Eye-in-Hand

A camera-mounting scheme where the camera is fixed to the robot arm's end-effector and moves along with it.

Eye-in-hand is a camera-mounting configuration in a hand-eye system: the camera is fixed to the arm's end-effector or gripper and moves along with it; the opposite configuration, with the camera fixed in the environment, is called ‘eye-to-hand.’ Its advantage is a close-up view of the target that's less likely to be blocked by the arm itself, which suits fine alignment and visual servoing. Its drawback is a narrow field of view with no global picture, and every observation has to be converted into the base frame by multiplying the end-effector pose (from forward kinematics) by a one-time-calibrated camera-to-end-effector transform. That transform comes from hand-eye calibration, classically formulated as AX = XB. The wrist camera used in learned policies is this configuration, and its images are often fed in alongside third-person cameras — the DROID platform, for example, mounts a ZED Mini stereo camera on each Franka arm's wrist.

ExampleDuring a grasp, a fixed third-person camera first roughly localizes the object; once the arm gets close, the system switches to the wrist camera's close-up view to fine-tune the gripper's position before closing it.

Also called

Camera Mounted on End-Effector

Related

Eye-to-Hand · Hand-Eye Calibration · Wrist Camera · Visual Servoing · Third-Person Camera · Forward Kinematics (FK)

Sources

MoveIt: Hand-Eye Calibration Tutorial
DROID: A Large-Scale In-the-Wild Robot Manipulation Dataset