WO2021258335A1

WO2021258335A1 - Diffractive optical element, tof depth sensor, and optical system and device

Info

Publication number: WO2021258335A1
Application number: PCT/CN2020/098107
Authority: WO
Inventors: 鞠晓山; 冯坤亮; 李宗政
Original assignee: 欧菲光集团股份有限公司; 欧菲微电子技术有限公司
Priority date: 2020-06-24
Filing date: 2020-06-24
Publication date: 2021-12-30

Abstract

A diffractive optical element (100), a TOF depth sensor, and an optical system and device. According to the diffractive optical element (100), a plurality of island-shaped structures are formed on a substrate (10), and the projection of each island-shaped structure (20) on the substrate (10) covers at least four pixel regions (110), thereby ensuring that a microstructure of the diffractive optical element (100) does not have an isolated island structure, i.e., ensuring that the microstructure of the diffractive optical element (100) does not have a particularly small bulge structure, thus facilitating large-scale replication by means of a nanoimprint lithography technology. The diffractive optical element (100) inhibits generation of an isolated island structure, i.e., ensuring the size of each island-shaped structure (20), and further ensuring that when the island-shaped structures (20) are demolded, the island-shaped structures (20) are not prone to being pulled out, and an isolated island structure is not prone to remaining.

Description

Diffractive optical element, TOF depth sensor, optical system and device

Technical field

This application relates to the technical field of optical element design, in particular to a diffractive optical element, TOF depth sensor, optical system and device.

Background technique

Diffractive optics are used in many applications such as optical storage, processing, sensing, and communication. Diffractive Optical Element (DOE) is a thin phase element that operates with the help of interference and diffraction to generate arbitrary distribution of light or help design in an optical system. The DOE design can be applied with lasers (for example, high-power lasers). In addition, DOE is used for waveshaping. For example, DOE can be used as a multi-spot beam splitter in beam shaping and beam profile modification. DOE can transform a single laser beam into light patterns of various simple or complex structures. DOE presents endless possibilities in different application fields. Although standard refractive optical elements such as mirrors and lenses are often bulky, expensive, and limited to specific uses, DOEs are generally lightweight, compact, easy to replicate, and capable of modulating complex waveforms. DOE is also useful in manipulating multispectral signals.

The traditional DOE structure includes a substrate and an island structure formed on the substrate. However, in the traditional DOE structure, the island-like structure is easily pulled off when the mold is released, and the island structure is likely to remain. The island structure is a convex structure with a particularly small size.

Summary of the invention

Based on this, it is necessary to provide a diffractive optical element, a TOF depth sensor, an optical system and a device for the technical problem that the traditional DOE structure is easy to be pulled off during mold release and the island structure is easy to remain.

A diffractive optical element, including:

The substrate is divided into several pixel areas;

A plurality of island-shaped structures are formed on the substrate and arranged in an array, and the projection of each island-shaped structure on the substrate covers at least four pixel regions.

A TOF depth sensor, including:

Laser projector, used to project periodic infrared laser signal with phase information to the space to be detected;

The diffractive optical element is arranged in the light emitting direction of the laser projector, and is used to evenly distribute a beam of incident infrared laser signal into L beams of outgoing infrared laser signals. After each outgoing infrared laser signal is projected to the measured target, it forms a reflection Signal, where L is a positive integer greater than 1; and

An image sensor for acquiring depth information according to the outgoing infrared laser signal and the reflected signal of the outgoing infrared laser signal;

Wherein, the diffractive optical element includes:

The substrate is divided into several pixel areas;

An optical system includes a diffractive optical element, and the diffractive optical element includes:

The substrate is divided into several pixel areas;

An optical device, including a diffractive optical element, the diffractive optical element including:

The substrate is divided into several pixel areas;

In the above diffractive optical element, by forming several island-shaped structures on the substrate, and the projection of each island-shaped structure on the substrate covers at least four pixel areas, it is ensured that there is no island structure in the microstructure of the diffractive optical element , Which ensures that there are no particularly small convex structures in the microstructure of the diffractive optical element, which facilitates a large number of replications through nanoimprint lithography. The above-mentioned diffractive optical element suppresses the generation of isolated island-like structures, that is, ensures the size of each island-like structure, and further ensures that the island-like structure is not easy to remain and is not easy to be removed when the island-like structure is released from the mold.

The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, purposes and advantages of this application will become apparent from the description, drawings and claims.

