Showing papers on "Waveplate published in 1975"

Rotating-compensator ellipsometer

Abstract: Plane polarized light is reflected from a surface of a sample film to produce an elliptically polarized reflected beam The reflected beam is passed sequentially through a rotating one-quarter wave plate and a fixed analyzer which transmits a beam whose intensity varies as a function of the rotational angle of the plate The transmitted beam impinges upon a photodetector which produces an electric signal proportional to the intensity of the transmitted light The rotating one-quarter wave plate cyclically varies the polarization of the beam, so that the electrical signal, when numerically Fourier analyzed, provides Fourier coefficients having both sin Δ and cos Δ terms, where the ellipsometric parameter Δ is the instantaneous phase difference between the parallel (Rp) and perpendicular (Rs) components of the electric vector of the elliptically polarized reflected beam; therefore, the phase difference Δ is uniquely and unambiguously defined in a single measurement Furthermore, the presence of both sin Δ and cos Δ terms permits Δ to be determined more accurately than is possible with the prior art rotating-analyzer ellipsometer Since the ellipsometric parameter ψ is also uniquely defined (tanψ=Rp /Rsub s), properties of the sample film can be computed Alternatively, the rotating quarter-wave plate may be placed in the path of the incident plane polarized beam

Dynamic magnetic bubble display system

Abstract: A dynamic pattern display and optical data processing system is provided including magnetic bubble devices which may be operated in real-time to produce two and three dimensional patterns such as holograms, kinoform lenses and complex filters. Th display pattern is obtained by directing a linearly polarized light beam through a combination including a one-quarter waveplate, a plurality of two-dimensional magnetic bubble arrays and another one-quarter wave plate, all combined in a stack arrangement. In one embodiment a combination is provided which functions as a phase filter and in another embodiment including more bubble arrays, the combination functions as a phase and intensity filter. The display patterns are multi-phase or multi-tone (gray scale) and multi-phase in character. Each magnetic bubble array in the phase and phase and intensity filter embodiments constitutes a layer which differs in thickness from the other magnetic bubble layers. Each magnetic bubble array is also electronically driven by its own bubble propagating circuit which produces, in most embodiments, a different "local phase" or "local transmissivity" which is a function of whether a bubble or an empty space is propagated to the location. The number of levels of transmitted phase or intensity and phase is an exponential function of the number of magnetic bubble layers, thus n layers provides 2 n steps of transmitted phase or intensity and phase modification and a four layer structure provides a sixteen level phase or phase and intensity display. The electronic portion of the structure may be driven by signals representing mathematical expressions, patterns, manual inputs and the like to generate holograms, kineform lenses, complex filters, three-dimensional television pictures, and other display and optical information processing applications.

Technique for eliminating undesirable reflections from optical systems

Abstract: Undesirable reflections from an element in an optical system are eliminatedy passing incoming light through a polarizer and a 45° optical rotator before it strikes the reflective element. The reflected light component is again rotated 45° by the rotator, for a total rotation of 90°, whereupon it is blocked from leaving the system by the polarizer. Alternatively, a quarter wave plate or other circular polarizing component may replace the rotator to result in a net rotation of the polarization of the reflected light by 90°.

A Spectrum Scanning Stokes Polarimeter

Abstract: A photoelectric polarimeter for measuring line profiles in all four Stokes parameters has been built and operates on the SPO 40 cm coronagraph in a joint project with Sacramento Peak Observatory. A description of the optical and electronic systems and the calibration scheme is presented. Performance parameters determined from observations are also given. The polarimeter package consisting of a pair of KDP's, a quarter wave plate, and a polarizing beam splitter is located at the prime focus of the coronagraph. Modulation of the KDP's encodes polarization information into intensity signals that are electronically detected. The scanning of the spectrum, accomplished by rotating the grating, permits Stokes line profiles to be recorded on magnetic tape for processing. The instrument can be used to scan any line from 3900 to 7000 A with a spectral resolution of 0.01 A. Polarizations as small as 0.001% are detectable. The polarimeter and observing system are computer controlled.