Abstract: A common-path, point-diffraction, phase-shifting interferometer uses a half wave plate having a diffractive element, such as pin hole. A coherent, polarized light source simultaneously generates a reference beam from the diffractive element and an object beam from remaining portions of the light going through the half wave plate. The reference beam has a nearly spherical wavefront. Each of the two beams possesses a different polarization state. The object and reference beams are then independently phase modulated by a polarization sensitive phase modulator that shifts phase an amount depending on applied voltage and depending on polarization state of the incident light. A polarizer is then used to provide the object and reference beams in the same polarization state with equal intensities so they can interfere to create an interferogram with near unity contrast.

Abstract: A common-path, point-diffraction, phase-shifting interferometer uses a half wave plate having a diffractive element, such as pin hole. A coherent, polarized light source simultaneously generates a reference beam from the diffractive element and an object beam from remaining portions of the light going through the half wave plate. The reference beam has a nearly spherical wavefront. Each of the two beams possesses a different polarization state. The object and reference beams are then independently phase modulated by a polarization sensitive phase modulator that shifts phase an amount depending on applied voltage and depending on polarization state of the incident light. A polarizer is then used to provide the object and reference beams in the same polarization state with equal intensities so they can interfere to create an interferogram with near unity contrast.

Abstract: A sonar apparatus using a phased array technique for steering an acoustical beam for scanning an underwater area. The sonar apparatus includes a scanning transducer having multiple elements for transmitting and steering the acoustical beam and receiving its reflection from an object, an electronic control circuit for generating steering information and computing a relative location of the object, and an input/output section for displaying the relative location to a user. The control circuit includes a software level/align control for compensating for mis-leveling or mis-alignment during installation, a scan control capable of selecting a scan center direction and a scan width in one degree increments, a forward gain control for optimizing the sensitivity of the sonar apparatus in a forward looking scan, and a combination of a time variable gain control and an autorange control for minimizing the reflection of sidelobes of the acoustical beam.