WO2004083795A2 - Systeme optique - Google Patents

Systeme optique Download PDF

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Publication number
WO2004083795A2
WO2004083795A2 PCT/US2003/039535 US0339535W WO2004083795A2 WO 2004083795 A2 WO2004083795 A2 WO 2004083795A2 US 0339535 W US0339535 W US 0339535W WO 2004083795 A2 WO2004083795 A2 WO 2004083795A2
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WO
WIPO (PCT)
Prior art keywords
optical system
detector
mirror
source
radiation
Prior art date
Application number
PCT/US2003/039535
Other languages
English (en)
Other versions
WO2004083795A3 (fr
Inventor
David Kane
Original Assignee
Arete Associates
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 Arete Associates filed Critical Arete Associates
Priority to AU2003300871A priority Critical patent/AU2003300871A1/en
Priority to CA002547915A priority patent/CA2547915A1/fr
Priority to EP03816402A priority patent/EP1579262A2/fr
Publication of WO2004083795A2 publication Critical patent/WO2004083795A2/fr
Publication of WO2004083795A3 publication Critical patent/WO2004083795A3/fr
Priority to US11/151,594 priority patent/US7297934B2/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/04—Optical or mechanical part supplementary adjustable parts
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/0242—Control or determination of height or angle information of sensors or receivers; Goniophotometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/0266—Field-of-view determination; Aiming or pointing of a photometer; Adjusting alignment; Encoding angular position; Size of the measurement area; Position tracking; Photodetection involving different fields of view for a single detector
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/04—Optical or mechanical part supplementary adjustable parts
    • G01J1/0403—Mechanical elements; Supports for optical elements; Scanning arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/04—Optical or mechanical part supplementary adjustable parts
    • G01J1/0407—Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings
    • G01J1/0411—Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings using focussing or collimating elements, i.e. lenses or mirrors; Aberration correction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/04—Optical or mechanical part supplementary adjustable parts
    • G01J1/0407—Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings
    • G01J1/0414—Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings using plane or convex mirrors, parallel phase plates, or plane beam-splitters
    • 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
    • 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
    • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
    • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
    • G01S3/782—Systems for determining direction or deviation from predetermined direction
    • G01S3/785—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system
    • G01S3/786—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system the desired condition being maintained automatically
    • 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
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
    • G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
    • 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
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/10—Scanning systems
    • G02B26/101—Scanning systems with both horizontal and vertical deflecting means, e.g. raster or XY scanners
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/64—Imaging systems using optical elements for stabilisation of the lateral and angular position of the image
    • G02B27/646—Imaging systems using optical elements for stabilisation of the lateral and angular position of the image compensating for small deviations, e.g. due to vibration or shake

Definitions

  • Kane et al .. application serial 10/142,654 "HIGH-SPEED, LOW- POWER OPTICAL MODULATION APPARATUS AND METHOD".
  • This invention relates generally to systems and methods for automatically detecting light from an object, determining direction or other characteristics (such as distance, spectral properties, or an image) of the detected light or the object, and possibly responding to the detected light.
  • Some conventional systems and methods for accomplishing these goals rely upon scan mirrors that receive signals from an object and relay them into an aperture of an optical system — and, for response, conversely receive signals from the optical-system aperture and return those signals toward the object. Some such systems and methods instead (or also) rely upon gimbals that support and reori- ent the entire optical system. Both approaches entail relatively high moments of inertia, and accordingly large motors and elevated power requirements .
  • gi bal controls are most typically good to roughly one degree or less , although some units capable of precision in tens of microradians are available for millions of dollars each.
  • Sensors using ocal-plane array e. ⁇ . quad cells , are typically precise to roughly ten degrees.
  • Other nonmechanical systems include quad cells behind fisheye lenses .
  • One rather unnoticed contributor to inadequate dynamic range is the direct relationship between gimbal angle or scan-mirror angle and excursion of the beam in the external scanned volume. That relationship is a natural one-to-one for a gimbal system, and one-to- two for a rotating mirror. Since the direct effect of mechanical rotation is relatively slow for gimbals, and relatively limited in overall angular excursion for scan mirrors, the external beam-angle excursion is either slow or limited, or both.
  • PSD position-sensing detector
  • PSD positional readout
  • the PSD reports position on its own sensitive surface, in units of distance from its nominal center along two orthogonal axes. To find angular mapping, typically these off-center coordinates are divided by the focal length of a final focusing element. Unfortunately these reported distances and therefore the angular mapping of a PSD are nonlinear, to the extent of several percent at the PSD edges — aggravating the analogous handicap introduced by a fish-eye or other wide-angle lens — and are also temperature sensitive.
  • the detector may report accurately that an optical source has been sensed, but fail to report accurately where that object is, unless it is near the nominal center, or origin of coordinates.
  • Such response usually intended to produce confusion as to the exact location of the vehicle, sometimes takes the form of returning a literally blinding flash of light toward the person or apparatus that is pointing the original source, to temporarily dazzle and confuse that source-controlling entity.
  • a response can be to eject from the vehicle many particles that strongly reflect the guide light, to instead confuse directional-control mechanisms of the moving object.
  • Accompanying either of these may be an entirely different kind of response, namely an effort to disable the source-pointing person or apparatus, or the object.
  • Such a disabling response, directed toward the object or source may take the form of either a physical article or of powerful radiation.
  • Still another desirable kind of response would be investigatory, i. e. determining the character of the guide beam or of the guided object; such information can be used to determine and report the nature of the guiding system itself, either for purposes of imtrtedi- ate efforts to confuse and avoid or for future protective-design work.
  • the person or apparatus pointing the source may be adjacent to the initial position of the object. In a sense this is the easiest case from the standpoint of protective response, because the source can be treated as a beacon for guidance of a disabling response that eliminates both the light source and the object — if the response is sufficiently prompt, so that the source and object are still not only in-line but also relatively close together. In another sense, however, this is a difficult case from the standpoint of confusion, because the object may have been designed to look (for its guidance) backward at the source rather than forward at the vehicle — in which event the ejection of reflecting particles cannot confuse the directional-control mechanisms of the object, as long as the pointing entity can keep the vehicle in view.
  • the person or apparatus pointing the source may, however, instead be at a different position — off to the side from the path of the object, and from a line between the source and the object. In this event, disabling both the source and object with a single response is not possible; but at least confusion can be more-readily produced since the object is necessarily designed to look forward at the vehicle, so that either the dazzling or the decoy-particle strategy, or both, can be effective.
