WO2020072484A1 - Mesure de foyer auxiliaire pour un dispositif de balayage 3d à radar laser - Google Patents

Mesure de foyer auxiliaire pour un dispositif de balayage 3d à radar laser

Info

Publication number
WO2020072484A1
WO2020072484A1 PCT/US2019/054054 US2019054054W WO2020072484A1 WO 2020072484 A1 WO2020072484 A1 WO 2020072484A1 US 2019054054 W US2019054054 W US 2019054054W WO 2020072484 A1 WO2020072484 A1 WO 2020072484A1
Authority
WO
WIPO (PCT)
Prior art keywords
measurement
focus
target
auxiliary
distance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2019/054054
Other languages
English (en)
Inventor
Daniel Gene Smith
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nikon Corp
Original Assignee
Nikon Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nikon Corp filed Critical Nikon Corp
Publication of WO2020072484A1 publication Critical patent/WO2020072484A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/86—Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4811—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4811—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver
    • G01S7/4812—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver transmitted and received beams following a coaxial path

Definitions

  • the disclosure pertains to laser surface profile and distance measurement apparatus.
  • Laser radar systems provide simple, convenient, non-contact measurements that aid single-operator object inspection.
  • Laser radar systems are particularly useful for inspection applications in which large objects are to be measured such as in the manufacture and assessment of aircraft, automobile, wind turbine, satellite, and other oversized parts.
  • Some conventional laser radar systems are described in U.S. Patents 4,733,609; 4,824,251; 4,830,486; 4,969,736; 5,114,226; 7,139,446; 7,925,134; and Japanese Patent 2,664,399 which are incorporated herein by reference.
  • a laser beam is directed to and scanned over a target surface, and portions of the laser beam that are reflected or scattered back to the laser radar are detected and processed to provide target information.
  • Heterodyne LRs that use optical heterodyne signals to determine range can provide measurement accuracies of less than 5 pm/meter.
  • Heterodyne LR is particularly well suited to very near objects (e.g., closer than one meter) such as might be encountered inside a 3D scan box.
  • heterodyne and other types of LR typically require directing a tightly focused laser beam to a target to achieve both fine spatial resolution and high SNR for strongly scattering objects.
  • Approaches are needed that can permit rapid, initial acquisition of surface data so that LR focus can be set, and LR measurements initiated promptly.
  • optical measurement apparatus include an auxiliary focus system situated to estimate a distance to at least a portion of a target and a focus mechanism situated to adjust a focus of a measurement beam at the target in response to the distance estimate.
  • the auxiliary focus system includes an auxiliary laser situated to direct an auxiliary beam to the portion of the target, and the distance is estimated based on a portion of the auxiliary beam returned from the target.
  • the auxiliary focus system includes an auxiliary detector situated to receive the portion of the auxiliary beam returned from the target.
  • the auxiliary focus system includes a modulator that applies an electrical amplitude modulation, frequency modulation, phase modulation, pulse modulation, or any combination thereof to the auxiliary beam, and the distance estimate is based on a detected modulation.
  • a measurement laser is situated to direct a measurement beam to the portion of the target, wherein the auxiliary focus system includes an auxiliary laser situated to direct an auxiliary beam to the portion of the target, and the estimated distance is based on a portion of the auxiliary beam returned to the target.
  • a measurement laser is situated to produce and direct a measurement beam and an auxiliary beam to the portion of the target.
  • a focus element is coupled to the focus mechanism so as to be translated by the focus mechanism, wherein the focus element includes one or more of a lens, a prism, or a mirror.
  • the measurement laser and the auxiliary laser emit respective beams at different wavelengths.
  • the auxiliary focus system includes a fringe projector situated to project a fringe pattern on at least the portion of the target, and the focus mechanism is adjustable in response to a detected fringe pattern.
  • an objective lens is situated to direct the measurement beam to the target and an image sensor is situated to image the projected fringe pattern through the objective lens or along the axis of the objective lens.
  • a beam scanner is situated to scan the auxiliary beam over the target area prior to the measurement beam.
  • the beam scanner is configured to scan the auxiliary beam at least one scan line prior to the measurement beam.
  • the auxiliary focus system includes an image sensor situated to produce at least two images of the target area and a processor coupled to receive the at least two images and establish at least one distance estimate based on the at least two images.
  • Methods comprise obtaining an initial distance estimate associated with at least one target area and based on the initial distance estimate, adjusting a focus element associated with a measurement beam.
  • An initially focused measurement beam is directed to the at least one target area based on the adjustment of the focus element and a final focus of the measurement beam is determined based on a returned portion of the measurement beam.
  • a target surface profile is obtained based on a returned portion of a finally focused measurement beam.
  • the initial distance is obtained by directing an auxiliary beam to the at least one target area, and detecting a time-of-flight of the auxiliary beam to the at least one target area.
  • the initial distance is obtained by directing an auxiliary beam to the at least one target area, and detecting a time-of-flight of the auxiliary beam to the at least one target area, wherein the auxiliary beam is a portion of the measurement beam.
  • the initial distance is obtained by directing an auxiliary beam to the at least one target area, and detecting a modulation of a detected portion of the auxiliary beam received from the at least one target area.
  • the modulation of the detected portion of the auxiliary beam is an electrical phase modulation, amplitude modulation, frequency modulation, or a combination thereof.
  • the final focus of the measurement beam is obtained based on a detected portion of the measurement beam returned from the target.
  • the final focus of the measurement beam is obtained based on an optical frequency modulation of a detected portion of the measurement beam returned from the target.
  • the initial distance is obtained by projecting a fringe pattern on the at least one target area, and detecting at least a portion of the projected fringe pattern.
  • the initial distance is obtained by obtaining at least one image that includes the target area, and processing the at least one image to obtain the initial distance.
  • FIG. 1 illustrates a laser radar system (LR) that includes an auxiliary focus system having two image sensors.
  • LR laser radar system
  • FIG. 2 illustrates an LR that includes an auxiliary focus system having a single image sensor.
  • FIG. 3 illustrates an LR that includes an auxiliary focus system having an auxiliary laser that propagates to a target via an LR objective and scanning system.
