Micro-diffractive Illuminator for Wide-Angle Surveillance
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Solution Overview
Problem
Current low-light video surveillance systems, particularly for wide-angle applications like multi-lane traffic license plate reading, face inefficiencies due to the inverse square law of illumination, leading to wasted light and inadequate foreground illumination, especially when dealing with multiple vehicle headlights and the need for synchronized pulsed illumination.
Innovation Solution
A surveillance illuminator system utilizing a micro-diffractive material in front of an infrared LED manifold to produce an elliptical Gaussian illumination pattern, optimizing light distribution for wide-angle views by being more directional horizontally than vertically, thus conserving power and reducing light pollution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a circularly diverging beam is used to illuminate a wide area, then the coverage area is increased, but the vertical illumination profile becomes suboptimal and light is wasted above the target area
Solution Approach 1:
The patent transforms the symmetric circular beam pattern into an asymmetric elliptical beam pattern. The micro-diffractive element modifies the circular LED beam into an ellipse with horizontal elongation, concentrating light in the horizontal direction while maintaining optimal vertical spread. This asymmetric shape matches the horizontal orientation of target areas (ground areas where vehicles travel), reducing light waste above and below the target while covering the required wide horizontal area.
Solution Approach 2:
The patent introduces anisotropic diffraction properties to the optical system by incorporating micro-diffractive elements with different diffraction characteristics in horizontal versus vertical dimensions. The micro-diffractive structure has a preferred orientation that diffracts light more strongly in the horizontal plane than in the vertical plane, effectively adding dimensional selectivity to the illumination pattern and enabling independent control of horizontal spread versus vertical concentration.
2Length of stationary object
If the peak of the light source is pointed at the farthest target point, then the farthest distance is optimized, but the foreground illumination becomes insufficient and light above the target is wasted
Solution Approach 1:
The patent applies local quality by creating different illumination intensities at different vertical positions within the beam. The micro-diffractive element is designed to concentrate light in the middle vertical portion of the beam (where the foreground and mid-range targets are located) while allowing controlled spread to the farthest distances. This local concentration of light quality in the vertical dimension ensures adequate foreground illumination without sacrificing maximum range coverage.
3Illumination intensity
If conventional refractive or reflective elements are used to focus illumination, then light distribution can be altered, but the system complexity increases and light conservation efficiency is limited
Solution Approach 1:
The patent replaces conventional mechanical optical elements (refractive lenses and reflective mirrors) with a micro-diffractive optical element that uses diffraction physics to achieve the same light distribution control. The micro-diffractive structure, consisting of sub-wavelength periodic patterns, manipulates light through interference and diffraction effects rather than through geometric refraction or reflection, thereby achieving complex beam shaping with a simpler, more integrated component that can be directly coupled to the LED source.
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
This solution enhances image capture quality by ensuring more efficient light usage, increasing the usable distance of illumination, and achieving a more even foreground-to-background illumination ratio, allowing for ultra-high quality image capture with reduced light requirements.
Implementation Method 1
a micro-diffractive material is placed in front of a light-emitting manifold such as a bank of infra-red LEDs to alter the shape of illumination on a target area
Implementation Method 2
Some of these systems utilize refractive or reflective elements to diffuse or focus illumination
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
An active infra-red surveillance illuminator uses a statistically mono-directional micro-diffractive material overlaid on a bank of light emitting diodes (LEDs) to refract light from the LEDs onto a target image. This delivers energy distribution profiles out to a distance to match the aspect ratios of current wide-angle target and wide-angle camera surveillance systems. The distribution of refracted light is elliptical. This distribution can vary by using different diffractive material in conjunction with various numbers, brightness and angles of the LEDs in an LED bank. The effective range of the illuminators is greatly extended with this type of illumination. By limiting infrared (IR) radiation down to a 10 degree vertical window it renders the IR illumination much more effective for surveillance imaging by providing much more effective power on wide, ground-level scenes, and particularly enables multi-lane license plate capture.