Optical Sensor Circuit with Shared Signal Conditioning Against Crosstalk
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Solution Overview
Problem
Existing sensor circuits with multiple optical sensors face issues with incorrect signal evaluation due to ambient light and crosstalk from neighboring sensors, leading to high error rates and complex constructions.
Innovation Solution
A sensor circuit design featuring multiple optical sensors with a common signal processing circuit, modulation resistors with different resistance values, and specific control signal inputs to enable independent control and evaluation of measurement signals, reducing crosstalk and simplifying the construction by using fewer components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple optical sensors are used in a sensor circuit, then the functionality of touch- and proximity-sensitive control elements is improved, but the risk of faulty signal evaluation due to ambient light and crosstalk increases
Solution Approach 1:
The patent divides the sensor circuit into independently controllable sensor groups, where each group can be activated separately through specific control signal inputs. This segmentation allows selective measurement of individual sensors or groups, preventing crosstalk between adjacent sensors and improving signal evaluation reliability.
Solution Approach 2:
The patent employs periodic activation of optical transmitters through control signal inputs, enabling time-multiplexed operation. By activating sensors in alternating sequences or specific time windows, the system can distinguish between signals from different sensors and filter out ambient light interference through synchronous detection.
2Reliability
If individual control signal inputs are provided for each optical sensor, then reliable separation and evaluation of measurement signals is achieved, but the number of control signal inputs and device complexity increases
Solution Approach 1:
The control signal inputs are segmented into specific individual inputs and a common input, allowing hierarchical control. Individual inputs enable selective activation of specific sensors or groups, while the common input provides overall control, reducing the total number of control lines needed compared to fully independent control for each sensor.
Solution Approach 2:
The patent provides control signal inputs for individual sensors or groups rather than requiring fully independent control for every single sensor. This partial individualization combined with common control achieves sufficient signal separation while limiting the growth of control signal complexity.
3Device complexity
If a common signal conditioning circuit is used for multiple optical receivers, then the sensor circuit construction is simplified and fewer components are required, but the measurement signals must be easily distinguishable through modulation
Solution Approach 1:
The patent uses modulation resistors with different resistance values connected to different optical receivers to change the electrical parameters of each sensor channel. This creates distinct signal characteristics (different modulation depths or frequencies) that allow the common signal conditioning circuit to distinguish between signals from different sensors through parameter-based identification.
4Measurement precision
If modulation resistors with different resistance values are connected in parallel to optical receivers, then measurement signals can be easily modulated and distinguished, but the number of passive components increases
Solution Approach 1:
Instead of using completely different modulation mechanisms for each sensor, the patent varies a single parameter (resistance value) of identical modulation resistors. This approach achieves signal distinction through parameter diversity rather than structural diversity, minimizing the increase in passive components while maintaining measurement precision.
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 design achieves a lower error rate in signal evaluation, simplifies the sensor circuit construction, and allows for the use of fewer active and passive components, maintaining safety standards while reducing the number of ADC channels and GPIO pins required.
Implementation Method 1
Each optical sensor comprises an optical transmitter, preferably an IR (infrared) transmitter, preferably in the form of a photodiode, and an optical receiver, preferably an IR receiver, preferably in the form of a phototransistor
Data Source
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AI summary
In a sensor circuit with multiple optical sensors, each comprising an optical transmitter (Dn) and an optical receiver (Tn), the optical transmitter (Dn) and optical receiver (Tn) of each optical sensor are connected to a specific control signal input (In), the optical transmitters (Dn) of the multiple optical sensors are connected to a common control signal input (Is), and the optical receivers (Tn) of the multiple optical sensors are connected to a common measurement signal output (Sx). A common signal conditioning circuit (SC), preferably comprising a high-pass filter circuit (HPF) and a peak detector (Gp1, Cp, Rp3), is connected between the optical receivers (Tn) of the multiple optical sensors and the common measurement signal output (Sx).