NanEye-An Endoscopy Sensor With 3-D Image Synchronization

In this paper, an innovative camera synchronization technique is presented, enabling the combination of two 1 mm × 1 mm sized cameras to produce a real-time 3-D image. The technique developed and implemented on an FPGA platform with an USB3 interface, allows minimal error synchronization of up to an eight individual self-timed cameras. Typically, a small self-timed camera modules do not allow external synchronization, but for stereo vision, 3-D reconstruction with multiple cameras, and applications requiring pulsed illumination, camera synchronization is required. The developed solution uses the power supply control to dynamically adapt their frame rate and frame phase. The control core overviews the operating frequency of each camera by measuring the line period in each frame based on a well-defined sampling signal. The frequency is then adjusted by varying the voltage level applied to the sensor using as a reference the error between the measured and desired line period. This allows for average synchronization errors below 0.02% at temperatures ranging from 0 °C to 60 °C. This paper will allow the implementation of smaller than 3-mm-diameter 3-D stereo vision equipment for medical endoscopy, such as disposable robotic or micro invasive surgery applications.