High-resolution solid-state LIDAR transmitter

Abstract

A solid-state LIDAR transmitter includes a laser array comprising first and second laser pixels, each of which generates first and second sub-aperture beams. A first microlens focuses the first and second sub-aperture beams generated by the first laser pixel and focuses the first and second sub-aperture beams generated by the second laser pixel. A second microlens directs the first and second sub-aperture beams generated by the first pixel so that they overlap in a plane. The lens projects the first sub-aperture beam generated by the first laser pixel and the first sub-aperture beam generated by the second laser pixel at different angles in the far field to achieve a desired spatial resolution of the LIDAR system.

Description

[0001] The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described in this application in any way.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application is a non-provisional application of U.S. Provisional Patent Application No. 62 / 881,354, entitled “High-Resolution Solid-State LIDAR Transmitter,” filed on July 31, 2019. The entire contents of U.S. Provisional Patent Application No. 62 / 881,354 are incorporated herein by reference. Background Art

[0004] Autonomous, self-driving, and semi-autonomous vehicles use a combination of different sensors and technologies, such as radar, image recognition cameras, and sonar, to detect and locate surrounding objects. These sensors enable many improvements in driver safety, including collision warnings, automatic emergency braking, lane departure warnings, lane keeping assist, adaptive cruise control, and automated driving. Among these sensor technologies, light detection and ranging (LIDAR) systems play a key role, enabling real-time, high-resolution 3D mapping of the surrounding environment.

[0005] Today, most commercially available LIDAR systems for autonomous vehicles utilize a small number of lasers combined with some method of mechanically scanning the environment. It is highly desirable that future autonomous vehicles utilize LIDAR systems based on solid-state semiconductors, which support fast scan rates and are easily combined with high reliability and a wide range of environmental operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present teachings, along with further advantages thereof, are described in more detail in the following detailed description in conjunction with the accompanying drawings, according to preferred and exemplary embodiments. Those skilled in the art will appreciate that the drawings described below are for illustration purposes only. The drawings are not necessarily to scale; instead, emphasis is generally placed on illustrating the principles of the present teachings. The drawings are not intended to limit the scope of the applicant's teachings in any way.

[0007] Figure 1 is a schematic diagram illustrating the operation of an embodiment of a high-resolution LIDAR system of the present teachings implemented in a vehicle.

[0008] Figure 2A A two-dimensional vertical cavity surface emitting laser (VCSEL) array that may be used in a high resolution LIDAR system of the present teachings is shown.

[0009] Figure 2B Shown Figure 2A Sub-aperture array of a two-dimensional VCSEL array.

[0010] Figure 3A Shown is the transmit optics system for projecting a beam from a laser array using two conventional volume lenses.

[0011] Figure 3B Shown Figure 3A An enlarged view of a portion of the launch optics system is shown.

[0012] Figure 3C Shown by the use of Figure 3A An array of lasers projects a beam to the launch optics system to produce a far-field pattern.

[0013] Figure 4A Shown is a transmission optical system for projecting a light beam from a laser array using a microlens array and a bulk lens.

[0014] Figure 4B Shown Figure 4A An enlarged view of a portion of the launch optics system is shown.

[0015] Figure 4C Shown by the use of Figure 4A An array of lasers projects a beam to the launch optics system to produce a far-field pattern.

[0016] Figure 5A An embodiment of a transmission optical system for projecting a beam from a laser array using two microlens arrays and a volume lens of the present teachings is shown.

[0017] Figure 5B Shown Figure 5A An enlarged view of a portion of the launch optics system is shown.

[0018] Figure 5C Shown by the use of Figure 5A An example of a far-field pattern produced by the launch optics of a laser array projecting a beam is shown.

[0019] Figure 6 A cross-sectional view of an embodiment of a double-sided microlens array aligned with a VCSEL array of the present teachings is shown.

[0020] Figure 7A A perspective view of one side of an embodiment of a double-sided microlens array of the present teachings is shown.

[0021] Figure 7B Instructions for display Figure 7A A perspective view of the other side of an embodiment of a double-sided microlens array.

[0022] Figure 8 An embodiment of a high-resolution LIDAR transmit system including multiple transmit optical systems of the present teachings is shown.

[0023] Figure 9A Shown is the far-field pattern of a single LIDAR transmitter using a system for projecting a beam from a laser array using two conventional volume lenses.

