Abstract: The present invention discloses an optical system for performing a laser photorefractive keratectomy operation on a cornea for vision correction. The optical system comprises a laser source emitting a laser beam. The optical system also includes a beam processing subsystem for receiving and processing the laser beam for generating a processed laser beam suitable for performing the keratectomy operation. The optical system further includes an energy delivery subsystem including a continuous energy-delivery control device which may include time-varying movable slits, rotating diaphragms, or combination of lens system with moving screen, for optically controlling the energy delivered to different areas of the cornea by the processed laser beam for performing the vision correction.

Abstract: An earth impedance determination and compensation system for use with a seismic vibrator utilizes output signals from accelerometers on the baseplate and reaction mass portions of the vibrator to create a signal indicative of the near-surface weathered earth layer impedance below the baseplate. The impedance signal is utilized to generate parameter signals which are indicative of the compressional and shear wave patterns generated by the baseplate and may be used to more rapidly and accurately design seismic source arrays to optimize the wave pattern emanating therefrom. One of the parameter signals is directly indicative of the travel time thickness of the weathered surface layer and may be used to accurately determine the static correction factor attributable solely to weathered layer topography.