Optical Distance Measurement Using Edge Sampling
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Solution Overview
Problem
Existing time-of-flight distance measurement technologies face challenges with high costs, power consumption, and complexity due to the use of monolithic analog-to-digital converters, especially at high sampling rates, and require downtime for data processing, which is impractical for continuous signal acquisition in low-cost hardware with limited memory capacity.
Innovation Solution
The method employs edge transitions from comparator outputs to reconstruct return signal waveforms, using edge sampling detection apparatus with data compression and slope estimation to achieve continuous signal acquisition and high processing gain, suitable for implementation in field-programmable gate arrays (FPGAs), and includes optical feedback for self-calibration and noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If monolithic analog-to-digital converters are used for high-speed signal digitization, then signal acquisition speed and measurement precision are improved, but device cost and power consumption increase significantly
Solution Approach 1:
The patent divides the signal processing function into two separate components: an analog sample-and-hold circuit that performs high-speed sampling, and a separate analog-to-digital converter that operates at lower speeds. This segmentation allows each component to be optimized independently, reducing the need for expensive high-speed monolithic converters while maintaining overall system performance.
Solution Approach 2:
The patent introduces an analog sample-and-hold circuit as an intermediary component between the high-frequency return signal and the analog-to-digital converter. This intermediary captures and holds the high-speed signal samples, allowing the ADC to process them at lower speeds, thereby reducing converter cost and power consumption while preserving signal integrity.
2Productivity
If high-speed analog-to-digital conversion is implemented, then signal acquisition rate is improved, but power consumption increases to unacceptable levels for battery-powered devices
Solution Approach 1:
The patent segments the power-intensive conversion function into two stages: a low-power analog sample-and-hold stage that performs high-speed sampling, and a separate ADC stage that consumes more power but operates at lower speeds. This segmentation enables continuous high-rate signal acquisition while keeping average power consumption within acceptable limits for battery-powered devices.
Solution Approach 2:
The patent employs periodic sampling where the analog sample-and-hold circuit continuously samples the return signal at high rates, but the ADC converts these samples periodically at lower rates. This periodic conversion approach maintains high signal acquisition capability while reducing the cumulative power consumption associated with continuous high-speed conversion.
3Reliability
If continuous signal acquisition is implemented, then measurement reliability is improved, but data processing complexity increases due to limited memory capacity
Solution Approach 1:
The patent extracts only the essential signal characteristics (amplitude and timing information) during the analog sample-and-hold stage, rather than storing complete high-resolution digital waveforms. This extraction approach reduces the volume of data that needs to be processed and stored, making continuous signal acquisition feasible with limited memory capacity while maintaining measurement reliability.
Solution Approach 2:
The patent performs preliminary signal processing and feature extraction in the analog domain before digital conversion. By pre-processing the signal to identify and store only critical parameters, the system reduces subsequent digital processing complexity and memory requirements, enabling continuous acquisition without overwhelming the limited computational resources.
Data Source
AI summary
A sensing device comprises a transmitter and a receiver. The transmitter repetitively emits a modulated electro-magnetic signal and the emitted signal interacts with an object producing a counter propagating return signal. The return signal is detected and converted into digital signals by the receiver via a reception channel through the use of edge transitions rather than logic levels from one or more comparator outputs to reconstruct the return signal waveform. Waveform acquisition and reconstruction are based on edge sampling. Methods of providing optical feedback using a moving waveguide in time-of-flight distance measurements are also disclosed.