A method of testing a device under test comprising providing a beam of light from a light source having a first wavelength. Imposing the beam of light on a test device over a spatial region within the test device substantially greater than the first wavelength, wherein the test device has a first state of refraction. Imposing the beam of light on the test device over a spatial region within the test device substantially greater than the first wavelength, wherein the test device has a second state of refraction. Obtaining data resulting from the interference of the first beam and the second beam within the device under test representative of the voltages within the region, wherein the first state of refraction is at a first voltage potential, and wherein the second state of refraction is at a second voltage potential different from the first voltage potential.

Voltage testing and measurement

A method of testing a device under test includes providing a beam of coherent light from a light source having a first wavelength, and imposing the beam of light on a test device over a spatial region within the test device substantially greater than the first wavelength, wherein the test device has a first state of birefringence. A second beam of light is imposed on the test device over a spatial region within the test device substantially greater than the first wavelength, wherein the test device has a second state of birefringence. Data representative of the interference of the first beam and the second beam within the bulk of the device under test is obtained representative of the voltages within the region

Method for testing a device under test including the interference of two beams

We demonstrate the optical reconstruction in the visible range (0.532μm) of digital holograms recorded at long IR wavelengths (10.6μm) by means of a spatial light modulator. By using an integrated recording-reconstruction system, it is, in fact, feasible to achieve direct imaging of holograms acquired outside the visible range, i.e., in the IR spectrum. By choosing a Fourier recording configuration, the reconstructed image, obtained at about a 20 times shorter wavelength than the acquisition image, exhibits minor aberrations, which do not significantly affect the optical reconstruction. The high NA achievable at a long IR wavelength allows us to image large objects at reasonable distances.

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Optical reconstruction of digital holograms recorded at 10.6 μm: route for 3D imaging at long infrared wavelengths

Digital holographic interferometry in the long-wave infrared domain has been developed by combining a CO2 laser and a microbolometer array The long wavelength allows large deformation measurements, which are of interest in the case of large space reflectors undergoing thermal changes when in orbit We review holography at such wavelengths and present some specific aspects related to this spectral range on our measurements For the design of our digital holographic interferometer, we studied the possibility of illuminating specular objects by a reflective diffuser We discuss the development of the interferometer and the results obtained on a representative space reflector, first in the laboratory and then during vacuum cryogenic test

Digital holographic interferometry with CO2 lasers and diffuse illumination applied to large space reflectors metrology

ew Tech n iq u es in D ig ial H o lo g ap h y E d ied b y P acal P iart This book is devoted to special techniques in digital holography. The authors establish a synthetic state of the art of important advances in the field of digital holography. They are interested in detailing advances related to fundamentals of digital holography, in-line holography, digital color holographic metrology, digital holographic microscopy, infrared holography and special techniques in full-field vibrometry.

New Techniques in Digital Holography

A search for recording media suitable for holography at wavelengths comparable to the 10.6 μm of a CO2 laser has led to the successful use of Saran Wrap plastic films and of thick acrylic plates. Holographic phase recording has been made with a 1-W single mode cw CO2 laser yielding incident intensities up to 3.5 W/cm2. Holographic reconstruction at a wavelength of 632.8 nm has given a diffraction efficiency up to 20%. At a wavelength of 10.6 μm, reconstruction by reflection on the silver-coated surface of an acrylic plate had a diffraction efficiency of 0.5%. It was observed that the recording is less linear on acrylic plates than on Saran Wrap films.

Plastic recording media for holography at 10.6 μm

Oil films of approximately 1-μm thickness on glass plates are used as a holographic recording medium at a 10.6-μm wavelength. This dynamic recording medium (on which the recording is not permanent) shows diffraction efficiencies up to 20% when reconstructing at 632.8 nm, the spatial frequency at the recording being as high as ~50 cycles/mm. Furthermore, the response time of these oil films when recording ir can be as small as 2 msec so that ir holography of moving objects is possible in real time.

Holographie en infrarouge sur de minces couches d'huile.

Phase holograms have been recorded on Takiwax films with pulsed TEA CO2 laser light. The reconstruction from these phase holograms is accomplished by transmission at a wavelength of 0.633 μm. Holographic characteristics of the recording medium, such as diffraction efficiency vs film thickness, exposure, and spatial frequency, are presented. The capability of Takiwax films to record ir holograms of plane objects and double-exposure holographic interferograms is demonstrated.

Pulsed ir holography on Takiwax films.

Holograms have been recorded with far‐infrared radiation (10.6 μm) on ’’Takiwax’’ films. The relief‐phase holograms obtained due to the thermal process involved are reconstructed, in real time, with He‐Ne laser light. Reconstruction from grating holograms in the infrared with 10.6‐μm CO2 laser radiation is also possible: diffraction efficiencies of up to 15% have been measured for two‐beam gratings.

M. Cormier

Papers

Plastic recording media for holography at 10.6 μm

Holographie en infrarouge sur de minces couches d'huile.

Pulsed ir holography on Takiwax films.

Infrared holography on commerical wax at 10.6 μm

Use of the TEM(10) laser mode for ir holography at 10.6 microm.