Multi-beam LIDAR using a zoom lens

Abstract

In one general aspect, an apparatus configured to monitor a distant object can include at least one source of electromagnetic radiation configured to generate a plurality of beams of electromagnetic radiation; and an optical system configured to project each of the plurality of beams of electromagnetic radiation onto a distant target object, the optical system including a zoom lens having a variable focal length and a controller configured to control the variable focal length of the zoom lens.

Description

[Technical Field]

[0001] (Related Applications) This application claims priority to and is a continuation of U.S. patent application Ser. No. 17 / 646,536, filed December 30, 2021, entitled "MULTI-BEAM LIDAR USING A ZOOM LENS," which in turn claims priority to U.S. provisional patent application Ser. No. 63 / 199,476, filed December 31, 2020, entitled "MULTIPLE-BEAM LIDAR USING A ZOOM LENS," the disclosure of which is incorporated herein by reference in its entirety.

[0002] This application also claims priority to U.S. Provisional Patent Application No. 63 / 199,476, filed December 31, 2020, entitled "MULTIPLE-BEAM LIDAR USING A ZOOM LENS."

[0003] (Technical field) This description relates to a multi-beam laser Light Detection and Ranging (LIDAR) system that uses zoom or variable focal length optics. [Background technology]

[0004] Some known LIDAR systems may use lasers to track objects. Some LIDAR systems may also be used to convert the vibration velocity of an object into an audio signal. However, known LIDAR systems used for object tracking and audio signal conversion are often relatively slow, inefficient, and / or inaccurate. Therefore, there is a need for systems, methods, and apparatus that address the challenges of the current state of the art and provide other new and innovative features. Summary of the Invention [Means for solving the problem]

[0005] (overview) In one general aspect, an apparatus configured to monitor a distant object can include at least one electromagnetic radiation source configured to generate a plurality of beams of electromagnetic radiation; and an optical system configured to project each of the plurality of beams of electromagnetic radiation onto a distant target object, the optical system including a zoom lens having a variable focal length and a controller configured to control the variable focal length of the zoom lens.

[0006] In another general aspect, a system configured to monitor a distant object can include a transmission subsystem configured to project multiple beams of electromagnetic radiation onto a distant target object, the transmission subsystem including a zoom lens having a variable focal length and a controller configured to control the variable focal length of the zoom lens; and an analyzer configured to generate multiple velocities based on the multiple beams of electromagnetic radiation reflected from the distant target object to determine a vibration velocity field on the distant object.

[0007] In another general aspect, a method may include projecting first multiple beams of electromagnetic radiation onto a distant target object via an optical system including a zoom lens having a variable focal length and a controller configured to control the variable focal length of the zoom lens; receiving second multiple beams of electromagnetic radiation resulting from the first multiple beams reflected from the distant target object; and analyzing the second multiple beams of electromagnetic radiation to generate multiple velocities and determine a vibration velocity field on the distant object.

[0008] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the detailed description and drawings, and from the claims. [Brief explanation of the drawings]

[0009] BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1A] FIG. 1A is a diagram illustrating a laser system including a laser subsystem.

[0010] [Figure 1B] FIG. 1B illustrates in greater detail components that may be included in at least one laser subsystem shown in FIG. 1A.

[0011] [Figure 2A] FIG. 2A is a diagram illustrating an exemplary object being tracked within the electronic environment illustrated in FIG.

[0012] [Figure 2B] FIG. 2B is a diagram illustrating an exemplary object being tracked within the electronic environment illustrated in FIG.

[0013] [Figure 2C] FIG. 2C is a diagram illustrating another exemplary object being tracked within the electronic environment illustrated in FIG.

[0014] [Figure 2D] FIG. 2D is a diagram illustrating another exemplary object being tracked within the electronic environment illustrated in FIG.

[0015] [Figure 2E] FIG. 2E is a diagram illustrating another exemplary object that may be tracked within the electronic environment illustrated in FIG.

[0016] [Figure 3A] FIG. 3A illustrates an example LIDAR system that generates multiple beams that enter the entrance of a zoom optical system.

[0017] [Figure 3B]FIG. 3B illustrates an exemplary zoom lens that changes focal length by moving a thin lens along the optical axis of the zoom optical system.

[0018] [Figure 3C] FIG. 3C illustrates an example zoom lens that changes focal length by changing aperture size and / or position within the zoom optical system.

[0019] [Figure 4A] FIG. 4A is a diagram illustrating an example pattern of multiple beams emitted by a multicore fiber as input to the zoom optics of a LIDAR system.

[0020] [Figure 4B] FIG. 4B is a diagram illustrating an example pattern near a distant object monitored by a LIDAR system.

[0021] [Figure 5] FIG. 5 illustrates a process associated with the embodiments described herein. DETAILED DESCRIPTION OF THE INVENTION

[0022] (Detailed explanation) The multi-beam LIDAR system is configured to generate multiple beams on a target at a specific distance, such that the beams have a specific spacing on the target. In some embodiments, the multiple beams of the multi-beam LIDAR system are generated from multiple laser subsystems. In some embodiments, the multiple beams of the multi-beam LIDAR system are generated from a multi-core fiber.

