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Based on Awaiba’s NanEye CMOS image sensor family and a FPGA platform with USB3 interface, the aim of this paper
is to demonstrate a novel technique to perfectly synchronize up to 8 individual self-timed cameras. Minimal form factor
self-timed camera modules of 1 mm x 1 mm or smaller do not generally allow external synchronization. However, for
stereo vision or 3D reconstruction with multiple cameras as well as for applications requiring pulsed illumination it is
required to synchronize multiple cameras. In this work, the challenge to synchronize multiple self-timed cameras with only
4 wire interface has been solved by adaptively regulating the power supply for each of the cameras to synchronize their
frame rate and frame phase. To that effect, a control core was created to constantly monitor the operating frequency of
each camera by measuring the line period in each frame based on a well-defined sampling signal. The frequency is adjusted
by varying the voltage level applied to the sensor based on the error between the measured line period and the desired line
period. To ensure phase synchronization between frames of multiple cameras, a Master-Slave interface was implemented.
A single camera is defined as the Master entity, with its operating frequency being controlled directly through a PC based
interface. The remaining cameras are setup in Slave mode and are interfaced directly with the Master camera control
module. This enables the remaining cameras to monitor its line and frame period and adjust their own to achieve phase
and frequency synchronization. The result of this work will allow the realization of smaller than 3mm diameter 3D stereo
vision equipment in medical endoscopic context, such as endoscopic surgical robotic or micro invasive surgery.
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