NZ755482B2 - Mirror assembly - Google Patents

Abstract

The present disclosure relates to optical systems, specifically light detection and ranging (LIDAR) systems. An example optical system includes a laser light source operable to emit laser light along a first axis and a mirror element with a plurality of reflective surfaces. The mirror element is configured to rotate about a second axis. The plurality of reflective surfaces is disposed about the second axis. The mirror element and the laser light source are coupled to a base structure, which is configured to rotate about a third axis. While the rotational angle of the mirror element is within an angular range, the emitted laser light interacts with both a first reflective surface and a second reflective surface of the plurality of reflective surfaces and is reflected into the environment by the first and second reflective surfaces. figured to rotate about a second axis. The plurality of reflective surfaces is disposed about the second axis. The mirror element and the laser light source are coupled to a base structure, which is configured to rotate about a third axis. While the rotational angle of the mirror element is within an angular range, the emitted laser light interacts with both a first reflective surface and a second reflective surface of the plurality of reflective surfaces and is reflected into the environment by the first and second reflective surfaces.

Description

MIRROR ASSEMBLY CROSS-REFERENCE TO RELATED ATIONS The present application claims the bene?t of priority from US. Patent Application No. l5/383,842, ?led December 19., 20l6, the content of which is herewith incorporated by reference.

BACKGROUND Unless otherwise indicated herein, the als described in this section are not prior art to the claims in this application and are not admitted to be prior art by ion in this section.

Light detection and ranging (LlDAR) systems utilize laser light to provide information about objects in an environment. For example, LIDAR systems can provide map data about a al environment. Some LTDAR systems include a scanning assembly con?gured to direct the laser light around the environment. Such scanning assemblies may include one or more moving mirrors.

SUMMARY The t disclosure generally relates to an optical system with a moving mirror assembly. In some embodiments, the moving mirror ly may be con?gured to rotate so as to direct laser light around an nment of the optical system. As described herein, some arrangements of the laser light source and the mirror ly may provide a very broad scanning angle (e.g., greater than 230 degrees), which may allow for more comprehensive object mapping within a given environment.

In a ?rst aspect, a system is provided. The system includes a laser light source operable to emit laser light along a first axis. The system also includes a mirror element with a plurality of re?ective surfaces. The mirror element is con?gured to rotate about a second axis. The plurality of re?ective surfaces is disposed about the second axis. The mirror element and the laser light source are coupled to a base structure. The base structure is con?gured to rotate about a third axis. The system further includes a controller configured to carry out operations. The operations e causing the mirror element to rotate about the second axis. The rotation about the second axis includes a ?rst angular range and a second angular range. The operations include causing the laser light source to emit laser light along the first axis such that the emitted laser light interacts with the mirror element. While the rotational angle of the mirror element is within the ?rst angular range, the emitted laser light interacts with a first re?ective e of the plurality of reflective surfaces and is re?ected into an environment by the first re?ective surface. While the rotational angle of the mirror element is within the second angular range, the emitted laser light interacts with both the ?rst re?ective e and a second re?ective surface of the plurality of re?ective surfaces and is re?ected into the environment by the ?rst and second re?ective surfaces. The operations further include causing the base structure to rotate about the third axis. {0006] In a second aspect, an optical system is provided. The optical system includes a laser light source operable to emit laser light along a first axis. The optical system also includes a mirror element having a plurality of re?ective surfaces. The mirror element is con?gured to rotate about a second axis The rotation about the second axis includes a first angular range and a second angular range The plurality of re?ective surfaces is ed about the second axis. The mirror element and the laser light source are coupled to a base structure The base structure is con?gured to rotate about a third axis. While the rotational angle of the mirror element is within the first angular range, the emitted laser light interacts with a first re?ective surface of the plurality of re?ective surfaces and is re?ected into an environment by the first ive surface. While the onal angle of the mirror element is within the second angular range, the emitted laser light interacts with both the first re?ective surface and a second re?ective surface of the plurality of re?ective surfaces and is re?ected into the environment by the first and second re?ective surfaces. The optical system includes at least one beam stop. The at least one beam stop is con?gured to prevent laser light from being emitted into the environment at angles e an emission angle range. {0007} Other aspects, ments, and implementations will become apparent to those of ordinary skill in the art by reading the following detailed description, with nce where riate to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 illustrates a system, according to an example embodiment.

Figure 2A illustrates an optical system, according to an example embodiment.

Figure 2B illustrates an optical system, according to an example embodiment.

Figure 2C illustrates an optical , according to an example embodiment.

Figure 3A illustrates an optical system, ing to an example embodiment.

Figure 3B illustrates an optical system, according to an example embodiment.

Figure 3C illustrates a re?ected. light angle versus mirror element reference angle graph, according to an example embodiment.

Figure 3D illustrates an optical , according to an example ment.

Figure 4 rates a mirror element, ing to an example embodiment.

Figure 5 illustrates an optical system, according to an example embodiment. {0018] Figure 6 illustrates a method, according to an example embodiment.

