Industrial applications of embedded materials have been increased in the recent years as the study of their mechanical properties. A particular interest is their homogeneousness which will determine a significant improvement or decay in the possible application. The optical system proposed here can show the internal micro structure and the internal displacements along a scanned volume through consecutives 2D tomographic and optical phase images. The volumetric information is retrieved by means of a liner stage which avoids the use of expensive tilting devices. Results show the response of homogeneous and in-homogeneous PMMA samples during controlled tests in order to find the simplest one which determines the sample’s condition.
A study in porcine femoral bones with and without the presence of cortical drilling is presented. An out of plane digital holographic interferometer is used to retrieve the optical phase during the controlled compression tests. These tests try to simulate physiological deformations in postmortem healthy bones and compare their mechanical response with those having a cortical hole. The cortical drilling technique is widely used in medical procedures to fix plaques and metallic frames to a bone recovering from a fracture. Several materials and drilling techniques are used for this purpose. In this work we analyze the superficial variations of the bone when different drilling diameters are used. By means of the optical phase it is possible to recover the superficial deformation of the tissue during a controlled deformation with high resolution. This information could give a better understand about the micro structural variations of the bone instead of a bulk response. As proof of principle, several tests were performed to register the modes and ranges of the displacements for compressive loads. From these tests notorious differences are observed between both groups of bones, having less structural stiffness the drilled ones as expected. However, the bone's characteristic to absorb and adjust itself due the load is also highly affected according to the number of holes. Results from different kind of samples (undrilled and drilled) are presented and discussed in this work.
The optical coherence tomography (OCT) technique has proved to be a useful method in biomedical areas such as ophthalmology, dentistry, dermatology, among many others. In all these applications the main target is to reconstruct the internal structure of the samples from which the physician’s expertise may recognize and diagnose the existence of a disease. Nowadays OCT has been applied one step further and is used to study the mechanics of some particular type of materials, where the resulting information involves more than just their internal structure and the measurement of parameters such as displacements, stress and strain. Here we report on a spectral OCT system used to image the internal 3D microstructure and displacement maps from a PMMA (Poly-methyl-methacrylate) sample, subjected to a deformation by a controlled three point bending and tilting. The internal mechanical response of the polymer is shown as consecutive 2D images.
A polarization sensitive Fourier domain optical coherence tomography system to measure the
birefringence response and the internal deformation of porcine corneas is presented. The optical
system uses polarized light to recover simultaneously the s and the p polarization states. A CMOS
camera records a fringe pattern which reconstructs the thickness of the porcine cornea. Combining
both p and s states a polarization retardation map is observed inside the tissue. The corneas are
deformed due a hydro static test which simulates different intra ocular pressure variations. Results
show simultaneously the thickness of the cornea, its birefringence response and its mechanical micro