US 5,510,626 AGranted

System and method for conditioning a radiation detector

AssigneeMinnesota Mining and Manufacturing Company

InventorsOwen L. Nelson, Jathan D. Edwards, Earl L. Cook, Padmanabham A. Arimilli

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Abstract

A system and method for conditioning a photoconductive radiation detector achieve charge redistribution within a photoconductive layer without the need for charge removal or charge injection techniques. A first conditioning voltage is applied across the detector to establish a first electric field. The first electric field is reversed relative to fields applied to the detector during image exposure and image read-out operations. While the first conditioning voltage is maintained, the photoconductive layer is exposed for a period of time to first conditioning radiation having one or more wavelengths selected to penetrate at least a portion of the photoconductive layer. A second conditioning voltage, less than the first conditioning voltage, then can be optionally applied across the detector to establish a forward bias electric field. While the second conditioning voltage is maintained, the photoconductive layer is exposed for a period of time to second, broad spectrum conditioning radiation. The detector can then be placed in a dark environment for a period of time, in a shorted condition, to dark-adapt the photoconductive layer.

Claims52

Dependent claims

A method for conditioning a radiation detector having a first conductive layer, a photoconductive layer disposed adjacent said first conductive layer, an insulative layer disposed adjacent said photoconductive layer opposite said first conductive layer, and a second conductive layer disposed adjacent said insulative layer opposite said photoconductive layer, said radiation detector forming a latent image in response to both application of an image exposure voltage across said first conductive layer and said second conductive layer and exposure of said detector to imaging radiation, and said latent image being read out during application of an image readout voltage across said first conductive layer and said second conductive layer and exposure of said detector to readout radiation, the conditioning method comprising the steps of:

applying a first conditioning voltage across said first conductive layer and said second conductive layer, said first conditioning voltage having a polarity opposite to a polarity of both said image exposure voltage and said image readout voltage, wherein said first conditioning voltage establishes a first electric field across said photoconductive layer;
exposing said photoconductive layer to first conditioning radiation having one or more wavelengths selected to penetrate at least a portion of said photoconductive layer, thereby releasing charge carriers trapped within said photoconductive layer to transport within said first electric field;
applying a second conditioning voltage across said first conductive layer and said second conductive layer, an absolute value of said second conditioning voltage being less than said first conditioning voltage, wherein said second conditioning voltage establishes a second electric field across said photoconductive layer in a direction opposite to said first electric field;
exposing said photoconductive layer to second conditioning radiation, wherein said photoconductive layer comprises a photoconductive material having an absorption edge, said second conditioning radiation including radiation having wavelengths less than a wavelength corresponding to said absorption edge;
and
dark-adapting said photoconductive layer.

3 more elements

A method for conditioning a radiation detector having a first conductive layer, a photoconductive layer disposed adjacent said first conductive layer, an insulative layer disposed adjacent said photoconductive layer opposite said first conductive layer, and a second conductive layer disposed adjacent said insulative layer opposite said photoconductive layer, said radiation detector forming a latent image in response to both application of an image exposure voltage across said first conductive layer and said second conductive layer and exposure to imaging radiation, and said latent image being read out during application of an image readout voltage across said first conductive layer and said second conductive layer and exposure of said detector to readout radiation, the conditioning method comprising the steps of:

applying a first conditioning voltage across said first conductive layer and said second conductive layer, said first conditioning voltage having a polarity opposite to a polarity of both said image exposure voltage and said image readout voltage, wherein said first conditioning voltage establishes a first electric field across said photoconductive layer;
and
exposing said photoconductive layer to first conditioning radiation having one or more wavelengths selected to penetrate at least a portion of said photoconductive layer, thereby releasing charge carriers trapped within said photoconductive layer to transport within said first electric field, wherein said photoconductive layer comprises a photoconductive material having an absorption edge, and said first conditioning radiation consists essentially of radiation having wavelengths greater than or equal to a wavelength corresponding to said absorption edge.