  • FIG. 4 illustrates another representative LR having an auxiliary focus system.
  • FIG. 5 illustrates another representative LR having an auxiliary focus system that uses a common laser and detector with the LR.
  • FIG. 6 illustrates a representative LR focus method
  • FIG. 7 illustrates another representative LR focus method.
  • FIGS. 8-9 illustrate auxiliary focus systems for LR using external LIDAR systems.
  • FIG. 10 illustrates a representative LR having an auxiliary focus system that uses a fringe projector.
  • FIG. 11 illustrates another representative LR having an auxiliary focus system that uses a fringe projector.
  • FIG. 12 is a block diagram illustrating a representative manufacturing method that includes profile measurement to determine whether manufactured structures or components are acceptable, and if one or more such manufactured structures can be repaired.
  • FIG. 13 is a block diagram of a representative method of tracking a tooling ball that is secured to a substrate or target.
  • FIG. 14 is a block diagram of a representative manufacturing system that includes a laser radar or other profile measurement system to manufacture components, and assess whether manufactured parts are defective or acceptable.
  • FIG. 15 is a schematic illustration of a laser radar system that includes an auxiliary focus system as disclosed herein.
  • FIG. 16 is a front view of a preferred type of laser radar system that can include an auxiliary focus system as disclosed herein.
  • FIG. 17 is a schematic illustration raster scanning associated with an auxiliary beam and a measurement beam.
  • FIG. 18 illustrates a representative scan system
  • values, procedures, or apparatus are referred to as“lowest”,“best”, “minimum,” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, or otherwise preferable to other selections.
  • image refers to a viewable, displayed, or projected image of an object, or a stored digital representation associated therewith.
  • Stored digital representations can be arranged as, for example, JPEG, TIFF, BMP, PDF or other formats, or as sequences of images such as MPEG or other formats.
  • one or more stored digital representations are processed to provide an initial distance estimate for use in focusing.
  • beams are described as propagating along one or more axes. Such axes generally are based on one or more line segments so that an axis can include a number of non- collinear segments as the axis is bent or folded or otherwise responsive to mirrors, prisms, lenses, and other optical elements.
  • the term“lens” is used herein to refer to a single refractive optical element (a singlet) or a compound lens that includes one or more singlets, doublets, or other elements.
  • beams are shaped or directed by refractive optical elements, but in other examples, reflective optical elements such as mirrors are used, or combinations of refractive and reflective elements are used.
  • Such optical systems can be referred to as dioptric, catoptric, and catadioptric, respectively.
  • Other types of refractive, reflective, diffractive, holographic and other optical elements can be used as may be convenient.
  • auxiliary measurements can be obtained by auxiliary beam scanning, line scanning, photogrammetry, fringe projection, or other approaches as described below.
  • An auxiliary focus signal can be provided using the scanning LR beam (or a portion of the LR beam scan, such as a scan line) or using a separate beam, using the LR optics or different optics.
  • Auxiliary focus scanning can direct an auxiliary beam (such as a line beam) along the LR beam path or a separate path, typically to irradiate a target portion prior to scanning with the LR measurement beam.
  • auxiliary focus is determined for only a portion of the target surface just in advance of LR measurement, or, alternatively, a larger or complete target area is imaged to establish an initial LR beam focus.
  • a photogrammetric system can be used, using one or more cameras that image at least portions of a surface to be scanned in advance of the LR measurement beam.
  • fringe projection systems can be used. Fringe projection can use a separate illumination system or can use the same optical system or objective lens as an LR.
  • a low-NA imaging channel can be used on a first scan of the object to sense fringes, and then a second scan can use the resulting information to set focus and scan with the LR.
  • a spatially displaced imaging channel is used that is one or more scan lines ahead of the LR scan.
  • range measurements can be made coaxially with the LR scan, if desired.
  • a LIDAR signal can be used that is obtained with the LR scan beam or an auxiliary beam.
  • the LIDAR signal can be acquired in advance of LR scanning.
  • a LIDAR beam could be directed along a common axis with the LR beam using a dichroic or polarizing or other beam splitter. Returned portions of the LIDAR beam can be detected with the LR detector or a separate detector using a beam splitter such as a fiber coupler, a beam splitter cube, or a plate beam splitter.
  • the LIDAR beam can be produced using the LR source prior to LR scanning or along with LR scanning based on a beam modulation that differs from that of LR scan.
  • the LIDAR modulation can be an AM or FM modulation that is different from an optical heterodyne swept modulation used by the LR.
  • modulation at electrical frequencies can be used that can be detected without an optical reference optical signal such as required by LR in swept frequency, heterodyne LR.
  • measurement beam wavelength is varied. For convenience, such a variation is referred to herein as an optical modulation. Amplitude, phase, or frequency modulations of a measurement beam at frequencies less than about 1 GHz are referred to as electrical modulations. For electrical modulations, change of laser wavelength is generally not intended.
  • FIG. 1 is a perspective view of a laser rangefinder 100 that includes a laser radar 102 secured to an altitude rotational stage 108 that is configured to rotate about an altitude axis 110.
  • the altitude stage 108 is secured to an azimuthal rotational stage 111 that is configured to rotate about an azimuthal axis 116.
  • the axes 110, 116 are generally intersecting orthogonal axes, and are described herein as azimuthal and altitude axes for convenience, as such axes may be arranged so as to be in arbitrary directions. For convenient illustration, control systems used for adjustment of rotation angles are not shown in FIG. 1.
  • the laser radar 102 includes optical and electrical systems configured to deliver an interrogation beam to a target from an aperture 104 along a laser radar axis 106.
  • the laser radar typically 102 includes a housing 103 that is secured to the altitude stage 108 so that the laser radar axis 106 can be scanned over the target with the altitude stage 108 and the azimuth stage 111.
  • Some portions of the laser radar 102 can be provided separately from the housing 103, and are not rotatable.
  • control electronics, fiber coupled lasers and/or detectors and associated transmitter and detector electronics, and signal processors can be located remotely.
  • a housed portion of the laser radar 102 includes transmit and receive optical systems.
  • the azimuthal stage 111 includes a rotatable platform 112 to which the altitude stage 108 is secured and a fixed platform 114. Rotation of the rotatable platform 112 about the axis 116 permits scanning of the laser radar axis 104 over a target.