Description of the drawings

In order to more clearly describe the technical solutions in the embodiments of the present application 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 drawings in the following description are only These are some embodiments of the application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

Fig. 1 is a schematic diagram of a plane structure of a diffractive optical element in an embodiment;

2 is a schematic diagram of the three-dimensional structure of a diffractive optical element in an embodiment;

Fig. 3 is a distribution diagram of bright spots of a diffractive optical element in an embodiment;

FIG. 4 is a schematic diagram of the structure of a TOF depth sensor in an embodiment;

FIG. 5 is a schematic diagram showing the arrangement of 8x8 light-emitting points in a misaligned arrangement of the laser projector in the TOF depth sensor in an embodiment;

FIG. 6 is a speckle distribution diagram of the laser projector in the TOF depth sensor in an embodiment after the offset arrangement of 8×8 luminous points is projected by the diffractive optical element.

Description of main components with icon numbers

Diffractive optical element 100

Base 10

Pixel area 110

Island structure 20

Laser projector 200

Image sensor 300

detailed description

In order to make the above objectives, features, and advantages of the present application more obvious and understandable, the specific implementation manners of the present application will be described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth in order to fully understand this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of this application. Therefore, this application is not limited by the specific implementation disclosed below.

It can be understood that the terms "first", "second", etc. used in this application can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first acquisition module may be referred to as the second acquisition module, and similarly, the second acquisition module may be referred to as the first acquisition module. Both the first acquisition module and the second acquisition module are acquisition modules, but they are not the same acquisition module.

It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or a central element may also exist. When an element is considered to be "connected" to another element, it can be directly connected to the other element or an intermediate element may be present at the same time.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of this application. The terminology used in the specification of the application herein is only for the purpose of describing specific embodiments, and is not intended to limit the application. The term "and/or" as used herein includes any and all combinations of one or more related listed items.

In one embodiment, as shown in FIG. 1, the present application provides a diffractive optical element 100. The diffractive optical element 100 includes a substrate 10 and a plurality of island-shaped structures 20.

Specifically, please refer to FIG. 2 together. The substrate 10 is divided into a plurality of pixel regions 110. Each pixel area 110 refers to the smallest unit capable of constructing the island-like structure. The plurality of island-shaped structures 20 are formed on the substrate 10. The several island-shaped structures 20 are arranged in an array. The projection of each island structure 20 on the substrate 10 covers at least four pixel regions 110.

It can be understood that the structure of the substrate 10 is not specifically limited. In an optional embodiment, the substrate 10 is a light-transmitting substrate 10 (for example, a transparent substrate 10). The substrate 10 may be a silicon crystal or a thin piece of silicon dioxide. The material of the substrate 10 may be one or more of sodium silicate glass, sapphire or fused silica.

It is understandable that the substrate 10 may also include a dielectric material layer, a light transparent material layer, or an anti-reflective material layer. The anti-reflection material reduces reflection when light travels through the diffractive optical element 100. In an optional embodiment, the material forming the anti-reflective material layer may be titanium dioxide.

It can be understood that each of the island-shaped structures 20 can be formed on the substrate 10 by using a standard photolithography process. The shape of the plurality of island-shaped structures 20 is not specifically limited, as long as the projection of each island-shaped structure 20 on the substrate 10 covers at least four pixel regions 110 to ensure that the microstructure of the diffractive optical element 100 There is no particularly small raised structure. In one of the optional embodiments, each of the island-shaped structures 20 is in the shape of a dog bone or a bow tie. Each of the island-like structures 20 is in the shape of a dog bone or a bow-tie. There is no island structure and the outer edge of each island-like structure 20 is smooth, so as to further ensure that the island-like structure 20 is not easy to leave the island structure when it is released from the mold. It is not easy to be removed. As shown in FIG. 2, the surface of each island-shaped structure 20 opposite to the substrate 10 may be flat. That is, each of the island-shaped structures 20 may be a mesa-shaped structure. The plurality of island-shaped structures 20 are not limited to being arranged in an evenly spaced array.

In an optional embodiment, the island-like structure 20 can be prepared by implementing the following steps: firstly, a polymer is coated; secondly, a mask having a three-dimensional (3-D) profile of the island-like structure 20 is used To perform nano-imprint; finally, to etch. The 3-D nanoimprint mask can be fabricated/built in N photolithography steps.

It can be understood that, in order to prepare the diffractive optical element 100, design data of the diffractive optical element 100 needs to be obtained. Specifically, the design data of the diffractive optical element 100 can be obtained through a controller such as a computer or a microprocessor. For example, by writing a corresponding control program in a computer, the projection of each island structure 20 on the substrate 10 is controlled to cover at least four pixel regions 110.