ED DESCRIPTION {0019] Example methods, devices, and systems are described . It should be understood that the words “example” and “exemplary” are used herein to mean “serving as an example, instance, or illustration.” Any embodiment or e described herein as being an “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or features. Other embodiments can be ed, and other changes can be made, without departing from the scope of the subject matter presented herein. {0020] Thus, the example embodiments described herein are not meant to be limiting.

Aspects of the present disclosure, as generally described herein, and rated in the , can be ed, substituted, combined, separated, and designed in a wide y of different con?gurations, all of which are contemplated herein. {0021] Further, unless context suggests otherwise, the features illustrated in each of the ?gures may be used in combination with one another. Thus, the ?gures should be generally viewed as component aspects of one or more overall ments, with the understanding that not all illustrated features are necessary for each embodiment.

I. Overview {0022] A light distance and ranging system (e. g., a LlDAR) may include a laser light source con?gured to illuminate a mirror along a ?rst axis. The mirror may be configured to rotate about a second axis, in which the second axis is perpendicular to the first axis. in an example embodiment, the mirror may include three mirror surfaces arranged in an equilateral triangle arrangement. While ng about the second axis, the mirror may be con?gured to direct the light from the laser light source into an environment of the system over a wide ?eld of view (eg, greater than 230 degrees about the second axis). By directing the light over such a large angular ?eld of ?ew, the LIDAR system may e ranging information within a larger three-dimensional volume.

In some ments, the laser light source may illuminate two of the three sides of the mirror at the same time. In such situations, beam stops may be positioned to prevent multiple simultaneous gs/signals. in an example embodiment, the mirror may be configured to provide interlaced scanning of the environment around the LIDAR system.

For instance, the mirror, its operating characteristics (e. g., rate of rotation), and a pulse rate of the laser light source may provide a first set of scan locations during a ?rst scan.

Subsequently, by continuing to rotate the mirror while keeping the other operating characteristics the same, the laser light may be directed towards a second set of scan locations.

In some embodiments, the first set of scan locations may be eaved with the second set of scan locations such that the laser light emitted from the laser light source is provided in an evenly distributed fashion (e.g in angle about the second axis).

In an example embodiment, the mirror may rotate about the second axis at a rotational frequency, Q, which could be about 30,000 revolutions per minute or 30 kRPM.

Furthermore, the mirror and the laser light source may rotate about a third axis at a rotational frequency, (I), which could be about 600 RPM. However, other rotational frequencies are possible. In an example ment, an interlaced condition may occur when {MD 2 2N+l, where N is an integer.

II. e Systems {0025] Figure 1 illustrates a system 100, according to an example embodiment. The system lOO may be, or may represent a portion of, a light detection and ranging (LIDAR) system. In example embodiments, system lOO may be a LlDAR system con?gured to provide information about an environment. For example, system IOO may be a LIDAR system for an autonomous vehicle, such as a self-driving car or an autonomous aerial vehicle {0026] System 100 includes a laser light source llO. In example embodiments, the laser light source llO may be operable to emit laser light along a first axis. The laser light source llO could be any source of laser light con?gured to provide substantially ated and/or coherent light. For instance, the laser light source llO could be a semiconductor waveguide laser, a fiber laser, an excimer laser, or another type of laser .

In example embodiments, the light emitted from the laser light source llO may include pulses of laser light. For instance, the laser light pulses may have durations in the l - 100 nanosecond range. However, other laser light pulse durations are possible.

The laser light emitted by the laser light source llO may have an emission wavelength within the ed (IR) ngth range, however other wavelengths are plated. For example, the emission wavelength could be in the e ngth spectrum or the ultraviolet (UV) wavelength spectrum. In an example embodiment, the emission wavelength may be about 905 nanometers. Alternatively, the emission wavelength could be about l.55 microns.

System 100 also includes a mirror element 120 with a plurality of ive surfaces 122. Speci?cally, the reflective surfaces l22 may be configured to re?ect light at, or substantially at, the emission wavelength. In some embodiments, the re?ective surfaces l22 may be formed from, and/or coated with, a metal, such as aluminturt, gold, silver, or another re?ective material. Additionally or alternatively, the reflective surfaces l22 may include a high re?ectance (HR) coating. In an example embodiment, the HR coating may include a dielectric- stack configured to re?ect incident light at the emission ngth. The dielectric stack may include, for example, a periodic layer system alternating between two materials having different indices of refraction. Other types of HR coatings are possible and contemplated .

In some e embodiments, the mirror element 120 may include three re?ective surfaces l22a, 122b, and l22c. Mirror elements l20 having more or less re?ective surfaces 122 are contemplated. For example, the mirror element 120 could include four or more reflective surfaces.

The mirror element l20 is con?gured to rotate about a second axis.

Furthermore, in some embodiments, the plurality of re?ective es may be disposed about the second axis. In such scenarios, the mirror element l20 may be shaped and each facet of the prism shape may be a reflective surface l22. In other words, the re?ective surfaces 122a, 122b, and l22c may be arranged symmetrically about the second axis such that the mirror element l2!) has a triangular prism shape. As an example, the first axis and the second axis may be perpendicular with respect to one another, however other arrangements of the first axis and the second axis are plated. In some embodiments, the first axis may intersect with the second axis.

