Abstract: An imaging lidar system for underwater applications is presented which is well suited for imaging and detecting underwater targets suspended above and on the bottom in shallow and coastal water. The present invention provides the capability for rapid and reliable search, detection, classification and localization of objects in the surf zone which may present hazards to navigation and utilization of coastal areas as well as undesirable effluents and biological fouling of underwater objects. The present invention provides an improved bottom tracker, improved ability to deal with brightness variation and surface glint, and computerized real time detection algorithms.

Abstract: An imaging UV/visible fluorosensing and Raman lidar system comprises an optical sensor for simultaneously measuring temporally, spatially and spectrally resolved laser backscatter from on the land, on or beneath the surface of bodies of water and in the atmosphere and utilizes "active" interrogation or "passive" interrogation for remotely and non-destructively probing the spectrally-dependent optical properties of a scene. In the "active" mode, the optical sensor of this invention comprises a transmitter (preferably a tunable solid state laser) which emits pulses of coherent light through a variable or adjustable field-of-view telescope whereupon the light pulses are then propagated towards a scene (e.g., land, sea or atmosphere). Thereafter, laser backscatter is collected by a second variable field-of-view telescope and directed to an imaging system and spectrally dispersive optical subsystem.

Abstract: An imaging UV/visible fluorosensing and Raman lidar system comprises an optical sensor for simultaneously measuring temporally, spatially and spectrally resolved laser backscatter from on the land, on or beneath the surface of bodies of water and in the atmosphere that utilizes "active" interrogation or "passive" interrogation for remotely and non-destructively probing the spectrally-dependent optical properties of a scene. In the "active" mode, the optical sensor comprises a transmitter (preferably a tunable solid state laser) which emits pulses of coherent light through a variable or adjustable field-of-view telescope whereupon the light pulses are then propagated towards a scene (e.g., land, sea or atmosphere). Thereafter, laser backscatter is collected by a second variable field-of-view telescope and directed to an imaging system and spectrally dispersive optical subsystem.

Abstract: An imaging lidar system is presented which is adapted to decrease the backscattering at the receiver when a target is viewed in reflection and to increase the backscattered reflection when the target is viewed in obscuration by operating the airborne lidar imaging system bistatically in the former case, and monostatically in the latter case. In accordance with a first embodiment of the present invention, a retractible prism and remote reflecting mirror are used to direct the laser transmitter beam downward. The reflecting mirror is offset so that there is a finite angle between the transmitter optical path and the path of the light reflected back into the CCD framing camera. The angle can be varied by moving the reflecting mirror along a track or rail with the appropriate adjustment to the mirror so that the transmitter beam is completely captured and directed downward to illuminate the area viewed by the camera.

Abstract: A new and improved adaptive optics wavefront tilt sensor having both very high sensitivity and wide dynamic range is presented. In accordance with this invention, distortion is induced in each subaperture beam by passing a high f-number beam through a field lens having large amounts of spherical aberration. The distortion provides transition from a wide dynamic range, low sensitivity wavefront tilt measurement to a narrow dynamic range, high sensitivity wavefront tilt measurement. This beam is then impinged on a single photodector which provides at least one electrical signal indicative of centroid position.

Abstract: A novel data processing technique is provided for detecting and locating a target from a plurality of two-dimensional images generated by an imaging sensor such as an imaging lidar system. The present invention processes this series of two dimensional images (made with one or more imaging detectors) in an optimal statistical fashion to reliably detect and locate targets. This invention is a process by which the images are mathematically modified to reduce the deleterious effects of noise and thereby provide the highest possible probability of detection while simultaneously maintaining a very low probability of false alarm. The data processing technique described herein also provides an estimate of the reliability of the detection, the target location and an output image to be displayed for visual confirmation and perhaps classification by the operator.

