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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. OCIS codes: 110.6770, 350.1260.

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. OCIS codes: 120.0120, 120.3180, 120.3940, 120.4800, 120.6650.

A device measuring the optical power of simple lenses by means of moire phenomena is described. The relevant equations are derived, and a working instrument is presented. A power measuring accuracy better than 0.25 [m.sup.-1] in the range of [+ or -]10 [m.sup.-1] is demonstrated. OCIS codes: 080.3630, 120.3930, 120.4120, 120.4570.

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. OCIS codes: 000.2850, 110.6770, 120.4800, 220.2740, 350.1260.

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. Key words: Surface scattering, speckle-field statistics, phase-shift interferometry.

The Florentine Istituto e Museo di Storia della 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.

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.sup -4]. OCIS codes: 120.0120, 120.3930, 120.4640, 120.6200.

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. OCIS codes: 090.0090, 090.1970, 090.2870, 090.5640.

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.