A computer, including a processor and a memory, the memory including instructions to be executed by the processor to receive an emitted polarized light beam at a lidar receiver that determines a polarization pattern and a distance to an object, wherein the polarization pattern is determined by comparing a linear polarization pattern and a circular polarization pattern and identify the object by processing the polarization pattern and the distance with a deep neural network, wherein the identity of the object can be metallic or non-metallic. The instructions can include further instructions to operate a vehicle based on the identified object.