PATENT DOCUMENT

Publication Number: US-9335220-B2
Application Number: US-201414302447-A
Country: US
Kind Code: B2

Title: Calibration of time-of-flight measurement using stray reflections

Abstract:
Sensing apparatus includes a transmitter, which emits a beam comprising optical pulses toward a scene, and a receiver, which receives reflections of the optical pulses and outputs electrical pulses in response thereto. Processing circuitry is coupled to the receiver so as to receive, in response to each of at least some of the optical pulses emitted by the transmitter, a first electrical pulse output by the receiver at a first time due to stray reflection within the apparatus and a second electrical pulse output by the receiver at a second time due to the beam reflected from the scene, and to generate a measure of a time of flight of the optical pulses to and from points in the scene by taking a difference between the respective first and second times of output of the first and second electrical pulses.

Claims:
The invention claimed is: 
     
       1. Sensing apparatus, comprising:
 a transmitter, which is configured to emit a beam comprising optical pulses toward a scene; 
 a receiver, which is configured to receive reflections of the optical pulses and to output electrical pulses in response thereto; 
 a scanner, comprising a scanning micromirror, which is configured to scan the beam over a scene, wherein the optical pulses are emitted and received at multiple angular positions of the scanner; and 
 processing circuitry, which is coupled to the receiver so as to receive, in response to each of at least some of the optical pulses emitted by the transmitter, a first electrical pulse output by the receiver at a first time due to an uncontrolled stray reflection from a surface of the scanning micromirror within the apparatus and a second electrical pulse output by the receiver at a second time due to the beam reflected from the scene, and to generate a measure of a time of flight of the optical pulses to and from points in the scene by taking a difference between the respective first and second times of output of the first and second electrical pulses. 
 
     
     
       2. The apparatus according to  claim 1 , wherein the processing circuitry is configured to generate a depth map of the scene responsively to the time of flight of the optical pulses. 
     
     
       3. The apparatus according to  claim 1 , wherein the first time is indicative of an inherent delay of the receiver in generating the electrical pulses in response to the arrival of the optical pulses, and wherein the processing circuitry is configured to calibrate the time of flight in order to correct for the inherent delay. 
     
     
       4. The apparatus according to  claim 3 , wherein the processing circuitry is configured to compute a moving average of the difference between the respective first and second times over a sequence of the optical pulses, and to calibrate the time of flight using the computed average. 
     
     
       5. A method for optical sensing, comprising:
 transmitting a beam comprising optical pulses from a sensing device toward a scene; 
 receiving reflections of the optical pulses in the sensing device; 
 scanning the beam over a scene by reflection from a scanning micromirror, whereby the optical pulses are emitted and received at multiple angular positions relative to the scene; 
 outputting electrical pulses from the sensing device in response to the received reflections, the electrical pulses comprising, in response to each of at least some of the transmitted optical pulses, a first electrical pulse output by the sensing device at a first time due to an uncontrolled stray reflection from a surface of the scanning micromirror within the sensing device and a second electrical pulse output by the sensing device at a second time due to the beam reflected from the scene; and 
 generating a measure of a time of flight of the optical pulses to and from points in the scene by taking a difference between the respective first and second times of output of the first and second electrical pulses. 
 
     
     
       6. The method according to  claim 5 , and comprising generating a depth map of the scene responsively to the time of flight of the optical pulses. 
     
     
       7. The method according to  claim 5 , wherein the first time is indicative of an inherent delay of the sensing device in generating the electrical pulses in response to the arrival of the optical pulses, and wherein generating the measure comprises calibrating the time of flight in order to correct for the inherent delay. 
     