Optionally, the step of obtaining the design data of the diffractive optical element 100 may be determining initial parameters. And according to the requirements of the dot matrix to generate a dot matrix target map, determine the number and distribution of the dot matrix. The light intensity and coordinates of each point in the dot matrix target image are adjusted. Specifically, the preset bright spot distribution is used as the optimized target value, the light intensity and coordinates of each point are adjusted through the correction intensity function, and the loop iterative until the target error value converges to generate the island-shaped structure 20 of the diffractive optical element 100 . It is determined whether the projection of each island-shaped structure 20 on the substrate covers at least four pixel regions 110. When the number of pixel regions 110 covered by the projection of the island-like structure 20 on the substrate is less than four, the current island-like structure 20 is removed to generate an island-like structure 20 that meets the requirements, and then the DOE phase map is output. . The DOE phase diagram includes design data of the diffractive optical element 100.

Of course, it is understandable that an island structure 20 will be formed in each iteration. The step of judging whether the projection of each of the island-shaped structures 20 on the substrate covers at least four pixel regions 110 may be after completing the step of loop iteration. The step of judging whether the projection of each island-shaped structure 20 on the substrate covers at least four pixel regions 110 may also be after any one iteration step. Specifically, the initial parameters may include incident light intensity distribution, wavelength, number of light spots, emission angle, working distance, spatial coordinates of the light-emitting source, and optical lens parameters. Taking the angular frequency scatter diagram of the speckles as the target (for example, as shown in Figure 3), the inverse Fourier transform is used to return the frequency domain to the spatial domain (DOE domain), bringing in the incident light intensity distribution, where the random phase is progressive Method to bring in

Among them, W1 and W2 are weights,

Is the new phase,

Is the phase of n-1 iterations,

Is the phase of the nth iteration. Then use the Fourier transform to bring it back to the frequency and bring the target to the correction intensity. After iterating 3 to 5 times, search for the island structure in the space domain. When the area of the island structure 20 is smaller than the area of the 4 pixel regions 110 It is regarded as an island structure, the current island structure 20 is removed, and the iteration is repeated. If the target error value converges, the iteration is completed and the DOE phase diagram is output.

In the above-mentioned diffractive optical element 100, a plurality of island-shaped structures 20 are formed on the substrate 10, and the projection of each island-shaped structure 20 on the substrate 10 covers at least four pixel regions 110, thereby ensuring the diffractive optical element 100 There is no island structure in the microstructure of the diffractive optical element 100, which ensures that there are no particularly small raised structures in the microstructure of the diffractive optical element 100, which facilitates a large number of replications through the nanoimprint lithography technology. The above-mentioned diffractive optical element 100 suppresses the generation of isolated island structures 20, that is, ensures the size of each island structure 20, thereby ensuring that the island structure 20 is not easy to remain and is not easily removed when the island structure 20 is removed from the mold.

Referring to FIG. 3, in one of the embodiments, the bright spots formed by the diffractive optical element 100 are arranged in a 3*3 array. The bright spot is a laser speckle projected by using the diffractive optical element 100 to split and project the incident laser light. That is, the number of dots of the diffractive optical element 100 is 9, and each dot has an equal intensity distribution. The number and distribution position of the bright spots formed by the diffractive optical element 100 are related to the position of each island structure 20 and the size of the light intensity. The magnitude of the light intensity is related to the value of the operating wavelength. Moreover, the value of the operating wavelength is affected by the depth of each of the island-shaped structures 20 in the direction perpendicular to the substrate 10. Therefore, the number and distribution position of the bright spots formed by the diffractive optical element 100 are related to the position of each island structure 20 and the depth of each island structure 20.

In this embodiment, by arranging the bright spots formed by the diffractive optical element 100 into a 3*3 array arrangement, a single-point laser speckle can be projected by the diffractive optical element 100 to form a 3*3 projection speckle. In order to ensure that there are not too many high-order speckles, the diffraction efficiency is improved.