[0023] Multi-beam LIDAR systems can measure distances simultaneously at multiple beam points. These distance measurements, along with pointing information, can be used to provide an (x,y,z) map of a surface for metrology processes. Spacing of measurement points is a common requirement in metrology processes. In other LIDAR processes, such as vibration and sound collection, beam spacing is important for multi-channel signal collection or target tracking based on 3D surface shape detection.

[0024] In multi-beam LIDAR systems, the array of LIDAR beam source points is typically fixed for efficient and simple system design. Using an efficient fixed-spaced beam source array, the LIDAR lens projects the source beam pattern onto the target. If the target distance is R, the LIDAR lens focal length is rf, and the beam spacing is dx, then the beam spacing dX on the target surface is given by:

number

[0025] Traditional LIDAR systems are typically single-beam, particularly in the aerospace and automotive industries. Moving to multi-beam systems can speed up and improve the accuracy of the metrology portion of the production process in these and other industries. Still, further improvements are possible. For example, a multi-beam LIDAR system used for one metrology application may not be useful in another application due to different beam spacing requirements.

[0026] In contrast to conventional LIDAR systems that cannot adapt to different beam spacing requirements, the improved technology uses variable focal length optics (e.g., zoom lenses) to project multiple beams onto the target according to the beam spacing requirements. Zoom multi-beam LIDAR systems have the potential to adapt to various measurement spacing requirements.

[0027] For example, the same system can be used to perform both multi-beam vibrometry and metrological multi-beam 3D imaging. In addition to applications for measuring multiple velocities to determine the velocity field of a distant target, improved technology can provide applications for measuring multiple distances that can be used to determine the 3D shape of a distant target. Both applications are optimized for speed and accuracy over beam spacing on the target. The optimal beam spacing for one application may differ from the optimal beam spacing for another application.

[0028] Unlike traditional LIDAR systems, the improved technology allows the beam spacing to be optimized for any application by adjusting the focal length of the zoom lens. Generally, the optimal beam spacing for velocity / audio measurement / detection is different from the optimal beam spacing for 3D measurement. By using a zoom lens with adjustable focal length, it is possible to obtain the optimal target beam spacing for both vibration measurement applications using a single source beam array and 3D imaging / 3D measurement.

[0029] FIG. 1A illustrates a laser system 100 (also referred to as a LIDAR (Light Detection And Ranging) system) configured to generate or measure the distance and / or velocity of an object 5, which may be stationary or moving relative to the laser system 100, using a laser subsystem 105. In some embodiments, the laser system 100 can be configured to transmit one or more laser beams. Thus, the laser system 100 can be configured to generate an array of beams, for example, for characterization (e.g., measurement) of the object 5. In some embodiments, the object 5 may be referred to as a target or target object 5. The laser system 100 can be used for frequency modulated continuous wave (FMCW) applications. Such applications can include metrology applications, including characterization of surfaces (e.g., metal surfaces of vehicles (e.g., airplanes, automobiles, etc.) in manufacturing environments).

[0030] Laser system 100 can implement a multi-beam distance measurement process that can improve the speed and accuracy of distance measurements in FMCW applications, for example. As a specific example, the single settling time when using multiple lasers from laser system 100 simultaneously can improve measurement efficiency over systems that use a single laser multiple times, where each use of a single laser is associated with a settling time resulting in multiple settling times. Laser system 100 can also be configured to account for various issues related to vibration of object 5 (which can be a rigid or non-rigid object) that can cause inaccuracies in characterization.

[0031] 1A, the LIDAR system 100 includes an analyzer 170 configured to analyze data based on the laser beams generated by the laser subsystems 105. In some embodiments, the analysis can include estimating the range and / or velocity of one or more of the laser subsystems 105.

[0032] 1A, the LIDAR system 100 includes zoom optics 180 configured to generate multiple spaced beams at the target 5 via an optical system having any one of multiple focal lengths.

[0033] 1B is a diagram illustrating in more detail components that may be included in at least one laser subsystem shown in FIG. 1A. Laser source 110 of laser subsystem 105 is configured to emit (e.g., generate, propagate) electromagnetic radiation at one or more frequencies, which may be, for example, a coherent emission (e.g., monochromatic emission) or a beam. For simplicity, the emission from laser source 110 will be referred to as electromagnetic radiation emission (e.g., electromagnetic radiation emission), emitted laser signal 10, or emitted light.