A method for conditioning a radiation detector having a first conductive layer, a photoconductive layer having amorphous selenium disposed adjacent said first conductive layer, an insulative layer disposed adjacent said photoconductive layer opposite said first conductive layer, and a second conductive layer disposed adjacent said insulative layer opposite said photoconductive layer, said radiation detector forming a latent image in response to both application of an image exposure voltage across said first conductive layer and said second conductive layer and exposure to imaging radiation, and said latent image being read out during application of an image readout voltage across said first conductive layer and said second conductive layer and exposure of said detector to readout radiation, the conditioning method comprising the steps of:

applying a first conditioning voltage across said first conductive layer and said second conductive layer, said first conditioning voltage having a polarity opposite to a polarity of both said image exposure voltage and said image readout voltage, and an absolute value of said first conditioning voltage being a factor of approximately 0.2 to 1.0 times an absolute value of said image readout voltage, wherein said first conditioning voltage establishes a first electric field across said photoconductive layer;
exposing said photoconductive layer to first conditioning radiation having one or more wavelengths selected to penetrate at least a portion of said photoconductive layer, thereby releasing charge carriers trapped within said photoconductive layer to transport within said first electric field, said first conditioning radiation including one or more wavelengths greater than or equal to 600 nanometers;
shorting said first conductive layer and said second conductive layer together to establish a second electric field across said photoconductive layer in a direction opposite to said first electric field;
exposing said photoconductive layer to second conditioning radiation, wherein said photoconductive layer comprises a photoconductive material having an absorption edge, said second conditioning radiation including radiation having wavelengths less than a wavelength corresponding to said absorption edge;
and
dark-adapting said photoconductive layer.

3 more elements

A system for conditioning a radiation detector having a first conductive layer, a photoconductive layer disposed adjacent said first conductive layer, an insulative layer disposed adjacent said photoconductive layer opposite said first conductive layer, and a second conductive layer disposed adjacent said insulative layer opposite said photoconductive layer, said radiation detector forming a latent image in response to both application of an image exposure voltage across said first conductive layer and said second conductive layer and exposure to imaging radiation, and said latent image being read out during application of an image readout voltage across said first conductive layer and said second conductive layer and exposure of said detector to readout radiation, the conditioning system comprising:

means for applying a first conditioning voltage across said first conductive layer and said second conductive layer, said first conditioning voltage having a polarity opposite to a polarity of both said image exposure voltage and said image readout voltage, wherein said first conditioning voltage establishes a first electric field across said photoconductive layer;
and
means for exposing said photoconductive layer to first conditioning radiation having one or more wavelengths selected to penetrate at least a portion of said photoconductive layer, thereby releasing charge carriers trapped within said photoconductive layer to transport within said first electric field, wherein said photoconductive layer comprises a photoconductive material having an absorption edge, and said first conditioning radiation consists essentially of radiation having wavelengths greater than or equal to a wavelength corresponding to said absorption edge.

A method for conditioning a radiation detector having a first conductive layer, a photoconductive layer disposed adjacent said first conductive layer, an insulative layer disposed adjacent said photoconductive layer opposite said first conductive layer, and a second conductive layer disposed adjacent said insulative layer opposite said photoconductive layer, said radiation detector forming a latent image in response to both application of an image exposure voltage across said first conductive layer and said second conductive layer and exposure to imaging radiation, and said latent image being read out during application of an image readout voltage across said first conductive layer and said second conductive layer and exposure of said detector to readout radiation, the conditioning method comprising the steps of:

applying a first conditioning voltage across said first conductive layer and said second conductive layer, said first conditioning voltage having a polarity opposite to a polarity of both said image exposure voltage and said image readout voltage, wherein an absolute value of said first Conditioning voltage is a factor of approximately 0.2 to 1.0 times an absolute value of said image readout voltage, and wherein said first conditioning voltage establishes a first electric field across said photoconductive layer;
and
exposing said photoconductive layer to first conditioning radiation having one or more wavelengths selected to penetrate at least a portion of said photoconductive layer, thereby releasing charge carriers trapped within said photoconductive layer to transport within said first electric field.

means for applying a first conditioning voltage across said first conductive layer and said second conductive layer, said first conditioning voltage having a polarity opposite to a polarity of both said image exposure voltage and said image readout voltage, wherein an absolute value of said first conditioning voltage is a factor of approximately 0.2 to 1.0 times an absolute value of said image readout voltage, and wherein said first conditioning voltage establishes a first electric field across said photoconductive layer;
and
means for exposing said photoconductive layer to first conditioning radiation having one or more wavelengths selected to penetrate at least a portion of said photoconductive layer, thereby releasing charge carriers trapped within said photoconductive layer to transport within said first electric field.

Dependencies are inferred from the claim text.