Proximity Sensor Segmentation for OLED Distance Accuracy
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Solution Overview
Problem
Proximity sensors positioned under low light transmittance screens, such as OLED displays, struggle to distinguish between objects at very short distances (e.g., a few millimeters) and those at long distances (e.g., several centimeters), leading to inaccurate triggering of screen on/off functions.
Innovation Solution
A proximity capture device with a proximity sensor comprising two photodiodes and a control circuit that weights and processes signals from these photodiodes to differentiate between short and long distances, using a state machine to manage the weighting coefficient and thresholds for accurate distance determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a proximity sensor is positioned under a low light transmittance screen (e.g., OLED display), then the device can maintain a compact design with the sensor integrated beneath the display, but the sensor fails to distinguish between very short distance (a few millimeters) and long distance (several centimeters) objects
Solution Approach 1:
The light detector is divided into multiple photodiodes (at least two) that are spatially separated. Each photodiode receives reflected light at different intensities depending on object distance, enabling the system to distinguish between very short and long distances by comparing the relative signal strengths from different detector segments.
Solution Approach 2:
Different regions of the light detector are assigned different functions - some photodiodes are positioned to detect light reflected from very close objects while others detect light from distant objects. This local differentiation allows the sensor to simultaneously measure multiple distance ranges with appropriate sensitivity in each region.
2Device complexity
If a proximity sensor uses a single photodiode to detect reflected light, then the device structure remains simple, but it cannot differentiate between objects at very short and long distances under low light transmittance screens
Solution Approach 1:
The light detector is segmented into multiple photodiodes positioned at different locations. This segmentation enables distance differentiation without requiring complex additional components, maintaining relative structural simplicity while achieving the needed measurement precision through spatial distribution of detector elements.
Solution Approach 2:
The solution transitions from a single-point detection approach to a multi-point spatial detection array. By adding the dimension of spatial distribution across multiple photodiodes, the system gains the capability to distinguish distance ranges without proportionally increasing overall device complexity.
3Device complexity
If the proximity sensor delivers a single output signal without dynamic weighting, then the processing is simple, but the sensor cannot adapt to differentiate distance ranges when screen light transmittance is low
Solution Approach 1:
The signal processing incorporates dynamic weighting coefficients that can be adjusted based on detected light levels and distance conditions. This dynamic adaptation allows the sensor to optimize its sensitivity and differentiation capability for different distance ranges, improving accuracy without requiring a completely complex processing system.
Solution Approach 2:
The system changes processing parameters (weighting coefficients) based on the operating conditions and detected signal characteristics. By dynamically adjusting these parameters, the sensor adapts to low light transmittance conditions and maintains accurate distance determination across varying object distances.
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
The solution effectively differentiates between very close and distant objects, improving the accuracy of screen on/off control without increasing device size or power consumption, thus addressing the limitations of existing proximity sensors under low light transmittance screens.
Implementation Method 1
the source emits a light beam, for example an infrared beam, being reflected by an object and picked up in return by the detector
Implementation Method 2
The detector may comprise one or more photodiodes
Implementation Method 3
The proximity sensor can be a sensor of the time-of-flight (ToF) type, in which case the processing unit can be configured to calculate the travel time between the emission of the light beam and its reception by the detector
Data Source
AI summary
The present disclosure relates to a proximity capture device that includes a proximity sensor having a light source and a light detector. The light detector includes at least one first photodiode configured to generate a first signal when it detects a first light signal emitted by the light source and reflected by an object and one second photodiode configured to generate a second signal when it detects a second light signal emitted by the light source and reflected by the object. The proximity sensor is configured to deliver an output signal based on weighting, with a weighting coefficient, the first signal differently from the second signal. The proximity capture device includes a control circuit configured to provide the weighting coefficient to the proximity sensor and receive the output signal, and to trigger from a first state in which the weighting coefficient has a first value, to a second state when the output signal crosses a first threshold; in the second state, apply to the weighting coefficient a second value different from the first value; and compare the output signal obtained by applying the second value and a second threshold so as to trigger from the second state to a third state if the output signal is less than the second threshold, or to trigger from the second state to a fourth state if the output signal is higher than the second threshold.