Pixel circuit, imaging integrated circuit, and method for image information acquisition
View Patent ↗A pixel circuit uses two storage transistors to store two image signal samples, which include a reference signal produced by background noise of the pixel circuit and a signal produced by optical exposure of a photodetector and the background noise of the pixel circuit. An imaging integrated circuit uses a pixel circuit array, which may contain a number of such pixel circuits, and a charge acquisition circuit configured to read out image information obtained by the pixel circuit array. The charge acquisition circuit uses a first amplifier and a serially connected differential integrator that includes a second amplifier, a first differential integrator section and a second differential integrator section for the read out. A method for image information acquisition involves obtaining image information using the pixel circuit array and reading out the image information obtained by the pixel circuit array using the charge acquisition circuit.
1. An imaging integrated circuit, the imaging integrated circuit comprising:
a pixel circuit array, wherein the pixel circuit array comprises a plurality of pixel circuits, and wherein each pixel circuit of the plurality of pixel circuits is configured to store a reference signal produced by background noise of the pixel circuit and to store a signal produced by optical exposure of a photodetector of the pixel circuit and the background noise of the pixel circuit; and
a charge acquisition circuit configured to read out image information obtained by the pixel circuit array, wherein the charge acquisition circuit comprises:
a first amplifier;
a differential integrator connected in series with the first amplifier, wherein the differential integrator comprises:
a second amplifier, wherein the first amplifier is used as a common mode regulator for the second amplifier;
a first differential integrator section; and
a second differential integrator section,
wherein each of the first and second differential integrator sections includes a capacitor, a first switch, a second switch, and a third switch, wherein the capacitor is connected in series with the second switch, the first switch is connected in parallel with the capacitor and the second switch, and the third switch is connected to the capacitor, the second switch and a common mode reference voltage terminal, and wherein the first switch and the third switch are controlled by a first control signal and the second switch is controlled by a second control signal.
2. The imaging integrated circuit of claim 1 , wherein the charge acquisition circuit further comprises:
a second integrator that includes a third amplifier;
a third integrator that includes a fourth amplifier;
first and second storage capacitors coupled to the second integrator and the differential integrator; and
third and fourth storage capacitors coupled to the third integrator and the differential integrator.
3. The imaging integrated circuit of claim 1 , further comprising:
logic NOR circuits that are connected to each pixel circuit of the pixel circuit array for selective read out;
a row selection shift register connected to the logic NOR circuits;
a pixel read assertion circuit connected to the logic NOR circuits;
a column selection shift register connected to the pixel read assertion circuit; and
a control pulse sequence generator connected to the row selection shift register, the pixel read assertion circuit and the column selection shift register to provide control signals.
4. The imaging integrated circuit of claim 2 , wherein each of the third and fourth amplifiers comprises:
a first input terminal connected to the pixel circuit array;
a second input terminal connected to a reference voltage terminal; and
an output terminal coupled to the first and second storage capacitors or the third and fourth storage capacitors.
5. The imaging integrated circuit of claim 4 , wherein the first storage capacitor is connected in series with a first switch circuit to the output terminal of the third amplifier, the second storage capacitor is connected in series with a second switch circuit to the output terminal of the third amplifier, the third storage capacitor is connected in series with a third switch circuit to the output terminal of the fourth amplifier, and the fourth storage capacitor is connected in series with a fourth switch circuit to the output terminal of the fourth amplifier, wherein the first storage capacitor and the first switch circuit is connected in parallel with the second storage capacitor and the second switch circuit, the third storage capacitor and the third switch circuit is connected in parallel with the fourth storage capacitor and the fourth switch circuit, wherein a fifth switch circuit is connected to the first storage capacitor and the first switch circuit and to the common mode reference voltage terminal, a sixth switch circuit is connected to the fourth storage capacitor and the fourth switch circuit and to the common mode reference voltage terminal, and wherein the first and second storage capacitors are connected to a seventh switch circuit, which is connected to the third storage capacitor and the third switch circuit, the third and fourth storage capacitors are connected to a eighth switch circuit, which is connected to the second storage capacitor and the second switch circuit.
6. The imaging integrated circuit of claim 4 , wherein each pixel circuit of the pixel circuit array further comprises:
a readout circuit coupled to the photodetector;
a first memory element coupled to the readout circuit, the first memory element comprising a first storage transistor configured to store the reference signal produced by the background noise of the pixel circuit;
a second memory element coupled to the readout circuit, the second memory element comprising a second storage transistor configured to store the signal produced by the optical exposure of the photodetector and the background noise of the pixel circuit;
a first output switch circuit coupled to the first memory element and a first output port of the pixel circuit;
a second output switch circuit coupled to the second memory element and a second output port of the pixel circuit; and
a third output switch circuit coupled to the readout circuit, the first memory element, the second memory element and a common reference terminal of the pixel circuit.
7. The imaging integrated circuit of claim 6 , wherein the first input terminal of the fourth amplifier is connected to the first output port of a target pixel circuit, the first input terminal of the third amplifier is connected to the second output port of the target pixel circuit, and the second input terminal of the third amplifier and the second input terminal of the fourth amplifier are connected to the common reference terminal of the target pixel circuit.
8. The imaging integrated circuit of claim 4 , wherein each of the second and third integrators further comprises a capacitor, a first switch, a second switch, and a third switch, wherein the capacitor is connected in series with the second switch, the first switch is connected in parallel with the capacitor and the second switch, and the third switch is connected to the capacitor, the second switch and the reference voltage terminal, and wherein the first switch and the capacitor are connected to the first input terminal of a corresponding amplifier and the first and second switches are connected to the output terminal of the corresponding amplifier.
9. A method for image information acquisition, the method comprising:
obtaining image information from a pixel circuit array having a plurality of pixel circuits, wherein the image information from a pixel circuit of the plurality of pixel circuits comprises a reference signal produced by background noise of the pixel circuit and a signal produced by optical exposure of a photodetector of the pixel circuit and the background noise of the pixel circuit; and
reading out the image information obtained by the pixel circuit array using a charge acquisition circuit, wherein the charge acquisition circuit comprises a first amplifier, a differential integrator connected in series with the first amplifier, wherein the differential integrator comprises a second amplifier, a first differential integrator section and a second differential integrator section, wherein the first amplifier is used as a common mode regulator for the second amplifier, wherein each of the first and second integrator sections includes a capacitor, a first switch, a second switch, and a third switch, wherein the capacitor is connected in series with the second switch, the first switch is connected in parallel with the capacitor and the second switch, and the third switch is connected to the capacitor, the second switch and a common mode reference voltage terminal, and wherein the first switch and the third switch are controlled by a first control signal and the second switch is controlled by a second control signal.
10. The method of claim 9 , wherein the photodetector of the pixel circuit is a photodiode, and wherein the image information from the pixel circuit comprises the reference signal produced by background noise of the pixel circuit and a signal produced by optical exposure of the photodiode of the pixel circuit and the background noise of the pixel circuit.
11. The method of claim 9 , wherein the charge acquisition circuit further comprises:
a second integrator that includes a third amplifier;
a third integrator that includes a fourth amplifier;
first and second storage capacitors coupled to the second integrator and the differential integrator; and
third and fourth storage capacitors coupled to the third integrator and the differential integrator.
12. The method of claim 11 , wherein each of the third and fourth amplifiers comprises:
a first input terminal connected to the pixel circuit array;
a second input terminal connected to a reference voltage terminal; and
an output terminal coupled to the first and second storage capacitors or the third and fourth storage capacitors.