Radiation detector, imaging device and electrode structure thereof, and method for acquiring an image
The present invention discloses a radiation detector, an imaging device and an electrode structure thereof, and a method for acquiring an image. The radiation detector comprises: a radiation sensitive film, a top electrode on the radiation sensitive film, and an array of pixel units electrically coupled to the radiation sensitive film. Each pixel unit comprises: a pixel electrode (which is configured to collect a charge signal in a pixel area of the radiation sensitive film), a storage capacitor, a reset transistor, a buffer transistor, a column strobe transistor, and a row strobe transistor. The column strobe transistor and the row strobe transistor are connected in series between the buffer transistor and the signal line, and transfer the voltage signal of the corresponding pixel unit in response to a column strobe signal and a row strobe signal. The radiation detector may be used for, for example, X-ray digital imaging.
1. A method for acquiring an image by using a radiation detector comprising the steps of:
a) applying a reset signal to each column of an array of pixel units to reset all pixel units;
b) turning off reset transistors, column strobe transistors and row strobe transistors of all the pixel units, collecting charge signals by pixel electrodes, and accumulating the charge signals on storage capacitors;
c) applying a column strobe signal to a first column of pixel units after a predetermined integrating time is reached, and then applying row strobe signals to corresponding pixel units in the first column sequentially, thereby turning on the column strobe transistor and the row strobe transistor of a corresponding pixel unit, so that electric potentials of pixel electrodes in the first column of pixel units are read one by one as sensing signals;
d) turning off the column strobe transistor and the row strobe transistors of the first column of pixel units, and applying a reset signal to the first column, thereby turning on the reset transistors of the first column of pixel units, that is, resetting the first column of pixel units;
e) turning off the reset transistors of the first column of pixel units, applying a column strobe signal to the first column of pixel units, and then applying row strobe signals to the corresponding pixel units in the column sequentially, thereby turning on the column strobe transistor and the row strobe transistor of the corresponding pixel unit, so that the electric potentials of the pixel electrodes of the first column of pixel units are read one by one as background signals;
f) repeating steps c) to e), and for other columns, reading the charge signals collected on the pixel electrodes on a pixel-by-pixel basis;
g) obtaining a frame of image by data processing after reading all the pixels, wherein, steps c) to g) are repeated to acquire multiple consecutive frames of images; and
h) applying a constant second bias voltage to a top electrode of a radiation sensitive film between each frame of image or several frames of images, so as to eliminate polarization phenomenon of the detector during an operation procedure, wherein a polarity of the second bias voltage is opposite to a polarity of a first bias voltage is applied to the top electrode of the radiation sensitive film.
2. The method according to claim 1 , wherein, the step g) further comprises subtracting the background signals from the sensing signals.
3. The method according to claim 1 , wherein, during step a) to step g), the first bias voltage is applied to the top electrode of the radiation sensitive film, so that a collecting electric field with a sufficient intensity is formed in a sensitive region of the radiation detector.
4. The method according to claim 3 , wherein, the first bias voltage is a negative bias voltage.
5. The method according to claim 3 , wherein, the first bias voltage is a positive bias voltage.