Optical Sensor Frequency Modulation for Ambient Light Interference
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Solution Overview
Problem
Optical sensors face interference issues due to external light, which can simulate a clear monitoring area even when objects are present, leading to malfunctions and inadequate sensitivity and resistance to interference.
Innovation Solution
The optical sensor modulates light beams with a sequence of signal sections having a predetermined frequency spectrum, and the evaluation unit performs spectral decomposition to check for specific frequency components and amplitudes/phases in received signals, ensuring accurate detection and high error tolerance against external light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the optical sensor uses simple light beam transmission without complex modulation, then the device complexity is reduced, but the resistance to interference from ambient light deteriorates
Solution Approach 1:
The patent applies periodic action by modulating the light beam with a periodic signal sequence consisting of multiple signal sections. Each signal section has a specific frequency spectrum that can be spectrally decomposed. This periodic modulation allows the receiver to distinguish the transmitted signal from ambient light interference through frequency analysis, thereby improving interference resistance without significantly increasing device complexity
Solution Approach 2:
The patent changes the frequency domain parameters of the light beam by modulating it with a specific signal sequence. The signal sections are designed with predetermined frequency spectra, and the receiver performs spectral decomposition to detect specific frequency components. This parameter transformation from time domain to frequency domain enables the system to reject ambient light interference that does not match the expected frequency signature
2Measurement precision
If the optical sensor increases sensitivity to detect objects at greater ranges, then the detection range is improved, but the susceptibility to ambient light interference worsens
Solution Approach 1:
The patent implements feedback through the evaluation unit that performs spectral decomposition of the received signal and compares the detected frequency components against expected values. The system uses the detected frequency spectrum information to verify whether the received signal matches the transmitted modulated signal pattern. This feedback mechanism allows the sensor to maintain high sensitivity while rejecting ambient light that does not contain the expected frequency components
Solution Approach 2:
The periodic modulation of the light beam with a specific signal sequence creates a unique frequency fingerprint that can be detected even at low signal levels. The receiver uses spectral decomposition to identify this periodic pattern, enabling high sensitivity detection while filtering out non-periodic ambient light interference
3Measurement precision
If the optical sensor performs full spectral decomposition of received signals, then the detection accuracy is improved, but the evaluation complexity and processing time increase
Solution Approach 1:
The patent extracts only the essential frequency components from the full spectrum of the received signal. Instead of analyzing the entire frequency spectrum, the evaluation unit identifies and evaluates specific frequency components that are characteristic of the transmitted signal sequence. This extraction approach maintains detection accuracy while significantly reducing evaluation complexity and processing requirements
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 enables reliable and error-tolerant detection of light beams, improving the sensor's resistance to interference and sensitivity, allowing for precise object detection even in the presence of external light sources.
Implementation Method 1
at least one transmitter (4) which emits light beams (3)
Implementation Method 2
at least one receiver (6) receiving light beams (3)
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5b
AI summary
The invention relates to an optical sensor 1 with at least one light beam emitting transmitter (4, 4.1-4.N), at least one light beam receiving receiver (6, 6.1-6.N), and an evaluation unit (9) in which an object detection signal is generated depending on the received signals (6a) from the receiver (6, 6.1-6.N). The light beams (3) are modulated with a sequence of signal segments (11). The modulated signal segments (11) have a predetermined spectrum in the frequency domain. On the receiving side, a spectral decomposition of the received signals (6a) is performed. In the evaluation unit (9), it is checked whether a number of predetermined frequency components are present in a spectrally decomposed received signal (6a). Depending on this, it is assessed whether the light rays (3) emitted by the transmitter (4, 4.1-4.N) have reached the receiver (6, 6.1-6.N) or not.