Optical Sensor Disturbance Light Rejection via Periodic Integration
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Solution Overview
Problem
Existing optical sensors malfunction when exposed to disturbance light, such as natural or illuminating light, which affects their ability to accurately sense object movement.
Innovation Solution
The optical sensor employs a light-emitting element, a light-receiving element, a driving circuit, an integrating circuit, and an output control circuit to differentiate between disturbance light and reflected light by integrating photocurrents during specific periods and outputting signals based on these differences, allowing it to function effectively even in the presence of disturbance light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical sensor is used to detect reflected light from an object, then the sensor can sense object position and movement, but the sensor malfunctions when exposed to disturbance light such as natural light or illuminating light
Solution Approach 1:
The light-emitting element emits light in periodic pulses rather than continuously. The driving circuit controls the light-emitting element to emit light during specific time periods (first and third periods) and remain off during other periods (second and fourth periods). This periodic emission allows the sensor to distinguish between reflected light (which arrives synchronously with the light pulse) and disturbance light (which is continuous or unsynchronized), thereby maintaining detection accuracy while achieving resistance to disturbance light.
Solution Approach 2:
The sensor continuously monitors the light-receiving element's output across multiple time periods, integrating useful information from both the light-emitting periods and the dark periods. By continuously comparing signals across different time windows and calculating differences, the system maintains uninterrupted object detection capability while effectively filtering out disturbance light through temporal analysis.
2Measurement precision
If the light-emitting element emits light continuously to ensure sufficient light for detection, then detection accuracy is maintained, but the sensor becomes highly susceptible to disturbance light
Solution Approach 1:
The light-emitting element operates in periodic pulses rather than continuously. This allows the system to achieve sufficient light intensity during emission periods for accurate detection while creating distinct temporal windows where no light is emitted, enabling the differentiation and rejection of continuous disturbance light signals.
Solution Approach 2:
The driving circuit pre-establishes a periodic emission pattern and timing synchronization before detection begins. The system prepares multiple time-period integration windows in advance, allowing it to systematically separate and analyze reflected light signals from disturbance light signals based on their temporal characteristics.
3Adaptability or versatility
If the optical sensor uses multiple light-receiving elements to detect object position and movement, then sensing capability is enhanced, but the device complexity increases
Solution Approach 1:
Multiple light-receiving elements are integrated into a single integrated circuit package, physically combining their functions. The circuit board integrates the driving circuit, integrating circuit, and output control circuit into a unified structure, reducing the number of discrete components and simplifying the overall device while maintaining enhanced sensing capability through the multiple photodetectors.
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 configuration enables the optical sensor to accurately sense object movement without malfunctioning due to disturbance light, ensuring reliable operation in various lighting conditions.
Implementation Method 1
a light-receiving element that generates a photocurrent upon receiving reflected light from an object to be sensed reflecting light emitted by the light-emitting element
Data Source
AI summary
An optical sensor includes: a driving circuit that turns off a light-emitting element during a first period, a second period, and a fourth period and that turns on the light-emitting element during a third period; an integrating circuit that outputs a first integrated-value difference (FID) and a second integrated-value difference (SID), the FID being a difference between an integrated value of a photocurrent generated by a light-receiving element in accordance with respective states of the light-emitting element during the first period and the second period, the SID being a difference between an integrated value of a photocurrent generated in accordance with respective state of the light-emitting element during the third period and the fourth period; and an output control circuit that outputs the SID when the FID is zero and that outputs a difference between the SID and the FID when the FID is not zero.