CMOS Image Sensor Comparator Initialization for Column Noise Control
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Solution Overview
Problem
CMOS image sensors experience increased P-phase variation and column fixed pattern noise during intermittent column operation, affecting image quality due to initialization failures and charge injection during non-operating comparator states.
Innovation Solution
The implementation of a pixel signal readout circuit with comparators that include initializing switches, allowing independent control of initialization signals for each column, and additional switches to manage capacitive coupling, reducing noise and improving image quality during intermittent operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If comparators are operated intermittently to reduce power consumption, then energy efficiency is improved, but P-phase variation and column fixed pattern noise increase
Solution Approach 1:
The patent applies preliminary action by initializing the comparator before intermittent operation. The initialization circuit resets the comparator state and clears any accumulated charge or voltage offset prior to the comparator being activated, thereby preventing P-phase variation and column fixed pattern noise while still allowing power-saving intermittent operation.
Solution Approach 2:
The patent introduces an intermediary initialization circuit between the comparator and the rest of the readout system. This intermediary component manages the comparator's state during intermittent operation, isolating the noise-generating effects from the main signal path while maintaining the power-saving benefits of intermittent operation.
2Stability of the object's composition
If initialization signals are applied to all comparators, then operating point stability is improved, but device complexity increases
Solution Approach 1:
The patent segments the initialization control by grouping comparators into basic units and applying initialization signals at the group level rather than individually to each comparator. This segmentation reduces the complexity of the control circuit while still providing adequate initialization coverage to maintain operating point stability.
Solution Approach 2:
The patent implements a universal initialization circuit that can serve multiple comparators simultaneously. This multi-functional initialization structure reduces overall device complexity by using a single control mechanism to manage the operating points of many comparators, rather than requiring separate control circuits for each comparator.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces P-phase variation and column fixed pattern noise, enhancing image quality by controlling initialization and capacitive coupling effectively, even during intermittent operations.
Implementation Method 1
a photodiode 11 as a photoelectric conversion element, and four transistors as active elements for one photodiode 11. The photodiode 11 photoelectrically converts an incident light into an amount of electric charge (here, it is an electron) corresponding to the amount of the incident light.
Data Source
AI summary
A solid-state imaging device and a camera system are provided. The solid-state imaging device capable of performing an intermittent operation includes a pixel unit and a pixel signal readout unit for reading out a pixel signal from the pixel unit in units of a plurality of pixels for each column. The pixel signal readout circuit includes a plurality of comparators and a plurality of counters whose operations are controlled by outputs of the comparators. Each of the comparators includes an initializing switch for determining an operating point for each column at a start of row operation, and is configured so that an initialization signal to be applied to the initializing switch is controlled independently in parallel only a basic unit of the initialization signal used for a horizontal intermittent operation, and the initializing switch is held in an off-state at a start of non-operating row.