Image Sensor Pixel Circuit Dynamic Range Extension
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image sensor systems face challenges in achieving a wide dynamic range in a single image frame due to limitations in pixel gain control, leading to difficulties in capturing scenes with both bright and dim objects effectively, especially in nighttime imaging, as all pixels must have the same dynamic range, which reduces spatial resolution when using pixels with different gains.
Innovation Solution
The solution involves an array of pixel circuits with multiple charge storage elements and gain select switches, allowing for selective connection of additional capacitors in parallel to adjust pixel gain, enabling individual pixels to have different response gains within a single image frame by activating specific gain control lines, thereby achieving a wider dynamic range without combining multiple frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If all pixels in the image sensor array are assigned the same dynamic range, then the system is simple to implement, but the ability to image scenes with both bright and dim objects is limited
Solution Approach 1:
The patent applies local quality by assigning different dynamic ranges to different pixels within the array. Specifically, pixels are divided into first and second groups, where first pixels have a first dynamic range optimized for bright objects and second pixels have a second dynamic range optimized for dim objects. This allows each region of the image sensor to be optimized for its specific imaging needs, resolving the contradiction between adaptability and complexity.
Solution Approach 2:
The patent segments the pixel array into multiple groups with different dynamic range characteristics. The pixel array is divided into first pixels and second pixels, each group having different integration capacitor sizes and corresponding dynamic ranges. This segmentation enables the system to simultaneously capture both bright and dim objects without requiring every pixel to have universally optimized performance.
2Adaptability or versatility
If multiple consecutive image frames are acquired with varying exposure times to achieve extended dynamic range, then the dynamic range is extended, but the frame acquisition rate is reduced
Solution Approach 1:
Instead of acquiring multiple time-exposed frames sequentially, the patent segments the spatial array of pixels into different dynamic range groups. This allows simultaneous acquisition of multiple dynamic range information in a single frame, maintaining the frame acquisition rate while extending the effective dynamic range through spatial diversity of pixel characteristics.
Solution Approach 2:
The patent transitions from temporal multiplexing (acquiring multiple frames at different times) to spatial multiplexing (using different pixels simultaneously). By distributing different dynamic range capabilities across the spatial array of pixels, the system achieves extended dynamic range without sacrificing frame rate, as all pixels operate simultaneously in the same time frame.
3Adaptability or versatility
If non-linear response characteristics are implemented in pixels to achieve wide dynamic range, then the dynamic range is extended, but other performance aspects of the pixel are compromised
Solution Approach 1:
The patent changes the parameter of integration capacitor size to achieve different dynamic ranges. By varying the capacitance value of integration capacitors across different pixel groups, the system achieves different gain characteristics and dynamic ranges while maintaining linear response behavior. This parameter change approach extends dynamic range without compromising the reliability and linearity of pixel performance.
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 allows for a single image frame with a wider dynamic range, maintaining spatial resolution by enabling individual pixel gain control, allowing both bright and dim objects to be imaged effectively without the need for combining multiple frames, thus overcoming the limitations of conventional systems.
Implementation Method 1
Each pixel circuit has a first charge storage element electrically connected across an amplifier and configured to store charge in response to light detected by an associated pixel
Data Source
AI summary
A read out integrated circuit includes (ROIC) an array of pixel circuits, each of which has a first charge storage element electrically connected across an amplifier, and a second charge storage element having a selectively activated electrical connection across the amplifier. First and second gain select switches are configured to control the selectively activated electrical connection so as to selectively place the second charge storage element in electrical parallel with the first charge storage element and cause both the first and said second charge storage elements to store charge in response to light detected by said associated pixel. The circuit includes gain control column lines, each gain control column line configured to control a plurality of the first gain select switches belonging to pixel circuits in an associated column of the array. The circuit also includes gain control row lines, each gain control row line configured to control a plurality of the second gain select switches belonging to pixel circuits in an associated row of the array.