[0024] Figure 9B Shown are the far-field patterns of multiple interleaved LIDAR transmitters using a system for projecting beams from a laser array using a microlens array and a conventional volume lens.

[0025] Figure 9C Shown are the far-field patterns of multiple interwoven LIDAR transmitters using an embodiment of a transmit optical system projecting beams from a laser array using two microlens arrays and a traditional volume lens of the present teachings. DETAILED DESCRIPTION

[0026] This teaching will now be described in more detail with reference to the exemplary embodiments of this teaching as shown in the accompanying drawings. Although this teaching has been described in conjunction with various embodiments and examples, this teaching is not intended to be limited to these embodiments. On the contrary, this teaching encompasses various replacements, modifications, and equivalents, as will be understood by those skilled in the art. Those of ordinary skill in the art who obtain this teaching will recognize additional embodiments, modifications, and embodiments and other fields of use within the scope of the present disclosure as described herein.

[0027] Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present teachings. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

[0028] Should be understood that the various steps of the method of this teaching can be in any order and / or performed simultaneously, as long as this teaching keeps being operable.In addition, should be understood that the apparatus and method of this teaching can include any number or all of the described embodiments, as long as this teaching keeps being operable.

[0029] The present teachings relate to light detection and ranging (LIDAR), a remote sensing method that uses lasers to measure the distance (range) to an object. A LIDAR system measures the distance to various objects or targets that reflect and / or scatter light. Autonomous vehicles utilize LIDAR systems to generate high-precision three-dimensional (3D) maps of their surroundings at high resolution. The systems and methods described herein are directed to providing a solid-state, pulsed time-of-flight (TOF) LIDAR system with a high level of reliability while also maintaining a long measurement range and relatively low cost. In particular, a LIDAR system according to the present teachings emits short-duration laser pulses and uses direct detection of the return pulses in the form of received return signal traces to measure the TOF to an object.

[0030] Furthermore, the LIDAR system of the present teachings is capable of using multiple laser pulses to detect objects with various performance metrics. For example, multiple laser pulses can be used to improve the signal-to-noise ratio (SNR). Multiple laser pulses can also be used to provide greater confidence in the detection of a particular object. For example, a specific number of laser pulses can be selected to provide a specific level of SNR and / or a specific confidence value associated with the detection of an object. This selection of the number of laser pulses can be combined with the selection of a single laser device or group of laser devices associated with a specific illumination pattern in the FOV.

[0031] A feature of the LIDAR system taught herein is that the emitters can emit light of different wavelengths. Thus, various emitters in the array can produce light having a different wavelength than other emitters. For example, emitters in one column or row can emit one wavelength, and emitters in alternate columns or rows can emit a different wavelength. Various wavelength patterns of emitting laser light having different wavelengths can be used, for example, to provide desired resolution, long-range operation within eye-safe limits of operation, and / or increase the data rate of the system. For example, see U.S. Patent Publication No. 20170307736A1 entitled “Multi-Wavelength LIDAR System” and U.S. Patent Publication No. 20180259623A1 entitled “Eye-Safe Scanning LIDAR System,” both of which are assigned to the present assignee. U.S. Patent Publications 20170307736A1 and 20180259623A1 are incorporated herein by reference.

[0032] Figure 11 is a schematic diagram illustrating the operation of a LIDAR system 100 of the present teachings implemented in a vehicle. The LIDAR system 100 includes a transmitting optical system, described in greater detail herein, that projects a light beam 102 generated by a laser array in the transmitting optical system toward a target scene. The LIDAR system also includes a receiver 103 that receives light 104 reflected from an object in the target scene, shown as a person 106. The LIDAR system also typically includes a controller that calculates distance information about the object (person 106) based on the reflected light.

[0033] In some embodiments, there is also an element that can scan or provide a specific pattern of light, which can be a static pattern or a dynamic pattern across the desired range and field of view (FOV). A portion of the reflected light from the object (person 106) is received by the receiver 103. In some embodiments, the receiver includes receiving optics and a detector element, which can be a detector array. The receiver and controller are used to convert the received signal light into a measurement result representing a point-by-point 3D map of the surrounding environment that falls within the range and FOV of the LIDAR system.