  • the laser rangefinder 100 also includes a first camera 130 and a second camera 140 that are secured to rotate with the laser radar housing 103.
  • the cameras 130, 140 are configured to image through apertures 132, 142 along imaging axes 134, 144, respectively, and provide images of at least some portions of a target or of areas situated about the laser radar axis 104.
  • the camera axes 134, 144 are substantially parallel to the laser radar axis and are orthogonal to and intersect the altitude axis 110.
  • the camera axes 134, 144 can be arranged to be intersecting or skew.
  • Images from the cameras 130, 140 are typically provided to a focus processor 150 that estimates a target distance based on the images.
  • the focus processor 150 is coupled to a focus mechanism (not shown in FIG. 1) that is situated to adjust a focus of a measurement beam at the target. Estimated distance can be obtained photogrammetrically, and focus is typically adjusted again based on a portion of the measurement beam returned from the target during LR operation. In most cases, final target surface data is acquired primarily based on the measurement beam, and the cameras 130, 140 permit a rapid initial focus which can reduce total measurement time. In other examples, measurement beam based distances are combined with camera-based estimates to obtain suitable surface measurements.
  • a camera need not be situated to rotate in both azimuth and elevation, but only to image a portion of a target for which focus data is to be obtained.
  • the relationship between the camera axes of the cameras 130 and 140 and the laser radar axis 106 may be fixed.
  • the camera axes of the cameras 130 and 140 and the laser radar axis 106 may be parallel to each other.
  • the cameras 130 and 140 may move together with the housing 103. Note that the relationship between the camera axes of the cameras 130 and 140 and the laser radar axis 106 may be changeable.
  • the focus processor 150 controls the focus mechanism (not shown) based on the images obtained by the cameras 130 and 140, so that the irradiation spot of the measurement beam irradiated by the laser radar 102 is focused on the target.
  • the intensity of light from the irradiation spot received by the laser radar 102 can be increased.
  • the S/N ratio of signals associated with the received measurement beam can be improved and measurement accuracy can be improved.
  • FIG. 2 illustrates a representative laser rangefinder 200 that includes a laser radar 202 situated to have a scan axis 204 that is directed to a target 205.
  • a camera 220 includes a lens 212 that is configured to form images at an image sensor 214. As shown in FIG. 2, the camera 220 has an axis 216 that is parallel to the scan axis 206. The camera axis 216 can be fixed or variable with respect to the scan axis 204.
  • An image processor 230 is coupled to receive image data from the image sensor 214 and estimate a target distance for use in focus adjustment.
  • a laser radar controller 232 processes laser radar data and controls the laser radar 202 to scan the target 205 and provide range estimates. Images can be obtained during scanning of either the laser radar 202 or the target 205 as indicated at 250, 251, respectively, and processed to determine distance estimates for focus adjustment.
  • the distance of the target 205 is estimated by moving the focus lens 212 (moving along the camera axis 216).
  • the distance of the target 205 is estimated based on information of the position of the focus lens 212 in a direction along the camera axis 216 when the contrast of the image on the image sensor 214 is the best.
  • the focus when the laser radar 202 performs the measurement can be adjusted to the target 205.
  • the intensity of light generated at the target 205 by irradiating the measurement beam can be increased, so that the S/N ratio can be improved and the measurement accuracy can be improved.
  • a laser radar system 300 includes a transmitter system 302 that is configured to couple an optical beam from one or more laser diodes or other light sources to an optical fiber 304 through a beam splitter 305 such as a beam splitter cube, a plate beam splitter, or a fiber coupler.
  • the optical beam exits the optical fiber 304 at a fiber end 306, typically at a cleaved or plane polished fiber end, and is directed along an axis 308 to a right angle prism 310 and a return mirror 332.
  • the return mirror 332 is situated along the axis 308 as folded by the right angle prism 310 to return the beam through the right angle prism 310 to an objective lens 314 that produces a focused beam that is directed to a target 316 and scanned over a region of interest with a scanning assembly 310.
  • Focus is typically adjusted by translating the right angle prism 310 along the axis 308. At least some portions of the beam are scattered, reflected, or otherwise returned to the objective lens 314 and coupled via the right angle prism 310 and the return mirror 332 to the fiber end 306 and to a receiver system 322.
  • the right angle prism 310 is secured to a focus mechanism 326 that is configured to translate the right angle prism 310 along the axis 308 to focus the beam at particular distance.
  • the returned portion of the beam can be used in laser radar processing to provide target coordinates.
  • the laser radar system 300 also includes a processing system 350 that is coupled to the transmitter system 302 and the receiver system 322. Based on transmitted and received optical signals, the processing system 350 can estimate distances and other coordinates associated with the target, or selected portions of the target 316. Measurement results are provided directly for user inspection or relayed to analysis systems.
  • the laser radar system 300 can be configured as a frequency modulated continuous wave system, as an amplitude or phase modulated system, or a combination of such systems as discussed further below.
  • FIG. 3 is illustrated with a right angle prism used to provide focus adjustment. Corner cubes or roof prisms (solid or air spaced) are generally superior, but a right angle prism permits convenient illustration.
  • the fiber 304 is a polarization maintaining fiber and the beam splitter 305 is a polarizing beam splitter.
  • the transmitter system 302 includes a swept frequency laser 302A (i.e., a measurement laser), an auxiliary laser 302B, and a pointing laser 302C that produce a swept frequency beam, an auxiliary focus beam, and a visible pointing beam, respectively, that are coupled by a coupler 303 such as a fiber coupler, dichroic beam splitter, or polarizing beam splitter to the fiber 304.
  • a coupler 303 such as a fiber coupler, dichroic beam splitter, or polarizing beam splitter to the fiber 304.
  • the visible pointing beam is available for visual alignment by an operator, and the swept frequency beam is used in swept frequency laser radar.
  • the auxiliary beam (and the other beams) are directed along the axis 308 to the target 316, and portions of each can be returned from the target 316 to the beam splitter 305. Any returned portion of the pointing beam is generally unused, and is typically blocked by one or more optical filters or is not coupled downstream by components used for the
