TOF Distance Sensor Reference Switching to Minimize Time Walk
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Solution Overview
Problem
Distance detection sensors using the pulse time-of-flight scheme face challenges in minimizing time distortion during distance measurement, particularly when the reflected signal amplitude is small, leading to temporal distortion and distance errors.
Innovation Solution
The proposed distance detection sensor includes a current-to-voltage converter, amplifier, comparator, reference value selector, time-to-digital converter, and digital signal processor, which transmit multiple pulses, change reference values, and calculate the time-of-flight peak time to minimize time walk error by completing a quadratic function and compensating for temperature, thereby reducing distance errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single reference value is used for distance measurement, then the device complexity is low, but time walk error increases leading to reduced measurement precision
Solution Approach 1:
The reference value is changed dynamically for each continuous transmit pulse instead of remaining fixed. The reference value selector continuously changes different reference values respectively corresponding to continuous receive pulses, which minimizes time walk error and improves distance measurement precision without requiring complex additional hardware
Solution Approach 2:
The reference value parameter is systematically varied across multiple measurement cycles. By changing the reference value for each continuous transmit pulse and calculating the average TOF time from multiple measurements, the system achieves higher precision distance measurement while maintaining relatively simple device architecture
2Measurement precision
If multiple continuous pulses are transmitted to minimize time walk error, then measurement precision improves, but the loss of time increases due to multiple measurements
Solution Approach 1:
Multiple continuous transmit pulses are transmitted in succession to the target, and the corresponding receive pulses are continuously received and processed. This continuous measurement approach allows for calculating the average TOF time from multiple measurements, improving precision while managing the time loss through efficient sequential processing
3Measurement precision
If temperature compensation is implemented, then measurement precision improves under varying temperature conditions, but device complexity increases
Solution Approach 1:
The temperature sensor continuously monitors the ambient temperature and provides feedback to the digital signal processor. The DSP uses this temperature information to compensate the calculated distance, correcting for temperature-induced variations in the speed of light. This feedback mechanism improves measurement precision across varying temperature conditions while adding minimal device complexity
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 effectively minimizes time walk error and distance distortion by calculating the peak time of the pulse and compensating for temperature, enhancing the accuracy of distance measurement even with small signal amplitudes.
Implementation Method 1
a photosensitive element configured to generate the detection signal
Implementation Method 2
a current-to-voltage converter configured to convert a current corresponding to a detection signal reflected from a target to a voltage
Data Source
AI summary
A distance detection sensor includes a current-to-voltage converter configured to convert a current corresponding to a detection signal reflected from a target to a voltage, an amplifier configured to amplify the converted voltage, a comparator configured to compare an output value of the amplifier with a reference value to generate a receive pulse, a reference value selector configured to select any one of a plurality of reference values as the reference value, and a time-to-digital converter configured to calculate time-of-light (TOF) time in response to the receive pulse output from the comparator. The reference value selector continuously changes different reference values respectively corresponding continuous receive pulses.