[0034] Some embodiments of LIDAR systems according to the present teachings use laser emitters comprising a laser array. In some embodiments, the laser array comprises a VCSEL laser emitter, which may include a top-emitting VCSEL, a bottom-emitting VCSEL, and / or various types of high-power VCSELs. The VCSEL array may be monolithic. The laser emitters may all share a common substrate, including a semiconductor substrate or a ceramic substrate. A single controlled laser emitter may include multiple subapertures, each of which emits a beam when the laser emitter is energized.

[0035] In some embodiments, in embodiments using one or more emitter arrays, the excitation of each laser and / or group of lasers can be controlled individually. Each individual emitter in the emitter array can emit independently, and the beam emitted by each laser emitter corresponds to a three-dimensional projection angle that only covers a portion of the overall system field of view. An example of such a LIDAR system is described in U.S. Patent Publication No. 2017 / 0307736A1, which is assigned to the present assignee. In addition, the number of pulses emitted by each laser or group of lasers can be controlled based on the desired performance goals of the LIDAR system. The duration and timing of the sequence can also be controlled. For example, see U.S. Provisional Patent Application No. 62 / 714,463 entitled "Distributed Modular Solid-State LIDAR System", which is assigned to the present assignee and incorporated herein by reference. See also U.S. Provisional Patent Application No. 62 / 859,349, entitled “Eye-Safe Long-Range Solid-State LIDAR System,” and U.S. Provisional Patent Application No. 62 / 866,119, entitled “Adaptive Multi-Pulse LIDAR System,” both of which are also assigned to the present assignee and incorporated herein by reference.

[0036] Another feature of the LIDAR system of the present teachings is that it can provide a compact, reliable transmitting optical assembly for a high-resolution LIDAR system. The transmitting optical assembly of the present teachings utilizes an array of solid-state lasers, which in some embodiments are fabricated on the same substrate. The substrate can be a semiconductor substrate. Electrical drive circuits are also fabricated on these array substrates, which allow each laser in the array to be individually controlled. These arrays can be two-dimensional arrays using regular row and column configurations. The electrical control drive scheme can be configured into a so-called matrix configuration, where individual lasers are addressed by appropriately applying electrical control signals to specific columns and specific rows containing the individual lasers. For example, see U.S. patent application No. 16 / 841,930 entitled "Solid-State LIDAR Transmitter with Laser Control," which is assigned to the present assignee and incorporated herein by reference.

[0037] Figure 2AA two-dimensional vertical cavity surface emitting laser (VCSEL) array 200 that can be used in a high-resolution LIDAR system of the present teachings is shown. The laser array 200 includes a 16×16 array of individual laser pixels 202, where each pixel 202 includes a 3×3 array of subapertures 204. In some embodiments, each pixel 202 can be individually addressed by applying the correct electrical control signals to the rows and columns corresponding to the pixels 202 in the array. Thus, each pixel 202 is independently excited, and all subapertures 204 within a pixel 202 are excited along with the excitation of the pixel 202. Thus, nine beams are provided for each excited pixel.

[0038] Array 200 has a pixel pitch 206 in the x-direction and a pixel pitch 208 in the y-direction. In some embodiments, the pixel pitch 206 in the x-direction is equal to the pixel pitch 208 in the y-direction. For example, in one particular embodiment, the pixel pitch in the x-direction is 250 μm and the pixel pitch in the y-direction is 250 μm. The number of elements in array 200 varies in various embodiments. In various embodiments, the array pixel pitch can take various values. It should be understood that although many of the examples provided herein describe arrays of specific sizes, the present teachings are not limited to any specific array size. A feature of the present teachings is that solid-state, microfabricated components can be easily and cost-effectively scaled to large sizes with high reliability.

[0039] Figure 2B Shown Figure 2A FIG. 2 shows a subaperture array 250 of a two-dimensional VCSEL array 200. A single pixel 202 is shown. Each pixel 202 has nine subapertures 204 arranged in a 3×3 array. Each pixel 202 has a subaperture spacing 252 in the x-direction and a subaperture spacing 254 in the y-direction. The subapertures 204 associated with a single pixel 202 are all simultaneously activated in response to appropriate electrical control signals. Thus, all subapertures 204 within a single pixel 202 are illuminated simultaneously. Therefore, when an electrical control signal is applied to a pixel 202, multiple light beams are generated, one from each aperture in the pixel. In some embodiments, the subaperture spacing 252 in the x-direction is equal to the subaperture spacing 254 in the y-direction. For example, in one specific embodiment, the subaperture spacing in the x-direction is 76 μm and the subaperture spacing in the y-direction is 76 μm. In various embodiments, the number of apertures in the subarray of a single pixel varies. In various embodiments, the array subaperture spacing can take on various values.

