Photodetector Histogram Filtering for Interference Light
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Solution Overview
Problem
Photodetectors face a challenge in maintaining distance measuring accuracy due to interference light, which affects the time-of-flight method used in distance measurement systems, such as radar machines, leading to reduced precision.
Innovation Solution
A photodetector system comprising a light-receiving element, histogram generation circuit, filter circuit, and representative value calculation circuit that detects light pulses, generates histograms, performs filter processing using a filter coefficient pattern, and excludes the maximum frequency value from filter processing to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the time-of-flight method is used for distance measurement, then distance measurement capability is achieved, but distance measuring accuracy deteriorates in the presence of interference light
Solution Approach 1:
The patent changes the parameter of using a pulse pattern with specific frequency characteristics to distinguish between desired light pulses and interference light. By modulating the light source at a specific frequency and using correlation detection, the system can filter out interference light with different frequency characteristics, thereby maintaining distance measuring accuracy in the presence of interference.
Solution Approach 2:
The patent introduces an intermediary correlation detection mechanism that processes the detected light pulses through a correlation calculator. This intermediary process compares the detected pulse pattern with the expected pattern from the light source, effectively filtering out interference light that does not match the expected correlation, thus resolving the accuracy deterioration problem.
2Adaptability or versatility
If multiple radar machines operate simultaneously, then coverage and functionality are improved, but interference among radar machines increases
Solution Approach 1:
The patent employs asymmetric frequency modulation patterns where each radar machine operates at a unique or distinct frequency pattern. This asymmetry in the pulse pattern allows the correlation detection system to distinguish between signals from different radar machines, enabling multiple systems to operate simultaneously without mutual interference while maintaining full coverage capability.
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 system effectively prevents a decrease in distance measuring accuracy even in the presence of interference light, ensuring precise distance measurements by filtering out interfering signals and emphasizing the representative values of the detected light pulses.
Implementation Method 1
a light-receiving element configured to be able to detect a plurality of light pulses having a predetermined pulse pattern
Data Source
AI summary
It is desirable to provide a photodetector making it possible to prevent distance measuring accuracy from lowering even when interference light exists. A photodetector of the disclosure includes: a light-receiving element (PD) configured to detect light pulses having a predetermined pulse pattern; a histogram generation circuit (22) configured to generate a first histogram (H1) based on detection timings in the light-receiving element (PD); a filter circuit (23) configured to generate a second histogram (H2) based on the first histogram (H1) by filter processing using a filter coefficient pattern corresponding to the pulse pattern; and a representative value calculation circuit (24) configured to calculate a representative value of the detection timings based on the second histogram (H2). The filter circuit (23) is configured to exclude, from targets of the filter processing, a first frequency value being a maximum value (MAX) among a first plurality of frequency values in the first histogram (H1) or a processing-target histogram being an intermediate histogram corresponding thereto.