Ambient Flicker Detection Circuits With Anti-Aliasing Sampling
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Solution Overview
Problem
Existing electronic devices with sensors struggle to accurately measure ambient light flicker, which can affect image and video quality captured by onboard cameras.
Innovation Solution
The use of a sigma-delta converter, a folding capacitive transimpedance amplifier (C-TIA) circuit, or a circuit with a digital filter and a current source to measure ambient light flicker, employing techniques such as fast Fourier transform (FFT), filtering, and non-uniform sampling to prevent aliasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sigma-delta converter is used to measure ambient light, then the output voltage can be reduced when it exceeds a threshold, but aliasing occurs in the measured flicker signals
Solution Approach 1:
The patent applies preliminary action by performing filtering operations on the output voltage signal before it is fully processed for flicker measurement. The digital filter removes aliased components from the signal in advance, preventing them from interfering with the subsequent flicker detection and FFT analysis, thus ensuring accurate measurements without aliasing contamination
Solution Approach 2:
The patent introduces an intermediary digital filter between the sigma-delta converter output and the flicker measurement process. This filter acts as a mediator that selectively removes unwanted aliased frequency components while preserving the genuine flicker signal, allowing accurate flicker detection without the harmful effects of aliasing
2Ease of manufacture
If uniform sampling is used to process the sigma-delta converter output, then the processing is simple, but flicker signals are attenuated
Solution Approach 1:
The patent applies dynamics by transitioning from uniform sampling to non-uniform sampling based on the trigger events of the sigma-delta converter. Instead of sampling at fixed intervals, the system dynamically adjusts sampling timing to capture the output voltage at meaningful moments (when triggers occur), preserving flicker signal integrity while maintaining processing feasibility
Solution Approach 2:
The patent changes the sampling parameter from fixed uniform intervals to variable non-uniform intervals based on trigger events. This parameter change allows the system to capture flicker signals more effectively by sampling at moments when actual changes occur, preventing signal attenuation while keeping the processing approach relatively simple
3Stability of the object's composition
If the capacitor reduces output voltage frequently to maintain threshold compliance, then the voltage stays within range, but the flicker measurement becomes inaccurate
Solution Approach 1:
The patent extracts the flicker information from the sigma-delta converter output at specific trigger moments when the capacitor reduces voltage. By counting triggers and analyzing the voltage at these extracted points, the system measures flicker without being confounded by the capacitor's frequent voltage reductions, thus maintaining both voltage stability and measurement accuracy
Solution Approach 2:
The patent uses partial action by measuring flicker based on a subset of the full signal - specifically, by analyzing triggers and voltage values at selected moments rather than continuously monitoring the entire output. This partial measurement approach avoids the distortion caused by frequent capacitor interventions while still capturing accurate flicker characteristics
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These solutions enable accurate detection of ambient light flicker, improving image and video quality by mitigating flicker-related issues and reducing aliasing effects.
Implementation Method 1
a photodiode generates charge in response to ambient light
Data Source
AI summary
An electronic device may have a sensor to measure ambient flicker. The sensor may be a sigma-delta converter. The flicker may be calculated based on the voltage output of the sigma-delta converter and the number of times the sigma-delta converter is triggered during a predetermined period, thereby reducing the voltage output. In particular, a fast Fourier transform (FFT) may be used on these values to determine the flicker. If desired, filtering and/or non-uniform sampling may be incorporated to avoid aliasing. Additionally or alternatively, a Lomb-Scargle spectral analysis may be used to prevent the attenuation of the measured flicker signals. As an alternative to using a sigma-delta converter to determine ambient flicker, a folding capacitive transimpedance amplifier (C-TIA) circuit or a circuit with an analog to digital converter and digital filter may be used to measure the ambient flicker.