The present disclosure provides an optical device for selecting specific matter, such as plant matter. The device comprises a light source for emitting light having at least (3) wavelengths and for generating a combined beam of light having the at least 3 wavelengths. The device further comprises an optical element for directing a plurality of light beams towards matter including the specific matter. The optical element has first surface portions through which in use the plurality of component light beams are directed to the matter including the specific matter. Each component light beam is directed through a respective first surface portion that has an optical property that is selected so that light intensity differences between the component light beams are reduced. The optical device also comprises an optical filter for filtering reflected component light beams such that an intensity of light is reduced in a wavelengths range outside one or more wavelengths ranges that include the at least three wavelengths. Further, the optical device comprises a detector for detecting the reflected component light beams.