A method includes exposing a sample etalon-object to sample incident radiation, resulting in a sample transmitted radiation and sample reflected radiation; exposing a reference etalon-object to reference incident radiation, resulting in a reference transmitted radiation and reference reflected radiation; and analyzing resultant radiation for a heterodyned spectrum. The sample transmitted radiation may become the reference incident radiation, and the reference transmitted radiation may become the resultant radiation. The reference transmitted radiation may become the sample incident radiation, and the sample transmitted radiation may become the resultant radiation. The sample transmitted radiation may become the reference incident radiation, and the reference reflected radiation may become the resultant radiation. The reference transmitted radiation may become the sample incident radiation, and the sample reflected radiation may become the resultant radiation.