Concurrent Projector-Camera Temporal Slot for Echo-Free Capture
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Solution Overview
Problem
Conventional methods for concurrent projector-camera systems suffer from 'visual echo' due to video feedback loops, which distort projected images and create ghosting effects, requiring complex synchronization and computational resources to mitigate.
Innovation Solution
The Concurrent Projector-Camera dynamically synchronizes projector lighting by compressing and shifting LED on-state times to create an intra-frame capture time slot, allowing image capture without projection corruption, thus eliminating visual echo without canceling entire frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional video feedback loop is used in projector-camera systems, then real-time image capture is achieved, but visual echo and ghosting effects occur due to projection interference
Solution Approach 1:
The projection frame is segmented into multiple sub-frames, with specific sub-frames designated for camera capture while others are used for projection. This temporal segmentation allows the camera to capture images during projection-free intervals, eliminating visual echo while maintaining real-time operation.
Solution Approach 2:
The system implements periodic switching between projection and capture modes within each frame cycle. The projector alternates between displaying content and remaining dark, with capture occurring during the dark intervals. This periodic action creates regular opportunities for echo-free image capture while maintaining continuous operation.
2Object-affected harmful factors
If entire frames are canceled for camera capture, then visual echo is eliminated, but projection brightness and continuity are reduced
Solution Approach 1:
Instead of canceling entire frames, the system cancels only specific sub-frames or portions of frames during which capture is needed. This partial action approach eliminates visual echo during capture intervals while maintaining projection brightness and continuity during other intervals, providing a balanced solution.
3Reliability
If complex synchronization is used to mitigate visual echo, then projection and capture coordination is improved, but device complexity increases
Solution Approach 1:
The system merges the projector and camera operations into a unified control framework where a single controller manages both devices. This consolidation simplifies synchronization by eliminating the need for complex inter-device communication and coordination protocols, reducing overall system complexity while maintaining reliable operation.
Data Source
AI summary
A “Concurrent Projector-Camera” uses an image projection device in combination with one or more cameras to enable various techniques that provide visually flicker-free projection of images or video, while real-time image or video capture is occurring in that same space. The Concurrent Projector-Camera provides this projection in a manner that eliminates video feedback into the real-time image or video capture. More specifically, the Concurrent Projector-Camera dynamically synchronizes a combination of projector lighting (or light-control points) on-state temporal compression in combination with on-state temporal shifting during each image frame projection to open a “capture time slot” for image capture during which no image is being projected. This capture time slot represents a tradeoff between image capture time and decreased brightness of the projected image. Examples of image projection devices include LED-LCD based projection devices, DLP-based projection devices using LED or laser illumination in combination with micromirror arrays, etc.