Single-element dot pattern projector

Abstract

To provide a suitable single-element dot pattern projector. [Solution] Disclosed herein is a single-element dot pattern projector with a meta-optical system. The projector includes a laser light source and a meta-surface chip integrated on the laser light source. The meta-surface chip includes a meta-surface element spaced apart from the laser light source at a distance equal to the collimating focal length of the meta-surface chip. The laser light source generates light that is diffracted through the meta-surface element to produce a dot pattern. The projector enabled by the meta-optical system is connected to a unique method of integrating the meta-optical system and to unique functionality that can be added to the dot pattern.

Description

Technical Field

[0001] (Cross - reference to Related Applications) This application claims the benefit and priority of U.S. Provisional Patent Application No. 63 / 192,962, filed May 25, 2021, titled "Single Flat Optical Element Dot Pattern Projector", which is hereby incorporated by reference in its entirety for all purposes under 35 U.S.C. § 119(e).

[0002] This disclosure is directed to a single - element dot - pattern projector with a metasurface (sometimes referred to as a metasurface optics) and a method of forming a dot pattern with a VCSEL array.

Background Art

[0003] A metasurface dot - pattern projector is an optical device that transforms a laser source or multiple laser sources into a large number of dots and collimates the output beam. Generally, the number of dots projected from the device exceeds that of the single or multiple laser sources, and the full - width at half - maximum (FWHM) of the divergence of the emitted light is standardized to be minimized. For example, a dot - pattern projector can transform a vertical - cavity surface - emitting laser (VCSEL) with 20 individual laser apertures into 20×N dots, and each dot is standardized to have an FWHM of less than 0.50 degrees.

[0004] Dot - pattern projectors have several applications in 3D sensing, but almost all 3D sensing dot - projector modules in consumer applications utilize VCSEL sources. The details of the dot pattern projected onto a scene depend on the application in which the projector is being used. In time - of - flight (TOF) imaging, the number of target dots in a far - field can be only 10 times the number of laser apertures. In structured light, in contrast, the number of dots projected can be 100 times the number of VCSEL apertures.

[0005] To achieve multiple goals for dot pattern projectors—namely, amplified VCSEL patterns, high collimation at laser output, and minimizing the overall shape factor of the device—dot pattern projector modules typically consist of many individual optical components. For example, a standard dot projector module designed to fit into a mobile device requires at least one, typically three, refractive lenses to collimate the laser beam, and one diffractive optical element (DOE) that replicates a baseline number of VCSEL apertures and will generate the desired number of dots in the far field. The complexity of the module consequently presents significant challenges for integration, and furthermore, the module thickness often exceeds the available space within the bezel of a phone, laptop, or display. The latter limitation leads to more complex integration schemes, such as folded optical paths. [Overview of the project] [Means for solving the problem]

[0006] This application relates to a single-element dot pattern projector with a metasurface (sometimes called a metaoptics system) and a method for forming a dot pattern with a VCSEL array.

[0007] Various embodiments of the present invention include a single-element dot pattern projector comprising a laser light source and a metasurface chip integrated on the laser light source. The metasurface chip includes a metasurface element spaced apart from the laser light source at a distance equal to the back focal length of the metasurface chip, and the laser light source generates light that is diffracted through the metasurface element to produce a dot pattern.

[0008] In various other embodiments, the laser light source includes a vertical-cavity surface-emitting laser (VCSEL).

[0009] In various other embodiments, the VCSEL includes a plurality of individual laser apertures.

[0010] In various other embodiments, individual laser apertures are configured to output dots having a full width at half maximum (FWHM) of less than 0.5 degrees.

[0011] Furthermore, in various other embodiments, the metasurface chip is given by the following equation, namely: [ka] and, [ka] The dimensions satisfy the following conditions, where B is the matching tolerance of the metasurface tip, θ is the angle when the laser source power drops to less than 0.5% of the total power, MSx is the width of the active area of ​​the metasurface tip in the x direction, VCSELx is the width of the laser source in the x direction, A is the estimated size of the laser source beam beyond VCSELx in the x direction, and C is the gap size between the laser source and the metasurface tip, which is equal to the back focal length of the metasurface tip.

[0012] Furthermore, in various other embodiments, the metasurface chip has a chip width in the x-direction of Msx+2*Border, where the border is a chip size that exceeds the estimated size of the light source beam in the x-direction.

