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

Abstract

The present application relates to a diffractive optical element, a time-of-flight depth sensor, an optical system, and a device. The diffractive optical element forms a plurality of island-like structures on a substrate, and the projection of each island-like structure on the substrate covers at least four pixel areas, thereby ensuring that there are no isolated island structures in the microstructure of the diffractive optical element. This ensures that there are no particularly small protruding structures in the microstructure of the diffractive optical element, which is conducive to large-scale replication using nanoimprint lithography technology. The diffractive optical element suppresses the generation of isolated island-like structures, ensuring the size of each island-like structure, thereby ensuring that the island-like structure is not likely to remain as an isolated island structure and is not easily removed when the island-like structure is released from the mold.

Description

Technical Field

[0001] The present application relates to the technical field of optical element design, and in particular to a diffractive optical element, a TOF depth sensor, an optical system and a device. Background Art

[0002] Diffractive optical devices are used in many applications such as optical storage, processing, sensing and communications. A diffractive optical element (DOE) is a thin phase element that operates by means of interference and diffraction to produce arbitrary distributions of light or to aid in the design of optical systems. DOE designs can be applied with lasers (e.g., high-power lasers). In addition, DOEs are used for wave shaping. For example, DOEs can be used as multi-spot beam splitters in beam shaping and beam profile modification. DOEs can transform a single laser beam into a variety of simple or complex structures of light patterns. DOEs present endless possibilities in different application areas. While 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 can modulate complex waveforms. DOEs are also useful in manipulating multispectral signals.

[0003] The traditional DOE structure includes a substrate and an island structure formed on the substrate. However, during demolding, the island structure is easily detached and leaves behind isolated island structures, which are extremely small protrusions. Summary of the Invention

[0004] Based on this, it is necessary to provide a diffractive optical element, TOF depth sensor, optical system and device to address the technical problems that traditional DOE structures are easily pulled off during demolding and are prone to leaving isolated island structures.

[0005] A diffractive optical element, comprising:

[0006] A substrate, divided into a number of pixel regions;

[0007] 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 areas.

[0008] By forming a plurality of island-like structures on a substrate, with each island-like structure projected onto the substrate covering at least four pixel areas, the diffractive optical element's microstructure is free of isolated island structures. This ensures that the diffractive optical element's microstructure is free of particularly small protruding structures, facilitating large-scale replication using nanoimprint lithography. The diffractive optical element suppresses the formation of isolated island-like structures, ensuring the size of each island-like structure. This, in turn, ensures that the island structures are unlikely to remain when released from the mold and are difficult to remove.

[0009] In one embodiment, the bright spots formed by the diffractive optical element are arranged in a 3*3 array.

[0010] By arranging the bright spots formed by the diffractive optical element in a 3*3 array, a single-point laser speckle can be projected through the diffractive optical element to form a 3*3 projection speckle, thereby ensuring that there are no excessive high-order speckles and improving the diffraction efficiency.

[0011] In one embodiment, the size of the pixel area is 190nm-200nm.

[0012] Setting the size of the pixel area to 190 nm-200 nm can make the outer edge of each island structure smooth, thereby further ensuring that the island structure is not easily removed when demolding.

[0013] In one embodiment, the height of each of the island structures along a direction perpendicular to the substrate is 450 nm to 750 nm, or 900 nm to 1 μm.

[0014] Setting the height of each island structure perpendicular to the substrate to 450nm-750nm or 900nm-1μm ensures that the operating wavelength range is within 1μm-900nm and 750-450nm. Operating wavelengths within this range ensure light intensity distribution, thereby improving the signal-to-noise ratio.

[0015] In one embodiment, the center distance between two adjacent island structures is 2.5 μm-5 μm.

[0016] The center distance between two adjacent island structures is set to 2.5 μm-5 μm, which ensures that the field angle of the projection speckle of the diffractive optical element is in the range of 40°-68° and the repetition period is small, thereby improving the diffraction efficiency.

