Electronic speckle pattern interferometry and digital holographic interferometry with microbolometer arrays at 106 μm

Abstract

Electronic speckle pattern interferometry and digital holographic interferometry are investigated at long infrared wavelengths. Using such wavelengths allows one to extend the measurement range and decrease the sensitivity of the techniques to external perturbations. We discuss the behavior of reflection by the object surfaces due to the long wavelength. We have developed different experimental configurations associating a CO(2) laser emitting at 10.6 μm and microbolometer arrays. Phase-shifting in-plane and out-of-plane electronic speckle pattern interferometry and lensless digital holographic interferometry are demonstrated on rotation measurements of a solid object.

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

“…However, Maack et al [25] have already shown that ESPI can be performed under such circumstances. Their works were carried out under visible light, and we extended this discussion in our earlier works to LWIR ESPI [21].…”

“…Recently we have proposed several setups using electronic recording of holograms and specklegrams with microbolometer arrays and a CO 2 laser for applications in interferometry of scattering objects, more specifically in-plane displacement measurements by ESPI [20] and out-of-plane displacement by both ESPI and lensless digital HI (DHI) [21]. The results presented there were obtained with early microbolometer technologies with small formats (320 × 240 pixels) and with the purpose of demonstrating the capabilities of LWIR holography techniques in applications of displacement measurement.…”

“…In [21] we discussed the problem of the specularity of the surface in the LWIR range. Following Yamaguchi [22], the surface becomes completely scattering and speckle appears when the laser wavelength is smaller than the surface roughness.…”

Simultaneous Temperature and Deformations Measurements Using Long-Wave Infrared Speckle Interferometry: A Novel Hybrid Technique for Industrial Nondestructive Testing

“…In particular it allows observing large objects and in metrology it allows measuring large displacements while rendering holography more immune to environmental perturbations, compared to holography in the visible. For metrology we demonstrated various holographic techniques in LWIR: speckle interferometry [2,4], DH interferometry [2][3][4] and shearography [4]. The LWIR holographic set-up generally makes use of microbolometer arrays based thermal imagers.…”

Digital Holographic Interferometry in the Long-Wave Infrared for the Testing of Large Aspheric Space Reflectors

“…In particular it allows observing large objects due to the fact that at such wavelengths the ratio between the wavelength and the pixel size allows reconstructing objects 5 to 10 times larger than with DH in visible light [2,3]. We already presented various configurations of LWIR DH interferometry and electronic speckle pattern interferometry for deformation metrology and non destructive testing [3,4]. In this paper we present the application of LWIR DH in interferometric testing of large deformation of large aspheric mirrors in the frame of a European Space Agency project.…”