  • One type of movable-mirror device that is known in various kinds of optical-detection systems is a single scan mirror of about 25 or 30 mm or more, consistent with the earlier statement of dimen- sions for conventional systems. Such mirrors are too bulky and heavy to overcome the previously discussed problems of response speed.
  • Another type of known movable-mirror device is a spinning cyl- inder with multiple mirrors carried on its outer surface.
  • Such a polyhedral construction does provide a movable mirror, sometimes disposed along an optical path between a detector and an entrance aperture.
  • Dimensions of each of the mirrors in such a device are typically in the tens of millimeters, also consistent with the previous indication of representative dimensions for conventional systems .
  • These mirror wheels are ordinarily made to spin continuously; hence the individual mirrors of such an array lack independent maneuverability for customized control movements. Accordingly they are poorly suited for practical use in rapid detection and tracking of a particular source object.
  • telescopes including astronomical tele- scopes — particularly of the type that has a movable mirror positioned between an entrance aperture and a detector.
  • any interest in such devices is academic, as the movable components are relatively huge and far too massive to be useful in any rapid-response system. Even more relevant is the typ- ical limitation of field of view, in telescopes, to less than ten degrees .
  • a device of this type generally comprises a continuous reflective membrane that is controllably bent and distorted to correct wavefront errors .
  • Such mirrors are typically at least 20 to 30 mm across .
  • MEMS microelectromechanical system
  • Such devices introduced some years ago by the Texas Instruments Company, and more recently in versions produced by Lucent Technologies and called an “optical switch”, most commonly take the form of arrays of very small mirrors — each on the order of ten to 500 microns across. At least in principle individual mirrors can be made available in the same format. In use these devices, while some are capable of continuous positional control, are most often only bistable, used for switching in optical information networks and also in an image-projection system for personal computers.
  • afocal lens packages used e. ⁇ . as lens focal-length extenders. These are commonplace in ordinary cameras. Almost all the optical devices discussed above, and most conspicuously the astronomical ones and MEMS devices , are known only in different fields from the present invention.
  • 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 an optical system for dynamically de- termining radiation characteristics, including associated angular direction, of an external article in a volume outside the system.
  • the optical system includes an optical detector and an entrance aperture.
  • the "at least one mirror” is disposed along an optical path between the detector and the entrance aperture, and is rotatable about plural axes — and each mirror of the "at least one” has dimensions in a range from thirty microns to five millimeters.
  • the foregoing may represent a description or definition of the first aspect or facet of the invention in its broadest or most general form. Even as couched in these broad terms, however, it can be seen that this facet of the invention importantly advances the art.
  • the specified mirror position, between detector and aperture can also be described as within or inside the optical system. Steering the incoming radiation beam (i . e. , maneuvering the sensitivity direction of the system) from within the system produces opportunities to obtain very large optical leverage, as compared with turning the entire system on gimbals or steering with mirrors external to the system. That is, the angle through which the beam outside the system turns can be made much larger than that through which the beam inside the system turns. (The latter angle is twice that through which the mirror turns . )
  • the beam cross-section inside the optical system is generally smaller than outside. Hence smaller, lighter optical ele- ments can be used, and this in turn means greater response speed with less power.
  • each mirror of the at least one mirror is a microelectro- mechanical mirror.
  • the optical system further includes a lens assembly disposed at the aperture to amplify the varying introduced by the at least one mirror. If this preference is observed, then it is further preferable that the lens assembly not focus the external article on any solid element of the optical system.
  • the system further include some means for automatically servocontrolling the at least one mirror to perform a raster scan of the volume; and that the at least one mirror be an array of mirrors having the dimensions stated.
  • the external article comprises a radiation source of a particular type, the characteristics comprise existence and presence of the source, and the optical system is for detecting the source and determining its angular location. In this case it is preferred that the optical detector be a detector for the radiation from the source of the particular type.
  • a subpreference is that the system further include some means for automatically responding to the detector by actively servocontrolling the at least one mirror to substantially center an image of a detected source on the detector.
  • the responding means comprise some means for continuing to servocontrol the at least one mirror to track the already-detected source substantially at the detector center.
  • the detector be either a position-sensing detector (PSD) or a quad cell.
  • the system further include some means for substituting a detector array for the detector, to image the already-detected source or associated objects, or both.
  • a detector array for the detector refers to a function that is substantially immediate, after detection, and that encompasses e. ⁇ . optically switching the array into place while the already-existing apparatus continues to function.
  • this is not meant to suggest building an apparatus with, initially, an array instead of a PSD or quad cell . (Certain other configurations discussed in this document, however, do relate to building such an apparatus . )
  • the system further include some means for automatically directing a response toward the detected source or an object associated therewith, or both. If this subpreference is observed, then still further preferably the response-directing means include some means for emitting a beam of radiation that uses the entrance aperture as an exit aperture, i. e. sharing the entrance aperture with the radiation from the source. In one preferred version of this apertur -sharing form of the invention, the response-directing means include some means for emitting a ranging beam pulse.
  • the external article comprises a radiation source
  • the characteristics include spectral properties of radiation from the source
  • the optical system is for determining the radiation spectrum of the source as a function of angular direction.
  • the optical detector is a spectrometer.
  • the system further include some means for automatically controlling the at least one mirror to perform a spe ⁇ tro ⁇ tetric raster scan of the spectrometer over the source; (2) the spectrometer be an i terferometric spectrometer, or grating- and/or prism-based spectrometer; and (3) — if the characteristics further include at least one temporal modulation pattern of radiation from the source — the system further include some means for analyzing the radiation to determine the at least one temporal modulation pattern as a function of angular direction.
  • the system further includes some means for gen ⁇ rat- ing a beam of radiation having the determined spectrum and the determined at least one temporal modulation pattern.
  • the detected spectral and temporal modulation characteristics of the received radiation be immediately transmitted to a remote station, e. ⁇ . a companion host or a base station, or both, for possible use in later avoidance of guidance by similar beams, particularly at other hosts.
  • a remote station e. ⁇ . a companion host or a base station, or both
  • this information is preferably transmitted in the form of interpreted and encoded data, although for some applications it is advantageous to simply relay e. ⁇ . the original modulation pattern as such. Two additional basic preferences will be taken up now.
