Digital Holographic Interferometry by Using Long Wave Infrared Radiation (CO₂ Laser)

Abstract

We show how digital holographic interferometry in the Long Wave InfraRed spectral range (LWIR) can be used for the investigation of mechanical structures. The 10.6 μm radiation is produced by a CO2 Laser. Experimental results showing that the method can be used to locate defects in a panel are presented and advantages and disadvantages of this approach are discussed.

Электроразрядный Химический HF-лазер --- Высококогерентный Источник Для Ик-Голографии. Перспективы Практического Применения

“…В настоящее время СО 2 -лазеры с успехом приме-няются как для диагностики плазмы [3,4], так и для интерферометрического контроля формы и деформации разнообразных объектов, таких как крупногабаритные зеркала [5], строительные сооружения [6], произведения искусства [7]. В последнем случае интерферограмма, фиксирующая скрытые дефекты произведения живопи-си, сохраненная на электронном носителе, выполняет функцию индивидуальной " идентификационной метки", снижающей вероятность подмены подлинника картины копией.…”

Speckle interferometry at 10 micrometers wavelength: a combined thermography and interferometry technique and its application in aeronautical nondestructive testing

“…The development of the set-up we use was already presented in several papers: we studied various configurations such as LWIR DHI [17] [18] , ESPI [18] and shearography [18] . The camera is a Jenoptik Variocam HR based on an uncooled microbolometer array with 640x480 pixels, each pixel being 25 µm wide.…”

Nondestructive testing by using long-wave infrared interferometric techniques with CO2lasers and microbolometer arrays

“…Our first step in this project was to assess the roughness of these samples, and we showed that most of the above cited materials have a roughness that is high enough to generate speckle with CO 2 lasers [23]. Preliminary DHI experiments were already reported with these samples [24].…”