Solid-State Image Sensor ADC with Dual Comparators and Gain Selection
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Solution Overview
Problem
The existing solid-state imaging elements face challenges in reducing power consumption while maintaining image quality, as the timing of comparison result inversion can deviate, leading to errors in digital signal conversion and image quality deterioration, and there is a trade-off between image quality, power consumption, and AD-conversion time.
Innovation Solution
A solid-state imaging element with dual comparators and counters that use different reference voltages with varying slopes, allowing for simultaneous operation and selection of digital signals based on input voltage levels to optimize gain and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single-slope type ADC with a common power source is used to reduce power consumption, then power consumption is reduced, but the timing of inversion of the comparison result deviates from ideal timing, causing errors in digital signal generation and deterioration of image quality
Solution Approach 1:
The patent divides the ADC system into two independent comparators (first comparator and second comparator) that operate simultaneously with different reference voltages. Each comparator processes a portion of the input voltage range, allowing the system to maintain accurate inversion timing for both segments while reducing the operational burden on individual components, thereby enabling power savings without sacrificing measurement precision.
2Device complexity
If a single gain is used for AD-conversion, then device complexity is reduced, but there is a trade-off between image quality, power consumption, and AD-conversion time when adjusting counter operation frequency
Solution Approach 1:
The patent implements dynamic gain selection by providing two comparators with different gains (first comparator with first gain, second comparator with second gain). The system dynamically selects which comparator to use based on the input voltage level and required conversion speed. This dynamic approach allows the system to optimize between conversion speed and power consumption without requiring a fixed complex multi-gain structure, thereby improving productivity while managing device complexity.
3Measurement precision
If the counter operation frequency is increased to improve dark region image quality, then image quality improves, but power consumption increases and AD-conversion time increases
Solution Approach 1:
The patent applies local quality by using different gains for different input voltage ranges. The first comparator with higher gain is used for lower input voltage levels (corresponding to dark regions), while the second comparator with lower gain is used for higher input voltage levels. This localized optimization ensures that dark region image quality is improved through higher gain without requiring the entire system to operate at high gain, thereby reducing overall power consumption and AD-conversion time.
Data Source
AI summary
Solid-state imaging elements that prevent deterioration of image quality, and reduce power consumption and AD-conversion time are disclosed. In one example, a solid-state imaging element includes a first comparator that uses a first voltage corresponding to an input voltage received from a first pixel, in reference to a first voltage difference between the input voltage and a first reference voltage, and that outputs a comparison result between the input voltage and the first reference voltage in reference to a second voltage difference, and a second comparator that outputs a comparison result of comparison between the input voltage and the second reference voltage in reference to a fourth voltage difference.