Pulsed Diode Driver Circuit for Compact HMD Displays
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Solution Overview
Problem
Existing wearable head-mounted display (HMD) technologies face challenges in achieving a compact and lightweight design due to the need for a large, bulky, and heavy display device, which can be uncomfortable for users, and require a compact, bright, fast, and energy-efficient light source for scanning projector displays.
Innovation Solution
A pulsed driver circuit for a diode light source is developed, comprising a power source, an inductor, and an on/off switch, where the control circuit keeps the switch closed to charge the inductor before opening, allowing a pulsed electrical current to flow through the diode light source, enabling efficient light emission with adjustable energy based on the charging time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional display device is used in HMD, then the display can present images, but the device becomes large, bulky, and heavy causing user discomfort
Solution Approach 1:
The patent extracts the display function from a conventional display panel and implements it through a scanning projector that generates images directly in angular space. By removing the intermediate screen and using a compact light source with scanning mirrors, the system achieves display functionality without the bulk and weight of traditional displays.
Solution Approach 2:
The patent replaces the mechanical display panel structure with an optical scanning system using a diode light source and scanning mirrors. This substitution eliminates the need for a large physical display surface while maintaining image presentation capability through angular domain imaging.
2Device complexity
If a conventional light source is used in scanning projector display, then the display can operate, but the system lacks compactness, brightness, speed, and energy efficiency
Solution Approach 1:
The patent employs periodic pulsing of the diode light source synchronized with the scanning mirror operation. By activating the light source only during specific time windows when the scanner is at the correct position, the system achieves high brightness during display while minimizing overall energy consumption and enabling compact design.
Solution Approach 2:
The patent changes the operational parameters of the light source from continuous operation to pulsed operation with specific duty cycles. This parameter change enables the light source to achieve peak brightness for compact imaging while maintaining energy efficiency and reducing thermal management requirements for compactness.
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 results in a compact, efficient, and adjustable light source for scanning projector displays, enhancing the usability and comfort of wearable HMDs by reducing size and weight while maintaining effective image projection.
Implementation Method 1
a powering circuit comprising a power source and an inductor sequentially coupled to the power source
Implementation Method 2
a pulsed driver for a diode light source
Data Source
AI summary
A powering circuit for a diode light source includes an inductor charged through an on/off switch. The charging occurs during a charging cycle for a controllable amount of time when the on/off switch is closed. The energy of the charged inductor is used to power the semiconductor light source by opening the on/off switch. In such a driving configuration, the ringing is nearly constant and thus may be suppressed using an appropriately configured circuit.