An optical head for a Raman spectroscopy system includes a housing an input configured to allow input radiation of a selected wavelength into the housing, a first lens disposed in an end of the housing to allow the input radiation to emit from the housing through the first lens and to receive reflected radiation including specular reflection and diffuse reflection, and a second lens disposed in the housing and configured to receive reflected radiation from the first lens. The optical head includes an output configured to receive the reflected radiation from the second lens. The optical head includes a blocking mirror disposed in the housing between the first lens and the second lens. The blocking mirror is configured and positioned to direct the radiation from the input to the first lens. The blocking mirror blocks at least a portion of specular reflection from reaching the second lens but allows diffuse reflection to the reach the second lens.