Projector Auto-Focus Using Camera Depth Map
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Solution Overview
Problem
Handheld projectors, such as those in smartphones and cameras, require manual focus correction each time the orientation of the projector and projecting surface changes, which is inconvenient and difficult to automate due to the need for simultaneous camera focus adjustment.
Innovation Solution
A method and system that uses a camera to capture images of a projected binary pattern, computes a depth map, and adjusts the projector focus based on the computed depth map, allowing for automatic focusing without user intervention, utilizing a hierarchical binary pattern to retain structural details and improve focus accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual focus correction is used in handheld projectors, then focus accuracy can be achieved, but user convenience deteriorates due to requiring manual intervention each time orientation changes
Solution Approach 1:
The projector system performs self-focus adjustment by projecting a binary pattern, capturing the image with an integrated camera, computing depth information, and automatically adjusting the lens position without user intervention. The system serves itself by using its own camera and processor to determine and execute the necessary focus correction.
Solution Approach 2:
The system projects a binary pattern and captures the reflected image with the camera, then computes depth information from the captured image. This feedback loop allows the system to determine the actual distance to the projection surface and adjust the focus accordingly, creating a closed-loop control system that automatically corrects focus based on measured conditions.
2Extent of automation
If automatic focus correction is implemented, then user convenience improves, but device complexity worsens due to requiring camera integration and depth map computation
Solution Approach 1:
The integrated camera serves multiple functions: it acts as both the projection surface detector and the image capture device for depth computation. The same camera that would be used for other imaging purposes in the handheld device is utilized for focus correction, eliminating the need for a separate dedicated sensor and reducing overall system complexity.
Solution Approach 2:
A binary pattern is projected as an intermediary element to enable depth computation. This pattern provides high-contrast reference points that facilitate accurate depth map generation from the captured image, serving as a mediator between the projector and camera to enable automatic focus adjustment without requiring complex direct measurement mechanisms.
3Measurement precision
If focus adjustment is made based on projection surface distance, then focus accuracy improves, but adaptability worsens when projecting on surfaces at varying distances across the field of view
Solution Approach 1:
The projection surface is divided into multiple depth zones represented by the depth map, which provides depth information for different regions of the field of view. This segmentation allows the system to identify the dominant depth plane and adjust focus accordingly, or to handle multiple planes by selecting the most appropriate focus distance based on the projected content and surface characteristics.
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 automatic and simultaneous focus correction of both the projector and camera in handheld devices, enhancing the accuracy and convenience of projecting digital content onto various surfaces without manual intervention.
Implementation Method 1
capturing an image of the projected binary pattern by a camera synchronized with the projector
Data Source
AI summary
A method of automatically focusing a projector in a projection system is provided that includes projecting, by the projector, a binary pattern on a projection surface, capturing an image of the projected binary pattern by a camera synchronized with the projector, computing a depth map from the captured image, and adjusting focus of the projector based on the computed depth map.