English:
[0002] Light detection and ranging (LIDAR) systems detect and determine the position of objects. In one example, a light beam is projected to a known position in a field of view. A light detector is focused on that position in the field of view and detects any reflection of the light from an object that may be in the field of view. The time the light travels is used to help determine the distance of the object. By scanning the light beam across the field, the position of objects in the field and an image of the objects can be determined.
[0003] A challenge with scanning-type LIDAR systems is scanning rapidly and accurately enough to capture movement of objects within the field. For example, in automotive applications, the LIDAR system must rapidly and accurately determine the movement of pedestrians and vehicles, as well as other objects. Mirrors have been applied to scan the beams. Other examples use gimbal mounts to move the entire light projection and detection system as one unit. However, it is difficult to operate these mechanical systems with sufficient accuracy. In addition, such systems are often bulky, have large power requirements, and require frequent maintenance and calibration to maintain accuracy.
[0005] FIGS. 1A and IB (collectively“FIG. 1) are diagrams illustrating light steering using phase light modulators (PLMs).
[0006] FIG. 2 is a side view of an example micromirror.
[0007] FIG. 3 is a top view of an example LIDAR apparatus.
[0008] FIGS. 4A-D (collectively“FIG. 4”) are views of a transmit portion of an example LIDAR apparatus and a scanning pattern used with the LIDAR apparatus.
[0009] FIGS. 5 A and 5B (collectively“FIG. 5”) are views of a receive portion of the LIDAR apparatus of FIG. 4.
[0010] FIG. 6 is a diagram of another example LIDAR apparatus.
[0011] FIG. 7 is a flow diagram of an example method.
[0012] FIG. 8 is a flow diagram of another example method.
[0013] In the drawings, corresponding numerals and symbols generally refer to corresponding parts unless otherwise indicated. The drawings are not necessarily drawn to scale.
[0014] In this description, the term“coupled” may include connections made with intervening elements, and additional elements and various connections may exist between any elements that are“coupled.” Elements referred to herein as“optically coupled” are elements that include a connection between the elements that involves transmission of light. Also as used herein, a “phase light modulator” (PLM) is a device with a plurality of pixels, wherein the PLM may modify the phase of light applied to each pixel. The PLM may reflect or transmit the applied light. The interference of the light from the phase modified pixels and/or phase unmodified pixels modulates the applied light.
[0015] In example arrangements, the problems of slow scan rates and a narrow field of view (FOV) for a phase light modulator (PLM) steered light source are solved by providing at least two light sources to a PLM such that the light from each light source scans a different FOV contemporaneously. In at least one example, the LIDAR apparatus has a single PLM device used for at least two light sources. The light sources have different angular orientations relative to the PLM. Because of the different angular orientations, each laser illuminates a point in a respective field of view (FOV), and all FOVs are scanned contemporaneously and tiled together. In accordance with an example, an apparatus includes a phase light modulator. The apparatus also includes a first light source optically coupled to the phase light modulator, the first light source configured to generate a first light beam and positioned to direct the first light beam to the phase light modulator at a first angle of incidence, the phase light modulator configured modulate the first light beam to provide a first modulated light beam and to direct the first modulated light beam to a first field of view responsive to the first light beam; and a second light source optically coupled to the phase light modulator, the second light source configured to generate a second light beam and positioned to direct the second light beam to the phase light modulator at a second angle of incidence, the phase light modulator configured modulate the second light beam to provide a second modulated light beam and to direct the second modulated light beam to a second field of view responsive to the second light beam. The apparatus also includes a first light detector optically coupled to the first field of view and configured to detect the first modulated light beam as reflected from the first field of view and a second light detector optically coupled to the second field of view and configured to detect the second modulated light beam as reflected from the second field of view.
[0016] An example PLM is a digital micromirror based PLM. This type of PLM device includes a number of digital micromirrors on the surface of a substrate. In examples, this type of PLM may include hundreds of thousands of micromirrors or more than a million micromirrors. Each micromirror is designed so that its vertical position above the substrate can be precisely positioned using electrostatic force applied to the micromirror by driving circuitry in the substrate. The phase of light reflected from a particular micromirror is determined by the vertical position of the micromirror (vertical with respect to the substrate, which is horizontal for this discussion). For example, if a first micromirror is a its full height above the substrate and an adjacent second micromirror is lowered one fourth of a wavelength, the light reflected from the second micromirror travels one-half wavelength (one quarter wavelength down plus one quarter wavelength up) relative to light reflected from the first micromirror. The light reflected from the first and second micromirrors will then interfere in a predictable manner. The pattern of phase changes on a PLM may be selected to provide a desired diffraction-like effect, such as steering or focusing the light. See, e.g. McManamon et al.,“Optical Phased Array Technology, Proc. of the IEEE, Vol. 84, No. 2, pp 269-298 (Feb. 1996), which is hereby incorporated by reference herein in its entirety. Arbitrary patterns such as spots or beams can be created at a desired distance in the field of view. Another example PLM is a liquid crystal type phase light modulator. With this type of PLM, a voltage applied at each pixel alters the liquid crystal at that pixel to cause a phase shift of the light. Liquid crystal PLMs may be transmissive or reflective.
[0017] FIGS. 1A and IB (collectively“FIG. 1) are diagrams illustrating light steering using PLMs. In this example, PLM 102 is a digital micromirror based PLM. In FIG. 1 A, micromirrors 104 of PLM 102 have a steering pattern selected to direct light 106 in direction 108. In FIG. IB, micromirrors 104 have a pattern selected to direct light 106 in a direction 110. Thus, PLM 102 can steer light in a desired direction. In addition to steering the light, PLM 102 can focus the light at a spot (focal point) at a desired distance.
