Monitoring the thinning dynamics of soap films by phase shift interferometry. The case of perfluoropolyether surfactants.

An interferometric method to monitor the thinning process of vertical soap films from a water solution of surfactant materials is reported. Raw data maps of optical path difference introduced by the film are obtained by conventional phase shift interferometry. Off-line re-processing of such raw data taking into account the layered structure of soap films leads to an accurate measurement of the geometrical thickness. As an example of data acquisition and processing, the measuring chain is demonstrated on perfluoropolyether surfactants; the section profile of vertical films is monitored from drawing to black film state, and quantitative data on the dynamics of the thinning process are presented. The interferometric method proves effective to the task, and lends itself to further investigate the physical properties of soap films.

Measuring the thickness of soap bubbles with phase-shift interferometry.

A model for the optical path difference introduced by a soap bubble in transmission is described. The model is then used with interferometric data to solve for the fringe order, and to define a procedure to extract the global film thickness in presence of turbulence flows occurring during the drainage process due to gravity. Experimental results on soap bubbles examined in single-pass phase-shift interferometry are presented.

Supercontinuum source tuned by an on-axis monochromator for fluorescence lifetime imaging.

We report on the application of an optically tunable coherent white light source, based on the supercontinuum generation from microstructured optical fibres, to fluorescence lifetime imaging (FLIM) microscopy and Foerster resonance energy transfer (FRET). A prototype lens based on monotonic longitudinal chromatic aberration is used for tuning the supercontinuum wavelengths from 400 to 1000 nm and acts as an axial monochromator, suitable for fibre delivery in confocal microscopy.

Galileo's telescope and the birth of instrumental optics: a review note.

Early steps tracing back to Galileo's telescope and to the birth of instrumental optics are reported. Particulars of lensmaking technology, basic optics laws, concepts of eye and vision, and issues on instrument trade and service are given. Achievements at the roots of our continuing advances in optical sciences are acknowledged.

Long-term deformation at room temperature observed in fused silica.

Cases of long-term deformation of fused silica flats are reported. The phenomenon is detected at the scale of the nanometer, and exhibits a time constant of the order of 9 years. The observed deformation appears related to gravity and constraints, but a change of physical properties locally resulting in non-homothetic behavior is also hypothesized.

Absolute planarity with three-flat test: an iterative approach with Zernike polynomials.

An iterative algorithm to analyze three-flat test data for absolute planarity measurements is presented. Using the properties of Zernike polynomial representations, results are achieved in a fast and effective manner. Details and demonstrative examples are provided.

Three-flat test with plates in horizontal posture.

Measuring flats in the horizontal posture with interferometers is analyzed in detail, taking into account the sag produced by gravity. A mathematical expression of the bending is provided for a plate supported at three unevenly spaced locations along the edge. It is shown that the azimuthal terms of the deformation can be recovered from a three-flat measuring procedure, while the pure radial terms can only be estimated. The effectiveness of the iterative algorithm for data processing is also demonstrated. Experimental comparison on a set of three flats in horizontal and upright posture is provided.

Intraocular lenses with surface aspherization: Interferometric study.

PURPOSE: To accurately evaluate in an optical laboratory 2 different types of intraocular lenses (IOLs). SETTING: Department of Oto-Neuro-Ophthalmological Surgical Sciences and CNR-Institute for Applied Optics, Florence Italy. METHODS: In this study, optical testing facilities based on interferometry were used. The IOLs were inspected with laser light, and interference patterns were acquired and processed, obtaining the physical parameters accounting for the lens behavior. Comparison of the respective performances within the pseudophakic eye was provided in terms of modulation transfer function (MTF) using lens diameters from 3.0 mm to 5.0 mm. The data were inserted in a mathematical model of the eye, and the relevant merit functions were computed with a ray-tracing program. RESULTS: Sample sets of both all-spherical IOLs and IOLs with aspherical surfaces were inspected. The interferometric maps showed clear evidence of the opposite wave aberration introduced by the different IOL types. With a 3.0 mm pupil diameter, both IOL types performed as almost ideal lenses, while with a 5.0 mm diameter, IOLs with aspherical surfaces effectively compensated for the spherical aberration of the cornea and had a significantly higher MTF. CONCLUSIONS: The interferometric approach to IOL testing provided accurate data on the physical parameters of the IOL. With a measuring and computing chain that includes eye modeling and ray tracing, it was possible to analyze in detail the process by which IOLs with aspherical surfaces compensate for the spherical aberration of the cornea under photopic, mesopic, and scotopic conditions.

Iterative algorithm for three flat test.

Absolute planarity measurements by interferometry are classically made using three flats, compared two by two in the course of four or more tests. Data reduction is performed with various analytical methods. Here we present instead a data processing algorithm that converges to solution numerically by iteration. Examples are presented both on synthetic interferograms and on experimental data. High accuracy and versatility of the approach are demonstrated.

Simple portable lens meter.

A device measuring the optical power of simple lenses by means of moiré phenomena is described. The relevant equations are derived, and a working instrument is presented. A power measuring accuracy better than 0.25 m(-1) in the range of +/- 10 m(-1) is demonstrated.

Seventeenth-century telescope optics of Torricelli, Divini, and Campani.

Optics of telescope makers Torricelli, Divini, and Campani dating back to the 17th century have been tested interferometrically. It was found that the optical polishing technology had progressed to thorough control over the surface figure and finish, while the nearly paraxial conditions of the aperture remained constant. The instruments that were examined exemplify the knowledge of optics of that time, particularly with respect to the early use of erector units in terrestrial telescopes.