Metasurface speckle projector and depth detection device

Abstract

The invention provides a metasurface type speckle projector and depth detection equipment, which can realize a speckle projection function based on a light source array by using a metasurface and avoid the common problem of zero-order bright spots or relatively strong background light when a diffractive optical element is used. The metasurface type speckle projector comprises a light source array used for emitting a plurality of conical light beams arranged in an array; the light modulation element has positive focal power, is arranged on the light emitting side of the light source array and is used for collecting the conical light beams from the light source array; and the metasurface element is arranged on one side, far away from the light source array, of the light modulation element and is used for regulating and controlling the light beams gathered by the light modulation element so as to form a plurality of collimated light beams projected towards different directions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of speckle projection, in particular to a metasurface speckle projector and a depth detection device. BACKGROUND

[0002] The speckle projector is a signal emitting element for measuring in three-dimensional space; whether it is based on time flight (TOF) or based on structured light triangulation, it needs to project the signal light to the specified direction in space to form a dot array on the target object. Generally speaking, when the speckle projector is used for time flight to measure the depth, different positions of the target object will be illuminated in time sequence; and when the speckle projector is used for structured light triangulation, different positions of the target object will be illuminated at the same time by the entire speckle dot array. In other words, the two speckle projectors applied in time flight measurement and structured light triangulation are basically similar in optical structure, because the time sequence control mainly relies on the circuit system and is irrelevant to the optical system structure.

[0003] According to the optical system structure, the existing speckle projectors are mainly divided into two types: the first type of speckle projector is configured with a single high-power coherent light source, and the light beam emitted by the coherent light source first passes through the beam expansion and collimation structure, and then is diffracted by the diffractive optical element (DOE) to form a diffractive speckle on the target object; the second type of speckle projector is configured with a light source array, and since the light source array already has a specific form of speckle pattern, projecting and imaging it can obtain the speckle pattern on the target object; at the same time, in order to increase the number of speckle dots, multiple diffraction can be used to copy the speckle pattern, so as to increase the number of speckle dots by N*M times, where N and M are the total diffraction order numbers in the horizontal and vertical directions respectively.

[0004] For the second type of speckle projector described above, the cone-shaped light beams emitted by the light source array will become parallel light beams after passing through the projection lens, and the propagation directions of the parallel light beams corresponding to the light sources at different positions of the light source array are different; further, after passing through the diffractive optical element (such as a grating), the parallel light beams will produce multiple diffraction orders, that is, in addition to propagating in the original direction, the parallel light beams will also be copied to the deflection direction due to the diffraction effect; in other words, for a single light source in the light source array, multiple diffraction spots will be generated at a distance after passing through the projection lens and the diffractive optical element.

[0005] However, on one hand, due to process limitations, the diffractive optical element generally has the problem of strong zero-order bright spots or background light, and the energy distribution of each diffraction order is uneven; although the microstructure of the diffractive optical element can be optimized to balance the energy of each order, the optimization design process of the microstructure of the diffractive optical element seriously depends on expensive commercial software, and a computer program also needs to be written to assist optimization, and the whole design process is not intuitive and the interpretability of the design scheme is poor. On the other hand, the diffractive optical element generally does not bear optical power, and if it is designed to bear optical power, the design freedom will be further limited, it is difficult to balance the energy distribution of each diffraction order, and the design difficulty is greatly increased. SUMMARY

[0006] An advantage of the present application is to provide a metasurface speckle projector and depth detection device which can use metasurfaces to realize speckle projection based on a light source array, avoiding the problem of strong zero-order bright spots or background light commonly existing when using diffractive optical elements.

[0007] Another advantage of the present application is to provide a metasurface speckle projector and depth detection device, wherein in one embodiment of the present application, the metasurface speckle projector can realize multi-directional projection function by multiplexing different regions of the metasurface, and has better design flexibility than diffractive optical elements.

[0008] Another advantage of the present application is to provide a metasurface speckle projector and depth detection device, wherein in one embodiment of the present application, the metasurface speckle projector can realize energy distribution in each projection direction by adjusting the area size of each region, and has high design freedom.

