Dual Gain Imaging Pixels Two-Read Method
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Solution Overview
Problem
Conventional image sensors face issues with electrical crosstalk and increased power consumption due to dual gain pixel readout methods, leading to large electrical offsets and the need for multiple ADC conversions, which result in artifacts and inefficiencies in producing high dynamic range images.
Innovation Solution
The implementation of dual gain image sensors with a reduced number of read operations and ADC conversions by using a two-read method that eliminates the need for a frame buffer and minimizes electrical offsets, achieved through specific control signal timing and charge transfer operations within the pixel circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dual gain pixels read out captured high-gain and low-gain image data in respective configurations, then dynamic range is improved, but electrical crosstalk causes large electrical offset between signals
Solution Approach 1:
The patent applies preliminary action by reading out the high-gain signal first and storing it in a frame buffer before reading out the low-gain signal. This timing sequence prevents electrical crosstalk between the two readout operations. The frame buffer holds the high-gain signal during the low-gain readout phase, eliminating the need for additional offset correction operations and reducing overall power consumption.
2Measurement precision
If four pixel read operations and analog to digital conversions are used to operate without a frame buffer, then measurement precision is maintained, but power consumption increases
Solution Approach 1:
The patent merges the frame buffer functionality with the existing pixel readout circuitry, eliminating the need for separate frame buffer hardware. By combining the high-gain and low-gain readout operations in a coordinated sequence where the high-gain signal is read first and held in the frame buffer during low-gain readout, the system achieves both signal accuracy and reduced power consumption without requiring additional dedicated buffer resources.
3Measurement precision
If three pixel reads and three ADC conversions are used with a frame buffer, then measurement precision is maintained, but additional power is required
Solution Approach 1:
The patent extracts the essential functionality of the frame buffer operation and implements it through a simplified readout sequence. By reading out the high-gain signal first and using the same readout circuitry to hold this signal during the low-gain readout phase, the system eliminates the need for additional frame buffer hardware and reduces the number of required ADC conversions while maintaining signal accuracy and reducing power consumption.
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 reduces power consumption and minimizes electrical offsets, enabling the production of high dynamic range images with fewer read operations and ADC conversions, thereby improving image quality and efficiency.
Implementation Method 1
Each pixel in the array of pixels may include a photodiode that accumulates charge in response to incident light
Data Source
AI summary
An imaging system may include an image sensor having an array of dual gain pixels. Each pixel may be operated using a two read method such that all signals are read in a high gain configuration in order to improve the speed or to reduce the power consumption of imaging operations. Each pixel may be operated using a two read, two analog-to-digital conversion method in which two sets of calibration data are stored. A high dynamic range (HDR) image signal may be produced for each pixel based on signals read from the pixel and on light conditions. The HDR image may be produced based on a combination of high and low gain signals and one or both of the two sets of calibration data. A system of equations may be used for generating the HDR image. The system of equations may include functions of light intensity.