In one of the embodiments, the size of the pixel area 110 is 190 nm-200 nm. It can be understood that when the pixel area 110 is circular, the size of the pixel area 110 is the length of the diameter of the circular area. When the pixel area 110 is rectangular, the size of the pixel area 110 is the length of the diagonal of the rectangular area. Etching is required to prepare the island structure 20. In each etching process, an integer multiple of the pixel region 110 can be etched away. If the size of the pixel area 110 is too large, it is easy for each island structure 20 to form a jagged outer edge. The jagged outer edge may cause the island structure 20 to be easily pulled out when it is removed from the mold. Therefore, setting the size of the pixel region 110 to be 190nm-200nm can make the outer edge of each island-shaped structure 20 smooth, so as to further ensure that the island-shaped structure 20 is not easily removed when it is released from the mold.

In one of the embodiments, the height of each island structure 20 along the direction perpendicular to the substrate 10 is 450 nm-750 nm, or 900 nm-1 μm.

Setting the height of each island structure 20 along the direction perpendicular to the substrate 10 to 450nm-750nm, or 900nm-1μm, can ensure that the operating wavelength ranges from 1um to 900nm and 750 to 450nm. When the operating wavelength is within this range, the light intensity distribution is ensured, thereby increasing the signal-to-noise ratio.

In one of the embodiments, the center distance between two adjacent island-shaped structures 20 is 2.5 μm-5 μm.

It is understandable that when the island-shaped structure 20 is a symmetrical structure, the center distance between two adjacent island-shaped structures 20 may be the distance between the center points of the two island-shaped structures 20. When the island-shaped structure 20 is an asymmetric structure, the center distance between two adjacent island-shaped structures 20 may be a certain position of one island-shaped structure 20 to the other island-shaped structure 20. The distance between the same locations. The center distance between two adjacent island-shaped structures 20 is 2.5 μm-5 μm, which is the minimum unit period, and the center distance between two adjacent island-shaped structures 20 is set to 2.5 μm-5 μm to ensure The field angle of the projected speckle of the diffractive optical element 100 ranges from 40° to 68°, and the repetition period is small, thereby improving the diffraction efficiency.

In one of the embodiments, the consistency of any two island-shaped structures 20 is greater than 82%. That is, the similarity of any two island-shaped structures 20 is greater than 82%, that is, all the island-shaped structures 20 have similar structural parameters, which improves the tolerance of alignment.

This application provides a diffractive optical element. The diffractive optical element includes a substrate 10 and a number of island-shaped structures 20. Several island structures 20 are arranged in an array at equal intervals. The size of the pixel area 110 is 3 μm. This arrangement can make the outer edge of each island-shaped structure 20 smooth, so as to further ensure that the island-shaped structure 20 is not easily removed when it is released from the mold. The height of each of the island-like structures 20 in the direction perpendicular to the substrate 10 is 0.94 μm. It can ensure that the operating wavelength is 0.94μm. This ensures the light intensity distribution, thereby improving the signal-to-noise ratio. The center distance between two adjacent island-shaped structures 20 is 4.7 m, which ensures the field angle of the projected speckle of the diffractive optical element 100. That is, FOV: H: 57.68°; V: 48.84°. The repetition period is small, which in turn improves the diffraction efficiency. The bright spots formed by the diffractive optical element 100 are arranged in a 3*3 array, so that a single-point laser speckle can be projected by the diffractive optical element 100 to form a 3*3 projection speckle, so as to ensure that there are no excessive high-order speckles. Speckle improves the diffraction efficiency.

In the above-mentioned diffractive optical element 100, a plurality of island-shaped structures 20 are formed on the substrate 10, and the projection of each island-shaped structure 20 on the substrate 10 covers at least four pixel regions 110, thereby ensuring the diffractive optical element 100 There is no island structure in the microstructure of the diffractive optical element 100, which ensures that there are no particularly small raised structures in the microstructure of the diffractive optical element 100, which facilitates a large number of replications through the nanoimprint lithography technology. The above-mentioned diffractive optical element 100 suppresses the generation of isolated island-like structures 20, that is, ensures the size of each island-like structure 20, thereby ensuring that the island-like structure 20 is not easy to remain and not easily removed when the island-like structure 20 is removed from the mold.

Please refer to Fig. 4, this application provides a TOF depth sensor. The TOF depth sensor includes a laser projector 200, a diffractive optical element 100 and an image sensor 300.

The laser projector 200 is used to project periodic infrared laser signals with phase information to the space to be detected. The diffractive optical element 100 is arranged in the light emitting direction of the laser projector 200. The diffractive optical element 100 is used for evenly distributing an incident infrared laser signal into an L beam of outgoing infrared laser signal. After each beam of outgoing infrared laser signal is projected to the measured target, a reflection signal is formed. Where L is a positive integer greater than 1. The image sensor 300 is used to obtain depth information according to the outgoing infrared laser signal and the reflected signal of the outgoing infrared laser signal.

