CMOS Imaging Shutter Synchronization for Flicker Reduction
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Solution Overview
Problem
XY address scanning-type imaging devices, such as CMOS imaging devices, face challenges in reducing fluorescent lamp flicker due to differences in exposure timing across pixels, leading to intensity and color changes, which deteriorate image quality, especially under fluorescent lamp illumination with varying power-supply frequencies and synchronization frequencies.
Innovation Solution
The imaging apparatus sets the electronic shutter speed to specific exposure times based on the vertical synchronization frequency, such as N/120 seconds or N/100 seconds, and reduces flicker components by estimating and correcting the video signal, eliminating the need to detect the power-supply frequency and enabling high-speed shutter operation for camera-shake correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If XY address scanning-type imaging device is used to photograph under fluorescent lamp illumination, then imaging speed and productivity are improved, but fluorescent lamp flicker causes intensity and color changes deteriorating image quality
Solution Approach 1:
The patent changes the exposure time parameter to specific values (N/120 seconds or N/100 seconds) based on the vertical synchronization frequency, which synchronizes the exposure timing with the fluorescent lamp's luminance change period. This parameter adjustment eliminates the flicker effect while maintaining the high imaging speed of XY address scanning-type devices.
Solution Approach 2:
The patent applies periodic action by setting the exposure time to match the period of the fluorescent lamp's luminance change (1/100 seconds or 1/120 seconds). By synchronizing the exposure timing with the periodic flicker cycle, the imaging device captures consistent light intensity across all pixels, eliminating flicker artifacts while maintaining high-speed operation.
2Reliability
If exposure time is set to match fluorescent lamp luminance change period (1/100 seconds), then flicker is eliminated, but shutter speed flexibility and adaptability are reduced
Solution Approach 1:
The patent introduces dynamic adaptability by providing multiple exposure time options (N/120 seconds when 120/fv is integer, or N/100 seconds when 100/fv is integer) based on the vertical synchronization frequency. This allows the system to dynamically select the appropriate exposure time setting that both eliminates flicker and maintains shutter speed flexibility for different imaging conditions.
3Measurement precision
If power-supply frequency detection is implemented to optimize flicker reduction, then flicker reduction precision is improved, but device complexity and detection difficulty increase
Solution Approach 1:
The patent replaces complex power-supply frequency detection systems with a simpler approach that uses predetermined exposure time settings based on standard vertical synchronization frequencies (60 Hz or 50 Hz). This eliminates the need for expensive and complex frequency detection hardware while achieving effective flicker reduction through standardized exposure time selection.
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 reduces flicker components across all pixels, improves image quality by stabilizing exposure times, and allows for high-speed shutter operation without detecting the power-supply frequency, enhancing image stability and camera-shake correction.
Implementation Method 1
an XY address scanning-type imaging device (imager, image sensor) such as a CMOS (Complementary Metal Oxide Semiconductor) imaging device
Data Source
AI summary
An XY address scanning-type imaging apparatus, such as a CMOS imaging apparatus, having a high-speed shutter which is capable of reducing fluorescent-lamp flicker components and which enhances electronic camera-shake correction. When the vertical synchronization frequency is denoted as fv (Hz) and N is a positive integer, the shutter is set to N/120 seconds when 120/fv is an integer, and the shutter is set to N/100 seconds when 100/fv is an integer. In the NTSC system, when camera-shake correction is ON, the shutter speed is set to fraction ( 1/120) seconds, and when camera-shake correction is OFF, the shutter speed is set to fraction ( 1/60) seconds. In the PAL system, when camera-shake correction is ON, the shutter speed is set to fraction ( 1/100) seconds, and when camera-shake correction is OFF, the shutter speed is set to fraction ( 1/50) seconds.