CMOS Image Sensor Charge Transfer Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CMOS image sensors face challenges in achieving both high light sensitivity and dynamic range, with existing solutions either compromising on sensitivity or dynamic range, and struggling to handle moving objects due to temporal offset in combined recordings.
Innovation Solution
The image sensor reads out charge generated in a single exposure process in multiple portions using at least three successive transfer control signals, allowing for increased dynamic range without compromising light sensitivity, by using a control device to manage charge transfers and capacitances, and employing a column amplifier circuit with partial value signal memories to combine and digitize partial measurement signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the readout node capacitance is kept small to ensure high light sensitivity, then the light sensitivity is improved, but the dynamic range is limited
Solution Approach 1:
The patent divides the charge readout process into multiple segments or portions. Instead of reading out the entire charge in a single step, the charge is transferred and read out in multiple successive portions using multiple transfer control signals. This segmentation allows the sensor to maintain a small readout node capacitance for high sensitivity while achieving an extended dynamic range by accumulating multiple partial readings.
2Adaptability or versatility
If multiple recordings with different exposure times are combined to increase dynamic range, then the dynamic range is improved, but temporal offset causes smearing of image information for moving objects
Solution Approach 1:
The patent performs preliminary actions by transferring and storing partial charge portions in separate memory locations during the same exposure period. Rather than combining recordings taken at different times, the system prepares multiple charge portions from a single exposure and stores them before final readout, eliminating temporal offset issues while maintaining dynamic range extension capability.
3Device complexity
If a single charge transfer is used to simplify the readout process, then the device complexity is reduced, but the dynamic range is limited
Solution Approach 1:
The patent introduces dynamic control through multiple transfer control signals with varying control values. The system dynamically adjusts the transfer process by applying different control signals in sequence, allowing the readout node to receive charge in multiple portions. This dynamic approach extends the dynamic range while keeping the additional complexity manageable through systematic control signal management.
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 by a factor corresponding to the number of charge transfers, maintaining high sensitivity and enabling effective recording of moving subjects by avoiding smearing of image information from different exposure times.
Implementation Method 1
The pixels each comprise a light-sensitive detector element in order to generate an electrical charge from incident light
Data Source
Figure 1
Figure 2
Figure 3~6
AI summary
The image sensor has multiple pixels (11) arranged in lines and columns. The pixels have a photosensitive detector element that produces an electrical load of incident light. A transfer gate (39) and a selection node (41) are provided in the pixels. The selection node is charge-coupled over the transfer gate with the detector element. A control unit (53) is designed such that each detector element transfers the produced load in multiple portions from the detector element to selection node during an individual illumination process. An independent claim is included for a method for selecting an image sensor, particularly a complementary metal-oxide semiconductor image sensor, for electronic cameras.