Digital Watermark Pre-distortion for Blur Correction
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Solution Overview
Problem
Handheld camera devices, such as cell phones, often capture images that are out of focus due to varying user settings, leading to distortion that hampers the detection of machine-readable codes like digital watermarks.
Innovation Solution
A method that pre-distorts digital watermarks to counteract expected distortions, such as lens blurring, by shifting phase components to ensure detectability, and embeds these pre-distorted signals in input data, or applies post-capture correction using filters to compensate for distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a user positions the camera close to capture high spatial frequency content, then the spatial resolution is improved, but the image becomes out of focus or blurred
Solution Approach 1:
The patent applies pre-distortion to the digital watermark signal before embedding, anticipating the blur that will occur during close-up capture. This preliminary modification prepares the signal to be restored to its original form after capture, resolving the contradiction between capturing high spatial frequency content and maintaining image focus.
Solution Approach 2:
The patent introduces a counter-distortion effect by pre-modifying the watermark signal with an inverse blur filter. This preliminary anti-action counteracts the expected blur from close-up capture, allowing the watermark to be reliably detected even when the image is out of focus.
2Reliability
If digital watermarking is applied to compensate for expected distortion, then detection reliability is improved, but the complexity of the watermarking process increases
Solution Approach 1:
The patent modifies the digital watermark signal by applying pre-distortion parameters that counteract expected capture blur. This parameter change in the signal processing domain improves detection reliability without requiring hardware modifications, balancing reliability improvement with acceptable process complexity.
3Measurement precision
If pre-distortion is applied to digital watermark signal, then detection accuracy is improved, but the complexity of the embedding process increases
Solution Approach 1:
The patent replaces physical optical correction mechanisms with digital signal processing. Instead of using complex optical systems to prevent blur, the invention uses computational pre-distortion of the watermark signal, substituting mechanical/optical complexity with software-based signal manipulation.
Data Source
AI summary
The disclosure relates generally to improving readability of machine-readable information, despite signal capture distortion. One claim recites a method comprising: obtaining input data, the input data representing imagery or video, the input data comprising test data and a machine-readable signal; determining characteristics associated with the test data to determine information regarding signal capture distortion of the input data; based on at least the characteristics, determining an amount of correction or counteracting to be applied to the input data; using a programmed processor, applying a determined amount of correction or counteracting to the input data; and analyzing corrected or counteracted input data to obtain the machine-readable signal. Of course, other claims and combinations are provided as well.