Laser Diode Pulse Width Check Circuit Using Current Comparison
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Solution Overview
Problem
There is a need for precise control of laser pulse width in augmented reality headsets to ensure proper functionality and user comfort, as existing techniques inadequately address the requirement for precise laser power and pulse width management.
Innovation Solution
A circuit is developed that includes a pulsed signal generator, reference current sources, and a comparison circuit to determine if the pulse width of the pulsed signal is within a given fraction of the reference clock pulse width, enabling proper operation of the laser driver and image formation in augmented reality headsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse width control is implemented in laser diode drivers for augmented reality headsets, then laser power and image quality are improved, but device complexity increases due to the need for additional control circuits and precision timing mechanisms
Solution Approach 1:
The patent replaces complex mechanical timing and control mechanisms with electrical signal processing. The pulse width check circuit uses electrical comparisons between the pulsed signal and reference clock signals to verify pulse width, eliminating the need for mechanical timers or complex microcontroller-based timing systems. This substitution of electrical fields for mechanical systems reduces device complexity while maintaining high measurement precision.
2Reliability
If precise laser pulse width control is implemented, then user comfort and functionality are improved, but manufacturing complexity increases due to tighter tolerances and more precise component requirements
Solution Approach 1:
The pulse width check circuit performs self-verification by comparing its own output pulses against a reference clock signal. The circuit automatically detects and flags pulse width errors without requiring external calibration or adjustment mechanisms. This self-service capability reduces manufacturing complexity by eliminating the need for precision-adjustable components or complex calibration procedures, while ensuring reliable operation through continuous self-monitoring.
3Measurement precision
If pulse width verification is added to the laser driver circuit, then operational accuracy is improved, but the circuit becomes more complex with additional components
Solution Approach 1:
The patent merges the pulse width verification function with the existing laser driver control circuitry. The check circuit shares timing signals and control logic with the main driver, combining multiple functions into a unified circuit architecture. This merging approach reduces the total component count compared to having separate verification and control systems, while maintaining high measurement precision through integrated signal processing.
Data Source
AI summary
A pulsed signal generator generates a pulsed signal having a pulse width configured to be equal to a given fraction of a pulse width of a reference clock. A reference current source outputs current having a reference magnitude, and a comparison current source outputs current having a magnitude that is a function of the reference magnitude and the given fraction. A comparison circuit compares a total current output by one of the reference current source and the comparison current source during pulses of the reference clock to a total current output by the other of the reference current source and the comparison current source during pulses of the pulsed signal equal in number to the pulses of the reference clock in order to determine whether the pulse width of the pulse signal is less than or equal to the given fraction of the pulse width of the reference clock.