     
       8. The method according to  claim 7 , wherein calibrating the time of flight comprises computing a moving average of the difference between the respective first and second times over a sequence of the optical pulses, and calibrating the time of flight using the computed average.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application 61/835,653, filed Jun. 17, 2013, and is related to U.S. patent application Ser. No. 13/766,801, filed Feb. 14, 2013 (published as U.S. 2013/0207970). This application is a continuation-in-part of U.S. patent application Ser. No. 13/798,231, filed Mar. 13, 2013 (published as U.S. 2013/0250387), claiming the benefit of U.S. Provisional Patent Application 61/614,029, filed Mar. 22, 2012. All of these related applications are assigned to the assignee of the present patent application, and their disclosures are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to methods and devices for projection and capture of optical radiation, and particularly to optical time-of-flight (TOF) sensing. 
     BACKGROUND 
     Various methods are known in the art for optical 3D mapping, i.e., generating a 3D profile of the surface of an object by processing an optical image of the object. This sort of 3D profile is also referred to as a 3D map, depth map or depth image, and 3D mapping is also referred to as depth mapping. 
     U.S. Patent Application Publication 2011/0279648 describes a method for constructing a 3D representation of a subject, which comprises capturing, with a camera, a 2D image of the subject. The method further comprises scanning a modulated illumination beam over the subject to illuminate, one at a time, a plurality of target regions of the subject, and measuring a modulation aspect of light from the illumination beam reflected from each of the target regions. A moving-mirror beam scanner is used to scan the illumination beam, and a photodetector is used to measure the modulation aspect. The method further comprises computing a depth aspect based on the modulation aspect measured for each of the target regions, and associating the depth aspect with a corresponding pixel of the 2D image. 
     U.S. Pat. No. 8,018,579 describes a three-dimensional imaging and display system in which user input is optically detected in an imaging volume by measuring the path length of an amplitude modulated scanning beam as a function of the phase shift thereof. Visual image user feedback concerning the detected user input is presented. 
     U.S. Pat. No. 7,952,781, whose disclosure is incorporated herein by reference, describes a method of scanning a light beam and a method of manufacturing a microelectromechanical system (MEMS), which can be incorporated in a scanning device. 
     U.S. Patent Application Publication 2012/0236379 describes a LADAR system that uses MEMS scanning. A scanning mirror includes a substrate that is patterned to include a mirror area, a frame around the mirror area, and a base around the frame. A set of actuators operate to rotate the mirror area about a first axis relative to the frame, and a second set of actuators rotate the frame about a second axis relative to the base. The scanning mirror can be fabricated using semiconductor processing techniques. Drivers for the scanning mirror may employ feedback loops that operate the mirror for triangular motions. Some embodiments of the scanning mirror can be used in a LADAR system for a Natural User Interface of a computing system. 
     The “MiniFaros” consortium, coordinated by SICK AG (Hamburg, Germany) has supported work on a new laser scanner for automotive applications. Further details are available on the minifaros.eu Web site. 
     SUMMARY 
     Embodiments of the present invention that are described hereinbelow provide improved apparatus and methods for depth mapping using a scanning beam. These embodiments are useful particularly (although not exclusively) in enhancing the accuracy of TOF-based measurements, both for depth mapping and for other optical measurement applications. 
     There is therefore provided, in accordance with an embodiment of the invention, sensing apparatus, including a transmitter, which is configured to emit a beam including optical pulses toward a scene, and a receiver, which is configured to receive reflections of the optical pulses and to output electrical pulses in response thereto. Processing circuitry is coupled to the receiver so as to receive, in response to each of at least some of the optical pulses emitted by the transmitter, a first electrical pulse output by the receiver at a first time due to stray reflection within the apparatus and a second electrical pulse output by the receiver at a second time due to the beam reflected from the scene, and to generate a measure of a time of flight of the optical pulses to and from points in the scene by taking a difference between the respective first and second times of output of the first and second electrical pulses. 
     In some embodiments, the apparatus includes a scanner, which is configured to scan the beam over a scene, wherein the optical pulses are emitted and received at multiple angular positions of the scanner. The processing circuitry may be configured to generate a depth map of the scene responsively to the time of flight of the optical pulses. 
