Metasurface speckle projector and depth detection device

Abstract

The utility model 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 problem of zero-order bright spots or stronger background light generally existing 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 utility model relates to the technical field of speckle projection, in particular to a metasurface type speckle projector and a depth detection device. Background Technique

[0002] The speckle projector is a signal emitting element for measurement in the three-dimensional space scale. Whether it is based on the time-of-flight method (TOF, Time of Flight) or the structured light triangulation method, the speckle projector is required to project the signal light to a specified orientation in space to form a dot matrix on the target object. Generally speaking, when the speckle projector is used for depth measurement by the time-of-flight method, different positions of the target object will be illuminated by the light spot in sequence; when the speckle projector is used for structured light triangulation, different positions of the target object will be illuminated by the entire speckle dot matrix simultaneously. In other words, the two speckle projectors applied in the time-of-flight method measurement and the structured light triangulation are basically similar in optical structure because the timing control is mainly realized by the circuit system and has nothing to do with the optical system structure.

[0003] According to the division of 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. The light beam emitted by the coherent light source first passes through an expanding and collimating structure and then is diffracted by a diffractive optical element (DOE) to form diffractive speckles on the target object; the second type of speckle projector is configured with a light source array. Since the light source array already has a specific form of speckle pattern, projecting and imaging it can obtain a speckle pattern on the target object. At the same time, usually in order to increase the number of speckles, the speckle pattern can be replicated by multi-level diffraction to increase the number of speckles by N*M times, where N and M are the total diffraction orders in the horizontal and vertical directions respectively.

[0004] For the above-mentioned second type of speckle projector, the conical light beam emitted by the light source array will become a parallel light beam after passing through the projection lens, and the propagation directions of the parallel light beams corresponding to the light sources at different positions on the light source array are different. Furthermore, after these parallel light beams pass through a diffractive optical element (such as a grating, etc.), multiple diffraction orders will be generated, that is, in addition to propagating along the original direction, the parallel light beams will also be replicated to propagate in the deflected 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 in the distance after passing through the projection lens and the diffractive optical element.

[0005] However, on the one hand, limited by process constraints, diffractive optical elements generally have problems such as strong zero-order bright spots or background light, and the energy distribution of each diffractive order is uneven; although in order to balance the energy of each order, it can be achieved by optimizing the microstructure of the diffractive optical element, but the process of optimizing the design of the microstructure of the diffractive optical element heavily relies on expensive commercial software and also requires writing computer programs to assist in optimization. The entire design process is not intuitive and the interpretability of the design scheme is poor. On the other hand, diffractive optical elements generally do not bear optical power. If they are designed to bear optical power, it will further limit the design freedom, making it difficult to balance the energy distribution of each diffractive order and greatly increasing the design difficulty. Summary of the Utility Model

[0006] One advantage of the present utility model is to provide a metasurface-based speckle projector and depth detection device, which can use a metasurface to achieve the speckle projection function based on a light source array, avoiding the problem of strong zero-order bright spots or background light that generally exists when using diffractive optical elements.

[0007] Another advantage of the present utility model is to provide a metasurface-based speckle projector and depth detection device. In one embodiment of the present utility model, the metasurface-based speckle projector can achieve the projection function in multiple directions by multiplexing different regions of the metasurface, having better design flexibility compared with diffractive optical elements.

[0008] Another advantage of the present utility model is to provide a metasurface-based speckle projector and depth detection device. In one embodiment of the present utility model, the metasurface-based speckle projector can adjust the energy distribution in each projection direction by adjusting the area size of each region, having a high degree of design freedom.

[0009] Another advantage of the present utility model is to provide a metasurface-based speckle projector and depth detection device. In one embodiment of the present utility model, the metasurface-based speckle projector can utilize the highly compatible processing technology of the metasurface and the light source array to greatly reduce the production cost.

[0010] Another advantage of the present utility model is to provide a metasurface-based speckle projector and depth detection device. To achieve the above purposes, expensive materials or complex structures do not need to be adopted in the present utility model. Therefore, the present utility model successfully and effectively provides a solution, not only providing a simple metasurface-based speckle projector and depth detection device, but also increasing the practicability and reliability of the metasurface-based speckle projector and depth detection device.

