Infrared LED Driver IC for Eye Safety in Driver Monitoring
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Solution Overview
Problem
Infrared light exposure in driver monitoring systems can harm human eyes, especially at night when ambient light is insufficient, and existing systems lack effective controls to limit exposure time and frequency.
Innovation Solution
The system employs a driver IC that controls infrared LEDs to limit exposure time and frequency by using external resistors to set thresholds, ensuring the frame period is greater than a threshold and the exposure time is below a certain limit, thereby reducing infrared light exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If infrared flash systems are used to illuminate the driver at night, then sufficient illumination is provided for driver monitoring, but over exposure to infrared light can harm the human eye
Solution Approach 1:
The patent implements periodic illumination by controlling the infrared LED to flash at specific intervals rather than continuously. The driver monitoring system captures images at discrete time points with infrared illumination occurring only during these capture moments, creating a periodic on-off pattern that reduces cumulative exposure while maintaining adequate illumination for image capture.
Solution Approach 2:
The system dynamically adjusts illumination parameters including flash duration, flash intensity, and flash timing based on driving conditions. The controller modulates the infrared LED output to provide maximum necessary illumination only when needed for image capture, then immediately reduces or stops illumination, creating a dynamic rather than static illumination pattern that minimizes exposure.
2Illumination intensity
If continuous infrared illumination is used for driver monitoring, then adequate lighting is maintained, but exposure time increases causing potential eye harm
Solution Approach 1:
The system uses periodic flashing instead of continuous illumination, where the infrared LED is activated only during brief intervals coinciding with image capture. This creates distinct on-off cycles where the illuminated state lasts only as long as needed to capture the driver image, then transitions to an off state, thereby limiting cumulative exposure time while maintaining adequate lighting during active capture periods.
Solution Approach 2:
The illumination is concentrated into brief, intense pulses that skip over extended periods of non-illumination. Rather than providing continuous low-level light, the system delivers sufficient illumination in short bursts that are just long enough to capture the necessary image data, then immediately terminates, effectively 'rushing through' the minimum required exposure duration.
3Illumination intensity
If high frequency infrared flashing is used to maintain illumination, then adequate lighting is provided, but frequency of exposure increases potential harm
Solution Approach 1:
The system employs periodic illumination synchronized with image capture requirements, where the infrared LED flashes at the same frequency as the camera frame rate. This coordination ensures that illumination occurs only when an image is being captured, eliminating unnecessary intermediate flashes that would increase exposure frequency without contributing to image quality, thus maintaining adequate lighting while limiting harmful exposure frequency.
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 effectively limits infrared light exposure to prevent eye harm by controlling the duration and frequency of illumination, ensuring safe operation of driver monitoring systems.
Implementation Method 1
repeatedly illuminating a field of view of an image sensor with infrared light from a light emitting diode (LED)
Data Source
AI summary
Limiting exposure to infrared light. At least some of the example embodiments are methods including: repeatedly illuminating a field of view of an image sensor with infrared light from a light emitting diode (LED), each illumination defining an exposure time, and time between contiguous illuminations defining a frame period; and forcing the frame period to be greater than a frame period threshold. Forcing the frame period to be greater than the frame period threshold may also include setting the frame period threshold by a first resistor coupled to a first terminal of a LED driver circuit. Setting the frame period threshold further may also include setting the frame period threshold by a first resistor coupled between ground and the first terminal of the LED driver circuit. The methods further include limiting exposure time of each illuminations to be less than an exposure time threshold.