Variable Adhesive Offset for Camera Lens Assembly
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Solution Overview
Problem
Existing camera assembly processes use a constant adhesive offset to compensate for curing shrinkage, which can lead to inconsistencies in modulation transfer function (MTF) ratios between center and corner values, causing either corner or center MTF values to drop below manufacturing specifications due to part-to-part variability in lens characteristics.
Innovation Solution
A method that determines a variable adhesive offset based on individual lens focus characteristics by calculating the ratio difference between actual and desired MTF ratios and considering the expansion characteristics of the adhesive, allowing for precise adjustment of the lens position before applying the adhesive to maintain optimal focus quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a constant adhesive offset is used to compensate for curing shrinkage, then the assembly process is simple and fast, but the MTF ratio consistency between center and corner values deteriorates due to part-to-part lens variability
Solution Approach 1:
The patent changes the adhesive offset parameter from a constant value to a variable value based on individual lens characteristics. Specifically, the offset is adjusted according to the ratio of corner MTF to center MTF for each lens, allowing the assembly process to adapt to part-to-part variability and maintain consistent MTF ratios across different lenses while accommodating the natural variations in lens focus characteristics
Solution Approach 2:
The patent performs preliminary measurement and calculation of the MTF ratio for each lens before applying the adhesive. By determining the corner MTF and center MTF values in advance and calculating the required offset adjustment before adhesive application, the system prepares the optimal offset value beforehand, ensuring precision without sacrificing assembly speed
2Ease of manufacture
If a constant adhesive offset is used, then the manufacturing process is simple, but the yield deteriorates due to MTF values dropping below specifications
Solution Approach 1:
The patent implements dynamic parameter adjustment by changing the adhesive offset based on measured lens characteristics. The system calculates the MTF ratio for each lens and adjusts the offset accordingly, ensuring that both center and corner MTF values remain within specification limits. This adaptive approach significantly improves yield by preventing out-of-spec conditions that would occur with a fixed offset
Solution Approach 2:
The patent incorporates a feedback mechanism where the measured MTF values (both corner and center) are used to determine the appropriate adhesive offset. The system measures the actual MTF characteristics, compares them against desired specifications, and adjusts the offset parameter accordingly. This closed-loop approach ensures high reliability by continuously adapting to actual lens performance
3Manufacturing precision
If a variable adhesive offset based on individual lens characteristics is used, then the MTF ratio consistency and yield improve, but the device complexity and measurement requirements increase
Solution Approach 1:
The patent enables the lens itself to provide the information needed for offset determination through its own MTF characteristics. By measuring the corner and center MTF values directly from the lens under test, the system uses the lens's inherent optical properties to determine the appropriate offset, eliminating the need for external classification or manual intervention
Solution Approach 2:
The patent transforms the complex measurement requirement into a straightforward parameter measurement by focusing on the MTF ratio. Rather than requiring complex multi-dimensional characterization, the system measures two key parameters (corner MTF and center MTF) and derives the offset from their ratio, simplifying the measurement system while maintaining high precision
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 improves camera assembly yield by 50% by compensating for lens depth of focus imbalance and reducing production fallout associated with using a constant adhesive offset, enabling a wider range of lens depth of focus variations to meet manufacturing specifications.
Implementation Method 1
the curing shrinkage of the adhesive used to fixedly couple or attach the lens to the imager
Implementation Method 2
an expansion-characteristic of the adhesive that is used to fixedly couple the lens to the imager
Data Source
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AI summary
A method (100) of assembling a camera (12) includes the steps of determining a focused-position (28) of a lens (14) relative to an imager (16) where an image (30) is focused on the imager (16), determining a first-factor (32) indicative of focus quality at a central-portion (34) of the imager (16), and determining a second-factor (36) indicative of focus quality at an outer-portion (38) of the imager (16). The outer-portion (38) is characterized as displaced radially outward from the central-portion (34). The method (100) also includes the steps of determining an actual-ratio (40) of the first-factor (32) and the second-factor (36), and determining an offset-position (42) of the lens (14) relative to the imager (16) based on the focused-position (28), a ratio-difference between the actual-ratio (40) and a desired-ratio (44), and an expansion-characteristic (46) of an adhesive (20) that is used to fixedly couple the lens (14) to the imager (16). The method (100) also includes the step (110) of applying the adhesive (20) to fixedly couple the lens (14) to the imager (16) while the lens (14) is in the offset-position (42).