[0013] In various other embodiments, the metasurface chip is integrated above the laser light source such that the laser light source outputs light through the gap between the metasurface element and the laser light source.

[0014] In various other embodiments, the metasurface chip is integrated above the back side of the laser light source so that light is output through the back side of the laser light source on the metasurface chip.

[0015] In still further various other embodiments, the metasurface chip is integrated above the front side of the laser light source such that light is output through the front side of the laser light source on the metasurface chip.

[0016] In still further various other embodiments, the gap is provided by the substrate of the metasurface chip.

[0017] In still further various other embodiments, the gap is provided by epoxy or air between the laser light source and the metasurface element.

[0018] In still further various other embodiments, the metasurface element is positioned on top of the substrate of the metasurface chip.

[0019] In still further various other embodiments, the metasurface chip provides both a lens function and a magnification function to the light from the laser light source.

[0020] In still further various other embodiments, the metasurface chip further provides a linear phase function to the light from the laser light source.

[0021] In still further various other embodiments, the dot pattern has an asymmetric pattern.

[0022] In still further various other embodiments, the laser light source is integrated into the chip, and the laser light source chip and the metasurface chip are integrated into a single monolithic module.

[0023] In still further various other embodiments, the metasurface element is woven into a plurality of hexagonal-shaped tiles.

[0024] Furthermore, many embodiments of the present invention are methods of forming a dot pattern using a laser light source, including providing a laser light source integrated within a chip, providing a metasurface chip including a metasurface element, integrating the laser light source chip and the metasurface chip such that the metasurface element is spaced from the laser light source by a distance equal to the back focal length of the metasurface chip, and generating light that is diffracted from the laser light source through the metasurface element to generate a dot pattern.

[0025] In various other embodiments, the laser light source includes a vertical cavity surface emitting laser (VCSEL).

[0026] In still various other embodiments, the metasurface chip has dimensions that satisfy the following equations, namely,

Chemical Formula

Chemical Formula

[0027] In still various other embodiments, the metasurface chip has a chip width in the x direction of Msx + 2*Border, where Border is the size of the chip exceeding the estimated size of the light source beam in the x direction.

[0028] Additional embodiments and features are described in part in the following description, and in part will be obvious to those skilled in the art upon closer examination of this specification, or can be learned through practice of the disclosure. A further understanding of the essence and merits of this disclosure can be achieved by referring to the remainder of this specification and the drawings, which form part of this disclosure. The present invention provides, for example, the following items: (Item 1) A single-element dot pattern projector, A laser light source, A metasurface chip integrated on the laser light source, the metasurface chip includes a metasurface element spaced apart from the laser light source by a distance equal to the back focal length of the metasurface chip, and the laser light source generates light that is diffracted through the metasurface element to produce a dot pattern. A projector equipped with the following features. (Item 2) The projector described in item 1 comprises a vertical-cavity surface-emitting laser (VCSEL) as the laser light source. (Item 3) The VCSEL is a projector as described in item 2, comprising a plurality of individual laser apertures. (Item 4) The projector according to item 3, wherein each of the laser apertures is configured to output a dot having a full width at half maximum (FWHM) of less than 0.5 degrees. (Item 5) The aforementioned meta-surface chip is given by the following equation, namely,

number

number

number

number

[0029] The description is presented as an exemplary embodiment of the present invention and should not be construed as a complete enumeration of the scope of the invention; it will be better understood by referring to the following figures.

[0030] [Figure 1A] Figure 1A provides a schematic diagram of a single meta-optical system positioned across a VCSEL array, according to an embodiment.

[0031] [Figure 1B] Figure 1B provides a schematic diagram of a single meta-optical system, according to an embodiment, which is directly integrated into a back-emitting VCSEL array die to form a monolithic unit.

[0032] [Figure 1C] Figure 1C provides a schematic diagram of a meta-optical system integrated into a front-emitting VCSEL array die according to an embodiment.

[0033] [Figure 2] Figure 2 provides a fully functional schematic diagram of a single meta-optical system according to an embodiment.

[0034] [Figure 3] Figure 3 provides an exemplary set of design parameters for a meta-optical system that combines all three functions within a single planar layer, according to an embodiment.