  • a coupler 323 receives returned portions of the swept frequency beam and the auxiliary beam and couples portions to a swept frequency detector 322A and an auxiliary detector 322B, respectively. If the swept frequency beam and the auxiliary beam are at different wavelengths, the coupler 323 can be a wavelength dependent coupler such as a fiber coupler or a dichroic beam splitter. In heterodyne laser radar, a portion of the swept frequency beam is directed to the swept frequency detector 322A as a local oscillator (LO) beam along an LO path 342 to produce a heterodyne output signal at the swept frequency detector 322A. Signals associated with the detected beam portions are coupled to a controller/signal processor 350.
  • LO local oscillator
  • the signal associated with the auxiliary laser beam is used to produce a range estimate.
  • the auxiliary laser beam can be a pulsed beam and a time of flight to the target 316 can be estimated.
  • the auxiliary beam can be amplitude modulated or frequency modulated, and modulation in the detected signal used to estimate target distance. Amplitude or frequency modulation is usually at electronic frequencies (less than a few 100 MHz).
  • the controller 350 Based on the estimated target distance, the controller 350 directs a focus signal to the focus adjustment mechanism 326 so that the swept frequency laser beam is suitably focused at the target 316.
  • auxiliary measurement time of flight (TOF) method
  • TOF time of flight
  • a laser radar 400 includes a transceiver 402 that includes an LR laser 404, an LR detector 406, and a coupler 408 that directs an LR measurement beam from the LR laser 404 along an axis 410 and directs a return portion of an LR beam from a target to the LR detector 406.
  • the laser radar 400 also includes an auxiliary (focus) transceiver 412 that includes a focus laser 414, a focus detector 416, and a focus coupler 418 that directs a focus beam from the focus laser 414 along an axis 420 and directs a return portion of a focus beam from a target to the focus detector 416.
  • a beam scanner 422 is coupled to scan the beams over a region of interest at the target.
  • a beam splitter 424 combines and separates focus and LR beams and a common objective 430 directs both beams to the target.
  • the axes 410, 420 are displaced from each other (and need not be parallel) so that the LR beam and the focus beam are incident to different portions of the target.
  • the focus beam is directed to a target area in advance of exposure of the target area to the LR beam so that a focus estimate can be obtained prior an LR measurement.
  • Both the LR detector 406 and the focus detector 416 produce electrical signals that are coupled to a controller 432 and are amplified, buffered, or otherwise processed to establish a preliminary focus and recording a sample surface profile, respectively. Based on the focus signal, the controller 432 couples a control signal to a focus mechanism 434.
  • an LR system 500 includes an LR laser modulator 502 that is coupled to a laser driver 504 to activate an LR laser 506 to direct an LR beam along an axis 510 via a coupler 508.
  • a focus modulator 512 is coupled to the laser driver 504 to apply a focus modulation to the LR laser output beam along with or in addition to a modulation associated with LR measurement. Portions of the LR beam returned from the target are coupled
  • LR detector 516 In swept frequency, heterodyne LR, an optical frequency difference between the portion of the LR beam returned from a target and an LO beam is used to provide a distance estimate.
  • a controller 550 is coupled to direct a focus signal to a focus mechanism 552 based on the portion of the detected LR signal having the focus modulation.
  • a single laser the LR laser
  • separate focus laser and detector are not needed.
  • a second detector can be used if desired so that there are dedicated detectors for LR measurement and focus adjustment.
  • swept frequency heterodyne LR control of laser frequency can be challenging and applying an additional focus modulation can interfere with swept frequency control.
  • an external modulator 505 such as an electro-optic, acousto-optic, electro-absorption, or other modulator implemented in a bulk material or a waveguide configuration.
  • Such an external optical modulator is situated outside of a laser cavity, but can be integrated on a common substrate with a laser diode.
  • laser gain modulation can introduce additional (unwanted) laser wavelength changes that are avoided with external modulation.
  • the example of FIG. 5 has the following effects in addition to the same effects as the effects of the examples of FIGS. 3 and 4. Since the LR laser output beam (measurement beam) and the auxiliary measurement beam (auxiliary beam) are supplied from a common irradiation source, the configuration can be simplified. As a result, it is possible to suppress degradation of measurement accuracy due to, for example, manufacturing errors. Further, the light generated by irradiating the target with the LR laser measurement beam and the light generated by irradiating the target with the auxiliary beam are received by the common light receiver 516, the configuration can be simplified. As a result, it is possible to suppress degradation of measurement accuracy due to, for example, manufacturing errors.
  • two or more laser diodes or other sources and corresponding detectors are used for LR measurement and focus measurements, respectively.
  • the sources can produce beams that differ in wavelength or polarization, and can have the same or different modulations that are independently selected.
  • a focus laser can be operated as a pulsed laser or can be amplitude and/or frequency modulated and pulse timing or amplitude and/or frequency modulation in a beam portion returned from a target used to adjust focus.
  • LR measurements can use the same or other approaches such as swept frequency heterodyne measurements.
  • a single LR laser can be used for LR and focus measurements.
  • a representative method 600 includes directing an auxiliary focus beam to a target at 602, and establishing a distance estimate for one, some, or all target locations of interest based on a returned portion of the auxiliary focus beam at 604.
  • a focus of an LR beam is adjusted, and at 608, an LR measurement of some or all target locations is obtained.
  • two or more images of the target are used to estimate focus.
  • the relationship (model) between information obtained by receiving the light generated by irradiating the target with the auxiliary beam and the driving amount of the focus mechanism can be obtained in advance, and the focusing operation 606 may be performed using the relationship (model) and the information obtained by receiving the light.
  • a table showing the above relationship can be prepared in advance, and the focusing operation (606) may be performed using the table and the information obtained by receiving the light.
  • a focus method 700 includes selecting a scan area at 702. At 704, an auxiliary focus beam is directed to a scan area or two or more images of the scan are obtained.
  • distance estimates are obtained for some or all locations in the scan area based on the auxiliary focus beam or the two or more images.
  • an LR beam is applied with a focus based on the previously determined distance estimate, and at 710, LR-based target
  • auxiliary focus beam is scanned over a selected number (one or more) scan lines, and the LR beam is then scanned over the same line or lines (such as a raster scan) with a pre-focus based on the prior scan.
  • the LR beam may require additional focusing but the total range of possible focus settings is reduced, permitting more rapid LR data acquisition.
  • Other pre-scan areas can be selected (or a vector scan can be used), or an entire target area of interest can be investigated to estimate LR focus.
