Time Holographic Interferometry Research Articles

Measurement of local convective heat transfer coefficients using three-dimensional interferometry

The reconstruction of the three-dimensional temperature distribution above a horizontal heated disk in air is used to determine the local heat transfer coefficients. Holographic interferometry is used to obtain instantaneous, three-dimensional information on the local index of refraction distribution. Several reconstruction procedures are tested under the constraints of limited field of view and limited fringe order data. These techniques are used to accurately measure the instantaneous local temperature distribution. Subsequently, the surface temperature gradients are specified by curve fitting procedures and the local heat transfer coefficients determined. The surface averaged Nusselt number agrees very well with previous studies in the literature. Real time holographic interferometry is also used to suggest some of the dynamic characteristics of the convective heat transfer process. Results show local instabilities in the form of distributed bursting of thermal energy from the surface. Also, at sufficiently high surface temperatures the entire temperature field shows evidence of oscillation or pulsation which indicates a global heat release mechanism.

Damage progression in compressively loaded laminates containing a circular cutout

A series of experiments have been performed to determine the mechanisms of failure in compressively loaded laminated plates in the presence of stress gradients generated by a circular cutout. Real time holographic interferometry and in situ photomicrography of the hole surface along with strain gauge measurements are used to study the progression of failure. The test specimens are multilayered composite flat plates that are loaded in compression. The laminates are made up of two material systems, T300/BP907 and IM7/8551-7. Two different lay-ups of both systems are investigated. The experimental results reveal that the failure is initiated as a localized instability in the 0 deg plies at the hole surface approximately at right angle to the loading direction. Subsequent to the 0 deg ply failure, extensive delamination cracking is observed with increasing load. The delaminated portions spread to the undamaged areas of the laminate by a combination of delamination buckling and growth, the buckling further enhancing the growth. '

Real time holographic interferometry by superimposing carrier patterns using image processing technique (In Japanese) 39324 Morimoto, Y.; Seguchi, Y.; Nakao, H. Journal of the Japanese Society for Non-Destructive Inspection, Vol. 37, No. 8, pp. 630–635 (Aug. 1988)

Real time holographic interferometry by superimposing carrier patterns using image processing technique (In Japanese) 39324 Morimoto, Y.; Seguchi, Y.; Nakao, H. Journal of the Japanese Society for Non-Destructive Inspection, Vol. 37, No. 8, pp. 630–635 (Aug. 1988)

Real time holographic interferometry by superimposing carrier patterns using image processing technique (In Japanese) : 39324 Morimoto, Y.; Seguchi, Y.; Nakao, H. Journal of the Japanese Society for Non-Destructive Inspection, Vol. 37, No. 8, pp. 630–635 (Aug. 1988)

Real time holographic interferometry by superimposing carrier patterns using image processing technique (In Japanese) : 39324 Morimoto, Y.; Seguchi, Y.; Nakao, H. Journal of the Japanese Society for Non-Destructive Inspection, Vol. 37, No. 8, pp. 630–635 (Aug. 1988)

Holographic interferometry evidence that β-decay energy can symmetrize solid deuterium–tritium samples

Thin solid samples of deuterium–tritium (DT) have been seen to sublime and redistribute within spherical inertial fusion targets due to the heat generated by beta decay. We have frozen thin DT samples within glass shells of 890 and 3750 μm diameter, and observed the evolution of the solid towards more symmetric distributions using real time holographic interferometry. Holographic interferometry provides more sensitivity than direct imaging or classical interferometry to observe the thin (10–30 μm) solid samples in these shells.

Phase measuring real time holographic interferometry with a tunable laser diode

A phase measuring technique allowing for quantitatively determining the phase of real time holographic fringers with a laser-diode source is described. The phase is changed to produce a relative phase difference between the two beams of reference and object arms in reconstruction by the stepwise wavelength change by variation of laser injection current. The angles of illumination directions across the whole object are used for extracting the exact phase profile of a deformed object. Experimental results are shown. Helpful data on the diffraction efficiency of laser-diode recording holograms and the wavelength tunability of laser diode are presented.

Interferometric testing of the spacing error of a plane diffraction grating

Two measuring methods of the plane diffraction grating spacing error are presented in this work. The first one resembles real- time holographic interferometry. The hologram is exposed when an object beam is the nth diffraction order, and is then illuminated by the - nth diffraction order wave. The second method makes use of double-exposure holographic interferometry. The first exposure is performed when the nth diffraction order is an object beam. During the second exposure the - nth diffraction order is an object beam. Both methods allow to measure the spacing error separately, not only from the grating surface error but also from the aberrations introduced by the other optical elements of the set-up.