[0035] [Figure 4] Figure 4 shows a ray trace of the projection lens function of a meta-optical system according to an embodiment.

[0036] [Figure 5] Figure 5 provides an example of a pattern designed for an IFOV of a metaoptical dot pattern projector according to an embodiment.

[0037] [Figure 6] Figure 6 provides a top view of a meta-optical system die according to an embodiment.

[0038] [Figure 7] Figure 7 provides a schematic side view of a single meta-optical system dot pattern projector according to an embodiment.

[0039] [Figure 8] Figure 8 provides an example of the calculated meta-optical system dimensions according to an embodiment.

[0040] [Figure 9] Figure 9 illustrates a cross-sectional view of a metasurface, including metasurface columns with a rectangular configuration.

[0041] [Figure 10] Figure 10 illustrates a cross-sectional view of a metasurface, including metasurface columns with a distorted structure.

[0042] [Figure 11] Figure 11 provides a measurement of a dot pattern formed by a single meta-optical dot pattern projector according to an embodiment.

[0043] [Figure 12] Figure 12 provides a dot pattern formed by a single meta-optical system according to an embodiment.

[0044] [Figure 13A] Figure 13A provides an example of a tiling pattern for a metasurface chip according to an embodiment.

[0045] [Figure 13B] Figure 13B illustrates an exemplary output from a metasurface chip with a rectangular tiling pattern.

[0046] [Figure 13C] Figure 13C illustrates exemplary output from a metasurface chip with a hexagonal tiling pattern.

[0047] [Figure 14] Figure 14 provides a schematic diagram of a partitioned meta-optical system dot pattern projector according to an embodiment. [Modes for carrying out the invention]

[0048] Detailed description of the invention Turning to the drawings, what is disclosed herein is a single-element dot pattern projector with a meta-surface (sometimes called a meta-optics system). Many embodiments describe various implementations of a planar meta-optics system, as they relate to optimizing the performance of the dot projector module while significantly simplifying the system. In additional embodiments, the design enabled by the meta-optics system leads to a unique way of integrating the meta-optics system and unique functionality that can be added to the dot pattern. Various embodiments also relate to forming a dot pattern with a VCSEL array as the source, however, it will be recognized that embodiments are also applicable to a variety of different laser light sources. For example, the laser light source may be a solid-state laser or any laser system and optical system.

[0049] In some embodiments, the use of a flat meta-optical system allows the system to be telecentric in object space (e.g., in the plane of the VCSEL aperture) and project the VCSEL aperture to infinity using only a single element. In various embodiments, the meta-optical system can be designed to impart a relatively simple phase profile, which is described as a radial extension of the phase profile. Embodiments can also add a multifunctional design to a single meta-optical system. Such a multifunctional design allows the optical system to impart three or more functions within a single meta-surface layer.

[0050] In exemplary embodiments, the lens function is provided as a diffraction function that creates M copies of each single VCSEL aperture within the same metasurface layer. This is in contrast to existing dot pattern projectors where the lens function may be provided by a separate refractive element and the replication function by a diffractive optical element (DOE). In some embodiments, the lens function may be combined within a single metasurface, which also has a first diffraction function that generates N copies of the VCSEL aperture over a relatively narrow field of view (inner field of view, i.e., IFOV) and a second diffraction function that further creates P copies of the IFOV pattern over a larger field of view (outer field of view, i.e., OFOV). In such embodiments, if the VCSEL array consists of Q apertures, the single metaoptics can generate Q × N × P collimated points of light in the far field. As a result of combining the refractive and diffractive lens functions within a single metasurface layer, all optical functions for a dot pattern projector may be provided on the same plane, which may result in a single focal length from the plane of the VCSELs.

[0051] The direct elimination of refractive lenses in a standard dot pattern projector provides a unique integration of the meta-optics system and the underlying VCSEL array. A typical dot projector module includes an air gap between the VCSEL array and the refractive lens. However, in the embodiments described herein, the meta-optics system can be directly integrated with the VCSEL array chip to create a monolithic module. Such direct integration can be achieved using front-emitting VCSELs. Epoxy may be used to fix the meta-optics die to the VCSEL array. In some embodiments, the meta-optics system can be integrated on a back-emitting VCSEL array. In this implementation, integration may be achieved through oxide bonding, a layer transfer process, or using optically transparent epoxy.

