Abstract: Techniques are described for real-time phase detection. For the phase detection, a signal is correlated with a frequency component of a frequency band whose phase is being detected, and the correlation includes predominantly decreasing weighting of past portions of the signals.

Abstract: Techniques are described for real-time phase detection. For the phase detection, a signal is correlated with a frequency component of a frequency band whose phase is being detected, and the correlation includes predominantly decreasing weighting of past portions of the signals.

Abstract: A method and apparatus for assisting a shooter in holding an aiming eye at a predetermined level relative to the barrel of a shotgun. Light is reflected or projected along a path extending at a predetermined rearward, so that the shooter's aiming eye receives a first image when it is at the proper level and a second image when it is above the proper level, thus indicating to the shooter when the aiming eye has been raised too high. The images may be different colors, produced by dispersing the beam by reflecting it from a diffraction grating or passing it through a prism. A lenticular sheet may also be used to create different colors or images that are received above and below the dividing plane. Moirè patterns may also be used to produce an image that shifts with movement of the aiming eye.