[0034] As shown in FIG. 1B, laser signal 10 can be split into multiple laser signals, such as at least laser signals 11-1 and 11-2, by splitter 125. In some embodiments, laser signal 11 can be derived from the split laser signals and can be referred to as a combined laser signal. As shown in FIG. 1B, an interferometer can be used to generate laser signal 11, which can be analyzed for one or more corrections by analyzer 170 (also called a demodulator) shown in FIG. 1A. In such embodiments, laser signal 10 can be further split (e.g., by splitter 125) into laser signal 11-1 and laser signal 11-2. Laser signal 11-1 can be reflected from object 5 as laser signal 11-4. Laser signal 11-2 can be delayed by delay 142C (which can be correlated in length) to form laser signal 11-3, which can be combined with laser signal 11-4 via combiner 140C. The laser signal 11 from the interferometer (also referred to as the interferometer signal) can be used to gather information about the laser signal 11 using detector 150C. The following description of laser signal 11 can apply to any of the component laser signals 11-1 through 11-4 that can be used to define laser signal 11, which can be a target laser signal or a laser signal subject to analysis by analyzer 170. Splitter 125 is illustrated as a single component for simplicity. In some embodiments, splitter 125 can include multiple splitters. Similarly, one or more of the combiners shown in FIG. 1B can be combined or can include additional combiners.

[0035] As shown in FIG. 1B , the laser subsystem 105 includes a frequency sweep module 120 (which can be used with multiple laser subsystems). The frequency sweep module 120 is configured to trigger the laser source 110 to generate various optical frequencies (also commonly referred to as frequencies), for example, by modulating the drive current of the laser source 110. Specifically, the frequency sweep module 120 is configured to trigger the laser source 110 to generate a pattern of optical frequencies (also referred to as a frequency pattern). For example, the frequency sweep module 120 can be configured to trigger the laser source 110 to generate a sinusoidal pattern of optical frequencies, a sawtooth pattern of optical frequencies, or the like. In some embodiments, the sawtooth pattern can have a portion (also referred to as an up-chirp) that continuously increases (e.g., monotonically, linearly, or nonlinearly) in optical frequency and a portion (also referred to as a down-chirp) that continuously decreases (e.g., monotonically, linearly, or nonlinearly) in optical frequency. Thus, the frequency pattern can have a period that includes an up-chirp and a down-chirp.

[0036] Laser subsystem 105 includes combiner 140C configured to receive laser signal 11-4 (also referred to as a reflected or scattered laser signal) (not shown) reflected from object 5 in response to emitted laser signal 11-1 (split from laser signal 10) from laser source 110 toward object 5. In some embodiments, the reflected laser signal (referred to as a return signal or return light) from object 5 may be mixed with a portion of emitted laser signal 10 (e.g., laser signal 11-3 delayed by delay unit 142C) and then analyzed by analyzer 170 (after being converted to an electrical signal by detector 150C).

[0037] The analyzer 170 of the laser subsystem 105 (which may be used with multiple laser subsystems and / or included within one or more laser subsystems) is configured to analyze the combination of the emitted laser signal 11-1 from the laser source 110 and the reflected laser signal 11-4 received by the combiner 140C. The emitted laser signal 11-1 may be emitted according to a pattern including an up-chirp followed by a down-chirp (or a down-chirp followed by an up-chirp). The combination of the frequency of the emitted laser signal 11-1 from the laser source 110 and the frequency of the reflected laser signal 11-4 received by the combiner 140C may be analyzed by the analyzer 170 to obtain or define a beat frequency or signal. In other words, the beat frequency is the sum of the change in signal frequency over the round trip (emitted laser signal) to the object 5 and back (reflected laser signal), and may include a Doppler frequency shift of the reflected laser signal due to movement of the relative distance between the laser subsystem 105 and the object 5. In some embodiments, the beat signal may have a relatively constant frequency or a changing frequency. In some embodiments, the combination of the frequency of the emitted laser signal 11-1 and the frequency of the reflected laser signal 11-4 may be referred to as a difference frequency, a beat frequency, or a round trip frequency.

[0038] The analyzer 170 may be configured to calculate a round trip time, which is the time from emitting the laser signal 11-1 to receiving the return of the reflected laser signal. The combination of the emitted laser signal 11-1 and the reflected laser signal 11-4 may be collectively referred to as a round trip laser signal. The analyzer 170 may also be configured to calculate distance and / or velocity based on the combination of the emitted laser signal 11-1 and the reflected laser signal 11-4.

[0039] The optical power of the laser output can vary significantly during a frequency pattern, such as a frequency sweep or an up-chirp / down-chirp, as a result of, for example, drive current modulation of the laser source 110. The frequency pattern can be non-ideal (e.g., deviate) from the specified frequency pattern due to, for example, an imperfect drive current signal and / or unavoidable thermal excitation of the laser source 110, which can cause changes in frequency, and / or phase, etc.

