Wide dynamic range digital imaging system and method
First Claim
1. A digital imaging device comprising:
- a top electrode layer;
a dielectric layer under the top electrode layer;
a sensor layer under the dielectric layer, comprising a photoconductive layer and a plurality of pixels, each pixel comprising a charge-collecting electrode;
a thin film transistor readout matrix connected to the charge-collecting electrodes; and
a variable power supply including a programmable controller, wherein the variable power supply under programmed control of the programmable controller provides voltages between the top electrode layer and the readout matrix of 3.0 kV to 1.5 kV, said voltages establishing electrical fields in said sensor layer between a minimum electrical field Ec, at which a signal-to-noise ratio of the device is relatively high but the device operates below a saturation point, and a higher electrical field E, at which the signal-to-noise ratio may be lower but is at least 50, and said programmable controller controls said variable power supply to provide a selected voltage between 3.0 kV and 1.5 kV suitable for attaining a desired signal-to-noise ratio for a selected object being imaged with said digital imaging device.
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Abstract
A digital x-ray imaging device and method. The imaging device comprises a top electrode layer; a dielectric layer; a sensor layer comprising a photoconductive layer and a plurality of pixels, each pixel comprising a charge-collecting electrode; a thin film transistor (TFT) readout matrix connected to the charge-collecting electrodes; and a variable power supply adapted to provide a range of voltages between the top electrode layer and the TFT readout matrix. The variable power supply may comprise a programmable power supply. The method comprises varying the voltage between the top electrode layer and the TFT readout matrix of a TFT-based direct digital x-ray imaging device to provide an acceptable signal-to-noise ratio over a greater range of exposures than provided at a single voltage. The method may be particularly useful in non-destructive testing applications.
23 Citations
16 Claims
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1. A digital imaging device comprising:
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a top electrode layer;
a dielectric layer under the top electrode layer;
a sensor layer under the dielectric layer, comprising a photoconductive layer and a plurality of pixels, each pixel comprising a charge-collecting electrode;
a thin film transistor readout matrix connected to the charge-collecting electrodes; and
a variable power supply including a programmable controller, wherein the variable power supply under programmed control of the programmable controller provides voltages between the top electrode layer and the readout matrix of 3.0 kV to 1.5 kV, said voltages establishing electrical fields in said sensor layer between a minimum electrical field Ec, at which a signal-to-noise ratio of the device is relatively high but the device operates below a saturation point, and a higher electrical field E, at which the signal-to-noise ratio may be lower but is at least 50, and said programmable controller controls said variable power supply to provide a selected voltage between 3.0 kV and 1.5 kV suitable for attaining a desired signal-to-noise ratio for a selected object being imaged with said digital imaging device. - View Dependent Claims (2, 3, 4, 5)
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6. A method for providing a broad dynamic range for a digital imaging device and controlling a signal-to-noise behavior of the device to maintain a signal-to-noise ratio of at least 50 and prevent saturation of the device, said device comprising a top electrode layer;
- a dielectric layer;
a sensor layer comprising a photoconductive layer and a plurality of pixels, each pixel comprising a charge-collecting electrode;
a thin film transistor readout matrix connected to the charge-collecting electrodes; and
a programmable controller programmed to control a power supply to supply a selected voltage between the top electrode layer and the readout matrix;
the method comprising varying the voltage between the top electrode and the readout matrix between 3.0 kV and 1.5 kV to provide signal-to-noise ratio of at least 50 over a range of exposures;
said step of varying said voltage comprising varying the voltage to establish clerical fields in said sensor between a minimum electrical field Ec at which the device has a relatively high signal-to-noise ratio but still remains below a saturation point, and a higher electrical field E, at which the device has a signal-to-noise ratio that may be lower but still is at least 50, and said varying further comprising ultimately setting said voltage at a level within said range suitable for attaining a desired signal-to-noise ratio for an object being examined with said device. - View Dependent Claims (7, 8, 9, 10)
- a dielectric layer;
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11. A method of operating a digital imaging device to image an object in a non-destructive testing process, said digital imaging device comprising a top electrode layer, a sensor layer comprising a photoconductive layer and a plurality of pixels, each pixel comprising a charge-collecting electrode, a thin film transistor readout matrix connected to the charge-collecting electrodes, and a programmable controller programmed to control a power supply to supply a selected voltage between the top electrode layer and the readout matrix;
- the method comprising the steps of selectively varying the voltage between the top electrode and the readout matrix to provide a signal-to-noise ratio of at least 50 over a range of exposures and to select a voltage within said range that establishes an electrical field in said sensor layer of at least a minimum value Ec and causes the digital imaging device to operate below a digital electronic saturation point, said selected voltage being suitable for attaining a selected signal-to-noise behavior for a selected object being imaged with said device in said non-destructive testing process.
- View Dependent Claims (12, 13, 14, 15, 16)
Specification