A Method for Designing an Optical Clock Beacon to Detect Highly Accurate Image Capture Time

Assessing the motion of moving objects from video footage captured using multiple recording devices requires precise timing and location data, which remains equally important in mobile recording systems. Although capturing high-precision clocks and analyzing these images are effective methods for obtaining accurate time information, a definitive method for precisely determining the capture time from images of rapidly time-varying clocks at various exposure durations is currently lacking. This paper introduces a design method for a dynamic optical marker called the Optical Clock Beacon (OCB), which indicates the current time by integrating multiple point light sources. Our goal is to enable accurate determination of the capture time from images. We present a method for estimating this time using image analysis and validate its accuracy. The simplest OCB configuration translates the binary representation of the current time into a Gray code, with each bit's state indicated by light sources of positive and negative logic. This approach allows the determination of an image capture time with precision matching of the exposure duration. Furthermore, we outline a design strategy that improves the time accuracy by making the light source configuration of each digit redundant, thus providing substantial design flexibility for the OCB. We also detail the prototype hardware and the image analysis system of the developed OCB, demonstrating through evaluation experiments that the anticipated time accuracy is achievable.