[0040] A linear chirp FMCW LIDAR can calculate range by determining the frequency of a delayed chirp that travels to and from a target (e.g., object 5) compared to the frequency of a chirp that travels down a local oscillator (LO) path in LIDAR system 100. In some embodiments, the LO path can include the path between splitter 125 and combiner 140C, which can include laser signal 11-2, delay 142C, and laser signal 11-3. When the target signal is combined with the LO signal (e.g., beaten against the LO signal), the frequency of the beat signal will be the difference frequency resulting from the (range-LO) delay:

number

[0041] As shown in FIG. 1B, the LO length is a length that correlates to the delay 142C. The term "distance - LO" can represent the difference in length associated with the interferometer signal obtained from the laser signal 10. In other words, the distance term can be a length associated with the laser signal 10, which can include the distance to the target (e.g., object 5), which can be the round-trip distance, and the LO term can be a length associated with a delayed version of the laser signal 10. Therefore, "distance - LO" can represent the length obtained from the beat of the laser signal 10 and the delayed version of the laser signal 10.

[0042] If the target has a non-zero velocity component (linear motion or vibration) v in the direction of increasing distance, then in the general case, equation (2) becomes:

number

[0043] When the target is vibrating so that v=v(t), it turns out that approximately:

number

[0044] It has been found that when multiple simultaneous distance measurements are made on a surface in close proximity (if the LO path is the same and the velocity is the same at each location), approximately:

number

[0045] The laser system 100 (and laser subsystem 105A, etc.) described above with respect to Figures 1A and 1B can provide various efficiencies. For example, in some embodiments, the frequency at each point in time is the sum of components proportional to range in the range direction (e.g., the range derivative) and velocity (which may be noise and may be related to the Doppler effect). This concept is expressed in equations (3) through (5) above. These components alternate between up-chirp and down-chirp data points, switching relative signs. For example, in the absence of a counter-chirp LIDAR architecture, multiple time points are processed to determine range and velocity.

[0046] In some embodiments, differential equations can be solved to determine the time history of distance and distance derivatives. In some known applications, such as metrology applications, simple approximations such as constant velocity can be used to estimate distance and velocity, or averaged over time to assume constant distance and zero-averaged velocity. This approach can slow the measurement process in environments with high vibrations (the magnitude or tolerance of vibrations can be determined, for example, using equation (4) above). In contrast, LIDAR systems 100 with multiple lasers (e.g., closely spaced laser beams) can significantly accelerate the measurement process, while also providing significant improvements in relative and absolute distance estimates, as well as relative azimuth and elevation angle estimates.

[0047] Specifically, some embodiments of the LIDAR system 100 can achieve improved absolute and relative distance accuracy because the vibration velocity field can change slowly as a function of position. Thus, velocity values ​​(e.g., magnitude) at relatively closely spaced points can be approximately the same, or in the worst case, can be approximated as linearly varying values ​​as a function of history and / or lateral distance. In some embodiments, velocity values ​​at closely spaced points can be approximately the same, or in the worst case, can be approximated as linearly varying values ​​as a function of x and y, where z is the Cartesian coordinate of the LIDAR beam direction. In some embodiments, for rigid objects, the instantaneous z velocity can vary exactly linearly as a function of x and y. Thus, the differential equations to solve for the distance and velocity time history at each point can be linked together. Simultaneous solution of the distance and velocity fields can reduce errors. Some embodiments of the LIDAR system 100 can achieve reduced relative distance errors between local points because the points are measured simultaneously, eliminating the possibility of distance movement. In some embodiments, there may be a substantial reduction in relative azimuth and elevation errors between local points because the relative azimuth and elevation of these points is due to the rigid structure of the multi-beam array of LIDAR system 100. In some embodiments, multiple measurements may be taken simultaneously in LIDAR system 100, thereby improving time or speed efficiency. Many metrology processes require measuring relatively closely spaced points to measure features. By measuring multiple points simultaneously, speed advantages can be gained.

[0048] In some embodiments, LIDAR system 100 can have multiple beams emanating from zoom optics 180, where simultaneous measurements using the multiple beams estimate both the range and / or velocity at each beam position simultaneously, and the various beam positions are sufficiently close in space to have substantially the same velocity (Doppler component). In other words, in some embodiments, LIDAR system 100 can have a first laser beam simultaneously transmitted from zoom optics 180 at a first position and a second laser beam simultaneously transmitted from zoom optics 180 at a second position, where simultaneous measurements calculated using the first and second laser beams estimate both the range and / or velocity at each of the first and second beam positions simultaneously, and the first and second beam positions can be sufficiently close in space such that the Doppler shifts of the first and second laser beams are substantially the same or linearly related. In some embodiments, measurements from LIDAR system 100 can be processed together by analyzer 170 to estimate a constant or linearly varying velocity of the surface, which can be used by analyzer 170 to correct the range estimates at each beam position.

[0049] The zoom optical system 180 can be configured with any of a number of focal lengths. For example, a first measurement process can be configured so that the object to be measured is located 1 meter from the exit of the zoom optical system 180, and a second measurement process can be configured so that the object is located 10 cm from the exit of the zoom optical system 180. In this case, a conventional LIDAR system with an optical system having a single focal length can provide accurate measurements for the first measurement process, but such a single focal length may not be suitable for accurate measurements for the second measurement process. Replacing the optical system with another optical system having a more appropriate focal length can be costly and prone to damage. In contrast, an improved LIDAR system 100 with a zoom optical system 180 having multiple focal lengths can provide accurate measurements for both the first and second measurement processes. Further details of the zoom optical system 180 are shown with reference to FIGS. 3A-C.

