Correlated Double Sampling Circuit with Timing-Controlled Band-Limitation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image sensors face challenges in reducing random noise without increasing the size of the signal processing unit, which affects the signal-to-noise ratio (SNR) due to intrinsic pixel variations and noise from the signal processing procedure.
Innovation Solution
A correlated double sampling (CDS) circuit with a timing-controlled band-limitation (TCBL) unit is introduced, which performs pre-charge and noise removal operations based on a timing control signal, effectively reducing random noise and improving the SNR without increasing the image sensor's size by using a sampling unit and a TCBL unit connected to the CDS circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional signal processing methods are used to reduce random noise, then noise reduction is achieved, but the size and complexity of the image sensor increases
Solution Approach 1:
The TCBL unit is merged with the existing CDS circuit structure, sharing the same operational framework and timing control mechanisms. The band-limitation function is integrated into the signal processing pipeline without requiring separate dedicated hardware blocks, thus reducing overall device complexity while maintaining noise reduction capability
Solution Approach 2:
The CDS circuit is designed to perform multiple functions: correlated double sampling for fixed pattern noise reduction, and timing-controlled band-limitation for random noise reduction. This multi-functionality allows a single circuit to address both types of noise without requiring additional specialized processing units
2Object-affected harmful factors
If the signal processing unit is enlarged to reduce random noise, then noise reduction performance improves, but the image sensor size increases
Solution Approach 1:
The invention changes the operational parameters of the existing CDS circuit by introducing timing-controlled band-limitation with specific frequency cutoff characteristics. By adjusting the ramp signal characteristics and timing control parameters, the circuit achieves random noise reduction without requiring physical enlargement of the sensor structure
3Object-affected harmful factors
If complex noise reduction techniques are applied, then random noise is reduced, but manufacturing complexity increases
Solution Approach 1:
The band-limitation filtering action is performed preliminarily within the CDS operation framework, using pre-defined ramp signals and timing control sequences. This preliminary filtering approach simplifies the manufacturing process by avoiding the need for complex post-processing circuits
Data Source
AI summary
A correlated double sampling (CDS) circuit included in an image sensor includes a sampling unit and a timing controlled band-limitation (TCBL) unit. The sampling unit is configured to generate an output signal by performing a CDS operation with respect to a reset component of an input signal and an image component of the input signal based on a ramp signal, the input signal being provided from a pixel array included in the image sensor. The TCBL unit is connected to the sampling unit, and is configured to remove noise from the output signal based on a timing control signal. The timing control signal is activated during a first comparison duration, in which a first comparison operation is performed with respect to the ramp signal and the reset component of the input signal, and during a second comparison duration, in which a second comparison operation is performed with respect to the ramp signal and the image component of the input signal.