Abstract: An imaging UV/visible fluorosensing and Raman lidar system comprises an optical sensor for simultaneously measuring temporally, spatially and spectrally resolved laser backscatter from on the land, on or beneath the surface of bodies of water and in the atmosphere. The present invention utilizes "active" interrogation or "passive" interrogation for remotely and non destructively probing the spectrally-dependent optical properties of a scene. In the "active" mode, the optical sensor of this invention comprises a transmitter (preferably a tunable solid state laser) which emits pulses of coherent light through a variable or adjustable field-of-view telescope whereupon the light pulses are then propagated towards a scene (e.g., land, sea or atmosphere). Thereafter, laser backscatter is collected by a second variable field-of-view telescope and directed to an imaging system and spectrally dispersive optical subsystem.

Abstract: A three dimensional range resolving imaging sensor is presented. The sensor comprises a transmitter for generating a light pulse which passes through beam homogenizer and a pair of Fresnel-Risley prisms. This pulse is then directed through an environmental window towards an object enveloped in a backscattering medium. A portion of the light pulse is reflected back towards the sensor. However, prior to detecting the return light pulse, a detector array is internally calibrated by exposure to a calibration pulse. This detector array preferably comprises a two-dimensional photo multiplier tube (PMT) array. A corresponding array of light tapers is disposed before the PMT array to increase the fill factor of the PMTs. Gain and offset corrections are made for each PMT from this exposure. The return pulse passes through the environmental window and impinges a pair of Fresnel-Risley scanner plates. These plates introduce a fixed angular deviation which is dependent on the orientation of the plates.

Abstract: An imaging lidar system for underwater applications is Presented which is well suited for imaging and detecting underwater targets suspended above and on the bottom in shallow and coastal water. The present invention provides the capability for rapid and reliable search, detection, classification and localization of objects in the surf zone which may present hazards to navigation and utilization of coastal areas as well as undesirable effluents and biological fouling of underwater objects. The present invention employs an improved bottom tracker for accurately measuring the distance between the imaging lidar system and the bottom.

Abstract: An underwater maneuverable vehicle is presented which carries an explosive charge and can be used for immediate removal or destruction of various menaces to navigation and other underwater hazards. The battery powered vehicle is air dropped from a platform which carries an imaging lidar system for detection and is operated and navigationally controlled in conjunction with an imaging lidar system. In accordance with an important feature of this invention, an optical lidar downlink is used to control the submerged underwater maneuverable vehicle from an airborne platform. The downlink is pulse spaced modulated. Command signals are secure, and are decoded aboard the vehicle. Control in speed, heading and depth, as well as command detonation are available using this technique.

Abstract: An imaging lidar apparatus for detecting and imaging an object enveloped by a backscattering medium which is at least partially transmitting to light is presented. The imaging lidar apparatus is mounted on an airborne platform and including light pulse generating means, reflected light pulse detection means and computer control means. A discrete vehicle is towed by a cable connected to the airborne platform. The discrete vehicle houses optics for receiving or transmitting light pulses. Fiber optic communication may be used to transmit the light pulses along the cable between the airborne platform and the towed vehicle.

Abstract: An airborne imaging lidar (light detection and ranging) sensor is provided which employs multiple pulsed laser transmitters, multiple gated and intensified array camera receivers, an optical scanner for increased field of regard, and a computer for system control, automatic target detection and display generation. The laser transmitters and multiple camera receivers are optically boresighted to the optical scanner (e.g., oscillating flat mirror) for an increased swath width perpendicular to the aircraft heading. The several laser transmitters are coupled for increased power and system sensitivity.

Abstract: An electro-optical camera system is presented. In accordance with the present invention, a light source (e.g. laser) is modulated by an electro-optic modulator (such as a Pockels cell) and transmitted out through an optical system toward a static target scene. The light backscattered from the target scene is then focused by the same optics back through the same Pockels cell onto a two-dimensional array camera such as a CCD or a CID (charge-couple device or charge injection device). A computer determines the frequency modulation period of each pixel in the array as the frequency of the electro-optic modulator is varied. This period is inversely proportional to the range of the target in the direction defined by the pixel location. Thus, all three spatial coordinates (two angles and a range) of each target area sensed by each pixel are determined. The computer will display the array of range data using a suitable output device such as a video display unit or a printer.