[0040] Figure 3A A transmission optical system 300 is shown for projecting a beam from a laser array 302 using two conventional body lenses 304, 306. The laser array 302 may be combined with, for example, Figure 2A-2BThe laser array 200 described is the same or similar.

[0041] Figure 3B yes Figure 3A FIG3 is an enlarged view of a portion of the transmit optical system 300 shown in FIG3 . The laser array 302 is shown in one dimension and includes individual pixels 308 and 310. Only two pixels are shown, pixel 1 308 and pixel 2 310. Pixels 308 and 310 each have an array of subapertures. Furthermore, subapertures A 312, B 314, and C 316 of pixel 1 308 and subapertures A 318, B 320, and C 322 of pixel 2 310 are shown in one dimension. A light beam 326 from each subaperture 312, 314, 316, 318, 320, 322 is emitted and diverges, as shown in enlarged view 324. The divergence angle of each light beam is related to the size of the corresponding subaperture.

[0042] Reference Figure 3A and Figure 3B , a separate diverging beam 326 passes through a body lens 304 with a focal length F1 at a distance from the array 302, and a second body lens 306 with a focal length F2 at a distance from the first body lens 304. The positions of the lenses 304, 306 and their focal lengths F1, F2 determine the projected far-field pattern of the transmit optical system 300. For this optical system, the two body lenses 304, 306 are configured to nominally generate an image of the laser array 302 in the far field. Thus, the laser array pattern is reconstructed in the far field, magnified to the desired size based on the lens configuration, and the sub-apertures from each pixel are spatially separated. The angular field of view (FOV) of each pixel is approximately the same as the angular spacing between pixels.

[0043] Figure 3C The far field pattern 350 produced by the transmitting optical system 300 is shown for projecting light from Figure 3A The far-field light spot at a range of 50 meters is shown for two vertically adjacent pixels, where each pixel includes a 3×3 subaperture array. This example far-field pattern 350 is produced at a distance of 50 meters from the optical system 300. Pattern 350 includes nine individual light spots 352 for each pixel region 354, 356. Each pixel region 354, 356 is separated by a distance of 0.9 meters at a range of 50 meters. The ratio of this pixel spot size to pixel pitch is ~0.9.

[0044] Figure 3A-3C Only a portion of a 16x16 laser array is shown, for example, each laser having nine subapertures. For a full 16x16 array, the pattern would appear as (16x3)x(16x3) spots, or 48x48 spots.

[0045] The spot size from the emitter in the far field can be reduced by using a small lens placed near the laser emitter to nominally collimate and / or focus each beam. Figure 4A Transmitting optics 400 are shown for projecting a beam from a laser array 402 using a microlens array 404 and a bulk lens 406 .

[0046] Figure 4B yes Figure 4A An enlarged view of a portion of the emission optical system 400 is shown in FIG. Figure 4A and Figure 4B In this emission optical system 400, the microlens array 404 has a pitch equal to the pixels (pixel 1 408 and pixel 2 410) in the array 402. The microlens array 404 collimates each subaperture of the pixels, subapertures A 412, B 414, and C 416 of pixel 1 408, and subapertures A 418, B 420, and C 422 of pixel 2 410. The microlens array 404 includes a plurality of lenslets 424, 426 that are spaced apart at the same pitch as the pixel pitch of the laser array 402.

[0047] Each lenslet 424, 426 collimates the light beam emitted from the corresponding pixel 408, 410. The collimated light beams from each subaperture 412, 414, 416, 418, 420, 422 overlap at a plane Z1 428 located one focal length from the lenslets 424, 426 in the microlens array 404. The body lens 406 has a focal length F2 and is located at a distance F2 from the plane Z1 428. The body lens 406 projects the light beams from each pixel along nominally parallel paths to the far field.

[0048] Figure 4C The far field pattern 450 produced by the transmitting optical system 400 is shown. Figure 4A The far-field pattern 450 results in two large light spots 452 and 454 separated by a distance 456 of 0.9 meters at a range of 50 meters. In large light spot 454, the beams from all nine subapertures of a single pixel 408 overlap. The ratio of this pixel spot size to the pixel pitch is approximately 0.5.

