Image Sensor Floating Diffusion Voltage Calibration
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Solution Overview
Problem
Image sensors often produce imperfect color signals due to optical and electrical cross talk, leading to color channel mismatch and image distortion, especially in low light conditions.
Innovation Solution
Applying a pre-readout voltage to the floating diffusion in the image sensor to compensate for color channel mismatch by setting it to a dark condition steady-state read voltage prior to image charge readout, ensuring consistent pixel output even in the absence of light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a color filter layer is used to achieve color imaging, then color image reconstruction is improved, but color channel mismatch and image distortion occur due to optical and electrical cross talk
Solution Approach 1:
The patent applies a preliminary voltage adjustment to the floating diffusion node before the actual image charge readout. By pre-setting the floating diffusion to a specific voltage level (e.g., ground potential or a calibrated reference voltage), the system compensates for color channel mismatch and cross-talk effects in advance, ensuring that subsequent pixel readings are accurate and consistent across all color channels.
Solution Approach 2:
The patent dynamically adjusts the voltage parameter of the floating diffusion node based on detected color channel mismatch characteristics. By changing the voltage level at the floating diffusion during different readout phases or based on calibration data, the system corrects for optical and electrical cross-talk, thereby improving color signal accuracy without requiring hardware redesign.
2Manufacturing precision
If miniaturization and integration are advanced to meet higher resolution demands, then device performance is improved, but color channel mismatch and cross talk increase
Solution Approach 1:
The patent introduces the floating diffusion node as an intermediary element between the photodiodes and the readout circuitry. By carefully controlling the voltage at this intermediate node, the system can compensate for the increased cross-talk and noise effects that arise from miniaturization, effectively decoupling the benefits of high-resolution manufacturing from the harmful side effects of color channel mismatch.
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 method reduces color channel mismatch, minimizing image artifacts and improving image quality by maintaining consistent pixel output across all colors, even in low light conditions.
Implementation Method 1
a floating diffusion coupled to receive image charge from the plurality of photodiodes
Data Source
AI summary
An image sensor includes a plurality of photodiodes disposed in a semiconductor material and a plurality of transfer transistors. Individual transfer transistors in the plurality of transfer transistors are coupled to individual photodiodes in the plurality of photodiodes. A floating diffusion is also coupled to the plurality of transfer transistors to receive image charge from the plurality of photodiodes. The floating diffusion is coupled to receive a preset voltage, and the preset voltage is substantially equal a dark condition steady-state read voltage.