Passive Skin Detection via Narrow Band Spectral Analysis
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Solution Overview
Problem
Current imaging technologies for detecting skin in visual images are limited by high false alarm rates, inability to distinguish skin from skin-like objects, and computational intensity, particularly in Hyper Spectral Imaging (HSI) systems which are costly and complex, making them unsuitable for real-time surveillance and reconnaissance.
Innovation Solution
A passive skin detection system using a collection optics system with narrow band visible light filters centered around 577 nm, an image capture system, and an image processing algorithm that compares relative intensities to identify absorption bands indicative of skin, reducing computational requirements and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional HSI sensor systems are used to detect skin through spectral measurement, then detection accuracy is improved, but data transmission requirements and computational complexity increase significantly
Solution Approach 1:
The patent extracts only the essential spectral information needed for skin detection by using a reduced set of narrow bands (5-10 nm width) centered at specific wavelengths (480-500 nm, 577 nm, 620-640 nm) where skin has characteristic absorption features. This selective extraction of critical spectral data maintains detection accuracy while dramatically reducing the data volume and processing complexity compared to full HSI systems.
Solution Approach 2:
The patent segments the spectral measurement process into three distinct narrow bands that correspond to specific absorption features of skin (oxyhemoglobin and deoxyhemoglobin). By dividing the continuous spectrum into these discrete, information-critical segments, the system achieves effective skin detection with minimal spectral data, reducing both transmission and computational requirements.
2Measurement precision
If full HSI sensors with many narrow spectral bands are used, then discrimination capability is improved, but system cost and complexity increase significantly
Solution Approach 1:
The patent applies partial action by using only three narrow spectral bands instead of the full complement of HSI bands. This selective approach focuses measurements only at wavelengths where skin has distinctive absorption characteristics, providing sufficient discrimination capability for accurate skin detection without the excessive complexity and cost of full HSI systems.
Solution Approach 2:
The patent employs inexpensive narrow bandpass filters (5-10 nm bandwidth) that can be manufactured cost-effectively, replacing expensive full HSI sensor arrays. These affordable, specialized filters enable the system to achieve the necessary spectral discrimination at a fraction of the cost of conventional HSI systems.
3Device complexity
If RGB color-matching methods are used to detect skin, then system simplicity is maintained, but false alarm rates increase due to inability to distinguish skin from skin-like objects
Solution Approach 1:
The patent changes the measurement parameters from broad RGB color bands to narrow spectral bands (5-10 nm) centered at specific wavelengths where skin has characteristic absorption features. This parameter transformation enables the system to detect the unique spectral signature of skin (oxyhemoglobin and deoxyhemoglobin absorption) rather than relying on superficial color matching, dramatically reducing false alarms while maintaining operational simplicity.
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 detects skin with reduced false alarms and computational complexity, enabling low-cost, accurate skin detection in various applications including military surveillance and security systems, suitable for use in unmanned aerial vehicles and heads-up displays.
Implementation Method 1
narrow band visible light filters centered around 577 nm
Implementation Method 2
image processing algorithm that compares relative intensities to identify absorption bands indicative of skin
Data Source
AI summary
A passive skin detection system includes a main body which houses a collection optics system having an image splitting device, a visible light filter mechanism having a plurality of narrow band filters and an image capture system. The image capture system stores visible light data as a plurality of digital images formed from a plurality of pixels. Each of the plurality of digital images is associated with visible light passed through a respective one of the plurality of narrow band filters. An image processing system, operatively connected to the image capture system, compares relative intensities of each of the plurality of digital images to identify one or more of the plurality of pixels having an absorption bandwidth indicating a presence of skin. The processing system determines whether a person, identified by his skin, is present in any of the images captured by the detection system.