Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
  • G02B6/3542—Non-blocking switch, e.g. with multiple potential paths between multiple inputs and outputs, the establishment of one switching path not preventing the establishment of further switching paths
• • 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
  • G01S17/88—Lidar systems specially adapted for specific applications
  • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
• • 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
• • 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
  • G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
• • 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
  • G01S7/4818—Constructional features, e.g. arrangements of optical elements using optical fibres
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
  • G02B26/004—Optical devices or arrangements for the control of light using movable or deformable optical elements based on a displacement or a deformation of a fluid
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
  • G02B6/3512—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/3538—Optical coupling means having switching means based on displacement or deformation of a liquid
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
  • G02B6/3544—2D constellations, i.e. with switching elements and switched beams located in a plane
  • G02B6/3546—NxM switch, i.e. a regular array of switches elements of matrix type constellation
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
  • G02B6/3554—3D constellations, i.e. with switching elements and switched beams located in a volume
  • G02B6/3556—NxM switch, i.e. regular arrays of switches elements of matrix type constellation
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/3564—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details
  • G02B6/3568—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details characterised by the actuating force
  • G02B6/3574—Mechanical force, e.g. pressure variations
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/3586—Control or adjustment details, e.g. calibrating
  • G02B6/3588—Control or adjustment details, e.g. calibrating of the processed beams, i.e. controlling during switching of orientation, alignment, or beam propagation properties such as intensity, size or shape

