ToF Sensor Characterization Using Opaque Cover
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Solution Overview
Problem
Time-of-Flight (ToF) sensors face challenges in accurately characterizing their performance due to environmental influences such as temperature, which affect measurement accuracy and require calibration to correct for distance measurement errors.
Innovation Solution
A method and apparatus utilizing a cover with adjustable transmittance, allowing the ToF sensor to perform measurements with the cover set to opaque, enabling the collection of measurement data for light reflected back, which is used to determine characterization data for correcting distance errors and calibrating the sensor's output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cover glass is used to protect the ToF sensor from the environment, then the sensor is protected, but the cover glass causes measurement errors due to light reflection and refraction
Solution Approach 1:
A characterization layer is introduced as an intermediary between the ToF sensor and the environment. This layer models the optical effects (reflection, refraction) of the cover glass, allowing the system to compensate for measurement errors caused by the protective cover without removing it.
Solution Approach 2:
The system changes the parameters used for distance calculation by applying correction factors derived from the characterization layer. These correction factors adjust the raw ToF measurements to account for the optical path differences introduced by the cover glass, thereby improving measurement precision while maintaining sensor protection.
2Adaptability or versatility
If environmental influences such as temperature are present, then the ToF sensor operates in real conditions, but measurement accuracy deteriorates
Solution Approach 1:
The system implements feedback by continuously characterizing the ToF sensor under various environmental conditions and using this characterization data to correct measurements in real-time. The characterization layer stores correction information that compensates for temperature and other environmental influences, allowing accurate operation in real-world conditions.
3Measurement precision
If calibration is performed to correct distance measurement errors, then measurement accuracy improves, but the complexity of the system increases
Solution Approach 1:
The calibration and characterization data are prepared in advance and stored in the characterization layer before actual measurements are taken. This preliminary action allows the system to apply pre-computed correction factors during operation, reducing the computational complexity and processing time required during real-time measurements while maintaining high accuracy.
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 allows for effective characterization of ToF sensors by correcting distance measurement errors and calibrating the output power, enhancing the accuracy and reliability of ToF measurements.
Implementation Method 1
performing at least one ToF measurement with the ToF sensor while the cover is opaque for obtaining measurement data for light reflected from the cover back to the ToF sensor
Implementation Method 2
Difference values representing a respective time period between sending pulses and received pulses are binned into a histogram
Data Source
Figure 1~2
Figure 3
AI summary
A method for characterizing a time-of-flight sensor is provided. The time-of-flight sensor is covered by a cover exhibiting an adjustable transmittance. The method includes selectively adjusting the transmittance of the cover such that the cover is opaque for light emittable by the time-of-flight sensor. Further, the method includes performing at least one time-of-flight measurement with the time-of-flight sensor while the cover is opaque for obtaining measurement data for light reflected from the cover back to the time-of-flight sensor. The method additionally includes determining characterization data based on the measurement data. The characterization data indicate a quantity related to the time-of-flight sensor.