Monolithic Microlens Array Fabrication on Image Sensors
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Solution Overview
Problem
Conventional light field cameras face challenges in precise placement of microlenses over image sensors due to mechanical bonding requirements, leading to misfocus and blurring, especially in compact artificial reality devices where form factor and cost are critical.
Innovation Solution
A manufacturing system that forms microlenses directly on the image sensor substrate, eliminating the need for mechanical bonding by using a monolithic process involving photoresist deposition, patterning, and thermal curing to create microlenses of specific dimensions that cover pixels, thereby reducing image blurring and enhancing robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical bonding is used to attach microlens array to image sensor, then alignment precision can be achieved, but the structure becomes complex and reliability decreases due to environmental factors affecting alignment
Solution Approach 1:
The patent merges the microlens array and image sensor into a single monolithic structure by forming microlenses directly on the sensor substrate using photoresist deposition and thermal reflow. This eliminates the mechanical bonding interface and associated alignment issues while maintaining manufacturing precision through integrated fabrication processes.
Solution Approach 2:
The patent extracts the microlens array from its traditional separate mechanical mounting and integrates it directly into the image sensor substrate. By removing the mechanical bonding layer and alignment mechanisms, the design simplifies the structure while improving reliability against environmental factors.
2Manufacturing precision
If mechanical bonding is used to attach microlens array to image sensor, then microlenses can be positioned over pixels, but production costs increase and manufacturing complexity increases
Solution Approach 1:
The patent combines the microlens fabrication process with the image sensor manufacturing process into a single monolithic flow. Photoresist is deposited and thermally reflowed directly on the sensor substrate in the same fabrication line, eliminating separate mechanical bonding steps and reducing both cost and complexity.
Solution Approach 2:
The patent replaces the mechanical bonding system with a thermal-reflow-based photoresist curing process. Instead of using adhesives or mechanical mounting structures, the microlenses are formed through controlled thermal processing that melts and reshapes the photoresist material directly onto the pixel array.
3Adaptability or versatility
If distance of separation between microlens array and image sensor is varied, then focus adjustment is possible, but misfocus and blurring occur
Solution Approach 1:
By merging the microlens array and image sensor into a monolithic structure with fixed sub-pixel spacing, the patent eliminates focus adjustment mechanisms. The fixed integration ensures precise focus while maintaining adaptability through the light field camera's computational processing capabilities.
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 reduces image blurring, minimizes the camera's form factor, lowers production costs, and allows for a lower power budget, making it suitable for compact artificial reality devices like head-mounted displays.
Implementation Method 1
The manufacturing system performs a patterning on the deposited layer to form one or more blocks of cured photoresists
Implementation Method 2
The manufacturing system performs a thermal curing of the one or more blocks of uncured photoresists to form an array of microlens
Data Source
AI summary
A method for monolithically fabricating a light field sensor with an array of microlens. Each microlens is formed directly on a surface including a plurality of pixels of the light field sensor formed on a wafer. The manufacturing system performs a preparation of the surface including the plurality of pixels formed on the wafer. The manufacturing system deposits a layer of photoresist on the surface of the wafer. The manufacturing system performs a patterning on the deposited layer to form one or more blocks of cured photoresists. The manufacturing system performs a thermal curing of the one or more blocks of uncured photoresists to form an array of microlens of the light field sensor. Each microlens covers at least one of the plurality of pixels of the light field sensor formed on the wafer.