CMOS Optical Sensor Scalable Repairing and Row Noise Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CMOS optical sensors face challenges in efficiently repairing defective readout channels and reducing temporal row noise, especially in large arrays, which affects image quality and manufacturing costs.
Innovation Solution
A scalable repairing scheme that adapts to any array size, using spare readout channels arranged in a repetitive pattern to replace defective channels and implement a digital row noise suppression method by calculating an average row noise value from spare channels and subtracting it from pixel values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a redundant readout channel is provided to repair defective channels, then reliability is improved, but device complexity increases
Solution Approach 1:
The readout circuitry is segmented into multiple groups, each containing a set of readout channels. Instead of providing a single global redundant channel, the patent divides the system into segments where each group can independently utilize spare channels within its own group, reducing overall complexity while maintaining reliability.
Solution Approach 2:
The patent introduces a group dimension to the readout channel organization. Channels are arranged in a two-dimensional structure (groups × channels per group), allowing redundant channels to be distributed across different groups rather than adding a single centralized backup, thereby reducing complexity.
2Reliability
If spare readout channels are distributed in groups throughout the readout circuitry, then reliability is improved, but area occupied increases
Solution Approach 1:
Instead of uniformly distributing spare channels throughout the entire readout circuitry, the patent applies local quality by concentrating spare channels within specific groups. Each group has its own spare channels localized to that group, reducing the overall area required while maintaining the ability to repair defective channels locally.
Solution Approach 2:
The patent implements partial redundancy by providing spare channels only in certain groups rather than in every group. This partial action approach reduces the total number of spare channels needed, thereby reducing area occupation while still achieving acceptable reliability through strategic placement.
3Reliability
If post-processing correction is applied to defective readout channels, then reliability is improved, but loss of time increases
Solution Approach 1:
The patent performs preliminary action by providing redundant readout channels that can immediately replace defective channels during the readout process itself, rather than requiring time-consuming post-processing corrections. The repair capability is built into the hardware, enabling real-time correction without delaying image acquisition or processing.
Data Source
AI summary
A CMOS optical sensor comprises spare readout channels to replace readout channels found defective at the end of the manufacturing process. These spare readout channels are dispatched over the width of the optical sensor (corresponding to the row direction) in the form of spare groups Gm1, Gm2, Gm3 of m spare readout channels each, m integer at least equal to 1. Each spare group is inserted between two successive default groups Gn1 and Gn2 of n default readout channels each and coupling means SW1 are configured to replace a defective default readout channel in a default group as well as any default readout channels of the group between the defective one and the spare group next to the default group of concern. Advantageously, for a row Rowi being currently selected for CDS reading each pixel in the row, a row noise level VRN<sub2>i </sub2>is obtained from the A spare readout channels that are not used in the implemented repairing scheme, by sampling an analogic DC reference signal by each of the A spare readout channels and averaging the A values Spk obtained. The row reference value VRN<sub2>i </sub2>is then subtracted from each of the pixel digital signal Si,j outputs for the current selected row, to finally obtain a signal value di,j with row noise suppression.