[0050] In some embodiments, to further refine the distance (and velocity) estimates, measurements at multiple times may be used by analyzer 170 to estimate the time history (e.g., evolution) of distance and velocity. For example, a first set of concurrent measurements at a first time may be used by analyzer 170 along with a second set of concurrent measurements at a second time to generate at least a portion of the distance and / or velocity time history. These different sets of concurrent measurements may be used by analyzer 170 to further refine the distance and / or velocity estimates.

[0051] In some embodiments, LIDAR system 100 can be configured such that multiple simultaneous measurements at points at a particular time made by LIDAR system 100 can be used by analyzer 170 to improve the relative distance between points at a particular time without regard to the accuracy of the absolute distance. Equation 2 can be rearranged to obtain the results for each beam:

number

[0052] In some embodiments, LIDAR system 100 can be configured such that a rigid physical structure defines the relative positions of the multi-beam arrays generated by laser subsystems 105A-105N of LIDAR system 100. This set of known relative positions can be used by analyzer 170 to generate improved relative measurements of the x, y, and / or z position of each point measured by laser subsystems 105A-105N.

[0053] In some embodiments, LIDAR system 100 can measure multiple points simultaneously, thereby having a high effective data rate, each point can have high absolute accuracy, and / or each point can have high relative accuracy as described above.

[0054] 2A and 2B illustrate an exemplary object 210 that can be observed (e.g., targeted) by tracking system 120. Object 210 can have any shape, but is represented as a circle in FIGS. 2A and 2B. In FIG. 2A, at time T1, point 220 on object 210 is observed by tracking system 120. At time T1, point 220 is located at (3, 3) in the (x, y) plane. As illustrated in FIG. 2B, at time T2, point 220 is located at (4, 3) in the (x, y) plane. The movement of the point can be the result of different types of motion of object 210. For example, object 220 may move from one position to another (translational movement), or object 220 may rotate (e.g., about an axis parallel to the y-axis of the x-y plane).

[0055] As illustrated in Figures 2C, 2D, and 2E, an individual's head or face 290 can be tracked or observed by tracking system 120. Specifically, a point or position 292 on head or face 290 can be observed. As illustrated in Figure 2C, at time T1, point 292 is located at (3, 2) in the (x, y) plane. At time T2, point 292 can be observed to be at (4, 2). The movement of the point can be the result of different types of movement. For example, the person or individual may rotate their head (e.g., about an axis parallel to the y-axis), as illustrated in Figure 2D. Alternatively, the person or individual may move their head (without rotating at all), as illustrated in Figure 2E.

[0056] Some LIDAR-based monitoring systems use a single beam dwell for vibration collection and audio rendering. Nevertheless, such LIDAR-based monitoring systems can be overly sensitive to noise and target movement. To reduce the effects of noise, an array of beams can be used to detect vibrations from a target area. However, such arrays can degrade the signal because the beam separation is greater than the coherence length of the vibration. In contrast, improved LIDAR-based systems use zoom optics 180 to generate an array of beams. The zoom optics 180 can generate an array of beams whose separation is much smaller than the coherence length, thus generating a vibration signal with an improved signal-to-noise ratio. These beams can be generated with different focal lengths so that the beams can provide accurate monitoring and / or tracking at various distances.

[0057] 3A is a diagram illustrating an example LIDAR system 300 that generates multiple beams that enter the input of a zoom lens 330. As shown in FIG. 3, the zoom optics 180 includes a multicore fiber 310, a coupler (or first optic) 320, and a zoom lens 330. In some embodiments, the LIDAR system 300 can generate multiple beams in alternative ways, such as using multiple laser subsystems.

[0058] The multicore fiber 310 is configured to accept electromagnetic radiation from the coupler 320 at an input port 314 and transmit the electromagnetic radiation to an output port 316. The multicore fiber 310 includes multiple fiber cores 312, each of which transmits electromagnetic radiation from the input port 314 of the multicore fiber 310 to its output port 316 by total internal reflection. In some embodiments, each fiber core 312 is a single-mode fiber. In some embodiments, each of the fiber cores is polarization-maintaining.

[0059] Zoom lens 330 is configured to image multiple beams at various distances near any number of target objects to be monitored and / or tracked. Further details of zoom lens 330 are shown with respect to Figures 3B-C.

[0060] 3B illustrates an exemplary zoom lens that changes its focal length by moving a thin lens 350 with an aperture 360 ​​along the optical axis of the zoom lens 330. For example, in some embodiments, in response to an indication that the focal length of the zoom lens 330 should be adjusted, the controller 326 performs the adjustment of the focal length of the zoom lens 330 by moving the position of the thin lens 350 along the optical axis. In some embodiments, the controller 332 moves the thin lens 350 to one of a fixed number of discrete positions along the optical axis corresponding to respective focal lengths. In some embodiments, the thin lens 350 may be attached to a movable mount that is attached to a piezoelectric transducer.

