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Precision Ultrasonic Wave Measurements With Simple Equipment

View Article: PubMed Central - PubMed

ABSTRACT

We describe the design and construction of a relatively simple, inexpensive laser interferometer system for accurate measurements of ultrasonic surface displacement waveforms in reasonably friendly environments. We show how analysis of a single waveform can provide both the calibration constant required for absolute measurements and an estimate of the uncertainty of these measurements. We demonstrate the performance of this interferometer by measuring ultrasonic waveforms generated by a novel conical-element ultrasonic transducer.

No MeSH data available.


Basic optical system system of the interferometer.
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f2-j65fic: Basic optical system system of the interferometer.

Mentions: The basic design of our instrument has been described in some detail previously [11]. The essential optical layout is shown in Fig. 2. It features a more-or-less in-line arrangement of both reference and sample beams. The expanded input laser beam is focused by the large lens through the beam splitter plate, BS, onto the specimen. The reference beam is reflected by the beam splitter to focus on the small mirror left of the beam splitter. The focused spot size on the specimen is about 0.02 mm diameter, much smaller than the shortest ultrasonic wavelengths to be measured. If necessary, the spot could be made much smaller by using a lens with shorter focal length. Thus the instrument acts as a point receiver, and neither flatness of the specimen surface nor a high quality optical polish are essential for good results. Non-reflecting specimens were also studied by cementing a tiny mirror on the surface, as explained below. For simplicity, Fig. 2 does not show a small device that redirects the horizontal interferometer beams 90° up or down for probing horizontal surfaces.


Precision Ultrasonic Wave Measurements With Simple Equipment
Basic optical system system of the interferometer.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4862816&req=5

f2-j65fic: Basic optical system system of the interferometer.
Mentions: The basic design of our instrument has been described in some detail previously [11]. The essential optical layout is shown in Fig. 2. It features a more-or-less in-line arrangement of both reference and sample beams. The expanded input laser beam is focused by the large lens through the beam splitter plate, BS, onto the specimen. The reference beam is reflected by the beam splitter to focus on the small mirror left of the beam splitter. The focused spot size on the specimen is about 0.02 mm diameter, much smaller than the shortest ultrasonic wavelengths to be measured. If necessary, the spot could be made much smaller by using a lens with shorter focal length. Thus the instrument acts as a point receiver, and neither flatness of the specimen surface nor a high quality optical polish are essential for good results. Non-reflecting specimens were also studied by cementing a tiny mirror on the surface, as explained below. For simplicity, Fig. 2 does not show a small device that redirects the horizontal interferometer beams 90° up or down for probing horizontal surfaces.

View Article: PubMed Central - PubMed

ABSTRACT

We describe the design and construction of a relatively simple, inexpensive laser interferometer system for accurate measurements of ultrasonic surface displacement waveforms in reasonably friendly environments. We show how analysis of a single waveform can provide both the calibration constant required for absolute measurements and an estimate of the uncertainty of these measurements. We demonstrate the performance of this interferometer by measuring ultrasonic waveforms generated by a novel conical-element ultrasonic transducer.

No MeSH data available.