Pixel Power Noise Copying for CMOS Image Sensor Signal Integrity
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Solution Overview
Problem
Conventional CMOS image sensors face challenges in effectively canceling pixel power noise, which causes signal distortion and image deterioration, especially in high-resolution images where pixel noise is more pronounced and varies randomly across columns.
Innovation Solution
A pixel power noise cancelling apparatus and method that involves copying and superimposing pixel power noise from each column onto a ramp signal, which is then compared with the pixel signal in a comparator, using a pixel power noise copy unit with a source follower structure to precisely replicate and cancel noise across different column locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If separate power supplies are used for the pixel array and ramp signal generator, then the chip size can be reduced and power consumption decreased, but pixel power noise and signal distortion occur
Solution Approach 1:
The patent uses a pixel power noise copy unit to create a copy of the pixel power noise and superimpose it on the ramp signal. This copying approach allows the noise to be intentionally introduced into the ramp signal so that it can be cancelled out during comparison, resolving the harmful effect of pixel power noise while maintaining separate power supplies for compact chip design
Solution Approach 2:
The patent converts the harmful pixel power noise into a beneficial element by intentionally generating and superimposing copied pixel power noise on the ramp signal. This allows the noise to be cancelled out during the comparison process, transforming what was previously a harmful interference into a useful mechanism for noise cancellation
2Reliability
If conventional noise cancellation methods are used, then uniform pixel power noise can be suppressed, but random pixel power noise with different magnitude and phase across columns cannot be effectively cancelled and may amplify signal distortion
Solution Approach 1:
The patent applies local quality by having each column's ramp signal processed individually through a pixel power noise copy unit that generates noise specific to that column. This allows the noise cancellation to account for column-specific variations in noise magnitude and phase, effectively handling random pixel power noise across different columns rather than applying a uniform cancellation approach
Solution Approach 2:
The patent creates a copy of the pixel power noise for each column and superimposes it on the corresponding ramp signal. This copying mechanism enables precise matching of noise characteristics (magnitude and phase) for each column, allowing effective cancellation of random pixel power noise without amplifying signal distortion
Data Source
AI summary
A pixel power noise cancelling apparatus may include: a ramp signal generator suitable for generating a ramp signal according to control of a controller; a pixel power noise copy unit suitable for copying a pixel power noise of a pixel column of a pixel array to superimpose on the ramp signal fed from the ramp signal generator to the pixel column and output a ramp signal with added pixel power noise; and a comparator suitable for comparing a pixel signal output by the pixel column with the ramp signal with added pixel power noise from the pixel power noise copy unit.