[0061] As shown in FIG. 3B, ray bundle 340 enters zoom lens 330. The effective entrance aperture of zoom lens 330 is at object-side principal plane 342, and the effective exit aperture of zoom lens 330 is at image-side principal plane 344. Image-side ray bundle 345 then forms an image at location 346. In response to an indication that the target is near location 374, the controller can adjust the focal length of zoom lens 330. In adjusting the focal length of zoom lens 330, because the principal planes of the optical system depend on all parameters of zoom lens 330 (e.g., the positions and radii of the lens element surfaces), controller 326 can change principal planes 342 and 344 to new principal planes 376 and 372, respectively.

[0062] In some embodiments, controller 332 can continuously adjust the position of thin lens 350 to position 355. That is, the focal length of zoom lens 330 can be continuously varied from minimum to maximum. In some embodiments, position 355 is one of a discrete set of possible positions of lens 350 along the optical axis.

[0063] In some embodiments, if the zoom lens has a discrete set of focal lengths, the controller 332 adjusts the focal length of the zoom lens 330 according to a metric. In some embodiments, the controller 332 can select the focal length based on the difference between the specified distance and the predicted image position at each of the set of focal lengths. In some embodiments, the controller 332 can select the focal length based on the difference between the predicted image at the specified focal length and the predicted image at each focal length. In some embodiments, the difference can be the average difference between the complex amplitude of the image over a region of the image plane.

[0064] FIG. 3C illustrates an example zoom lens 330 that changes focal length by changing the size and / or position of aperture 360 ​​within zoom lens 330. As shown in FIG. 3C, aperture 360 ​​may be constricted (i.e., have a smaller diameter); in some embodiments, aperture 360 ​​may be enlarged (i.e., have a larger diameter). Changing the diameter of aperture 360 ​​to the diameter of aperture 365 can change the focal length of zoom lens 330. However, in some embodiments, controller 332 moves the position of aperture 360 ​​to a different position along the optical axis in response to a request to adjust the focal length of zoom lens 330. In some embodiments, the controller can change the diameter and / or position of the aperture in discrete steps.

[0065] FIG. 4A illustrates an exemplary pattern of multiple beams emitted by a multicore fiber 310 as input to the zoom optics of a LIDAR system. As shown in FIG. 4A, the beams emitted from the multicore fiber 310 are arranged in a pattern. The pattern shown in FIG. 4A is an example, and the improved LIDAR system disclosed herein is not limited to such a pattern. The pattern may be designed to maximize the number of beams within the vibration coherence length. The pattern may be designed to cover a sufficiently wide area on the target so that the target's movement can be effectively tracked based on the LIDAR signal.

[0066] As shown in FIG. 4A , the beams emitted from the multicore fiber 310 are arranged in a regular regular polygonal pattern, in this case a hexagonal pattern, with spacing 420, although other shapes (e.g., triangular, square, pentagonal, heptagonal, octagonal, etc.) are possible. The pattern shown in FIG. 4A is an example, and the improved LIDAR systems disclosed herein are not limited to such patterns. The pattern may be designed to maximize the number of beams within the vibration coherence length. The pattern may be designed to cover a sufficiently large area on the target so that the target's movement can be effectively tracked based on the LIDAR signal.

[0067] 4B is a diagram illustrating an example pattern 430 near a distant object monitored by the LIDAR system based on the pattern 420 of beams input to the zoom lens 330. As shown in FIG. 4B, the beams remain in a hexagonal pattern and have spacing 440. The spacing 440 depends on the image quality provided by the zoom lens 330. In some embodiments, the controller 332 determines the focal length of the zoom lens 330 by considering the spacing 440 relative to the spacing 420.

[0068] In some embodiments, zoom optical system 300 is configured to image the pattern of the beam (i.e., pattern 410) onto a target surface. For example, a target surface near an object to be monitored and / or tracked may be selected to optimize the image of the beam (e.g., optimize sharpness).

[0069] 3, coupler (i.e., first optic) 320 is configured to couple light from laser system 100 into each fiber core 312 at the input 314 of multicore fiber 310. In some embodiments, coupler 320 outputs a beam of electromagnetic radiation having a divergence angle approximately equal to the numerical aperture of each fiber core 312.

[0070] The optical system (i.e., second optical system) 330 is configured to direct the electromagnetic radiation emitted from each of the fiber cores 312 at the output 316 of the multicore fiber 310 into a substantially parallel beam that is directed toward the target 5. Because the beams are produced by the emission of electromagnetic radiation from the fiber cores 312 within the multicore fiber 310, the beams are much closer together (i.e., have a smaller coherence distance from each other) than in conventional LIDAR systems that use multiple lasers to generate a group of beams at the target 5.