[0011] To achieve at least one of the above advantages or other advantages and purposes of the present utility model, the present utility model provides a metasurface-based speckle projector, including:

[0012] A light source array for emitting a plurality of conical light beams arranged in an array;

[0013] An optical modulation element with positive optical power, which is arranged on the light-emitting side of the light source array for converging the conical light beams from the light source array; and

[0014] A metasurface element, which is arranged on the side of the optical modulation element away from the light source array for regulating the light beam converged by the optical modulation element to form a plurality of collimated light beams projected in different directions.

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

[0016] In an embodiment of the present application, a plurality of the metasurface regions are arranged in an array on the side surface of the metasurface element close to 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.

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

[0018] In an embodiment of the present application, the light deflection ability of each metasurface region satisfies the relational expression:

[0019]

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

[0021] In an embodiment of the present application, each metasurface region on the metasurface element has a different phase gradient.

[0022] In an embodiment of the present application, the total phase distribution of the metasurface element satisfies the relational expression:

[0023] φ2(x, y) = φ b (x, y) + φ i，j (x, y);

[0024] 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 an inclined phase factor added in the projection direction, where i and j respectively represent the abscissa and ordinate of each of the metasurface regions on the metasurface element.

[0025] In one embodiment of the present application, different-sized or differently-structured nanocolumns are periodically arranged in different metasurface regions of the metasurface element.

[0026] In one embodiment of the present application, each of the nanocolumns has at least four axes of symmetry.

[0027] In one embodiment of the present application, the surface of the metasurface element on the side away from the light modulation element is a plane.

[0028] In one 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.

[0029] In one embodiment of the present application, the surface of the light modulation element on the side close to the light source array is a metasurface, and the surface of the light modulation element on the side away from the light source array is a plane.

[0030] According to another aspect of the present application, the present application further provides a depth detection device, including:

[0031] Any one of the above-mentioned metasurface speckle projectors, configured to project signal light onto a target object to form a speckle pattern; and

[0032] A receiving module, correspondingly arranged on one side of the metasurface speckle projector, configured to receive the optical signal reflected back by the target object to obtain depth information. Description of the Drawings

[0033] Figure 1 is a schematic structural diagram of a metasurface speckle projector according to an embodiment of the present application;

[0034] Figure 2 shows a schematic projection light path diagram of a light-emitting point on the axis in the metasurface speckle projector according to the above embodiment of the present application;

[0035] Figure 3 shows a schematic projection light path diagram of a light-emitting point outside the axis in the metasurface speckle projector according to the above embodiment of the present application;

[0036] Figure 4 shows a first example of a metasurface element in the metasurface speckle projector according to the above embodiment of the present application;

[0037] Figure 5Shows a second example of the metasurface element in the metasurface speckle projector according to the above embodiments of the present application;

[0038] Figure 6 Shows a schematic diagram of the arrangement of nanocolumns in the metasurface region of the metasurface element according to the above embodiments of the present application.

[0039] Main element symbol description: 1, metasurface speckle projector; 10, light source array; 20, light modulation element; 21, metasurface; 22, plane; 30, metasurface element; 300, metasurface region; 31, nanocolumn.

[0040] The above main element symbol description further describes the present application in detail in conjunction with the accompanying drawings and specific embodiments. Specific embodiments

[0041] The following description is used to disclose the present utility model so that those skilled in the art can implement the present utility model. The preferred embodiments described below are only examples, and other obvious variations can be conceived by those skilled in the art. The basic principles defined in the following description can be applied to other implementation schemes, variant schemes, improvement schemes, equivalent schemes, and other technical schemes that do not depart from the spirit and scope of the present utility model.

[0042] Those skilled in the art should understand that in the disclosure of the present utility model, the orientation or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present utility model.

[0043] In the present utility model, the term "a" 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, while in other embodiments, the number of this element can be multiple. Unless it is clearly indicated in the disclosure of the present utility model that the number of this element is only one, the term "a" cannot be understood as being unique or single, and the term "a" cannot be understood as a limitation on the quantity.