System 100 additionally includes a base structure l30. The mirror element 120 and the laser light source llO may be d to the base structure BC. In some embodiments, the base structure 130 may be configured to rotate about a third axis. While a variety of arrangements of the third axis are contemplated, an example embodiment includes the third axis being parallel to or collinear with the first axis.

System l00 further includes one or more beam stops 140. The beam stop(s) I40 may be con?gured to prevent laser light from being ed into the environment at angles outside a predetermined emission angle range. Additionally or alternatively, beam stop(s) l40 may be positioned so as to prevent multiple simultaneous readings/signals. In e embodiments, the emission angle range could be expressed as the range of angles with respect to the mirror element 120 that may receive laser light emission from system 100.

In other words, the emission angle range may represent the angles from which ranging information may be obtained from the environment around the system IOO. In some ments, the emission angle range may be defined with respect to the second axis. In such scenarios, the emission angle range may be greater than 230 degrees.

The system l00 includes a controller l50 con?gured to carry out operations.

In example embodiments, the controller 150 may include one or more logic blocks, a programmable logic device (PLD), a ?eld programmable gate array (FPGAL and/or an application-specific integrated circuit (ASIC). Other types of controller circuits are contemplated in the present disclosure. in some embodiments, the controller 150 may include one or more processors l52 and a memory 154. In such scenarios, the processor(s) 152 may be red to execute instructions stored in the memory l54 so as to carry out the operations.

The ions include causing the mirror element lZO to rotate about the second axis. As an example, the mirror t lZO may rotate about the second axis at rotational frequency Q. The on about the second axis includes a ?rst angular range and a second angular range. in some embodiments, the mirror element 120 may rotate about the second axis at a rotational frequency of about 30 kRPM. Other rotational frequencies of mirror element lZO are possible. For example, the mirror t 120 may rotate about the second axis within a rotational frequency range n l00 RPM and 100 kRPM.

The operations also include causing the laser light source llO to emit laser light along the first axis such that the emitted laser light interacts with the mirror element 120.

The ions onally include, while the onal angle of the mirror element l20 is within the first angular range, causing the emitted laser light to interact with a ?rst re?ective surface (e.g., l22a) of the plurality of re?ective surfaces l22r Upon interacting with the first re?ective e, the re?ected laser light is re?ected into an environment by the first reflective surface. {0038] The operations also include, while the rotational angle of the mirror element is within the second angular range, causing the emitted laser light to ct with both the ?rst re?ective surface (cg, 122a) and a second re?ective surface (cg, 122b) of the plurality of re?ective surfaces l22. The re?ected laser light is re?ected into the nment by the ?rst and. second re?ective surfaces.

The operations also include causing the base structure 130 to rotate about the third axis. The base structure may rotate about the third axis at rotational frequency (1). As an example, the base structure 130 may rotate about the third axis at a rotational frequency of about 600 RPM. Other rotational frequencies are possible. For instance, the base ure 130 may rotate about the third axis at rotational frequencies between l0 RPM and lo kRPM.

The system 100 also includes one or more actuators 160. The actuators 160 may include DC motors con?gured to rotate the mirror element 120 and/or the base structure I30. Furthermore, the actuator I60 may include an actuator to adjust a position and/or angle of the laser light source lIO. In some embodiments, the actuators 160 may include one or more actuators configured to adjust a position and/or angle of the beam stop(s) l40. That is, in such a scenario, the actuators 160 may move the beam stops 140 so as to adjust the emission angle range and/or avoid multiple simultaneous readings.

Optionally, the operations may also include, while the rotational angle of the mirror element is within a third angular range, causing the emitted laser light to interact with a third reflective surface (e.g., l22c) of the plurality of reflective surfaces. In such scenarios, the reflected laser light may be reflected into the environment by the third tive surface. {0042] In some embodiments, the operations further include ing the system in an aced condition. In such scenarios, the interlaced ion may occur when N+l, where N is an integer. An interlaced condition may provide a desired laser scanning pattern for scanning the three-dimensional environment around the system IOU.

Namely, the desired laser ng pattern may include overlapping scanning areas and/or may provide for less time between subsequent scans for a given location within the environment. ng the time between uent scans may provide better safety as more up—to—date information may be available about the nment, such as map data and/or object data. {0043] In some embodiments, causing the laser light source Hi) to emit laser light may include causing the laser light source to emit laser light pulses based on at least one of rotational frequency 9. or rotational frequency (1).

Figures 2A, 2B, and 2C illustrate optical systems according to various e embodiments. The optical systems bed in relation to Figures 2A, 2B, and 2C may be similar or identical to the system 100 illustrated and described with regard to Figure 1.

Figure 2A illustrates an optical system 200, according to an example embodiment. In some embodiments, optical system 200 may be part of a laser—based distance and ranging (LIDAR) system.

