Pixel circuit with constant voltage biased photodiode and related imaging method
First Claim
Patent Images
1. An imaging system having a pixel array that includes a plurality of pixel circuits, each pixel circuit comprising:
- a photodiode configured to generate charges in response to light or radiation;
a biasing circuit configured to provide a constant bias voltage across the photodiode to drain the charges generated by the photodiode;
a first charge-to-voltage converter configured to accumulate the charges drained by the biasing circuit and convert the accumulated charges into a corresponding output voltage;
a second charge-to-voltage converter; and
a gain-switching circuit configured to select the second charge-to-voltage converter to accumulate the charges generated by the photodiode in response to detection of the output voltage exceeding a threshold voltage.
6 Assignments
0 Petitions
Accused Products
Abstract
An imaging system includes a plurality of pixel circuits each having a photodiode, a biasing circuit and a charge-to-voltage converter. The photodiode is configured to generate charges in response to light or radiation. The biasing circuit is configured to provide a constant bias voltage across the photodiode so as to drain the charges generated by the photodiode. The charge-to-voltage converter is configured to accumulate the charges drained by the biasing circuit and convert the accumulated charges into a corresponding output voltage.
22 Citations
16 Claims
-
1. An imaging system having a pixel array that includes a plurality of pixel circuits, each pixel circuit comprising:
-
a photodiode configured to generate charges in response to light or radiation; a biasing circuit configured to provide a constant bias voltage across the photodiode to drain the charges generated by the photodiode; a first charge-to-voltage converter configured to accumulate the charges drained by the biasing circuit and convert the accumulated charges into a corresponding output voltage; a second charge-to-voltage converter; and a gain-switching circuit configured to select the second charge-to-voltage converter to accumulate the charges generated by the photodiode in response to detection of the output voltage exceeding a threshold voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. An imaging method, comprising:
-
maintaining a voltage established across a photodiode at a constant value to drain charges generated by the photodiode in response to light or radiation; accumulating the charges drained from the photodiode in a first charge-to-voltage converter and converting the accumulated charges into a corresponding output voltage during an image acquisition period; and acquiring a signal sample by reading the output voltage during a readout period subsequent to the image acquisition period. - View Dependent Claims (14, 15, 16)
-
Specification