Mobile Camera Focus Stacking for All-in-Focus Imaging
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Solution Overview
Problem
Mobile cameras with shallow depth-of-field struggle to generate all-in-focus images, particularly in scenarios requiring multiple objects at different focal distances to be in clear focus, such as landscape or medical photography, due to limitations in existing technologies for quick and responsive user experiences.
Innovation Solution
User equipment with depth, contrast, or phase-detection sensors segments the image into focal distances, sweeps an autofocus lens to capture images at each distance, and combines these images to create an all-in-focus image, utilizing a buffer to avoid redundant focal distances and enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a shallow depth-of-field is used to achieve narrow focus and artistic quality, then portrait and artistic photography quality is improved, but the ability to capture all-in-focus images with multiple objects at different focal distances deteriorates
Solution Approach 1:
The patent segments the image into multiple depth ranges (foreground, midground, background) and captures separate images for each segment by sweeping the autofocus lens through different focal distances. This allows each segment to be captured at its optimal focus distance while maintaining the ability to combine them into a single all-in-focus image, thus resolving the contradiction between shallow depth-of-field for portraits and deep depth-of-field for landscapes.
2Manufacturing precision
If the autofocus lens sweeps through all focal distances to capture all-in-focus images, then imaging quality is improved, but capture time and responsiveness deteriorate
Solution Approach 1:
The patent performs preliminary actions by capturing images at multiple focal distances in advance and storing them in a buffer before the actual capture moment. When an all-in-focus image is needed, the system can quickly assemble from pre-captured images rather than sweeping through all focal distances in real-time, significantly reducing capture time while maintaining image quality.
Solution Approach 2:
The patent captures images at more focal distances than strictly necessary (excessive action), storing them in a buffer for future use. This allows the system to avoid redundant sweeping operations when creating all-in-focus images, as the required focal distance images are already available in the buffer, thus reducing capture time without sacrificing quality.
3Productivity
If the autofocus lens sweeps rapidly through focal distances to reduce sweep time, then capture speed is improved, but image quality and focus accuracy deteriorate
Solution Approach 1:
The patent performs preliminary focus accuracy calibration and captures reference images at various focal distances in advance. When rapid all-in-focus capture is needed, the system uses these pre-captured images from the buffer, eliminating the need for real-time sweeping and focus adjustment, thus achieving both high capture speed and high focus accuracy simultaneously.
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 mobile cameras to produce high-quality all-in-focus images efficiently, maintaining the ability to capture narrowly-focused portraits while addressing the limitations of shallow depth-of-field, thus improving imaging capabilities.
Implementation Method 1
sweeping an autofocus lens of the mobile camera to one or more of the focal distances from the set of focal distances, and capturing a sample image at each of the one or more of the focal distances
Implementation Method 2
a lens driven by a voice coil motor (VCM) or a microelectromechanical (MEMS) magnetic actuator
Implementation Method 3
a lens driven by a voice coil motor (VCM) or a microelectromechanical (MEMS) magnetic actuator
Data Source
AI summary
The present disclosure describes systems and techniques directed to producing an all-in-focus image with a camera of a mobile device, in particular, cameras with shallow depth-of-field. User equipment includes a sensor for determining distance to an object in a camera's field-of-view. Based on a depth map of the field-of-view, a plurality of segments is inferred, each segment defining a unique focus area within the camera's field-of-view. An autofocus lens of the camera sweeps to a respective focal distance associated with each of the plurality of segments. The camera captures sample images at each focal distance swept by the autofocus lens. The user equipment produces an all-in-focus image by combining or merging portions of the captured sample images.