Fig. 1. (A) Principle of phase-shifting digital photoelasticity. (B) Principle of multi-wavelength digital photoelasticity. P₁, P₂: polarizers; Q₁, Q₂: quarter-wave plates; S: sample; L: lens; PLCMOS: polarization camera.

Fig. 2. Schematic of single-shot multi-wavelength photoelasticity measurement. LED (λ₁/λ₂): LED with λ₁ = 528 nm or λ₂ = 508 nm; P: polarizer; G1, G2: gratings; BS: beam splitter.

Fig. 3. (A) Setup of the single-shot dual-wavelength digital photoelasticity. (B) The loaded sample. (C) The intensity of the illumination on sample surface. The white bar represents 1 mm in the spatial domain.

Fig. 4. Experimental verifications of single-shot dual-wavelength digital photoelasticity. (A1), (A2) Intensity images of single-shot dual-wavelength digital photoelasticity; (B1), (B2) the spectra of the intensity images; (C1), (C2) dark and bright intensity images of λ₂; (D1), (D2) dark and bright intensity images of λ₁; (E1), (E2) cos2πδλ1, cos2πδλ2; (F) wrapped δ; and (G) the measured maximum shearing stress. The white bar represents 1 mm in the spatial domain.

Fig. 5. Quantitative comparison. (A)–(F) Intensity images of phase shifting photoelasticity; (G) wrapped phase retardation; (H) maximum shearing stress; (I) difference between phase-shifting photoelasticity and single-shot dual-wavelength digital photoelasticity; and (J) cross-sectional δ comparisons in both horizontal and vertical axes. The white bar represents 1 mm in the spatial domain.