Reflective Concentrator Layout for Vehicle Camera Red Glow Mitigation
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Solution Overview
Problem
Current imaging systems using NIR or IR LED illumination for vehicle interior monitoring suffer from the visibility of 'red glow' due to the human eye's sensitivity to these wavelengths, particularly when viewed on axis to the fovea, which affects applications like security cameras and automotive ADAS.
Innovation Solution
A reflective concentrator, such as a compound parabolic concentrator (CPC), redirects NIR or IR light off-axis to eliminate visibility, using a design that disperses the light to avoid direct alignment with the human eye.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If NIR or IR LED illumination is used for vehicle interior monitoring, then the illumination is not readily visible to the human eye, but the human eye can still perceive red glow when viewed on axis to the fovea
Solution Approach 1:
The patent applies a reflective concentrator that redirects NIR/IR light from the original on-axis path to off-axis directions. This dimensional change in light propagation path moves the illumination away from the foveal region where red glow is perceived, while maintaining effective illumination of the monitoring field of view.
Solution Approach 2:
The reflective concentrator acts as an intermediary optical element between the NIR/IR LED source and the field of view. It mediates the light path by reflecting and redirecting the illumination, preventing direct on-axis visibility while maintaining the illumination's effectiveness for the imaging system.
2Object-affected harmful factors
If bandpass filtering is used to filter out visible light, then the red glow is reduced, but the NIR or IR LED transmission still reaches the human eye when viewed on axis
Solution Approach 1:
The reflective concentrator extracts and redirects the harmful on-axis light path separately from the useful off-axis illumination path. By taking out the on-axis component through reflection, it prevents this light from reaching the foveal region while preserving the off-axis illumination that provides effective monitoring.
Solution Approach 2:
Instead of relying solely on spectral filtering, the patent uses spatial redirection to solve the problem. The reflective concentrator changes the dimensional path of the light, directing it away from the on-axis foveal region where red glow is perceived, while maintaining transmission through the required wavelengths.
3Illumination intensity
If the intensity of the NIR/IR LED is increased to improve illumination, then the red glow becomes more visible, but reducing intensity compromises illumination effectiveness
Solution Approach 1:
The reflective concentrator resolves the intensity-visibility contradiction by changing the spatial dimension of light propagation. It allows high-intensity NIR/IR illumination to be directed off-axis, preventing the red glow from reaching the foveal region while maintaining sufficient illumination intensity for effective monitoring.
Solution Approach 2:
The reflective concentrator serves as an intermediary that decouples the relationship between illumination intensity and red glow visibility. It enables high-intensity illumination to be effective for monitoring while preventing the intensity from translating into visible red glow by redirecting the light path away from the foveal region.
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 solution effectively mitigates the 'red glow' issue by redirecting NIR or IR light, ensuring it is not visible to the human eye, thereby enhancing the functionality and sensitivity of the camera system without reducing LED intensity or increasing pulse duration.
Implementation Method 1
A reflective concentrator, such as a compound parabolic concentrator (CPC), redirects NIR or IR light off-axis to eliminate visibility
Implementation Method 2
The design also disperses the NIR or IR light so that the human eye is no longer able to perceive the light as red glow
Data Source
AI summary
A camera assembly for mitigating red glow is provided. A camera assembly may be configured for attachment to a vehicle. The camera assembly may include an imaging sensor and a light assembly. The imaging sensor may be configured to detect objects within a field of view. The light assembly may be configured to illuminate the field of view. The light assembly may include a light source that comprises a infra-red or near infra-red light emitting diode. The light source may oriented to be hidden from the field of view. A reflective concentrator may be configured to direct light from the light source to the field of view.