Microlens Array Bonding for Temperature-Stable Sensor Alignment
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Solution Overview
Problem
Microlens arrays in plenoptic cameras face misalignment issues due to mechanical stresses, warpage, and thermal expansion differences between materials, leading to performance degradation, especially in miniaturized systems where tight tolerances and temperature stability are critical.
Innovation Solution
The optical system employs a thermally conductive adhesive to bond the microlens array directly to the image sensor, with strategically applied glue drops or lines, and uses supporting blocks to maintain parallelism, while a resin layer and elastic adhesive layer help absorb thermal expansions, minimizing mechanical stresses and warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the microlens array is mechanically attached to the image sensor using conventional methods (direct gluing, holders), then assembly is simplified, but misalignments occur due to mechanical stresses and thermal expansion differences
Solution Approach 1:
The patent introduces an intermediary compensation layer between the microlens array and image sensor that actively compensates for misalignments caused by mechanical stresses and thermal expansion. This layer serves as a mediator that absorbs dimensional changes and maintains parallel alignment, resolving the contradiction between simple assembly and precise alignment.
Solution Approach 2:
The patent employs materials with specific thermal expansion coefficients that match or compensate for the differential expansion between the microlens array and image sensor. By carefully selecting and combining materials with different thermal parameters, the system maintains alignment stability across temperature variations while keeping the assembly process simple.
2Manufacturing precision
If tight tolerances are enforced for parallel alignment between microlens array and image sensor, then optical performance is improved, but the system becomes highly sensitive to temperature changes and mechanical stresses
Solution Approach 1:
The patent incorporates a compensation layer designed beforehand to cushion and absorb the effects of thermal expansion and mechanical stresses. This layer is specifically engineered to counteract the dimensional changes that would otherwise cause misalignment, allowing tight tolerances to be maintained without excessive sensitivity to environmental variations.
Solution Approach 2:
The patent uses composite material structures combining elements with different thermal expansion properties. The compensation layer is formed from materials strategically selected to create a composite structure that remains dimensionally stable across temperature ranges, thereby maintaining alignment precision while improving temperature stability.
3Stability of the object's composition
If the image sensor is rigidly mounted to the PCB or substrate, then mechanical stability is improved, but warpage occurs due to thermal expansion differences
Solution Approach 1:
The patent employs a flexible compensation layer or film between the image sensor and PCB that can deform to accommodate thermal expansion differences. This thin film structure provides mechanical stability while allowing controlled deformation to prevent warpage, resolving the contradiction between rigidity and shape stability.
Solution Approach 2:
The patent selects materials for the mounting structure with thermal expansion parameters carefully matched to the image sensor and PCB. By adjusting the thermal parameters of the intermediate materials, the system achieves both mechanical stability and resistance to warpage under temperature variations.
4Volume of moving object
If miniaturization is pursued to reduce device size, then compactness is improved, but alignment tolerances become tighter and more difficult to maintain
Solution Approach 1:
The patent introduces a compensation layer that acts as a mediator to maintain alignment in miniaturized systems. This layer compensates for the reduced tolerance margins inherent in compact designs, allowing the device to be miniaturized without sacrificing alignment precision.
Solution Approach 2:
The patent uses materials with matched thermal expansion coefficients and controlled mechanical properties to maintain alignment in miniaturized configurations. By carefully selecting material parameters and designing the compensation layer thickness and composition, the system achieves tight alignment tolerances necessary for compact device sizes.
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 the need for complex calibration data, maintains alignment stability across temperature changes, and improves the overall performance of the camera by ensuring precise parallel alignment between the microlens array and the image sensor.
Implementation Method 1
The microlens array is directly bonded to the image sensor with a thermally conductive adhesive, a glue or a foam
Implementation Method 2
Another source of problems that can result on misalignments is the different thermal expansion coefficients between the stiffener (and/or the PCB), the image sensor and the microlens array
Data Source
Figure 1
Figure 2
Figure 3A~3C
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.