Display Watermark Embedding With Temporal Phase Inversion for Camera Capture
Solution Overview
Problem
Existing display devices lack the ability to embed watermarks that are imperceptible to human eyes but can be captured by cameras, making it difficult to trace the source of images displayed on these devices.
Innovation Solution
A watermark embedding method that utilizes a processing circuit to generate grayscale information based on time series data and predetermined programs, embedding the watermark signal into the input video signal such that it alternates between high and low grayscale at frequencies imperceptible to humans but can be captured by cameras.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a watermark is embedded into the video signal using conventional methods, then the watermark can be captured by a camera, but the watermark becomes visible to human eyes
Solution Approach 1:
The patent changes the temporal frequency parameter of the watermark signal to be above the human visual system's temporal resolution threshold (typically above 60Hz). By modulating the watermark at these high frequencies and utilizing opposite phases during dark and bright state periods, the watermark becomes imperceptible to human eyes while remaining detectable by cameras that can resolve these temporal variations.
Solution Approach 2:
The patent employs periodic modulation of the watermark signal with opposite phases during dark state and bright state periods of each cycle. This periodic action at high frequency creates a temporal pattern that exploits the difference between human visual persistence and camera exposure timing, making the watermark invisible to humans but captureable by cameras.
2Object-affected harmful factors
If the watermark signal uses high frequency alternation between dark and bright states, then the watermark becomes imperceptible to human eyes, but the complexity of generating and embedding the watermark increases
Solution Approach 1:
The patent implements dynamic phase inversion of the watermark signal based on the display's brightness state. The processing circuit dynamically switches the watermark phase between positive and negative states synchronized with the display's dark and bright periods. This dynamic adaptation allows high-frequency temporal modulation without requiring complex multi-dimensional encoding, simplifying the overall system while achieving imperceptibility.
3Object-affected harmful factors
If the watermark is embedded with opposite phases during dark and bright state periods, then the watermark is hard to be perceived by human eyes, but the precision of controlling the video signal increases
Solution Approach 1:
The patent employs feedback mechanisms where the processing circuit monitors the display's brightness state and adjusts the watermark phase accordingly. By using the display's own brightness cycles as a reference signal, the system achieves precise synchronization of phase inversions without requiring external timing signals, thereby reducing the precision requirements for external control while maintaining high signal control accuracy.
Data Source
AI summary
A watermark embedding method includes the following steps. The input video signal is received by a processing circuit. Grayscale information of a watermark signal is generated by the processing circuit according to a time series data and a predetermined plane. During a dark sate and a bright state in each of a plurality of consecutive periods, phases of the time series data are opposite and integral values of the grayscales of the predetermined plane are the same. The processing circuit embeds the watermark signal into the input video signal to generate an output video signal with the watermark information. The display panel displays an image according to the output video signal.