  • the optical detector be an imager detector — in other words, a detector that is used as part of an imager, or as an imager.
  • the system may actually be initially built with an imager detector, rather than necessarily involving substitution of such a detector, during operation, for a position-sensing or other directionality detector.
  • the preference under consideration now encompasses both an as-built system with imager detector, and a system that can substitute such a detector for a directionality device during operation.
  • the system further include some means for automatically controlling the at least one mirror to perform an imaging raster scan of the detector over the object or scene.
  • raster here is not limited to the traditional video scan of e. q. a serpentine scan pattern, but rather is to be understood in its broader sense of a predetermined pattern of scanning to cover substantially an entire area. In fact a particularly important subpreference is that the raster be a spiraling scan pat- tern.
  • the detector be an infrared detector, or a visible-light detector, or a single-pixel detector, or a detector that has si few pis ⁇ els. As will be appreciated, some of these are mutually exclusive.
  • the final basic preference to be considered here, in relation to the first main independent aspect or facet of the invention, is applicable if the external article comprises an object or scene of interest, and the characteristics comprise distance data for different portions, respectively, of the object or scene, and the optical system is for forming the distance data.
  • the optical detector includes a distance-determining receiver.
  • the distance-determining receiver includes a single-pixel re ⁇ ei- ver, and the system further includes some means for controlling the at least one mirror to perform a raster scan of the single-pixel receiver over the object or scene; (2) the distance-determining system includes a receiver having a few pixels, and the system further includes some means for controlling the at least one mirror to perform a raster scan of the few-pixels receiver over the object or scene; and (3) the system further includes a distance-determining transmitter that uses the entrance aperture as also an exit aperture for a pulsed excitation beam.
  • the invention is an optical system for impairing function or structural integrity of an external article in a volume outside the optical system — including controlled effect upon the article as a function of angular direction.
  • the optical system includes a laser, and an exit aperture.
  • the "at least one mirror” is disposed along an optical path between the laser and the exit aperture, and rotatable about plural axes; and each mirror of the "at least one” has dimensions in a range from thirty microns to five millimeters .
  • the advantages of the mirror placement and size recited here are closely analogous to those identified above for the first aspect or facet of the invention.
  • many important characteristics of optical systems are independent of light-propagation direction through the systems — i. e.. of whether the system is one that receives and responds to radiation, or one that generates and transmits the radiation.
  • the second 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 further includes some means for using the exit aperture as an entrance aperture, to receive a sensing beam from an optical source in the volume.
  • system further include some means for controlling the at least one mirror to perform a raster scan of the laser over the external article.
  • the optical system include a vibration sensor, and some means for applying information from the sensor to stabilize lines of sight of the small movable mirrors .
  • the invention is apparatus for dynamically detecting and determining radiation characteristics, including associated angular direction, of an article outside the apparatus.
  • the apparatus includes an optical detector.
  • the apparatus also includes at least one microelectromechanical mirror for causing the detector to address varying portions of the article.
  • microelectromechanical mirror is verbal shorthand for "microelectromechanical system mirror” , or “MEMS mirror” , established commercial products introduced by the Texas Instruments Company and Lucent Technologies, among others.
  • the optical system further includes a lens assembly disposed at the aperture to amplify the varying introduced by the at least one microelectromechanical mirror. If this preference is observed, then a further preference is that the lens assembly be "afocal" — i. e. , that it not focus the external article on any solid element of the optical system.
  • the system include some means for automatically servocontrolling the at least one microelectromechanical mirror to perform a raster scan of the volume.
  • the previ- ous note about the definition of "raster” is applicable here as well .
  • the at least one microelectromechanical mirror be an array of microelectromechanical mirrors .
  • the external article comprises a radiation source of a particular type
  • the characteristics comprise existence and presence of the source
  • the optical system is for detecting the source and determining its angular location.
  • the optical detector is a detector for radiation from the source of the particular type.
  • the optical system further include some means for automatically responding to the detector by actively servocontrolling the at least one microelectromechanical mirror to substantially center an image of a detected source on the detector.
  • the responding means include some means for continuing to servocontrol the at least one microelectromechanical mirror to track the already-detected source substantially at the detector center.
  • these servocontrol embodiments of the invention are powerful in their ability to yield stable and precise angular readouts, from the typically built-in mirror position-sensor feedback signals — and these output data, particularly for angles well off-axis, are far more precise than available from off-axis readings of typically temperature-sensitive optical detectors.
  • PSD position-sensing detector
  • These devices enable the optical system to determine off-axis direction and approximate magnitude, directly from PSD signals — and these signals can therefore be used for proportional, integral and/or derivative servocontrol, if desired, in the feedback loop.
  • This type of servosyste accordingly can operated in a damped mode, especially valuable when the overall system is called upon to operate at the margins of its dynami ⁇ -re- sponse capability.
  • the system further include some means for substituting a detector array for the detector, to image the already-detected source or associated objects, or both.
  • the system further include some means for automatically directing a response toward the detected source or an object associated therewith, or both.
  • the response-directing means include some means for emitting a beam of radiation that uses the en- trance aperture as an exit aperture, sharing the entrance aperture with the radiation from the source.
  • the external article comprises a radiation source
  • the characteristics include spectral properties of radiation from the source
  • the optical system is for determining the radiation spectrum of the source as a function of angular direction.
  • the optical detector is a spectrometer.
  • the system further include some means for automatically controlling the at least one microelectromechanical mirror to perform a spectrometric raster scan of the spectrometer over the source.
  • the system further include some means for analyzing the radiation to determine the at least one modulation pattern as a function of angular direction. In this event it is still further preferable that the system include some means for generating a beam of radiation having the determined spectrum and the determined at least one temporal modulation pattern.
  • the detected spectral and temporal modulation characteristics of the received radiation be transmitted to a remote station.
  • the external article comprises an object or scene
  • the characteristics comprise an image of the object or scene
  • the optical system is for forming the image.
  • the optical detector is an imager detector; and the system also includes some means for automatically controlling the at least one microelectromechanical mirror to perform an imaging raster scan (once again as broadly defined) of the detector over the object or scene.
  • the external article comprises an object or scene
  • the characteristics comprise range data for different portions, respectively, of the object or scene
  • the optical system is for forming the range data.
  • the optical detector includes a distance-determining receiver.
