Fig. 1. Optical arrangements: (a) circular polariscope and (b) plane polariscope.

Fig. 2. Experimentally obtained images of a disc under diametrical compression using the four-step approach: (a)–(d) I0–I3. (e)–(g). Fringe maps of R, G, and B planes calculated using Eq. (5).

Fig. 3. (a) Resolved isochromatic fringe orders using Eq. (6). (b) Fringe order variation along line cd and the fitted curve. (c) Variation of ei of point R using Eq. (6). (d) Separated parts for isochromatic determination. (e) Whole-field refined results. (f) RGB results, refined results, and theoretical results along line cd; (g) RGB results, refined results, and theoretical results along line cd using a circular polariscope arrangement following Ajovalsit et al.

Fig. 4. Procedure of isochromatic determination.

Fig. 5. (a) Injection-molded polycarbonate cover. (b)–(d) Fringe maps of R, G, and B planes in the center part of the cover calculated using Eq. (5). (e) Resolved fringe orders using Eq. (6). (f) Refined fringe orders.