Definitions

• This invention relates generally to micromechanical and related modulation of optical circuits and networks; and more particularly to methods and apparatus for providing faster switching or modulation with lower power than heretofore required for imaging.
• Jackel assigned to Bell Communication. That patent teaches use of a chemically (to be more specific, electrolytically) creatable and destroyable bubble, and its implications on total internal reflection, for optical modulation.
• lidar and related imaging systems are bulky and heavy, and require relatively high operating power — leading to operational inconvenience and expense. Curiously enough, one reason for these undesirable characteristics is the bulk and weight associated with apertures used in transmitting and then receiving optical signals.
• a related persistent problem in known lidar systems is maintenance of good signal separation as between different parts of an object region of interest.
• the Bowker patent mentioned above projects a fan-shaped pulse beam to a wide-cross-track region of the ocean surface (and interior) — and receives reflection back from the entire region.
• This adaptability should not be limited to use in different applications, but should also allow the flexibility to choose instrumentation and light sources depending on one's needs and preferences for a given project.
• Another economic factor of concern includes power requirements for driving any attached light sources. Still another is the circuitry necessary to satisfy these power requirements.
• the present invention introduces such refinement.
• the invention has several major facets or aspects, which can be used in- dependently — although, to best optimize enjoyment of their advantages, certain of these aspects or facets are best practiced (and most-preferably practiced) in conjunction together.
• the invention is a system for use with one or more features to be detected and ranged. (That is to say, the features are not themselves part of the invention but rather are part of the operating environment of context of the invention . )
• This system includes a source for generating a lidar beam; and also at least one transceiver for directing the beam to — and collecting light reflected from — the one or more features. Also included are a lidar detector for time-resolving the reflected beam; and a beam splitter for passing light from the source to the transceiver, and from the transceiver to the detector.
• the beam splitter is configured so that — in passing light bidirectionally to and from a particular point of the one or more features — the splitter passes light through substantially a single corresponding common point of a corresponding transceiver.
• the splitter pass light through substantially a single corresponding common point of the splitter itself.
• the beam splitter be a fractionally-transmitting optical element — and in this case further preferably the splitter is a substantially passive optical element.
• the splitter be actively switched to route (1) the generated beam from the source, but (2) the reflected beam to the detector .
• the invention is a system for use with one or more features to be detected and ranged — and includes a lidar-beam source. It also includes at least one transceiver for directing the beam to, and collecting light reflected from, the one or more features .
• This system also includes a lidar detector for time-resolving the reflected beam.
• the transceiver In passing light bidirectionally to and from a particular point of the one or more features, the transceiver passes light through substantially a single corresponding common point of the transceiver.
• the described lidar system establishes conjugate points in the object field, where the physical features of interest reside, and in the transceiver.
• a point is established in the object field that corresponds with a point in the transceiver — and multiple such one-to-one correspondences are established, for multiple points of the object and transceiver respectively.
• Such conjugate relationships in routing the light from and back to the transceiver afford a much higher degree of precision and accuracy than heretofore possible, in identifying or localizing the features that are detected and ranged.
• the transceiver includes a fiber-optic element and free-space imaging optics; and it is the imaging optics that establish conjugate points of the one or more features, for substantially each fiber of the fiber-optic element.
• the invention is a system for use with one or more features to be detected and ranged.
• This system includes a lidar light-beam source; and also at least one transceiver for directing a lidar beam from the source to, and collecting the beam reflected from, the one or more features.
• the system also includes a lidar detector for time-resolving the reflected beam. Also included are some means for steering successive time segments of the beam to and from particular points , selectively, of the one or more f atures .
• steering means include several possible choices : at least one micromechanical mirror, or optical-switching fabric, or liquid-crystal display, or device having signal-controlled birefringence, or other type of device employing nonlinear optical material .
• micromechanical encompasses microscopic-scale mechanical elements that are powered or actuated, or both, electrically or electronically — but also elements powered or actuated optically, or biologically, or thermally, or by other sorts of signals or energy flows including such phenomena that are not yet commercially implemented now.
• the at least one transceiver includes plural transceivers
• the steering means include means for successively selecting different ones of the transceivers .
• the steering means include means for successively selecting different particular points addressed through a transceiver; these two preferences are mutually compatible, and capable of being practiced together .
• the invention is a system for use with features to be detected and ranged.
• features themselves are not part of the invention but rather represent its operating environment, or context.
• the system includes a lidar light-beam source, and plural transceivers — each for directing a lidar beam from the source to, and collecting light reflected from, a particular one or more of the features respectively.
• the system of this fourth facet of the invention also includes a lidar detector for time-resolving the reflected beam; and some means for steering successive time segments of the beam to and from particular ones, selectively, of the plural transceivers respectively.
• this fourth facet of the invention extends the above-stated benefits of the third aspect even further, to the case of plural transceivers .
• Such transceivers can readily cover not only an entire full three-dimensional field of view (i. e. , 4 ⁇ steradians) from a particular point in space, but also — through specialized routing of e. q. optic-fiber bundles in the transceivers — simultaneous monitoring of supplementary special views within enclosures, or through spectrometric evaluation systems, and so forth .
• the steering means include some means for successively selecting different particular points addressed through a transceiver.
• the invention is a system for use with one or more features to be detected and ranged.
• This system includes a lidar light-beam source.
