CMOS Image Sensor Optical Black Area Reduction
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Solution Overview
Problem
Conventional CMOS image sensors have a large optical black area due to an equal number of optical black pixel rows as active pixel rows, which reduces the available area for active pixel rows and introduces noise in image signals.
Innovation Solution
Sharing an optical black pixel row among multiple active pixel rows to generate optical black signals, allowing for a smaller optical black area while maintaining accurate image signal correction through an image signal processor that subtracts optical black signals from image signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an equal number of optical black pixel rows as active pixel rows is used, then accurate dark signal generation is achieved, but the optical black area becomes large reducing active pixel area
Solution Approach 1:
A single optical black pixel row is designed to serve multiple active pixel rows by sequentially generating dark signals for each group of active rows. The optical black pixel row is activated during specific time periods to provide dark signals that are used for correcting multiple different active pixel rows, making one component perform multiple functions that would traditionally require separate components for each active row.
2Measurement precision
If a separate optical black pixel row is formed for each active pixel row, then accurate pixel-by-pixel correction is achieved, but the device complexity and area increase
Solution Approach 1:
Multiple optical black pixel rows are merged into a single optical black pixel row. Instead of having separate optical black rows for each active pixel row, the invention combines them into one shared row that sequentially serves all active rows. This merging reduces structural complexity while maintaining correction functionality through time-division multiplexing and signal labeling mechanisms.
Solution Approach 2:
The optical black pixel row operates periodically to generate dark signals for different active pixel rows at different time periods. During specific activation periods, the optical black row generates dark signals for particular active rows, creating a periodic pattern of operation that allows one row to serve multiple functions over time, thereby reducing spatial requirements while maintaining functional completeness.
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 the size of the optical black area, increases the availability of space for active pixel rows, and effectively removes noise from image signals by sharing the optical black pixel row among multiple active pixel rows.
Implementation Method 1
A CMOS image sensor is a photo-electric conversion device that converts an image into electrical signals
Implementation Method 2
the image signal from the active pixel array and the optical black signal from the optical black area are converted into digital signals using a ramp signal in a CDS (correlated double sampling) method
Data Source
AI summary
A CMOS image sensor includes a plurality of active pixel rows and an optical black pixel row. The optical black pixel row is activated to generate a respective optical black signal upon activation of each of at least two of the active pixel rows. Such sharing of the optical black pixel row reduces the optical black area of the CMOS image sensor.