[0018] FIG. 2 is a side view of an example micromirror like one of micromirrors 104 (FIG. 1). Platform 204 connects to two platform electrodes 212 via platform posts 214. Post 208 supports mirror 210 above platform 204. As shown in FIG. 2, when a voltage is applied to driving electrode 206 and a reference voltage (e.g. ground) is applied to platform electrodes 212, an electrostatic force pulls platform 204, and thus mirror 210, down. The amount of movement is determined by the applied voltage. In other examples, pixel 202 uses two or more driving electrodes 206 that are individually addressable by driving circuitry (not shown). The applied electrostatic force is proportional to the area of a driving electrodes 206 and platform 204. Thus, using multiple electrodes the amount of force, and thus the vertical position of mirror 210 can be precisely controlled by selecting the driving electrode 206 or combination of driving electrodes 206, while applying the same voltage to each selected one of driving electrodes 206. The phase shift provided by pixel 202 is determined by the vertical positioning of mirror 210. For example, if a pixel lowers by one-quarter wavelength (1/4 l), light reflected from that pixel will travel an additional one-half wavelength (1/4 l down to the mirror and 1/4 l back) relative to a pixel that is not lowered. In another example, if a pixel lowers by one-eighth wavelength (1/8 l), light reflected from that pixel will travel an additional one-quarter wavelength (1/8 l down to the mirror and 1/8 l back) relative to a pixel that is not lowered.
[0019] FIG. 3 is a top view of an example LIDAR apparatus 300. Light source 302 is a laser in in this example. In an example, light source 302 provides near infrared laser light. Light source 302 provides light through collimating lens 304 to transmit PLM 306. Transmit PLM 306 provides a configurable phase pattern to the light that directs the light to target 308. In the example of FIG. 3, target 308 is on the surface of an object 310, which is an automobile. Light reflected from object 310 is focused by receive PLM 312 to detector 314 through lens 316. Because the point at which the light is directed by transmit PLM 306 is known, detection of reflected light by detector 314 indicates that an object is at that point. In this example, detector 314 is an avalanche photo diode. Transmit PLM 306 scans the field of view while receive PLM 312 scans the field of view seen by the APD to match the target 308 to which transmit PLM is scanning. This allows example LIDAR apparatus 300 to determine the distance and contour of object 310.
[0020] LIDAR apparatus 300 has limitations. For example, each pattern on the PLM corresponds to steering the light beam in a particular direction. A significant amount of time is required for the transmit PLM 306 and receive PLM 312 to change from one pattern to another. For example, if a new pattern’s data load time is 50ps, and the frame time is 100ms, then only 2,000 points can be captured, which is a resolution of only -65x30. A higher resolution is preferable. In addition, LIDAR scanning of large field-of-view (FOV) is difficult. Scanning an area larger than 60x20 degrees a with 0.1 degree beam width, 10 Hz frame rate requires a PLM update rate of greater than 1 million samples/second. However, the size of the mirrors in the PLM limits the field of view and the wavelength of the light limit the FOV. For a pixel size of about IOm square using near infrared light, the FOV of current PLM devices is limited to just a few degrees. Receive PLM 312 allows rejection of ambient light by directing light from a narrow angle to the detector. However, scanning a large FOV requires wide-angle optics. Wide angle optics require a small aperture size that limits the signal strength received at detector 314.
[0021] FIGS. 4A-D (collectively“FIG. 4”) are views of a transmit portion 402 of an example LIDAR apparatus 400. FIG. 4A is a top view of transmit portion 402. As used herein, the terms “top view” and“side view” indicate the relative orientation of the figures and do not denote any other relationship. For example, the“top” or“side” of LIDAR apparatus 400 may be in any of a number of orientations in a particular installation of example LIDAR apparatus 400. Example LIDAR apparatus 400 includes three light sources: first light source 404, second light source 406 and third light source 408. Controller 401 controls the light output of first light source 404, second light source 406 and third light source 408. Example LIDAR apparatus 400 includes three light sources in this example but may include two, four, or more light sources, which may be arranged in a one-dimensional or two-dimensional array. In addition, in this example, first light source 404, second light source 406 and third light source 408 are near-infrared laser diodes but may be other types of light sources, such ultraviolet light sources. First light source 404 provides first light beam 410 through first collimating lens 412 at a first angle of incidence relative to transmit PLM 414. Transmit PLM 414 is a digital micromirror based PLM in this example. In other examples, transmit PLM 414 is a reflective or transmissive liquid crystal phase light modulator. In accordance with a steering pattern applied to transmit PLM 414 by controller 401, the first output of transmit PLM 414 in response to first light beam 410 is first modulated light beam 416 having a first output angle of reflection. The first angle of incidence of first light source 404 and the steering pattern on transmit PLM 414 determine the output angle of reflection to the first focal point 411. In this example, the first angle of incidence directs first modulated light beam 416 to a first focal point 411 on object 450 in first field of view (FOV) 418.
[0022] Second light source 406 provides second light beam 420 through second collimating lens 422 at a second angle of incidence relative to transmit PLM 414. In accordance with a steering pattern applied to transmit PLM 414 by controller 401, the output of transmit PLM 414 in response to second light beam 420 is second modulated light beam 426 having a second angle of reflection. At any given time, the steering pattern on transmit PLM 414 is constant. Therefore, the difference between the second angle of reflection and the first angle of reflection is determined by the difference between the second angle of incidence and the first angle of incidence. As with the first angle of reflection, the second angle of reflection of second light source 406 and the pattern on transmit PLM 414 determine the second angle of reflection. In this example, the second angle of reflection directs second modulated light beam 426 to a second focal point 421 on object 450 in second FOV 428.
[0023] Third light source 408 provides third light beam 430 through third collimating lens 432 at a third angle of incidence relative to transmit PLM 414. In accordance with a steering pattern applied to transmit PLM 414 by controller 401, the output of transmit PLM 414 in response to third light beam 430 is third modulated light beam 436 having a third angle of reflection. At any given time, the steering pattern on transmit PLM 414 is constant. Therefore, the difference between the third angle of reflection and the first and second angles of reflection is determined by the difference between the third angle of incidence and the first and second angles of incidence. As with the first and second angles of reflection, the third angle of incidence of third light source 408 and the pattern on transmit PLM 414 determine third angle of reflection. In this example, the third angle of reflection directs third modulated light beam 436 to a third focal point 431 on object 450 in third FOV 438. In summary, transmit PLM 414 contemporaneously directs light from first light source 404, second light source 406 and third light source 408 to points in first FOV 418, second FOV 428 and third FOV 438, respectively.
