Muzzle Flash Detection Using SPADs and Narrowband Filters
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Solution Overview
Problem
Current gun muzzle flash detection systems, particularly those using CMOS image sensors, face performance limitations and low signal-to-noise ratio in the visible spectrum, making them ineffective for modern military and law enforcement applications.
Innovation Solution
A device employing a narrowband filter and single photon avalanche diodes (SPADs) to detect muzzle flash photons, utilizing a signal processor that analyzes digital detection signals for correlation, differences, and weighted sums to differentiate between muzzle flash and light interference, with an optional guard bandpass filter for interference reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CMOS image sensors are used for muzzle flash detection, then the system benefits from low cost and low power consumption, but the signal-to-noise ratio deteriorates making detection ineffective
Solution Approach 1:
The patent changes the operating parameters of the sensor by using SPADs operated in Geiger mode with bias above breakdown voltage, and selects specific wavelength parameters using narrowband filters centered at 589nm and 769nm to match muzzle flash emission spectra, thereby achieving high sensitivity detection
Solution Approach 2:
The patent employs a composite detection system combining multiple SPAD pixels with different narrowband filters (589nm and 769nm) to detect muzzle flash across multiple spectral lines, leveraging the composite spectral signature for robust detection while maintaining low cost
2Illumination intensity
If broad spectrum detection is used to capture all visible light, then the system captures more light signals, but light interference from sunlight increases causing false positives
Solution Approach 1:
The patent applies local quality by using narrowband filters that selectively pass only specific wavelength ranges (centered at 589nm and 769nm) corresponding to muzzle flash emission lines, while blocking other wavelengths including sunlight, thereby achieving spectral selectivity at the sensor level
Solution Approach 2:
The patent exploits the spectral color characteristics of muzzle flash by filtering for specific wavelength bands (589nm sodium doublet and 769nm potassium line) that correspond to the chemical composition of propellant combustion, effectively distinguishing muzzle flash from broadband sunlight interference
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
Enables effective detection of muzzle flash in the visible spectrum with high sensitivity and low noise, reducing false positives from sunlight interference and improving detection reliability.
Implementation Method 1
a first single photon avalanche diode (SPAD) arranged to detect photons of the main signal waveband during different points in time and to output first digital detection signals representative of the photons of the main signal waveband
Implementation Method 2
a narrowband filter that may be arranged to pass radiation within a main signal waveband in which a muzzle flash is expected to include energy above a first energy threshold
Implementation Method 3
In Geiger mode, the SPAD is biased above its breakdown voltage (BV), and a single photo-electron theoretically initiates a self-propagating avalanche caused by the iterative multiplication of both the electrons and holes at high internal-electric Field strengths. This phenomenon is known as an avalanche breakdown.
Data Source
AI summary
A device that may include a narrowband filter that is arranged to pass radiation within a main signal waveband in which a muzzle flash is expected to include energy above a first energy threshold; a first single photon avalanche diode (SPAD) arranged to detect photons of the main signal waveband during different points in time and to output first digital detection signals representative of the photons of the main signal waveband; and a signal processor that is arranged to receive the first digital detection signals and to detect, in response to at least the first digital detection signals, the muzzle flash.