     Typically, the first time is indicative of an inherent delay of the receiver in generating the electrical pulses in response to the arrival of the optical pulses, and the processing circuitry is configured to calibrate the time of flight in order to correct for the inherent delay. The processing circuitry may be configured to compute a moving average of the difference between the respective first and second times over a sequence of the optical pulses, and to calibrate the time of flight using the computed average. 
     There is also provided, in accordance with an embodiment of the present invention, a method for optical sensing, which includes transmitting a beam including optical pulses from a sensing device toward a scene. Reflections of the optical pulses are received in the sensing device, which outputs electrical pulses from the sensing device in response to the received reflections. The electrical pulses include, in response to each of at least some of the transmitted optical pulses, a first electrical pulse output by the sensing device at a first time due to stray reflection within the sensing device and a second electrical pulse output by the sensing device at a second time due to the beam reflected from the scene. A measure of a time of flight of the optical pulses to and from points in the scene is generated by taking a difference between the respective first and second times of output of the first and second electrical pulses. 
     The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic, pictorial illustration of a depth mapping system, in accordance with an embodiment of the present invention; 
         FIG. 2  is a block diagram that schematically shows functional components of a depth engine, in accordance with an embodiment of the present invention; 
         FIG. 3  is a schematic, pictorial illustration of an optical scanning head, in accordance with an embodiment of the present invention; and 
         FIG. 4  is a schematic plot of signals output by a receiver in an optical scanning head, in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Some embodiments of the present invention that are described hereinbelow provide depth engines that generate 3D mapping data by measuring the time of flight of a scanning beam. A light transmitter, such as a laser, directs short pulses of light toward a scanning mirror, which scans the light beam over a scene of interest within a certain scan range. A receiver, such as a sensitive, high-speed photodiode (for example, an avalanche photodiode) receives light returned from the scene via the same scanning mirror. Processing circuitry measures the time delay between the transmitted and received light pulses at each point in the scan. This delay is indicative of the distance traveled by the light beam, and hence of the depth of the object surface at the scan point. The processing circuitry may use the depth data thus extracted in producing a 3D map of the scene. 
     Embodiments of the present invention that are described herein provide methods for beam synchronization and calibration that can be used advantageously with the scanners described above, as well as in other types of TOF-based measurement systems. TOF-based scanners are almost inevitably subject to stray reflections, which reflect or otherwise scatter from optical surfaces within the scanner back toward the receiver. In general, such stray reflections are regarded as noise, and designers of the scanners do their best to eliminate them. In the embodiments that are described herein, however, the stray reflections are used intentionally in calibrating the TOF measurements. 
     A photodetector in the scanning head—typically the same detector that is used to receive light returned from the scene in the sort of scanning head that is described above—receives stray reflections from surfaces in the scanning head each time the transmitter is pulsed. These stray light pulses travel no more than a few centimeters between the transmitter and the photodetector, and the optical time of flight of the stray light pulses should therefore be insignificant—no more than a few tenths of a nanosecond. In practice, however, the measured delay between each electrical pulse that is input to the transmitter and the corresponding pulse that is output from the receiver in response to the stray light will be longer, due to inherent delays in the system electronics. Moreover, this delay typically varies from one scanning head to another and may vary over time (due to changes in temperature, for example) within any given scanning head. 
     The pulses that are output by the receiver in response to light reflected from the scene are subject to these same inherent delays, which introduce inaccuracy and uncertainty into the actual TOF measurements. To eliminate this inaccuracy and uncertainty, in embodiments of the present invention, the inherent delay of the system electronics is calibrated by measuring the apparent delay in the time of arrival of stray light pulses (i.e., the delay between each electrical pulse that is input to the transmitter and the corresponding pulse that is output from the receiver in response to the stray light, as explained above). This measurement provides a baseline delay, which is then subtracted from the actual TOF measurements in order to correct for the inherent delay of the electronics. The resulting calibrated TOF measurements will thus accurately reflect the optical time of flight—and hence the actual distance—to surfaces in the scene. The calibration may be updated dynamically during operation of the scanning head in order to account and correct for changes in the baseline delay over time. 