[0024] FIG. 4B is a view of the fields of view as shown by view line 4B-4B of FIG. 4A. FIG. 4B is a view from the perspective of transmit PLM 414 facing first FOV 418, second FOV 428 and third FOV 438. For a given steering pattern on transmit PLM 414, first light source 404, second light source 406 and third light source 408 illuminate one point in each of first FOV 418, second FOV 428 and third FOV 438, respectively. By changing the steering pattern of transmit PLM 414, transmit portion 402 scans each FOV. In this example, first scanning points 442, second scanning points 452 and third scanning points 462 are scanned in a raster scan manner, as illustrated in FIG. 4B. However, other scanning methods may be used such as random scanning. As shown in FIG. 4B, in this example, the size of first FOV 418, second FOV 428 and third FOV 438 is selected so that first FOV 418, second FOV 428 and third FOV 438 avoid extraneous diffraction orders produced by light diffracting from the steering pattern on transmit PLM 414. In other examples, the FOVs overlap to provide more accurate, but slower, scanning. In these examples, any extraneous diffraction orders must be corrected after detection.
[0025] FIG. 4C is side view of transmit portion 402 of example LIDAR apparatus 400. FIG. 4C is a view looking across the face of transmit PLM 414 from the direction of third light source 408, which is from view 4C-4C of FIG. 4A. Third light source 408 blocks the view of first light source 404 and second light source 406 from this perspective. In addition, third collimating lens 432 blocks the view of first collimating lens 412 and second collimating lens 422. For simplicity, only third light beam 430 and third modulated light beam 436 are shown in FIG. 4C. As can be seen from FIG. 4C, third light beam 430 and third modulated light beam 436 are not in the same plane. In this example, this avoids interference of third light source 408 with third modulated light beam 436. A specific configuration of light sources is shown in this example vis-a-vis transmit PLM 414. Other examples may use different configurations. In addition, other examples may use two, four or more light sources.
[0026] FIG. 4D is a top view of another example transmit portion 405 of another example LIDAR apparatus 403. In this example apparatus, one light source 407 produces first modulated light beam 416, second modulated light beam 426 and third modulated light beam 436. Light source 407 provides light beam 423 through collimating lens 425. Transmit PLM 414 in this example does not use a single steering pattern, but rather uses three steering patterns. In an example, three different steering patterns would be applied to three different portions of transmit PLM 414. Three steering patterns are used in this example. However, two, four or more steering patterns may be used. In addition, the example of FIG. 4D includes one light source at one angle of incidence. However, using multiple light sources at multiple angles of incidence along with multiple steering patterns applied to transmit PLM 414 multiplies the number of fields of view that can be illuminated contemporaneously. For example, three light sources applied to a transmit PLM having three steering patterns can illuminated nine fields of view contemporaneously .
[0027] In the example of FIG. 4D, three steering patterns applied to transmit PLM 414 produce light first modulated light beam 416, second modulated light beam 426 and third modulated light beam 436, which illuminate object 450 at first focal point 411, second focal point 421 and third focal point 431, respectively, in first FOV 418, second FOV 428 and third FOV 438, respectively. The steering pattern scans the fields of view as described above with regard to FIG. 4 A and 4B. The example of FIG. 4D limits the amount of light provided to each focal point to one-third or less of the luminance provided by light source 407 because each steering pattern is applied to one-third or less of the area of transmit PLM 414.
[0028] FIGS. 5A and 5B (collectively“FIG. 5”) are views of a receive portion 502 of example LIDAR apparatus 400 (FIG. 4). FIG. 5A shows a top view of receive portion 502. Controller 501 is like controller 401 (FIG. 4). First detector 504, second detector 506 and third detector 508 detect light reflecting off an object in first FOV 518, second FOV 528 and third FOV 538, respectively. First FOV 518, second FOV 528 and third FOV 538 correspond to first FOV 418, second FOV 428 and third FOV 438 (FIG. 4). First focal point 511, second focal point 521 and third focal point 531 correspond to first focal point 411, second focal point 421 and third focal point 431 (FIG. 4), respectively. First detector 504 detects first focal point 511 in first FOV 518 illuminated by first light source 404 (FIG. 4). Second detector 506 detects second focal point
[0029] Receive PLM 514 focuses first reflected light beam 516 reflected from object 550 at a first focal point 511 in first FOV 518 as first received light beam 510 onto first detector 504 through first receiving lens 512. Receive PLM 514 is a digital micromirror based PLM in this example. In other examples, receive PLM 514 is a reflective or transmissive liquid crystal phase light modulator. Controller 501 receives the output of first detector 504 for further processing. First focal point 511 in first FOV 518 corresponds to first focal point 411 in first FOV 418 (FIG. 4). A fourth angle of reflection of first detector 504 and a steering and a focusing pattern on receive PLM 514 provided by controller 501 determine a fourth angle of incidence of the first focal point 511 relative to receive PLM 514. In an example, the fourth angle of reflection is different from the first angle of incidence to allow positioning of first detector 504 in such a way that first light source 404 (FIG. 4) and first detector 504 do not interfere with each other. Selecting a steering and focusing pattern on receive PLM 514 as provided by controller 501 steers the focus of first reflected light beam 516 to first focal point 511 on object 550. The first focal point 511 of first reflected light beam 516 is the first focal point 411 to which first modulated light beam 416 (FIG. 4) is directed. As first modulated light 416 (FIG. 4) scans first FOV 418 (FIG. 4), the focus of first reflected light beam 516 scans the same points to which first modulated light 416 (FIG. 4) is directed. In this example, first detector 504 is an avalanche photo diode. If first detector 504 detects light from first light source 404 (FIG. 4) reflected from first focal point 511 of first reflected light beam 516, this detected light indicates that an object 550 is at that point. Scanning all of first FOV 518 determines the shape and position of object 550 that may be in first FOV 518. In examples, transmit PLM 414 (FIG. 4) and receive PLM 514 are the same PLM. However, because the pattern on PLM 414/514 in this example must both focus the transmit and receive light, an example using one, combined PLM requires positioning of the light sources and detectors in configurations that may not be practicable in certain situations. Using a separate PLM for the receive and transmit sections as in the example of FIGS. 4 and 5 allows for greater flexibility of positioning components of the LIDAR apparatus.
