Curved-Substrate Image Sensor for Full-Frame Autofocus
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Solution Overview
Problem
Current image sensors face challenges in achieving optimal optical and electrical characteristics, particularly in autofocus operations, where peripheral regions often remain out of focus and require manual adjustment, leading to inefficiencies in image sharpness and focus accuracy.
Innovation Solution
The image sensor design incorporates a semiconductor substrate with curved surfaces in the active pixel array region and micro-lenses, along with a pixel separation structure, to split incident light into multiple beams, allowing for phase difference detection and autofocus adjustments, thereby improving focus accuracy across the entire image frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional flat semiconductor substrate is used, then the manufacturing process is simple, but the peripheral regions remain out of focus and focus accuracy deteriorates
Solution Approach 1:
The semiconductor substrate is designed with a curved surface instead of a flat surface. The curvature radius is specifically controlled to be greater than the focal length of the imaging lens, which enables the substrate to focus light from peripheral regions accurately while maintaining good optical characteristics across the entire image frame.
2Volume of moving object
If the semiconductor substrate is made thinner to reduce size, then the device size is minimized, but the photoelectric conversion efficiency and signal quality deteriorate
Solution Approach 1:
The substrate thickness is optimized locally rather than uniformly. The curved surface design allows different regions of the substrate to have appropriate thickness characteristics, enabling thin substrate construction while maintaining sufficient photoelectric conversion efficiency in critical regions.
3Measurement precision
If manual focus adjustment is used for peripheral regions, then focus can be achieved, but the operation time increases and productivity decreases
Solution Approach 1:
The curved substrate design enables the imaging system to automatically achieve focus across the entire field of view without requiring manual intervention. The curvature itself provides the optical path correction needed for peripheral regions, allowing the system to self-correct focus issues that would otherwise require manual adjustment.
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 design enhances autofocus capabilities, ensuring sharper images by accurately detecting phase differences and adjusting lens positions, thus improving focus precision and reducing manual adjustments.
Implementation Method 1
a plurality of curved surfaces that is convex toward the plurality of micro-lenses
Implementation Method 2
a plurality of micro-lenses disposed on the active pixel array region and corresponding to the plurality of pixel regions
Implementation Method 3
a first photoelectric conversion region and a second photoelectric conversion region disposed in the active pixel array region
Data Source
AI summary
An image sensor includes: a semiconductor substrate including a first surface and a second surface opposite to the first surface, the semiconductor substrate including an active pixel array region and a light-shield region; a first pixel separation region disposed in the active pixel array region and defining a plurality of pixel regions; a first photoelectric conversion region and a second photoelectric conversion region disposed in the active pixel array region and in each of the plurality of pixel regions; and a plurality of micro-lenses disposed on the active pixel array region and corresponding to the plurality of pixel regions. The semiconductor substrate of the active pixel array region includes a plurality of curved surfaces that is convex toward the plurality of micro-lenses. The semiconductor substrate of the light-shield region includes the plurality of curved surfaces, and wherein the image sensor is configured to receive light at the second surface.