[0017] In one embodiment, the consistency between any two island structures is greater than 82%.

[0018] The consistency between any two island structures is greater than 82%, that is, all island structures have similar structural parameters, thereby improving alignment tolerance.

[0019] In one embodiment, each of the island structures is dog-bone shaped or bow-tie shaped.

[0020] Each of the island structures is dog-bone-shaped or bow-tie-shaped, without isolated island structures, and the outer edge of each island structure is smooth, so as to further ensure that the island structure is not likely to remain when the island structure is demoulded and is not easily removed.

[0021] A TOF depth sensor, comprising:

[0022] A laser projector, used for projecting a periodic infrared laser signal with phase information into the detected space;

[0023] A diffractive optical element as described in any of the above embodiments, disposed in the light-emitting direction of the laser projector, for uniformly distributing an incident infrared laser signal into L outgoing infrared laser signals, each outgoing infrared laser signal forming a reflected signal after being projected onto a target, wherein L is a positive integer greater than 1; and

[0024] An image sensor is used to obtain depth information based on the outgoing infrared laser signal and the reflection signal of the outgoing infrared laser signal.

[0025] The TOF depth sensor utilizes a diffractive optical element to split the incident laser beam and project a laser speckle pattern, replacing the existing floodlighting method achieved through a diffuser. This improves interference resistance during distance measurement. Furthermore, the diffractive optical element suppresses the formation of isolated island structures, ensuring the size of each island structure. This, in turn, ensures that these island structures are less likely to remain and are difficult to remove during demolding.

[0026] An optical system comprises the diffractive optical element described in any one of the above embodiments.

[0027] The diffractive optical element in the above optical system forms a plurality of island-like structures on the substrate, with each island-like structure's projection on the substrate covering at least four pixel areas. This ensures that the diffractive optical element's microstructure is free of isolated island structures, that is, free of particularly small protrusions. This facilitates large-scale replication using nanoimprint lithography. The diffractive optical element suppresses the formation of isolated island-like structures, ensuring the size of each island-like structure. This, in turn, ensures that the island structures are unlikely to remain after demolding and are difficult to remove.

[0028] An optical device comprises the optical system described in the above embodiment.

[0029] By forming a plurality of island-like structures on a substrate, with each island-like structure projected onto the substrate covering at least four pixel areas, the optical device ensures that the diffractive optical element's microstructure is free of isolated island structures. This ensures that the diffractive optical element's microstructure is free of particularly small protrusions, facilitating large-scale replication using nanoimprint lithography. The diffractive optical element suppresses the formation of isolated island-like structures, ensuring the size of each island-like structure. This, in turn, ensures that no isolated island structures remain when the island structures are released from the mold, and that they are difficult to remove. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 Schematic diagram of the planar structure of a diffractive optical element in one embodiment;

[0032] Figure 2 is a schematic diagram of a three-dimensional structure of a diffractive optical element in one embodiment;

[0033] Figure 3 is a bright spot distribution diagram of a diffractive optical element in one embodiment;

[0034] Figure 4 Schematic diagram of the structure of a TOF depth sensor in one embodiment;

[0035] Figure 5 A schematic diagram of a staggered arrangement of 8x8 light-emitting points of a laser projector in a TOF depth sensor in one embodiment;

[0036] Figure 6 This is a speckle distribution diagram of 8x8 staggered light points of a laser projector in a TOF depth sensor in one embodiment after being projected by a diffractive optical element.

[0037] Description of the main components

[0038] Diffractive optical element 100

[0039] Base 10

[0040] Pixel area 110

[0041] Island structure 20

[0042] Laser Projector 200

[0043] Image sensor 300 DETAILED DESCRIPTION

[0044] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0045] It will be understood that the terms "first," "second," and the like, as used herein, may be used to describe various elements herein, but these elements are not limited by these terms. These terms are used solely to distinguish a first element from another element. For example, a first acquisition module may be referred to as a second acquisition module, and similarly, a second acquisition module may be referred to as a first acquisition module, without departing from the scope of this application. The first acquisition module and the second acquisition module are both acquisition modules, but they are not the same acquisition module.

