  Sensor fusion has become a popular topic in robotics. However, conventional
fusion methods encounter many difficulties, such as data representation
differences, sensor variations, and extrinsic calibration. For example, the
calibration methods used for LiDAR-camera fusion often require manual operation
and auxiliary calibration targets. Implicit neural representations (INRs) have
been developed for 3D scenes, and the volume density distribution involved in
an INR unifies the scene information obtained by different types of sensors.
Therefore, we propose implicit neural fusion (INF) for LiDAR and camera. INF
first trains a neural density field of the target scene using LiDAR frames.
Then, a separate neural color field is trained using camera images and the
trained neural density field. Along with the training process, INF both
estimates LiDAR poses and optimizes extrinsic parameters. Our experiments
demonstrate the high accuracy and stable performance of the proposed method.