     The approach adopted by embodiments of the present invention is advantageous, inter alia, in that it can make use of existing components—including the light transmitter and the photodetector—in order to perform calibration functions, and requires essentially no additional hardware. This approach thus enhances the accuracy of the scanning head, using signals that are normally regarded as “noise,” at almost no added cost. Although one embodiment is described in detail hereinbelow with reference to the design of a particular sort of sensing device that is used in a scanning head in the specific context of 3D mapping, the principles of the present invention may similarly be applied to other types of sensing devices and scanners, for both 3D mapping and other applications. 
       FIG. 1  is a schematic, pictorial illustration of a depth mapping system  20 , in accordance with an embodiment of the present invention. The system is based on a scanning depth engine  22 , which captures 3D scene information in a volume of interest (VOI)  30  that includes one or more objects. In this example, the objects comprise at least parts of the bodies of users  28 . Engine  22  outputs a sequence of frames containing depth data to a computer  24 , which processes and extracts high-level information from the map data. This high-level information may be provided, for example, to an application running on computer  24 , which drives a display screen  26  accordingly. 
     Computer  24  processes data generated by engine  22  in order to reconstruct a depth map of VOI  30  containing users  28 . In one embodiment, engine  22  emits pulses of light while scanning over the scene and measures the relative delay of the pulses reflected back from the scene. A processor in engine  22  or in computer  24  then computes the 3D coordinates of points in the scene (including points on the surfaces of the users&#39; bodies) based on the time of flight of the light pulses at each measured point (X,Y) in the scene. This approach gives the depth (Z) coordinates of points in the scene relative to the location of engine  22  and permits dynamic zooming and shift of the region that is scanned within the scene. Implementation and operation of the depth engine are described in greater detail in the above-mentioned U.S. Patent Application Publication 2013/0207970. 
     Although computer  24  is shown in  FIG. 1 , by way of example, as a separate unit from depth engine  22 , some or all of the processing functions of the computer may be performed by a suitable microprocessor and software or by dedicated circuitry within the housing of the depth engine or otherwise associated with the depth engine. As another alternative, at least some of these processing functions may be carried out by a suitable processor that is integrated with display screen  26  (in a television set, for example) or with any other suitable sort of computerized device, such as a game console or media player. The sensing functions of engine  22  may likewise be integrated into computer  24  or other computerized apparatus that is to be controlled by the depth output. 
     For simplicity and clarity in the description that follows, a set of Cartesian axes is marked in  FIG. 1 . The Z-axis is taken to be parallel to the optical axis of depth engine  22 . The frontal plane of the depth engine is taken to be the X-Y plane, with the X-axis as the horizontal. These axes, however, are defined solely for the sake of convenience. Other geometrical configurations of the depth engine and its volume of interest may alternatively be used and are considered to be within the scope of the present invention. 
     Scanner designs and other details of the depth engine that support the above sorts of schemes are described with reference to the figures that follow. 
       FIG. 2  is a block diagram that schematically shows functional components of depth engine  22 , in accordance with an embodiment of the present invention. Engine  22  comprises an optical head  40 , which serves as the sensing device of the depth engine, and a controller  42  (also referred to as a processor), which may be implemented as an application-specific integrated circuit (ASIC), as indicated in the figure. 
     Optical head  40  comprises a transmitter  44 , such as a laser diode, whose output is collimated by a suitable lens. Transmitter  44  outputs a beam of light, which may comprise visible, infrared, and/or ultraviolet radiation (all of which are referred to as “light” in the context of the present description and in the claims). A laser driver, which may similarly be implemented in an ASIC  53 , modulates the laser output, so that it emits short pulses, typically with sub-nanosecond rise time. The laser beam is directed toward a scanning micromirror  46 , which may be produced and driven using MEMS technology, as described in the above-mentioned U.S. Patent Application Publication 2013/0207970. The micromirror scans a beam  38  over the scene, possibly via projection and collection optics, such as a suitable lens (not shown). 
