초록 ▼

An imaging system incorporating a scanned array of infrared detectors for presentation of scene data on a display includes gain normalization circuitry coupled to individual ones of the detectors of the detector array. The normalization circuitry is structured as a feedback loop introducing euality

An imaging system incorporating a scanned array of infrared detectors for presentation of scene data on a display includes gain normalization circuitry coupled to individual ones of the detectors of the detector array. The normalization circuitry is structured as a feedback loop introducing euality between the magnitude of an average value of a detector signal and a reference signal. The imaging system comprises a set of channels connecting with respective ones of the detectors, each channel having adaptive gain control circuitry. A common value of the reference signal is applied to each channel for uniformity in a displayed image. The averaging time is several times greater than the duration of a single scan in the scanning of the detector array so as the display is relatively free of nonuniformities associated with differing responsivities of the detectors to infrared radiation. A nonlinear gain function is produced by connection of multipliers and/or logarithmic circuitry in a forward branch of the loop. A feed forward branch includes a filter coupled to the multipliers for adaptive accentuation of higher frequencies of the signal spectrum to enhance subject edge lines. A noise reduction circuit reduces a maximum value of gain for low incremental values of detector signal to exclude noise where signal data is substantially absent.

대표청구항 ▼

An imaging system comprising: an array of radiation detectors arranged along the vertical dimension of a scanning pattern; means for directing radiation from a subject, distant from said system, toward said array of detectors to permit a viewing of said subject by said system, said directing means i

An imaging system comprising: an array of radiation detectors arranged along the vertical dimension of a scanning pattern; means for directing radiation from a subject, distant from said system, toward said array of detectors to permit a viewing of said subject by said system, said directing means including means for scanning said radiation along a set of scan lines sweeping out adjacent regions of the subject with a scan interval of predetermined duration to provide a two-dimensional raster scan of a scene including said subject, each of said detectors providing a signal in response to radiation incident upon the detector; means for displaying data to be carried by signals of respective ones of said detectors to present an image of the scene containing said subject; signal processing means interconnecting said displaying means with said array of detectors, said signal processing means including gain normalizing means for amplifying individual ones of said detector signals with a gain varying inversely to average signal strength; wherein said normalizing means is configured as a feedback loop and includes nonlinear means for introducing a nonlinear gain characteristic, said normalizing means including enhancement means for clarifying edge lines of said subject, said nonlinear means coacting with said enhancement means to provide an adaptive enhancement characteristic dependent on the strength of signals from the corresponding detectors; and wherein said normalizing means includes noise reduction means coupled to said enhancement means for reducing the gain of said gain characteristic for near-zero incremental values of a detector signal.