[0044] In the description of the present utility model, it should be understood that terms such as "first", "second", etc. are only for descriptive purposes and cannot be construed as indicating or implying relative importance. In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, the terms "connected" and "joined" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through a medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0045] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. 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 utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0046] Considering that when the existing speckle projectors form a speckle array by utilizing the diffraction effect of the diffractive optical element, there are not only common problems such as strong zero-order bright spots or background light, but also uneven energy distribution in each diffraction order; at the same time, the diffractive optical element generally does not bear the optical power. Even if it can be designed to bear the optical power, it will further limit its design freedom, making it difficult to balance the energy distribution of each diffraction order and greatly increasing the design difficulty. Therefore, this application creatively proposes a metasurface-based speckle projector and a depth detection device, which can use the metasurface to achieve the speckle projection function based on the light source array, avoiding the common problems of strong zero-order bright spots or background light when using diffractive optical elements.

[0047] Specifically, referring to the accompanying drawings of this application Figures 1 to 6, according to an embodiment of the present application, a depth detection device is provided, which may 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 onto a target object to form a speckle pattern; the receiving module is correspondingly arranged on one side of the metasurface speckle projector 1, and is used to receive the optical 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, and only needs to rely on the circuit system to correspondingly control the projection timing of the signal light, which will not be elaborated in the present application.

[0048] More specifically, as Figures 1 to 3 shown, the metasurface speckle projector 1 may include a light source array 10, an optical modulation element 20 with positive optical power, and a metasurface element 30. The light source array 10 is used to emit a plurality of conical light beams arranged in an array. The optical modulation element 20 is arranged on the light emitting side of the light source array 10 and is used to converge the conical light beams from the light source array 10. The metasurface element 30 is arranged on the side of the optical modulation element 20 away from the light source array 10 and is used to regulate the light beams converged by the optical modulation element 20 to form a plurality of collimated light beams projected in different directions.

[0049] In this way, the light beams emitted by the light source array 10 are first converged after passing through the optical modulation element 20, and then further converged into collimated light beams after passing through the metasurface element 30, and are projected in multiple directions to form a speckle pattern on the target object. In particular, as Figure 2 shown, for the on-axis light emitting points in the light source array 10, the final multiple projection directions of the emitted light will be symmetrically distributed with respect to the optical axis; while as Figure 3 shown, 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 light beam of the off-axis light emitting points.

[0050] It should be noted that the metasurface speckle projector 1 of the present application uses the metasurface element 30 to replace the diffractive optical element in the existing speckle projector, so as to avoid the problem of strong zero-order bright spots or background light commonly existing when using diffractive optical elements while realizing the speckle projection function based on the light source array 10; at the same time, since the processing process of the metasurface in the metasurface element 30 is highly compatible with the processing process 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 projectors have a high production cost because the production process of the light source array is difficult to be compatible with the production process of the lens or diffractive optical element, and they belong to independent production lines respectively.

[0051] Exemplarily, the light source array 10 can be, but is not limited to, implemented as 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, and each light-emitting element is used to emit a conical beam, so as to emit a plurality of conical beams arranged in an array.

[0052] Optionally, as Figures 1 to 5 shown, the metasurface element 30 has a plurality of metasurface regions 300 corresponding one-to-one to a plurality of projection directions; 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-direction 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 projectors that use multi-level diffraction of diffractive optical elements to achieve multi-direction projection, the projection directions of different metasurface regions 300 in the metasurface element 30 of the present application can be flexibly designed, and its design freedom is much greater than the existing diffractive optical element solutions.

[0053] Optionally, as Figure 1 、 Figure 4 and Figure 5 shown, the plurality of metasurface regions 300 are arranged in an array on the side surface of the metasurface element 30 close to 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, so as to further converge the beam converged by the light modulation element 20 to form a collimated beam, while ensuring that the collimated beams formed by the conical beams from the same light-emitting element after being regulated by different metasurface regions 300 do not cross each other, which helps to simplify the multiplexing design of the metasurface regions 300, avoid the overlapping of the collimated beams formed by the conical beams from different light-emitting elements after being regulated by different metasurface regions 300 at the target object, and better form a speckle pattern on the target object.