• It also includes at least one transceiver for directing a lidar beam from the source to, and collecting the beam reflected from, the one or more features; and a lidar detector for time- resolving the reflected beam.
• This system also includes one or more micromechanical devices for routing the beam.
• micromechanical devices include microelectromechanical systems (MEMS) such as the units sold by the Texas Instruments Company under that name. Such devices also, however, include essentially microscopic-scale devices that are not actuated, controlled or powered electrically or electron!cally.
• MEMS microelectromechanical systems
• micromechanical devices is likewise meant to encom- pass any other forms of input power and control, whether or not available commercially at the time of this writing.
• forms may include thermal signals , or may include natural or artificial biological components (e. g. neurons) integrated into the system.
• biological components e. g. neurons
• this fifth facet of the invention through use of micromechanical equipment in steering a lidar beam — provides a hitherto unattainable degree of speed and maneuverability in monitoring an extraordinarily broad viewing field.
• This use of components is also particularly beneficial in that such apparatus is very readily amenable to placement within (rather than outside) the optical system, according to certain other facets of the invention discussed in this document.
• the fifth major aspect of the invention thus significantly advances the art, nevertheless to optimize enjoyment of its benefits preferably the invention is practiced in conjunction with certain additional features or characteristics.
• the devices include an array of multiple micromechanical devices.
• the devices include a fabric made up of an array of multiple micromechanical switches — each switch being generally such as set forth in the previously mentioned optical cross-connect patent document.
• the switches are regularly arrayed according to a coordinate system; and the system further includes a processor having some means for controlling the switches in common, in groupings by dimensions of the coordinate system. If this last-mentioned preference is observed, then still further in turn as a subpreference the coordinate system is substantially rectangular; and the groupings of switches are substantially by row and column of the array.
• the coordinate system is substantially closest-packing -u-
• the switches be grouped substantially by linear sequence within the closest-packing array.
• the coordinate system be substantially polar or spiral; and the switches be grouped substantially by polar coordinates or spiral raster within the array.
• the array includes multiple mirrors; and further includes a processor having means for controlling mechanical manipulation of the mirrors.
• the mirrors be regularly arrayed according to a coordinate system; and that the processor include some means for controlling the mirrors in common, in groupings by dimensions of the coordinate system.
• the processor include some means for controlling the mirrors to provide a ripple-propagating row or column corresponding to features of the at least one transceiver.
• the one or more mechanical devices include at least one mirror successively angled to select particular linear groups of features of the at least one transceiver.
• the at least one mirror be successively angled about an axis defined along substantially a single direction.
• the one or more mechanical devices preferably include at least one mirror successively angled to select individual pixels or pixel groups of the at least one transceiver.
• the at least one mirror is successively angled about plural axes defined along corresponding plural directions .
• the invention is a system for use with one or more features to be detected and ranged.
• the system includes a lidar light-beam source; and at least one transceiver for directing a lidar beam from the source to, and collecting the beam reflected from, the one or more features.
• a lidar detector for time-resolving the reflected beam; and one or more liquid-crystal devices for routing the beam.
• liquid-crystal devices while not micromechanical in nature per se — partakes of some of the same characteristics as the combination with micromechanical devices recited for the fifth facet above; and accordingly confers certain of the same benefits .
• Design and manu acturing capability for liquid-crystal devices already is very broadly established and available on an extremely economical basis — as well as in high volumes.
• liquid-crystal technology offers significant advantages for inexpensive rapid start-up of commercial exploitation, for this facet of the invention.
• the devices include an array of multiple liquid- crystal devices; and the system further includes a processor for controlling the devices.
• This facet of the invention is subject to generally the same preferences mentioned above for other steering or routing devices: array of the liquid-crystal devices according to a coordinate system; and control of those devices in common, in groupings by dimensions of the coordinate system.
• the system is substantially rectangular, or closest-packing, or polar or spiral; and the devices are grouped to follow suit.
• the invention is a system for use with one or more features to be detected and ranged.
• the system includes a lidar light-beam source; at least one transceiver for directing a lidar beam from the source to, and collecting the beam reflected from, the one or more features; a lidar detector for time-resolving the reflected beam; and one or more controlled-birefringence or other nonlinear-optics devices for routing the beam.
• controlled-birefringence units offer advantages that are analogous to those of micromechanical devices.
• Some birefringence devices like micromechanical mirrors also have the capability of controllable magnitude of deflection. Such angular control can be exploited to provide plural different directions of pointing per device (i. e. , pointing control that is multilevel rather than binary) , simply through variation of the control voltage or other signal .
• the seventh major aspect of the invention thus significantly advances the art, nevertheless to optimize enjoyment of its benefits preferably the invention is practiced in conjunction with certain additional features or characteristics.
• some of the main preferences are as described above for liquid-crystal devices.
• the invention is a system for use with one or more features.
• the system includes a source for generating a light beam.
• the fabric is for routing the light beam to the features selectively.
• this aspect of the invention sweeps more broadly than some of those discussed earlier, as this facet of the invention is not necessarily itself a lidar system or part of a lidar system.
• the general advantages of this aspect of the invention encompass extremely versatile capability for steering a light beam in myriad different applications.
• the switch fabric is a fundamental new tool of optics control that can be used in common microillumination, and pattern-modulated signaling; but also can be used as well in the most exotic imaginable high- technology systems that impose extremely stringent demands of complexity, of timing, of lightweight and compact configuration, and yet also of economy.