The optical system 200 es a laser light source ZIO that may be le to emit laser light along a first axis 214. As illustrated in Figure 2A, the first axis 2l4 may be along (or parallel to) the y-direction. As such, the laser light source 2l0 may emit laser light 212 along the y-axis. As described. with regard to laser light source llO, laser light source 2l0 may include a semiconductor laser, a fiber laser, or another type of light source con?gured to provide a coherent pulse of light.

The l system 200 also includes a mirror element 220. The mirror element 220 includes a plurality of re?ective surfaces 222a, 222b, and. 222C. The mirror element 220 is con?gured to rotate about a second axis 224. As illustrated in Figure 2A, the second axis 224 may be parallel to the z direction. The plurality of re?ective surfaces 222 is disposed about the second axis 224. For example, the plurality of re?ective es 222 may include three reflective surfaces (222a, 222b, and 222C) arranged symmetrically about the second axis such that the mirror element 220 has a triangular prism shape.

In some embodiments, the ?rst axis (eg, the axis along which laser light 2l2 is emitted) may intersect the second axis 224. Furthermore, the ?rst axis 214 may be perpendicular to the second axis 224.

In example embodiments, the l system 200 also es a mirror element actuator con?gured to rotate the mirror element 220 about the second axis at rotational frequency Q. The mirror element actuator may include a stepper motor, a brushed or brushless DC motor, or another type of rotational actuator. In other words, the mirror element actuator may be con?gured to rotate the mirror element 220 in a desired ion 226 at a desired onal frequency 52. {0049] Although not expressly depicted in Figure 2A, the mirror element 220 and the laser light 2l0 source are coupled. to a base structure 230. In some embodiments, the base ure 230 is con?gured to rotate about a third axis. Furthermore, in an example embodiment, the third axis may be l with the first axis 2l4 tag, the y—axis). In some ments, the optical system 200 includes a base structure actuator con?gured to rotate the base structure in a desired direction 232 about the third axis at rotational frequency (1).

The base structure actuator may include a rotational actuator such as a stepper motor or a brushed or brushless DC motor.

The optical system 200 also includes at least one beam stop 240. The beam stop 240 may e one or more beam dumps, optically opaque als, and/or beam blocking materials. The beam stop 240 may be formed from a r, metal, fabric, or other materials. The at least one beam stop 240 may be con?gured to prevent laser light from being emitted into the environment at angles outside an emission angle range. In an example embodiment, the emission angle range may be greater than 230 s about the second axis 224. As described herein, the beam stop 240 may be positioned to prevent multiple simultaneous readings/signals.

In example optical systems, while a rotational angle of the mirror element 220 is within a first angular range, the emitted laser light 2l2 interacts with a ?rst reflective surface 222a of the plurality of ive surfaces 222 and is re?ected as re?ected light 2l6 into an environment by the ?rst re?ective surface 222a. In some ments, the emitted laser light 212 may have a beam width, such as 2 millimeters. Other beam widths are possible.

Furthermore, in some embodiments, while the onal angle of the mirror element 220 is within a second angular range, the emitted laser light 212 interacts with both the ?rst reflective surface 222a and a second re?ective surface 222b of the plurality of re?ective surfaces 222. In such a scenario, the emitted laser light 212 is reflected as re?ected light 216 into the environment by the first and second re?ective surfaces 222a and 222b. Put another way, as bed above, the emitted laser light 212 may have a beam width of 2 millimeters. A ?rst portion (e.g a ?rst half of the beam width) of the d laser light 2l2 may interact with the ?rst re?ective surface 222a and a second portion (cg, a second half of the beam width) of the emitted laser light 2l2 may interact with the second re?ective surface 222b. {0053] Figure 2B illustrates an optical system 250, according to an e embodiment. Optical system 250 may be similar or cal to optical system 200, illustrated and described in reference to Figure 2A. Optical system 250 may include a housing 252. The housing 252 may be optically transparent to the wavelength(s) of the emitted light 212 and re?ected light 216. For example, housing 252 may be more than 90% transparent to the ed light 2l6. in example embodiments, the housing 252 may be coupled to the beam stop 240 and the mirror element 220.

Figure 2C illustrates an optical system 260, according to an example embodiment. The optical system 260 may be r or cal to optical systems 200 and 250 as illustrated and described in nce to Figures 2A and 213. in an example ment, the mirror element 220 may be oriented at a given angle with respect to the second axis 224 such that incident laser light 2 l2 interacts with two re?ective surfaces of the mirror element 220. That is, laser light 212 may interact with ?rst re?ective surface 222a and second re?ective surface 222b. The laser light 212 may be re?ected in a first portion as re?ected light 264 and in a second portion as re?ected light 266. The range of angles between re?ected light 264 and re?ected light 266 may define an emission angle range 268.

The emission angle range 268 may be more than 230 degrees.

Figures 3A and 3B illustrate two different orientations of the mirror element 220 in optical system 300. Optical system 300 may be similar or identical to optical systems 200, 250, and 260 as illustrated and described with nce to Figures 2A, 2B, and 2C.

