The optical characteristics of digitally recorded holographic optical elements by the wavefront recording method are measured with a Shack-Hartmann wavefront sensor and their performances as an optical element are compared with those of a spherical mirror and an analog holographic optical element with use of the reconstructed wavefront by Zernike polynomial. The comparison shows that the digitally recorded holographic optical elements can work as a spherical mirror/lens, but it introduces wavefront aberration much more than the mirror and the analog holographic optical element.
Thermal image is used to visualize the crack forming and progressing process in mortar prisms added with carbon fibers of five different percentages of 0.0 %, 0.5 %, 1.0 %, 1.5 % and 2.0% in volume, with the time variations of the surface temperature of the prisms while applying forces through a universal testing machine. The surface temperatures are smoothly increasing as the force increases but they reveal sudden temperature increases at the time of crack forming in the prisms. It turns that the sudden temperature increase in the prisms is appeared at the aggregated carbon fibers along the crack paths. The time of increasing matches closely to the crack on-set time determined by a panchromatic camera. Since the fibers along the crack path are more stressed for the given force because they resist more to the force than the mortar itself, their temperatures increase much more than the neighboring mortar. Hence the temperature variation in the aggregated fibers along the crack path informs before the actual crack appearance.
The wavefront distortions in a digitally recorded HOE which has the property of a spherical mirror is measured with a Shack-Hartmann wave front sensor to estimate its functional performance. The performance is compared with those in the reconstructed image from Fresnel zone patterns which are displayed on DMDs of different pixel shapes, and with an analog type HOE and a Spherical mirror. The distortion distributions from these samples are not too different from each other. All are revealing spherical mirror properties, though the mirror quality is not the same. This informs that the HOE really work as a spherical mirror. However, the focused beam size of the HOE is much bigger than those of other samples.
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