Image Sensor Counter Circuit with D-Latch for Noise-Stable Conversion
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Solution Overview
Problem
Existing image sensors face challenges in reducing noise and coupling influences during the conversion of analog signals to digital signals, particularly in high-definition imaging, due to fluctuations in complement control signals affecting the accuracy of complement operations.
Innovation Solution
Incorporating a counter with a division function and a D-latch to perform stable complement and division operations, which reduces the impact of coupling and enables effective reset multiple sampling techniques, thereby enhancing noise reduction and image reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a counter is used to convert analog signals to digital signals in high-definition image sensors, then the conversion capability is improved, but noise and coupling influences increase due to fluctuations in complement control signals
Solution Approach 1:
The patent introduces a D-latch as an intermediary component between the complement control signal and the counter. The D-latch stabilizes the complement control signal by latching it during the counting operation, preventing fluctuations from directly affecting the counter. This intermediary element isolates the counter from harmful signal variations, reducing noise and coupling influences while maintaining accurate analog-to-digital conversion capability
2Reliability
If complement operations are performed during analog-to-digital conversion, then the digital signal accuracy is improved, but the system becomes sensitive to fluctuations in complement control signals
Solution Approach 1:
The patent applies preliminary action by stabilizing the complement control signal before it is used in the complement operation. The D-latch captures and holds the complement control signal at a stable state prior to the counting operation, ensuring that the signal does not fluctuate during the critical complement operation. This preliminary stabilization ensures reliable digital signal accuracy while maintaining system stability
3Object-affected harmful factors
If reset multiple sampling techniques are applied to reduce noise, then the image quality is improved, but the complexity of the counter circuit increases
Solution Approach 1:
The D-latch serves as a simple intermediary that enables reset multiple sampling techniques without significantly increasing circuit complexity. By providing a stable complement control signal through the latch, the system can perform multiple sampling operations to reduce noise. The D-latch adds minimal complexity compared to the benefits gained from noise reduction through multiple sampling
Data Source
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AI summary
An image sensor includes a pixel sensor configured to sense an incident light and to output an analog sampling signal; a sampling unit comparing the sampling signal and a ramp signal, and outputting a comparison signal having a duration that is indicative of the amplitude of the sampling signal; and a counter counting a length of the comparison signal based on a clock signal and first and second complement control signals. The counter includes an AND gate ANDing the comparison signal and the clock signal; and a counting unit triggered at a falling edge of the AND gate output to output a count value. The counting unit includes a complement operation controller storing an inverted count value that is an inversion of the count value in response to the first complement control signal, and outputting the inverted count value in response to the second complement control signal; and a D-flip-flop that is set or reset depending on the inverted count value, and outputs the count value.