[0052] In many embodiments, the flat meta-optical system is located at a distance from the VCSEL equal to the back focal length of the meta-surface elements on the meta-surface chip. Therefore, in such devices, the augmentation function and focal length of the collimating lens can be coplanar. For example, both functions may be imparted within a single meta-surface at the same distance from the VCSEL array. This contrasts with a standard dot pattern projector, where the focal length of the collimating lens may be in a different plane from the augmentation function. For example, the lens function may be at a focal length distance away from the VCSEL array plane, while the diffractive optical element imparting the augmentation function may be in a separate plane from the refractive lens, at an additional displacement from it. Furthermore, in contrast to the embodiments described herein, in a standard dot pattern projector, the light incident on the diffractive optical element (DOE) (e.g., the optical system performing pattern augmentation) may already be collimated by a separate refractive lens or multiple lenses. However, with respect to a single meta-optical dot pattern projector, since there are no other collimating or lensing elements prior to the light being incident on the meta-optical system, the light incident on the meta-optical system (which is also the plane of the amplification function) can diverge with the same divergence angle as the VCSEL, and the principal ray angle of the light can be 0 degrees at all points along the meta-optical system. The light incident on the meta-optical system cannot be separately collimated prior to being incident on the meta-optical system.

[0053] In some embodiments, a single meta-optical dot projector may include a large module field of view (FOV) compared to a conventional projector. In this embodiment, the diagonal module FOV may be approximately 150 degrees. The inclusion of a flat optical system may allow the meta-optical dot projector to bend light at high angles. As light is bent at high angles, a multi-level DOE may have significant vinening caused by different physical heights. In contrast to a multi-level DOE, a meta-optical system may have only a single physical height.

[0054] Implementing a dot projector with a meta-optics system also allows for the conferring of additional unique functionality to the device. In conventional dot projectors, including standard optics, the dots in the projected dot pattern may not be polarized, or all dots may nominally have the same polarization (e.g., unpreferential polarization). In some embodiments, a meta-optics dot pattern projector may allow the polarization of each individual dot to be controlled. In such embodiments, the meta-surface dot pattern projector takes either unpolarized, partially polarized, or single-polarized light incident from a VCSEL array and converts the emitted light into two arbitrary orthogonal polarization states. In some embodiments, the dot pattern may be separated into two preferential polarizations for the left and right halves of the projected pattern. Alternatively, all rows of dots or neighboring dots may have opposite polarizations. In some specific cases, the two polarizations of a dot may be left- and right-hand circular polarizations. In some embodiments, the meta-optics system may convert the emitted light into more than two polarization states.

[0055] Specifically, in various embodiments of dot pattern projectors for structured light applications, it may be advantageous to project random or pseudo-random output patterns onto the field. Such randomness can be achieved by introducing a random distribution when setting up the VCSEL apertures in a VCSEL array. The dot pattern can then be generated by replicating the random array of VCSEL apertures in the far field. This method is typically implemented due to the limitations in the functionality of multiplying DOE used in conventional dot pattern projectors. In some embodiments, the metasurface dot projectors described herein allow for complete control of the phase of light from 0 to 2pi in a single flat optical plane. This allows for the conferring of asymmetric and arbitrary patterns compared to binary diffraction, which can only produce symmetric patterns or multilevel DOEs, requiring multiple physical heights within the underlying structure to generate the 0 to 2pi phase shift. The metaoptics allow for the conversion of arbitrary radiation patterns into different output arbitrary radiation patterns. Therefore, when a single meta-optical system is used in a dot pattern projector, a random dot array collimated to the far field using a VCSEL array can be generated using a regular grid (e.g., non-random) of VCSEL apertures. Importantly, the meta-optical system can generate a dot pattern that is random across the entire module FOV in the far field. In contrast, in conventional dot pattern projectors, each individual tile may have a random array of dots, but that random array may be repeated.

[0056] In conventional dot projectors, the desired module FOV and the number of times the pattern can be multiplied (e.g., the number of dots generated in the far field) can set the projection FOV. Given this fact from a standard paraxial optical system, the number of pattern replications can set the total track length of the module. In some embodiments, a single meta-optical system can directly convert a regular VCSEL array into a far-field pattern, which can eliminate this limitation. Instead, the module FOV directly sets the total track length, potentially allowing for significantly thinner modules.