[0030] Receive PLM 514 and second receiving lens 522 focus second reflected light beam 526 reflected from object 550 at a second focal point 521 in second FOV 528 as second received light beam 520 to second detector 506. Controller 501 receives the output of second detector 506 for further processing. Second focal point 521 in second FOV 528 corresponds to second focal point 421 in second FOV 428 (FIG. 4). A fifth angle of reflection of second detector 506 relative to receive PLM 514 and the focusing pattern on receive PLM 514 determine a fifth angle of incidence of the second focal point 521 relative to receive PLM 514. In an example, the fifth angle of reflection is different from the second angle of incidence to allow positioning of first detector 506 in such a way that first light source 406 (FIG. 4) and first detector 506 do not interfere with each other. The second focal point 521 of second reflected light beam 526 is the second focal point 421 of second FOV 428 to which second modulated light beam 426 (FIG. 4) is directed. At any given time, the steering pattern on receive PLM 514 is constant. Therefore, the difference between the fifth angle of incidence and the fourth angle of incidence is determined by difference between the fifth angle of reflection and the fourth angle of refection. As with the fourth angle of reflection, the fifth angle of reflection of second detector 506 and the pattern on receive PLM 514 determines fifth angle of incidence. As second modulated light beam 426 (FIG. 4) scans second FOV 428, the second focal point 521 of second reflected light bean 526 scans the same second focal point 421 to which second modulated light beam 426 (FIG. 4) is directed. In this example, second detector 506 is an avalanche photo diode. If second detector 506 detects light from second light source 406 (FIG. 4) reflected from object 550 at the second focal point 521, this detected light indicates that object 550 is at that point. Scanning all of second FOV 528 determines the shape and position of an object that may be in second FOV 528.
[0032] FIG. 5B is side view of receive portion 502 of example LIDAR apparatus 400. FIG. 5B is view 5B-5B of FIG. 5A looking across the face of receive PLM 514 from the direction of third detector 508. Third detector 508 blocks the view of first detector 504 and second detector 506 from this perspective. In addition, third receiving lens 532 blocks the view of first receiving lens 512 and second receiving lens 522. For simplicity, only third received light beam 530 and third reflected light beam 536 are shown in FIG. 5B. As shown in FIG. 5B, third received light beam 530 and third reflected light beam 536 are not in the same plane. In this example, this avoids interference of third detector 508 with third reflected light beam 536. A specific configuration of light sources is shown in this example vis-a-vis receive PLM 514. Other examples may use different configurations. In addition, other examples may use two, four or more detectors. In another example, the FOV or tiled FOVs as in the example of FIGS. 4 and 5, can be expanded by illuminating with a diverging laser beam. Examples of using divergent light beams are described in Makowski, et ak,“Simple Holographic Projection in Color,” Opt. Express 20, 22 (Oct. 2012) and Maimone et ak,“Holographic Near-Eye Displays for Virtual and Augmented Reality,” ACM Transactions on Graphics, Voh 36, No. 4, Article 85 (July 2017), which are hereby incorporated by reference herein in their entirety.
[0033] FIG. 6 is a diagram of another example LIDAR apparatus 600. Light source 602 is a laser in in this example. In an example, light source 602 provides near infrared laser light. Light source 602 provides divergent light beam 603 to transmit PLM 606, which provides a modulated light beam 605 in response to the divergent light beam 603 output from light source 602. Rather than use a collimating lens as in the example of FIG. 3, transmit PLM 606 provides a configurable phase pattern to the light that both directs modulated light beam 605 to target 608 and provides an optical power or curvature that focuses the divergent light beam 603 from light source 602 to focus on focal point 611. Thus, by using a phase pattern with an optical power to focus divergent light from light source 602, example LIDAR apparatus 600 eliminates the additional expense and manufacturing complication of using a collimating lens. In the example of FIG. 6, focal point 611 is on the surface of an object 610, which is an automobile. Receive PLM 612 includes a pattern that focuses light reflected from object 610 at the focal point 611 onto detector 614. In this example, the pattern on receive PLM 612 includes both a steering function and an optical power or curvature that focuses the light directly onto detector 614. Thus, an additional lens that focuses and“de-collimates” light from focal point 611 on to detector 614 is not necessary. Transmit PLM 606 and receive PLM 612 are a digital micromirror based PLM in this example. In other examples, either or both of transmit PLM 606 and receive PLM 612 are reflective or transmissive liquid crystal phase light modulators. Controller 601 controls the patterns on transmit PLM 606 and receive PLM 612, and controls the light provided by light source 602 and receives the detected light signal from detector 614. Because controller 601 knows the point at which transmit PLM 606 directs the light from light source 602, detection of reflected light by detector 614 indicates that an object is at that point. In this example, detector 614 is an avalanche photo diode. Transmit PLM 606 scans the field of view while receive PLM 612 is adjusted to focus on the focal point 611 to which transmit PLM 606 is scanning. This allows example LIDAR apparatus 600 to determine the distance and contour of object 610. In another example, with a configuration using multiple light sources and detectors like that of FIGS. 4 and 5, the light sources can provide divergent light and the PLMs can provide an optical power as with the example of FIG. 6, thus eliminating the need for collimating lenses at the output of the light sources and focusing lenses at the input of the detectors.