[0009] Another advantage of the present application is to provide a metasurface speckle projector and depth detection device, wherein in one embodiment of the present application, the metasurface speckle projector can use highly compatible metasurfaces and light source array processing technology to greatly reduce production costs.

[0010] Another advantage of the present application is to provide a metasurface speckle projector and depth detection device, wherein in order to achieve the above-mentioned purpose, expensive materials or complex structures are not required in the present application. Therefore, the present application successfully and effectively provides a solution, not only providing a simple metasurface speckle projector and depth detection device, but also increasing the practicability and reliability of the metasurface speckle projector and depth detection device.

[0011] In order to achieve the above-mentioned at least one advantage or other advantages and purposes of the present application, the present application provides a metasurface speckle projector, comprising:

[0012] an array of light sources configured to emit a plurality of cone beams arranged in an array;

[0013] a light modulating element having positive focal power disposed on a light emitting side of the array of light sources configured to converge the cone beams from the array of light sources; and

[0014] a metasurface element disposed on a side of the light modulating element distal to the array of light sources configured to steer the light beams converged by the light modulating element to form a plurality of collimated beams projected in different directions.

[0015] In an embodiment of the present application, the metasurface element has a plurality of metasurface regions corresponding to the plurality of projection directions one-to-one.

[0016] In an embodiment of the present application, the plurality of metasurface regions are arranged in an array on a side surface of the metasurface element proximal to the light modulating element; and the projection direction corresponding to each of the metasurface regions is consistent with the orientation of the metasurface region on the metasurface element.

[0017] In an embodiment of the present application, the plurality of metasurface regions are arranged in a 2*2 array or a 3*3 array.

[0018] In an embodiment of the present application, the light deflection capability of each of the metasurface regions satisfies the relationship:

[0019]

[0020] wherein n1 and θ1 represent the refractive index and the incident angle on the incident side of the metasurface region respectively; n2 and θ2 represent the refractive index and the exit angle on the exit side of the metasurface region respectively; λ represents the wavelength; and dφ / dr represents the phase gradient.

[0021] In an embodiment of the present application, the phase gradient of each of the metasurface regions on the metasurface element is different.

[0022] In an embodiment of the present application, the total phase distribution of the metasurface element satisfies the relationship: φ2(x, y) = φ b (x, y) + φ i，j (x, y);

[0023] wherein φ2(x, y) represents the total phase factor of the metasurface element; φ b (x, y) represents the aberration compensation factor of the metasurface element; and φ i，j (x, y) represents the tilt phase factor added according to the projection direction, wherein i and j represent the horizontal coordinate and the vertical coordinate of each of the metasurface regions on the metasurface element respectively.

[0024] In an embodiment of the present application, the metasurface element is periodically arranged with nano-pillars of different sizes or different structures in different metasurface regions.

[0025] In an embodiment of the present application, each of the nano-pillars has at least four symmetry axes.

[0026] In an embodiment of the present application, a side surface of the metasurface element distal to the light modulation element is planar.

[0027] In an embodiment of the present application, the light modulation element is selected from one of a refractive lens, a diffractive optical element, and a metasurface element.

[0028] In an embodiment of the present application, a side surface of the light modulation element proximal to the light source array is a metasurface, and a side surface of the light modulation element distal to the light source array is planar.

[0029] According to another aspect of the present application, the present application further provides a depth probing device, comprising:

[0030] The metasurface speckle projector as described above is used to project signal light to a target object to form a speckle pattern; and

[0031] A receiving module is correspondingly arranged on a side of the metasurface speckle projector, and is used to receive light signals reflected back by the target object to obtain depth information. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a structural schematic diagram of a metasurface speckle projector according to an embodiment of the present application;

[0033] Figure 2 shows a schematic diagram of a projection light path of an on-axis light emitting point in a metasurface speckle projector according to the above embodiment of the present application;

[0034] Figure 3 shows a schematic diagram of a projection light path of an off-axis light emitting point in a metasurface speckle projector according to the above embodiment of the present application;

[0035] Figure 4 shows a first example of a metasurface element in a metasurface speckle projector according to the above embodiment of the present application;

[0036] Figure 5 shows a second example of a metasurface element in a metasurface speckle projector according to the above embodiment of the present application;

[0037] Figure 6 shows a schematic diagram of nano-pillar arrangement of a metasurface region in a metasurface element according to the above embodiment of the present application.