  • the focus estimation at 706 is not required as in the example of FIG. 6. Instead of focus estimation, the driving amount of the focus mechanism can be directly obtained.
  • LIDAR light detection and ranging systems
  • the LIDAR can provide an approximate distance that is used to establish an initial LR focus to reduce a range of focus needed for LR
  • an LR system 800 includes an LR such as a heterodyne LR 802 having an objective lens 806 that is coupled to a focus mechanism 804 that is adapted to displace the objective lens 806 along an LR axis 808.
  • a LIDAR 810 is situated to direct an auxiliary beam along the axis 808 or along a displaced or tilted axis such as axis 814.
  • An LR measurement beam and the LIDAR beam can be combined with a beam splitter 816 and directed to a target along the common axis 808 or axes 808, 814, respectively.
  • the LIDAR 810 is coupled to the LR 802 to provide an auxiliary focus signal so that the LR can be approximately focused, typically increasing the speed with which the fine focus needed for LR can be adjusted.
  • an LR system 900 includes an LR 902 having an objective lens 906 that is coupled to a focus mechanism 904 that is adapted to displace the objective lens 906 along an LR axis 908.
  • a LIDAR 910 is situated to direct an auxiliary beam to the LR 902 for combination with an LR measurement beam using a beam splitter. The LIDAR beam and the LR measurement beam are directed to a target along the axis 908 with the objective lens 906.
  • the LIDAR 910 is also coupled to the LR 902 to provide an auxiliary focus signal so that the LR can be approximately focused prior to LR measurement.
  • optical path lengths to a target for an auxiliary beam and an LR beam differ due to, for example, placement of beam splitters or how beams are combined. Any difference in auxiliary beam path length can be compensated in focus estimates to provide a more accurate focus for an LR.
  • focus is adjusted with translation of an objective lens, but focus can be adjusted in other ways such as translation of a corner cube as illustrated above.
  • a measurement system 1000 comprises a fringe projector 1002 situated to direct a patterned beam to a target along an axis 1004.
  • an LR 1006 directs a measurement beam from a laser diode 1007 along an axis 1008 and an image sensor 1010 is situated to produce an image of the projected fringes along the axis 1008.
  • a beam splitter 1020 is situated to separate the LR measurement beam and radiation associated with fringe imaging. The fringe image is used by a processor 130 to estimate distance and initiate a focus adjustment.
  • a measurement system 1100 comprises a fringe projector 1102 is coupled to a first beam splitter 1104 and a second beam splitter 1106 to direct a patterned beam to a target along an axis 1108.
  • An LR 1120 directs a measurement beam along the axis 1108 via the second beam splitter 1106.
  • An image sensor 1130 is situated to receive radiation associated with the fringe pattern from the first beam splitter 1104, and produce an image of the projected fringe pattern. Based on the fringe pattern, LR focus can be adjusted.
  • the projected fringes are imaged and/or projected using an LR objective lens 1122.
  • FIG. 12 is a flowchart showing a representative manufacture method 1200 that can incorporate manufacturing systems such as illustrated in FIG. 14.
  • design information is obtained or created corresponding to a shape of a structure to be manufactured.
  • the structure is manufactured or“shaped” based on the design information.
  • coordinates, dimensions, or other features of the manufactured structure are measured with a profile measurement system such as the laser radar systems described above to obtain shape information corresponding to the structure as manufactured.
  • the manufactured structure is inspected based on a comparison of actual and design dimensions, coordinates, manufacturing tolerance, or other structure parameters.
  • the manufactured part is accepted and processing ends at 1214. If the manufacture part is determined to be defective at 1210 by, for example, the manufacture inspector 1432 of the controller 1430 as shown in FIG. 14, then at 1212 it can be determined whether the manufacture part is repairable.
  • the manufactured part is reprocess or repaired at 1216, and then measured, inspected, and reevaluated at 1206, 1208, 1210, respectively. If the manufactured part is determined to be unrepairable at 1212, the process ends at 1214.
  • a manufactured structure can be evaluated to determine if the structure is defective or non-defective. Further, if a manufactured structure is determined to be defective, reprocessing can be initiated if the part is deemed to be repairable based on design and actual structure dimensions and features. By repeating the measurement, inspection, and evaluation processes, defective parts can be reprocessed, and parts that are defective but that are not repairable can be discarded.
  • FIGS. 12 and 14 are exemplary only, and other arrangements can be used. However, in many cases, inclusion of auxiliary focus can produce measurement more rapidly.
  • FIG. 13 illustrates a representative method of tracking a tooling ball that is secured to a substrate or target.
  • One or more tooling balls can be secured to a target to provide reference points for coordinate determinations.
  • Tooling balls generally include a reflective ball-shaped surface in order to provide ample reflection of an interrogation beam in a laser-based
  • a tooling ball location is identified and recorded based on returned portions of a scanned interrogation optical beam.
  • the optical beam can be scanned in a variety of patterns such as circles, spirals, w’s, or zig-zags so as to track a tooling ball.
  • the identified location is evaluated to determine a position with respect to a primary scan.
  • the primary scan is adjusted at 1306 so that the tooling ball location is at a preferred location with respect to the primary scan. Typically, the primary scan is adjusted so that the tooling location is approximately centered within a primary scan range.
  • a determination is made regarding additional scanning. In some cases, an auxiliary focus system is used to establish an initial focus for scanning an interrogation beam.
  • FIG. 14 illustrates a representative manufacturing system 1400 suitable for producing one or more components of a ship, airplane, or part of other systems or apparatus, and for evaluating and reprocessing such manufactured components.
  • the system 1400 typically includes a shape or profile measurement system 1405 such as the laser radar system as discussed above.
  • the manufacturing system 1400 also includes a design system 1410, a shaping system 1420, a controller 1430, and a repair system 1440.
  • the controller 1430 includes coordinate storage 1431 configured to store measured and design coordinates or other characteristics of one or more manufactured structures as designed and/or measured.
  • the coordinate storage 1431 is generally a computer readable medium such as hard disk, random access memory, or other memory device.
  • the design system 1410, the shaping system 1420, the shape measurement system 1405, and a repair system 1440 communicate via a communication bus 1415 using a network protocol.
  • the design system 1410 is configured to create design information corresponding to shape, coordinates, dimensions, or other features of a structure to be manufactured, and to communicate the created design information to the shaping system 1420.
