Abstract: This invention provides a compact, fuel-efficient internal combustion engine that can be used to provide rotating shaft output power to a wide variety of mobile and stationary applications. It is based on a two-stroke free-piston gas generator that implements the homogeneous charge compression ignition (HCCI) combustion principle for essentially constant-volume combustion, and it employs a variable piston stroke to maintain a high level of efficiency across a wide range of loads and speeds. A rotary device, which may be of either an aerodynamic or positive displacement type, converts the energetic gas stream to power at a rotating shaft.

Abstract: A method and apparatus for detecting small shifts in optical wavelength is provided. Light having a known wavelength is directed towards a target volume in the atmosphere. Light reflected from the target volume is received and mixed with differentially delayed copies of itself to produce three interference signals. The interference signals are taken at delays spanning one-half the wavelength of the transmitted signal. The intensity of the signal at the three different delays is measured simultaneously, from which the wavelength of the reflected signal can be determined.