Color Registration of Underwater Images for Underwater Sensing with Consideration of Light Attenuation

Colors of objects observed in underwater environments are different from those in air. This is because the light intensity decreases with the distance from objects in water by light attenuation. Robots on the ground or in air usually recognize surrounding environments by using images acquired with cameras. The same is/will be true of underwater robots. However, recognition methods in air based on image processing techniques may become invalid in water because of light attenuation. Therefore, we propose a color registration method of underwater images. The proposed method estimates underwater environments where images are acquired, in other words, parameters essential to color registration, by using more than two images. After estimating parameters, color registration is executed with consideration of light attenuation. The effectiveness of the proposed method is verified through experiments

A visually-guided position control method, in underwater conditions, using an inexpensive remotely operated vehicle

Ponència presentada a 9th Martech International Workshop on Marine Technology (MARTECH 2021), Vigo, 16-18 juny, 202

A visually-guided position control method, in underwater conditions, using an inexpensive remotely operated vehicle

Peer Reviewe

Simulating underwater depth environment condition using lighting system design

The major obstacle faced by the underwater environment system is the extreme loss of color and contrast when submerged to any significant depth whereby the image quality produced is low. The studies can be easily done by developing the prototype that may imitate the underwater environment. In order to develop the prototype, suitable lighting system are used where it act as an imitator for underwater environment with different depth. Next the color option that use for the imitator prototype should be suitable for underwater lighting system. By using both suitable lighting system and color option for the system, this prototype might be able to produce image that can be comparable with the actual environment. The water tank is the best choice as the medium for imitating and it’s attached with the red curtain in order to create the environment without any unwanted lighting source. The underwater flood light is use for the lighting system and creates the scenery of the lighting underwater environment. The brightness of the light can be adjustable by adjusting the input voltage. In order to capture and record the image of the imitated underwater, the underwater camera and recordable receiver display is used. Lastly, since the underwater environment has noise the automatic pump is applied to create the ambient noise. The result shows that the appropriate combination of color and the brightness based on different depth it may produce the precise hue and saturation with the actual environment system

Color-accurate underwater imaging using perceptual adaptive illumination

Capturing color in water is challenging due to the heavy non-uniform attenuation of light in water across the visible spectrum, which results in dramatic hue shifts toward blue. Yet observing color in water is important for monitoring and surveillance as well as marine biology studies related to species identification, individual and group behavior, and ecosystem health and activity monitoring. Underwater robots are equipped with motor control for large scale transects but they lack sensors that enable capturing color-accurate underwater images. We present a method for color-accurate imaging in water called perceptual adaptive illumination. This method dynamically mixes the illumination of an object in a distance-dependent way using a controllable multi-color light source. The color mix compensates correctly for color loss and results in an image whose color composition is equivalent to rendering the object in air. Experiments were conducted with a color palette in the pool and at three different coral reefs sites, and with an underwater robot collecting image data with the new sensor.United States. Office of Naval Research (Project N000140911051

A Mirror-Based Active Vision System for Underwater Robots: From the Design to Active Object Tracking Application

A mirror-based active system capable of changing the view’s direction of a pre-existing fixed camera is presented. The aim of this research work is to extend the perceptual tracking capabilities of an underwater robot without altering its structure. The ability to control the view’s direction allows the robot to explore its entire surroundings without any actual displacement, which can be useful for more effective motion planning and for different navigation strategies, such as object tracking and/or obstacle evasion, which are of great importance for natural preservation in environments as complex and fragile as coral reefs. Active vision systems based on mirrors had been used mainly in terrestrial platforms to capture the motion of fast projectiles using high-speed cameras of considerable size and weight, but they had not been used on underwater platforms. In this sense, our approach incorporates a lightweight design adapted to an underwater robot using affordable and easy-access technology (i.e., 3D printing). Our active system consists of two arranged mirrors, one of which remains static in front of the robot’s camera, while the orientation of the second mirror is controlled by two servomotors. Object tracking is performed by using only the pixels contained on the homography of a defined area in the active mirror. HSV color space is used to reduce lighting change effects. Since color and geometry information of the tracking object are previously known, a window filter is applied over the H-channel for color blobs detection, then, noise is filtered and the object’s centroid is estimated. If the object is lost, a Kalman filter is applied to predict its position. Finally, with this information, an image PD controller computes the servomotor articular values. We have carried out experiments in real environments, testing our active vision system in an object-tracking application where an artificial object is manually displaced on the periphery of the robot and the mirror system is automatically reconfigured to keep such object focused by the camera, having satisfactory results in real time for detecting objects of low complexity and in poor lighting conditions

Color registration of underwater images for underwater sensing with consideration of light attenuation

Abstract-Colors of objects observed in underwater environments are different from those in air. This is because the light intensity decreases with the distance from objects in water by light attenuation. Robots on the ground or in air usually recognize surrounding environments by using images acquired with cameras. The same is / will be true of underwater robots. However, recognition methods in air based on image processing techniques may become invalid in water because of light attenuation. Therefore, we propose a color registration method of underwater images. The proposed method estimates underwater environments where images are acquired, in other words, parameters essential to color registration, by using more than two images. After estimating parameters, color registration is executed with consideration of light attenuation. The effectiveness of the proposed method is verified through experiments