Column ADC Bit-Memory Switching for Defect-Tolerant Image Sensors
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Solution Overview
Problem
The existing image pickup apparatus with column AD circuits faces an increase in circuit area due to the provision of data switching units for each column AD circuit, leading to a decrease in image quality and increased circuit scale.
Innovation Solution
The apparatus includes a selection unit with a memory unit comprising a first and second bit memory, allowing the selection of bit memories to hold digital signals, and a switching unit that rearranges bit outputs based on defects, reducing the need for individual switching units in each AD conversion unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a data switching unit is provided to each column AD circuit to suppress data deficit caused by defects, then image quality is maintained, but circuit area is increased
Solution Approach 1:
The patent merges the data switching functionality from individual column AD circuits into a single shared selection unit. Instead of having separate switching units in each AD conversion unit, one selection unit is provided that is shared by all AD conversion units, achieving the same defect compensation function while reducing overall circuit area.
Solution Approach 2:
The selection unit serves multiple AD conversion units simultaneously, performing the function of data switching for all columns through a single unified structure. This multi-functional approach allows one switching unit to replace what would otherwise require multiple separate switching units, thereby reducing circuit area while maintaining reliability.
2Reliability
If multiple data switching units are provided in parallel column AD circuits, then data deficit is compensated, but device complexity is increased
Solution Approach 1:
The patent combines multiple data switching units into a single selection unit that handles data routing for all AD conversion units. This consolidation reduces device complexity by eliminating redundant switching structures while maintaining the capability to compensate for data deficits caused by defects in any column.
Solution Approach 2:
The selection unit acts as an intermediary between the multiple AD conversion units and the output, centralizing the data switching function. This intermediary structure simplifies the overall circuit architecture by providing a single point of control for data routing instead of requiring independent switching units in each parallel path.
Data Source
AI summary
The present invention relates to a technology for providing a selection unit configured to perform selection of a bit memory that holds a signal of a first bit of a digital signal from among a plurality of bit memories commonly in a memory unit in each of a plurality of AD conversion units.