Abstract: A wavefront aberration sensor includes a beam splitter, one or more aberration sensor modules and a photodetector for sensing total light power. The aberration sensor modules each provide two voltage outputs from a pair of photodetectors. Differences in the voltage pairs are normalized by the total light power to represent signed aberration amplitudes of phase aberrations present in an input optical beam. The aberration amplitudes may be combined in a digital computer to provide a reconstructed wavefront.

Abstract: A segmented mirror control system comprises an array of structural elements (e.g. mirrors) which can be actively positioned to maintain an accurate pre-determined overall shape. The present invention is "active" and so may be characterized as an Active Segmented Mirror Control "ASMC". The segments of a mirror or the reflecting panels, in for example, a radiotelescope, may be continually adjusted with ASMC to provide an accurate reflecting mirror of very large diameter even when disturbed by external forces. ASMC is a closed loop control system. That is, an array of sensors is first used to measure differential position errors. This data is then processed to determine position actuator commands. Finally, these commands are used to move the segments until the sensors are nulled and the desired shape is obtained.

Abstract: Variable time delay range gating across an image is accomplished using a single imaging camera. In a preferred embodiment, the imaging camera of the present invention accomplishes adapted range gating and comprises a lens which focuses light onto a substrate having an array of gating electrodes mounted thereon. Both the electrode array and substrate are transparent to light so that the light focussed by the lens passes through the electrode array and substrate to strike a photocathode. The camera of this invention also includes a multiple output power supply connected between the electrode array and a microchannel plate amplifier, an anode, and an imaging array detector which is connected to the anode through a fiber optic bundle. The imaging camera of the present invention will effect adaptive range gating for overcoming the intensity variations and imaging plane problems associated with known light imaging detection and range (lidar) systems.

Abstract: A system is presented for the remote detection and imaging of objects at night. In accordance with the present invention, a laser is used to generate short pulses of infrared light with pulse widths on the order of nanoseconds. The laser light is expanded by optics and projected at the target scene. An intensified CCD (charge coupled device) camera is electronically shuttered after an appropriate time delay such that the image formed by the camera is composed of infrared light backscattered by the target from a range of r.

Abstract: An improved imaging light detection and ranging (lidar) system is presented which provides variable time delay range gating across a selected image. Variable time delay range gating across an image is accomplished using a plurality of imaging cameras which are individually triggered after preselected delays to obtain multiple subimages. These multiple subimages are then put together in a mosaic in a computer to provide a complete image of a target plane using only one light pulse.

Abstract: A novel timing control method is utilized in conjunction with an imaging lidar system of the type disclosed in U.S. Pat. No. 4,862,257. This novel timing control is employed in applications wherein the lidar system is mounted on an airborne platform. The timing control method of this invention completely eliminates the glint detector with associated signal conditioner used in the system of U.S. Pat. No. 4,862,257, and instead, relies upon a signal derived from the aircraft altimeter to continually provide platform altitude status. Since the entire system is under the control of a computer, the altimeter signal can be interpreted and used to adjust total delay so as to automatically track changing platform altitude. It is now possible to initiate all timing from the occurrence of the laser "lamp fire" signal. The total delay to camera "gate on" is now the "lamp-to-laser" delay, plus round trip platform altitude delay (computer from the altimeter signal), plus desired water depth delay, less system delays.

Abstract: A system is presented for the remote detection of the diffuse attenuation coefficient or K factor over very large areas and over relatively short time periods; and for determining depth in a body of water or other medium. In accordance with the present invention, a laser is used to generate short pulses of light with pulse widths on the order of nanoseconds. The laser light is expanded by optics and projected into the water or other medium. An intensified CCD (charge coupled device) camera is electronically shuttered after an appropriate time delay such that the image formed by the camera is composed of light backscattered by the water from a layer of range z and a thickness of .DELTA.z. The signal detected by the camera is S.sub.i. If several measurements of S.sub.i are made at known time delay differences such that the differences of range gates z.sub.i are also known, then K can be calculated.