[0046] It should be noted that when an element is referred to as being “disposed on” another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0048] In one embodiment, Figure 1 As shown, the present application provides a diffractive optical element 100. The diffractive optical element 100 includes a substrate 10 and a plurality of island structures 20.

[0049] For details, please refer to Figure 2 The substrate 10 is divided into a plurality of pixel regions 110. Each pixel region 110 is the smallest unit capable of constructing the island structure. The plurality of island structures 20 are formed on the substrate 10. The plurality of island 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.

[0050] It is 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 (e.g., a transparent substrate 10). The substrate 10 can be a silicon crystal or a silicon dioxide sheet. The material of the substrate 10 can be one or more of sodium silicate glass, sapphire, or fused silica.

[0051] It is understood that the substrate 10 may further include a dielectric material layer, a light-transparent material layer, or an anti-reflection material layer. The anti-reflection material reduces reflection when light passes through the diffractive optical element 100. In an optional embodiment, the material forming the anti-reflection material layer may be titanium dioxide.

[0052] It is understandable that each of the island-like structures 20 can be formed on the substrate 10 using a standard photolithography process. The shapes of the several island-like structures 20 are not specifically limited, as long as the projection of each of the island-like structures 20 on the substrate 10 covers at least four pixel areas 110 to ensure that there are no particularly small protruding structures in the microstructure of the diffraction optical element 100. In one optional embodiment, each of the island-like structures 20 is dog-bone-shaped or bow-tie-shaped. Each of the island-like structures 20 is dog-bone-shaped or bow-tie-shaped, has no isolated 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 prone to residual isolated island structure and is not easily removed when the island-like structure 20 is demolded. Figure 2 As shown, the surface of each island structure 20 facing the substrate 10 can be a plane. That is, each island structure 20 can be a table-like structure. The island structures 20 are not limited to being arranged in an array with equal intervals.

[0053] In an alternative embodiment, the island structures 20 can be fabricated by first coating with a polymer, then performing nanoimprinting using a mask having a three-dimensional (3D) profile of the island structures 20, and finally performing etching. The 3D nanoimprint mask can be fabricated / constructed in N photolithography steps.

[0054] It is understood that in order to prepare the diffractive optical element 100, it is necessary to obtain the design data of the diffractive optical element 100. Specifically, the design data of the diffractive optical element 100 can be obtained by a controller such as a computer or a microprocessor. For example, a corresponding control program can be written into the computer to control the projection of each island structure 20 on the substrate 10 to cover at least four pixel areas 110.

[0055] Optionally, the step of obtaining the design data of the diffractive optical element 100 may be to determine the initial parameters. And generate a dot matrix target map according to the dot matrix requirements, and determine the number and distribution position of the dot matrix. Adjust the light intensity and coordinates of each point in the dot matrix target map. Specifically, with the preset bright spot distribution as the optimization target value, adjust the light intensity and coordinates of each point by correcting the intensity function, and iterate until the target error value converges to generate the island structure 20 of the diffractive optical element 100. Determine whether the projection of each island structure 20 on the substrate covers at least four pixel areas 110. When the number of pixel areas 110 covered by the projection of the island structure 20 on the substrate is less than four, remove the current island structure 20 to generate an island structure 20 that meets the requirements, and then output the DOE phase map. The DOE phase map includes the design data of the diffractive optical element 100.

