Raytheon Company

Casey T Streuber

Kent P Pflibsen

Michael P Easton

Michael Kennedy Burkland

Page Elizabeth King

Kristofer E Tvedt

A Semi-Active Laser sensor for determining a line-of-site to a target includes: a receiver for receiving a plurality of target pulses; a processor for starting a target track for pulses that cross a noise threshold opening a pulse gate within the target track; and for every laser pulse received within the pulse gate crossing the noise threshold, determining a time index relative to the pulse gate center; and a memory for storing the pulses that cross the noise threshold and their respective time index, wherein the processor further temporally offsets the stored pulses based on their corresponding time indexes, sums the offset pulses together to generate a summed pulse signal, and determines the line-of-sight error to the target from the summed pulse signal.

Semi-active laser pulse stacking

A spectrally-scanned hyperspectral EO sensor trades the temporal properties of spectral information content for instantaneous situation awareness by capturing an image frame and scanning the spectral scene (wavelength) to build up spectral content. The objective optical system, preferably including a chromatic aberration enhancing device, separates spectral components of the incident radiation. A focus cell is used to adjust a relative axial focus position of the objective optical system with respect to a detector to at least two different axial focus positions to adjust the image position and read out an image frame for a spectrally-weighted component. A processor computes a relative spatial image contrast from a plurality of image frames at different wavelengths as a function of encoded focus cell position. A mechanism may be configured to move the enhancing device in and out of the optical path to form a dual gray-scale and hyperspectral EO sensor. Existing sensors may be retrofit to form the hyperspectral or dual-mode EO sensor.

Spectrally-scanned hyperspectral electro-optical sensor for instantaneous situational awareness

An EO sensor is configured to time multiplex a primary optical channel that provides high detection sensitivity to maintain high SNR and a multi-filtered optical channel that provides detection in different measurement bands (e.g. spectral, polarization, amplitude or phase). The channels may, for example, be time multiplexed based on range to target or within each integration period of the EO sensor. The multi-filtered optical channel uses a field directing array to sample the FOV to form different optical sub-channels that are filtered by different optical filters. These sub-channels may be spatially multiplexed onto different sub-regions of the detector or may be time multiplexed onto the entire detector. The light modulator used to time multiplex the primary and multi-filtered optical channels may be used to time de-multiplex spatially overlapping regions of the FOV onto a pixel of the detector in order to detect high spatial resolution images with low resolution detectors.

Time-multiplexed broadband and multi-filtered electro-optic sensor

A shared-aperture EO imaging and ranging sensor is implemented by time multiplexing an optical imaging channel and an optical ranging channel. The optical ranging channel is allocated the 'unused portion' of each frame; that portion of the frame that is reserved from electronics processing of the imaging channel. The electronics processing of ranging channel is performed during the integration period of the next frame. This allows ranging to be provided without sacrificing the performance of the imaging channel. Ranging may be provided using either 'coded aperture' or &#x201c;wavefront coding&#x201d;.

Shared-aperture electro-optic imaging and ranging sensor

A digitally scanned multi-cell EO sensor comprises a low-resolution multi-cell imaging detector. An array of optical focusing elements decomposes the sensor's FOV into at least four sub-fields. A sub-field directing array and focusing optic direct the optical radiation onto the imaging detector. In a first tilt mode, the optical radiation from the sub-fields is directed into at least four spatially separated sub-regions that each map to a different detector cell. A high-resolution spatial light modulator (SLM) digitally scans the FOV to select different portions of the FOV to map onto the different detector cells to time demultiplex spatially overlapping portions of the FOV onto each detector cell to stitch together a sub-image of a selected area of the FOV up to the native resolution of the SLM.

Digitally scanned multi-cell electro-optic sensor

A discrete wavefront measurement device uses a variable transmission filter (VTF) to decouple the dynamic range of tilt angle measurements in the wavefront from the spatial sampling resolution and the measurement sensitivity as regards the physics of the readout. This approach allows the discrete wavefront measurement device to be configured to a specified dynamic range, transverse sampling resolution and measurement sensitivity at low cost.