[0038] Main element symbol explanation: 1, super-surface speckle projector; 10, light source array; 20, light modulation element; 21, super-surface; 22, plane; 30, super-surface element; 300, super-surface area; 31, nanocolumn.

[0039] The above main element symbol explanation further details the present application in combination with the drawings and the specific embodiments. DETAILED DESCRIPTION

[0040] The following description is provided to enable those skilled in the art to carry out the application. The preferred embodiments in the following description are only examples and other obvious modifications can be made by those skilled in the art. The basic principles defined in the following description can be applied to other embodiments, modifications, improvements, equivalents and other technical solutions without departing from the spirit and scope of the present application.

[0041] Those skilled in the art should understand that in the disclosure of the present application, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the above terms cannot be understood as a limitation of the present application.

[0042] In the present application, the term "one" in the claims and the specification should be understood as "one or more", that is, in one embodiment, the number of one element can be one, and in another embodiment, the number of the element can be multiple. Unless it is explicitly shown in the disclosure of the present application that the number of the element is only one, the term "one" cannot be understood as unique or single, and the term "one" cannot be understood as a limitation on the number.

[0043] In the description of the present application, it should be understood that "first", "second", etc. are only for the purpose of description and cannot be understood as indicating or implying relative importance. In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, "connected", "connected" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through a medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, different embodiments or examples described in the specification and the features of different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0045] In view of the fact that the existing speckle projector not only generally has the problem of strong zero-order bright speckle or background light when forming a speckle array by using the diffraction effect of a diffractive optical element, but also has the problem of uneven energy distribution of each diffraction order, and the diffractive optical element generally does not bear optical power, even if it can be designed to bear optical power, but it will further limit the design freedom, it is difficult to balance the energy distribution of each diffraction order, and it greatly increases the design difficulty. Therefore, the present application creatively proposes a metasurface speckle projector and a depth detection device, which can use a metasurface to realize a speckle projection function based on a light source array, avoiding the problem of strong zero-order bright speckle or background light generally existing when using a diffractive optical element.

[0046] Specifically, referring to the drawings of the specification of the present application Figures 1 to 6 , according to one embodiment of the present application, a depth detection device can include a metasurface speckle projector 1 and a receiving module (not shown in the figure); the metasurface speckle projector 1 is used to project signal light to a target object to form a speckle dot array; the receiving module is correspondingly arranged on one side of the metasurface speckle projector 1, and is used to receive the light signal reflected back by the target object to obtain depth information. It can be understood that the depth detection device mentioned in the present application can be implemented as a TOF camera or a structured light camera, which only needs to rely on the corresponding control of the projection timing of the signal light, and the present application will not be described again.

[0047] More specifically, as Figures 1 to 3 shown, the metasurface speckle projector 1 can include a light source array 10, a light modulation element 20 with positive optical power, and a metasurface element 30. The light source array 10 is used to emit a plurality of cone-shaped light beams arranged in an array. The light modulation element 20 is arranged on the light-emitting side of the light source array 10, and is used to converge the cone-shaped light beams from the light source array 10. The metasurface element 30 is arranged on the side of the light modulation element 20 away from the light source array 10, and is used to regulate the light beams converged by the light modulation element 20 to form a plurality of collimated light beams projected in different directions.

[0048] Thus, the light beams emitted by the light source array 10 are first converged after passing through the light modulation element 20, and then further converged into a collimated light beam after passing through the metasurface element 30, and are projected in multiple directions to form a speckle dot array on the target object. In particular, as shown in Figure 2 , for the on-axis light emitting points in the light source array 10, the final multiple projection directions of the emitted light are symmetrically distributed relative to the optical axis; and as shown in Figure 3 , for the off-axis light emitting points in the light source array 10, the final multiple projection directions of the emitted light are distributed on both sides of the conjugate beam of the off-axis light emitting point.

