Holographic techniques at long wave infrared wavelengths

For industrial applications, holographic interferometry and electronic speckle pattern interferometry techniques using visible laser light are often too sensitive to external perturbations. Consequently they require too much stability, preventing their widespread use in field applications. One simple idea to overcome this problem is to increase the wavelength of the laser light. We considered the 10 µm wavelength range corresponding to well known CO2 laser and because imagers exist in this spectral range. One other important advantage is that the strain/displacement measurement range is larger than the equivalent techniques in visible light. We will present the preliminary experiences performed so far with components available in our lab. Mainly, we show in-plane electronic speckle pattern interferometry and for the first time digital holographic interferometry. We also discuss specific problems related to the wavelength increase