[0034] FIG. 7 is a flow diagram of an example method 700. Step 702 is directing a first light beam from a first light source to a first input of a phase light modulator. A light source such as first light source 404 (FIG. 4) provides the first light beam. The phase light modulator is like transmit PLM 414 (FIG. 4). Step 704 is modulating the first light beam using the phase light modulator to provide a first modulated light beam directed to a first field of view. The first modulated light beam is like modulated first modulated light beam 416 (FIG. 4). The first field of view is like first FOV 418 (FIG. 4). Step 706 is directing a second light beam from a second light source to the phase light modulator. A light source such as second light source 406 (FIG. 4) provides the second light beam. Step 708 is modulating the second light beam using the phase light modulator to provide a second modulated light beam directed to a second field of view. The second modulated light beam is like second modulated light beam 426 (FIG. 4). The second field of view is like second FOV 428 (FIG. 4). Step 710 is detecting the first light beam as reflected from the first field of view using a first light detector. The first light detector is like first detector 504 (FIG. 5). Step 712 is detecting the second light beam as reflected from the second field of view using a second light detector. The second light detector is light second detector 506 (FIG. 5).
[0035] FIG. 8 is a flow diagram of another example method 800. Step 802 is directing a divergent light beam from a light source to a phase light modulator. The divergent light source is like light source 602 (FIG. 6). The phase light modulator is like transmit PLM 606. Step 804 is modulating the divergent light beam using the phase light modulator to provide a modulated output beam directed to a field of view. The field of view is like target 608 (FIG. 6). Step 806 is detecting the light modulated output as reflected from the field of view using a light detector. The light detector is like detector 614 (FIG. 6).
[0036] Modifications are possible in the described examples, and other examples are possible, within the scope of the claims.

中文:
[0002]光检测和测距(LIDAR)系统检测并确定对象的位置。在一个示例中,光束被投射到视野中的已知位置。光检测器聚焦在视野中的那个位置,并检测来自可能在视野中的对象的光的任何反射。光传播的时间用于帮助确定对象的距离。通过横跨场扫描光束,可以确定场中对象的位置和对象的图像。
[0003]扫描型LIDAR系统的一个挑战是足够快速和准确地扫描以捕获场内对象的运动。例如,在汽车应用中,LIDAR系统必须快速且准确地确定行人和车辆以及其它对象的运动。已经应用镜子来扫描光束。其它示例使用万向架将整个光投射和检测系统作为一个单元移动。然而,很难以足够的精度操作这些机械系统。此外,此类系统通常体积庞大,具有大的功率要求,并且需要经常维护和校准以保持精度。
[0005]图1A和图1B(统称为“图1”)是示出使用相位光调制器(PLM)的光转向的图。
[0006]图2是示例微镜的侧视图。
[0007]图3是示例LIDAR设备的顶视图。
[0008]图4A至图4D(统称为“图4”)是示例LIDAR设备的发射部分和与LIDAR设备一起使用的扫描模式的视图。
[0009]图5A和图5B(统称为“图5”)是图4的LIDAR设备的接收部分的视图。
[0010]图6是另一示例LIDAR设备的图。
[0011]图7是示例方法的流程图。
[0012]图8是另一示例方法的流程图。
[0013]在附图中,除非另有说明,否则对应的数字和符号一般指对应的部分。附图不一定按比例绘制。
[0014]在本说明书中,术语“耦合”可以包括与中间元件形成的连接,并且附加元件和各种连接可以存在于“耦合”的任何元件之间。在此称为“光耦合”的元件是包括元件之间的涉及光传输的连接的元件。同样如本文所用,“相位光调制器”(PLM)是具有多个像素的装置,其中PLM可以修改施加到每个像素的光的相位。PLM可以反射或透射施加的光。来自相位修改像素和/或相位未修改像素的光的干涉调制所施加的光。
