Image Sensor Switching Circuit for Noise Reduction
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Solution Overview
Problem
Noise in image sensors negatively affects the quality of images produced, and existing methods have limitations in effectively addressing noise properties, particularly band noise and temporal noise, which impact the performance and linearity of image sensors.
Innovation Solution
The image sensor incorporates a switching circuit that connects or disconnects the input terminals of samplers based on operational modes and noise properties, using ramp voltage paths to optimize noise reduction and improve linearity, while also reducing power consumption and circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple ramp voltage paths are used to reduce noise, then noise properties are improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic switching between different ramp voltage paths based on operational conditions. The switching circuit selectively connects samplers to different ramp voltage paths (first, second, third paths) depending on the operational mode, enabling the system to adapt to varying noise conditions while maintaining manageable circuit complexity through controlled configurability rather than permanent multi-path architecture.
Solution Approach 2:
The patent divides the ramp voltage generation into multiple separate paths (first ramp voltage path, second ramp voltage path, third ramp voltage path), each potentially serving different functional requirements. This segmentation allows independent optimization of each path and selective activation based on noise reduction needs, resolving the contradiction by providing modular noise reduction capability.
2Reliability
If samplers are connected to common ramp voltage path to reduce temporal noise, then temporal noise is reduced, but band noise increases
Solution Approach 1:
The system dynamically switches between different connection configurations: connecting samplers to a common ramp voltage path when temporal noise reduction is prioritized, and disconnecting them to different paths when band noise reduction is needed. This dynamic reconfiguration allows the system to address different noise types based on operational conditions without being locked into a fixed architecture.
Solution Approach 2:
The patent changes the connectivity parameter of the sampling circuit by using switching elements to connect or disconnect samplers from common or individual ramp voltage paths. This parameter change (connection state) enables the system to optimize noise properties by adjusting the electrical configuration rather than changing physical hardware.
3Reliability
If switching circuit is used to connect/disconnect sampler input terminals, then noise reduction is improved, but device complexity increases
Solution Approach 1:
The patent extracts the noise reduction function into a separate switching circuit module that operates independently from the core sampling and pixel array functions. By isolating the switching control logic and ramp voltage path selection into dedicated components, the complexity is contained and managed separately, allowing the main imaging function to remain simple while adding noise reduction capability through modular extraction.
Data Source
AI summary
An image sensor including: a pixel array having a plurality of pixels connected to a plurality of row lines and a plurality of column lines; a plurality of ramp buffers configured to output a ramp voltage generated by a ramp voltage generator; a sampling circuit including a plurality of samplers, each of the plurality of samplers having a first input terminal for receiving the ramp voltage and a second input terminal connected to one of the plurality of column lines; and a switching circuit configured to connect the first input terminals of the samplers to each other or disconnect the first input terminals of the samplers from each other.