Fig. 1. Schematic diagram of system coordinates

Fig. 2. Schematic of the experimental system of reflective off-axis IPDHM

Fig. 3. Correction results of surface fitting method for different polynomials. (a) 6-term quadratic polynomial; (b) 9-term quadratic polynomial; (c) Zernike higher order polynomial

Fig. 4. Experimental results of two-step phase subtraction method for micro-step. (a) Backgroud area hologram; (b) Micro-step hologram; (c) Reconstructed amplitude of background area; (d) Reconstructed amplitude of micro-step; (e) Unwrapped phase of backgroud area; (f) Unwrapped phase of micro-step; (g) Height distribution of micro-step; (h) 3D diagram of micro-step

Fig. 5. Comparison of experimental results of two-step phase subtraction method and surface fitting method

Fig. 6. Experimental results of the microfluidic chip channel. (a) Background area hologram; (b) Channel hologram; (c) Reproducted amplitude of background area; (d) Reproducted amplitude of channel; (e) Unwrapped phase of background area; (f) Unwrapped phase of channel; (g) Depth of channel; (h) 3D diagram of channel

Fig. 7. Experimental results of fractured surface defect. (a) Reproducted amplitude of channel and defect; (b) Magnified view of defect’s reproducted amplitude; (c) Depth of defect; (d) Depth distribution of the horizontal line in (c); (e) 3D diagram of defect

Fig. 8. Experimental results of defective surface defect. (a) Reproducted amplitude of channel and defect; (b) Magnified view of defect’s reproducted amplitude; (c) Depth of channel and defect ; (d) Depth distribution of the horizontal line in (c); (d) 3D diagram of defect

Table 1. Comparison of micro-step height errors by each phase distortion correction method