[0049] It is worth noting that the metasurface speckle projector 1 of the present application uses a metasurface element 30 to replace the diffractive optical element in the existing speckle projector, so as to realize the speckle projection function based on the light source array 10 while avoiding the problem of strong background light or zero-order bright spot commonly existing when using a diffractive optical element; at the same time, since the processing technology of the metasurface in the metasurface element 30 is highly compatible with the processing technology of the light source array 10, the metasurface speckle projector 1 of the present application can greatly reduce the production cost. It can be understood that the existing speckle projector has a high production cost due to the difficulty in compatibility between the production process of the light source array and the production process of the lens or diffractive optical element, which belong to independent production lines.

[0050] Exemplarily, the light source array 10 can be but not limited to a VCSEL (Vertical Cavity Surface Emitting Laser) array or an LED (Light Emitting Diode) array; in other words, the light source array 10 has a plurality of light emitting elements arranged in an array, each light emitting element being used to emit a cone-shaped light beam, thereby emitting a plurality of cone-shaped light beams arranged in an array.

[0051] Optionally, as shown in Figures 1 to 5 , the metasurface element 30 has a plurality of metasurface regions 300 corresponding to the multiple projection directions one by one; in other words, the metasurface on the metasurface element 30 is divided into a plurality of metasurface regions 300, and the number of the metasurface regions 300 is equal to the number of the projection directions of the metasurface speckle projector 1, so that the multi-directional projection function of the metasurface speckle projector 1 is essentially realized by multiplexing different regions of the metasurface. It can be understood that, compared with the existing speckle projector which realizes multi-directional projection by using multi-order diffraction of diffractive optical elements, the projection directions of different metasurface regions 300 in the metasurface element 30 of the present application can be designed flexibly, and the design freedom is much greater than the existing diffractive optical element scheme.

[0052] Optionally, as shown in Figure 1 , Figure 4 , and Figure 5As shown, multiple metasurface regions 300 are arrayed on one side of the metasurface element 30 near the light modulation element 20, and the projection direction corresponding to each metasurface region 300 is consistent with the orientation of the metasurface region 300 on the metasurface element 30. This is to further converge the light beam converged by the light modulation element 20 to form a collimated beam, while ensuring that the multiple collimated beams formed by the conical beams from the same light-emitting element after being modulated by different metasurface regions 300 do not cross each other. This helps to simplify the reuse design of the metasurface regions 300, avoid the multiple collimated beams formed by the conical beams from different light-emitting elements after being modulated by different metasurface regions 300 from overlapping at the target object, and better form a speckle array on the target object.

[0053] Exemplarily, in the first example of this application, such as Figure 4 As shown, the multiple metasurface regions 300 on the metasurface element 30 can be arranged in a 3*3 array; correspondingly, the metasurface element 30 has nine projection directions. For example, the metasurface region 300 located at the center of the metasurface element 30 can be denoted as region [0,0], and its corresponding projection direction is directly forward, i.e., projecting towards the front; the metasurface region 300 located on the upper side of the metasurface element 30 can be denoted as region [0,1], and its corresponding projection direction is directly upward, i.e., projecting towards the top; the metasurface region 300 located on the lower side of the metasurface element 30 can be denoted as region [0,-1], and its corresponding projection direction is directly downward, i.e., projecting towards the bottom; the metasurface region 300 located on the left side of the metasurface element 30 can be denoted as region [-1,0], and its corresponding projection direction is directly to the left, i.e., projecting towards the left; the metasurface region 300 located on the right side of the metasurface element 30 can be denoted as region [...]. [1,0], whose corresponding projection direction is directly to the right, that is, projecting towards the right; the metasurface region 300 located at the upper right corner of the metasurface element 30 can be denoted as region [1,1], whose corresponding projection direction is upper right, that is, projecting towards the upper right; the metasurface region 300 located at the lower right corner of the metasurface element 30 can be denoted as region [1,-1], whose corresponding projection direction is lower right, that is, projecting towards the lower right; the metasurface region 300 located at the upper left corner of the metasurface element 30 can be denoted as region [-1,1], whose corresponding projection direction is upper left, that is, projecting towards the upper left; the metasurface region 300 located at the lower left corner of the metasurface element 30 can be denoted as region [-1,-1], whose corresponding projection direction is lower left, that is, projecting towards the lower left.

