CMOS Image Sensor Readout Timing for Black Reference
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Solution Overview
Problem
In CMOS image sensors, acquiring a black reference signal is challenging when processing units are arranged in correspondence with respective pixel blocks, leading to issues during the readout of open pixel signals.
Innovation Solution
The image sensor is designed with a pixel unit comprising light-shielded and light-unshielded blocks, where the controller controls parallel readout operations to end the readout of light-shielded pixel signals before starting the readout of light-unshielded signals, allowing for correction of black levels and signal variations during the readout process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If processing units are arranged in correspondence with respective pixel blocks to enable parallel readout, then readout speed is improved, but the ability to acquire black reference signals is lost
Solution Approach 1:
The patent applies preliminary action by completing the readout of light-shielded pixels (OB pixels) before starting the readout of light-unshielded pixels (open pixels). This sequencing ensures that black reference signals are acquired in advance, providing the necessary reference for subsequent signal processing while maintaining parallel readout architecture.
Solution Approach 2:
The patent segments the pixel array into distinct light-shielded pixel blocks and light-unshielded pixel blocks, each processed by corresponding processing units. This segmentation allows independent control of readout timing for different pixel types, enabling the sequential processing of OB pixels followed by open pixels within the parallel architecture.
2Measurement precision
If OB pixels are arranged in upper and left portions of the screen for correction processing, then signal correction capability is improved, but readout timing coordination becomes complex in parallel architecture
Solution Approach 1:
The patent applies local quality by assigning different functional roles to different spatial regions: light-shielded pixel blocks (OB pixels) positioned in upper and left portions are dedicated to reference signal generation, while light-unshielded pixel blocks are dedicated to image signal acquisition. Each processing unit processes its corresponding pixel block with appropriate timing, simplifying overall coordination.
Data Source
AI summary
An image sensor comprises: a pixel unit including a plurality of first blocks each of which includes a plurality of first pixels shielded from light and a plurality of second blocks each of which includes a plurality of second pixels that are not shielded from light; and a controller that controls a plurality of readout operations for processing, in parallel, pixel signals read out from the plurality of first blocks and the plurality of second blocks in the pixel unit. The controller performs control so as to end readout of pixel signals from at least a predetermined portion of the first pixels included in each of the plurality of first blocks, before readout of pixel signals from the plurality of second blocks is started.