[0056] Of course, it is understandable that since each iteration will form an island structure 20. The step of judging whether the projection of each island structure 20 on the substrate covers at least four pixel areas 110 may be after completing the step of loop iteration. The step of judging whether the projection of each island structure 20 on the substrate covers at least four pixel areas 110 may also be after any 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 source, and optical lens parameters. The goal is to generate an angular frequency distribution diagram of speckles (for example, Figure 3 As shown), the frequency domain is returned to the spatial domain (DOE domain) by inverse Fourier transform, and the incident light intensity distribution is introduced, where the random phase is introduced by the gradual method. Among them, W1, W2 are weights, For the new phase, is the phase of n-1 iterations, The phase of the nth iteration is then returned to frequency using a Fourier transform, and the target is brought into the corrected intensity. After 3 to 5 iterations, the island structure is searched for in the spatial domain. When the area of ​​the island structure 20 is smaller than the area of ​​the 4-pixel region 110, it is considered 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 map is output.

[0057] The diffractive optical element 100 described above forms a plurality of island structures 20 on the substrate 10, with each island structure 20 projecting onto the substrate 10 to cover at least four pixel areas 110. This ensures that there are no isolated island structures within the microstructure of the diffractive optical element 100, that is, no particularly small protruding structures within the microstructure of the diffractive optical element 100. This facilitates mass replication using nanoimprint lithography. The diffractive optical element 100 described above suppresses the formation of isolated island structures 20, ensuring the size of each island structure 20. This further ensures that the island structures 20 are unlikely to remain when demolded and are difficult to remove.

[0058] See Figure 3 In one embodiment, the bright spots formed by the diffractive optical element 100 are arranged in a 3*3 array. The bright spots are laser speckles projected by splitting the incident laser beam using the diffractive optical element 100. That is, the number of dot arrays of the diffractive optical element 100 is 9, and each dot has equal intensity distribution. The number and distribution positions of the bright spots formed by the diffractive optical element 100 are related to the position of each of the island structures 20 and the magnitude 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 structures 20 along the direction perpendicular to the substrate 10. Therefore, the number and distribution positions of the bright spots formed by the diffractive optical element 100 are related to the position of each of the island structures 20 and the depth of each of the island structures 20.

[0059] In this embodiment, by setting the bright spots formed by the diffractive optical element 100 to be arranged in a 3*3 array, a single-point laser speckle can be projected through the diffractive optical element 100 to form a 3*3 projection speckle, thereby ensuring that there are no excessive high-order speckles and improving the diffraction efficiency.

[0060] In one embodiment, the size of the pixel area 110 is 190nm-200nm. It is understandable 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 area 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 will cause the island structure 20 to be easily removed when it is demolded. Therefore, setting the size of the pixel area 110 to 190nm-200nm can make the outer edge of each island structure 20 smooth, so as to further ensure that the island structure 20 is not easily removed when it is demolded.

[0061] In one embodiment, the height of each of the island structures 20 along a direction perpendicular to the substrate 10 is 450 nm-750 nm, or 900 nm-1 μm.

[0062] Setting the height of each island structure 20 perpendicular to the substrate 10 to 450nm-750nm or 900nm-1μm ensures that the operating wavelength range is within 1μm-900nm and 750-450nm. Operating wavelengths within this range ensure light intensity distribution, thereby improving the signal-to-noise ratio.

[0063] In one embodiment, the center distance between two adjacent island structures 20 is 2.5 μm-5 μm.

[0064] It is understood that when the island structures 20 are symmetrical, the center distance between two adjacent island structures 20 may be the distance between the center points of the two island structures 20. When the island structures 20 are asymmetrical, the center distance between two adjacent island structures 20 may be the distance between a certain position of one island structure 20 and the same position of the other island structure 20. The center distance between two adjacent island structures 20 is 2.5 μm-5 μm, which is the minimum unit period. Setting the center distance between two adjacent island structures 20 to 2.5 μm-5 μm ensures that the field angle of the projected speckle of the diffractive optical element 100 is within a range of 40°-68°, with a small repetition period, thereby improving the diffraction efficiency.