• the eighth major aspect of the invention thus significantly advances the art, nevertheless to optimize enjoyment of its benefits preferably the invention is practiced in conjunction with certain additional features or characteristics.
• the system also includes at least one transmitter for directing the beam to the one or more features; and the switch fabric directs light to particular portions of the transmitter.
• the system further include a processor for controlling the switches; that the fabric be arranged in three dimensions to provide groups of the switches aligned with the particular portions of the transmitter; and that the transmitter present an at-least-two-dimensional array of optical conductors corresponding with the switch groups. It is also preferred that the fabric be folded to provide plural planes of the switches — or coiled to provide plural layers of switches .
• the transmitter include a transceiver for directing the beam to and from the one or more features, to collect reflected portions of the beam; and that the fabric direct light to and from said particular portions of the transmitter. If this preference is employed then a subpreference is that the system further include a detector receiving the reflected beam from the transmitter and fabric — with the fabric directing light (1) from the source and (2) to the detector, respectively .
• the beam can be pulsed, or continuous-wave but subjected to a m ⁇ dula- tion pattern — and in either case can be synchronously detected to enable time-resolving of light reflected or returned from features of interest.
• the time-resolved light can also be interpreted to detect and range the features .
• An interpretive output signal can then be applied to image the features — or, in other types of systems, to avoid or meet, or otherwise navigate relative, to the one or more features.
• the control can for instance include a vehicle that has at least partly automatic navigation; or an advisory system for assisting a human operator in such complex operation.
• the invention is a system for use with input or output devices, or both, and with at least one light beam.
• the input and output devices and the light beam are not part of the invention itself — but rather form the environment of the invention .
• the system includes a fabric made up of micromechanical light switches for routing the light beam selectively.
• the fabric is arrangeable in three dimensions to provide groups of the switches aligned with particular ones of the input or output devices, or both.
• the fabric provides a unique kind, or quality, of input/output capability.
• the fabric is not limited to use in lidar systems, but rather is applicable to provide extremely complex subdivision and steering or switching of light beams separately provided, in innumerable different industrial applications.
• the ninth major aspect of the invention thus significantly advances the art, nevertheless to optimize enjoyment of its benefits preferably the invention is practiced in conjunction with certain additional features or characteristics.
• the fabric is arranged in three dimensions to align with particular the input or output devices, or both.
• the system — in combination with the input or output devices, or both — is such that the input or output devices, or both, present an at-least-two-dimensional array of optical conductors corresponding with the switch groups.
• a still-further nested preference in this case is that the groups of switches direct light to and from par- ticular portions of the array.
• the source be embedded within the fabric.
• a detector too, be embedded within the fabric.
• the fabric be foldable, or folded, to provide plural planes of the switches.
• Another is that it be coilable or coiled, to yield plural layers of switches.
• the invention is a system for use with light that is reflected, by a reflecting entity, from a source to a destination.
• a reflecting entity a reflecting entity
• This system includes a bidirectional beam splitter made up of micromechanical light switches for routing the light beam selectively. The switches are switchable rapidly enough to establish at least two distinct routes that include:
• the switches are switchable rapidly enough to change routing between the first route and the second during a time interval between passage of the light from the source to the reflecting entity and return of the same reflected light from the reflecting entity.
• this system includes an element called a "beam splitter” because it can be used in place of a conventional or classical half-silvered mirror, one that enables direction of a light beam into two different, separate paths from a single identical point along on an optical path.
• a beam splitter Such conventional devices thus share a light-beam and its path spatially — but the present system, although also causing divergence from a single identical point, instead shares the beam and the beam path temporally. In this sense it is generally analogous to a simple macroscopic chopper mirror, but switches the beam far more rapidly and controlla- bly than possible heretofore.
• the invention is practiced in conjunction with certain additional eatures or characteristics .
• the system is for use with light that is a pulse beam or a modulated continuous-wave beam; and the pulse or a modulation signature, respectively, is of duration in one or more of these ranges :
• the beam splitter have substantially no reflecting surface that loses more than a few percent of the light passing therethrough, along either route.
• this preference plainly distinguishes a conventional beam-splitter that ordinarily loses forty to sixty percent of the light energy in one or the other route .
• the invention is an optical system for use with one or more features to be characterized by light reflected therefrom.
• the system includes a source for generating a light beam, and a detector receiving the reflected beam.
• the system further includes some means for directing the beam from the source to the one or more features and collecting the reflected beam from the one or more features.
• the system further includes a directional scanner for selectively pointing the directing means .
• the scanner is disposed:
• the system is a lidar system, and the source generates a pulse beam or a modulated continuous-wave beam.
• the directing means include at least one micromechanical device.
• the micromechanical device be a steerable mirror, or a steerable array of mirrors ; or an array of optical switches or three-dimensionally arranged array of such switches.
• the directing means include at least one liquid-crystal device, or at least one controlled-birefringence device or other nonlinear-optics device.
• the invention is a method for concurrently producing light pulses and distributing the pulses to features, or use in detecting and ranging those eatures .
• the method uses a light source, at least one light detector, and an array of micromechanical optical switches such as — merely by way of example — the fabric discussed above or the basic optical cross-connect grid introduced in the above-mentioned patent document of Kane et al .
• the method includes the step of operating the source to form a generally continuous light beam, and, during that operating step, passing the generally continuous light beam into the array of switches .
• the method also includes the step of — during the passing step — setting the switches to direct the generally continuous beam toward a first one of the features.
