ToF Sensor Cover Characterization via Coded Modulation
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Solution Overview
Problem
Time-of-Flight (ToF) sensors and their cover glasses influence measurement accuracy due to environmental factors and spurious reflections, necessitating a method to characterize the sensor and cover for improved performance.
Innovation Solution
Performing coded modulation measurements with a ToF sensor to obtain measurement data for light reflected from the cover, adjusting pulse durations and time-shifts in illumination and reference signals to mitigate responses to reflections behind the cover, and determining characterization data for distance error correction and output power control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cover glass is used to protect the ToF module from the environment, then protection and reliability are improved, but measurement accuracy deteriorates due to influence on light measurements
Solution Approach 1:
The patent performs preliminary characterization measurements of the cover glass properties (transparency, reflectivity) before actual operation. This allows the system to pre-determine correction factors and compensate for the cover glass's influence on measurements, thereby maintaining measurement accuracy while retaining the protective cover glass.
Solution Approach 2:
The patent implements feedback mechanisms by continuously monitoring and comparing actual measurements against expected values, and by using the characterized cover glass properties to dynamically adjust measurement corrections. This feedback loop enables the system to compensate for the cover glass's optical influence in real-time operation.
2Measurement precision
If coded modulation measurements are performed to characterize the cover, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes the ToF sensor serve multiple functions: it performs both normal distance measurement operations and characterization measurements of the cover glass. By using the same sensor hardware for both purposes, the patent avoids adding separate dedicated characterization equipment, thereby limiting the increase in device complexity while achieving accurate characterization.
Solution Approach 2:
The patent changes operational parameters (illumination signal characteristics, measurement modes) to enable characterization measurements. By modulating the illumination signal with specific patterns and adjusting measurement parameters, the system extracts cover glass properties without requiring physically different hardware, thus maintaining system simplicity.
3Measurement precision
If the measurement range is configured to end shortly after the cover, then response to reflections behind the cover is mitigated, but measurement range is reduced
Solution Approach 1:
The patent dynamically adjusts the measurement range configuration based on the specific characterization being performed. During normal operation, the full measurement range is utilized. During characterization measurements, the range is temporarily restricted to shortly-after-the-cover distances to isolate reflections, and then restored for full-range operations. This dynamic adjustment resolves the contradiction between reflection isolation and measurement range.
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 method effectively characterizes the ToF sensor and cover, correcting distance measurement errors and maintaining constant output power, while isolating responses to reflections from the cover, thereby enhancing measurement accuracy and reliability.
Implementation Method 1
An illumination element of the ToF sensor for emitting the light generates the light for the at least one coded modulation measurement based on an illumination signal exhibiting an alternating series of high and low pulses of varying duration
Implementation Method 2
Electronic circuitry of a light capturing element of the ToF sensor for measuring the light reflected from the cover is driven for the at least one coded modulation measurement based on a reference signal exhibiting an alternating series of high and low pulses of varying duration
Implementation Method 3
A ToF sensor configured to perform at least one coded modulation measurement for obtaining measurement data for light reflected from the cover back to the ToF sensor
Data Source
Figure 1~2
Figure 3
AI summary
A method for characterizing a time-of-flight sensor and/or a cover covering the time-of-flight sensor is provided. The method includes performing at least one coded modulation measurement with the time-of-flight sensor for obtaining measurement data for light reflected from the cover back to the time-of-flight sensor. A measurement range of the time-of-flight sensor is configured to end shortly after the cover for the at least one coded modulation measurement. Further, the method includes determining characterization data based on the measurement data, wherein the characterization data indicate a quantity related to the time-of-flight sensor and/or the cover.