[0065] In one embodiment, the consistency of any two island structures 20 is greater than 82%, that is, the similarity of any two island structures 20 is greater than 82%, that is, all island structures 20 have similar structural parameters, which improves alignment tolerance.

[0066] The present application provides a diffraction optical element. The diffraction optical element includes a substrate 10 and a plurality of island structures 20. The plurality of island structures 20 are arranged in an array at equal intervals. The size of the pixel area 110 is 3 μm. This setting can make the outer edge of each island structure 20 smooth, so as to further ensure that the island structure 20 is not easily removed when demolding. The height of each island structure 20 in the direction perpendicular to the substrate 10 is 0.94 μm. The operating wavelength can be ensured to be 0.94 μm. This ensures the light intensity distribution, thereby improving the signal-to-noise ratio. The center distance between two adjacent island structures 20 is 4.7 μm, which ensures the field of view of the projected speckle of the diffraction optical element 100. That is, FOV: H: 57.68°; V: 48.84°. The repetition period is small, thereby improving 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 forms a 3*3 projection speckle after being projected by the diffractive optical element 100, thereby ensuring that there are no excessive high-order speckles and improving the diffraction efficiency.

[0067] The diffractive optical element 100 described above forms a plurality of island structures 20 on the substrate 10, with each island structure 20 projecting onto the substrate 10 to cover at least four pixel areas 110. This ensures that there are no isolated island structures within the microstructure of the diffractive optical element 100, that is, no particularly small protruding structures within the microstructure of the diffractive optical element 100. This facilitates mass replication using nanoimprint lithography. The diffractive optical element 100 described above suppresses the formation of isolated island structures 20, ensuring the size of each island structure 20. This further ensures that the island structures 20 are unlikely to remain when demolded and are difficult to remove.

[0068] See Figure 4 The present application provides a TOF depth sensor, which includes a laser projector 200 , a diffractive optical element 100 , and an image sensor 300 .

[0069] The laser projector 200 is used to project a periodic infrared laser signal with phase information into the detected space. The diffraction optical element 100 is arranged in the light emitting direction of the laser projector 200. The diffraction optical element 100 is used to evenly distribute a beam of incident infrared laser signal into L beams of outgoing infrared laser signals. After each beam of outgoing infrared laser signal is projected onto the target to be measured, a reflection signal is formed. Wherein L is a positive integer greater than 1. The image sensor 300 is used to obtain depth information based on the outgoing infrared laser signal and the reflection signal of the outgoing infrared laser signal.

[0070] The diffractive optical element 100 includes a substrate 10 and a plurality of island structures 20. The substrate 10 is divided into a plurality of pixel regions 110. Each pixel region 110 is the smallest unit capable of constructing the island structure. The plurality of island structures 20 are formed on the substrate 10. The plurality of island 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.

[0071] It is 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 (e.g., a transparent substrate 10). The substrate 10 can be a silicon crystal or a silicon dioxide sheet. The material of the substrate 10 can be one or more of sodium silicate glass, sapphire, or fused silica.

[0072] It is understood that the substrate 10 may further include a dielectric material layer, a light-transparent material layer, or an anti-reflection material layer. The anti-reflection material reduces reflection when light passes through the diffractive optical element 100. In an optional embodiment, the material forming the anti-reflection material layer may be titanium dioxide.

[0073] It is understandable that each of the island-like structures 20 can be formed on the substrate 10 using a standard photolithography process. The shapes of the several island-like structures 20 are not specifically limited, as long as the projection of each of the island-like structures 20 on the substrate 10 covers at least four pixel areas 110 to ensure that there are no particularly small protruding structures in the microstructure of the diffraction optical element 100. In one optional embodiment, each of the island-like structures 20 is dog-bone-shaped or bow-tie-shaped. Each of the island-like structures 20 is dog-bone-shaped or bow-tie-shaped, has no isolated 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 prone to residual isolated island structure and is not easily removed when the island-like structure 20 is demolded. Figure 2 As shown, the surface of each island structure 20 facing the substrate 10 can be a plane. That is, each island structure 20 can be a table-like structure. The island structures 20 are not limited to being arranged in an array with equal intervals.

