Infrared Camera Illuminator Detection via Rotating Filter Wheel
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Solution Overview
Problem
Law enforcement faces challenges in detecting and locating security cameras, especially those using infrared illuminators, due to the inability of existing night vision systems and cameras to distinguish between visible and infrared energy, leading to confusion with other light sources and making it difficult to identify camera presence covertly.
Innovation Solution
A system employing temporally and spatially sequenced band-pass or band-block filters to differentiate narrow-band infrared LED illuminators from broadband light sources by making the former appear to flash, while minimizing visual clutter from non-infrared sources, allowing for the detection of infrared energy sources, including those not in direct line of sight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If night vision systems and cameras are used to detect infrared energy, then the ability to see in the dark is improved, but the ability to distinguish infrared illuminators from other light sources deteriorates due to background clutter
Solution Approach 1:
The patent applies periodic action by using a rotating filter wheel that alternates between different spectral filters (infrared-pass and visible-pass filters). This periodic filtering causes infrared illuminators to appear as blinking or flashing sources in the captured images, while broadband visible light sources remain relatively stable. The temporal modulation created by this periodic filtering enables automatic or manual identification of camera illuminators against the background of other light sources.
2Illumination intensity
If broadband visible light sources are present to aid human vision, then visibility is improved, but the detection of narrow-band infrared illuminators deteriorates due to energy magnitude differences and spectral overlap
Solution Approach 1:
The patent applies segmentation by dividing the spectral detection task into separate channels using different optical filters. The rotating filter wheel segments the broadband light spectrum, allowing the infrared-pass filter to isolate narrow-band infrared illuminators from the visible spectrum where broadband sources dominate. This spectral segmentation enables the detection system to focus on specific wavelength ranges, reducing the overwhelming influence of high-intensity visible light sources.
Solution Approach 2:
The patent uses optical filters as intermediary elements between the light sources and the camera sensor. These filters act as mediators that selectively transmit or block specific wavelength ranges. The infrared-pass filter serves as an intermediary that allows infrared illuminator energy to reach the sensor while blocking most visible light from broadband sources, thereby enabling discrimination between narrow-band infrared sources and broadband visible sources.
3Adaptability or versatility
If conventional cameras image both visible and infrared energy without distinction, then the overall imaging capability is maintained, but the ability to covertly detect camera locations deteriorates due to inability to identify illuminators
Solution Approach 1:
The rotating filter wheel creates periodic temporal modulation in the captured images, where infrared illuminators appear to blink or flash at the rotation frequency of the filter wheel. This periodic appearance provides a distinctive signature that can be automatically detected or manually identified, solving the problem of covert camera location identification while maintaining the camera's ability to image both visible and infrared energy throughout the rotation cycle.
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
Effectively identifies and locates infrared camera illuminators by making them stand out from other light sources, reducing visual noise, and enabling covert detection of security cameras before they come into view, even when they are indirectly illuminating objects.
Implementation Method 1
The introduction of a temporally and/or spatially sequenced band pass or band block filter or filters prior to the imaging system
Implementation Method 2
The camera illuminators previously mentioned typically employ a plurality of infrared LEDs as a source of illumination
Implementation Method 3
This night vision equipment functions by amplifying the available light and producing an image from this light
Implementation Method 4
employing a rotating filter wheel or oscillating filter mechanism
Data Source
AI summary
A method and apparatus is described whereby invisible camera illuminators may be readily identified and located. In one embodiment the method of detecting the presence of an imaging system producing an invisible illuminator includes introducing a first optical filter capable of blocking energy from an LED infrared illuminator band source and allow energy from broadband visible light source to pass with minimal attenuation; and introducing a second optical filter that permits most of the energy from said infrared illuminator to pass and blocks a substantial portion of said broadband visible light; wherein said filtered LED infrared illuminator and said broadband visible light blink on and off.