Electronic speckle pattern interferometry using diode laser stroboscopic illumination

Duncan J. Anderson, Jesus D. Valera, Julian D C Jones

Research output: Contribution to journalArticle

Abstract

An electronic speckle pattern interferometer (ESPI) using stroboscopic illumination from a diode laser, and its application in vibration measurement, are described. Diode lasers are readily frequency (FM) and power modulated (AM) via control of their injection current; they are inexpensive and compatible with the single-mode optical fibres used in the described system. However, their modest peak power output demands the use of high-duty-cycle pulses, so that it was necessary to synchronize the illumination with the turning points of the vibration. This was achieved by operating the ESPI system in conjunction with a laser vibrometer. Injection-current-induced FM of diode lasers is non-uniform for modulation frequencies less than about 10 MHz, and to achieve successful stroboscopic illumination an electronic equalization stage was included to shape the current pulse, and hence compensate for the non-uniform FM.

Original languageEnglish
Pages (from-to)475-480
Number of pages6
JournalEngineering Optics
Volume6
Issue number4
Publication statusPublished - Nov 1993

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