[0074] In an alternative embodiment, the island structures 20 can be fabricated by first coating with a polymer, then performing nanoimprinting using a mask having a three-dimensional (3D) profile of the island structures 20, and finally performing etching. The 3D nanoimprint mask can be fabricated / constructed in N photolithography steps.

[0075] It is understood that in order to prepare the diffractive optical element 100, it is necessary to obtain the design data of the diffractive optical element 100. Specifically, the design data of the diffractive optical element 100 can be obtained by a controller such as a computer or a microprocessor. For example, a corresponding control program can be written into the computer to control the projection of each island structure 20 on the substrate 10 to cover at least four pixel areas 110.

[0076] Optionally, the step of obtaining the design data of the diffractive optical element 100 may be to determine the initial parameters. And generate a dot matrix target map according to the dot matrix requirements, and determine the number and distribution position of the dot matrix. Adjust the light intensity and coordinates of each point in the dot matrix target map. Specifically, with the preset bright spot distribution as the optimization target value, adjust the light intensity and coordinates of each point by correcting the intensity function, and iterate until the target error value converges to generate the island structure 20 of the diffractive optical element 100. Determine whether the projection of each island structure 20 on the substrate covers at least four pixel areas 110. When the number of pixel areas 110 covered by the projection of the island structure 20 on the substrate is less than four, remove the current island structure 20 to generate an island structure 20 that meets the requirements, and then output the DOE phase map. The DOE phase map includes the design data of the diffractive optical element 100.

[0077] Of course, it is understandable that since each iteration will form an island structure 20. The step of judging whether the projection of each island structure 20 on the substrate covers at least four pixel areas 110 may be after completing the step of loop iteration. The step of judging whether the projection of each island structure 20 on the substrate covers at least four pixel areas 110 may also be after any 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 source, and optical lens parameters. The goal is to generate an angular frequency distribution diagram of speckles (for example, Figure 3 As shown), the frequency domain is returned to the spatial domain (DOE domain) by inverse Fourier transform, and the incident light intensity distribution is introduced, where the random phase is introduced by the gradual method. Among them, W1, W2 are weights, For the new phase, is the phase of n-1 iterations, The phase of the nth iteration is then returned to frequency using a Fourier transform, and the target is brought into the corrected intensity. After 3 to 5 iterations, the island structure is searched for in the spatial domain. When the area of ​​the island structure 20 is smaller than the area of ​​the 4-pixel region 110, it is considered 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 map is output.

[0078] The TOF depth sensor utilizes a diffractive optical element 100 to split the incident laser beam and project a laser speckle pattern, replacing the existing floodlighting method implemented by a diffuser. This improves interference resistance during distance measurement. Furthermore, the diffractive optical element 100 suppresses the formation of isolated island structures 20, ensuring the size of each island structure 20. This, in turn, ensures that the island structures 20 are not easily left behind during demolding and are difficult to remove.

[0079] The current mainstream ToF emitting device is composed of a VCSEL plus a diffuser optical diffuser. It can detect faces or 3D object shapes. However, if it encounters stray light reflected from the environment, it will affect the judgment result. This embodiment uses a DOE to evenly distribute the modulated incident laser into L beams of outgoing light. After the sub-beams reach the target, laser speckles are formed. The pattern projected by the laser speckles is controlled. By matching the laser speckles with the pixel position and field of view of the image sensor 300, the phase difference between the incident light and the outgoing light is calculated to obtain depth information. At the same power consumption, the energy per unit area of ​​the light is increased, thereby improving the signal-to-noise ratio.

