Photosensitive Sensor Dual Shutter Mode Pixel Design
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Solution Overview
Problem
Existing photosensitive sensors face challenges in simultaneously operating in global shutter mode and rolling shutter mode without increasing complexity, size, or cost, particularly when capturing near-infrared and color images.
Innovation Solution
A photosensitive sensor design that includes a pixel structure with two transfer gates, a source-follower transistor, and a reset transistor, allowing the sensor to switch between global shutter and rolling shutter modes by controlling the transfer gates and amplification stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pixel is designed with memory node and read node for global shutter mode, then global shutter capability is achieved, but device complexity increases
Solution Approach 1:
The pixel structure is designed to perform multiple functions: it can operate in global shutter mode using the memory node and read node path, and in rolling shutter mode using the direct photosensitive region to read node path. This multi-functionality allows a single pixel design to support both shutter modes without requiring separate pixel structures for each mode.
Solution Approach 2:
The pixel incorporates switching mechanisms (transfer gates and mode selection circuitry) that dynamically reconfigure the signal path based on the selected shutter mode. In global shutter mode, the signal flows through the memory node for temporary storage; in rolling shutter mode, the signal flows directly from the photosensitive region to the read node, eliminating the memory node from the signal path.
2Adaptability or versatility
If direct transmission from memory node to read node is used for rolling shutter mode, then rolling shutter capability is achieved, but noise increases significantly
Solution Approach 1:
The pixel design segments the signal transmission path into two distinct routes: one for global shutter mode (through memory node with amplification stages) and one for rolling shutter mode (direct path). By separating these paths, the design allows each mode to use its optimal signal transmission route, enabling rolling shutter operation while maintaining signal quality through proper path selection.
3Adaptability or versatility
If mirror type current sources are introduced to enable rolling shutter mode in global shutter pixels, then rolling shutter capability is achieved, but transistor count and device complexity increase substantially
Solution Approach 1:
The pixel design uses universal components (transfer gates, amplification stages, read nodes) that serve both global shutter and rolling shutter modes. The same read node and amplification infrastructure is used in both modes, eliminating the need for additional mirror type current sources or specialized components for rolling shutter operation.
Solution Approach 2:
The design merges the global shutter and rolling shutter functionalities into a single integrated pixel structure. The read node and amplification stages serve dual purposes: storing and reading signals in global shutter mode, and directly reading signals in rolling shutter mode. This consolidation avoids the need for separate dedicated circuits for each shutter mode.
4Device complexity
If common command line is used for memory node access, then circuit simplicity is maintained, but current supply capability is insufficient for reading all pixels in a row
Solution Approach 1:
The design segments the readout operation by enabling selective activation of pixels within a row. While the command line remains common and simple, the system can activate and read only the necessary subset of pixels in each row, distributing the current demand over time and avoiding the need for the command line to supply excessive current simultaneously to all pixels.
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
Enables the sensor to acquire signals effectively in both global shutter and rolling shutter modes without increasing complexity or cost, improving acquisition quality and versatility.
Implementation Method 1
a photosensitive region configured to photogenerate electric charges
Data Source
AI summary
A photosensitive sensor is capable of operating in a global shutter mode and in a rolling shutter mode. The sensor includes at least one pixel with a photosensitive region configured to photogenerate charges. A first transfer gate is configured to transfer photogenerated charges from the photosensitive region to a transfer node. A source-follower transistor is configured to transmit a reading signal to a read node, in the global shutter mode, in a manner controlled by a potential of the photogenerated charges on the transfer node. A second transfer gate is configured to transfer the photogenerated charges from the photosensitive region to the read node in the rolling shutter mode.