Namely, as illustrated in Figure 3A, the mirror element 220 may be oriented such that an angle 303 n reference marker 302 and first axis 214 is imately 15 degrees. In such a scenario, laser light 212 emitted from the laser light source 210 may interact with reflective e 222a to form re?ected light 304. For example, upon interacting with the re?ective surface 222a, the re?ected light 304 may be directed at a +90 degree angle with respect to first axis 214.

As illustrated in Figure 3B, the mirror element 220 may be ed such that reference marker 312 is oriented along first axis 214. In such a scenario, laser light 212 emitted from the laser light source 210 may interact with both re?ective surface 222a and re?ective surface 222C to provide two different re?ected light rays. For example, upon interacting with re?ective surface 222a and ive surface 222C, the d laser light 212 may be re?ected as re?ected light 314 and re?ected light 316. In some embodiments, an emission angle range between re?ected light 3l4 and re?ected light 3 16 could be more than 230 degrees. {0058] Figure 3C rates a reflected light angle versus mirror element reference angle graph 330, according to an example embodiment. The graph 330 shows how the re?ected light angle changes as the mirror element 220 rotates about the second axis 224. In example embodiments, the re?ected light angle may be de?ned as an angle between the re?ected light ray (egg re?ected light 304) and the first axis 2l4. The graph 330 rates the three-fold symmetry when the mirror element 220 is shaped like a triangular prism. It will be understood. that if the mirror element 220 takes on a different shape (e.g., a rectangular solid), the angle symmetry and emission angle range may change accordingly. {0059] Graph point 332 illustrates the scenario described in Figure 3A. Namely, when the mirror t reference angle 303 is approximately 15 degrees, the re?ected light angle of re?ected light 304 may be approximately + 90 degrees.

Furthermore, graph points 334 and 336 illustrate the scenario bed with reference to Figure 3B. Namely, when the mirror element reference angle is zero degrees, emission light 212 may be re?ected via the two reflective surfaces 222a and 222b. In such a scenario, reflected light 314 may relate to graph point 334 (e.g, re?ected light angle of + 115 degrees) and re?ected light 3 l6 may relate to graph point 336 (eg, re?ected light angle of — 115 degrees). It will be tood that graph 330 illustrates an example embodiment and that many other re?ected light angle and mirror element reference angle onships are possible. All such other relationships are contemplated herein.

In some embodiments, as illustrated in graph 330, emission light may be re?ected in two different directions within an overlap range. As an example, overlap range 338 may represent a mirror element reference angle range over which the emission light is re?ected in different directions. This overlap range 338 represents a range of angles of the mirror element 220 in which the laser light interacts with two re?ective es of the mirror element 220. Outside of this overlap range 338, the laser light interacts with only one reflective e of the mirror t 220. This overlap range 338 may repeat based on symmetry of the mirror element 220. In graph 330, the overlap range 338 could be approximately l0 degrees wide, but other overlap ranges are possible. In some embodiments, the overlap range 338 may be adjusted based on the emission beam spot size, mirror t facet geometry, and/or beam stop position. {0062] Figure 3D illustrates an optical system 340, according to an e embodiment. Speci?cally, Figure 3D illustrates a further possible orientation of the mirror element 220. For example, mirror element 220 may rotate counterclockwise with respect to the scenario illustrated in Figure 3B. That is, the mirror element 220 may be oriented such that reference marker 342 is oriented approximately 1 degree cotmterclockwise with respect to the ?rst axis 214. In such a scenario, laser light 2l2 emitted from the laser light source 210 may interact with both re?ective surface 222a and re?ective surface 222C to provide two different re?ected light rays 344 and 346. However, in contrast to Figure 3B, the reflected light rays 344 and 346 need not be re?ected at the same angle with respect to the first axis 214 and need not have a r beam width or beam size. For example, upon interacting with re?ective surface 222a and re?ective surface 222e, the emitted laser light 2l2 may be ed as re?ected light 344 and re?ected light 346. In such a scenario, based at least on a larger n of laser light 212 interacting with re?ective e 222a, ed light 344 may have a larger beam size. Conversely, reflected light 346 may have a r beam size because a smaller portion of laser light 212 interacts with re?ective surface 222e, Furthermore, based on the position of beam stop 240, re?ected light 344 may be emitted into the environment around the optical system 340 s re?ected light 346 may be “stopped,” absorbed, or otherwise attenuated by the beam stop 240.

While Figures 2A, 2B, 2C, 3A, 3B, and 3D rate laser light '2l2 as having a certain beam width, it will be understood that laser light 212 may have a beam width that is larger or smaller in relation to the mirror element 220. In example embodiments. the laser light 212 may have a beam width that is a larger fraction of the mirror size. In such scenarios, in reference to Figure 3C, a full mirror revolution may include a larger angular range where the laser light 212 is split into two re?ected beams.

