Imaging Device Focus Offset Compensation via Pixel Aperture Design
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Solution Overview
Problem
As imaging devices are miniaturized, accurately aligning and focusing lenses with image sensors becomes increasingly difficult due to small incremental height adjustments required, often resulting in assembly defects and lower yields due to misalignment and focus errors.
Innovation Solution
The design involves positioning the image sensor at a distance from the lens's optical center such that the focus offset gap is compensated by selecting pixel dimensions and aperture numbers, ensuring that 2·P·FN≧X, where P is the pixel dimension, FN is the aperture number, and X is the focus offset gap, thereby automatically correcting for mechanical tolerances and alignment issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the lens barrel and image sensor are miniaturized to reduce device size, then the imaging device becomes more compact, but the alignment and focusing precision becomes increasingly difficult to achieve
Solution Approach 1:
The patent changes the design parameters by introducing a focus offset gap X between the lens and image sensor, and by selecting pixel dimensions P and aperture numbers FN to satisfy the relationship 2·P·FN≧X. This parameter-based approach allows the system to compensate for alignment errors and maintain focus precision despite miniaturization.
2Manufacturing precision
If the focus offset gap X is introduced to compensate for alignment errors, then the focusing accuracy is improved, but the device structure becomes more complex
Solution Approach 1:
The focus offset gap design allows the imaging device to self-compensate for alignment errors through the mathematical relationship between pixel dimension, aperture number, and focus offset. The system uses its own inherent parameters (P, FN, X) to automatically correct focus issues without requiring additional active compensation mechanisms or complex adjustment procedures.
3Ease of manufacture
If mechanical tolerances and machining variations are present in the lens assembly, then the assembly process becomes more realistic and manufacturable, but focus offset gaps are introduced that degrade image quality
Solution Approach 1:
The patent converts the harmful effect of mechanical tolerances and machining variations into a beneficial design feature. Instead of trying to eliminate focus offset gaps through stricter tolerances, the design accepts these inevitable variations and uses the relationship 2·P·FN≧X to compensate for them, turning a manufacturing challenge into a design advantage that improves overall system robustness.
Data Source
AI summary
An imaging device comprises a lens barrel having a lens opening, and a lens positioned in the lens opening of the lens barrel, the lens having an optical center, a focal length F, an aperture diameter D, and an aperture number FN=F/D. An image sensor comprises an array of light sensing pixels that each have a dimension P, the sensor spaced apart a distance S from the optical center of the lens such that a focus offset gap X=F−S. The pixel dimension P and aperture number FN are selected such that 2·P·FN≧X.