[0049] Notice, Figure 4AOnly three subapertures 412, 414, 416 of pixel 1 408 are shown because it is a side view, but the far-field pattern 450 is illustrated in two dimensions and thus shows the spots provided by all nine subapertures of pixel 1 408. This is similar for pixel 2 410 and the associated spot 452. The ratio of the pixel spot size to the pixel pitch for this transmit optical system is ~0.5.

[0050] use Figures 4A-4C The LIDAR system of the transmit optical system 400 shown in FIG already has improved resolution because it already reduces the spot size compared to a system that does not use microlenses for collimation. However, a feature of the present teachings is the recognition that the use of two patterned back-to-back microlens arrays can provide further improvements in LIDAR system resolution.

[0051] Figure 5A An embodiment of a transmission optical system 500 of the present teachings for projecting a light beam from a laser array 502 using two microlens arrays 504 , 506 and a bulk lens 508 is shown.

[0052] Figure 5B yes Figure 5A An enlarged view of a portion of the emission optical system 500 is shown in FIG. Figure 5A and Figure 5B, one microlens array 504 has lenslets 510, 512, 514 spaced at a pitch equal to the pixels (pixel 1 516, pixel 2 518, and pixel 3 520) in the laser array 502. The other microlens array 506 has lenslets 522, 524, 526, 528, 530, 532, 534, 536, 538 spaced at a pitch equal to the subapertures 540, 542, 544, 546, 548, 550, 552, 554, 556 of the laser array 502. Thus, the microlens 506 includes one lenslet per subaperture, and the microlens 504 includes one lenslet per pixel. The microlens array 506 acts on each light beam generated in each sub-aperture 540, 542, 544, 546, 548, 550, 552, 554, 556 so that each sub-aperture light beam is focused without changing the propagation axis of those light beams. The microlens 504 redirects the light beams from each sub-aperture 540, 542, 544, 546, 548, 550, 552, 554, 556 so that they overlap at the back focal plane Z1 558 of the lenslets 510, 512, 514. Therefore, the light beams from each sub-aperture 540, 542, 544, 546, 548, 550, 552, 554, 556 are focused at the overlapping plane at the back focal plane Z1 558 by the combined action of the microlens array 506 and the microlens array 504. The volume lens 508 is positioned at a distance from plane Z1 558 equal to the focal length F2 of the lens 508. The combination of the microlens arrays 504 and 506 produces an intermediate real image of an array of light spots with the same spacing as the laser array 502 on plane Z1 558. The volume lens 508 projects each light spot from Z1 558 to a different angle in the far field. The specific projection angle from the volume lens 508 is a function of the perpendicular distance of the corresponding array light spot from the system's principal optical axis.

[0053] A feature of the present teachings is the use of two back-to-back microlens arrays 504, 506 that are used to focus the beams from each subaperture and direct them to overlap at the back focal plane of the second lens 504. As can be clearly seen from the scale bar 560 in the magnified view 562, the two microlens arrays 504, 506 are very compact in design, and the nominally focused overlapping beams appear at a distance of less than 2 mm from the laser array 502. In some embodiments, the microlens arrays 504, 506 are fabricated on the front and back surfaces of the same substrate. This advantageously provides a very compact system that is easy to assemble. In some embodiments, the microlens arrays 504, 506 are fabricated on separate substrates. In some embodiments, one or both of the microlens arrays 504, 506 can be refractive optical elements. In some embodiments, one or both of the microlens arrays 504, 506 can be diffractive optical elements. In some embodiments, one or both of the microlens arrays 504, 506 can be holographic optical elements.

[0054] Figure 5C An embodiment of a far-field pattern 580 generated by a transmitting optical system 500 is shown for transmitting light from a source. Figure 5A The laser array 502 projects a beam. The far-field spot at a range of 50 meters is shown for two vertically adjacent pixels, where each pixel includes a 3×3 sub-aperture array. Note that Figure 5A The system diagram shows a side view of a 2-dimensional array, but Figure 5C A two-dimensional pattern in a plane perpendicular to the main axis is shown. For clarity, only a portion of the system is shown. The far-field pattern 580 results in two small spots 582 and 584, which are separated by a distance 586 of 0.9 meters at a range of 50 meters. Only the spots 582 and 584 of two pixels 516 and 518 are shown. There is 1.06 degrees between the pixels, resulting in a separation distance 586 of 0.9 meters at a range of 50 meters. The ratio of this pixel spot size to the pixel pitch is ~0.1. The ultimate resolution is determined by the spot size of one pixel relative to the spot separation between the spots of adjacent pixels. Therefore, the emission optical system of the present teachings advantageously provides a much smaller ratio of pixel spot size to pixel pitch in the far field. This improves system resolution and also allows efficient and scalable interleaving of multiple emission optical systems, which provides many benefits for data collection, including supporting high data collection rates and flexibility in illumination patterns and timing.