[0015]在示例布置中,相位光调制器(PLM)转向光源的慢扫描速率和窄视野(FOV)问题通过向PLM提供至少两个光源使得来自每个光源的光同时扫描不同的FOV来解决。在至少一个示例中,LIDAR设备具有用于至少两个光源的单个PLM装置。光源相对于PLM具有不同的角度取向。由于不同的角度取向,每个激光照射相应视野(FOV)中的一个点,并且所有FOV同时扫描并平铺在一起。根据示例,一种设备包括相位光调制器。该设备还包括光学耦合到相位光调制器的第一光源,第一光源被配置为生成第一光束并且被定位以将第一光束以第一入射角引导到相位光调制器,相位光调制器被配置为调制第一光束以提供第一调制光束并且响应于第一光束将第一调制光束引导到第一视野;以及光学耦合到相位光调制器的第二光源,第二光源被配置为生成第二光束并且被定位以将第二光束以第二入射角引导到相位光调制器,相位光调制器被配置为调制第二光束以提供第二调制光束并且响应于第二光束将第二调制光束引导到第二视野。该设备还包括光学耦合到第一视野并被配置为检测如从第一视野反射的第一调制光束的第一光检测器以及光学耦合到第二视野并被配置为检测如从第二视野反射的第二调制光束的第二光检测器。
[0016]示例PLM是基于数字微镜的PLM。该类型的PLM装置在基板表面上包括许多数字微镜。在示例中,该类型的PLM可以包括数十万个微镜或超过一百万个微镜。每个微镜都被设计成使得它在基板之上的竖直位置可以通过驱动基板中的电路使用施加到微镜的静电力来精确定位。从特定微镜反射的光的相位由微镜的竖直位置(相对于基板竖直,在本讨论中基板为水平)确定。例如,如果第一微镜位于基板之上的整个高度,而相邻的第二微镜降低四分之一波长,则从第二微镜反射的光将相对于从第一微镜反射的光传播二分之一波长(向下的四分之一波长加上向上的四分之一波长)。从第一微镜和第二微镜反射的光然后将以可预测的方式干涉。可以选择PLM上的相位变化模式以提供所需的类似衍射的效果,诸如转向或聚焦光。参见例如McManamon等人的“Optical Phased Array Technology”(Proceedings of the IEEE,第84卷第2号第269-298页(1996.02)),其通过引用整体并入本文。可以在视野中的所需距离处创建任意模式,诸如斑点或光束。另一个示例PLM是液晶型相位光调制器。使用该类型的PLM,施加在每个像素处的电压会改变该像素处的液晶,从而导致光的相移。液晶PLM可以是透射式的或反射式的。
[0017]图1A和图1B(统称为“图1”)是示出使用PLM的光转向的图。在该示例中,PLM 102是基于数字微镜的PLM。在图1A中,PLM 102的微镜104具有被选择以在方向108中引导光106的转向模式。在图1B中,微镜104具有被选择以在方向110中引导光106的模式。因此,PLM 102可以在所需方向中将光转向。除了将光转向之外,PLM 102还可以将光聚焦在所需距离处的斑点(焦点)处。
[0018]图2是类似于微镜104(图1)之一的示例微镜的侧视图。平台204经由平台柱214连接到两个平台电极212。柱208支撑平台204上方的镜子210。如图2中所示,当电压被施加到驱动电极206并且参考电压(例如接地)被施加到平台电极212时,静电力将平台204拉下,并因此拉下镜子210。运动量由施加的电压确定。在其它示例中,像素202使用可由驱动电路(未示出)单独寻址的两个或更多个驱动电极206。施加的静电力与驱动电极206和平台204的面积成正比。因此,使用多个电极,可以通过选择驱动电极206或驱动电极206的组合来精确控制力的大小,以及因此镜子210的竖直位置,同时对驱动电极206中的每个所选驱动电极施加相同的电压。由像素202提供的相移由镜子210的竖直定位确定。例如,如果像素降低四分之一波长(1/4λ),相对于未降低的像素,从该像素反射的光将传播附加的二分之一波长(1/4λ向下到达镜子,并且1/4λ返回)。在另一个示例中,如果一个像素降低八分之一波长(1/8λ),则相对于未降低的像素,从该像素反射的光将传播附加的四分之一波长(1/8λ向下到达镜子,并且1/8λ返回)。
[0019]图3是示例LIDAR设备300的顶视图。在该示例中,光源302是激光器。在示例中,光源302提供近红外激光。光源302提供光通过准直透镜304到发射PLM 306。发射PLM 306向光提供可配置的相位模式,其将光引导至目标308。在图3的示例中,目标308在对象310的表面上,该对象310是汽车。从对象310反射的光被接收PLM 312通过透镜316聚焦到检测器314。因为光被发射PLM 306引导的点是已知的,所以检测器314对反射光的检测指示在该点处有对象。在该示例中,检测器314是雪崩光电二极管。发射PLM 306扫描视野,而接收PLM 312扫描APD看到的视野以匹配发射PLM正在扫描的目标308。这允许示例LIDAR设备300确定对象310的距离和轮廓。
[0020]LIDAR设备300具有局限性。例如,PLM上的每个模式对应于在特定方向中将光束转向。发射PLM 306和接收PLM 312从一种模式改变到另一种模式需要大量时间。例如,如果新模式的数据加载时间为50μs,并且帧时间为100ms,则只能捕获2000个点,分辨率仅为约65x30。更高的分辨率是优选的。此外,大视野(FOV)的LIDAR扫描很困难。以0.1度波束宽度、10Hz帧速率扫描大于60x20度的区域需要大于100万个样本/秒的PLM更新率。然而,PLM中镜子的大小限制了视野,并且光的波长限制了FOV。对于使用近红外光的约10μ平方像素大小,当前PLM装置的FOV仅限于几度。接收PLM 312允许通过将光从窄角度引导到检测器来拒绝环境光。然而,扫描大FOV需要广角光学器件。广角光学器件需要限制在检测器314处接收到的信号强度的小孔径大小。
[0021]图4A至图4D(统称为“图4”)是示例LIDAR设备400的发射部分402的视图。图4A是发射部分402的顶视图。如本文所使用的,术语“顶视图”和“侧视图”指示图的相对取向并且不表示任何其它关系。例如,LIDAR设备400的“顶部”或“侧面”可以处于示例LIDAR设备400的特定安装中的多个取向中的任何一个。示例LIDAR设备400包括三个光源:第一光源404、第二光源406和第三光源408。控制器401控制第一光源404、第二光源406和第三光源408的光输出。示例LIDAR设备400在该示例中包括三个光源,但可以包括两个、四个或更多光源,该光源可以布置在一维或二维阵列中。此外,在该示例中,第一光源404、第二光源406和第三光源408是近红外激光二极管,但也可以是其它类型的光源,诸如紫外光源。第一光源404以相对于发射PLM 414的第一入射角提供第一光束410通过第一准直透镜412。在该示例中,发射PLM 414是基于数字微镜的PLM。在其它示例中,发射PLM 414是反射或透射液晶相位光调制器。根据由控制器401施加到发射PLM 414的转向模式,发射PLM 414响应于第一光束410的第一输出是具有第一输出反射角的第一调制光束416。第一光源404的第一入射角和发射PLM 414上的转向模式确定反射到第一焦点411的输出角。在该示例中,第一入射角将第一调制光束416引导到第一视野(FOV)418中的对象450上的第一焦点411。