  • the receiver include a single-pixel receiver; and that the system include some means for controlling the at least one mirror to perform a raster scan of the receiver over the object or scene. It is furthermore preferred that the system include a distance-determining transmitter which uses the entrance aperture as also an exit aperture for a pulsed excitation beam.
  • the optical system include a vibration sensor, and some means for applying information from that sensor to stabilize lines of sight of the microelectromechanical mirrors.
  • the invention is an optical system for impairing function or structural integrity of an article outside the apparatus — particularly including controlled effect upon the article as a function of angular direction.
  • the optical system includes a laser, and an exit aperture.
  • the system also includes at least one microelectromechanical mirror for causing the laser to address varying portions of the article, to impair function or structural integrity of corresponding portions of that article.
  • the foregoing may represent a description or definition of the fourth aspect or facet of the invention in its broadest or most general form. Even as couched in these broad terms, however, it can be seen that this facet of the invention importantly advances the art. In particular, this facet of the invention extends the above- mentioned extraordinary benefits of MEMS mirrors in a beam-steering system, from the environment of optical-source detection into the context of projecting a disruptive beam.
  • the optical system further include some means for controlling the at least one mirror to perform a raster scan of the laser over the external article.
  • the optical system further include some means for controlling the at least one mirror to perform a raster scan of the laser over the external article.
  • the invention is apparatus for detecting and determining angular direction of radiation from an external source.
  • the apparatus includes an optical system having a detector component that reports relative location of incident radiation on a sensitive surface of the detector component.
  • the apparatus also includes at least one mirror for causing the detector component to address varying portions of a volume outside the optical system.
  • the apparatus also includes some means for automatically responding to the detector component by actively servocontrolling the at least one mirror to substantially center an image of a detected source on the detector component.
  • the detector component includes a position-sensing detector (PSD) ; or includes a quad cell; or includes a focal-plane array — but in this latter case, preferably the detector component further includes a processor operating a program for analyzing data from the focal-plane array.
  • PSD position-sensing detector
  • each mirror of the at least one mirror be a microelectromechanical mirror.
  • the at least one mirror be an array of microele ⁇ trome- chanical mirrors.
  • rays can all be made parallel — or different sectors can look in di er- ent directions. This has the benefit of being able to track different sources or other articles simultaneously. Also, a group of mirrors has a greater effective aperture for energy collection.
  • the apparatus further include an optical-system aperture, and a lens disposed at the aperture to amplify the varying introduced by the at least one mirror.
  • a subpreference is that the lens at the aperture not focus the radiation from the external source.
  • the apparatus further include some means for automatically controlling the at least one mirror to perform a raster scan of the volume.
  • the servocontrolling means continue to servocontrol the at least one mirror to track the already-detected source substantially at the detector center.
  • the apparatus further include some means for substituting a detector array for the detector, to image the already-detected source or associated objects, or both. The meaning of "substituting" here is as discussed earlier.
  • the apparatus further include some means for automatically directing a response toward the detected source or an object associated therewith, or both.
  • a subpreference is that the apparatus further include an entrance aperture for collecting radiation from the source; and that the response-directing means include some means for emitting a beam of radiation that uses the entrance aperture as an exit aperture, sharing the entrance aperture with the radiation from the source.
  • the response-directing means include some means for emitting a ranging beam pulse.
  • the invention is an optical system for varying angular direction, outside the optical system, of a transmitted or received beam of collimated radiation.
  • the optical system includes a physical-interaction stage where the transmitted beam is generated, or the received beam is intercepted by utilization means .
  • the system also includes at least one movable mirror for varying direction, outside the optical system, of the beam — by rotation of beam direction at the mirror through a particular angle.
  • the system includes some means for multiplying the particu- lar angle by a desired factor; and the at least one movable mirror is disposed along an optical path between these angle-multiplying means and the physical-interaction stage.
  • the multiplying means include plural focal elements, in series, that have respectively different focal lengths.
  • the desired factor is equal to a ratio of the focal lengths.
  • the beam-angle multiplication feature enables a very broad beam sweep, or scanning range, outside the optical system in response to a relatively modest angular excursion of the movable mirror inside the system.
  • This broad sweep is achieved without sac- rifice of angular sensitivity or precision in mirror position; hence this system makes a major contribution to dynamic range in detected angle.
  • the sixth major aspect of the invention thus signifi- cantly advances the art, nevertheless to optimise enjoyment of its benefits preferably the invention is practiced in conjunction with certain additional features or characteristics.
  • the focal elements are lenses.
  • the focal elements focus the collimated beam to a virtual, substantially point image and form another collimated beam from the substantially point image. If this basic preference is observed, then a subpreference is that the focal elements form the virtual , substantially point image between the focal elements .
  • the plural focal elements are disposed between the movable mirror and: ⁇ an exit aperture, if the beam is a transmitted beam; or
  • the focal lengths are in the ratio of approximately 1:3 or 3:1, and accordingly the desired factor is approximately 3 or 1/3, respectively. More generally, usable ratios fall representatively in the range of 1:2 to 1:4, yielding facto s between 4 (or 1/4) and 2 (or 1/2) .
  • the plural focal elements comprise more than two focal elements, and the ratio of focal lengths equals a ratio of (1) a first composite effective focal length of a subgroup of two or more of the focal elements, and (2) an effective focal length of all remaining focal elements .
  • Fig. 1 is a block diagram, with most portions symbolically in side elevation but certain other portions (an aperture-lens assembly 14 and a lens/detector assembly 22) symbolically in isometric projection, of a basic first function — namely, a detection function — for preferred apparatus embodiments of the invention;
  • Fig. 2 is a like diagram showing an extension of the preferred apparatus embodiments to encompass a second function, namely optical analysis ;
  • Fig. 3 is another like diagram but now showing a further extension to encompass dual forms of yet a third function, namely response;
  • Fig. 4 is a multiapplication block diagram representing appa- ratus and procedures, using the apparatus embodiments of Figs. 1 through 3 for the above-mentioned and still other functions, and in a number of variegated applications;
  • Fig. 5 is a diagram generally like Figs. 1 through 3 but with the lens and detector assemblies 14, 22 enlarged for presentation of details;
  • Fig. 6 is a diagram conceptually representing a spiral-scanning raster pattern for use in any of the Fig. 1 through Fig. 5 systems and methods .
  • the invention provides a low-cost sensor system 10 (Fig. 1) capable of detecting and locating active illumination sources — or objects illuminated by such sources.
