Phase-Detect Autofocus Dual-Pixel Sensor Design
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Solution Overview
Problem
Dual pixel autofocus systems can introduce imaging artifacts due to the division of pixels into sub-pixels, leading to defect pixels and reduced image quality.
Innovation Solution
A phase-detect autofocus system utilizing two standard-sized pixels with distinct color filters, where a micro-lens spans both pixels to capture phase differences in spatial frequency information, allowing for defect-less and low-defect autofocus without compromising image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If pixels are divided into sub-pixels for phase-detection autofocus, then autofocus capability is improved, but imaging quality deteriorates due to defect pixels and artifacts
Solution Approach 1:
The pixel array is segmented into dedicated autofocus pixels and standard imaging pixels. Each autofocus pixel is further divided into two sub-pixels with distinct color filters (e.g., red and green) to capture phase information, while standard pixels maintain full imaging capability. This segmentation allows simultaneous autofocus functionality and high-quality imaging without compromising either.
Solution Approach 2:
Different regions of the pixel array are assigned different functions with optimized characteristics. Autofocus pixels use specific color filter combinations (e.g., RG or GB pairs) to maximize phase detection accuracy, while standard pixels use conventional color filters for optimal image quality. This local optimization resolves the contradiction by allowing each region to excel at its specific function.
2Measurement precision
If dedicated autofocus pixels are used, then autofocus precision is improved, but the quantity of usable imaging pixels is reduced
Solution Approach 1:
Autofocus pixels are designed to serve dual purposes: they provide precise phase-detection autofocus information through their sub-pixel structure, and they also contribute to the overall image data. The color information from autofocus pixels can be integrated into the final image, effectively increasing the total usable pixel count while maintaining dedicated autofocus capability.
Solution Approach 2:
Instead of dedicating entire pixels exclusively to autofocus (which would maximize autofocus precision but minimize imaging pixels), the invention uses partial action by dividing each autofocus pixel into two sub-pixels. This partial division provides sufficient phase information for precise autofocus while retaining enough pixel area to contribute meaningful imaging data, achieving a practical balance between the two competing requirements.
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
Enables precise and efficient autofocus with minimal imaging artifacts, maintaining high image quality by using adjacent pixels with different color filters and micro-lenses to determine focus, and allowing for adaptive use based on lighting conditions.
Implementation Method 1
phase-detect autofocus system utilizing two standard-sized pixels with distinct color filters, where a micro-lens spans both pixels to capture phase differences in spatial frequency information
Implementation Method 2
a micro-lens spans both pixels to capture phase differences
Data Source
AI summary
In various embodiments, methods, techniques, and related apparatuses for phase-detect autofocus devices are disclosed. In one embodiment, a phase-detect system includes a first color filter formed over a first pixel and a second pixel formed adjacent to the first pixel with a second color filter being formed over the second pixel. The second color filter has a color different from a color of the first color filter. A micro-lens spans the first pixel and the second pixel, configured to capture a phase difference in spatial frequency information present in an imaged scene. The first pixel and the second pixel are placed adjacent to each other in at least one of a horizontal direction, a vertical direction, and/or a diagonal direction, with an arrangement of the two pixels being replicated at either regular and/or irregular intervals across the sensor. Other methods and apparatuses are disclosed.