Microlens Sag Profile Layout for Low-Divergence Beam Quality
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Solution Overview
Problem
Existing microlens arrays in optical projection devices face limitations in achieving high beam quality due to diffraction issues, particularly when the microlens diameter is small, and require costly and complex lens systems to achieve desired beam conditioning and imaging.
Innovation Solution
The use of microlens arrays with varying sag profiles over the substrate, where focal powers and tilt angles change from a central region to a peripheral region, allowing for optimized beam refraction and correction of aberrations in conjunction with projection optics, even with simple optical elements like plastic singlets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If microlens diameter is reduced to increase emitter density, then array integration is improved, but diffraction issues worsen and beam quality deteriorates
Solution Approach 1:
The patent applies local quality by varying the sag profile of microlenses based on their position in the array. Central microlenses have different focal powers than peripheral microlenses, with each lens optimized for its specific location. This localized optimization compensates for diffraction effects that become more pronounced at smaller diameters, maintaining beam quality across the entire array while allowing high emitter density.
2Reliability
If conventional lens systems are used to achieve desired beam conditioning, then beam quality is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the beam conditioning function directly into the microlens array structure itself. By integrating position-dependent focal power variations into the microlens design, the system combines focusing, beam shaping, and aberration correction into a single component layer, eliminating the need for separate complex lens systems while maintaining high beam quality.
Solution Approach 2:
The patent changes the focal power parameter of microlenses as a function of their position in the array. Central microlenses have higher focal power while peripheral microlenses have lower focal power, creating a gradient that optimizes beam conditioning across the entire array. This parameter variation allows simple microlens structures to achieve complex beam control functions.
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 approach enhances the far-field beam quality and reduces the burden on projection optics by aligning the sag profiles of microlenses with the projection optics, achieving low divergence and correcting for aberrations, thereby improving the overall optical performance.
Implementation Method 1
The microlenses have respective sag profiles that vary over an area of the substrate. The second array includes at least first microlenses in a central region of the substrate and second microlenses in a peripheral region of the substrate, such that the first microlenses have respective first focal powers, while the second microlenses have respective second focal powers
Implementation Method 2
The sag profiles are defined such that the microlenses have respective focal powers that decrease gradually from the first focal powers to the second focal powers in a radial direction over the area of the substrate. This approach enhances the far-field beam quality and reduces the burden on projection optics by aligning the sag profiles of microlenses with the projection optics, achieving low divergence and correcting for aberrations
Data Source
AI summary
An optical device includes a first array of emitters disposed on a substrate and configured to emit respective beams of optical radiation in a direction perpendicular to the substrate. A second array of microlenses is positioned on the substrate in alignment with the respective beams of the emitters, having respective sag profiles that vary over an area of the substrate. The second array includes at least first microlenses in a central region of the substrate and second microlenses in a peripheral region of the substrate, such that the first microlenses have respective first focal powers, while the second microlenses have respective second focal powers, which are less than the first focal powers.