Windshield-Reflected IR Occupant Imaging for Occlusion-Free Monitoring
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Solution Overview
Problem
Existing vehicle occupant monitoring systems face challenges in capturing clear and unobstructed images of occupants while minimizing the impact of ambient light and maintaining a non-intrusive camera placement, especially in vehicles where direct sunlight and driver movements can cause image occlusions.
Innovation Solution
The system employs an infrared (IR) camera and reflective coating on the windshield, utilizing folded optics principles to capture occupant images reflected on the windshield, with the camera placed within or behind the instrument panel, and incorporates a high pulse intensity, short duration gated exposure to effectively monitor occupants under various ambient conditions, including direct sunlight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera is placed directly in front of the driver to capture clear images, then image quality is improved, but the camera view is blocked by driver and steering wheel movements
Solution Approach 1:
The patent transitions from a direct frontal camera view to a reflected view through the windshield. The camera is positioned in the instrument panel and captures images via reflection off the windshield glass, effectively changing the optical path from a straight line to a folded path through a different spatial dimension. This allows the camera to view the driver without being blocked by steering wheel movements.
Solution Approach 2:
The windshield glass acts as an intermediary optical element between the camera and the driver. Instead of direct line-of-sight imaging, the system uses the windshield's reflective surface to mediate the image capture process, allowing indirect observation that avoids occlusion from driver and steering wheel movements.
2Area of stationary object
If the camera is positioned to capture all front-row passengers, then monitoring coverage is improved, but image occlusion from driver movements increases
Solution Approach 1:
By using the windshield as a reflective surface, the system creates a virtual image plane that provides an unobstructed view of all front-row passengers. The reflected optical path allows the camera to capture a wide field of view including both driver and passengers without the physical obstructions that would block a direct view.
3Illumination intensity
If ambient light is captured along with IR light, then natural scene information is improved, but image quality under sunlight deteriorates
Solution Approach 1:
The system applies selective spectral sensitivity to the camera sensor, making it responsive only to infrared wavelengths while being insensitive to visible ambient light. This local quality in the spectral domain allows the camera to capture IR illumination information without being affected by sunlight and other visible light sources.
Solution Approach 2:
The patent exploits the spectral characteristics of IR illumination versus ambient visible light. By tuning the camera to detect only IR wavelengths, the system effectively filters out ambient light interference while capturing the desired IR-illuminated scene, creating a form of spectral selectivity analogous to color filtering.
4Ease of operation
If the camera is placed inside the instrument panel facing the windshield, then the system is non-intrusive, but image capture efficiency decreases
Solution Approach 1:
The system uses time-modulated IR illumination with pulsed operation. The IR light source emits periodic pulses synchronized with the camera's exposure timing, creating a gated imaging system. This periodic action allows efficient capture of reflected IR light from occupants while maintaining the non-intrusive camera placement in the instrument panel.
Solution Approach 2:
The time-modulated IR illumination provides continuous monitoring capability through synchronized pulsed illumination and camera exposure. The system maintains continuous surveillance by rapidly repeating the illumination-exposure cycle, ensuring uninterrupted occupant monitoring despite the indirect reflected optical path.
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 approach allows for efficient occupant monitoring that captures clear images of all front-row passengers, reduces image occlusions from driver and steering wheel movements, and eliminates or minimizes the capture of ambient light, ensuring effective monitoring across a range of circumstances.
Implementation Method 1
a first light source to generate first infrared (IR) light illuminating at least part of the body of an occupant of a vehicle
Implementation Method 2
an IR reflective surface to reflect second IR light reflected from the body of the occupant
Data Source
AI summary
An occupant monitoring system for a vehicle comprises: a first light source to generate first infrared (IR) light illuminating at least part of the body of an occupant of a vehicle, wherein the first light source is time modulated with a duty cycle; an IR reflective surface to reflect second IR light reflected from the body of the occupant; and a first IR camera to receive at least part of the second IR light reflected by the IR reflective surface, wherein the first IR camera is time modulated with the duty cycle of the first light source.