Proximity Sensor Crosstalk Compensation With Coarse and Fine Charging
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Solution Overview
Problem
Proximity sensors face challenges in accurately detecting targets due to optical crosstalk, which is the unwanted reflection of optical signals from disturbing objects, leading to noise components in the reflected signal that interfere with the useful signal from the target, especially in applications requiring extended range and high resolution.
Innovation Solution
A proximity sensor system with a crosstalk compensation circuit that includes a first charging circuit for coarse crosstalk compensation and a second charging circuit, configured as an offset adjustment circuit for an operational amplifier, to isolate and cancel out noise components, allowing the output signal to be dependent only on the useful component of the reflected signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a proximity sensor uses optical signals to detect targets at extended range, then the detection range is improved, but optical crosstalk from disturbing objects increases causing noise in the reflected signal
Solution Approach 1:
The patent segments the crosstalk compensation into two distinct parts: a first charging circuit for coarse crosstalk compensation and a second charging circuit for fine crosstalk compensation. This segmentation allows the system to handle both large-range and high-resolution compensation requirements independently, resolving the contradiction between extended detection range and noise reduction.
Solution Approach 2:
The patent performs preliminary crosstalk compensation by charging capacitors with compensation charges before the actual measurement. The first charging circuit pre-compensates for the majority of crosstalk, and the second charging circuit fine-tunes the compensation. This preliminary action removes the harmful optical crosstalk effect before it interferes with the target detection, enabling extended range measurement with high resolution.
2Device complexity
If a single charging circuit is used for crosstalk compensation, then the device complexity is reduced, but the compensation range and resolution cannot be maintained simultaneously
Solution Approach 1:
The patent divides the charging circuit into two specialized sub-circuits: a first charging circuit with a first capacitor for coarse compensation and a second charging circuit with a second capacitor for fine compensation. Each sub-circuit is optimized for its specific function, with the first handling large compensation ranges and the second providing high-resolution adjustments. This segmentation achieves both extended compensation range and high precision while keeping each individual circuit relatively simple.
Solution Approach 2:
The patent implements dynamic control of the two charging circuits through a control circuit that independently adjusts the charging amounts of the first and second capacitors. This dynamic adjustment allows the system to adapt to different crosstalk conditions, providing coarse compensation when needed and fine-tuning when high precision is required, thereby achieving both extended range and high resolution compensation.
3Reliability
If crosstalk compensation is applied, then the noise component is reduced, but the device complexity increases due to additional charging circuits
Solution Approach 1:
The patent segments the crosstalk compensation function into two distinct charging circuits with different capacities and functions. The first charging circuit handles the bulk of the compensation with a larger capacitor, while the second charging circuit provides fine-adjustment capability with a smaller capacitor. This segmentation achieves high signal accuracy by addressing both large and small crosstalk variations, while the modular structure keeps the complexity manageable through clear functional separation.
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 provides a wide crosstalk compensation range while maintaining fine resolution, effectively filtering out noise and enhancing the accuracy of target detection and distance measurement in proximity sensing applications, such as in mobile phones without the need for physical holes for signal transmission.
Implementation Method 1
a first charging circuit to provide a first charge and a second charging circuit to provide a second charge, the first and the second charge being applied to the signal node
Implementation Method 2
The second charging circuit, in particular, is configured as an offset adjustment circuit for an operational amplifier
Data Source
AI summary
A proximity sensor (1) with crosstalk compensation comprises a transmitting circuit (10) to transmit a signal to be reflected at a target (2) and a disturbing object (3), and a receiving circuit (20) to receive a reflected signal (RS) having a useful component (RSI) and a noise component (RS2). The receiving circuit (20) comprises an output node (A20) to provide an output signal (Vout2) in dependence from the distance of the proximity sensor (1) from the target (2). The receiving circuit (20) comprises a crosstalk compensation circuit (100) comprising a first charging circuit (110) to provide a first charge for for coarse crosstalk compensation and a second charging circuit (120) to provide a second charge for fine crosstalk compensation. A control circuit (30) sets an amount of the first and the second charge so that the output signal (Vout2) of the crosstalk compensation circuit (100) is dependent on the useful component (RSI) and independent on the noise component (RS2) of the reflected signal (RS).