Fast-Pulse LED Driver Circuit for High-Speed Metrology Imaging
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Solution Overview
Problem
Current high-speed metrology imaging systems, particularly those using tunable acoustic gradient (TAG) lenses, are limited by the speed and accuracy of existing driver circuits and illumination systems, which struggle to provide bright and short illumination pulses necessary for precise measurements of moving or vibrating workpieces.
Innovation Solution
A high-power fast-pulse driver and illumination system that overdrives LEDs using high currents and current densities, operating at low duty cycles or in burst modes, and incorporates Gallium Nitride FETs to achieve shorter pulse widths and higher pulse rates, integrated into a compact PCB layout to minimize inductance and maximize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If manufacturer-recommended currents are used to drive the illumination source, then LED lifetime is preserved, but illumination pulse brightness and speed are insufficient for high-speed metrology imaging
Solution Approach 1:
The illumination source is driven with periodic high-current pulses at low duty cycles (e.g., 2% or less), allowing the LED to operate at high brightness during brief intervals while remaining cool enough to preserve lifetime. This pulsed operation mode enables the LED to deliver peak performance for high-speed imaging without sustained thermal damage.
Solution Approach 2:
The driver circuit dynamically adjusts operating conditions by switching between different pulse width modulation modes, enabling the system to adapt illumination intensity and pulse duration based on measurement requirements while maintaining LED reliability through controlled thermal management.
2Illumination intensity
If higher currents are used to drive the illumination source, then illumination intensity increases, but LED lifetime decreases due to excessive heat and stress
Solution Approach 1:
The system uses periodic high-current pulses with low duty cycles to deliver intense illumination only when needed for imaging, keeping the LED cool during off-periods. This allows peak brightness levels much higher than continuous operation would permit, while preserving LED lifetime through thermal management.
Solution Approach 2:
The driver circuit changes operating parameters by delivering high current densities (higher than manufacturer recommendations) during brief pulses, then allowing recovery periods. This dynamic parameter adjustment enables high illumination intensity without sustained thermal damage to the LED.
3Speed
If conventional driver circuits are used, then system simplicity is maintained, but pulse width and pulse rate are insufficient for TAG lens-based high-speed imaging
Solution Approach 1:
The driver circuit is designed to deliver high-current pulses with widths in the nanosecond to microsecond range and rates exceeding 70 kHz, parameters necessary for synchronizing with TAG lens operation. The circuit uses specialized components like Gallium Nitride FETs and optimized PCB layouts to achieve these performance parameters.
Solution Approach 2:
The patent extracts and emphasizes the critical driver circuit functions needed for high-speed operation, separating the pulse generation and control logic into a dedicated driver module. This allows the rest of the imaging system to focus on optical and mechanical components while the driver handles temporal control.
4Duration of action of moving object
If manufacturer-recommended current densities are used, then LED reliability is maintained, but illumination pulse duration cannot be shortened sufficiently for high-speed imaging
Solution Approach 1:
The illumination source is driven with periodic high-current pulses at low duty cycles (e.g., 2% or less), allowing the LED to operate at high brightness during brief intervals while remaining cool enough to preserve lifetime. This pulsed operation mode enables the LED to deliver peak performance for high-speed imaging without sustained thermal damage.
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 system enhances the speed and accuracy of metrology imaging by enabling faster and more versatile illumination, supporting multiple focus planes and extended depth of focus, while preserving LED lifetime through efficient power management.
Implementation Method 1
A high-power fast-pulse driver and illumination system for high speed metrology imaging is provided, which includes an illumination source and a driver circuit configured to overdrive the illumination source using high currents and/or high current densities
Implementation Method 2
node N2, coupled via an inductor L12 to node N1
Implementation Method 3
node N3, coupled via one or more capacitors C23 to node N2
Implementation Method 4
node N4, coupled via element E43 to node N3, coupled via one or more diodes D42 to node N2
Data Source
AI summary
A high-power fast-pulse driver and illumination system for high speed metrology imaging is provided, which includes an illumination source and a driver circuit configured to overdrive the illumination source using high currents and/or high current densities. The high currents are currents higher than manufacturer-recommended currents used to drive the illumination source and the high current densities are current densities higher than manufacturer-recommended current densities used to drive the illumination source. The illumination source is operated using a lifetime preserving technique selected from a first technique of operating the illumination source at low duty cycles of 2% or less or a second technique of operating the illumination source in a burst mode at higher duty cycles for short intervals. The driver and illumination system may be incorporated in a variable focus lens (VFL) system, to define multiple exposure increments for acquiring one or more images focused at one or more focus planes.