Image Sensor Ramp Comparison Circuit for Fast Multi-Sampled Readout
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Solution Overview
Problem
Existing image sensors face challenges in reducing sampling time during readout operations, which affects the efficiency of capturing pixel signals multiple times, leading to increased readout times and noise reduction limitations.
Innovation Solution
The implementation of an image sensor system that includes an analog comparator, counter, and digital comparing circuit to compare pixel signals with ramp signals and reference codes, allowing for efficient sampling and noise reduction by generating digital signals based on comparison results, thereby reducing readout time and improving noise handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pixel signals are sampled multiple times during readout time to improve noise reduction, then noise reduction capability is improved, but readout time increases
Solution Approach 1:
The patent applies preliminary action by pre-generating multiple ramp signals with different signal levels before the actual sampling process. These ramp signals are prepared in advance and stored, allowing the pixel signals to be quickly compared against them during readout without requiring time-consuming signal generation, thus enabling multiple samples while maintaining short readout time
Solution Approach 2:
The patent segments the readout process into multiple independent sampling operations, where pixel signals are divided into multiple groups and each group is sampled separately against different ramp signals. This segmentation allows parallel processing of multiple samples and enables efficient utilization of the readout time, achieving both multiple sampling and short overall readout time
2Productivity
If multiple ramp signals with different signal levels are generated and stored, then sampling efficiency is improved, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple ramp signal generators into a single integrated circuit that can generate multiple ramp signals with different signal levels simultaneously. By combining these functions into one unified structure rather than using separate generators for each ramp signal, the circuit complexity is reduced while maintaining the ability to perform efficient multi-level sampling
Data Source
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AI summary
An image sensor for sampling a pixel signal a plurality of times during a readout time includes an analog comparator configured to compare a signal level of the pixel signal with a signal level of a target ramp signal that is any one of a plurality of ramp signals, a counter configured to output counting data based on a comparison result of the analog comparator, and a digital comparing circuit configured to compare a binary value of a target reference code corresponding to the target ramp signal with a binary value of the counting data and determine whether to output a digital signal corresponding to the counting data to a data output circuit based on a result of the comparison between the binary value of the counting data and the binary value of the target reference code.