SPAD Light Ranging Histogram Updates for Low-Signal Accuracy
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Solution Overview
Problem
Existing light ranging apparatuses face challenges in maintaining ranging accuracy and positional resolution due to varying travel times of light when measuring moving objects, leading to increased power consumption and calculation load during histogram accumulation across the entire measurement range.
Innovation Solution
The apparatus employs a light source with a rotating polygon mirror to scan in both horizontal and vertical directions, using a light receiving unit with SPADs to generate histograms selectively for low signal intensities, reducing the number of accumulations required by updating only when signal intensities meet specific thresholds, and adjusting accumulation based on disturbance light quantity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If histogram accumulation is performed across the entire measurement range, then ranging accuracy is maintained, but power consumption and calculation load increase
Solution Approach 1:
The measurement range is divided into multiple regions (first measurement region and second measurement region) based on signal intensity thresholds. The apparatus selectively performs histogram accumulation only in regions where signal intensity is below the threshold, rather than processing the entire measurement range uniformly. This segmentation reduces unnecessary calculations in high-signal regions, thereby lowering power consumption while maintaining accuracy where needed.
Solution Approach 2:
Different processing strategies are applied to different regions of the measurement range. In regions with low signal intensity, full histogram accumulation is performed to ensure accuracy. In regions with high signal intensity, the apparatus uses alternative processing methods that reduce calculation load. This local differentiation optimizes the balance between measurement precision and power consumption across the entire field of view.
2Measurement precision
If histogram accumulation is performed across the entire measurement range, then ranging accuracy is maintained, but calculation load increases
Solution Approach 1:
The measurement range is segmented into multiple regions based on signal intensity characteristics. The apparatus identifies regions where signal intensity exceeds a predetermined threshold and excludes them from full histogram accumulation processing. This segmentation reduces the total number of calculations required while maintaining measurement accuracy in the regions where it is most critical (low signal intensity regions).
Solution Approach 2:
Instead of performing complete histogram accumulation across the entire measurement range, the apparatus applies partial accumulation only to the necessary regions (where signal intensity is below the threshold). This partial action approach reduces calculation load by avoiding excessive processing in regions where full accumulation is not needed, while still providing sufficient measurement accuracy where required.
3Measurement precision
If signal intensity threshold is set low, then more regions are processed, but power consumption increases
Solution Approach 1:
The apparatus dynamically adjusts the signal intensity threshold parameter based on measurement conditions. By optimizing the threshold value, the system achieves the desired balance between processing coverage and power consumption. The threshold is set to include sufficient regions for accurate measurement while excluding regions where processing would be unnecessarily energy-intensive, thereby optimizing the parameter to resolve the contradiction.
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 maintains ranging accuracy and reduces power consumption by minimizing unnecessary histogram updates and calculations, improving signal-to-noise ratio and measurement precision.
Implementation Method 1
a light source that emits light irradiating a predetermined range; a light receiving unit having a plurality of light receiving elements capable of outputting a pulse signal in response to incidence of reflected light from an object irradiated by the light
Implementation Method 2
a light receiving unit having a plurality of light receiving elements capable of outputting a pulse signal in response to incidence of reflected light
Data Source
AI summary
A light ranging apparatus is provided with a light source; a light receiving unit having a plurality of light receiving elements capable of outputting a pulse signal; a summing unit calculating a sum value by summing the number of pulses; a histogram generation unit generating a histogram that records the sum value; a peak detecting unit acquiring the sum value of the peak in the histogram to be a signal intensity and calculating a distance value; and a first low signal intensity detecting unit detecting a low signal intensity lower than a predetermined first threshold. The histogram generation unit repeatedly acquires and accumulates the sum value for the histogram where the low signal intensity is detected until the signal intensity becomes the first threshold or more, thereby updating the histogram; and the peak detecting unit calculates a new distance value from the updated histogram.