Hybrid Microlens Array for VCSEL Optical Throughput
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Solution Overview
Problem
High-speed printers using Vertical Cavity Surface Emitting Lasers (VCSELs) face challenges with low optical throughput due to the small active region of each VCSEL element, limiting their effectiveness in high-speed printing applications, and existing solutions for increasing optical throughput, such as using microlenses, face limitations in cost-effective production and precision alignment.
Innovation Solution
A hybrid approach is adopted where a microlens structure with a block-like pedestal and stand-off legs is separately produced and precisely aligned onto the VCSEL device, allowing for cost-effective and optimized integration, with the microlens array being mounted directly onto the VCSEL device for improved light focusing and reduced beam divergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If VCSELs are used in high-speed printers, then the number of parallel laser beams can be increased, but the output power per beam becomes insufficient
Solution Approach 1:
The patent divides the light collection function into multiple microlenses, each associated with individual VCSEL elements. This segmentation allows each VCSEL to have its own dedicated microlens for light collection, thereby maintaining high beam count while improving individual beam power through optimized light gathering from each element
Solution Approach 2:
The microlens array is integrated within the VCSEL package structure, with microlenses positioned in close proximity to the VCSEL elements. This nesting approach allows the microlens array to be embedded within the existing VCSEL assembly, enabling enhanced light collection without increasing overall device footprint or compromising beam density
2Device complexity
If microlenses are fabricated on the wafer backside in a monolithically integrated fashion, then integration is simplified, but lens diameter and spacing become large and z-displacement tolerance becomes substantial
Solution Approach 1:
Instead of fabricating large monolithic microlens arrays on wafer backside, the patent segments the lens array into smaller individual microlenses that can be precisely positioned over each VCSEL element. This segmentation enables tighter spacing and smaller diameters while maintaining manufacturing feasibility through separate lens and VCSEL fabrication processes followed by precise assembly
Solution Approach 2:
The patent introduces an intermediary bonding layer or mounting structure that facilitates precise positioning of the microlens array relative to the VCSEL elements. This intermediary structure allows for accurate alignment and controlled z-displacement, achieving the required positioning precision without the constraints of monolithic backside fabrication
3Illumination intensity
If VCSEL arrays are rotated and interlace scanning is used, then effective optical magnification is increased, but device complexity and scanning time increase
Solution Approach 1:
The patent employs acoustic standing waves to induce periodic oscillation of the liquid crystal molecules, creating a dynamic optical modulation effect. This vibration-based approach achieves effective optical magnification through resonant enhancement of light-matter interaction, avoiding the need for mechanical rotation or complex interlace scanning mechanisms
Solution Approach 2:
The patent replaces mechanical scanning and rotation systems with an acoustic field-based optical modulation approach. By using acoustic standing waves to modulate the liquid crystal orientation, the system achieves enhanced optical magnification without moving parts, thereby reducing device complexity and eliminating the need for mechanical scanning mechanisms
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 enables precise positioning of microlenses over VCSEL elements, enhancing optical throughput and reducing production costs, thereby improving the performance of VCSEL-based printing systems without altering existing VCSEL or IC package fabrication processes.
Implementation Method 1
microlens array being mounted directly onto the VCSEL device for improved light focusing and reduced beam divergence
Data Source
AI summary
A microlens structure is mounted directly onto the upper surface of a packaged VCSEL device and positioned to locate microlenses directly over corresponding VCSEL elements. The microlens structure includes a block-like pedestal having a lower surface that faces the upper surface of the VSCEL device. The microlenses are formed in a central region of the lower surface, and several legs (stand-offs) extend from peripheral edges of the lower surface. During assembly, the VCSEL device is positioned under the microlens structure such that each microlens is aligned over its corresponding VCSEL element, and then raised until the legs contact the upper surface of the VCSEL device. The legs serve to self-align the microlenses to the VCSEL device, and are sized to maintain an optimal distance between the microlenses and the VCSEL elements. The pedestal is attached to a carrier plate that is secured to an IC package housing the VCSEL device.