A comparison of optical and numerical methods for analyzing structural vibrations

An optical holographic interferometry method has been used to determine the resonant frequencies, mode shapes, and peak displacement amplitudes of an irregular, clamped, vibrating plate. The plate was driven by an electromagnetic shaker with swept sine wave execution and resonances were observed by time holographic interferometry. Mode shapes at several resonant frequencies were then photographed by a time‐average holographic interferometry method. The observed resonant shapes were compared with predictions obtained by two finite element programs (GIFTS and NASTRAN). Facilities required for each method of solution and procedures for collecting and interpreting mode shape data will be described. Applications of the optical and numerical methods to problems involving damped vibrating structures will be discussed. [Research supported by DTNSRDC and ONR.]

Real time acoustic imaging by holographic interferometry

A two-step real time acoustic imaging system is presented. The system incorporates a novel acoustic image coupler which transfers an acoustical interference pattern from a water-bounded to an air-bounded surface with vibration amplitude amplification. An original technique termed stepbiased real time holographic interferometry is used to convert the amplified mechanical vibration pattern, which carries all information about the insonified object, into a visual image with improved sensitivity.

Real time acoustic imaging by holographic interferometry.

A two-step real time acoustic imaging system is presented. The system incorporates a novel acoustic image coupler which transfers an acoustical interference pattern from a water-bounded to an air-bounded surface with vibration amplitude amplification. An original technique termed step-biased real time holographic interferometry is used to convert the amplified mechanical vibration pattern, which carries all information about the insonified object, into a visual image with improved sensitivity.

Absorption measurement of the optical materials by real time holographic interferometry

A new calorimetric technique is described for measuring a small absorption coefficient using real time holographic interferometry. The wavefront reconstructed by the hologram interferes with the wavefront which is deformed by the change of the optical path length caused by the temperature rise of the sample under radiation of an argon laser beam (1W, λ = 488 nm). From the movement of the fringes temporal and spatial temperature variation is measured, and fitting these values to the theoretical ones we obtain an absorption coefficient β = 0.14 (cm -1) of Corning glass filter No. 3–80 at λ = 488 nm.

Experimental Techniques in Real Time Holographic Interferometry II - Minimization of Depolarization Effects

The fringe contrast observed in real time holographic interferometry is often poor due to depolarization induced by the object. This paper describes the results of an experiment to determine the effect of surface preparation on depolarization.

Experimental Techniques in Real Time Holographic Interferometry I - Reduction of Emulsion Shrinkage Effects

When an object being tested and its holographic image are 'superimposed for real time holographic interferometry studies a distorted fringe field is normally observed as a result of emulsion shrinkage on the hologram plate. A liquid gate is commonly employed to eliminate emulsion shrinkage effects. This paper describes an alternative technique for reducing these effects which requires only that the plate be overexposed and underdeveloped.

Printed Circuit Board Evaluation by Holographic Interferometry

Application of real time holographic interferometry for the examination of a printed circuit board is described. The procedures and the resulting holographic interferograms of two specific studies are presented: (1) The heat conduction of a spacer used for mounting transistors on a heat sink, and (2) the detection of inner layer short circuits on a multilayer printed circuit board.

ホログラフィ干渉法によるボルト締結体の変形測定

This paper describes the experimental results on the deformation of the bolted twin plates measured by real time holographic interferometry. The data obtained by this experiment show the next three conclusions.(1) The shape of the deformation is conical except the small range of the rim of the plate. And the deformation is not so small and it spreads over so large area that its effect should not be omitted when the spring constant of the plate is calculated.(2) The deformation of the bolt-head is measured accurately which had not been measured till this experiment. And its three dimensional shape is conical except the bottom of the dent. And the quantity of the deformation is not so small that its effect should be considered when the spring constant of the plate is calculated.(3) The residual plastic deformation of the plate after the unloading of the compressive overload over the elastic region is measured. Though its quantity is very small, it spreads over the wide area. The results stated above show good agreement with those obtained with another instrument.

Holographic Technique for Determining the Phase of Vibrating Objects

A means is demonstrated for determining the phase of vibrating objects by using either time average holography or real time holographic interferometry. The technique consists of vibrating a mirror in either the object or reference leg at the same frequency as the object and observing the effects on the fringe pattern when either the phase or amplitude of the mirror vibration is altered. Proper adjustment of these parameters places an interferometric node (fringe-contrast maximum) at any object point. The phase is then known from the phase of the vibrating mirror.

General Evaluation of Sonar Transducers by Average Time Holographic Interferometry

A brief explanation of the average time holographic interferometry technique applied to the evaluation of sonar transducers [R. M. Grant and W. Von Winkle, “Interferometric Holography as a Tool for the Study of Flexures in Active Sonar Transducers,” paper invited and presented at the First Intern. Conf. Laser App. Paris, France (July 1967)] will be presented. In addition to a brief theoretical discussion of the average time technique, examples will be given of the application of the above technique to both design and nondestructive testing of sonar transducers. Results will be given for both single elements and arrays.