Furthermore, while Figures 2A, 2B, 2C, 3A, 3B, and 3D illustrate laser light source 210 as being ed so as to emit laser light 2l2 along a ?rst axis 214 that intersects the second axis 224, other arrangements are possible. For example, in some embodiments, laser light source 210 may be arranged so as to emit laser light 212 along an axis that does not intersect the second axis 224. For instance.‘ laser light source 210 may be arranged off- axis, tilted, or shifted away from the ?rst axis 214 and/or the second axis 224. Such asymmetric arrangements may provide greater angle coverage and/or higher resolution coverage along one side of the mirror element 220 as ed to another side. In an e embodiment, the laser light source 2l0 may be positioned with respect to the mirror element 220 so as to provide greater angular coverage for a portion of the environment located within particularly desirable angular ranges (e.g., -45 degrees to +20 degrees from horizontal). Other arrangements of laser light source 2l0 and design considerations with regard to such arrangements are possible and contemplated herein.

Figure 4 illustrates a mirror element 400, according to an example embodiment. Mirror element 400 may be similar to mirror elements 120 or 220 as rated and described with reference to s l, 2A, 2B, 2C, 3A, and 313. Mirror element 400 may include re?ective surfaces 422a, 422b, and 4220. The re?ective surfaces 422a, 422b, and 4220 may be configured to be highly reflective for incident laser light 450 at or around a given emission wavelength. For example, the reflective surfaces 422a, 422b, and 422c may re?ect more than 90% of incident light having an on wavelength of 1.55 microns. {0066] Mirror element 400 may additionally include a e 430. The mirror element 400 may be con?gured to rotate about the spindle 430, which may be along a rotational axis 432. The rotational axis 432 may be similar or identical to second axis 224 as illustrated in Figures 2A, 2B, 2C, 3A, and 3B and described elsewhere herein. Namely, spindle 430 and mirror element 400 may be configured to rotate in a clockwise and/or counter ise direction with respect to the rotational axis 432. In some ments, the e 430 may be rotated via a mirror element actuator (e.g., a DC motor or a stepper motor).

In some ments, the mirror element 400 may be hollow, at least in part.

That is, at least some material in an inner portion 4l0 of the mirror element 400 may be removed. , inner portion 410 may be empty or may include air.

As the mirror element 400 rotates about the rotational axis 432, incident light may be ed from one or more reflective surfaces of the mirror element toward an environment of the mirror element 400. For example, as rated in Figure 4, incident laser light 450 may ct with the ?rst reflective e 422a at an interaction location 424. An angle of nce of the incident laser light 450 with respect to the reflective surface 422a may determine a reflectance angle for ed light 452.

Figure 5 illustrates an optical system 500, according to an example embodiment. The optical system 500 may be, at least in part, similar or identical to optical systems 200, 250, 260, and 300 and mirror element 400 as illustrated and described with regard to Figures 2A. 2B, 2C, 3A, 3B, and 4. For example, l system 500 may e a mirror element 508 having re?ective surfaces 510a, SlOb, and 5 lOc. The mirror element 508 may be coupled to spindle 512, which may be configured to rotate about an axis of rotation 514. {0070] Similar to optical system 200, optical system 500 may include beam stop 520 and a laser light source 530. ln an example embodiment, the laser light source 530 may emit laser light 534 via an optical element 532 (e.g, a lens and/or a diffuser). The emitted laser light 534 may interact with the re?ective surface 5l0a and be re?ected into the environment of the l system. {0071] The optical system 500 may also include an l receiver 540. The optical receiver 540 may be configured to receive light 544 from the environment around the optical system 200 via an optical element 542 (eg, a condenser lens). Based on the received light 544, the optical er 540 may provide information about a scene of the environment around the optical system 200. The optical receiver 540 may include a detector array. The detector array may include a plurality of single photon avalanche detectors (SPADS).

Additionally or alternatively, the detector array may include other types of photodetectors configured to detect light 544.

The laser light source 530 and the portion of the mirror element 508 upon which the d laser light 534 is incident may be termed the transmit path. The portion of the mirror element 508 with which the received light 544 interacts and the optical receiver 540 may be termed the receive path. in embodiments illustrated herein, the transmit path and the receive path may be parallel. In such a scenario, the transmit path and receive path may be arranged so that a laser light pulse is transmitted into the environment. interacts with the environment (eg, via re?ection from an object) and is re?ected back to the receiver. The transmit path and the receive path may be segregated to reduce noise and avoid cross talk and/or false signals. Accordingly, the optical system 200 may include a light baf?e 550 that may be positioned between the transmit path and the receive path {0073] The optical system 500 may include a base portion 560 that may be coupled to the optical receiver 540, the laser light source 530, the beam stop 520, and an actuator con?gured to rotate the mirror element 508. Namely, the base n 560 may be ured to rotate about a third axis 562, which may be parallel to the transmit path and/or the receive path.

III. Example Methods {0074] Figure 6 illustrates a method 600, according to an example ment.

Method 600 may include one or more steps or blocks, which may be carried out in any order.