• the method further includes the step of then resetting the switches to interrupt directing of the generally continuous beam toward the first one of the features .
• the setting and resetting steps cooperate to form a pulse of light directed toward the first one of the features .
• the resetting step also concurrently routes the pulse of light that is reflected from the first one of the features to the at least one detector.
• the method includes the step of — concurrently with the resetting step — time-resolving the reflected light to detect and range the first one of the features .
• the method includes the step of then iterating the setting, resetting and time-resolving steps — but with respect to second and subsequent ones of the features . This iteration thus successively detects and ranges the second and subsequent ones of the features .
• this twelfth aspect of the invention basically time-shares much of the apparatus , enabling time-overlapped independent detection and ranging of features in different parts of the overall visual field.
• the overall field can thereby be surveyed in a fraction of the time needed by conventional methods.
• the resetting step interrupts the directing step by instead directing the generally continuous beam toward the next one of the features in turn — substantially immediately, with substantially negligible intervening interval .
• This way of practicing the twelfth facet of the invention represents a still-higher degree of time-overlap — or temporal shingling, so to speak.
• the invention permits the detection and ranging of the second and some subsequent features to proceed while directing of pulses with respect to later features is already ongoing.
• the method utilizes multiple light detectors; and the iterating step routes subsequent reflected pulses of light to respective differ- ent ones of the multiple detectors.
• Fig. 1 is a block diagram representing an exemplary application of a preferred embodiment
• Fig. 2 is an elevational view of a preferred prototype embodiment, showing laser light illuminating one column of an optical array and with white dots representing unilluminated sam- pie locations of the array members;
• Fig. 3 is a block diagram of a preferred embodiment particularly showing its major assemblies
• Fig. 4 is a conceptual diagram of a prior-art optical system having separate transmitting and receiving optics
• Fig. 5 is a conceptual diagram of a transmitter/receiver assembly that is one of the Fig. 3 major assemblies — showing a conjugate relationship between focal-plane elements (FP) in the object plane and in the image plane
• Fig. 6 is an elevational view, somewhat schematic, of a preferred embodiment of the invention with a single-axis MEMS scanning mirror that scans among entire rows of the object field at a time, and with substantially direct optical connection from a beam-steering unit to a transceiver;
• Fig. 7 is a like view of a similar system but having an optical extension, in the form of a flexible optical-fiber light pipe, between the beam-steering unit and transceiver;
• Fig. 8a is a schematic diagram of a mirror array near the image plane in a preferred embodiment, showing a process of laser- beam projection along the face of the array and beam deflection by a column of mirrors in the array — the beam then continuing to corresponding field locations in the object plane;
• Fig. 8b is a like view showing a continuation of the Fig. 8a process, with the beam now deflected from another mirror column in a corresponding field location later in the series;
• Fig. 9 is a like view, but showing relationships within the beam as it is manipulated by the mirrors in passing both to and back from the object plane;
• Fig. 10 is a conceptual diagram of a prior-art external scan mirror, rotating to increase the field of view for an associated optical s stem;
• Fig. 11 is a like view of another prior-art optical system, gimbal-mounted to increase its field of view;
• Fig. 12 is a view like Fig. 3 but at a somewhat higher level and also including utilization means connected at the output of the system;
• Fig. 13 is a view like Figs. 6 and 7 but with a two-axis MEMS mirror to scan an object field in a raster-like rather than row-wise sequence;
• Fig. 14 is a combination of plan and elevational schematic diagrams, also with mask design, for a MEMS scan mirror in a preferred prototype of the invention
• Fig. 15 is a schematic diagram of a preferred embodiment of the invention showing a MEMS beam steering subassembly as a so- called "pinwheel" cartridge, attached by a fiber ribbon to other components of the system assembly;
• Fig. 16 is a diagram of a preferred embodiment of the invention using an optical switch fabric for beam steering
• Fig. 17 is a multipart diagram, adapted from the Kane patent document mentioned earlier — showing:
• Fig. 18 is a set of comparative illustrations summarizing the general state of the art
• FIG. 19 is a two-part diagram of a FASA unit used in preferred embodiments of the invention, the upper portion of the diagram being in plan, and the lower portion in elevational cross- section — and showing the actuator relaxed so that the liquid level is relatively low;
• Fig. 20 is another elevational cross-section like the bottom part of Fig. 19, but with the actuator extended to push the diaphragm and thereby liquid upward, expelling some fluid from the reservoir into the well ;
• Fig. 21 is a like view for another preferred embodiment
• Fig. 22 is a conceptual diagram suggesting disposition of a large multiplicity of such switches on a single chip or in a fabric
• Fig. 23 is a pair of cross-sectional elevations analogous to Figs. 20 and 21 but showing expulsion or acquisition of optical- switching fluid in the FASA well;
• Fig. 24 is a plan view showing one preferred form of the optical switch fabric.
• Fig. 25 is a conceptual diagram including grouped elevational and perspective views of components in a preferred em- bodiment analogous to that of Fig. 15. DETAILED DESCRIPTION
• the invention is used as an optical system, or as part of an optical system, for detection and ranging as well as imaging (Fig. 1) .
• the imaging applications can be active or passive depending on the result desired.
• a source is used to illuminate an object of interest.
• Passive imaging instead collects illumination emitted from the object, or reflected from the environment, to form an image of an object of interest.
• imaging applications are applied to many fields including but not limited to industrial automation, aerospace, industrial inspection, intelligence, and reverse engineering (i . e. regeneration of detailed engineering designs from already- built hardware) as well as guidance and control (Fig. 1) .
• the last-mentioned field includes applications such as collision avoidance, object interception and vehicle rendezvous. In these applications, measured values for location and velocity of an object are used to calculate appropriate vehicle-motion commands. Manip- ulation of such calculations is known among persons of ordinary skill in this field.
• main assemblies are a system assembly 50 (Fig. 3) and one or more transmitter/receiver (TX/RX) assemblies 11.
• TX/RX transmitter/receiver
• the structure and components of these assemblies vary and can easily be adapted for specific applications or for use with existing equipment.
• Additional components can be added to the system to further monitor or process the imaging data.