[0055] Figure 6A cross-sectional view 600 of an embodiment of a double-sided microlens array 602 aligned with a VCSEL array 604 according to the present teachings is shown. The VCSEL includes five pixels 606, 608, 610, 612, 614. Each pixel 606, 608, 610, 612, 614 includes nine subapertures. For example, three subapertures 616, 618, 620 can be seen in the cross-sectional view 600 of the pixel. The pixels are arranged in an array with a pitch 622. Five pixel lenslets 624, 626, 628, 630, 632 are formed on a first surface 634 of a substrate 636. The pixel lenslets 624, 626, 628, 630, 632 are arranged in an array with a pitch 638 and match the array of pixels 606, 608, 610, 612, 614 in the VCSEL array 604. Formed on the second surface 638 of the substrate 636 are subaperture lenslets 640, which are arranged at a pitch 642 that matches the pitch of the subapertures of the VCSEL array 604. This microlens array 602 configuration can be referred to as a double-sided microlens. In one specific embodiment, the pixel pitch is 250 μm and the subaperture pitch is 76 μm. In some embodiments, the laser array 604 and the microlens array 602 are one-dimensional. Furthermore, in some embodiments, the laser array 604 and the microlens array 602 are two-dimensional. In various embodiments, the laser array 604 and the microlens array 602 include different numbers of pixels, subapertures, pixel lenslets, and / or subaperture lenslets. In some embodiments, the pixel pitch 622 is not an integer multiple of the subaperture pitch 642. In some embodiments, the subaperture pitch 642 does not extend across the boundaries of the pixels.

[0056] In some embodiments, the sub-aperture lenslet 640 side of the microlens array 602 is positioned closest to the VCSEL array 604. The pixel lenslet surface 634 is positioned farthest from the VCSEL array 604, with each lenslet 624, 626, 628, 630, 632 centered directly above the pixel. Figure 6 This positioning is specifically shown in FIG for the pixel lenslet 628 above the pixel 610. The subaperture lenslet is centered directly above the subaperture. Figure 6 This is shown for example for a sub-aperture lenslet 640 above a sub-aperture 644 .

[0057] Figure 7AA perspective view 700 is illustrated showing one side of an embodiment of a double-sided microlens array 702 of the present teachings. Pixel lenslets 704 are formed on one surface 706 of a substrate 708. The lenslets 704 have a pitch that matches the pitch of, for example, a VCSEL array, such that there is one lens per pixel in embodiments of an emission optical system of the present teachings. A 5×5 array of lenslets 704 is shown in perspective view 700. Subaperture lenslets 712 are visible on the other surface 710 of substrate 708.

[0058] Figure 7B The diagram shows Figure 7A A perspective view 750 of the other side of the double-sided microlens array. Circle 752 highlights a 9×9 array of sub-aperture lenslets 754 formed on the other surface 710 of the substrate. The pitch of the sub-aperture lenslets 754 matches the pitch of the sub-apertures of a matching laser array (e.g., a VCSEL array). There are nine sub-aperture lenslets per pixel.

[0059] Figure 8 An embodiment of a high-resolution LIDAR transmit system 800 including multiple transmit optical systems 802, 804 of the present teachings is shown. One feature of the present invention is that the two microlens array configurations described herein enable the use of separate transmit optical systems that are aligned so that the total FOV generated by one transmit optical system 802 is offset from the total FOV generated by the second transmit optical system 804 by less than one pixel FOV. This type of configuration may be referred to as an interleaved configuration. By interleaving the light from the two transmit optical systems 802, 804, the spatial resolution of a LIDAR system including the interleaved transmit systems 800 is greatly improved compared to a LIDAR system using only one transmit optical system.

