Projector-Camera Frame Timing to Hide Projected Images in Video
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Solution Overview
Problem
Existing methods for recording videos using projectors fail to effectively prevent the projected image from appearing in the final video, requiring inefficient post-processing techniques like chroma key or background removal.
Innovation Solution
A device and method that control the projection and exposure frame cycles of a projector and camera to intermittently pause the projected image during specific intervals, ensuring the projected image does not appear in the recorded video while maintaining its visibility to the user.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the projector continuously projects digital information onto the screen board, then the visual effect and information display are improved, but the projected content is captured in the video recording, diminishing the presenter's explanation effectiveness
Solution Approach 1:
The projector alternates between projection and non-projection states in periodic cycles. During projection periods, digital information is displayed for user visibility. During non-projection periods, the screen board is empty so the camera captures only the presenter's actions without projected content interference. This periodic switching resolves the contradiction by making projected content visible to users while preventing it from appearing in recorded videos.
2Loss of information
If chroma key or background removal techniques are used to remove projected content from video, then the presenter's explanation effectiveness is improved, but additional processing time is required
Solution Approach 1:
The system performs preliminary action by controlling the projector to stop projection before the camera captures each frame. This prevents projected content from being recorded in the first place, eliminating the need for post-processing removal techniques. The contradiction is resolved by preventing the problem at the source rather than requiring additional processing time to remove projected content after recording.
3Manufacturing precision
If the projection frame cycle is shortened to reduce projected image appearance in video, then the captured video quality is improved, but the user's continuous perception of projected image may be affected
Solution Approach 1:
The system optimizes parameters by setting the projection frame cycle duration and non-projection time period within specific ranges (20-50ms total cycle, with non-projection occupying 40-60% of the cycle). These parameter changes ensure the projection periods are sufficient for user perception while non-projection periods are adequate to prevent camera capture of projected content, resolving the contradiction between video accuracy and perception continuity.
Data Source
AI summary
The present invention relates to a device for filming a video using a projector, which comprises: a projector that receives an image for a projection from an external device or internal memory and projects the image onto a screen board; a camera for creating the video by filming the screen board on which the image is projected; a controller that controls a projection frame cycle of the projector and an exposure cycle of the camera. The controller controls a time schedule for the projection frame cycle of the projector for filming the video. The time schedule includes a projection time period when the projection is cast, and a non-projection time period when no projection occurs. The non-projection time period is controlled within the range of 40% to 60% of the projection frame cycle.