     Pulses of light reflected back from the scene reflect from scanning mirror  46  onto a receiver  48 . (Alternatively, in place of a single mirror shared by the transmitter and the receiver, a pair of synchronized mirrors may be used.) The receiver typically comprises a sensitive, high-speed photodetector, such as an avalanche photodiode (APD), along with a sensitive amplifier, such as a transimpedance amplifier (TIA), which amplifies the electrical pulses output by the photodetector. These pulses are indicative of the times of flight of the corresponding pulses of light. 
     The pulses that are output by receiver  48  are processed by controller  42  in order to extract depth (Z) values as a function of scan location (X,Y). For this purpose, the pulses may be digitized by a high-speed analog/digital converter (A2D)  56 , and the resulting digital values may be processed by depth processing logic  50 . The corresponding depth values may be output to computer  24  via a USB port  58  or other suitable interface. 
     Typically, a given projected light pulse will result in (at least) two reflected light pulses that are detected by receiver  48 —a first pulse due to stray light reflected from a surface or surfaces in or associated with optical head  40 , followed by a second pulse reflected from a surface of an object in VOI  30 . Logic  50  is configured to process both pulses, giving two corresponding delay values (baseline and actual object) at the corresponding pixel. These dual delay values may be used by logic  50  (or alternatively by computer  24 ) in calibrating the actual object delays and thus generating a more accurate depth map of the scene. 
     Controller  42  also comprises a power converter  57 , to provide electrical power to the components of engine  22 , and components that control the transmit, receive, and scanning functions of optical head  40 . For example, a MEMS control circuit  52  in controller  42  may direct commands to the optical head to modify the scanning ranges of mirror  46 . A laser control circuit  54  and a receiver control circuit  55  likewise control aspects of the operation of transmitter  44  and receiver  48 , such as amplitude, gain, offset, and bias. Position sensors associated with the scanning mirror, such as suitable inductive or capacitive sensors (not shown), may provide position feedback to the MEMS control function. Additionally or alternatively, reflections from a diffraction grating on mirror  46  may be sensed and processed in order to verify proper operation of the scanner and/or to calibrate the angular scale and speed of the scan, as described in the above-mentioned U.S. Patent Application Publication 2013/0250387. 
       FIG. 3  is a schematic, pictorial illustration showing elements of optical head  40 , in accordance with an embodiment of the present invention. Transmitter  44  emits pulses of light toward a polarizing beamsplitter  60 . Typically, only a small area of the beamsplitter, directly in the light path of transmitter  44 , is coated for reflection, while the remainder of the beamsplitter is fully transparent (or even anti-reflection coated) to permit returned light to pass through to receiver  48 . The light from transmitter  44  reflects off beamsplitter and is then directed by a folding mirror  62  toward scanning micromirror  46 . A MEMS scanner  64  scans micromirror  46  in X- and Y-directions with the desired scan frequency and amplitude. 
     Details of the micromirror and scanner are described in the above-mentioned U.S. Patent Application Publication 2013/0207970. Scanner  64  may be produced and operate on principles similar to those described in the above-mentioned U.S. Pat. No. 7,952,781, modified to enable two-dimensional scanning of a single micromirror  46 . Dual-axis MEMS-based scanners of this type are described further in PCT Patent Application PCT/IB2013/056101, filed Jul. 25, 2013 (published as WO 2014/016794), which is incorporated herein by reference. Alternative embodiments of the present invention, however, may use scanners of other types that are known in the art, including designs that use two single-axis scanners (such as those described in U.S. Pat. No. 7,952,781, for example). 
     Light pulses returned from VOI  30  strike micromirror  46 , which reflects the light via turning mirror  62  through beamsplitter  60 . Receiver  48  senses the returned light pulses and generates corresponding electrical pulses. To enhance sensitivity of detection, the overall area of beamsplitter  60  and the aperture of receiver  48  are considerably larger than the area of the transmitted beam, and the beamsplitter is accordingly patterned, i.e., the reflective coating extends over only the part of its surface on which the transmitted beam is incident. The reverse side of the beamsplitter may have a bandpass coating, to prevent light outside the emission band of transmitter  44  from reaching the receiver. It is also desirable that micromirror  46  be as large as possible, within the inertial constraints imposed by the scanner. For example, the area of the micromirror may be about 3-30 mm 2 . 
