Head Eye Tracking Light Source Preheating
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Solution Overview
Problem
Head/eye tracking systems face challenges in suppressing ambient light, particularly sunlight, due to temperature variations affecting LED light sources, which lead to inefficient power usage and reduced system performance.
Innovation Solution
A head/eye tracking system that includes a preheating mechanism for the light source to maintain a stable operating temperature, ensuring the band-pass filter matches the LED emission spectrum, thereby reducing temperature drift and allowing for effective suppression of ambient light without increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pass-band of the filter is widened to accommodate LED temperature drift, then the LED power can be maintained at 1-2 W, but more sunlight passes through the filter reducing suppression effectiveness
Solution Approach 1:
The patent applies preliminary action by preheating the LED to its operating temperature before the tracking system begins operation. This ensures the LED is already at a stable temperature when active, preventing wavelength drift during actual use. The preheating phase occurs in advance, so when the system operates, the LED maintains consistent emission characteristics without requiring a wider filter pass-band.
Solution Approach 2:
The patent changes the temperature parameter of the LED by applying controlled heating. By actively managing the LED temperature and maintaining it within a specific range during operation, the emission wavelength remains stable. This parameter control allows the use of a narrow filter pass-band (±25 nm) while still accommodating temperature variations through active thermal management.
2Object-affected harmful factors
If the LED power is increased to compensate for wavelength shift, then the filter pass-band can remain narrow for sunlight suppression, but power consumption increases by a factor of two or three
Solution Approach 1:
The patent uses preliminary action by preheating the LED before operation. This ensures the LED reaches its optimal operating temperature in advance, stabilizing its emission wavelength. As a result, the system can maintain a narrow filter pass-band for effective sunlight suppression without needing to increase LED power during active tracking.
Solution Approach 2:
The patent ensures continuous useful action by maintaining the LED at a stable operating temperature throughout operation. The preheating phase establishes a baseline temperature, and then the system maintains this temperature range during active use. This continuous thermal management ensures consistent wavelength output, allowing narrow filter operation without power increases.
3Object-affected harmful factors
If a narrow filter pass-band is used to block sunlight, then ambient light suppression is improved, but the system becomes sensitive to LED temperature drift
Solution Approach 1:
The patent applies preliminary action by preheating the LED to its operating temperature before the tracking system becomes active. This ensures that when the system operates with a narrow filter pass-band, the LED is already at a stable temperature and will not drift significantly during use. The preheating phase occurs in advance, eliminating temperature drift concerns during actual tracking operation.
Solution Approach 2:
The patent controls the temperature parameter of the LED through active heating. By maintaining the LED within a specific temperature range during operation, the emission wavelength remains stable and compatible with the narrow filter pass-band. This parameter control enables the system to use narrow filtering for sunlight suppression without becoming sensitive to temperature variations.
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 preheating mechanism stabilizes the LED's operating temperature, improving the matching between the light source and filter, reducing start-up time, and maintaining system performance across varying temperatures without the need for increased power.
Implementation Method 1
a heat source arranged in proximity to the light source and configured to preheat the light source
Data Source
AI summary
A head/eye tracking system comprising an image sensor for acquiring images of a user, a narrow band light source for illuminating the eyes, and a band-pass filter arranged between the eyes and the image acquisition device and having a pass-band corresponding to the emission spectrum of the light source at a predefined operating temperature. The system further comprises a heat source arranged in proximity to the light source and configured to preheat the light source to reach the predefined operating temperature. By shortening the period during which large temperature variation takes place, sub-optimal performance of the system can be accepted during this short period, thereby relaxing the requirements on light source and filter design.