Distance Measuring Device Jitter Correction via Histogram Averaging
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Solution Overview
Problem
Existing distance measuring devices using the direct time of flight (dToF) method face challenges in accurately measuring distance due to fluctuations in power supply voltage, which cause jitter in the oscillator and result in variations in the frequency distribution of the histogram.
Innovation Solution
A distance measuring device is designed with an oscillator that generates a first clock signal with an oscillation frequency changing with power supply voltage fluctuations. This device includes a jitter detection unit that averages count values to detect jitter, and a histogram correction unit that corrects the histogram based on detected jitter to ensure accurate distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the oscillator frequency changes with power supply voltage fluctuations, then the device can operate with simple power supply design, but the histogram frequency distribution varies causing measurement errors
Solution Approach 1:
The patent implements feedback by detecting the actual oscillator frequency (through counting clock cycles in a fixed period) and using this information to correct the histogram data. The system measures the frequency deviation caused by power supply fluctuations and applies compensation to the distance measurement results, thereby resolving the measurement accuracy issue while maintaining simple power supply design.
Solution Approach 2:
The patent changes the parameter approach by not trying to maintain constant oscillator frequency through complex power supply regulation, but instead allowing frequency to vary and measuring the actual frequency value. This measured frequency parameter is then used to correct the histogram, transforming the frequency instability from a problem into a measurable correction factor.
2Productivity
If multiple light receiving elements are used simultaneously, then the light reception efficiency is improved, but the power supply voltage temporarily decreases causing oscillator jitter
Solution Approach 1:
The system uses feedback to detect the oscillator frequency deviation that occurs during simultaneous operation of multiple light receiving elements. By counting the actual number of clock cycles in a fixed period, the system measures the frequency jitter caused by power supply fluctuations and uses this information to correct the distance measurement, maintaining reliability while preserving high productivity.
Solution Approach 2:
The system performs self-diagnosis and self-correction by automatically detecting its own oscillator frequency deviations and applying corrections to the measurement results. The jitter detection unit monitors the oscillator performance and the histogram correction unit automatically compensates for the detected deviations, enabling the system to maintain accuracy despite the temporary power supply decreases caused by simultaneous operation of multiple receivers.
3Measurement precision
If jitter detection and histogram correction functions are added, then the distance measurement accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent applies multi-functionality by designing the counting unit to serve dual purposes: it both counts the number of received light photons (for histogram generation) and counts the oscillator clock cycles (for jitter detection). This unified approach allows the system to perform multiple functions with shared hardware resources, improving measurement accuracy while minimizing the increase in device complexity.
Solution Approach 2:
The system uses its existing operational parameters (clock signal periods and count values) to simultaneously perform both distance measurement and jitter detection without requiring completely separate dedicated hardware. The same counting mechanism that records light reception events also measures oscillator frequency, enabling the system to self-diagnose and self-correct measurement errors with minimal additional complexity.
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
The device effectively measures distance accurately by correcting for jitter-induced variations in the histogram, thereby reducing the impact of power supply voltage fluctuations on measurement accuracy.
Implementation Method 1
a light receiving element that emits a light signal to an object and receives a reflected light signal from the object
Data Source
AI summary
To make it possible to accurately measure a distance without depending on fluctuation in a power supply voltage. A distance measuring device includes: an oscillator that generates a first clock signal whose oscillation frequency changes according to the fluctuation in the power supply voltage; a first counting unit that repeats operation of counting the number of the first clock signals in a first period set in advance a plurality of times; a jitter detection unit that performs averaging processing of count values for the plurality of times by the first counting unit to detect jitter due to the fluctuation in the power supply voltage; a light receiving element that emits a light signal to an object and receives a reflected light signal from the object every second period including a plurality of the first periods; a first histogram generation unit that generates a first histogram representing an appearance frequency for each of timings at which the reflected light signal is received; and a distance calculation unit that measures a distance to the object on the basis of the first histogram.