  • the sensor system of the invention can also respond to the detected light source by returning a light beam 38 (Fig. 3) or an object, and in some cases by initiating a distance-determining or other investigation (Function 4, Fig. 4) of the source or objects associated with the source.
  • initial detection of a radiation source or illuminated object is qualified by filters that implement expectations as to the characteristics of such sources or objects that are of interest. For instance, when anticipated sources are infrared, or are in other particular spectral regions, spectral filters are placed at convenient positions in the optical path — usually but not necessarily associated with the fold mirror 21, and in particular taking the form of bandpass optical reflection/- transmission filters.
  • the fold mirror can be advantageously implemented as a beam split- ter, and incident-beam selectivity is simply an additional one of such purposes.
  • a dichroic or other bandpass or bandblocking filter can be used, as an alternative to a fold mirror 21.
  • the filter transmits these undesired components to a radiation sink or auxiliary detection system 55, while reflecting the desired radiation components to the detector — or conversely, depending on preferred system configuration.
  • Such advance filtering is not limited to spectral characteristics .
  • the signal 25 from the optoelectronic detector 24 is advantageously filtered electronically 56 to exclude d. c. sources or sources having no significant bandwidth activity above a specific threshold frequency — or, more restrictively, to pass only a. c. signals having a particular specified modulation pattern or class of patterns .
  • the system detector 24 is a PSD, which has the ability to report positional coordinates ⁇ , ⁇ Y (on the PSD' s own surface, Fig. 5) of an impinging optical beam from a source 1 in a region without the necessity of scanning the region. As noted elsewhere in this document, it is also necessary to determine the mirror position. From these data and known characteristics of the associated optics, as explained above, angular position 8 X , ⁇ ⁇ of the source is readily calculated.
  • a PSD is nonlinear and temperature sensitive when measuring large off-axis coordinates ⁇ X, ⁇ Y and thus angles ⁇ x , ⁇ ⁇ .
  • These drawbacks are neutralized, in preferred forms of the present invention, by operating in a null-balance mode as detailed below — so that the system relies on the PSD primarily only to determine whether the source is off axis and, if so, then in which direction; and not for quantitative reporting of large off- axis coordinates or their associated angles.
  • the system very rapidly servocontrols itself to keep incident rays 13 at the center of the detector field.
  • Most pref- erably such servocontrol 27 is implemented by one or more microelectromechanical (MEMS) mirrors 15 disposed inside the optical system 10, i. e. along the optical path between the detector 24 and the collecting aperture 14, 45 (Fig. 5) of the system.
  • MEMS microelectromechanical
  • Such mirrors have extraordinarily low mass and inertia, and corresponding extremely high response speed — thus obviating the problem of sluggish response in earlier systems.
  • Placing the mirror or mirrors inside the system gains yet further advantages of angular displacement speed, in the visible volume 11 of space outside the optical system, particularly if a lens 45 is placed at the aperture to optically magnify the angular displacement of the mirrors .
  • This particular arrangement for servocontrol of the incoming light, to center the beam on the detector, is particularly advantageous when using a PSD. Whereas that type of detector measures large off-axis angles somewhat inaccurately, the system is easily made extremely accurate in measuring the angular correction 28 applied by the MEMS system to bring the source to the central, null position.
  • Such transforms include the magnification factor introduced by the afocal package 14, as discussed at length elsewhere in this document, and also include the local calibration of the mirror actuator- stem positions relative to an internal standard, and also distortion in the afocal array 14 as well as the final focusing optic 23, and so forth.
  • the PSD itself can effectively monitor a far larger angular region 11 than it can image. This is a major advantage never fully exploited in conventional systems because of failure to use internal mirrors, or very small mirrors, and because of failure to servo the input source to a reproducible centerpoint on the detector. Nevertheless a still further major advantage is gained by raster scanning 16 the PSD.
  • the basic principle behind this is that the system views a small part of the field of regard at any instant in time, yet expands its coverage by searching for incident rays, thereby covering the entire field of regard 11. As will be seen, practical field of view using the various forms of the invention can range, representatively, from 20° to 180°.
  • the optical system has been successfully servocontrolled to an incident ray when both coordinates ⁇ x and ⁇ Y (Fig. 5) of the ray on the sensitive detector surface are aero as measured by the two-dimensional ("2-D") detector assembly (or in the case of a 1-D detec- tor, when ⁇ X or ⁇ Y is zero and the scan-mirror positions are noted) .
  • the system can function to determine not only angular location of the incident ray but also its wavelength ⁇ and coded temporal modulation f (t) ; or can direct similar or different light rays 35-38 (Fig.
  • an auxiliary laser 42 can be directed 41 to emit a very bright beam 43 of identical wavelength ⁇ and temporal modulation f (t) onto a nearby (but progressively diverging) surface. This arrangement can closely mimic the original beam but in a different guiding location, and thereby draw off the object from the intended destination.
  • variable-position fold mirror 21, 21' (Figs. 2, 3 and 5); however, for simultaneous operations as noted earlier such a mirror can be replaced by a beam splitter, e. ⁇ . a polarized one for maximum radiation transfer, or by spectral-band-wise splitting devices such as dichroic filters.
  • the sensor system is ordinarily located on a host (Fig. 4) .
  • a host is readily selected to optimize use of the invention for particular applications.
  • the host can be a vehicle including an automobile or truck, sea vessel, airplane, spacecraft, satellite or projectile, or even simply a human or animal or their paraphernalia.
  • Hosts are not limited to these examples, but can basically consist of any carrier — even a stationary one — capable of supporting and maintaining the sensor, and exposing it to various kinds of articles or objects.
  • the sensor method or system specifications can vary and be op- timized for use in particular applications .
  • One of ordinary skill in the art can select preferred configurations of the system to suit a particular application.
  • the system can monitor a field of regard at approximately 10 Hs frame rate — evidencing the excellent sensitivity of the inven- tion at high frequencies.
  • the invention is capable, however, of monitoring in a range on the order of 1 Hz to 1 kHz — or even 10 kHz, depending on size of articles of interest, and the detector field of view. Overall, the invention provides a high degree of angular accuracy in determining the approach path of an incident ray.
  • Plural such sensor systems can be grouped and coordinated to provide up to 4 ⁇ steradian coverage — i . e. , for sensing in all directions at once. This kind of observation is appropriate for a host that is in the air or in outer space, and in some circumstances for a host that is waterborne. For a host on land, and for a water- surface-craft host in other circumstances (particularly, no need to monitor below the water surface) 2 ⁇ steradian coverage ordinarily is entirely sufficient.
