Relaxation time and viscosity of fused silica glass at room temperature.

Cases of long-term deformation of fused silica glass at room temperature attributed to the action of gravity have been reported. Further experimental investigations now provide evidence of time-dependent viscous behavior, with a time constant of the order of 10 years. Data relating to a pair of fused silica reference plates are presented, showing the overall deformation occurred over the years; considerations on the pertaining viscosity with aging are also given. An account of the observed relaxation process in terms of the Kelvin-Voigt model for linear viscoelasticity is provided.

One-Step 360 degrees Rainbow Holography with Two Spherical Mirrors.

A new optical configuration producing one-step 360 degrees rainbow holograms is presented. The method makes use of two concave mirrors in confocal position, with an annular aperture between the two. An experimental demonstration is given.

Measuring the refractive index of thin liquid films with a spectrometer.

We discuss the manufacture and use of a prism pair to measure the refractive index of thin liquid films with a spectrometer. The method requires only a drop of liquid and is accurate to ~2 x 10(-4).

Absolute measurement of planarity with Fritz's method: uncertainty evaluation.

Fritz's method [Opt. Eng. 23, 379 (1984)] of using Zernike polynomials to assess the absolute planarity of test plates is revisited. A refinement is described that takes into account the data decorrelation that appears in experiments. An uncertainty balance is defined by propagation of error contributions through the steps of the method. The resultant measuring procedure is demonstrated on a data set from experiments, and a nanometer level of uncertainty is achieved.

Multiphase homodyne interferometry: analysis of some error sources.

Some sources of error with multiphase homodyne interferometry are reviewed. A major advantage over the classic two-channel approach is that the inaccuracies that originate from laser-power fluctuations and drifts are shown to be automatically compensated for by proper adjustment of the light beams.

Characterization of the scattering properties of a mirror by speckle-field statistics.

The statistics of partially developed speckle patterns produced by reflection under coherent illumination can be used to determine the scattering properties of a mirror. The theory of the approach is presented, showing that in proper conditions the standard deviation of the speckle-field distribution expresses the finish grade of the reflecting surface. Interferometric measurements are described, and experiments on selected samples are reported.

Three-channel Homodyne Interferometer.

A three-channel homodyne interferometer based on a structured delay plate is described. Detection and data acquisition are performed with standard optoelectronics in a PC environment. The device, which is used as a displacement sensor, features sub-nanometric sensitivity.

Telescopes of galileo.

The Florentine Istituto e Museo di Storia delta Scienza houses two complete telescopes and a single objective lens (reconstructed from several fragments) that can be attributed to Galileo. These optics have been partially dismantled and made available for optical testing with state-of-the-art equipment. The lenses were investigated individually; the focal length and the radii of curvature were measured, and the optical layout of the instruments was worked out. The optical quality of the surfaces and the overall performance of the two complete telescopes have been evaluated interferometrically at a wavelength of 633 nm (with a He-Ne laser source). It was found in particular that the optics of Galileo came close to attaining diffraction-limited operation.

Denisyuk hologram recording with a laser diode.

Making Denisyuk holograms in the near IR with a laser diode is reported, tuning reconstruction to the visible.

Design of optical-waveguide homogeneous refracting lenses.

A class of multielement homogeneous refracting lenses for optical waveguides is presented, and their design procedure is described. These lenses appear to be particularly suitable for use in integrated optical processors, as they can be fabricated by fully planar photolithography and reliable diffusion processes either in glass or in lithium niobate; their optical characteristics can be very good. For example, the design of an f/3.3 waveguide optical system, constituted by five elements, with no field curvature and very well corrected up to a 20 degrees total field of view, is presented.

Zero-path-difference rainbow holography.

Rainbow holography without the use of a slit has been demonstrated by combining Abramson's light-in-flight approach [Opt. Lett. 3, 121 (1978)] with Benton's rainbow technique [J. Opt. Soc. Am. 59, 1545 (A) 1969]. The system natural slit-shaped pupil whose extent and position are determined by the experimental parameters.

Fourier processing with phase-reflection gratings.

The use of phase reflection gratings for Fourier filtering in the object space is described, and the optical transfer function for resonance at normal incidence is given. Experiments prove in good agreement with theory.

MTF measurement via diffraction shearing with optically superimposed gratings.

The use of double grating diffraction shearing for measurement of MTF is demonstrated. By superimposing two gratings optically we avoid the problem of grating contact and subsequent degradation. This simple and economical method is especially advantageous for optical systems with large pupil for which a rotating plate interferometer becomes prohibitively expensive.