• a spectrometer or photodiode spectrophotom ter is added to collect additional imaging information for signals both inside and outside the visible spectrum and for creating data libraries based on these signals .
• one or more processors are added in preferred embodiments to coordinate imaging information or for automating responses to the information received.
• the automatic responses include an advisory or alarm system used to alert an operator or a command to perform additional automated or robotic responses such as operating a vehicle or other apparatus.
• the TX/RX assembly 11 includes projection optics 12 and a projector 14 located at the image plane 10 of the optics (Fig. 5) .
• Use of fiber optics 16, in constructing the projector 14, provides the flexibility to remotely locate one or more of the assemblies in remote or hazardous locations or to uniformly distribute the fields of view of the individual assemblies to achieve an overall field that is a full hemisphere or even a sphere.
• each assembly can stand alone, providing a narrow field of view, or can be replicated and grouped together (Fig. 3) , the system can be customized to provide practically any particularly desired overall field of view 20.
• the assembly is not limited to the view from a single TX/RX unit; instead it can provide 2 ⁇ - or even a 4 ⁇ -steradian field of view.
• Another advantage of this system is that it eliminates the need for separate transmission and reception optics (Fig. 4) since only a single element is required to perform both operations.
• Fig. 4 We conceptualize the relationship by referring to the corresponding points of the TX/RX image plane and the object plane as conjugate focal-plane elements.
• Each focal-plane element 18 (Fig. 5) of the projector corresponds to a focal-plane element in the object plane 22.
• This conjugate relationship is maintained for both transmitted and re- ceived photons , since both operations are performed by the same focal-plane element — passing light in both directions, as already discussed.
• Work on some preferred embodiments has shown the TX path from the laser subassembly to have an operational net transmission of forty-six percent and the return incoming signal from a scene to have an anticipated twenty-five percent transmission to the detector.
• the system assembly 50 can include five major subassemblies . These subasse - blies include a detecting device 52 , a laser 70 or other light source, and a mi ⁇ roelectromechanical system (MEMS) 60 — or more generally a micromechanical system, as components of this system are not necessarily operated or powered electrically.
• the system assembly can further include beam steering 62 and beam splitting 64 subassembly devices.
• these subassemblies be integrated so that the output of the source subassembly is projected onto a fi- ber bundle array 16 attached to the beam splitter.
• the beam can be transmitted via free space or through fiber-optic cables, but for detection and ranging ordinarily at least the final segment directed to remote features of interest is by free space . Where free-space transmission is used, usually lens assemblies direct the light appropriately.
• the beam splitter 64 separates an outgoing optical signal from a returning optical signal — both routed by the beam steering subassembly. This arrangement enables outgoing light from a source such as a laser to be directed to objects of interest, and returning, reflected light to pass in the opposite direction to the detector subassembly.
• the beam steering subassembly 62 is responsible for switching the outgoing laser signal and incoming optical signal returns between the TX/RX projector elements and the system assembly.
• the source subassembly can consist of any of a variety of light sources. In particularly preferred embodiments it is a lidar system. (The term lidar or “light detection and ranging” encompasses use of any optical source, including “ladar” in which the light comes from a laser . )
• the light source be controllable, for example with the use of a sensor controller. This can be done using a master clock signal and controlling laser integrated with the beam steering device and other system components.
• passive imaging requires neither a laser subassembly nor a beam splitter, since as noted above there is no outgoing light signal. Therefore, during passive imaging, an energy signal (i . e. a flow of photons) from an observed scene or object is directly transferred from the beam steering subassembly to the detector.
• This type of passive imaging typically provides two-dimensional information. Active imaging, in which an object or scene of interest is illuminated by the system, can be used to acquire three-dimensional imaging information. This is accomplished by the use of a modulated or pulsed illumination source e . CT. a modulated or pulsed laser. In the case of a frequency-modulated beam, it is used to continuously illuminate a scene.
• the resultant returning signal from the scene can then be detected and processed to determine ranging information based on the frequency pattern embedded in the original beam.
• This ranging information can then be used to provide depth to the resulting image.
• the ranging information is based on the pulse pattern of the resulting incoming signal from the scene.
• a processor is used to interpret the time-resolved beam for detecting and ranging. It is also used to control the light source and to synchronize it with the detector subassembly .
• a preferred embodiment of the invention uses a staring or flash lidar system that captures an entire time-resolved scene at an instant in time and a MEMS scan mirror for the beam steering subassembly (Fig. 7) .
• An outgoing signal begins at the laser subassembly, which in this example is a pulsed laser capable of active imaging.
• collimating optics are helpful, even though the laser or other source light may be nomi- nally collimated.
• the pulsed laser beam passes through a polarized beam splitter and is then reflected by the MEMS beam steering mirror to guide the transmitted lidar beam onto a line of a fiber optic ar- ray.
• the light is transmitted along the fiber pigtail and terminates in the image plane of the TX/RX optics.
• the MEMS scan mirror rotates about a single axis , steering the colli ated beams of light from a line of fiber bundles illuminated by the laser.
• the scan mirror is aligned so that it moves forward by one row in the fiber array for each laser pulse, with each row mapped to a portion of the TX/RX optical field of view.
• TX/RX optics exits the TX/RX optics from each fiber in the image plane — illuminated at its other end by the laser light reflected from the MEMS scan mirror. The light is then projected to its conjugate location in object space.
• the return radiation is focused on the outer face of the fiber array, entering the conjugate fiber in image space —that is, the same fiber from which the excitation beam originated.
• the laser energy reflected to the optic fiber travels back through the fiber, reflects again at the scan mirror, but is then redirected to the lidar detector by the beam splitter.
• the line array scanning system used can be interfaced with either lineal or areal detector arrays .
• the beam steering subassembly can be made up of any of a variety of instruments to meet particular needs or preferences.
• a basic function of this subassembly is to coordinate incoming and outgoing signals in a controlled manner.