[0057] In some embodiments, it may be desirable for the projected dot pattern to be distorted along a certain angular direction. Specifically, the field of view of a standard dot projector may be symmetrical about the optical axis. However, in some embodiments, it may be desirable to compensate, optically rather than mechanically, for cases where the optical axis of the dot projector is not perpendicular to the plane of the object. In some embodiments, the meta-optical dot pattern projector may include an additional linear phase function, e.g., φ(x) = Ax, in addition to the lens and pattern multiplication function, where x is a Cartesian coordinate and A is a phase constant. Again, such asymmetry cannot be introduced from a standard dot projector. However, by using a single meta-optical approach according to the embodiments, designs with arbitrary asymmetry with respect to the output FOV can be included.

[0058] Depending on the embodiment, the general design degrees of freedom of the meta-optics approach also allow unique aspects to be affixed to the individual tiles of the dot pattern itself. Specifically, the meta-optics projection can allow each tile to have a different focal length, dot size, unique wavefront, or inclination relative to the wavefront. Such degrees of freedom allow for unique optimization of tiles at larger angles within the module field of view compared to smaller angles within the field of view. The ability to optimize each individual tile also allows each tile to have a unique pattern on the inner field of view. This allows, for example, to uniquely define the dot density in different regions within the illumination field.

[0059] Exemplary Embodiments The following embodiments are provided as examples and should not be construed as limiting the scope of this disclosure.

[0060] Figure 1A illustrates a single meta-optical dot projector according to one embodiment of the present invention. The projector includes a VCSEL 104 and a meta-surface chip 102 positioned across the VCSEL 104. A gap 106 is positioned between the VCSEL 104 and the meta-surface chip 102 such that light from the VCSEL 104 is output through the gap 106 on the meta-surface chip 102. The gap 106 may be air. The meta-surface chip 102 may include a meta-surface that both focuses and doubles the light from the VCSEL 104 to generate a dot pattern 108. The VCSEL 104 may be a front-side output type VCSEL.

[0061] Figure 1B illustrates a single meta-optical dot projector according to one embodiment of the present invention. The operation of the projector in Figure 1B is similar to that of Figure 1A. The VCSEL 104a may be a back-side output type VCSEL, which can output light from the back side of the VCSEL 104a. The meta-surface chip 102a may include a substrate, which may be in direct contact with the VCSEL 104a, or a gap may be created between the meta-surface 110a of the meta-surface chip 102a and the VCSEL 104a.

[0062] Figure 1C illustrates a single meta-optical dot projector according to one embodiment of the present invention. The operation of the projector in Figure 1C is similar to that of Figure 1B. Furthermore, the projector in Figure 1C includes many components numbered in the same way as the projector in Figure 1B. A detailed description of these components will not be repeated. The VCSEL 104 may be a front-side output type VCSEL, similar to the projector described in relation to Figure 1A.

[0063] Advantageously, the metasurface chip may be directly integrated into a back-side or front-side emitting VCSEL array die to create a monolithic unit. The VCSELs 104 and 104a may output light with wavelengths of 940 ± 10 nm or 850 ± 10 nm.

[0064] Figure 2 shows a fully functional schematic diagram of a single meta-optical dot projector produced by one embodiment of the present invention. The collimation function of the single meta-optical system can produce a projection with a certain horizontal field of view (HFOV). The meta-optical system also produces an inner dot pattern with an inner horizontal field of view (IHFOV). The IHFOV is generally much narrower than the projected HFOV. The IHFOV and projected HFOV may be replicated by a third function, namely a tiling function. The tiling HFOV is shown in the schematic diagram. The combination of these three functions gives the dot projector a fully modular HFOV, as shown in the schematic diagram. In various embodiments, all of these functions can be achieved by a single meta-optical system in a single plane within a module. Figure 3 shows an exemplary set of design parameters for a meta-optical system that combines all three functions within a single planar layer according to an embodiment.

[0065] Figure 4 provides ray tracing of the projection lens function of the meta-optical system according to an embodiment. As can be seen from the image, it is possible to achieve telecentric performance using a flat meta-optical system. This is important for the function of a dot projector, in particular when achieving high off-axis collimation. In this embodiment, the lens uses relatively simple radial phase expansion, utilizing only terms up to the sixth order. However, in some embodiments, higher-order terms can be added as desired.