  • the design system 1410 can communicate design information to the coordinate storage 1431 of the controller 1430 for storage.
  • Design information typically includes information indicating the coordinates of some or all features of a structure to be produced.
  • the shaping system 1420 is configured to produce a structure based on the design information provided by the design system 1410.
  • the shaping processes provided by the shaping system 1420 can include casting, forging, cutting, or other process.
  • the shape measurement system 1405 is configured to measure the coordinates of one or more features of the manufactured structure and communicate the information indicating measured coordinates or other information related to structure shape to the controller 1430.
  • a manufacture inspector 1432 of the controller 1430 is configured to obtain design information from the coordinate storage 1431, and compare information such as coordinates or other shape information received from the profile measuring apparatus such as described above with design information read out from the coordinate storage 1431.
  • the manufacture inspector 1432 is generally provided as a processor and a series of computer-executable instructions that are stored in a tangible computer readable medium such as random access memory, a flash drive, a hard disk, or other physical devices. Based on the comparison of design and actual structure data, the manufacture inspector 1432 can determine whether or not the manufacture structure is shaped in accordance with the design information, generally based on one or more design tolerances that can also be stored in the coordinate storage 1431.
  • the manufacture inspector 1432 can determine whether or not the manufactured structure is defective or non-defective. When the structure is not shaped in accordance with the design information (and is defective), then the manufacture inspector 1432 determines whether or not the structure is repairable. If repairable, then the manufacture inspector 1432 can identify defective portions of the manufactured structure, and provide suitable coordinates or other repair data.
  • the manufacture inspector 1432 is configured to produce one or more repair instructions or repair data and forward repair instructions and repair data to the repair system 1440. Such repair data can include locations requiring repair, the extent of re-shaping required, or other repair data.
  • the repair system 1440 is configured to process defective portions of the manufactured structure based on the repair data. Use of auxiliary focus methods and apparatus permit more rapid detection of locations in need of repair.
  • FIG. 15 shows a laser radar system 1500 that can be used with any or all of the disclosed embodiments.
  • the laser radar system 1500 includes a pointing laser 1502 that produces a pointing beam in a visible (e.g., red) wavelength range, and a measurement laser 1504 that produces a measurement beam in a different (e.g., infrared or IR) wavelength range, and directs (transmits) the pointing and measurement beams to an output 1520 of the laser radar system 1500.
  • the pointing beam is used to identify a point on a target 1506 at which the measurement beam is directed.
  • the pointing beam laser source and the measurement beam laser source are generally different.
  • a control unit 1508 can control the laser radar system 1500.
  • the laser radar system 1500 includes a control unit, but in other examples, a control unit can be provided separately and coupled to the laser radar system 1500.
  • the measurement beam may pass through a beam splitter 1510 which directs the measurement beam (and the pointing beam) along a measurement path 1512 to the target 1506.
  • a portion of the measurement beam is directed by the beam splitter 1502 through a free space or fiber optic optical path so that a portion of the measurement beam is processed as described in U.S. Pat. Nos. 4,733,609, 4,824,251, 4,830,486, 4,969,736, 5,114,226, 7,139,446, 7,925,134, and Japanese Patent No. 2,664,399.
  • the measurement beam portion that is directed along the measurement path 1512 is reflected from the target 1506 and a portion of the reflected or scattered measurement beam is received back at the laser radar system 1500, where it is directed to a detector 1513 by a beam splitter 1514. This beam portion is detected and processed to provide information about the target 1506.
  • optical heterodyne detection provides a source light beam which is directed to a target, and a portion is reflected or scattered from the target and returned. The returned light beam is then mixed with a local oscillator light beam on a photodetector to provide optical interference signals which may be processed to provide detailed information about the target.
  • a laser radar assembly 1600 incudes a scan assembly 1604 in which an objective lens 1606 directs a measurement beam (and a pointing beam) and an auxiliary beam to a target.
  • a rotary stage 1608 permits rotation about an azimuthal axis 1610 and a rotational actuator 1612 permits rotation about an elevation axis 1614.
  • One or more electrical and/or optical cables 1616 couples electrical and optical signals to and from a base 1620 that contains electronics 1622 (such as photodetector amplifiers, scan controllers, laser drivers) and optical components 1624 (such as fiber components, laser diodes, detectors). If image based auxiliary focusing is intended, one or more image sensors and associated optics such as camera 1630 can be secured to the scanning assembly 1604.
  • measurements are carried out by a laser radar by directing a measurement beam to a target surface.
  • a laser based tool such as laser radar or laser tracker can direct one or more beams to suitable targets such as mirrors, corner cubes, tooling balls, or other reflectors.
  • a target area 1700 is scanned as defined by a raster pattern 1702 that includes representative scan lines 1704, 1706.
  • An auxiliary beam is directed to an area 1709 to scan along the scan line 1706 as shown by arrow 1708. With such a scan, initial focal distances for a subsequent measurement beam scan can be obtained.
  • a measurement beam is directed to an area 1711 that is scanned along the scan line 1704 as shown by arrow 1710.
  • each scan line is scanned by the auxiliary beam to provide a focus estimate prior to scanning with a measurement beam.
  • the auxiliary scan can be one, two, or more scan lines ahead of the measurement beam.
  • the auxiliary beam can be scanned along the scan line 1704 just in advance of the measurement beam scan as indicated by arrow 1718.
  • initial focus estimates for the entire target area 1700 are obtained prior to measurement beam scanning.
  • pre-scan approaches can also be used with other scan patterns such as arbitrary scans, vector scanning, or“W” shaped scans.
  • some or all image portions can be obtained or processed in advance of measurement beam scanning.
  • a representative system 1800 for scanning an auxiliary beam and a measurement beam is illustrated in FIG. 18.
  • An objective lens 1802 receives the auxiliary beam and the measurement beam and directs the beams at different angles with respect to an axis 1803.
  • a scan mirror 1808 that is coupled to a rotary stage 1810 receives the beams and directs the beams to a target.
  • the beams can be co-planar but need not be.
  • the measurement and auxiliary beams are directed along the same or parallel axes to a target.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Optical Radar Systems And Details Thereof (AREA)

