Single-Slope ADC Ramp Prediction for Faster Image Sensor Readout
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Solution Overview
Problem
In imaging devices using single-slope analog-digital converters, increasing pixel count and accuracy lead to longer analog-digital conversion times, necessitating a method to shorten conversion time without compromising resolution.
Innovation Solution
An analog-digital converter that acquires voltage values of an analog signal during the settling period, calculates a predicted convergence voltage, generates a ramp wave reference signal based on this value, and measures the time period until intersection, allowing for the derivation of a convergence voltage value, thereby reducing conversion time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of pixels and definition increase to improve imaging quality, then manufacturing precision and measurement precision improve, but the analog-digital conversion time doubles
Solution Approach 1:
The patent applies preliminary action by acquiring the voltage value of the analog signal during the settling period before the main conversion process. This preliminary measurement allows the system to predict the convergence voltage value and generate an appropriately inclined ramp wave reference signal in advance, thereby reducing the counting time required during the actual conversion while maintaining high accuracy for increased pixel counts
2Productivity
If the inclination of the ramp wave reference signal is increased to shorten conversion time, then productivity improves, but measurement precision may be compromised
Solution Approach 1:
The patent applies dynamics by adaptively adjusting the inclination of the ramp wave reference signal based on the predicted convergence voltage value. Instead of using a fixed inclination, the system dynamically determines the appropriate slope to match the expected signal characteristics, enabling faster conversion while preserving measurement precision through optimized signal matching
3Productivity
If counter circuit performs up-counting or down-counting to increase reading speed, then productivity improves, but the count time still doubles with increased pixel definition
Solution Approach 1:
The patent applies parameter changes by modifying the inclination parameter of the ramp wave reference signal based on the predicted convergence voltage value. This parameter adjustment reduces the time required for the counter circuit to complete its counting operation, thereby decreasing count time and improving reading speed even when handling increased pixel counts with higher definition requirements
Data Source
AI summary
An analog-digital converter that includes voltage acquisition circuitry that acquires a voltage value of an analog signal in a settling period, calculation circuitry that calculates a predicted convergence voltage value of the analog signal based on the voltage value of the acquired analog signal, reference signal generation circuitry that generates a ramp wave reference signal based on the predicted convergence voltage value, comparison circuitry that compares the voltage value of the analog signal with the ramp wave, measurement circuitry that measures a time period from a generation of the reference signal to a time before the voltage value of the analog signal intersects with the ramp wave of the reference signal, and addition circuitry that derives a convergence voltage value of the analog signal by adding a voltage value corresponding to the measured time period and a voltage value based on the predicted convergence voltage value.