The diffractive optical element 100 includes a substrate 10 and a plurality of island-shaped structures 20. The substrate 10 is divided into a plurality of pixel regions 110. Each pixel area 110 refers to the smallest unit capable of constructing the island-like structure. The plurality of island-shaped structures 20 are formed on the substrate 10. The plurality of island-shaped structures 20 are arranged in an array. The projection of each island structure 20 on the substrate 10 covers at least four pixel regions 110.

Of course, it is understandable that an island structure 20 will be formed in each iteration. The step of judging whether the projection of each island-shaped structure 20 on the substrate covers at least four pixel regions 110 may be after completing the step of loop iteration. The step of judging whether the projection of each island-shaped structure 20 on the substrate covers at least four pixel regions 110 may also be after any one iteration step. Specifically, the initial parameters may include incident light intensity distribution, wavelength, number of light spots, emission angle, working distance, spatial coordinates of the light-emitting source, and optical lens parameters. Taking the angular frequency scatter diagram of the speckles as the target (for example, as shown in Figure 3), the inverse Fourier transform is used to return the frequency domain to the spatial domain (DOE domain), bringing in the incident light intensity distribution, where the random phase is progressive Method to bring in

Among them, W1 and W2 are weights,

Is the new phase,

Is the phase of n-1 iterations,

The above TOF depth sensor uses the diffractive optical element 100 to split the incident laser beam and project the laser speckle, instead of the existing flood lighting realized by the diffuser, and improves the anti-interference ability during distance measurement. Moreover, the diffractive optical element 100 suppresses the generation of isolated island structures 20, that is, ensures the size of each island structure 20, thereby ensuring that the island structure 20 is not easy to remain and is not easily removed when the island structure 20 is released from the mold.

The current mainstream ToF emitting device is composed of VCSEL plus Diffuser optical diffuser. It can detect human faces or 3D object shapes. However, if you encounter stray light reflected by the environment, it will affect the judgment result. In this embodiment, the modulated incident laser light is uniformly distributed into L beams of outgoing light by using DOE. After the sub-beams reach the target, the laser speckle is formed, and the pattern projected by the laser speckle is controlled. The pixel position is matched with the field of view, the phase difference between the incident light and the emitted light is calculated, and the depth information is obtained. Under the same power consumption, the energy per unit area of the light is higher, and the signal-to-noise ratio is improved.

It can be understood that the L beam of emitted light can be 9 beams of emitted light. That is, the bright spots formed by the diffractive optical element 100 are arranged in a 3*3 array. As shown in FIG. 5, when the laser projector 200 has a 1/2 pitch offset arrangement of 8*8 luminous points. After the diffractive optical element 100, a 24*24 beam is formed. The 24*24 outgoing light beams form a 24*24 speckle distribution as shown in FIG. 6 on the object to be measured at a distance of 10070 cm from the diffractive optical element.

By setting the bright spots formed by the diffractive optical element 100 into a 3*3 array arrangement, a single-point laser speckle can be projected by the diffractive optical element 100 to form a 3*3 projection speckle to ensure that there is no excessive High-order speckles to improve the signal-to-noise ratio. For example, for a 3*3 projection speckle, the energy of each point is the total energy divided by nine. Assuming that the output power is 3W, it is divided into 9 projection speckles, and each projection speckle is divided into 1/3W. Compared with the background light noise (<1mW), the signal-to-noise ratio is naturally improved.

This application provides an optical system. The above-mentioned optical system includes the diffractive optical element 100 according to any one of the above-mentioned embodiments.

In the diffractive optical element 100 in the above-mentioned optical system, several island-shaped structures 20 are formed on the substrate 10, and the projection of each island-shaped structure 20 on the substrate 10 covers at least four pixel regions 110, ensuring There is no island structure in the microstructure of the diffractive optical element 100, that is, it is ensured that there is no particularly small convex structure in the microstructure of the diffractive optical element 100, which facilitates a large number of replications by nanoimprint lithography technology. The above-mentioned diffractive optical element 100 suppresses the generation of isolated island-like structures 20, that is, ensures the size of each island-like structure 20, thereby ensuring that the island-like structure 20 is not easy to remain and not easily removed when the island-like structure 20 is removed from the mold.

This application provides an optical device. The optical device includes the optical system described in the above embodiment.

