Image sensor with active reset and randomly addressable pixels
View Patent ↗An imaging array having one or more columns of pixels is disclosed. Each pixel includes a photodiode including first and second terminals, a local reset circuit for connecting the first terminal to a column reset line; and a buffer circuit for selectively connecting the first terminal to a column bit line in response to a word select signal. Each column also includes a column reset circuit having an operational amplifier and a low-pass filter. The operational amplifier has a first input connected to the column bit line for that column and a second input connected to a reset signal generator that generates a reset signal during a reset cycle. The output of the operational amplifier is connected to the column reset line during the reset cycle. In one embodiment, the gain of the operational amplifier and the passband of the low-pass filter are varied during the reset cycle.
1. An imaging array comprising:
a first plurality of pixels, each pixel comprising:
a photodiode including first and second terminals;
a local reset circuit for connecting said first terminal to a first column reset line; and
a buffer circuit for selectively connecting said first terminal to a first column bit line in response to a word select signal; and
a first column reset circuit comprising an operational amplifier and a low-pass filter, said operational amplifier having a first input connected to said first column bit line, a said second input connected to a reset signal generator that generates a reset signal during a reset cycle, and an output selectively connected to said first column reset line.
2. The imaging array of claim 1 wherein said operational amplifier has a gain that is determined by a gain control signal.
3. The imaging array of claim 2 wherein said operational amplifier comprises a plurality of component operational amplifiers Connected in parallel, each component operational amplifier having a different gain, each component operational amplifier being selectable by said gain control signal.
4. The imaging array of claim 2 wherein said gain of said operational amplifier is varied during said reset cycle.
5. The imaging array of claim 1 wherein said low-pass filter has a passband that is determined by a low-pass filter control signal.
6. The imaging array of claim 5 wherein said passband of said low-pass filter is varied during said reset cycle.
7. The imaging array of claim 6 wherein said low-pass filter comprising a capacitor that is connected to said first column reset line during said reset cycle.
8. The imaging array of claim 1 further comprising:
a second plurality of pixels, each pixel comprising:
a photodiode including first and second terminals;
a local reset circuit for connecting said first terminal to a second column reset line; and
a buffer circuit for selectively connecting said second terminal to a second column bit line in response to a word select signal; and
a second column reset circuit comprising an operational amplifier and a low-pass filter, said operational amplifier having a first input connected to said second column bit line, said second input connected to said reset signal, and an output selectively connected to said second column reset line.
9. The imaging array of claim 1 wherein the first column reset line and the first column bit line are selectively coupled together by the operational amplifier.
10. The imaging array of claim 8 wherein the second column reset line and the second column bit line are selectively coupled together by the operational amplifier.