Optical Distance Measurement Pulse Sequencing to Avoid Aliasing
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Solution Overview
Problem
Existing optical distance measurement methods for driverless navigation face limitations in maximizing measurement range due to aliasing effects and energy distribution issues, which lead to inaccurate object positioning and restricted range, especially when trying to scan small areas at great distances.
Innovation Solution
A method that transmits a sequence of measurement pulses with varying temporal pulse intervals defined by a specific set, allowing for unambiguous determination of the sequence runtime and maximizing energy output, thereby increasing the measurement range without aliasing effects, using a time-of-flight method with a sequence of measurement pulses where each pulse has a temporal width T(pulse) and intervals forming a first set {T(delay)+i*T(pulse): i from 0 to j, ensuring only one element for all values of i, and using an optimal filter for signal evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If energy is distributed across multiple measurement pulses to achieve greater measurement range, then measurement range is improved, but aliasing effects occur leading to ambiguous reflection assignment
Solution Approach 1:
The patent applies periodic action by transmitting measurement pulses in structured sequences with specific temporal patterns. The pulse sequences are designed with predetermined intervals and timing relationships that allow the sensor to distinguish between reflections from different pulses, even when multiple pulses are transmitted in quick succession. This periodic structure enables energy distribution across multiple pulses while maintaining unambiguous reflection assignment through the known temporal pattern.
Solution Approach 2:
The patent implements preliminary action by pre-defining the temporal structure of pulse sequences before transmission. The timing patterns, intervals, and sequence structures are predetermined and stored in the system, allowing the sensor to anticipate when reflections from each pulse should arrive. This preliminary structuring of the measurement process enables the system to process multiple pulses efficiently without aliasing, as the evaluation unit can pre-prepare the appropriate correlation templates or timing windows for each expected reflection.
2Power
If measurement pulses are emitted in quick succession to maximize energy output, then energy efficiency is improved, but the transit time of the sequence cannot be unambiguously determined
Solution Approach 1:
The patent applies feedback by using the known transmitted pulse sequence structure to evaluate and interpret the received reflections. The system compares the actual received signal against the predetermined pulse sequence template, using correlation or matching techniques to determine the transit time. This feedback loop between the known transmitted pattern and the received signal allows unambiguous determination of sequence runtime even when pulses are emitted in quick succession, as the evaluation unit can distinguish each reflection based on its position in the known sequence pattern.
Solution Approach 2:
The patent implements copying by creating a temporal copy or replica of the transmitted pulse sequence structure in the evaluation process. The predetermined pulse sequence pattern is stored as a reference template that is correlated with the received signal. This copying of the temporal structure allows the system to identify and measure the transit time of each pulse in the sequence, maintaining unambiguous determination even with high-rate pulse transmission, because the evaluation unit has a copy of the expected pattern to match against the actual reflections.
3Measurement precision
If waiting time between pulses is extended to avoid aliasing, then reflection assignment accuracy is improved, but measurement time increases
Solution Approach 1:
The patent resolves this contradiction by implementing periodic action with structured pulse sequences that have optimized temporal characteristics. Instead of using simple uniform spacing with large intervals, the system transmits pulses in patterns with varying intervals that are designed to avoid aliasing while minimizing total measurement time. The periodic structure allows the sensor to process multiple pulses faster than would be possible with conservative uniform spacing, because the known pattern enables more efficient correlation-based evaluation that can handle higher pulse rates without aliasing errors.
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 enables unambiguous determination of the sequence runtime, increases the measurement range, and allows for efficient scanning of both small and large distance ranges without the need for prolonged waiting times between pulses, effectively minimizing aliasing effects and maximizing energy output.
Implementation Method 1
They are based on the time-of-flight principle, whereby a scanning sensor, in particular a LIDAR (short for 'light detection and ranging') sensor, is used for the measurement. This sensor periodically emits measurement pulses that are reflected by objects, and the reflected measurement pulses are detected. By determining the travel time of the measurement pulses from the sensor to the objects and back, the distance to these objects can be deduced using the speed of light.
Implementation Method 2
a scanning sensor, in particular a LIDAR (short for 'light detection and ranging') sensor, is used for the measurement. This sensor periodically emits measurement pulses that are reflected by objects
Data Source
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AI summary
A method (100) for optical distance measurement is proposed, comprising the emission (101) of a plurality of measurement pulses (22), the reflection (102) of emitted measurement pulses (22) from at least one object, and the reception (103) of reflected measurement pulses (22). A sequence (20) of measurement pulses (22) is emitted, wherein the sequence (20) comprises temporal pulse intervals (24) between temporally successive measurement pulses (22), and wherein each measurement pulse (22) of the sequence (20) has a temporal pulse width (23) of T(pulse). The pulse intervals (24) form a first set, the first set being defined by {T(delay)+i*T(pulse): i is an element of the natural numbers between 0 and j}, where for all values of i T(delay)+i*T(pulse) < (2T(delay)+2T(pulse)), where the first set includes only one element for each value of i between 0 and j, and where T(delay) defines a pulse interval basis unit (25).