[0054] Furthermore, in the second example of this application, such as Figure 5As shown, the plurality of super surface regions 300 on the super surface element 30 can also be arranged in a 2*2 array; correspondingly, the super surface element 30 has four projection directions, i.e., the super surface region 300 on the upper right corner of the super surface element 30 can be recorded as region [1, 1], and the corresponding projection direction is the upper right, i.e., projection towards the upper right; the super surface region 300 on the lower right corner of the super surface element 30 can be recorded as region [1, -1], and the corresponding projection direction is the lower right, i.e., projection towards the lower right; the super surface region 300 on the upper left corner of the super surface element 30 can be recorded as region [-1, 1], and the corresponding projection direction is the upper left, i.e., projection towards the upper left; the super surface region 300 on the lower left corner of the super surface element 30 can be recorded as region [-1, -1], and the corresponding projection direction is the lower left, i.e., projection towards the lower left.

[0055] It is worth noting that the light deflection capability of each super surface region 300 in the super surface element 30 of the present application satisfies the relationship:

[0056]

[0057] In the formula, n1 and θ1 represent the refractive index and the incidence angle of the incident side of the super surface region 300, respectively; n2 and θ2 represent the refractive index and the exit angle of the exit side of the super surface region 300, respectively; λ represents the wavelength; dφ / dr represents the phase gradient. It can be understood that the phase gradient referred to in the present application refers to the rate of change of phase in the gradient direction.

[0058] Optionally, each super surface region 300 in the super surface element 30 has a different phase gradient. In this way, the super surface regions 300 located at different positions on the super surface element 30 are designed to have different phase gradients, which can achieve targeted adjustment of the light beam shape in order to meet the needs of the speckle array.

[0059] In addition, the total phase distribution of the super surface element 30 satisfies the relationship: φ2(x, y) = φ b (x, y) + φ i，j (x, y);

[0060] In the formula, φ2(x, y) represents the total phase factor of the super surface element 30; φ b (x, y) represents the aberration compensation factor of the super surface element 30; φ i，j (x, y) represents the tilt phase factor added according to the projection direction, where i and j represent the horizontal coordinate and vertical coordinate of each super surface region 300 on the super surface element 30, respectively. It can be understood that i = 1, j = -1 in the super surface region 300 on the lower right corner of the super surface element 30, i.e., recorded as region [1, -1].

[0061] According to the above embodiments of the present application, as shown in Figure 6 The metasurface element 30 is periodically arranged with nano-pillars 31 of different sizes or different structures in different metasurface regions 300 to meet the requirements of different metasurface regions 300 in different projection directions.

[0062] Optionally, each nano-pillar 31 has at least four symmetry axes. For example, the nano-pillar 31 can be, but is not limited to, one or more of a cylindrical pillar, a square pillar, a cross pillar, and a hexagonal pillar.

[0063] It is worth noting that the energy distribution of the metasurface element 30 in each projection direction can be achieved by adjusting the area size of each metasurface region 300 on the metasurface element 30, with a high degree of freedom. Preferably, the area of each metasurface region 300 on the metasurface element 30 is equal to ensure that the energy distribution of the metasurface element 30 in each projection direction remains consistent.

[0064] In addition, the side surface of the metasurface element 30 away from the light modulating element 20 is implemented as a plane, which not only simplifies the design of the metasurface region 300, but also ensures that the outermost surface of the metasurface speckle projector 1 remains flat for cleaning and to avoid dirt adhesion.

[0065] According to the above embodiments of the present application, as shown in Figure 1 The light modulating element 20 can be, but is not limited to, another metasurface element, and the light deflection capability of the light modulating element 20 also satisfies the relationship:

[0066]

[0067] In the formula, n1 and θ1 represent the refractive index and the incidence angle of the incident side of the light modulating element 20, respectively; n2 and θ2 represent the refractive index and the exit angle of the exit side of the light modulating element 20, respectively; λ represents the wavelength; and dφ / dr represents the phase gradient.

[0068] Optionally, as shown in Figure 1 The side surface of the light modulating element 20 close to the light source array 10 is a metasurface 21, and the side surface of the light modulating element 20 away from the light source array 10 is a plane 22; in other words, the side surface of the light modulating element 20 close to the light source array 10 is provided with micro-nano structures to better converge the cone-shaped light beam emitted via the light source array 10.

