Hollow Light Integrator for DMD Illuminator Thermal Management
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Solution Overview
Problem
Conventional UV curing devices, such as short arc mercury lamps and laser diodes, suffer from low radiance, short lifetimes, and high maintenance costs, while prepackaged LEDs face thermal impedance issues leading to reduced output and lifespan, limiting their effectiveness in high-intensity applications like maskless lithography and 3D printing.
Innovation Solution
A UV LED digital micromirror device illuminator utilizing a three-way telecentric optical imaging system with a keystone corrected and tilted hollow light integrator, along with a telecentric stop and parallelogram-shaped field stop, enhances light intensity and uniformity by reclaiming lost light and optimizing thermal management, resulting in a high radiance, long-lasting, and cost-effective illumination source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If prepackaged LEDs are used, then device complexity is reduced, but thermal impedance increases leading to reduced output and lifespan
Solution Approach 1:
The patent divides the LED assembly into separate functional components: the LED die is mounted on a printed circuit board (PCB) with dedicated thermal vias and copper planes for heat dissipation, rather than using a prepackaged LED module. This segmentation allows independent optimization of thermal management and electrical connections, reducing thermal impedance while maintaining device simplicity.
Solution Approach 2:
The patent introduces an intermediary thermal management structure between the LED die and the housing: a heat sink with thermal vias and copper planes that acts as a heat transfer medium. This intermediary structure efficiently conducts heat away from the LED junction without requiring complex prepackaged LED designs, thereby improving reliability while keeping the overall device simple.
2Illumination intensity
If conventional arc lamps are used, then illumination intensity is achieved, but lifetime is reduced to hundreds of hours
Solution Approach 1:
The patent changes the fundamental operating parameters from arc discharge (conventional lamps) to electroluminescence in LEDs. This parameter change enables sustained operation for tens of thousands of hours while maintaining high illumination intensity through efficient light emission from the semiconductor material, eliminating the short lifetime issue of arc lamps.
3Device complexity
If conventional LED optical designs are used, then device simplicity is maintained, but radiance is reduced due to thermal management limitations
Solution Approach 1:
The patent addresses thermal management by adding a vertical dimension for heat dissipation: thermal vias extend through multiple layers of the PCB to copper planes, creating a three-dimensional thermal conduction path. This dimensional approach efficiently removes heat without increasing the lateral footprint or complicating the optical design, thereby maintaining high radiance while keeping the device simple.
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 provides a highly reliable and high-power density source of uniform UV illumination, significantly increasing throughput and reducing thermal load and stray light, thereby improving image contrast and extending the lifespan of the DMD device.
Implementation Method 1
a plurality of inside walls extending along an axis from the input aperture to the output aperture. Each of the inside walls includes a reflective surface
Data Source
AI summary
Described are optical systems for a digital micromirror device (DMD) illuminator. The optical systems include a LED array, a tapered non-imaging collection optic, a reflective stop and a telecentric lens system. The telecentric lens system is disposed along an optical axis defined between the tapered non-imaging collection optic and the reflective stop. The telecentric lens system is configured as a first half of a symmetric one to one imager for an object plane on the optical axis and as a second half of the symmetric one to one imager for optical energy reflected from the reflective aperture stop. The optical systems reclaim optical energy emitted by the LED array that does not initially pass through the reflective stop and provide an improved intensity distribution at the DMD. Reductions in stray light and the thermal loads on the illuminator and DMD are achieved relative to conventional illumination systems for DMDs.