Lag compensating X-ray detector and method of driving the same

1. An X-ray detecting system, comprising:

an X-ray detector comprising:

a plurality of photo-sensing pixels, each of the photo-sensing pixels comprising to photodiode that generates an electrical detection signal corresponding to an incident light and a switching device that transmits the detection signal;

a gate driver sequentially applying gate pulses to the switching, devices of the photo-sensing pixels via a plurality of gate lines, the switching devices of the photo-sensing pixels being turned on by the gate pulses; and

a read-out integrated circuit reading out the detection signal generated from the plurality of photo-sensing pixels; and

a signal processing unit reading the detection signal output from the read-out integrated circuit and producing a diode signal level from the detection signal, the signal processing unit storing a decay curve of each of the photo-sensing pixels, the decay curve representing a decay tendency of the diode signal level according to a number of gate scans, the detection signal sequentially including an offset image, an X-ray image following the offset image, and a dark image following the X-ray image, the incident light being applied to the photo-sensing pixels during a time period between the offset image and the X-ray image, the signal processing unit setting the diode signal level at a signal level of the X-ray image if the signal level of the X-ray image is less than a signal saturation level, the signal processing unit setting, the diode signal level at a signal level of the decay curve corresponding to a signal level of the dark image if the signal level of the X-ray image is no less than the signal saturation level, the gate driver sequentially applying gate pulses to the gate lines to perform at least one gate scan during a time period between the X-ray image and the dark image.

2. The X-ray detecting system of claim 1 , wherein the signal processing unit storing a fitting curve of each of the photo-sensing pixels, the fitting curve representing a rate of an image lag according to the number of gate scans, the signal processing unit setting an image lag of the X-ray image at a value of the fitting curve corresponding to the diode signal level.

3. The X-ray detecting system of claim 2 , wherein the signal processing unit comprises:

a diode signal level calculating unit calculating the diode signal level from the X-ray image and the dark image using the decay curve;

an image lag estimating unit estimating the image lag of the X-ray image from the diode signal level using the fitting curve; and

an image lag compensating unit subtracting the image lag of the X-ray image from the X-ray image to obtain an image lag compensated X-ray image.

4. The X-ray detecting system of claim 3 , wherein the signal processing unit further comprises:

a decay curve storing unit storing the decay curve; and

a fitting curve storing unit storing the fitting curve.

5. The X-ray detecting system of claim 3 , wherein the signal processing unit further comprises an offset image removing unit subtracting the offset image from the X-ray image or from the image lag compensated X-ray image to remove the offset image from the X-ray image.

6. The X-ray detecting system of claim 2 , wherein the decay curve and the fitting curve vary according to the photo-sensing pixel.

7. A method of driving an X-ray detecting system, the method comprising:

exposing an X-ray detector to an X-ray;

obtaining an X-ray detection signal in the X-ray detector;

outputting the detection signal from the X-ray detector to a signal processing unit, the detection signal output to the signal processing unit sequentially including an offset image, an X-ray image following the offset image, and a dark image following the X-ray image, a plurality of photo-sensing pixels of the X-ray detector being exposed to the X-ray during a time period between the offset image and the X-ray image;

setting a diode signal level at a signal level of the X-ray image if the signal level of the X-ray image is less than a signal saturation level;

setting the diode signal level at a signal level of a decay curve corresponding to a signal level of the dark image if the signal level of the X-ray image is no less than the signal saturation level, the signal processing unit storing a decay curve of each of the plurality of photo-sensing pixels of the X-ray detector, the decay curve representing a decay tendency of the diode signal level according to a number of gate scans; and

performing at least one gate scan during a time period between the X-ray image and the dark image.

8. The method of claim 7 , wherein the signal processing unit stores a fitting curve of each of the photo-sensing pixels of the X-ray detector, the fitting curve representing a rate of an image, lag according to the number of gate scans, the method further comprising setting an image lag of the X-ray image at a value of the fitting curve corresponding to the diode signal level.

9. The method of claim 8 , further comprising subtracting the image lag of the X-ray image from the X-ray image to obtain an image lag compensated X-ray image.

10. The method of claim 9 , further comprising subtracting the offset image from the X-ray image or from the image lag compensated X-ray image to remove the as et image from the X-ray image.

11. The method of claim 8 , wherein the decay curve and the fitting curve vary according to the photo-sensing pixel.