Charge Multiplying CCD Sensor Routing for Dynamic Range
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Solution Overview
Problem
Conventional Charge Coupled Device (CCD) image sensors face limitations in dynamic range due to charge packet blooming when using charge multiplying shift registers, which can lead to loss of detail in both bright and dark image regions, as the entire image must be read out to prevent blooming, thereby missing the benefit of charge multiplication in dark areas.
Innovation Solution
An image sensor system with a charge directing switch that selectively routes charge packets to either a charge multiplying horizontal shift register or a discharging element based on the number of charge carriers, allowing for non-destructive sensing and preventing saturation, and utilizing a computing device to manage the routing and apply gain ratios to pixel signals from different output channels for enhanced dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charge multiplication is applied to all charge packets to improve detection of dark regions, then sensitivity in dark regions is improved, but bright regions saturate the charge multiplying shift register causing blooming
Solution Approach 1:
The patent applies different processing paths to different regions of the image based on local charge packet characteristics. Charge packets from dark regions are routed through the charge multiplying shift register for amplification, while charge packets from bright regions are routed directly to the output amplifier, preventing saturation and blooming in the multiplying register.
Solution Approach 2:
The patent segments the charge packet flow into two separate paths: one path through the charge multiplying shift register for low-signal amplification, and another direct path to the output amplifier for high-signal charge packets. This segmentation allows simultaneous optimization for both dark and bright region detection.
2Object-affected harmful factors
If the entire image is read out through the charge multiplying shift register to prevent blooming, then charge blooming is prevented, but dark regions lose the benefit of charge multiplication
Solution Approach 1:
The patent divides the charge packet population into two groups based on signal intensity and routes them through different paths. This segmentation allows the system to prevent blooming for bright regions while simultaneously providing charge multiplication for dark regions, optimizing both objectives concurrently.
Solution Approach 2:
The patent dynamically routes each charge packet based on its individual signal level characteristics. The routing decision is made adaptively for each charge packet rather than applying a fixed readout path to the entire image, allowing optimal processing for each region's specific requirements.
3Device complexity
If a single output amplifier is used to simplify the system, then device complexity is reduced, but dynamic range is limited by the amplifier's minimum noise level
Solution Approach 1:
The patent makes the charge multiplying shift register serve multiple functions: it acts as a signal amplifier for dark regions and as a protective element preventing blooming for bright regions. This multi-functionality allows the system to handle both low and high signal levels effectively without requiring additional specialized components.
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 enhances the dynamic range of CCD image sensors by preventing charge blooming and allowing for charge multiplication only when necessary, enabling the detection of a wider range of charge packets without saturating the shift registers, thus improving the quality of images with both bright and dark regions.
Implementation Method 1
Charge multiplication occurs in charge multiplying HCCD shift register 110 through the application of large electric fields to the gate electrodes (not shown) overlying HCCD shift register 110 during charge transfer. The large electric fields produce a signal larger than originally collected in the pixels in pixel array 100.
Implementation Method 2
Pixel array 100 includes vertical charge-coupled device (CCD) shift registers (not shown) that shift charge packets from a row of pixels 102
Data Source
AI summary
A method for producing an image sensor includes: providing a horizontal shift register electrically connected to a pixel array for receiving charge packets from the pixel array; providing a non-destructive sense node connected to an output of the horizontal shift register; providing a charge directing switch electrically connected to the non-destructive sense node, where the charge directing switch includes first and second outputs; providing a charge multiplying horizontal shift register electrically connected to the first output of the charge directing switch; and providing a discharging element connected to the second output of the charge directing switch.