Short-working-distance optical imaging system and method for surface detection of underwater structures

In the surface imaging of underwater structures, long working distance will reduce image quality due to the turbidity of water. To acquire high definition and large field of view (FOV) images for surface detection, a short-working-distance underwater imaging system is proposed based on camera array. A multi-view calibration and rectification method is developed. A look-up table (LUT) method and a multi-resolution spline (MRS) method are applied to stitch array images real-time and seamlessly. Experiments both in the air and in the water are conducted. Strength and weakness of the LUT and MRS methods are discussed. Based on the results, the effectiveness in surface detection of underwater structures is verified.     

Conceptual rotational mode design for optical conical scanning imaging small satellites

This paper focuses upon the novel optical conical scanning imaging working mode design for small satellites. This kind of satellite employs only one inclined optical camera achieving wide-swath imaging via a rotational motion about the nadir axis either by the camera or by the satellite. Three working modes are designed, i.e., high-speed rotational mode, low-speed rotational mode,and variable-speed rotational mode. For the high-speed and low-speed working modes, the camera rotates at a constant speed and the corresponding angular velocity is derived under the consideration of guaranteed coverage and minimized overlap. To improve the system performance, an enhanced working mode taking advantages of both the high-speed rotational mode and lowspeed rotational mode is proposed. Working in this variable-speed rotational mode, the camera rotates slowly to get high-quality pictures when it works, while it rotates rapidly to reduce the energy consumption and save the storage during which period the camera is turned off to minimize the overlap. All these working modes are illustrated in detail, and numerical simulation tests are conducted to validate their effectiveness.