Observation of micro-characters using three-dimensional shape measurement method based on speckle interferometry

Role of Phase Information Propagation in the Realisation of Super-resolution Based on Speckle Interferometry

“…Furthermore, the use of plane waves as the reference light of the speckle interferometer enables deformation measurements to be performed using only two speckle patterns before and after deformation. This has been demonstrated in previous reports [17,[21][22][23].…”

“…Figure 7b shows the results of measuring this reflection-type diffraction grating using the optical system shown in Figure 2a. Furthermore, this method can be used not only to observe the microstructure of the repeating structure shown in Figure 7 but also to capture three-dimensional structures, such as microspheres and microcharacters [22], as reported previously.…”

“…Assuming, for example, that the measurement cross-section of the measurement object shown in Figure 1a can be expressed as f(x) and that a lateral shift δx is assigned to the measurement object, as shown in Figure 1b, the shape displacement occurring at each measurement point can be expressed as f(x + δx) − f(x). The displacement of the shape at each of these points is then accurately measured using speckle interferometry [20][21][22], and the pseudo-differential value {f(x) − f(x + δx)}/δx in the shift direction with respect to the shape is obtained by dividing the detected displacement by the transverse shift amount. Furthermore, the shape of the measurement object can be reconstructed by integrating the pseudo-differential value [17,22].…”

“…The displacement of the shape at each of these points is then accurately measured using speckle interferometry [20][21][22], and the pseudo-differential value {f(x) − f(x + δx)}/δx in the shift direction with respect to the shape is obtained by dividing the detected displacement by the transverse shift amount. Furthermore, the shape of the measurement object can be reconstructed by integrating the pseudo-differential value [17,22]. Through this computational process, structures beyond the diffraction limit were observed.…”

“…To avoid these problems, in the current study, I used an electromagnetic field simulation software (COMSOL Multiphysics) to investigate the physical phenomena in which the observation of microstructures beyond the diffraction limit was achieved using a new super-resolution technology based on speckle interferometry techniques [21][22][23]. A computer simulation model used in a previous report [23], shown in Figure 3a, was used as the optical system model in this study.…”