CMOS Image Sensor Comparator Initialization for Intermittent Readout
Find Innovative SolutionsGenerate Solutions
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 AC coupling issues during comparator non-operating periods.
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, ensuring the comparator is in an off-state during non-operating rows, thereby reducing feed-through and charge injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the comparator is operated intermittently to reduce power consumption, then energy efficiency is improved, but P-phase variation and column fixed pattern noise increase due to initialization failures
Solution Approach 1:
The initialization switch is turned on before the comparator operation to pre-establish the proper operating point, ensuring that the comparator is fully initialized before intermittent operation begins, thereby preventing initialization failures during non-operating periods
Solution Approach 2:
The initialization switch is dynamically controlled based on the operational state of the comparator, being turned on during non-operating rows and turned off during operating rows, allowing the system to adapt its initialization behavior to the intermittent operation mode
2Reliability
If the initializing switch is continuously on to ensure proper initialization, then initialization reliability is improved, but feed-through and charge injection increase
Solution Approach 1:
The initialization switch is activated periodically only during non-operating rows and deactivated during operating rows, creating a rhythmic on-off pattern that provides necessary initialization while minimizing the duration of switch conduction to reduce feed-through and charge injection effects
Solution Approach 2:
The initialization is performed in advance during non-operating rows before the comparator enters its operating state, ensuring the comparator is properly initialized before it begins signal processing, thereby eliminating the need for continuous initialization
3Object-affected harmful factors
If additional initialization control switches are added to manage capacitive coupling, then noise reduction is improved, but device complexity increases
Solution Approach 1:
The harmful capacitive coupling effects are extracted and separately controlled by dedicated initialization control switches, isolating the noise-generating mechanisms from the main comparator operation and allowing independent management of different noise sources
Solution Approach 2:
Different initialization control switches are applied to different parts of the comparator circuit to address specific local noise issues, with each switch controlling the initialization of particular nodes or stages where capacitive coupling problems occur
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 minimizing noise components 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.