• the beam steering subassembly consists of a MEMS or other mirror system, or an optical switch fabric, or a liquid crystal device (LCD) or a signal controlled birefringence device. These options are discussed separately below.
• Such an array located at or near the image plane of an optical system can be used to scan an outgoing beam of light across the field of view belonging to the optical system.
• Such scanning in object space is set up by directing a sheet- or fan-shaped light beam to skim along the face of the mirror array (Figs. 8a, 8b) .
• any one of the mirrors When any one of the mirrors is deployed out of the array plane (i . e. tilted up out of the plane of the array) , that mirror intercepts its corresponding portion of the beam and redirects that portion outward at an angle from the face of the array.
• Preferred embodiments use an entire column, rather than just a single one, of the MEMS mirrors in one field location 1 (Fig. 8a) to intercept the fan-shaped beam skimming along the common plane of the undeployed mirrors .
• a column of the mirrors is selectively deployed to stand out from that plane at a forty-five degree angle and thus reflect the beam down the optic axis of the projection system.
• Other field locations N are successively addressable in the same manner.
• the return energy is collected by the same optical system and redirected by a beam splitter to a detector array.
• the source continuously projects light in a planar configuration onto a MEMS-mirror projection array (Fig. 9) near the image plane. Both the outgoing signal and an incoming signal pass through the imaging optics .
• the image-plane field locations are conjugate to the object plane field locations — as are the projection array and receiver array locations, respectively.
• Resulting image-signal pulses arrive in a kilohertz range.
• this embodiment has a relatively narrow field of view because the convergence distance of the projected fan-shaped light beam is limited to only a few object-plane rows. This limitation, evidently associated with diffraction, can be mitigated by operation at shorter wavelengths.
• this embodiment is relatively slower than other preferred embodiments described in this document. Nevertheless, this example is well suited for space-based and other applications that are amenable to slower imaging.
• the beam steering subassembly is a MEMS scanning mirror placed within the optical system.
• This phrase means that the mirror precedes an exit pupil, with respect to light being transmitted to objects of interest; and follows an entry pupil, with respect to a return beam from such objects (as noted earlier in the "Summary of the Disclosure" section of this document) .
• Use of such a mirror increases the field of regard with no need for extra apparatus such as a gimbal mechanism, gimbal drive train — both seriously subject to wear — or the associated relatively high-power drive circuit.
• a single point in the field of regard is interrogated at an instant in time by either a one- or two-axis MEMS scan mirror (Fig.
• a conventional small tiltable mirror can be used instead of a MEMS mirror.
• the mirror can be set to do an arbitrary scan, or a raster scan, of a scene.
• one single optical fiber — instead of a row of fibers — is addressed at a time (Fig. 13) .
• a two-axis mirror is preferred so that any point in the n-by-m fiber-optic array can be addressed randomly (i . e. in an arbitrary sequence) .
• This embodiment is preferred for a laser-designator operation or a detector configuration that has only a single photosensitive site.
• a microlens array or a lens system can be in- serted to focus outgoing signals onto the fiber optics array.
• a group of mirrors can be used together if a large enough outgoing light beam is used and the system is structured to address one fiber at a time rather than a whole row of the fiber optic array.
• Preferred embodiments of the invention are amenable to extremely great latitude in dimensions, numbers of fibers, and operating speeds . That is because the invention generally works well without regard to specific values of these parameters. Thus for each project these variables depend very strongly upon the application, the kinds and sizes of objects to be considered, and the available resources — particularly including funding, permissible lead time to complete the work, and the commercial packages (fiber bundles etc.) with closest dimensions that happen to be found.
• an oscillating scan mirror may be, merely by way of example, in a range from a few tens of microns wide to several millimeters or more; such a mirror may be roughly square, or may have a high aspect ratio such as 25:1 or 50:1.
• the most preferable tested embodiments use e. q. silicon scan mirrors in the range of 150 to 200 ⁇ m x 1 to 10 mm; but again these dimensions are not at all limiting.
• Such a mirror typically rotates about its own axis with an excursion in the range of ⁇ 1° to ⁇ 10°.
• the scan mirrors are assembled in a pinwheel-shaped cartridge (Fig. 15) , consisting of five four- mirror silicon MEMS substrates .
• each MEMS scan mirror can address a fiber array that is on the order of tens to hundreds of fiber elements in each direction.
• such an array can be very generally square or can have an aspect ratio that is rather high, e. q. 10:1 or even 100:1 — these parameters merely echoing the shapes and other characteristics expected for features of interest.
• Particularly successful assemblies have used square arrays of fibers, between thirty and forty fibers on a side, e. q. a 33- row by 33-column fiber array. Such an array can be addressed at a rate of one row per few tens of microseconds, e. q. 40 to 70 ⁇ sec. This procedure typically results in addressing ten thousand to several tens of thousands of fibers in each assembly, at a rate of 10 to 500 Hz or more. Again only by way of example, four of these assemblies can cover a 6° x 6° field of view at 400 ⁇ rad sample spacing.
• An exemplary scan mirror (Fig. 14) for such a "pinwheel” system works well in a preferable pinwheel mirror-containing beam steering assembly (Fig. 15) .
• a laser beam is directed onto laser projection optics that focus the beam onto the aforementioned beam splitter.
• this outgoing signal is directed to fiber-ribbon coupling optics that couple the detector to a beam steering subassembly; both these modules are preferably fabricated as independent cartridge units .
• the outgoing beam encounters MEMS coupling optics which direct it to the MEMS selection mirror.
• the beam is focused on one of four scan-mirror substrates projecting inward from the edges of the assembly like angled spokes of a wheel .
• the beam then travels along fiber coupling optics to the fiber array, with dimensions in the ranges noted above — from which the beam is directed onto the next of the four scan-mirror substrates .
• the beam continues along in this manner until it is directed out of the assembly cartridge/module via a fiber pigtail, a half- inch in diameter, leading to the TX/RX assembly. Returning signals follow a reverse path along the pigtail and into the beam steering assembly, eventually leading to the detector.
• the beam steering subassembly is an optical switch fabric.
• several planes of optical switch fabric configured in a nonblocking arrangement replace the previously mentioned beam splitter and beam steering mechanisms.
• the switch planes are attached together by optically continuous “jumpers” — or equivalently formed in a continuous strip, one or more rows being unused at the turnaround points between planes.