[0071] In some embodiments, the optical system 330 includes collimating optics configured to direct electromagnetic radiation from the output 316 of the multicore fiber 310 in a direction parallel to an axis toward a distant target 5. In some embodiments, the axis is aimed at a specific point or area on the target 5. In some embodiments, the axis is configured to track the target 5 as it moves. In some embodiments, the collimating optics of the optical system 330 have a numerical aperture approximately equal to the numerical aperture of each fiber core 312.

[0072] In some embodiments, the optical system 330 includes an optical system configured to focus electromagnetic radiation from the output 316 of the multicore fiber 310 onto a distant target 5, i.e., to image the end of the multicore fiber onto the target. In some embodiments, the optical system 330 is configured to form an image on the target 5.

[0073] Figure 5 illustrates a process 500 associated with embodiments described herein. As shown in Figure 5, at 510, laser system 100 projects a first plurality of beams of electromagnetic radiation (e.g., beams 11-1) onto a distant target object (e.g., object 5) via an optical system (e.g., zoom optical system 300) that includes a zoom lens having a variable focal length (e.g., zoom lens 330) and a controller (e.g., controller 326) configured to control the variable focal length of the zoom lens.

[0074] At 520, a second plurality of beams of electromagnetic radiation (eg, beams 11-4) resulting from the first plurality of beams reflected from a distant target object are received, for example, at detector 150C.

[0075] At 530, the second plurality of beams of electromagnetic radiation are analyzed, for example by analyzer 170, to generate a plurality of velocities and determine the vibration velocity field on the distant object.

[0076] In some embodiments, for example, one or more portions of the components shown in laser system 100 of FIGS. 1A and 1B may be or include hardware-based modules (e.g., digital signal processors (DSPs), field programmable gate arrays (FPGAs), memory), firmware modules, and / or software-based modules (e.g., modules of computer code, a series of computer-readable instructions that can be executed by a computer). For example, in some embodiments, one or more portions of laser subsystem 105 may be or include software modules configured to be executed by at least one processor (not shown). In some embodiments, the functionality of the components may be included in different modules and / or different components than those shown in FIGS. 1A and 1B.

[0077] In some embodiments, one or more components of laser subsystem 105 may be or include a processor configured to process instructions stored in a memory. For example, analyzer 170 (and / or a portion thereof) may be a combination of a processor and memory configured to execute instructions related to processing to perform one or more functions.

[0078] Although not shown, in some embodiments, components of the laser subsystem 105 (or portions thereof) can be configured to operate within, for example, a data center (e.g., a cloud computing environment), a computer system, and / or one or more server / host devices. In some embodiments, components of the laser subsystem 105 (or portions thereof) can be configured to operate within a network. As such, the laser subsystem 105 (or portions thereof) can be configured to function within various types of network environments that may include one or more devices and / or one or more server devices. For example, the network may be or include a local area network (LAN) and / or a wide area network (WAN), etc. The network may be or include, for example, a wireless network implemented using gateway devices, bridges, and / or switches, etc. The network may include and / or have one or more segments based on various protocols, such as the Internet Protocol (IP) and / or proprietary protocols. The network may include at least a portion of the Internet.

[0079] In some embodiments, the memory may be any type of memory, such as random access memory, disk drive memory, and / or flash memory, etc. In some embodiments, the memory may be implemented as two or more memory components (e.g., two or more RAM components or disk drive memory) associated with components of the laser subsystem 105.

[0080] Implementations of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or combinations thereof. Implementations may also be implemented as a computer program product, i.e., a computer program tangibly embodied on an information carrier, for example, in a machine-readable storage device (computer-readable medium, non-transitory computer-readable storage medium, tangible computer-readable storage medium), or in a propagated signal for processing by, or controlling the operation of, a data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. Computer programs, such as the computer program(s) described above, may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including a stand-alone program or a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program can be deployed for processing on one computer or on multiple computers located at one site or distributed across multiple sites and interconnected by a communications network.

[0081] The method steps may be performed by one or more programmable processors which execute a computer program to perform functions by operating on input data to generate output. The method steps may also be performed by, and an apparatus may be implemented as, special purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0082] Processors suitable for processing a computer program include, by way of example, both general-purpose and special-purpose microprocessors, and any one or more processors of any kind of digital computer. Typically, a processor receives instructions and data from a read-only memory or a random-access memory, or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer also includes one or more mass storage devices for storing data, such as magnetic, magneto-optical, or optical disks, or may be operatively coupled to receive, transmit, or transmit data thereto. Information carriers suitable for embodying computer program instructions and data include, by way of example, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and all forms of non-volatile memory, including CD-ROM and DVD-ROM disks. The processor and memory may be supplemented by, or contained within, special-purpose logic circuitry.

[0083] To provide for user interaction, implementations can be performed on a computer that includes a display device, such as a liquid crystal display (LCD) monitor, that presents information to the user, as well as a keyboard and pointing device, such as a mouse or trackball, that allows the user to provide input to the computer. Other types of devices can be used to provide user interaction as well; for example, feedback provided to the user can be in any form, such as sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and user input can be received in any form, including acoustic input, voice input, or tactile input.

