Light-to-Frequency Converter for Accurate Low-Photocurrent Sensing
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Solution Overview
Problem
Light-to-frequency conversion in optical sensors, such as those used in mobile devices, often fails to provide accurate estimates of incident light in low light conditions due to errors associated with low photocurrent counts, leading to larger measurement errors compared to bright light conditions.
Innovation Solution
A method and arrangement that utilize a photodiode, an analog-to-digital converter, and a signal processing unit to generate a digital output signal by converting photocurrent into asynchronous and fractional time counts, accounting for errors through charge balancing and integration periods, allowing for accurate measurement even at low counts and extending the dynamic range of operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional light-to-frequency conversion is used in low light conditions, then the device complexity remains simple, but the measurement precision deteriorates due to low photocurrent counts and larger errors
Solution Approach 1:
The patent segments the light-to-frequency conversion process into distinct functional blocks: photodiode for photocurrent generation, analog-to-digital converter for charge balancing operation, counter for counting clock cycles, and signal processing unit for determining the output signal. This segmentation allows each component to be optimized independently, achieving high measurement precision through sophisticated processing while maintaining manageable overall device complexity through modular architecture.
Solution Approach 2:
The patent introduces an analog-to-digital converter as an intermediary component between the photodiode and the counter. This intermediary performs charge balancing operations that convert the analog photocurrent into a form suitable for digital processing, enabling accurate measurement of low photocurrents by translating them into countable digital signals through the mediation of reference charge packages and clock signal synchronization.
2Measurement precision
If integration time is increased to improve low light measurement, then the measurement precision improves, but the productivity decreases due to longer measurement periods
Solution Approach 1:
The patent employs periodic action through the use of clock signals with specific frequencies that drive the conversion process. The counter counts clock cycles during the integration period, and the periodic nature of the clock signal enables precise time measurement and synchronization. This periodic action allows the system to achieve high measurement precision through multiple clock cycles while maintaining productivity by using efficient clock frequencies and completing conversions in optimized time periods.
Solution Approach 2:
The patent utilizes parameter changes by varying the integration time and clock signal frequency to optimize the balance between measurement precision and productivity. The system can adjust the number of clock cycles counted and the duration of integration periods to match different lighting conditions, achieving high accuracy in low light through longer integration when needed while maintaining faster response in brighter conditions through shorter integration periods.
3Adaptability or versatility
If conventional conversion methods are used, then the device operates in bright light conditions with adequate precision, but the adaptability deteriorates in low light and varying lighting conditions
Solution Approach 1:
The patent implements dynamics through the signal processing unit that dynamically adjusts the conversion process based on the measured photocurrent levels and integration results. The system can adapt its operation to varying lighting conditions by processing the counted clock cycles and fractional time counts to produce accurate output signals across different light levels, enabling the converter to dynamically optimize its performance for both bright and low light environments.
Solution Approach 2:
The patent achieves universality through the analog-to-digital converter that handles multiple functions: charge balancing operations for photocurrent conversion, reference charge package generation, and synchronization with clock signals. This multi-functional component enables the system to accurately measure photocurrents across a wide range of lighting conditions, from bright to low light, using the same hardware architecture, thereby providing universal adaptability without requiring separate conversion circuits for different lighting scenarios.
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
This approach enables accurate measurement of low photocurrents with reduced errors, improves measurement accuracy in less integration time, and is immune to modulation frequencies like 50/60 Hz, thereby enhancing the dynamic range and power efficiency of light-to-frequency conversion.
Implementation Method 1
a photocurrent is generated by means of a photodiode
Data Source
AI summary
A method for light-to-frequency conversion comprises generating a photocurrent by means of a photodiode and converting the photocurrent into a digital comparator output signal in a charge balancing operation depending on a first clock signal. From the digital comparator output signal an asynchronous count is determined and comprises an integer number of counts depending on the first clock signal. From the digital comparator output signal a fractional time count is determined and depends on a second clock signal. Finally, from the asynchronous count and from the fractional time count a digital output signal is calculated which is indicative of the photocurrent generated by the photodiode. The method may be carried out by an exemplary light-to-frequency converter equipped with a photodiode.