Furthermore, steps or blocks may be added or removed within the scope of the t sure The steps or blocks of method 600 may be carried out once, continuously, periodically, or over discrete amounts of time. {0075] Method 600 may include operations carried out entirely, or in part, by controller 150 as illustrated and bed in nce to Figure 1. Furthermore, method 600 may be carried out in ation with, or by utilizing, some or all elements of system l00, optical systems 200, 250, 260, 300, or 500, or mirror element 400 as illustrated and described in reference to Figures l, 2A, 2B, 2C, 3A, 3B, 4, and 5. {0076] Block 602 includes causing a laser light source to emit laser light along the ?rst axis such that the emitted laser light interacts with a mirror element. {0077] Block 604 includes causing the mirror element to rotate about a second axis.

The mirror element may rotate about the second axis at rotational frequency 9.. In some embodiments, the mirror element may rotate about the second axis at a onal frequency of about 30 kRPM. Other rotational frequencies of mirror element are possible. For example, the mirror element may rotate about the second axis within a rotational frequency range between lOO RPM and mo kRPM. {0078] In an example embodiment, the mirror element includes a plurality of re?ective surfaces. The plurality of reflective surfaces are disposed about the second axis.

The mirror element and the laser light source are coupled to a base structure. The base structure is con?gured to rotate about a third axis. {0079] In some embodiments, the rotation of the mirror element about the second axis includes a ?rst angular range and a second angular range. The interaction between the emitted laser light and the mirror element may be different based on whether the mirror t is within the ?rst angular range or the second r range. For example, while the rotational angle of the mirror element is within the ?rst angular range, the emitted laser light may interact with only one re?ective surface (e.g., a first re?ective surface) of the plurality of re?ective surfaces. In such a scenario, the laser light is re?ected into an environment by the first re?ective surface.

However, while the rotational angle of the mirror t is within the second angular range, the emitted laser light may interact with both the first re?ective surface and a second re?ective e of the plurality of re?ective surfaces. In such a scenario, the emitted laser light may be re?ected into the environment by the ?rst re?ective surface and the second re?ective surface. {0081] Block 406 es causing the base structure to rotate about the third axis.

The base structure may rotate about the third axis at rotational ncy (1). As an example, the base structure may rotate about the third axis at a onal frequency of about 600 RPM.

Other rotational ncies are possible. For instance, the base ure l30 may rotate about the third axis at rotational frequencies between l0 RPM and 10 kRPM. {0082] In some embodiments, the method 600 may also include operating the optical system in an interlaced condition. In some embodiments, the interlaced condition may provide information about the environment with higher resolution (e.g., by utilizing interleaved scan points). In such scenarios, the interlaced condition may occur when Q/Q)=2N+l, where N is an integer. An interlaced condition may e a desired laser scanning pattern for scanning the three-dimensional environment around the optical system. {0083] In some embodiments, the interlaced condition may provide for safer operation of equipped vehicles at least because more closely spaced scan locations may allow easier detection of a small object at a given distance. For example, a non- interlaced ion may include scan ons that are spaced 4 inches from one another at a range of 10 feet. In an example embodiment, an interlaced condition may provide scan locations that are spaced 2 inches from one another at a range of IO feet. It will be tood that other ways of interlacing or varying a set of scan locations between an initial scan and a subsequent scan so as to increase scanning resolution are contemplated herein.

In some ments, the interlaced ion may include a higher order interlacing scenario where it may take 3, 4, or more revolutions of the mirror element before a given scan location is “rescanned” with a laser light pulse. In such a scenario, Q/(I) =O\l><l<)+l, where N is an integer and k is the number of complete revolutions of the mirror element before a laser light pulse is emitted along the same axis with respect to the mirror element and/or the system generally.

In other ments, an irrational interlacing condition is possible. That is, the irrational interlacing condition could include a scenario in which the succession of laser light pulses is arranged such that pulses are never quite d along the same axis as prior pulses. In such a scenario, Q/(D may be an irrational value (e.g., a value that cannot be expressed as a ratio of integers). It will be understood that other operational modes are possible for controlling how laser light pulses are emitted into the environment. [0086} The particular arrangements shown in the Figures should not be viewed as ng. It should be understood that other embodiments may include more or less of each element shown in a given Figure. Further‘ some of the illustrated elements may be combined or omitted. Yet further, an illustrative embodiment may include elements that are not illustrated in the Figures. {0087] A step or block that ents a processing of information can pond to circuitry that can be con?gured to perform the speci?c logical functions of a herein-described method or technique. Alternatively or additionally. a step or block that represents a sing of information can correspond to a module, a segment, or a portion of program code (including d data). The program code can include one or more instructions executable by a processor for implementing speci?c l functions or actions in the method or technique. The program code and/or related data can be stored on any type of computer readable medium such as a e device including a disk, hard drive, or other storage medium. {0088} The computer readable medium can also include non-transitory computer readable media such as computer-readable media that store data for short periods of time like register memory, processor cache, and random access memory (RAM). The computer le media can also include non-transitory er readable media that store program code and/or data for longer periods of time. Thus, the computer readable media may include secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media can also be any other volatile or latile storage systems. A er readable medium can be considered a computer readable storage medium, for example, or a tangible storage device.

While various examples and embodiments have been disclosed, other examples and embodiments will be nt to those skilled in the art. The various disclosed examples and embodiments are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims.

