Element for an optical measurement system

An element for optical measurement system comprising a first crown extending circumferentially around an axis and comprising at least one first optical lens, and a second crown located radially outside of the first crown and surrounding the first crown and comprising at least one second optical lens where at least one first lens is aligned with at least one second lens, the first and second crowns are made of the same material so as to form a unitary element, said element comprising centering or alignment means located near at least one second lens and intended to engage with additional centering or alignment means of an optical emitter or receiver, and said element further comprising a calibrated passage opening, intended for the passage of a flow comprising a sample to be analyzed, located and oriented along said axis of the first and second crowns and opening out in a space delimited by the first crown and forming a measurement chamber through which said fluid is intended to pass.