In the above-mentioned optical device, a plurality of island-shaped structures 20 are formed on the substrate 10, and the projection of each island-shaped structure 20 on the substrate 10 covers at least four pixel regions 110, thereby ensuring the microscopic size of the diffractive optical element 100. There is no island structure in the structure, that is, it is ensured that there is no particularly small convex structure in the microstructure of the diffractive optical element 100, which is beneficial to a large number of replications by nanoimprint lithography technology. The above-mentioned diffractive optical element 100 suppresses the generation of isolated island-like structures 20, that is, ensures the size of each island-like structure 20, thereby ensuring that the island-like structure 20 is not easy to remain and not easily removed when the island-like structure 20 is removed from the mold.

The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the various technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, All should be considered as the scope of this specification.

The above-mentioned embodiments only express several implementation manners of the present application, and their description is relatively specific and detailed, but they should not be understood as a limitation on the scope of the patent application. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can be made, and these all fall within the protection scope of this application. Therefore, the scope of protection of the patent of this application shall be subject to the appended claims.

Claims

A diffractive optical element, characterized in that it comprises:

The substrate is divided into several pixel areas;

A plurality of island-shaped structures are formed on the substrate and arranged in an array, and the projection of each island-shaped structure on the substrate covers at least four pixel regions.
The diffractive optical element according to claim 1, wherein the bright spots formed by the projection of the diffractive optical element are arranged in a 3*3 array.
The diffractive optical element according to claim 1, wherein the size of the pixel area is 190nm-200nm.
The diffractive optical element according to claim 1, wherein the height of each of the island-shaped structures in a direction perpendicular to the substrate is 450 nm to 750 nm.
The diffractive optical element according to claim 1, wherein the height of each of the island-shaped structures in a direction perpendicular to the substrate is 900 nm-1 μm.
The diffractive optical element according to claim 1, wherein the center distance between two adjacent island-shaped structures is 2.5 μm-5 μm.
The diffractive optical element according to claim 1, wherein the consistency of any two island-shaped structures is greater than 82%.
The diffractive optical element according to claim 1, wherein each of the island-shaped structures is in the shape of a dog bone or a bow tie.
The diffractive optical element according to claim 1, wherein the substrate is a light-transmitting substrate.
The diffractive optical element according to claim 1, wherein the material of the substrate is one or more of sodium silicate glass, sapphire or fused silica.
The diffractive optical element according to claim 1, wherein the substrate comprises a dielectric material layer, a light transparent material layer, or an anti-reflection material layer.
A TOF depth sensor, characterized in that it comprises:

Laser projector, used to project periodic infrared laser signal with phase information to the space to be detected;

The diffractive optical element is arranged in the light emitting direction of the laser projector, and is used to evenly distribute a beam of infrared laser signals into L beams of outgoing infrared laser signals. After each outgoing infrared laser signal is projected to the target to be measured, a reflection signal is formed , Where L is a positive integer greater than 1; and

An image sensor for acquiring depth information according to the outgoing infrared laser signal and the reflected signal of the outgoing infrared laser signal;

Wherein, the diffractive optical element includes:

The substrate is divided into several pixel areas;

A plurality of island-shaped structures are formed on the substrate and arranged in an array, and the projection of each island-shaped structure on the substrate covers at least four pixel regions.
The depth sensor of claim 12, wherein the bright spots projected by the diffractive optical element are arranged in a 3*3 array.
The depth sensor according to claim 12, wherein the size of the pixel area is 190nm-200nm.
The depth sensor according to claim 12, wherein the height of each of the island-shaped structures in a direction perpendicular to the substrate is 450 nm-750 nm.
The depth sensor according to claim 12, wherein the height of each of the island-shaped structures in a direction perpendicular to the substrate is 900 nm-1 μm.
The depth sensor according to claim 12, wherein the center distance between two adjacent island-shaped structures is 2.5 μm-5 μm.
The depth sensor according to claim 12, wherein the consistency of any two island-shaped structures is greater than 82%.
An optical system, characterized in that it comprises a diffractive optical element, and the diffractive optical element comprises:

The substrate is divided into several pixel areas;

A plurality of island-shaped structures are formed on the substrate and arranged in an array, and the projection of each island-shaped structure on the substrate covers at least four pixel regions.
An optical device, characterized in that it comprises a diffractive optical element, and the diffractive optical element comprises:

The substrate is divided into several pixel areas;

A plurality of island-shaped structures are formed on the substrate and arranged in an array, and the projection of each island-shaped structure on the substrate covers at least four pixel regions.