Abstract

La présente invention concerne un système de focalisation auxiliaire couplé à un mécanisme d'ajustement de foyer pour simplifier la focalisation d'un radar laser. Un faisceau de focalisation auxiliaire, un projecteur de frange ou une caméra peut être utilisé pour déterminer une distance cible, de telle sorte que la focalisation peut être réglée à une distance initiale. Dans certains cas, une modulation de faisceau de mesure électrique est utilisée pour déterminer la focalisation initiale. Un radar laser (LR) (400) comprend un émetteur-récepteur (402) qui comprend un laser LR (404), un détecteur LR (406) et un coupleur (408) qui dirige un faisceau de mesure LR à partir du laser LR (404) le long d'un axe (410) et dirige une partie de retour d'un faisceau LR depuis une cible vers le détecteur LR (406). Le radar laser (400) comprend également un émetteur-récepteur auxiliaire (foyer) (412) qui comprend un laser de focalisation (414), un détecteur de focalisation (416) et un coupleur de focalisation (418) qui dirige un faisceau de focalisation à partir du laser de focalisation (414) le long d'un axe (420) et dirige une partie de retour d'un faisceau de focalisation depuis une cible vers le détecteur de focalisation (416). Un dispositif de balayage de faisceau (422) est couplé pour balayer les faisceaux sur une région d'intérêt au niveau de la cible. Un diviseur de faisceau (424) combine et sépare les faisceaux de focalisation et LR et un objectif commun (430) dirige les deux faisceaux vers la cible. Les axes (410, 420) sont déplacés l'un de l'autre de façon que le faisceau LR et le faisceau de focalisation soient incidents sur différentes parties de la cible. Généralement, le faisceau de focalisation est dirigé vers une zone cible avant que la zone cible soit exposée au faisceau LR, de sorte qu'une estimation de focalisation peut être obtenue avant une mesure LR. Le détecteur LR (406) et le détecteur de focalisation (416) produisent des signaux électriques qui sont couplés à un dispositif de commande (432) et sont traités pour établir une focalisation préliminaire et enregistrer un profil de surface d'échantillon, respectivement. Sur la base du signal de focalisation, le dispositif de commande (432) couple un signal de commande à un mécanisme de focalisation (434). En variante, un projecteur de frange dirige un faisceau à motifs vers la cible, dont l'image de franges est utilisée pour estimer la distance et initier un ajustement de foyer. Les procédés et l'appareil de l'invention peuvent être utilisés dans divers systèmes de fabrication, par exemple pour produire un ou plusieurs composants d'un navire, d'un avion ou d'une pièce d'autres systèmes ou appareils, et pour évaluer et retraiter de tels composants fabriqués
PCT/US2019/054054 2018-10-01 2019-10-01 Mesure de foyer auxiliaire pour un dispositif de balayage 3d à radar laser Ceased WO2020072484A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201862739749P 2018-10-01 2018-10-01
US62/739,749 2018-10-01