[0054] Exemplarily, in the first example of the present application, as Figure 4As shown, the multiple metasurface regions 300 on the metasurface element 30 can be distributed in a 3×3 array; correspondingly, the metasurface element 30 has nine projection directions. For example, the metasurface region 300 at the center of the metasurface element 30 can be denoted as region [0, 0], and its corresponding projection direction is directly forward, that is, projecting forward; the metasurface region 300 on the upper side of the metasurface element 30 can be denoted as region [0, 1], and its corresponding projection direction is directly upward, that is, projecting upward; the metasurface region 300 on the lower side of the metasurface element 30 can be denoted as region [0, -1], and its corresponding projection direction is directly downward, that is, projecting downward; the metasurface region 300 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, that is, projecting to the left; the metasurface region 300 on the right side of the metasurface element 30 can be denoted as region [1, 0], and its corresponding projection direction is directly to the right, that is, projecting to the right; the metasurface region 300 at the upper right corner of the metasurface element 30 can be denoted as region [1, 1], and its corresponding projection direction is upper right, that is, projecting to the upper right; the metasurface region 300 at the lower right corner of the metasurface element 30 can be denoted as region [1, -1], and its corresponding projection direction is lower right, that is, projecting to the lower right; the metasurface region 300 at the upper left corner of the metasurface element 30 can be denoted as region [-1, 1], and its corresponding projection direction is upper left, that is, projecting to the upper left; the metasurface region 300 at the lower left corner of the metasurface element 30 can be denoted as region [-1, -1], and its corresponding projection direction is lower left, that is, projecting to the lower left.

[0055] In addition, in the second example of the present application, as Figure 5 shown, the multiple metasurface regions 300 on the metasurface element 30 can also be distributed in a 2×2 array; correspondingly, the metasurface element 30 has four projection directions, that is: the metasurface region 300 at the upper right corner of the metasurface element 30 can be denoted as region [1, 1], and its corresponding projection direction is upper right, that is, projecting to the upper right; the metasurface region 300 at the lower right corner of the metasurface element 30 can be denoted as region [1, -1], and its corresponding projection direction is lower right, that is, projecting to the lower right; the metasurface region 300 at the upper left corner of the metasurface element 30 can be denoted as region [-1, 1], and its corresponding projection direction is upper left, that is, projecting to the upper left; the metasurface region 300 at the lower left corner of the metasurface element 30 can be denoted as region [-1, -1], and its corresponding projection direction is lower left, that is, projecting to the lower left.

[0056] It should be noted that the light deflection ability of each metasurface region 300 in the metasurface element 30 of the present application satisfies the relational expression:

[0057]

[0058] In the formula, n1 and θ1 respectively represent the refractive index and the incident angle on the incident side of the metasurface region 300; n2 and θ2 respectively represent the refractive index and the exit angle on the exit side of the metasurface region 300; λ represents the wavelength; dφ / dr represents the phase gradient. It can be understood that the phase gradient mentioned in this application refers to the phase change rate in the gradient direction.

[0059] Optionally, each metasurface region 300 in the metasurface element 30 has a different phase gradient. In this way, the metasurface regions 300 located at different positions on the metasurface element 30 are designed with different phase gradients, which can achieve targeted adjustment of the beam shape to meet the requirements of the speckle pattern.

[0060] In addition, the total phase distribution of the metasurface element 30 satisfies the relational expression:

[0061] φ2(x, y) = φ b (x, y) + φ i，j (x, y);

[0062] In the formula, φ2(x, y) represents the total phase factor of the metasurface element 30; φ b (x, y) represents the aberration compensation factor of the metasurface element 30; φ i，j (x, y) represents the tilt phase factor added according to the projection direction, where i and j respectively represent the abscissa and ordinate of each metasurface region 300 on the metasurface element 30. It can be understood that for the metasurface region 300 located in the lower right corner of the metasurface element 30, i = 1 and j = -1, which is denoted as region [1, -1].

[0063] According to the above embodiments of the present application, as Figure 6 shown, the metasurface element 30 is periodically arranged with nano-columns 31 of different sizes or different structures in different metasurface regions 300 to meet the requirements of the corresponding projection directions for the metasurface regions 300 at different positions.

[0064] Optionally, each nano-column 31 has at least four symmetry axes. For example, the nano-column 31 can be implemented as, but not limited to, one or more of a cylindrical column, a square column, a cross column, and a hexagonal column.

[0065] It should be noted that the energy distribution of the metasurface element 30 in each projection direction can be achieved by adjusting the area sizes of the respective metasurface regions 300 on the metasurface element 30, which has a high degree of freedom. Preferably, the areas of the respective metasurface regions 300 on the metasurface element 30 are equal to ensure that the energy distribution of the metasurface element 30 in each projection direction is consistent.

