Target Designation Method Using Underwater Video Camera Calibrated with Multi-link Manipulator

Abstract

The paper focuses on developing a method for creating accurate target designations for a multi-link manipulator installed on AUV for various technological operations. These target designations consist of spatial straight lines passing through observed points on work object surfaces, created with the help of underwater monocular video cameras mounted on the AUV. The protective housings of these video cameras consist of thick glass that separate different media due to environment high external pressure, and usually introduce significant optical distortions in the captured images. To correct these distortions, a new calibration method for underwater video cameras is proposed. This method uses a known ray-tracing approach to account for light refraction at media boundaries (with unknown pre-determined refractive indices: air-glass-water) and eliminate lens distortions. This method is applicable for calibrating video cameras with glass of various shapes (flat, cylindrical, etc.). It not only enables accurate determination of the spatial line parameters on which a visible point of an observed object lies but also – after camera calibration – ensures accurate designation targeting of working tools of these manipulators to target work points. The effectiveness of this method has been confirmed by experimental results.