Abstract: To improve the current stage of aquaculture, underwater environment monitoring, water quality testing, and other fields of personnel operation difficulties, low efficiency, an observation type underwater robot with water sample collection function is designed. It is equipped with sensors and water sample collection devices to collect environmental water information. Firstly, the experiment of water sample collection is carried out to verify its movement ability and water sample collection ability. Then aiming at the images collected from natural waters, the dynamic threshold white balance method is used to eliminate the influence of light source intensity and color deviation. Finally, we use three algorithms: contrast stretch, histogram equalization and contrast
limited adaptive histogram equalization (CLAHE: Contrast Limited Adaptive Histogram Equalization) to enhance the image, and choose contrast, information entropy, and average gradient to evaluate the image quality. The experimental results show that the design has the characteristics of flexible operation and strong interaction, and the CLAHE method improves the details of the underwater image. The design provides a new way for scientific research experiments, underwater environment detection, water quality detection, environmental protection, etc.

Key words: underwater robot, water sample collection, image enhancement, image quality evaluation