Arete Associates

J Kent Bowker

Stephen C Lubard

John W McLean

David N Sitter, Jr

Anthony D Gleckler

John M Wartman

Stephen G Miller

Clive Bolton

The system and method relate to detection of objects that are submerged, or partially submerged (e.g. floating), relative to a water surface. One aspect of the invention emits LIDAR fan-beam pulses and analyzes return-pulse portions to determine water-surface orientations and derive submerged-object images corrected for refractive distortion. Another defines simulated images of submerged objects as seen through waves in a water surface, prepares an algorithm for applying a three-dimensional image of the water surface in refractive correction of LIDAR imaging through waves&#x2014;and also models application of the algorithm to the images, and finally specifies the LIDAR-system optics. Yet another emits nearly horizontal pulses to illuminate small exposed objects at tens of kilometers, detects reflected portions and images successive such portions with a streak-tube subsystem. Still others make special provisions for airborne objects.

Lidar with streak-tube imaging, including hazard detection in marine applications; related optics

The system images the volume of a turbid medium and detects the contents. The medium can be water or air, or living tissue, or almost any other material which is at least partially light-transmissive. The system includes a light source for producing a series of discrete fan-shaped pulse beams that are substantially uniform in intensity or have been peaked at the edges of the fan to illuminate sections of the medium, a streak tube with a large, thin-slit-shaped photocathode for collecting the maximum amount of light from weak returns, a field-limiting slit disposed in front of the cathode for removing multiply scattered light, a large-aperture optical element for collecting and focusing the reflected portions of the pulse beam on the field-limiting slit and the cathode, and an array of detectors. A volume display of the medium is generated by translating the transmitter and receiver normal to the longitudinal axis of the pulse beam, to illuminate adjacent sections of the medium, and combining the sections to provide a volume display. All, or substantially all, of the light returned from each pulse beam is used. Vehicle motion can be used to provide the scan of the beam. Applications range from foggy sky surveillance at multiple-kilometer scale to location of fractional-millimeter tumors in a human breast.

Confocal-reflection streak lidar apparatus with strip-shaped photocathode, for applications at a wide range of scales

In some aspects of the invention, a LIDAR subsystem or other means at an elevated position emit thin fan-beam light pulses at a shallow angle, and detect reflected portions of the pulses at a like angle; a streak-tube subsystem or other means image successive reflected portions to detect objects, for example near a water craft if the elevated position is on such a craft (e.g., a mast or high bridge). In some aspects, the imaging means perform the imaging in a way that tightly localizes reflection from a water surface near the objects, to facilitate detecting the objects despite proximity to the surface. Some preferred embodiments apply a correction for energy reduction, or depth errors, near lateral ends of the fan beam; a lenslet array is preferred for applying the correction. Preferably the shallow angle is in a range of approximately one to fifteen degrees, more preferably approximately two to ten degrees, ideally roughly five degrees.

Lidar with streak-tube imaging,including hazard detection in marine applications; related optics

Surface relief of a finger is read using an optical-fiber prism unit, with fiber terminations at one end to contact the surface, and at the other for light passages along fibers from the first. Light enters where NA&lt;0.5 and fiber diameter is constant with longitudinal position. The device is in a 1.4-2 L case, with a battery or power unit, converter to form a corresponding data array for verifying, digital signal processor to do the verifying, and output to indicate or implement a decision. The optical fiber prism unit has a substantially circular cylindrical wall defining a longitudinal axis, fused optical fibers parallel to the longitudinal axis, a traverser face for output of a skin pattern image from the prism and a generally elliptical angled face for contacting such a skin pattern.

Economical skin-pattern-acquisition and analysis apparatus for access

Surface relief of a finger etc. is read using an optical-fiber prism unit, with fiber terminations at one end to contact the surface, and at the other for light passage along fibers from the first. Light enters where NA&lt;0.5 and fiber diameter is constant with longitudinal position. The device is in a 1.4-2 L case, with a battery or power input, converter to form a corresponding data array for verifying, digital signal processor to do the verifying, and output to indicate or implement a decision. A video controller (with custom-programmed logic circuit) operates the sensors to develop the data array; an ADC digitizes the array; memory holds an authorized-user skin-pattern template, firmware for the processor, and data used in verifying; an output register holds the decision signal--all on a control, address, and data bus. High-power, radiative elements and a fast high-impedance data reader are on a common board in an isolating layout. The prism unit is cylindrical, held by a cylindrical-section cradle and forming a novel condenser lens to support lights and couple light to the prism. The imager has a cylindrical wall, transverse face for output of a skin pattern, and angled elliptical face to contact skin. To make many optical-fiber prisms each with one transverse and one angled face, transverse and angled cuts through a fused-fiber cylinder are alternated. The verifier can be within, and respond to the analysis to control, a door handle or lock: a hand need not move from reading position to open the door.

At a first end of an optic-fiber prism assembly are fiber terminations to contact a relieved surface, e. g. finger (stabilized by a handgrip). In a region where fiber diameter is essentially constant with longitudinal position, light enters the prism, crosses the fibers and enters individual fibers through their sidewalls, lighting the terminations. To allow crosslighting of the assembly, the fiber-optic numerical aperture (NA) is small: preferably not exceeding one-half. Due to fingerprint etc. detail, fractions of light pass along the fibers; at the assembly second end a detector responds with an electrical-signal array based on the surface relief. The signals are processed to check finger etc. identity and applied to control access to a personal weapon, other equipment, facilities, data, or a money service. FTIR ('frustrated total internal reflection') bright- and dark-field versions have various benefits. For use of small, low-cost detectors--and/or internal-mirror versions that light the finger straight-on--the assembly has a separate element, e. g. a high-NA fiber-optic taper with extramural absorption or 'EMA' material (no entry light crosses it). For a weapon, a unitary antibypassing module (which matches a weapon port, and must be present) holds part of the access-control and firing systems. Bullets etc. fire only on a special signal from the module.

Fingerprint-acquisition apparatus for access control; personal weapon

At a first end of an optic-fiber prism assembly are fiber terminations to contact a relieved surface, e.g. finger (stabilized by a handgrip). In a region where fiber diameter is essentially constant with longitudinal position, light enters the prism, crosses the fibers and enters individual fibers through their sidewalls, lighting the terminations. To allow crosslighting of the assembly, the fiber-optic numerical aperture (NA) is small: preferably not exceeding one-half. Due to fingerprint etc. detail, fractions of light pass along the fibers; at the assembly second end a detector responds with an electrical-signal array based on the surface relief. The signals are processed to check finger etc. identity and applied to control access to a personal weapon, other equipment, facilities, data, or a money service. FTIR ('frustrated total internal reflection') bright- and dark-field versions have various benefits. For use of small, low-cost detectors--and/or internal-mirror versions that light the finger straight-on--the assembly has a separate element, e.g. a high-NA fiber-optic taper with extramural absorption or 'EMA' material (no entry light crosses it). For a weapon, a unitary antibypassing module (which matches a weapon port, and must be present) holds part of the access-control and firing systems. Bullets etc. fire only on a special signal from the module.

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Essex, MA, United States of America

J Kent Bowker