Image Sensor Voltage Supply Grid Clamping for H-Banding Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Image sensors experience deleterious h-banding artifacts due to voltage variations in the AVDD grid, particularly in images with high contrast between bright and dark areas, leading to inconsistent image quality.
Innovation Solution
The implementation of a clamping mechanism in the image sensor system, where a proximate row of pixels is used to mitigate voltage changes in the AVDD grid during readout, reducing current fluctuations and maintaining consistent voltage levels across the active row, thereby minimizing h-banding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clamping mechanism is implemented to reduce voltage variations in the AVDD grid, then image quality consistency is improved, but device complexity increases
Solution Approach 1:
The patent implements a self-service mechanism where the image sensor system uses its own pixel structure to clamp the AVDD grid voltage. The pixel's floating diffusion node and transfer transistor are configured to automatically regulate voltage variations during readout operations, eliminating the need for external voltage regulation circuits and reducing overall device complexity while improving image quality consistency
Solution Approach 2:
The patent makes the pixel structure multi-functional by enabling it to serve both its primary function of detecting light signals and a secondary function of clamping the AVDD grid voltage. The same pixel components (floating diffusion node, transfer transistor) are used for both signal transfer and voltage regulation, reducing the need for additional dedicated clamping circuits and thereby managing device complexity
2Productivity
If the readout speed is increased to improve productivity, then manufacturing efficiency is improved, but voltage stability deteriorates leading to h-banding artifacts
Solution Approach 1:
The patent applies preliminary action by pre-configuring the pixel's transfer transistor and floating diffusion node to maintain stable voltage levels before the actual readout operation begins. The pixel structure is designed to establish stable voltage conditions in advance, allowing faster readout speeds to be achieved without compromising voltage stability and avoiding h-banding artifacts
Data Source
AI summary
An image sensing device includes an image sensing circuit, a voltage supply grid, bitlines, and a control circuit. The image sensing circuit includes pixels arranged in rows and columns. Each one of the bitlines is coupled to a corresponding one of the columns. The voltage supply grid is coupled to the pixels. The control circuit is coupled to output at least a row select signal and a transfer signal to the rows. Each one of the rows is selectively coupled to the bitlines to selectively output image data signals in response to the row select signal and the transfer signal. Each one of the rows is further selectively coupled to the bitlines to selectively clamp the bitlines in response to the row select signal and the transfer signal. Each one of the rows is selectively decoupled from the bitlines in response to the row select signal.