[0022]第二光源406以相对于发射PLM 414的第二入射角提供第二光束420通过第二准直透镜422。根据由控制器401施加到发射PLM 414的转向模式,响应于第二光束420的发射PLM414的输出是具有第二反射角的第二调制光束426。在任何给定时间,发射PLM 414上的转向模式是恒定的。因此,第二反射角与第一反射角的差由第二入射角与第一入射角的差确定。与第一反射角一样,第二光源406的第二反射角和发射PLM 414上的模式确定第二反射角。在该示例中,第二反射角将第二调制光束426引导到第二FOV 428中对象450上的第二焦点421。
[0023]第三光源408以相对于发射PLM 414的第三入射角提供第三光束430通过第三准直透镜432。根据由控制器401施加到发射PLM 414的转向模式,响应于第三光束430的发射PLM414的输出是具有第三反射角的第三调制光束436。在任何给定时间,发射PLM 414上的转向模式是恒定的。因此,第三反射角与第一反射角和第二反射角之间的差由第三入射角与第一反射角和第二入射角之间的差确定。与第一反射角和第二反射角一样,第三光源408的第三入射角和发射PLM 414上的模式确定第三反射角。在该示例中,第三反射角将第三调制光束436引导到第三FOV 438中对象450上的第三焦点431。总而言之,发射PLM 414同时将来自第一光源404、第二光源406和第三光源408的光分别引导到第一FOV 418、第二FOV 428和第三FOV 438中的点。
[0024]图4B是由图4A的视线4B-4B所示的视野的视图。图4B是从面向第一FOV 418、第二FOV 428和第三FOV 438的发射PLM 414的角度的视图。对于发射PLM 414上的给定转向模式,第一光源404、第二光源406和第三光源408分别照射第一FOV 418、第二FOV 428和第三FOV 438中的每一个FOV的一个点。通过改变发射PLM 414的转向模式,发射部分402扫描每个FOV。在该示例中,如图4B中所示,以光栅扫描方式扫描第一扫描点442、第二扫描点452和第三扫描点462。然而,可以使用其它扫描方法,诸如随机扫描。如图4B中所示,在该示例中,第一FOV 418、第二FOV 428和第三FOV 438的大小被选择为使得第一FOV 418、第二FOV 428和第三FOV 438避免由从发射PLM 414上的转向模式衍射的光所产生的无关的衍射级。在其它示例中,FOV重叠以提供更准确但更慢的扫描。在这些示例中,必须在检测后校正任何无关的衍射级。
[0025]图4C是示例LIDAR设备400的发射部分402的侧视图。图4C是从第三光源408的方向横跨发射PLM 414的面看的视图,其是从图4A的4C-4C看的。从该角度看,第三光源408阻挡了第一光源404和第二光源406的视图。此外,第三准直透镜432遮挡了第一准直透镜412和第二准直透镜422的视图。为简单起见,图4C中仅示出了第三光束430和第三调制光束436。从图4C中可以看出,第三光束430和第三调制光束436不在同一平面内。在该示例中,这避免了第三光源408与第三调制光束436的干扰。在该示例中相对于发射PLM 414示出了光源的特定配置。其它示例可以使用不同的配置。此外,其它示例可以使用两个、四个或更多个光源。
[0026]图4D是另一示例LIDAR设备403的另一示例发射部分405的顶视图。在该示例设备中,一个光源407产生第一调制光束416、第二调制光束426和第三调制光束436。光源407提供光束423通过准直透镜425。本示例中的发射PLM 414不使用单个转向模式,而是使用三个转向模式。在示例中,三个不同的转向模式将应用于发射PLM 414的三个不同部分。在该示例中使用了三个转向模式。然而,可以使用两个、四个或更多个转向模式。此外,图4D的示例包括以一个入射角的一个光源。然而,使用以多个入射角的多个光源以及应用于发射PLM414的多个转向模式,可以成倍增加可以同时照射的视野数量。例如,应用于具有三个转向模式的发射PLM的三个光源可以同时照射九个视野。
[0027]在图4D的示例中,应用于发射PLM 414的三个转向模式产生光第一调制光束416、第二调制光束426和第三调制光束436,其分别在第一FOV 418、第二FOV 428和第三FOV 438中的第一焦点411、第二焦点421和第三焦点431处分别照射对象450。如上面关于图4A和图4B所描述的,转向模式扫描视野。因为每个转向模式被应用到发射PLM 414的区域的三分之一或更少,所以图4D的示例将提供给每个焦点的光量限制为由光源407提供的亮度的三分之一或更少。
[0028]图5A和图5B(统称为“图5”)是示例LIDAR设备400(图4)的接收部分502的视图。图5A示出接收部分502的顶视图。控制器501类似于控制器401(图4)。第一检测器504、第二检测器506和第三检测器508分别检测从第一FOV 518、第二FOV 528和第三FOV 538中的对象反射的光。第一FOV 518、第二FOV 528和第三FOV 538对应于第一FOV 418、第二FOV 428和第三FOV 438(图4)。第一焦点511、第二焦点521和第三焦点531分别对应于第一焦点411、第二焦点421和第三焦点431(图4)。第一检测器504检测由第一光源404(图4)照射的第一FOV518中的第一焦点511。第二检测器506检测由第二光源406(图4)照射的第二FOV 528中的第二焦点521。第三检测器508检测由第三光源408(图4)照射的第三FOV 538中的第三焦点531。对象550对应于对象450(图4)。
[0029]接收PLM 514将从对象550在第一FOV 518中的第一焦点511处反射的第一反射光束516作为第一接收光束510通过第一接收透镜512聚焦到第一检测器504上。在该示例中,接收PLM 514是基于数字微镜的PLM。在其它示例中,接收PLM 514是反射式或透射式液晶相位光调制器。控制器501接收第一检测器504的输出用于进一步处理。第一FOV 518中的第一焦点511对应于第一FOV 418(图4)中的第一焦点411。第一检测器504的第四反射角以及由控制器501提供的接收PLM 514上的转向和聚焦模式确定第一焦点511相对于接收PLM 514的第四入射角。在示例中,第四反射角不同于第一入射角以允许以第一光源404(图4)和第一检测器504彼此不干扰的方式定位第一检测器504。选择由控制器501提供的接收PLM 514上的转向和聚焦模式将第一反射光束516的焦点转向对象550上的第一焦点511。第一反射光束516的第一焦点511是第一调制光束416(图4)所指向的第一焦点411。随着第一调制光416(图4)扫描第一FOV 418(图4),第一反射光束516的焦点扫描第一调制光416(图4)所指向的相同点。在该示例中,第一检测器504是雪崩光电二极管。如果第一检测器504检测到从第一反射光束516的第一焦点511反射的来自第一光源404(图4)的光,则该检测到的光指示对象550在该点处。扫描所有第一FOV 518确定可能在第一FOV 518中的对象550的形状和位置。在示例中,发射PLM 414(图4)和接收PLM 514是相同的PLM。然而,由于该示例中PLM414/514上的模式必须同时聚焦发射光和接收光,因此使用一个组合PLM的示例需要将光源和检测器定位在在某些情况下可能不切实际的配置中。如图4和图5的示例中那样,使用用于接收部分和发射部分的单独的PLM允许LIDAR设备的定位部件的更大灵活性。