[0066] Figure 5 provides an example of a pattern designed for IHFOV in a meta-optical dot pattern projector according to an embodiment. In this embodiment (meaning illustrative, not limiting), IHFOV can be achieved by selecting a diffraction grid with 3 × 5 diffraction orders. Within this grid, some orders are designed to be "on" and others to be "off," so that the "on" grid has a certain light intensity, and the "off" grid will have substantially little or ideally no light intensity. In some embodiments, it may be advantageous to have some rotational symmetry with respect to the "on" orders. Such symmetry promotes certain important performance metrics, such as minimizing stray light and increasing dot contrast.

[0067] Figure 6 is a schematic top view of a metasurface chip according to one embodiment of the present invention. Unlike conventional refractive lenses, which are generally radially symmetrical, the metasurface chip may be square or rectangular in shape. The metasurface chip 600 may include an active area 602 surrounded by a boundary 604. The active area 602 may include various metasurface elements. The metasurface chip may also include orientation and alignment base point marks 606, which may be used during the manufacturing of the chip. The active area 602 may include an X dimension MSx and a Y dimension MSy. MSx and MSy can be determined by the VCSEL divergence and total track length (TTL).

[0068] The metasurface element may include a high refractive index structure, which is integrated onto a substrate. The metasurface element may also be a high refractive index structure, which is embedded within a dielectric material. For example, the metasurface element may include a high refractive index dielectric (e.g., silicon) embedded within a low refractive index dielectric (e.g., SiO2). The high refractive index structure may be a column, which is positioned on the substrate. The column may have a number of cross-sections, including circular, rectangular, and / or cruciform. The column may have a high aspect ratio. The column may have a height of 600 nm to 800 nm. In some embodiments, the column may have a height of about 700 nm. The diameter of the column may be 80 nm to 300 nm. An example of the metasurface element is disclosed in U.S. Patent Publication No. 2019 / 0064532, filed on 31 August 2018, titled "Transmissive Metasurface Lens Integration" (to be incorporated as a whole by reference for any purpose). In some embodiments, the anti-reflective layer may be positioned above and / or below the metasurface element.

[0069] Figure 7 provides a schematic side view of a single meta-optical dot pattern projector, including the meta-surface chip 600 of Figure 6. The projector includes a VCSEL array 702, which emits light with a beam width including a divergence angle θ. The VCSEL 702 may be spaced apart from the meta-surface chip by a distance equal to the back focal length C of the meta-surface chip, which may be equal to the focal length. Assuming a back focal length C, the VCSEL divergence angle θ and the VCSEL array dimension VCSELx may result in certain dimensions relative to the meta-surface chip 600. These dimensions may be calculated by the following equations. [ka] B may be the matching tolerance of the metasurface tip 600, which may be 25 μm. The divergence angle θ may be the angle at which the VCSEL power drops to less than 0.5% of the total power. MSx may be the width of the active area of ​​the metasurface tip in the x-direction. VCSELx may be the width of the light source in the x-direction. A may be the estimated size of the light source beam beyond VCSELx in the x-direction. Border is the size of the tip beyond the estimated size of the light source beam in the x-direction.

[0070] The dimensions of the VCSEL array 702 can provide a unique mapping to the metasurface chip 600 dimensions. A certain metasurface chip 600 dimension may be selected to maximize the amount of light striking the metasurface chip 600, but the dimensions can also be fabricated to be substantially smaller to produce a smaller meta-optical system size at the expense of power lost from the VCSEL array 702 and not projected onto the dot pattern. As can be seen from the figure, unlike conventional dot pattern projectors, the light incident on the plane of the multiplication function can be diverged by a divergence angle θ. Figure 8 provides an example of a calculated metasurface chip 600 dimension according to an embodiment.

[0071] The metasurface may have a grid or pitch. A unit cell may be defined as a single column of the metasurface, and the columns may be spaced apart from their centers by the unit cell grid or pitch. The diameter of the columns may vary, which gives the metasurface its function. In general, two basis vectors define the grid on which the metasurface is defined. The spacing or pitch may be a subwavelength of λ / 2. A supercell helps define the tiling function of the metasurface, which is also defined by the basis vectors. Given a target diffraction angle, the supercell basis vector is the reciprocal lattice vector of the target wave vector. The target diffraction angle may be the target wave vector.