• optical switch fabric itself can be formed in many different configurations.
• FASA fluid-based actuator stroke-amplification
• This embodiment is an all-optical crossconnect system that uniquely "switches” incoming light from fiber-optic channels 1 through N into outgoing channels 1 through M (Fig. 17) .
• waveguides are configured in a grid arrangement, with some of the waveguides lying along one direction for incoming light, in channels 1 through N (Fig. 18) , and others along an orthogonal direction for outgoing light, channels 1 through M.
• a FASA well At each intersection is a FASA well that is at a 45° angle, with a column perpendicular to the waveguide gridwork as shown.
• At the base of each column is the reservoir for the FASA module and its forcing actuator.
• TIR total internal reflection
• a FASA module is located at each horizontal/vertical waveguide intersection or node. By virtue of its ability to independently switch each FASA unit, the assemblage becomes an optical- switch array or fabric.
• the FASA waveguide mesh is a relatively rigid or stiff grid, with the optical-guideway column extending perpendicularly through the waveguide grid (Fig. 17) .
• Such grids can instead be made flexible — for example using the previously mentioned “jumpers", or unused intermediate fiber rows — to form a variety of structures that include but are not limited to a spiral, coil, serpentine figure, folded sheet, roll or pinwheel .
• a particularly preferred embodiment uses a multilayered S-shaped configuration of the optical switch fabric (Fig. 16) .
• the flexibility of such fabric configurations allows a user to adapt the optical switch system to meet specific needs or preferences.
• the layers of the fabric are planar; however, nonplanar layers are also possible, as long as the nonplanarity is acceptable in terms of the total-internal reflection within the waveguide .
• the layers are best produced using lithographic techniques known in the art. This enables spacing within the layers to be very accurate even at spacings below one micron. In preferred embodiments, spacing between the folds of a folded fabric is typically on the order of 100 to 250 ⁇ m.
• the fiber pipe connects sheets of the fabric without actual folding; the pipe simply connects edges of one sheet to another sheet layered on it, while allowing both sheets to lie flat. If a faulty or unsuccessful junction is produced, however, it may preclude the use of one or more rows in the fiber — depending on where in the fiber the f ulty junction resides .
• the fabric layers are accurately aligned with corresponding fibers in the TX/RX assembly by the use of V-grooves formed — also using a lithography process — in the adjacent waveguide faces. These grooves align the waveguide channels to the fabric so that the connection from the fabric through to the lens system is consistent.
• the optical switch fabric can also be adapted to work directly with light sources to not only steer an outgoing beam but modulate or pulse it as well .
• the sources may be very small lasers, LEDs or the like — embedded within the fabric or connected along edges, etc.
• the fabric receives continuous- wave (CW) light — preferably laser light — from the source and switches the light briefly to each projector, or fiber row, or individual fiber in turn.
• CW continuous- wave
• the result is to strobe each conjugate point, or defined group of points, on a pulse basis even though the optical input to the fabric is CW. Nodes in the fabric then switch to receive and redirect any returning pulse or modulated light signal to the detector subassembly — while at the same time strobing the next conjugate point in succession.
• This sequential operation can proceed continuously, sending light pulses to many object-plane features in quick succession, provided that multiple detectors are present (e. q. embedded in the fabric itself) to collect the temporally overlapping return beams .
• multiple detectors e. q. embedded in the fabric itself
• return beams continue to arrive, trailing for periods of time that depend on object distance, after all the outbound pulses are completed.
• operation is typically limited to emitting just one pulse while collecting each immediately preceding return beam, respectively. This enables CW-light pulsing and re- turn for all the features within the duration of one return-beam collection times the number of separate features pulsed — a significantly longer time than for the multidetector embodiment, but still significantly less than conventionally.
• Pulsing can also be accomplished by splitting the original outgoing light into two standing waves and directing one counter to the other within a single waveguide (optical fiber) . If the polarization states of the two component beams are maintained but the second beam is phase shifted by 180 degrees — while both travel along the same path — the two beams interfere destrue- tively. (This technique is reported in the literature, for other applications.) A pulse is created by phase-shifting the second beam back and forth.
• LCD Liquid Crystal Devices
• the beam steering subassembly is replaced by components such as liquid crystal devices, used singly or in an array.
• An LCD does not emit light but has the ability to control light passing through it.
• a voltage is applied to polarization plates surrounding a liquid crystal medium, the direction of polarization of the medium changes. This in turn controls whether light passing into the medium is reflected from the crystals or passes through.
• LCD control is generally much slower than the switch-fabric or tilting-mirror systems discussed earlier.
• the arrangement of LCDs can vary when used in an array.
• discrete areas in an LCD are tightly grouped — as in consumer-electronics displays (wristwat- ches, vehicle control panels, etc.) .
• the individual areas are, advantageously arranged in a coordinate system of rows and columns — or in polar, spiral, or serpentine arrangements.
• different optical-control devices are used for the beam steering subassembly — particular- ly, one or more signal-controlled birefringence devices or other nonlinear-optics devices. Examples include small Kerr or Bragg cells, singly or in an array.
• These devices route the outgoing and returning signal beams, as with the MEMS and LCD devices discussed above, but here by ro- tating the plane of optical polarization.
• the device By placing the device between crossed polarizers, the device can be made to serve as a high-speed shutter; alternatively the directional control obtainable straightforwardly through variable refraction can be used to provide multiple steering states .
• These devices too are advanta- geously arranged according to a coordinate system or an array.

Landscapes

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

Applications Claiming Priority (3)

Publications (1)

Family

ID=29550094

Family Applications (1)

Country Status (4)

Cited By (2)

Families Citing this family (15)

Family Cites Families (11)

• 2003
  • 2003-05-16 WO PCT/US2003/016062 patent/WO2003098263A2/en not_active Application Discontinuation
  • 2003-05-16 AU AU2003241557A patent/AU2003241557A1/xx not_active Abandoned
  • 2003-05-16 CA CA002486197A patent/CA2486197A1/en not_active Abandoned
  • 2003-05-16 EP EP03731303A patent/EP1508057A2/de not_active Withdrawn

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events