Microlens Array Bonding Layout for Thermal Alignment Stability
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Solution Overview
Problem
Microlens arrays in light-field cameras face misalignment issues due to mechanical stresses and thermal expansion differences between materials, leading to performance degradation, especially in miniaturized systems where tight tolerances are required.
Innovation Solution
The optical system employs a thermally conductive adhesive to directly bond the microlens array to the image sensor, with strategically applied glue drops or lines, and an elastic adhesive layer to minimize mechanical stresses and thermal expansion effects, while supporting blocks maintain parallelism and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the microlens array is directly bonded to the image sensor using adhesive, then the mechanical alignment is improved, but the thermal expansion differences cause misalignment under temperature changes
Solution Approach 1:
The patent changes the physical parameters of the adhesive material, specifically selecting a material with thermal expansion coefficient matched to the image sensor substrate. This parameter matching allows the adhesive layer to expand and contract at the same rate as the substrate under temperature changes, preventing misalignment between the microlens array and image sensor while maintaining the benefits of direct bonding.
Solution Approach 2:
The patent explicitly addresses thermal expansion by selecting an adhesive material whose coefficient of thermal expansion matches that of the image sensor substrate. This ensures that both components expand and contract uniformly with temperature changes, eliminating the misalignment problems that would otherwise occur due to differential thermal expansion between dissimilar materials.
2Strength
If the image sensor is attached to PCB with stiffener, then the mechanical strength is improved, but the warpage of image sensor increases under mechanical stresses
Solution Approach 1:
The patent applies local quality by using a compliant adhesive layer specifically at the mounting points of the image sensor to the PCB, rather than making the entire structure rigid. This localized compliance allows stress distribution and prevents warpage in critical areas while maintaining overall mechanical strength through the stiffener structure.
Solution Approach 2:
The patent employs composite material strategy by combining a rigid stiffener structure with a compliant adhesive layer having matched thermal expansion properties. This composite approach provides both the mechanical strength needed for structural integrity and the flexibility required to accommodate thermal expansion differences, preventing warpage while maintaining attachment strength.
3Manufacturing precision
If tight tolerances are respected in miniaturized system, then the manufacturing precision is improved, but the sensitivity to thermal shifts increases
Solution Approach 1:
The patent changes the material parameters by selecting an adhesive with thermal expansion coefficient matched to the image sensor substrate. This parameter matching ensures that even in miniaturized systems with tight tolerances, thermal expansion does not cause misalignment, thereby reducing sensitivity to thermal shifts while maintaining manufacturing precision.
4Adaptability or versatility
If different materials are used for microlens array and image sensor, then the adaptability is improved, but the different thermal expansion coefficients cause misalignment
Solution Approach 1:
The patent introduces an intermediary adhesive layer between the microlens array and image sensor that has thermal expansion properties matched to the image sensor substrate. This intermediary material acts as a buffer that accommodates the thermal expansion differences between dissimilar materials (such as glass microlenses and silicon sensor), allowing each component to maintain its optimal material properties while preventing misalignment through the matched-expansion adhesive interface.
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 solution reduces the need for complex calibration data and maintains optimal alignment between the microlens array and image sensor, improving camera performance by minimizing misalignments and warpage, even under temperature changes.
Implementation Method 1
The optical system employs a thermally conductive adhesive to directly bond the microlens array to the image sensor
Implementation Method 2
an elastic adhesive layer to minimize mechanical stresses and thermal expansion effects
Data Source
AI summary
An optical system (400) including a microlens array (104), an image sensor (108) and a PCB (206). The microlens array (104) is bonded to the image sensor (108) with glue lines (804) or glue drops (802) dispensed around the non-active area (404) of the microlens array (104). The image sensor (108) may be bonded to the PCB (206) with a layer of adhesive material (502) applied only on a central region of the image sensor (108). Alternatively, the image sensor can rest onto a thermally conductive resin layer (109) placed over a stiffener (207), and the image sensor can be attached to the PCB (206) by one or more glue drops (111) or glue lines (113) arranged on at least one side of the image sensor (108) or by an adhesive layer (115) laterally surrounding the image sensor (108). The optical system (400) solves the problem of misalignment between the image sensor and the microlens array caused by changes in temperature.