[0072] The unit cell pitch may be selected such that an integer multiple of the unit cell is equal to the target diffraction angle pitch. In the simplest case, this satisfies the following equation: [ka] N is an integer value. unitcell This is a unit cell lattice, and suepercell This is the target diffraction angle grating. When passed through the diffraction grating equation, lattice suepercell This can be calculated from the target angle using the following equation. [ka] n is the refractive index of the medium, λ is the design wavelength, and θ is the refractive index of the medium. target is the target diffraction angle. In the general case, higher-order diffraction angles can be targeted such that the following equation is satisfied. [ka] M is an integer that labels the targeted diffraction order.

[0073] Since the unit cell lies on a 2D grid, the lattice supercell constraint can generally be satisfied such that the following equation is satisfied. [ka] The lattice vectors are not orthogonal, or cannot be aligned in the x or y directions. N1, N2, N3, and N4 are all integers.

[0074] In the case of a rectangle, the unit cell grid can be (400 nm, 0 nm) and (0 nm, 300 nm), which are mapped to supercell grids of (1,600 nm, 0 nm) and (0 nm, 900 nm) using integer multiples (4, 0) and (0, 3), respectively. Figure 9 illustrates a cross-sectional view of a metasurface including metasurface columns with a rectangular configuration. As shown, the unit cell grid 902 can be (400 nm, 0 nm) and (0 nm, 300 nm), and the supercell grid 904 can be (1,600 nm, 0 nm) and (0 nm, 900 nm). The integer multiples can be (4, 0) and (0, 3), respectively.

[0075] In the case of distortion, the unit cells can be (400 nm, 0 nm) and (100 nm, 200 nm), which are mapped to supercell grids of (1,600 nm, 0 nm) and (0 nm, 800 nm) using integer multiples of (4, 0) and (-1, 4), respectively. Figure 10 illustrates a cross-sectional view of a metasurface including metasurface columns with a distortion configuration. As shown, the unit cell grid 1002 can be (400 nm, 0 nm) and (100 nm, 200 nm), and the supercell grid 1004 can be (1,600 nm, 0 nm) and (0 nm, 800 nm). The integer multiples can be (4, 0) and (-1, 4), respectively.

[0076] Figure 11 illustrates an exemplary measurement of a dot pattern formed by a single meta-optical dot pattern projector described herein, according to an embodiment. The inset image shows a magnified view of the central region of the projected dot pattern. Such a dot projector may have 40,000 to 50,000 individual dots projected from a VCSEL array using a significantly smaller aperture. The dot pattern, in this case, is a random array of dots projected, typically for use in structured light applications.

[0077] Figure 12 illustrates an exemplary dot pattern formed by a single meta-optical dot pattern projector described herein, according to an embodiment. The dot pattern is a regular array of dots, with approximately 1,000 unique dots projected from a VCSEL array using significantly fewer dots. Such a dot pattern may be used in various applications, such as time-of-flight cameras.

[0078] Figure 13A provides an embodiment of a tiling pattern for a metasurface chip according to an embodiment. As shown, the metasurface chip may include a hexagonal tiling pattern 1102. Instead of rectangular tiling, diffraction order may be tiled into a hexagonal array. If the VCSEL chip also has a hexagonal boundary, the dots may be tiled in the far field. A standard dot projector may project light that is significantly distorted at the edges of the field of view. Light at the corners is generally not imaged onto the image sensor and is therefore wasted. From a metaoptics dot pattern projector, the projected pattern can be shared so that a larger fraction of the projected light will hit the image sensor.

[0079] Figure 13B illustrates an exemplary output from a metasurface chip with a rectangular tiling pattern. The output may include pincushion distortion. The output can be imaged by an image sensor 1104. As illustrated, wasted light 1106 traveling beyond the image sensor 1104 may exist. Figure 13C illustrates an exemplary output from a metasurface chip with a hexagonal tiling pattern. An exemplary hexagonal tiling pattern is illustrated in Figure 13A. The output may include pincushion distortion. The output can be imaged by an image sensor 1104. As illustrated, wasted light 1106 traveling beyond the image sensor 1104 may exist. However, the wasted light 1106 may be less than that of the metasurface chip with the rectangular tiling pattern illustrated in Figure 13B. By using thoughtful tiling and design choices, wasted light 1106 can be minimized. This may be impossible using a typical dot projector with a fixed-size lens.