Discrete wavefront sampling using a variable transmission filter

A motionless focus evaluation test station is provided for measuring detector position error of EO sensors that do not possess dynamic focus capability. A positionally-fixed source emits EM radiation that diverges along an optical axis of the test station. Collimating optics collimate the EM radiation and direct it along the optical axis to the EO sensor. A positionally-fixed target is placed in the path of the diverging EM radiation nominally at the focal plane of the collimating optics. The target comprises a limiting aperture that exhibits an induced shift in optical focus at different positions along the aperture such that different positions on the target are imaged to different focal planes at the detector. The detector captures an image of the target that is blurred to either side of the spatial position that is optically conjugate to the actual detector position. A processor processes the image to measure the blur as function of spatial position to measure the actual detector position and output detector position error from a desired detector position.

Motionless focus evaluation test station for electro-optic (EO) sensors

A system and method for wavefront measurement of an EO sensor is performed in-situ using the sensor's EO detector in a manner that disambiguates the local wavefront measurements for different sub-pupils in time and maximizes the dynamic range for measuring the local wavefronts. A single sub-pupil sized optical beam is traced in a spatial pattern over the EO sensor's entrance pupil to serially illuminate a temporal sequence of sub-pupils to form a serially addressed sub-pupil screen. The EO detector and video card capture a video signal for one sub-pupil at a time as the optical beam traces the spatial pattern. The video signal is routed to a computer processor that generates a spatio-temporal mapping of the spatial positions of the sub-pupils in the sub-pupil screen to the temporal positions of frames in the video signal. The computer processor uses the mapping to process the video signal to compute a wavefront estimate spanning the entrance pupil.

Serially addressed sub-pupil screen for in situ electro-optical sensor wavefront measurement

A dual-mode sensor uses the active guidance radiation as a 'guide star' to generate a wavefront error estimate for the primary optical element in-situ without interfering with the generation of either the active guidance or passive imaging guidance signals. An array of optical focusing elements performs the normal function of spatially encoding an angle of incidence of the active guidance radiation at an entrance pupil onto an active imaging detector. The array also performs an additional function of spatially encoding wavefront tilt deviations emanating from sub-pupils of an exit pupil onto the active imaging detector. A processor processes the electrical signals from the imaging detector in accordance with the respective spatial encodings to generate an active guidance signal and the wavefront error estimate for the primary optical element.

Dual-mode electro-optic sensor and method of using target designation as a guide star for wavefront error estimation

A radiation detector includes material for absorbing incident radiation, and for providing a response to heating caused by the absorption of photons from the incident radiation. The radiation detector may include multiple pixels, each with one or more layers of absorbing material. The absorbing material may include black (microstructured) silicon, which has the advantage of being a good absorber of radiation in the short wave infrared (SWIR) wavelengths (as well as ultraviolet (UV) wavelengths and visible light wavelengths). The radiation detector may include multiple pixels, each separately responding to radiation incident on that pixel, and each including black silicon (as well as possibly other absorptive materials). The pixels of the detector may each have cantilevered attachment to a frame of the detector, with differences in coefficient of thermal expansion of materials of the pixels causing deflection of parts of the pixels due to heating from absorption of radiation.

Radiation detector with microstructured silicon

A SAL seeker focuses laser energy reflected off a target into a spot on the surface of a multi-segment non-imaging detector. A matched filter is responsive to the normalized detector response to estimate an angle measurement to the target. The matched filter is particularly well-suited for use in wide FOV systems as it unambiguously selects the angle measurement over the extended FOV whereas the conventional centroid calculation introduces ambiguity. The centroid calculation and angle selection may be used to improve the search and selection of the matched filter. Alternately, the matched filter may be used to disambiguate the angle selection based on the centroid calculation.

Angle measurement for a wide field-of-view (WFOV) semi-active laser (SAL) seeker

A fixed-source array test station provides a cost-effective high-throughput test bed for testing optical sensors that require stimulus at fixed angular positions. A SAL seeker requires stimulus at fixed angular position across its FOV to calibrate its spatial transfer function (STF). An array of fixed collimated sources at different angular positions is aligned so that their beams overlap the entrance pupil of the sensor under test. Each source may comprise an inexpensive light emitting diode (LED) or vertical cavity surface emitting laser (VCSEL) and collimator. To simplify alignment the sources may be positioned on and perpendicular to the surface of a sphere with the seeker's entrance pupil located at the center of the sphere. The sources are activated in accordance with an activation profile in order to calibrate or otherwise test the sensor.

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Tucson, AZ, United States of America

Casey T Streuber