[0060] Interleaving will only have uniform spacing between the light spots generated by each of the two different transmit optical systems at one target distance (sometimes referred to as perfect interleaving). However, because the separation between transmit optical systems 802, 804 can be very small, in some embodiments, the separation is on the order of 10 millimeters, and in some embodiments, the target distance is on the order of 10 meters, even imperfect interleaving is acceptable and improves resolution. Therefore, it is possible to improve resolution over a range of target distances by interleaving transmit optical systems 802, 804 using the transmit optical systems of the present teachings. Figure 8 An interleaved spot array 806 at a target distance is shown illustrating the interleaving of a first spot array 808 from the transmit optical system 802 and a second spot array 810 from the transmit optical system 804 .

[0061] Figure 9A Shows the use of Figure 3AFar-field pattern 900 for a single solid-state LIDAR transmitter for a system projecting a beam from a laser array using two conventional bulk lenses is shown. Pixel spot size 902 and pixel pitch 904 are nominally the same. Pixel spot size 902 is a full pixel. All subaperture spots are illuminated by a control signal applied to excite that pixel and associated subaperture. Therefore, it is not possible to interleave pixel spots 906 from two different transmit optical systems using only two bulk lenses without microlenses. For this system, the pixel spot size in the far field is close to the pixel pitch. Consequently, there is no room to interleave the spots and provide improved resolution by using two transmit optical systems.

[0062] Figure 9B The far field pattern 930 of multiple interleaved solid-state LIDAR transmitters using a system for projecting beams from a laser array using, for example, Figure 4A A microlens array and a conventional volume lens are shown. In this configuration, the spot size from a single excitation pixel is shown as a shaded spot 932, which is smaller than the pixel FOV pitch 934. For this system, the ratio of the pixel spot size to the pixel pitch in the far field is close to 0.5. Therefore, in this case, four emission optical systems can be interleaved, for example. This produces four different pixel spots 932, 936, 938, and 940 associated with four different emission optical systems. Interleaving the spots from four different emission optical systems increases the spatial resolution by a factor of two in each dimension.

[0063] Figure 9C The far field pattern 950 of multiple interwoven solid-state LIDAR transmitters using an embodiment of a transmit optical system for projecting beams from a laser array using two microlens arrays and a conventional volume lens of the present teachings is shown. This embodiment of the transmit optical system can be, for example, Figure 5A . In this configuration, the size of the pixel spot 952 of a single pixel spot 954 is very small compared to the pixel FOV pitch 956. In some embodiments, the ratio of the pixel spot size to the pixel pitch in the far field is less than 0.1. The spots 954 from at least nine transmit optical systems can be interleaved to increase spatial resolution. Different shading is used to illustrate the pixel spots from different transmit optical systems.

[0064] Combine Figures 9A-9C The described examples show far-field patterns 900, 930, 950 produced by a VCSEL array having a 3x3 grid of pixels, where each pixel comprises a 3x3 grid of subapertures. Scaling to different array sizes and / or shapes for pixel and / or subaperture sizes and / or shapes is a straightforward extension.

[0065] Thus, one feature of an emission optical system utilizing a combination of subaperture microlenses, pixel microlenses, and volume lenses is that the spatial resolution is sufficiently improved to allow for interleaving of the emission optical system, where the subaperture microlenses are used to focus the beams from the VCSEL pixel subaperture emitters, the pixel microlenses are used to redirect the subaperture beams to their focal points at the points of overlap, and the volume lenses are used to project the subaperture beams in each pixel to different angles in the far field. This improvement is due in part to achieving a smaller ratio of the far-field pixel spot size to the pixel pitch. The different projection angles in the far field are based on the position of a particular pixel beam relative to the central axis or principal axis of the volume lens. Thus, by using volume lenses with different focal lengths and positions, a variety of far-field projection angles can be achieved.

[0066] equivalent

[0067] Although the applicant's teachings are described in conjunction with various embodiments, the applicant's teachings are not intended to be limited to these embodiments. On the contrary, as will be appreciated by those skilled in the art, the applicant's teachings encompass various alternatives, modifications, and equivalents that can be made therein without departing from the spirit and scope of the present teachings.

