Time-of-flight Distance Measurement Waveform Monitoring
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Solution Overview
Problem
Time-of-flight distance measurement devices face challenges in monitoring the shape of the light emission waveform without interrupting distance measurement, leading to potential errors in distance calculation due to variations in the light emission waveform, such as duty cycle and rising time, which existing methods struggle to accurately correct, especially in dynamic environments.
Innovation Solution
The device employs a light emitting device that emits modulated light with a repetitive pattern, a light receiving device that distributes charges to storage capacitors, and a signal processing unit that calculates distances using sampled values. The control unit drives the light receiving device according to a sequence with a matrix of phase number n, allowing for linear calculation of sampled values based on a rank n matrix, enabling restoration of waveforms equivalent to those sampled at 1/n steps, and detection of waveform abnormalities, thereby correcting distance calculation results and alerting potential malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the light receiving device continuously accumulates charges for distance measurement, then the distance measurement continues without interruption, but the waveform shape cannot be monitored
Solution Approach 1:
The patent divides the charge accumulation process into multiple segments corresponding to different phase periods. By distributing charges to multiple storage capacitors across different phases (0°, 45°, 90°, 135°, etc.), the system can simultaneously perform distance measurement and waveform monitoring without interrupting either function. Each phase segment provides both distance information and waveform shape information.
Solution Approach 2:
The patent transforms the single-dimensional charge accumulation into multi-dimensional sampling by introducing phase as an additional dimension. By sampling at multiple phase points within one modulation period and using matrix operations, the system reconstructs waveform information while maintaining continuous distance measurement, effectively adding a temporal-phase dimension to the measurement process.
2Measurement precision
If the sampling rate is increased to monitor waveform shape, then the waveform shape can be accurately detected, but the distance measurement efficiency decreases
Solution Approach 1:
The patent employs periodic sampling at multiple fixed phase points (0°, 45°, 90°, 135°, etc.) within each modulation period. This periodic multi-phase sampling approach allows the system to capture sufficient waveform information for shape detection while maintaining efficient distance measurement throughput, as the sampling pattern repeats predictably and enables batch processing.
Solution Approach 2:
The patent changes the sampling parameter from single-point temporal sampling to multi-point phase sampling. By measuring at multiple phase offsets within one period and using matrix-based reconstruction, the system achieves accurate waveform shape detection without requiring a proportionally higher sampling rate, thus maintaining measurement efficiency.
3Measurement precision
If correction values are applied based on predetermined lookup tables, then distance calculation accuracy improves, but the system cannot adapt to dynamic waveform changes
Solution Approach 1:
The patent implements a feedback mechanism where the actual waveform shape is continuously monitored through multi-phase sampling and compared against ideal waveforms. Based on detected deviations in waveform shape (such as duty cycle variations or rising time changes), the system dynamically adjusts correction values for distance calculations, enabling real-time adaptation to waveform changes while maintaining accuracy.
Solution Approach 2:
The patent transitions from static correction values in lookup tables to dynamic correction that adapts to real-time waveform conditions. By continuously monitoring waveform shape parameters and adjusting correction factors accordingly, the system becomes adaptable to dynamic environmental changes, temperature variations, and component aging effects that alter the light emission waveform.
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 continuous monitoring of the light emission waveform shape, enabling appropriate countermeasures and accurate distance calculations by detecting errors such as duty cycle and rising time, ensuring reliable operation even in changing environments.
Implementation Method 1
a light emitting device emits a modulated light toward a space, the modulated light being modulated in a pattern having a repetitive period
Implementation Method 2
a light receiving device distributes a charge to a plurality of storage capacitors to store the charge, the charge corresponding to an incident light including a reflected light obtained by reflecting the modulated light on a target object
Data Source
AI summary
In a time-of-flight distance measurement device, a light receiving device is driven by a sequence having a matrix of a phase number n, a value sampled on the basis of the n rank matrix with respect to the phase number n is linearly calculated, and a waveform equivalent to the waveform sampled in a 1/n step is detected. A linear operation is performed on a sampled value based on the matrix with the rank n with respect to the phase number n, thereby being capable of restoring the waveform equivalent to the waveform sampled in the 1/n steps, and determining whether the shape of the light emission waveform is normal, or not. As a result, the shape of the light emission waveform can be monitored without interrupting a distance measurement.