  • the sensor of the invention has the ability to monitor wavelengths ranging from ultraviolet (UV) to infrared (IR) , particularly up to the midIR range.
  • UV ultraviolet
  • IR infrared
  • a MEMS mirror is limited in range to plus-or-minus ten to fifteen degrees about one or two orthogonal axes, i. e. through an overall excursion 16 of roughly 20° (Fig. 5) to 30° for each axis.
  • a lens assembly 14 is advantageously used to significantly increase this range optically.
  • the invention eliminates use of large external scan mirrors and gimbals; as a result the invention is more rugged, and yet actually less expensive and several orders lighter and more compact than conventional sensor systems.
  • the size of the system depending on the application, is on the order of one millimeter, or less, to a few centimeters — rather than on the order of one centimeter to tens of centimeters as described earlier for conventional units.
  • Dimensions of an oscillating scan mirror 15 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 aspect ratio should be approximately the square root of two, since the mirror surface — when at the center of its range of excursions — is inclined at 45° to both the incident and reflected beams. Accordingly the most preferable tested embodiments use e. q. silicon scan mirrors in the range of 1.5 x 2.1 mm (note that 2.1); but again these dimensions are not at all limit- ing. Such a mirror typically rotates about its own axis with an excursion in the range of ⁇ 1° to ⁇ 10° — or even ⁇ 15° as previously noted.
  • the system mass can be made just one-tenth to one kilogram, also generally several orders of magnitude lower than that of com- parable known devices.
  • Angular resolution is readily placed in the submilliradian or even tens-of-microradians range, i. e. less than three minutes of arc or even under one minute, versus the previously noted tens to hundreds of milliradians (two-thirds of a degree to tens of degrees) for sensors heretofore.
  • Yet another major and remarkable advantage of the invention is that the system can eventually use off-the-shelf technology, requiring no expensive custom parts or instrumentation.
  • the most highly preferred embodiments of the invention call for a custom MEMS mirror array of at least 5 x 5 mirrors — and more preferably 10 x 10 and even 30 x 30 mirrors — each individual mirror being 1.5 x 2.1 mm, and with an afocal lens assembly that follows custom optical specifications but is otherwise conventionally fabricated. It is anticipated that these component designs will quickly become standard in the field, and very shortly be available as commercial off-the-shelf units .
  • the invention can redirect a new beam 43 (Fig. 3) of light (usually generated locally — i. e. on the same platform) laterally for guidance of any objects away from the host.
  • the invention can also provide determination of wavelength ⁇ and frequency-modulation information f (t) in the received beam, so that those characteristics of the received rays can be mimicked 41 in the new beam — which is relayed to another location, either for communications purposes or to lead an approaching object to a different destination.
  • the new beam can be directed back along the same path 38 as received rays 13, to the extent that the field of regard of the optical system (or of the system together with other such optical sys- terns being operated in parallel) is broad enough to provide appropriate directions for the new beam.
  • Preferred embodiments of the method of the invention, corre- sponding to the apparatus discussed above, include the steps or functions of:
  • the first of these functions preferably includes these constituent steps:
  • STEP 1 Incident rays 13 from a light source 1 illuminate the system, on its host platform, at a relative angle B ⁇ f ⁇ ⁇ .
  • An afocal lens assembly 14 reduces a collimated or nominally collimated incident or exiting ray angle, ⁇ x , ⁇ y (i. e. , outside the optical system) by the ratio of the two focal lengths designed into the assembly, 1:3 in this example, resulting in much smaller of -axis angles of ⁇ /3, ⁇ y/3 inside the optical system 10 — i. e. at the scan mirror or mirrors 15.
  • This arrangement is optimal to effectively, or virtually, bring the incident rays within the native scan range of the MEMS scan system.
  • the lens assembly 14 is described as "afocal” because it is not used to focus the incoming rays directly onto the detector 24; rather the primary lens 45 forms (inside the lens assembly) only a vir- tual image 4.4 , which the secondary lens 46 then recollimates — but only if the incoming beam 13a, 13 is itself at least approximately collimated — to produce substantially parallel rays in the beam approaching the detector assembly 22.
  • STEP 3 The MEMS scan mirror continuously raster- cans the field of regard.
  • the MEMS scan mirror intercepts laser energy at the corresponding original angles ⁇ x , ⁇ y (and reduced angles ⁇ x /3, ⁇ y/3) , the detector detects the energy and in turn transmits the signal to the control processor.
  • the relative position reported at that same instant by the MEMS scan mirror assembly, and therefore corresponding to ⁇ x , ⁇ ⁇ is recorded by the control processor 26.
  • a conventional two-axis angle sensor (not shown) that measures shaft angle of the MEMS mirror has been precalibrated to provide the corresponding field of regard angle ( ⁇ x , ⁇ y ) relative to the optical axis.
  • STEP 4 The 2-D detector is fitted with a reimaging lens that focuses the incident beam at its conjugate location on the detector, relative to the system axis, provided that (1) the MEMS scan mirror is at an appropriate angle to direct the beam into the detector field of view, and (2) the incoming beam, within the envelope of extreme captured rays 13, 13a (Fig. 5) , is collimated or very nearly so. This arrangement tends to somewhat diffuse the image of relatively nearby sources on the detector, and thus limit the response to light from relatively remote sources .
  • the detector is thus aided in essentially disregarding illumination from nearby sources, which for purposes of preferred embodi- ments of the present invention are deemed to be most-typically irrelevant. (As will be understood, contrary assumptions can be implemented instead, if desired, in other — generally conventional — optical trains . ) Such exclusion of illumination that is not of interest, however, is generally secondary in relation to other selec- tive features in the system — e. q. spectral filtering 21, 55, and a. c. signal filtering 56 or other arrangements for enhancing sensitivity to anticipated known modulation patterns .
  • the position-sensing detector next comes into play, sensing not only presence of the illumination but also the displacements ⁇ X, ⁇ Y of its focal point (conjugate location) from the optical axis — and generating corresponding ⁇ X, ⁇ Y signals for transmission to the control processor.
  • each angle ⁇ x or ⁇ ⁇ equals the corresponding ⁇ X or ⁇ Y coordinate divided by the 2-D detector imaging-optic focal length f D (Fig. 5) — subject to the angle-scaling effect of the afocal assembly 14, discussed at "step 2" above.
