Sensing of Objects in Water by Computer Vision Techniques

在这项研究中，我们提出了三种新的方法来测量水中物体的三维形状：1)用激光测距仪测量水箱中物体的三维形状；2)用装有机械手的激光测距仪测量水中物体的三维形状；3)用立体摄像系统对水下环境中的气泡噪声进行稳健的观测。在应用视觉传感器测量液体中的物体时，会遇到图像失真的问题。这是由于光在气液交界处的折射引起的，而失真的图像会给测距的三角测量带来误差。我们提出的方法可以测量液体中物体表面的精确三维坐标，用于计算折射效应。2)构建了一个由六自由度机械手和激光测距仪组成的新型传感系统。在移动机械手的同时，可以测量物体在水中的三维形状、位置和方向。3)对于水下环境中的观察，有时会遇到气泡干扰场景的困难。它还有一个问题，当相机被放置在防水玻璃板后面的空气中时，空气和水的边界面上会发生折射，导致图像的几何失真。为此，我们提出了一种用于水下环境观测的稳健观测方法，该方法通过图像处理去除气泡图像，并在考虑折射的情况下进行三维测量，实验结果验证了该方法的有效性。

In this study, we proposed three new methods that can measure 3-D shapes of objects in water as follows:1)3-D Measurement of Objects in Water Tank with a Laser Range Finder, 2)3-D Measurement of Objects in Water with a Laser Range Finder Equipped with a Manipulator, and 3)Robust Observation in Underwater Environments against Bubble Noises with a Stereo Camera System.As to 1), we proposed 3-D measurement method of objects' shapes in liquid by using a spot light and a slit light, respectively. When applying vision sensors to measuring objects in liquid, we meet the problem of an image distortion. It is caused by the refraction of the light on the boundary between the air and the liquid, and the distorted image brings errors in a triangulation for the range measurement. Our proposed method can measure the accurate 3-D coordinates of object surfaces in liquid taken for calculating the refraction effect.As to 2), we constructed a new sensing system that consisted of 6DOF manipulator and a laser range finder. 3-D shapes, positions, and orientations of objects in water could be measured while moving the manipulator.As to 3), observation in underwater environments meets the difficulty that scenes are sometimes disturbed by air bubbles. It has also the problem that, when a camera is set in air behind a watertight glass plate, refraction occurs at the boundary surface between air and water, resulting in geometrical distortion of images. Therefore, we proposed a robust observation method for underwater environments observation, which is realized by image processing for bubble image removal and three-dimensional measurement where refraction is taken into account.The effectiveness of our proposed methods was verified through experimental results.