The interferometer is manufactured as a solid cast aluminum block and is completely sealed. The FT/IR-4000 uses a 45 deg Michelson interferometer and the FT/IR-6000 uses a 28-degree Michelson interferometer. A near frictionless bearing (without the need for a gas supply) supports the moving mirror, which is driven by a ‘voice coil’ for accurate vibration free movement.  Laser tracking of the moving mirror is made using Accutrac™ with the latest in digital signal processing. The standard KRS-5 windows prevent hygroscopic damage often seen with KBr windows used on some products.