  • STEP 6 The ⁇ x , ⁇ y incident-ray relative position as then measured by the MEMS scan-mirror local angle sensors are made available, for later functions, as an accurate line-of-sight location of the incident ray relative to the system axis .
  • the second function of the system basically includes determining the wavelength and any accompanying temporal or spectral modulation of the incident ray or signal. Continuing the above sequence:
  • Step 7 A fold mirror 21 (Fig. 2) rotates to direct the inci- dent beam 13 to a spectrometer or photodiode 31.
  • the fold mirror is basically a simple, motorized mirror that redirects light; but in other preferred embodiments this mirror can be replaced by a MEMS mirror or, as noted earlier, a beam splitter.
  • One or more splitters, in tandem as appropriate, are particularly advantageous to permit simultaneous operations of different types, e. q. detection, spectral analysis, imaging, distance probing, or active response — and combinations of these.
  • Step 8 A spectrometer 31 determines the incident ray wavelength; and either the detector in the spectrometer acquires any temporal or spectral intensity or wavelength or temporal modulation to be detected and sent 32 to the control processor. Portions of this task may be assigned to the PSD 24, filter 56 (Fig. 1) and processor 26 for data acquisition during earlier steps 5 and 6.
  • the third system function is most typically an optical response that can take any of several forms.
  • One such form (Fig. 3), which makes use of the directional information collected in the first function, is generation and projection of a very bright beam of radiation opposite the incident ray, to temporarily dazzle or confuse an operator or aiming-control apparatus at the source.
  • STEP 7 The fold mirror 21 (Fig. 3) rotates from its earlier positions 21' to align a powerful laser 34 along the optical axis, and thereby along the known path to the source.
  • STEP 8 The laser transmits a temporarily blinding beam 35-38 in a direction opposite the incident rays 13, but back along the same path, in response to a command 33 from the control processor 26.
  • a fourth function uses the information collected in the second function to generate and project a precisely wavelength-matched and temporal-modulation-matched beam to a nearby location, preferably one that progressively moves away from the host position, to draw any guided object away from the host. Friendly as well as hostile guided rendezvous can be facilitated in this way.
  • This fourth fun ⁇ - tion includes issuance of a processor command 41 (Fig. 3) — with necessary data ⁇ , f (t) — to the auxiliary light source, e. q. tunable modulated laser 42.
  • the determined information is advantageously transmitted (preferably as interpreted, encoded data) to a remote station to document, e. . for subsequent refined avoidance, what has occurred.
  • auxiliary laser 42 it is possible to use the previously en- tioned laser 34 — i . e. ,the one that can be aligned with the main optical path through the lens assembly 14. This option is particularly practical in the case of a plural-sensor-system apparatus configured to scan 2 ⁇ or 4.K steradians as previously discussed. In such applications essentially all locations are within the scanned range of at least some one of the component sensor systems .
  • FIG. 4 A complex of other possible responses, and alternative applications of the information gathered in the first two functions, is within the scope of the invention (Fig. 4) .
  • One such response is initiation of a distance probe operation to collect additional information about any such object that may be associated with the beam, or about facilities at the source, or both.
  • Several of the references cited at the beginning of this document provide very extensive information about distance-determining capabilities and design. Other ranging methods may be substituted as desired.
  • This form of the invention can also be used for any of various other applications, such as for example transmission of modulated optical signals for free-space laser communications.
  • additional components may be added, such as additional processing capability for further pro- cessing data, an annunciator for alerting an operator or connecting to an alarm for monitoring the system, or robotics for performing additional functions in response to the detection.
  • Particularly preferred applications include use of the system in a vehicle or other host for detection of objects, or use of the system as a guide for a laser communications telescope — for which the system "communicates” angular, wavelength, frequency- modulation (or other temporal modulation) or other information between two telescopes . Also included is use of the system for continuous observation purposes such as recognition and location of emergency distress signals e. q. a beacon, or flares, or identification of approaching vehicles.
  • emergency distress signals e. q. a beacon, or flares, or identification of approaching vehicles.
  • Fig. 4 is not intended to be exhaustive; i. e. , not all functions of the invention described and discussed in this document appear in that drawing. Because of the versatility of the system and its many func- tions, it has a wide range of applications spanning industries as diver e as telecommunications , optics, automotive, marine, aerospace, continuing observation, and search and rescue.
  • the sen- sor system utilizes a two-axis scan mirror (Fig. 5) of dimensions
  • a two- axis scan mirror is not a requirement; a single-axis scan mirror with one-dimensional detector can be substituted.
  • the ⁇ 10° or ⁇ 15° sweep 16, i. e. 20° or 30° full-excursion, of the MEMS mirror or mirrors 15 is doubled — by the effect of reflection — to produce a 40° or 60° deflection of the beam at that point.
  • the MEMS system in turn, is behind a lens assembly whose focal-length ratio (typically 1:3) triples that 40° or 60° deflection to provide, typically, a 120° to 180° overall field of regard.
  • the two-axis MEMS scan mirror operating at approximately four mil- liradians for approximately the magnification (again, typically three) times 2 ⁇ /d, repeatedly sweeps the full 120° x 120° volume at more than 10 Hz. This then is the frame rate for a complete scan of that field of regard.
  • the ray is projected — through its reimaging lens — onto the detector when the MEMS two-axis scanning mirror is at the corresponding angular position.
  • the MEMS scan-mirror control system then drives the scan mirror to maintain the incident ray on the detector, ideally a position-sensing photodiode detector as described earlier — and preferably at its center.
  • This detector provides positional closed-loop feedback to the scan mirror, driving the focal point to minimize the ⁇ X and ⁇ Y coordinates. In other words the beam is driven to the native origin on the photosensitive surface of the diode.
  • the angular positions of the mirror provide the corresponding azimuth and elevation angles ⁇ x , ⁇ y of the incident rays — based on the corresponding error coordinates ⁇ X, ⁇ Y at the detector surface, and the corresponding known relative mirror angles as explained earlier.
  • Limiting uncertainty of the input collimated laser-beam angle is the limiting resolution of the 2-D detector divided by the reimaging lens focal length f D .
  • the system advantageously includes a multiposition relay mirror (or fold mirror etc. ) to alternatively direct the incident beam to other detectors such as a spectrometer used to determine incident-ray wavelength — or a beam- splitter to do so concurrently.
