Laser Scanner Time-of-Flight Correlation for Higher Distance Resolution
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Solution Overview
Problem
Existing distance measurement systems, particularly those using laser scanners, face challenges in achieving high resolution and accuracy while maintaining cost-effectiveness, as increasing sampling rates to improve resolution can be expensive and result in diminishing returns without corresponding advancements in laser pulse speed.
Innovation Solution
The system employs a laser scanner with a logarithmic amplifier, an antialiasing filter, and a high signal sample rate, combined with a cross-correlation method using a template with a faster sample rate, to determine distance with enhanced resolution, and applies different light detection thresholds for varying distances to optimize sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the signal sample rate is increased to improve distance measurement resolution, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates a template copy of the expected reflected laser pulse waveform and performs cross-correlation between this template and the actual received signal. This allows the system to achieve high measurement precision without requiring an excessively high sampling rate, as the cross-correlation process can precisely determine time-of-flight even with moderate sampling rates by comparing the received signal against the known template waveform.
Solution Approach 2:
The patent applies a logarithmic amplifier to compress the dynamic range of the received signal before sampling. This parameter transformation allows the system to effectively utilize the available sampling rate by optimizing the signal distribution, thereby improving measurement precision without proportionally increasing the sampling rate and associated device complexity.
2Measurement precision
If the sampling rate is increased to improve distance measurement accuracy, then measurement precision is improved, but cost increases
Solution Approach 1:
By using a template copy of the expected pulse waveform and performing cross-correlation, the system achieves high measurement accuracy without requiring expensive high-speed sampling hardware. The cross-correlation algorithm can precisely determine time-of-flight values even with moderate sampling rates, significantly reducing the cost of the ADC and associated electronics while maintaining high measurement accuracy.
Solution Approach 2:
The patent employs a logarithmic amplifier to compress the dynamic range of the received signal, allowing the use of a lower-resolution, lower-cost ADC. This approach sacrifices some signal dynamic range information but achieves sufficient measurement accuracy at a fraction of the cost of using a high-speed, high-resolution ADC that would be required for direct high-precision time-of-flight measurement.
3Measurement precision
If the template sample rate is increased to improve distance determination precision, then measurement precision is improved, but processing complexity increases
Solution Approach 1:
The patent applies a logarithmic amplifier to the received signal before sampling, which compresses the dynamic range and transforms the signal characteristics. This parameter change allows the cross-correlation process to achieve high precision distance determination with a moderate template sample rate, as the logarithmic transformation enhances the correlation peak sharpness and reduces the impact of noise and signal variations.
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 precise distance determination with a resolution of 5 mm to 75 mm, effectively increasing the sampling rate without the need for expensive high-speed lasers, thereby improving measurement accuracy and cost-effectiveness.
Implementation Method 1
an optical sensor configured to generate analog signals from light of one of the laser pulses that is reflected by an object
Implementation Method 2
A logarithmic amplifier can be configured to amplify the analog signals to have a second dynamic range that is smaller than the first dynamic range
Implementation Method 3
The laser scanner can have a capacitor between the optical sensor and the logarithmic amplifier. The capacitor can be configured to attenuate direct current (DC) components of the analog signals
Implementation Method 4
An antialiasing filter can be configured to attenuate frequency content of the analog signals, such as above a threshold frequency
Implementation Method 5
a laser light source configured to output laser pulses
Implementation Method 6
determine a time-of-flight value based at least in part on the cross-correlation, and determine a distance to the object based at least in part on the time-of-flight value
Data Source
AI summary
A laser scanner can include a light source to output laser pulses, and an optical sensor to generate analog signals, having a first dynamic range, from light of the laser pulses that is reflected by an object. A logarithmic amplifier can amplify the analog signals to have a second dynamic range that is smaller than the first dynamic range. An analog to digital converter can convert the analog signals to digital signal samples having a signal sample rate. A template can represent an expected return reflection signal, and can have a template sample rate that is higher than the signal sample rate. A processor can perform a cross-correlation between the digital signal samples and the template, determine a time-of-flight value based at least in part on the cross-correlation, and determine a distance to the object based at least in part on the time-of-flight value.