Camera Timestamp Offset Calibration Using Optical Flash Timing
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Solution Overview
Problem
Augmented reality devices face challenges in accurately synchronizing virtual objects with the real world due to inaccuracies in image capture timestamping, which affects tracking and placement of AR objects.
Innovation Solution
A method and system for determining an image capture timestamp offset by generating optical flashes at a specific rate, capturing images at a different rate, and analyzing intensity to adjust camera timestamping, ensuring accurate alignment and synchronization of virtual content with the real world.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image capture timestamping is used for AR device tracking, then virtual objects can be placed in the real world, but timestamp inaccuracies cause misalignment between virtual and real-world content
Solution Approach 1:
The patent replaces mechanical timestamping mechanisms with an optical measurement system. By using optical flashes at known intervals and measuring their arrival times at the camera sensor, the system determines the actual image capture timestamp through optical timing rather than relying on hardware clock timestamps, thereby achieving higher precision timestamp measurement
Solution Approach 2:
The patent introduces optical flashes as an intermediary reference signal. These flashes serve as a known temporal reference that mediates between the camera's internal timestamping system and the actual image capture time, allowing the system to calculate and correct timestamp offsets by comparing expected flash arrival times with actual captured timings
2Ease of operation
If hardware clock timestamps are used for image capture, then timing information is readily available, but timestamp errors affect AR object placement accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the measured timestamp offset from optical flash timing is used to correct the hardware clock timestamps. The system continuously monitors the difference between expected and actual flash arrival times, calculates the offset, and applies correction to subsequent timestamping, thereby maintaining placement accuracy while preserving the ease of hardware timestamp generation
Solution Approach 2:
The patent changes the timestamp parameter by introducing a correction value derived from optical measurements. Instead of using raw hardware clock timestamps, the system adjusts the timestamp parameter by adding or subtracting the measured offset, transforming inaccurate timestamps into corrected timestamps that accurately reflect actual image capture times
Data Source
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AI summary
A method of determining an image capture timestamp offset or error includes generating optical flashes at an optical flash rate. A set of images of the optical flashes are captured at an image capture rate. The image capture rate is different from the optical flash rate, and each image includes an associated image timestamp. Signals associated with the generation of the optical flashes are also timestamped. The intensity of each image in the set of images is determined, and the image having the greatest intensity in the set of images is identified. The timestamp offset or error is determined as the difference between the timestamp of the image having the greatest intensity and the timestamp of the corresponding optical flash.