Dummy Pixel Array as Mask ROM in Image Sensors
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Solution Overview
Problem
Conventional image sensors require additional memory regions, such as flash memory or EEPROM, to store digital codes for image signal processing, which increases chip size and circuit complexity.
Innovation Solution
A dummy pixel array is used as a mask read-only memory (ROM) in the image sensor, employing a switch-controlled 4T pixel structure to store data by turning on or off the switch, allowing for the storage of operation codes without additional memory blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If additional memory regions (flash memory or EEPROM) are used to store digital codes, then the image sensor can store operation codes, but the chip size and circuit complexity increase
Solution Approach 1:
The patent merges the dummy pixel array, originally intended only for optical compensation, with memory storage functionality. By integrating operation code storage into the existing dummy pixel structure, the invention eliminates the need for separate memory regions, thereby reducing circuit complexity while maintaining storage capability
Solution Approach 2:
The dummy pixel array is赋予 dual functionality: it continues to serve its traditional role in optical compensation while simultaneously functioning as a memory storage device for operation codes. This multi-functionality approach allows the same hardware structure to perform multiple tasks, reducing overall device complexity
2Loss of information
If additional memory regions (flash memory or EEPROM) are used to store digital codes, then the image sensor can store operation codes, but the chip size increases
Solution Approach 1:
The patent combines the memory storage function with the existing dummy pixel array structure. By utilizing the already-present dummy pixels for dual purposes (optical compensation and data storage), the invention avoids adding separate memory blocks, thereby preventing chip size increase
Solution Approach 2:
The dummy pixel array serves itself by storing operation codes within its own structure. The floating diffusion nodes within the dummy pixels are repurposed to hold digital code data, allowing the structure to provide storage services without requiring external or additional components
Data Source
AI summary
An image sensor includes a dummy pixel array with at least one dummy pixel, a pixel array with a plurality of main pixels, and a data processing unit configured to process a signal provided from the main pixels. The dummy pixel includes: a first switch having a first terminal receiving a first voltage and a second terminal coupled to a floating node; a second switch having a first terminal receiving a second voltage; a third switch coupled between a second terminal of the second switch and the floating node; and a driving element configured to drive a first terminal thereof according to a voltage level applied to the floating node.