Fig. 1. Online 3D measurement system based on Stoilov algorithm

Fig. 2. Original simulation data. (a) Measured object; (b) reflectance distribution; (c) the first deformed pattern I1(x,y); (d) the second deformed pattern I2(x,y)

Fig. 3. Extraction of the modulation patterns in the simulation. (a)Spectrum distribution of the composite dual-frequency deformed pattern; (b) area of the positive first-level frequency spectrum after filtering; (c) modulation pattern

Fig. 4. Phase calculation directly after pixel matching in the simulation. (a) The first composite dual-frequency deformed pattern I'1(x,y) after pixel matching; (b) the second composite dual-frequency deformed pattern I'2(x,y) after pixel matching; (c) reconstructed object; (d) error distribution; (e) section cross at x=250 for the measured object and the reconstructed object; (f) section cross at y=250 for the measured object and the reconstructed object

Fig. 5. Phase calculation after filtering out the low-frequency component in the simulation. (a) Frequency spectrum distribution of the composite deformed pattern after pixel matching; (b) frequency spectrum area of the low-frequency component after filtering; (c) the first deformed pattern of the low-frequency component I'FL1(x,y); (d) the second deformed pattern of the low-frequency component I'FL2(x,y); (e) reconstructed object; (f) error distribution; (g) section cross at x=250 for the measured obje

Fig. 6. Measured object and deformed patterns. (a) Measured object; (b) the first deformed pattern I1(x,y); (c) the second deformed pattern I2(x,y)

Fig. 7. Measured object in the spectral distribution and the deformed patterns. (a) Measured object in the spectral distribution of the composite dual-frequency deformed pattern; (b) positive first-level frequency spectrum area of the high-frequency fringe after filtering; (c) modulation pattern

Fig. 8. 3D reconstruction of the measured object. (a) The first composite dual-frequency deformed pattern I'1(x,y) after pixel matching; (b) the second composite dual-frequency deformed pattern I'2(x,y) after pixel matching; (c) reconstructed object; (d) cross section at y=340 for the reconstructed object by the proposed method and the filtering method

Table 1. Measurement errors of planes with height of 3, 5 and 10 mm