Laser Distance Module Sampling Shift for ADC Error Compensation
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Solution Overview
Problem
Fast analog-to-digital converters (ADCs) in distance measuring devices, such as laser trackers and scanners, face conversion errors due to timing, gain, and offset differences between ADC stages, leading to measurement inaccuracies and periodic distance errors, which are not fully corrected by internal or external calibration methods.
Innovation Solution
The method involves shifting the reception signals relative to the ADC sampling pattern to create multiple sampling points with varying signal values, allowing for error cancellation through averaging, particularly by ensuring identical sampling points are detected by multiple ADC stages, and using temporal shifts to compensate for ADC conversion errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fast ADCs with multiple conversion stages are used to achieve high sampling rates, then productivity is improved, but measurement precision deteriorates due to timing, gain, and offset errors between stages
Solution Approach 1:
The patent changes the temporal parameters of sampling by introducing variable sampling instants and temporal shifts between different ADC stages. Instead of fixed sampling times, the system dynamically adjusts sampling moments to compensate for timing errors (skew) between ADC stages, thereby maintaining measurement precision while achieving high sampling rates
Solution Approach 2:
The system implements feedback mechanisms where timing errors, gain errors, and offset errors are continuously measured and compensated. The control unit adjusts sampling instants and applies correction factors based on measured errors from calibration signals, creating a closed-loop system that maintains precision despite using multiple parallel ADC stages for high-speed operation
2Measurement precision
If internal and external calibration methods are applied to correct ADC errors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system performs self-calibration using test signals generated internally within the distance measuring device. The calibration unit creates known test signals that pass through the same signal path as measurement signals, allowing the system to automatically determine and correct its own timing, gain, and offset errors without requiring external calibration equipment or complex external systems
Solution Approach 2:
The patent combines multiple calibration functions (timing calibration, gain calibration, offset calibration) into a single integrated calibration unit. This unified approach consolidates what would otherwise be separate calibration systems, reducing overall device complexity while maintaining comprehensive error correction capabilities across all ADC stages
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 significantly reduces measurement errors by averaging out the contributions of ADC conversion errors, improving distance measurement accuracy and resolution, even under noisy conditions, and is effective for both interleaved and pipelined ADC architectures.
Implementation Method 1
a transmitting unit (2) for generating transmission signals (4), in particular by means of pulsed laser measurement radiation
Implementation Method 2
a receiving unit (3) for receiving at least portions of the transmission signals (4) reflected at the target object (5)
Data Source
AI summary
A distance measuring method and an electronic laser distance measuring module, in particular for use in a distance measuring apparatus, especially configured as a laser tracker, tachymeter, laser scanner, or profiler, for fast signal detection with an analog-to-digital converter, wherein conversion errors that arise in the context of a signal digitization, in particular timing, gain and offset errors of the ADC, are compensated for by means of variation of the sampling instants.