Lee O. Heflinger

Moiré Gauging Using Optical Interference Patterns

This paper describes a moiré technique for gauging surface deformations of an object or differences in the surface configuration of two similar objects. A grid pattern is generated on the object by illuminating it with a laser interference pattern, and a master negative is made by photographing the illuminated object with a view camera. With the negative occupying its original position, the moiré pattern corresponding to changes in the object can be observed in real time by viewing the image of the deformed or second object through the negative. The technique is noncontacting and quantitative. It is useful with objects of any size, and its sensitivity can be easily adjusted to suit the application.

Wideband holographic correction of an aberrated telescope objective

The imaging properties of a holographically corrected telescope are presented for broadband illumination using a single grating to correct for dispersion. High quality, broadband images approaching the performance of diffraction limited instruments are obtained from severely aberrated refractor and reflector telescope objectives.

Thermal Expansion Coefficient Measurement of Diffusely Reflecting Samples by Holographic Interferometry

Double exposure holographic interferometry is used to measure thermal expansion coefficients of diffusely reflecting small samples of arbitrary shape. A particular arrangement is used to obtain insensitivity to rigid body motions, simplifying the support and heating of the specimen. The expansion coefficient is easily determined from the readout photograph by a simple formula.

Coherence length measured directly by holography

We present a holographic method for measuring directly the complete temporal coherence function of a pulsed laser on a single pulse. The method is easy to implement and yields the exact coherence length even or lasers with complex spectral content where the conventional method using a Fabry-Perot interferometer would fail.

Thermal Expansion Coefficient Measurements of Specularly Reflecting Samples

A simple method is described for obtaining the expansion coefficient of specularly reflecting objects. The method photographically records the interference pattern of laser light reflected from the object. The moire beat between interference patterns recorded at two temperatures gives the expansion coefficient. When limited to smooth round objects, the technique is insensitive to rigid body motions of the specimens.

SUPERFAST PINCH STUDIES

An apparatus designed to accelerate protons of a hydrogen plasma to energies of 1 kev or more by means of the radially converging magnetic piston of a longitudinal pinch has been constructed. A capacitor charged to voltages of up to 350 kv is discharged through the plasma, producing currents of up to 75 ka. The ringing frequency is 18 Mc, so that the rate of current rise is about 0.8 × 1013 amp/sec. Radially converging luminous fronts with maximum velocities in excess of 50 cm/μsec are observed and are interpreted as shock waves driven by a magnetic piston. Magnetic probe measurements and measurements of the electric field at the wall of the discharge tube show that much of the magnetic flux introduced during the first half‐cycle is trapped in the hot plasma. The effects of varying such parameters as the total current, the initial pressure of gas, the type of gas, and the frequency of the discharge have been investigated. The experimental results are interpreted in terms of the classical Rosenbluth‐Garwin...

Holography On Space Shuttle

A holographic recording system will be flown on the NASA Space Shuttle (SL-3 mission) to record fluid phenomena under low-zero gravity conditions; namely, solution growth of crystals and fluid convection. A 25 milliwatt helium neon laser will be the illuminator for two orthogonal hologram recorders and a real time schlieren monitor. The holograms will be re-recorded on S0-253 films vacuum clamped to optical flats. Processing and analysis of the holographic records will all be after the Shuttles return.

High average power frequency doubling

High average power second harmonic generation in crystals with finite absorption at the fundamental or harmonic wavelength creates unique problems. In addition to generating significant OPD which degrades the beam quality, heating of the crystal creates conditions which can be inherently temporally unstable. As the crystal is tuned towards phase matching, rapid changes in temperature cause the crystal to drift away from phase matching conditions which is followed by reduced frequency conversion. Experiments are in progress with three crystals, KTP, KD*P and KNbO/sub 3/, which have vastly different characteristics, to assess their potential for high average power doubling.<<ETX>>