Phase-Coded Optical Pulse Ranging for Long-Distance Measurement
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Solution Overview
Problem
Existing distance-measurement methods face challenges in accurately determining the association between transmitted and received optical pulses when the distance to the target object is long or the transmission period of pulses is short, leading to incorrect distance calculations.
Innovation Solution
A distance-measurement apparatus and method that generate transmission pulses with varying phase differences in different regions, allowing for the detection of phase differences in received reflected pulses to accurately associate them with their corresponding transmission pulses, thereby calculating the distance based on the receiving and transmitting timings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transmission period of optical pulses is shortened to increase measurement speed, then productivity is improved, but the ability to associate reflected light with transmitted pulses deteriorates when distance is long
Solution Approach 1:
The patent changes the phase parameter of transmitted optical pulses to create unique phase signatures for each pulse. By modulating the phase of transmitted pulses and detecting the corresponding phase in reflected pulses, the system can reliably associate reflected light with its originating transmitted pulse even when the transmission period is short and multiple pulses are transmitted before a reflection returns. This resolves the contradiction by maintaining pulse association accuracy through phase encoding rather than relying solely on time-based separation.
2Length of stationary object
If the distance to the target object is long, then the measurement range is improved, but the time for pulse round trip exceeds the transmission period causing measurement ambiguity
Solution Approach 1:
The patent applies phase modulation to encode timing information in the phase domain rather than relying solely on time-of-flight measurements. By imparting distinct phase characteristics to transmitted pulses and detecting these phase characteristics in reflected pulses, the system preserves pulse identification information even when the round-trip time exceeds the transmission period. This allows long-distance measurement without losing the association between transmitted and reflected pulses.
Solution Approach 2:
The patent introduces phase modulation as an intermediary mechanism to bridge the gap between transmitted and reflected pulses. The phase encoding acts as a mediator that carries identification information through the extended time delay, allowing the system to maintain pulse association even when direct temporal correlation would fail due to long measurement distances.
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
Enables accurate distance measurement irrespective of the distance to the target object or the transmission period of pulses, without the need to increase the pulse period, thus maintaining measurement speed and accuracy.
Implementation Method 1
a phase difference between phases in a plurality of respective regions of the transmission pulse is changed according to a transmission order of the transmission pulses
Implementation Method 2
a phase difference between phases in a plurality of respective regions of the received reflected pulse
Implementation Method 3
a distance to the distance-measurement-target object is calculated by emitting a modulated optical pulse toward the distance-measurement-target object and receiving a reflection of the modulated optical pulse
Data Source
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AI summary
A distance-measurement apparatus capable of properly measuring a distance to a distance-measurement-target object irrespective of the distance thereto or the transmission period of transmission pulses is provided. Generation unit (2) generates a plurality of transmission pulses, the plurality of transmission pulses being formed so that phases in a plurality of respective regions of the transmission pulse can be different from each other, and being formed so that a phase difference between the phases in the plurality of respective regions of the transmission pulse is changed according to a transmission order of the transmission pulses. Transmission unit (4) repeatedly transmits the generated transmission pulses. Receiving unit (6) receives reflected pulses of the transmission pulses reflected on a distance-measurement-target object (90). Detection unit (8) detects a phase difference between phases in a plurality of respective regions of the received reflected pulse. Distance calculation unit (10) calculates a distance to the distance-measurement-target object (90) based on a receiving timing of the received reflected pulse and a transmitting timing of the transmission pulse corresponding to the phase difference detected from the reflected pulse.