[0084] The implementation may be performed in a computing system that includes back-end components such as, for example, a data server, or includes middleware components, e.g., an application server, or includes front-end components, e.g., a client computer having a graphical user interface or a web browser through which a user can interact with the implementation, or any combination of such back-end, middleware, or front-end components. The components may be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include local area networks (LANs) and wide area networks (WANs), e.g., the Internet.

[0085] While certain features of the above embodiments have been illustrated as described herein, many modifications, substitutions, changes, and equivalents will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as being within the scope of the embodiments. It should be understood that the embodiments have been presented by way of example only, and not by way of limitation, and that various changes in form and detail are possible. Any portion of the apparatus and / or methods described herein may be combined in any combination, except in mutually exclusive combinations. The embodiments described herein may include various combinations and / or subcombinations of the functions, components, and / or features of the different embodiments described.

Claims

1. 1. An apparatus configured to monitor a distant object, comprising: at least one source of electromagnetic radiation configured to generate a plurality of beams of electromagnetic radiation; and an optical system configured to project each of the plurality of beams of electromagnetic radiation onto the distant target object, the optical system including a zoom lens having a variable focal length and a controller configured to control the variable focal length of the zoom lens; The apparatus comprising:

2. The apparatus of claim 1 , wherein the multiple beams are generated using a multicore fiber.

3. The apparatus of claim 1 , wherein the multiple beams are generated using multiple laser subsystems.

4. 10. The apparatus of claim 1, wherein the multiple beams are generated using multiple optical fibers arranged in a fixed spatial pattern.

5. 2. The apparatus of claim 1, wherein the zoom lens has a plurality of discrete focal lengths, and the controller is configured to set the variable focal length of the zoom lens to one of the plurality of discrete focal lengths and to no other focal lengths.

6. at least one of the plurality of beams of electromagnetic radiation is provided to the zoom lens via an optical fiber; and The apparatus of claim 1 , wherein the numerical aperture of the optical system is based on the numerical aperture of the optical fiber.

7. The apparatus of claim 1 , wherein the controller configured to control the variable focal length of the zoom lens is further configured to perform an automatic zoom adjustment based on at least one specified criterion.

8. 8. The apparatus of claim 7, wherein the at least one criterion comprises a sharpness measure of the multiple beams of electromagnetic radiation onto a distant target object evaluated in the vicinity of the distant target.

9. 8. The apparatus of claim 7, wherein the at least one criterion comprises a deviation from a minimum beam spacing of the multiple beams of electromagnetic radiation on a distant target object evaluated in the vicinity of the distant target.

10. 8. The apparatus of claim 7, wherein the at least one criterion comprises a measure based on a deviation of a geometry of the multiple beams of electromagnetic radiation on the distant target from a specified geometry.

11. 1. A system configured to monitor a remote object, comprising: a transmission subsystem configured to project a plurality of beams of electromagnetic radiation onto the distant target object, the transmission subsystem including a zoom lens having a variable focal length and a controller configured to control the variable focal length of the zoom lens; and an analyzer configured to generate a plurality of velocities based on the plurality of beams of electromagnetic radiation reflected from the distant target object to determine a vibration velocity field on the distant object; The system comprising:

12. 12. The system of claim 11, wherein the multiple beams are generated using a multicore fiber.

13. The system of claim 11 , wherein the multiple beams are generated using multiple laser subsystems.

14. 12. The system of claim 11, wherein the multiple beams are generated using multiple optical fibers arranged in a fixed spatial pattern.

15. 12. The system of claim 11, wherein the zoom lens has a plurality of discrete focal lengths, and the controller is configured to set the variable focal length of the zoom lens to one of the plurality of discrete focal lengths and to no other focal lengths.

16. 12. The system of claim 11, wherein the controller configured to control the variable focal length of the zoom lens is further configured to perform automatic zoom adjustment based on at least one specified criterion.

17. 12. The system of claim 11, wherein the analyzer configured to generate a plurality of velocities based on the plurality of beams of electromagnetic radiation reflected from the distant target object is further configured to generate the plurality of velocities based on a designated subset of the plurality of beams of electromagnetic radiation reflected from the distant target object.

18. projecting the first plurality of beams of electromagnetic radiation onto a distant target object via an optical system including a zoom lens having a variable focal length and a controller configured to control the variable focal length of the zoom lens; receiving a second plurality of beams of electromagnetic radiation resulting from the first plurality of beams reflected from the distant target object; and analyzing the second plurality of beams of electromagnetic radiation to generate a plurality of velocities and determine a vibration velocity field on the distant object; A method comprising:

19. projecting the first plurality of beams of electromagnetic radiation onto the distant target object; 20. The method of claim 18, comprising adjusting the variable focal length of the zoom lens based on specified criteria.

20. 20. The method of claim 19, wherein the criteria comprises a sharpness measure of the multiple beams of electromagnetic radiation onto a distant target object evaluated in the vicinity of the distant target.

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