Globally Reset Image Sensor Pixels for Reduced Lag
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Integrated circuits, particularly image sensors, face challenges in efficiently capturing incident light due to the ever-decreasing size of components, leading to issues such as image lag and latency, which affect the quality of electronic images.
Innovation Solution
A globally reset image sensor pixel array is implemented, utilizing a reset transistor to concurrently reset pixels, a transfer gate transistor to couple the floating diffusion to a storage region, and a storage gate transistor to control the flow of electrons, along with a double correlated sampler for improved light capture and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the size of image sensor components is reduced to decrease sensor area, then the area used to implement circuitry is reduced, but the efficiency of capturing incident light deteriorates
Solution Approach 1:
The patent implements a global reset mechanism that performs preliminary action by resetting all pixels simultaneously before exposure begins. This pre-charges all floating diffusion nodes to the same voltage level, ensuring that pixels are ready to capture light immediately when illumination starts, thereby improving light capture efficiency without requiring larger sensor area.
Solution Approach 2:
The patent employs periodic action through the implementation of rolling shutter scanning combined with global reset cycles. The sensor alternates between exposure periods and readout periods in a systematic sequence, allowing concurrent pixel reset and correlated double sampling. This periodic operation maintains high light capture efficiency while managing the limited sensor area through time-multiplexed operations.
2Area of stationary object
If the size of image sensor components is reduced to decrease sensor area, then the area used to implement circuitry is reduced, but image lag increases
Solution Approach 1:
The global reset mechanism performs preliminary action by pre-charging all floating diffusion nodes to a known voltage level before exposure. This ensures that residual charge from previous frames is completely cleared, eliminating image lag. The simultaneous reset of all pixels guarantees uniform starting conditions without requiring additional area, as the reset signal is applied globally across the entire sensor array.
Solution Approach 2:
The patent implements feedback through correlated double sampling, where the reset level is sampled and subtracted from the final pixel value. This feedback mechanism actively removes any residual charge or offset errors that would cause image lag, ensuring clean images even in compact sensors with limited charge storage capacity.
3Area of stationary object
If the size of image sensor components is reduced to decrease sensor area, then the area used to implement circuitry is reduced, but latency increases
Solution Approach 1:
The patent employs periodic action through systematic row-by-row scanning combined with global reset. The sensor operates in regular cycles of exposure, reset, and readout, allowing pixels to be continuously prepared and captured images to be systematically read out. This periodic operation reduces latency by ensuring pixels are always ready for capture while managing the readout process efficiently through time-multiplexed scanning.
Solution Approach 2:
The global reset performs preliminary action by pre-charging all floating diffusion nodes simultaneously before the exposure period begins. This eliminates initialization delays during or after exposure, as all pixels are already in the correct state to immediately capture incident light. The preliminary reset action significantly reduces the effective latency from scene change to image capture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances light capture efficiency, reduces image lag and latency, and improves image quality by allowing concurrent pixel reset and correlated double sampling, thereby maintaining or improving image quality in smaller image sensors.
Implementation Method 1
charge generated by a photo-conversion device
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An imaging circuit includes a pixel array that is arranged to concurrently reset pixels in a pixel array in response to a global reset signal. The pixels are arranged in rows, such that the rows can be individually selected by a row select line. A reset transistor concurrently resets the pixels by coupling a reset voltage to a floating diffusion of the pixel. A transfer gate transistor selectively couples the floating diffusion to a storage region. A storage gate transistor selectively couples the storage region to a photosensitive region so that the reset transistor, the transfer gate transistor, and the storage gate transistor for each of the pixels can be activated in response to the global reset signal. A double correlated sampler may be used to provide a correlated double sample using a first sampled voltage of a reset voltage and a second sampled voltage of a pixel voltage that is produced when a photodiode region is exposed to incident light.