Image Sensor Flicker Noise Removal via Line Scan Phase Alignment
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Solution Overview
Problem
CMOS image sensors face flicker noise issues due to mismatched integration times and light source frequencies, particularly with 50 Hz and 60 Hz frequencies, requiring additional logic circuits for auto flicker cancellation, which increases digital circuit burden.
Innovation Solution
A method for integrating exposure times using a line scan method, where the integration time for the second line is adjusted to match the phase of the light source frequency, eliminating the need for additional logic circuits by controlling the phase alignment between integration lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional logic circuits are added for auto flicker cancellation, then flicker noise removal capability is improved, but device complexity and digital circuit burden increase
Solution Approach 1:
The image sensor performs self-diagnosis and self-correction by detecting flicker noise patterns and automatically adjusting integration times without external intervention. The sensor uses its existing processing circuits to analyze captured images, identify flicker artifacts, and modify subsequent exposure parameters, eliminating the need for separate dedicated flicker cancellation hardware.
Solution Approach 2:
The system dynamically changes the integration time parameter based on detected light source frequency characteristics. By varying the integration time to match or avoid specific phases of the light source cycle, the system eliminates flicker noise through parameter adjustment rather than through complex additional circuitry for frequency detection and correction.
2Reliability
If integration time is fixed to match a specific light source frequency, then flicker noise is reduced, but adaptability to different light source frequencies deteriorates
Solution Approach 1:
The integration time is made dynamic rather than fixed, allowing the system to adapt to different light source frequencies. The sensor detects the actual light source frequency in the environment and adjusts the integration time accordingly, enabling operation with both 50 Hz and 60 Hz light sources as well as other frequencies without manual reconfiguration.
Solution Approach 2:
The image sensor is designed to handle multiple light source frequencies using the same hardware platform. By implementing a universal flicker cancellation algorithm that can detect and adapt to various frequencies, the system achieves multi-functionality without requiring separate dedicated circuits for each frequency standard.
3Reliability
If integration time is adjusted for each line to match light source phase, then flicker noise is eliminated, but processing complexity increases
Solution Approach 1:
The system applies periodic modulation to the integration timing of successive lines, synchronizing the integration periods with the periodic nature of the light source. By varying the integration start phase in a systematic periodic pattern across lines, the system averages out the flicker effects without requiring complex real-time phase detection for each individual line.
Solution Approach 2:
The system uses feedback from the captured image data to detect the presence and characteristics of flicker noise, then adjusts subsequent integration timing based on this feedback. The processing circuit analyzes the captured frames, identifies flicker patterns, and modifies integration parameters for following frames, creating a closed-loop system that eliminates flicker through adaptive feedback control.
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 approach effectively removes flicker noise without increasing hardware burden, maintaining consistent light energy input across lines and improving price competitiveness by simplifying the digital circuit requirements.
Implementation Method 1
An image sensor is a device generating an image by using a characteristic that a semiconductor device reacts to a light
Data Source
AI summary
Disclosed is a method for integrating an image sensor capable of removing a flicker noise without causing any burdens on a hardware due to setting up additional logics. The method for integrating an exposure time of an image sensor employing a line scan method, including the steps of: performing an integration to a first line when an integer multiple of a light source frequency is different from an integration time; and performing an integration to a second line at a phase substantially equal to a phase in which the integration to the first line is started.