Dual-Comparator Pixel Readout for Wide Dynamic Range Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image sensors have a narrow dynamic range in their analog-to-digital converters, making it difficult to accurately convert pixel signals from a wide range of illuminance levels, particularly in varying light conditions.
Innovation Solution
A solid-state imaging element with a dual comparator system and capacitor units of different gains, where the capacitance ratios between input capacitive elements determine the gains of each comparator, allowing for wide dynamic range imaging by selecting the appropriate output signal based on illuminance levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single comparator is used for AD conversion, then the device complexity is low, but the dynamic range is narrow and cannot handle wide illuminance ranges
Solution Approach 1:
The patent divides the single comparator into two separate comparators (first comparator and second comparator), each handling different portions of the dynamic range. The first comparator processes signals with a first gain while the second comparator processes signals with a second gain, allowing the system to cover a wider overall dynamic range by segmenting the conversion task across multiple specialized components.
Solution Approach 2:
The patent implements dynamic gain switching by selecting between two capacitor units with different capacitance values based on the input signal level. The capacitor unit selection circuit dynamically switches between the first capacitor unit (first gain) and the second capacitor unit (second gain) to optimize the conversion process for different illuminance conditions, making the system adaptable rather than static.
2Measurement precision
If the capacitance ratio between input capacitive elements is changed to adjust gain, then the sensitivity and dynamic range are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent changes the capacitance parameter of the capacitor units to achieve different gain levels. By providing at least two capacitor units with different capacitance values (first capacitor unit with first capacitance, second capacitor unit with second capacitance), the system can adjust the gain by selecting different capacitor units, thereby achieving accurate AD conversion across different signal levels while managing manufacturing tolerances through discrete capacitor selection rather than continuous adjustment.
Data Source
AI summary
Solid-state imaging elements are disclosed. In one example, a solid-state imaging element includes a plurality of pixels. A pixel signal line transmits a pixel signal of a pixel, a reference signal line transmits a reference signal to be compared with the pixel signal, a first comparator outputs a first output signal according to the pixel signal on the basis of a voltage difference between the pixel signal and the reference signal, a second comparator outputs a second output signal according to the pixel signal on the basis of the voltage difference between the pixel signal and the reference signal, a first capacitor unit between the pixel signal line or the reference signal line and the first comparator and set to a first gain, and a second capacitor unit between the pixel signal line or the reference signal line and the second comparator and set to a second gain.