CMOS Image Sensor Sampling Circuit with Dynamic Switching for Gain Control
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Solution Overview
Problem
Current CMOS image sensors face challenges in increasing image signal gain without compromising processing speed, leading to inadequate low-light image acquisition due to the simplicity of existing sampling control circuit structures.
Innovation Solution
An image signal sampling circuit with a working module control circuit, including source, ground, and between-column switch groups, allows for flexible operation modes such as 1/X sub-sampling, where the control unit manages switch connections to increase signal gain by connecting switches in series, effectively doubling or multiplying the sampled signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gain is increased to improve low-light image acquisition, then the image signal gain is improved, but the processing speed is compromised
Solution Approach 1:
The patent implements dynamic switching between different sampling modes (full sampling and sub-sampling) based on lighting conditions. The control circuit dynamically adjusts the switching state of pixel columns, enabling the system to adaptively select between speed-optimized full sampling and gain-optimized sub-sampling modes, thus resolving the contradiction between processing speed and image signal gain.
Solution Approach 2:
The patent changes the sampling parameter by implementing 1/X sub-sampling mode where only 1/X of the pixel columns are actively sampling at any given time. This parameter change allows the system to accumulate signal over longer periods for improved gain while maintaining the ability to switch back to full sampling for speed-critical operations.
2Measurement precision
If a complex backend processing is added to magnify the sampled signal, then the image signal gain is improved, but the device complexity increases
Solution Approach 1:
The patent merges the gain enhancement function directly into the sampling stage by implementing signal accumulation at the pixel column level through controlled switching. Instead of adding a separate backend magnification stage, the circuit combines sampling and signal amplification functions, eliminating the need for complex post-sampling processing while achieving the desired gain improvement.
Solution Approach 2:
The patent segments the pixel array into multiple columns that can be independently controlled and switched. By dividing the pixel columns into groups that can be selectively activated for sub-sampling, the system achieves gain enhancement through distributed signal accumulation across multiple segments, avoiding the need for a single complex centralized processing stage.
3Measurement precision
If sub-sampling mode is implemented to increase gain, then the image signal gain is improved, but the chip area may increase
Solution Approach 1:
The patent implements a universal switching circuit that serves multiple functions: it enables both full sampling mode for speed-critical applications and sub-sampling mode for gain-critical applications. The same switching infrastructure supports different sampling configurations without requiring dedicated hardware for each mode, thus achieving gain improvement without proportionally increasing chip area.
Data Source
AI summary
This invention discloses a type of image signal sampling circuits and methods. The circuit includes: a signal acquisition unit, a column read out unit, and a working module control circuit. The control circuit includes: a control unit, a source column switch group, a ground column switch group, and a between-column switch group. Each sampling column circuit is equipped with a source column switch and a ground column switch. The source column switch is connected between the inputs of the signal source and the signal acquisition unit. The ground column switch is connected between the ground and the bottom of the signal acquisition unit. The input of the column read out unit is connected to the input of the signal acquisition unit and the output is used to send out the sampled signal. A between-column switch is installed between the input of a front column signal acquisition unit and the bottom of a back signal acquisition unit. The control unit is used to control the switch in each switch group for connected or disconnected operation according to the sampling working module. Employing this invention can realize gain in the image sensor signal, improvement with circuit structure, achieving minimal chip area, and lowered cost.