Lens Module Assembly for Stable Back Focus Under Adhesive Swelling
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Solution Overview
Problem
The swelling or shrinkage of adhesives used in lens modules due to environmental changes affects the resolution and imaging quality, as the thickness variations are unpredictable and uncontrollable, leading to back focus variation and degradation of imaging performance.
Innovation Solution
The use of bonding layers with the same thickness and material at designated positions in the lens module, ensuring synchronous swelling or shrinkage to maintain a consistent distance between the image sensor and the optical center, thereby stabilizing the imaging plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If AA glue is used between lens and lens holder for fixation and focusing, then the lens can be securely fixed and focused, but the glue thickness variation and shrinkage cause back focus variation of 4 μm or greater, affecting imaging quality
Solution Approach 1:
The patent divides the bonding function into two separate bonding layers: a first bonding layer between the lens holder and substrate, and a second bonding layer between the lens unit and lens holder. This segmentation allows each layer to be optimized independently for its specific function while reducing overall thickness variation and shrinkage impact on back focus precision.
Solution Approach 2:
The patent changes the material parameters of the bonding layers by selecting specific adhesive materials with controlled shrinkage characteristics. The first and second bonding layers use adhesives with different shrinkage rates or shrinkage compensation properties to maintain stable back focus distance despite environmental changes.
2Strength
If UV+ heat curing glue is used for bonding, then the bonding strength is improved, but the glue shrinks during curing process causing uncontrollable thickness change and affecting imaging quality
Solution Approach 1:
The patent changes the curing parameters and material selection by using adhesives with different curing characteristics. The first and second bonding layers may use adhesives with different UV/heat curing properties or shrinkage compensation characteristics to maintain thickness stability during and after curing.
Solution Approach 2:
The patent applies shrinkage compensation design by pre-calculating and compensating for the shrinkage that will occur during curing. The bonding layers are designed with thickness and material properties that account for future shrinkage, ensuring stable back focus distance after curing completes.
3Reliability
If glue is used in wet working environment, then the bonding is maintained, but the glue absorbs water vapor and swells, causing unpredictable thickness change and affecting resolution and imaging quality
Solution Approach 1:
The patent uses composite bonding structures with different adhesive materials having different hygroscopic properties. The first and second bonding layers may combine adhesives with complementary moisture absorption characteristics to cancel out overall swelling effects in humid environments.
Solution Approach 2:
The patent changes the material parameters by selecting adhesives with different moisture absorption coefficients and swelling characteristics. The bonding layers are designed with material properties that minimize or compensate for environmental moisture absorption, maintaining stable thickness under varying humidity conditions.
4Device complexity
If single bonding layer is used, then the structure is simple, but the thickness variation and shrinkage are uncontrollable and affect imaging quality
Solution Approach 1:
The patent segments the single bonding layer into two separate bonding layers with different functions and material properties. This segmentation enables independent optimization of each layer for its specific bonding purpose while reducing overall thickness variation and improving back focus precision control.
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 maintains the imaging quality by canceling out offset amounts caused by bonding layer variations, improving resolution and ensuring the image sensor remains in the focal plane, thus enhancing the lens module's performance.
Implementation Method 1
the glue itself may absorb water vapor continuously, and then swell after absorbing moisture
Implementation Method 2
the glue itself may absorb water vapor continuously, and then swell after absorbing moisture
Implementation Method 3
the glue may dehydrate gradually and then shrink in a dry environment
Data Source
AI summary
The present invention provides a lens module and a method for assembling the lens module. The lens module comprises: a base; a PCB, which is disposed on the base; a lens unit, which comprises one or more lenses and is disposed on the base; a first bonding layer, which is disposed between the base and the PCB to bond the base and the PCB together; and a second bonding layer, which is disposed between the base and the lens unit to bond the base and the lens unit together.