Claims (4)

1. CLAIMS l. A system comprising: a laser light source operable to emit laser light along a ?rst axis; a mirror t comprising a plurality of re?ective es, wherein the mirror element is red to rotate about a second axis, wherein the plurality of re?ective surfaces is disposed about the second axis, wherein the mirror element and the laser light source are coupled to a base structure, n the base structure is con?gured to rotate about a third axis; and a controller con?gured to carry out operations, the operations comprising: causing the mirror element to rotate about the second axis, wherein the rotation about the second axis comprises a ?rst angular range and a second angular range; causing the laser light source to emit laser light along the ?rst axis such that the emitted laser light interacts with the mirror element, wherein: while a rotational angle of the mirror element is within the ?rst angular range, the emitted laser light interacts with a ?rst re?ective e of the plurality of reflective surfaces and is re?ected into an environment by the ?rst re?ective surface; and while the rotational angle of the mirror element is within the second angular range, the emitted laser light interacts with both the first re?ective surface and a second ive e of the plurality of re?ective surfaces and is re?ected into the environment by the first and second re?ective surfaces; and causing the base structure to rotate about the third axis.
2. 2. The system of claim l, further comprising at least one beam stop, wherein the at least one beam stop is con?gured to prevent laser light from being re?ected into the environment at angles outside an emission angle range.
3. 3. The system of claim l, wherein the plurality of re?ective surfaces ses three re?ective surfaces arranged symmetrically about the second axis such that the mirror element has a triangular prism shape.
4. 4. The system of claim 3, wherein while the rotational angle of the mirror element is within a third angular range, the d laser light interacts with a third re?ective surface of the plurality of re?ective surfaces and is reflected into the nment by the third reflective 5. The system of claim 1, wherein the first axis intersects with the second axis. 6. The system of claim 1, wherein the first axis is perpendicular to the second axis. 7. The system of claim 1, wherein the emitted laser light is reflecting into the environment through an emission angle range about the second axis, wherein the emission angle range is greater than 230 degrees. 8. The system of claim 1, wherein causing the mirror t to rotate about the second axis comprises causing the mirror element to rotate about the second axis at about 30 kRPM. 9. The system of claim l, wherein causing the base ure to rotate about the third axis comprises causing the base structure to rotate about the third axis at about 600 RPM. l0. The system of claim 1, wherein causing the mirror element to rotate about the second axis comprises causing the mirror element to rotate about the second axis at rotational frequency 9, wherein causing the base ure to rotate about the third axis comprises causing the base structure to rotate about the third axis at rotational frequency (1), n the operations further comprise operating the system in an interlaced condition. wherein the interlaced condition occurs while Q/(I)=2N+l. where N is an integer. ii. The system of claim 1, wherein the system is part of a laser-based distance and g system. 12. The system of claim 1, wherein causing the mirror element to rotate about the second axis comprises causing the mirror element to rotate about the second axis at rotational frequency 9, wherein causing the base structure to rotate about the third axis comprises causing the base ure to rotate about the third axis at rotational frequency (D, wherein causing the laser light source to emit laser light comprises causing the laser light source to emit laser light pulses based on at least one of rotational frequency Q or rotational frequency 13. An optical system comprising: a laser light source le to emit laser light along a first axis; a mirror t comprising a plurality of re?ective surfaces, wherein the mirror element is ured. to rotate about a second axis, wherein the rotation about the second axis comprises a first angular range and a second angular range, wherein the plurality of reflective surfaces is disposed about the second axis, wherein the mirror element and the laser light source are coupled to a base structure, wherein the base structure is configured to rotate about a third axis, wherein: while a rotational angle of the mirror element is within the first angular range, the emitted laser light interacts with a first tive surface of the plurality of reflective es and is reflected into an environment by the first re?ective surface; and while the rotational angle of the mirror element is within the second angular range, the emitted laser light interacts with both the ?rst reflective surface and a second re?ective surface of the plurality of reflective surfaces and is reflected into the environment by the first and second tive surfaces; and at least one beam stop, wherein the at least one beam stop is con?gured to prevent laser light from being emitted into the environment at angles outside an on angle range. l4‘ The optical system of claim l3, further comprising a mirror element actuator configured to rotate the mirror element about the second axis at rotational frequency Qt ii The optical system of claim l3, further comprising a base structure actuator configured to rotate the base structure about the third axis at rotational frequency (D. l6. The l system of claim l3, n the optical system is part of a laser-based distance and ranging system 17. The optical system of claim 13, wherein the ?rst axis intersects with the second axis. l8. The optical system of claim 13, wherein the ?rst axis is perpendicular to the second axis. 19. The optical system of claim 13, wherein the emission angle range is greater than 230 degrees about the second axis 20. The optical system of claim l3, wherein the ity of re?ective surfaces ses three re?ective surfaces arranged symmetrically about the second axis such that the mirror element has a triangular prism shape. Laser Light Sourcem Mirror Element 12 llerL50 Reflective Surface 122 Processor(s)? Reflective Surfacel 2b Reflective Surface@ Memory 1i Base Structure 13 Actuators 160