Publications (1)

Publication Number Publication Date
WO2020072484A1 true WO2020072484A1 (fr) 2020-04-09

Family

ID=68290363

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2019/054054 Ceased WO2020072484A1 (fr) 2018-10-01 2019-10-01 Mesure de foyer auxiliaire pour un dispositif de balayage 3d à radar laser

Country Status (1)

Country Link
WO (1) WO2020072484A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112761092A (zh) * 2020-12-10 2021-05-07 南京熊猫电子股份有限公司 一种基于激光雷达探测技术的闸机设备及运行方法

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4733609A (en) 1987-04-03 1988-03-29 Digital Signal Corporation Laser proximity sensor
US4824251A (en) 1987-09-25 1989-04-25 Digital Signal Corporation Optical position sensor using coherent detection and polarization preserving optical fiber
US4830486A (en) 1984-03-16 1989-05-16 Goodwin Frank E Frequency modulated lasar radar
US4969736A (en) 1988-06-17 1990-11-13 Slotwinski Anthony R Integrated fiber optic coupled proximity sensor for robotic end effectors and tools
US5114226A (en) 1987-03-20 1992-05-19 Digital Optronics Corporation 3-Dimensional vision system utilizing coherent optical detection
JP2664399B2 (ja) 1987-03-20 1997-10-15 デジタル・オプトロニクス・コーポレイシヨン コヒーレント光検出法を用いた３次元ビジョンシステム
US7139446B2 (en) 2005-02-17 2006-11-21 Metris Usa Inc. Compact fiber optic geometry for a counter-chirp FMCW coherent laser radar
US7925134B2 (en) 2005-03-17 2011-04-12 Nikon Metrology Nv Precision length standard for coherent laser radar
EP3015881A2 (fr) * 2014-10-31 2016-05-04 Rockwell Automation Safety AG Mesure de distance absolue pour des capteurs à durée de vol
US20180252894A1 (en) * 2015-09-11 2018-09-06 Heptagon Micro Optics Pte. Ltd. Imaging devices having autofocus control

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4830486A (en) 1984-03-16 1989-05-16 Goodwin Frank E Frequency modulated lasar radar
US5114226A (en) 1987-03-20 1992-05-19 Digital Optronics Corporation 3-Dimensional vision system utilizing coherent optical detection
JP2664399B2 (ja) 1987-03-20 1997-10-15 デジタル・オプトロニクス・コーポレイシヨン コヒーレント光検出法を用いた３次元ビジョンシステム
US4733609A (en) 1987-04-03 1988-03-29 Digital Signal Corporation Laser proximity sensor
US4824251A (en) 1987-09-25 1989-04-25 Digital Signal Corporation Optical position sensor using coherent detection and polarization preserving optical fiber
US4969736A (en) 1988-06-17 1990-11-13 Slotwinski Anthony R Integrated fiber optic coupled proximity sensor for robotic end effectors and tools
US7139446B2 (en) 2005-02-17 2006-11-21 Metris Usa Inc. Compact fiber optic geometry for a counter-chirp FMCW coherent laser radar
US7925134B2 (en) 2005-03-17 2011-04-12 Nikon Metrology Nv Precision length standard for coherent laser radar
EP3015881A2 (fr) * 2014-10-31 2016-05-04 Rockwell Automation Safety AG Mesure de distance absolue pour des capteurs à durée de vol
US20180252894A1 (en) * 2015-09-11 2018-09-06 Heptagon Micro Optics Pte. Ltd. Imaging devices having autofocus control

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112761092A (zh) * 2020-12-10 2021-05-07 南京熊猫电子股份有限公司 一种基于激光雷达探测技术的闸机设备及运行方法

Similar Documents

Publication Publication Date Title
US10663292B2 (en) Quality inspection system and method of operation
US11680794B2 (en) Low drift reference for laser radar
US7701592B2 (en) Method and apparatus for combining a targetless optical measurement function and optical projection of information
US10139492B2 (en) Radar systems with dual fiber coupled lasers
JP7149256B2 (ja) Ｌｉｄａｒに基づく３次元撮像のための統合された照射及び検出
CN105699983B (zh) 激光跟踪器、提供附加测量功能的方法以及计算机可读存储介质
US9638799B2 (en) Scan mirrors for laser radar
CN107192380B (zh) 确定目标的工业坐标位置的激光跟踪器、方法及存储介质
CN202133379U (zh) 一种自校准型激光收发光轴平行度测量装置
JP7697886B2 (ja) 装置及び構造物の製造方法
KR20170134945A (ko) 개선된 구조를 갖는 라이다 광학장치
US10197668B2 (en) Eighth wave corner cube retarder for laser radar
CN108931784A (zh) 基于激光频率扫描干涉测距的三维测量系统
JP2016212098A (ja) 焦点調整機構を有するスキャナ・トラッカ複合装置
US20200025559A1 (en) Apparatus and method for capturing an object surface by electromagnetic radiation
WO2020072484A1 (fr) Mesure de foyer auxiliaire pour un dispositif de balayage 3d à radar laser
CN217604922U (zh) 深度数据测量头和局部深度数据测量设备
CN215813342U (zh) 深度数据测量头和局部深度数据测量设备
CN117665837A (zh) 基于主动投射点激光的测量装置和方法
JPH01203918A (ja) 測定装置と物体との間の光学的距離測定方法
JPH04166790A (ja) 走査光学系

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 19790373

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 19790373

Country of ref document: EP

Kind code of ref document: A1