[0080] Figure 14 provides a schematic diagram of a partitioned meta-optical dot pattern projector according to an embodiment. As shown, a VCSEL array can output light toward a meta-optical system comprising a substrate 1202 and a meta-optical microlens array 1204. In such a case, the VCSEL light is incident on the meta-optical microlens array 1204. However, in this embodiment, the meta-optical microlens array 1204 may be partitioned using sub-compartments 1204a. Each sub-compartment can be uniquely designed to impart a specific function to the output wavefront. For example, each sub-compartment 1204a may include an additional phase gradient, which can be placed on the output light. Such implementation can lead to substantially thinner modules.

[0081] The doctrine of equality Therefore, although the present invention has been described in certain specific aspects, many additional modifications and variations will be obvious to those skilled in the art. Accordingly, it should be understood that the present invention can be practiced in ways other than those specifically described. Accordingly, the embodiments of the present invention should be considered illustrative and not restrictive in all respects.

Claims

1. A single-element dot pattern projector, A laser light source, A metasurface chip integrated on the laser light source, the metasurface chip comprising a metasurface, the metasurface including a metasurface element spaced apart from the laser light source by a distance equal to the back focal length of the metasurface, and the laser light source generating light diffracted through the metasurface element to produce a dot pattern. Equipped with, The metasurface is integrated above the laser light source such that the laser light source outputs light through the gap between the metasurface element and the laser light source. The gap is provided by epoxy or air between the laser light source and the metasurface element. The metasurface provides both lens and amplification functions to the light from the laser light source in a single-element dot pattern projector.

2. The single-element dot pattern projector according to claim 1, wherein the laser light source comprises a vertical cavity surface-emitting laser (VCSEL).

3. The VCSEL is a single-element dot pattern projector according to claim 2, comprising a plurality of individual laser apertures.

4. The single-element dot pattern projector according to claim 3, wherein each of the laser apertures is configured to output dots having a full width at half maximum (FWHM) of less than 0.5 degrees.

5. The meta surface is defined by the following equation, namely, [Math 1] and, [Math 2] Having dimensions that satisfy the following conditions, B is the matching tolerance of the meta surface, and θ is the angle when the laser light source power drops to less than 0.5% of the total power. A single-element dot pattern projector according to claim 2, wherein MSx is the width of the active area of ​​the metasurface in the x-direction, VCSELx is the width of the laser light source in the x-direction, A is the estimated size of the laser light source beam beyond VCSELx in the x-direction, and C is the gap size between the laser light source and the metasurface, which is equal to the back focal length of the metasurface.

6. The single-element dot pattern projector according to claim 5, wherein the metasurface has a width in the x-direction of MSx + 2*Border, and the Border is the size of the metasurface that exceeds the estimated size of the laser light source beam in the x-direction.

7. The single-element dot pattern projector according to claim 1, wherein the metasurface is a single planar metasurface.

8. The single-element dot pattern projector according to claim 1, wherein the metasurface is integrated above the back side of the laser light source such that light is output onto the metasurface through the back side of the laser light source.

9. The single-element dot pattern projector according to claim 1, wherein the metasurface is integrated above the front side of the laser light source such that light is output onto the metasurface through the front side of the laser light source.

10. The gap is provided by the substrate of the metasurface, as described in claim 1, for the single-element dot pattern projector.

11. The single-element dot pattern projector according to claim 1, wherein the meta-surface element is positioned on top of the substrate of the meta-surface.

12. The single-element dot pattern projector according to claim 1, wherein the metasurface further provides a linear phase function to the light from the laser light source.

13. The single-element dot pattern projector according to claim 1, wherein the dot pattern has an asymmetric pattern.

14. The single-element dot pattern projector according to claim 1, wherein the laser light source is integrated into a chip, and the chip and the metasurface are integrated into a single monolithic module.

15. The single-element dot pattern projector according to claim 1, wherein the meta-surface elements are arranged into a plurality of hexagonal tiles.

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