Image Sensor Reference Voltage Switching for High-SNR Video
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Digital still cameras have low video image quality due to their relatively low sensitivity image sensors compared to camcorders, which results in a lower signal-to-noise ratio (SNR) during video recording without degrading the frame rate.
Innovation Solution
An image sensor with a pixel array, reference voltage generation unit, and analog-digital conversion unit that operates in both still image capturing and video recording modes, generating a reference voltage that changes at a constant rate in still mode and alternately decreases and increases in video mode, allowing for high sensitivity and SNR without degrading frame rate, and performs correlated double sampling and binning operations to enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital still cameras use a relatively low sensitivity image sensor compared to camcorders, then the frame rate can be maintained, but the video image quality and signal-to-noise ratio deteriorate
Solution Approach 1:
The image sensor dynamically switches between two operation modes: a first mode for still image capturing with standard exposure time, and a second mode for video recording with extended exposure time. This dynamic adaptation allows the sensor to maintain high sensitivity and signal-to-noise ratio in video mode by accumulating light over a longer period, while preserving frame rate performance through efficient mode transition and processing architecture
Solution Approach 2:
The patent changes the exposure time parameter based on operation mode. In video recording mode, the exposure time is extended beyond the standard period, allowing photons to accumulate longer on the photoelectric conversion elements. This parameter change directly improves signal-to-noise ratio and video image quality without compromising frame rate, as the extended exposure is compensated by the dual-mode processing architecture
2Measurement precision
If the exposure time is extended in video recording mode, then the sensitivity and signal-to-noise ratio improve, but the frame rate may be degraded
Solution Approach 1:
The patent segments the video recording operation into distinct phases: an extended exposure period for light accumulation, followed by a rapid readout and processing phase. By separating the light accumulation function from the data output function, the system can extend exposure time to improve signal-to-noise ratio while maintaining high frame rate through efficient parallel processing of multiple pixels during the readout phase
Solution Approach 2:
The image sensor performs preliminary light accumulation during an extended exposure period before the actual readout and processing begins. This preliminary action of gathering photons over a longer time window ensures sufficient signal strength is captured upfront, allowing subsequent fast processing to maintain frame rate without sacrificing signal-to-noise ratio
3Productivity
If the analog-digital conversion unit operates at different speeds in different modes, then the conversion efficiency may improve, but the system complexity and control difficulty increase
Solution Approach 1:
The analog-digital conversion unit is designed with universal operation capability that functions identically in both still image and video recording modes. The same conversion circuitry and processing logic handle both modes, eliminating the need for separate conversion paths or speed adjustment mechanisms. This universal design maintains conversion efficiency while reducing system complexity and control overhead
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
The solution provides high sensitivity and SNR for image sensors without degrading frame rate, improving video image quality by effectively handling shorter exposure times in video recording mode and reducing noise through binning operations.
Implementation Method 1
each of the pixels detects incident light and generates an analog signal in response to the detected incident light
Data Source
AI summary
An image sensor includes a reference voltage generation unit that generates a reference voltage that alternately decreases and increases at a constant rate in an operation mode of the image sensor to convert analog signals of detected incident light to a digital value using the reference voltage to determine an intensity of the incident light with high sensitivity and high signal-to-noise ratio.