Phase retrieval holography can suppress twin image problem of Gabor holography which causes blurred objects at a reconstructed focus position. We compared three-dimensional trajectories of spray droplets between conventional Gabor holography and developed phase retrieval holography under the high-speed imaging conditions to confirm the suppression of the twin image problem. Droplets sprayed from a nebulizer (Panasonic, EW-KA30- W) have an average diameter of 40.0 μm, mean velocity of 0.65 m/sec and Reynolds number of 0.2, respectively. Two holograms using phase retrieval holography were recorded two high-speed cameras (FASTCAM Mini UX100, Photron, frame rate: 4000 fps). It is found that phase retrieval holography has denser trajectories than Gabor holography because of suppressing the twin image problem. Additionally, number of the detected points of phase retrieval holography is almost 20 times higher than that of Gabor holography at each time step.
This paper proposed the detection method for the depth position of a dot to calibrate along the depth direction of two cameras, which is performed with obtaining the reconstruction distances to match the reconstructed volumes at each camera. We determined the reconstruction distance of each camera by using the dot-array plate and the proposed detection method of a dot. The reconstruction distance is calculated as the position that the variance of the real and the imaginary part of dots becomes a minimum value. We investigate the effect of dot spacing in the dot-array plate by comparing the error between the calculated distance and the true distance in numerical simulation. In addition, the effect of this method is also experimentally confirmed.
This paper presents a noninvasive evaluation system of fractured bone based on speckle interferometry using a modified
evaluation index for higher performance, and the experiments are carried out to examine the feasibility in evaluating
bone fracture healing and the influence of some system parameters on the performance. From experimental results, it is
shown that the presence of fractured part of bone and the state of bone fracture healing are successfully estimated by
observing fine speckle fringes on the object surface. The proposed evaluation index also can successfully express the
difference between the cases with cut and without it. Since most system parameters are found not to affect the
performance of the present technique, the present technique is expected to be applied to various patients that have
considerable individual variability.
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