CMOS TDI Sensor Rolling Shutter Pixel Offset Synchronization
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Solution Overview
Problem
CMOS image sensors face challenges in implementing time delay and integration (TDI) with rolling shutter pixels, leading to noise issues, geometric distortion, and modulation transfer function degradation due to asynchronous integration periods across pixels, which are exacerbated by the need for additional sample and hold circuitry and complex architectures.
Innovation Solution
A CMOS image sensor with a two-dimensional array of photosensitive elements aligned in the along track direction, featuring physical offsets between columns to synchronize integration periods, and a control circuit for sequential sampling and integration of TDI frames, which compensates for the movement of the subject and synchronizes integration periods across the array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If rolling shutter pixels are used to achieve TDI functionality, then power consumption is reduced and integration capability is improved, but geometric distortion and modulation transfer function degradation occur due to asynchronous integration periods
Solution Approach 1:
The patent applies parameter changes by introducing physical offsets between adjacent pixels in the along-track direction to compensate for the time-dependent readout sequence. This spatial parameter adjustment synchronizes the effective integration timing across pixels, eliminating geometric distortion while preserving the low power consumption benefits of rolling shutter operation.
2Manufacturing precision
If additional sample and hold circuitry is added to synchronize integration periods, then geometric distortion is reduced, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts and eliminates the need for additional sample and hold circuitry by implementing synchronization through physical pixel offsets alone. This approach achieves geometric distortion correction using only the pixel array structure itself, avoiding the complexity and power consumption associated with extra circuitry.
3Manufacturing precision
If physical offsets are introduced between pixels to synchronize integration, then modulation transfer function is improved, but fill factor is reduced
Solution Approach 1:
The patent applies local quality by introducing physical offsets only in the along-track direction between adjacent pixels, while maintaining normal pixel spacing in the across-track direction. This localized adjustment synchronizes integration timing without significantly impacting the overall fill factor, as the offset is confined to a specific spatial dimension.
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 solution improves the signal-to-noise ratio and modulation transfer function in the along track direction, reducing geometric distortion and eliminating the need for additional sample and hold circuitry, while maintaining low power consumption and high integration capabilities.
Implementation Method 1
a two-dimensional array of photosensitive elements operable in a rolling shutter mode
Data Source
AI summary
An improved complementary metal oxide semiconductor image sensor for time delay and integration imaging is provided that utilizes rolling shutter pixels. Columns of rolling shutter pixels in the CMOS image array are provided with a space between adjacent pixels to provide synchronization with movement of the subject in the along track direction. Preferably, the physical offset between the pixels is 1/Nth of a pixel pitch for a column having N rows.