VCSEL Array Lighting for Homogeneous Far-Field Illumination
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Solution Overview
Problem
Infrared camera systems for traffic surveillance and area security face challenges with inhomogeneous illumination due to light sources having an inhomogeneous intensity distribution in the far field, leading to inhomogeneous images.
Innovation Solution
A lighting apparatus comprising an array of vertical-cavity surface-emitting lasers (VCSELs) with emission cones that intersect in a specific plane, combined with an emission lens unit, where the distance between the light sources and the lens unit is set to either the sum or difference of the lens's focal length and the intersection plane's distance, ensuring homogeneous intensity distribution in the far field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional light emitting diodes are used for illumination, then the device complexity is reduced and cost is lowered, but the intensity distribution in the far field becomes inhomogeneous leading to poor image quality
Solution Approach 1:
The illumination system is segmented into multiple VCSEL light sources arranged in an array, where each light source emits a cone-shaped beam. By dividing the illumination into multiple discrete sources with specific geometric arrangements, the system achieves homogeneous intensity distribution through controlled overlap of emission cones, resolving the contradiction between simplicity and uniformity.
Solution Approach 2:
The patent changes key parameters including using VCSELs instead of conventional LEDs, arranging light sources in specific geometric patterns, and positioning an emission lens unit at a specific distance (equal to the focal length) to transform the intersection plane to the far field. These parameter changes convert the inhomogeneous Gaussian distribution into a homogeneous intensity distribution.
2Manufacturing precision
If vertical-cavity surface-emitting lasers are used instead of conventional light sources, then homogeneous intensity distribution is achieved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The system uses an array of multiple VCSELs instead of a single conventional light source. Each VCSEL is a standardized component that can be manufactured independently, and their collective arrangement in a specific geometric pattern achieves the homogeneous intensity distribution. This segmentation approach makes the system more manufacturable compared to using a single complex light source.
Solution Approach 2:
The patent changes the light source parameter from conventional LEDs to VCSELs, which have specific emission characteristics (cone-shaped beams with controlled divergence). This parameter change enables homogeneous intensity distribution when combined with the specific array arrangement and lens positioning, despite the increased manufacturing complexity of VCSELs themselves.
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 configuration results in a more homogeneous intensity distribution in the far field, reducing speckle contrast and ensuring a uniform image acquisition by the camera system, tailored to match the viewing angle and emission angle for enhanced imaging.
Implementation Method 1
an emission lens unit for homogenizing the intensity distribution in the far field, wherein the array of the light sources and the emission lens unit are arranged such that i) the emission cones traverse the emission lens unit
Implementation Method 2
US 2010/0097468 A1 discloses an active infra-red surveillance illuminator using a statistically mono-directional micro-diffractive material overlaid on a bank of light emitting diodes to refract light from the LEDs onto a target image
Data Source
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AI summary
The invention relates to a lighting apparatus (1) comprising an array (2) of light sources (3) emitting emission cones (4) with edges (5) which intersect in an intersection plane and a lens unit (7) for homogenizing the intensity distribution in the far field. The array of the light sources and the lens unit are arranged such that i) the emission cones traverse the lens unit and ii) the distance ( s ) between the array of the light sources and the lens unit deviates from the sum of or the difference between a) the focal length f of the lens unit and b) the distance t between the intersection plane and the array (2) of the light sources (3) by 20 percent or less. This configuration leads to an intermixture of the emission cones in the far field such that the intensity distribution in the far field is substantially homogeneous.