Raytheon Company

Santa Barbara Research Center

Hughes Electronics Corporation

William A Radford

Adam M Kennedy

Michael S Ray

Michael D Jack

Paul R Norton

Richard H Wyles

Jerry A Wilson

Robert K Dodds

Daniel F Murphy

Jessica K Wyles

In certain embodiments, a detection device includes a structure having an entrance that permits radiation to enter the structure and a radiation detector operable to detect radiation that enters the structure. The device also includes a microshutter array coupled to the structure and aligned with the entrance, the array comprising a plurality of microshutter cells operable to move between a first position in which that microshutter cell prevents radiation of a first wavelength from passing through a portion of the entrance and a second position in which that microshutter cell permits the radiation of the first wavelength to pass through the portion of the entrance. The device further includes an actuating device operable to define a first entrance pupil having a first f-number by moving a plurality of microshutter cells associated with the first f-number.

Variable aperture optical device having a microshutter

A focal plane array (FPA) of infrared (IR) radiation detectors ( ), such as an array of microbolometers, includes an active area ( A) containing a plurality of IR radiation detectors, a readout integrated circuit (ROIC) ( ) that is mechanically and electrically coupled to the active area and, disposed on the ROIC, a plurality of heater elements ( A) that are located and operated so as to provide a substantially uniform thermal distribution across at least the active area. The FPA further includes a plurality of temperature sensors ( B), individual ones of which are spatially associated with one of the heater elements for sensing the temperature in the vicinity of the associated heater element for providing closed loop operation of the associated heater element. In one embodiment pairs of the heater elements and associated temperature sensors are distributed in a substantially uniform manner across at least a top or a bottom surface of the ROIC, while in another embodiment pairs of the heater elements and associated temperature sensors, or only the heater elements, are distributed in accordance with a predetermined thermal profile of the FPA. The plurality of heater elements may each be composed of a silicon resistance, and the plurality of temperature sensors may each be each composed of a silicon temperature sensor.

Method and apparatus providing focal plane array active thermal control elements

A microbolometer detector element (10) for a focal plane array is provided including an optically absorptive material structure (12) characterized by an electrical resistivity that varies as a function of its temperature coupled in spaced relation to a thermal isolation structure (20). The thermal isolation structure (20) is coupled in spaced relation to a sensor (34) connected to the optically absorptive material structure (12) for sensing the absorptive structure's (12) electrical resistivity. The thermal isolation structure (20) facilitates very high fill factors even when the pixel size is shrunk below the baseline fifty micron size. The thickness of the optically absorptive material structure (12) and the thermal isolation structure (20) can be independently controlled since the thermal isolation structure (20) is disposed in spaced relation under the absorptive material structure (12). The thermal isolation structure (20) can be made several times longer than prior art designs to increase the thermal isolation of the optically absorptive material structure (12) and to increase pixel responsivity. The thermal isolation structure (20) may include a planar member (26) for reflecting incident optical radiation not absorbed by the absorptive material (12) back to the absorptive material (12). In a preferred embodiment of the present invention, the absorptive structure (12) is a polycrystalline semiconductive layer supported above the thermal isolation structure (20) by downwardly projecting leg members (18). The thermal isolation structure (20) also includes downwardly projecting leg members (28) for supporting it in spaced relation above a silicon substrate surface (30) overlying an integrated readout circuit (34).

Advanced small pixel high fill factor uncooled focal plane array

An array of photodetectors is constructed of IR radiation-responsive Group II-VI alloy semiconductor material, such as HgCdTe. A novel photodetector structure utilizes internal reflections from mesa (10, 10') sidewalls and/or from reflective material (22) that is applied to the mesa sidewalls to achieve a concentration of incident infrared radiation into a significantly smaller radiation absorbing region (16). The resulting self-focusing or light piping effect enables the leakage current and other noise-generating processes to be minimized, while providing an effective large optical collection area. The fabrication of specular, flat, sloped mesa sidewalls is preferably accomplished by a reactive ion etch process. Signal crosstalk between photodetectors is reduced or eliminated since the radiation absorbing regions are fully delineated and isolated from one another by deep trenches that define the mesa sidewalls. Thus, the diffusion of optically generated carriers from one photodetector to an adjacent photodetector is prevented.

Self-focusing detector pixel structure having improved sensitivity

An integrated photovoltaic detector includes a reference photovoltaic detector and an active photovoltaic detector in a series connection. The reference detector produces a dark current that opposes the active detector's dark current. The active detector effectively masks the reference detector from incident illumination so that the active detector produces photocurrent but the reference detector does not. The band gap of the reference detector is preferably matched to the active detector so that their dark currents are substantially matched over a temperature range. As a result, the current read out of the integrated detector at the series connection is approximately equal to the photocurrent generated by the active detector. This improves the detector's SNR, signal resolution, and useful operating temperature range.

Photovoltaic detector with integrated dark current offset correction

A method for fabricating a plurality of semiconductor photodetectors and an array of same produced by the method. The method includes a first step of selectively removing semiconductor material to form a channel within a semiconductor material for physically isolating a first photodetector from a second photodetector, the semiconductor material having a characteristic energy bandgap. The method includes a second step of selectively increasing the carrier concentration of the semiconductor material within a bottom region of the channel for preventing minority charge carriers from diffusing under the channel from a region associated with the first photodetector to a region associated with the second photodetector. The step of selectively removing is accomplished by the steps of providing a patterned mask upon the semiconductor material and selectively removing the underlying semiconductor material through an opening within the mask. The step of selectively increasing the carrier concentration includes a step of ion implanting the semiconductor material through the opening within the mask.

Growing community of inventors

Santa Barbara, CA, United States of America

William A Radford