Optical Sensor ADC with Two-Phase Light Sensing Under Dark Glass
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Solution Overview
Problem
Existing optical sensor arrangements for ambient light sensing face challenges in achieving high sensitivity, particularly under low light conditions, due to the attenuation of incident light by covering materials like dark glass, and require improved digitalization methods to accurately measure light levels for applications such as display management and exposure control.
Innovation Solution
The optical sensor arrangement employs a two-phase digitalization process, where the first phase performs rough digitalization through charge balancing, and the second phase uses successive approximation for fine digitalization, utilizing an amplifier, comparator, and capacitors to generate a digital value of the sensor current, allowing for precise measurement of ambient light brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a photodiode is buried underneath dark glass for stylish appearance, then aesthetic appearance is improved, but light sensitivity deteriorates due to strong attenuation of incident light
Solution Approach 1:
The patent divides the digitalization process into two distinct phases: a first phase for rough digitalization and a second phase for fine digitalization. This segmentation allows the system to handle the wide dynamic range of light intensities that pass through the dark glass, maintaining measurement precision despite the attenuation. The dual-phase approach enables accurate measurement of both very low and very high light levels that reach the photodiode underneath the dark glass.
Solution Approach 2:
The patent changes the operating parameters of the analog-to-digital converter between two phases. In the first phase, the converter operates with parameters optimized for rough digitalization of higher light levels. In the second phase, parameters are adjusted for fine digitalization of residual light signals. This parameter switching enables the system to maintain high sensitivity across the full range of attenuated light intensities.
2Device complexity
If a single analog-to-digital converter is used for light sensing, then device complexity is reduced, but measurement precision deteriorates due to inability to perform both rough and fine digitalization
Solution Approach 1:
The patent implements a dynamic switching mechanism between two operational modes of the analog-to-digital converter. The converter dynamically transitions from a first conversion operation optimized for rough digitalization to a second conversion operation optimized for fine digitalization. This dynamic operation allows a single converter to effectively perform the functions that would otherwise require multiple specialized converters, maintaining measurement precision while managing device complexity.
Solution Approach 2:
The patent employs periodic switching between two conversion phases: a first phase for rough digitalization and a second phase for fine digitalization. This periodic action allows the system to systematically process light signals through different digitalization stages, ensuring both rough and fine measurement capabilities are achieved within a single converter architecture.
3Measurement precision
If integration time is increased to improve sensitivity in low light conditions, then measurement precision is improved, but productivity deteriorates due to longer measurement time
Solution Approach 1:
The patent applies partial action by performing rough digitalization first, which provides a preliminary measurement result quickly. Then, only if higher precision is needed, the system performs additional fine digitalization. This partial approach allows the system to obtain sufficient measurement results in many cases without completing the full integration process, thereby improving productivity while maintaining the ability to achieve high sensitivity when required.
Solution Approach 2:
The patent performs preliminary rough digitalization in the first phase before committing to the full integration time required for fine digitalization. This preliminary action provides an initial measurement estimate that can be used immediately, improving productivity. The system can then decide whether to invest the additional time for fine digitalization based on the requirements, thus balancing measurement precision and speed.
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 enhances the sensitivity and accuracy of ambient light sensing, enabling effective dynamic adjustment of display panel brightness and exposure control, while optimizing power consumption and avoiding saturation issues.
Implementation Method 1
a photodiode for providing a sensor current
Data Source
Figure 1A
Figure 1B
Figure 1C~1D
AI summary
An optical sensor arrangement (10) comprises a photodiode (11) for providing a sensor current (IPD) and an analog-to-digital converter arrangement (12) which is coupled to the photodiode (11) and determines a digital value of the sensor current (IPD) in a charge balancing operation in a first phase (A) and in another conversion operation in a second phase (B).