[0069] It is worth noting that in other examples of the present application, the light modulation element 20 can also be implemented as a refractive lens or a diffractive optical element, as long as it can achieve the converging of the cone-shaped light beams emitted via the light source array 10, and the present application will not repeat it here.

[0070] In addition, the metasurface element 30 of the present application can be, but is not limited to, fabricated on a light-transmitting substrate by a photolithography or nanoimprint process. For example, when the nanoimprint process is used to fabricate the metasurface optical structure: first, photoresist is coated on the surface of the light-transmitting substrate; then, a mold is used for imprinting, and after curing by light / heat, the mold is demolded; then, after removing the residual photoresist, the light-transmitting substrate is etched; finally, all the photoresist is removed to fabricate the metasurface optical structure on the light-transmitting substrate. Alternatively, when the photolithography process is used to fabricate the metasurface optical structure: first, photoresist is coated on the surface of the light-transmitting substrate; then, it is exposed and developed to form a photoresist mask; then, the light-transmitting substrate is etched; finally, all the photoresist is removed to fabricate the metasurface optical structure on the light-transmitting substrate.

[0071] The technical features of the above embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present disclosure.

[0072] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application.

Claims

1. A metasurface speckle projector, characterized in that, include: A light source array used to emit multiple conical beams arranged in an array; A light modulation element with positive optical power is disposed on the light-emitting side of the light source array to converge the conical light beam from the light source array; as well as A metasurface element is disposed on the side of the light modulation element away from the light source array, and is used to modulate the light beam converged by the light modulation element to form multiple collimated light beams projected in different directions.

2. The metasurface speckle projector according to claim 1, characterized in that, The metasurface element has multiple metasurface regions that correspond one-to-one with multiple projection directions.

3. The metasurface speckle projector according to claim 2, characterized in that, Multiple metasurface regions are arranged in an array on the surface of the metasurface element near the optical modulation element; and the projection direction corresponding to each metasurface region is consistent with the orientation of the metasurface region on the metasurface element.

4. The metasurface speckle projector according to claim 3, characterized in that, The multiple metasurface regions are distributed in a 2*2 array or a 3*3 array.

5. The metasurface speckle projector according to claim 2, characterized in that, The light deflection capability of each of the metasurface regions satisfies the following relationship: In the formula, n1 and θ1 represent the refractive index and incident angle of the incident side of the metasurface region, respectively; n2 and θ2 represent the refractive index and exit angle of the exit side of the metasurface region, respectively; λ represents the wavelength; and dφ / dr represents the phase gradient.

6. The metasurface speckle projector according to claim 5, characterized in that, Each of the metasurface regions on the metasurface element has a different phase gradient.

7. The metasurface speckle projector according to claim 2, characterized in that, The overall phase distribution of the metasurface element satisfies the following relationship: φ2(x,y)=φ b (x,y)+φ i，j (x,y); In the formula, φ2(x, y) represents the total phase factor of the metasurface element; φ b (x, y) represents the aberration compensation factor of the metasurface element; φ i，j (x, y) represents the tilt phase factor added according to the projection direction, where i and j represent the abscissa and ordinate of each metasurface region on the metasurface element, respectively.

8. The metasurface speckle projector according to claim 2, characterized in that, The metasurface element has nanopillars of different sizes or structures arranged periodically in different regions of the metasurface; each nanopillar has at least four axes of symmetry.

9. The metasurface speckle projector according to any one of claims 1 to 8, characterized in that, The surface of the metasurface element that is away from the optical modulation element is planar.

10. The metasurface speckle projector according to any one of claims 1 to 8, characterized in that, The optical modulation element is selected from one of the following: a refractive lens, a diffractive optical element, and a metasurface element.

11. A depth detection device, characterized in that, include: The metasurface speckle projector as described in any one of claims 1 to 10 is used to project signal light onto a target object to form a speckle array; and A receiving module is correspondingly disposed on one side of the metasurface speckle projector to receive the light signal reflected back by the target object to obtain depth information.

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