Abstract: A method to produce a matched pair of polarizing filters includes the mounting of a first linear polarizer and a second linear polarizer in a beam of light, rotating the second linear polarizer to obtain maximum extinction of the beam of light, inserting a first quarter-wave optical retarder in the beam of light and rotating the first quarter-wave optical retarder to obtain maximum extinction of the beam of light, subsequently rotating the first quarter-wave optical retarder over an angle of 45 degrees, inserting a second quarter-wave optical retarder, rotating the second quarter-wave optical retarder to obtain maximum extinction of the beam of light before securing the first linear polarizer, the first quarter-wave optical retarder and the second linear polarizer and the second quarter-wave optical retarder. A method and apparatus to analyze a sample include birefringent particles suspended in a fluid.

Abstract: An apparatus to obtain images of a target by an underwater video camera in a waterproof container wherein the target is illuminated by a laser beam. The shutter of the video camera is kept closed until a laser pulse has covered the distance to the target and nearly back to reduce the effect of reflection of the laser pulse by particles in the water. A holographic beam shaper in the path of the laser beam before a diverging lens is used to provide a 4 by 3 aspect ratio the same as the camera to illuminate the target.

Abstract: An apparatus to obtain images of a target by an underwater video camera in a waterproof container wherein the target is illuminated by a laser beam. The shutter of the video camera is kept closed until a laser pulse has covered the distance to the target and nearly back to reduce the effect of reflection of the laser pulse by particles in the water. A holographic beam shaper in the path of the laser beam before a diverging lens is used to provide a 4 by 3 aspect ratio the same as the camera to illuminate the target.

Abstract: Light amplification for use in an optical amplifier or optical resonator can be obtained by exciting cadmium-mercury molecular dimer with an electron beam sustained discharge. Light amplification can also be obtained by exciting a mercury-ammonia complex with an electron beam sustained discharge or with mercury radiation at 2,537 Angstroms produced in an electron beam sustained discharge.