Proximity Sensor Sequencing for Ambient Light Cancellation
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Solution Overview
Problem
Proximity sensors in portable devices face significant errors due to ambient light interference, particularly when the sensing time interval between light-source turn-on and turn-off states is long, leading to incomplete subtraction of ambient light components and increased noise in sensing results.
Innovation Solution
The method involves adjusting the execution sequence of light-source turn-on and turn-off operations into groups with consecutive pairs, allowing for effective cancellation of ambient-light components without increasing the operation frequency, thereby reducing noise in the sensing result.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensing time interval between light-source turn-on and turn-off operations is shortened, then the ambient light component subtraction accuracy is improved, but the operation frequency increases beyond device capabilities
Solution Approach 1:
The patent divides the sensing operations into multiple groups, where each group contains an odd number of light-source turn-on operations followed by an odd number of light-source turn-off operations. This segmentation allows the system to process ambient light subtraction in manageable segments rather than requiring a single high-frequency operation, thus improving subtraction accuracy without exceeding device operation frequency limits.
Solution Approach 2:
The patent changes the parameter of operation sequencing by arranging odd-numbered turn-on operations followed by odd-numbered turn-off operations in groups. This parameter change in the operation sequence allows for better ambient light cancellation while maintaining feasible operation frequencies within device capabilities.
2Speed
If the sensing time interval between light-source turn-on and turn-off operations is lengthened, then the operation frequency is reduced within device capabilities, but the ambient light component subtraction accuracy deteriorates
Solution Approach 1:
By segmenting the sensing operations into groups with multiple turn-on and turn-off cycles, the patent achieves effective ambient light subtraction over a longer total time period while keeping individual operation intervals within device capabilities. The segmented approach accumulates cancellation效果 across multiple cycles.
Solution Approach 2:
The patent employs periodic action by repeating the pattern of odd-numbered turn-on operations followed by odd-numbered turn-off operations in groups. This periodic structure allows the system to operate at feasible frequencies while achieving superior ambient light cancellation through multiple cycles of measurement and subtraction.
3Ease of manufacture
If the proximity sensor is positioned below the panel, then the device structure is simplified and full-screen display is achieved, but the light intensity received by the optical sensor is reduced
Solution Approach 1:
The patent employs multiple continuous cycles of light-source turn-on and turn-off operations within each group. This continuity of useful action accumulates the weak light signals from the reflected light and enhances the ambient light cancellation effect, enabling accurate proximity sensing even with reduced light intensity from the sensor's position below the panel.
Solution Approach 2:
By using periodic action with multiple turn-on and turn-off cycles in each group, the patent amplifies the weak reflected light signals through repeated measurement cycles. The periodic operation pattern allows the optical sensor to accumulate sufficient signal data despite the reduced light intensity caused by its position below the panel.
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 significantly reduces ambient-light noise in the sensing result, maintaining high accuracy even when proximity sensors are positioned below panels with reduced light intensity, achieving noise levels below ±50 units.
Implementation Method 1
a light-emitting unit 101 (for example, a light-emitting diode LED, a laser diode LD) generates light L. The light L is reflected by a reflector (for example, a human body or reflective objects) and generates corresponding reflection light.
Implementation Method 2
The reflection light is received by an optical sensor 103 (for example, a photodiode PD) and hence providing the sensing result for distance.
Implementation Method 3
the components of the ambient light A received during the light-source turn-off operation p2 will be higher than the component of the ambient light A received during the light-source turn-on operation p1. Thereby, after a processing circuit 107 integrates the sensing signal output by the optical sensor 103, the ambient-light component a in the integration over the light-source turn-on operation p1 will be smaller than the ambient-light component b in the integration over the light-source turn-off operation p2.
Data Source
AI summary
An operation method of a proximity sensor comprises: controlling a light-emitting element by a processing circuit. Such control includes a plurality of light source on and light source off operations. An optical sensor receives light and outputs a sensing signal corresponding to the intensity of the light. The processing circuit computes the sensing signal to produce a sensing result. The plurality of light source on and light source off operations includes a group having two light sources on operations and two light sources off operations. The two light sources on operations in the group or the two light sources off operations in the group are performed consecutively. In this way, the ambient light components of the light source on and off operations may cancel out each other to reduce the ambient light components contained in the sensing results.