the target wavelength _λi , and:

Wherein, n ₁ is the refractive index of the prism base (100), t _{x, y} is the thickness of the prism base (100) in the light propagation direction corresponding to the metasurface structure unit (x, y), n ₂ is the refractive index of the free-form surface prism (20), and T _{x, y} is the thickness of the free-form surface prism (20) in the light propagation direction corresponding to the metasurface structure unit (x, y). The compensator according to claim 3, wherein the target wavelengths include wavelengths in the visible light band, and the target wavelengths at least include wavelengths corresponding to yellow light, green light, red light, and purple light; A smaller value of the weight coefficients of the yellow light and the green light is not smaller than a larger value of the weight coefficients of the red light and the violet light. The compensator according to claim 1, characterized in that the compensating element (200) comprises a transparent base layer (210) and a plurality of nanostructures (220). The compensator according to claim 5, characterized in that, the nanostructure (220) is an upright structure with a central axis in the height direction, and the nanostructure (220) has a first symmetry plane and the same A second plane of symmetry perpendicular to the first plane of symmetry; The intersection line between the first symmetry plane and the second symmetry plane is the central axis, the intersection line between the first symmetry plane and the nanostructure (220), and the second symmetry plane The shape of the intersection line between the nanostructures (220) is the same. The compensator according to claim 6, wherein the nanostructure (220) is a cylinder or a regular prism with 4n side edges; Alternatively, the nanostructure (220) is a cylindrical or regular prism cavity structure with 4n side edges; Alternatively, the nanostructure (220) is an at least partially hollow cylinder or a regular prism with 4n side edges, and the hollow of the nanostructure (220) is a cylindrical cavity or a regular prism with 4n side edges. body structure; Alternatively, the nanostructure (220) is a cylindrical or regular prism cavity structure with 4n side edges, and the cavity structure is provided with a cylinder or a regular prism with 4n side edges. The compensator according to any one of claims 1-7, characterized in that, the compensating element (200) is arranged on the light incident side of the prism base (100); The incident direction of light directed at the metasurface structure unit, and the light rays sequentially passing through the metasurface structure unit, the prism base (100) and the free-form surface on the light exit side of the prism base (100) The outgoing directions behind the prisms (20) are the same. The compensator according to claim 8, characterized in that, the surface shape of the light-emitting side of the prism base (100) is the same as the surface shape of the side of the free-form surface prism (20) close to the prism base (100) match. The compensator according to claim 9, characterized in that, the surface shape of the light-emitting side of the prism base (100) is a concave free-form surface. The compensator according to claim 9, characterized in that the refractive index of the prism base (100) is the same as that of the free-form surface prism (20). The compensator according to any one of Claim 8, characterized in that, the side of the compensating element (200) away from the prism base (100) is provided with a tempered film and/or an anti-reflection film. An image display device, characterized by comprising: a free-form surface prism (20) and the compensator (10) according to any one of claims 1-12. The image display device according to claim 13, characterized in that, the free-form surface prism (20) comprises a transmissive surface (21), a transflective surface (22) and a beam-splitting surface (23); the beam-splitting surface (23) is A side near the light exit side of the prism base (100) of the compensator (10); The transmission surface (21) is used to transmit external imaging light, and the imaging light transmitted by the transmission surface (21) is directed to the transflective surface (22); The transflective surface (22) is used to totally reflect the imaging light transmitted by the transmissive surface (21) to the spectroscopic surface (23); The light splitting surface (23) is used to reflect the imaging light totally reflected by the transflective surface (22) to the transflective surface (22); The transflective surface (22) is also used for transmitting the imaging light reflected by the light splitting surface (23). The compensator (10) according to claim 14, characterized in that the transflective surface (22) is a concave spherical surface. The image display device according to claim 14, characterized in that, the transmittance ratio of the dichroic surface (23) is not less than (I _max -I ₀ )/I ₀ ; wherein, I _max is the ratio of the external imaging light The maximum brightness, I ₀ is the maximum brightness required for imaging. The image display device according to any one of claims 13-16, further comprising an image source (30); The image source (30) is used for emitting imaging light directed to the free-form surface prism (20). A near-eye projection display device, characterized by comprising the image display device according to any one of claims 13-17. A preparation method of a compensator, characterized in that it comprises: setting an isolation layer (2) on the temporary base (1); setting a transparent base layer (210) on the side of the isolation layer (2) away from the temporary base (1); A structural layer (3) is arranged on the side of the transparent base layer (210) away from the isolation layer (2); Structuring a plurality of nanostructures (220) on the structural layer (3); removing the isolation layer (2), transferring the separated transparent base layer (210) and a plurality of nanostructures (220) to one side of the prism base (100) to make the compensator; Wherein, the metasurface structure unit comprising the nanostructure (220) is used to compensate the phase of the light passing through the metasurface structure unit; The outgoing directions after passing through the metasurface structure unit, the prism substrate (100) and the free-form surface prism (20) on the light exit side of the prism substrate (100) are the same. The preparation method according to claim 19, characterized in that, Before the removal of the isolation layer (2), it also includes: setting a transfer layer (4) on the surface of the nanostructure (220); The transfer of the separated transparent base layer (210) and a plurality of nanostructures (220) to the light incident side of the prism base (100) includes: The separated transparent base layer (210), the nanostructure (220) and the transfer layer (4) are transferred to the light incident side of the prism base (100), and the transparent base layer (210) is pasted one side of the prism base (100); and The transfer layer (4) is removed. The preparation method according to claim 19, characterized in that, setting the transparent base layer (210) on the side of the isolation layer (2) away from the temporary base (1) comprises: The transfer layer (4) is arranged on the side of the isolation layer (2) away from the temporary substrate (1), and then the transfer layer (4) is arranged on the side away from the isolation layer (2). transparent base layer (210); The transfer of the separated transparent base layer (210) and a plurality of nanostructures (220) to the light incident side of the prism base (100) includes: transferring the separated transparent base layer (210), the nanostructure (220) and the transfer layer (4) to the light incident side of the prism substrate (100), and bonding the nanostructure (220) one side of the prism base (100); and The transfer layer (4) is removed.

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