     The specific mechanical and optical designs of the optical head shown in  FIG. 3  are described here by way of example, and alternative designs implementing similar principles are considered to be within the scope of the present invention. Other examples of optoelectronic modules in which the principles of the present invention may be applied are described in the above-mentioned U.S. Patent Application Publication 2013/0207970. 
       FIG. 4  is a schematic plot of signals output by receiver  48  during a scan of micromirror  46 , in accordance with an embodiment of the invention. Each horizontal line in  FIG. 4  corresponds to the signal output by receiver  48 , as a function of time, in response to one light pulse emitted by transmitter  44  at time=0, as micromirror  46  scans in the Y-direction. For simplicity, the pictured example assumes the pulses to be emitted at scan intervals of 1°, although in practice the angular separation between successive pulses is generally smaller and may vary with time or other system parameters. Although this simplified plot shows only a single pulse corresponding to each distance measurement at each angle, in practice more complex patterns of pulses may be used, and the principles of the present invention are equally applicable regardless of the choice of such a pulse pattern. 
     Each of the light pulses is reflected back from a corresponding point in the scene being scanned by optical head  40 , and the returning optical pulse causes receiver  48  to output an electrical pulse at a time indicated by a corresponding peak  90  at the right side of the figure. The time delay of each peak  90  (in nanoseconds) is indicative of the round-trip time of flight of the light pulse to and from the corresponding point in the scene, and hence of the distance of the point from the optical head. 
     In addition, a small part of the light in each pulse output by transmitter  44  reflects back to receiver  48  from one or more of the surfaces within or in proximity to optical head  40 . (The term “in proximity” in this context may include, for example, other optical surfaces within depth engine  22 , but generally not nearby objects in VOI  30 .) These stray reflections may reach the receiver, for example, due to uncontrolled reflection and/or scattering from the surfaces of micromirror  46 , beamsplitter  60  or folding mirror  62 . Corresponding peaks  92 , indicating the electrical pulses output by receiver  48  in response to these stray reflections, appear at the left side of the figure. The time delay of peaks  92  is very short, since the pulses return to receiver  48  directly, typically less than a nanosecond after being emitted from transmitter  44 . Thus, the observed delay of peaks  92  actually reflects the inherent electronic delays within the circuits of depth engine  22 , as explained above. Depth processing logic  50  may take the difference between the times of output of the pulses from receiver  48  due to the beam reflected from the scene and the pulses due to stray reflections by subtracting the duration of the delay of peaks  92  from the longer delay of peaks  90 . This difference gives an accurate measure of the actual time of flight of the optical pulses, from which the electronic delays in depth engine  22  have been calibrated out. 
     The delays of stray light peaks  92  may vary with system conditions, such as temperature, but such delays are usually slowly varying, and therefore can be dealt with by suitable calibration in order to avoid degrading the quality of the position measurements. For example, logic  50  may compute a moving average of the delay of peaks  92  over a sequence of the optical pulses in order to filter out short-term jitter, and may then subtract this average delay from the measured delay of each peak  90  in order to give the desired calibrated TOF values. 
     The advantages of this approach are not limited to the specific device architecture that is shown in  FIGS. 2 and 3 , but may rather be used in other sorts of scanning systems, particularly (although not exclusively) MEMS-based scanning systems. It will thus be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.

Metadata:
Filing Date: 20140612
Publication Date: 20160510
Grant Date: 20160510
Priority Date: 20120322
Inventors: SHPUNT ALEXANDER
ERLICH RAVIV
Assignee: APPLE INC
CPC Classifications: [{"code": "G01S7/4817", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S17/89", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/1814", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J11/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B26/101", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01S7/497", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S7/4817", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S7/497", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S7/4817", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S17/89", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B26/101", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/1814", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/1814", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01S7/497", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J11/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S17/89", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B26/101", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 51619858