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US 6,642,496 B1Granted
Two dimensional optical shading gain compensation for imaging sensors
AssigneeRaytheon Company
InventorDavid J. Gulbransen
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AssigneeRaytheon Company
InventorDavid J. Gulbransen
Estimating the term…
In a first aspect of these teachings there is provided a radiation sensor that includes sensor optics having an entrance aperture and a two dimensional array of unit cells (10) spaced away from the aperture. Each unit cell includes a radiation detector (D1) having an output coupled to an input of a gain element, and each gain element is constructed so as to have at least one component with a value selected to set the gain of the gain element to a value that is a function of the unit cell's location along an x-axis and along a y-axis within the two dimensional array. In this manner a compensation is made for a variation of scene illumination across the two dimensional array, where the variation in scene illumination results from a relative intensity of the energy impinging on a unit area of the two dimensional array that varies, for example, by the fourth power of cosine θ, where θ is an angle referenced to an optical axis of the radiation sensor. In a further aspect the radiation sensor includes a plurality of column readout circuits individual ones of which are switchably coupled to individual ones of the unit cells of one of the columns of unit cells. Each of the column readout circuits is constructed to have a first stage having a gain element with a-least one component that has a value selected to set the gain of the gain element to a value that is a function of the location of the column within the two dimensional array, and is further constructed to include a second stage having an input coupled to the first stage. The second stage includes a gain element having a gain that is varied as a function of a location within the two dimensional array of a row of unit cells that is being readout. In this case a combination of the gain of the first stage and the gain of the second stage compensates for a variation of scene illumination across the two dimensional array, where the variation in scene illumination results from the relative intensity of the energy impinging on the unit area of the two dimensional array that varies by the fourth power of cosine θ.
A radiation sensor comprising sensor optics having an entrance aperture and a two dimensional array of unit cells spaced away from said aperture, each said unit cell comprising a radiation detector having an output coupled to an input of a gain element, each gain element comprising a least one component having a value selected to set the gain of said gain element to a value that is a function of the unit cell's location along an x-axis and along a y-axis within said two dimensional array for compensating for a variation of scene illumination across said two dimensional array, where the variation in scene illumination results from a relative intensity of the energy impinging on a unit area of the two dimensional array.
A radiation sensor comprising sensor optics having an entrance aperture and a two dimensional array of unit cells arranged in y rows and x columns of unit cells and spaced away from said aperture, each said unit cell comprising a radiation detector having an output coupled to an input of a gain element, said radiation sensor further comprising a plurality of column readout circuits individual ones of which are switchably coupled to individual ones of unit cells of one of said columns of unit cells, each said column readout circuit comprising a first stage having a gain element comprising a least one component having a value selected to set the gain of said gain element to a value that is a function of the location of the column within said two dimensional array, and a second stage having an input coupled to said first stage, said second stage comprising a gain element having a gain that is varied as a function of a location within said two dimensional array of a row of unit cells that is being readout, wherein a combination of the gain of said first stage and a gain of said second stage compensates for a variation of scene illumination across said two dimensional array, where the variation in scene illumination results from a relative intensity of the energy impinging on a unit area of the two dimensional array.
A method for operating a radiation sensor comprising sensor optics having an entrance aperture and a two dimensional array of unit cells arranged in y rows and x columns of unit cells and spaced away from said aperture, where each said unit cell comprises a radiation detector having an output coupled to an input of a gain element and where said radiation sensor further comprises a plurality of column readout circuits individual ones of which are switchably coupled to individual ones of unit cells of one of said columns of unit cells, comprising:
Dependencies are inferred from the claim text.