Imaging device, monitoring device, and electronic appliance
View Patent ↗An imaging device capable of detecting differences with low power consumption is provided. The imaging device includes a pixel including a photoelectric conversion element and a transistor; an analog processing circuit; and a digital processing circuit. The imaging device is operated in a first mode and a second mode. In the first mode, the analog processing circuit detects a difference between first imaging data taken by the pixel and second imaging data taken by the pixel and generates a trigger signal on the basis of the value of the difference. In the second mode, the digital processing circuit converts third imaging data taken by the pixel into digital data. Switching from the first mode to the second mode is performed on the basis of the trigger signal.
1. An imaging device comprising:
a pixel comprising a photoelectric conversion element, first to fifth transistors, and first and second capacitors;
an analog processing circuit; and
a digital processing circuit,
wherein the imaging device operates in a first mode and a second mode,
wherein in the first mode, difference data between first imaging data taken by the pixel at a first time and second imaging data taken by the pixel at a second time is obtained by the pixel, and the analog processing circuit performs a sum-of-absolute-difference operation of the difference data and generates a trigger signal when a movement is detected from the first and second imaging data,
wherein in the second mode, the digital processing circuit converts third imaging data taken by the pixel at a third time into digital data,
wherein switching from the first mode to the second mode is performed on the basis of the trigger signal,
wherein one of a source and a drain of the first transistor is electrically connected to the photoelectric conversion element,
wherein the other of the source and the drain of the first transistor is electrically connected to one of a source and a drain of the second transistor and a first terminal of the first capacitor,
wherein one of a source and a drain of the third transistor is electrically connected to a second terminal of the first capacitor, a first terminal of the second capacitor, and a gate of the fourth transistor,
wherein one of a source and a drain of the fourth transistor is electrically connected to one of a source and a drain of the fifth transistor, and
wherein the other of the source and the drain of the fifth transistor is electrically connected to the analog processing circuit.
2. The imaging device according to claim 1 ,
wherein the analog processing circuit supplies current in accordance with a difference between a reference current value and a current value, and generates the trigger signal in response to the current, and
wherein the current value is determined by a difference between the first imaging data and the second imaging data.
3. The imaging device according to claim 1 , wherein the analog processing circuit includes a subtraction circuit, an absolute value circuit, and an adder circuit.
4. The imaging device according to claim 1 , wherein the digital processing circuit includes an A/D converter circuit.
5. The imaging device according to claim 1 , wherein switching from the second mode to the first mode is performed in the imaging device when a predetermined period of time has passed.
6. A monitoring device comprising:
a camera including the imaging device according to claim 1 ;
a display device electrically connected to the camera;
a memory device electrically connected to the camera; and
an alarm device electrically connected to the camera.
7. An electronic appliance comprising:
the imaging device according to claim 1 ; and
an operation key.
8. The imaging device according to claim 1 , wherein the first imaging data and the second imaging data are analog signals.
9. An imaging device comprising:
a pixel comprising a photoelectric conversion element, first to fifth transistors, and first and second capacitors;
an analog processing circuit; and
a digital processing circuit,
wherein the imaging device operates in a first mode and a second mode,
wherein in the first mode, difference data between first imaging data taken by the pixel at a first time and second imaging data taken by the pixel at a second time is stored in the pixel, and the analog processing circuit reads the difference data to perform a sum-of-absolute-difference operation of the difference data and generates a trigger signal when a movement is detected from the first and second imaging data,
wherein in the second mode, third imaging data taken by the pixel at a third time is stored in the pixel, the digital processing circuit converts the third imaging data into digital data,
wherein switching from the first mode to the second mode is performed on the basis of the trigger signal,
wherein one of a source and a drain of the first transistor is electrically connected to the photoelectric conversion element,
wherein the other of the source and the drain of the first transistor is electrically connected to one of a source and a drain of the second transistor and a first terminal of the first capacitor,
wherein one of a source and a drain of the third transistor is electrically connected to a second terminal of the first capacitor, a first terminal of the second capacitor, and a gate of the fourth transistor,
wherein one of a source and a drain of the fourth transistor is electrically connected to one of a source and a drain of the fifth transistor, and
wherein the other of the source and the drain of the fifth transistor is electrically connected to the analog processing circuit.
10. The imaging device according to claim 9 ,
wherein the analog processing circuit supplies current in accordance with a difference between a reference current value and a current value, and generates the trigger signal in response to the current, and
wherein the current value is determined by the difference data.
11. The imaging device according to claim 9 , wherein the analog processing circuit includes a subtraction circuit, an absolute value circuit, and an adder circuit.
12. The imaging device according to claim 9 , wherein the digital processing circuit includes an A/D converter circuit.
13. The imaging device according to claim 9 , wherein switching from the second mode to the first mode is performed in the imaging device when a predetermined period of time has passed.
14. A monitoring device comprising:
a camera including the imaging device according to claim 9 ;
a display device electrically connected to the camera;
a memory device electrically connected to the camera; and
an alarm device electrically connected to the camera.
15. An electronic appliance comprising:
the imaging device according to claim 9 ; and
an operation key.
16. The imaging device according to claim 9 , wherein the first imaging data and the second imaging data are analog signals.