Solid-State Imaging Device Dual Ground Line Streaking Reduction
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Solution Overview
Problem
MOS solid-state imaging devices suffer from streaking issues due to fluctuations in current, affecting the output signal and resulting in poor imaging, particularly with high-intensity light exposure, as existing solutions like current-source transistor saturation do not fully address the problem.
Innovation Solution
The implementation of a solid-state imaging device with a dual ground line system, where a first ground line supplies current sources and a second ground line supplies column amplification circuits, interconnected at each pixel column, to stabilize ground potential and offset variations, combined with holding circuits and column AD conversion circuits for simultaneous signal amplification, reset, and conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common ground line is used for both current sources and column amplification circuits, then device complexity is reduced, but ground potential fluctuation causes streaking in output images
Solution Approach 1:
The common ground line is segmented into two separate ground lines: a first ground line for current sources and a second ground line for column amplification circuits. This segmentation prevents ground potential fluctuation from affecting both circuits simultaneously, eliminating streaking while maintaining reasonable device complexity.
Solution Approach 2:
A ground potential stabilization circuit is introduced as an intermediary between the first and second ground lines. This circuit monitors and stabilizes the ground potential for the column amplification circuits, preventing fluctuation-induced streaking without requiring complete isolation of the ground systems.
2Stability of the object's composition
If current-source transistor is kept in saturation region using a limiter, then current stability is improved, but streaking is not fully reduced due to other causes
Solution Approach 1:
The ground potential fluctuation factor is extracted and isolated from the current stability control system. By separating the ground lines, the patent addresses streaking caused by ground potential changes independently from current-source transistor saturation control, achieving comprehensive streaking reduction.
Solution Approach 2:
The patent changes the ground potential parameter for column amplification circuits by providing a dedicated second ground line with stabilization circuitry. This parameter change prevents ground potential fluctuation from causing streaking, complementing the current stability measures.
3Reliability
If ground potential fluctuation occurs in signal-readout path, then current variation affects all column amplification circuits, but dual ground line system increases device complexity
Solution Approach 1:
The ground system is segmented into two independent lines, preventing current variation from affecting all column amplification circuits simultaneously. This segmentation maintains current stability while managing device complexity through systematic separation of ground paths.
Data Source
AI summary
The solid-state imaging device having pixels that are arranged in rows and columns and convert optical signals to electric signals to output the electric signals as voltage signals includes column signal lines each provided for a corresponding one of the columns and transmitting, in the direction of the columns, voltage signals outputted from the pixels, current sources each provided for and connected to a corresponding one of the column signal lines, column amplification circuits each provided for a corresponding one of the column signal lines and amplifying the voltage signals transmitted through the column signal lines, a current-source ground potential supply line supplying the current sources with ground potential, and a column amplification circuit ground potential supply line supplying the column amplification circuits with ground potential. The current-source ground potential supply line and the column amplification circuit ground potential supply line are interconnected at positions corresponding to the columns.