[0080] It is understandable that the L beams of outgoing light can be 9 beams of outgoing light. That is, the bright spots formed by the diffractive optical element 100 are arranged in a 3*3 array. Figure 5 As shown, when the laser projector 200 has 8*8 light points arranged at a 1 / 2 pitch offset, 24*24 beams are formed after passing through the diffractive optical element 100. The 24*24 beams are formed on the target to be measured at a distance of 10070cm from the diffractive optical element. Figure 6 The 24*24 speckle distribution is shown.

[0081] By arranging the bright spots formed by the diffractive optical element 100 in a 3x3 array, a single point of laser speckle can be projected through the diffractive optical element 100 to form a 3x3 array of projected speckles. This ensures that there is no excessive high-order speckle, thereby improving the signal-to-noise ratio. For example, in a 3x3 array of projected speckles, the energy of each point is the total energy divided by nine. Assuming an output power of 3W, this is distributed among nine projected speckles, with each projected speckle receiving 1 / 3W. This naturally improves the signal-to-noise ratio compared to background light noise (<1mW).

[0082] The present application provides an optical system, which includes the diffractive optical element 100 described in any one of the above embodiments.

[0083] The diffractive optical element 100 in the above-described optical system forms a plurality of island structures 20 on the substrate 10, with each island structure 20 projecting onto the substrate 10 to cover at least four pixel areas 110. This ensures that the diffractive optical element 100's microstructure is free of isolated island structures, i.e., free of particularly small protruding structures. This facilitates mass replication using nanoimprint lithography. The diffractive optical element 100 suppresses the formation of isolated island structures 20, ensuring the size of each island structure 20. This, in turn, ensures that the island structures 20 are unlikely to remain when released from the mold and are difficult to remove.

[0084] The present application provides an optical device, which includes the optical system described in the above embodiment.

[0085] The optical device described above forms a plurality of island structures 20 on the substrate 10, with each island structure 20 projecting onto the substrate 10 to cover at least four pixel areas 110. This ensures that the microstructure of the diffractive optical element 100 is free of isolated island structures, i.e., free of particularly small protruding structures. This facilitates mass replication using nanoimprint lithography. The diffractive optical element 100 suppresses the formation of isolated island structures 20, ensuring the size of each island structure 20. This, in turn, ensures that the island structures 20 are unlikely to remain when demolded and are difficult to remove.

[0086] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0087] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A diffractive optical element, characterized in that: include: A substrate, divided into a number of pixel regions; A plurality of island-like structures are formed on the substrate and arranged in an array, wherein the projection of each island-like structure on the substrate covers at least four pixel areas; Each of the island structures is dog-bone shaped or bow-tie shaped.

2. The diffractive optical element according to claim 1, wherein The bright spots formed by the projection of the diffraction optical element are arranged in a 3*3 array.

3. The diffractive optical element according to claim 1, wherein The size of the pixel area is 190nm-200nm.

4. The diffractive optical element according to claim 1, wherein The height of each of the island structures along a direction perpendicular to the substrate is 450 nm to 750 nm, or 900 nm to 1 μm.

5. The diffractive optical element according to claim 1, wherein The center distance between two adjacent island structures is 2.5 μm-5 μm.

6. The diffractive optical element according to claim 1, wherein The consistency between any two island structures is greater than 82%.

7. A TOF depth sensor, characterized in that: include: A laser projector, used for projecting a periodic infrared laser signal with phase information into the detected space; The diffractive optical element according to any one of claims 1 to 6, arranged in the light emitting direction of the laser projector, and configured to evenly distribute a beam of infrared laser signal into L outgoing infrared laser signals, each outgoing infrared laser signal forming a reflected signal after being projected onto a target, wherein L is a positive integer greater than 1; as well as An image sensor is used to obtain depth information based on the outgoing infrared laser signal and the reflection signal of the outgoing infrared laser signal.

8. An optical system, characterized in that The diffractive optical element comprises the diffractive optical element according to any one of claims 1 to 6.

9. An optical device, characterized in that: Comprising the optical system according to claim 8.

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