[0030]接收PLM 514和第二接收透镜522将从对象550在第二FOV 528中的第二焦点521处反射的第二反射光束526作为第二接收光束520聚集到第二检测器506。控制器501接收第二检测器506的输出用于进一步处理。第二FOV 528中的第二焦点521对应于第二FOV 428(图4)中的第二焦点421。第二检测器506相对于接收PLM 514的第五反射角和接收PLM 514上的聚焦模式确定第二焦点521相对于接收PLM 514的第五入射角。在示例中,第五反射角不同于第二入射角以允许以第一光源406(图4)和第一检测器506彼此不干扰的方式定位第一检测器506。第二反射光束526的第二焦点521是第二调制光束426(图4)所指向的第二FOV 428的第二焦点421。在任何给定时间,接收PLM 514上的转向模式是恒定的。因此,第五入射角和第四入射角之间的差由第五反射角和第四反射角之间的差确定。与第四反射角一样,第二检测器506的第五反射角和接收PLM 514上的模式确定第五入射角。随着第二调制光束426(图4)扫描第二FOV 428,第二反射光束526的第二焦点521扫描第二调制光束426(图4)所指向的同一第二焦点421。在该示例中,第二检测器506是雪崩光电二极管。如果第二检测器506检测到从对象550的第二焦点521处反射的来自第二光源406(图4)的光,则该检测到的光指示对象550在该点处。扫描所有第二FOV 528确定可能在第二FOV 528中的对象的形状和位置。
[0032]图5B是示例LIDAR设备400的接收部分502的侧视图。图5B是从第三检测器508的方向横跨接收PLM 514的面看的图5A的视图5B-5B。从该角度看,第三检测器508阻挡了第一检测器504和第二检测器506的视图。此外,第三接收透镜532阻挡了第一接收透镜512和第二接收透镜522的视图。为简单起见,图5B中仅示出了第三接收光束530和第三反射光束536。如图5B中所示,第三接收光束530和第三反射光束536不在同一平面内。在该示例中,这避免了第三检测器508与第三反射光束536的干扰。在该示例中示出了相对于接收PLM 514的光源的特定配置。其它示例可以使用不同的配置。此外,其它示例可以使用两个、四个或更多个检测器。在另一个示例中,如图4和图5的示例中的FOV或平铺FOV,可以通过用发散的激光束照射来扩展。使用发散光束的示例在Makowski等人的“Simple Holographic Projectionin Color,”(Opt.Express 20,22(2012.02))和Maimone等人的“Holographic Near-EyeDisplays for Virtual and Augmented Reality,”(ACM Transactions on Graphics,第36卷第4号,文章85(2017.07))中描述,其全部内容通过引用并入本文。
[0033]图6是另一示例LIDAR设备600的图。在该示例中,光源602是激光器。在示例中,光源602提供近红外激光。光源602提供发散光束603到发射PLM 606,该发射PLM 606响应于从光源602输出的发散光束603而提供调制光束605。并非使用如图3的示例中的准直透镜,发射PLM 606向光提供可配置的相位模式,其将调制光束605引导到目标608并提供将来自光源602的发散光束603聚焦以聚焦在焦点611上的光功率或曲率。因此,通过使用具有光功率的相位模式来聚焦来自光源602的发散光,示例LIDAR设备600消除了使用准直透镜的附加费用和制造复杂性。在图6的示例中,焦点611在对象610的表面上,该对象610是汽车。接收PLM 612包括将从焦点611处的对象610反射的光聚焦到检测器614上的模式。在该示例中,接收PLM 612上的模式包括转向功能和将光直接聚焦到检测器614上的光功率或曲率。因此,不需要将来自焦点611的光聚焦和“去准直”到检测器614上的附加透镜。在该示例中,发射PLM 606和接收PLM 612是基于数字微镜的PLM。在其它示例中,发射PLM 606和接收PLM612中的一个或二者是反射式或透射式液晶相位光调制器。控制器601控制发射PLM 606和接收PLM 612上的模式,并控制光源602提供的光并从检测器614接收检测到的光信号。因为控制器601知道发射PLM 606引导来自光源602的光的点,检测器614对反射光的检测指示对象在该点处。在该示例中,检测器614是雪崩光电二极管。发射PLM 606扫描视野,而接收PLM612被调节以聚焦在发射PLM 606正在扫描的焦点611上。这允许示例LIDAR设备600确定对象610的距离和轮廓。在另一个示例中,采用使用多个光源和检测器的配置,如图4和图5那样,光源可以提供发散光并且PLM可以提供光功率,与图6的示例一样,从而消除了对光源输出处的透镜准直和检测器输入处的透镜聚焦的需要。
[0034]图7是示例方法700的流程图。步骤702将来自第一光源的第一光束引导到相位光调制器的第一输入。诸如第一光源404(图4)的光源提供第一光束。相位光调制器类似于发射PLM 414(图4)。步骤704是使用相位光调制器调制第一光束以提供引导到第一视野的第一调制光束。第一调制光束类似于调制的第一调制光束416(图4)。第一视野类似于第一FOV418(图4)。步骤706是将来自第二光源的第二光束引导到相位光调制器。诸如第二光源406(图4)的光源提供第二光束。步骤708是使用相位光调制器调制第二光束以提供引导到第二视野的第二调制光束。第二调制光束类似于第二调制光束426(图4)。第二视野类似于第二FOV 428(图4)。步骤710是使用第一光检测器检测从第一视野反射的第一光束。第一光检测器类似于第一检测器504(图5)。步骤712是使用第二光检测器检测从第二视野反射的第二光束。第二光检测器是光第二检测器506(图5)。
[0035]图8是另一示例方法800的流程图。步骤802是将来自光源的发散光束引导到相位光调制器。发散光源类似于光源602(图6)。相位光调制器类似于发射PLM 606。步骤804是使用相位光调制器调制发散光束以提供引导到视野的调制输出光束。视野类似于目标608(图6)。步骤806是使用光检测器检测如从视野反射的光调制输出。光检测器类似于检测器614(图6)。
[0036]在权利要求的范围内,在所描述的示例中的修改是可能的,并且其它示例也是可能的。