Laser Diode Modulation for Wearable HUD Image Quality
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Solution Overview
Problem
Conventional laser projectors in wearable heads-up displays (WHUDs) face issues with mode hopping, which causes wavelength shifts and degrades image quality due to prolonged laser on-times and short laser-off periods, leading to potential color misalignments and deformations in the displayed image.
Innovation Solution
A WHUD system that includes a laser projector with a controller modulating the laser diode to be off during a portion of the pixel on-time, reducing the likelihood of mode hopping by shortening the laser on-time and maintaining equal total power delivery, using a holographic optical element to redirect laser light, and detectors to monitor and adjust for deviations in angle and wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the laser diode is kept on during the entire pixel on-time to maintain continuous light output, then the brightness is maintained, but mode hopping occurs causing wavelength shifts and image quality degradation
Solution Approach 1:
The laser diode is modulated to turn on and off periodically during the pixel on-time, creating pulsed light output instead of continuous operation. This periodic action prevents mode hopping by limiting the duration the laser remains in a potentially unstable state, while still delivering sufficient total light energy to maintain image brightness and quality.
Solution Approach 2:
The controller预先 determines the optimal on/off timing pattern for the laser diode within each pixel on-time period. By pre-planning when the laser should be active and inactive, the system prevents mode hopping before it can occur, ensuring wavelength stability and image quality without requiring reactive corrections.
2Reliability
If the laser on-time is shortened to prevent mode hopping, then wavelength stability is improved, but the total light output power may be reduced
Solution Approach 1:
The controller dynamically adjusts the laser diode's operating parameters, specifically the on-time duration and peak intensity, to optimize performance. By changing these parameters within acceptable ranges, the system maintains wavelength stability through shorter on-times while compensating for reduced duty cycle by increasing peak intensity, thereby preserving total light output power.
Solution Approach 2:
The laser diode operation transitions from a static continuous-on state to a dynamic pulsed state with variable on/off timing. This dynamic control allows the system to adapt the laser's operational characteristics in real-time, balancing wavelength stability requirements with total power delivery needs by adjusting the pulse width and intensity according to display requirements.
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 reduces the likelihood of mode hopping, maintaining image quality by adjusting laser on and off times, ensuring consistent power delivery, and minimizing detectable shifts in wavelength and angle, thus preventing color misalignments and deformations in the displayed image.
Implementation Method 1
a laser diode to emit laser light
Implementation Method 2
the controller communicatively coupled and operable to modulate the laser diode during the pixel on-time
Implementation Method 3
a holographic optical element to receive the laser light from the laser projector and redirect the laser light towards an eye of a user
Data Source
AI summary
There is provided a wearable heads-up display (WHUD) having a laser projector to generate a display image. The display image can have a pixel having a pixel on-time. Furthermore, the laser projector can have a laser diode to emit laser light. The WHUD can also include a controller communicatively coupled to the laser diode. The controller can modulate the laser diode during the pixel on-time to be off during a laser off-time of the pixel on-time and on during a laser on-time of the pixel on-time. Moreover, the WHUD can include a holographic optical element to receive the laser light from the laser projector and redirect the laser light towards an eye of a user of the WHUD.