SPAD TOF Ranging With Threshold Pulse Counting
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Solution Overview
Problem
Existing distance measurement methods using the TOF method suffer from reduced accuracy due to disturbance light or noise interference in the SPAD sensor, which affects the histogram and compromises the precision of distance calculations.
Innovation Solution
A distance information acquisition device and method that utilizes a light receiving unit with a counting unit to count pulsed light reflected by an object, outputting one-bit signals only when the count exceeds a predetermined value, and constructs micro-frames and sub-frames to generate distance images, thereby reducing noise influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a SPAD sensor is used to detect reflected light in the TOF method, then distance measurement capability is achieved, but noise from disturbance light reduces measurement accuracy
Solution Approach 1:
The patent segments the detection process into multiple gating periods divided into micro-frames, where each micro-frame captures light within a specific time window. By dividing the overall detection period into smaller segments (micro-frames), the system can identify and exclude noise that occurs outside the expected reflection time windows, thereby improving distance measurement accuracy while maintaining noise rejection capability.
Solution Approach 2:
The patent employs periodic gating periods with multiple micro-frames within each period, where light detection is performed in synchronized intervals. This periodic structure allows the system to distinguish between actual reflected light (which arrives at predictable intervals) and random noise (which does not follow the periodic pattern), thus enhancing measurement precision while filtering disturbance light.
2Adaptability or versatility
If multiple gating periods are used to improve distance measurement range, then more comprehensive distance data is obtained, but noise accumulation increases
Solution Approach 1:
Each gating period is segmented into multiple micro-frames, allowing the system to process distance data from different time intervals separately. This segmentation enables comprehensive distance measurement coverage while identifying and excluding noise that appears in specific micro-frames, preventing noise accumulation even when multiple gating periods are used to extend measurement range.
Solution Approach 2:
The system uses feedback mechanisms to analyze detection results from multiple micro-frames and gating periods, identifying patterns that indicate noise versus valid reflections. By comparing results across multiple periods and using feedback to adjust detection parameters, the system maintains adaptability for various distance ranges while actively suppressing noise accumulation through intelligent data filtering.
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
Enhances the accuracy of distance information acquisition by effectively filtering out noise and improving the precision of distance measurements.
Implementation Method 1
a light receiving unit (30) including a photoelectric conversion unit and configured to detect a pulsed light emitted from a light emitting unit (12) and reflected by an object
Data Source
AI summary
A distance information acquisition device includes a light receiving unit that detects a pulsed light reflected by an object in a measurement target area, and a signal processing unit that acquires information concerning a distance to the object based on information detected by the light receiving unit. The light receiving unit includes a counter that counts the number of pulsed light detected in each of distance ranges defined according to a time period from timing the pulsed light is emitted to timing the pulsed light is detected, and outputs one-bit signals indicating the pulsed light is detected, when a count value of the pulsed light is not less than a predetermined value of 2 or more. The one-bit signal constitutes a micro-frame, the micro-frames acquired for the same distance range constitute a sub-frame, and the sub-frames acquired for different distance ranges constitute a ranging frame for generating a distance image.