[0066] In addition, the surface of the metasurface element 30 on the side away from the light modulation element 20 is implemented as a plane, which can not only simplify the design of the metasurface region 300, but also ensure that the outermost surface of the metasurface speckle projector 1 remains flat for cleaning to avoid dirt attachment.

[0067] According to the above embodiments of the present application, as Figure 1 shown, the light modulation element 20 can be, but is not limited to, implemented as another metasurface element, and the light deflection ability of the light modulation element 20 also satisfies the relationship:

[0068]

[0069] In the formula, n1 and θ1 respectively represent the refractive index and the incident angle on the incident side of the light modulation element 20; n2 and θ2 respectively represent the refractive index and the exit angle on the exit side of the light modulation element 20; λ represents the wavelength; dφ / dr represents the phase gradient.

[0070] Optionally, as Figure 1 shown, the surface of the light modulation element 20 on the side close to the light source array 10 is a metasurface 21, and the surface of the light modulation element 20 on the side away from the light source array 10 is a plane 22; in other words, the surface of the light modulation element 20 on the side close to the light source array 10 is provided with micro-nano structures to better converge the conical light beam emitted by the light source array 10.

[0071] It should be noted 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 converging the conical light beam emitted by the light source array 10, which will not be elaborated herein.

[0072] In addition, the metasurface element 30 of the present application can, but is not limited to, fabricate the metasurface optical structure on the light-transmitting substrate through lithography or nanoimprinting processes. For example, when fabricating the metasurface optical structure using the nanoimprinting process: First, apply a photoresist on the surface of the light-transmitting substrate; then, use a mold for imprinting and demold after curing by light / heat, etc.; next, after removing the residual photoresist, etch the light-transmitting substrate; finally, remove all the photoresist to fabricate the metasurface optical structure on the light-transmitting substrate. Alternatively, when fabricating the metasurface optical structure using the lithography process: First, apply a photoresist on the surface of the light-transmitting substrate; then, perform exposure and development to form a photoresist mask; next, etch the light-transmitting substrate; finally, remove all the photoresist to fabricate the metasurface optical structure on the light-transmitting substrate.

[0073] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0074] The above embodiments only represent several implementation manners of the present utility model, and the description thereof is relatively specific and detailed. However, it should not be construed as a limitation on the scope of the utility model patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several modifications and improvements can still be made, and these all belong to the protection scope of the present utility model.

Claims

1. A metasurface speckle projector, characterized in that: include: A light source array, used for emitting a plurality of conical light beams arranged in an array; A light modulation element with positive optical power, arranged on the light-emitting side of the light source array, for converging the cone-shaped light beam from the light source array; as well as The metasurface element is arranged on a side of the light modulation element away from the light source array, and is used to regulate the light beam gathered by the light modulation element to form a plurality of collimated light beams projected in different directions.

2. The metasurface speckle projector according to claim 1, characterized in that: The metasurface element has a plurality of metasurface regions corresponding one-to-one to a plurality of projection directions.

3. The metasurface speckle projector according to claim 2, characterized in that: A plurality of metasurface area arrays are arranged on a side surface of the metasurface element close to the light modulation element; and the projection direction corresponding to each metasurface area is consistent with the position of the metasurface area on the metasurface element.

4. The metasurface speckle projector according to claim 3, characterized in that: The plurality of super surface 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 metasurface region satisfies the relationship: In the formula, n1 and θ1 represent the refractive index and the incident angle of the incident side of the metasurface region, respectively; n2 and θ2 represent the refractive index and the exit angle of the exit side of the metasurface region, respectively; λ represents the wavelength; 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 total phase distribution of the metasurface element satisfies the relationship: φ2(x,y)=φ b (x,y)+φ i，j (x,y); 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; φ i，j (x, y) represents the tilt phase factor added according to the projection direction, wherein i and j represent the abscissa and ordinate of each of the metasurface regions on the metasurface element, respectively.

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

9. The metasurface speckle projector according to any one of claims 1 to 8, characterized in that: A surface on one side of the metasurface element away from the light modulation element is a plane.

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

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

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