Claims

1. A solid-state light detection and ranging (LIDAR) transmitter comprising: a) Laser array, comprising: i) a first laser pixel comprising a first sub-aperture and a second sub-aperture positioned at a first sub-aperture interval, each of the first sub-aperture and the second sub-aperture of the first laser pixel generating a corresponding sub-aperture beam when excited; and ii) a second laser pixel, the second laser pixel comprising a first sub-aperture and a second sub-aperture positioned at a second sub-aperture spacing, each of the first sub-aperture and the second sub-aperture of the second laser pixel generating a corresponding sub-aperture beam when excited, the first laser pixel and the second laser pixel being positioned relative to each other at the pixel spacing; b) a first microlens, the first microlens comprising a first sub-aperture lenslet and a second sub-aperture lenslet positioned at the first sub-aperture interval and comprising a third sub-aperture lenslet and a fourth sub-aperture lenslet positioned at the second sub-aperture interval, the first microlens being positioned such that the first sub-aperture lenslet is in an optical path of a first sub-aperture beam generated by the first sub-aperture of the first laser pixel, the second sub-aperture lenslet is in an optical path of a second sub-aperture beam generated by the second sub-aperture of the first laser pixel, the third sub-aperture lenslet is in an optical path of the first sub-aperture beam generated by the first sub-aperture of the second laser pixel, and the fourth sub-aperture lenslet is in an optical path of the second sub-aperture beam generated by the second sub-aperture of the second laser pixel, the first microlens being configured to focus the first and second sub-aperture beams generated by the first and second sub-apertures of the first laser pixel and to focus the first and second sub-aperture beams generated by the first and second sub-apertures of the second laser pixel; c) a second microlens, the second microlens comprising a first pixel lenslet and a second pixel lenslet positioned relative to each other at the pixel pitch, wherein the first pixel lenslet is positioned in optical paths of both a first sub-aperture beam and a second sub-aperture beam generated by the first sub-aperture and the second sub-aperture beam of the first laser pixel, the second microlens being configured to guide the first sub-aperture beam and the second sub-aperture beam generated by the first sub-aperture and the second sub-aperture beam of the first laser pixel such that the first sub-aperture beam and the second sub-aperture beam generated by the first sub-aperture and the second sub-aperture beam of the first laser pixel overlap at a plane; and d) a lens positioned in paths of a first sub-aperture beam and a second sub-aperture beam generated by the first sub-aperture and the second sub-aperture beam of the first laser pixel, the lens being configured to project the first sub-aperture beam generated by the first sub-aperture of the first laser pixel and the first sub-aperture beam generated by the first sub-aperture of the second laser pixel at different angles in a far field to achieve a desired spatial resolution of the solid-state light detection and ranging (LIDAR) transmitter.

2. The solid-state light detection and ranging (LIDAR) transmitter of claim 1, wherein: The laser array includes a one-dimensional laser array.

3. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein: The laser array includes a two-dimensional laser array.

4. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein: The laser array includes an array of vertical cavity surface emitting lasers (VCSELs).

5. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein at least one of the first microlens and the second microlens is formed on a same side of a substrate.

6. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein: The first microlens and the second microlens are configured such that a ratio of a far-field pixel spot size to a pixel pitch is less than 1.

7. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein: The first microlens and the second microlens are configured such that a ratio of a far-field pixel spot size to a pixel pitch is less than 0.

5.

8. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein: The first microlens and the second microlens are configured such that a ratio of a far-field pixel spot size to a pixel pitch is less than 0.

2.

9. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein: The second microlens array is configured such that the plane is located at a distance from the second microlens that is equal to the focal length of the first pixel lenslet.

10. The solid-state light detection and ranging (LIDAR) transmitter of claim 1, wherein: The second microlens array is configured such that the plane is located at a distance of less than 2 mm from the laser array.

11. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein: The lens is positioned at a distance from the plane equal to the focal length of the lens.

12. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein the first microlens, the second microlens, and at least one of the lens are configured to project the first sub-aperture beam and the second sub-aperture beam of the first pixel such that the first sub-aperture beam and the second sub-aperture beam of the first pixel overlap in the far field, such that the solid-state light detection and ranging (LIDAR) transmitter achieves a resolution of less than 0.2 degrees.

13. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein at least one of the first microlens array and the second microlens array comprises a refractive optical element.

14. The solid-state light detection and ranging (LIDAR) transmitter of claim 1 , wherein: At least one of the first microlens array and the second microlens array includes a diffractive optical element.

15. The solid-state light detection and ranging (LIDAR) transmitter of claim 1, wherein: At least one of the first microlens array and the second microlens array includes a holographic optical element.

16. The solid-state light detection and ranging (LIDAR) transmitter of claim 1, wherein: The first microlens is configured to focus the first sub-aperture beam and the second sub-aperture beam of the first pixel at the plane, and to focus the first sub-aperture beam and the second sub-aperture beam of the second pixel at the plane.

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