  • a multiposition relay mirror or fold mirror etc.
  • quad cells, focal plane arrays, or line arrays such as a charge-coupled device (CCD) or other light sensitive arrays can be used instead.
  • CCD charge-coupled device
  • each individual detector of an array can be provided with its own individual microlens. Nevertheless the previously mentioned quantization effect remains a concern, and array detectors are generally slower than PSDs, particularly when taking into account the neces- sary algorithmic procedures for readout and interpretation of optical signals .
  • the same multiposition mirror can also serve to route output rays, from an onboard laser or other bright lamp, back along the original optical path toward the source of the initially detected incident beam — to blind the source operator, or locate the source facility, or communicate with it, all as set forth earlier.
  • a vibration-sensing subsystem 57 (Figs. 1 and 2) adjacent to the scan mirror or mirrors, and a correctional-data path 58 for flow of vibration information from the outputs of these sensors to the main processor.
  • a vibration-sensing subsystem 57 (Figs. 1 and 2) adjacent to the scan mirror or mirrors, and a correctional-data path 58 for flow of vibration information from the outputs of these sensors to the main processor.
  • This sensing module 57 with its correction path 58 enables a spectrometer, or an imaging system or distance-determining system, that is part of the invention embodiments to form a stable, high-resolution 2-D or 3-D image despite vibration in the host platform.
  • the vibration sensor includes a gyroscope or set of accelerometers , separated by known lever arms. These devices provide enough information — most typically with respect to five degrees of freedom — to enable the system to incorporate compensating maneuvers of its moving mirrors, canceling out the effects of such vibration.
  • Sensing elements 57 positioned along the plane of a supporting base of the moving mirror or mirror assembly 15 can for example include three linked accelerometers sensitive to motion normal to that plane, and two others sensitive to motion within that plane — ordi- narily but not necessarily parallel to orthogonal edges of the base.
  • Such vibration-sensing devices in effect define instantaneous characteristics of any host-platform vibration.
  • Such sensing subsystems in themselves are well known and conventional. The data they produce must flow to the processor 26 and be interpreted promptly enough to enable effective feedback into the control circuits of the moving mirror or mirrors , to achieve cancellation within the desired imaging accuracy of the overall system.
  • raster scans are advantageously performed using a spiraling pattern 59 (Fig. 6) .
  • a spiraling pattern 59 Fig. 6
  • executing such a pattern is most typically far more energy-efficient and fast than tracing a more-conventional rectangular-envelope serpentine pattern.
  • the sequence reverses direction at each end — i. e.. outward in one scan, inward in the next, and so forth.
  • the number and pitch of the spiral revolutions should be selected with care to obtain good resolution without significant gaps in the image.

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Abstract

La présente invention, dans des modes de réalisation préférés, a trait à des miroirs à systèmes mécaniques microélectriques ou des petits miroirs au sein d'un système optique fonctionnant en boucle fermée. Ces miroirs orientent une source lumineuse externe, ou une lumière de génération interne, sur un objet, et détectent la lumière réfléchie à partir dudit objet sur un détecteur qui détecte la source. Des capteurs locaux mesurent les angles de miroir par rapport au système. Les sorties des capteurs et de détecteur fournissent une source de localisation par rapport au système. Dans un mode de réalisation préféré, les miroirs à systèmes mécaniques microélectriques, et les champs observés par le détecteur, sont entraînés dans une matrice recueillant une image bidimensionnelle ou tridimensionnelle de la région balayée. L'énergie atteignant le détecteur peut être utilisée pour l'analyse des caractéristiques d'objets, ou avec un éventuel module optique actif de détection de distance pour la création d'images bidimensionnelles ou tridimensionnelles, basées sur la réflexion par l'objet de la lumière renvoyée vers le système. Dans certaines applications, il est possible de générer une réponse. L'invention peut détecter des sources et des emplacements pour diverses applications.
PCT/US2003/039535 2002-12-13 2003-12-12 Systeme optique WO2004083795A2 (fr)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1717599A1 (fr) * 2005-04-21 2006-11-02 Diehl BGT Defence GmbH & Co.KG Dispositif destiné à la visualisation d'un champ visuel sur un détecteur
WO2007065643A1 (fr) * 2005-12-09 2007-06-14 Diehl Bgt Defence Gmbh & Co. Kg Vibromètre
WO2008018955A2 (fr) * 2006-06-27 2008-02-14 Arete' Associates Configuration de lidar de type caméra
WO2008076444A1 (fr) * 2006-12-16 2008-06-26 Arete' Associates Système optique perfectionné
EP2426459A3 (fr) * 2010-09-02 2014-07-16 Kabushiki Kaisha Topcon Procédé de mesure et dispositif de mesure
CN106768369A (zh) * 2017-03-22 2017-05-31 普雷恩（北京）通用航空股份有限公司 机载告警装置

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CN107255820B (zh) * 2017-05-25 2021-08-24 深圳拓邦股份有限公司 一种激光测距装置
CN108828625A (zh) * 2018-08-27 2018-11-16 安徽科创中光科技有限公司 一种沙式定理成像激光雷达反演大气能见度的装置及方法
CN109270515B (zh) * 2018-11-29 2020-06-16 北京理工大学 可变扫描区域同轴收发扫描激光雷达

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1717599A1 (fr) * 2005-04-21 2006-11-02 Diehl BGT Defence GmbH & Co.KG Dispositif destiné à la visualisation d'un champ visuel sur un détecteur
WO2007065643A1 (fr) * 2005-12-09 2007-06-14 Diehl Bgt Defence Gmbh & Co. Kg Vibromètre
WO2008018955A2 (fr) * 2006-06-27 2008-02-14 Arete' Associates Configuration de lidar de type caméra
WO2008018955A3 (fr) * 2006-06-27 2008-09-25 Arete Associates Configuration de lidar de type caméra
WO2008076444A1 (fr) * 2006-12-16 2008-06-26 Arete' Associates Système optique perfectionné
EP2426459A3 (fr) * 2010-09-02 2014-07-16 Kabushiki Kaisha Topcon Procédé de mesure et dispositif de mesure
US8934009B2 (en) 2010-09-02 2015-01-13 Kabushiki Kaisha Topcon Measuring method and measuring device
CN106768369A (zh) * 2017-03-22 2017-05-31 普雷恩（北京）通用航空股份有限公司 机载告警装置

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